Stainless Steel Seamless Pipe: ASTM A312 TP304 vs TP316
Stainless steel seamless pipe is the default answer for corrosive, hygienic and high-purity process lines. The ASTM A312 standard covers the seamless austenitic grades most exporters need. Here is how to choose correctly.
ASTM A312 at a Glance
ASTM A312 covers seamless, welded and heavily cold-worked austenitic stainless steel pipe for high-temperature and general corrosive service. The two grades you will quote nine times out of ten are TP304 and TP316.
TP304 vs TP316: The Real Difference
| Property | TP304 | TP316 |
|---|---|---|
| Cr (%) | 18.0–20.0 | 16.0–18.0 |
| Ni (%) | 8.0–10.5 | 10.0–14.0 |
| Mo (%) | — | 2.0–3.0 |
| Corrosion resistance | Good (general) | Better (pitting & chlorides) |
| Relative cost | Lower | Higher |
The molybdenum in TP316 is the key difference. It substantially improves resistance to pitting and crevice corrosion, especially in chloride environments — coastal air, seawater, brine and many chemical media.
Rule of thumb: use TP304 for clean water, food, beverage, most chemicals and general sanitary lines. Move to TP316 when chlorides, seawater or aggressive acids are present, or when the customer’s specification demands it.
Low-Carbon Variants: TP304L and TP316L
The L stands for low carbon (≤0.03% C). Lower carbon prevents sensitization — chromium carbide precipitation at grain boundaries during welding — which otherwise leads to intergranular corrosion.
For welded process lines, specify the L grades or require a solution-annealed (solution heat-treated) delivery condition. Many projects simply default to 304L/316L for weldbility and safety.
Standards and Chinese Equivalents
- ASTM A312 / A269 (American)
- GB/T 14976 — Chinese equivalent (0Cr18Ni9 → 304, 0Cr17Ni12Mo2 → 316)
- EN 10216-5 (European)
Tell your supplier which standard your project recognizes. Supplying dual-standard certification is common and helps clear customs and inspections.
Ordering Checklist
- Grade: TP304 / TP304L / TP316 / TP316L (or TP321/TP347H for high-temperature)
- OD and wall thickness
- Seamless vs welded (A312 covers both — confirm you need seamless)
- Surface finish: pickled, annealed, bright
- Hydrostatic or air test, eddy-current test if required
- MTC with heat number traceability
Xbang Supply Supply
Xbang Supply (山东信邦金属材料有限公司) supplies ASTM A312 seamless stainless pipe in TP304, TP304L, TP316 and TP316L, plus GB/T 14976 equivalents, with full mill certifications and third-party inspection. Share your medium, temperature and environment, and we will confirm the right grade within 24 hours.
