What is 317LMN stainless steel?

317LMN (UNS S31726, EN 1.4439) is a low-carbon austenitic chromium-nickel-molybdenum stainless steel with 4 to 5 percent molybdenum and 0.10 to 0.20 percent nitrogen. The molybdenum and nitrogen give it corrosion resistance better than 316L and 317L, particularly in acidic chloride service, and a higher yield strength than 317L.

What is the UNS and EN equivalent of 317LMN?

317LMN is UNS S31726 in the USA and EN material number 1.4439, designation X2CrNiMoN17-13-5, in Europe. In ASTM A182/A182M it is Grade F48.

Is 317LMN covered by ASTM A182 for forgings?

Yes. ASTM A182/A182M lists UNS S31726 as Grade F48, with minimum tensile strength 550 MPa (80 ksi), minimum 0.2 percent yield strength 240 MPa (35 ksi), minimum elongation 40 percent and minimum reduction of area 50 percent. Grade F47 is the related S31725 (317LM) grade, which has a lower nitrogen limit.

What is the PREN of 317LMN?

Using PREN = Cr + 3.3Mo + 30N, 317LMN has a pitting resistance equivalent of about 38, against about 25 for 316, 30 for 317L, 34 for 317LM and 36 for 904L. It sits below 6Mo superaustenitic grades at about 48.

Can 317LMN be used in the as-welded condition?

Yes. Carbon is held to 0.030 percent maximum, so 317LMN can be used as welded without chromium carbide precipitation at the grain boundaries. Post-weld heat treatment is not necessary. It is welded by TIG/GTAW, MIG/GMAW, MMAW and SAW.

Where should 317LMN not be used?

Do not select 317LMN for strongly oxidizing acids such as nitric acid, because molybdenum-bearing alloys generally do not perform well there. Like all austenitic stainless steels it also remains susceptible to chloride stress corrosion cracking, although the higher molybdenum makes it more resistant than 304/304L.

Who supplies 317LMN open-die forgings?

Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, makes 317LMN forged rings, seamless rolled rings, flanges, shafts, bars, discs, sleeves and tube sheets to customer drawings. Phone +86-189-2135-9659, email sales@steelforgepieces.com.

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317LMN Forgings: UNS S31726 / EN 1.4439 / ASTM A182 F48

Q: At what temperature is 317LMN forged and annealed?

317LMN is forged at 1150 to 1205 C (2100 to 2200 F), then annealed at 1080 to 1175 C (1975 to 2150 F) followed by air cooling or water quenching. It cannot be hardened by heat treatment, only by cold working.

Open-die forged rings, seamless rolled rings, flanges, shafts, bars, discs, sleeves and tube sheets, made to drawing by Jiangyin Jiangnan Metal Co., Ltd.

317LMN (UNS S31726, EN 1.4439, X2CrNiMoN17-13-5) is a low-carbon austenitic chromium-nickel-molybdenum stainless steel containing 4 to 5 percent molybdenum and 0.10 to 0.20 percent nitrogen. The higher molybdenum content together with the nitrogen addition gives corrosion resistance better than 316L and 317L, above all in acidic chloride service, and the nitrogen also raises its yield strength above that of 317L. For forgings the grade appears in ASTM A182/A182M as Grade F48.

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu, China. We make 317LMN forgings to customer drawings, with ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388 and certification to EN 10204 3.1 or 3.2. Phone 0086-189-2135-9659, email sales@steelforgepieces.com.

UNSS31726

EN / W.Nr.1.4439

ASTM A182Grade F48

PRENabout 38

StructureAustenitic

Density8.0 g/cm³

Designations and Equivalents

Cross-reference for 317LMN. Order against the specification your design code requires.
System	Designation
AISI / trade name	317LMN
UNS (USA)	S31726
ASTM A182 / A182M (forgings, flanges, fittings, valves)	Grade F48
EN material number	1.4439
EN designation	X2CrNiMoN17-13-5
France NF	Z3CND18-14-05Az
Related grade	317LM = UNS S31725 = A182 Grade F47 (lower nitrogen)

Specifications by product form. Forgings and flanges: ASTM A182 Grade F48. Bars and shapes: ASTM A276/A276M UNS S31726. Plate: ASTM A240 and ASME SA240. In Europe grade 1.4439 appears in EN 10088-2 and EN 10088-3 for general purposes, EN 10028-7 for flat products for pressure purposes, EN 10272 for bars for pressure purposes, EN 10216-5 for seamless tubes and EN 10222-5 for forgings for pressure purposes.

