MIG welders explained
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MIG is an acronym for Metal Inert Gas. MIG welders work using an arc welding process with a continuous solid wire electrode that's fed automatically through the welding gun at a constant pre-set speed. The electrode melts with the metal workpiece to create a weld pool that's used as a filler metal to form the joint.
There are two ways that a MIG welder can produce a shielding gas to protect the weld pool and metal from reacting with airborne contaminants. First, the welding gun can feed gas from a canister alongside the electrode. Or a flux-cored wire electrode containing a shielding gas releasing material can be used.
MIG welders are perfect for beginners because they are easy to use. They produce a neat and clean weld with no slag (waste material), so there's less post-weld cleaning required. They deposit the weld pool at a higher rate than other types of welders, so welding tasks can be completed in less time. And the continuously fed wire electrode means less time is wasted compared to welders, where you must frequently stop to change the electrode. In addition, the flux-cored electrode option works well on dirty or rusty materials, but the continuous wire electrode method requires the base metals to be clean before welding.
There are also a few disadvantages. Such as, the initial set-up and maintenance costs are high. They can only be used in non-draughty conditions (so they can't be used outside). And they are less efficient if you need to use them for long periods due to their low duty cycle (i.e., the amount of downtime they need to cool down between uses).
MIG welders are best used for joining steel, stainless steel and aluminium in a wide variety of thicknesses.
What gas is needed for a MIG welder?
Argon is the best gas for MIG welding. It can be used on its own or mixed with one or two other gases such as helium and carbon dioxide to allow deeper penetration into the metal.
Are MIG welders AC or DC?
MIG welders use a DC current for welding, providing a smooth welding output, less spatter (metal particles thrown out as it welds), and a more stable arc.
MIG welding diagram
A MIG welder is made up of the following features and functions:
Welding machine: this plugs into an electricity supply and feeds the electrical current into the base metal and electrode.
Ground clamp: this is attached to the base metal and is connected to the welding machine by a cable.
Welding gun: this is connected to the welding machine via a cable.
Gas nozzle: this runs through the welding gun to supply the shielding gas. It's connected to a gas canister.
Contact tube: this copper tube runs through the welding gun and supplies the electrode with an electrical current.
Consumable electrode: this runs through the contact tube.
Arc: the electrical current that jumps between the electrode and the base metal to create extreme heat.
Welding pool: the molten pool of metal created by the electrode used to form the joint.
Gas shield: the protective layer of gas surrounding the welding pool.
Parent and weld metal: the two pieces of metal which are being joined together.
Welding is a hazardous activity that can expose workers to many dangers. Find out how to manage these risks.
Welding is a fabrication process that permanently joins two materials, usually metals, by enough heat to melt the material being joined. Sometimes pressure, or a combination of heat and pressure, can be used to weld materials together. Welding is used across industry for construction, maintenance, and repair work, as well as to manufacture equipment, machinery, and tools.
You must have controls in place to eliminate or manage welding risks, as many can cause immediate and life-threatening danger to workers.
Workers could inhale fume gases and vapours from:
Containers that have had flammable or combustible substances in them are a fire and explosion hazard while being welded. Welding these containers must be supervised by a suitably qualified person. Make sure you check all containers before you begin work.
Containers that have contained:
Check AS .1 () Safety in welding and allied processes, Part 1: Fire precautions for guidance on managing and supervising these hazards
There's a risk of workers inhaling toxic gases, fumes or getting an electric shock if they're welding in:
Welding is hot work that can have fire and explosion risks.
Less experienced welders, or those unfamiliar with the tools, may risk injuries from poor work practices.
Hazards specific to welding include the following.
Welding fumes are complex mixtures of metallic oxides, silicates and fluorides and some can cause cancer and other ill health effects.
Welding fumes form when metal heats above its boiling point. As the metal cools it condenses into particles so small they can easily be breathed into the lungs.
Welding fumes can contain particles from the electrode and the material being welded. Any coatings or residues left on metals can also break down during welding and cause toxic fumes.
