Abstract
Austenitic stainless steel (AUS) is one of the most widely used stainless steels for its excellent corrosion resistance and mechanical properties. AUS steel S31723 is a low-carbon, high Cr-Ni austenitic stainless steel with excellent corrosion resistance and high temperature oxidation resistance, making it ideal for use in industrial applications such as chemical processing, oil and gas production, food processing, and aviation. This paper presents an overview of the chemical composition, physical and mechanical properties, and corrosion resistance of AUS S31723 steel. The microstructures, processing, fabrication methods, and weldability of S31723 steel are also discussed.
Introduction
The AUS or austenitic stainless steel family of materials represents is a class of stainless steels that are characterized by its austenitic structure. AUS are chromium-nickel alloys that show a high degree of corrosion and oxidation resistance, mechanical strength, and other useful properties. AUS steel S31723 is one of the more popular AUS materials for its superior performance in terms of mechanical properties, corrosion resistance, and weldability. S31723 steel is a low-carbon, high Cr-Ni austenitic stainless steel that comes in the form of bars, plates, sheets, and tubing. The chemical composition of S31723 steel is presented in Table 1.
Table 1. Chemical Composition of S31723 Steel
Element Content (wt%)
C 0.03
Mn 1.50
Si 1.00
P 0.035
S 0.030
Cr 18.00
Ni 14.00
Mo 8.00
Physical and Mechanical Properties
The physical and mechanical properties of S31723 steel are displayed in Table 2. Steel S31723 is capable of withstanding temperatures up to 900°C and is known to have excellent formability and good weldability.
Table 2. Physical and Mechanical Properties of S31723 Steel
Properties Value
Density 7.80 g/cm³
Tensile Strength 550–675 MPa
Yield Strength 325–370 MPa
Elongation (% in 50 mm) 19–25
Thermal Conductivity 26.3 W/m⋅K
Thermal Expansion (10–6K−1) 17.2
Corrosion Resistance
Due to the high chromium and nickel content, AUS S31723 demonstrates excellent corrosion resistance in a number of different environments. It is especially effective at providing corrosion resistance in acidic and oxidizing media when compared to other stainless steels. S31723 has good chloride stress corrosion cracking (SSCC) resistance and has been shown to resist pitting, crevice corrosion and intergranular corrosion.
Microstructures and Processing
The microstructure of S31723 consists mainly of face-centered cubic (FCC) austenite grains and unalloyed carbides present at the grain boundaries. With an effective grain size of 8 ~ 10 μm, S31723 is relatively ductile and exhibits good low-temperature toughness. This material can be readily cold and hot worked, including rolling, forging, deep drawing, and extrusion.
Fabrication and Weldability
The fabrication process of S31723 requires special precautions as it is susceptible to sensitization due to the presence of chromium carbides at the grain boundaries. These carbides can lead to intergranular corrosion when exposed to temperatures exceeding 480°C. In order to avoid this issue, fabrication during welding should be done below 220–550°C to prevent chromium carbide precipitation.
When it comes to welding, S31723 steel is well suited for conventional welding processes such as gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and shielded metal arc welding (SMAW). However, it is important to note that hot working and welding at temperatures higher than 650°C should be avoided to minimize the formation of chromium carbides.
Conclusion
AUS S31723 is a low-carbon, high-Cr-Ni austenitic stainless steel that is known for its excellent corrosion resistance and mechanical properties. It is capable of withstanding temperatures up to 900°C and is readily cold and hot worked. When welded, S31723 requires special precautions to avoid sensitization due to the presence of chromium carbides at the grain boundaries. S31723 is well suited for conventional welding processes such as the GTAW, GMAW, and SMAW. In conclusion, S31723 steel is an ideal choice for use in industrial applications such as chemical processing, oil and gas production, food processing, and aviation.
