Tooling Steel for Advanced Stamping

& Forming Applications

Blanking AHSSAdvanced high strength steels (AHSS) are work materials with tensile strengths ranging from 500-1600MPa (72-232ksi). Tool-ing for AHSS have some of the highest demands of any blanking application. These high demands on tooling cause premature wear, chipping, galling and plastic deformation. In order to pro-long tooling life with high hardness and high strength steel, it is essential that advanced tooling materials are used.

Types of AHSSTransformation Induced Plasticity (TRIP): Tensile strengths are typically between 500-1000MPa (72-145ksi) and are the first generation of AHSS. Of the current AHSS, these have the best formability because they increase in strength as they are formed/stretched. TRIP steels consist of retained austenite, martensite, banite and ferrite. The retained austenite transforms into marten-site during the forming process, increasing the strength as the material is stretched.

Dual Phase (DP): Tensile strengths are typically between 500-1,000MPa (72-145ksi). The microstructure consists of two phases: one being ferrite and the other being martensite. Ferrite is a soft phase that has good formability. Martensite is a hard phase that gives the material its strength and hardness.

Martensitic (M): Tensile strengths are typically up to 1,600MPa (232ksi). The microstructure consists of martensite. Martensite is a hard phase that gives the material its strength and hardness. These grades are difficult to process. High strength steels have similar chemistries to carbon steels that are currently being used. Martensitic steels are produced by transforming the austenite phase by rapid quenching to martensite.

Second and Third Generation Work Materials: The second generation work materials include twinning- induced plasticity (TWIP), light weight induced plasticity (L-IP) and austenitic stainless steel (AUST SS). These alloys have excellent material characteristics, but the alloying elements can make the grades more costly. Finally, the third generation is the newest of the advanced steels, and are currently under development. These grades will improve the ductility of the first generation, and be more affordable than second generation alloys.

2.0 14-16% 14-16% 14% 12-14% 0.08”

1.5 14% 12-14% 12-14% 12% 0.06”

1.0 12-14% 12% 10-12% 10-12% 0.04”

0.5 12% 10-12% 10% 10% 0.02”

DP 800MPa

(116 KSI)

DP 1,000MPa

(145 KSI)

DP 1,200MPa

(175 KSI)

M 1,400MPa

(203 KSI)

Sheet MaterialThickness (mm)

Sheet MaterialStrength(ksi)

General Die Clearance for AHSS General Tooling Materials for Blanking AHSS

1200-1400 Caldie, Vanadis 4 Extra, Vanadis 8,

S693 Microclean, K294 Microclean

Caldie, Vanadis 4 Extra, Vanadis 8,

S390 Microclean, S693 Microclean

174-203

800-1200 Vanadis 4 Extra, Caldie, K340 Isodur / Sleipner,

S693 Microclean,K294 Microclean

Vanadis 4 Extra, Caldie, K340 Isodur / Sleipner,

S693 Microclean

116-174

500-800 Vanadis 4 Extra, Caldie, K340 Isodur /Sleipner,

S693 Microclean,K294 Microclean

Vanadis 4 Extra, Caldie, K340 Isodur / Sleipner,

S693 Microclean

72-116

<1.5 mm(<0.06”)

>1.5 mm(>0.06”)

Sheet MaterialStrength (ksi)

Sheet MaterialStrength (MPa)

General Tooling Discussion:The most common tooling material for cold work applications is D2. When working with AHSS, D2 can prematurely chip or wear, decreasing production performance. When working with AHSS, a good starting point to replace chipping or wearing D2 is BOHLER K340 ISODUR or Uddeholm Sleipner. When chip-ping resistance and more wear resistance is needed, the best option is powder metallurgy (PM) tool steel grades Uddeholm Vanadis 4 Extra SuperClean or Uddeholm Vanadis 8 SuperClean. In applications where gross chipping and cracking are the major failure, Uddeholm Caldie is an excellent choice. These newly de-veloped grades are thermally processed to provide better stabili-ty under pressure than older alloys.

