AISI 321 / 1.4541 / SUS321 Stainless Steel: Properties and Welding Guide

AISI 321 / 1.4541 / SUS321 Stainless Steel

Grade 321 is the grade of choice for applications up to about 900 C, combining high strength, resistance to scaling and phase stability with resistance to subsequent aqueous corrosion. It is a titanium-stabilized austenitic stainless steel equivalent across AISI 321, EN 1.4541 and JIS SUS321 (UNS S32100).

 

Equivalent Grades of AISI 321

Standard System	Grade
UNS (USA)	S32100
ASTM	TP321 (tubes), 321 (plates & sheets)
EN (Europe)	1.4541 / X6CrNiTi18‑10
JIS (Japan)	SUS321
GB (China)	06Cr18Ni11Ti

 

Chemical Composition (Weight %) of AISI 321

Element	Content Range
Carbon (C)	≤0.08
Manganese (Mn)	≤2.00
Silicon (Si)	≤1.00
Phosphorus (P)	≤0.045
Sulfur (S)	≤0.030
Chromium (Cr)	17.00‑19.00
Nickel (Ni)	9.00‑12.00
Nitrogen (N)	≤0.10
Titanium (Ti)	Min. 5×(C+N), ≤0.70

 

Mechanical Properties (Solution‑Annealed Condition, ASTM A312)

Property	Requirement
Tensile Strength	≥515 MPa
0.2% Offset Yield Strength	≥205 MPa
Elongation (50 mm)	≥40%
Brinell Hardness (HB)	≤217
Rockwell Hardness (HRB)	≤95

 

Physical Properties (Typical Values, Room Temperature)

Property	Typical Value	Remarks
Density	7.92 g/cm³	At 20℃
Melting Range	1398‑1446 ℃
Tensile Modulus of Elasticity	193 GPa	At room temperature
Specific Heat Capacity	500 J/(kg·℃)	20‑100℃
Thermal Conductivity	16.1 W/(m·K)	Measured at 100℃
Mean Coefficient of Linear Thermal Expansion	16.6×10⁻⁶ /℃	20‑100℃
Electrical Resistivity	0.72 μΩ·m	At 20℃
Magnetic Property	Essentially non‑magnetic in solution‑annealed condition	Slight magnetism may appear after cold‑working

 

Operating‑Temperature Comparison: TP321 vs TP321H

Note: TP321 (UNS S32100, C ≤0.08%) and TP321H (UNS S32109, C:0.04‑0.10%) share the same sensitization temperature range. The main difference lies in high‑temperature creep‑rupture strength.

Item	TP321 (UNS S32100)	TP321H (UNS S32109)
Sensitization range	427‑816 ℃, Ti‑stabilized against intergranular corrosion	427‑816 ℃, Ti‑stabilized against intergranular corrosion
Continuous oxidation temp (non‑pressure)	Max 870 ℃	Max 870‑900 ℃
Recommended continuous pressurized piping service	≤600‑700 ℃; creep strength drops rapidly above 700 ℃	Suitable for long‑term pressure service at 700‑800 ℃ with superior creep‑rupture strength
Intermittent short‑cycle service	Short‑term up to 900 ℃, derate under pressure	Short‑term up to 925 ℃, smaller derating for pressure loads
Pressure‑bearing performance above 700 ℃	Moderate, not preferred for long‑term high‑temp pressure service	Excellent, higher allowable design stress per ASME standard
Typical applications	Medium‑temperature service, thermal cycling, no post‑weld annealing, low‑pressure conditions	Boiler superheaters, reheaters, high‑temperature & high‑pressure process piping for long‑term service above 700 ℃

Key Characteristics of AISI 321 / 1.4541 / SUS321 Stainless Steel

1.What is the core advantage of TP321 stainless steel?

TP321 is stabilized by titanium addition. It inhibits chromium carbide precipitation at grain boundaries after welding and effectively prevents intergranular corrosion in the weld‑affected zone, making it suitable for working conditions where post‑weld solution annealing cannot be performed.

 

2.What high‑temperature advantages does TP321 have compared with 304?

