AGMA 923-B05

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AGMA INFORMATION SHEET(This Information Sheet is NOT an AG MA Standard)

A G M A 9 2 3 - B 0 5

AGMA 923- B05

AMERICAN GEAR MANUFACTURERS ASSOCIATION

Metallurgical Specifications for Steel

Gearing

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ii

Metallurgical Specifications for Steel Gearing AGMA 923--B05

CAUTION NOTICE: AGMA technical publications are subject to constant improvement,

revision, or withdrawal as dictated by experience. Any person who refers to any AGMA

technical publication should be sure that the publicationis the latest available from the As-

sociation on the subject matter.

[Tables or other self--supporting sections may be quoted or extracted. Citations should

read: See AGMA 923--B05, Metallurgical Specifications for Steel Gearing, published by

the American Gear Manufacturers Association, 500 Montgomery Street, Suite 350,

Alexandria, Virginia 22314, http://www.agma.org.]

Approved May 3, 2005

ABSTRACT

This document identifies metallurgical quality characteristics which are important to the performance of steel

gearing. The AGMA gear rating standards identify performance levels of gearing by heat treatmentmethodand

grade number. For each heat treatment method and AGMA grade number, acceptance criteria are given for

various metallurgical characteristics identified in this document.

Published by

American Gear Manufacturers Association500 Montgomery Street, Suite 350, Alexandria, Virginia 22314

Copyright © 2005 by American Gear Manufacturers Association

All rights reserved.

No part of this publication may be reproduced in any form, in an electronicretrieval system or otherwise, without prior written permission of the publisher.

Printed in the United States of America

ISBN: 1--55589--848--3

American Gear

Manufacturers

Association

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AGMA 923--B05AMERICAN GEAR MANUFACTURERS ASSOCIATION

iii© AGMA 2005 ---- All rights reserved

Contents

Page

Foreword iv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 Scope 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 Normative references 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 Definitions 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4 Procedures 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 Metallurgical requirements 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Bibliography 31. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Tables

1 Metallurgical characteristics for through hardened gearing 15. . . . . . . . . . . . . . .

2 Metallurgical characteristics for carburize and hardened gearing 17. . . . . . . . .

3 Metallurgical characteristics for induction or flame hardened gearing 22. . . . . .

4 Metallurgical characteristics for nitrided gearing 27. . . . . . . . . . . . . . . . . . . . . . . .

Figures

1 Continuous carbide network 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 Semi--continuous carbide network 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 Discontinuous carbides 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4 Dispersed carbides 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 Solid on shaft pinion blank 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6 Bore style gearing blank 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7 Disc style gearing blank 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8 Web style gear blank 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9 Intergranular oxidation in carburized gearing 7. . . . . . . . . . . . . . . . . . . . . . . . . . . .

10 Non--martensitic transformation products in carburized gearing 8. . . . . . . . . . .

11 Tempered martensite and 5% retained austenite in carburized gearing 10. . . .

12 Tempered martensite and 20% retained austenite in carburized gearing 10. . .

13 Tempered martensite and 30% retained austenite in carburized gearing 10. . .

14 Variations in hardening pattern obtainable on gear teeth with flame orinduction hardening 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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AGMA 923--B05 AMERICAN GEAR MANUFACTURERS ASSOCIATION

iv © AGMA 2005 ---- All rights reserved

Foreword

[The foreword, footnotes and annexes, if any, in this document are provided for

informational purposes only and are not to be construed as a part of AGMA Information

Sheet 923--B05, Metallurgical Specifications for Steel Gearing.]

In November, 1984, an ad hoc Metallurgy and Gear Rating Committee met to define the

factors required to qualifythe variousmetallurgical quality grades that were to be introduced

into thegear rating standard that eventuallybecame ANSI/AGMA 2001-- B88, Fundamental Rating Factors and Calculation Methods for Involute Spur and Helical Gear Teeth.

In May, 1988, ANSI/AGMA 6033--A88, Standard for Marine Propulsion Gear Units -- Part 1,

Materials, was published using a short list of metallurgical factors in table form.

In September, 1988, ANSI/AGMA 2001--B88 was published using metallurgical factors in

table form.

Starting in July, 1992, AGMA representatives participated in writing ISO 6336--5,

Calculation of Load Capacity of Spur and Helical Gears -- Part 5: Strength and Quality of

Materials , which was a modification of the tables in ANSI/AGMA and DIN Standards.

In February, 1993,AGMA 6002--B93, Design Guide for Vehicle Spur andHelicalGears ,was

published using a modified version of the tables used in ANSI/AGMA 2001--B88.

In September, 1993, the AGMA Metallurgy and Materials Committee accepted the task ofconsolidating the various tables to avoid redundancies and conflicting requirements, and

started work on AGMA 923--A00, Metallurgical Specifications for Steel Gearing.

In January, 1995, a revised ANSI/AGMA 2001--C95 was published using a version of the

ANSI/AGMA 2001--B88 tables as revised by the AGMA Helical Gear Rating Committee.

In November, 1997, a revised ANSI/AGMA 2003--B97, Rating the Pitting Resistance and

Bending Strength of Generated Straight Bevel, Zerol Bevel and Spiral Bevel Gear Teeth ,

was published using a version of theANSI/AGMA2001--B88 tablesas revised by theAGMA

Bevel Gearing Committee.

The committee reviewed all metallurgical tables of the gear rating standards ANSI/AGMA

2001--B88, ANSI/AGMA 2003--A86, and ISO 6336--5:1996 and their proposed revisions to

develop consolidated tables describing the metallurgical characteristics associated witheach specific type of heat treatment and metallurgical quality grade. Effort was made to

reference ISO specifications where possible. The consolidated tables were submitted to

the gear rating committees for their agreement and are published here for reference by

other standards.

AGMA’s goal is to develop a consistent metallurgical specification which reflects the quality

requirementsfor steel gearing. AGMA 923--A00 wassuch a document,and wasintended to

be consistent with the applicable portions of ISO 6336--5:1996, to the extent possible while

the two standards were in parallel development. The AGMA Technical Division Executive

Committee approved the publication of AGMA 923--A00 in August, 2000.

This edition of the information sheet, AGMA 923--B05, incorporates changes to item 8,

microstructure, of table 1, Metallurgical characteristics for through hardened gearing. The

balance of the document remains unchanged. The AGMA Technical Division Executive

Committee approved the publication of AGMA 923--B05 in May, 2005.

Suggestions for improvement of this information sheet will be welcome. They should be

sent to the American Gear Manufacturers Association, 500 Montgomery Street, Suite 350,

Alexandria, Virginia 22314.

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v© AGMA 2005 ---- All rights reserved

PERSONNEL of the AGMA Metallurgy and Materials Committee

Chairman: Phil Terry Lufkin Industries, Inc.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Vice Chairman: Dale J. Weires Boeing Defense & Space Group. . . . . . . . . . . . . . . . . . . . . . .

ACTIVE MEMBERS

C. Berndt Caterpillar, Inc.. . . . . . . . . . . . . . . . . . . . . . . . . .I. Botto FFE Minerals. . . . . . . . . . . . . . . . . . . . . . . . . . . .

D. Breuer Metal Improvement Company. . . . . . . . . . . . . . . . . . . . . . . . .R.J. Cunningham Consultant. . . . . . . . . . . . . . . . . . .G. Diehl Philadelphia Gear Corporation. . . . . . . . . . . . . . . . . . . . . . . . . . .D. Herring The Herring Group, Inc.. . . . . . . . . . . . . . . . . . . . . . . . .D.R. McVittie Gear Engineers, Inc.. . . . . . . . . . . . . . . . . . . . . .J. Mertz Falk Corporation. . . . . . . . . . . . . . . . . . . . . . . . . . .R.L. Schwettman Xtek, Inc.. . . . . . . . . . . . . . . . . . .M. Stein Applied Process Southridge, Inc.. . . . . . . . . . . . . . . . . . . . . . . . . . .J.B. Walenta Caterpillar, Inc.. . . . . . . . . . . . . . . . . . . . . . .L.L. Witte General Motors Corporation/Allison Transmission Division. . . . . . . . . . . . . . . . . . . . . . . . . .

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vi © AGMA 2005 ---- All rights reserved

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1

© AGMA 2005 ---- All rights reserved


American Gear ManufacturersAssociation --

MetallurgicalSpecifications for Steel

Gearing

1 Scope

This information sheet recommends steel material

and metallurgical quality characteristics for use in

conjunction with AGMA gear rating standards. This

information sheet identifies specifications and re-

quirements for various metallurgical quality grades

for through hardened, carburize and hardened,

induction and flame hardened, and nitrided gearing.

Characteristics covered include raw material, heat

treatment and post heat treat processing, and their

associated inspections. Topics related to gear de-

signand rating,such as case depth,stressnumbers,

andquality controlsampling plans arenot included inthis document.

2 Normative references

The following standards contain provisions which,

throughreference in this text,constitute provisionsof

this document. At the time of initial development, the

editions shown were valid. All standards are subject

to revision, and parties to agreements based on this

document are encouraged to investigate the possi-bility of applying the most recent editions of the

standards shown below.

AGMA 904--C96, Metric Usage

ANSI/AGMA 1010--E95, Appearance of Gear Teeth

-- Terminology of Wear and Failure

ANSI/AGMA 1012--F90, Gear Nomenclature,

Definitions of Terms with Symbols

ANSI/AGMA 2001--C95, Fundamental Rating

Factors and Calculation Methods for Involute Spur

and Helical Gear Teeth

ANSI/AGMA 2003--B97, Rating the Pitting

Resistance and Bending Strength of Generated Straight Bevel, Zerol Bevel and Spiral Bevel Gear

Teeth

ANSI/AGMA 2004--B89, Gear Materials and Heat

Treatment Manual

ANSI/AGMA 2007--B92, Surface Temper Etch

Inspection After Grinding

ANSI/AGMA 6002--B93, Design Guide for Vehicle

Spur and Helical Gears

ANSI/AGMA 6032--A94, Standard for Marine Gear

Units: Rating

ASTM A29--99, Specification forSteel Bars, Carbon and Alloy, Hot--Wrought and Cold--Finished,

General Requirements for

ASTM A148--93b(1998), Specification for Steel

Castings, High Strength, for Structural Purposes

ASTM A255--99, Test Method for Determining

Hardenability of Steel

ASTM A275--98, Test Method for Magnetic Particle

Examination of Steel Forgings

ASTM A290--95(1999), Specification for Carbon

and Alloy Steel Forgings for Rings for Reduction

Gears ASTM A291--95(1999), Specification for Steel

Forgings, Carbon and Alloy, for Pinions, Gears and

Shafts for Reduction Gears

ASTM A304--96, Specification for Carbon and Alloy

Steel Bars Subject to End--Quench Hardenability

Requirements

ASTM A322--91(1996), Specification for Steel Bars,

Alloy, Standard Grades

ASTM A370--97a, Test Methods and Definitions for

Mechanical Testing of Steel Products

ASTM A388--95, Practice for Ultrasonic Examination of Heavy Steel Forgings

ASTM A519--96, Specification for Seamless

Carbon and Alloy Steel Mechanical Tubing

ASTM A534--94, Specification for Carburizing

Steels for Anti--Friction Bearings

ASTM A609--91(1997), Practice for Castings,

Carbon, Low--Alloy, and Martensitic Stainless

Steel, Ultrasonic Examination Thereof

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2 © AGMA 2005 ---- All rights reserved

