Effect of Thermal Aging on Impact Toughness of Electron Beam-Welded AISI 316 Stainless Steel

Abstract

Thick section of cold-rolled austenite stainless steel AISI 316 is widely used in heat exchangers, jet engines, furnace parts, exhaust manifolds, fast breeder test rector, etc., because of its high strength, corrosion, and pitting resistance properties at high working temperature 400–550 °C approximately. Electron beam welding is considered as highly efficient welding process in order to achieve high-quality welds with low heat-affected zone. In this paper, single-pass narrow gap square butt welding of 18-mm-thick plates using electron beam welding at constant accelerating voltage 150 kV, beam current 90 mA, welding travel speed 600 mm/min, and beam oscillation in circular pattern was investigated. The impact toughness and metallurgical properties in as-welded condition and after imparting post-weld thermal aging (PWTA) at 750 °C for 24 h were also investigated in this piece of work. The full penetration had been achieved in single pass by optimizing the relationship between welding parameters (beam accelerating voltage, beam current, welding travel speed, and beam oscillation). The results showed that welding of plates without filler metal leads to defect-free welds. The average impact toughness conducted by Charpy impact test at cryogenic temperature (−40 °C) in as-welded samples was recorded as 284 J, and after aged at 750 °C for 24 h it reduced to 180 J.