347/347H Stainless Steel Plate – High-Performance Heat-Resistant Alloy
Sandmeyer Steel Company stocks Alloy 347 stainless steel plate in thicknesses from 3/16″ through 4″. A high carbon version, Alloy 347H (UNS S34709) stainless steel plate, can also be ordered in the same thickness range.
Available thicknesses for Alloy 347/347H:
| 3/16" | 1/4" | 5/16" | 3/8" | 1/2" | 5/8" | 3/4" | 7/8" | 1" | 1 1/8" |
| 4.8mm | 6.3mm | 7.9mm | 9.5mm | 12.7mm | 15.9mm | 19mm | 22.2mm | 25.4mm | 28.6mm |
| 1 1/4" | 1 1/2" | 1 3/4" | 2" | 2 1/4" | 2 1/2" | 2 3/4" | 3" | 3 1/2" | 4" |
| 31.8mm | 38.1mm | 44.5mm | 50.8mm | 57.2mm | 63.5mm | 69.9mm | 76.2mm | 88.9mm | 101.6mm |
Alloy 347 (S34700) is stabilized stainless steel plate which offers as its main advantage an excellent resistance to intergranular corrosion following exposure to temperatures in the chromium carbide precipitation range from 800 to 1500°F (427 to 816°C). Alloy 347 stainless steel plate is stabilized by the addition of columbium and tantalum.
Alloy 347 stainless steel plate is also advantageous for high temperature service because of its good mechanical properties. Alloy 347 stainless steel plate offers higher creep and stress rupture properties than Alloy 304 and, particularly, Alloy 304L, which might also be considered for exposures where sensitization and intergranular corrosion are concerns.
Specification Sheet Overview
for Alloy 347/347H (UNS S34700, S34709):
General Properties
Alloy 347 (UNS S34700) is columbium stabilized austenitic stainless steel plate 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.
Alloy 347H (UNS S3409) stainless steel plate is the higher carbon (0.04 – 0.10) version of the alloy. It was developed for enhanced creep resistance and for higher strength at temperatures above 1000°F (537°C). In most instances, the carbon content of the plate enables dual certification.
Alloy 347 stainless steel plate cannot be hardened by heat treatment, only by cold working. It can be easily welded and processed by standard shop fabrication practices.
Applications
- Chemical Processing
- Food Processing – equipment and storage
- Petroleum Refining – fluid catalytic cracking units, polythionic acid service
- Pharmaceutical Production
- Waste Heat Recovery – recuperators
Corrosion Resistance
Alloy 347 stainless steel plate 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. In this temperature range, the overall corrosion resistance of Alloy 347 stainless steel plate is superior to Alloy 321 stainless steel plate. Alloy 347 also performs somewhat better than Alloy 321 in strongly oxidizing environments up to 1500°F (816°C).
The alloy can be used in nitric solutions, most diluted organic acids at moderate temperatures and in 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 stainless steel plate does not perform well in chloride solutions, even in small concentrations, or in sulfuric acid.
Chemical Analysis
Weight % (all values are maximum unless a range is otherwise indicated)
| Element | 347 | 347H |
|---|---|---|
| Chromium | 17.00 min.-19.00 max. | 17.00 min.-19.00 max. |
| Nickel | 9.00 min.-13.00 max. | 9.00 min.-13.00 max. |
| Carbon | 0.08 | 0.04 min.-0.10 max. |
| Manganese | 2.00 | 2.00 |
| Phosphorus | 0.045 | 0.045 |
| Sulfur | 0.03 | 0.03 |
| Silicon | 0.75 | 0.75 |
| Columbium & Tantalum | 10 x (C + N) min.-1.00 max. | 8 x (C + N) min.-1.00 max. |
| Iron | Balance | Balance |
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
Mean Coefficient of Thermal Expansion
| °F | °C | in/in °F | cm/cm °C |
| 68-212 | 20-100 | 9.2 x 10-6 | 16.0 x 10-6 |
| 68-1112 | 20-600 | 10.5 x 10-6 | 18.9 x 10-6 |
| 68-1832 | 20-1000 | 11.4 x 10-6 | 20.5 x 10-6 |
Mechanical Properties
Typical Values at 68°F (20°C)
0.2% Offset | Strength | in 2 in. | |||
|---|---|---|---|---|---|
| psi (min.) | (MPa) | psi (min.) | (MPa) | % (min.) | (max.) |
| 30,000 | 205 | 75,000 | 515 | 40 | 201 Brinell |
Fabrication Data
Alloy 347 stainless steel plate can be easily welded and processed by standard shop fabrication practices.
Cold Forming
The alloy is quite ductile and forms easily.
Hot Forming
The high sulfur content of Alloy 303 also has a detrimental impact on hot workability. If hot forming is required, once again, 304 should be considered as an alternate selection.
