Temper Bead Welding - iaea.org · PDF fileWelding & Repair Technology Center - Objective How technology is transferred ... to Support the Excavate and Weld Repair (EWR) Methodology

© 2017 Electric Power Research Institute, Inc. All rights reserved.

Greg Frederick WRTC Program Manager

Nick Mohr Technical Leader

IAEA-Technical Meeting on Dissimilar Metal Welding Experiences and Lessons Learned

July 11-14, 2017

Vienna, Austria

Temper Bead Welding

2 © 2017 Electric Power Research Institute, Inc. All rights reserved.

Temper Bead Welding

Presentation Outline:

Electric Power Research Institute (EPRI) Background

EPRI Welding and Repair Technology Center (WRTC)

Background

Temper Bead Welding Background

Application of Temper Bead for Dissimilar Metal Weld (DMW)

Repairs

Questions


EPRI’s Mission

Advancing safe, reliable, affordable, and environmentally

responsible electricity for society through global collaboration,

thought leadership and science & technology innovation


Corporate Strategic Direction

Innovative solutions that enable the transformation

of power systems to be more flexible, resilient, and

connected to provide society with safe, reliable,

affordable, and environmentally responsible electricity

+


Three Key Aspects of EPRI

Collaborative Bring together scientists, engineers,

academic researchers, and industry experts

Independent Objective, scientifically based

results address reliability,

efficiency, affordability, health,

safety, and the environment

Nonprofit Chartered to serve the

public benefit


Born in a Blackout

Founded in 1972 as an independent, nonprofit center for

public interest energy and environmental research

New York City, The Great Northeast Blackout, 1965


Our Members…

450+ participants in more than

30 countries

EPRI members generate approximately

90% of the electricity in the United

States

International funding – nearly 25% of

EPRI’s research, development, and

demonstrations


EPRI Membership Funding by Type

Co

op

erative 4%

International

Fed

eral/State

Mu

nicip

al

1%

Investor-Owned

55% 28% 6% 5%

December 31, 2016 (unaudited results)

Ind

epen

den

t Po

wer P

rod

ucer

5%

Co

op

erative


Program Overview

WRTC


Program Overview

Mission and Objective

WRTC – Committees and Meetings

WRTC – Who We Are


Welding & Repair Technology Center-Mission

As nuclear power producing facilities age, there is an increasing need for

technology to provide effective solutions and to support life extension

objectives

Focus on both tactical issues and strategic research

Provide a framework for identifying, prioritizing, and tracking fabrication

and repair related technology “gaps”

– Technical Advisory Committee (TAC), EPRI staff, Integration Committee

– Facilities (metallurgical lab, welding lab, materials labs, etc.)

– Collaboration–National Labs, Universities, Internal

Lead R&D activities and technology development to supplying the

necessary “TOOL” to address current and future repair, fabrication, and

mitigation issues


Welding & Repair Technology Center - Objective

Establish technologies to address gaps in repair and

replacement technology for nuclear power generation

components and transfer that technology

– Improve material performance and component life

extension

– Develop field-usable applications of technology

focused on the repair and replacement

– Increase plant availability and reduce repair costs

and schedule

– Support implementation - technical interactions with

Code, regulators and service vendors

– Create forums for sharing operating experience

Information exchange on repair, fabrication, weld

program issues, and industry emerging issues

Provide access to materials, welding, and repair

experts/peers across the nuclear industry

Suppliers, Vendors,

National Labs,

Universities

Nuclear Utilities

Collaborative

Technology

Development,

Integration and

Implementation Solutions

Inputs

EPRI


Welding & Repair Technology Center - Objective

How technology is transferred…..

