UNS S31725 Forgings ASTM A182 Grade F47, commonly called 317LM. Rolled rings, flanges, shafts, discs and tube sheets, melted and forged in one works.

S31725 sits in the 317 family. What separates it from plain 317L is molybdenum at 4.0 to 5.0 percent, with nickel lifted to 13.0 to 17.5 percent so the structure stays fully austenitic at that molybdenum level. The 0.030 percent carbon ceiling is the reason for the L in 317LM: it holds back chromium carbide precipitation at grain boundaries during welding, so the alloy keeps its corrosion resistance in the as-welded state.

One point causes repeated confusion on enquiries. The designation 317LM is a trade name attached to a slightly wider composition band in general reference data, while S31725 is the UNS number tied to the narrower limits written into ASTM specifications. For a forged flange or a rolled ring going into a coded vessel, order against ASTM A182 Grade F47 and the question disappears.

Sources: ASTM A182/A182M grade table; ASTM A240 UNS S31725 cross-reference sheet.

Two columns, because the forging specification and the plate specification are not word for word identical. A182 Grade F47 is the one that governs rings, flanges, discs and valve parts.

Sources: ASTM A182/A182M Grade F47 composition table; ASTM A240 UNS S31725 data sheet. Order against the current edition of the governing standard.

Room temperature, solution annealed and water quenched.

Note on tensile strength: ASTM A240 for S31725 states 515 MPa minimum, equivalent to 75 ksi. One published tabulation of ASTM A182/A182M lists 525 MPa minimum for the same UNS number. The two differ by rounding of the ksi figure. Where the number matters contractually, confirm it against the edition named on your purchase order and we will test to that value. Modulus, Poisson's ratio and density are typical published values for 317LM and are not acceptance criteria.

Everything below happens inside this plant. Fourteen heat-treatment furnaces sit on site, including two well-type furnaces 15 m deep for vertical quenching of long shafts, so nothing is sent out and nothing waits in a queue at a subcontractor.

Heat treatment requirement per ASTM A182/A182M; soak band per published technical data for grade 317LM. Press, mill and furnace capacities are this works' own equipment list.

The reason anyone pays the premium over 316L is localised attack in chloride-bearing and acidic service. Molybdenum is doing most of that work.

Applying the usual index, PREN = %Cr + 3.3 × %Mo + 16 × %N, to the A182 F47 limits gives roughly 31 at the lean end and about 38 at the rich end. Lean corner: 18 + 3.3 × 4.0 = 31.2. Rich corner: 20 + 3.3 × 5.0 + 16 × 0.10 = 38.1. For context, a PREN around 32 to 35 is often cited as the minimum considered suitable for seawater duty in austenitic and duplex grades, which tells you that S31725 straddles that line rather than clearing it comfortably.

Two practical consequences. Actual PREN depends on where the heat lands inside the band, so if your specification sets a floor, write it on the purchase order and we will select the heat and report the calculated figure on the certificate. And PREN is a ranking index, not a prediction: temperature, chloride concentration, pH, crevice geometry and flow velocity decide whether a material survives. Treat it as a shortlist tool and confirm the selection against your actual service conditions.

Formula and the 32 to 35 seawater guidance per published technical references on pitting resistance equivalent number; composition limits per ASTM A182 Grade F47.

Open-die and ring-rolled work, made to your drawing. No castings, no welded fabrications, no purchased billet of unknown origin.

Capacities are this works' installed equipment. Jiangyin Jiangnan Metal Co., Ltd., Zhouzhuang Town, Jiangyin, Jiangsu, China.

The grade was developed against sulphuric acid compounds, and that is still where most of it goes. Chloride-bearing process streams account for the rest.

Application areas per published technical data for grade 317LM, mapped against the product forms this works supplies.

S31725 runs the electric arc furnace, ladle furnace and vacuum oxygen decarburisation route, which is what gets carbon down to 0.030 percent without burning out the chromium. Heats to 60 tonnes. Electroslag remelting is available where a cleaner, more homogeneous structure is wanted on a critical part.

Test scope is fixed by the purchase order. ASTM A262 Practice E is commonly called up on low-carbon austenitic grades going into corrosive duty.

Honest answer first: plenty of enquiries that arrive asking for S31725 are better served one grade either side of it. Here is how the shortlist usually resolves.

Tell us the medium, the temperature and the chloride level in your enquiry and we will say which of these we would quote, including when the answer is the cheaper grade.

• A182 F44
• 904L
• Sanicro 28
• Alloy 24
• A182 F51
• A182 F53
• A182 F55
• A182 F347
• A182 F321
• Nitronic 50
• Inconel 625
• Incoloy 825