By Bruce Morrett, Solid Wire Product Manager, Hobart Brothers
Edited by Bruce Vernyi, editor-in-chief

Solid wire produces clean-looking welds on thinner metals.

Self-shielded flux cored wire does not require a separate shielding gas, which makes it ideal for welding outdoors or windy conditions.


Gas metal arc welding (GMAW) and flux cored arc welding (FCAW) have different characteristics that welding operators must evaluate when making a selection for welding applications.

To achieve the best results, the following factors have to be considered:
Thickness of the material.
The use of the correct shielding gas.
The correct settings for wire feed speed and voltage. The location of the work site.
And, finally, the desired appearance of the final weld.

There is no "one-size-fits-all" solution for welding, and all of these variables will affect the operator's decision on whether to use solid or flux cored wire. Here are the basics that are needed to understand solid and flux cored wire and ways to maximize the advantages of each.

The Basics
Solid wires require a shielding gas that is delivered from a pressurized gas bottle. Mild steel solid wires, a common type, usually are plated with copper to prevent oxidation, to aid in electrical conductivity and to help increase the life of the welding contact tip.

The shielding gas protects the molten weld pool from contaminants that are present in the atmosphere. The most common shielding gas combination for solid wires is 75 percent Argon and 25 percent CO2. When using solid wire outdoors, the operator should use caution and prevent wind from blowing the shielding gas coverage away from the welding arc. Windshields may need to be used in those instances.

There are two types of flux cored wires: those that require gas-shielding and those that are self-shielded.

Flux cored wires that require gas-shielding produce slag that is relatively easy to remove. The operator may consider using gas-shielded flux cored wires when welding thicker metals or in outof-position applications. Gas-shielded flux cored wires have a flux coating that solidifies more quickly than the molten weld material. That creates a "shelf" that holds the molten pool when welding overhead or vertically up.

Self-shielded flux cored wire does not require external shielding gas. The weld pool is protected by gas generated when flux from the wire is burned. As a result, self-shielded flux cored wire is more portable because it does not require an external gas tank.

Factors to consider When choosing Appearance
Most welding operators believe that weld appearance is an important factor. When an operator works on materials that is less than 3/16 in. and as thin as 24-gauge sheet metal, solid wire will produce a clean looking weld. For example, a short circuit transfer with .030-inch solid wire set at 18 volts to 19 volts with 160 amps to 170 amps and using 75 percent Argon and 25 percent CO2 shielding gas usually will produce little spatter, and will create a smaller heat affected area while reducing the reduce chances of burn-through. As a result, many hobbyists who work with thinner applications prefer to use solid wire.

Location
Operators also should consider the location of the work site when choosing between solid and flux cored wire. There are certain environments, such as windy locations, in which solid wire or gas-shielded flux cored wire cannot be used because exposing the shielding gas to wind could compromise the weld integrity. Typically, the loss of shielding gas would produce porosity that would be visible in the weld bead.

On the other hand, self-shielded flux cored wire is ideal for welding outdoors or in windy conditions. The operator does not have to set up windscreens to protect the shielding gases from being blown away because the shielding gas is generated from the burning flux. Since self-shielded flux cored wire does not require external shielding gas, it is also more portable than solid wire. This portability is ideal in field applications where equipment could break down. Selfshielded flux cored wire also provides excellent penetration when an operator is welding thicker metals, such as sheet that is 16 gauge and above, Thickness, Type of Application and Parameter Settings

Many novice operators attempt to use "a-onesize-fits-all" wire and shielding gas combination for multiple applications. The most common wire and gas combinations (for solid wire) are .035-inch diameter wire with 75 percent Argon and 25 percent CO2 shielding gas. When welding thicker material, however, operators must consider welding power source output, and the diameter of the welding wire. If .035-inch wire is selected for thicker materials, and the power source is plugged into a 115-volt circuit, the resulting amperage output may not be sufficient to make quality welds. The chance of "cold lap" or "lack of fusion" can increase.

Using too small of a solid wire for applications in which the base metal is thick, such as on A-frames of an automobile, increases the likelihood that there will be less penetration in the root. More than one welding pass could be required to complete such a weld, but the misapplication of solid wire, even when its composition is strong enough for the application, may not provide the penetration needed for the thicker material.

Although it is more expensive than solid wire, flux cored wire can help operators to improve productivity. Flux cored wire typically has the ability to handle the welding of dirtier materials that may have higher levels of rust, mill scale, or oil.

Although cleaning is always the proper method of preparing the steel, flux cored wires contain de-oxidizing elements that trap these contaminants in the weld pool and hold them in the slag coverage. These features can minimize pre-cleaning time and prevent the associated weld problems found when welding "dirtier" steels. Flux cored wire also can increase penetration on the sidewalls, and offers the advantage of better deposition rates, which is the amount of weld metal deposited in a given time period, measured in pounds per hour, compared to solid wire. Although the operator initially spends more on materials for flux cored wire, savings can be realized through less welding time.

Which is better, solid wire or flux cored wire?
Neither wire is superior over the other. They simply have different properties that work better on certain applications. As far as performance, both types of wire produce sound welds with good weld bead appearance when they are applied correctly and used with the proper parameter settings.

Both are relatively easy to use for the operator, but an operator may like solid wire better for applications with thinner base materials for several reasons: There is no slag to remove; it is ready to paint; and the weld beads may be more aesthetically pleasing.

The most important thing for operators to remember is not to fall into the "one-size-fits-all" mindset. Solid wire, gas-shielded flux cored wire and self-shielded flux cored wire all work well provided they are used correctly.

The type of wire an operator chooses will depend upon the location of the work site, the thickness of the application, the use of the proper shielding gas combination and the type of power source that is available. Still, to achieve the best possible results, the operator must be willing to make adjustments based on the worksite variables and consider having both solid and flux cored wire available.