2507 Stainless Steel is a ferritic – austenitic (duplex) stainless steel. The following is a detailed introduction from the aspects of its chemical composition, performance characteristics, application fields, processing and treatment, etc.:
Chemical Composition
Carbon (C) : The content is ≤ 0.03%. The low carbon content greatly reduces the risk of carbide precipitation in the grain boundaries during heat treatment and enhances the resistance to intergranular corrosion.
Silicon (Si) : The content is ≤ 0.80%. It can improve the strength and hardness of the steel, and to a certain extent, enhance the oxidation resistance of the steel.
Manganese (Mn) : The content is ≤ 1.2%. It can improve the strength and toughness of the steel and also improve the hot working performance of the steel.
Chromium (Cr) : The content is between 24% and 26%. It is the main element that makes stainless steel have corrosion resistance. It can form a dense oxide film on the surface of the steel to prevent the internal metal from further oxidation and corrosion.
Nickel (Ni) : The content is between 6% and 8%. It can improve the toughness and corrosion resistance of the steel, and at the same time, when combined with chromium, it enhances the stability of stainless steel in various corrosive environments.
Molybdenum (Mo) : The content is between 3% and 5%. It can enhance the corrosion resistance of the steel in reducing media and improve the resistance to pitting corrosion, crevice corrosion and uniform corrosion.
Nitrogen (N) : The content is between 0.24% and 0.32%. It can improve the strength and corrosion resistance of the steel, especially has a significant effect on improving the pitting and crevice corrosion resistance.
Sulfur (S) : The content is ≤ 0.02%. It is a harmful element. Too high content will reduce the toughness and corrosion resistance of the steel.
Phosphorus (P) : The content is ≤ 0.035%. It is also a harmful element, which will reduce the toughness and cold bending performance of the steel, so its content should be strictly controlled.
Performance Characteristics
Mechanical Properties
High Strength : The tensile strength σb is ≥ 730Mpa, the yield strength is high, and the yield strength with 0.2% residual deformation is ≥ 550MPa, which is much higher than that of ordinary stainless steel. It is suitable for structural components bearing high pressure and high load.
Good Toughness : The elongation δ is ≥ 20%, the impact strength is high, and it has good impact resistance, which can maintain the integrity of the structure in different environments.
Low Work Hardening Tendency : During processing, the increase in hardness is relatively slow, which is convenient for cold working forming operations.
Corrosion Resistance
Resistance to Pitting and Crevice Corrosion : The high content of chromium, molybdenum and nitrogen makes it have strong resistance to chloride ions, etc., and it is not easy to suffer from pitting and crevice corrosion in chloride – containing environments.
Resistance to Uniform Corrosion : It has strong resistance to overall corrosion of organic acids such as formic acid and acetic acid, and inorganic acids, especially inorganic acids containing chlorides.
Resistance to Stress Corrosion Cracking : Its duplex microstructure gives it excellent resistance to stress corrosion cracking, which can effectively prevent stress corrosion cracking in harsh working environments.
Application Fields
Oil and Gas Industry : It is used in heat exchanger tubes, water treatment and supply systems, fire fighting systems, water spray systems, water stabilization systems of offshore oil platforms, as well as subsea equipment, underwater pipelines, etc.
Chemical Processing Industry : It can be made into reactors, towers, storage tanks, pipelines, etc. in chemical equipment, which can resist the erosion of various corrosive media.
Energy Industry : Such as flue gas desulfurization systems (FGD systems), industrial scrubbing systems, absorption towers, pipelines in thermal power generation, etc., which can effectively resist the corrosion of acidic gases and liquids.
Seawater Desalination Field : In seawater desalination equipment, such as high – pressure reverse osmosis (RO) devices, seawater pipelines, etc., it can withstand the corrosion of seawater and ensure the long – term stable operation of the equipment.
Pulp and Paper Industry : It is used in equipment and pipelines for processing corrosive chemicals, such as digesters, bleaching equipment, pulp conveying pipelines, etc.
Processing and Treatment
Hot Working : The hot forming temperature should be between 1010°C and 1230°C. After hot working, solution treatment is required to obtain good performance.
Cold Working : Cold working operations such as cold bending, cold rolling and cold drawing can be carried out. However, due to its high strength, a large force is required during cold working, and attention should be paid to controlling the processing deformation to avoid defects such as cracks.
Welding : A variety of welding methods can be used, such as SMAW (Shielded Metal Arc Welding), GTAW (Gas Tungsten Arc Welding), PAW (Plasma Arc Welding), FCW (Flux – Cored Arc Welding) or SAW (Submerged Arc Welding), etc. During welding, it is usually recommended to use matching welding materials such as ER2594 welding wire or E2594 electrode.