Tempering is possible because of the instability of the martensite, the principal constituent of hardenedsteel.
由于马氏体这一淬硬钢主要成分的不稳定性，使得回火成为可能。
2
To reheat hardenedsteel or hardened cast iron to some temperature below the eutectoid temperature for the purpose of decreasing hardness and increasing toughness.
重新加热硬化钢或硬化铸铁至某一温度，低于共析温度下，使硬度降低，韧度增加。
3
The final structure obtained from tempering a fully hardenedsteel is called tempered martensite.