Heat treatment temperatures
Pick a steel to see typical hardening, quench and tempering temperatures, plus temper colours for small tools.
Safety: quench oil can catch fire. Use a metal container with a lid big enough to smother flames, quench oil rather than old engine oil, and never quench over a plastic floor. Wear a face shield, leather gloves and long sleeves; keep water away from hot oil. Work outdoors or with good ventilation, and keep a CO₂ or powder extinguisher to hand.
How it works, guides and notes
How to use these figures
All temperatures here are typical ranges from steel suppliers’ datasheets and are marked EST: your bar’s certificate or the supplier’s datasheet always wins. Heat evenly, soak at temperature (roughly 15–30 minutes per 25 mm of section), quench, then temper straight away while the part is still hand-warm.
- Harden: heat to the hardening range. A magnet stops sticking just below the right temperature for plain carbon steels; go a little hotter.
- Quench: plunge vertically and move the part up and down (not round in circles) to break up the steam layer.
- Temper: clean a patch bright and reheat gently until the colour you want runs to the working end, or temper in a kitchen-style oven for an hour.
Temper colours
Colours depend on time at temperature, the steel and the light, so use them as a guide only EST.
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