JIS SUS316 Stainless Steel: Molybdenum-Enhanced Austenitic Grade for Corrosive Environments
JIS SUS316 stainless steel (equivalent to ASTM 316/UNS S31600) is a high-performance austenitic grade distinguished by its 2-3% molybdenum addition, which significantly enhances corrosion resistance in chloride-rich and acidic environments. With a balanced composition of 16-18% chromium and 10-14% nickel, SUS316 excels in marine, chemical processing, and pharmaceutical applications where standard 304 grades would fail. This technical guide covers its metallurgical properties, production methods, industrial applications, and comparative advantages over similar alloys.
1. Chemical Composition (JIS G4304/G4305 Standard)
| Element | Content Range | Function |
|---|---|---|
| Carbon (C) | ≤ 0.08% | Minimized to prevent intergranular corrosion; improves weldability |
| Chromium (Cr) | 16.00 – 18.00% | Forms passive Cr₂O₃ oxide layer; provides baseline corrosion resistance |
| Nickel (Ni) | 10.00 – 14.00% | Stabilizes austenitic microstructure; enhances ductility and cryogenic toughness |
| Molybdenum (Mo) | 2.00 – 3.00% | Critical for pitting/crevice corrosion resistance in chloride environments |
| Manganese (Mn) | ≤ 2.00% | Improves hot workability; partial nickel substitute for cost control |
| Silicon (Si) | ≤ 1.00% | Enhances oxidation resistance; aids in deoxidation during melting |
| Phosphorus (P) | ≤ 0.045% | Residual impurity; controlled to maintain mechanical properties |
| Sulfur (S) | ≤ 0.030% | Minimized to prevent hot cracking during fabrication |
| Nitrogen (N) | ≤ 0.10% | Optional addition to stabilize austenite and improve strength |
2. Mechanical Properties at Room Temperature
- Tensile Strength (σb): ≥ 520 MPa (JIS G4304 minimum requirement)
- Yield Strength (σ0.2): ≥ 205 MPa (0.2% proof stress for structural integrity)
- Elongation (δ): ≥ 40% (superior formability for deep drawing and complex shapes)
- Hardness (HB): ≤ 217 (Brinell scale; suitable for machining and polishing)
- Impact Toughness (CVN): ≥ 31 J at -196°C (retains ductility in cryogenic applications)
- Density: 8.00 g/cm³ (standard for austenitic stainless steels)
3. Manufacturing Process Overview
- Melting: Electric arc furnace (EAF) followed by argon oxygen decarburization (AOD) to achieve ultra-low carbon content and precise alloy composition. Vacuum degassing optional for critical applications.
- Hot Rolling: Conducted at 1150-1260°C with controlled cooling to prevent sensitization. Water quenching maintains full austenitic structure.
- Cold Rolling: For thin gauges (≤ 6mm), multi-stage cold reduction with intermediate annealing at 1050-1120°C to achieve desired temper (1/4H, 1/2H, or full hard).
- Heat Treatment: Solution annealing at 1010-1150°C followed by rapid water quenching to dissolve intermetallic phases and restore corrosion resistance.
- Surface Finishing: Pickling in nitric-hydrofluoric acid bath to remove scale; optional electropolishing for medical/pharmaceutical grades. Common finishes: 2B (matte), BA (bright annealed), No.4 (brushed).
- Quality Control: 100% eddy current testing for surface defects; ultrasonic testing for thick plates (> 10mm). PMI testing verifies alloy composition.
4. Primary Industrial Applications
Marine & Coastal Engineering
Shipbuilding components, offshore platform handrails, desalination plant piping, and seawater cooling systems — resistant to saltwater corrosion and biofouling.
Chemical Processing
Reactors, storage tanks, and piping for sulfuric acid, phosphoric acid, and chloride-containing chemicals. Compliant with ASME BPE standards for pharmaceutical bioreactors.
Medical & Pharmaceutical
Surgical instruments, implants, and sterile processing equipment. Electropolished SUS316L variants meet ISO 5832-1 and ASTM F138 standards for biocompatibility.
Food & Beverage Processing
High-salt food production (soy sauce, pickles), brewery fermentation tanks, and dairy processing equipment — FDA/EC 1935/2004 compliant for direct food contact.
Architectural & Structural
Coastal building facades, bridge cables, and urban infrastructure in high-pollution areas. Superior resistance to atmospheric corrosion compared to SUS304.
Oil & Gas
Subsea pipelines, valve trim, and refinery equipment for H₂S-containing environments. NACE MR0175/ISO 15156 certified for sour service applications.
5. Comparison with Related Grades (SUS316 vs SUS316L vs SUS316Ti)
| Grade | Carbon Content | Key Features | Typical Applications |
|---|---|---|---|
| SUS316 | ≤ 0.08% | Standard molybdenum-bearing grade; balanced properties | General corrosive environments (non-welded or lightly welded) |
| SUS316L | ≤ 0.03% | Low-carbon variant; superior weldability and intergranular corrosion resistance | Heavy-welded structures (tanks, pipelines) in chemical/pharma industries |
| SUS316Ti | ≤ 0.08% + Ti | Titanium-stabilized; prevents chromium carbide precipitation during welding | High-temperature applications (400-800°C) where sensitization is a risk |
| SUS316H | 0.04-0.10% | High-carbon variant; enhanced creep resistance at elevated temperatures | Pressure vessels, heat exchangers operating above 500°C |
6. Selection Guidelines & Technical Considerations
- Chloride Resistance: While superior to SUS304, SUS316 is limited to < 1000ppm chloride concentrations for long-term exposure. For higher concentrations (e.g., seawater evaporation), consider SUS317L or duplex 2205.
- Welding Procedures: Use ER316L filler metal for autogenous welding; maintain interpass temperature below 150°C to avoid sensitization. Post-weld annealing recommended for critical applications.
- Surface Finish Selection:
- 2B: Standard mill finish for industrial applications
- BA: Bright annealed for decorative/pharmaceutical uses
- No.4: Brushed finish for architectural and food contact surfaces
- Electropolished: Mandatory for medical implants and ultra-clean environments
- Temperature Limits:
- Continuous Service: Up to 870°C in air (scaling resistance)
- Intermittent Service: Up to 925°C (avoid thermal cycling)
- Cryogenic: Retains ductility down to -269°C (liquid helium temperatures)
- Certification Requirements: Request EN 10204 3.1/3.2 mill test certificates for critical applications. PED 2014/68/EU compliance may be required for pressure equipment in Europe.
7. Request a SUS316 Stainless Steel Quote
For customized JIS SUS316/SUS316L stainless steel products — including sheets, coils, pipes, bars, and precision strips — contact our technical sales team. We provide full material traceability, third-party inspection reports, and competitive pricing for bulk orders. Special finishes (electropolished, PVD coated) and non-standard dimensions available upon request.
“`