Japanese Welding Guideline for Duplex Stainless Steels

Abstract

A Japanese welding guideline for duplex stainless steels (DSSs)1) has been developed in a Sub-Committee of Chemical Plant Welding Research Committee in the Japan Welding Engineering Society. The guideline recommends 13 key points as a basis to prevent the unforeseen corrosion of weldments, which are based on practical experience in Japanese Oil & Gas and Chemical industries and similar published guidelines. The principal concept is how to obtain an acceptable ratio of ferrite/austenite phase balance along with no detrimental intermetallic compounds in the weld metal and heat affected zone. For the weld metal, consumable selection, the shielding and purging gas composition and weld heat input control are most critical. For HAZ, the nitrogen content of the base metal is most critical. This guideline is developed for DSS welders and welding engineers so as to understand the difference of DSS from standard austenitic stainless steel. This guideline is composed of three parts, the first is 13 basic recommendations, the second is to explain some technical aspects for these 13 key points and the third contains comprehensive data relating DSS base metal and weld metal including some important key points for each step of fabrication to understand the welding characteristics of DSS clearly. This paper introduces the basic 13 recommendations for guidance purpose in addition to the mandatory requirements of the construction code in Japan.