UNS S38108 Austenitic Stainless Steel
Introduction
UNS S38108 is an Austenitic steel with a Cr-Ni-Si composition. It is a low-cost stainless steel that offers enhanced strength and ductility compared to other 400 series steels, making it an attractive material choice for industrial and consumer applications. The UNS S38108 designation applies to the UNS S21325 variant with its MAX Si content, which is approximately 4.0%, and to the UNS S38110 variant with a slightly lower Si content of approximately 3.5%.
Chemical Composition
The chemical composition of UNS S38108 consists of:
• Carbon (C): 0.03 – 0.08%
• Manganese (Mn): 2.0% max
• Silicon (Si): 4.0% max
• Phosphorus (P): 0.045% max
• Sulfur (S): 0.03% max
• Chromium (Cr): 18.0 – 20.0%
• Nickel (Ni): 3.0 – 5.0%
• Iron (Fe): Balance
• Copper (Cu): 0.75% max
• Nitrogen (N): 0.10% max
• Other elements such as Boron (B) 0.006% and Titanium (Ti) 0.05% can be added in trace amounts.
Properties and Applications
UNS S38108 is one of the most common grades of Austenitic stainless steel. It has good general corrosion resistance, outstanding formability and weldability, and excellent workability. It has very good stress corrosion cracking resistance and good ductility, making it ideal for a variety of applications.
Due to its excellent properties, UNS S38108 has found application in a wide range of industries, such as:
• Food processing
• Chemical processing
• Oil and gas
• Power generation
• Mining
• Pharmaceutical
• Aerospace
• Automotive
• Electronics
• Architecture
• Medical devices
• Marine applications
• Construction
Physical Properties
UNS S38108 has a density of 8.03 g/cm3 and a melting point range of 1398 –1425˚C. Its tensile strength can reach 580 – 620 MPa, and its yield strength can reach 300 – 320 MPa. Its elongation at break is 40 – 50%.
Welding
UNS S38108 can be welded by both Shielded Metal Arc Welding (SMAW) and Gas Metal Arc Welding (GMAW) methods. It is recommended that the weld joint be stress relieved before welding. The weld joint should be cleaned before post-weld heat treatment by grinding off dirt and oxide films, and then pickling it in a 10% nitric acid solution.
The weld metal should be matched to the base metal and the welding process should be controlled so that the weld metal composition is not higher than the base metal. An incorrect weld metal composition or an excessive heat input can reduce corrosion and mechanical properties.
Heat Treatment
UNS S38108 is not normally heat treated. However, when fabricated in lower strengths, it can be heat treated at temperatures up to 1150°C for stress relief. Stress relief should not be performed above 1150°C, as this can lead to a reduction in surface oxide films, which can result in intergranular corrosion.
Fabrication
UNS S38108 can be hot-worked, cold-worked, machined and welded. It is recommended to use hot-working for parts that require greater strength, and cold-working for parts that require greater ductility.
Machining of UNS S38108 can be done using the usual tooling and machining methods, such as turning, tapping, shaping and grinding. Cutting, drilling and machining should be done using low cutting speeds, using recommended cutting fluids and large, rigid tools.
Specialty Coatings
UNS S38108 can be electroplated with nickel or chromium to further enhance its corrosion resistance and make it more suitable for a variety of applications. It is also available with specialty PTFE coatings, which help protect against abrasion and chemical corrosion.
Conclusion
UNS S38108 is an Austenitic stainless steel with good general corrosion resistance, outstanding formability and weldability, and excellent workability. It has very good stress corrosion cracking resistance and good ductility, making it ideal for a variety of industrial and consumer applications. It can be welded and machined, and is available with specialty coatings for enhanced corrosion resistance.
