Austenitic stainless steel / Mo-bearing
UNS S31600 Forgings Type 316, EN 1.4401, X5CrNiMo17-12-2, ASTM A182 F316. Rolled rings, flanges, bars, discs, shafts, sleeves and tube sheets.
UNS S31600 is the standard molybdenum-bearing austenitic stainless steel, holding 16.0 to 18.0% chromium, 10.0 to 14.0% nickel and 2.00 to 3.00% molybdenum. The molybdenum is what separates it from Type 304 and is the reason it resists pitting and crevice attack in chloride-bearing media.
Jiangyin Jiangnan Metal melts this grade in its own furnaces by electric arc, ladle refining and vacuum oxygen decarburisation, then forges, heat treats, machines and tests it on one site. The certificate traces a shipped part back to its melt number rather than to a purchased billet.
- UNS
- S31600
- EN
- 1.4401
- Molybdenum
- 2.00 to 3.00%
- Tensile
- 515 MPa minimum
- Yield 0.2%
- 205 MPa minimum
- Anneal
- 1010 to 1120 °C, cool rapidly
- Max ring
- OD 6,000 mm
- Max piece
- 30,000 kg
- Minimum
- 10 kg, no minimum piece count
- Lead time
- 20 to 60 days
- Certificate
- EN 10204 3.1 or 3.2
Designations and equivalents
S31600 carries a different name in nearly every system, and buyers often enquire under one of the others. The last two rows are different materials, not aliases: carbon content separates them.
| System | Designation |
|---|---|
| UNS | S31600 |
| AISI type | 316 |
| EN number | 1.4401 |
| EN name | X5CrNiMo17-12-2 |
| Old British BS | 316S31 (En 58H, 58J) |
| Swedish SS | 2347 |
| Japanese JIS | SUS 316 |
| Forging spec | ASTM A182 F316 |
| Low carbon | S31603, 316L, 1.4404, A182 F316L |
| High carbon | S31609, 316H |
Chemical composition
Weight per cent. The two columns differ only in the silicon limit, which is 0.75% for flat-rolled product under ASTM A240 and 1.00% for forgings under ASTM A182 F316.
| Element | Min | Max, A240 | Max, A182 F316 |
|---|---|---|---|
| Carbon | – | 0.08 | 0.08 |
| Manganese | – | 2.00 | 2.00 |
| Silicon | – | 0.75 | 1.00 |
| Phosphorus | – | 0.045 | 0.045 |
| Sulfur | – | 0.030 | 0.030 |
| Chromium | 16.0 | 18.0 | 18.0 |
| Nickel | 10.0 | 14.0 | 14.0 |
| Molybdenum | 2.00 | 3.00 | 3.00 |
| Nitrogen | – | 0.10 | 0.10 |
| Iron | Balance | ||
Melting route for this grade at this works: electric arc furnace, ladle furnace, then vacuum oxygen decarburisation where low carbon or tight nitrogen control is called for. Electroslag remelting is available where a customer specifies improved cleanliness or segregation control.
Mechanical and physical properties
Room-temperature minima in the solution-annealed condition. Requirements follow the product form, so state the governing specification on the enquiry. Forgings are accepted against A182 F316, bar against A479, plate against A240.
| Property | ASTM A182 F316, forgings | ASTM A240 and A479 |
|---|---|---|
| Tensile strength | 515 MPa (75 ksi) | 515 MPa (75 ksi) |
| Yield strength, 0.2% offset | 205 MPa (30 ksi) | 205 MPa (30 ksi) |
| Elongation | 30% in 50 mm or 4D | 40% in 50 mm |
| Reduction of area | 50% | Not specified |
| Hardness, max | Per order and test plan | 217 HB / 95 HRB |
Some datasheets list a compressive strength of 170 MPa against this grade. ASTM specifies no compressive strength for austenitic stainless steel, and 170 MPa is in fact the minimum yield strength of 316L (S31603). Treat that figure as a transcription error rather than a design value.
Typical physical properties
| Property | Value |
|---|---|
| Density | 8,000 kg/m³ |
| Elastic modulus | 193 GPa |
| Thermal expansion, 0 to 100 °C | 15.9 µm/m·°C |
| Thermal expansion, 0 to 538 °C | 17.5 µm/m·°C |
| Thermal conductivity at 100 °C | 16.3 W/m·K |
| Specific heat, 0 to 100 °C | 500 J/kg·K |
| Electrical resistivity | 740 nΩ·m |
| Solution treatment | 1010 to 1120 °C, cool rapidly |
S31600 cannot be hardened by thermal treatment. Strength above the annealed minima comes only from cold work.
Corrosion and heat resistance
S31600 behaves well across a wide range of atmospheric environments and corrosive media, and is generally more resistant than Type 304. Its limits are worth stating plainly, because the grade is specified past them more often than any other stainless.
It is commonly called the standard marine grade, but it is not resistant to warm sea water. In many marine environments it shows surface corrosion, usually as brown staining, and that is particularly associated with crevices and rough surface finishes. It is subject to pitting and crevice corrosion in warm chloride environments and to stress corrosion cracking above roughly 60 °C. It is considered resistant to potable water carrying up to about 1,000 mg/L chloride at ambient temperature, falling to about 500 mg/L at 60 °C.
Oxidation resistance is good in intermittent service to 870 °C and in continuous service to 925 °C. Continuous use between 425 and 860 °C is not recommended where aqueous corrosion resistance afterwards matters, because of carbide precipitation. Heavy welded sections in S31600 need post-weld annealing for full corrosion resistance; 316L does not.
