Study And Application Of Optimal Process Of Selective Laser Melting For H13 Die Steel

Selective laser melting technology is one of the methods of forming metal materials in additive manufacturing.It uses high-energy laser beams to act on the melting-solidification process of metal powders.Through the principle of "discrete-stacking",layer-by-layer melting,solidification,and accumulation are used to construct a three-dimensional entity.Selective laser melting technology has great advantages in forming complex parts,traditional manufacturing methods cannot be manufactured,and rapid response.Combining selected laser melting technology with mold production can solve the problems of long manufacturing cycle,high cost and difficult processing in the traditional manufacturing process..In this paper,the domestic gas atomized H13 metal powder is used as the research object,and the mechanical properties of the molded parts are improved by studying and optimizing the molding process and tempering heat treatment.Taking laser power,scanning speed,lap distance,and laser energy density as reference factors for the influence of forming density,use optical microscope(OM)and scanning electron microscope(SEM)to observe the microstructure and fracture morphology of H13 mold steel forming samples,Use X-ray diffractometer(XRD)to analyze the phase composition.This article first studied the influence of different process parameters(laser power,scanning speed,scanning distance)on the density of SLM molded samples,and studied the macroscopic hardness of molded samples under different laser energy densities.SLM molding H13 mold steel has a maximum density of 99.1% under the optimal molding process.The corresponding optimal molding process is laser power 250 W,scanning speed 1000mm/s,overlap distance 0.1mm,and powder thickness 35?m.Under the optimal forming process,SLM is used to form H13 die steel with higher density specimens to analyze the microstructure and mechanical properties.Study the tensile properties,impact properties,and macro-hardness of specimens under the optimal molding process.The main phase composition of SLM forming H13 die steel is composed of bcc structured martensite and fcc structured austenite.The mechanical properties are higher under the optimal molding process parameters,and the macroscopic microhardness is 49.3HRC.Under different forming angles,the highest tensile strength of the 0° formed sample is 1820.9,and the elongation at break is 9.5%;the lowest tensile strength of the 90° formed sample is 1551.2MPa,and the lowest elongation at break is 6.4%.The impact energy is 3.275.In order to improve the performance of SLM forming H13 die steel,different tempering temperature heat treatments are carried out for H13 die steel.After tempering heat treatment,the retained austenite in the structure is decomposed and transformed into tempered martensite.After tempering at 600?/2h,the hardness of the sample rises to 55.3HRC,the tensile strength rises to 2165.8MPa,and the impact energy increases to 4.32J;the elongation at break after tempering heat treatment at 650?/2h The maximum rate is 12.1%,and the maximum impact energy is 8.06 J.A simulation analysis of the factors affecting the cooling effect of the conformal cooling channel is carried out.The factors affecting the cooling time of the conformal cooling channel are from large to small,respectively,the distance between adjacent water channels>the distance between the center of the conformal cooling channel and the molding surface>the conformal cooling channel diameter.The smaller the distance between adjacent water channels,the smaller the distance between the center of the conformal cooling channel and the surface of the mold,the shorter the cooling time and the higher the cooling effect.