Effect of Quenching Temperature on Si-Mn Steel Microstructure and Mechanical Properties after Intercritical Insulation+Q＆P Process

Low carbon Si-Mn steel was processed through intercritical insulation-quenching-partition,and effect of quenching temperature on microstructure and mechanical properties of Q&P steel was studied by means of field emission scanning electron microscopy,X-ray diffraction and tensile tests.The results show that quenching temperature at 220℃ generates the best comprehensive mechanical performance where tensile strength is 1 400 MPa,elongation is 13.3%,product of strength and elongation up to 18 620 MPa·%.With the increase of quenching temperature,the tensile strength of experimental steel decreases gradually,the ductility has increased,and lath martensite content reduce,carbide particles increase,there also has been a small amount of massive martensite structure.Intercritical Mn partition complements the lack of carbon partitioning during Q&P process which leads to final retained austenite at room temperature consisting ofa small amount of carbon-rich austenite and Mn-rich residual austenite with carbon partitioning.Quenching at 220℃ provides the experimental steel a good plasticity.