JIS SUS321 Stainless Steel: The Ultimate Guide to Properties, Uses & More

If you need a stainless steel that handles high heat and resists corrosion—like in aerospace engines or chemical reactors—JIS SUS321 stainless steel is the answer. Its secret? Added titanium, which locks in carbon to prevent heat-induced cracking. This guide breaks down everything you need to know to use it for high-temperature, demanding projects.

1. Material Properties of JIS SUS321 Stainless Steel

JIS SUS321 stainless steel stands out for its heat resistance and strength, all thanks to its unique material properties. Let’s start with what makes it special:

Alloy Composition

The key to its performance is titanium content—a stabilizer that sets it apart from SUS304 or SUS316. Here’s the detailed breakdown:

Mechanical & Physical Properties

It balances high-temperature strength and flexibility, making it ideal for extreme environments. Here’s how it performs:

An aerospace supplier in the U.S. uses SUS321 for engine exhaust parts. Its high tensile strength (515 MPa) withstands 800°C temperatures, while titanium prevents cracking during repeated heating and cooling.

2. Applications of JIS SUS321 Stainless Steel

Thanks to its heat resistance and corrosion protection, JIS SUS321 stainless steel is used in industries where extreme temperatures are common. Here are its top applications:

• Aerospace Components: Engine exhaust parts, fuel lines, and turbine casings. A Japanese aerospace firm uses SUS321 for jet engine heat shields—no cracking after 10,000 flight hours.
• Chemical Processing Plants: High-temperature reactors and heat exchangers (handles 600–800°C). A German chemical plant uses SUS321 for ethylene production reactors—resists corrosion from hot chemicals.
• Automotive Parts: Exhaust manifolds and turbocharger components (handles engine heat). A car manufacturer in South Korea uses SUS321 for turbo parts—lasts 2x longer than regular stainless steel.
• Food Processing Equipment: High-temperature ovens and sterilizers (meets food safety standards). A bakery in France uses SUS321 for bread ovens—resists oxidation from 700°C heat.
• Marine Applications: High-temperature marine engines (e.g., ship propulsion systems). A shipyard in Norway uses SUS321 for cruise ship engine parts—resists saltwater corrosion and engine heat.
• Pharmaceutical Equipment: Steam sterilizers (autoclaves) that reach 134°C. A Swiss pharma company uses SUS321 for autoclave chambers—no corrosion from repeated steam exposure.

3. Manufacturing Processes for JIS SUS321 Stainless Steel

JIS SUS321 stainless steel is workable, but its titanium content requires minor adjustments to manufacturing. Here are the key manufacturing processes:

1. Hot Rolling: Heated to 1100–1200°C and rolled into thick plates, bars, or pipe blanks. Used for large parts like aerospace engine casings. A steel mill in China uses hot rolling for SUS321 bars—ensures uniform titanium distribution.
2. Cold Rolling: Done at room temperature to make thin sheets (e.g., heat exchanger tubes). Improves surface smoothness—critical for high-temperature sealing.
3. Annealing: Heated to 1050–1150°C and quenched in water. Softens the steel after cold working and activates titanium (binds with carbon). A fabricator anneals SUS321 sheets before forming exhaust parts—prevents cracking.
4. Pickling: Treated with nitric acid to remove scale (from rolling or welding). Enhances the oxide layer—key for high-temperature corrosion resistance. A heat exchanger maker pickles SUS321 tubes—ensures no rust during use.
5. Machining: Drilled, milled, or turned with high-speed steel (HSS) or carbide tools. Use coolant to avoid overheating (titanium can slightly harden the steel). A machine shop uses carbide tools to make SUS321 turbo parts—achieves precise tolerances.
6. Forming: Deep drawing (for oven liners) and bending (for exhaust manifolds) are easy, thanks to 40% elongation. An automotive supplier bends SUS321 into exhaust manifolds—no cracks from shaping.

4. Corrosion Resistance of JIS SUS321 Stainless Steel

JIS SUS321 stainless steel excels at resisting corrosion—especially in high heat. Here’s how it performs:

• Intergranular Corrosion Resistance: Titanium binds with carbon, preventing carbide precipitation (a cause of cracking in high heat). A test compared SUS304 and SUS321 at 650°C—SUS304 cracked in 2 months, while SUS321 stayed intact.
• Pitting Resistance: Chromium forms a protective layer that resists small holes in mild chlorides (e.g., tap water). It performs similarly to SUS304—ideal for non-marine high-heat parts.
• Stress Corrosion Cracking (SCC): Resists SCC in high heat and mild chemicals. A chemical plant uses SUS321 for pressurized hot water pipes—no cracking under 100 bar pressure.
• High-Temperature Oxidation Resistance: Chromium prevents rust even at 800°C. An aerospace lab tested SUS321 in 800°C air—only 0.01 mm of oxidation after 1000 hours.
• Surface Treatment: Passivation (nitric acid treatment) thickens the oxide layer. A food equipment maker passivates SUS321 ovens—extends their life by 3x.