ASTM A751--96, Test Methods, Practices, and

Terminology for Chemical Analysis of Steel

Products

ASTM A837--91(1996)1, Specification for Steel

Forgings, Alloy, for Carburizing Applications

ASTM A866--94, Specification for Medium Carbon

Anti--Friction Bearing Steel

ASTM A919--84 (1993)1, Terminology Relating to Heat Treatment of Metals

ASTM A941--99a, Terminology Relating to Steel,

Stainless Steel, Related Alloys, and Ferroalloys

ASTM A956--97, Test Method for Equotip Hardness

Testing of Steel Products

ASTM E3--95, Practice for Preparation of

Metallographic Specimens

ASTM E8--99, Test Methods for Tension Testing of

Metallic Materials

ASTM E10--98, Test Method for Brinell Hardness of Metallic Materials

ASTM E18--98, Test Methods for Rockwell

Hardness and Rockwell Superficial Hardness of

Metallic Materials

ASTM E23--98, Test Methods for Notched Bar

Impact Testing of Metallic Materials

ASTM E45--972, Test Methods for Determining the

Inclusion Content of Steel

ASTM E92--82(1997)2, Test Method for Vickers

Hardness of Metallic Materials ASTM E110--82(1997)2, Test Method for

Indentation Hardness of Metallic Materials by

Portable Hardness Testers

ASTM E112--96, Test Methods for Determining

Average Grain Size

ASTM E125--63(1997), Reference Photographs for

Magnetic Particle Indications on Ferrous Castings

ASTM E140--971, HardnessConversion Tables for

Metals (Relationship Among Brinell Hardness,

Vickers Hardness, Rockwell Hardness, Rockwell

Superficial Hardness, Knoop Hardness, and

Scleroscope Hardness)

ASTM E350--95(1997)1, Test Methods for

Chemical Analysis of Carbon Steel, Low--Alloy

Steel, Silicon Electrical Steel, Ingot Iron, and

Wrought Iron

ASTM E384--89(1997)2, Test Method for

Microhardness of Materials

ASTM E407--99, Practice for Microetching Metals

and Alloys

ASTM E415--99, Test Method for Optical Emission

Vacuum Spectrometric Analysis of Carbon and

Low--Alloy Steel

ASTM E428--92, Practice for Fabrication and

Control of Steel Reference Blocks Used in

Ultrasonic Inspection ASTM E709--95, Guide for Magnetic Particle

Examination

ASTM E1077--91, Test Methods for Estimating the

Depth of Decarburization of Steel Specimens

ASTM E1444--94a, Practice for Magnetic Particle

Examination

ISO 642:1979, Steel -- Hardenability test by end

quenching (Jominy test)

ISO 643:1983, Steels -- Micrographic determination

of the ferritic or austenitic grain size ISO 683--1:1987, Heat--treatablesteels, alloy steels

and free--cutting steels -- Part 1: Direct --hardening

unalloyed and low--alloyed wrought steel in form of

different black products

ISO 683--11:1987, Heat--treatable steels, alloy

steels and free--cutting steels -- Part 11: Wrought

case--hardening steels

ISO 4967:1979, Steel -- Determination of content of

non--metallic inclusions -- micrographic method

using standard diagrams

ISO 6336--5:1996, Calculation of load capacity of

spurand helical gears -- Part5: Strengthand quality

of materials

ISO 14104:1995, Surface temper etch inspection

after grinding

SAE/AMS 2300G, Premium Aircraft--Quality Steel

Cleanliness, Magnetic Particle Inspection

Procedure

SAE/AMS 2301H, Cleanliness, Aircraft Quality

Steel Magnetic Particle Inspection Procedure

SAE/AMS 2304, Special Aircraft--Quality Steel Cleanliness, Magnetic Particle Inspection

Procedure

SAE/AMS--S--13165, Shot Peening of Metal Parts

SAE J419 Dec 83, Methods of Measuring

Decarburization

SAE J422 Dec 83, Microscopic Determination of

Inclusions in Steels

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SAE J423 Dec 83, Methods of Measuring Case

Depth

SAE J864 May 93, Surface Hardness Testing with

Files

3 Definitions

The terms used in this document, wherever applica-

ble, conform to AGMA 904--B89, ANSI/AGMA

1012--F90, and ASTM A919, but they have been

modified to cover only those concepts applicable to

this document. For definitions of technical terms not

included in this clause, see ANSI/AGMA 1012--F90,

ANSI/AGMA 2004--B89, ASTM A919, and ASTM

A941. Key terms used in this document are defined

as follows:

NOTE: These definitions may differ from those in other

AGMA publications. The user should not assume thatfamiliar terms can be used without a careful study of

their definitions.

alloy steel: A steel containingspecified quantities of

alloying elements (other than carbon and the

commonly accepted amounts of manganese, cop-

per, silicon, sulfur, and phosphorus) added to

increase hardenability and to affect changes in

mechanical properties.

annealing: The heating to and holding at a suitable

temperature above the upper transformation tem-

perature and then cooling, typically in the furnace ata suitable rate, for reducing hardness, improving

machinability, producing a desired microstructure,or

obtaining desired mechanical properties.

austenite: A solid solution of one or more elements

in face--centered cubic iron. In carbon and low alloy

steels this phase is stable only at elevated

temperatures and is non--magnetic.

austenitizing: The forming of austenite by heating

a ferrous material into the transformation range

(partial austenitizing) or above the transformation

range (complete austenitizing).

bainite: An aggregate of ferrite and cementite

resulting from the transformation of austenite at

temperatures below the pearlite range but above the

martensite start temperature. Its appearance is

feathery if formed in the upper part of the bainite

transformation range and acicular, resembling

tempered martensite, if formed in the lower part.

banding: A segregated structure consisting of

alternating, nearly parallel bands of different chemi-

cal composition, typically aligned in the direction of

primary hot working. Segregation is frequently

expressed as a departure from the average

chemical composition. Elements which tend to

segregate are sulfur, phosphorus, carbon, silicon,

and manganese.

base hardness: The surface hardness in the tooth

area that was developed by through hardening and

not changed by subsequent heat treatments. If the

material selected has adequate hardenability for the

required hardness and section size combination,

this surface hardness represents the expected

hardness at the intersection of the root circleand the

centerline of the tooth at mid--face width. Base

hardness is applicable to through hardened, induc-

tion hardened, flame hardened, and nitrided

gearing, but not to carburize and hardened gearing.

bending strength: The bending strength of gear

teeth related to their resistance to gear tooth bending

failure. Bending failure is a fatigue phenomenon

usually resulting in cracking at the tooth root fillet.

Typical cracks and fractures are illustrated in ANSI/

AGMA 1010--E95. See standards such as ANSI/

AGMA 2001--C95, ANSI/AGMA 2003--B97,

ANSI/AGMA 6002--B93, or ANSI/AGMA 6032--A94.

capable of: The producer documents that the

material was produced with the processing steps

and controls that the producer has established to

assure compliance with the specification, but the

testing to confirm compliance is not required.

carbide: A microstructural phase which is a

compound of metal (M) and carbon (C) having the

chemical formula of MxCy. See figures 1 through 4

for photomicrographs of various classifications of

carbide structures (white constituent) in tempered

martensite.

carbon potential: A measure of the ability of a

furnace environment containing active carbon to

alter or maintain, under prescribed conditions, thecarbon content of the steel.

carbon restoration: Carburizing to replace the

carbon lost in the surface layer due to previous

thermal processing.

carbon steel: A steel having no specified minimum

quantity of alloying elements except manganese

and silicon.

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5% nital etch400 X mag.

Figure 1 -- Continuous carbide network


Figure 2 -- Semi--continuous carbide network


Figure 3 -- Discontinuous carbides


Figure 4 -- Dispersed carbides

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5


carburizing: A heat treatment process in which an

austenitized steel is brought into contact with a

carbonaceous atmosphere of sufficient carbon po-

tential to cause adsorption of carbon at the surface

and by diffusion to create a concentration gradient.

Carburizing is generally followed by quenching and

reheating (tempering) of an item to produce a

hardened and tempered case.

case: The outer portion that has been made harder

than the inner portion (see core hardness) as a result

of altered composition, microstructure, or both, by

treatments such as carburize and hardening,

induction hardening, flame hardening, and nitriding.

case depth: See the specific type of case depth

such as effective or total case depth.

case hardening: The generic terminology covering

carburize and nitride hardening applicable to steel

that change the chemical composition and micro-structure of the surface layer by adsorption of

carbon, nitrogen, or a mixture of the two and by

diffusion, create a chemical composition gradient.

Adsorption of carbon processes involve a subse-

quent quenching to harden, while adsorption of

nitrogen does not require quenching to harden.

case hardness: For carburize and hardened

gearingand induction or flame hardened gearing the

hardness is measured at 0.002--0.004 inches (0.05 --

0.10 mm) below the surface using a microhardnesstest technique.

For nitriding specifications surface hardness is

typically used rather than case hardness.

Case hardness is not to be confused with surface

hardness which is taken directly on thesurface using

a conventional or portable hardness tester.

cementite: A hard compound of iron and carbon,

known chemically as iron carbide, having the

chemical formula Fe3C.

cold treatment: The preferred terminology for

cooling carburize and hardened parts to tempera-

tures typically below minus 80°F (minus 60°C) to

reduce retained austenite. Cold treatment is also

known as sub--zero treatment or deep freezing. If

cooled to below minus 300°F (minus 185°C), the

correct terminology is deep cryogenic treatment.

controlling section: Thesectionsizewhich hasthe

greatest effect in determining the rate of cooling

during quenching at a location where the specified

hardness is required. Figures 5 through 8 illustrate

the controlling section size for various gearing

configurations whose teeth are machined after heat

treatment and whose hardness must be maintained

at the roots of the teeth. The maximum permitted

section size for an alloy steel increases with the

hardenability of the alloy steel.

Teeth

8 in(200mm)

(150mm)6 in Controlling section:

8 in (200 mm) diameter

6 in(150mm)

Figure 5 -- Solid on shaft pinion blank

8 in(200 mm)

Teeth

Controlling section: 2 in(50 mm) wall thickness

4 in(100 mm)

12 in

(300 mm)

NOTE: If the bore diameter is less than 20 percent of

thelength of the bore, then the controlling section is de-

termined by figures 5 or 7.

Figure 6 -- Bore style gearing blank

Teeth

12 in

1.5 in(300 mm)

(40 mm)

Controlling section: 2 in(50 mm) thickness

2 in(50 mm)

Figure 7 -- Disc style gearing blank

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Controlling section: 2 in(50 mm) rim thickness

8”(200 mm)

32 in(800 mm)

36 in(900 mm)

Teeth

Figure 8 -- Web style gear blank

Note that a flat plate with thickness equal to the

diameter of a round bar will cool slower than the bar.

The thickness of a plate equivalent in cooling rate to

that of a round bar (equivalent controlling section

size) is 0.7 times the bar diameter.

The controlling section size for the selection of an

appropriate type of steel and specified hardness

combination must consider part configuration at the

time of heat treatment. Special stock additional

allowances, such as those used to minimize distor-

tion during heat treatment, must be considered.

converted hardness: The hardness number re-

ported on a scale different from the scale used for

hardness testing. For example an actual microhard-

ness test reading of 542 HK500 has a converted

hardnessof 50 HRC and would be properly reported

as 50 HRC (542 HK500) with the hardness numberand scale in parentheses representing the actual

testing result and method.

core hardness: The hardness at the intersection of

the root circle and the centerline of the tooth at

mid--face width that was developed during the

hardening of carburized gearing. An alternative

location is given by ISO 6336--5, table 4, item 8.

