Study On Carbon Steel Cut Wire Shot Used For Shot Peening

Cut wire shot was the most commonly used metal abrasive for shot peening. It was widely used to process the metal parts which need to continually bear the alternating stress of automotive, aerospace, locomotive, wind power, construction machinery and other industries. There were no porosity, loose, segregation and other defects inside the cut wire shot, and its particle size distribution was uniform, which could result in uniform residual stress distribution and surface quality on the surface of parts and was conducived to improving the effect of shot peening of parts significantly.In this paper, the produce processing of 65 steel cut wire shot that drawing from 5.5mm diameter hot steel rod, then cutting, conditioning to the final product was studied, the drawing process and internal metallographic structure transformation of 65 steel wire were emphatically analyzed and discussed. The characteristics of wear and impact of 45 steel,65 steel,72 steel and 82 steel cut wire shot with different particle size were studied too. Metallographic microscope, microhardness tester, tensile testing machine, carbon sulfur analyzer and silicon manganese phosphorus analyzer were used in this paper to measure the metallographic structure, hardness, tensile strength, chemical composition and other technical indexes of cut wire shot respectively. And the diameter changes of steel wire during the wire drawing process was measured by screw micrometer. The impact wear failure process and impact process of shot peenning used cut wire shot was simulated in Ervin Test Machine. The surface coverage of the specimens was evaluated with coverage standard sample block, and the surface roughness of specimens was measured by the stylus roughness tester. The changing process of wear morphology of cut wire shot was recorded by scanner. The surface morphology of shot under different wear degree was investigated by Scanning Electron Microscope (SEM).The results show that the cross-section area reduction rate in the process of wire drawing was gradually decreasing in general, in which the second reduction rate was the maximum. After drawing, there was a violent distortion of pearlite microstructure in the transverse section of steel wire, and the grains were significantly refined.In the longitudinal section, the proeutectoid ferrite pearlite microstructure and the pearlite microstructure were deformation coordinationlly, and the grains were significantly elongated, the interlamellar spacing of pearlite microstructure decreases, and gradually turned to consistent with the drawing direction,which result in fibrous tissue structure eventually. The impact wear failure process of cut wire shot can be divided into three stages:conditioned stage, stable wear stage, severe wear stage, the wear failure forms of three stages were adhesive wear, surface peeling and block fracture respectively. Under the same carbon content, the wear rate of large size cut wire shot was slower than that of small size particles.However, the wear rate of severe wear stage of large size cut wire shot was faster than that of small size particles.The larger the size of the cut wire shot, the faster the wear failure rate of it in comprehensive. Under the same particle size, The higher the carbon content of cut wire shot, the greater the hardness, and result in the faster the wear failure rate eventually; After annealing under 300℃, 400℃ and 500℃, the wear failure rate of cut wire shot was decrease than before as well as the tensile strength and hardness, and with the increase of annealing temperature, the wear failure rate decrease contiually. Under the same carbon content, the larger the size of cut wire shot, the more impact cycles was needed for the surface of test piece to reach 100% coverage. However, the increase of the particle could result in its hardness decrease simultaneously, the surface roughness of the test piece was not increased with the increase of the particle size. Under a certain polishing capacity, there exists a particle size that can obtain the minimum surface roughness of test piece. Under the same particle size, the higher the carbon content of cut wire shot, the higher the surface roughness value of test piece, and the less impact cycles was needed for the surface of test piece to achieve 100% coverage.