SS 347 and SS304 are both austenitic stainless steels, but they serve different roles in engineering and industrial applications. The main difference lies in the presence of niobium in SS 347, which makes it more suitable for high-temperature and welded applications where resistance to intergranular corrosion is essential.
| Feature | SS 304 | SS 347 |
|---|---|---|
| UNS Number | S30400 | S34700 |
| Stabilizing Element | None | Niobium (Nb) |
| Intergranular Corrosion Resistance | Moderate (needs post-weld treatment) | Excellent (no heat treatment needed) |
| High-Temperature Resistance | Up to 870°C (short term) | Excellent for continuous use up to 900°C |
| Weldability | Excellent, but prone to carbide precipitation | Excellent, stabilized against weld decay |
| Cost | Lower | Slightly higher due to Nb addition |
| Element | SS 304 (%) | SS 347 (%) |
|---|---|---|
| Chromium (Cr) | 18.0 – 20.0 | 17.0 – 19.0 |
| Nickel (Ni) | 8.0 – 10.5 | 9.0 – 13.0 |
| Carbon (C) | ≤ 0.08 | ≤ 0.08 |
| Niobium (Nb) | - | ≥ 10 × C (typically 0.3 – 1.0%) |
| Manganese (Mn) | ≤ 2.0 | ≤ 2.0 |
| Property | SS 304 | SS 347 |
|---|---|---|
| Tensile Strength (MPa) | ≥ 515 | ≥ 515 |
| Yield Strength 0.2% (MPa) | ≥ 205 | ≥ 205 |
| Elongation (% in 50 mm) | ≥ 40 | ≥ 40 |
| Hardness (Brinell, max HB) | ≤ 201 | ≤ 201 |
| Modulus of Elasticity (GPa) | ~193 | ~193 |
| Property | SS 304 | SS 347 |
|---|---|---|
| Density (g/cm³) | 7.93 | 7.93 |
| Thermal Conductivity at 100°C (W/m·K) | ~16.2 | ~14.6 |
| Specific Heat Capacity (J/kg·K) | ~500 | ~500 |
| Electrical Resistivity (μΩ·cm) | ~72 | ~78 |
| Thermal Expansion Coefficient (µm/m·K, 20–100°C) | ~17.2 | ~16.0 |
| Melting Range (°C) | 1400–1450 | 1398–1446 |
| Magnetic Permeability (annealed) | Non-magnetic | Non-magnetic |
Due to the niobium (Nb) stabilization treatment, SS347 can inhibit the precipitation of grain boundary carbides at 870℃, maintain creep resistance and intergranular corrosion resistance, and can still maintain 70% of the room temperature yield strength at 593℃.
while SS304 is prone to precipitate chromium carbides above 425℃, resulting in weakening of grain boundaries, and the maximum operating temperature is 650℃, and the yield strength retention rate at the same temperature is only 50%. Therefore, 347 is more suitable for high-temperature scenes such as furnace components and heat exchangers, while 304 is limited to medium-temperature environments such as food processing.
We supply SS 304 and SS 347 stainless steel sheets, pipes, tubes, and fittings in accordance with ASTM, ASME, and EN standards. Contact our technical team for:Material test certificates (MTCs),Custom sizing or cutting,Advice on high-temperature material selection!
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