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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
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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
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3. Microstructure
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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
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4. Die life for stamping
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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
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4.2 Wear resistance test (ASTM G99-05, Pin-on-disc test)
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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
4. Die life for stamping
8%Cr
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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
4. Die life for stamping
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5. Heat treatment deformation
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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
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6. Hardness
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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
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0
1
2
3
4
5
Dimensionalchanges
Welding
Hardness
Toughness
Wearresistance
Machinability
10
7. Summary
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• 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
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2. Die life for stamping
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.
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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
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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.
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2. Die life for stamping
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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