TP321 offers better high‑temperature strength and creep resistance than 304. It can be used long‑term within the temperature range of 427‑816 ℃ for boilers, heat exchangers and high‑temperature process piping, whereas standard 304 is susceptible to sensitization‑induced intergranular corrosion within this temperature range.

 

3.How about the processing and welding performance of TP321?

It possesses good weldability, stamping and bending formability. It retains intergranular corrosion resistance without post‑weld solution heat treatment, which greatly reduces on‑site construction costs.

 

4.What about the corrosion‑resistance performance of TP321?

Its general uniform corrosion resistance is close to that of 304 and performs well in oxidizing media such as nitric acid. Its major strength lies in mitigating intergranular corrosion risks caused by welding, while its chloride‑ion corrosion resistance is lower than that of 316.

 

Applications of AISI 321 / 1.4541 / SUS321 Stainless Steel

1.Boiler & Thermal Equipment: Boiler superheaters, reheaters and high‑temperature heat exchangers for long‑term high‑temperature service to avoid welding‑induced intergranular corrosion.

2.Petrochemical High‑temperature Process Piping: High‑temperature pipelines and steam lines for refinery and petrochemical units, pressure‑bearing pipes where post‑weld heat treatment is unavailable.

3.Exhaust & Flue‑gas Systems: Industrial furnace and power‑plant exhaust ducts and chimney pipes under alternating high‑temperature conditions.

4.Thermal Heat Exchangers: Tubular high‑temperature heat exchangers and waste‑heat recovery tube bundles.

5.Aerospace & Thermal‑power Equipment: High‑temperature thermal pipelines and heat‑resistant tubing for engine accessories.

6.Food & Pharmaceutical High‑temperature Equipment: High‑temperature sterilization equipment and process piping without requirement for post‑weld solution annealing.

Supplier Introduction of AISI 321 / 1.4541 / SUS321 Stainless Steel

GNEE is a professional Chinese manufacturer and exporter of AISI 321 (UNS S32100, EN 1.4541) titanium‑stabilized austenitic stainless steel. We supply TP321 seamless / welded tubes, bars, plates, coils and matching pipe fittings and forgings, and the upgraded grade TP321H is also available. All products are manufactured in strict compliance with ASTM, EN and JIS standards, and complete inspections including PMI spectroscopic composition verification, dimensional measurement, hydrostatic test, eddy‑current test and mechanical‑property tests are performed prior to delivery.

 

Thanks to its titanium‑stabilized design, AISI 321 delivers excellent intergranular corrosion resistance after welding. It is suitable for service conditions including boiler superheaters, petrochemical high‑temperature pipelines, flue‑gas ducts and high‑temperature heat exchangers. We offer deep‑processing services such as cut‑to‑size, beveling and polishing, and provide standard seaworthy anti‑rust export packaging. We serve global engineering projects in power, petrochemical, thermal‑energy, food and pharmaceutical industries. Bulk orders, small‑volume trial orders and sample requests are all acceptable.

Please feel free to contact us for material selection, technical confirmation and project quotation to get complete supporting solutions.

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FAQ

1.How to choose between TP321 and 304 stainless steel?

TP321 is titanium‑stabilized with excellent intergranular corrosion resistance after welding, suitable for 427‑816 ℃ high‑temperature conditions. 304 lacks titanium stabilization and tends to suffer sensitization intergranular corrosion within this temperature range. For ordinary corrosion environments at room temperature, 304 offers better cost‑performance.

 

2.What is the difference between TP321 and TP321H, and when should TP321H be selected?

TP321H has increased carbon content and much higher high‑temperature creep‑rupture strength than standard TP321. TP321H is preferred for long‑term pressure‑bearing service above 700 ℃ such as boiler superheaters and reheaters. Standard TP321 works for medium‑temperature conditions below 700 ℃.

 

3.Is heat treatment required for TP321 after welding?

Post‑weld solution annealing is not required for standard welding. Titanium combines preferentially with carbon and nitrogen to restrain chromium carbide precipitation at grain boundaries and maintain intergranular corrosion resistance.