Weldability of 22MnB5 after hot stamping by TIG welding processes

Tungsten Inert Gas (TIG) welding technology was employed to study the weldability of THQ50-C filler metal of 4 mm sheet thickness 22MnB5 after hot stamping. The microstructures and mechanical properties of the welding joints under different welding parameters were analyzed. Results show that, under the condition of DC-TIG welding, welding defects were found when the welding current is 60 A and 100 A; at 80 A welding current no macroscopical were found on the test pieces, but widmanstatten structure appeared in weld metal. While the DC pulse TIG welding was applied, high quality joint was available when the average welding current was only 60 A. The weld metal, coarse and fine grain zones of Heat Affected Zone (HAZ) were all composed of ferrite and pearlite; lath martensite, lower bainite and pearlite distributed in high temperature tempering zone of HAZ; granular carbide was separated out from the lath martensite in low temperature tempering zone of HAZ. Microhardness of the test pieces increased with the distance from the weld center, but the tensile strength was 631 MPa, about 42.1% of that of base material.