# SUS 317L Forgings, UNS S31703 / EN 1.4438, to ASTM A182 F317L

**Manufacturer:** Jiangyin Jiangnan Metal Co., Ltd. — open-die forging factory
**Address:** No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, 214423
**Tel:** 0086-189-2135-9659 | **Email:** sales@steelforgepieces.com
**Page:** https://www.steelforgepieces.com/Stainless-Steel/SUS-317L.html
**Updated:** 4 October 2026

## Summary

SUS 317L is the JIS designation for a molybdenum-bearing low carbon austenitic stainless steel, the same material as UNS S31703, AISI 317L and EN 1.4438 (X2CrNiMo18-15-4). It contains 18 to 20 % chromium, 11 to 15 % nickel and 3 to 4 % molybdenum, with carbon held to 0.030 % maximum. The raised molybdenum improves resistance to chloride pitting and crevice corrosion over 304L and 316L; the low carbon prevents chromium carbide precipitation during welding, so the grade serves as welded. It cannot be hardened by heat treatment. Jiangyin Jiangnan Metal Co., Ltd. forges SUS 317L to ASTM A182 F317L as seamless rolled rings, flanges, shafts, discs, bars, sleeves, bushings and tube sheets, with ultrasonic testing to ASTM A388, EN 10228-3 or SEP 1921 and certificates to EN 10204 3.1 or 3.2.

## Key data

| Item | Value |
|---|---|
| JIS designation | SUS 317L |
| UNS number | S31703 |
| EN number | 1.4438 |
| EN name | X2CrNiMo18-15-4 |
| Forging specification | ASTM A182 / A182M F317L |
| Tensile strength, min | 485 MPa (70 ksi) |
| Yield strength 0.2 %, min | 170 MPa (25 ksi) |
| Elongation in 50 mm or 4D, min | 30 % |
| Reduction of area, min | 50 % |
| Solution anneal | 1010–1121 °C, rapid cool |
| Pitting resistance equivalent | about 29.7 (range 27.9–33.2) |
| Density | 7.89 g/cm³ |
| Structure | austenitic, non-magnetic when annealed |
| Hardenable by heat treatment | no, cold work only |
| Certification | EN 10204 3.1 or 3.2 |

## Chemical composition (weight %, balance Fe)

Single figures are maximum values.

| Element | ASTM A182 F317L (forgings) | ASTM A240 / UNS S31703 |
|---|---|---|
| Cr | 18.0–20.0 | 18.0–20.0 |
| Ni | 11.0–15.0 | 11.0–15.0 |
| Mo | 3.0–4.0 | 3.0–4.0 |
| C | 0.030 max | 0.030 max |
| Mn | 2.00 max | 2.00 max |
| Si | 1.00 max | 0.75 max |
| P | 0.045 max | 0.045 max |
| S | 0.030 max | 0.030 max |
| N | not specified | 0.10 max |

Some secondary datasheets quote 0.08 % carbon for F317L. That limit belongs to non-L grade 317. Confirm against the edition of ASTM A182 named on the purchase order. Jiangyin Jiangnan Metal supplies to 0.030 % maximum as standard.

## Mechanical properties, solution annealed

| Property | A182 F317L forgings, min | A240 plate, min | Typical annealed |
|---|---|---|---|
| Tensile strength | 485 MPa (70 ksi) | 515 MPa (75 ksi) | 595 MPa (86,300 psi) |
| Yield strength 0.2 % offset | 170 MPa (25 ksi) | 205 MPa (30 ksi) | 260 MPa (37,700 psi) |
| Elongation, 50 mm or 4D | 30 % | 40 % | 55 % |
| Reduction of area | 50 % | not specified | — |
| Hardness, Rockwell B | not specified | 95 max | 85 |
| Modulus of elasticity | 200 GPa (29,000 ksi) | | |
| Poisson's ratio | 0.27–0.30 | | |

