A Study on the Mechanical Properties of Structural Steels by Welding at High Temperature

This research is to show the mechanical properties of structural steels by welding at high temperature. Welding parts are divided with weld metal and HAZ(Heat Affected Zone). HAZ is formed by interval from welding heat source and heating and cooling rates. Then, the change of both microstructure and mechanical properties occurs. Discontinuity of mechanical and chemical property at HAZ is the cause of safety decrease of structure. At this point, in this research, tensile tests at high temperature with test pieces of base metal and weld metal of SS400 and SM490 are accomplished. Furthermore, the effect on steel by welding throughout the microstructure's observation at welding parts and fractural parts. From the results, the mechanical properties of both SS400 and SM490 are standardized without welding or non-welding. Moreover, after tensile tests, The volume fraction of ferrite and pearlite is analyzed with microstructure of fractural parts of test pieces of weld metal. As a result, it is verified that the fragility parts of test pieces of weld metal are base metal