About Alloy
347 (S34700) is a stabilized, austenitic, chromium steel containing columbium which allows for the elimination of carbide precipitation, and, consequently, intergranualr corrosion. Alloy 347 is stabilized by the additions of chromium and tantalum and offers higher creep and stress rupture properties than alloy 304 and 304L which may also be used for exposures where sensitization and intergranular corrosion are of concern. The addition of columbium also allows 347 to have excellent corrosion resistance, even superior to that of alloy 321. 347H is the higher carbon composition form of 347 and demonstrates improved high temperature and creep properties.
347 stainless steel plate is also advantageous for high temperature service because of its good mechanical properties. 347 stainless steel plate offers higher creep and stress rupture properties than 304 and, particularly, 304L, which might also be considered for exposures where sensitization and intergranular corrosion are concerns.
Product Form & Standard
AMS 5512 Sheet / strip / plate (steel, corrosion and heat resistant, sheet, strip and plate 18Cr 10.5Ni)
AMS 5556 Seamless/ welded tube
AMS 5558 Welded /thin wall tube
AMS 5571 Seamless tube
AMS 5575 Welded tube
AMS 5646 Bars / wire / forging
AMS 5654 Bars (aircraft quality)
AMS 5674 Wire
AMS 5680 Wire
Chemical Composition
| Element | 347 | 347H |
| Cr | 17.0-24.0 | 17.0-24.0 |
| Ni | 9.0-13.0 | 9.0-13.0 |
| C | 0.08 max | 0.04-0.1 |
| Mn | 2.0 max | 2.0 max |
| P | 0.045 max | 0.045 max |
| S | 0.03 max | 0.03 max |
| Si | 0.75 max | 0.75 max |
| Co+Ta | 10 * (C + N) -1.00 | 8* (C + N) -1.00 |
Mechanical Properties
| Material | Yield Strength (ksi) | Tensile Strength (ksi) | Tensile Strength (ksi) | Hardness HB |
| Alloy 347 Sheet AMS 5512 Solution | 25 | 70-105 | 40 | - |
| Alloy 347 Bar AMS 5646 Solution | - | - | - | 255 max |
Application
● Aerospace – piston engine manifolds
● Chemical Processing
● Expansion Joints
● Food Processing – equipment and storage
● Petroleum Refining – polythionic acid service
● Waste Treatment – thermal oxidizers
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