M42 High Speed Steel

M42 high speed steel tool bits are supplied in flats, squares and rounds. Commonly supplied in standards sizes though non standard metric and imperial sizes can be produced within a few weeks, subject to availability of suitable raw material.

Pre heat the M42 high speed steel slowly and uniformly to 650-760°C and equalise. Then increase more quickly to the forging temperature of 1010-1150°C and equalise prior to forging. Do not allow the forging temperature to drop below 980°C, if this occurs re heating will be necessary. Always cool the high speed steel very slowly after forging.

Annealing of M42  is recommended after hot working and before re hardening. Heat the M42 high speed steel to 850°C at a rate of no more than 220°C per hour. Always hold at temperature for one hour per 25mm of thickness (with two hours being minimum). Furnace cool slowly. The M42 annealed hardness achieved should be 269 Brinell or lower.

If tools produced from M42 high speed steel are heavily machined or ground it is recommended to stress relieve after machining and prior to hardening to minimise the possibility of distortion. To stress relieve heat the component to 600-650°C and soak well (approximately two hours) Cool slowly in the furnace. The M42 tools can be finish machined before heat treatment.

For best results harden the M42 in a vacuum or controlled furnace, or in a properly rectified salt bath. Pre heat the steel thoroughly to 820-870°C then transfer to the high temperature salt bath or furnace. The exact hardening temperature to use for M42 will depend on the type of work being treated, but in general components should be hardened from the range of 1160-1180°C in salt, or 1180-1190°C in atmosphere or vacuum furnaces. After a short hold at the hardening temperature, quench the component without further soaking into salt at 540-595°C or warm oil. If salt quenched allow the component to equalise at the bath temperature and then complete the quench in still air.

M42 tool steel components can be tempered between 510-595°C. Components require a minimum tempering temperature of 540°C and it is recommended to provide suitable relief to the hardening stresses. Triple tempering is recommended with a minimum of two hours at temperature per cycle. The component should be cooled in still air to room temperature between tempering treatments.