The material must have adequate hardenability for

the required hardness and section size combination

for the required core hardness to be achieved. Thequench severity must also be adequate in order to

achieve the required core hardness.

The term core hardness is applicable to carburize

and hardened gearing. Induction, flame, and nitride

hardened gearing may use the term base hardness.

The core hardness of non--tooth portions (such as

journal areas of carburize and hardened gearing), is

the hardness at a specified location such as surface,

quarter radius, mid--radius, or centerline.

decarburization: The loss of carbon from the

near--surface of a ferrous material.

deoxidizing: The removal of oxygen from molten

steel by addition of suitable elements, such as silicon

and aluminum which react with oxygen, primarily

forming discard slag.

direct quenching: The quenching of carburized

gearing directly after the carburizing operation,

generally from a reduced temperature within the

austenitic range.

effective case depth: The distance from the

finished tooth surface to a specific sub--surface

hardness value. Stock removal done after heat

treating will reduce the as heattreated effective case

depth and potentially the surface hardness.

Carburize and hardened The effective case depth is measured normal to the

finished gear surface to a location where the

hardness number is 50 HRC (542 HK500 or 515

HV500 min) by conversion from a microhardness test

result. Note that ISO 6336--5 uses 550 HV500 min,

which converts to 52.4 HRC or 583 HK500, as its

criterion for determining the effective case depth. It

is recognized that the effective case depth of

carburize and hardened gear teeth varies with

location on the gear tooth.

Induction and flame hardened For Grades 1 and 2 gearing, the effective case depth

is measured from the finished surface to a location

where the hardness number is equivalentto 10 HRC

numbers below the specified minimum surface

hardness. Grade 3 induction hardened gearing uses

the carburize and hardened definition for its effective

case depth definition. Note that ISO 6336--5 uses

the distance from the surface to the location where

the hardness is equal to 80% of the specified

minimum surface hardness as its criterion for

determining the effective case depth.

Nitrided

The effective case depth is measured from the

finished surface to a location where the hardness

number is equivalent to 40.8 HRC(421 HK500 or 400

HV500 min) by conversion from a microhardness test

result. If the core hardness is more than 38.9 HRC

(391 HK500 or380 HV500min), core hardness plus 54

HK500 or50HV500min (4.6HRC) may beused asthe

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7


definition of nitrided effective case depth. Note that

this is the same definition used in ISO 6336--5.

ferrite: A solid solution of one or more elements in

body--centered cubic iron. In carbon and alloy steels

this phase is stable at room temperature.

flame hardening: A case hardening process in

which only the surface layer of the work piece is

heated by a flame to above the upper transformation

temperature and immediately quenched.

free ferrite: The ferrite that is formed directly during

cooling without simultaneous formation of carbide.

grain size: The dimensions of the grains, or

crystals, in a polycrystalline metal exclusive of

twinned regions and sub--grains when present. The

ASTM grain size is a designation bearing a relation-

ship to average intercept distance at 100 diameters

magnification. Commercial grain size is categorized

as either coarse (grain size 1--4) or fine (grain size 5or finer).

hardenability: The property of a ferrous alloy that

determines the depth and distribution of hardness

induced by quenching.

hardened depth: For induction or flame hardened

gearing, alternative terminology for effective case

depth.

hardness: See specific kind of hardness such as

base, case, core or surface.

hardness conversion chart: A published docu-

ment for use in converting from one hardness testing

scale to another.

Hardness conversion charts should be used with

great caution since discrepancies of 0.3 HRC

numbers at30 HRC to3.9 HRC numbers at60 HRC,havebeen noted between various published conver-

sion charts. Therefore, it is suggested that the

conversion chart used for testing and reporting be

specified. Some of the more popular hardness

conversion charts are found in ASTM A370, ASTM

E140, ISO 6336--5, and certain individual corporate

documents and standards. For this document,

ASTM A370 is used and should be used whenever

no other document is specified.

induction hardening: A surface hardening process

in which only the surface layer of the work piece isheated by electrically induced currents to above the

upper transformation temperature and immediately

quenched.

intergranular oxidation (IGO): The preferential

oxidization of certain alloying elements along grain

boundaries during gas carburizing. See figure9 fora

photomicrograph of intergranular oxides (black

constituent).

Unetched400 X mag.

Figure 9 -- Intergranular oxidation in carburized gearing

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linear indication: An indication with length at least

three times its width.

marquench: Quenching into a liquid media whose

temperature is above the martensite start trans-

formation temperature, typically 300 -- 500°F (150 --

260°C), held at this temperature until temperature is

uniform throughout, and then cooled to form

martensite. Marquenching is used to achievereduced distortion when compared to conventional

quenching.

martensite: A generic term for microstructures

formed by the diffusionless phase transformation of

austenite. Martensite is characterized by an acicular

or needle--like pattern in the microstructure and is

the hardest of the austenitic transformation products

in steel.

microsegregation: The non--uniformdistribution of

alloying elements, impurities, or phases observed

primarily in the microstructure of the material.

nitriding: The introduction of nascent nitrogen into

a suitable solid ferrous alloy by holding at a suitable

temperature in contact with a nitrogenous material.

Adsorption of nascent nitrogen produces case

hardening without quenching.

non--martensitic structures: Inclusive terminolo-

gy for ferrite, carbide, retained austenite, pearlite,

and bainite due to incomplete transformation to

martensite or incomplete austenization. Retained

austenite is not included in the quantitative

metallographic measurement of non--martensitic

structures.

non--martensitic transformation products: Inclu-sive terminology for ferrite, cementite, pearlite, and

upper bainite in the surface microstructure of

carburize hardened gearing due to incomplete

transformation to martensite. See figure 10 for a

photograph of non--martensitic transformation prod-

ucts in martensite.

normalizing: The heating of a ferrous alloy to a

suitable temperature above the transformation

range and then cooling, typically in air, to a

temperature substantially below the transformation

range.

pearlite: A microstructural constituent consisting of

lamellar ferrite and cementite resulting from the

transformation of austenite at temperatures above

the bainite range.


Figure 10 -- Non --martensitic transformation products in carburized gearing

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9


pitting resistance: Endurance limit adequate to

resist contact fatigue. Initial pitting and progressive

pitting are illustrated and discussed in ANSI/AGMA

1010--E95. See standards such as ANSI/AGMA

2001--C95, ANSI/AGMA 2003--B97, ANSI/AGMA

6002--B93, or ANSI/AGMA 6032--A94.

process control test coupon: For carburize and

hardened gearing or nitrided gearing, a test couponused primarily to monitor the consistency of the heat

treatment process in terms of carbon or nitrogen

penetration and case microstructure. Sometimes

called a standardized test coupon. For procedures

associated with process control test coupons, see

4.2.1.

Due to differences in quench cooling rates and

hardenability, the microstructure and hardness of

process control test coupons used for carburize and

hardened gearingmay not be the same as that ofthe

finished gear tooth.

reduction ratio: In forging and rolling, the ratio of

the cross sectional area of the rough cast ingot or

continuously cast billet to the final cross--sectional

area. The reduction ratio is calculated by the

following equation:

RR = A

B

C

D

E

G

F

H (1)

where

RR is reduction ratio;

A is the cross sectional area of the cast ingot

or continuous cast billet, in2 (mm2).

For bar stock and forged shafting including step

shafts for solid on shaft pinion blanks as in figure 5:

B is the cross sectional area at the finished

largest forging diameter in the area where

the teeth will be, in2 (mm2); and,

C, D, E, F, G and H = 1.

For upset forged gearing blanks as in figures 7 and 8:

B is the cross sectional area of the billet prior

to upsetting, in2 (mm2);

C is the height of the cutoffingot prior to upset-

ting, inch (mm);

D is the height of the finish forged upset blank

before piercing, inch (mm); and

E, F, G and H = 1.

For forged or rolled rings:

B is the cross sectional area of the billet prior

to upsetting, in2 (mm2);

C is the height of the cutoffingot prior to upset-

ting, inch (mm);

D is the height of the upset blank after upset-

ting before piercing, inch (mm);

E is theheightof theupsetblank after piercing,inch (mm);

F is the wall thickness of the upset blank after

piercing, before any bore expansion

associated with piercing, inch (mm);

G isthe heightof the finish forged orrolledring,

inch (mm);

H is the wall thickness of the finish forged or

rolled ring, inch (mm).

representative test coupon: A test coupon de-

signed to represent the quenching rate of the

finished gearing tooth. If the coupon is to be usedonly to determine the case properties, it can be

smaller than one used to determine the core

properties of the gear tooth. A representative test

coupon sized for determining the core hardness and

microstructure can also be used for determining the

case properties or as a process control test coupon.

A representative test coupon sized for determining

the case properties can also be used as a process

control test coupon but not for determining core

properties unless substantiated by documented test

data. For procedures associated with representative

test coupons, see 4.2.2.

retained austenite: The metastable austenite

retained within a quenched microstructure. The

amount of retained austenite is a function of carbon

content, alloy content (especially nickel and

manganese), quench temperature and subsequent

thermal or mechanical treatments. See figures 11,

12 and 13 for examples of visual estimates of

retained austenite (white constituent) in tempered

martensite. More precise measurements of retained

austenite can be obtained by X--ray diffraction

techniques.shot peening: A cold working process performed

by bombarding the surface of a part with small

spherical media. This results in a thin layer of high

magnitude residual surface compressive stress and

generally improves the bending strength in the roots

of gear teeth. Shot peening should not be confused

with grit blasting or shot blasting which are cleaning

operations.

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5% nital etch 400X mag.

Figure 11 -- Tempered martensite and 5%

retained austenite in carburized gearing







specialty nitriding steel: A steel typically alloyed

with 1% aluminum to provide higher surface hard-

ness after nitriding than normally attained with

nitrided through hardening steels.

standardized test coupon: Alternate terminologyfor a process control test coupon.

subcritical anneal: Reheating to a temperature

below the transformation range. For carburized

gearing the temperature is typically 1200--1250°F

(650--675°C) and is done after carburizing and

before hardening.

surface hardening: The generic terminology for

selective induction or flame heating of a surface

layer and then quenching that layer to produce a

hardened surface layer that may be thinner than the

heated area, but is harder than the unheated base

material. With induction or flame hardening there is

no significant alteration of the chemical composition

of the surface layer.

surface hardness: The hardness measured

directly on the functional surface, after appropriate

surface preparation. Surface hardness is not to be

confused with case hardness, which is taken on a

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11


metallographic cross section using a microhardness

tester.

tempering: The reheating of a hardened ferrous

alloy part to a temperature below the transformation

range, and then cooling it at any rate.

test bar: A sample used for tensile or impact

strength testing. Also used as alternate terminology

for a test coupon used for hardness andmicrostructure testing.

test coupon: See specific type of test coupon such

as process control or representative.

total case depth: For carburized gearing the

maximum depth of diffused carbon.

The total case depth for induction or flame hardened

gearing is usually assumed to be the same as the

hardened and effective case depths.

