TIG welding of advanced high strength steel sheets

To reduce self-weight, car manufacturers and machine part producers tend to parts made of high strength steels and advanced high strength steels. The load bearing capacity of these components depends largely on the quality of the welds, therefore the joining of such high strength steels sheets by automatized tungsten inert gas (TIG) welding without filler metal was investigated. The selected steel grades were transformation induced plasticity (TRIP) steel (with 1000 MPa ultimate tensile strength) and twinning induced plasticity (TWIP) steel (with 800 MPa ultimate tensile strength). The weldability of both steel grades without filler metal and without pre heating and post weld heat treatment was investigated also in dissimilar joints. The visual and metallographic examinations, hardness measurements and tensile testing showed that the usability of this welding process to weld good TWIP-TWIP joints is good, to TRIP-TRIP joints is limited and to TRIP-TWIP joints is poor