Tool STEEL (High alloy steels)
What is Tool Steel?
Alloy steels are divided into two main classes:
- Low-alloy steel – With a total of less than 5% of alloying elements.
- High-alloy stee – With a total of more than 5% of alloying elements.
- The 5% mark is not a formal standard. Some publications mark the crossover at 8%.
In “real life”, people refer to “Low-alloy steel” as “Alloy steel” and to High-alloy steel” as “Tool steel”. The nickname tool steel comes from the fact that the primary usage of this material group is the production of cutting, pressing, extruding tools, and other tools.
Pros and cons of Tool Steel (Compared to alloy steel)
- Besides the additional quantity of alloying elements, tool steel alloys also have a much higher carbon content. Alloy steels have between 0.2 and 1.0% of carbon, while tool steels usually have 1%-2%. You can learn more about the influence of carbon in our article about carbon steel.
- Higher-strength: A strong alloy steel like SAE 4340 has a tensile strength of 10,800 psi (745 Mpa), while a common tool steel alloy such as O1 has 26,100 psi (1,800 Mpa). An advantage of 240%. And there are also tool steel alloys that come close to 50,000 psi (3000 Mpa)
- Better hardenability: Tool Steel alloys can reach higher hardness levels after heat treatment and thus have better wear resistance.
- Higher price.
- Lower machinability of 20-45% compared with alloy steels having a machinability range of 40-75%. Learn more about tool steel machinability here.
- Lower cutting speeds increase the final product cost due to slower cycle times.
Tool Steels Classification
|A2-A10||Air-hardening, cold-work steels||Carbon content of 0.7-1.25% leads to lower machinability||30-40%|
|O1-O7||Oil-hardening cold-work steels||Carbon content of 1-1.5% leads to lower machinability||30-40%|
|D2-D7||High-carbon, high-chromium, cold-work steels||Very high Carbon content of 1.5-2.5% leads to poor machinability||20-30%|
|H10-H19||Chromium hot-work steels||Medium Carbon content around 0.4% with Chromium around 5%||50-60%|
|M1-M62||Molybdenum based high-speed steels||Molybdenum 5-10% / Tungsten 2-10%||20-40%|