Through comprehensive

documentation

Direct communication (meeting

report outs)

Rapid-response assistance

(Information Exchange)

Training and Workshops

Computer Based Training Options

Peer interaction

Welding and Repair Technology Center:

Technical Basis and Residual Stress Studies

to Support the Excavate and Weld Repair

(EWR) Methodology for Mitigation of SCC in

ASME Class 1 Butt Welds


Welding & Repair Technology Center

11 Research Focus Areas (RFA) established to address WRTC Core and Support areas: – RFA 1: Nickel-Base Filler Metal Weldability and New Alloy development

– RFA 2: Irradiated Materials Welding Solutions

– RFA 3: Identify, Research, Develop, and Mature Advanced Welding Processes

– RFA 4: Optimize Joining, Fabrication, and Repair Processes (including Welding Residual Stress)

– RFA 5: Small Bore Piping Asset

– RFA 6: Transfer & Promote Fabrication & Joining Technologies into Codes, Standards, & Regulations

– RFA 7: Buried Pipe Asset Management / Repair Solutions

– RFA 8: Repair Solutions for Structures: Containment, Fuel Pool Asset Management, Spent Fuel Storage

– RFA 9: Tactical Implementation of Repair Methods

– RFA 10: Document & Evaluate Operating Experience for Welding & Repair Programs

– RFA 11: Thermal spray, Coatings, and Hardfacing Applications


EPRI Welding & Repair Technology Center (WRTC)

EPRI - Charlotte, NC

• ~200 EPRI staff; 8 are WRTC staff

• WRTC staff and labs are in Buildings 1

• Building 1- welding labs, laser labs, metallurgical labs, material archives

2

1 3

1


WRTC Meeting Strategy

WRTC Technical Advisory Meeting (TAC) and Technical Programs

Two meetings per year (June and December)

– Session: Research Focus Area Reviews (Code Issues,

Training, Alloy 52, etc.)

– Session: Operating Experience (OE) and emerging issues,

Information Exchange

– Session: Demonstrations/Training both meetings

– Breakouts sessions (Technology Gap)

Goals

– Maintain a high level of communication and peer interaction

– Increase understanding of WRTC capabilities, organization,

and staff

– Identify work scope that is important to industry

– Identify work scope that is important to

industry


WRTC TEAM

Greg Frederick

WRTC Program Manager

[email protected]

Ben Sutton

Technical Leader

[email protected]

Dana Couch

Senior Technical Leader

[email protected]

Steve McCracken

Senior Technical Leader

[email protected]

Stacey Wells

Assistant III

[email protected]

Jon Tatman

Technical Leader

[email protected]

Nick Mohr

Technical Leader

[email protected]

mailto:[email protected]








WRTC TEAM-Continued

David Gandy

Materials Technical Executive

[email protected]

Robin Dyle

Materials Technical Executive

[email protected]

• MK Havens

• Kendal McCord

A

B

Metallurgy Laboratories Welding Laboratories

• Mitch Hargadine

• David Hansen

• Scott Bailey




WRTC Team–Where We Are

United States (TAC)

22 of 22 U.S. Utility Organizations participate in WRTC (all

operating BWR and PWRs)

International Participation (TAC)

CANDU Owners Group (COG) – Canada, Romania

CEZ A.S. – Czech Republic

Chubu Electric Power Co., Inc. – Japan

Chugoku Electric Power Co., Inc. - Japan

Comision Federal de Electricidad (CFE) - Mexico

Electricite de France S.A. (EDF/MAI) – France

Emirates Nuclear Energy Corporation - United Arab

Emirates

Eskom - South Africa

Horizon Nuclear – United Kingdom

Kansai Electric Power Co, Inc – Japan

Korea Hydro and Nuclear Power Co. - Korea

Kyushu - Japan

MVM Hungarian Electric (Paks) – Hungary

Nucleoelectrica Argentina S.A. – Argentina

Shikoku Electric Power Co – Japan

The Tokyo Electric Power Company, Incorporated

(TEPCO) - Japan

UNESA – A.E. Industria Electrica - Spain

Non-Utility Memberships

IHI Corporation – Japan

Fluor Enterprises

AZZ WSI LLC – Welding Services Inc.

AREVA

Westinghouse

KAPL/Bettis – Bechtel Marine Propulsion Corp.

Rolls Royce

BWXT Nuclear Operations Group (BWXT) (2017)

Doosan Heavy Industry (2018)


Temper Bead Welding


Temper Bead Welding

ASME Code Section IX defines temper bead (TB) welding as [1]:

“a weld bead placed at a specific location in or at the surface of a weld for the purpose of

affecting the metallurgical properties of the heat‐affected zone or previously deposited

weld metal. The bead may be above, flush with, or below the surrounding base metal

surface. If above the base metal surface, the beads may cover all or only part of the weld

deposit and may or may not be removed following welding.”