Tooling Solutions for Blanking AHSSIn the table on the lower right are general tooling material recom-mendations for various strengths and thicknesses of AHSS. As the sheet material strength and thickness increases, the wear on the tooling material will also increase. The tooling material’s hardness is also very important. It needs to be high enough to resist plastic deformation, but not so high as to cause premature chipping or cracking. In general, as a starting point, we recommend a hard-ness of 58-62 HRC.

In the table on the lower left are some general guidelines for die clearances with AHSS. A good starting point for most high strength sheet materials is 10-12% die clearance.

Surface treatments are also a topic of discussion when blanking AHSS. In our experience if adhesive wear and galling are domi-nant the work material is usually below 1,000MPa (145ksi). In such cases, surface treatments can be considered. On the other hand, for sheet materials over a strength of 1,000MPa, galling is not as dominant as chipping. If chipping of the tool steel substrate takes place, surface treatments will not offer any improvement in perfor-mance.

Blanking HSLA

Forming AHSS and HSLA

Typical yield strengths of High Strength Low Alloy HSLA sheet steel are 300-800MPa (43-116ksi). These materials get their strength from small additions of elements like niobium and titani-um. HSLA work materials have a tendency to cause premature chipping, wear and galling of tooling materials.

GeneralIt is common to find HSLA work materials in a wide variety of thickness ranging from 1mm-11mm (0.04”-0.43”). When work-ing with HSLA work materials, D2 can prematurely chip or wear decreasing production performance. A good starting point to re-place chipping or wearing D2 is BOHLER K340 ISODUR. For longer production runs where resistance to chipping and wear is needed, the best alternative is powder metallurgy (PM) tool steel Uddeholm Vanadis 4 Extra SuperClean or Uddeholm Va-nadis 8 SuperClean. In applications with thick HSLA work ma-terial where gross chipping and cracking are the major failure, Uddeholm Caldie is an excellent choice. In the table that follows are general recommendations for tooling materials when work-ing with HSLA work materials. As with AHSS, sheet material strength, thickness and length of production run are important information to know when choosing your tooling mate-rial. HSLA work materials increase the wear on tooling materials.

This increased wear is caused by the hardness and strength of the work material. With thinner sheets of HSLA more convention-al tooling materials can be used. As thicker work material is used, more advanced tooling materials are needed. Typical working hardness for tooling materials should be 55-62 HRC. With high strength low alloy work materials, galling and adhesive wear can be a more common failure. In order to help combat galling and adhesive wear surface treatments can be used.

These are only intended for general recommendations; for com-plete recommendations please contact the Bohler-Uddeholm Technical Support Department.

In general, forming AHSS and HSLA work materials is more difficult than mild steels. Despite the high strength of AHSS and HSLA work materials the formability is relatively good. Some of the concerns with forming AHSS and HSLA work materials are spring back, excessive tooling wear, galling and part surface finish.

Tooling Solutions for Forming AHSS and HSLA Work MaterialsTo help reduce galling and poor part surface finish, most form sections receive a surface treatment and highly polished sur-face. An ideal surface roughness would be 2 µm (79 µin) on working surfaces. Surface treatments can be CVD (chemical vapor deposition), PVD (physical vapor deposition), nitriding or duplex surface treatment. Duplex surface treatments are a combination of two coatings, for example, nitriding and PVD coating. It is important to have a quality substrate when using surface treatments. The tooling materials should have a reduced amount of non-metallic inclusions (high cleanliness, to reduce stress risers), good hardenability, dimensional stability during surface treatment, and retention of hardness after surface treat-ing. Tooling materials to replace D2 are: BOHLER K340 ISODUR / Uddeholm Sleipner for improved chipping resistance and re-duced scoring, Uddeholm Caldie for high toughness and high hardness substrate material, and Uddeholm Vanadis 4 Extra SuperClean as a high toughness material for forming sections.

