Effect of heat input modification on duplex stainless weld quality Available to Purchase

Laser welding has the potential to be the perfect tool for joining stainless steel autogenously. High weld quality and productivity can be ensured by establishing a keyhole for narrow and deep penetration. Heat tint on the surface may decrease the corrosion resistance; hence such discoloration has to be removed or avoided. With laser welding, it is possible to minimize the weld bead and root oxidization and thereby decrease the need for post-weld cleaning. The rapid cooling rate encountered may, however, cause unfavorable phase balance in duplex stainless weld metals, why these often require addition of over alloyed filler metal or even post-weld annealing. One solution is to use laser hybrid welding to increase the heat input and to more effectively add filler metal, but this is not as attractive for thin materials and in continuous production. Modern high-brightness lasers offer high power and excellent beam quality via optical fibers. These have great potential to further improve the welding speed, but the difficultties in obtaining suitable phase balance remain or would even be enhanced. This study concentrates on testing the effect of focal spot size and shape on the weld microstructure in order to define the suitability of dynamic beam forming (transverse and longitudinally) for welding of thin duplex stainless steel sheets in butt joint configuration. The differences between various focal spot configurations are analyzed in terms of weldability and resulting microstructure. The effect of focal spot size and shape can be seen as the larger spot results in higher heat input, longer cooling time and thus affects the weld metal microstructure.