Study The Influence Of Tempering Process On Torsion Properties Of W6Mo5Cr4V2 High Speed Steel

As its excellent performance,W6Mo5Cr4V2 high speed steel has been widely used as mold steel and component material. Because of the high content of carbon element and alloying elements, it formed various kinds of carbide species, therefore, according to the different conditions of use established a large number of heat treatment process.Compara with alloy structure steel,high speed steel which is used as drive shaft can increase drive torque, decrease the shaft's size, raise structure's stiffness and extand service life. Focus on studying the impact of the micro-mechanism of the torsional property, according to the dislocation theory and carbide inclusions strengthening theory, proposed to metal carbide as a second-phase particle strengthening mechanism, the high elasticity modulus of the second-phase particles of uniform distribution to improve the material's overall elasticity modulus, so that a higher shear modulus of materials.According to the role of shear stress conditions, uniformity of the defects distribution can effectively improve the material shear strength, so the distribution of metal carbide can effectively improve the shear strength of the material, while fine and dispersed matel carbide particles allow material microdefects size decreases, thereby enhancing the fatigue properties of materials. The research studyed from the three aspects of shear modulus, shear strength, torsional fatigue properties,and a reasonable heat treatment process has been proposed, in order to improve the torsion performance of the material.According to the study the micro-mechanism of high speed steel,combined with the actual situation of production, this paper presents three tempering heat treatment process on the material,the sample at 500℃,550℃,600℃tempered three times, and the each processed group of specimens will test the mechanical properties in RNJ-500 test machines, hardness in HR-150A hardness test and analysis microstructure.Analyzing the test results, we find that the torsion property bacame much better and both shear modulus and strength got a larger value after tempering three times at 500℃; the material can obtain greater surface hardness, higher strength, and better tensile and pressure performance after tempering three times at 550℃;the material can obtain larger shear modulus, but less than the hardness, it is only suitable for the pure torsion force situation after tempering three times at 600℃. Together the test results with the microstructure, we found that the composition of metal carbides, the content, distribution and other factors effecting effectively the torsion property of the material and verify the feasibility of the initial micro-assumptions.Analyzing the microstructure, we find that the alloy-carbon as the second phase particles in W6Mo5Cr4V2, with small diffusion, defects and small size, and can improve the material shear modulus, shear strength and fatigue performance, good mechanical properties.