Increasing the Efficiency of Metalform Tooling
for Advanced High Strength Steels
By: Brett Krause and Tom Bell
of Bohler Uddeholm Corporation
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Introduction
• Information on Bohler Uddeholm
• Newly developed tool steel and processing
– What makes it different
• Properties of the tool steel
– Compared to current tool steel
• Current cold roll tooling case studies
• Tool Steels for Blanking and Forming of AHSS
– What works best and why
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Bohler Uddeholm
• World largest producer of Tool Steel
– Austria, Sweden, Brazil
• Distribution in 37 countries
• In North America
– 15 service locations
– 400 employees
– Downstream processing
• Value added: cutting, grinding, and machining
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Introduction
• Trends
– New steel making processes
– Trim and Draw die tooling
– Rolls for cold rolling of strip steel
• Suggested improvements for making steel more
efficiently
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What’s new
• New process for producing tool steel
– Conventionally produced with addition of ESR
– Spray form
• New alloys that offer superior performance
to commonly used tool steels
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Background and History of
Dan Spray Process
• Process similar to Spray Forming or Thermal
Spray techniques for hard surface coatings
• Positioned between conventional ingot
metallurgy and P/M process metallurgy
• Developed in the mid 1970’s by researchers
who formed Osprey Metals Company
• Many different types of alloys can be
produced by this process such as Al and Si
alloys, copper alloys and iron alloys
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What is the Dan Spray
Process?
• A metal stream is atomized
• The atomized droplets are
collected by a substrate
which allows a pre-form to be
made in the form of tube and
billets
• Eliminates HIP’ing
• The pre-forms are ready for
further processing such as
rolling or forging
Tundish
Melting furnace
Spray formed
billet
Spray chamber
Collector disc
Exhaust
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Microstructure Comparison
Conventional
P/M
Spray Form
25µm
3.5µm
10µm
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Spray Form Material for Roll
Tooling
Grades
LCV Spray Form
M1
M2
8% Cr
D2
C
1.4
0.8
0.8
1.1
1.55
Si
1.0
0.4
0.3
0.9
0.25
Composition (wt%)
Mn
Cr
Mo
0.6
4.6
3.2
0.3
3.8
8.7
0.3
4.1
5.0
0.4
8.3
2.1
0.35
11.8
0.8
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V
3.7
1.4
2.0
0.5
0.95
W
1.8
6.1
Spray Form - Property
Comparison
Increasing chipping resistance
Conventional Metallurgy Grades
Spray formed Metallurgy Grades
S7
O1
8% Cr
A2
LCV Spray Form
M1
M2
D2
Increasing Wear Resistance
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Case study – LCV Spray Form
Cold rolling
Sendzimir Z- High Mill
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Case study – LCV Spray Form
Cold rolling - work roll at four high mill
COMPANY:
PRODUCT:
ROLLING MILL:
ROLL DIMENSION:
COMMENT:
Sandvik Materials Technology, Sweden.
Cold rolled high carbon, high chromium steel.
Four high cold roll mill - three in line, Initial cold rolling of hot rolled
strip to t = 0.9 – 3.8 mm
Work roll, Ø271x1555 mm.
The surface at the roll bearing position is significantly better for LCV Spray Form.
Phase 2 is to reduce regrinding depth to 0,10 mm for LCV Spray Form. Grinding
with CBN is to be preferred.
Phase 3 is to replace ROP 20 with LCV Spray Form in all three roll positions.
Phase 4 is to improve performance further by increasing hardness of
-. from 59 to 61 HRC - 63 HRC
LCV Spray Form
RESULT:
ROP 20
(H13 MOD.)
(0.7%C, 5.3%Cr, 1.1%Mo, 0.5%V)
LCV Spray Form – Phase
1 Work Roll LCV Spray Form
2nd Work Roll ROP 20
3rd Work Roll ROP 20
Production Tonnage / Regrind
8 coils
28 coils
Failure Mechanism
Abrasive Wear
Abrasive Wear
Regrind Depth
0.3mm
0.3mm
Hardness
59 – 61 HRC
59 - 61 HRC
st
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Case study – LCV Spray Form
Cold rolling - work roll at four high mill
COMPANY:
PRODUCT:
ROLLING MILL:
ROLL DIMENSION:
COMMENT:
RESULT:
Produced tonnage/regrind
Failure mechanism
Regrinding depth
Hardness
Sandvik Materials Technology, Sweden.
Cold rolled high carbon, high chromium steel.
Four high cold roll mill. Intermediate mill,
T = 0.8 – 1.7 mm.
Work roll, Ø 160 x 1245/510 mm.
The surface at the roll bearing position is significantly better
for LCV Spray Form.
ROP 20
(H13 mod.)
