Development of multi-cycle quenching–partitioning–tempering process and its applications in engineering

AbstractQuenching–partitioning–tempering (Q–P–T) steels have become a new member of the family of advanced high strength steels. Previous research indicates that steels treated by the Q–P–T process exhibit better combinations of strength and elongation than those treated by traditional quenching and tempering (QT this has been attributed to the lower quenching stress and larger amount of retained austenite in the Q–P–T steels. In the present paper, the concept of water–air alternately timed quenching (ATQ) technology, in effect a multi-cycle Q–P–T (MQ–P–T) process, is presented. The principles of ATQ technology and related equipment are introduced. Examples given of workpieces treated by ATQ technology include a 718 steel plastic die, a 42CrMo4 marine crankshaft and a wind-electric spindle. Unlike single-stage water quenching, oil quenching or quenching in aqueous polymer solution, ATQ avoids cracking of large workpieces during heat treatment and can produce high levels of mechanical properties. This n...