Leading stainless steel rod and bar Suppliers in China

DUPLEX 2507 STAINLESS STEEL ROD AND BAR

• Daxun Alloys Stainless Steels inventory currently contains Duplex 2507 Round Bar and Flat Bar, which isare available in both cold rolled and hot rolled forms. This super duplex stainless steel bar contains 25% chromium, 4% molybdenum and 7% nickel. The alloy is suitable for applications requiring high strength and corrosion resistance, such as chemical processing, petrochemical and seawater equipment. The steel has strong resistance to chloride stress corrosion cracking, good thermal conductivity and a low coefficient of thermal expansion. The high chromium, molybdenum and nickel content provides excellent resistance to pitting, crevice and general corrosion.

Applications

• • Oil and gas:
  • Offshore platforms, heat exchangers, water systems
  • Fire-fighting, injection, and ballast water systems
  • Chemical processing:
  • Heat exchangers, vessels, and piping
  • Desalination:
  • High-pressure RO systems and seawater piping
  • Mechanical and structural components:
  • High-strength, corrosion-resistant parts
  • Power industry:
  • FGD systems, scrubber systems, absorber towers
  • Ducting and piping
  • Export Destinations: Our 2507 stainless steel round bars are exported to various countries, including Costa Rica and South Korea, highlighting our global reach and the international demand for our high-quality products.

Standards

• ASTM/ASME ………. A240 – UNS S32750
  EURONORM………… 1.4410 – X2 Cr Ni MoN 25.7.4
  AFNOR……………….. Z3 CN 25.06 Az

CORROSION RESISTANCE

General corrosion

SAF 2507™ exhibits excellent resistance to general corrosion. It is highly resistant to corrosion by organic acids. In 10% formic and 50% acetic acid, it experiences less than 0.05 mm/year. This outperforms ASTM 316L, which has a corrosion rate higher than 0.2 mm/year. SAF 2507™ remains resistant even in contaminated acids (see Figures 5 and 6).

Figure 4. Isocorrosion diagram in formic acid. The curves represent a corrosion rate of 0.1 mm/year (4 mpy) in stagnant test solution.

Figure 5. Corrosion rate of various alloys in 80% acetic acid with 2000 ppm chloride ions at 90°C.

Figure 6. Corrosion rate of various alloys in concentrated acetic acid with 200 ppm chloride ions.

SAF 2507™ exhibits excellent resistance to general corrosion. It is highly resistant to corrosion by organic acids. In 10% formic and 50% acetic acid, it experiences less than 0.05 mm/year. This outperforms ASTM 316L, which has a corrosion rate higher than 0.2 mm/year. SAF 2507™ remains resistant even in contaminated acids (see Figures 5 and 6).

Figure 7. Isocorrosion diagram in naturally aerated sulfuric acid. The curves represent a corrosion rate of 0.1 mm/year (4 mpy) in a stagnant test solution.

Figure 8. Isocorrosion diagram, 0.1 mm/year (4 mpy) in a naturally aerated sulfuric acid containing 2000 ppm chloride ions.

Figure 9. Isocorrosion diagram in hydrochloric acid. The curves represent a corrosion rate of 0.1 mm/year (4 mpy) in stagnant test solution.

SAF 2507™ excels in resisting inorganic acids, often surpassing high-alloy austenitic stainless steels. Isocorrosion diagrams reveal its strength against sulfuric and hydrochloric acids. The alloy thrives in terephthalic acid plants, proving its exceptional resistance. It offers a competitive edge over high-alloyed austenitics and nickel alloys. In environments where standard austenitic stainless steels falter, SAF 2507™ stands strong. Its performance in harsh chemical settings makes it a top choice. Industries dealing with corrosive acids find SAF 2507™ to be a reliable solution. The alloy’s versatility shines in various concentration ranges of inorganic acids.

To ensure the highest quality, all products undergo rigorous testing and third-party inspection before packaging.

Pitting and crevice corrosion

Stainless steel’s resistance to pitting and crevice corrosion hinges on key elements. Chromium, molybdenum, and nitrogen content significantly impact its performance. The manufacturing process plays a vital role in corrosion resistance. Welding and other fabrication methods can affect the steel’s durability. SAF 2507™’s composition is optimized for superior corrosion resistance. Its high alloy content ensures robust protection against localized corrosion. Proper manufacturing techniques enhance the material’s service life. In challenging environments, SAF 2507™ stands out for its resilience.

The PRE (Pitting Resistance Equivalent) number is a parameter used to compare the resistance to pitting in chloride environments. It is defined as PRE = %Cr + 3.3 x %Mo + 16 x %N (in weight-%). In duplex stainless steels, the pitting corrosion resistance is determined by the PRE value in both the ferrite and austenite phases. The phase with the lowest PRE value limits the actual pitting corrosion resistance. SAF 2507™ has been carefully balanced to achieve equal PRE values in both phases.

