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Mig Welder: Definition, Process and Tips

Metal inert gas (MIG) welding creates a strong bond between the two metals by fusing two pieces of metal with a consumable electrode filler. Unlike TIG, MIG welding uses a consumable wire as an electrode and the filler material. It is also called wire welding or gas metal arc welding (GMAW). 

In TIG welding, on the other hand, the metal surfaces are directly heated and joined by a tungsten tip. This comprehensive article explains everything you need to know about MIG welding, including its process, key parameters, and tips for improving welds.

What Is a Mig Welder?

MIG welder

A MIG welder, a Metal Inert Gas welder, is a specialized welding machine that uses an electric arc to fuse metal pieces. This process, technically called Gas Metal Arc Welding (GMAW), involves feeding a continuous solid wire electrode through a welding gun. As the wire passes through the gun, it melts and combines with the base metals to form a strong joint. The welding gun also emits a shielding gas that covers the weld area from atmospheric contamination, ensuring a cleaner and stronger weld.

The MIG welding process is known for its ease of use and efficiency, making it a popular choice in various industries. Because of the continuous wire feed, it allows for faster welding speeds compared to other methods. This not only increases productivity but also results in smoother, cleaner welds with minimal spatter. The process is versatile and can be used to weld different metals, including mild steel, stainless steel, and aluminum. Each requires specific types of wire and gas mixtures to achieve optimal results.

Critical Parameters of Choosing a Mig Welder

 

MIG welder

When selecting a MIG welder, several vital parameters must be considered to ensure the equipment meets your needs and requirements. These parameters include:

Power Output

This is measured in amperage (amps). Higher amperage allows for welding thicker materials, while lower amperage suits thinner materials. Choosing a welder with an appropriate power range for the types of projects you plan to undertake is essential. For example, a welder with a range of 30-140 amps is sufficient for light to medium-duty tasks, while industrial applications require a welder with 200 amps or more.

Duty Cycle

The duty cycle shows the percentage in time a welder can work at a given output without overheating in 10 minutes. For instance, a 60% duty cycle at 100 amps means the welder can run for 6 minutes continuously before needing a 4-minute cool-down period. A higher duty cycle is preferable for more extended or demanding welding tasks, as it reduces downtime and increases productivity.

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Wire Feed Speed

The wire feed speed, measured in inches per minute (IPM), determines how quickly the wire is fed through the welding gun. Adjustable wire feed speed is crucial for matching the welding speed to the material thickness and desired weld quality. Consistent and smooth wire feeding is essential for producing stable welds.

Voltage Settings

MIG welders typically offer adjustable voltage settings to control the arc length and heat input. Variable voltage settings allow for greater flexibility in welding different materials and thicknesses. Some welders feature infinite voltage control, providing precise adjustments for optimal welding performance.

Portability and Size

The portability and size of a welder MIG are essential considerations, especially if you need to transport the welder between job sites or have limited workspace. Lightweight and compact models are easier to handle and store but may offer lower power output than larger, more robust machines.

Gas Compatibility

The type of shielding gas used in MIG welding affects the weld quality and suitability for different metals. Ensure the welder is compatible with the shielding gas you plan to use, whether pure argon, argon-CO2 mixtures, or other specialized gases. Some welders are designed for flux-cored wire, which does not require external gas shielding and can be used in outdoor or windy conditions.

How to Weld With a Mig Welder

Welding with a MIG welder involves several crucial steps to ensure efficiency, safety, and high-quality results. The process begins with preparation, emphasizing the importance of safety gear, such as a welding helmet, gloves, flame-resistant clothing, and safety boots. Ensuring a well-ventilated workspace and having a fire extinguisher on hand is also essential. Setting up the welder involves connecting it to a power source and attaching the ground clamp to a clean, unpainted workpiece section. 

Selecting the correct wire type and shielding gas for the material is vital, with typical choices being ER70S-6 for mild steel, ER308L for stainless steel, and ER4043 for aluminum. Adjusting the wire feed speed and voltage according to the material’s thickness and type is necessary for optimal performance. Once prepared, the next step is to clean the workpiece, removing any rust, paint, oil, or contaminants to ensure better MIG weld quality. Positioning the welding gun correctly, at a 10-15 degree angle from vertical and pointing in the direction of travel, helps control the weld pool and shield gas coverage. 

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Striking the arc involves pulling the trigger to start the gas and wire flow and maintaining a consistent distance of about 1/4 inch between the gun tip and the workpiece. Employing a steady hand to move the welding gun along the joint, using techniques such as straight push, pull, or weave motions, is crucial for achieving the desired weld bead appearance. Consistent travel speed is necessary to avoid overheating or undercutting the weld.

