This article analyzes the core differences between 321 stainless steel and 316 stainless steel from the dimensions of chemical composition, corrosion resistance, high temperature stability, processing performance and industry application, providing a reference for material selection.
SS321 VS SS316 Stainless Steel: Chemical Composition
| Component | SS321 Stainless Steel | SS316 Stainless Steel |
|---|---|---|
| Chromium (Cr) | 18% | 16–18% |
| Nickel (Ni) | 9% | 10–14% |
| Titanium (Ti) | ≥5×Carbon content (e.g., 0.3–0.8%) | - |
| Molybdenum (Mo) | - | 2–3% |
| Carbon (C) | ≤0.08% | ≤0.08% (≤0.03% for SS316L) |
S321 vs SS316 Stainless Steel: Corrosion Resistance
Strengths: Titanium stabilization provides exceptional intergranular corrosion resistance during welding or high-temperature exposure (450–800°C), making it ideal for multi-pass welding applications.
Limitations: Weaker pitting resistance in chloride-rich environments (e.g., seawater, salt spray) compared to SS316.
Strengths: Molybdenum addition excels in acidic, alkaline, and chloride environments (e.g., marine engineering, chemical media), with a higher Pitting Resistance Equivalent Number (PREN ≥25) than SS321 (PREN ≈19).
Limitations: Prolonged exposure to high temperatures (>800°C) may cause embrittlement due to sigma (σ) phase precipitation.
SS321 vs SS316 Stainless Steel: High-Temperature Performance
Temperature Range: Continuous use up to 800–900°C, with short-term tolerance of 925°C.
Applications: Aircraft engine exhaust pipes, heat exchanger tube sheets, and high-temperature furnace components requiring repeated welding or thermal cycling.
Recommended Temperature: ≤800°C; molybdenum migration may reduce corrosion resistance at higher temperatures.
Alternatives: For extreme heat, consider 347 stainless steel (Nb-stabilized) or nickel-based alloys.
SS321 vs SS316 Stainless Steel: Machining & Welding Performance
Titanium minimizes chromium carbide (Cr₂₃C₆) precipitation in the heat-affected zone, eliminating the need for post-weld annealing and supporting multi-pass welding.
Requires controlled heat input to prevent hot cracking; recommended to use molybdenum-containing filler metal (e.g., ER316L) for compatibility.
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