Tool Steel
Tool steels are high-carbon alloy steels that can be hardened to around 55–65 HRC for dies, punches, moulds, cutting tools and wear parts. Main groups include cold-work (D2, O1), hot-work (H13) and plastic mould (P20) steels.
What it is
Cold-work steels like D2 (high chromium) give excellent wear resistance for blanking dies and shear blades; O1 is an oil-hardening general tool steel. Hot-work steels like H13 keep hardness at high temperatures for forging and die-casting dies. P20 is supplied pre-hardened for plastic moulds.
Parts are usually rough machined in the annealed state, hardened and tempered, then ground or wire-cut to size.
Typical applications
- Press tools, punches and dies
- Plastic injection moulds
- Forging and die-casting dies
- Shear blades and knives
- Gauges and wear parts
Materials & grades
- D2 / D3 (cold work)
- O1 / OHNS (oil hardening)
- H11 / H13 (hot work)
- P20 (pre-hardened mould steel)
- A2, S7 (shock resistant)
Points to consider
- Machine before hardening; finish by grinding or EDM after.
- Leave allowance for heat-treatment distortion.
- Choose grade by wear, toughness and temperature needs.
- Stress relieve after heavy roughing on large dies.
Frequently asked questions
What is the best tool steel for punches and dies?
D2 is widely used for wear resistance in cold-work dies; A2 or S7 offer more toughness where chipping is a problem.
What is OHNS steel?
Oil Hardening Non-Shrinking steel, equivalent to O1, a general-purpose tool steel for gauges, punches and dies.
Can tool steel be machined after hardening?
Only by grinding, hard milling or EDM; conventional machining is done in the annealed state.