Chemical Composition

Weight percent. Single values are maximum unless a range is shown. Limits per ASTM A182/A182M Grade F48 (UNS S31726).
Element	Content (%)
Carbon, C	0.030 max
Chromium, Cr	17.0 to 20.0
Nickel, Ni	13.5 to 17.5
Molybdenum, Mo	4.0 to 5.0
Nitrogen, N	0.10 to 0.20
Manganese, Mn	2.00 max
Silicon, Si	0.75 max
Phosphorus, P	0.045 max
Sulfur, S	0.030 max
Iron, Fe	Balance

Limits differ between product forms. ASTM A276/A276M for S31726 bar gives nickel as 14.5 to 17.5 percent and silicon as 1.00 percent max, which is not the same as the A182 forging limits above. EN 1.4439 limits also differ from the ASTM limits. State the governing standard on your enquiry and we will melt and certify to that standard instead of to a generic 317LMN.

Mechanical Properties

Two different sets of figures are published for this grade and they are not interchangeable. The first column is the specified minimum a mill certificate has to meet. The second is the typical value an annealed product usually reaches.

Room temperature properties, annealed condition.
Property	Specified minimum, ASTM A182 F48	Typical, annealed
Tensile strength	550 MPa (80 ksi) min	614 MPa (89 ksi)
Yield strength, 0.2% offset	240 MPa (35 ksi) min	317 MPa (46 ksi)
Elongation (2 in. or 4D)	40% min	53%
Reduction of area	50% min	69%
Hardness	96 HRB max per plate specification	about 80 HRB

ASTM A276/A276M bar carries the same 550 MPa, 240 MPa and 40 percent minimums. Typical figures are third-party datasheet values for reference. The governing numbers for your order are the ones on the mill certificate.

Physical Properties

Property	Metric	Imperial
Density	8.0 g/cm³	0.290 lb/in³
Modulus of elasticity	200 GPa	29.0 x 10⁶ psi
Melting range	1393 to 1443 °C	2540 to 2630 °F
Specific heat (0 to 100 °C)	502 J/kg·K	0.12 BTU/lb·°F
Thermal conductivity at 100 °C	about 15 W/m·K (converted)	8.7 BTU/hr/ft²/ft/°F
Electrical resistivity at 20 °C	85.1 µΩ·cm	33.5 µΩ·in
Mean coefficient of thermal expansion, 20 to 100 °C	16.03 x 10^-6 /°C	8.9 x 10^-6 /°F
Magnetic response	Non-magnetic in the annealed condition, may become slightly magnetic after cold work

Corrosion Resistance and PREN

The chromium, molybdenum and nitrogen content of 317LMN improves its resistance to pitting and crevice corrosion in chlorides and other halides. As a pitting resistance equivalent, PREN = Cr + 3.3Mo + 30N, the grade sits well above the common 300 series but below the 6Mo superaustenitics.

Comparative pitting resistance equivalent. A relative measure only, not a service guarantee.
Alloy	PRE	Alloy	PRE
316	25	317LMN	38
317L	30	6Mo superaustenitic	48
317LM	34	Alloy 625	52
904L	36	Alloy C-276	69

In service the alloy resists sulfuric acid, hydrochloric acid, acidic chlorides and phosphoric acid, and it is used for the hot organic and fatty acids found in food and pharmaceutical processing. Carbon is held to 0.030 percent max, so this is the grade to pick where a part will see the chromium carbide precipitation range of 427 to 816 °C (800 to 1500 °F). The nitrogen content also retards sigma phase as well as carbides.

Two limits to design around. Molybdenum-bearing alloys generally do not perform well in strongly oxidizing acids, so do not select 317LMN for nitric acid service. Second, like all austenitic stainless steels it stays susceptible to chloride stress corrosion cracking. The higher molybdenum makes it more resistant than 304/304L, but it is not immune. Where SCC governs the choice, ask us about duplex grades such as F51 and F53, or nickel alloys such as 825 and 625.

Forging, Heat Treatment, Welding and Machining

Forging and heat treatment

317LMN is forged at 1150 to 1205 °C (2100 to 2200 °F) and then annealed at 1080 to 1175 °C (1975 to 2150 °F), followed by air cooling or water quenching. The grade cannot be hardened by heat treatment. Strength is raised only by cold working. Our melting route is EAF plus VOD, with ESR available when the enquiry calls for it.

Welding

The grade is welded by TIG/GTAW, MIG/GMAW, MMAW and SAW. Post-weld heat treatment is not necessary, and the low carbon level allows as-welded service without grain boundary carbide precipitation. Use matching or over-alloyed filler and clean the weld properly afterwards so the passive film re-forms. For autogenous welds, the best corrosion resistance comes from post-weld annealing and pickling.

Machining

The cold work hardening rate makes 317LMN less machinable than 410 stainless steel. Use rigid setups, sharp tooling, heavy feeds and slow speeds, and do not let the tool dwell. As a starting point, HSS turning at 3 mm depth of cut runs at roughly 18 to 23 m/min (59 to 75 ft/min) with cutting oil, and carbide at the same depth runs at roughly 85 to 95 m/min (279 to 313 ft/min). We can supply parts as forged, rough machined to an agreed allowance, or finish machined.