## Physical properties, annealed

| Property | Metric | Imperial |
|---|---|---|
| Density | 7.89 g/cm³ | 0.285 lb/in³ |
| Melting range | 1390–1440 °C | 2540–2630 °F |
| Specific heat 0–100 °C | 502 J/kg·K | 0.12 Btu/lb·°F |
| Thermal conductivity at 20 °C | 14 W/m·K | 8.1 Btu/hr·ft·°F |
| Mean thermal expansion 20–100 °C | 16.2 µm/m·°C | 8.9 × 10⁻⁶/°F |
| Electrical resistivity at 20 °C | 85.1 µΩ·cm | 33.5 µΩ·in |
| Magnetic response | non-magnetic when annealed | |

## Equivalent designations

| System | Designation |
|---|---|
| Japan, JIS | SUS 317L |
| USA, AISI and UNS | 317L; S31703 |
| Europe, EN | 1.4438; X2CrNiMo18-15-4 |
| United Kingdom, BS | 317S12 |
| France, AFNOR | Z3CND19-15-04 |
| Sweden, SS | 2367 |
| Finland, SFS | 770 |
| Product standards | ASTM A182 forgings; A240 and ASME SA240 plate; A213, A249, A312, A774, A778, A813, A814 |

Cross-reference tables indicate nearest known equivalents only. For a contractual order, work from the source standard.

## Corrosion behaviour and service limits

317L resists sulphuric acid, acidic chloride and phosphoric acid, and handles the hot organic and fatty acids found in food and pharmaceutical plant. In strongly oxidising acids such as nitric, molybdenum-bearing grades perform worse than molybdenum-free grades, so 317L is not the correct selection there.

PREN = %Cr + 3.3 × %Mo + 16 × %N.

| Alloy | Cr % | Mo % | N % | PREN |
|---|---|---|---|---|
| 304 | 18.0 | — | 0.06 | 19.0 |
| 316 | 16.5 | 2.1 | 0.05 | 24.2 |
| 317L | 18.5 | 3.1 | 0.06 | 29.7 |
| 6 % Mo super austenitic | 20.5 | 6.2 | 0.22 | 44.5 |

**Limitation.** A PREN near 32 is the figure usually cited as the minimum for seawater pitting resistance, and 317L typically falls below it at 29.7. The grade also remains susceptible to chloride stress corrosion cracking, although it resists it better than 304L. For seawater, produced water or deepwater duty, specify ASTM A182 F44 (6 % molybdenum) or 904L instead.

## Forging route and heat treatment

Published hot working ranges differ between mill datasheets. Both are given rather than averaged.

| Operation | Published range A | Published range B |
|---|---|---|
| Hot working | 1149–1260 °C | 900–1150 °C |
| Minimum finishing temperature | 927 °C | 950 °C |
| Solution anneal | 1010–1121 °C | 1080–1180 °C |
| Cooling | rapid cool or quench | rapid cool or quench |
| Hardening | not possible by heat treatment; cold work only | |

Melting is by electric arc furnace with ladle refining and vacuum oxygen decarburisation to hold carbon at 0.030 % maximum. Electroslag remelting is available where a cleaner structure is specified. Because the steel is melted in the works that forges it, certification traces a finished part to its melt number rather than to a purchased billet.

**Machining.** Low speed, constant positive feed, no dwell, because the alloy work hardens. The chip is long and stringy so chip breakers are recommended. Harder going than 304. Carbide tooling roughly 70–110 m/min depending on depth of cut; high speed steel roughly 11–30 m/min with cutting oil.

**Welding.** Weldable by normal fusion and resistance processes with no post-weld heat treatment. Filler metal AWS E317L or ER317L. Oxyacetylene welding should not be used.

## Forged products in SUS 317L

- Seamless rolled rings, radial-axial rolled, rectangular or contoured section
- Forged rings, retaining rings, valve seat rings, gear ring blanks, slewing rings
- Flanges: weld neck, blind, slip-on, socket weld, lap joint, orifice, to ASME B16.5 and B16.47 or to drawing
- Shafts: stepped, pinion, eccentric, spindles
- Round bar, flat bar and blocks
- Discs, heat exchanger tube sheets and covers, proof machined for volumetric inspection
- Hollow bar, sleeves, bushings and liners
- Valve bodies, bonnets, stems, blocks and seat rings
- Nozzles, manifolds, rolls, wheels and open-die shapes to customer drawing

