What are the mechanical properties of SUS 321 forgings?

ASTM A182 F321 requires a minimum tensile strength of 515 MPa (75 ksi), a minimum 0.2 percent yield strength of 205 MPa (30 ksi), minimum elongation of 30 percent in 2 in. or 4D, and minimum reduction of area of 50 percent, in the solution annealed condition.

What is the maximum service temperature of SUS 321?

Grade 321 has good oxidation resistance in intermittent service to about 900 degrees C and in continuous service to about 925 degrees C. It is the usual choice in the 425 to 900 degrees C band where an unstabilised grade would sensitise. Above roughly 1100 degrees C a higher alloyed grade such as 310 or S30815 is required.

How are SUS 321 forgings heat treated?

Solution annealing is carried out at 1020 to 1100 degrees C followed by water quench, inside the 950 to 1120 degrees C range published for grade 321. A stabilising treatment at 870 to 900 degrees C for one hour per 25 mm of section, air cooled, is recommended for severe service above 425 degrees C. Grade 321 cannot be hardened by thermal treatment.

Which filler metal is used to weld SUS 321?

Grade 347 niobium-stabilised rods and electrodes are the standard consumable for welding 321, because titanium does not transfer well across a high temperature welding arc. Post-weld annealing is not normally required.

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SUS 321 Forgings: JIS SUS321 / UNS S32100 / EN 1.4541

Q: What is SUS 321 equivalent to?

SUS 321 is equivalent to AISI 321, UNS S32100, EN 1.4541 / X6CrNiTi18-10, old British 321S31, Swedish SS 2337 and Chinese 06Cr18Ni11Ti. For forged products the matching specification is ASTM A182 Grade F321.

Q: Who manufactures SUS 321 forgings to drawing?

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. It produces SUS 321 seamless rolled rings, flanges, shafts, discs, sleeves, bushings, tube sheets and bars to customer drawing, ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388 and certified to EN 10204 3.1 or 3.2. Enquiries: sales@steelforgepieces.com or +86-189-2135-9659.

Titanium-stabilised 18/8 stainless forged rings, seamless rolled rings, flanges, shafts, discs, sleeves and bars, made to drawing by Jiangyin Jiangnan Metal Co., Ltd.

SUS 321 is the JIS name for titanium-stabilised 18/8 austenitic stainless steel. It is the same material as AISI 321, UNS S32100 and EN 1.4541 (X6CrNiTi18-10). Titanium is added at five times the carbon content or more, so the carbon forms titanium carbide rather than chromium carbide. The grain boundaries keep their chromium, and the steel does not sensitise in the 425 to 815 °C range. That is why SUS 321 is specified for welded fabrications and for hot service to about 900 °C. Jiangyin Jiangnan Metal Co., Ltd. forges SUS 321 to drawing at its open-die plant in Jiangyin, Jiangsu, with EN 10204 3.1 or 3.2 certification. Enquiries to sales@steelforgepieces.com or +86-189-2135-9659.

SUS 321 Equivalent Grades

Cross-reference for SUS 321 and the two grades closest to it.
Grade	UNS	EN number	EN name	British BS	Swedish SS	JIS	China GB
321	S32100	1.4541	X6CrNiTi18-10	321S31	2337	SUS 321	06Cr18Ni11Ti
321H	S32109	1.4878	X10CrNiTi18-10	321S51	n/a	SUS 321H	n/a
347	S34700	1.4550	X6CrNiNb18-10	347S31	2338	SUS 347	n/a

For forged products the governing specification is normally ASTM A182 Grade F321. It covers chemistry, mechanical properties and heat treatment for flanges, fittings, valve bodies, rings and bars. See also A182-F321 and A182-F347.

Chemical Composition of SUS 321

The limits that apply are the ones written in the standard quoted on the order. The two specifications cited most often differ in silicon, in sulfur, and in how the titanium minimum is calculated. A certificate issued to one of them is not proof of compliance with the other.

