Self-shielded Flux-Cored Arc-Welding process

FCAW per the American Welding Society, or flux-cored for short, is different in that it uses a wire which contains materials in its core that, when burned by the heat of the arc, produce shielding gases and fluxing agents to help produce a sound weld, without need for the external shielding gas. We achieve a sound weld, but in a very different way. We have internal shielding instead of external shielding. The shielding is very positive and can endure a strong breeze. The arc is forceful, but has spatter. When finished, the weld is covered with a slag that usually needs to be removed. A "drag" angle for the gun is specified which improves operator visibility. The settings on the wire feeder welder are slightly more critical for this process. Improper technique will have results that are magnified. This type of welding is primarily performed on mild steel applications outdoors. The Innershield® .035" NR-211-MP is often used for the 115 volt machines and the .045" Innershield NR-211-MP is typically used in the 230 volt machines. Farmers have found that these products can save a planting or harvest by repairing a broken machine out in the middle of the field in record time.

General Usage Rules

MIG


As a rule of thumb, it is recommended to use a compact 115 volt input (or 230 volt) MIG wire feeder welder indoors on clean new steel that is 24 to 12 gauge thick. 12 gauge is a little less than 1/8" thick. 24 gauge is less than 1/16" thick. The smallest wire (.025") will make it the easiest to weld the thinnest (24 gauge) material. The .030" diameter wire will weld a little faster deposition rate. If you need to weld 1/8" to ¼" thick material with MIG, you will need the higher capacity compact machine which will require 230 volt input. The higher amperage range of this machine can better handle your welding needs in a single pass and you may not have to waste time with second or third passes. The 230 volt machine could also run .035" diameter wire. To MIG weld material more than ¼" thick, you need a higher capacity truly industrial machine. If most of your welding will be performed indoors on clean material that is less than 1/8" thick, a MIG machine that operates on 115 volts is probably your best bet for economic reasons in that a 230 volt input machine will be more expensive.

Flux-Cored


The flux-cored process is only recommended on materials as thin as 20 gauge, a bit thicker than the 24 gauge we said for MIG. In general, this process is best for welding thicker materials with a single pass, especially if you need to weld outdoors such as to repair a tractor out in the field. A 115 volt flux-cored machine using an electrode such as .035" Innershield NR-211-MP will generally allow you to weld steel up to ¼"thick. Note that this is more than double the thickness maximum of 12 gauge with MIG on 115 volts. With the proper electrode on a proper machine, such as .045" Innershield NR-211MP, and a 230 volt input machine, you can weld steel up to 1/2" thick. Note that Innershield® NR-211-MP requires that the machine be setup for DC negative polarity.

Advantages/Disadvantages

While there are advantages and disadvantages to both processes, we will try to outline for you some of the most common.

MIG


Advantages

The best choice when cosmetic appearance is an issue since it provides lower spatter levels than flux-cored. The arc is soft and less likely to burn through thin material.
The lower spatter associated with MIG welding also means no slag to chip off and faster cleaning time.
MIG welding is the easiest type of welding to learn and is more forgiving if the operator is somewhat erratic in holding arc length or providing a steady travel speed. Procedure settings are more forgiving.
If you are skilled and get specific proper guns, shielding gas, liners, drive rolls, and electrode, MIG can weld a wider range of material including thinner materials and different materials such as stainless, nickel alloys or aluminum.
Disadvantages

Since a bottle of external shielding gas is required, MIG welding may not be the process of choice if you are looking for something that offers portability and convenience. MIG also requires additional equipment such as a hose, regulator, solenoid (electric valve) in the wire feeder and flowmeter.
The welder's first job is to prepare the surface by removing paint, rust and any surface contamination.
MIG has a soft arc which will not properly weld thicker materials (10 gauge would be the maximum thickness that MIG could soundly weld with the 115 volt compact wire feeder welder we are referring to or ¼" with the 230 volt input compact wire feeder welder.) As the thickness of the material (steel) increases, the risk of cold lapping also increases because the heat input needed for good fusion is just not possible with these small machines.
Flux-Cored


Advantages

The Self-Shielded electrodes are optimal for outdoor procedures since the flux is built into the wire for positive shielding even in windy conditions. An external shielding gas and additional equipment are not needed, so setting up is simpler, faster and easier.
The flux-cored process is most suited for applications with thicker materials as it is less prone to cold lapping.
Disadvantages

It is not recommended for very thin materials (less than 20 gauge).
When flux-cored welding, machine settings need to be precise. A slight change in a **** position can make a big difference in the arc. In addition, the gun position is more critical in that it must be held consistently, and at the proper angle, to create a good weld.
This process creates spatter and slag that may need to be cleaned for painting or finishing.
It should be noted that the same machine can be used to weld with both MIG and flux-cored processes though a special package is usually needed to change from one application to the other. Drive rolls, shielding gas, gun liners, contact tips and procedure settings need to be addressed when changing processes.