Using optimized welding parameters for wire processes is key to avoiding weld defects and discontinuities that lead to rework, lost productivity and increased costs. They can also help ensure that the expected mechanical properties are achieved from the chosen filler metal. 

That’s why it’s important to pay attention to the processes’ essential variables such as amperage and voltage, which can be found on a filler metal’s data sheet or the application’s Welding Procedure Specification (WPS). Other factors like shielding gas and travel speed also can impact results. The aim is to have all parameters optimized for the specific application so that they don’t negatively affect one another. 

Amperage
The wire type, diameter and wire feed speed determine how much amperage it takes to melt it. When a welding operator increases wire feed speed, the amperage increases; when wire feed speed decreases, so does the amperage. Amperage also changes with contact-tip-to-work distance, increasing when it’s shorter and decreasing when it’s longer.

Too low of amperage can lead to several problems, including a convex or ropey bead profile, lack of fusion and lack of joint penetration through the root. Operators may also notice that the arc isn’t as stable when the amperage is lower, particularly when welding thicker materials. 

While some welding operators may want to run higher amperages to gain more deposition, if this setting is too high, it can result in burn-through on the base material.
When determining amperage for an application, consult the filler metal data sheet and WPS, which both provide recommendations for amperage settings for a wire. As a general rule, applications require approximately 1 amp per 0.001 inch of material thickness; however, it can vary by application. Larger diameter wires require higher amperage settings, and in some instances, it may be possible to use a larger wire in a flat and horizontal position at higher amperages to gain better deposition.

Voltage
Voltage in a wire process affects several factors, including arc length, arc stability and weld bead width since it influences the fluidity of the weld pool. A higher voltage will increase arc length, while lower voltage decreases arc length. Additionally, the mode of transfer, including short circuit, globular and spray, is determined by the amount of voltage commanded and the shielding gas.

If the voltage is set too low, it can cause an erratic, poor running arc. The poor running arc often generates an increase in spatter due to the wire shorting out in the weld pool. Low voltage can also result in lack of proper side wall tie in and excessive reinforcement since the weld isn’t wetting out at the toes properly.

Conversely, if the voltage is too high, it can lead to wider arc and a weld pool that is too fluid, which causes the weld bead to be too flat. Too high of voltage can potentially cause worm tracking or porosity on the surface of the weld and decreased penetration, as well as undercut due to the weld pool being too hot and fluid. 

Again, to gain the best results, welding operators should consult the filler metal data sheet and WPS. They should also keep a consistent contact tip-to-work distance. If the arc becomes erratic, the welding operator should lower the voltage in small increments (this is recommended more so when using 100% CO₂). An erratic arc or an arc flutter can also be caused by too high of voltage as well, typically when using mixed gases.  

In both instances, it’s important to stay within the recommended operating window. When the voltage has been optimized for a given wire feed speed, operator should hear a slight crackle (also called whisper shorts). No spatter is expelled from the arc when this occurs. 

Shielding gas
Shielding gas is another parameter that affects wire welding processes, including the transfer mode in conjunction with amperage and voltage. 

Using 100% CO₂ shielding gas provides good penetration but tends to create a slightly less stable arc and generate more spatter than a shielding gas containing argon. 100% CO₂ is typically used with gas-shielded flux-cored wire operating in a globular transfer mode at higher voltages. In this mode, the end of the welding wire forms a large ball (twice the size of the wire being used) that crosses the arc into the weld pool. It is recommended for 1/8-inch base materials or thicker. This shielding gas can be paired with a solid wire and can also increase penetration profiles, but it is not widely used due to cosmetic reasons. 

An argon/CO₂ mixture provides the smoothest and most stable arc for metal-cored wires. 80% argon is the minimum needed to efficiently achieve a spray transfer with these wires; however, a 90% argon/10% CO₂ mixture is the most used. In the spray transfer mode, the wire melts into small droplets and is transferred across the arc into the weld pool (due to the pinching-off effect of the elevated argon shielding gas), resulting in faster travel speeds and high deposition rates.  

A balance of 75% argon with 25% CO₂ is the most common gas mixture for gas-shielded flux-cored wires that are capable of or recommended for use with mixed gases. This gas mixture is also commonly used in short-circuit transfer mode when welding with solid wires.

Filler metal data sheets provide the required shielding gas mixture, as does a WPS. 

Travel speed
Generally speaking, using too slow of a travel speed will create large weld sizes and increase amperage, which can possibly lead to burn-through on thinner base materials and lack of penetration through the root on thicker materials. Amperage increases because the arc is riding to far back in the weld pool. Too slow of travel speeds can cause parts to be overwelded, which increases costs for labor, wire and gas for each part. When welding with flux-cored wires, slag entrapment may occur with too slow of travel speeds. 

Traveling too fast in the welding process produces a narrow, ropey weld bead and undercut It requires increasing wire feed speed and voltage to create the desired weld size at that travel speed. 
To get the right travel speed, operators need to pay attention to the weld pool, keep the arc on the leading edge to the front third of the weld pool. 

Final thoughts
Consistently following the WPS and the filler metal data sheets can help ensure that a welding operator is using the right parameters for the application. That, in turn, helps create quality welds, while avoiding downtime for rework that negatively affects productivity and increases labor and material costs.