Quenching-Partitioning-Tempering Process and Its Engineering Feasibility of 900 MPa Grade Hot-Rolled Plate

Two kinds of experimental low alloy steels were prepared based on composition design.Following Quenching-Partitioning-Tempering(Q-P-T) process with the combination of water quenching plus tempering in salt bath,both the steels exhibited high yield strength of over 900 MPa combined with good elongation of above 15%,which would be the basis of self-designed the single-cycle passing underwater quenching equipment applied in Q-P-T process of hot-rolled plate for engineering feasibility.Microstructure characterization indicates that for Q-P-T steels,high strength is attributed to dislocation-type lath martensite matrix and dispersive distributed alloying-carbides in martensite matrix,while relatively high elongation results from flake-like retained austenite between martensite laths,comparing with the steels treated by conditional Quenching Tempering(QT) process.In addition,the role of retained austenite in Q-P-T steels and the feasibility of online Q-P-T process treated by multi-cycle passing underwater quenching equipment for different hot-rolled plates in thickness were discussed.