The total case depth for nitrided gearing is the

distance from the surface to the depth at which the

HRC hardness number is 110% of the hardness

number for the core.

total nominal alloy content: The sum of the

mid--points of the specified ranges for all alloying

elements added to increase hardenability (e.g., Mn,

Cr, Ni, Mo).

transformation temperature: The temperature at

which a phase change occurs.

traveling indication: An uninterrupted ultrasonic

testing signal on the displaywhich moves horizontal-ly on the sweep line as the transducer is moved on

the scanning surface. Travel of the signal indicates

varied depth of the discontinuity from the scanning

surface, often indicative of a crack.

4 Procedures

4.1 Recommended test methods

The test methods listed in this clause are to be used

whenno other method is clearly definedor specified.

These are the methods to be used for evaluations to

the requirements of clause 5.

Testing of the actual part is preferred and should

always be used whenever practical. However,

properly selected test coupons can also be used.

The dimensions in this document are always to be

measured normal (not oblique) to the surface.

Banding -- See microsegregation.

Carbon -- See surface carbon.

Case hardness

For carburize and hardened gearing, unless

otherwise specified, the case hardness is deter-

mined at a location 1/2 of tooth height (or from a

representative test coupon).

For induction or flame hardened gearing, unless

otherwise specified, the case hardness is deter-

mined at a location 1/4 of tooth height above the

root.

For nitrided gearing, unless otherwise specified,

the case hardness is determined at a location 1/2

of tooth height (or from a process control or

representative test coupon).

Chemistry -- Analyzed per ASTM A751.

Core hardness -- Per a standard or superficial

hardness testing method listed under “hardness”.

Decarburization -- Per any of three methods:

Method 1 -- File hardness

The flanks of a tooth are file hardness tested per

SAEJ864 or ISO 6336--5, annex D with lack of file

hardness indicating possible decarburization or

non--martensitic structures.

Method 2 -- Reduction of hardness

Surface hardness readings are taken in the same

area using two different hardness testing loads,

such as HRC and HR15N with major loads of 150

kg and 15 kg respectively. The two sets of read-ings are compared using a standard hardness

conversion chart, such as ASTM A370, ASTM

E140or ISO 6336--5, annex C. Decarburization is

indicated by a lower converted hardness for the

lighter load compared to that from the heavier

load, presuming that proper hardness testing

techniques were used for both sets of tests.

Method 3 -- Metallographic evaluation

A metallographicspecimenis prepared perASTM

E3, etched per ASTM E407, and evaluated per

ASTM E1077 or SAE J419.

Effective case depth -- Per SAE J423 microhard-

ness test method. For carburize and hardened

gearing and nitrided gearing, unless otherwise

specified, the effective case depth is determined at a

location 1/2 of tooth height (or from a representative

test coupon).

For induction or flame hardened gearing, unless

otherwise specified, the effective case depth is

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determinedat a location 1/4of tooth heightabove the

root.

Grain size -- Per ASTM E112 or ISO 643.

Hardenability -- Per ASTM A255 or ISO 642

end--quench test or by hardenability calculation per

ASTM A255.

Hardness -- Listed below are each method and theassociated processes which are tested by that

method.

ASTM E10, Brinell hardness testing

-- Through hardened parts

-- Base hardness of flame, induction, or nitride

hardened parts

ASTM E18, Rockwell hardness testing


-- Carburize and hardened parts

-- Flame and induction hardened parts

-- Nitrided parts

ASTM E92, Vicker’s hardness testing




-- Nitrided parts

ASTM E384, Microhardness testing



-- Nitrided parts

If standard bench top hardness testing cannot be

accomplished as stated in ASTM E10 or ASTM E18,

portable testing may be accomplished by ASTM

E110 or other appropriate methods.

Measurement of surface hardness per ASTM E18 is

used as a nondestructive method to evaluate the

conformity of individual work pieces to the surface

hardness requirements. The measurement method

should be appropriate for the size and configuration

of the work pieces. The teeth area requirements for

hardness measurements include the root of the

tooth. Alternate methods of hardness measure-

ment, including file testing in accordance with SAE

J864 or ISO 6336--5, annex D, may be used.

Dueto the state of the art of alternate microhardness

testing methods, results may vary by the equivalent

of three pointsHRC from actual HRC measurements

per ASTM E18. The significance and interpretation

of those results needs to be agreed upon between

the parties.

Intergranular oxides -- In the unetched condition,

see metallography and figure 9.

Magnetic particle -- Per ASTM E1444 regardless of

form, or alternatively ASTM E125 for raw castings,ASTM A275 for raw forgings, or ASTM E709 for

finished gearing.

Mechanical testing -- Per ASTM E8 for tensile

testing and ASTM E23 for impact testing (also see

hardness).

Metallography -- Performed at a magnification of

400 -- 600 diameters. Metallographic samples shall

be prepared per ASTM E3 and etched per ASTM

E407, except for intergranular oxidation which shall

be evaluated in the unetched condition.

Microhardness -- See hardness.

Microsegregation -- Analyzed per ASTM A534.

Acceptance criteria is not specified but is to be

agreed upon.

Microstructure -- See metallography.

Nonmetallic inclusions -- Per any of the following

methods:

-- SAE/AMS 2301, for aircraft steels

-- ASTM A534, for carburizing bearing steels

-- ASTM A866, for through hardening bearing

steels

-- ASTM E45, for inclusion count

-- ISO 4967, by comparison to micrographic

diagrams, Method B, Plate II with 0.3 in2 (200

mm2) inspection area

-- SAE J422, by comparison to micrographic

diagrams

Surface carbon -- Perone of the following methods:

Method 1 -- Spectrometric

Per ASTM E415.

Method 2 -- Combustion

The combustion method utilizes chips from a ma-

chiningcut of 0.001 -- 0.004 inch (0.02 -- 0.10 mm)

in thickness on a carbon control specimen. The

chips from this cut are collected and analyzed by

combustion for carbon content per ASTM E350.

The specimen should be machined dry with high

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13


speed cutting tools on centers, and at least one

gram of clean chips free of contamination should

be used for analysis.

Both methods require that prior to carburizing the

process control specimen, sufficient stock be ma-

chined from the surface to be carburized, in order

to remove all material with non--uniform surface

chemistry.

Surface temper -- Per ANSI/AGMA 2007--B92 or

ISO 14104.

Test coupons -- Microstructure, microhardness and

core hardness characteristics may be determined

from either actual parts or test coupons. See 4.2 for

the specific type of test coupon (process control or

representative).

Ultrasonic inspection -- Ultrasonic inspection is

recommended for large parts to detect flaws before

incurring the expense of machining. When ultrason-

ic inspection is specified, the following guidelinesshall apply:

-- For wrought products the straight beam pro-

cedures described in ASTM A388 shall apply. Ei-

ther the flat bottom hole or back reflection method

may be used.

The sensitivity for the flat bottom hole method

shall utilize standard test blocks per ASTM E428

with the reflector size as specified in tables 1

through4 of this information sheet. The metal test

distance for the blocks shall be 4.000 inches

(101.6 mm). This sensitivity shall be used whenradially scanning the portion of the wrought mate-

rial that will comprise the tooth area. The tooth

area includes only those portions of the gearing

material where the teeth will be located to a depth

below the finished tooth tips of at least 1.5 times

the tooth height. The balance of the part may be

scanned using a distance amplitude correction

curve (DAC) whose construction is detailed in

ASTM A388.

-- For cast products the straight beam proce-

dures described in ASTM A609 shall apply. The

back reflection method shall be used.

4.2 Test coupons

4.2.1 Process control test coupons

Process control test coupons are used to monitor

various heat treatment process parameters, their

variation, their interactions, and to verify that these

parameters are maintained within their expected

control range. The process control test coupons

may be made of varioussteel grades, differentsizes,

and differing geometry depending on the parameter

to be monitored and the heat treat facility’s quality

control plan. Process control test coupons are not

intended to be used for final acceptance.

The properties of a process control coupon may be

correlated by experience to the properties of thefinished gearing with regard to hardness and case

depth. The process control test coupon

microstructure may be correlated to the condition of

the finished gear. The method of correlation should

be documented.

Process control test coupons may be used to

determine surface carbon concentration, carbon

penetration, carbon gradients, nitride depth, white

layer thickness, intergranular oxidation depth, and

process repeatability. Shim stock is often used to

monitor atmospheric carbon potential. Variations

from expected process control limits are used asindicators of unacceptable heat treat process varia-

tions. As long as the process control test coupons

are within expected control limits, the parts being

heat treated should have the expected metallurgical

properties.

The process control test coupon for carburize and

hardening should have minimum dimensions of 5/8

inch (16 mm) diameter by 2 inches (50 mm) long and

is suitable for gearing 4.5 normal diametral pitch (5.6

module) and finer. A 1 inch (25 mm) diameter by 2

inches (50 mm) long coupon may be used for

coarser pitch (module) carburized gearing to 1.5

normal diametral pitch (17 mm module). The size of

the coupon for coarser than 1.5 normal diametral

pitch (17 module) gearing should be agreed upon,

and should approximate the inscribed diameter at

mid height of the tooth cross section. The coupon

length should be a minimum of 2 times the diameter.

Test disks or plates may be used whose minimum

thickness is 70 percent of the appropriate test bar

diameter. The minimum inscribed diameter on a test

disc (or plate dimensions) should be three times its

thickness.

For determination of case hardness, case depth,

and case microstructure, the process control test

coupon should be examined on a section normal to

its axis and at least one diameter from the end of the

test coupon. Case hardness is to be measured by a

microhardness method at a depth 0.002 to 0.004

inch (0.05 to 0.10 mm) below the surface. Any

post--heat treat stock removal must be considered.

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4.2.2 Representative test coupon

The representative test coupon shall be from the

same grade of alloy steel with similar hardenability

as the production part, but need not necessarily be

from the same heat of steel. Representative test

coupon proportions of a minimum diameter of 6

divided by the normal diametral pitch (6 times

module)but not less than 5/8 inch diameter (16 mm),

and a minimum length 2 times its diameter, as used

in ISO 6336--5, are recommended. A representative

test coupon may contain a tooth form that will be

used to verify the heat treat process.

With customer approval, representative test coupon

proportions of a minimum diameter of 3 divided by

the normal diametral pitch (3 times module) but not

less than 5/8 inch diameter (16 mm), and a minimum

length 2 times its diameter, as used in ISO 6336--5,

are recommended.

A representative test coupon should have the same

heattreat condition prior to carburizing as the part(s)represented. This coupon should remain with the

part(s) represented throughout the entire heat treat

process, with the possible exception of heat

treatments prior to carburizing.

The representative test coupon, when positioned in

a heat treat load in the same general area but

separate from thepiece part, is intended to represent

the metallurgy of the heat treated tooth section. The

microstructure at the center of the minimum size

representative test coupon approximates the core

microstructure of the tooth section.

5 Metallurgical requirements

The metallurgical characteristics identified in the

tables of this clause are intended to be used for all

steel gearing. Metallurgical characteristics defined

in the tables of this clause are intended to assure the

quality of the finished gear teeth.

Individual AGMA rating standards may have specific

modifications to the metallurgical characteristics

grading; but the intent is to formalize the assump-

tions and definitions on which the various AGMA

standards are based. These characteristics should

be compatible, wherever possible, with ISO 6336--5.

Users of this document must be aware that the

Grade 1, Grade 2 and Grade 3 gearing produced by

different heat treatment processes have different

ratings. Refer to the applicable gear rating

standards for specific gear ratings.

