Effect of post-welding heat treatment on the mechanical and microstructural properties of extra high-strength steel weld metals, for application on mooring equipment

Abstract

Evaluation was performed of a weld metal with tensile strength higher than 860 MPa for welding R4 grade steel of standard W22 of the International Association of Classification Societies, Ltd. Multipass joints were welded with preheating at 200 and 250°C, using the coated electrode process with a 4.0-mm-diameter consumable, the basic composition of which was: C – 0.06%, Mn – 1.89% and Ni – 2.95%. After welding, mechanical and metallographic tests were performed on samples entirely removed from the metal deposited in conditions as-welded and after post-weld heat treatment performed at 600°C for 2 h. The results show that the weld metals obtained have mechanical properties suitable for all conditions of analysis, providing properties superior to the minimum required for welding R4 grade steel used on petroleum platform mooring equipment. The metallographic analysis enabled identification of the microstructure and explanation of the behaviour of the mechanical properties after post-weld heat treatment.