4.2 Welding rod, filler wires and materials

Different welding process uses different types of filler material to aid the mechanism. A brief description to the types of filler rod/wire they use, to have a visualization of how they are fitted for the actual welding process, watch the videos from post 4.1 Welding terminologies.

SMAW - Uses a generally thicker rod with flux. Flux help produce shielding gas, adds alloying element to strengthen weld, reduces cooling rates when doing each pass. Manual feeding of weld stick is required.

Electrodes are usually classified in 4 numbers E-XXXX or E-6015
First two numbers refers to the yield strength in kpsi, 60 refers to 60k psi.
Third number refers to the welding position --> 0, All position. 1, Horizontal & flat
Fourth number refers to the electrode type

 There are 3 main types of electrodes based on the Fourth number:
a) Cellulose - No. 0, 1. High moisture content, good for joining thick sheet metal
b) Rutile - No. 2,3,4. Good for thin sheet metal.
c) Basic  - No. 5,6,8. Low hydrogen type, requires oven or hot box. Good for eliminated hydrogen embrittle cracking, when moisture is broken down by the high temperatures.

FCAW - Uses a hollow filler wire, filled with flux at the core. Basically same properties as above, however it comes in a wire coil, filler wire is automatically dispensed, no need for manual feeding.

GMAW - Same automatic feeding of filler wire like FCAW, but uses a shielding gas and no flux wires are required.

GTAW - Uses a thin and long filler rod without flux. The stick is hand held and melted with the tungsten torch.

Electrode sizes

These rods & wires comes in different sizes as well, usually depending on the application of weld:

1) Weld build up, usually use a thicker rod to speed up the process

2) Welding small pipes, use a small rod for better control 

3) Welding larger pipes, use a thicker rod to reduce weld time.

Benefits of thick filler rod

- Improve speed of material deposition

- Reduce number of passes (improves speed, good for weld build up jobs)

Benefits of thin filler rod

- Better control of welding process

- Increased number of passes 

Filler Rod Materials

Filler wire should preferably match the material of the base metal, in cases where dissimilar metals needs to be joint there are special application filler wires available. Here are some examples but not all listed for common stainless steels:

Base Metal A	Base Metal B	Recommended Filler material
SS301/302/303/304/305	SS301/302/303/304/305	SS308L
SS304/SS316/L	A106/A53, CS	SS309L
SS301/302/303/304/305	SS409	SS309L
SS301/302/303/304/305	SS316L	SS309L
SS316L	SS316L	SS316L

SS309L, a very versatile filler material, good for joining dissimilar stainless steels. However it contains no molybdenum which SS316L requires.

Stainless steel 316 has high carbon content and is not recommended as SS316L for welding. Due to the high carbon content, carbon tends to combine with chromium at grain boundary and the depletion of elemental chromium leads to localized corrosion. Strongly recommend SS316L, if the component needs to be welded and 316 material needs to be used.

Hardfacing, whenever repairs are required to a surface which requires increased hardness for erosion resistance, for example metal valve trims or injector tips, hardfacing electrodes such as Stellite is recommended. Cobalt is the main ingredient to give the extra hardness.