Individual customers and manufacturers may have

specific modifications to the metallurgical grade

requirements or special material and processing

conditions that are not covered in these tables.

These modifications and special conditions are

permissible with mutual agreement.

The following tables establish reasonable minimum

limits for each material and metallurgical character-

istic that will allow gearing, which meet dimensional

tolerances, to meet the minimum expectations of the

gear rating design standards. As individual gearing

designs increase in size and complexity of features,

they become more difficult to manufacture, heat

treat, and inspect. This document, as a general rule,

does not differentiate based on gearing size.

However, where necessary, specific notation is

made to reflect the special processing methods,

techniques and inspections required for large gear

manufacturing.

All requirements for a metallurgical quality grade

must be met in order to use the stress value, from the

AGMA rating standard, for that grade. This can be

accomplished by specifically certifying each require-

ment where necessary, or by establishing practices

and procedures to obtain the requirements on a

production basis. It is not the intent of this document

that all requirements for metallurgical quality grade

be certified, but that practices and procedures be

established for their compliance on a production

basis. Intermediate values are not classified since

the effect of deviations from the quality standardscannot be evaluated easily. Specific sampling plans

and test methods need to be addressed by either the

manufacturer, the customer, or both.

The various characteristics are listed in the order in

which that characteristic is typically evaluated during

the manufacturing sequence. Each individual

characteristic has the same item number in tables 1,

2, 3 and 4 whenever it is used, regardless of which

table it appears. Some characteristics are only

applicable to specific heat treat methods. Therefore,

some item numbers are not used in some tables.

Characteristics that are typically evaluated at the

same time are grouped by having the same number

before the decimal point, and modified with different

numbers after the decimal point for the individual

characteristics evaluated at that time.

5.1 Through hardened gearing

The major metallurgical characteristics that affect

through hardened gearing performance are shown

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15


in table 1. The minimum acceptable requirements

for each factor for metallurgical quality Grades 1 and

2 are specified. All criteria in any given grade must

be met to qualify for the stress number associated

with that metallurgical quality grade.

Table 1 -- Metallurgical characteristics for through hardened gearing

Item Characteristic1) 2) Grade 1 Grade 2

1 Material chemistry Not specified or

verified.

Test report only. Medium carbon alloy steel.

0.025% maximum sulfur.2 Grain size Verification not

required.Predominantly 5 or finer. Test report only.

3 Hardenability Not specified. A minimum hardenability which is appropriate for part size andquench severity should be specified.

4 Non--metallic inclusions(cleanliness, steelmaking) 3)

Not specified. Wrought gearingCapable of meeting (certification not required)

SAE/AMS 2301, ASTM A866 or SAE J422 S2--O2Cast gears

Only permissible if primarily round (Type 1) sulfide inclusions.

5.1 Material form Forgings per either ASTM A290 or ASTM A291Bar stock per ASTM A29, ASTM A304 or ISO 683--1

Castings per ASTM A148Tubing per ASTM A519

5.2 Material reduction ratio(wrought only)

Notl specified. -- At least 7 to 1 for strand or continuous cast-- At least 3 to 1 for ingot cast4) 5)

6 Heat treatment Not specified. Quench and temper900°F (480°C) minimum temper.

7 Mechanical properties afterheat treatment6)

Hardness testing is required. Other mechanical testing is required only if specified.

8 Microstructure3) Not specified. Sound metallurgical practice dictates that the microstructure require-ments in the tooth area should be predominantly tempered martensitewith limited upper transformation products (ferrite, upper bainite and finepearlite). Themicrostructureshall be free of blocky ferrite (due to incom-plete austenization) with the following limits for non--martensitic uppertransformation products:

Controlling section size, Non--martensitic structures,

inch maximumat least less than---- 5 5%5 10 10%

10 15 20%15 -- -- Hardness must be obtained at

roots with 900°F minimum temper

Controlling section size, Non--martensitic structures,mm maximum

at least less than---- 125 5%

125 250 10%250 375 20%375 -- -- Hardness must be obtained at

roots with 480°C minimum temper

9 Ultrasonic inspection3) 5)

Wrought material.Either method is acceptable.

Inspection recommended to the following limits:

-- Flat bottom hole (FBH)technique

Not specified. -- No indications givinga signalresponse greater than an 8/64 inch (3.18mm) reference standard.-- No indications giving a signal response greater than 50% of the samereference standard if accompanied by a 50% loss of back reflection.-- No indications which are continuous over an area twice the diameterof the search unit.

(continued)

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Table 1 (concluded )

Item Characteristic1) 2) Grade 1 Grade 2

9 (continued)

-- Back reflection technique Not specified. -- No indications giving a signal response greater than 15% of backreflection.-- No multiple indications that lower the amplitude of the first backreflection by more than 40%.-- No traveling indications whose amplitude is greater than 10% of back

reflection and length is greater than 0.75 inch (19 mm).

Castings

-- Back reflection technique Not specified. -- ASTM A609 Level 1 from outside surface to 1.5 times tooth heightbelow finished tooth tips.-- ASTM A609 Level 2 greater than 1.5 times tooth height below finishedtooth tips.

16 Surface microstructureconsidering subsequent stockremoval

Should meet the following surface related characteristic:

16.3 Decarburization. Any of the fol-lowing methods are acceptable

-- Method 1. File testing. Not applicable. Not applicable.

-- Method 2. Reduction ofsurface hardness by two loadmethod.6)

Not specified. Maximum 2 HRC points or equivalent by conversion.

-- Method 3. Metallographicevaluation.

Not specified. No total or partial decarburization apparent on the finished gear tooth.

21 Surface cracks7) 8) Cracks, bursts, seams and laps are not permissible in functional areas of finished gearing.

22 Magnetic particle inspection offinished gearing5) 7) 8) 9)

-- Below the pitch line Not specified.

Inspection recommended to the following limits:

No indications.

-- Above the pitch line

Normaldiametral pitch Module

at less more at

least than than most---- 3 8 ----3 10 2.5 810 ---- ---- 2.5

Not specified.

Indication, maximum

inch mm1/8 3.2

3/32 2.41/16 1.6

23 Shot peening10) Shot peening per SAE/AMS--S--13165 may be used to increase surface residual compressivestress.

NOTES:1) See clause 3 for definitions and clause 4 for test methods.2) The metallurgical requirements assume homogeneous composition. In practice, microsegregation and banding occurs in steelsThis microsegregation can produce variations in microstructure and properties that need to be assessed.3) The grade requirements for non--metallic inclusion, ultrasonic and microstructure characteristics apply only to those portions of thegearing material where the teeth will be located to a depth below the finished tooth tip of at least 1.5 times the tooth height.4) A 7 to 1 minimum reduction ratio is recommended. For large gearing where this reduction ratio is not physically obtainable, lesserreduction ratios may be used down to a minimum of 3 to 1.

5) In--process ultrasonic and/or magnetic particle inspection of gearing blanks is recommended for large diameter parts to detect flawsbefore incurring the expense of further machining.6) See ASTM A370, ASTM E140 or ISO 6336--5, annex C for hardness conversion tables.7) Removal of defects that exceed the stated limits is acceptable, provided the integrity of the gear is not compromised.8) Cracks in non--functional areas require engineering disposition.9) Limits: maximum of one indication per inch (25 mm) of face width with a maximum of five such indications on any one tooth flank.Indications less than 1/32 inch (0.8 mm) are not considered.10) It is recommended that ANSI/AGMA 2004--B89 be reviewed to determine if the benefits of surface residual compressive stressachieved by shot peening may be beneficial to the particular application. Shot peening of the flanks of gear teeth should be reviewed toensure that no detrimental effects are caused to the gear set.

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17


5.2 Carburize and hardened gearing


carburize and hardened gearing performance are

shown in table 2. Neither carbonitrided nor nitrocar-

burized gearing is covered by this document. The

minimum acceptable requirements for each factor

for metallurgical quality Grades 1, 2 and 3 are

specified. All criteria in any given grade must be met

to qualify for the stress number associated with that

metallurgical quality grade.

Table 2 -- Metallurgical characteristics for carburize and hardened gearing

Item Characteristic1) 2) Grade 1 Grade 2 Grade 3

1 Material chemistry Specified, but notverified.

Test report only. Alloy steel.0.025% maximum sulfur.3)

Test report only. Alloy steel.0.015% maximum sulfur.3)

2 Grain size Predominantly 5 or finer. Test report only.

3 Hardenability Verificationnot required.

A minimum hardenability which is appropriate for part size and quenchseverity should be specified.

4 Non--metallic inclusions Not specif ied. Wrought gearing Wrought gearing

(cleanliness, steelmaking)3) 4) Alternative A:-- Capable of meeting bearing qual-ity per ASTM A534

Alternative B, all of the following:-- The steel must be certified:

-- electric furnace practice

-- ladle refined-- deoxidized-- vacuum degassed-- bottom poured ingot or strand

casted-- protected from reoxidation

during teeming or casting

-- capable of oxygen content of20 ppm maximum

-- capable of cleanliness con-

firmation by either ASTM E45 orISO 4967MethodB Plate IIwith0.3inch2 (200 mm2) inspection area.

Acceptable if does not exceed:

Alternative A:-- Certified ASTM A534

Alternative B, all of the following:-- The steel must be certified:

-- electric furnace practice-- ladle refined-- deoxidized

-- vacuum degassed-- bottom poured ingot-- protected from reoxidation

during teeming or casting

-- oxygen content of 20 ppmmaximum

-- certified cleanliness by eitherASTM E45 or ISO 4967 Method B

Plate II with 0.3 inch2 (200 mm2)in-spection area. Acceptable if doesnot exceed:

Type Fine ThickA (sulfide) 3.0 3.0B (alumina) 2.5 1.5C (silicate) 2.5 1.5

D (globular oxide) 2.0 1.5

Type Fine ThickA (sulfide) 2.5 1.5B (alumina) 2.0 1.0C (silicate) 0.5 0.5

D (globular oxide) 1.0 1.0

Alternative C:Capable of meeting SAE/AMS2301 or SAE J422, S2--O2

Alternative D:5)

Magnetic particle inspection of fin-ished gearing to the requirementsof Item 22, Grade 3.

Alternative C:Certified SAE/AMS 2300 orSAE/AMS 2304.

Cast gears

Only permissible if primarily round(Type 1) sulfide inclusions.

Cast gears

Not permitted.

5.1 Material form Forgings per ASTM A837 and either ASTM A290 or ASTM A291

Bar stock per ASTM A29, ASTM A304 or ISO 683--11Tubing per ASTM A519

Castings per ASTM A148. Castings not permitted.


Not specified. -- At least 7 to 1 for strand or continuous cast-- At least 3 to 1 for ingot cast 6) 7)

(continued)

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Table 2 (continued )




Inspection recommended to thefollowing limits:

Inspection required to the followinlimits:


Not specified. -- No indications giving a signal re-sponse greater than an 8/64 inch(3.18 mm) reference standard.

-- No indications giving a signalresponse greater than 50% of thereference standard if accompaniedby a 50% loss of back reflection.-- No indications which arecontinuous over an area twice thediameter of the search unit.

-- No indications giving a signal response greater than a 5/64 inch(1.98 mm) reference standard.

-- No indications giving a signal response greater than 50%of thereference standard if accompanied ba 50% loss of back reflection.-- No indications which are continuousover an area twice thediameteof the search unit.

