Selection of Tool Steel for Compound Dies
In metal fabrication, a compound die performs multiple cutting operations—typically blanking and piercing—in a single press stroke at one station. Because cutting and slug discharge occur simultaneously, wear is concentrated at cutting edges and along the material flow path, making edge durability the dominant factor in tool life.
These dies operate under cold-working conditions (generally below 200°C), where failure is driven by mechanical load rather than thermal effects. Tool life is primarily governed by abrasive wear from inclusions or scale and adhesive wear (galling) from metal-to-metal contact. As a result, material selection should focus on edge retention and resistance to chipping, rather than hot hardness or thermal fatigue.
Selection Factors
Material selection for compound dies should be guided by the dominant failure mode rather than by general property rankings.
Wear resistance versus toughness defines the primary trade-off. High wear resistance, achieved through high hardness and carbide content, is required to maintain sharp edges in long production runs. However, increased carbide volume reduces toughness, raising the risk of edge chipping or cracking. This balance must be adjusted based on material thickness and edge geometry: thicker sections and complex punches shift the requirement toward toughness, while thin, high-volume stamping favors wear resistance.
Dimensional stability during heat treatment is a practical constraint. Compound dies rely on tight clearances, and distortion directly affects cutting accuracy and tool life. Air-hardening steels are generally preferred because they reduce quenching stress and minimize dimensional change compared to oil-hardening grades.
Working hardness typically ranges from 56 to 62 HRC. At lower hardness, edges deform under load; at higher hardness, brittle failure becomes more likely. The optimal hardness depends on whether the dominant failure mode is wear or chipping.
Recommended Tool Steels
AISI D2 Tool Steel |1.2379 | SKD11
D2 is selected when wear is the primary limiting factor. Its high chromium carbide content provides strong resistance to abrasive wear and edge rounding, making it suitable for long production runs. Its lower toughness limits its use in thick-section cutting or fragile geometries where chipping is likely.
Typical hardness: 58–62 HRC.
Best suited for high-volume production where edge wear dominates.
AISI A2 Tool Steel | 1.2363 | SKD12
A2 provides a balanced combination of wear resistance and toughness. Compared to D2, it offers better resistance to chipping while maintaining adequate wear performance. It is commonly used when both wear and fracture risks are present.
Typical hardness: 57–60 HRC.
Best suited for general-purpose compound dies with moderate-to-high production volumes.
AISI S7 Tool Steel Supplier | DIN 1.2355
S7 is used when fracture is the primary failure mode. Its high impact toughness reduces the risk of catastrophic cracking in thick materials or fragile punch sections. However, its lower wear resistance results in faster edge wear.
Typical hardness: 54–58 HRC.
Best suited for heavy-gauge materials and high-impact conditions.
AISI O1 Tool Steel | 1.2510 | SKS3
O1 is used where cost control is more important than maximum tool life. It provides acceptable hardness and edge retention for simpler applications, but its lower wear resistance and higher risk of distortion limit its use in precision or high-volume dies.
Typical hardness: 58–60 HRC.
Best suited for short runs and low-complexity tooling.
Summary Table
| Tool Steel Grade | Primary Attributes | Typical Hardness | Best Application |
| AISI D2 | High wear resistance; high carbide content | 58–62 HRC | High-volume production |
| AISI A2 | Balanced wear resistance and toughness | 57–60 HRC | General-purpose dies |
| AISI O1 | Economical; moderate performance | 58–60 HRC | Short runs; simple tools |
| AISI S7 | High impact resistance | 54–58 HRC | Thick materials; high shock |