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CO2 Slab Laser Keyhole Welding of a 30 CrMnSi Steel
J. Liu, H. Zhang and Y. Shi

This paper investigated laser welding technology on 30 CrMnSi steel by slab CO2 laser in order to reduce its welding distortion and improve its welding efficiency. The microstructure of the welded joints was examined with scanning electron microscope (SEM), while the properties were investigated by mean of microhardness tester and tensile testing machine. The tensile strength of the laser welded joint was at least 110 MPa higher than that of the base metal (BM). A ductile fracture generated in the BM and the dimple was present, while a brittle fracture generated in the heat affected zone (HAZ) and the quasi-cleavage fracture was present. It would be greatly improving productivity and reducing the welding distortion to use laser welding instead of gas tungsten arc welding (GTAW). Under the condition of the laser power of 4 kW and welding speed of 8 m/min, the welding distortion got the minimum, which was less 0.1 mm warp on the length of 100 mm along the direction of the welding seam of the sample. It is much less than the welding distortion of GTAW, which is more than 6 mm warp on the length of 100 mm along the direction of the welding seam of the sample, under the usual condition of the current of 130A and welding speed of 0.12 m/ in.

Keywords: CO2 slab laser, laser welding, microstructure, mechanical properties, fracture, gas tungsten arc welding (GTAW), welding distortion, welding efficiency

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