## Working envelope

| Item | Limit | Set by |
|---|---|---|
| Rolled ring outside diameter | 50 to 6,000 mm | 6 m radial-axial ring mill; upset and punch below range |
| Single piece weight | up to 30 t | 6,300 t press, 60 t maximum heat |
| Shaft turned length | up to 14,000 mm | C61160 horizontal lathe, 15 m well furnace |
| Disc and tube sheet diameter | up to 5,000 mm | 5,000 mm vertical turning lathe |
| Bored cylinders | 1,600 mm dia × 10,000 mm | CNC deep-hole drilling machine |
| Minimum order | 10 kg | no minimum piece count |
| Lead time | 20 to 60 days | size, heat treatment and machining |

## Testing and certification

Ultrasonic testing to ASTM A388, EN 10228-3 or SEP 1921, to the acceptance class stated on the order. Certificates to EN 10204 3.1, or 3.2 with third-party witness such as TUV, BV, DNV or Lloyd's Register. Available on request: intergranular corrosion testing to ASTM A262 Practice E, PMI, ferrite measurement, impact testing, grain size, hardness survey and dimensional report. Works approvals: CCS, BV, DNV, LR, NK.

## Applications

Flue gas desulphurisation and air pollution control equipment; chemical and petrochemical process plant; petroleum refining, including catalytic recovery systems and recuperators; pulp and paper mill equipment; condensers in fossil-fired and nuclear power stations; food, beverage and pharmaceutical plant handling hot organic and fatty acids; slurry tanks, stack liners, tanks and valve internals.

## FAQ

**What is SUS 317L?**
The JIS name for a molybdenum-bearing low carbon austenitic stainless steel, equivalent to UNS S31703, AISI 317L and EN 1.4438. Cr 18–20 %, Ni 11–15 %, Mo 3–4 %, C 0.030 % max.

**What is the difference between 316L and 317L?**
Molybdenum, mainly: 3–4 % against roughly 2 %, with more chromium and nickel. Typical PREN rises from about 24.2 to about 29.7, improving resistance to pitting and crevice corrosion in chloride, sulphurous and halide service.

**What are the mechanical minimums for ASTM A182 F317L?**
Tensile 485 MPa (70 ksi) min, 0.2 % yield 170 MPa (25 ksi) min, elongation 30 % min in 50 mm or 4D, reduction of area 50 % min. Typical annealed values are higher, near 595 MPa and 260 MPa.

**Can SUS 317L be hardened by heat treatment?**
No. It is austenitic. Solution anneal and quench is the supply condition; cold work is the only route to higher strength.

**Is 317L suitable for seawater?**
Usually not. PREN about 29.7 against roughly 32 commonly cited for seawater, and the grade remains open to chloride stress corrosion cracking. Specify ASTM A182 F44 or 904L.

**Does 317L need post-weld heat treatment?**
No. Carbon at 0.030 % maximum prevents sensitisation, so the material serves as welded. Use E317L or ER317L filler; do not use oxyacetylene.

**How large a forging can be produced?**
Up to 30 t single piece from a 60 t heat on a 6,300 t press. Rings from 50 to 6,000 mm outside diameter, shafts to 14,000 mm turned length, discs to 5,000 mm diameter. Minimum order 10 kg.

**What certification is supplied?**
EN 10204 3.1 as standard, 3.2 with third-party witness on request, plus ultrasonic testing to ASTM A388, EN 10228-3 or SEP 1921.

## Contact

Jiangyin Jiangnan Metal Co., Ltd.
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, 214423
Tel, WhatsApp, WeChat: 0086-189-2135-9659
Email: sales@steelforgepieces.com
Office hours: Monday to Saturday, 08:00–17:30 China Standard Time (UTC+8)

## Sources

Sandmeyer Steel specification sheet for Alloy 317L and 317 (UNS S31703, W.Nr. 1.4438); AZoM datasheet for stainless steel grade 317L; published summaries of ASTM A182 / A182M grade F317L; SteelNumber cross-reference for JIS SUS317L. Figures are for guidance. The governing document is the standard named on the purchase order.