What is High Speed Steel?

What is High Speed Steel?

High Speed Steel (HSS or HS) is a subset of tool steels, commonly used in tool bits and cutting tools.

HSS steel is often used in power-saw blades and drill bits. It is superior to the older high-carbon steel tools used extensively through the 1940s in that it can withstand higher temperatures without losing its temper (hardness). This property allows High Speed Steel to cut faster than high carbon steel, hence the name high-speed steel. At room temperature, in their generally recommended heat treatment, High speed steel grades generally display high hardness (above HRC60) and abrasion resistance (generally linked to tungsten and vanadium content often used in HSS) compared with common carbon and tool steels.

The heat treatment used is also a major component of what defines high speed steel, as its martensitic structure contributes to its high hardness. This is achieved by austenizing to nearly the steel’s melting temperature, then quenching in a salt bath or by air cooling and multiple tempering cycles to convert any remaining austenite to martensite.

HSS describes multiple alloys, these traits are common to all of them:

High alloy content, primarily tungsten or molybdenum, with lesser amounts of chromium, vanadium and cobalt;

High carbon content—a minimum of 0.65% by weight, but commonly anywhere from 0.8% to 1.5% carbon content;

Rockwell hardness of at least 64 HRC at room temperature;

A heat treatment process that produces a high quantity of complex metallic carbides—chiefly tungsten, molybdenum and vanadium carbides—suspended in a steel substrate, which results in hardness and wear resistance.