Study On The Heat Treatment Characteristic Of5Cr5MoSiV1Steel For Disc Cutter Rings Of TBM

With the rapid development of economic and acceleration of urbanization in China, more and more tunnel projects such as subways will be constructed in future. Shield method is the most commonly used construction method in tunnel projects due to its advantage of rapid construction speed, strong adaptability to geological conditions and little impact on the surrounding environment.Soil is cut by shield tools during tunnels construction using shield method. Shield tools work under the abominable conditions of strong extrusion, high torque, strong impact and high abrasive because of the high strength and high hardness rock mass as well as the complexity of geological conditions, so shield tools are the most easily defective components during digging process. According to the defects such as low strength, poor wear resistance and short service life of domestic shield tools, effect of different heat treatment process parameters (including heating temperature, soaking time and cooling method) during annealing, quenching and tempering on microstructure and mechanical properties of5Cr5MoSiV1steel for disc cutter rings of TBM were investigated in this paper.Then a best heat treatment process parameters suitable for5Cr5MoSiV1was summarized in order to prolong service life of domestic disc cutter rings and reduce cost of project construction. The main contents of this paper includes:1.Forming process of spherical carbides during annealing was analyzed firstly, and then effect of different annealing temperatures and soaking times on quantity, size, species distribution of carbide particles and annealing hardness of5Cr5MoSiVl steel were studied,the best process parameters for spheroidizing annealing was selected finally.2.Effect of different quenching temperatures, soaking times and cooling methods on austenite grain growth behavior, microstructure and mechanical properties of5Cr5MoSiVl steel were investigated, and quantitative relation for austenite grain sizes of tested steel changed along with quenching temperature and soaking time, quenching hardness of tested steel changed along with soaking time were determined respectively by regression analysis method at the same time, the best process parameters for quenching was selected at last.3.Tempering process for quenched steel was described firstly, and then effect of different tempering temperatures and soaking times on tempering microstructure and mechanical properties of5Cr5MoSiVl steel were studied, quantitative relation between tempering hardness of tested steel and soaking times was determined by the variant linear regression analysis method at the same time, the best process parameters for tempering was selected finally.