The temper bead welding definition is broad and can be interpreted differently depending

on the industry it is being applied. However, one common purpose is the elimination of

postweld heat treatment (PWHT), but make note that stress relief does not occur.


Temper Bead Welding

Temper Bead

Welding

Consistent Layer

Temper Bead

Technique

Controlled Deposition Technique Half-Bead

Technique

Alternate Temper Bead

Technique

• Machine GTAW or SMAW technique

• Ambient preheat (10°C)

• Grinding of layers not required

• 3 layers minimum

• Can be done remotely

• No postweld hydrogen bakeout after

welding

• Main objective tempered HAZ

• Typically SMAW technique

• Preheat typical (≈200°C)

• Grinding not required


• Typically, higher heat input ratio for

second layer

• Main objective eliminate coarse

grain zone (grain refinement)

• SMAW technique

• Preheat required (177°C)

• Typically, progressively larger

electrode diameters used

• Half of layer 1 is ground off before the

next layer is deposited

• Main objectives tempering and grain

refinement

• Postweld hydrogen bakeout (230°C-

290°C)

• Machine GTAW technique

• Preheat required (150°C)

• Grinding of layers not required


• Can be done remotely

• Main objectives tempering and

grain refinement

• Postweld hydrogen bakeout

(230°C-290°C)

There are many temper bead techniques [2]


Temper Bead Welding

The desired metallurgical effect of temper bead welding is largely dependent on the

industry. In general, the goal for temper bead welding can be summarized as:

Nuclear: achieving a tempered heat affected zone (HAZ) (ideally tempered martensite)

with acceptable fracture toughness

Fossil: achieving grain refinement in the HAZ to avoid reheat cracking

Oil and Gas: achieving a HAZ with hardness not above a specified value

The term “temper bead” welding is used generically but the purpose and end goal can be

different depending on the industry. This discussion will focus on nuclear applications.


Temper Bead Welding

Why is tempered martensite desired?

Answer- Very good fracture toughness

[3] Tempered Martensite + Tempered Pearlite

Tempered Martensite + Tempered Bainite

Tempered Martensite


Temper Bead Welding

How is Temper Bead Welding done:

Precision placement of weld beads deposited using a qualified range of heat input

Precision placement of weld layers (US code cases have typically stated three temper

bead layers are required)

TB Layer 1

TB Layer 2

TB Layer 3


Temper Bead Welding

Heat input or power ratio is required to be maintained within the qualified range of the

welding procedure specification (WPS)- ASME Code

Heat input should be documented for all temper bead weld layers. Welds should be

identified and heat input/power ratio documented on a bead log.

Heat input and power ratio equations are provided below.

𝐻𝑒𝑎𝑡 𝐼𝑛𝑝𝑢𝑡 =𝑉𝑜𝑙𝑡𝑎𝑔𝑒∗𝐴𝑚𝑝𝑒𝑟𝑎𝑔𝑒∗60

𝑇𝑟𝑎𝑣𝑒𝑙 𝑆𝑝𝑒𝑒𝑑

𝑃𝑜𝑤𝑒𝑟 𝑅𝑎𝑡𝑖𝑜 =𝑉𝑜𝑙𝑡𝑎𝑔𝑒∗𝐴𝑚𝑝𝑒𝑟𝑎𝑔𝑒

[𝑊𝐹𝑆

𝑇𝑆∗𝐴𝑓]

*wire feed speed (WFS), travel speed (TS), cross sectional area of filler metal (Af)


Temper Bead Welding

The purpose of monitoring the heat input and power ratio is to make sure a certain range

of thermal energy is placed into the base material. This ensures that subsequent weld

layers temper the HAZ from the previous weld beads while keeping the relative size of

HAZ the same.

For gas tungsten arc welding (GTAW) the power ratio is frequently used because it

accounts for the energy required to melt the bare wire (i.e. more energy used to melt the

filler metal leaves less thermal energy for the base material)

HAZ


Temper Bead Welding

Goals of Temper Bead Welding for Nuclear Applications:

Eliminate heat treatment

– Temper bead welding can be used without elevated preheat, post weld heat

treatment, and post weld hydrogen bakeout

Effectively temper the HAZ

Mechanical properties at least as good as the unaffected base material

– In most cases, the HAZ will actually demonstrate better mechanical properties

due to the increased proportion on tempered martensite compared to the

unaffected base material

Recall from continuous cooling transformation (CCT) diagrams. A relatively

small weld HAZ is being quenched compared to when the base material was

processed. The base material with larger mass is more difficult to obtain

optimum microstructure.


