Research On The Laser Beam Welding Behavior Of The Dissimilar Metals M42High-speed Steel And X32High-strength Steel

The welding of dissimilar metals can not only take full advantage of the bestperformance of different materials, but also reduce the costs, thus being widely used ina variety of industries. With its high efficiency, low sawing loss, and wideadaptability，Bi-metal band saw blades plays an increasingly important role in theprocessing industry. Bi-metal band saw blade is developed in the recent years,whichuses the high speed steel （HSS） M42with high heat resistance and wear resistance asthe tooth portion material, and the high-strength steel X32with high strength andtoughness as the saw tape backing material, It is though welding that its teeth andbacking come together. However, the high volume of the carbon in both HSS M42and the high-strength steel X32, thus their weldability is poor, besides, both thephysical and chemical properties of the two materials are far away from each other, sothe traditional welding methods has many limitations for them. Laser beam weldinghas the advantages of high power density, small spot diameter, concentrated energy,small weld heat affected zone, small thermal deformation and so on，thus it has anexcellent performance on welding of dissi milar metals containing high melting pointalloy elements. This paper studied the behavior of the laser welding of dissimilarmetals based on the manufacturing process of the Bi-metal band saw blades.The Laser welding welding process of the high-speed steel wire M42and thehigh-strength steel strip X32was carried out, the microstructure evolution and thedistribution of connectors microhardness of the CO₂laser welding of dissimilar metalwere analyzed and discussed. The influences of different welding process on the jointmicrostructure and mechanical properties were also studied systematically, theinfluences of annealing after welding on joint organization, and the influence of theregulation of the annealing temperature and annealing holding time on t he hardness ofthe weld were also studied and its functional relationship is fitted.The organization of the joints of CO₂laser welding of dissimilar metal of the HSSM42and high-strength steel X32is equiaxed grains and columnar dendrites, the centerof the weld is equiaxed grain area, both sides of the center of the weld are thecolumnar crystals and columnar dendrites. Near the fusion line and close to the side ofthe tooth material M42, the directionality of the columnar grain structure is disrupted,and close to this area than the X32side columnar grains near the fusion line of columnar grains finer. Joints and a small amount of residual austenite to martensitethe hardness of the joint weld zone at side closes to the tooth material is higher thanthe hardness at the side closes to the back material, and the hardness of the fusionzone is higher than the center of weld in the side closes to the tooth material.With the increase of the speed of laser welding, the amount of the equiaxed grainsincreases, the amount of the cellular dendrite and dendrites decreases. Close to theM42fusion boundary， columnar grain to equiaxed grain. with the decrease of thelaser power, the center of the weld zone， the number of dendrites increase, the centerof the weld zone and equiaxed grains reduce, and base metal fusion boundary columnarcrystals larger scope. The bending breaking of the joints of the laser beam welding ofdissimilar metal often occurs in the area near the fusion line close to the high-speedsteel M42. Studies show that the welding process，when the welding power is2754W,and the welding speed is14m/min, the welded joints are flat, smooth, and free ofmacro-defects, thus the microstructure and properties is the best, with the bendingstrength of112Mpa and reached a band saw welding performance indicatorsAnnealing at800℃for2h, the weld hardness can be decreased below to380HV1,and the balling effect of the welded zone will also be satisfied, reducing the hardnessof the welded zone, and eliminating the welding stress. and the hardness will reach theannealing hardness requirements. The hardness of the weld matches with the logarithmof the time in a linear relationship, and the reciprocal of the hardness of the weldmatches with the annealing temperature in a linear relationship.