Experimental Study on Tensile Mechanical Properties of S30408 and S31603 Stainless Steel at Low Temperature

In recent years, the application of cryogenic liquids has significantly expanded across energy, aerospace, chemical engineering, and biomedical industries, driven by industrial upgrading and technological breakthroughs. As critical equipment supporting liquefied natural gas storage, rocket propulsion systems, cryogenic reactors, and cellular cryopreservation facilities, the safety and economic performance of cryogenic pressure vessels have attracted widespread interdisciplinary attention. Austenitic stainless steel, known for its excellent welding performance and outstanding low-temperature properties, is widely used in the manufacturing of cryogenic vessels. Lightweight design has become the dominant development direction for future cryogenic vessels, and the danger posed by the occurrence of low-temperature brittle fracture of steel is significant. Therefore, it is essential for designers to have a comprehensive understanding of the performance evolution of materials at low temperatures, ensuring the safety of cryogenic pressure vessels while pursuing lightweight designs. A series of the low-temperature tensile tests were carried out to obtain the tensile properties of two austenitic stainless steels S30408 and S31603 at low temperature, including stress-strain curve, yield strength, tensile strength, elongation and reduction of area. A comprehensive analysis of the mechanical property variations at low temperatures was performed. The characteristics and patterns of fracture morphologies of the tensile specimens at different temperatures were observed and analyzed using a scanning electron microscope. The results show that S30408 and S31603 exhibit significant low-temperature strengthening but display reduced plasticity, with yield strength and tensile strength increasing linearly as temperature decreases, while post-fracture elongation and reduction of area decrease. With decreasing temperature, both materials exhibit progressive dimple refinement and smoothing of the shear lip region, accompanied by an increase in α′ martensite content. While S31603 exhibits superior ductility retention (delaying through-thickness crack formation to 77 K compared to 150 K in S30408), S30408 demonstrates higher tensile strength.