Special Requirements of Stamping Die Steel
Stamping dies work under impact, vibration, friction, high pressure, and tensile, bending and torsional loads - sometimes at higher temperatures (such as cold extrusion). Working conditions are complex, and wear, fatigue, fracture and deformation are common failure modes. The requirements for die materials are therefore higher than for general dies, and they differ by die type.
1) Punching Die Material Requirements
For thin-plate punching dies: high wear resistance and hardness.
For thick-plate punching dies: additionally high compressive yield point (to prevent die breakage or collapse), high fracture resistance, high bending strength and toughness.
2) Deep-Drawing Die Material Requirements
The working parts need good anti-adhesion (anti-galling), high wear resistance and hardness, certain strength and toughness, good cutting performance, and small heat-treatment deformation.
3) Cold-Extrusion Die Material Requirements
High strength and hardness, high wear resistance, and certain toughness to avoid impact fracture; because extrusion generates a large temperature rise, the material should also have heat-resistance fatigue strength and thermal hardness.
Types of Stamping Die Materials
Materials for stamping dies include steel, cemented carbide, steel-bonded cemented carbide, zinc-based alloy, low-melting-point alloy, aluminum bronze and polymer materials. Steel-based materials dominate; the commonly used types are:
Carbon tool steel (T8A, T10A): good processing performance and low price, but poor hardenability and red hardness, large heat-treatment deformation and low load capacity.
Low-alloy tool steel (CrWMn, 9Mn2V, 7CrSiMnMoV, 6CrNiSiMnMoV): reduced quenching deformation and cracking, improved hardenability and better wear resistance than carbon tool steel.
High-carbon high-chromium tool steel (Cr12, Cr12MoV, Cr12Mo1V1/D2): good hardenability and wear resistance with very small heat-treatment deformation; carbide segregation is serious, so repeated upsetting forging is needed to improve uniformity.
High-carbon medium-chromium tool steel (Cr4W2MoV, Cr6WV, Cr5MoV): less eutectic carbide, uniform carbide distribution, small heat-treatment deformation and good dimensional stability.
High-speed steel (W18Cr4V, W6Mo5Cr4V2/M2, 6W6Mo5Cr4V): the highest hardness, wear resistance and compressive strength of die steels, with high load capacity; reforming improves carbide distribution.
Matrix steel (6Cr4W3Mo2VNb, 7Cr7Mo2V2Si, 5Cr4Mo3SiMnVAl): high-speed-steel-base compositions with better fatigue strength and toughness at lower material cost - high-strength, high-toughness cold-work die steels.
Cemented carbide (WC-Co): the highest hardness and wear resistance but poor bending strength and toughness; low-cobalt grades for small-impact high-wear dies, high-cobalt grades for larger impacts.
Steel-bonded cemented carbide: powder-metallurgy material with TiC/WC hard phases in a steel binder - machinable, weldable, forgeable and heat-treatable, reaching 68–73 HRC after quenching and tempering.
Frequently Asked Questions
Q: What material is best for a punching die?
A: For thin plates, high-carbon high-chromium steel such as Cr12MoV with high wear resistance; for thick plates, grades with additional fracture resistance and toughness.
Q: Why is Cr12MoV popular for stamping dies?
A: It offers good hardenability, high wear resistance and very small heat-treatment deformation, making it the standard high-wear micro-deformation die steel.
Q: What is the difference between high-speed steel and matrix steel?
A: Matrix steel uses a high-speed-steel base composition with adjusted carbon to improve toughness and fatigue strength while retaining wear resistance, at lower cost.
Q: When is cemented carbide used for dies?
A: For maximum hardness and wear life in small-impact, high-wear applications; for large impacts, choose higher-cobalt grades or steel-bonded carbide for toughness.
