Austenitic (duplex) stainless steel 2507 melting point and density, solid solution and solid state properties

2507 is a ferritic-austenitic (duplex) stainless steel with excellent resistance to pitting corrosion, crevice corrosion and uniform corrosion.

The crack oxidation behavior of 2507 duplex stainless steel was studied, and its mechanism was discussed. Oxidation experiments and characterization analyzes were conducted on the samples using electrochemical methods and SEM analysis methods respectively. The results show that there are differences in the oxidation behavior of cracks in 2507 duplex stainless steel under different temperatures and atmospheres. When the temperature is high, the oxides will form larger pores inside the cracks, leading to crack expansion and deformation.

Mechanical properties

Tensile strength δb/MPa: 800-1000

Yield strength δ0.2/MPa: ≥550

Elongation δ5/%: ≥25

Hardness (HV): 290

2507 duplex stainless steel is a high-strength, high-corrosion-resistant material that is widely used in marine industry, chemical industry, energy and other fields. However, during use, due to long-term exposure to mechanical stress and environmental atmosphere, cracks in stainless steel will gradually expand and seriously affect the performance of the material. Therefore, the study of crack behavior and exploration of the oxidation mechanism of cracks are crucial to improving the corrosion resistance of materials and extending their service life.

Chemical composition of 2507 stainless steel:

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

2507 duplex stainless steel was selected as the experimental material and cut into circular samples with a diameter of 10mm. Mechanical stretching method is used to process cracks with a length of 3 mm on the surface. The prepared samples need to be surface cleaned and polished before experiments to ensure that the surface is flat and free of impurities.

After suitable solution treatment of 2507 stainless steel, the microstructure of this steel has an ideal dual-phase structure with an α/γ ratio of approximately 50/50. When the solid solution temperature is above 1050°C, the number of ferrite phases in the steel will increase as the temperature increases. However, due to the high nitrogen content, the phase ratio of the steel will not change significantly below 1300°C. If this steel is not aged at different temperatures (or affected by heat), γ2 will be formed on the α+γ matrix and δ, χ, R, α` intermetallic phases and Cr2N and other oxides will precipitate. Due to the carbon content in the steel Low (generally 0.01%-0.02%), so there are generally no carbides in steel.

In the experiment, the samples were exposed to different atmospheres (such as air, moisture and high temperature and high pressure atmosphere) and tested at different temperatures. Place the sample into an aqueous solution compatible with the electrolyte for electrochemical oxidation experiments. During the experiment, the degree of oxidation and changes in chemical substances on the sample surface were monitored.

Application areas

Pulp and paper industry, seawater desalination, flue gas purification, heat exchangers, chemical tanker piping systems, seawater systems, etc.

There are differences in the oxidation behavior of cracks in 2507 duplex stainless steel under different temperatures and atmospheres. Under normal temperature and humid atmosphere, oxides are mainly distributed on the crack surface and open pores. When the temperature is high, the oxides will form larger pores within the cracks, leading to crack expansion and deformation. Under high-temperature and high-pressure atmosphere, the compounds formed between oxides and cracks will cause strong crack expansion.