You're halfway through a bead and the torch goes dead. That interruption is your welder's thermal protection doing its job. TIG welder duty cycle explained in plain terms is simply how long you can weld before the machine needs to cool down.
Most brands rate that time over a 10-minute window, per the IEC 60974-1 standard. A 60% duty cycle at 200 amps means six minutes of welding and four minutes of rest. That number shapes how you plan a job, how long your machine lasts, and what you should buy next.
Quick Answer
TIG welder duty cycle explained simply: duty cycle is weld time out of 10 minutes. The rest is cooling. Ratings pair with an amperage. 40% at 250A is not 40% at 150A.
Lower the amps or shorten passes for longer weld time. Buy a bigger machine if you need more.
How Duty Cycle Actually Works
The 10-Minute Window
Every duty cycle rating assumes a 10-minute cycle. You weld for X minutes, then the machine rests. That cycle repeats continuously.
If the spec says 60% at 200A, you get six minutes of actual welding followed by four minutes of rest. This is not 60% of your whole day. It is every 10 minutes, over and over.
What "At Rated Amperage" Really Means
The amperage part matters just as much as the percentage. A rating of 60% at 200A only applies when you're welding at 200A. Drop to 150A and the duty cycle usually climbs.
Push to 220A and it falls fast. A machine rated 100% at 120A might only manage 30% at 200A. That's why so many owners feel cheated.
They buy a 200A welder, then discover it can't run 200A for long.
Why Percentages Mislead Beginners
Percentages look simple until you look closer. Ambient temperature, input voltage, cooling fan airflow, and even an undersized extension cord all change the real number. The duty cycle on the sticker is measured under controlled conditions.
Your workshop is probably dustier and warmer. If you're welding in a hot garage in July, assume your real duty cycle sits 10% to 20% below the label. Our research across current models shows that this gap is the number one cause of "my welder keeps tripping" complaints.
How to Calculate Your Real Duty Cycle
Step 1: Find Your Machine's Duty Cycle Chart
Most inverter TIG welders have a chart on the back panel or in the manual. It lists amperage values and matching duty cycle percentages. Don't eyeball it.
Get the actual chart for your model. If you're new to the process, start with the basic TIG process overview so the other terms make sense.
Step 2: Match Your Actual Amperage
Say you're welding at 150A. Your machine might be advertised as 60% at 200A. That doesn't mean you get 60% at 150A.
Check the row for 150A. It might show 100%, which means you can weld indefinitely at that setting. The sticker on the front is marketing.
The chart is truth.
Step 3: Time Your Weld Passes
Take a stopwatch and record how long each continuous weld actually lasts. Most hobby TIG beads are under two minutes. A long root pass on pipe might run three minutes.
That number becomes your "weld time per cycle."
Step 4: Factor In Ambient Temperature
Manufacturer specs usually assume a 40°C ambient temperature. If your shop is hotter, derate the duty cycle. A good rule of thumb is roughly 5% less duty cycle for every 5°C above 40°C.
If you're working in a 50°C shop, a 60% rating might be closer to 50%. Keep the machine out of direct sun and let the fan breathe.
What Good Looks Like
Here's a sample chart for a typical 200A inverter machine:
| Amperage | Rated Duty Cycle | Max Weld Time per 10 Minutes |
|---|---|---|
| 120A | 100% | 10 minutes |
| 150A | 80% | 8 minutes |
| 200A | 60% | 6 minutes |
| 250A | 35% | 3.5 minutes |
If your normal weld time stays under the max, you're safe. If it goes over, change something.
How to Calculate Your Weld Sequence
Measure Your Average Pass Length
Let's say you're laying 150mm beads at 180A. Each pass takes about 90 seconds. Your machine is rated 60% at 180A, so you have six minutes of weld time per 10-minute cycle.
That means you can run about four passes before you need a four-minute break.
Build In Your Cooling Time
Don't just stop and stare at the piece. Use the break productively. Grind the next joint.
Clean the filler rod. Check fit-up. Adjust the tungsten.
Start the next pass only when the math says you're back under the limit.
When to Rotate Between Two Workpieces
If you're fabricating multiple parts, work two pieces at once. Weld a pass on piece A. While it cools, fit up piece B.
Weld piece B. Then switch back. You still get the same amount of welding per 10 minutes, but the machine gets natural recovery time instead of sitting at max temperature.
The same logic applies to all the other welding processes. If you ever compare a MIG machine side by side, you'll see the same 10-minute window. Duty cycle is not a TIG-only rule.
