이종판재의 점용접 조건과 조직 및 인장시험 특성에 관한 연구

A Study on the Metallography Examination and Tensile Test Characteristics of Spot Welding Condition and Dissimilar Metal Plates

A study of Metallography examination results indicate dendrite structure. It was known that after spot welding finer structures appear at the center and boundary nugget area than the parent metallic area. These grain refinements may be caused by the induced thermal stresses originated potential introduction. Subsequently, the hardness increases. The tear fracture at tensile tests appears on the edges of HAZ area where hardness is lower. The tearing fracture possesses the highest breaking strength among three modes so it is regarded the ideal fracture. Optimized spot welded SCP1 and STS304-2B posses tear fracture when tested. Those that satisfy nugget diameter and thickness within KS B 0850 standard show the best tensile strength tests at welding current 6.5kA, pressure to 300kgf. At thest conditions yield strength was 170MPa at 0.2% of the offset Proper welding conditions of dissimilar materials STS304-2B SCP1 are welding current of 6.5kA, pressure in the range of 250kgf ~ 350kgf. The optimum conditions for spot welding are welding current of 6.5kA and 300kgf pressure. The maximum tensile strength was 302MPa at these conditions.