How to Heat-treat SAE 4130 Alloy Steel?

SAE 4130 is the SAE-AISI designation for this material. Equivalent to 1.7218, 25CrMo4 and SCM430. It is widely used for a variety of applications in the oil and gas sector. Typical applications include components such as valve bodies, pumps and fittings.
As for heat treatment, the heat treatment temperatures, including rate of heating, cooling and soaking times will vary due to factors such as the shape and size of each component. Other considerations during the heat treatment process include the type of furnace, quenching medium and work piece transfer facilities.
Forging: Preheat carefully, then raise temperature to 950-1200°C for forging. Do not forge below 950°C.
Annealing: Heat the SAE 4130 slowly to 850°C and allow enough time for the steel to be thoroughly heated. Cool slowly in the furnace to 480°C followed by air cooling.
Hardening: SAE 4130 steel is usually supplied ready heat treated with a hardness of 18-22HRC. If further heat treatment is required annealed SAE 4130 should be heated slowly to 870-890°C and after adequate soaking at this temperature quench in oil. Temper as soon as tools reach room temperature.
Tempering: Heat carefully to a suitable temperature selected by reference to a tempering chart or table (usually between 400-570°C, soak at the temperature for 2 hours per 25mm of ruling section, then all to cool in the air. Tempering between 250-375°C is not advised as tempering within this range will seriously reduce the impact value.
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