Some welding fumes are easy to see, but many are too small to be seen with the naked eye.
Graphic: Relative size of welding-fume particle
Your exposure to welding fumes can be affected by the:
Gas welding usually produces less fume than electric welding, except for processes involving heavy cutting and gouging.
Note:
Some welding risks may be less obvious, with health effects showing later. For example, there are both short-term and long-term effects to the lungs caused by exposure to toxic gases, fumes and airborne contaminants when welding.
Acute or prolonged exposure to welding fumes may result in:
Phil's story
Phil's story is a first-hand account of how breathing in welding fumes over a long period of time without adequate controls caused him to suffer occupational asthma, a permanent respiratory condition.
Gases are sometimes used when you're welding or cutting. Gases or vapours might also be produced when coatings or chemical residues are not removed from metals before you begin welding. These gases and vapours can be hazardous.
Gases used in the welding or cutting process:
Gases and vapours produced from the welding or cutting process:
Gases and vapours produced from thermal breakdown of coatings:
The health effects of prolonged exposure to welding gases and vapours include:
Some activities outside of work, like cigarette smoking, can worsen the adverse health effects or respiratory hazards related to welding.
See below for information about the controls required protect against welding gases and organic vapours.
Ozone is formed in the welding arc when the electric arc interacts with atmospheric oxygen and can be hazardous when you breathe it in.
The health effects of ozone will depend on the amount you breathe in and can include:
Electric arc and laser welding emit ultraviolet (UV), visible light and infra-red radiation. Gas welding emits visible light and infra-red radiation. Radiation from welding may cause injury to both the eyes and skin.
Some welding electrodes contain low-level radioactive material, for example, red-tipped TIG electrodes, 2% thoriated, contain thorium oxide. You should use appropriate PPE and dust-collection systems when grinding thoriated welding electrodes to prevent inhaling radioactive dust.
The effects and type of radiation on the body will depend on:
Workers directly involved in the welding process are at greatest risk, however other workers in the workplace or passers-by could also be exposed to radiation.
Eye disorders can occur from exposure to all forms of welding radiation and may include:
Skin damage can occur from exposure to UV radiation and includes:
See below for advice on controls that can protect workers from UV and infra-red radiation.
Welding fumes and UV radiation emitted during welding are categorised as Group 1 carcinogens (carcinogenic to humans) according to the International Agency for Research on Cancer (IARC) in . You can read more about the new IARC classification.
Workers and management can work together to reduce the risks of hazards at work. A safe place of work benefits everyone. Access more information about how you can create safe work.
The Welding processes code of practice (PDF, 0.95 MB) outlines requirements for specific situations where welding is done, such as working in confined spaces (PDF, 1.43 MB)
As a worker, you must take reasonable care for your own health and safety and make sure your work doesn't impact on the health and safety of others. You must comply with any reasonable instructions given relating to risk control measures and emergency procedures. You should also make sure you work according to any training or information that's been provided to you.
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Welding should only be done by competent and skilled workers. You should know the right way to do the work and how to prevent harming yourself and others.
If you're an employer or person conducting a business or undertaking (PCBU), you have a duty to manage risks, as outlined in the Work Health and Safety Act (WHS Act). Use the practical advice in the How to manage work health and safety risks Code of Practice (PDF, 0.65 MB).
Following the four-step risk management process below will help you meet your responsibilities.
The first step in managing welding risks is to identify all hazards that can cause harm.
You can identify potential hazards by:
A risk assessment may help:
When you're assessing risks from welding, take into account:
You should review the Welding processes code of practice (PDF, 0.95 MB) for risk assessment guidance for specific welding hazards.
The Welding processes code of practice (PDF, 0.95 MB) recommends control measures your workplace can put in place. Control measures can include:
You should provide workers who carry out welding with information and training about:
See below for specific risk controls.
You should regularly review welding risk controls to make sure they are effective. You can read more about when work health and safety laws require you to review your risk controls.
