Type 347 / 347H stainless steel is an austenitic grade of chromium steel, which contains columbium as a stabilizing element. Tantalum can also be added for achieving stabilization. This eliminates the carbide precipitation, as well as intergranular corrosion in steel pipes. Type 347 / 347H stainless steel pipes offer higher creep and stress rupture properties than grade 304 and 304L. This makes them suitable for exposures to sensitization and intergranular corrosion. Moreover, the inclusion of columbium allows 347 pipes to have excellent corrosion resistance, even superior to that of 321 stainless steel pipes. However, 347H steel is the higher carbon composition substitute of stainless steel pipe grade 347. Therefore, 347H steel tubes offer improved high temperature and creep properties.
Following are the properties of 347 / 347H stainless steel pipes offered by Arch City Steel & Alloy:
347 / 347H stainless steel tubes/pipes are considered to be the most weldable among all high grade steels pipes
They can be welded by all commercial processes
347 / 347H stainless steel tubes and pipes offer an annealing temperature range of 1800 to 2000°F
They can be stress relief annealed without any danger of subsequent intergranular corrosion within the carbide precipitation range of 800 to 1500°F
Cannot be hardened by heat treatment
347 / 347H pipes are frequently used for fabrication of equipment that ought to be used under severe corrosive conditions. Also, they are commonly used in petroleum refining industries. Major applications include:
| Typical Chemical Composition % (max values, unless noted) | ||||||||
| Grade | 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 |