1. Introduction
UNS S31254 (1.4547) or ASTM A182 F44, also known as Alloy 254 SMO, is a high-end stainless steel and one of the most common super austenitic grades. It increases the corrosion resistance of stainless steel by making it airtight and adding molybdenum and nitrogen. This combination of elements gives it superior stainless properties compared to other materials. Originally developed by Avesta Pjätteryd and Uddeholm in Sweden, 1.4547 is often referred to as 6-Moly, 6-Mo or 6M, since it contains 6% molybdenum.
Due to its exceptional corrosion resistance, 1.4547 finds its applications in oil and gas, marine and offshore, waste and water treatment, pulp and paper industries and food industry. This alloy is approved by several major bodies of the marine sector, such as the American Bureau of Shipping (ABS), Det Norske Veritas (DNV) and Lloyd’s Register of Shipping Marine and Offshore (LRS).
2. Properties and Material
1.4547 has a wide range of properties and it is also considered a material for high temperature applications. It contains Manganese (Mn) as a principal alloying element. It also has Copper (Cu), Nitrogen (N) and contents of Chromium (Cr) and Nickel (Ni) as secondary alloying elements. This grade has an outstanding corrosion resistance, uncommon in stainless steel.
1.4547 typically contains up to 14.9% Chromium, 20% - 22% Nickel, 6% Molybdenum, 1.6% - 3% Manganese, 0.15 - 0.8% Copper, 0.18 - 0.5% Nitrogen, as well as 0.3% - 0.6% Low Carbon and trace amounts of other elements. The alloy is normally delivered in the annealed or solution heat-treated condition for better formability and machinability. The material has excellent bound properties and high resistance to crevice and pitting corrosion, as well as stress corrosion cracking (SCC) in chloride environments.
3. Manufacturing Processes
1.4547 (Alloy 254 SMO) is useful in the manufacturing of a number of products which are exposed to aggressive environments. The alloy can be applied in the structural units, oil and gas production on the stationary production areas and in the marine environment. In the oil and gas industry, the alloy can be used for the production of pipes, umbilicals, reactors, flanges, manifolds, heat exchangers and other components.
1.4547 can be manufactured in a variety of shapes and possible forms, including sheets, plates, bars, wires and pipes. Common manufacturing processes applied to create products from this alloy are rolling, welding and forging, amongst other metallurgical treatments. The weldability of the material is considered to be good and it is usually welded with filler materials of the same or matched composition.
4. Applications
1.4547 (Alloy 254 SMO) is known for its high-corrosion resistance, pitting and crevice corrosion resistance, and stress corrosion cracking resistance. Aside from the oil and gas industry, it is also successfully implemented in many other applications, such as:
• Marine and offshore industries: This grade of stainless steel is commonly used for the manufacturing of shipbuilding components, such as marine propellers, turbines, pumps and compressors and offshore production equipment.
• Chemical processing: It can be used in the tank spargers and baffles in the plant equipment, which may come into contact with process fluids and aggressive chemicals.
• Electric equipment: In terms of their high corrosion resistance and excellent mechanical properties, 1.4547 is ideally suited for submarines and other electrical equipment, such as components and subsea power cables.
• Pollution control: The alloy is used in the production of scrubbers and filtration systems in the pollution control industry, where it is specifically resistant to corrosion from by-products and acids.
This grade of stainless steel is a great fit for many applications, in offshore and marine engineering, oil and gas industry, chemical processing industry, pollution control and electrical equipment, due to its unparalleled corrosion resistance and excellent low temperature mechanical characteristics.
5. Conclusion
1.4547 (Alloy 254 SMO) is a high-end stainless steel containing Manganese, Copper, Nitrogen, Chromium, and Nickel as principal alloying elements. It provides excellent corrosion protection, stress corrosion cracking resistance and pitting and crevice corrosion resistance higher than that of other stainless steels. The alloy is approved in many major offshore and marine bodies, such as the American Bureau of Shipping (ABS), Det Norske Veritas (DNV) and Lloyd’s Register of Shipping Marine and Offshore (LRS).
1.4547 grade stainless steel provides numerous advantages, including excellent mechanical characteristics and corrosion resistance in a variety of high-end applications. It is used extensively in the oil and gas, marine and offshore, and chemical processing industries. It is also suitable for electric and pollution control equipment, due to its excellent resistance to both corrosion and low temperature.
