Chemical Composition and Microstructure of SUS 310S
SUS 310S is an austenitic stainless steel commonly used in industrial furnaces, petrochemical plants and flare stacks for its good oxidation resistance and high-temperature strength. It is often mistakenly referred to as “super” stainless steel due to its excellent mechanical properties and high corrosion resistance. SUS 310S is a variant of the 310 austenitic stainless steel. In addition to the 310manganese and nickel added to the basic 22Cr-12Ni steel, it also includes 25Cr-7Mo-4Nb which is used to enhance its thermal resistance (Figure 1). The composition of SUS 310S is balanced to make it austenitic in nature, which results in good formability and weldability.
In terms of its chemical composition, SUS 310S consists primarily of iron, chromium, manganese, nickel and silicon, in addition to smaller amounts of molybdenum, nitrogen, sulfur and phosphorus. The composition of SUS 310S is distinctive from other stainless steels in that it contains a higher percentage of chromium and molybdenum and it also has a lower carbon content (0.08%).
In terms of its microstructure, SUS 310S is a martensitic microstructure. It is composed of alpha-iron gamma-iron, ferrite and carbides (Figure 2). Alpha-iron is the hardest and most desirable form of iron because it contributes to the strength of the alloy. Gamma-iron contains a small amount of carbon and is fairly soft when compared to alpha-iron. Ferrite is an extremely small particle which is not as desirable as alpha-iron because it makes the alloy more brittle. Carbides are the strongest form of iron and they contribute to the hardness and wear resistance of the alloy.
SUS 310S has remarkable mechanical properties, especially in terms of its resistance to oxidation, high-temperature strength and its excellent ductility. Its oxidation resistance and high-temperature strength come from its chromium and molybdenum content and its excellent ductility is due to its martensitic microstructure. When exposed to temperatures up to 2,400F (1,349C), SUS 310S retains its good oxidation resistance, high-temperature strength and excellent ductility.
SUS 310S is commonly used for petrochemical equipment, industrial furnaces and flare stacks due to its excellent corrosion resistance and high-temperature strength. It is also used to manufacture aircraft components because of its good ductility and outstanding mechanical properties.
Overall, SUS 310S is an outstanding stainless steel alloy with excellent mechanical properties, oxidation resistance and high temperature strength. Its unique composition and microstructure make it an ideal choice for applications requiring high temperature resistance and good oxidation resistance.
