Stainless Steel Grades

Ten stainless steel grades with composition, minimum strength, magnetism and corrosion resistance.

Stainless steel is steel with at least 10.5 percent chromium, which forms a thin protective oxide film. The grades fall into families: austenitic (304, 316: non-magnetic, tough and easy to weld), ferritic (430) and martensitic (410: magnetic, hardenable), and duplex (2205, 2507: very strong and resistant to chloride cracking).

This table compares ten common grades by composition, minimum strength, magnetism and corrosion resistance.

The table

10 rows

Grade	Family	Chromium (percent)	Nickel (percent)	Molybdenum (percent)	Minimum yield (MPa)	Minimum tensile (MPa)	Minimum yield (ksi)	Minimum tensile (ksi)	Magnetic	Corrosion resistance
304	Austenitic	18	8	0	205	515	29.7	74.7	No (slightly when cold worked)	Good: general purpose
304L	Austenitic	18	8	0	170	485	24.7	70.3	No	Good: better after welding
316	Austenitic	16 to 18	10 to 14	2 to 3	205	515	29.7	74.7	No	Very good: chlorides and acids
316L	Austenitic	16 to 18	10 to 14	2 to 3	170	485	24.7	70.3	No	Very good: better after welding
321	Austenitic	17	9	0 (Ti added)	205	515	29.7	74.7	No	Good: for use at 425 to 850 C
310S	Austenitic	24 to 26	19 to 22	0	205	515	29.7	74.7	No	Good: for heat to 1 100 C
430	Ferritic	16 to 18	0	0	205	450	29.7	65.3	Yes	Fair: mild atmosphere
410	Martensitic	11.5 to 13.5	0	0	205	450	29.7	65.3	Yes (hardenable)	Fair: mild corrosion, hard when heat treated
2205	Duplex	22	5	3	450	655	65.3	95	Yes	Excellent: chlorides and stress cracking
2507	Super duplex	25	7	4	550	795	79.8	115.3	Yes	Outstanding: seawater

Source and notes: Nominal compositions and minimum annealed plate properties from ASTM A240 / A240M (ksi converted from MPa). Corrosion ratings are qualitative. Cold working raises the strength of austenitic grades well above the annealed minimums; the grades marked L are low in carbon so they resist sensitization after welding.

How to use this table

Pick the family for the job: austenitic for general use, duplex for strength in chlorides, martensitic when you need hardness.
Within a family, add molybdenum (316, 2205) for pitting resistance in salt and chemicals.
Use the L grades (304L, 316L) for welded parts that cannot be heat treated afterwards.

Worked example: duplex against austenitic

304 has a minimum yield of 205 MPa; 2205 duplex has 450 MPa, which is 2.2 times higher.
For a pressure part, the wall needed is roughly inversely proportional to the allowable stress, so 2205 can be about 54 percent thinner for the same pressure (subject to code rules and the fabrication limits).

Notes and cautions

Austenitic grades are normally non-magnetic, but cold working (bending, forming) can make them slightly magnetic.
“Stainless” is not “stain-proof”: chlorides (salt, bleach) can pit 304; 316 or duplex is better near the sea.
Cold working raises the strength of austenitic grades far above the annealed minimums shown.

FAQ

What is the difference between 304 and 316?

316 contains 2 to 3 percent molybdenum, which gives much better resistance to pitting and crevice corrosion in chlorides and acids. It costs more.

What does the L in 316L mean?

Low carbon (0.03 percent maximum). It resists sensitization (loss of corrosion resistance next to a weld) better than the standard grade.

Is stainless steel magnetic?

Ferritic, martensitic and duplex grades are; the common austenitic grades (304, 316) are not, or only slightly after cold work.

Sources

ASTM A240 / A240M (chromium and chromium-nickel stainless steel plate, sheet and strip): minimum annealed properties; ASTM A276; EN 10088-1 for the European designations.
Nominal compositions and minimum annealed plate properties from ASTM A240 / A240M (ksi converted from MPa). Corrosion ratings are qualitative. Cold working raises the strength of austenitic grades well above the annealed minimums; the grades marked L are low in carbon so they resist sensitization after welding.