321 Stainless Steel Pipe/Tube
321 Stainless Steel Pipe/Tube | High-Temperature Corrosion Resistance
Certificated：ISO9001:2015, CE, ROHS
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Description
What is the 321 Stainless Steel Pipe/Tube?
321 Stainless Steel is a stabilized austenitic stainless steel, similar to Type 304, but with the crucial addition of titanium. This titanium content acts as a stabilizing agent, preventing the formation of chromium carbides during welding and high-temperature service. Without this stabilization, chromium carbides can precipitate along grain boundaries in the temperature range of 800°F to 1500°F (427°C to 816°C), leading to a condition known as “sensitization,” which makes the steel susceptible to intergranular corrosion.
This makes 321 a prime choice for applications where the material is subjected to high temperatures and welding, and where post-weld annealing is not possible. It is a non-magnetic grade that cannot be hardened by heat treatment, but it does have excellent toughness, even at cryogenic temperatures.
The “H” version, 321H (UNS S32109), is a modification of 321 with a higher carbon content, which provides improved high-temperature strength and creep resistance.
321 Stainless Steel Pipe/Tube Specifications
| Parameter | Details |
|---|---|
| Material Grade | 321 / 321H |
| Standard | ASTM A312, A213, A269, A778, etc. |
| Size Range | 1/8” NB to 24” NB |
| Thickness | SCH 5S to SCH XXS |
| Type | Seamless, ERW, Welded, Fabricated |
| Length | Single random, double random, or custom |
| Surface Finish | Annealed, pickled, polished |
| Shape | Round, square, rectangular |
Chemical Composition (ASTM A312/A213)
| Element | % Composition | Element | % Composition |
|---|---|---|---|
| Carbon (C) | ≤0.08 | Chromium (Cr) | 17.0–19.0 |
| Manganese (Mn) | ≤2.0 | Nickel (Ni) | 9.0–12.0 |
| Silicon (Si) | ≤0.75 | Titanium (Ti) | ≥5×C, ≤0.70 |
| Phosphorus (P) | ≤0.045 | Iron (Fe) | Balance |
| Sulfur (S) | ≤0.030 |
Mechanical Properties
| Property | Value | Standard |
|---|---|---|
| Tensile Strength | ≥515 MPa (75 ksi) | ASTM A312 |
| Yield Strength | ≥205 MPa (30 ksi) | ASTM A312 |
| Elongation | ≥35% | ASTM A312 |
| Hardness (Brinell) | ≤217 HB | ASTM A213 |
Physical Properties
| Property | Value |
|---|---|
| Density | 8.0 g/cm³ |
| Melting Point | 1450°C (2642°F) |
| Thermal Expansion (20–100°C) | 16.6 µm/m°C |
| Thermal Conductivity | 16.3 W/m·K |
Advantages of 321 Pipes/Tubes
🔥 High-Temperature Stability: Resists scaling up to 1650°F (899°C); ideal for cyclic heating/cooling.
⚙️ Weldability: Titanium stabilization prevents weld decay; no post-weld annealing required.
🛡️ Corrosion Resistance: Resists organic acids, alkaline solutions, & atmospheric corrosion.
❄️ Cryogenic Toughness: Maintains ductility at sub-zero temperatures.
💪 Stress Rupture Strength: Superior to 304/304L in sustained high-heat applications.
Applications of 321 Stainless Steel Tube
Comparison of Stainless Steel Pipe/Tube Grades
| Property | 321 SS | 304 SS | 316 SS |
|---|---|---|---|
| Stabilizing element | Titanium | None | Molybdenum |
| Intergranular corrosion resistance | Excellent | Moderate | Excellent |
| High-temperature performance | Up to 870°C | Up to 870°C | Up to 870°C |
| Chloride corrosion resistance | Moderate | Moderate | High |
| Weldability | Good | Excellent | Excellent |
| Cost | Moderate | Lower | Higher |
| Typical use | High-temp, welded | General use | Corrosive environments |
How to Choose the Right Stainless Steel Pipe/Tube
✅ Consider the environment — for high-temperature or welded environments, 321 stainless steel is a perfect choice.
✅ Assess corrosion exposure — for marine or high-chloride environments, 316 stainless steel may be better.
✅ Review mechanical needs — consider strength, yield, and creep resistance.
✅ Verify standards — check ASTM, EN, or JIS standards for your industry requirements.
✅ Balance cost vs. performance — 321 is cost-effective for heat resistance, while 316 is ideal for chlorides, and 304 is best for general use.
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