Machining
The cold work hardening rate of 347 stainless steel plate makes it less machinable than 410 stainless steel, but similar to 304. The table below provides relevant machining data.
| Operation | Tool | Lubrication | ||||||
|---|---|---|---|---|---|---|---|---|
| Depth-mm | Depth-in | Feed-mm/t | Feed-in/t | Speed-m/min | Speed-ft/min | |||
| Turning | High Speed Steel | Cutting Oil | 6 | .23 | 0.5 | .019 | 12-16 | 39-52 |
| Turning | High Speed Steel | Cutting Oil | 3 | .11 | 0.4 | .016 | 18-23 | 59-75 |
| Turning | High Speed Steel | Cutting Oil | 1 | .04 | 0.2 | .008 | 23-28 | 75-92 |
| Turning | Carbide | Dry or Cutting Oil | 6 | .23 | 0.5 | .019 | 67-76 | 220-249 |
| Turning | Carbide | Dry or Cutting Oil | 3 | .11 | 0.4 | .016 | 81-90 | 266-295 |
| Turning | Carbide | Dry or Cutting Oil | 1 | .04 | 0.2 | .008 | 99-108 | 325-354 |
| Depth of cut-mm | Depth of cut-in | Feed-mm/t | Feed-in/t | Speed-m/min | Speed-ft/min | |||
| Cutting | High Speed Steel | Cutting Oil | 1.5 | .06 | 0.03-0.05 | .0012-.0020 | 16-21 | 52-69 |
| Cutting | High Speed Steel | Cutting Oil | 3 | .11 | 0.04-0.06 | .0016-.0024 | 17-22 | 56-72 |
| Cutting | High Speed Steel | Cutting Oil | 6 | .23 | 0.05-0.07 | .0020-.0027 | 18-23 | 59-75 |
| Drill ø mm | Drill ø in | Feed-mm/t | Feed-in/t | Speed-m/min | Speed-ft/min | |||
| Drilling | High Speed Steel | Cutting Oil | 1.5 | .06 | 0.02-0.03 | .0007-.0012 | 9-13 | 29-42 |
| Drilling | High Speed Steel | Cutting Oil | 3 | .11 | 0.05-0.06 | .0020-.0024 | 11-15 | 36-49 |
| Drilling | High Speed Steel | Cutting Oil | 6 | .23 | 0.08-0.09 | .0031-.0035 | 11-15 | 36-49 |
| Drilling | High Speed Steel | Cutting Oil | 12 | .48 | 0.09-0.10 | .0035-.0039 | 11-15 | 36-49 |
| Feed-mm/t | Feed-in/t | Speed-m/min | Speed-ft/min | |||||
| Milling Profiling | High Speed Steel | Cutting Oil | 0.05-0.10 | .002-.004 | 11-21 | 36-69 | ||
Welding
Alloy 347 stainless steel plate can be readily welded by most standard processes. A post weld heat treatment is not necessary.
Alloy 347/347H Stainless Steel – Frequently Asked Questions
1. What is Alloy 347/347H stainless steel?
Alloy 347 (UNS S34709) is a columbium-stabilized austenitic stainless steel designed for superior resistance to intergranular corrosion after exposure to elevated temperatures in the chromium carbide precipitation range (800–1500°F / 427–816°C). Alloy 347H is the higher carbon version (0.04–0.10%) that offers improved creep strength above 1000°F (537°C).
2. What are typical applications for Alloy 347/347H?
Alloy 347/347H is commonly used in high-temperature and chemically aggressive environments, such as:
• Chemical processing
• Petroleum refining
• Pharmaceutical production
• Waste heat recovery systems
• Food processing and storage equipment
3. How does Alloy 347/347H perform in corrosive environments?
It provides good general corrosion resistance and excellent intergranular corrosion resistance after exposure to elevated temperatures. It performs well in nitric acid, diluted organic acids, phosphoric acid (cold and up to 10% at high temps), and polythionic acid environments. It is not suitable for chloride-rich or sulfuric acid service.
4. Can Alloy 347/347H be welded?
Yes. It can be readily welded using most standard methods without the need for post-weld heat treatment. For optimal corrosion resistance, cleaning of the weld area and the use of matching filler material are recommended.
5. What are the mechanical properties of Alloy 347/347H stainless steel?
Typical values at 68°F (20°C):
• Yield Strength (0.2% offset): 30,000 psi (205 MPa)
• Ultimate Tensile Strength: 75,000 psi (515 MPa)
• Elongation in 2″: 40% (minimum)
• Hardness: 201 Brinell (maximum)
6. What are the physical properties of Alloy 347/347H?
• 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 × 10⁶ psi (193 GPa)
• Thermal Conductivity at 200°F: 13.3 BTU/hr/ft²/ft/°F (16.3 W/m-K)
• Electrical Resistivity: 72 Microhm-cm at 20°F
7. Is Alloy 347/347H magnetic?
No. It is non-magnetic in the annealed condition but may become slightly magnetic after cold working.
8. What standards apply to Alloy 347/347H stainless steel?
• ASTM A240
• ASME SA240
• AMS 5512
9. What thicknesses does Sandmeyer Steel stock for Alloy 347/347H plate?
Sandmeyer Steel stocks Alloy 347/347H stainless steel plate in thicknesses from 3/16″ (4.8 mm) through 4″ (101.6 mm).