JIS SUS347 Stainless Steel
SUS347 Stainless Steel: High-Temperature Austenitic Nb-Stabilized Plate & Coil per JIS G4304/G4305
SUS347 is a niobium-stabilized austenitic stainless steel for plates and coils under JIS G4304 and G4305, offering excellent intergranular corrosion resistance and high-temperature strength.
Hot rolling, cold rolling, solution annealing, pickling, descaling, bright annealing, forming, welding, machining
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JIS SUS347 Stainless Steel Introduction
SUS347 is a niobium-stabilized austenitic stainless steel supplied as hot-rolled or cold-rolled plate, sheet, and coil according to JIS G4304 and JIS G4305. The addition of niobium (columbium) strongly suppresses the precipitation of chromium carbides, thereby preventing intergranular corrosion sensitization during welding or long-term exposure at temperatures between 425°C and 850°C. This stabilization allows SUS347 to maintain excellent mechanical properties and corrosion resistance in aggressive environments, including many organic and inorganic chemicals. The grade exhibits good creep strength and oxidation resistance at elevated temperatures, making it suitable for continuous service up to approximately 800°C. Typical delivery condition is solution annealed and descaled, providing an austenitic microstructure with good ductility and toughness. SUS347 is widely used in chemical processing equipment, heat exchangers, boiler components, high-temperature structural parts, and nuclear reactor vessels where resistance to intergranular attack and sustained high-temperature performance are critical.
JIS SUS347 Stainless Steel Chemical Composition
The composition conforms to JIS G4304 Table 2 for austenitic grade SUS347. Niobium is added to meet the stabilization requirement Nb ≥ 10 × C% and ≤ 1.00%, ensuring full carbon stabilization against intergranular chromium carbide precipitation.
| Element | Value (mass %) | Remarks |
|---|---|---|
| C | ≤0.08 | |
| Si | ≤1.00 | |
| Mn | ≤2.00 | |
| P | ≤0.045 | |
| S | ≤0.030 | |
| Cr | 17.00 – 19.00 | |
| Ni | 9.00 – 13.00 | |
| Nb | ≥10×C% to ≤1.00 | or Nb+Ta |
JIS SUS347 Stainless Steel Thermal & Electrical Physical Properties
Physical properties are typical for SUS347 in solution-annealed condition. Values are derived from published data for 18Cr-10Ni-Nb type stainless steels and are suitable for engineering calculations. Thermal expansion, thermal conductivity, and electrical resistivity change with temperature; thus multiple lines are provided for key ranges.
| Property | Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7.9 | g/cm³ | 20°C |
| Modulus of Elasticity (E) | 200 | GPa | 20°C, static |
| Shear Modulus (G) | 77 | GPa | 20°C, calculated from E and ν |
| Poisson's Ratio (ν) | 0.30 | – | 20°C |
| Thermal Expansion Coefficient (α) | 16.5 | 10⁻⁶/K | 20–100°C |
| Thermal Expansion Coefficient (α) | 17.0 | 10⁻⁶/K | 20–200°C |
| Thermal Expansion Coefficient (α) | 17.5 | 10⁻⁶/K | 20–300°C |
| Thermal Expansion Coefficient (α) | 18.0 | 10⁻⁶/K | 20–400°C |
| Thermal Expansion Coefficient (α) | 18.5 | 10⁻⁶/K | 20–500°C |
| Thermal Conductivity (λ) | 15 | W/(m·K) | 20°C |
| Thermal Conductivity (λ) | 16 | W/(m·K) | 100°C |
| Thermal Conductivity (λ) | 21 | W/(m·K) | 500°C |
| Specific Heat Capacity (c) | 500 | J/(kg·K) | 20°C |
| Electrical Resistivity (ρ_e) | 0.73 | Ω·mm²/m | 20°C |
JIS SUS347 Stainless Steel Mechanical Properties
Minimum mechanical properties as specified in JIS G4304 Table 4 for hot-rolled plates (applicable also to G4305 cold-rolled products after proper annealing). Property values vary with product thickness; where multiple requirements exist, they are listed as separate rows. Bend testing is applicable for products with thickness ≤25 mm.
