Let’s first start with the basics: what is MIG welding? Well, it’s important to know that there are several different types of metal welding, from arc to friction to MIG. MIG stands for “metal inert gas.” MIG is a subtype of arc welding, also known as gas metal arc welding. This means that in the welding process, you would join two pieces of metal using an arc.
Below, we’ll go into more detail on the MIG welding method and talk about specific MIG welding equipment, how to prepare your MIG weld, essential safety precautions, and the MIG welding technique, as well as some troubleshooting.
Understanding MIG Welding
Now that we understand MIG welding basics, let’s go into more specifics: uses, applications, mechanics, and relevant equipment.
How Does MIG Welding Work?
First, it’s necessary to break down the anatomical components in the MIG welding process. You have:
- Parent metal – This is the material you will be directly operating on to create a joined product.
- Filler metal – This is the metal you will add to the welding process to create the joint.
- Weld metal – This is the composite metal that melts and is retained during the weld formation.
- Heat-affected zone (HAZ, but not HAZardous!) – This is the specific part of the parent metal that neither melts nor is retained from welding.
- Fusion line – This is the “boundary” line that separates the HAZ and the weld metal.
- Weld zone – This is the part of the surface area of the metal that includes the HAZ and the weld metal.
- Electrode – This is the wire electrode you will use to initiate and sustain the weld. It’s what gives the welding machine its “juice.”
Now let’s dive into the actual process of MIG welding.
- Once you have everything correctly set up, you will be ready to initiate your weld.
- Press the trigger of the welding machine to enable an arc to form between the end of the electrode and the metal you are operating on. Note that this wire electrode serves two purposes in the welding process: one, it is the heat and electricity source for the machine, and two, it is actually the filler metal material itself for the weld.
- Feed the MIG welding wire continuously through a contact tube. This is a positively charged wire electrode.
- Now, you need to know that there are four modes of MIG welding.
- The first is a short-circuiting mode. In a low-energy – therefore low-heat – process, the wire electrode undergoes a continuous deposition by way of small, repeated, intervallic short-circuits. Short-circuiting mode is practicable in all four basic welding positions.
- The second is a globular mode. The only difference between short circuit and globular modes is that in globular mode, the wire undergoes continual deposition through a combination of short circuits and drops induced by gravity. In this mode, the electrode never comes into contact with the workpiece. Globular mode offers advantages, including high-speed welding, cost-effective use of CO2 gas and electrodes, and more.
- The third is spray mode. This differs from the two abovementioned modes in that it is produced by high-energy metal transfer. The wire is still fed continuously, but spray mode has small metal droplets of consistent size in a consistent stream. Advantages of this high-energy mode include superior electrode efficiency at 98%, high deposition rate, consistent weld bead appearance, compatibility with an extensive range of filler metal types, and easy cleaning.
- The last mode is pulsed mode. This can also be considered a subtype of spray mode in that the electric current is highly controlled between low and high levels. In terms of the metal transfer, there is only one molten metal droplet every time the current vacillates to the higher end of the energy spectrum. Pulsed mode is often seen as the most advantageous type of MIG welding mode because it doesn’t spatter, is free of fusion defects, has superior electrode efficiency at 98%, and can be used in both automation and robotics settings.
Another part of the MIG welding process involves what is known as shielding gasses. You will use these gasses to prevent the reaction between O2 and other atmospheric elements and the weld pool of molten metal. There are other forms of shielding gasses, and they each have additional functions.
Relevant Equipment for MIG Welding
The equipment you will need for your MIG welding job is as follows:
- Welding machine
- Power source
- Wire electrode
- Shielding gas
- Tool for cutting metal
- Angle grinder
- Accessories such as clamps and a welding cart
- MIG welding-specific clothing (gloves, boots, jacket)
- Welding helmet
Having all of these tools will ensure proper and safe job performance.
The following are imperative safety precautions you must take to safely and properly perform a MIG welding job.
- Check walkways, workspace, and work leads to make sure there aren’t any slip or trip hazards present.
- Make sure the work area is free of oil, grease, and flammable material.
- Make sure the work area and equipment are dry to avoid electric shocks.
- Check that gloves, work leads, and welding gun are in good condition.
- Before you start, make sure the fume extractor unit is on.
- Put up safety screens or close the UV curtain to protect others.
Remember to NEVER use faulty or defective equipment.
Operational Safety Checks
- Ensure you’re using the correct current, wire feed, voltage, and gas flow for the machine.
- Ensure the work return cables firmly come into contact for an effective electrical connection.
- Never allow the welder to run unattended.
- Avoid welding flashes and use UV safety curtains as needed.
- Inspect the welding shield and tip for damage regularly.
- Turn off the fume extraction and the machine.
- Close the gas cylinder valve.
- Hang up the welding cables and gun
- Leave the work area safe and tidy.
- Electric shocks
- Radiation burns to the eyes or body
- Flying sparks
- Welding fumes
- Body burns due to hot or molten materials
- Cuts and lacerations
Frequently Asked Questions
1. What metals can I weld with MIG welding?
A lot! Carbon steel, stainless steel, aluminum, magnesium, copper, nickel, silicon bronze, and other alloys.
2. How do I choose the right shielding gas?
First, knowing about the different types of shielding gasses is important. They are argon (Ag), carbon dioxide (CO2), and a special mixture of helium (He) with other gasses.
3. Can I weld thicker materials with MIG welding?
Yes, you can. MIG welding is suitable for a wider variety of metal thicknesses than standard welding.