254SMO is an austenitic stainless steel. Because of its high molybdenum content, it has high resistance to spot corrosion and crevice corrosion. This grade of stainless steel is developed for use in environments containing halides such as seawater. 254SMO also has good resistance to uniform corrosion. Especially in acid containing halide, the steel is superior to ordinary stainless steel. Its C content is<0.03%, so it is called pure austenitic stainless steel (<0.01% is also called super austenitic stainless steel). Super stainless steel is a kind of special stainless steel, which is different from ordinary stainless steel in chemical composition. It refers to a kind of high alloy stainless steel containing high nickel, high chromium and high molybdenum. 254SMo, which contains 6% Mo, has very good local corrosion resistance. Under the conditions of sea water, air inflation, crevice and low-speed scouring, it has good pitting corrosion resistance (PI ≥ 40) and good stress corrosion resistance. It is a substitute material for Ni based alloys and titanium alloys. Secondly, in terms of high-temperature or corrosion resistance, it has better high-temperature or corrosion resistance, which is irreplaceable for 304 stainless steel. In addition, from the classification of stainless steel, the metallographic structure of special stainless steel is a stable austenitic metallographic structure.
As this special stainless steel is a high alloy material, its manufacturing process is quite complex. Generally, people can only rely on traditional processes to manufacture this special stainless steel, such as pouring, forging, rolling, etc.
254SMo carbon (C) ≤ 0.02, manganese (Mn) ≤ 1.00, nickel (Ni) 17.5 ～ 18.5, silicon (Si) ≤ 0.8, phosphorus (P) ≤ 0.03, sulfur (S) ≤ 0.01, chromium (Cr) 19.5 ～ 20.5, copper (Cu) 0.5 ～ 1.0, molybdenum (Mo) 6.0 ～ 6.5
UNS S31254、DIN/EN 1.4547、ASTM A280、ASME SA-240
Supporting welding materials
ERNiCrMo-3 welding wire, ENiCrMo-3 welding rod
1. Oceans: marine structures of marine environment, seawater desalination, mariculture, seawater heat exchange, etc.
2. Environmental protection: flue gas desulfurization device for thermal power generation, wastewater treatment, etc.
3. Energy field: atomic power generation, comprehensive utilization of coal, tidal power generation, etc.
4. Petrochemical industry: oil refining, chemical equipment, etc.
5. Food field: salt making, soy sauce brewing, etc.
6. High concentration chloride environment: paper industry, various bleaching devices.
High temperature resistance
1. A large number of field experiments and use experience show that even at slightly higher temperatures, 254SMO also has high crevice corrosion resistance in seawater, and only a few kinds of stainless steel have this performance.
2. The corrosion resistance of 254SMO in acid solutions and oxidizing halide solutions, such as those required for bleaching production in the paper industry, can be compared with that of nickel base alloys and titanium alloys with strong corrosion resistance.
3. Because 254SMO has a high nitrogen content, its mechanical strength is higher than other kinds of austenitic stainless steel. In addition, 254SMO has high ductility, impact strength and good weldability.
4. The high molybdenum content of 254SMO can make it have a higher oxidation rate during annealing, so it has a rougher surface than ordinary stainless steel after pickling. However, this has no adverse effect on the corrosion resistance of the steel.