A. Roshanghias, Sharif University of Technology, Tehran, MO, Iran; A. H. Kokabi, M. Barzegari, Sharif University of Technology, Tehran, Iran
A new ultrahigh strength low alloy steel DIN 1.6959 (35NiCrMoV123) having an ultimate tensile strength and yield strength of above 1,320 and 1,130 MPa,respectively, has a carbon equivalent value of nearly 0.9 that classifies it as a ‘very difficult to weld’ steel. Hence, in the present study, the weldability of this steel under different heat treatment conditions (HT-1 and HT-2) have been studied. In HT-1 condition, the plates were welded in hardened and tempered condition and no Further heat treatment was given after welding, while in HT-2 condition, the annealed plates were subjected to welding followed by hardening and tempering heat treatments. In this study tensile properties, fracture toughness, and microstructure features were investigated Experimental results indicate that by exerting acurate preheat; interpass and postweld heat treatment also suitable filler metal for GTAW, weld metal and HAZ show comparable mechanical properties to base metal.
Summary: 35NiCrMoV123 STEEL is a new aerospace pressure vessel steel. till now there werent any attempt to weld this ultrahigh strength steel due to their poor weldability.
welding is a major step in fabrication of most of the pressure vessel and our results include welding of annealed and quenched-temper plates specially for repair application
