High-Speed Tool Steels
High Speed Steels are a high-performance subset of tool steels, that are able to machine materials at high cutting speeds, thus the name High Speed Steel. This subset of tool steels is characterized high hardness (above 60 Rockwell C) and high wear resistance. The primary alloying elements of high speed steels are a combination of carbon, chromium, vanadium, molybdenum or tungsten, and sometimes cobalt. The main reason cobalt is added in some grades of high speed steel is to increase the hot hardness which increases the cutting efficiency of tools when high temperatures are reached. There are three types of High Speed Steels: Tungsten-type grades (i.e. T1), Molybdenum-type grades (i.e. M2, M4), and Cobalt-type grades (i.e. T15, M42).
High-Speed Tool Steel Grades:
M2 – M4 – M42 – T1 – T15
M2 High-Speed Tool Steel
M2 is a tungsten-molybdenum high speed steel that is characterized by a well-balanced combination of toughness, wear resistance, and red-hardness properties. M2 is one of the most popular and widely used high speed steels in the world because of its exceptional qualities and relative economy.
M4 High-Speed Tool Steel
M4 is a molybdenum-tungsten high speed steel that is characterized by its high abrasion, wear resistance, transverse bend strength, and impact toughness. This specialty high speed steel was developed to have a greater abrasion and wear resistance for high tool life quality and cutting speeds. M4 has a very high carbon and vanadium content that provides it’s a high abrasion and wear resistance. M4 is more difficult to machine in the annealed condition and it is more resistant to grinding in the hardened condition in comparison to other grades. It can be hardened in excess of 65 Rockwell C Hardness (HRC).
M42 High-Speed Tool Steel
M42 is a cobalt-molybdenum super high speed steel that is known for its superior red-hardness in comparison to M2 steel. The addition of cobalt to the composition of M42 provides a good balance of toughness and hardness. M42 high speed steel may be heat treated to (68 – 70 HRC). This grade is an excellent choice for applications that require high red-hardness and is well suited for various cutting tools, milling cutters, twist drills, taps, gear hobs, form tools, thread rolling dies, reamers, saws, knives, broaches, and more.
T1 High-Speed Tool Steel
T1 is the original tungsten-type high speed steel that has a good combination of toughness and red-hardness. It has generally been replaced in most applications by M2 high speed steel.
T15 High-Speed Tool Steel
T15 is a tungsten type super high speed steel that contains vanadium and cobalt. The high content of vanadium provides excellent abrasion and wear resistance. The cobalt content in this grade provides very high resistance to softening at high service temperatures (red-hardness). T15 high speed steel can be heat treated as high as 67 HRC. The properties of this T15 steel allow it to retain its hardness and sharp cutting edges.