317L Stainless Steel Equivalent Grades and Properties

What Is 317L Stainless Steel?

317L is a low-carbon, molybdenum-rich austenitic stainless steel standardised as UNS S31703. Its principal equivalents are EN 1.4438 and X2CrNiMo18-15-4, together with the Chinese designation 022Cr19Ni13Mo3 published in GB/T 20878 and used for plate and sheet in GB/T 3280. With 3.0-4.0% molybdenum and 11-15% nickel, the grade sits clearly above 316L in pitting resistance and general corrosion resistance.

That extra molybdenum is why 317L is specified for chloride-rich and acidic service, where 316L would pit or crevice corrode. The 0.030% carbon ceiling keeps the alloy weldable in heavy sections without a post-weld solution anneal, and the annealed structure is fully austenitic and effectively non-magnetic.

Equivalents Across Standards

Standard	Designation
ASTM / ASME	Type 317L, UNS S31703
EN 10088-2 and EN 10028-7	1.4438, X2CrNiMo18-15-4
GB/T 20878 and GB/T 3280	022Cr19Ni13Mo3
JIS G4304 and G4305	SUS317L
ISO 9328-2	X2CrNiMo18-15-4

The higher-carbon parent grade 317, UNS S31700, shares the same chromium, nickel and molybdenum ranges but permits up to 0.08% carbon, which is why welded equipment is almost always specified in the L version.

Chemical Composition

Element	ASTM A240 317 (S31700)	ASTM A240 317L (S31703)	ASTM A240 316L (S31603)
Carbon (C)	0.08 max	0.030 max	0.030 max
Silicon (Si)	0.75 max	0.75 max	0.75 max
Manganese (Mn)	2.00 max	2.00 max	2.00 max
Phosphorus (P)	0.045 max	0.045 max	0.045 max
Sulfur (S)	0.030 max	0.030 max	0.030 max
Chromium (Cr)	18.0-20.0	18.0-20.0	16.0-18.0
Nickel (Ni)	11.0-15.0	11.0-15.0	10.0-14.0
Molybdenum (Mo)	3.00-4.00	3.00-4.00	2.00-3.00
Nitrogen (N)	0.10 max	0.10 max	0.10 max

Values are percent by mass. The gap against 316L is concentrated in chromium and molybdenum, the two elements that control passive film stability in chloride environments.

Mechanical Properties and Corrosion Performance

Property	317L	316L for comparison
Tensile strength, annealed	515 MPa min	485 MPa min
0.2% proof strength	205 MPa min	170 MPa min
Elongation in 50 mm	40% min	40% min
Density	about 8.00 g/cm3	about 8.00 g/cm3
Modulus of elasticity	about 200 GPa	about 193-200 GPa
Pitting resistance equivalent number	about 30-33	about 24-26

PREN is calculated as chromium plus 3.3 times molybdenum plus 16 times nitrogen. The higher chromium and molybdenum of 317L lift it roughly five to seven points above 316L, which raises the critical pitting temperature and extends service life in chloride-rich process streams and acid media.

How 317L Compares with 317, 316L and 304

317 versus 317L. Identical chromium, nickel and molybdenum ranges; only the carbon ceiling differs, at 0.08% against 0.030%. The lower carbon of 317L gives better weldability and resistance to intergranular corrosion.

316L versus 317L. 316L is more economical and adequate for moderately corrosive duty. 317L costs more but resists pitting, crevice corrosion and chemical attack in aggressive chloride and acid environments.

304 versus 317L. 304 is a general-purpose 18/8 grade for mild duty, while 317L is specified wherever chloride or acid attack, or high-purity requirements, rule out the leaner alloy.

Strength. The molybdenum-bearing grades are closely matched in annealed tensile and proof values, so corrosion resistance rather than strength normally decides the grade.

Applications and Fabrication

Fabrication follows standard austenitic practice. 317L is welded with matching ER317L filler metal; 316L consumables are acceptable for some lower-duty joints where dilution is controlled and the corrosion allowance covers the small molybdenum difference. Cold forming and machining behave like 316L, with rapid work hardening that calls for staged reductions, generous bend radii and positive-rake tooling.

Typical applications include:

Chemical and petrochemical reactors, columns, heat exchangers and process piping.

Flue gas desulphurisation scrubbers, ducting and absorber internals.

Pulp and paper bleach plants, digesters and chlorine dioxide handling lines.

Phosphoric, sulfuric and acetic acid service in fertilizer and chemical plants.

Marine and offshore piping, seawater cooling systems and high-purity water circuits.

Dye, pharmaceutical and food processing equipment where product purity matters.

FAQ

Q: What is 317L stainless steel equivalent to?
317L is UNS S31703 in the ASTM and ASME system, EN 1.4438 and X2CrNiMo18-15-4 in Europe, SUS317L in JIS, and 022Cr19Ni13Mo3 in GB/T 20878 and GB/T 3280. All describe the same chromium-nickel-molybdenum austenitic chemistry with 0.030% maximum carbon.

Q: Is 317L stainless steel magnetic?
Annealed 317L is austenitic and non-magnetic. Cold working or welding can induce a small amount of strain-induced martensite and produce a weak magnetic response.

Q: What is the difference between 317 and 317L?
Carbon content. 317 allows up to 0.08% carbon while 317L is limited to 0.030%. The lower carbon of 317L delivers better weldability and resistance to intergranular corrosion, especially after welding.

Q: How does 317L compare with 316L?
317L carries higher molybdenum and nickel, so it resists pitting, crevice corrosion and chemical attack better than 316L, with a PREN roughly five to seven points higher. 316L remains the more economical choice for moderately corrosive environments.

Q: Is 317L better than 304 stainless steel?
For aggressive media, yes. 317L resists chloride and acid attack far better than 304 because of its molybdenum and nickel content, while 304 stays cost-effective for mild atmospheric or indoor duty.

Q: What is 317L stainless steel used for?
Chemical and petrochemical process equipment, flue gas desulphurisation systems, pulp and paper bleach lines, acid service in fertilizer plants, marine and offshore piping, and high-purity water circuits.