Stainless Steel 321
Stainless steel is the branded metal of present times. It can be applied successfully in modern needs. Its value can be utilized across various engineering productions. Stainless steel is recyclable, sustainable, and versatile in nature.
Stainless steel is a ferrous carbon alloy that contains chromium at least 11%. The famous property of corrosion resistance is contributed by the added chromium. Chromium forms a protective layer of chromium oxide and prevents corrosion. It makes stainless steel bright finished. Other alloying agents include nickel and molybdenum.
Austenitic steel is the most commercially used stainless steel worldwide. It represents strength, formability, resistance, and hardness. Austenitic stainless steel is high chromium and nickel grades. It exhibits superior corrosion resistance and considerable mechanical properties. This stainless steel cannot be hardened by cold-working and non-magnetic in nature.
Grade 321 Stainless Steel
Stainless steel Grade 321 is stabilized austenitic stainless steel. It is stabilized with added titanium with the presence of chromium and nickel in the composition. Titanium prevents the formation of chromium carbide precipitation from welding or exposure to high temperatures. Grade 321 is not sensitive to the carbide precipitation, which is formed after or during welding. It offers excellent corrosion resistance to intergranular corrosion after welding.
Stainless steel Grade 321 exhibits excellent forming and welding characteristics and holds good toughness at cryogenic temperature. It cannot be hardened by heat-treatment and it is non-magnetic in nature.
It is used often in applications that require intermittent heating between the temperature range of 427-899ºC, and for welding where post-weld annealing is not required. Most widely used in the aerospace industry, chemical processing, etc.
Chemical Composition
| Element | Percentage (%) |
| Carbon (C) | 0.08 max |
| Chromium (Cr) | 17.0 – 19.0 |
| Nickel (Ni) | 9.0 – 12.0 |
| Titanium (Ti) | ≥ 5 × C (min) |
| Manganese (Mn)+ | 2.0 max |
| Silicon (Si) | 1.0 max |
| Phosphorus (P) | 0.045 max |
| Sulfur (S) | 0.030 max |
| Iron (Fe) | Balance |
Mechanical Composition
| Property | Value |
| Tensile Strength | 515 MPa (min) |
| Yield Strength | 205 MPa (min) |
| Elongation | 40% (min) |
| Hardness (Brinell) | 217 HB max |
| Density | 8.0 g/cm³ |
| Melting Range | 1399 – 1420°C |
Physical Properties
| Property | Value |
| Thermal Conductivity | 16.2 W/m·K |
| Electrical Resistivity | 0.72 µΩ·m |
| Modulus of Elasticity | 193 GPa |
| Magnetic Properties | Non-magnetic (slightly magnetic after cold work) |
Equivalent Grade
| Standard | Grade |
| AISI / ASTM | 321 |
| EN | 1.4541 |
| JIS | SUS 321 |
| DIN | X6CrNiTi18-10 |
| IS | 321 |
Possible Alternative Grades of Grade 321
Grade 347 can be used as an alternation for grade 321.
Grade 304L can be used as it provides resistance to intergranular corrosion, but it is appropriate for high-temperature strengthening.
- Stainless steel Grade 304 H
- Stainless steel Grade 310
Corrosion Resistance
SS 321 Grade offers excellent corrosion resistance comparable to grade 304. It offers improved corrosion resistance in the chromium carbide precipitation range of 427-816°C. It offers improved intergranular corrosion resistance due to the addition of titanium.
Stress corrosion cracking can occur above 60°C. It also provides resistance to organic and inorganic acids at moderate temperatures. SS Grade 321 is prone to pitting and crevice corrosion in a warm chloride atmosphere.
Stainless steel 321 Grade can be used with diluted organic acids, phosphoric acid at low to moderate temperature. It can provide resistance to polythionic acid stress corrosion.
Heat Resistance
SS Grade 321 stainless steel offers a scaling resistance of 900°C in intermittent conditions and 925°C in continuous operations.
Oxidation Resistance
Stainless steel Grade 321 displays good oxidation resistance up to 870°C.
Hot Forming
- Grade 321 SS can be formed hot, by working in the temperature range of 1149- 1260°C. This grade is not suggested to work below the temperature of 927°C.
- Grade 321 must undergo annealing after exposure to a high temperature to obtain maximum corrosion resistance.
Cold Forming
Grade 321 SS has good ductility and can be formed easily.
Heat Treatment
- Annealing can be performed by heating in the temperature range of 950-1120°C followed by cooling for obtaining maximum corrosion resistance.
- Tempering is done by heating the material to 700°C for 1-2 hours, followed by air cooling.
- Stainless Steel Grade 321 cannot be hardened by heat treatment.
Welding
Grade 321 shows excellent weldability, as the addition of titanium prevents carbide precipitation during welding. Austenitic stainless steel can be welded by common fusion and welded techniques, with and without filler metals. Grade 347 electrodes are suggested for welding grade 321. The high silicon content of grade 347 can also be used.
