347 stainless steel is a columbium stabilized austenitic stainless steel grade with good general corrosion resistance and somewhat better resistance in strong oxidizing conditions than 321 (UNS S32100). It has excellent resistance to intergranular corrosion after exposure to temperatures in the chromium carbide precipitation range of 800 – 1500°F (427 – 816°C). The alloy has good oxidation resistance and creep strength to 1500°F (816°C). It also possesses good low-temperature toughness.
347H stainless steel is the higher carbon (0.04 – 0.10) version of the alloy. It was developed for enhanced creep resistance and higher strength at temperatures above 1000°F (537°C).
347/347H Stainless Steel Chemical Properties
| C | Cr | Mn | Ni | P | S | Si | Cb/Ta | |
|---|---|---|---|---|---|---|---|---|
| 347 | 0.08 Max | Min: 17.0 Max: 20.0 | 2.0 Max | Min: 9.0 Max: 13.0 | 0.04 Max | 0.30 Max | 0.75 Max | Min:10x C Max: 1.0 |
| 347H | Min: 0.04 Max: 0.10 | Min: 17.0 Max: 20.0 | 2.0 Max | Min: 9.0 Max: 13.0 | 0.03 Max | 0.30 Max | 0.75 Max | Min:10x C Max: 1.0 |
347/347H Stainless Steel Mechanical Properties
| Grade | Tensile Strength Ksi (MPa) Min | Yield Strength 0.2% Ksi Offset Ksi (MPa) Min | Elongation (% In 50mm) Min | Hardness (Brinell) MAX | Hardness (Rockwell B) MAX |
|---|---|---|---|---|---|
| 347/347H | 75 (515) | 30 (205) | 40 | 201 | 95 |
Physical Properties Of 347 / 347H Stainless Steel
Density
0.288 lbs/in3
7.96 g/cm3
Specific Heat
0.12 BTU/lb-°F (32 – 212°F)
500 J/kg-°K (0 – 100°C)
Modulus of Elasticity
28.0 x 106 psi
193 GPa
Thermal Conductivity 200°F (100°C)
133 BTU/hr/ft2/ft/°F
16.3 W/m-°K
Melting Range
2550 – 2635°F
1398 – 1446°C
Electrical Resistivity
72 Microhm-cm at 20°F
Corrosion Resistance
Alloy 347 stainless steel exhibits good general corrosion resistance that is comparable to 304. It was developed for use in the chromium carbide precipitation range of 800 – 1500°F (427 – 816°C) where un-stabilized alloys such as 304 are subject to intergranular attack.
The alloy can be used in nitric solutions, most diluted organic acids at moderate temperatures and pure phosphoric acid at lower temperatures and up to 10% diluted solutions at elevated temperatures. Alloy 347 stainless steel plate resists polythionic acid stress corrosion cracking in hydrocarbon service. It can also be utilized in chloride or fluoride-free caustic solutions at moderate temperatures.
Alloy 347/347H stainless steel does not perform well in chloride solutions, even in small concentrations, or in sulfuric acid.
Machinability
Machining grade 347H stainless steel is slightly tougher than that of grade 304 steel. However, the hardenability of this steel can be minimized by the use of constant positive feeds and slow speeds.
Welding
347/347H has excellent weldability and is suitable for the full range of conventional welding methods (like MMA, MIG, MAG, TIG, SAW, LBW, or RSW), except gas welding.
Grade 347H stainless steel can be welded using most of the resistance and fusion methods. Oxyacetylene welding is not preferred for this steel.
Hot Working
Forging, upsetting and other hot work processes can be performed at 1149 to 1232°C (2100 to 2250°F). The grade 347H steel has to be water-quenched and annealed to obtain maximum hardness.
Cold Working
347/347H can be readily formed and fabricated by the full range of cold-forming operations. It can be used in heading, drawing, and bending. Any cold working operations will increase the strength and hardness of the material and may leave it slightly magnetic. Work hardening is accentuated by the partial transformation of the austenite phase of the material to hard martensite.
Heat Treatment
Grade 347H stainless steel can be annealed at temperatures ranging from 1010 to 1193°C (1850 to 2000°F) and then quenched with water.
Hardening
Grade 347H stainless steel cannot be hardened by heat treatment. The hardness and strength of the steel can be increased through cold working.
Equivalent Grades Of 347 Stainless Steel
| EU EN | USA | Russia GOST |
|---|---|---|
| X6CrNiNb18-10 | 347 | 08KH18N12B |
ALLOY 347/347H (UNS S34700/S34709)
347, 347H, 1.4450 Stainless Steel Comparison
| Standard | Grade | C | Mn | Cr | Ni |
|---|---|---|---|---|---|
| ASTM A240 | 347 | ≤0.08 | ≤2.00 | 17.0-19.0 | 9.0-13.0 |
| ASTM A240 | 347H | 0.04-0.10 | ≤2.00 | 17.0-19.0 | 9.0-13.0 |
| EN 10028-7 | 1.4550 | ≤0.08 | ≤2.00 | 17.00-19.00 | 9.00-12.00 |
| EN 10088-2 | 1.4550 | ≤0.08 | ≤2.0 | 17.0-19.0 | 9.0-12.0 |
| EN 10088-3 | 1.4550 | ≤0.08 | ≤2.0 | 17.0-19.0 | 9.0-12.0 |
Related References
- ASTM A240/ASME SB240, Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications
- ASTM A480, Standard Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip
- EN 10088-2, Stainless steels. Technical delivery conditions for sheet/plate and strip of corrosion-resisting steels for general purposes
- EN 10088-3, Stainless steels. Technical delivery conditions for semi-finished products, bars, rods, wire, sections and bright products of corrosion-resisting steels for general purposes
- EN 10088-4, Stainless steels. Technical delivery conditions for sheet/plate and strip of corrosion-resisting steels for construction purposes
- EN 10088-5, Stainless steels. Technical delivery conditions for bars, rods, wire, sections and bright products of corrosion-resisting steels for construction purposes
- ASTM A249, Standard Specification for Welded Austenitic Steel Boiler, Superheater, Heat-Exchanger, and Condenser Tubes
- ASTM A213, Standard Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes
- ASTM A312, Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes
- ASTM A276, Standard Specification for Stainless Steel Bars and Shape