SUS316 Stainless Steel

SUS316 is a molybdenum-containing austenitic stainless steel (16-18% Cr, 10-14% Ni, 2-3% Mo), offering superior corrosion resistance than SUS304. Molybdenum enhances pitting resistance in chloride environments, making it the top choice for harsh conditions.

Chemical Composition (wt%): C ≤0.08, Si ≤1.00, Mn ≤2.00, P ≤0.045, S ≤0.030, Cr=16.00-18.00, Ni=10.00-14.00, Mo=2.00-3.00, Fe=Balance

Mechanical Properties: Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Hardness (HB) ≤217

Performance Advantages: Excellent chloride corrosion resistance; strong resistance to acids/bases; good high-temp oxidation resistance; non-magnetic and weldable.

Equivalent Grades: ASTM A240 316, EN 1.4401, UNS S31600

Applications: Marine equipment, coastal architecture, chemical processing, pharmaceutical machinery, seawater desalination systems, pulp and paper industry.

FAQ

1. Q: How does molybdenum improve SUS316's corrosion resistance? A: Molybdenum (2-3%) forms a dense molybdenum oxide layer on the surface, which is more stable than Cr oxide. In chloride environments (seawater, salt spray), it prevents pitting and crevice corrosion-issues that plague SUS304. Molybdenum also enhances resistance to sulfuric acid and organic acids, making SUS316 suitable for chemical tanks handling aggressive fluids. This molybdenum addition is the core advantage over SUS304.

2. Q: Is SUS316 completely immune to seawater corrosion? A: No, but it's far more resistant than SUS304. It can withstand long-term seawater immersion for 5-10 years without significant pitting. However, in high-velocity seawater (tidal zones) or with sediment buildup, crevice corrosion may occur. To enhance durability, use a polished surface (reduces sediment attachment) and regular maintenance. For extreme marine conditions (submarine parts), use super duplex stainless steel instead.

3. Q: Why is SUS316 used in the pharmaceutical industry? A: It meets GMP standards for two reasons. First, its excellent corrosion resistance prevents contamination from pharmaceutical chemicals (acids, alkalis). Second, its smooth surface is easy to sterilize (high-temperature steam, chemical disinfectants) without residue. Unlike SUS304, it resists corrosion from cleaning agents like peracetic acid, ensuring drug purity and production safety.

4. Q: What welding precautions apply to SUS316? A: Use ER316 filler metal to maintain Mo content. Control heat input (120-160A for MIG) to avoid overheating, which reduces corrosion resistance. For thick plates, preheat to 100-150°C to prevent cold cracking. Post-weld cleaning (pickling, passivation) removes oxide scale and restores the passive film. Avoid using SUS304 filler metal, as it lacks Mo and weakens the weld zone's corrosion resistance.

5. Q: How to choose between SUS304 and SUS316? A: Consider the environment. Choose SUS304 for dry, mild environments (kitchenware, indoor decoration) for cost savings. Choose SUS316 for chloride-rich (coastal, seawater), acidic (chemical plants), or high-humidity (pharmaceutical) environments. SUS316 is 30-50% more expensive than SUS304, so balance performance needs and budget-don't overspecify or underspecify.