| Property | Required Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Yield Strength (0.2% offset, ReH) | ≥205 | MPa | Room temperature, solution annealed |
| Tensile Strength (Rm) | ≥520 | MPa | Room temperature, solution annealed |
| Elongation (A) | ≥40 | % | Thickness t ≤ 8 mm |
| Elongation (A) | ≥35 | % | 8 < t ≤ 25 mm |
| Elongation (A) | ≥30 | % | 25 < t ≤ 50 mm |
| Brinell Hardness | ≤187 | HBW | Solution annealed, typical conversion |
| Rockwell Hardness | ≤90 | HRB | Solution annealed, typical conversion |
| Vickers Hardness | ≤200 | HV | Solution annealed, typical conversion |
| Bend Test (180°) | Inner radius = 0.5 × t | – | Applicable for t ≤ 25 mm, no cracks allow |
JIS SUS347 Stainless Steel Fully Equivalent International Grades & Substitution Recommendations
| Country/Region | Standard | Designation | Remarks |
|---|---|---|---|
| Japan | JIS G4304 / G4305 | SUS347 | Original specification |
| USA | ASTM A240 / A480 | UNS S34700 | Fully equivalent Nb-stabilized grade |
| European Union | EN 10088-2 | X6CrNiNb18-10 (1.4550) | Same chemistry and stabilization principle |
| China | GB/T 4237 / GB/T 3280 | 06Cr18Ni11Nb (S34779) | Matched chemical composition and mechanical requirements |
| International | ISO 15510 | X6CrNiNb18-10 | General equivalent for flat products |
JIS SUS347 Stainless Steel Application Introduction
SUS347 is selected for equipment that must resist intergranular corrosion after welding or prolonged exposure to oxidizing environments at high temperatures. It is also favored where good creep and rupture strength are required up to approximately 800°C. The niobium stabilization minimizes the need for post-weld heat treatment in many fabrications. Industries: chemical processing, power generation, aerospace, oil & gas, food and beverage. Products: pressure vessels, heat exchangers, boiler shells, superheater tubes, reactor components, exhaust manifolds. Components: welded shells, tube sheets, expansion joints, high-temperature fasteners, furnace parts.
Product Applications: Welded pressure vessels and reactors, Shell-and-tube heat exchangers, Superheater and reheater tubing, Boiler drums and headers, High-temperature piping systems, Nuclear reactor vessel internals, Exhaust manifolds and catalytic converter shells, Fabricated plate and coil components for furnace applications
Processed into products: Tube sheets and baffle plates in heat exchangers, Expansion joints and bellows, Welded nozzles and flanges for high-temperature service, High-temperature bolts, studs, and nuts, Burner components and combustion chambers, Furnace trays, baskets, and radiant tubes, Food processing conveyors and mixing vessels
Application industries: Chemical and petrochemical processing, Oil and gas upstream and downstream equipment, Power generation (conventional and nuclear), Aerospace engine components, Food and beverage processing equipment, Heat exchanger and boiler manufacturing, Automotive exhaust systems (high-temperature sections)
JIS SUS347 Stainless Steel Near-Equivalent & Alternative Stainless Steel Grades
| Country/Region | Standard | Designation | Remarks/Analysis |
|---|---|---|---|
| Japan | JIS G4304 / G4305 | SUS304 | Unstabilized 18Cr-8Ni; lower intergranular corrosion resistance in as-welded condition but readily available for non-welded applications |
| Japan | JIS G4304 / G4305 | SUS321 | Titanium-stabilized 18Cr-9Ni-Ti; similar stabilization principle, comparable high-temperature strength, but Ti-stabilized vs Nb-stabilized |
| Japan | JIS G4304 / G4305 | SUS347H | High-carbon variant of SUS347 with improved high-temperature creep strength; C content 0.04–0.10%; suitable for above 550°C but may have lower weldability |
| USA | ASTM A240 | S30400 (304) | Common 18-8 austenitic stainless; susceptible to sensitization; often replaced by 347 when welding or long-term high-temperature exposure is required |
| USA | ASTM A240 | S32100 (321) | Ti-stabilized equivalent to 347; mechanical properties are similar; selection between 321 and 347 often based on specific service conditions and cost |
Notes:
Heat treatment: Solution annealing at 1010–1120°C followed by rapid cooling (water or air). Stabilization anneal is not normally required because the Nb addition is sufficient; however, if required for severe service, 870–900°C may be applied. Welding: Welds can be made with all common processes (SMAW, GTAW, GMAW, SAW) using filler metals such as AWS ER347 or E347. No post-weld heat treatment is necessary for many corrosion-resistant applications, but stress relief at 870–900°C may be used for dimensional stability. Machining: SUS347 has higher work hardening and lower thermal conductivity than alloy steels; use rigid machines, sharp tools, and adequate coolant. Availability: Standard forms include hot-rolled plate (JIS G4304) and cold-rolled sheet/coil (JIS G4305) with surface finishes like No.1, 2B, and BA. Restrictions: Maximum continuous service temperature is approximately 800°C in oxidizing atmosphere; prolonged exposure above this temperature may lead to sigma-phase embrittlement. Reduce sulfur attack risk by maintaining low oxygen content in sulfidizing environments.
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