Estudo da compatibilidade metalúrgica de juntas soldadas de metais dissimilares utilizados no setor de petróleo e gás.

Abstract

This study aimed to evaluate the influence of the first and second buttering layer with nickel alloys of dissimilar welded joints on the susceptibility to embrittlement, by examining the influence of the welding parameters and the type of shielding gas on these joints with and without different heat treatments, on the microstructure, hardness, impact resistance and the level of residual stresses in the HAZ of these welded joint. For this an experimental design was done in order to define the best parameters for buttering and filling of the weld joint. GMAW process was used. AISI 8630 and C-Mn steels were used as base metal and AWS ER NiCrMo-3 wire as filler metal. Pure Argon and a mixture Argon/ helium was used as shielding gas. After the determination of buttering parameters it was performed the filling of the joints also varying the shielding gas. Different heat treatments of stress relief (HTSR) were performed in the joints with a layer of buttering with the temperatures of 720 ˚ C for 4 hours, 676 ˚C for 3 hours and the joints with and without buttering in the temperature of 676 ˚ C for 2 hours. From the welded joints, samples were taken for characterization by microhardness tests and impact toughness test (Charpy). The results showed that application of the double layer of buttering technique is effective in the reduction of brittleness of the joints, promoting a significative reduced in the coarse grain region and increasing impact resistence similar of those obtained by HTSR.