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| Property | Value |
|---|---|
| UNS Number | S34700 / S34709 |
| ASTM/ASME Standard | ASTM A193/A194, ASME SA193/SA194 |
| Tensile Strength | 620 MPa min |
| Yield Strength | 240 MPa min |
| Density | 8.03 g/cm³ |
| Max Service Temperature | 870°C (intermittent) |
| Element | Composition (%) |
|---|---|
| Cr | 17.0–19.0 |
| Ni | 9.0–13.0 |
| Nb+Ta | ≥10×C |
| Mn | ≤2.0 |
| C | ≤0.08 |
| Si | ≤0.75 |
| Fe | bal |
SS 347/347H fasteners derive their unique properties from a carefully balanced alloy composition featuring chromium (17-19%) and nickel (9-13%) as primary constituents, with niobium (columbium) stabilization being the defining characteristic of this grade. The niobium addition, typically 10 times the carbon content, prevents chromium carbide precipitation at grain boundaries during welding or elevated temperature exposure. This stabilization mechanism significantly enhances resistance to intergranular corrosion. The 347H variant maintains a controlled carbon range of 0.04-0.10% to optimize high-temperature strength properties.
These compositional advantages translate into exceptional engineering benefits for fastener applications, including superior resistance to intergranular attack in weld-affected zones, excellent oxidation resistance up to 870°C, and reliable mechanical strength across a broad temperature spectrum. The corrosion resistance profile makes these fasteners ideal for chemical processing, petrochemical, and power generation industries where sustained high-temperature exposure and corrosive environments are common. Their stable microstructure ensures long-term joint integrity, reduced maintenance requirements, and dependable performance in critical bolting applications subjected to thermal cycling and aggressive process conditions.
Specifications
SS 347 / 347H Fasteners are stainless steel fastening components defined by their mechanical properties, dimensional tolerances, and technical data for high-temperature service. Available in coordinated sizes and forms, they balance strength, corrosion resistance, and stability, with specifications governed by applicable material and dimensional standards.
| Property | Value |
|---|---|
| Tensile Strength | 620 MPa min |
| Yield Strength (0.2% Offset) | 240 MPa min |
| Elongation | 35% min |
| Reduction of Area | 50% min |
| Hardness | ≤ 96 HRB / 210 HB |
| Modulus of Elasticity | 200 GPa |
| Thermal Expansion (20-100°C) | 16.6 x10⁻⁶/°C |
| Thermal Conductivity | 16.3 W/m·K |
| Density | 8.03 g/cm³ |
| Melting Range | 1400-1425°C |
| Max Service Temperature | 870°C intermittent |
| Standard Type | Details |
|---|---|
| Bolt Standard | ASTM A193 Gr. B8C/B8CA |
| Stud Bolt Standard | ASTM A193, API 20B |
| Nut Standard | ASTM A194 Gr. 8C |
| Washer Standard | ASME B18.22.1, DIN 125 |
| Thread Form | UNC, UNF, Metric Coarse/Fine |
| Diameter Range | M6 to M100 / 1/4" to 4" |
| Length Range | 10mm to 500mm |
| Product Forms | Hex bolts, studs, nuts, washers, screws |
| Custom Sizes | Available on request |
| Manufacturing Standards | ASME B18.2.1, ISO 4014/4017 |
| Inspection Standards | NACE MR0175, EN 10204 3.1 |
Applications
