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Microstructural Analysis of a Laser-Metal Active Gas (MAG) Hybrid Welded Invar Steel Joint
X-H. Zhan, Y. Liu, J. Chen, W-M. Ou, C. Gu and Y-H. Wei

Two Invar steel plates with a thickness of 19.05 mm were welded by laser-metal active gas (MAG) hybrid welding technique using the Invar M93 solder wire. Three contrast experiments were conducted to analyse the influences of processing parameters on surface morphology, weld width and penetration. The hybrid welding processing parameters which preliminarily identified were optimized. The experiments results illustrate that the 19.05 mm thick Invar steel welding, should be completed at least three layers weld welding and using Technique 1 can get qualified welding joint. Meanwhile, the heat input of weld bead centre is dominated by laser, the fusion and crystallization speed is very high, the grain is refined and equiaxial line appeared. While the heat input of area where deviated from centre depends on arc, columnar line appeared in this area.

Keywords: Fibre laser, Invar steel, laser-metal active gas (MAG) hybrid welding, microstructure, morphology, grain, penetration, heat affected zone (HAZ)

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