Development and Application of Multicycle Quenching-Partitioning-Tempering Process

Our previous research indicates that steels treated by quenching-partitioning-tempering (Q-P-T) process exhibit better combination of strength and elongation than that by traditional quenching and tempering (Q&T) process, which is attributed to lower quenching stress and more retained austenite in the Q-P-T steels. Q-P-T steels have become a new member of advanced high strength steels. In this paper, we introduce the principle of water-air alternately timed quenching (ATQ) technology, which is in fact a multicycle Q-P-T (MQ-P-T) process. The principle of ATQ technology related to equipment will be introduced. Instead of a single water-quenching, oil-quenching or aqueous polymer solution-quenching, ATQ technology avoids cracking of a large-sized workpiece during heat treatment and leads to required mechanical properties. This novel process has provided benefits in economy and environmental protection for more than ten years in China. Finally, we introduce the study of hot-rolled steel plate treated by Q-P-T process with a passing underwater quenching equipment. Based on this study MQ-P-T process is suggested to be suitable for engineering application in hot-rolled steel plates of various thicknesses.