If you’re looking for a complete guide on 347 stainless steel welding, you’ve come to the right place. In this article, we’ll cover everything you need to know about welding this particular type of stainless steel, including what it is, its properties, and Welding tips on how to weld it.
What is 347 Stainless Steel?
347 stainless steel is an austenitic chromium steel containing columbium. Its composition is similar to 304, with the addition of columbium and tantalum. Columbium stabilizes this microstructure which gives 347 superior corrosion resistance compared to other stainless steels. This material is often used in high temperature applications such as exhaust manifolds, turbochargers, and furnace parts.
347 Stainless Steel Material Specification
The UNS Number of 347 Stainless Steel is S34700 & 347H is S34709. The Welding P-Number for 347 & 347H Stainless steel is P8 & Group Number–1.
The most widely used material specification for 347 Stainless Steel are:
- ASTM A240: Plate, sheets & strips
- ASTM A249: Welded Tubes
- ASTM A312: Seamless & welded tubes
- ASTM A358: Fusion welded pipe
- ASTM A376: Seamless Pipe
- ASTM A403: Wrought Piping fitting
- ASTM A409, A813, 814: welded Pipe
- ASTM A479: Bars & shape
- ASTM A182, A965: Forgings
- JIS G4303: Bars & shapes
- AMS 5512, 5680 & 5646
347 Stainless Steel Equivalent Materials
347 stainless steel is similar in composition to 321 stainless steel, with added Columbium instead of Titanium.
347 Equivalent materials are:
- EN 1.4550
- AMS 5512
- AMS 5680
- AFNOR Z6 CNNb 18-10
347 Stainless Steel Composition
347 stainless steel is an austenitic chromium steel containing columbium. The chemical composition of 347 & 347H Stainless Steel are given in the below table:
|Carbon (C)||0.08 Max.||0.04 – 0.10|
|Manganese (Mn)||2.0 Max.||2.0 Max.|
|Silicon (Si)||0.75 Max.||0.75 Max.|
|Sulfur (S)||0.03 Max.||0.03 Max.|
|Phosphorus (P)||0.045 Max.||0.045 Max.|
|Chromium (Cr)||17- 19.0||17- 19.0|
|Nickel (Ni)||9- 13||9- 13|
|Columbium + Tantalum||10 x (C+N) min. – 1.00 max||Cb 8 × C min, 1.0 Max.|
347 Stainless Steel Properties
347 stainless steel is an austenitic chromium steel containing columbium (substituted for titanium like is SS321), which is used for enhanced intergranular corrosion resistance.347 stainless is also advantageous for high temperature service because of its good mechanical properties. Some of the key properties of 347 stainless steel are outlined in the following Table.
|Tensile Strength, min Ksi (MPa)||75 (515)||75 (515)|
|Tensile Strength, min Ksi (MPa)||30 ( 205)||30 ( 205)|
|Hardness Max, Brinell ( Rockwell)||201 HBW (92 HRBW)||201 HBW (92 HRBW)|
|Toughness||Supplementary Requirements||Supplementary Requirements|
347 Stainless Steel Welding Rod, Electrode & Filler Wire
347 Stainless Steel is an austenitic stainless steel that contains chromium, nickel and columbium.
347 Stainless Steel welding rod, electrode and filler wire are used for welding in applications requires to have a matching weld chemistry of 347. Most common 347 & 347H Stainless Steel Welding Rod, Electrodes & Filler wires are ER347, E347-15 and outlined in below table:
- E347-15/ E347-16/ E347-17: For Stick Welding of 347 steel
- ER347, E16-8-2: For TIG & MIG welding of SS347
- E347T0-3: For FCAW Welding of 347 Steel
- EC347: Metal core wire for 347 Steel Welding
TIG welding 347 & 347H Stainless Steel
347 Stainless Steel Welding with TIG is carried out using ER347 filler wire rod (AWS A5.9). For 347 steel exposed to high temperature, welding is carried out using ER16-8-2 (AWS A5.9). ER16-8-2 is beneficial to avoid the reheat cracking that can occur in brittle 347 stainless steel.
100%Ar or 25%Argon-75%Heium is used for weld shielding gas for 347 TIG Welding. Weld using low to medium heat input is recommended for SS347 Welding.
Stick Welding (SMAW) 347 & 347H Stainless Steel
Stick Welding (SMAW) of 347 Stainless Steel Welding is carried out using E347-15/ E347-16/ E347-17 type welding rod.
E16-8-2 rod is used for 347 Stainless Steel Welding that is exposed to high temperature service (mainly for repair activities).
