Comparison Of SUS321 And SUS304: Titanium-Stabilized Vs General-Purpose Austenitic Stainless Steel

SUS321 and SUS304 are austenitic stainless steels with different performance orientations, with the core difference being that SUS321 adds titanium for stabilization. Titanium stabilization eliminates intergranular corrosion after welding, and improves high-temperature stability, making them suitable for different welding and high-temperature environment requirements.

Core Parameter Comparison

Parameter	SUS321 Stainless Steel	SUS304 Stainless Steel
Chemical Composition (wt%)	C≤0.08, Si≤1.00, Mn≤2.00, P≤0.045, S≤0.030, Cr=17.00-19.00, Ni=9.00-12.00, Ti=4×C-0.70, Fe=Balance	C≤0.08, Si≤1.00, Mn≤2.00, P≤0.045, S≤0.030, Cr=18.00-20.00, Ni=8.00-10.50, Fe=Balance
Mechanical Properties (Annealed)	Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Hardness ≤201HB	Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Hardness ≤201HB
Service Temperature	-196℃ to 870℃ (continuous service)	-196℃ to 870℃ (continuous service)
Equivalent Grades	EN 1.4541, UNS S32100, AISI 321	EN 1.4301, UNS S30400, AISI 304

Key Performance Differences: 1. Intergranular corrosion resistance: SUS321's titanium stabilization eliminates intergranular corrosion after welding; SUS304 is prone to intergranular corrosion in the weld heat-affected zone without post-weld annealing. 2. High-temperature stability: SUS321's TiC carbides improve high-temperature stability, more suitable for long-term high-temperature service; SUS304's grain boundaries are prone to embrittlement at high temperatures. 3. Weldability: Both have good weldability; SUS321 does not require post-weld heat treatment, while SUS304 needs it for harsh environments. 4. Cost: SUS321 is 20-30% more expensive than SUS304. 5. Formability: Both have excellent formability, with no obvious difference.

Applicable Scenario Distinction: SUS321 is suitable for welding-intensive high-temperature components, such as aero-engine exhaust pipes, boiler heat exchanger tubes, and chemical reaction vessels. SUS304 is suitable for general low-corrosion, non-welding or post-weld heat-treatable components, such as food processing equipment, decorative pipelines, and indoor storage tanks.

Practical Q&A

Q1: Why is SUS321 preferred for welding-intensive high-temperature components?

A1: Its titanium stabilization avoids intergranular corrosion after welding, ensuring corrosion resistance and structural stability of the weld area without post-weld heat treatment, reducing processing costs.

Q2: Can SUS304 replace SUS321 in welding high-temperature components?

A2: No. SUS304's weld area is prone to intergranular corrosion and embrittlement at high temperatures, which will lead to component failure; SUS321 is the mandatory material for such scenarios.

Q3: What welding materials are used for SUS321?

A3: Use ER321 welding wire; control heat input ≤180J/mm to avoid overheating; post-weld passivation treatment is recommended to improve corrosion resistance.

Q4: What is the difference in nickel content between SUS321 and SUS304?

A4: SUS321 has a higher nickel content upper limit (12.00%) than SUS304 (10.50%), which improves austenite stability and low-temperature toughness.

Q5: How to select between SUS321 and SUS304?

A5: Choose SUS304 if cost is a priority and the component is non-welding or post-weld heat-treatable; choose SUS321 if the component is welding-intensive or used in high-temperature environments requiring intergranular corrosion resistance.