Do Multiple Temper Cycles Soften Steel?
Do Multiple Temper Cycles Soften Steel?
(OP)
Let's say a steel component is tempered from full hard back to a certian hardness by tempering at xxxF for 1 hour.
The part is allowed to cool and then the xxxF cycle is repeated perhaps several times.
Would the part become progressivly softer?
The steel we are working with is 5160 at a target hardness of 44Rc.
The question has come up as some parts were found to be below spec on hardness and we are thinking that the parts may have been run through the tempering furnace several times.
many thanks
The part is allowed to cool and then the xxxF cycle is repeated perhaps several times.
Would the part become progressivly softer?
The steel we are working with is 5160 at a target hardness of 44Rc.
The question has come up as some parts were found to be below spec on hardness and we are thinking that the parts may have been run through the tempering furnace several times.
many thanks





RE: Do Multiple Temper Cycles Soften Steel?
RE: Do Multiple Temper Cycles Soften Steel?
RE: Do Multiple Temper Cycles Soften Steel?
Rapidly quenching the part transforms the austenitic structure to a martensitic structure, and in the as-quenched condition freshly formed martensite is extremely brittle. The purpose in tempering the part is to soften the martensite that is formed during the quenching procedure. Since the part will also have some amount of retained austenite after quenching, the first temper will also transform some amount of this retained austenite to untempered martensite. The second temper softens this freshly transformed martensite, but some amount of the remaining retained austenite will then transform to martensite, and so you can see why multiple tempers are required. And yes, mutiple tempers will reduce the hardness of the part for this reason. But the degree to which the part softens is a strong function of the tempering temperature that is used.
Maui
RE: Do Multiple Temper Cycles Soften Steel?
RE: Do Multiple Temper Cycles Soften Steel?
Some steels require additional tempering cycles to have sufficient toughness for their required service.