In this paper, systematic work is presented that shows the steps for realizing a hybrid welded tailored blank that is formed to a pot for induction heating. The bottom is made of ferritic stainless steel and the sides of austenitic stainless steel. Only the bottom will then interact directly with the induction heater.
All weld tests were made with a 2.6 kW CO2 laser delivering 1.5 kW at the workpiece. A special integrated hybrid welding head with a closed shield chamber was developed. Initially, the TIG power required to make quality hybrid welds was identified at gap distances from 0 to 0.9 mm. Trials were made in 2 mm AISI 316L as linear butt welds. A special clamping device for circular tailored blank welding with root shielding was then designed. Blanks with weld line positions of 142, 144 and 146 mm diameter were deep drawn in a 250 ton press and finally rolled.
The welds were analyzed according to ISO 13-919.1, corrosion tested based on a saline vapor solution, hardness tested and metallurgically judged.
The laser/TIG hybrid welding process is able to bridge gaps of up to 0.7 mm with high quality (level B) as opposed to only 0.15 mm with autogenously laser butt welding. Optimum TIG current settings increase from 0 amp at zero gap to 90 amp at 0.7 mm gap.
The corrosion resistance of the hybrid welded tailored blanks is reduced when adding a TIG energy source to the laser. The higher the voltage, the worse the corrosion. Hardness tests showed values increasing from 340 to 380 Hv when increasing the current from 15 to 75 ampere, respectively. These values are similar to pure laser welding. The seam consists of a duplex structure, with austenite lying in a matrix of ferrite. The grain size in the HAZ of the ferrite increases at increasing TIG current levels.
Rotational symmetrical blanks consisting of a 4 mm inner blank welded to a 2 mm outer blank were successfully hybrid welded. The blanks were successfully deep drawn to a depth of 56 mm and finally rolled to a height of 112 mm.