Research On Quenching And Tempering Treatment Process Of 7CrSiMnMoV Steel

7CrSiMnMoV steel with high toughness and good process performance, It has wide range of quenching temperature and better quenching degree. It is widely used in manufacturing cold working dies. By optimizing the heat treatment parameters to improve 7CrSiMnMoV steel microstructure and mechanical properties to meet the requirements of modern mold industry, it has some practical value.The heat treatment process for 7CrSiMnMoV steel was studied in this paper.By analyzing the effects of quenching temperature, quenching agent, quenching holding time, tempering temperature and tempering holding time on microstructrue and mechanical properties of 7CrSiMnMoV steel, the heat treatment process parameters of 7CrSiMnMoV steel were optimized. The main conclusions of the thesis were as follows:(1) The microstructrue of 7CrSiMnMoV steel after different quenching treatments are quenching martensite and retained austenite. Quenching martensite is the mixture of plate martensite and lath martensite.(2) By compared different influences of quenching agent and quenching holding time on 7CrSiMnMoV steel microstructure and mechanical properties, obtained two kinds of better quenching processes:900? air quenching x 600s and 880"C air quenching×600s. Hardness of first heat treatment process of 7CrSiMnMoV steel is 67.1HRC, the impact energy is 14.7J, and the tensile strength is 983.0Mpa; Hardness of second heat treatment process of 7CrSiMnMoV steel is 66.3HRC, the impact energy is 14.7J, and the tensile strength is 1018.1Mpa. The fracture mode of 7CrSiMnMoV steel is ductile and quasicleavage fracture.(3) The microstructure of 7CrSiMnMoV steel after tempered at different temperatures and different tempering holding time are retained austenite, carbide and tempered martensites which still exhibits the lath and plate morpgology. The best tempering process parameters is 250?×1.5h.(4) In this experiment, there were two optimun heat tratment processes of 7CrSiMnMoV steel. The first one is 900? air quenching×600s+250? tempering× 1.5h. Hardness of this heat treatment process of 7CrSiMnMoV steel is 59.9HRC, the impact energy is 22J, and the tensile strength is 1797.2Mpa. The second one is 880? air quenching x 600s+250? tempering×1.5h. Hardness of this heat treatment process of 7CrSiMnMoV steel is 59.6HRC, the impact energy is 28.3J, and the tensile strength is 1744.9Mpa. The fracture mode of 7CrSiMnMoV steel is ductile and quasicleavage fracture.