(0.7%C, 5 .3%Cr, 1 .1%Mo, 0 .5%V)
5 coils
Abrasive wear
0.15 mm
59 - 61 HRC
8%Cr steel
7-8 coils
Abrasive wear
0.15 mm
59 - 61 HRC
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LCV
Spray Form
17-20 coils
Abrasive wear
0.05 mm
59 - 61 HRC
Case study – LCV Spray Form
Calibration roll for manufacturing
of welded stainless tube
COMPANY:
AST, Sweden.
PRODUCT:
Stainless tube, Ø38 mm.
WORK MATERIAL:
18/8 steel.
TOOL DIMENSION:
Calibration roll direct after annealing, which is
the most severe roll position from wear point
of view, Ø 150 x 70 mm.
RESULT:
LCV Spray Form
D2
Hardness
62 HRC
60 HRC
Produced hours/regrind
310 h
100 h
Failure
mechanism
Minor abrasive
wear
Abrasive wear,
galling
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Case study – LCV Spray Form
Circular slitting knife
COMPANY:
Sandvik Steel AB, Sweden.
PRODUCT:
Valve band (for shock absorbers).
WORK MATERIAL:
High carbon steel (20C), t = 0.6 mm, 1200 MPa.
TOOL DIMENSION:
Circular slitting knife, Ø 210 x 7 mm.
RESULT:
Sandvik has contacted their suppliers and asked
them to make circular slitting knives in LCV Spray Form
M2
Produced
coils / regrind
Failure
mechanism
Hardness
LCV Spray Form
10 – 11 coils
20 – 22 coils
Abrasive wear
Abrasive wear
62 HRC
62 HRC
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Work Material Testing
Performed
70
High Strength
Stainless Steels
60
IF
Formability, A80 (%)
50
Grades of AHSS
Tested
Mild Steel
40
Bake Hardenable
30
Trip-steel
20
HSLA
DP-steel
10
Mart. steel
0
200
29
400
600
800
1000
1200
1400 MPa
116
145
174
203 KSI
58
87
~125HB ~180HB ~22HRC ~33HRC ~38HRC ~44HRC
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UHS Work Material – 1400
Mpa
Flat punch
15 000
Flat punch with a PVD coating
12 000
9 000
Force,N
Chamfered punch
6 000
3 000
0
0
0,005
0,01
0,015
0,02
0,025
-3 000
This shock wave can be
avoided by a chamfer
Time,s
Punch Material P/M 4%V at 60 HRC
~30 % force reduction
by chamfered punch
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0,03
UHS Work Material – 1400
Mpa
Die Clearance
Tool wear after 200 000 strokes
Tool steel: P/M 4%V at 60 HRC
Punch wear (µm2)
15 000
12 000
11000 µm 2
9618 µm 2
9 000
6 000
5675 µm 2
3 000
0
0
2
4
6
8
10
12
Die clearance, % of strip thickness
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14
16
UHS Work Material – 1400
Mpa
Surface Coatings
Results after 100 000 strokes
Tool material
P/M 4%V
P/M 4%V
P/M 4%V
P/M 4%V
Hardness
60 HRC
60 HRC
60 HRC
60 HRC
Coating
TiN
TiC (CVD)
TiCN
TiAlN
All four examples showed spalled surface coatings
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Die clearance
6%, 10%
6%, 10%
10%
10%
UHS Work Material – 1400
Mpa
Wear Mechanism –
6% die clearance
50 000
( S7) - 58 HRC
(D2) - 58 HRC
40 000
Punch wear (µm2)
P/M 4%V - 58 HRC
30 000
20 000
10 000
0
0
50 000
100 000
150 000
200 000
Number of blanks made
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250 000
UHS Work Material – 1400
Mpa
Wear Mechanism after 140 000 Strokes
AISI S7
AISI D2
P/M 4%V
“Constant” abrasive wear
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AHS Work Material – 1200 Mpa;
Production Environment test of Blanking
Punch
Example 3
Tool Steels
8% Cr Tool Steel
D2
P/M 4% V
P/M 4% V Improved
Appearance after 50 000 strokes
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UHS Work Material – 800 Mpa
Surface Coating
Comparison after 200 000 strokes
Galling problems
with uncoated tool
Uncoated punch
No galling with coating
PVD coated with TiAlN
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Other feedback with using alternative
tooling materials with AHSS
• Caldie Bar Stock: New die steel an alternative:
– Easily Weldable
– Flame and Thru-Hardenable
– Inserted into cast steel / iron base
• Can be used for forming, blanking and trimming of Advanced High
Strength (AHS) work materials.
• Carmo Granshots: Castable Tool Steel
– Has the ability to be through hardened
• Smaller cross sections
– Easily Weldable
– Easily flame-hardenable
– Trim and Draw dies
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Conclusion
• For Cold Rolling Roltec offers superior
wear resistance and surface finish for cold
forming rolls.
• Vanadis 4 Extra and Caldie give an
excellent combination of chipping
resistance, compressive strength and wear
resistance for blanking and forming of
AHSS
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Great Tooling Starts Here!
Thanks for your attention
Any Questions?
www.bucorp.com
1-800-METAL-20
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