Buying or renting a welder? To figure out what kind is right for your project, consider what each type of welder can do, the materials you need to weld and the power requirements and output of the machines.

Welding types explained: MIG vs. TIG vs. flux-cored vs. stick

MIG, TIG, flux-cored and stick are types of arc welding. In arc welding, a power supply creates an electric arc between a metal stick, called the electrode, and the base material. It melts the metals where they meet.

Arc welders use either direct (DC) or alternating (AC) current and consumable or non-consumable electrodes. Consumable electrodes melt and contribute to the weld.

These welders protect the weld area, also called a molten weld pool, from the atmosphere either directly, through shielding gases (inert or semi-inert), or indirectly, using a welding agent, or flux. This protection prevents the hot metal from reacting to oxygen, nitrogen, carbon dioxide and water vapor in the air.

MIG welding

MIG (metal inert gas) welding, also called gas metal arc welding, uses a continuously fed, solid wire electrode that melts into the weld. An inert shielding gas, typically carbon dioxide (CO₂) or a blend of CO₂ and argon, protects the molten weld pool from the air. The gas flows from a separate container through the welder. MIG welding uses DC power more often than AC.

Flux-cored arc welding (FCAW)

Like MIG welding, flux-cored arc welding (FCAW) uses a continuous wire feed, but to protect the weld pool it uses a flux. The flux sits within the hollow electrode wire and reacts with the welding arc to generate the shielding gas. This shielding process makes FCAW appropriate for welding outdoors, where wind might otherwise interfere with the bonding process. FCAW uses DC as a power source.

TIG welding

TIG stands for tungsten inert gas welding. TIG welding and is also known as gas tungsten arc welding (GTAW). Like MIG welding, it uses an inert gas for shielding. The main difference between MIG and TIG is that TIG uses a non-consumable electrode. The tungsten acts as a torch that melts the metal or a filler material. TIG welding typically uses DC or AC/DC.

Stick welding

Stick welding, one of the most common arc welding techniques, is also called shielded metal arc welding, or SMAW. It uses a flux-coated electrode to form the weld. Stick welding is similar to FCAW in that the electricity passing through the electrode reacts with a flux compound to generate the shielding gas. Stick welding typically uses DC current.

Arc welding uses: Applications for each type of welder

Here is an overview of what kinds of projects and metals each welder can handle.

MIG welders: Benefits and uses

MIG is one the easiest welding processes to learn. That’s one reason a MIG welder is considered the best welder for home use. It produces fewer fumes, is affordable, requires less heat and is versatile.

A MIG welder is used for welding various metals and alloys, including steel, stainless steel and aluminum alloys. It can be used on metals ranging from extremely thin (starting at 24-gauge) to 1/2-inch thick. It provides better control on thinner metals.

Popular uses for MIG welders include general fabrication for maintenance and DIY work as well as automotive, farming and metal art applications.

Flux-cored arc welders (FCAW): Benefits and uses

If your next welding project involves both heavy materials and the possibility of working outdoors, consider a flux-cored arc welder. Popular uses include general fabrication, maintenance, DIY work and farming.

With the right filler metal and flux composition, this machine works well with carbon steel, stainless steel and low-alloy steels. If you’re weighing MIG vs. flux, know that non-ferrous metals such as aluminum, brass, gold and nickel will not work with flux-cored welding. But thanks to the flux, FCAW can be used on metals contaminated by dirt, rust or paint.

TIG welders: Benefits and uses

A TIG welder is useful in tight quarters because it doesn’t create smoke, fumes or sparks. It’s also a practical choice for applications that require a clean appearance.

TIG is appropriate for ferrous metals and non-ferrous metals such as aluminum. It creates high-quality, precision welds and is used in the automotive, aerospace, ship building and repair industries. Because it can operate at low amperages, it’s also used for welding extremely thin materials such as foils and lightweight metal sheets. Some consider it the best welder for aluminum, though MIG is also suitable for aluminum. The only metal TIG isn’t suitable for is cast iron.

TIG welding comes with a long learning curve. It takes practice to avoid overheating and cracking the metal being bonded. TIG also requires a constant current power source. AC should be used when welding aluminum, while DC is used for steel and stainless steel.

