Research On The Process Of Laser Selective Melting And Forming Of H13 Steel Mold

Selectine laser melting is one of the grestest potential techniques in the field of Additive Manufacturing,it has the advantages of low cost and short manufacturing cycle.In addition,the formed parts have fine grain,uniform structure,high density and excellent mechanical properties.In this paper,laser selective melting technology was used,45 steel was selected as the substrate material,and H13 steel powder was used as the laser selective melting material,experimental research on SLM forming H13 steel was carried out.The orthogonal experiment was established by three factors:laser power,scanning speed and powder thickness.The optimal process plan for melting and forming H13 steel in laser selection was determined by the dimensional accuracy of the formed sample.On this basis,the method of single factor analysis is adopted.The effects of scanning speed,laser power,powder thickness,scanning pitch and laser energy density on microstructure and properties of laser-selected H13 steel were studied by using scanning electron microscope,optical microscope,friction and wear tester,and corresponding detection means system.The main research contents and results are as follows:1.The research on the dimensional accuracy,surface roughness and densification of H13steel in laser selective melting process was analyzed and carried out.In the orthogonal experiment,the factors that have the greatest influence on the dimensional accuracy of the formed specimen by orthogonal analysis are laser power,scanning speed and powder thickness.Then,the density and roughness of the laser-selected H13 steel were studied by single factor experiment.the results show that when the laser power is 220W,the scanning speed is800mm/s,the powder thickness is 0.02mm,and the scanning pitch is 0.08mm,the density of the formed H13 steel sample reaches 98.16%,and the roughness reaches the minimum value of10.1μm.2.The effects of various process parameters on the microstructure and properties of the melt-formed H13 steel in laser selection were analyzed.The research shows that:the surface microstructure of the formed H13 steel samples is mainly composed of martensite and retained austenite under different laser energy densities.With the increase of laser energy density,the retained austenite content gradually increased.At different laser energy densities,a large number of cell(dendritic)crystals existed on the surface of each sample,and a large number of columnar(dendritic)crystals appeared on the side,and there was no element segregation in the sample.3.The effect of laser energy density on the mechanical properties of laser-selected H13steel was studied.As the laser energy density increases,the hardness of the upper surface of the formed H13 steel sample first decreases and then increases.When the laser energy density is172 J/mm~3,the microhardness of the upper surface of the sample reaches a maximum of 681.04HV,and the formed H13 steel sample has anisotropy:the microhardness of the side is slightly lower than its upper surface.The effect of laser energy density on the tensile properties of H13steel samples was studied.The results show that when the laser energy density is 172J/mm~3,the tensile strength of H13 steel in the laser selective zone is preferably 1637Mpa,and the yield strength reaches the maximum value of 1234Mpa.the performance is similar to the forged sample,and higher than the tensile properties of the cast sample;however,the elongation of the SLM-formed H13 steel sample is lower than that of the forged sample.The effect of laser energy density on the friction and wear properties of H13 steel samples was studied.The results show that the friction and wear modes of SLM forming H13 steel are mainly combined with abrasive wear and adhesive wear,the wear resistance of the sample is best when the laser energy density is 172 J/mm~3.The effect of laser energy density on the residual stress of laser-selected H13 steel was studied.The results show that the internal stress of the sample increases with the increase of laser energy density.The effect of vacuum tempering on microstructure,microhardness and wear resistance of H13 steels melted and formed in laser precinct was studied.The results showed that the structure of H13 steels was more uniform,the hardness and wear resistance were improved,and the performance was obviously better than that of the forged sample,and the residual stress inside the sample was significantly reduced.The mold cooling channel is designed,and the model is melted by laser selection through the optimum technological parameters.The results show that the mold cooling system has good forming effect.