Stainless Steel Grades Chart (Printable)
Composition, PREN and typical uses for the grades instrumentation buyers actually quote — not an encyclopedia. Values are ASTM A240 composition limits; exact heats vary, and the mill certificate governs.
Grades at a glance
| Grade | Carbon max | Chromium | Nickel | Molybdenum | Stabilizer | Approx. PREN | Typical instrumentation use |
|---|---|---|---|---|---|---|---|
| 304 | 0.08% | 18–20% | 8–10.5% | — | — | 18–20 | General duty, panels, mild environments |
| 304L | 0.03% | 18–20% | 8–12% | — | — | 18–21 | Welded assemblies where low carbon helps |
| 316 | 0.08% | 16–18% | 10–14% | 2–3% | — | ≈23–26 | Chloride-bearing service: tube, fittings, valves |
| 316L | 0.03% | 16–18% | 10–14% | 2–3% | — | ≈23–26 | Welded pharma, chemical and process duty |
| 321 | 0.08% | 17–19% | 9–12% | — | Ti 5×(C+N) min | 18–21 | High-temperature runs, expansion duty |
| 347 | 0.08% | 17–19% | 9–13% | — | Nb 10×C min | 18–21 | Welded high-temperature equipment |
How to use this chart
PREN — pitting resistance equivalent, %Cr + 3.3 × %Mo + 16 × %N — is the screening number for chloride pitting; the 316/316L figures are approximate because nitrogen is not listed in the composition columns. The L grades cap carbon at 0.03% for welded service, and the stabilizer columns show what sets 321 and 347 apart for elevated-temperature duty. Grades 310, 904L and duplex sit outside this chart deliberately: they are quoted per project, not from a wall chart.
From our guides: 304 vs 316 for fittings and316 vs 316L for welded assemblies. State grade per line on theRFQ — the mill certificate carries the actual heat values.