Multitek Indonesia: Jurnal Ilmiah

Steel and copper are widely used for various types of construction, due to both materials have complementary properties. This research is aimed to investigate the effect of the surface properties of base metal on the microstructure and mechanical strength between carbon steel and copper joint. Joining is carried out by brazing. The surface conditions of both metals were obtained by sandpaper from grids of 100, 500, 1000, 1500 and 2000. Surface roughness was characterized using a TR200 surface roughness tester machine. The microstructure of the brazed area was observed using a scanning electron microscope (SEM) after going through the polishing and etching. The mechanical strength of the joints was tested using a universal testing machine (UTM). From the microstructure observations, it was found that the filler metal was able to fill the joint gap in each variation of surface roughness. Based on mechanical tests, tensile strength increases when the surface becomes smoother. Maximum tensile strength reaches 7741,8854 N/mm2 at Ra 0,13. So it can be concluded that the strength of the joint is influenced by the surface roughness of the base metal.