Innovative Cold Stamping Die Steel “SLD-i - · PDF file• Precise shape by low heat treatment deformation • Longer die life and better galling resistance than D2 by optimizing

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Innovative Cold Stamping Die Steel “SLD-i” *Our innovative standard cold stamping tool steel, SLD-i, complies with AISI D2.

HITACHI CONFIDENTIAL

May 2015

Hitachi Metals America, Ltd.

© Hitachi Metals, Ltd. All rights reserved.

© Hitachi, Ltd. 2014. All rights reserved.

1. Alloy design for SLD-i 2. Microstructure 3. Die life for stamping 4. Machinability 5. Heat treatment deformation 6. Hardness 7. Summary

Contents

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Raw material

Machining before heat treatment

Heat treatment

Machining after heat treatment

Shape adjustment

Mill run (stamping)

Challenges for D2

Wide variation

Rough machining

Large deformation

Large machining

amount

Several times adjustment

Short / variation in

lifetime

Alloy design of SLD-i

Stabilized Near-net

shape machining

Excellent property of inhibiting a deformation

Small machining

amount -> Cost

reduction

Decrease in a frequency of adjustment

-> cost / lead time saving

Longer / stabilized lifetime

1. Alloy design for SLD-i

1.2 Comparison between D2 and SLD-i at different process

1.1 Value proposition of SLD-i • Precise shape by low heat treatment deformation • Longer die life and better galling resistance than D2 by

optimizing carbide distribution • Same heat treatment condition as D2



© Hitachi, Ltd. 2014. All rights reserved. 3 © Hitachi Metals, Ltd. All rights reserved.

Duc

tility

(Tou

ghne

ss)

Good Wear resistance

Goo

d

SLD-i has better wear resistance as D2

because of optimizing carbide distribution.

2. Wear resistance and chipping resistance

Powder metal (4 Vanadium)

SLD-i D2

M2

A2

S7

8Cr steel



3. Microstructure


8%Cr SLD-i D2

Small, dense & homogeneous carbide distribution will contribute to • Small & isotropic heat

treatment deformation • Good galling & wear

resistance • Achieve higher hardness

than D2

Coarse & directional carbide distribution • Large & anisotropic heat

treatment deformation • Medium galling & wear

resistance • Characteristics will be

affected by grain direction

Small & sparse carbide distribution • Large heat treatment

deformation • Worse galling & wear

resistance • Good toughness &

machinability

200μm 200μm 200μm



4. Die life for stamping


4.1 TD coated by US Kondo

Spec 73.86±0.01 mm SLD-i Sample 1 73.863 mm

Sample 2 73.856 mm Sample 3 73.859 mm Sample 4 73.867 mm Sample 5 73.859 mm Pass rate 100% (5/5)

Pass rate of D2 10%

http://uskondo.com/

OD: 75mm

Punch dies for burring of hub bearing

Application Grade Coating Die life Punch dies for burring

SLD-i TD coated More than 500,000 hits WITHOUT repairing

D2 TD coated 10,000 – 100,000 hits with repairing

http://uskondo.com/

http://uskondo.com/



4.2 Wear resistance test (ASTM G99-05, Pin-on-disc test)


0 2E-14 4E-14 6E-14 8E-14

8Cr

D2/1.2379

SLD-Isotropy

Specific wear volume / (m2/N)

SLD-i

*20～25mm (t), W/4 x T/2, length dimension

Test piece

Disc

Schematic diagram of test condition

Good Poor Item Condition

Test piece*

Grade SLD-i, D2, 8Cr

Shape Φ8 x 3pcs each

Hardness 60HRC

Disc Grind stone (Al2O3, #32; 300-425μm)

Surface pressure 7.8MPa

Grind speed 0.42m/sec

Grind length 377m

SLD-i improved wear resistance compared with D2 and 8Cr steel by optimizing carbide distribution.

<Conditions> <Results>

D2


8%Cr



Initiation point and direction of galling

Load

Bead

Punch Die

Work piece

Schematic diagram of test condition © Hitachi Metals, Ltd. All rights reserved.

