PENGARUH VARIASI MEDIA PENDINGIN SETELAH PWHT PENGELASAN SMAW BAJA ST37 TERHADAP KETANGGUHAN DAN STRUKTUR MIKRO

Abstract

This study focuses on welding low carbon steel ST37, which is widely used in the automotive industry, particularly for motorcycle chassis. One common issue in welding is the cracking or breaking of the chassis in the Heat Affected Zone (HAZ), caused by residual stress. To reduce residual stress, the commonly used method is post weld heat treatment (PWHT), followed by cooling. This research uses an experimental method by varying cooling media after PWHT on SMAW welding. Impact and microstructure tests were conducted after the PWHT and cooling processes. The results showed that specimens cooled with vegetable oil had an impact value of 0.788 J/mm², with oil 0.905 J/mm², and without cooling media 1.095 J/mm². The results of the microstructure analysis show that the ferrite phase is more dominant due to the slow cooling rate. Conversely, when the cooling rate increases, the impact strength tends to decrease as pearlite and martensite phases form. Thus, it can be concluded that the use of a cooling medium accelerates the cooling rate, which ultimately reduces the impact strength.