Health monitoring
Health monitoring detects changes in a worker's health because of exposure to certain substances. The Welding processes code of practice outlines when and how you must provide health monitoring.
Some controls are more effective than others. The Welding processes code of practice outlines specific ways to control risks according to the hierarchy of risk controls.
Eliminating a risk is the most effective way of keeping your workers safe.
You can eliminate welding risks by designing fabrications to include pre-cast components or extruded shapes that don't need welding.
You can reduce risks by:
Choose a welding technique and consumables that makes less fume and/or UV radiation.
You can read more about the amount of welding fume produced by different types of welding on the Cancer Council website.
Use automated welding systems and process enclosures to remove the worker and/or permit the operator to stay clear of the welding plume and exposure to radiation.
Photograph: Automated welding system
Use jigs to turn material being welded so workers do not have to stand directly over the welding plume.
If you can't eliminate the hazard and associated risks, you should minimise the risks using the following controls.
Ventilation can reduce exposure to fumes and other airborne contaminants. A combination of local exhaust and forced dilution ventilation is best practice. Local exhaust ventilation (LEV) systems remove gases, fumes, dusts and vapours at the source before they can mix with the room air.
You should use natural ventilation, such as open windows or doors, only for general comfort. Natural ventilation doesn't reliably dilute or disperse airborne contaminants in the work area.
The following are examples of local exhaust ventilation systems suitable for welding operations include.
These draw away welding fumes and gases away from where they can be breathed in by the worker. They need to have sufficient air speed to keep the welding fumes and gases from rising into the breathing zone of the worker. Ensure work pieces don't cover too much of the ducting or the exhaust effect will be lost.
Portable hoods attached to flexible ducts placed as close as practical to the work will draw welding fumes and gases away from the worker's breathing zone. The optimal location for the hood is about 1 duct diameter from the arc. They should have a minimum air velocity of 0.5 m/s across the welding arc.
Photograph: A worker using a portable hood to draw welding fume away from their breathing zone
Ensure welding plumes do not enter the welder's breathing zone by positioning LEV hoods correctly.
On-torch extraction systems remove fumes and gases very close to the source. They can be very effective on flat and vertical surfaces, in corners and around flanges. Approximately 90 per cent of welding fume is captured when using on-torch extraction systems.
Watch a video on the effectiveness of on-torch extraction.
NOTE:
Using fans or leaving doors and windows open is not as effective as using LEV to control fumes.
Prevent other workers breathing in welding fumes and gases by separating welding from other workplace activities. Use non-flammable welding screens and partitions to protect other workers from radiation hazards.
Train workers who weld in:
You should not rely on personal protective equipment (PPE) or respiratory protective equipment (RPE) alone to protect workers from inhalation and radiation risks.
NOTE:
A welding helmet alone is not effective at keeping you safe from fumes, gases and vapours and may cause contaminants to be trapped within the helmet.
PPE to protect workers from UV radiation and burns includes:
Welding work requires specific RPE to prevent breathing in fumes, gases and vapours.
Where there is a safe level of oxygen:
Powered air-purifying respirators (PARPs) supply filtered air to the workers breathing zone and can be incorporated into welding helmets. Because filtered air is constantly flowing into the headpiece under pressure, leakage of contaminants into the helmet is greatly reduced.
Photograph: Worker welding wearing an air-fed welding helmet
Supplied-air respirators must be used where:
or
You may also need a supplied-air respirator to protect against some gases and vapours that can't be effectively filtered, such as argon or carbon monoxide when working in a confined space.
Find out more about selecting and using RPE .
Consultative committee for work-related fatalities and serious incidents
The committee was established to ensure there is an ongoing consultative forum for injured workers and families affected by a workplace death, illness or serious incident. Read more about the committee.
The following Standards provide additional guidance on how to manage risks associated with welding.
Carefully read all relevant codes of practice to make sure your business is complying with the health and safety duties in the WHS Act and Electrical Safety Act.
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