Temper Bead Welding

Example CCT: SA-508

Base Metal-

Slower Cooling Rate

Weld-

Rapid Cooling Rate


Temper Bead Welding

Currently, the following welding processes are permitted to be used to deposit a temper

bead weldment for ASME Section III and ASME Section XI applications:

Machine/automatic GTAW (Left)

Manual shielded metal arc welding (SMAW) (Right)

Currently, gas metal arc welding (GMAW) is not permitted, but research may

demonstrate that it is acceptable.


Temper Bead Welding

Example Code Rules (ASME)

Code rules

– ASME Section III-NB (NB-4622.9 in 2015 Code) [4]

– ASME Section XI (IWA-4600 in 2015 Code) [5]

– However, these usually require preheat and postweld hydrogen bakeout. Many heat treatments are

not possible due to fluid in the system. The latest methods, improvements, and rules are found in

the following Code Cases. The improvements will eventually filter through to the main sections.

Code Cases

– N-638-8 (Ambient temperature temper bead using machine GTAW) [6]

Reduced preheat (50°F min), qualification clarifications (coupon simulated PWHT and impact

specimens), and peening clarifications.

– N-839 (Ambient temperature temper bead using SMAW) [7]

Reduced preheat (50°F min) and no post weld hydrogen bakeout

– Unfortunately, these are not approved by the Nuclear Regulatory Commission (NRC) (N-638-4 is

conditionally accepted) and would require regulatory relief for US plants. Non-US plants may be

able to use code cases as guidance in their country.


Temper Bead Welding


Application of Temper Bead for Dissimilar Metal

Weld (DMW) Repairs


Dissimilar Metal Weld Repair

Structural Weld Overlays – SCC resistant materials are deposited on the outside of pipe/nozzle such that the

deposit is considered the structural boundary. The residual stress from shrinkage can create compressive stress on the inside of the pipe/nozzle. Two types of overlays:

Full Structural Weld Overlay (FSWOL): weld overlay designed to take all loads

Optimized Weld Overlay (OWOL): weld overlay and a fraction of base material designed to take all loads.

Inlays and Onlays – SCC resistant material are applied on the inside surface of pipe/nozzle DMW creating

a resistant barrier to SCC

Excavate and Weld Repair – Partial removal of susceptible material from the outside of the pipe/nozzle that is then

replaced by resistant filler metal

Traditional Cut-Out and Replace – Remove all susceptible material and reweld using resistant materials (not practical in

many situations)-Not discussed


Structural Weld Overlay

FSWOL assumes a full 360° circumferential through wall flaw

OWOL assumes a full 360° circumferential flaw only 75% through wall

– The thickness of the weld overlay is less because some structural credit is provided to the underlying base material

Both FSWOL and OWOL are intended to place crack tip in compression (if applicable) and use SCC resistant filler metal

Applicable ASME Code Cases: N-504-X [9], N-740-X [10], an N-754-X [11]

[8] [8]


Structural Weld Overlay

Temper Bead Layers


Inlay or Onlay

Inlay requires machining of small groove and then replacing SCC susceptible material with resistant material.

Onlay does not prohibit machining a groove, but also provides SCC resistant material barrier Both are intended to provide SCC resistant barrier (i.e. Nickel alloy with Cr 28% or greater) Temper bead welding would be likely when welding on ferritic material or within 3mm of ferritic

materials Applicable ASME Code Case: N-766-X [13]

Typical Inlay [12] Typical Onlay [12]


Typical Inlay [10]

Inlay of Onlay

Temper Bead Layers


Excavate and Weld Repair (EWR)

Schematic of EWR for

82/182 PWSCC Mitigation [15] Schematic of Partial Arc [15]

General approach: Replace some of the SCC susceptible material with resistant material

– In many situation repairs via inlay/onlay or WOL is not possible or practical

Four types of EWR (summarized)

– Type 1A EWR: No surface connected or subsurface defect detected AND wetted surface has tensile stresses no greater than 69MPa after