Applications
Grade 321 is mainly used in:
- Aircrafts exhaustp
- Heat exchangers
- Spiral welded tube
- Furnace parts
- Welded equipment
- Chemical processing equipment
- Refinery equipment
- Thermal oxidizers
FAQ Sections
Q1. What is SS 321 stainless steel?
SS 321 (UNS S32100) is a titanium-stabilized austenitic stainless steel. It belongs to the 300-series family and contains 17–19% chromium and 9–12% nickel, with titanium added at a minimum of 5× the carbon content. The titanium addition prevents chromium carbide precipitation during welding and high-temperature exposure — a problem that affects standard Grade 304.
Because of this stabilization, SS 321 retains excellent corrosion resistance even after prolonged service in the 427–899°C temperature range, making it one of the most widely used grades in aerospace, chemical processing, and heat exchanger applications.
Q2. What temperature can SS 321 stainless steel withstand?
SS 321 can withstand the following temperatures in service:
- Intermittent service: scaling resistance up to 900°C
- Continuous service: up to 925°C
- Oxidation resistance: up to 870°C
- Hot forming range: 1149–1260°C
It is particularly suited to applications requiring intermittent heating in the 427–899°C range where post-weld annealing is impractical. Below 427°C, standard Grade 304 or 316 may be used instead.
Q3. What is the difference between SS 321 and SS 304?
The primary difference is titanium stabilization. SS 321 contains titanium (min 5× carbon content), while SS 304 does not. This makes SS 321 resistant to sensitization — the process where chromium carbides form at grain boundaries after exposure to temperatures between 425–850°C, causing a loss of corrosion resistance in 304.
In practical terms: use SS 304 for general-purpose, ambient-temperature, and moderate-temperature applications. Choose SS 321 when the component will be welded (without post-weld annealing) or used continuously in high-temperature environments where intergranular corrosion is a concern.
Q4. What is the difference between SS 321 and SS 347?
Both grades are stabilized austenitic steels designed to prevent sensitization, but they use different stabilizing elements
- SS 321 is stabilized with titanium — performs well in most high-temperature applications
- SS 347 is stabilized with niobium (columbium) — offers slightly better high-temperature strength and is the preferred filler metal when welding SS 321
Grade 347 electrodes are specifically recommended for welding Grade 321, as titanium is lost during the welding arc and niobium provides the equivalent stabilization in the weld pool.
Q5. Is SS 321 stainless steel magnetic?
SS 321 is non-magnetic in its annealed (solution-treated) condition. Like all austenitic stainless steels, it has a fully austenitic microstructure which is inherently non-magnetic.
However, SS 321 can become slightly magnetic after cold working (such as cold drawing, stamping, or machining), as cold work can partially transform the austenite to martensite. This is a minor effect compared to ferritic or martensitic grades (400 series), and the material is generally considered non-magnetic for most engineering purposes.
Q6. What welding filler metal should be used for SS 321?
Grade 347 electrodes and filler wire are the recommended choice for welding SS 321. Titanium — the stabilizing element in 321 — is largely lost during the welding arc, so a niobium-stabilized filler (347) is used to provide equivalent sensitization resistance in the weld deposit.
SS 321 can be welded using common fusion techniques including TIG (GTAW), MIG (GMAW), and stick (SMAW) welding, with or without filler metals. Post-weld annealing is generally not required when 347 filler is used — this is one of the key advantages of the 321 grade over unstabilized 304.
Q7. What are the main applications of SS 321 stainless steel?
SS 321 is primarily used in high-temperature and weld-intensive applications where standard 304 would suffer from sensitization. Key application areas include:
- Aerospace — aircraft exhaust systems, jet engine components, and expansion bellows
- Chemical processing — reactors, pressure vessels, and piping exposed to elevated temperatures
- Heat exchangers — spiral-welded tubes and shell-and-tube exchangers
- Refinery equipment — thermal oxidizers, furnace parts, and reformer tubes
- Power generation — boiler components and steam headers
- Food processing — high-temperature cooking and sterilization equipment
Ambica Steels supplies SS 321 in round bars, hex bars, flat bars, square bars, fine wire, and cold heading wire for all these industries.
Q8. How can I buy SS 321 stainless steel from Ambica Steels in India?
Ambica Steels supplies SS 321 in multiple product forms — round bars, hex bars, flat bars, square bars, wires — from its manufacturing facility in New Delhi, India, with export to 75+ countries.
You can:
- Buy online instantly via Ambica.One — check live inventory and place orders
- Request a quote or call-back via the contact page
- Email: dm@ambicasteels.com or info@ambicasteels.com
- Call: +91 (11) 47034400
Mill test certificates (EN 10204 3.1/3.2), NABL lab reports, and third-party inspection are available on request.
321 Round Bars 321 Fine Wire
321 Hex Bars 321 General Purpose Wire
321 Flat Bars 321 Cold Heading Wire
321 Square Bars
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