Study On Microstructure And Carbide Control And Mechanism Of M50T Steel

M50, which is 8Cr4M44V and classified as the second generation of bearing steel,is a kind of main material using in aircraft engine spindle bearing.lt is widely used at the temperature of as high as 315 ℃. Through the traditional process of smelting, M50 has reached a higher level on the control of the purity. Ho we ver,M50 is insufficien in the microstructure and the improvement of the carbidet and we need to the domestic research on this subject.M50T steel is a special kind of M50 steel by directional solidification electroslag smelting. First, in this paper, we analyzed the microstructure and the carbide of M50 steel with different smelting process,by optical microscope (OM) and scanning electron microscope (SEM) experiment. It was found that t M50T steel smelting by the special directional electroslag smelting could get more granula and Improved the eutectic ledeburite organization in the as-cast structure, forging state annealing organization, Quenching tempering organization technology after treatment. Secondly, with the method of hot compression deformation,we made a further explore about M50T steel’s refinement and the improvement of carbide, and the effect on the mechanical properties of steel. We hae gotten the M50T’s thermodynamic equilibrium thermodynamic calculated from Fe-C phase diagram by software of Thermo-Calc.then, we were informed of the completed austenitizing temperature that is 1175 ℃. Through OM and SEM and microhardness tester,we viewed the microstructure and hardness of the specimens after hot compression testing. Through OM and SEM and microhardness tester,we viewed the microstructure and hardness of the specimens after hot compression testing, in order to investigate the influence of deformation parameters on deformed microstructure such as the dynamically recrystallized grain size and the fraction, morphology and distribution of carbides. Found that with the increase of the deformation, dynamic recrystallization fraction increases, the grain has the smallest size on the deformation of 60% and large granular carbides decreases with the increase of the deformation. In order to make dynamic M50T keep detailed in subsequent heating process and have a high hardness room temperature, do the solid solution heat treatment experiment on the grain growth mechanism of M50T steel, to explore the relationship between carbide further study of solid solution and the change of hardness. The results show that M50T steel could keep a small grain size, have dense concentrationis small carbide particles in 1050℃.The variety of reinforcement mechanism under the joint action has made the steel more higher quenching hardnessin in 1050℃ than other high temperature.