Stick welders: Benefits and uses

Because it relies on a flux-coated electrode, stick welding is a good choice when working on projects in unfavorable environments such as wind or rain. Portability and lower sensitivity to dirt or paint at the weld point makes stick welders a popular option for use in remote locations. They are practical only on steel, stainless steel and cast iron and have limitations with thinner metals.

Stick welding requires a higher skill level than the other types of welding. Electrode sticks can be only so long, and work must be stopped to replace them once they’re consumed. Stick welding is also slow and produces slag, or residue, that must be chipped away after welding is complete. Common applications include pipelines, farm machinery and underwater welding.

Materials: Matching the material to the welder

To choose the best welder, consider the material you need to weld. Here’s a snapshot of which welders are compatible with commonly used metals and alloys.

• Steel and stainless steel: MIG, FCAW, stick and DC-powered TIG welders
• Titanium: DC-powered TIG welders
• Magnesium alloy: AC-powered TIG welders
• Aluminum: MIG and AC-powered TIG welders
• Cast iron: FCAW and stick welders
• Copper and brass: DC-powered TIG welders

What size welder do I need?

The size or output of a welder is determined by voltage, amps and rated duty cycle.

Many welding machines run off 110 or 120 volts, the same as a low-power household outlet. Heavy-duty machines require 220 to 240 volts. Some machines are dual voltage.

Voltage and amps together will determine if you need to upgrade any circuits to use the welder you want. Look at a machine’s input amps (what it requires to operate) and not output amps (what the machine can generate). Some 110V machines can run off of a standard outlet, but some others can’t because they require 50 amps or more to run.

The last number to consider is duty cycle, which is typically listed on the front of the welder.

What is duty cycle?

Duty cycle is the percentage of time within a 10-minute timeframe that the machine can be safely operated at a given amperage. After that time the machine will reset to allow for a cooldown period.

For example, if a welder has a duty cycle of 60% and an amperage of 180, it will weld at that amperage continuously for six minutes and cool down for four minutes. Reducing the amperage increases duty cycle and vice versa. Keep in mind that thin metals require less amperage than thick metals.

Here’s a look at the duty cycles of different machines:

MIG: MIG welders generally have a duty cycle of 30% to 50%, so you can expect three to five minutes of continuous arc welding out of every 10 minutes.

Flux-cored: The duty cycle is generally about 40%, so you can expect three to four minutes of operation out of every 10 minutes.

TIG: Duty cycle on TIG machines varies considerably. With low amperage machines suitable for most applications (thinner metals and smaller parts), you can often achieve a duty cycle of 100%. To weld thicker metals such as pipe joints, you would want to use a TIG welder with a higher amperage, such as this dual voltage TIG welder.

Stick: Duty cycle on stick welders is generally less than 25%, so you’ll get only about 2.5 minutes of welding operation out of every 10 minutes.

Amps and metal thickness

Amps determine how thick a material the machine can handle. You need roughly 1 amp of power for every .001 inch of steel thickness.

Here is a general guide to the steel thickness that can be welded in a single pass:

• A 140-amp machine: up to about 1/4 inch
• A 180-amp machine: between 5/16 inch and 3/8 inch
• A 200-amp machine: between 3/8 inch and 7/16 inch
• A 250-amp machine: 1/2 inch

Stainless steel requires 10 to 15% less heat input, while aluminum requires about 25% more.

Welding safety tips

No matter what kind of machine you choose, these safety tips apply. Read the user’s manual and follow the manufacturer’s guidance on how and where welding equipment should be used. Wear the appropriate PPE. For welding units that require compressed gas, follow the supplier’s recommendations for safe transport and storage.

Good training is crucial to safe welding. United Rentals offers welding safety classes online in English and Spanish.

Recommended PPE for welding includes:
 

• Welding gloves
• A helmet with full eye protection
• Welder’s jacket to protect from heat/flame
• Welding pants (with no cuff)
• Welding respirator/dust mask to protect you from noxious gases
• Welding work boots that are flame and slip resistant
• Ear protection

Visit our online marketplace to browse our selection of welders and welding accessories.