Stainless Steel PMI

Cr-Ni-Mo decision logic for the most common PMI challenge in process industries.

Intermediate30 min

Decision tree

1. Ni < 1%? → Likely ferritic (430) — magnetic check helps
2. Mo > 1.5%? → Likely 316 family
3. Cr ~18%, Ni ~8%, no Mo → 304 or 321 (context: temperature service)
4. Cr > 22%, Ni > 18% → 310 or high-alloy austenitic

Practice

Use the [AI Material Expert](/en/ai) with readings like `Cr 18 Ni 8` or `Cr 17 Ni 10 Mo 2.5`.

Compare grades: [304 vs 316](/en/compare/304-vs-316) · [304 vs 430](/en/compare/304-vs-430)

Topics covered

304 / 316 / 321
Ferritic vs austenitic
Decision trees

PMI Checklist →Glossary →

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Knowledge Check

Test what you learned — score 70% or higher to pass.

Question 1 of 3

Which element best distinguishes 316 from 304?

Question 2 of 3

Ni below 1% strongly suggests which stainless family?

Question 3 of 3