Cold-work steels
Cold-work tool steels are tool steels used for forming materials at room temperature or at slightly raised temperatures (~ 200°C). Specifically, tools for blanking metallic and non-metallic materials, including cold-forming tools, are manufactured from these steels.
Fundamentally, cold-work tool steels are high carbon steels (0.5-1.5%). The water-quenched W-grades are essentially high carbon plain carbon-manganese steels. Steel grades of the O series (oil-hardening), the A series (air-hardening), and the D series (high carbon-chromium) contain additional alloying elements that provide high hardenability and wear resistance as well as average toughness and heat softening resistance.
The four major alloying elements in such tool steels are tungsten, chromium, vanadium, and molybdenum. These alloys increase the steels’ hardenability and thus require a less severe quenching process with a lower risk of quench cracking and distortion. All four elements are strong carbide formers, also providing secondary hardening and tempering resistance.
| Defining property | AISI-SAE grade | Significant characteristics |
|---|---|---|
| Water-quenched | W | Molybdenum alloying optional |
| Cold-working | O | Oil-hardening, O6-0.3% molybdenum, cold-work steel used for gauges, cutting tools, woodworking tools and knives |
| A | Air-hardening, low distortion during heat treatment, balance of wear resistance and toughness, all molybdenum alloyed – 0.15-1.8% | |
| D | High carbon, high chromium, 0.9% molybdenum, very high wear resistance but not as tough as lower alloyed steels | |
| Hot-working | H | H1-H19 – chromium base H20-H39 – tungsten base H40-H59 – molybdenum base |
| Plastic moulding | P | Low segregation: reduced alloying of silicon, manganese and chromium Through hardenability: increased molybdenum and vanadium |
| High-speed | T | Tungsten base (today mostly replaced by M22) |
| M | Molybdenum base | |
| Shock resisting | S | Chromium-tungsten, silicon-molybdenum, silicon-manganese alloying, very high impact toughness and relatively low abrasion resistance |
| Special purpose | L | Low alloy, high toughness |
| F | Carbon-tungsten alloying, substantially more wear resistant than W-type tool steel |
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