The Research On Laser Swing Welding Of Dissimilar Steels For Cutting Tools And Microstructure And Properties Of Joints

Compared with the international famous manufacturers,China,as a large country of household knives production,has a relatively backward production process,and there is still a big gap in production technology.Therefore,it is the key to improving the competitiveness of cutting tool products in China to upgrade cutting tool production equipment,create new cutting tool technology and develop high-performance cutting tool materials.3Cr13 stainless steel is a kind of traditional material for kitchen knife.It is difficult to meet the requirements of high-performance knife due to its low sharpness and wear resistance.VG10 steel has excellent strength,corrosion resistance,wear resistance and other properties,and is usually used to make high-performance tools.With the core idea of"good steel is used on the cutting edge",the research group welded the high-performance cutting tool material VG10 and 3Cr13 by laser swing welding technology.VG10 is used as the cutting edge of the tool,and 3Cr13 is used as the tool body.This method improves the tool performance and reduces the production cost of high-end household tools.Due to the high requirements of laser welding quality on tooling,the experiment uses a swing laser welding method to increase the weld width,thereby reducing the requirements on the tooling and improving the products qualification rate.The main process parameters of laser swing welding are laser power,welding speed,defocus amount,swing frequency,swing amplitude,etc.The influence of the main process parameters on the shape of the weld was analyzed through single-factor experiments,and the better welding process parameters were found using orthogonal tests.The relationship between phase and temperature in the equilibrium state of 3Cr13 and VG10base metal was calculated by JMATPro software.The phase composition and microstructure of weld,fusion zone and heat affected zone were analyzed by XRD,SEM and EPMA,and the microhardness distribution of welded joint was measured.The test results show that the weld is mainlyα-phase and M₇C₃.From the fusion line to the center of the weld,the structure gradually changes from plane crystals to cell crystals,cell dendrites,dendrites,columnar crystals,and equiaxed crystals.There is microsegregation in the weld structure,in which C and Cr elements are enriched in the grain boundaries,Fe elements are enriched in the grains,and bar-like M₇C₃ precipitates at the grain boundaries.There is a C migration phenomenon on the base material side near the fusion line,in which a needle-like martensite structure is generated on the3Cr13 side,and a non-convective mixing zone exists in the fusion zone on the VG10side,where massive,structures are embedded in the base material,A layer of carbide M₇C₃ was formed on the island-like structure.The hardness of the base metal on both sides of the fusion line is the largest,and the hardness change in the weld zone is small.The hardness in the heat affected zone gradually decreases with increasing distance from the center of the weld.The hardness of VG10 is higher than that of 3Cr13.In addition,the non-standard impact fracture shows that the entire welded joint is brittle fracture,in which the base material is cleavage fracture and the rest is quasi-cleavage fracture.Image software was used to count the distribution of carbides in different areas of the joint.The effect of quenching process on the microstructure and properties of the joint was studied.It was found that as the quenching temperature increased,the content of carbides gradually decreased,and the large lump primary carbide in the original material could not be eliminated by heat treatment.It was found that quenching can significantly improve the overall hardness of the welded joint.Under the process of 1050℃quenching+200℃tempering,the highest hardness of VG10 is about 830HV.The corrosion resistances of welded joints under different heat treatment processes were evaluated by electrochemical corrosion tests.The results show that the increase of quenching temperature makes more carbides dissolve in the original austenite grains,so under the same tempering process,the carbide content of the quenching process with higher temperature is less,and the chromium-poor phenomenon of matrix structure is reduced,which makes the corrosion resistance of the sample become better.