Effect of Post-Weld Heat-Treatment on Corrosion and Microstructure Properties of Electric Arc Welded Mild Steels

Abstract

Welding has been an incredibly important process used to join metals in several industrial applications, such as manufacturing, construction, automotive and aerospace sectors. It has been reported that welded joints sometimes exhibit poor corrosion resistance, due to the changes in the weld surface or HAZ chemical composition, residual stress and metallurgical structure. Therefore, there is a need to enhance welds corrosion resistance and microstructure properties through PWHT. In this study, PWHTs effect on the corrosion and microstructure properties of two MSs, SAE 1015 and 1010, which were fused by electric metal arc welding, was examined. The MS samples, with different chemical compositions, were cut to the desired dimensions, separately welded and, thereafter, subjected to PWHT, at 650, 750, 850 and 950 ºC, for 1 h. The corrosion and microstructure properties of the PWHT MS samples immersed in 3.5 wt.% NaCl were then investigated, using PDP and SEM, respectively. For the PWHT SAE 1015 and 1010 MS samples, the lowest CR values were 34.240 and 35.793 mm/year, at 650 ºC, while the highest were 90.16 and 60.10 mm/year, at 950 ºC, respectively. For the AW SAE 1015 and 1010 MS samples, the CR values were 107.54 and 118.09 mm/year, respectively. The SEM images revealed smaller grain sizes and boundaries and less porosity for PWHT MS samples at 650 ºC than for those at 950 ºC. Therefore, the first ones are recommended for advanced industrial applications.