DIE WEAR IN STAMPING OF
ADVANCED HIGH STRENGTH
STEEL (AHSS) SHEETS
TERM PROJECT;
ME-475/575- INTRODUCTION TO LUBRICATION, FRICTION AND WEAR
Simeng Liang, Ruiyan Yang, Saeid Nasheralahkami
December 1, 2015
OAKLAND UNIVERSITY
SCHOOL OF ENGINEERING & COMPUTER SCIENCE
DEPARTMENT OF MECHANICAL ENGINEERING
Layout
• Introduction to AHSS
• Wear Mechanisms in Sheet Metal Forming
• Types of Tool Wear in Forming of AHSS
• Effective Parameters on Die Wear in Stamping of AHSS
• Summary and Conclusion
2
Introduction to AHSS
• Automotive industry’s need
for steel – high strength and
enhanced formability
• AHSS has been increasingly
replacing mild steels and
conventional HSS
INCREASED STRENGTH
DECREASED
FORMABILITY
• AHSS; improves safety and
fuel economy
• AHSS ;
DP, CP, TRIP and MART
• New generation of AHSS ;
TWIP, ferritic-bainitic,
boron-manganese alloy
steels
S. Sadagopan, Formability Characterization Of Advanced High-Strength
Steels, Great Design in Steel Seminar, 2004, Livonia, MI.
3
Application of AHSS
An Example of Recent Application of AHSS/EHSS/UHSS in
2013 Volvo-V40 Body Structure
Source: http://www.boronextrication.com/
4
Tribology in Stamping of AHSS
Forming of AHSS; higher contact pressures
and temperatures at the tool-sheet
interface / hard microstructure of AHSS
galling, abrasive and adhesive
wear in the tool  reduce tool life
5
Wear Mechanisms in Sheet Metal Forming
 Wear is damage to a solid surface, involving loss or displacement of
material
 Several superimposed wear mechanisms  Difficulty of the assessment
of the wear behavior of dies
 Wear mechanism 
four basic fundamental
phenomena
(next slide)
Schulder, Metal Forming Handbook, Springer-Verlag Berlin Heidelberg, 1998
6
Wear Mechanisms in Sheet Metal Forming
1. Wear at surface layer
Frictional heating, lubricant and the surrounding medium
 built-up of an interface layer at the die/material interface
The lower shear strength of the interface layers
 their removal under frictional shear stress
2. Adhesion
also called; Cold welding / Galling
localized bonding between contacting solid surfaces
material transfer between the two surfaces or loss from either surface
similar material structures of the frictional partners
higher tendency to develop adhesive wear
may cause plastic deformation at the peaks of the roughness of surfaces
3. Abrasion
hard particles forced against and moving along a solid surface
The difference in the hardness between the two surfaces main factor
relative movement  heat hardness drops reducing resistance to wear
generally inevitable long-term wear effect on the die
4. Surface fatigue
mechanical, thermal or chemical stress-related conditions
separation of micro- and macroscopic material particles
fatigue is common in high speed/cycle cutting tools
7
Types of Tool Wear/Failure in Forming of AHSS
1.
Side/Flank/Vertical wall Wear
combination of adhesive wear, fatigue wear, and abrasive wear
increases the clearance between the punch and the die &
increases deformation (edge draw-in) of the work piece during shearing
2.
Face Wear
the punch edges to become round and obtuse
reduce the sharpness of the punch during shearing
increase the deformation of the punched work piece
the burrs of parts become larger
the noise level in the press also becomes very high
J. J. Hernández, P. Franco, M. Estrems &
F. Faura,, Modelling and experimental
analysis of the effects of tool wear on
form errors in stainless steel blanking,
Journal
of
Materials
Processing
Technology, 2006, 180(1–3), 143-150.
