STAINLESS STEEL SEAMLESS PIPE ASME SA312 TP904L B674 UNS N08904 1.4539
STAINLESS STEEL SEAMLESS PIPE ASME SA312 TP904L B674 UNS N08904 1.4539
TP904L is a high-alloyed super-austenitic stainless steel (UNS N08904, W.Nr. 1.4539) designed for exceptional corrosion resistance in highly aggressive environments. By adding molybdenum (Mo) and copper (Cu) to the chromium-nickel matrix, its performance far exceeds that of conventional 304 and 316L stainless steels, particularly in reducing acid media and chloride-bearing solutions.
Why 904L is "Super" Austenitic
1. Superior Resistance to Reducing Acids – The combined addition of Mo (4.0–5.0%) and Cu (1.0–2.0%) is the key. This enables 904L to withstand sulfuric acid up to 70°C (158°F) at various concentrations, and phosphoric acid and acetic acid over a wide range. It also provides excellent resistance to chloride-induced pitting, crevice corrosion, and stress corrosion cracking (SCC).
2. Extra-Low Carbon & Weldability – The ≤0.02% carbon content prevents chromium carbide precipitation at grain boundaries during welding. This effectively eliminates the risk of intergranular corrosion, giving 904L excellent weldability without the need for post-weld heat treatment in most cases.
Key Limitations & Selection Notes
Temperature Limit – 904L is not designed for ultra-high-temperature service. Its recommended maximum long-term operating temperature is approximately 450°C (840°F). Above this, its mechanical strength and creep resistance diminish significantly.
Specific Media Limitations – While excellent in reducing acids, 904L performs worse than molybdenum-free stainless steels (e.g., 304) in strongly oxidizing acids like nitric acid. In hydrochloric acid, it is only suitable for very low concentrations (1–2%).
Some of the quality tests carried out by us includes:
| Corrosion Test | Conducted only when specially requested by the client |
| Chemical Analysis | Test done as per required quality standards |
| Destructive / Mechanical Testing | Tensile | Hardness | Flattening | Flare | Flange |
| Reverse-bend and Re. flat tests | Carried out in full compliance with relevant standards & ASTM A-450 and A-530 norms, which ensures trouble-free expansion, welding & use at customers end |
| Eddy Current Testing | Done to detect homogeneities in subsurface by using Digital Flaw-mark Testing System |
| Hydrostatic Testing | 100% Hydrostatic Testing carried out according to ASTM-A 450 norms for checking tube leakage, and biggest pressure we can support 20Mpa/7s . |
| Air Under Pressure Test | To check any evidence of air leakage |
| Visual Inspection | After passivation, every single length of tubes & pipes is subjected to thorough visual inspection by trained staff for detecting surface flaws & other imperfections |
904L Chemical Composition %
| C | Cr | Cu | Mn | Mo | Ni | P | S | Si |
| Max | Max | Max | Max | Max | ||||
| 0.02 | 19.0-23.0 | 1.0-2.0 | 2.0 | 4.0-5.0 | 23.0-28.0 | 0.045 | 0.035 | 1.0 |
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