ASTM A789 ASME SA 789 SAF 2507 UNS S32750 (EN 10216 – 5 1.4410) Stainless Steel is super duplex stainless steel with 25% chromium, 4% molybdenum, and 7% nickel designed for demanding applications which require exceptional strength and corrosion resistance, such as chemical process, petrochemical, and seawater equipment. The steel has excellent resistance to chloride stress corrosion cracking, high thermal conductivity, and a low coefficient of thermal expansion.
S32750 Stainless Steel have enhanced pitting and crevice corrosion resistance when compared with 300-series austenitic stainless steel or conventional duplex alloys. This can be attributed to the enhanced levels of chromium, molybdenum and nitrogen found in these materials. Alloy 2507 is the most common “super” duplex grade.
Guanyu Steel Tube Super Duplex 2507 Stainless Steel Pipe Corrosion Resistance
1. Usual Corrosive
The higher chromium and molybdenum content of SAF 2507 has a strong resistance to overall corrosion of organic acids such as formic acid, acetic acid, etc. The SAF2507 alloy has a strong resistance to inorganic acids, especially those containing chloride The corrosion resistance.
Compared to 904L, SAF2507 has a stronger corrosion resistance to diluted sulfuric acid ions. 904L is an austenitic alloy that is designed to withstand pure sulfuric acid corrosion.
316L grade can not be used in hydrochloric acid environment, it may be subject to local corrosion or corrosion.
SAF2507 can be used for dilution of hydrochloric acid environment, has a strong anti-stain and anti-fissure corrosion ability.
2. intergranular corrosion
The lower carbon content of the nSAF 2507 greatly reduces the risk of carbide precipitation in the intergranular phase during heat treatment, and therefore the alloy has a strong ability to resist intergranular corrosion associated with carbides.
3. Stress corrosion cracking
The compound structure of SAF 2507 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 in the construction and other aspects is almost inevitable, which makes the stainless steel in the chloride environment more susceptible to corrosion.
SAF 2507 has a strong ability to crack corrosion resistance. SAF 2507 containing 2000ppm chloride ion in the sulfuric acid corrosion curve 0.1 mm / year; Corrosion curve in hydrochloric acid 0.1 mm / year.
Mechanical properties: SAF 2507 has a high compressive strength, impact strength and low coefficient of thermal expansion and high thermal conductivity. These features apply to many structural parts and mechanical parts. SAF 2507 impact strength is high, not long-term placed Higher than 570 ° F in the temperature environment, this may weaken its toughness. Tensile strength: σb ≥ 730Mpa; Elongation: δ ≥ 20%
Supporting welding consumables: ER2594 welding wire, E2594 electrode
Applications: pulp and paper industry, desalination, flue gas purification, heat exchangers, chemical tanker piping systems, seawater systems.
SUPER DUPLEX 2507 STAINLESS STEEL PIPE CHEMICAL COMPOSITION:
| STEEL Grade | C≤ | Mn≤ | Si≤ | S≤ | P≤ | Cr | Ni | Mo | Cu≤ | N |
| S32750（SAF2507）00Cr25Ni7Mo4N | 0.03 | 1.2 | 0.8 | 0.02 | 0.035 | 24/26 | 6.0/8.0 | 3.0/5.0 | 0.5 | 0.24/0.32 |
| S31803（SAF2205）00Cr22Ni5Mo3N | 0.03 | 2.0 | 1.0 | 0.02 | 0.03 | 21/23 | 4.5/6.5 | 2.5/3.5 | 0.08/0.20 | |
| S31500(3RE60)00Cr18Ni5Mo3Si2 | 0.03 | 1.2/2.0 | 1.4/2.0 | 0.03 | 0.03 | 18/19 | 4.255.25 | 2.5/3.0 | 0.05/0.10 |
After proper solution treatment of 2507 stainless steel, the microstructure of the steel is more ideal than the dual phase structure of alpha / gamma ratio of 50/50. When the solution temperature is above 1050 DEG C, the ferrite phase number increases with the increase of temperature, but because of the high nitrogen content, there is no significant change in the phase ratio below 1300. This steel without aging at different temperature (or heat effect), in the alpha + gamma matrix will be formed and delta gamma 2, x, R, alpha ` intermetallic phases and Cr2N oxide precipitates, because the carbon content of the steel is low (usually 0.01%-0.02%), so in general no carbide steel.SUPER DUPLEX 2507 STAINLESS STEEL PIPE MECHANICAL PROPERTY:
| STEEL GRADE | Heat treatment temperature℃ | σb (Mpa)≥ | σs(Mpa)≥ | δ%≥ | Hardness≤ | |
| Brinell | Rockwell | |||||
| S32750（SAF2507）00Cr25Ni7Mo4N | 1025-1125Water quenching | 800 | 550 | 15 | 310 | 32 |
| S31803（SAF2205）00Cr22Ni5Mo3N | 1020-1100Water quenching | 620 | 450 | 25 | 290 | 30.5 |
| S31500(3RE60)00Cr18Ni5Mo3Si2 | 980-1040Water quenching | 630 | 440 | 30 | 290 | 30.5 |
