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O1 Tool Steel Heat Treatment Information

We often get asked for some heat treatment information to be supplied with our Ground Flat Stock and Gauge Plate, and while the basics are supplied on the labels with the dimensions and cast numbers, we thought it may help if we did a more in depth guide! And don't forget, we always like to see what you have made from our ground flat stock and gauge plate!


Working and Heat Treatment:-

Forging. Heat slowly and begin forging at 980/1000 degrees centigrade. Do not allow temperature to fall below 800 degrees centigrade re-heating if necessary. Annealing will be necessary after forging.

Annealing. All of our Ground Flat Stock and Gauge plate is supplied in the annealed machinable condition. Re-annealing will only be necessary it the steel has been forged by the tool maker. To anneal, heat slowly and uniformly in a closed box or tube to 740/760 degrees centigrade. Maintain at the temperature and allow to cool with the furnace until the temperature falls below 500 degrees centigrade. Withdraw from box or tube and allow to cool in air to shop temperature. Annealed hardness will be in the region of 229 Brinell.

Stress Relieving. When tool are heavily machined, ground or subjected to cold work, the relief of the internal strains is essential before hardening. Stress relieving should be done after rough machining. To stress relieve, heat carefully to 670/700 degrees centigrade. Soak well and to cool in air. The tool may then be finish machined before hardening.

Hardening. Heat slowly and if possible pre-heat at 300/500 degrees centigrade before raising to the hardening temperature of 780/820 degrees centigrade. Pre-heating is especially desirable for complex sections. Soak thoroughly, allowing 30 minutes per inch of ruling section before quenching. Light sections should be quenched in oil from the lower end of the hardening range. Long slender sections should always be suspended in the furnace for heating and quenched by plunging vertically into the oil bath. Tempering is always needed after hardening.

Tempering. Temper between 150 and 350 degrees centigrade according to the requirements of the job and by reference to the tempering curve. Soak for one hour at the tempering temperature. Where possible, use an air-circulating furnace.