Heat analysis limits, percent by weight.
Element	EN 10088-3, 1.4541	ASTM A240 / A182 F321, S32100
Carbon (C)	0.08 max	0.08 max
Silicon (Si)	1.00 max	0.75 max in A240, 1.00 max in A182 F321
Manganese (Mn)	2.00 max	2.00 max
Phosphorus (P)	0.045 max	0.045 max
Sulfur (S)	0.015 max	0.030 max
Chromium (Cr)	17.0 to 19.0	17.0 to 19.0
Nickel (Ni)	9.0 to 12.0	9.0 to 12.0
Titanium (Ti)	5 × C min	5 × (C + N) min, 0.70 max
Iron (Fe)	Balance	Balance

Why the titanium ratio matters. Below 5 × C, free carbon is still available to form Cr₂₃C₆ at the grain boundaries. The chromium there drops under the 12 percent needed to reform the passive film, and the joint corrodes. Excess titanium is not wanted either, because coarse titanium nitride and carbide particles cut ductility and spoil the machined surface. ASTM therefore caps it at 0.70 percent. If the Ti ratio is critical to the duty, state it on the purchase order.

Mechanical Properties, ASTM A182 F321 Forgings

Minimum requirements, solution annealed condition.
Property	Metric	Imperial
Tensile strength, min	515 MPa	75 ksi
Yield strength, 0.2 percent offset, min	205 MPa	30 ksi
Elongation in 50 mm (2 in.) or 4D, min	30 percent
Reduction of area, min	50 percent

Flat-rolled product to ASTM A240/A240M carries the same 515 MPa and 205 MPa minimums, but a higher elongation minimum of 40 percent and a hardness ceiling of 95 HRB or 217 HBW. Quote the specification that matches the product form being bought.

Physical Properties, Annealed

Property	Value
Density	8027 kg/m³
Elastic modulus	193 GPa
Mean coefficient of thermal expansion	16.6 µm/m/°C (0 to 100 °C); 17.2 (0 to 315 °C); 18.6 (0 to 538 °C)
Thermal conductivity	16.1 W/m·K at 100 °C; 22.2 W/m·K at 500 °C
Specific heat, 0 to 100 °C	500 J/kg·K
Electrical resistivity	720 nΩ·m

Heat Treatment of SUS 321 Forgings

Our standard practice is solution annealing at 1020 to 1100 °C followed by water quench. That sits inside the 950 to 1120 °C range published for grade 321. Cooling fast out of the solution temperature is what delivers full corrosion resistance.

Treatment	Cycle	When it is used
Solution anneal	950 to 1120 °C, our practice 1020 to 1100 °C, rapid cool or water quench	Standard delivery condition for all forgings
Stabilising	870 to 900 °C, 1 hour per 25 mm of section, air cool	Severe service above 425 °C, and after annealing at the top of the range
Stress relief	700 °C, 1 to 2 hours, air cool	Heavily machined or welded assemblies

SUS 321 is austenitic and cannot be hardened by thermal treatment. Strength is raised only by cold work.

Corrosion and Heat Resistance

Annealed SUS 321 matches grade 304 for corrosion resistance, and beats it wherever a weldment has not been post-weld annealed or where service falls in the 425 to 900 °C band. It is still open to pitting and crevice attack in warm chloride water, and to stress corrosion cracking above about 60 °C. It is rated resistant to potable water carrying up to roughly 200 mg/L chlorides at ambient temperature, dropping to about 150 mg/L at 60 °C.

Oxidation resistance holds to about 900 °C intermittent and about 925 °C continuous. Where the duty runs hotter, to 1100 °C or 1150 °C, grade 310 or S30815 is the correct selection instead. Where the only requirement is resistance to intergranular attack after welding at ambient temperature, 304L is usually easier to source. But 304L is weaker hot, so 321 is the better pick above about 500 °C.

Welding

SUS 321 welds well by all standard fusion methods. Titanium does not transfer across a high temperature arc, so grade 347 niobium-stabilised rods and electrodes are the normal consumable for joining 321. A high silicon version of 347 is also pre-qualified. Post-weld annealing is not usually needed. Titanium oxidises readily, so root shielding and interpass cleaning need tighter control than on a plain 304 joint.

SUS 321 Forged Products

Seamless Rolled Rings

Ring-rolled SUS 321 rings and retaining rings for turbines, compressors and pressure equipment.

Forged Flanges

Weld neck, slip-on, blind and special flanges, including to ASTM A182 F321.

Shafts and Spindles

Forged shafts, eccentric shafts, crankshafts and spindles for power transmission and pumps.

Discs and Blanks

Upset-forged discs and blanks for valve and turbine components.