After completing the weld, it is important to inspect it for uniformity, proper penetration, and absence of defects like cracks or porosity. A good weld should be smooth and evenly distributed. Cleaning the weld area with a chipping hammer and wire brush removes any slag or spatter, ensuring a neat finish and preparing it for further processing, such as painting or coating. Finally, allowing the workpiece and welder to cool down after extended use and checking the MIG welding machine for any signs of overheating will ensure it is ready for future tasks. 

Differences Between a Mig Welder and a Tig Welder

MIG welding process

A lot of people often confuse MIG welders for TIG welding. However, they are pretty different, and these are some of the differences:

Weld Strength

MIG welds are thought to be weaker than TIG welded connections. This results from the concentrated, narrow arc that TIG welders create, which is more effective in piercing metal. Additionally, well-executed TIG beads are smooth and typically have minimal flaws, such as holes in the bead. A more robust joint results from fewer defects because of weakening welds.

Many may argue that the minimal number of visible faults and the measured penetration indicate that the TIG welds are stronger when done correctly. That assertion has a great deal of validity. But that might be simplifying things too much. Solid and long-lasting welds can be achieved using either technique. Additionally, you can use a MIG welder to improve penetration and strength by taking specific steps. 

 Weld Speed

MIG welders are faster for manufacturing. TIG welding costs money but yields neat, attractive welds. Weld puddle movement and filler rod supply cannot be accomplished as quickly by TIG welders as by MIG welders. In addition, air-cooled torches overheat when TIG welders run for extended periods. This implies using a more sophisticated and costly water-cooled torch instead.

A MIG welder, on the other hand, automatically feeds the electrode/filler material. Because of its broader and rounder arc, it dissipates heat more effectively. These characteristics enable operators to use an air-cooled torch to produce longer runs and quickly shift the puddle using a MIG welder.

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Welding Gas

A shielding gas keeps naturally occurring reactive gases in the air from the weld puddle. Shielding gas is essential for a high-quality weld since it introduces pollutants into the weld. However, there are differences between the common shielding gases utilized in the TIG and MIG processes.

Pure argon gas is typically used in TIG welding. Using a non-reactive gas like argon is necessary since the tungsten electrode is more susceptible to reactive gases like CO2 and oxygen. However, argon may need to be blended with other gases, such as hydrogen, helium, or nitrogen, for specific purposes.

MIG welders, on the other hand, typically employ a mixture of carbon dioxide and argon, such as 75% argon and 25% CO2. The arc is stabilized, and enhanced penetration is achieved with a modest amount of CO2. (Learn more about MIG welding gases here.) Nevertheless, the MIG gas varies depending on the application. For instance, you must use 100% argon while MIG welding aluminum. Alternatively, pure CO2 can be used for MIG welding, which is less expensive and improves weld penetration (albeit with drawbacks).

Tips for Mig Welding

Check out the following tip to ensure quality welds in MIG welding:

  • Before welding, measure the electrode extension using a gauge or a ruler.
  • The ideal distance between the gun nozzle and the workpiece is 1/4 to 3/8 inch.
  • Keep the wire and nozzle away from the workpiece to prevent spattering and shorten the electrode extension.
  • The wire should not be pulled or pushed because doing so will alter the electrode extension and result in wire feed issues.
  • Before welding, check the welding settings with a metre or digital display.
  • Modifying the welding settings by the material, thickness, joint type, and position.
  • Maintaining a constant travel speed and angle to keep a steady arc and a homogeneous weld bead.
  • To find out if the welding settings have changed, pay attention to the sound made by the arc and observe the weld pool.
  • Sandpaper, wire brushes, grinders, and other instruments can clean the base metal of any surface impurities.
  • Solvents like acetone can remove any remaining oil or grease from the bare metal.
  • Because stainless steel and aluminum are easily oxidized, clean them using a stainless steel brush.

Conclusion

MIG welding is one of the most used techniques because it is an affordable, versatile process, particularly in industrial settings. It is widely utilized in the sheet metal business but is also frequently applied to thicker workpieces.

The MIG process is perhaps the most often utilised welding technique in serial production, aside from spot welding, because it can be automated with welding robots. This procedure is widely employed in place of resistance and cold welding in the automotive industry. It makes sense that businesses most frequently turn to MIG/MAG welding to boost production capacity while maintaining acceptable quality and efficiency.