Processing Parameters Optimization, Microstructures and Properties of Laser Welded FV520B Steel
DENG Dewei1,2, LYU Jie1, MA Yushan3, ZHANG Yong2, HUANG Zhiye2
1 School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China 2 Shenyang Blower Works Group Corporation, Shenyang 110869, China 3 Wuzhong Instrument Co., Ltd., Wuzhong 751100, China
Abstract: The laser welding parameters of FV520B steel plate were optimized by orthogonal tests in order to provide a foundation for the impeller bac-king weld. The welding parameter was initially selected by the range analysis method. A narrow parameter range of laser welding was determined by taking the weld penetration as response. The optimized weld parameters were determined as spot diameter of 1.2 mm, power of 4.2 kW, and welding speed of 35 mm/s. Under these parameters, the microstructure in fusion zone (FZ) of the butt self-fusion weld was composed of the white martensite, the black δ ferrite and a small amount of carbides. The delta ferrite exhibits worm-shape and lath shape. The linear energy density of laser has a great influence on the weld penetration. The weld penetration increases with increasing linear energy density according to an approximate power function relation, while the Vickers hardness decreases slightly with increasing linear energy density. The hardness of the FZ in butt weld under the optimized parameters is slightly lower than that of the base metal (BM), and also the softening occurs in heat affected zone (HAZ) significantly. Due to the existence of weld defects, the yield strength and ultimate tensile strength of the weld are lower than those of the BM. However, the weld without or with a few of surface weld defects presents a higher strength than BM.
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2021, Vol. 35 
