SUS312L Austenitic Stainless Steel
SUS312L Austenitic Stainless Steel: Superior Corrosion Resistance for Chemical & Marine Equipment
Explore SUS312L stainless steel under JIS G4304/G4305: chemical composition, mechanical properties, thermal conductivity, and equivalent grades for demanding industrial applications.
Hot rolling, cold rolling, solution annealing, pickling, cutting, forming, welding
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SUS312L Austenitic Stainless Steel Introduction
SUS312L is a low-carbon austenitic stainless steel standardized under JIS G4304 (hot-rolled) and JIS G4305 (cold-rolled). It features a carefully balanced alloy content with chromium, nickel, molybdenum, and copper, providing excellent resistance to sulfuric acid and other reducing environments. This grade exhibits good weldability and formability, making it suitable for chemical processing, pollution control, and marine engineering. Its low carbon content minimizes intergranular corrosion after welding.Key characteristics:
- Excellent resistance to sulfuric acid and chloride stress corrosion cracking
- Good strength and ductility in the solution-annealed condition
- Weldable without post-weld annealing for most applications
- Available as plates, sheets, and coils
SUS312L Austenitic Stainless Steel Chemical Composition
The alloying elements of SUS312L are tailored for corrosion resistance in reducing acids. Copper and molybdenum synergistically enhance resistance to sulfuric acid. The low carbon content prevents chromium carbide precipitation during welding.
| Element | Standard Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | ≤0.030 | Low carbon ensures weldability |
| Silicon (Si) | ≤1.00 | |
| Manganese (Mn) | ≤2.00 | |
| Phosphorus (P) | ≤0.045 | |
| Sulfur (S) | ≤0.030 | |
| Chromium (Cr) | 19.00 – 21.00 | Key for passivity |
| Nickel (Ni) | 5.50 – 7.50 | Austenite stabilizer |
| Molybdenum (Mo) | 1.50 – 2.50 | Pitting and acid resistance |
| Copper (Cu) | 1.00 – 2.00 | Sulfuric acid resistance |
| Nitrogen (N) | ≤0.05 | Not always specified; residual |
SUS312L Austenitic Stainless Steel Thermal and Electrical Physical Properties
Values are typical for SUS312L in annealed condition at room temperature unless noted. Density, modulus, and thermal expansion are close to standard austenitic stainless steels, with slight variations due to alloying.
| Property | Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 8.0 | g/cm³ | At 20°C |
| Elastic Modulus (E) | 193 | GPa | Tension, room temperature |
| Shear Modulus (G) | 74 | GPa | Calculated from E and typical ν |
| Poisson's Ratio (ν) | 0.30 | – | At room temperature |
| Thermal Expansion Coefficient (α) | 16.5 | 10⁻⁶/K | 20 – 100°C range |
| Thermal Expansion Coefficient (α) | 17.5 | 10⁻⁶/K | 20 – 200°C range |
| Thermal Expansion Coefficient (α) | 18.5 | 10⁻⁶/K | 20 – 300°C range |
| Thermal Conductivity (λ) | 15.0 | W/(m·K) | At 100°C |
| Thermal Conductivity (λ) | 16.3 | W/(m·K) | At 300°C |
| Specific Heat Capacity | 500 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρ_e) | 0.85 | μΩ·m | At 20°C |
SUS312L Austenitic Stainless Steel Mechanical Properties
These properties apply to solution-annealed condition as per JIS G4304/G4305. Tensile test data is for plates/sheets up to 8 mm thickness. Impact values are not mandatory but often reported at room temperature.
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥205 | MPa | Room temperature, 0.2% offset |
| Tensile Strength (Rm) | ≥520 | MPa | Room temperature |
| Elongation (A) | ≥40 | % | Gauge length 50 mm, thickness ≤8 mm |
| Hardness (HBW) | ≤187 | HBW | Brinell, typical maximum |
| Hardness (HRB) | ≤90 | HRB | Rockwell B, typical maximum |
| Bending test | No cracks at 180° bend | – | Bend diameter = thickness, for sheets/plates |
SUS312L Austenitic Stainless Steel Direct Equivalent Grades and Substitutes
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A240 | UNS S31200 | Closest UNS number; mechanical and chemical similarity, but check exact limits |
| International | ISO 15510 | X2CrNiMoCu20-6-1 | Approximate match, may have slight differences in Mn and Ni ranges |
| Europe | EN 10088-2 | 1.4335 | Designation X2CrNi20-6-2Cu; very close but verify Mo and Cu limits |
SUS312L Austenitic Stainless Steel Application Introduction
SUS312L is engineered for environments where sulfuric acid and other reducing media are present. Its unique copper-molybdenum combination provides resistance to both uniform and localized corrosion. It is not intended for high-temperature structural service, but excels in wet corrosive conditions up to about 400°C.Typical uses:
Product Applications: Sulfuric acid storage tanks and piping, Heat exchangers for chemical plants, Scrubbers and absorption towers, Pickling equipment, Condenser tubes, Offshore platform components exposed to sour gas
Processed into products: Tank shells and bottoms, Heat exchanger plates and tubes, Pump casings and impellers, Valve bodies, Fittings and flanges, Welded pipes and fabricated vessels
Application industries: Chemical processing, Oil & gas (downstream, refining), Pollution control (flue gas desulfurization), Marine engineering, Fertilizer production, Pulp and paper
SUS312L Austenitic Stainless Steel Similar / Alternative Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G4304 | SUS316L | Common austenitic with 2-3% Mo but no Cu; lower sulfuric acid resistance |
| Japan | JIS G4304 | SUS317L | Higher Mo (3-4%), better pitting resistance but less optimized for reducing acids |
| USA | ASTM A240 | 316L (UNS S31603) | Widely used, lacks copper; may corrode faster in warm dilute sulfuric acid |
| USA/Europe | ASTM/EN | 904L (UNS N08904 / 1.4539) | Higher Ni, Mo, Cu; superior corrosion resistance but more expensive |
| Europe | EN 10088 | 1.4539 (X1NiCrMoCu25-20-5) | Super austenitic with excellent acid resistance, a step-up from SUS312L |
Notes:
Weldability: SUS312L can be welded by all common processes (TIG, MIG, SMAW) using matching filler metals (e.g., AWS ER312). Post-weld heat treatment is usually not required, but a full solution anneal can restore maximum corrosion resistance. Surface condition: pickled or bright annealed surfaces offer best corrosion performance. Service temperature range: from cryogenic to approximately 400°C for corrosion applications; mechanical properties at elevated temperatures decline above 400°C. Fabrication practices such as forming and machining are similar to 304L/316L, but work-hardening rate is slightly higher due to copper content.
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