23.10 tempering is a heat treatment applied to hardened steels that is best defined as which of the following (one correct answer): (a) heating and soaking at a temperature above the austenitizing level followed by rapid cooling, (b) heating and soaking at a temperature above the austenitizing level followed by slow cooling, (c) heating and soaking at a temperature below the austenitizing level followed by rapid cooling, or (d) heating and soaking at a temperature below the austenitizing level followed by slow cooling,?

The correct answer is (a), heating and soaking at a temperature above the austenitizing level followed by rapid cooling.

Explanation:

Tempering is a heat treatment that is performed to change microstructure of steel and increase it's hardness.

It is done by heating above the austenitizing level, because for this heat treatment it's necesary to heat the steel to get austenite structure that is the alotropic form of gamma iron.

The procedure of tempering, continues with rapid cooling, because this way you get the microstructure with the best hardness properties, that is martensite.

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