24 July 2021 Duplex Stainless Steel
SAF2507 Duplex Stainless Steel Bar
SAF2507 is a ferritic-austenitic (duplex) stainless steel that combines the most beneficial properties of many ferritic and austenitic steels and has a very high content of chromium and molybdenum Good resistance to pitting, crevice corrosion and uniform corrosion. Biphasic microstructure ensures that the steel has a high resistance to stress corrosion cracking, and mechanical strength is also high.
Typical 2507 duplex stainless steel microstructure
2507 stainless steel used in the oil and gas industry; offshore oil and gas platform (heat exchanger tubes, water treatment and water supply systems, fire protection systems, water spray systems, water stabilization systems; petrochemical equipment; desalination (desalination) equipment High-pressure pipe, sea water pipe), mechanical and structural components that require both high strength and high corrosion resistance, and fuel (waste) gas purification equipment Main components: 25Cr-7Ni-4Mo-0.27N
National standards:
ASTM / ASME: A240 - UNS S32750
EURONORM: 1.4410 - X2 Cr Ni MoN 25.7.4
AFNOR: Z3 CN 25.06 Az
DIN / EN 1.4410, ASME SA-240
Corrosion resistance
1. Corrosion
The higher chromium and molybdenum content of SAF 2507 gives it greater resistance to monolithic corrosion of organic acids such as formic acid, acetic acid, etc. SAF 2507 alloy also has strong resistance to inorganic acids, especially those containing chloride Corrosion resistance.
Compared to 904L, SAF2507 is more corrosion resistant to diluted chloride ion mixed sulfuric acid.904L is an austenitic alloy designed to resist pure sulfuric acid corrosion.
316L grade can not be used in hydrochloric acid environment, it may be subject to local corrosion or overall corrosion .SAF2507 can be used in diluted hydrochloric acid environment, with strong resistance to damage and crevice corrosion resistance.
2. Intergranular corrosion
The lower carbon content of the nSAF 2507 greatly reduces the risk of carbide precipitation in the intergranular during heat treatment and therefore the alloy has strong resistance to intergranular corrosion associated with carbides.
3. Stress corrosion cracking
SAF 2507 duplex structure so that it has a strong resistance to stress corrosion cracking. Due to its high alloy content, SAF 2507 has better corrosion resistance and strength than 2205.
Cracks are almost inevitable in construction and other aspects, making stainless steel more susceptible to corrosion in the chloride environment .SAF 2507 has a strong resistance to crack corrosion .SAF 2507 in sulfuric acid containing 2000ppm chloride ion corrosion curve 0.1 mm / year; Equal corrosion curve in hydrochloric acid 0.1 mm / year.
Mechanical properties: SAF 2507 has high compressive strength, impact strength and lower thermal expansion coefficient and high thermal conductivity of these characteristics apply to many structural parts and mechanical parts. SAF 2507 high impact strength, should not be placed in a long-term Above a temperature of 570 ° F, this may reduce its toughness Tensile strength: σb ≥ 730Mpa Elongation: δ ≥ 20%
Supporting welding consumables: ER2594 wire, E2594 electrode
Applications: Pulp and paper industry, desalination, flue gas purification, heat exchangers, chemical tanker piping, seawater systems.
2507 stainless steel chemical composition:
C≤0.03, Si≤0.80, Mn≤1.2, Cr: 24-26, Ni: 6-8, S≤0.02, P≤0.035, Mo: 3-5, N: 0.24-0.32
After the proper solution treatment of 2507 stainless steel, the microstructure of this steel has a preferable double phase structure with α / γ of about 50/50. When the solution temperature is above 1050 ℃, the amount of ferrite phase in steel will increase with the increase of temperature. However, due to the high content of nitrogen, there will be no significant change in phase ratio just below 1300 ℃. If the steel without aging under different temperature (or affected by heat), there will γ2 formation and δ, χ, R, α 'intermetallic phases and Cr2N and other oxides on the α + γ matrix precipitation, due to the carbon content of steel Low (usually 0.01% -0.02%), so there is generally no carbide in the steel.
2507 stainless steel mechanical properties:
First, 2507 duplex stainless steel tube at room temperature mechanical properties:
Steel varieties: wall thickness ≤ 20mm; δb / MPa: 800-1000, δ0.2 / MPa: ≥ 550, δ5 /%: ≥ 25, hardness (HV): 290
Second, 2507 duplex stainless steel at room temperature - 200 ℃ mechanical properties:
Steel varieties temperature / ℃ δb / MPa
Room temperature ≥530
Plate 100 ≥ 450
200 ≥400
Third, 2507 large-caliber seamless pipe mechanical properties
Outside diameter × wall thickness δb / MPa δ0.2 / MPa δ5 /% Hardness (HV)
273.0 mm × 4.19 mm 894 644 40 284
323.9 mm × 4.57 mm 858 662 45 270
406.4 mm × 4.74 mm 854 657 41 272