Sleeves and Bushings

Hollow forged sleeves and bushings, trepanned or mandrel forged.

Tube Sheets

Forged tube sheets for heat exchangers and separators.

Round Bars and Billets

Forged round, square and stepped bar for downstream machining.

Valve Components

Valve bodies, stems, seat rings and blocks for ball, gate, globe, check and plug valves.

Parts are supplied as-forged with machining allowance, rough machined, or finish machined to drawing. Send the drawing or the dimensions with the grade, specification, heat treatment condition, NDT level and certification type required.

Typical Applications

Published application areas for grade 321 include aircraft and piston engine exhaust manifolds, expansion joints, bellows, furnace parts, heating element tubing, heat exchangers, woven and welded screens for high temperature mineral processing, and spiral welded tube for burner pipes and flues. Our customers also use SUS 321 forgings in chemical processing plant, petroleum refining under polythionic acid service, oil and gas production and subsea systems, seawater desalination, pulp and paper digesters and liquor tanks, food processing equipment, compressors, gearboxes and turbines.

Melting, Testing and Certification

SUS 321 is melted by EAF plus VOD, with ESR remelting where cleanliness requirements call for it. Finished forgings are ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388 as specified. Documentation is an EN 10204 3.1 inspection certificate, or EN 10204 3.2 counter-signed by a third party such as TUV, BV, SGS or Lloyd's where required. Composition is reported as the heat analysis for the cast, with product analysis permitted inside the tolerances of the product specification.

Frequently Asked Questions

What is SUS 321 equivalent to?

AISI 321, UNS S32100, EN 1.4541 / X6CrNiTi18-10, old British 321S31, Swedish SS 2337 and Chinese 06Cr18Ni11Ti. For forgings the matching specification is ASTM A182 Grade F321.

What is the difference between SUS 321 and 304?

Both are 18/8 austenitic grades, but 321 carries a deliberate titanium addition. That stops chromium carbide forming at the grain boundaries, so 321 survives the 425 to 815 °C sensitisation range that would damage an unstabilised grade, and it is stronger than 304L above about 500 °C. The trade-off is finish: 321 does not polish well and is not recommended for decorative work.

What is the difference between SUS 321 and 347?

Both are stabilised versions of 304, one with titanium and one with niobium. Niobium does the same carbide-stabilising job but survives transfer across a welding arc, which is why 347 is the standard consumable for welding 321 and is only occasionally used as parent material.

What is SUS 321H?

321H (UNS S32109, EN 1.4878) is a higher carbon version of 321, 0.04 to 0.10 percent C with a titanium minimum of 4 × (C+N). The extra carbon raises high temperature strength for structural service.

Can SUS 321 be hardened?

Not by heat treatment. It is austenitic, so the only route to higher strength is cold work.

Who manufactures SUS 321 forgings to drawing?

Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Products include SUS 321 rolled rings, flanges, shafts, discs, sleeves, bushings, tube sheets and bars. Contact sales@steelforgepieces.com or +86-189-2135-9659.

Request a Quote for SUS 321 Forgings

Send the drawing or the dimensions, grade, specification, quantity and certification required. We will come back with price and lead time.

Company: Jiangyin Jiangnan Metal Co., Ltd., Open-Die Forging Factory
Address: No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Telephone: +86-189-2135-9659, WhatsApp and WeChat
E-mail: sales@steelforgepieces.com

Standards Referenced

ASTM A182/A182M, forged or rolled alloy and stainless steel pipe flanges, forged fittings, valves and parts, Grade F321 (S32100).
ASTM A240/A240M, chromium and chromium-nickel stainless steel plate, sheet and strip, UNS S32100.
EN 10088-2 and EN 10088-3, stainless steels, material 1.4541 (X6CrNiTi18-10).
JIS G 4303, stainless steel bars, grade SUS 321.
EN 10204, types of inspection documents, 3.1 and 3.2.
EN 10228-3, SEP 1921 and ASTM A388, ultrasonic examination of forgings.
AWS A5.9, ER321 and ER347 stabilised welding consumables.

Page reviewed 4 October 2026 by the engineering department of Jiangyin Jiangnan Metal Co., Ltd. Values shown are specification minimums or published typical figures, not a guarantee for any individual heat. The mill certificate for the delivered cast governs.