317LMN Forged Products We Make

Everything is made to your drawing or specification. There is no fixed catalogue.

Forged rings and seamless rolled rings
Forged flanges and blind flanges
Forged round bars, shafts, spindles and eccentric shafts
Forged discs, disks and blanks
Forged sleeves, bushings and hollow bars
Forged tube sheets and tube plates

Forged tubes, pipes and nozzles
Valve bodies, valve blocks, stems and seat rings
Forged rolls and roller shafts
Gear blanks and gear forgings
Forged crankshafts and manifolds
Open-die forgings and forged blocks to drawing

Typical Applications

Flue gas desulfurization: absorbers, stack liners, ducts, dampers, fans
Chemical and petrochemical processing: reactors, columns, towers, process modules
Pulp and paper: bleaching plant, pulp liquor, acid dyestuffs
Pressure equipment: pressure vessels, air receivers, shell and tube heat exchangers

Air pollution control: scrubbers and pollution control equipment
Food, beverage and pharmaceutical: hot organic and fatty acid duty
Oil and gas: valves, wellhead and Christmas tree components
Marine and coastal: chloride-exposed structures and infrastructure

Inspection, Testing and Certification

Our 317LMN forgings are ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388 as stated on the order. Material certification is issued to EN 10204 3.1, or EN 10204 3.2 with a third party witness such as TUV, SGS, BV or Lloyd's where required. Chemical analysis, mechanical testing, intergranular corrosion testing to ASTM A262, PMI, dimensional reports and NDT reports can all go into the document package.

Frequently Asked Questions

What is the difference between 317LMN, 317LM and 317L?

All three are low-carbon molybdenum-bearing austenitics, but molybdenum and nitrogen rise across the family and so does pitting resistance. PRE is about 30 for 317L, 34 for 317LM and 38 for 317LMN. In ASTM A182 the forging grades are F47 for S31725 (317LM, nitrogen 0.10 percent max) and F48 for S31726 (317LMN, nitrogen 0.10 to 0.20 percent). The nitrogen in 317LMN also gives it a higher yield strength than 317L.

Is 317LMN a superaustenitic grade?

No. 317LMN is a high-molybdenum austenitic stainless steel, not a 6Mo superaustenitic and not a nickel-base alloy. Its PRE of about 38 puts it between 904L at 36 and the 6Mo grades at 48. If your specification needs 6Mo performance, look at A182 F44 instead.

Can you supply small quantities or a single prototype forging?

Yes. We work from single pieces and prototypes up to repeat production batches. Send the drawing, the governing standard, the quantity and the certification level you need and we will quote. Email sales@steelforgepieces.com.

What do you need in order to quote a 317LMN forging?

A drawing or the finished dimensions, the standard to certify against such as ASTM A182 F48, the quantity, the delivery condition (as forged, rough machined or finish machined), the NDT requirement, the certification level (EN 10204 3.1 or 3.2), and your destination port.

Is 317LMN magnetic?

It is non-magnetic in the annealed condition but can become slightly magnetic after cold working. It cannot be hardened by heat treatment, only by cold work.

Request a 317LMN Forging Quotation

Send us the size or the drawing of the 317LMN forged part you need, whether rings, flanges, shafts, discs, bars or tube sheets, and we will come back with price and lead time.

Jiangyin Jiangnan Metal Co., Ltd., Open-Die Forging Factory
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Tel 0086-189-2135-9659 Email sales@steelforgepieces.com

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Related Grades

A182 F44 (6Mo) 904L A182 F51 (2205) A182 F53 (2507) A182 F55 Nitronic 50 Sanicro 28 Alloy 31 Incoloy 825

Technical References

ASTM A182/A182M, Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service. Grade F48, UNS S31726.
ASTM A276/A276M, Stainless Steel Bars and Shapes, UNS S31726.
ASTM A240 and ASME SA240, plate specification for Alloy 317LMN.
EN 10088-2, EN 10088-3, EN 10028-7, EN 10272, EN 10216-5 and EN 10222-5, grade 1.4439, X2CrNiMoN17-13-5.
Sandmeyer Steel, Alloy 317LMN (UNS S31726) specification sheet. PRE comparison, physical properties and fabrication data.
AZoM, Stainless Steel Grade 317LMN (UNS S31726). Typical mechanical properties, forging and annealing temperatures.

Last updated 28 September 2026. The data on this page is taken from the published standards and datasheets listed above and is given for information. Property values are not a warranty of suitability for any particular application. The governing values for an order are those stated on the mill certificate.