Stick Welding of SS347H Stainless Steel is carried out with E347 rod or E16-8-2 welding rod.
347 Stainless Steel Welding by MIG (GMAW)
MIG (GMAW) welding of SS347 Steel is carried out using ER347 & E16-8-2 type filler wires.
Various shielding gases combinations are available for MIG (GMAW) welding of 347 & other stainless steel. The mostly used welding shielding gas for stainless steel welding are:
- 95-98% Argon + 2-5% Oxygen,
- 97-98% Argon + 2-3% Carbon Dioxide,
- 90% Helium + 7-8% Argon +2-3% Carbon Dioxide.
Flux Core arc welding (FCAW) of 347 Stainless Steel Welding
FCAW or Flux cored arc welding of 347 stainless steel is carried out using E347T0-3 type flux cored wire (AWS A5.22). The wire is self shielded type and not requires any external welding gas to shield the weld pool. Welding using low heat input is required to maintain the high austenite in weld metal.
Welding 347 Stainless Steel to Carbon Steel
347 Stainless Steel Welding to Carbon Steel is carried out using E309L Stick welding rod. ER309LSi is used for TIG & MIG welding of 347 stainless steel to carbon steel, mild steel and low alloy steel. E309L & ER309L type welding rod are used for application temperature up to 600 °F (315 °C).
other fillers such as ENiFeCr-3 & ENiCr-3 type filler wire are used for temperature range above 600 °F (315 °C).
Welding 347 Stainless Steel to 316
Stick Welding of 347 to 316 stainless steel is carried out using E347-15 or E316-15 welding rod. TIG & MIG welding of 347 to 316 is welded with ER316 or ER347 type filler wire.
Similarly, welding of 347 to 316L is carried out using E347 or E316L Stick welding rod. ER347 & ER316L is used for TIG & MIG welding of 347 to 316L stainless steel welding.
Welding 347 Stainless Steel to 304
Stick Welding of 347 to 304 stainless steel is carried out using E347-15 or E308-15/ E308L-15 welding rod. TIG & MIG welding of 347 to 304 is welded with ER308L or ER347 type filler wire.
347 Stainless Steel Temperature Range
347 Stainless Steel is an austenitic stainless steel that contains chromium, nickel, and columbium. The high concentrations of these elements give 347 Stainless Steel excellent corrosion resistance, especially to intergranular corrosion for high temperature application compared to 304, 316 & 321 grades stainless steel.
Chromium & Columbium (Niobium) also gives this steel good oxidation resistance at high temperatures. 347 Stainless Steel is generally used in applications where welding is required and where operating temperatures are within the range of 800 – 1500°F or 427 – 816°C.
347 Stainless Steel vs. 316 Stainless Steel
347 Stainless Steel is often used in high temperature applications due to its good mechanical properties and resistance to scaling. However, 316 Stainless Steel is a better choice for welding due to its lower carbon content.
Both 347 Stainless Steel and 316 Stainless Steel are austenitic stainless steels, meaning they are non-magnetic and can be easily welded. However, 347 Stainless Steel contains columbium, which helps to stabilize the material during welding, preventing intergranular corrosion & provide high temperature strength compared to 316. Also 316 Stainless Steel does not contain columbium, making it prone to sensitization during welding.
In terms of composition, 347 Stainless Steel has a higher carbon content than 316 Stainless Steel. This makes 347 Stainless Steel more susceptible to scaling at high temperatures. However, 347 Stainless Steel has better mechanical properties than 316 Stainless Steel, making it a better choice for high temperature applications where scaling is not a concern.
347 Stainless Steel vs. 304 Stainless Steel
Both 347 stainless steel and 304 stainless steel are austenitic, meaning they are non-magnetic and can be easily welded. However, 347 stainless steel has a higher chromium content than 304 stainless steel, giving it better corrosion resistance & strength at room & high temperature.
304 stainless steel is the most common type of stainless steel used in welding applications, due to its good weldability and relatively low cost. However, 347 stainless steel is better choice than 304 for high temperature & corrosion prone applications s due to its superior corrosion resistance & high strength.
347 Stainless Steel Features & Advantages
347 Stainless Steel is an austenitic chromium steel which contains columbium (also called Niobium-Nb). This columbium allows for the steel to have excellent intergranular corrosion resistance, meaning that it will resist the formation of chromium carbides at the grain boundaries.
This makes 347 Stainless Steel ideal for use in welding operations, as it means that the steel will not be susceptible to Intergranular corrosion (IGC).
347 Stainless Steel also has a high resistance to stress corrosion cracking, making it ideal for use in environments where there is a risk of exposure to chlorides or other corrosive chemicals.