Where high abrasive wear resistance is required, Uddeholm Vanadis 8 SuperClean excels. Severe galling can be remedied with Uddeholm Vancron 40 SuperClean, a nitride containing PM steel with superior galling resistance.

General recommendations on tooling materials for forming are listed below. For long run tooling, Physical Vapor Deposition (PVD) coatings should be considered as well as tooling materials with very low coefficients of surface friction. Uddeholm Vancron 40 SuperClean because of its low coefficient of surface friction and superior anti-galling properties can be used uncoated. Also, testing has shown that just a nitride layer is not sufficient for long run tooling, although using a nitride layer as a base for PVD sur-face treatment can in some cases help improve the performance of the tooling.

General Tooling Materials for Blanking

300-600 Bohler-Uddeholm S7 MQ / Compax Supreme,

A2 or D2, W360 Isobloc, Caldie, K340 Isodur / Sleipner

S693 Microclean, Vanadis 4 Extra, Vanadis 8

K294 Microclean

Caldie, K340 Isodur / Sleipner,

S693 Microclean, Vanadis 4 Extra, Vanadis 8

K294 Microclean

43-87

<1.5 mm(<0.06”)

>1.5 mm(>0.06”)

Sheet Thickness

Sheet MaterialStrength (ksi)

Sheet MaterialStrength (MPa)

General Tooling Materials for Forming AHSS

800-1400 (116-203 KSI)

Caldie, Vanadis 4 Extra, Vanadis 8, S693 Microclean, Vancron 40, K340 Isodur/ Sleipner

570-800 (83-116 KSI)

Caldie, Vanadis 4 Extra, S693 Microclean, Vancron 40, K340 Isodur / Sleipner, AISI D2

330-570 (48-83 KSI)

Caldie, Vanadis 4 Extra, S693 Microclean, Vancron 40, K340 Ecostar/Isodur, AISI D2, AISI A2

Sheet MaterialStrength (MPa)

PVD

Failure Mechanisms for Advanced Stamping and Forming ApplicationsChipping: The most common failure mechanism with blanking AHSS. Chipping is related to the stresses in the process and the fatigue resistance of the tooling material.

Wear: Results in a material loss on the tooling material and is related to the tooling materials hardness, carbide type and volume. Wear can also be related to the sheet material type, the application and the process conditions.

Plastic Deformation: Occurs if the process stresses are higher than the compressive strength of the tool steel.

BOHLER W360 ISOBLOC 52-58

BOHLER K340 ISODUR / Uddeholm Sleipner 58-63

Uddeholm Caldie 58-62

Uddeholm Vanadis 4 Extra SuperClean 58-64

BOHLER S693 MICROCLEAN 58-64

BOHLER K294 MICROCLEAN 58-64

Uddeholm Vanadis 8 SuperClean 58-64

BOHLER S390 MICROCLEAN 58-67

Uddeholm Vancron 40 SuperClean 58-64

BOHLER UDDEHOLM A2 56-60

BOHLER UDDEHOLM D2 58-62

Uddeholm Compax Supreme /

BOHLER UDDEHOLM S7 MQ

50-56

Cracking: Occurs when process stresses are higher than the tensile strength and/or fatigue strength of the tooling material.

Galling: Is a physical and/or chemical adhesion of the work material to the tool surface. The severity of galling depends on the surface finish and chemical compositionof the tool steel and work material.

Properties Comparison of Tooling Materials for Advanced Stamping and Forming Applications

For additional information please contact the Bohler-Uddeholm Technical Support Departmentby calling (800) 638-2520.

info@bucorp.com www.bucorp.com

Tooling Materials

Uddeholm Compax Supreme / BOHLER-UDDEHOLM S7 (MQ): A high quality conventionally produced S7. High toughness, medium wear resistance. Typical working hardness 50-56 HRC.

