Tool Steels are a variety of alloy steels with carbon (generally between 0.5% to 1.5%) that are very well suited to make tools. The major alloying elements they may contain are Tungsten, Molybdenum, Vanadium, Chromium , Cobalt among others, together or in different combination. They offer the required degree of hardness, resistance to abrasion and deformation and the ability to hold cutting edge even at high temperatures. As a result tool steels are suited for their use in the shaping of other materials.
High-speed steel (HSS or HS) is a subset of tool steels, commonly used in tool bits and cutting tools. T-type and M-type tool steels are used for cutting tools when strength and hardness must be retained at high temperatures.
| M | M1, M7, M10 | Molybdenum |
| M30, M33, M34, M42, M43, M46, M47 | Molybdenum, Cobalt | |
| M2, M3, M4 | Molybdenum, Tungsten | |
| M6, M15, M35, M36< M41, M44, M45 | Molybdenum, Tungsten, Cobalt | |
| T | T1, T2, T3, T7, T9 | Tungsten |
| T4, T5, T6, T8, T15 | Tungsten, cobalt |
This is a group of three tool steels: oil-hardening, air-hardening, and high carbon-chromium. The steels in the group have high hardenability and wear resistance, with average toughness.
| A | A2-A10 | Air hardening, Medium alloys |
| D | D2-D7 | High carbon, high chromium |
| O | O1 – O7 | Oil hardening, Low carbon |
H-group tool steels were specifically developed to maintain strength and hardness while exposed to prolonged elevated temperatures. H-group tool steels were developed for strength and hardness during prolonged exposure to elevated temperatures.
H1 to H19 are based on a chromium content of 5%
H20 to H39 are based on a tungsten content of 9-18% and a chromium content of 3–4% H40 to H59 are molybdenum based.
| H | H 10, H11, H12, H13 | Chromium, Molybdenum |
| H14, H16, H19, H23 | Chromium, Tungsten | |
| H20, H21, H22, H24, H25, H26 | Tungsten | |
| H15, H41, H42, H43 | Molybdenum |
P-type tool steel is short for plastic mold steels. Common steel grades like P20, 420 etc. S-type tool steel is an air or oil hardened Shock resistant toolsteel.
| S | S1, S3 | Tungsten |
| S2, S4, S5, S6 | Silicon | |
| S7 | Chromium | |
| P | P1- P20, P21 | Low carbon mold steel |
