Alloy 347 (1.4550) is a stabilized stainless steel which offers as its main advantage an excellent resistance to intergranular corrosion following exposure to temperature in the chromium carbide precipitation range from 800 to 1500°F (427 to 816°C). Alloy 347 is austenitic chromium steel containing columbium stabilized by the addition of columbium and tantalum.
Alloy 347 stainless steel pipe is also advantageous for high temperature service because of its good mechanical properties. Alloy 347 stainless steel tubing 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.
347 stainless steel has a high resistance to prolonged heat and corrosion making it well suited for engine, power generation, welded fabrications and other high heat applications. 347 stainless steel offers good mechanical properties with higher creep and stress rupture characteristics than other grades, such as 304. 347 stainless steel is also advantageous in applications that require omission of the annealing process after welding.
Similar to 321 stainless, 347 uses columbium as a stabilizing element to maximize its principal feature: resistance to intergranular corrosion. It can be used in applications requiring repeated heating in the range of 800 and 1650 F (427-899 C).
General Properties
Chemical Composition
Resistance to Corrosion
Physical Properties
Mechanical Properties
Elevated Temperature Oxidation Resistance
Heat Treatment
Fabrication
Physical Properties of 347/347H Alloys in the Annealed Condition at -20°F to +100°F
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Tensile Strength |
Yield Strength |
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| Alloy |
UNS
Design |
Spec |
psi |
MPa |
ksi |
psi |
MPa |
ksi |
Elongation in 2 inches (min.) % |
Grain Size Req. |
Maximum Harndess |
Modulus of Elasticity
(x106 psi) |
Mean Coefficient of Thermal Expansion (IN./IN./°F x 10-6) |
Thermal Conductivity (BTU-in/ft2-h-°F) |
| 347 |
S34700 |
— |
75,000 |
515 |
— |
30,000 |
205 |
— |
35 |
— |
— |
29.0 |
9.2 |
— |
| 347H |
S34709 |
— |
75,000 |
515 |
— |
30,000 |
205 |
— |
35 |
7 or coarser |
— |
29.0 |
9.2 |
— |
Composition of 347/347H stainless steel pipe
| Grade |
347 |
347H |
| UNS Designation |
S34700 |
S34709 |
| Carbon (C) Max. |
0.08 |
0.04–0.10 |
| Manganese (Mn) Max. |
2.00 |
2.00 |
| Phosphorous (P) Max. |
0.04 |
0.04 |
| Sulphur (S) Max. |
0.03 |
0.03 |
| Silicon (Si) Max. |
0.75 |
0.75 |
| Chromium (Cr) |
17.0–20.0 |
17.0–20.0 |
| Nickel (Ni) |
9.0–13.0 |
9.0–13.0 |
| Molybdenum (Mo) |
— |
— |
| Nitrogen (N) |
— |
— |
| Iron (Fe) |
Bal. |
Bal. |
| Other Elements |
Cb+Ta=10xC-1.0 |
Cb+Ta=8xC-1.0 |
347/347H Product Range
| Alloy |
UNS Designation |
Werkstoff NR. |
Specifications* |
| 347 |
S34700 |
1.4550 |
A269, A/SA249, A/SA312 |
| 347H |
S34709 |
— |
A/SA249, A/SA312 |
*Note: The specifications noted including ASTM, ASME, or other applicable authorities are correct at the time of publication. Other specifications may apply for use of these materials in different applications.
Availability
Seamless Pipe 1/2" - 12"
Weld Pipe 8" - 12"
Butt-Weld Flanges 1/2" - W
Bar 1" - 12"
Specifications
ASTM A312, A403, A182, A479, A276
ASME
SA312, SA403, SA182, SA479, SA276
Description
These types of stainless are austenitic chromium steels containing columbium. They are recommended for parts fabricated by welding which cannot be subsequently annealed. These types also are used for parts which are intermittently heated and cooled to temperatures between 800 deg. and 1600 deg.F. The addition of columbium produces a stabilized type of stainless that eliminates carbide precipitation, and consequently, intergranular corrosion.
Design Features
• Superior general corrosion resistance over Type 321 due to stabilization with columbium.
• Reduced tendencies to form continuous networks of chromium carbides at the grain boundaries.
• Better high temperature properties than 304 or 304L. Generally used for parts which are intermittently heated up to 1500 deg. F. For continuous service the maximum temperature is 1650 deg. F.
• Type 347H has high carbon (.04 - . 10) for better high temperature creep properties.
• Improved intergranular corrosion resistance.
Typical Applications
High temperature chemical process, Heat exchanger tubes
Refineries
High temperature steam service
Tensile Requirements
Tensile Strength (KSI) 75
Yield Strength (KSI) 30
KSI can be converted to MPA (Megapascals) by multiplying by 6.89
Benefits of 347 Stainless Steel
- Higher creep stress and rupture properties when compared with 304
- Ideal for high temperature service
- Overcomes sensitization and intergranular corrosion concerns
- Can be used in elevated temperature applications for ASME Boiler and Pressure Vessel Code applications
- Due to stabilisation the material offers better overall corrosion resistance when compared to 304/304L
- Excellent mechanical properties
- A high carbon version (347H) is also available
Typical Uses
- Heat exchangers
- High temperature steam service
- High temperature chemical process
Corrosion Resistance
The following table is for reference only, many factors can affect the corrosive resistance, a corrosion test for each application should be applied.
Typical Room Temperature Mechanical Properties 347
Stainless Annealed 1900f (1038c) 1” rd bar
| 0.2% Yield Strength |
Ultimate Tensile Strength |
% Elongation in 2” (50.8mm) |
% Reduction of Area |
Brinell Hardness |
Izod Impact Strength |
| ksi |
Mpa |
ksi |
Mpa |
Ft-lb |
J |
| 37 |
255 |
90 |
621 |
50 |
65 |
150 |
110 |
149 |
Heat Treatment
- Annealing:
- Heat to 1850/2000 F (1010/1093c) and quench in water. Brinell hardness approximately 150.
- Hardening:
- Cannot be hardened by heat treatment, it can only be hardened through cold working.
- Stabilizing:
- If temperature during use is expected up to 1600 degrees, stabilizing between 1550/1650f (843/899c) can be used for optimum ntergranular corrosion.
- Machinability:
- When machining 347 its chip is tough and stringy, use rigid tooling with heavy cuts to prevent work hardening.
- Specifications:
- AMS 5646 ASTM A182 ASTM A276 ASTM A314 ASTM A473 QQS 763 ASME SA182 EN10204 DIN3.1B
- Shapes Manufactured:
- Flat Bars, Square Bars, Round Bars, Rings, Hollows, Discs, Blocks and special Shapes. Send us a drawing to see how we can save you material and Machining time!
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