WELDING VARIABLES BASICS

Aristotle once noted that “quality is not an act, it is a habit.” This quote is certainly true of welding. While the goal of welding is clear, the alchemy that makes it happen is far from simple. Thankfully, by taking the time to understand and master the variables of welding, it is possible to ensure quality welds on most occasions.

Although not exhaustive, the following list presents 7 influential welding variables. Mastering these will enable more skill and consistency in weld outputs.

Variables 1 & 2: Amperage and Wire Feed Speed (WFS)

“Amperage” describes the volume and speed at which electricity flows through a circuit. In welding, amperage influences the level of joint penetration that wire feed speed (WFS) will have. The higher the amperage, the greater the joint penetration will be (and vice versa).    Amperage also impacts contact-tip-to-work distances (CTWD). Less amperage will create a greater distance while increased amperage will lessen the distance. In other words, amperage controls the weld penetration of the base metal. Additionally, amperage influences melt-off-rate as well as weld bead appearance (amperage that is too high can result in a dull, flaky weld).

Welders need to keep these factors in mind so that they can ensure the amperage supports their desired WFS speed and level of joint penetration. As with most skills in life, practice makes perfect.

Variable 3: Base Material

The base material is the metal or alloy that is being welded, soldered, or cut. The following is a list of common types of welding materials:
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• Aluminum
• Cast Iron

• Copper

• Magnesium

• Nickel Alloys ​
• Steel

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​While each of these metals can be used as a base material, it is important for welders to study the different characteristics of each. In order to choose the right metal for the task, a welder must consider factors such as strength, conductivity, flexibility, and heat sensitivity/melting points. For instance, steel is a versatile and strong metal, but can also flake and rust from oxidation; cast iron is not as ductile as other metals; magnesium has flammable shavings. Knowing how each metal responds to different welding methods allows welders to avoid mishaps and ensures a quality, finished product.

Variable 4: Shielding Gas

In welding, shielding gases prevent the molten weld from interacting with gases in the air atmosphere. Protection from this exposure helps to determine arc stability, weld penetration, and mechanical properties of the finished product as well as to prevent spattering and holes within the weld bead.

Each shielding gas has different effects. They can be combined to enhance different properties. Carbon dioxide (CO2), for instance, provides deep penetration, but less arc stability and more spattering.  Adding argon to CO2 mitigates these negatives while also allowing higher tensile strengths and more aesthetic value.

With such benefits at stake, taking the time to learn about the strengths/weaknesses of different shielding gases and combinations will be well worth the effort. Learn more about how to choose a shielding gas for your application here. 

Variables 5 & 6: Travel Speed and Heat Input

The speed at which arc moves along the weld joint is known as “travel speed.” Measured in IPM (inches per minute), changes in travel speed affect heat input in that faster speeds produce less heat. Different base materials react differently to heat, so controlling travel speed is necessary to ensure a good weld. Burn-through, poor penetration, and undesirable weld bead sizes are some of the defects that can occur if the travel speed/heat input are insufficiently matched with the base material.

Variable 7: Voltage

Last but not least on this list, voltage is the variable that adjusts arc length. Higher voltage increases heat and produces a longer and wider arc, while lower voltage produces a shorter, narrower arc. Because voltage impacts the shape of the weld profile and weld bead (in short, everything that is above the surface of a weld), it is important that it is neither too high nor too low. A voltage that is too low can also prevent fusion.

Welders should play around with voltage and adjust as needed. It is important to practice with the same equipment that will be used for projects because the voltage in reality may not always match the voltage reading on the power source.

Putting Everything Together

In order to become a master of the trade, welders should experience with each variable in isolation (to determine its effects) as well as in various combinations. It is through trial and error that the best possible formula can be determined. In welding, one size does not fit all, and variables that may be detrimental in one case may be perfect for another (e.g. a lower WFS is ideal for shirt-circuit welding). Working to master the parts of the welding process that can be controlled will result more consistently in quality welds.

The Earlbeck Technical Center offers courses that will teach the welding operator how to select the correct variables for their application. To learn more about our courses, click here to get additional details.

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