BOHLER W360 ISOBLOC®: An ESR produced high toughness, medium wear resistance tool steel. Typical working hardness is 52-58 HRC obtained by high temperature tempering.

Uddeholm Caldie®: An ESR produced high toughness medium wear resistance tool steel. Typical working hardness is 58-62 HRC obtained by high temperature tempering. Readily weldable with matching filler rods available.

BOHLER K340 ISODUR® / Uddeholm Sleipner®: Medium toughness, good wear resistance 8% Chromium alloy tool steel. Typical working hardness of 58-63 HRC is obtained by high temperature tempering. ISODUR is ESR remelted.

Uddeholm Vanadis® 4 Extra SuperClean: High toughness with good wear resistance PM tool steel. Excellent when work material is thicker and gummier. Typical hardness range is 58-64 HRC obtained by high temperature tempering.

Bohler-Uddeholm Tooling Materials

Uddeholm Dievar®

Uddeholm Orvar® Superior (PREMIUM H13)

Uddeholm Compax Supreme / BOHLER-UDDEHOLM S7 (MQ)

Uddeholm Caldie®

Uddeholm Vanadis® 4 Extra SuperClean

BOHLER S693/S692 MICROCLEAN® (PM M4)

BOHLER S390 MICROCLEAN®

BOHLER K294 MICROCLEAN® (PM A11)

AISI 01

AISI A2

AISI D2

BOHLER K340 ISODUR®

Uddeholm Sleipner®

Conventional Steels

ESR/P-ESR Steels

PM – Cold Work Tool Steels

PM – High Speed Steels

Chi

ppin

g R

esis

tanc

e

Abrasive Wear Resistance

AISI M2

BOHLER W360 ISOBLOC®

Uddeholm Vanadis® 8 SuperClean

BOHLER S693 MICROCLEAN®: Medium toughness with good wear resistance PM M4 high speed steel. Typical hardness range is 58-64 HRC obtained by high temperature tempering.

BOHLER K294 MICROCLEAN®: Our PM A11 (10% Vanadium) tool steel with excellent wear resistance. Typical hardness range is 58-64 HRC obtained by high temperature tempering.

Uddeholm Vanadis® 8 SuperClean: Excellent combina-tion of toughness and wear resistance. Replaces PM M4 and PM A11 alloys. Hardness 58-64 HRC.

Uddeholm Vancron® 40 SuperClean: A PM tool steel with excellent resistance to galling and adhesive wear. Excellent machinability. Typical hardness range is 58-64 HRC.

BOHLER S390 MICROCLEAN®: A Modified PM T15 high speed steel with excellent compressive strength for fine blanking and stamping of high hardness work material. Steel can be hardened to 67 HRC.

MATERIALIZING VISIONS © 2014, Bohler-Uddeholm Corporation

Double Melt Metallurgy: The second melt in double melt metallurgy is Electro-Slag Remelting (ESR). A benefit of this process is the breaking down of the carbide structure, which improves chipping resistance in grades containing primary carbides. Another benefit is improving cleanliness, which also improves the chipping resistance and fatigue strength.

Powder Metallurgical Tool Steels: Powder Metallurgy (PM) has been around for numerous decades. PM offers small evenly distributed carbides because of the rapid cooling. Through continuous improvement of the process, the reduction of Non-Metallic Inclusions (NMI) has helped improve chipping resistance, which for high strength work materials improves tooling performance.

Advanced Tool Steel Production Techniques

MATERIALIZING VISIONS © 2017, Bohler-Uddeholm Corporation

TOOLING STEEL FOR ADVANCED STAMPING & FORMING APPLICATIONS

Bohler-Uddeholm Corporation2505 Millennium Drive, Elgin, IL 60124

info@bucorp.com www.bucorp.com (800) 638-2520

This information is based on our present state of knowledge and is intended to provide general notes on our products and their uses. It should not therefore be construed as a warranty of specific properties of the products described or a warranty for fitness for a particular purpose. Rev. May 15, 2017. BU-B007