-- Back reflection technique Not specified. -- No indications giving a signal re-sponse greater than 15% of backreflection.-- No multiple indications that lowerthe amplitude of the first back re-flection by more than 40%.-- No traveling indications whoseamplitude is greater than 10% of

back reflection and length is great-er than 0.75 inch (19 mm).

-- No indications giving a signal response greater than 10% of bacreflection.-- No multiple indications that lowethe amplitude of the first back reflection by more than 20%.-- No traveling indications whosamplitude is greater than 10% o

back reflection and length is greater than 0.50 inch (13 mm).

Castings

-- Back reflection technique Not specified. -- ASTM A609 Level 1 from outsidesurface to 1.5 times tooth heightbelow finished tooth tips.-- ASTM A609 Level 2 greater than1.5 times tooth height below fin-ished tooth tips.

11 Tempering after case

hardening

Recommended. Required.

12 Surface hardness in tooth area.Alternative method of inspec-

tion is case hardness.8) 9) 10)

Should meet the following characteristics:

-- Tooth flank 55--64 HRC orequivalent

58--64 HRC or equivalent 58--64 HRC or equivalent

-- Tooth root

-- Normal diametral pitch 3(module 8) and coarser

53 HRC minimum orequivalent

56 HRC minimum or equivalent 58 HRC minimum or equivalent

-- Normal diametral pitchfiner than 3 (module 8)

55 HRC minimum orequivalent

58 HRC minimum or equivalent 58 HRC minimum or equivalent

13 Case depth consideringsubsequent stock removal


13.1 Effective case depth in finishedcondition 10) 11)

Minimum and maximum effective case depth requirements for the tooth should be specified inaccordance with the appropriate rating standard.

13.2 Effective case depth minimumat root radius, as determined bybending strength rating.10) 11)

12)

Not specified. 50% ofminimum specified effectivecase at 1/2 tooth heightrecommended.

66% of minimum specified effectivecase at 1/2 tooth heighrecommended.

14 Core hardness after case hard-ening 12) 13)

-- For pitting resistance rating

-- For bending strength rating

Not specified.

21 HRC minimum

21 HRC minimum

25 HRC minimum

21 HRC minimum

30 HRC minimum14)

(continued)

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19


Table 2 (continued)


15 Surface carbon (typical)15)

For up to 2.5% total nominalalloy content2.5% to 3.5% total nominalalloy contentOver 3.5% total nominal alloycontent

0.60 -- 1.10%C

0.60 -- 1.10%C

0.60 -- 1.10%C

0.60 -- 1.10%C

0.60 -- 1.00%C

0.65 -- 0.95%C

0.60 -- 1.00%C

0.60 -- 1.00%C

0.65 -- 0.95%C

16 Surface microstructure consid-ering subsequent stock remov-al 12) 16)

The first 0.002 -- 0.003 inch (0.05 -- 0.08 mm) of case microstructure in the tooth area shouldmeet the surface hardness requirement of the specific grade and also meet the following sur-face related characteristics and the requirements of Item 17:

16.1 Intergranular oxidation (IGO)(see figure 9)

Minimum specified effectivecase depth

inch (mm)at less at lessleast than least than-- -- 0.030 -- -- (0.75)0.030 0.060 (0.75) (1.50)0.060 0.090 (1.50) (2.25)0.090 0.120 (2.25) (3.00)0.120 ---- (3.00) ----

Not specified.

Maximum allowable depthinch (mm)

0.0007 (17)0.0010 (25)0.0015 (38)0.0020 (50)0.0025 (60)

Maximum allowable depth

inch (mm)0.0005 (12)0.0008 (20)0.0008 (20)0.0010 (25)0.0012 (30)

16.2 Non--martensitic transforma-tion products (see figure 10)17)

Not specified.


inch (mm)at less at lessleast than least than-- -- 0.030 -- -- (0.75)0.030 0.060 (0.75) (1.50)0.060 0.090 (1.50) (2.25)0.090 0.120 (2.25) (3.00)0.120 ---- (3.00) ----


inch (mm)0.0007 (17)0.0010 (25)0.0015 (38)0.0020 (50)0.0025 (60)


inch (mm)0.0005 (12)0.0008 (20)0.0008 (20)0.0010 (25)0.0012 (30)

16.3 Decarburization. Any of thefollowing methods areacceptable.

-- Method 1. File testing. Not specified. Gear tooth surfaces must be file hard to the minimum surface hardness.

-- Method 2 . Reduction of sur-face hardness by two loadmethod or reduction of casehardness.10)

Not specified. Maximum 3 HRC points or equiva-lent below maximum measuredhardness by conversion, butmeasuring at least 58 HRC orequivalent by conversion in thefinished state.

Maximum 1.5 HRC points or equiv-alent below maximum measuredhardness by conversion, butmeasuring at least 58 HRC orequivalent by conversion in thefinished state.



inch (mm)

at less at lessleast than least than-- -- 0.030 -- -- (0.75)0.030 0.060 (0.75) (1.50)0.060 0.090 (1.50) (2.25)0.090 0.120 (2.25) (3.00)0.120 ---- (3.00) ----

Not specified. No partial decarburization appar-ent on active tooth profile. No fer-rite (total decarburization) is per-missible in the case microstructureof the gear tooth.

Maximum allowable depth in rootinch (mm)

0.0007 (17)0.0010 (25)0.0015 (38)0.0020 (50)0.0025 (60)

No partial decarburization appar-enton thegear tooth. No ferrite (to-tal decarburization) is permissiblein the case microstructure of thegear tooth.

17 Case microstructure consider-ing subsequent stock removal,disregarding corner effects 12)

Themicrostructure of thefirst20% of theminimum specifiedeffective case depth shouldbe pre-dominantlytempered martensite. Additionalrequirements for the case microstructure are givenin Item 16 and the following case related characteristics:

(continued)

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17.1 Carbide precipitation in thecase.

Continuous carbidenetwork per figure 1is not acceptable,but semi--continu-ous carbide networkper figure 2 is

acceptable.

Semi--continuous carbide networkper figure 2 is not acceptable, butdiscontinuous carbides per figure 3are acceptable. Maximum accept-able lengthof any carbide is 0.0008inch (0.02 mm).

Discontinuous carbides per figure3 are not acceptable, butdispersedcarbides per figure 4 are acceptable.

17.2 Retained austenite in thecase.9)

Not specified. Retained austenite 30% maximum determined metallographically bcomparison with figure 13. Rejection of piece parts shall only be basedon case hardness. The minimum microhardness at 0.004 inch (0.1 mmor through the area of highest retained austenite shall be 58 HRC (690HK500).10) 16)

17.3 Microstructure of the case to adepth of 0.010 inch (0.25 mm)or the first 20% of the minimumspecified effective case depth,whichever is smaller, along theflank (for pitting resistancerating). 18)

Not specified.Untempered mar-tensite is accept-able.

Primarily tempered martensite with5% maximum non--martensiticstructures, carbide precipitationper Item 17.1, retained austeniteperItem 17.2, andother surface mi-crostructures as defined underItems 16.1 through 16.3.

Primarily tempered martensite witonly trace non--martensitic structures permissible, carbide precipitation per Item 17.1, retained austenite per Item 17.2, and other surface microstructures as defined under Items 16.1 through 16.3.

17.4 Microstructure of the case froma depth of 0.010 inch (0.25 mm)or the first 20% of the minimumspecified effective case depth,whichever is smaller, to a depthequal to 40% of the minimumspecified effective case depthalong the flank (for pittingresistance rating). 18)

Untempered mar-tensite is accept-able.

-- Normal diametral pitch 3(module 8) and coarser.

Not specified. Not specified. Not specified.

-- Normal diametral pitch finerthan 3 (module 8).

Not specified. 5% maximum non--martensiticstructures.

Only trace non--martensitistructures.

17.5 Microstructure of the case to adepth of 0.010 inch (0.25 mm)or the first 20% of the minimumspecified effective case depth,whichever is smaller,at therootfillet (for bending strengthrating). 18)

Not specified. Un-tempered marten-site is acceptable.

Primarily tempered martensite with10% maximum non--martensiticstructures, carbide precipitationper Item 17.1, retained austeniteperItem 17.2, andother surface mi-crostructures as defined underItems 16.1 through 16.3.

Primarily tempered martensite wit5% maximum non--martensitistructures, carbide precipitatioper Item 17.1, retained austenitperItem 17.2, andother surface mcrostructures as defined undeItems 16.1 through 16.3.

17.6 Microstructure of the case froma depth of 0.010 inch (0.25 mm)or the first 20% of the minimumspecified effective case depth,whichever is smaller, to a depthequal to 40% of the minimumspecified effective case depth

at the root fillet (for bendingstrength rating). 18)

Untempered mar-tensite is accept-able.

-- Normal diametral pitch 3(module 8) and coarser.

Not specified. Not specified. Not specified.

-- Normal diametral pitch finerthan 3 (module 8).

Not specified. 10% maximum non--martensiticstructures.

5% maximum non--martensitistructures.

17.7 Microcracks in case (cracksacross more than one platelet)

Not specified. 10 maximum per 0.0001 in2 (0.064mm2) field. 9) 19)

(continued)

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21




18 Core microstructure4) 12) Not specified. Sound metallurgical practice dictates that the core microstructure re-quirements are maintained in the tooth area to a depth of twice the mini-mum specified effective case depth or 0.100 inch (2.5 mm), whicheveris less, below the minimum specified effective case depth. The micro-structure in this zone should be predominantly tempered martensite.This microstructure zone should be free of blocky ferrite, pearlite, and

measurable bainite. Below this zone the core microstructure should befree of blocky ferrite and be primarily tempered martensite with someacicular ferrite and bainite permissible.

20 Surface temper etch inspectionof ground teeth

Not specified. FB2, which allows light temperingon 25% of functional area.

FB1, which allows light temperingon 10% of functional area.

21 Surface cracks20) Cracks, bursts, seams and laps are not permissible infunctional areas of finished gearing.21)

Cracks, bursts, seams andlaps arenot permissible in any area of fin-ished gearing.

22 Magnetic particle inspection offinished gearing 7) 20) 21) 22)


Inspection required to the followinglimits:

-- Below the pitch line Not specified. No indications. No indications.


Normal

diametral pitch Moduleat less more atleast than than most---- 3 8 -- --3 10 2.5 810 ---- -- -- 2.5

Not specified.

Indication, maximum

inch mm1/8 3.23/32 2.41/16 1.6

Indication, maximum

inch mm3/32 2.41/16 1.61/32 0.8

23 Shot peening 23) Shot peening per SAE/AMS--S--13165 may be used to increase surface residual compressivestress.

NOTES:1) See clause 3 for definitions and clause 4 for test methods.2) The metallurgical requirements assume homogeneous composition. In practice, microsegregation and banding occurs in steels.This microsegregation can produce variations in microstructure and properties that need to be assessed.3) Intentional additions of calcium or calcium alloys for deoxidation or inclusion and shape control are not permitted unless specificallyapproved by the purchaser. The use of lime or fluorspar, or both, in the steelmaking slag is acceptable.4) The grade requirements for non--metallic inclusion, ultrasonic, and microstructure characteristics apply only to those portions of thegear material where the teeth will be located to a depth below the finished tooth tip of at least 1.5 times the tooth height.5) Care should be exercised when using Alternative D because of the risk of rejection after the expense of further manufacturing pro-cesses.6) A 7 to 1 minimum reduction ratio is recommended. For large gearing where this reduction ratio is not physically obtainable, lesserreduction ratios may be used down to a minimum of 3 to 1.7) In--process ultrasonic and/or magnetic particle inspection of gearing blanks is recommended for large diameter parts to detect flawsbefore incurring the expense of further machining.8) Root hardness may be less than flank hardness, depending on the size of the gear and the quench process.9) If cold treatment is performed, it is recommended that it be preceded by tempering at 300°F (150°C) minimum in order to minimizeformationof microcracks. Retempering is required after cold treatment. Cold treatmentshould notbe used to transformlarge amounts ofretained austenite (e.g., 50%) to gain excessive improvements in hardness, even with prior tempering.10) See ASTM A370, ASTM E140 or ISO 6336--5, annex C for hardness conversion tables.