EWR

– Type 1B EWR: Surface or subsurface defect (or no pre-exam) AND wetted surface has tensile stresses no greater than 69MPa after EWR

– Type 2A EWR: No surface connected or subsurface defect detected, but wetted surface has tensile stresses greater than 69MPa after

EWR

– Type 2B EWR: Surface or subsurface defect (or no pre-exam), but wetted surface has tensile stresses greater than 69MPa after EWR

EWR can be full 360 degree, or partial arc, and can be used on similar or dissimilar metal welds

Applicable ASME Code Case: N-847 [14]


Stainless Steel

Buffer Layer(s)

Temperbead

Layers

Stainless Steel

Safe End

Low Alloy

Steel Nozzle

82/182

Weld

Schematic of EWR for 82/182 Repair/Mitigation

Stainless Clad

182 Butter

Excavate and Weld Repair

Temper Bead Layers


Summary

There are many temper bead techniques, each with specific objectives

Temper bead welding has been used successfully for many repairs In many cases, the use of temper bead welding is necessary for

these repairs to be done in the field – Temper bead welding can be used without preheat – Temper bead welding can be used without PWHT – Temper bead welding can be used without postweld hydrogen

bakeout – Temper bead welding can be used with machine GTAW or manual

SMAW Temper bead is frequently used in conjunction with other dissimilar

metal repairs such as weld overlays, inlay/onlay, and excavate and weld repairs


Questions


References 1. ASME Boiler and Pressure Vessel Code Section IX, Qualification Standard for Welding, Brazing, and Fusing Procedures; Welders;

Brazers; and Welding, Brazing, and Fusing Operators, 2015 Edition.

2. Welding and Repair Technology Center: Shielded Metal Arc Temper Bead Welding. EPRI, Palo Alto, CA: 2015. 3002005536.

3. Lundin, C.D. and Mohammed, S., “Effect of Welding Conditions on Transformation and Properties of Heat Affected Zones in LWR Vessel

Steels”, NUREG/CR-3873

4. ASME Boiler and Pressure Vessel Code Section III-NB, Rules for Construction of Nuclear Facility Components, Division 1 – Subsection

NB Class 1 Components, 2015 Edition.

5. ASME Boiler and Pressure Vessel Code Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, 2015 Edition.

6. ASME Section XI Code Case N-638-8, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead

Technique, Approved November 5, 2014

7. ASME Section XI Code Case N-839, Similar and Dissimilar Metal Welding Using Ambient Temperature SMAW Temper Bead Technique,

Approved September 4, 2014

8. Welding and Repair Technology Center: Overlay Handbook. EPRI, Palo Alto, CA: 2013. 3002000616

9. ASME Section XI Code Case N-504-4, Alternative Rules for Repair of Classes 1, 2, and 3 Austenitic Stainless Steel Piping, Approved

July 14, 2006

10. ASME Section XI Code Case N-740-2, Full Structural Dissimilar Metal Weld Overlay for Repair or Mitigation of Class 1, 2, and 3 Items,

Approved November 10, 2008

11. ASME Section XI Code Case N-754-1, Optimized Structural Dissimilar Metal Weld Overlay for Mitigation of PWR Class 1 Items,

Approved February 28, 2013

12. Marlette, S.E. et al., Technical Basis for Case N-766-1 Nickel Alloy Reactor Coolant Inlay and Onlay for Mitigation of PWR Full

Penetration Circumferential Nickel Alloy Welds in Class 1 Items, ASME International (2012).

13. ASME Section XI Code Case N-766-1, Nickel Alloy Reactor Coolant Inlay and Onlay for Mitigation of PWR Full Penetration

Circumferential Nickel Alloy Dissimilar Metal Welds in Class 1 Items, Approved April 7, 2013

14. ASME Section XI Code Case N-847, Partial Excavation and Deposition of Weld Metal for Mitigation of Class 1 Items, Approved October

24, 2016

15. McCracken, S., Welding and Repair Technology Center TAC Meeting, 06E-ASME Section XI Activities Presentation, December 5-8,

Palm Coast, FL


Together…Shaping the Future of Electricity

Documents

Temper Bead Welding - iaea.org · PDF fileWelding & Repair Technology Center - Objective How technology is transferred ... to Support the Excavate and Weld Repair (EWR) Methodology