When to specify something else
| Grade | Reason to choose it over 316 |
|---|---|
| 316L | Heavy welded sections, or service in the carbide precipitation range |
| 316Ti | Better resistance around 600 to 900 °C |
| 316N | Higher strength than standard 316 |
| 317L | Higher chloride resistance than 316L at similar stress corrosion resistance |
| 904L | Much higher chloride resistance at elevated temperature, good formability |
| 2205 / A182 F51 | Much higher chloride resistance at elevated temperature and higher strength |
| A182 F44 | Six per cent molybdenum austenitic for severe chloride duty |
What we forge in S31600
Every item is forged from one piece of steel melted on site. No welding, no casting, no purchased billet of unknown origin. Size limits below are set by the equipment named in the right-hand column.
| Form | Typical use | Limit and equipment |
|---|---|---|
| Seamless rolled rings | Flange rings, bearing races, gear ring blanks, slewing rings | To OD 6,000 mm on the 6 m radial-axial mill; from OD 50 mm by upset and punch |
| Forged flanges and nozzles | Pressure vessels, heat exchangers, piping to ASME B16.5 and B16.47 | Pressed and rolled, A182 F316 acceptance |
| Discs, tube sheets, covers | Heat exchangers, vessel closures, blind flanges | To 5,000 mm machined diameter on the vertical lathe |
| Round bars and blocks | Machining stock, valve stems, fasteners | Forged, rough turned or peeled |
| Shafts and spindles | Pumps, mixers, compressors, gearboxes, eccentric shafts | To 14,000 mm turned length; 15 m well furnace for vertical quench |
| Sleeves, bushings, cylinders | Subsea equipment, pulp and paper, chemical plant | To 1,600 mm diameter by 10,000 mm on the CNC deep-hole driller |
| Valve and wellhead parts | Bodies, bonnets, seat rings, stems, blocks, manifolds | API 6A and NACE MR0175 / ISO 15156 on request |
Where it goes
Chemical and petrochemical plant, including pressure vessels, tanks, heat exchangers and piping. Petroleum refining, including polythionic acid service and catalytic recovery systems. Pulp and paper digesters, liquor tanks and paper machines. Food processing and storage. Pharmaceutical and biochemical production. Offshore and onshore oil and gas equipment. Industrial air compressors, power generators and nitrogen generators. Ball, gate, globe, check and plug valves. Shipbuilding and general heavy machinery.
Testing and certification
Each order runs against a written test plan agreed before production. Heat treatment is recorded on furnace charts tied to the melt number.
Ultrasonic testing is carried out to EN 10228-3, SEP 1921 or ASTM A388 as specified. Liquid penetrant inspection, positive material identification, intergranular corrosion testing to ASTM A262 and ferrite measurement are available on request. Material certificates are issued to EN 10204 3.1, or to 3.2 with third-party inspection by TUV, SGS, BV or Lloyd's where a project calls for it. The works holds CCS, BV, DNV, LR and NK approvals.
What we need to quote
A drawing, or the finished dimensions. For a ring that means outside diameter, inside diameter and height; for a disc or tube sheet, diameter and thickness. With that, send the quantity, the governing specification such as ASTM A182 F316 or ASTM A479 S31600, the certificate level, any NDT requirement, the delivery condition wanted as forged, rough machined or finish machined, and the destination port. Quotations normally go back within one working day.
Questions we are asked
Is UNS S31600 the same as 316 stainless steel?
Yes. S31600 is the Unified Numbering System designation for AISI Type 316. The same steel is 1.4401 or X5CrNiMo17-12-2 in Europe, 316S31 in the old British system and SUS 316 in Japan. Ordered as a forged pressure part it becomes ASTM A182 Grade F316.
What is the difference between S31600 and S31603?
Carbon, and therefore strength. S31600 permits up to 0.08% carbon and must reach 515 MPa tensile and 205 MPa yield. S31603, which is 316L, is held to 0.03% carbon, which makes it immune to sensitisation and the right choice for heavy welded sections, at lower minima of 485 MPa tensile and 170 MPa yield.
How much molybdenum is in UNS S31600, and why does it matter?
Between 2.00 and 3.00%. Molybdenum is the addition that distinguishes 316 from 304, and it is what gives the grade its resistance to pitting and crevice corrosion in chloride environments. A composition table for this grade that shows no molybdenum is incomplete.
Can S31600 be hardened by heat treatment?
No. Austenitic grades cannot be hardened thermally, only by cold work. The standard treatment is solution annealing between 1010 and 1120 °C followed by rapid cooling. Where a hardenable stainless forging is needed, 17-4 PH or PH 13-8 Mo are the usual choices.
Is S31600 suitable for sea water?
Not for warm sea water. It is widely called the standard marine grade and performs acceptably in splash and atmospheric marine exposure, but in many marine environments it stains brown and corrodes at crevices and rough surfaces. For immersed or warm chloride duty, move to duplex 2205, 904L or a six per cent molybdenum austenitic.
Who supplies custom S31600 open-die forgings?
Jiangyin Jiangnan Metal Co., Ltd., an integrated melting works and open-die forge at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, in operation since 1997. The plant forges S31600 rings, flanges, bars, discs, shafts, sleeves and tube sheets to customer drawings, up to OD 6,000 mm and 30 tonnes a piece, with EN 10204 3.1 or 3.2 certificates. Telephone +86 189 2135 9659, email sales@steelforgepieces.com.
What is the minimum order?
Ten kilogrammes, with no minimum piece count, so single prototype forgings are accepted. Lead time runs 20 to 60 days according to size, heat treatment and the amount of machining.
Other stainless grades forged here
Composition and property limits taken from ASTM A182/A182M F316, ASTM A240/A240M and ASTM A479 requirements and from the Atlas Steels grade 316 data sheet. Figures are specification minima or typical values; confirm against the current edition of the governing standard before design use. Reviewed by the technical department, Jiangyin Jiangnan Metal Co., Ltd. .
Send the drawing, get a price
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China