Selecting the Right stainless steel Grade
Not all stainless steel is created equal. While SS 304 and 316 are the most common, high-temperature or highly corrosive environments often require specialized stabilized grades like 321 or 347. This guide helps you make the right metallurgical choice.
1. SS 304: The General Purpose Standard
The most common stainless steel grade, containing 18% Chromium and 8% Nickel. Excellent for general industrial use but susceptible to pitting in chloride (marine) environments.
2. SS 316: The Marine Grade
Added Molybdenum (2-3%) provides superior resistance to chlorides and acids. This is the baseline for marine, pharmaceutical, and chemical processing industries.
3. SS 321: The High-Temperature Choice
Stabilized with Titanium, SS 321 is designed to prevent intergranular corrosion when exposed to temperatures in the 425-815°C range. Ideal for exhaust systems and aircraft components.
4. SS 347: The Heavy-Duty Stabilized Grade
Stabilized with Columbium and Tantalum, SS 347 offers slightly better creep resistance than 321 at very high temperatures, often used in high-pressure steam environments.
| Property | SS 304 | SS 316 | SS 321 / 347 |
|---|---|---|---|
| Corrosion Resistance | Good | Excellent | Excellent (High Temp) |
| Max Temp (Continuous) | 800°C | 870°C | 900°C+ |
| Chloride Resistance | Poor | High | Moderate |
| Weldability | Excellent | Excellent | Superior (No Annealing) |
| Common Application | Food, Dairy | Marine, Pharma | Aerospace, Exhaust |
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