1000

1500

2000

2500

3000

3500

SLD ICT-SLD D2 ICT-D2 S-MAGIC

しわ押さえ力(kgf)

1000

1500

2000

2500

3000

3500

4000

4500

SLD ICT-SLD D2 ICT-D2 S-MAGIC

しわ押さえ力(kgf)

1000

1500

2000

2500

Hol

ding

Pre

ssur

e / k

g・f

D2 SLD-i

Good

Poor

Improved Galling resistance

<Results>

SLD-i has achieved good galling resistance by optimizing carbide size and reducing the abrasive wear starting from carbides.

Item Condition Length of Stroke 60mm Pressing Velocity 60spm

Lubricant Rust prevention oil *delivery condition

Work 980MPa HSS

Work Thickness 1.4mm (No ‘Zn’ plating） Clearance:5%

Die surface condition

Polished by #8000 paper (2-4μm)

<Conditions> 4.3 Galling resistance




5. Heat treatment deformation


5.3 Lab test

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

SLD-i D2 8%Cr

Dim

ensi

onal

Cha

nge

(%)

Length

Width

Specimen size： 18Tx25Wx30L(mm) Austenitizing: 1030oC Tempering: SLD-I, D2 500oC 2h+2h 8%Cr 520oC 2h+2h

Good

Poor

5.2 Heat treatment test by Die maker Width Length Height

SLD-i Sample 1 Nominal size (mm) 270.4 83.4 70.3 Deformation (mm) +0.25 +0.05 +0.35

Sample 2 Nominal size (mm) 60.31 95.95 70.7 Deformation (mm) +0.11 +0.17 +0.1

Sample 3 Nominal size (mm) 290.3 200.36 70.6 Deformation (mm) +0.12 +0.29 +0.04

Deformation of D2 & 8%Cr ±0.3 mm – ±0.6 mm



6. Hardness


Tempering curve

Grade Chemical composition (wt％) C Si Mn Cr Mo V

SLD-i Within the D2 spec

D2 1.40- 1.60

0.30- 0.50

0.30- 0.50

11.0- 13.0

0.70- 1.20

0.50- 1.10

Reference: Chemical composition of SLD-i is within the D2 spec

53

55

57

59

61

63

65

430 450 470 490 510 530 550

Har

dnes

s (H

RC

)

Tempering temp.(oC) As

quenched

SLD-i

8Cr Steel

D2


© Hitachi, Ltd. 2014. All rights reserved.

0

1

2

3

4

5

Dimensionalchanges

Welding

Hardness

Toughness

Wearresistance

Machinability

10

7. Summary


• Die life of TD coated SLD-i was improved more than 5 times vs TD coated D2.

• Smaller and isotropic heat treatment deformation was achieved compared with D2 and 8%Cr.

• Same heat treatment condition with D2. <Cobweb chart>

SLD-i

8Cr Steel D2




2.5 Relationship between carbide distribution and wear resistance

Wear mode

Carbide distribution Preferable microstructure Large / Sparse Small / Dense

High pressure

area

D2

Sliding area

Powder metal

Impact and adhesive wear resistances are related to the carbide distribution.


Large Contact area Pressure

Deep wear depth

Die

Work

Deep wear depth

Sliding Long distance Die

Work

Short distance

Shallow wear depth

Sliding Die

Work

Carbide

Die

Work

Pressure Small

Contact area

Shallow wear depth



2.6 Relationship between wear resistance for High pressure and sliding area

Slid

ing

area

Good High pressure area

Goo

d

D2

Powder metal SLD-i

SLD-i is optimized the impact wear resistance and adhesive wear resistance.




© Hitachi, Ltd. 2014. All rights reserved. © Hitachi Metals, Ltd. All rights reserved.

4. Heat treatment deformation

4.1 Relationship between heat treatment deformation and carbide distribution

Isotropy Dimensional change Microstructure Pattern diagram of heat

treatment dimensional change

D2 Poor Large

SLD-i Excellent Small

Carbide

Matrix

100μm

100μm

Wid

th

Length

Wid

th

Length

• Heat treatment deformation (isotropy and dimensional change) is susceptible to carbide distribution

• Deformation of SLD-i is small and isotropic because of even and small carbide distribution

14

Documents

Innovative Cold Stamping Die Steel “SLD-i - · PDF file• Precise shape by low heat treatment deformation • Longer die life and better galling resistance than D2 by optimizing