SAF 2507™ seamless tubes boast a minimum PRE value of 42.5. This surpasses other 25Cr duplex steels, like UNS S31260, significantly. The ASTM G48 test rigorously evaluates pitting and crevice corrosion resistance. It exposes steel to harsh 6% FeCI3 solutions, with and without crevices. A modified version increases temperature until pitting occurs. Figure 11 displays critical pitting and crevice temperatures from this test. Potentiostatic tests reveal performance in varied chloride and acidic environments. These tests use high potentials, exceeding typical seawater conditions. As a result, critical temperatures are lower than in most practical applications. SAF 2507™ consistently demonstrates superior corrosion resistance in these demanding tests.

Figure 10. Critical pitting and crevice temperatures in 6% FeCl₃, 24h (similar to ASTM G48).

SAF 2507™ and 6Mo+N show similar pitting resistance in 6% FeCl3. Tests in natural seawater evaluated critical crevice corrosion temperatures. The potential applied was 150 mV vs SCE, with temperature increases every 24 hours. Results are presented in the accompanying table. Crevice corrosion propagation rates were also measured at different temperatures. SAF 2507™ demonstrated remarkably low propagation rates compared to 6Mo+N alloy. Its rates were approximately ten times lower, showcasing superior corrosion resistance. This performance highlights SAF 2507™’s effectiveness in challenging marine environments. The data underscores its suitability for applications requiring exceptional corrosion resistance.

In these tests the propagation rates of initiated crevice corrosion attacks, at 15-50°C (59-122°F) and an applied potential of 150 mV vs SCE were also determined. These were found to be around ten times lower for SAF™ 2507 than for the 6Mo+N alloy.

Figure 11. Critical pitting temperatures (CPT) at varying concentrations of sodium chloride, from 3 to 25%

The CPT values were determined potentiostatically at +600 mV SCE with surfaces ground using 600 grit paper.

Stress corrosion cracking

SAF 2507™ shows remarkable resistance to chloride-induced stress corrosion cracking (SCC). Figure 13 displays its performance in high-temperature chloride solutions. The alloy resists SCC in up to 1000 ppm Cl⁻ at 300°C. It also withstands 10000 ppm Cl⁻ at 250°C without cracking. U-bend tests in hot brine further prove its durability. SAF 2507™ maintains integrity in 40% CaCl₂ at high temperatures. Its threshold stress exceeds 90% of tensile strength for both base metal and welds. Figure 14 reveals its superiority in acidified conditions compared to SAF 2205™. Even in boiling 45% MgCl₂, SAF 2507™ retains half its proof strength. These results underscore SAF 2507™’s exceptional SCC resistance across various harsh environments, partly due to its low thermal expansion.

Figure 13. SCC resistance in oxygen-bearing (abt. 8 ppm) neutral chloride solutions. Testing time 1000 hours. Applied stress equal to proof strength at testing temperature.

Figure 14. Results of SCC tests with constant load in 40% CaCl₂, pH=1.5, at 100 °C (210°F) with aerated test solution.

Figure 15. Constant load SCC tests in NACE solution at room temperature (NACE TM 0177).

Hydrogen Induced Stress Cracking (HISC)

The acceptable stress without HISC occurring for products with different austenite spacing is illustrated in figure 16.

Intergranular corrosion

SAF 2507™ shows excellent resistance to intergranular corrosion. Its balanced composition allows quick austenite reformation in weld-affected zones. This microstructure ensures strong corrosion resistance. The alloy passes the ASTM A262 Practice E (Strauss test) without issues.

Erosion corrosion

SAF 2507™ excels in erosion corrosion resistance. Its mechanical properties and corrosion resistance contribute to this strength. Tests in sand-containing media prove its superiority over austenitic stainless steels. Figure 17 compares mass loss rates of different alloys. SAF 2507™ outperforms SAF 2205™ and 6Mo+N austenitic steel. These tests used synthetic seawater with silica sand at various velocities. The results highlight SAF 2507™’s durability in erosive environments. This makes it ideal for applications facing both corrosion and erosion challenges.

Figure 17. Relative mass loss rate after testing of the resistance against erosion corrosion.

PROCESSING

2507-S32750 grade stainless steel round bars

Stainless steel round bars can be easily ordered in a wide range of sizes. Simply select the grade of steel you require and we will provide bars in lengths ranging from 500mm to 6 meters, and diameters ranging from 3mm to 500mm. We even give you the option of ordering in metric or imperial sizes. If you want something that is not a standard size, that’s no problem. We offer unlimited free cuts to length. Using state-of-the-art bandsaws to ensure accuracy and repeatability, we can precisely meet your requirements every time. Just let us know when ordering.