Pengaruh Perlakuan Panas Pasca Pengelasan Terhadap Laju Perambatan Retak Lelah Baja SS 400

Low carbon steel welding problems are the non-homogenous structure, the high residual stress, and inclusion. These conditions will increase the fatigue crack growth rate effectively. Post weld heat treatments (PWHT) can be estimated to minimize these problems. In this research, the influence of post weld heat treatments on crack growth rate of SS 400 steel was investigated. Carbon dioxide shielded GMAW process was used on butt joint of 9 mm thick SS 400 steel raw material. Four conditions of PWHT, i.e. P1, P2, P3, and P4 were treated on welding joint. For first condition, the specimen was held for 1 hour at 150 °C furnace temperature, then heated to 750 °C and held for 2 hours, then cooled in air to room temperature (P1). For 2nd condition (P2), the specimen was treated as in P1, except it was held for 1 hour at 450 °C furnace temperature. For third condition (P3), the specimen was cooled in air to room temperature, then heated to 750°C and held for 2 hours, followed by air cooling to room temperature. For fourth condition (P4), the specimen was treated as in P3, except it was cooled in the furnace at a rate of 50°C/hour to room temperature. The crack growth rate tests were carried out on 6,5 mm thick of compact tension specimen (CTS). The results were compared with the welded specimen without treatment (C1) and the base material (BM). The result shows that PWHT decreases crack growth rate on weld metal and HAZ effectively. The highest crack growth rate of transversal butt joint on weld metal was welding specimen without treatment (C1), having Paris constant number (n) = 4.21, and the lowest was P4, with n = 3.01. PWHT decreased the weld metal crack growth rate 20.19-28.503 % compare to Cl and decreased 2.687-10.149 % compare to BM. The crack growth rate of HAZ by PWHT increased 4.437-17.065 % compare to Cl. The lowest of HAZ crack growth rate of longitudinal butt joint was P4 with n = 4.066 and the lowest of weld metal crack growth rate of longitudinal butt joint was P2 with n = 2.61 Key words: fatigue crack growth rate, post weld heat treatment, Paris constant numbe