The Basic Study On Laser Welding Technology And Performance Of CRH Austenitic Stainless Steel

The met stable301LN’ cold rolled sheets are the main materials in manufacturing railway body. They are welded mainly using resistance spot welding with low quantity of heat input because of their cold hardening characteristics. But the spot welding structure is only applied to under the speed of250km/h on account of the poor air-tightness. The laser welding has high-energy density melt soldering and low quantity of heat input. It is good methods that spot weld using on the shell plating is replaced by laser seam weld and solve the poor air-rightness of train body.In this paper, the laser welding of301LN and304sheets were studied. The microstructure, the bead phase, energy spectrum analysis and micro hardness of austenitic stainless steel laser welding joint were researched. The summing-up of laser and spot welding were contrasted. Different laser power, welding speed and defocusing amount impacting on bead formation was’ discussed. The tensile behavior and the fractures model of301LN and304laser butt and lap were deliberated. The tensile property affected by different attended mode and welding parameter was researched. The tensile distinction of laser welding sample and plate and spot welding was checked. The stress and strain distribution of tensile sample and fracture mechanism using FEA was analyzed.The results showed that, laser welding seam organization of the austenitic stainless steel mainly included γ austenitic and bits of d ferrite. The γ austenitic of301LN laser lap weld contained96.1%volume fraction, The main elements of weld bead including Cr, Ni and Fe was uniform distributed, no composition segregation. The micro hardness of301LN laser bead was higher than304.The faster cooling rate, the smaller grain. The penetration and width size of weld would be increased with the laser power going up and weld speed falling in certain extent, but width size increased seldom. The penetration would be deeper and width would be narrower with absolute value of defocus distance increasing. The penetration of negative defocus was deeper than positive.301LN-DLT can be welded using laser, but301LN-HT can’t. To lap weld, the penetration deeper, the better tensile property without affecting body appearance quality. The maximum stress value occurred in fusion zone and weld center for butt welding. The maximum stress value of lap and incomplete welding emerged in fusion zone of internal surface and easy to appear craze of tensile and fatigue, the stress of outer surface was twice than inner. To301LN, fracture had observed dimple for ductile fracture.