Research On The Welding Behavior Between The Cemented Carbide YG8 And The High-Strength Steel D6A

The welding of dissimilar metals can not only take full advantage of the best performance of different materials, but also reduce the costs, thus being widely used in a variety of industries. With its high efficiency, low sawing loss, and wide adaptability, Bi-metal band saw blades plays an increasingly important role in the processing industry. Bi-metal band saw blade is developed in the recent years,which uses the Cemented carbide wires YG8 with high heat resistance and wear resistance as the tooth portion material, and the high-strength steel D6A with high strength and toughness as the saw tape backing material, It is though welding that its teeth and backing come together. However, the physical and chemical properties of the two materials are far away from each other, so the traditional welding methods has many limitations for them. Laser beam welding has 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 an excellent performance on welding of dissimilar metals containing high melting point alloy elements. This paper studied the behavior of the laser welding of dissimilar metals based on the manufacturing process of the Bi-metal band saw blades.The Laser welding welding process of the Cemented carbide wires YG8 and the high-strength steel strip D6A was carried out, the microstructure evolution and the distribution of connectors microhardness of the CO2 laser welding of dissimilar metal were analyzed and discussed. The influences of different welding process on the joint microstructure and mechanical properties were also studied systematically, the influences of annealing after welding on joint organization, and the influence of the regulation of the D6A after heat treatment on the hardness of the weld were also studied and its functional relationship is fitted. The organization of the joints of CO2 laser welding of dissimilar metal of the Cemented carbide wires YG8 and high-strength steel D6A is afterbirth-like crystal and equiaxed grains, by YG8 lateral to the center of the weld, growth changes for mixed dendrites and cellular crystal even only cellular isometric crystal to the center, has not obvious growth direction. Near the fusion line and close to the side of the tooth material YG8. Joints weld zone at side closes to the tooth material is higher than the hardness at the side closes to the back material, and the hardness of the fusion zone is higher than the center of weld in the side closes to the tooth material.From D6A lateral to the center of the weld, the growth of the crystal changed from cellular crystal to dendritic and then transfer to equiaxed grains, with a strong growth orientation. At the same time, the dendritic grain turns to growth perpendicular to the centerline of the weld gradually and become small, since the welding speed increased.The bending breaking of the joints of the laser beam welding of dissimilar metal often occurs in the area near the fusion line close to the Cemented carbide wires YG8. Studies show that the welding process, when the welding power is 3960 W, and the welding speed is 9 m/min, the welded joints are flat, smooth, and free of macro-defects, thus the microstructure and properties is the best, with the bending strength of 395MPa and reached a band saw welding performance indicatorsAfter the heat treatment of backing material D6A, the Co element in YG8 weld fusion zone is less than that of tooth material. However, the content of Co in the area of the weld and D6A is relatively increased compared with D6A that without heat treatment. It indicated that the narrow weld is helpful to the diffusion of Co element. Otherwise, the W and C content are basically the same, while the fluctuation of Fe content is more obvious in the weld.