700Mpa-level high-strength hot rolling Q and P steel and manufacturing method thereof

摘要

A 700 Mpa-level high-strength hot rolling Q&P steel and the method of manufacturing the same, which steel has the chemical compositions in weight percentage as follows: C: 0.15%˜0.40%; Si: 1.0%˜2.0%; Mn: 1.5%˜3.0%; P: less than or equal to 0.015%; S: less than or equal to 0.005%; Al: 0.3%˜1.0%; N: less than or equal to 0.006%; Ti: 0.005%˜0.015%, the remainders being Fe; it having a yield strength of more than or equal to 700 Mpa, a tensile strength of more than or equal to 1300 Mpa and an elongation rate of more than 10%. Through reasonable design on the compositions and on the basis of the compositions of common C—Mn steel, the present invention improves the content of Si to restrict the precipitation of cementite, performs the micro-Ti treatment to refine the austenite grains, and improves the content of Al to quicken the austenite transformation dynamics during the air cooling process; at the same time, combines the hot rolling process with the staged cooling process to obtain the structures of proeutectoid ferrite plus martensite plus retained austenite and reduces the cost of alloy elements substantially.