English Audio Request

High-speed steel tools are so named because they were developed to cut at higher speeds. First produced in the early 1900s, high-speed steels are the most highly alloyed of the tool steels. They can be hardened to various depths, have good wear resistance, and are relatively inexpensive. Because of their toughness and high resistance to fracture, high-speed steels are especially suitable for high positive rake-angle tools (those with small included angles), for interrupted cuts, and for machine tools with low stiffness that are subject to vibration and chatter.
There are two basic types of high-speed steels: molybdenum (M series) and tungsten (T series). The M series contains up to about 10% molybdenum, with chromium, vanadium, tungsten, and cobalt as alloying elements. The T series contains 12% to 18% tungsten, with chromium, vanadium, and cobalt as alloying elements. The M series generally has higher abrasion resistance than the T series, undergoes less distortion during heat treating, and is less expensive. Consequently, 95% of all high-speed steel tools are made of M-series steels.
High-speed-steel tools are available in wrought, cast, and sintered (powder-metallurgy) forms. They can be coated for improved performance. High-speed-steel tools may also be subjected to surface treatments, such as case hardening for improved hardness and wear resistance or steam treatment at elevated temperatures to develop a black oxide layer for improved performance - for instance, to reduce built-up edge formation.
High-speed steels account for the largest tonnage of tool materials used today, followed by various die steels and carbides. They are used in a wide variety of cutting operations requiring complex tool shapes, such as drills, reamers, taps and gear cutters. Their most important limitation is the cutting speeds that can be employed, which are low relative to those of carbide tools.