Die Steel Improvements for AHSS Applications

HITACHI Intro

? Steel Production Methods for Die & Tooling Steels

? Typical Failure modes of Die Steels for AHSS

? Solutions to improve Tooling Performances

?Steel Types, Coatings

? Hot Stamping Die Steels

? Pre Hardened Die Steels

? Grain Oriented Die Steel Study

Ask Your Tool Steel supplier……

? Test Certifications (actuals from Mill Source )

? Method of Manufacturing

? Forged, Rolled , etc.

? Recommended Heat Treat

Surface Coating advancements have greatly improved steel performances.

Part material

? Aluminum or Steel: What type & thickness?

? Press Size (Servo or Mechanical) & Strokes per minute cycle

? Current Die Construction

? Progressive or Transfer?

? Castings? Inserts?

? Tooling steels used ?

? What coating?

? Die Clearance

? Heat Treating Recipe

? Welding (In House? Outsource? Consumable used?)

? Failure Observations: What Happened?

? What's been tried so far?

Coarse & directional carbide

? Large & anisotropic deformation after heat treatment

? Medium galling & wear resistance

? Characteristics will be affected by grain direction Small, dense & homogeneous carbide

? Small & isotropic deformation after heat treatment

? Same HT & Chem as D2

? Good galling & wear resistance

? Achieve higher hardness than

Machining of Pre-Hard Tool Steels @ 60 HRC

? 1) Machine Tool

? Rigid Construction:

? High Spindle Speed:20,000+

? 2) Cutting Tool

? Solid Carbide with ductile properties for interrupted cut

? 3) Consistent substrate of Die Steel

? Demands on Die Materials

?Wear

?Conductivity

?Watch for industry developments on 3D Additive Mfg. inserts w/ conformal cooling lines

? Use of higher alloyed Die Steel

?  Upgrade to a NADCA Class C Hot Work Steel in place of AISI H13

1. Conductivity

? Class B H13 is 32.6 @ 600C  Class C is 35.8 @ 600C

? Better for heat conductivity than H13 means better cycle times .

2. Toughness:

? Why? Higher Impact Values (charpy) prevent cracking on the surface of Hot Stamping Dies close to the cooling channel .

3. Wear:

? Why? NADCA Class C ( HITACHI DAC-MAGIC ) is higher strength under high temperature. Diesurfaces can reach ~ 400C & higher alloyed steels are needed to extend wear.

4. Coatablity

? Coatable and Wear resistance at room temperature, almost same as H13.

? Review Die Standards & allow for areas requiring better tooling steels in trouble-spots

? Compare results with other steels in side by side like- environments

? Insist on controlled HT path & Welding steps

? Ask for grain orientation on larger cross sections

? “If you can’t use a better tool steel, use your tool steel better”