It’s not as chloride-resistant as SUS316 (avoid full seawater submersion), but it’s unbeatable for high-heat, mild-corrosion environments.

5. Welding JIS SUS321 Stainless Steel

JIS SUS321 stainless steel has good weldability, but you need to match the filler to its titanium content. Here’s how to do it right:

• Welding Processes: TIG (Tungsten Inert Gas) is best for thin parts (e.g., heat exchanger tubes), while MIG (Metal Inert Gas) works for thicker sections (e.g., engine casings). A welder in Australia uses TIG for SUS321 aerospace parts—creates clean, strong welds.
• Welding Rods: Use titanium-stabilized fillers like AWS ER321 or ER347. Avoid non-stabilized fillers (e.g., ER308)—they lack titanium, leading to intergranular corrosion. An automotive welder once used ER308— the weld cracked in 6 months of engine heat.
• Welding Gases: Use argon (for TIG) or argon-2% CO₂ (for MIG) to protect the weld from oxygen. Prevents oxidation and weak spots in high heat.
• Post-Weld Heat Treatment: Rarely needed (titanium stabilizes the weld), but annealing at 1050–1150°C removes stress for critical parts (e.g., aerospace components). A structural fabricator anneals SUS321 welds for jet engine parts—ensures no cracking.
• Welding Inspection: Use X-ray testing for high-heat parts. A quality team tests SUS321 welds—catches tiny defects before they fail in extreme temperatures.
• Welding Safety: Wear a heat-resistant jacket and helmet—SUS321 produces intense sparks during welding.

6. Standards and Specifications for JIS SUS321 Stainless Steel

To ensure quality, JIS SUS321 stainless steel follows strict global standards. Here’s what you need to know:

• JIS G4303: The Japanese Industrial Standard for cold-rolled stainless steel sheets (covers SUS321’s dimensions and titanium content).
• ASTM A240: The U.S. standard (ASTM A240 Type 321 is equivalent)—you can use them interchangeably.
• EN 10088: The European standard (EN 10088-2 X6CrNiTi18-10 is the equivalent grade).
• ISO Standards: ISO 15510 specifies its chemical composition (including titanium) and mechanical properties.
• Material Certification: Ask for a Mill Test Certificate (MTC) to verify titanium content (5×C – 0.70%). An aerospace client requires MTCs for all SUS321 parts—ensures heat resistance.
• Quality Control: Manufacturers test for titanium distribution and high-temperature corrosion resistance. A steel supplier rejects batches with insufficient titanium—they won’t resist intergranular corrosion.

7. Comparison with Other Materials

How does JIS SUS321 stainless steel stack up against other common materials? Here’s a clear breakdown:

For high-heat applications (600–800°C) like aerospace engines or chemical reactors, SUS321 offers the best balance of performance and cost—beating SUS304 in heat resistance and titanium in affordability.

Yigu Technology’s Perspective on JIS SUS321 Stainless Steel

At Yigu Technology, JIS SUS321 is our top recommendation for clients in aerospace, automotive, and high-heat chemical sectors. Its titanium content solves the intergranular corrosion issue that plagues SUS304 in extreme temperatures, while its strength handles pressure. We help clients optimize welding (using ER321 fillers) and manufacturing to maximize lifespan—whether it’s for jet engine parts or industrial ovens. While it costs more than SUS304, its reliability in high heat makes it a smart long-term investment.

FAQ About JIS SUS321 Stainless Steel

1. Why is titanium added to JIS SUS321?
   Titanium binds with carbon in the steel, preventing carbide precipitation. This stops intergranular corrosion— a common issue in SUS304 when heated above 450°C, making SUS321 ideal for high-heat projects.
2. Can JIS SUS321 be used in seawater?
   It’s not ideal. While it resists mild chlorides, it lacks the molybdenum in SUS316. For full seawater submersion (e.g., marine hulls), use SUS316—SUS321 may pit in constant saltwater.
3. Is JIS SUS321 magnetic?
   No—like SUS304 and SUS316, it has an austenitic microstructure, which makes it non-magnetic. This is a quick way to tell it apart from magnetic steels like SUS430.