H13 Steel Carbide Spheroidization Process And Organization Of The Mechanical Properties Of The Study

H13 steel is the representative hot mould steel, mainly uses in aluminum die casting mould, hot forging mould and hot extrusion mould. It is widely used in the home and abroad. H13 steel is beared very large sudden cool and sudden hot, impact, wear, thermal fatigue, plastic deformation and mechanical damage during service process. So the characteristics of resistance to these phenomena are required. Compared with import H13 steel, domestic H13 steel is still having lots of deficiencies, such as banding segregation is more serious, premature cracking appearance during in the service, service life is too short and the impact toughness is too low. The spheroidizing annealing of H13 steel has an important significance for homogeneous microstructure, decrease hardness and improve mechanical properties. Spheroidizing annealing needs take a long time in the industrial production; this will increase the production cycle and costs. Therefore, studying the mechanism of spheroidizing annealing has an important theoretical basis for finding the optimal spheroidizing annealing process and reducing costs.Annealing condition is the supplying structure condition of mould suppliers, their good and bad of spheroidizing annealing directly influence the final performance. Tool & mould steel should be carried spheroidizing annealing after forging or rolling, due to high carbon and high alloy content, in order to homogeneous microstructure, decrease hardness and convenience to machining. But there are lots of factors that can influence the spheroidizing annealing microstructure, such as the number and size of residual carbides in annealing heating, heating temperature, heating rate, holding time, cooling rate, the content of alloy elements and organization microstructure.In this paper, a series of spheroidizing annealing test was used and through OM, SEM, TEM, EDS, phase analysis.et. al to study the effect of different factors on carbides. The effect of different spheroidizing annealing on mechanical performance was also analyzed. In addition, the thermodynamic equilibrium microstructure and carbides transformation was also analyzed by Thermo-calc software. Through the analysis basis on the test data, the following major conclusions were obtained. (1) Different microstructures of H13 steels have different spheroidizing mechanization of carbides during spheroidizing annealing. When the microstructure is martensite, the spheroidizing speed is faster, but the carbides particle is smaller, the hardness is higher; when the structure is pearlite, the spheroidizing speed is slower, but the carbides particle is bigger, the hardness is lower.(2) Austenitizing condition is the key factor to the pearlite spheroidization of H13 steel. Suitable austenitizing temperature and time can make the number and size of residual carbides keeping an optimal value so as to provide effective conditions for spheroidization.(3) Suitable spheroidizing annealing process can improve the mechanical properties of annealing and quenching of H13 steel.(4) The main carbides type of annealing condition in H13 steel are:MC,M6C,M7C3,M23C6. Different type carbide contained different major alloy elements, so have different effect on properties. The morphology and distribution of carbides also influence the mechanical properties of H13 steel.