8
Types of Tool Wear/Failure in Forming of AHSS
3. Chipping
 some micro crushes, fragments and breakage on the cutting edges
 caused by repeated impact loads or thermal shocks
 If the surface of the punch is too rough or if the turning feed marks of the
machining process are retained then chipping of the punch cutting edges would
occur easily
 is a result of high stresses, exceeding the fatigue strength of the tool material
S. Y. Luo, Studies on the Wear Conditions and the
Sheared Edges in Punching, Wear, 1997, 208, pp.
81–90
Uddeholm & SSAB, Tooling Solutions For Advanced
High Strength Steels, Selection Guidelines, 2008.
9
Types of Tool Wear/Failure in Forming of AHSS
4.
Cracking
 many irregular micro-cracks on the face of the tool edges
 result of mechanical fatigue or thermal
fatigue during shearing
5.
Gross Fracture
6.
Galling (Pick-up)
 chipping and cracks during shearing
 macro-fracture appearance
 a result of fatigue failure
 a result of heavy friction forces due to
the sliding contact and the adhesive
nature of the work material
 related to adhesive wear
S. Y. Luo, Studies on the Wear Conditions
and the Sheared Edges in Punching, Wear,
1997, 208, pp. 81–90.
Galling Wear
Uddeholm & SSAB, Tooling Solutions For Advanced
High Strength Steels, Selection Guidelines, 2008.
10
Effective Parameters on Die Wear - AHSS
1. Substrate Material of die
2. Die coating
3. Lubrication
4. Die radius
5. Sheet material type & Coating
6. Hot stamping of AHSS
 In the next slides, we are going to see how these parameters affect
the die wear based on the review of some technical papers.
11
Effective Parameters on Die Wear - AHSS
1. Die Wear and Coating Galling in Stamping Advanced High Strength Steels
• AHSS Sheets:
Dual phase (DP) 590 and 780 steels
with galvanized (GI) and
galvannealed (GA) coatings
• Die Materials
and coatings:
• Experimental
method:
• Evaluation
methods:
reciprocal cyclic bend test system to
evaluate stamping conditions and their
effects on die wear and coating galling
- Wear based on the die weight
difference ratio before & after test
- Roughness; stylus contact type
Profilometer & Laser 3D Scanner
H. Shih, M. F. Shi, Die Wear and Coating Galling in Stamping Advanced High Strength Steels, Proceedings of the ASME 2011
IMECE2011, Nov. 11-17, 2011, Denver, Colorado, USA.
12
Effective Parameters on Die Wear - AHSS
1. Die Wear and Coating Galling in Stamping Advanced High Strength Steels
• Results:
Sheet: DP780
 Die materials with a special surface coating treatment (TDVC, Chrome, CrN)
 very good wear resistance regardless of sheet metal coatings,
 Die materials without the coating (IN, D2)  relatively poor wear resistance.
 A smooth die material with high stiffness and a tough coating is highly
recommended for stamping AHSS.
H. Shih, M. F. Shi, Die Wear and Coating Galling in Stamping Advanced High Strength Steels, Proceedings of the ASME 2011
IMECE2011, Nov. 11-17, 2011, Denver, Colorado, USA.
13
Effective Parameters on Die Wear - AHSS
2. Investigation on Tribological Behavior of Advanced High Strength Steels:
Influence of Hot Stamping Process Parameters
Sheet:
Die:
•
Using hot strip drawing tribo-simulator  Measurement of friction coefficient as functions
of temp & drawing speed
 critical temp for the occurrence of massive adhesive wear is 600°C at which the
friction coefficient starts to increase greatly.
X. Tian, Y. Zhang & J. Li, Investigation on Tribological Behavior of Advanced High Strength Steels: Influence of Hot Stamping
Process Parameters, Tribology Letters, 2012, 45, pp, 489–495
14
Effective Parameters on Die Wear - AHSS
3. Die Wear in Stamping of Advanced High Strength Steels – Investigations
on the Effects of Substrate Material and Hard-Coatings
Fig. 6. (a) Specific wear rates for “coating type effect”, (b) Specific wear rates for “substrate material effect”
• There is no distinct performance
difference among the coating type.
