ASTM A312 / ASME SA312 TP304 TP304N TP304LN Stainless Steel Seamless Pipe
ASTM A312 TP304 / 1.4301 / 06Cr19Ni10 Stainless Steel Seamless Pipe Cold Drawn Pipe
Corrosion & Heat Resistance of ASTM A312 TP304, TP304N, TP304LN Stainless Steel Seamless Pipe
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General corrosion: All three are equivalent in most non-chloride environments (food, organics, oxidizing acids).
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Sensitization risk (weld heat affected zone):
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TP304 – susceptible (carbide precipitation 425–870°C)
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TP304N – same as 304
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TP304LN – resistant (low carbon)
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Chloride pitting/crevice: All have same PREN ≈ 18-19 – not recommended for seawater or high-chloride hot water.
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Oxidation resistance: Good up to 870°C intermittent, 925°C continuous (same for all).
| ASTM Grade | UNS | EN | GB/T | JIS |
|---|---|---|---|---|
| TP304 | S30400 | 1.4301 (X5CrNi18-10) | 06Cr19Ni10 | SUS304 |
| TP304N | S30451 | 1.4315 (X5CrNiN19-9) | 06Cr19Ni10N | SUS304N1 |
| TP304LN | S30453 | 1.4311 (X2CrNiN18-10) | 022Cr19Ni10N | SUS304LN |
| SS | Ni | Fe | Cr | C | Si | Mn | P | S | N |
| 304 | 8 – 11 | Balance | 18 – 20 | 0.08 max | 0.75 max | 2 max | 0.040 max | 0.030 max | |
| 304N | 8 – 11 | Balance | 18 – 20 | 0.08 max | 0.75 max | 2 max | 0.040 max | 0.030 max | 0.10 – 0.16 |
| 304LN | 8 – 11 | Balance | 18 – 20 | 0.035 max | 0.75 max | 2 max | 0.040 max | 0.030 max | 0.10 – 0.16 |
Comparative Advantages & Limitations of ASTM A312 TP304, TP304N, TP304LN Stainless Steel Seamless Pipe
| Grade | Strengths | Weaknesses / Best Use |
|---|---|---|
| TP304 | Good general corrosion resistance, excellent formability, widely available | Lower strength; sensitization possible if welded heavy sections without post-weld anneal |
| TP304N | Higher yield and tensile strength (≈15–20% increase) than 304; useful for pressure rating or lighter walls | Not for severe corrosive service after welding (same C as 304) – still sensitizes |
| TP304LN | Combines low carbon (no sensitization, weldable in thick sections) + N for added strength; best of both worlds | Slightly higher cost than 304/304L; less common stock |
TP304 (standard)
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General chemical piping (low chloride)
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Food, dairy, brewery
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Heat exchangers (moderate temp)
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Sanitary tubing
TP304N
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High-pressure gas/liquid lines where higher strength allows thinner wall (cost saving)
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Pressure vessels (ASME Section VIII)
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Piping systems requiring reduced weight (offshore topside, platform piping)
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Where 304 strength is insufficient but 316 not needed
TP304LN
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Welded structures / heavy-wall pipe where post-weld heat treatment is impractical
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Nuclear secondary systems (low carbon + N gives good properties and weldability)
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Cryogenic service (austenite stable, good toughness)
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High-temperature service requiring long-term aging resistance
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