11) When specifying minimum case depth,note that the“optimum” values forpitting resistance andbending strength capacity arenot thesame. A maximum case depth is prescribed in order to minimize the risk of embrittlement in the tooth area, including the tips.12) See clauses 3 and 4 for a discussion of test coupons.13) Core hardness requirements for pitting resistance and bending strength are considered independently. The gear rating may be lim-ited by either pitting resistance or bending strength for the selected metallurgical quality grade and its core hardness requirement.14) Minimum hardness of 30 HRCfor Grade 3 maybe difficultto achieve on coarsepitchgearing. Dueto thetoothsectionsize of 3 normaldiametral pitch (8 module) gearing and coarser, the alternate (ISO) core hardness test location may be used provided documented test-ing or experience is available.

(continued)

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NOTES:15) Optimum pitting resistance is best achieved at surface carbon levels above the eutectoid carbon for a given alloy chemistry.16) If excessive, salvage may be possible by processes such as shot peening per Item 23 or by grinding provided the integrity of thegearing is not compromised.17) At maximum allowable depths the surface may not be file hard and may not have the expected residual stress profile.18) Bainite, observable at 200X, that extends from the core microstructure into the case area is considered a ratable characteristic.This bainite is the result of slower heat extraction rates due to part section size, mass of furnace load, marginal agitation, elevated

quenchant temperatures, and generally follows alloy segregation and material flow lines. The bainite that results in a fine pepperstructure at 400 -- 600X, but is still not resolvable at 800X, is considered nonratable (trace).19) Maximum limit of microcracks (Item 17.5) for Grade 3 gearing may be difficult to achieve if cold treatment is used to transform theretained austenite level to 30% maximum.20) Removal of defects that exceed the stated limits is acceptable, provided the integrity of the gear is not compromised.21) Cracks in nonfunctional areas require engineering disposition.22) Limits: maximum of one indication per inch (25 mm) of face width with a maximum of five such indications on any one tooth flank.Indications less than 1/32 inch (0.8 mm) are not considered.23) It is recommended that ANSI/AGMA 2004--B89 be reviewed to determine if the benefits of surface residual compressive stressachieved by shot peening maybe beneficial to theparticular application. Shot peening of theflanks of gear teeth shouldbe reviewed toensure that no detrimental effects are caused to the gear set.

5.3 Induction or flame hardened gearing


induction or flame hardened gearing performance

are shown in table 3. The minimum acceptable

requirements for each factor for metallurgical quality

Grades 1,2 and3 are specified. Grade3 is restrictedto contour spin induction Type A (Contour) harden-

ing only. All criteria in any given grade mustbe met to

qualify for the stress number associated with that


Table 3 -- Metallurgical characteristics for induction or flame hardened gearing

Item Characteristic1) 2) Grade 1 Grade 2 Grade 3Spin induction Type A

(Contour) only

1 Material chemistry Not specified orverified. Test report only.0.025% maximum sulfur forwrought.

Test report only.0.015% maximum sulfur forwrought.

2 Grain size Predominantly 5or finer. Verifica-tion not required.

Predominantly 5 or finer. Test report only.

3 Hardenability Not specif ied. A minimum hardenability which is appropriate for part size and quenchseverity should be specified.


Not specified. Wrought gearing

Capable of meeting (certificationnot required) SAE/AMS 2301,ASTM A866 or SAE J422 S2--O2

Cast gears

Only permissible if primarily

round (Type 1) sulfide inclusions.

Wrought gearing


Cast gears

Not permitted

5.1 Material form Forgings per either ASTM A290 or ASTM A291Bar stock per ASTM A29, ASTM A304 or ISO 683--1

Tubing per ASTM A519

Castings per ASTM A148. Castings not permitted.


Not specified. -- At least 7 to 1 for strand or continuous cast

-- At least 3 to 1 for ingot cast 4) 5)

6 Heat treatment prior to surfacehardening

Not specified. Quench and temper900°F (480°C) minimum temper.

(continued)

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23




(Contour) only

7 Mechanical properties prior tosurface hardening. See alsoItem 14. 6) 7)

Not specified. 28 HRC minimum. Other mechani-cal testing is required only if speci-fied.

30 HRC minimum. Other mechani-cal testing is required only if speci-fied.

8 Microstructure prior to surfacehardening3)

Not specified. Sound metallurgical practice dictates that the core microstructure re-quirements aremaintained inthe tooth area to a depthtwicethe minimum

specified effective case depth or 0.100 inch (2.5 mm), whichever is less,below the minimum specified effective case depth. The microstructurein this zone should be predominantly tempered martensite that is free ofblocky ferrite, pearlite, and measurable bainite observable at 400--600X.

Below this zone the core microstructure should be primarily temperedmartensite and free of blocky ferrite with the following limits:

Controlling section size, Non--martensitic structures,inch maximum

at least less than---- 5 5%5 10 10%












Not specified. -- No indications giving a signal re-sponse greater than an 8/64 inch

(3.18 mm) reference standard.

-- No indications giving a signalresponse greater than 50% of thereference standard if accompanied

by a 50% loss of back reflection.-- No indications which arecontinuous over an area twice the

diameter of the search unit.

-- No indications giving a signal re-sponse greater than a 5/64 inch

(1.98 mm) reference standard.

-- No indications giving a signalresponse greater than 50% of thereference standard if accompanied

by a 50% loss of back reflection.-- No indications which arecontinuous over an area twice the

diameter of the search unit.



-- No indications giving a signal re-sponse greater than 10% of backreflection.-- No multiple indications that lowerthe amplitude of the first back re-flection by more than 20%.-- No traveling indications whoseamplitude is greater than 10% of


Castings

-- Back reflection technique Not specified. -- ASTM A609 Level 1 from outsidesurface to 1.5 times tooth heightbelow finished tooth tips.-- ASTM A609 Level 2 greater than1.5 times tooth height below fin-ished tooth tips.

(continued)

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(Contour) only

10 Overheating, especially at thetooth tips and end faces 8)

Avoid surface temperatures that result in grain growth, incipient melting or unfavorableresidual stresses. Larger chamfers minimize this problem.

11 Tempering after surfacehardening

1 hour minimum at temperature furnace temper is required.9)

12 Surface hardness on a repre-sentative surface. Alternativemethod of inspection is casehardness. 7) 8)

50 HRC minimum or 54 HRC minimum as required byrating standard. 58--64 HRC or equivalent

13 Case depth considering subse-quent stock removal. Also seeItem 19. 7) 8) 10)


13.1 Effective case depth in finishedcondition

Minimum and maximum effective case depth should bespecified in accordance with the rating standard. Ahardening pattern per figure 14 shall be specified.

Minimum and maximum effectivecase depth should be specified inaccordance with the rating stan-dard. Figure 14 Type A contourpattern only shall be specified.

13.2 Effective case depth minimumat root radius, or on representa-tive sample with same

geometry and material as workpiece, as determined bybending strength rating.

Not specified. 50% ofminimum specified effectivecase at 1/4 tooth height above theroot recommended.

100% of minimum specified effec-tive case at 1/4 tooth height abovetheroot recommended,and 66% of

minimum specified effective caseat the root.

14 Base hardness after surfacehardening.

Also see Item 7. 6) 7) 8) 10)

Not specified. 28 HRC minimum 30 HRC minimum

17 Case microstructure consider-ing subsequent stock removal,disregarding corner

effects8) 10) 11)

The first 20% of the case microstructure should be predominantly tempered martensite. Themicrostructure should be free of undissolved pearlite observable at 100X and measurablebainite observable at 400 -- 600X.

The following case microstructure characteristics for each grade must be met:

17.3 Microstructure of case alongflank (for pitting resistancerating).

Primarily fineacicular marten-site.

Primarily fine acicular temperedmartensite. Non--martensitic struc-tures anywhere in the case should

not exceed 5%.

Primarily fine acicular temperedmartensite with no non--martensiticstructures.

17.5 Microstructure at root (forbending strength rating).

Primarily fineacicular marten-site.

Primarily fine acicular temperedmartensite. Non--martensitic struc-tures anywhere in the case shouldnot exceed 10%.

Primarily fine acicular temperedmartensite. Non--martensitic struc-tures anywhere in the case shouldnot exceed 5%.

19 Heat affected zone. Also seeItem 13. 8) 10)

Induction and flame hardening heat treatments have a characteristic heat affected zone thatis caused by the surface heating process. This zone can have lower hardness and differentmicrostructure than the base material. The case depth specification should be establishedto avoid gear failure which might initiate in this zone.

20 Surface temper etch inspectionof ground teeth

Not specified. FB2, which allows light temperingon 25% of functional area.

FB1, which allows light temperingon 10% of functional area.

21 Surface cracks 12) 13) Cracks, bursts, seams and laps are not permissible in functional areas of finished gearing.

22 Magnetic particle inspection offinished gearing5) 12) 13) 14)

Inspection to the following limits:

-- Below the pitch line Not specified. No indications. No indications.-- Above the pitch line

Normaldiametral pitch Module

at less more atleast than than most---- 3 8 -- --3 10 2.5 810 ---- -- -- 2.5

Not specified.

Indication, maximum

inch mm1/8 3.23/32 2.41/16 1.6

Indication, maximum

inch mm3/32 2.41/16 1.61/32 0.8

(continued)

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25




(Contour) only

23 Shot peening 15) Shot peening per SAE/AMS--S--13165 may be used to increase surface residualcompressive stress.

NOTES:1) See clause 3 for definitions and clause 4 for test methods.2) The metallurgical requirements assume homogeneous composition. In practice, microsegregation and banding occurs in steels.This microsegregation can produce variations in microstructure and properties that need to be assessed.3) The graderequirements for non--metallic inclusion,ultrasonic, and microstructure characteristicsapply only to thoseportions of thegear material where the teeth will be located to a depth below the finished tooth tip of at least 1.5 times the tooth height.4) A 7 to 1 minimum reduction ratio is recommended. For large gearing where this reduction ratio is not physically obtainable, lesserreduction ratios may be used down to a minimum of 3 to 1.5) In--process ultrasonic and/or magnetic particle inspection of gearing blanks is recommended for large diameter parts to detectflaws before incurring the expense of further machining.6) Mechanical properties, includingcore hardness,may notbe thesame after inductionor flame hardeningas they were beforeinduc-tion or flame hardening.7) See ASTM A370, ASTM E140 or ISO 6336--5, annex C for hardness conversion tables.8) See clauses 3 and 4 for a discussion on test coupons.9) Induction tempering is recommended for Grade 3 as a crack preventing stress relief heat treatment prior to furnace tempering.10)

The hardness pattern, depth, facilities and process method must be established, documented and verified to be repeatable. Theprocess equipment and methods must be sufficiently accurate to reproduce the specified results. Excessive case depth can generateunfavorable residual stress conditions.11) Microstructure analysis of induction hardened test specimens have shown indications of undissolved pearlite or “ghost pearlite”.This is especially true with rapid (short) heating cycles. This “ghost pearlite” should not be present.12) Removal of defects that exceed the stated limits is acceptable, provided the integrity of the gear is not compromised.13) Cracks in non--functional areas require engineering disposition.14) Limits: maximum of oneindication perinch of face width with a maximum of five such indicationson anyone tooth flank. Indicationsless than 1/32 inch (0.8 mm) are not considered.15) It is recommended that ANSI/AGMA 2004--B89 be reviewed to determine if the benefits of surface residual compressive stressachieved by shot peening may be beneficial to theparticular application.Shot peening of theflanks of gear teeth shouldbe reviewed toensure that no detrimental effects are caused to the gear set.