• the higher substrate hardness
higher wear resistance.
Ö. N. Cora, A. Ağcayazı, K. Namiki, H. Sofuoğlu and M. Koç, Die wear in stamping of advanced high strength steels –
investigations on the effects of substrate material and hard-coatings, Tribology International, 2012, 52, pp. 50–60.
15
Effective Parameters on Die Wear - AHSS
4. Experimental Investigations on Wear Resistance Characteristics of Alternative
Die Materials for Stamping of Advanced High-Strength Steels (AHSS)
• Wear performances of some
different, uncoated die materials
(AISI D2, Vanadis 4, Vancron 40,
K340 ISODUR, Caldie, Carmo,
0050A)
on DP600 AHSS.
• Hardness is one of the most
important parameters in wear
• plastic squeezing is taken as
more effective than adhesive
wear mechanism for the steel
samples.
O. N. Cora & M. Koc, Experimental investigations on wear resistance characteristics of alternative die materials for stamping of
advanced high-strength steels (AHSS), International Journal of Machine Tools & Manufacture, 2009, 49, pp. 897–905.
16
Effective Parameters on Die Wear - AHSS
5. Evaluation of Tool Materials, Coatings and Lubricants in Forming Galvanized
Advanced High Strength Steels (AHSS)
• the straight oil lubricants and dry film lubricants shows better
performance to reduce galling and interface contamination on the GA
coated sheet with uncoated tools at 170 Mpa
• lubes A and B were successful while sheet specimens coated by other
lubes were fractured during deep drawing
• TiCN coating showed the best effectiveness in reducing galling under all
test conditions.
H. Kim, S. Han, Q. Yan and T. Altan, Evaluation of tool materials, coatings and lubricants in forming galvanized advanced
high strength steels (AHSS), CIRP Annals-Manufacturing Technology, 2008, 57, pp. 299–304.
17
Effective Parameters on Die Wear - AHSS
6. Investigation of Die Radius Arc Profile on Wear Behaviour in Sheet
Metal Processing of Advanced High Strength Steels
• The profile of the draw die radius has a significant effect
• Using a combination of circular high elliptical curved geometries can
achieve a low contact pressure distribution and lower corresponding
wear
X. Z. Wang, S. H. Masood, Investigation of die radius arc profile on wear behaviour in sheet metal processing of advanced high
strength steels, Materials and Design, 2011, 32, pp.1118-1128.
18
Effective Parameters on Die Wear - AHSS
7. The Effect of the Die Radius Profile Accuracy on Wear in Sheet Metal Stamping
• The small variations
a shape inherent variations associated with the machining
• Grinding and polishing processes typically used to manufacture stamping dies and
die corner inserts.
• Small shape defects at the die corner radius
a significant increase in local contact
pressure, explaining the large adverse changes in tool life.
M. P. Pereira, M. Weiss, B. F. Rolfe and T. B. Hilditch, The effect of the die radius profile accuracy on wear in sheet metal
19
stamping, International Journal of Machine Tools & Manufacture, 2013, 66, pp. 44–53.
Summary and Conclusion
1. Objectives; realizing the effective parameters on die wear in stamping of AHSS, How
to improve the wear resistant performance by tool material, coating, lubricant, ….
2. Tool materials should be selected by considering the most concerned failure mode.
3. The proper coating with a low coefficient of friction is crucial to reduce galling and
tool wear.
4. The tool’s surface quality affects galling and a smooth die material is highly
recommended for stamping AHSS.
5. The profile of the draw die radius has a significant effect on the wear distribution.
6. Local contact pressure between the sheet and tool affects all types of tool failure. As
stamping of AHSS requires increased contact pressure, the probability to observe
tool wear and galling increases significantly.
7. Forming AHSS requires better-performing lubricants, possibly with extremepressure (EP) additives.
20
Thanks for Your
Attention