Reheating quenched martensite, usually to 150 to 650 °C, and holding before cooling. Carbon precipitates as fine carbides and quench stresses relax, so hardness falls while toughness and dimensional stability rise. Temperature sets the result: a 4140 part stays near 50 HRC tempered at 205 °C and drops to about 30 HRC at 595 °C. Tempering should start as soon as parts cool to hand-warm after the quench.
Temper at 400 for two hours, check one, and if it's still over 60 bump it to 425.
Temper as soon as the parts are cool enough to hold. Leaving high-carbon parts untempered overnight is how they crack on the bench.
Also heard as
- temper
- draw
- drawing
Related terms
Martensite
The hard, needle-like phase that forms when austenite is quenched fast enough to trap its carbon.
Double tempering
Tempering a part twice, cooling to room temperature in between, to temper martensite formed after the first.
Draw
Shop word for tempering, as in drawing hardened steel back to a softer, tougher hardness.
Temper colors
Thin oxide colors, from pale straw to blue, that form on clean steel as it is heated in air.
Q&T
Quench and temper: hardening steel by quenching, then tempering it back to a set strength and toughness.