LASER/TIG HYBRID WELDING OF POT FOR INDUCTION HEATER (209)

摘要

In this paper, systematic work is presented that showsthe steps for realizing a hybrid welded tailored blankthat is formed to a pot for induction heating. Thebottom is made of ferritic stainless steel and the sidesof austenitic stainless steel. Only the bottom will theninteract directly with the induction heater.All weld tests were made with a 2.6 kW CO2 laserdelivering 1.5 kW at the workpiece. A specialintegrated hybrid welding head with a closed shieldchamber was developed. Initially, the TIG powerrequired to make quality hybrid welds was identified atgap distances from 0 to 0.9 mm. Trials were made in 2mm AISI 316L as linear butt welds. A specialclamping device for circular tailored blank weldingwith root shielding was then designed. Blanks withweld line positions of 142, 144 and 146 mm diameterwere 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 bridgegaps of up to 0.7 mm with high quality (level B) asopposed to only 0.15 mm with autogenously laser buttwelding. Optimum TIG current settings increase from0 amp at zero gap to 90 amp at 0.7 mm gap.The corrosion resistance of the hybrid welded tailoredblanks is reduced when adding a TIG energy source tothe laser. The higher the voltage, the worse thecorrosion. Hardness tests showed values increasingfrom 340 to 380 Hv when increasing the current from15 to 75 ampere, respectively. These values are similarto pure laser welding. The seam consists of a duplexstructure, with austenite lying in a matrix of ferrite.The grain size in the HAZ of the ferrite increases atincreasing TIG current levels.Rotational symmetrical blanks consisting of a 4 mminner blank welded to a 2 mm outer blank weresuccessfully hybrid welded. The blanks were successfully deep drawn to a depth of 56 mm andfinally rolled to a height of 112 mm.