Welding procedure development for welding of high strength carbon steel cladded with austenitic stainless steel 316L by using overmatching filler metal.

摘要

This work aims to develop welding procedure for small diameter longitudinal welded clad pipe made from clad plate. High strength carbon steel base metal bonded with 316L stainless steel clad layer was used in this study. The dissimilar materials at the weld joint and accessibility limitation of small diameter present difficulty in welding process selection to achieve weld soundness. The joint and welding sequence are designed to avoid solidification cracking. Nickel base over matching filler is used on the clad side. Typical joint configuration is double V groove weld without clad peel back to minimize the number of passes inside the pipe. Firstly, welding is done on the carbon steel side by using Shielded Metal Arc Welding (SMAW) and Submerged Arc Welding (SAW) with carbon steel electrodes. Then, welding on the clad side is done by using ERNiCrMo-3 filler metal. Two different procedures for the clad side are studied. The first procedure is to weld the clad side by using Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding pulse current (GMAW-pulse) and another procedure is to weld the clad side by using the SAW procedure. Hot cracking was observed in the case of SAW procedure at the clad weld centerline due to high heat input and high level of dilution. Mechanical properties and microstructure are evaluated. Clad weld by use of GTAW and GMAW-pulse could give sound weld metal. The tensile and yield strength of all weld metal were found to be greater than that of base metal and 100% shear failures were observed. Charpy impact energy of weld and HAZ at -10°C was found to be over 100 joules. Hardness of weld and HAZ area are surveyed over the weld cross section to determine local hardening. Additionally intergranular corrosion testing was carried out on the clad weld side and then bend testing was done. No crack was observed. Therefore, GTAW and GMAW-pulse clad weld procedure could give required properties according to clad line pipe standard, reduce cost of production and increase productivity compared to the peel back method.