Method for manufacturing welded joints, method for calculating manufacturing conditions for welded joints, and welded joints

Abstract

Even when welding duplex stainless steel with high heat input, the sigma phase does not precipitate, ensuring toughness and corrosion resistance. [Solution] The method for manufacturing a welded joint includes a step of welding a base material, which is a duplex stainless steel in which the main phases are a ferrite phase and an austenite phase, with a weld metal. The base material contains, by mass%, 20% to 28% Cr, 0.1% to 5.0% Mo, and 0.1% to 0.4% N. The ferrite content of the base material is 30% to 70% by volume. The heat input in the welding process is less than or equal to the upper limit of heat input Q (J / mm) expressed by the following (Equation 1). Q = 280 × h + {80 × ([Cr] + [Mo])} 2 -4870×([Cr]+[Mo])+73800} (Formula 1) (However, in (Equation 1), [Cr] represents the Cr content (mass%), [Mo] represents the Mo content (mass%), and h represents the thickness of the base material (mm).)

Images