We are familiar with stainless steel, and there are many grades.Today we will learn about the 2507 duplex stainless steel pipe.
The main component of 2507 duplex stainless steel pipe is 25Cr-7Ni-4Mo-0.27N, which is a ferritic-austenitic (duplex) stainless steel.
2507 duplex stainless steel has high chromium and molybdenum content, and has strong overall corrosion resistance to organic acids such as formic acid and acetic acid.
The microstructure of 2507 duplex stainless steel ensures that the steel has high resistance to stress corrosion cracking and high mechanical strength.
Due to its unique advantages, 2507 duplex stainless steel is widely used in petrochemical equipment, seawater and wastewater treatment equipment, oil pipelines, papermaking machinery and other industrial fields.
2507 duplex stainless steel is also used in desalination (desalination) equipment (and high-pressure pipes in equipment, seawater pipes) and combustion (waste) gas purification equipment.
In recent years, it has also been studied and applied in the field of bridge load-bearing structure, and has a good development prospect.
Features of 2507 Duplex Stainless Steel
1) Strong corrosion resistance
The higher chromium and molybdenum content of SAF2507 makes it have strong resistance to overall corrosion of organic acids such as formic acid and acetic acid.
SAF2507 alloy also has strong corrosion resistance to inorganic acids, especially those containing chlorides.
SAF2507 can be used in dilute hydrochloric acid environment, and has strong anti-spot damage and anti-crevice corrosion ability.
2) Strong resistance to intergranular corrosion
The lower carbon content of 2507 duplex stainless steel greatly reduces the risk of intergranular carbide precipitation during heat treatment.
Therefore, this alloy is highly resistant to carbide-related intergranular corrosion.
3) Strong resistance to stress corrosion cracking
The duplex structure of SAF2507 makes it highly resistant to stress corrosion cracking.
Due to its higher alloy content, the corrosion resistance and strength of SAF2507 are better than those of 2205.
SAF2507 has a strong ability to resist crack corrosion, the isocorrosion curve in sulfuric acid containing 2000ppm chloride ions is 0.1mm/year, and the isocorrosion curve in hydrochloric acid is 0.1mm/year.
Mechanical properties of 2507 duplex stainless steel
Tensile strength: σb≥730Mpa; Elongation: δ≥20%.
SAF2507 has high compressive strength, impact strength and low thermal expansion coefficient and high thermal conductivity. These properties apply to many structural and mechanical components.
SAF2507 has high impact strength and should not be exposed to temperatures above 570°F for long periods of time, which may weaken its toughness.
2507 Duplex Stainless Steel Pipe Safe Use Restrictions and Requirements
1) It is necessary to control the ratio of ferrite phase to austenite phase. The most suitable ratio is about half of the ferrite and austenite phases. The number of stages cannot exceed 65% to guarantee the best overall performance.
2) Master the structure transformation law of duplex stainless steel pipes, and be familiar with the TTT and CT transformation curves of various steels.
This is the key to properly guiding duplex stainless steel heat treatment and hot forming process recipes. Duplex stainless steels are more sensitive to brittle phase precipitation than austenitic stainless steels.
3) The continuous working temperature range of the duplex stainless steel tube is -50≤250℃, the lower limit depends on the brittle transition temperature of the steel, the upper limit is 475℃ brittle, and the upper limit temperature cannot exceed 300℃.
4) The duplex stainless steel pipe needs to be rapidly cooled after solution treatment. Slow cooling can lead to the precipitation of brittle phases, leading to a decrease in toughness, especially localized corrosion resistance.
5) The lower limit temperature of hot working and hot forming of high chromium molybdenum duplex stainless steel pipe should not be less than 950℃.
The lower limit temperature of super duplex stainless steel 2507 cannot be lower than 980 ℃ low chromium molybdenum duplex stainless steel 2304. Surface cracks caused by brittle phase precipitation are avoided.
6) Austenitic stainless steel cannot be processed at 650-800 °C, and can only be solution annealed.
7) Must be familiar with the welding rules of 2507 duplex stainless steel pipes, not all austenitic stainless steel pipes can be welded.
8) When selecting duplex stainless steels in different corrosive environments, attention should be paid to the corrosion resistance of the steel.
Although duplex stainless steel has good local corrosion resistance, for duplex stainless steel, it also has a suitable range of medium conditions, including temperature, pressure, medium concentration, pH value, etc., which need to be selected carefully.
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