N08904 and S31254 are both super austenitic stainless steels, which have achieved corrosion resistance far beyond conventional stainless steels through high alloy design. They are widely used in harsh corrosive environments such as chemical, marine, and environmental protection. HT PIPE is a SS904l and ss254smo supplier with 15+ export experience. Contact us for more information and quotes for free!
n08904 and s31254 chemical composition
| Element | N08904 (Mass Fraction, %) | S31254 (Mass Fraction, %) |
|---|---|---|
| Carbon (C) | ≤0.020 | ≤0.020 |
| Silicon (Si) | ≤1.00 | ≤0.80 |
| Manganese (Mn) | ≤2.00 | ≤1.00 |
| Phosphorus (P) | ≤0.045 | ≤0.030 |
| Sulfur (S) | ≤0.035 | ≤0.010 |
| Chromium (Cr) | 19.00～23.00 | 19.50～20.50 |
| Nickel (Ni) | 23.00～28.00 | 17.50～18.50 |
| Molybdenum (Mo) | 4.00～5.00 | 6.00～6.50 |
| Nitrogen (N) | ≤0.10 | 0.18～0.22 |
| Copper (Cu) | 1.00～2.00 | 0.50～1.00 |
| Iron (Fe) | Balance | Balance |
Technical Overview: The Core Differences
The primary differentiator between these two alloys is their position on the metallurgy scale:
UNS N08904 (904L) is a highly alloyed austenitic stainless steel containing low carbon and high levels of copper, designed originally to resist severe sulfuric acid environments.
UNS S31254 (254 SMO) is classified as a super austenitic stainless steel. It features a massive 6% molybdenum boost alongside a deliberate nitrogen addition, engineered specifically for high-chloride seawater and bleaching applications.
N08904 and S31254 Resistance to pitting and crevice corrosion
The PREN value of N08904 is about 36, and it performs well in reducing acids such as dilute sulfuric acid and phosphoric acid. ss904l has a certain resistance to pitting and crevice corrosion, but its performance is limited in high chloride ion environments.
The PREN value of S31254 is ≥ 43, and some batches can reach 42-44, far exceeding N08904. This material can withstand environments with chloride ion concentration ≤ 50000ppm, and its pitting rate is only 1/10 of 316L stainless steel.
UNS N08904 and UNS S31254 Acid and alkali corrosion resistance
N08904 has outstanding performance in harsh acidic media, especially in pure phosphoric acid, and can withstand corrosion from media such as acetic acid, ammonium phosphate, electrolyte, oxalic acid, superphosphate, zinc sulfate, etc.
S31254 has good resistance to oxidizing acids (such as nitric acid) and reducing acids (such as sulfuric acid and hydrochloric acid), but its targeted performance in pure phosphoric acid is not as good as N08904.
N08904 and S31254 Other corrosion resistance properties
Stress corrosion cracking resistance: Both suppress the risk of cracking in chloride environments through high alloy content, but S31254 has better cracking resistance in high-temperature and high chloride ion environments.
Antibacterial performance: The high chromium content of S31254 can form a dense passivation film, inhibit microbial adhesion, and comply with FDA/EC1935 food grade standards. N08904 does not have a clear publicly available antibacterial performance certification.
904l and 254smo Hot processing technology
N08904: At room temperature, uns n08904 has a pure austenitic structure and undergoes no structural transformation stress from liquid phase to solid phase. However, it is prone to coarsening of grains and intergranular enrichment of low melting point materials, which may lead to internal microcracks.
S31254: The hot working temperature range is 982-1149 ℃ (1800-2100 ° F). Exceeding this range will lead to an increase in material oxide scale and a decrease in processing performance. After hot processing, annealing treatment (1149-1204 ℃) and water quenching are required to restore maximum corrosion resistance.
ss254smo and ss904l cold working process
N08904: The cold working performance is affected by the austenite structure, and the plasticity is good. However, due to the high alloy content, a large pressure is required for cold working, and there is no clear publicly available data on the specific hardening rate.
S31254: Cold working can use traditional methods. After cold working, the material strength and toughness can be further improved, and its hardening can only be achieved through cold working, which does not respond to heat treatment hardening.
N08904 and S31254 welding process
N08904: 904L uses welding materials that match super austenitic stainless steel. It controls the welding temperature to avoid coarse grains.
S31254: Special welding materials are required for welding, and the recommended welding wire is AWS A5.14 ERNiCrMo-3 or alloy 625. The welding rod must comply with AWS A5.11 ENiCrMo-12 standard, and insufficient strength caused by unfilled welding materials should be avoided during the welding process.