8/15/2019 AGMA 923-B05




Spin hardening

Flank hardening (tooth to tooth)

Flank and root hardening (tooth to tooth)

Type AGrades 1 and 2 only

Type A Type BGrades 1 and 2 only

Induction coilor flame head

Inductor or flame head Inductor or flame head

Inductor or flame head

(Non--contour)Grades 1 and 2 only

Inductor coil

Type A(Contour)

Grades 1, 2 and 3

Top lands are not fully hardened

Induction coilor flame head

Type BGrades 1 and 2 only

Type BGrades 1 and 2 only

NOTE:

-- Type A indicates that flanks and roots are hardened for contour or non--contour patterns.

-- Only spin hardening Type A (Contour) is applicable to Grade 3.

-- Type B indicates that the flanks are hardened only to the form diameter.

-- For Type B the full active profile must be hardened with the transition zone not in the root fillet area.

Figure 14 -- Variations in hardening pattern obtainable on gear teeth with flame or inductionhardening

5.4 Nitrided gearing


nitrided gearing performance are shown in table 4.

These characteristics are not necessarily applicable

to carbonitrided or nitrocarburized gearing, neither

of which are covered by this document. The

minimum acceptable requirements for each factor

for metallurgical quality Grades 1, 2 and 3 are

specified. All criteria in any givengrade must be met

to qualify for the stress number associated with that


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Table 4 -- Metallurgical characteristics for nitrided gearing


1 Material chemistry3) Not specified orverified.

Test report only. Medium carbonalloy steel. 0.025 % maximum

sulfur .

Test report only. Medium carbonalloy steel. 0.015 % maximum

sulfur .

2 Grain size Predominantly 5 or finer. Test report only.

3 Hardenability Not specified. A minimum hardenability which isappropriate for part size andquench severity should be speci-

fied.

A minimum hardenability verifiedby certification, calculation or testwhich is appropriate for part size

and quench severity should bespecified.


Not specified. Wrought gearing


Cast gears

Not permitted.

Wrought gearing

Certified to SAE/AMS 2304,ASTM A866 or SAE J422 S2--O2

Cast gears

Not permitted.

5.1 Material form Forgings per either ASTM A290 or ASTM A291

Bar stock per ASTM A29, ASTM A304 or ISO 683--1Tubing per ASTM A519Castings not permitted.


Not specified. -- At least 7 to 1 strand or continuous cast-- At least 3 to 1 ingot cast5) 6)

6 Heat treatment prior to casehardening

Quench and temper with tempering temperature 900°F (480°C) minimum and 50F° (28C°)minimum above the nitriding temperature.

7 Mechanical properties prior tocase hardening. Also see Item14.7) 8)

Hardness testing is required. Other mechanical testing required only if specified.

8 Microstructure prior to casehardening. Also see Item

16.3.

4)

Not specified. Sound metallurgical practice dictates that the core microstructure re-quirements aremaintained inthe tooth area to a depthtwicethe minimum

specified effective case depth or 0.100 inch (2.5 mm), whichever is less,below the minimum specified effective case depth. The microstructurein this zone should be predominantly tempered martensite. This micro-structure should be free of blocky ferrite, pearlite,and measurablebainiteobservable at 400--600X. Below this zone the core microstructure

shouldbe free of blocky ferrite andbe primarilytempered martensite withthe following limits:

Controlling section size, Non--martensitic structures,inch maximum

at least less than---- 5 5%5 10 10%







(continued)

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Not specified. -- No indications giving a signal re-sponse greater than an 8/64 inch(3.18 mm) reference standard.

-- No indications giving a signal re-sponse greater than a 5/64 inch(1.98 mm) reference standard.

-- No indications giving a signalresponse greater than 50% of thereference standard if accompaniedby a 50% loss of back reflection.

-- No indications giving a signalresponse greater than 50% of thereference standard if accompaniedby a 50% loss of back reflection.

-- No indications which arecontinuous over an area twice thediameter of the search unit.

-- No indications which arecontinuous over an area twice thediameter of the search unit.



-- No indications giving a signal re-sponse greater than 10% of backreflection.-- No multiple indications that lowerthe amplitude of the first back re-flection by more than 20%.-- No traveling indications whoseamplitude is greater than 10% of


12 Surface hardness on a repre-sentative surface. Alternativemethod of inspection is casehardness. 7)

-- Specialty nitriding steels9) Either 89 -- 93 HR15N, 650 -- 900 HV or 690 -- 900 HK

-- Through hardening steels Either 83 min HR15N, 450 min HV or 470 min HK

13 Case depth considering subse-quent stock removal10)

Should meet either of the following characteristics:

13.1 Effective case depth in finishedcondition

Minimum effective case depth requirements for the tooth should be specified in accordancewith the appropriate rating standard.

13.3 Total case depth in finished

condition

Minimum total case depth requirements for the tooth should be specified in accordance with

the appropriate rating standard.14 Core hardness after case hard-

ening. Also see item 7.7)28 HRC minimum 32 HRC minimum

16 Surface microstructureconsidering subsequent stockremoval 10)

The first 0.002 -- 0.003 inch (0.05 -- 0.08 mm) of case microstructure in the tooth area shouldmeet thesurface hardness requirement of the specific grade and also meet thefollowing sur-face related characteristics and the requirements of Item 17:

16.3 Decarburization. No decarburization permitted on surface to be nitrided.

-- Method 1. Not applicable.

-- Method 2. Reduction of hard-ness by two load method. 7)

Not specified. Maximum 2 HRC points or equiva-lent below maximum measuredhardness by conversion.

No reduction in hardness belowmaximum measured hardness byconversion is permissible.


Not specified. No partial decarburization appar-ent except in unground roots.

No partial decarburizationapparent.

16.4 Epsilon (Á) nitride (white layer)along flank or in root

Minimum specifiedeffective case depth

inch (mm)at less at less

least than least than-- -- 0.015 -- -- (0.37)0.015 ---- (0.37) ----

Maximumallowable depthinch (mm)0.0010 (0.025)0.0010 (0.025)


0.0008 (0.019)0.0008 (0.019)


0.0005 (0.012)0.0008 (0.019)

(continued)

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29




17 Case microstructure consider-ing subsequent stock removal,disregarding corner effects

The first 20% of the case microstructure should be predominantly tempered martensite withinterspersedÁnitride. The microstructure should be free of blocky ferrite, pearlite, and mea-surable bainite.

20 Surface temper inspection The normal inspection methods, as defined in ANSI/AGMA 2007--B92 or ISO 14104, are notapplicable to nitrided gearing. Care must be taken when grinding nitrided surfaces to ensurethat no harmful surface conditions are produced in the grinding process.

21 Surface cracks 11) 12) Cracks, bursts, seams and laps are not permitted in

functional areas of finished gearing.

Cracks, bursts, seams andlaps are

notpermitted in anyarea of finishedgearing.

22 Magnetic particle inspection offinished gearing 6) 11) 12) 13)


Inspection required to thefollowing limits:

-- Below the pitch line Not specified. No indications. No indications.


Normaldiametral pitch Moduleat less more atleast than than most-- -- 3 8 -- --3 10 2.5 810 -- -- -- -- 2.5

Not specified.

Indication, maximum

inch mm1/8 3.23/32 2.41/16 1.6

Indication, maximum

inch mm3/32 2.41/16 1.61/32 0.8

23 Shot peening Not recommended.

NOTES:1) See clause 3 for definitions and clause 4 for test methods.2) The metallurgical requirements assume homogeneous composition. In practice, microsegregation and banding occurs in steels.This microsegregation can produce variations in microstructure and properties that need to be assessed.3) Chemistry must include adequate nitridable alloying elements such as chromium, aluminum, vanadium or molybdenum.4) The grade requirements for nonmetallic inclusion, ultrasonic and microstructure characteristics apply only to those portions of thegear material where the teeth will be located to a depth below the finished tooth tip of at least 1.5 times the tooth height.5) A 7 to 1 minimum reduction ratio is recommended. For large gearing where this reduction ratio is not physically obtainable, lesserreduction ratios may be used down to a minimum of 3 to 1.6) In--process ultrasonic and/or magnetic particle inspection of gearing blanks is recommended for large diameter parts to detectflaws before incurring the expense of further machining.7) See ASTM A370, ASTM E140 or ISO 6336--5, annex C for hardness conversion tables.8) Mechanical properties including core hardness may not be the same after nitride hardening as they were before nitride hardening.

9) Specialty nitriding steels are typically alloyed with 1% aluminum to provide higher surface hardness after nitriding than normallyattained with nitrided through hardening steels.10) For a discussion of test coupons see clauses 3 and 4.11) Removal of defects that exceed the stated limits is acceptable, provided the integrity of the gear is not compromised.12) Cracks in non--functional areas require engineering disposition.13) Limits: maximum of one indication per inch (25 mm) of face width with a maximum of five such indications on any one tooth flank.Indications less than 1/32 inch (0.8 mm) are not considered.

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Bibliography

The following documents are either referenced in the text of AGMA 923--B05, Metallurgical Specifications for

Steel Gearing, or indicated for additional information.

ANSI/AGMA 6033--B98, Materials for Marine Pro-

pulsion Gearing

ASM Handbook, Volume 1 -- Properties and selec-

tion: Irons, steels and high--performance alloys ,

ASM International, Materials Park, Ohio, 1990

ASM Handbook, Volume 4 -- Heat treating , ASM

International, Materials Park, Ohio, 1991

Boyer, Howard E., Ed., Hardness Testing, ASM

International, Materials Park, Ohio, 1987

Doane, D.V. and Semchyshen, M., Modern carbu-

rized nickel alloy steel , NickelDevelopment Institute,

Toronto, 1990

Heat Treater’s Guide -- Practices and procedures for

irons and steels , ASM International, Materials Park,

Ohio, 1995

Kern, Roy F. and Suess, Manfred E., Steel Selection

-- A guide for improving performance and profits ,

John Wiley & Sons, New York, 1979

Krauss, G., Steels: Heat Treatment and Processing

Principles, ASM International, Materials Park, Ohio,

1996

Parish, Geoffrey, Carburizing: Microstructures and

Properties, ASM International, Materials Park, Ohio,

1999Practical Data for Metallurgists , 14th edition, The

Timken Company, Canton, Ohio, 1999

Reed--Hill, R.E., Physical Metallurgy Principles , D.

Van Nostrand, New York, 1973

Totten, G.E., and Howes, M.A.H., Steel Heat Treat-

ment Handbook , Marcel Dekker, New York, 1997

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AGMA 923-B05