TIG Welders: Amperage, AC/DC and Duty Cycle Explained for Buyers

Pick a TIG welder by the metals you weld and the thickness you need to join: DC-only machines handle steel and stainless, while AC/DC machines are needed for aluminum. Check amperage range, duty cycle, input power and foot pedal control, and learn safe practice with proper protective gear before striking an arc.

What TIG Welding Is Good At

TIG (GTAW) welding uses a non-consumable tungsten electrode and a shielding gas, usually argon, to create precise, clean welds on thin to medium material. It offers excellent control, which makes it popular for automotive work, bicycle frames, stainless fabrication, aluminum projects and artistic metalwork. It is slower and demands more skill than MIG or stick welding, so expect a learning curve.

AC/DC or DC Only?

This is the first big decision. DC TIG welds steel, stainless steel, and other ferrous metals well. AC output is needed for aluminum and magnesium because it cleans the oxide layer on the surface. If you plan to weld aluminum even occasionally, buy an AC/DC machine. If you weld only steel and stainless, a DC-only machine costs less and is simpler.

Amperage, Duty Cycle and Input Power

Amperage range tells you what thickness you can weld. As a very rough guide, welders typically need about one amp per thousandth of an inch of material for steel, so a 200 amp machine suits much of what a home shop will encounter. Check the minimum amps too, because low-end stability matters for thin sheet metal.

Duty cycle expresses how many minutes out of ten a machine can weld at a given amperage without overheating. A 60 percent duty cycle at 150 amps is more useful than the headline maximum amps at a low duty cycle. Look for duty cycle ratings at amperages you will actually use.

Input power is crucial. Many welders run on 120V or 240V, and some are dual-voltage. A 240V circuit gives more capacity, but you must have the correct outlet and breaker. Hire a licensed electrician if you need to install one, and follow the manual’s requirements.

Features Worth Having

• Foot pedal or finger remote: Lets you adjust amperage while welding, essential for good TIG technique.
• High-frequency start or lift arc: HF is smoother; lift-arc avoids interference with electronics.
• Pulse function: Helps control heat on thin material.
• AC balance and frequency: Fine-tunes aluminum welds.
• Gas solenoid and flow control: Ensures proper shielding.
• Torch type: Air-cooled torches suit lighter work; water-cooled suits long, high-amp welding.

Consider a machine bundled with a torch and pedal, or shop for a 200 amp AC/DC TIG welder if you want aluminum capability. For basic steel work, a DC TIG stick inverter welder may be enough.

Consumables and Safety Gear

Budget for argon gas and a regulator, tungsten electrodes, filler rods, gloves and an auto-darkening helmet. TIG gloves are thinner for dexterity but must protect from heat and UV. Wear long sleeves of natural, flame-resistant fabrics and closed leather shoes. Ensure ventilation and keep flammables away from the work area.

Welding has risks: arc flash, burns, fumes and electric shock. Follow the manufacturer’s instructions and consider training from a community college, a local welding supplier or an experienced welder. Store gas cylinders upright and secured, and never weld on containers that held flammable materials.

Preparation Matters

TIG is unforgiving of dirty metal. Clean steel with a dedicated stainless brush and a solvent, and remove oxide on aluminum right before welding. Good fit-up and consistent travel speed produce better results than any feature on the machine.

Shop Setup and Learning Path

A TIG setup needs more than the welder. Plan a clean bench with a good ground clamp, adequate ventilation or fume extraction, a fire extinguisher nearby and a place to store the gas cylinder securely. Stable lighting helps you see the puddle, and a comfortable stool or standing mat reduces fatigue. Keep a log of the settings that worked for different thicknesses.

Practice on scrap before real projects. Start with simple beads on flat steel, then try corner and tee joints, and only then move to aluminum or stainless. Many local welding classes and supply shops offer short courses, and some sellers include basic tutorial materials with their machines. Used machines can be good value, but check that the torch, pedal and regulator are included and in good condition, and that the seller can demonstrate that it works.

Warranty and support are worth comparing. TIG machines contain sensitive electronics, so look for coverage on the power source, and find out how and where repairs are handled. Reputable sellers publish clear manuals and wiring information, and an active user community can help with troubleshooting. Be wary of machines with vague specifications or missing safety certifications.

Frequently Asked Questions

Can I TIG weld aluminum with a DC machine?

Not properly. Aluminum needs AC output to break up the oxide layer, so an AC/DC machine is required.

Do I need a foot pedal?

It is highly recommended for control. Some machines offer a torch-mounted amperage control as an alternative.

Is TIG harder to learn than MIG?

Generally yes, since you coordinate torch, filler and pedal. With practice it produces very clean results.