Duty Cycle Benchmarks by Machine Type
| Machine Type | Typical Duty Cycle at Max Amps | Best For |
|---|---|---|
| Transformer-based TIG | 20% to 40% | Occasional shop use, light repairs |
| Inverter-based TIG, 110V input | 20% to 30% at max, 100% at low amps | Thin sheet metal, home use |
| Inverter-based TIG, 220V input | 40% to 60% at max | General fabrication, most serious hobbyists |
| Industrial 3-phase TIG | 100% at rated amperage | Production work, long multi-pass welds |
These are general ranges, not guarantees. Every model has its own chart. As of 2026, most entry-level inverters advertise 60% at 200A as their sweet spot.
Transformer machines get hot quicker because the internal components are bigger and less efficient. Inverter machines convert power more efficiently, which is why they dominate the market now.
Look at the chart, not the marketing number. A 20% rating at 200A might still be a great machine if you only weld at 100A.
Buying a TIG Welder? What Duty Cycle Ratings Really Tell You
20% Duty Cycle Machines
These give you about two minutes of weld time out of every 10. They're fine for tacking, thin material, and short beads. If you plan to weld long joints or thick flanges, skip them.
You'll spend more time waiting than welding.
40% Duty Cycle Machines
Four minutes out of 10 is a reasonable middle ground. Most home-shop projects fit inside that window. If you're weighing the MIG vs.
TIG tradeoffs before buying, a 40% TIG machine is acceptable for light steel and aluminum work.
60% to 100% Duty Cycle Machines
Six minutes or more out of 10 opens up real production work. A 100% duty cycle at your normal amperage means you never stop for the machine. You only stop to reposition, change filler, or switch pieces.
This is what you want for pipe welding, truck repairs, or anyone charging by the hour.
The Real Question
Don't ask "What's the max amperage?" Ask "What amperage will I actually run, and what duty cycle do I get there?" A 250A machine rated 20% at max might still give 100% at 120A. That's entirely fine for aluminum body panels and thin steel.
Mistakes to Avoid With Duty Cycle
Trusting the Sticker Without the Chart
The front of the machine says "200A." The chart says 35% at 200A. Those two numbers tell very different stories. Always check the chart.
Pushing Through Repeated Thermal Shutdowns
The thermal overload switch protects the machine. If it trips, something is too hot. Forcing it back on cause damage to the rectifier and the transformer.
If it trips twice in an hour, slow down and let it cool.
Forgetting That Thick Material Changes Everything
Heavy steel sucks heat out of the joint, but it also makes you run longer passes and higher amperage. Both push you closer to the duty cycle limit. If you're working thick plate, plan more breaks or lower your amps slightly.
Ignoring Ventilation
Duty cycle assumes decent airflow around the machine. If the welder is shoved into a corner or covered with a rag, the cooling fan does nothing. Keep the vents clear, especially on hot days.
How to Handle Long Welding Jobs Without Overheating
Lower the Amperage Where You Can
Dropping from 200A to 170A can turn a 35% duty cycle into 60% on some machines. The weld might be slightly slower, but you stop less. Often that's the faster total job.
Use Multiple Joints
Set up two identical parts. Weld a pass on one, then the other. This gives the machine recovery time while keeping your hands busy.
Production fabricators do this instinctively.
Add a Fan, But Keep It Safe
A portable fan pointed at the welder's cooling vents can help reduce thermal trips. Don't blow the arc or the shielding gas. Keep the fan behind the machine, aimed at the case.
Use Pulse Mode If You Have It
Pulse welding lowers the average current. A 180A peak with a low background current means less total heat in the machine. It's not a magic fix, but it can keep you under the trip point on a long seam.
Real Scenarios: What Duty Cycle Looks Like in Practice
Scenario A: Hobbyist on Thin Sheet Metal
You're welding 1.5mm steel at 110A. Your machine is rated 60% at 120A. Each weld is about 20 seconds.
You stop to reposition the clamps, brush the area, and check the fit. You'll never hit the limit. The duty cycle is effectively a non-issue.
Scenario B: Fabricator Running Long Root Passes
You're welding stainless pipe at 180A. Each root pass takes 90 seconds. At 60% duty cycle, you have six minutes of weld time.
After three passes, you're at four and a half minutes. The fourth pass plus setup pushes you over. The fix: alternate between two pipe joints so the welder cools before you return.
Scenario C: Mobile Welder on a Hot Summer Day
It's 38°C outside and the machine is in the back of a truck. Your 40% duty cycle rating becomes something closer to 30%. You lower the amperage to 160A and switch to shorter passes.
If you're doing a lot of aluminum work in heat, the aluminum welding methods are also affected, since AC output runs the machine harder.
FAQs About TIG Welder Duty Cycle
Is duty cycle the same for AC and DC?
No. AC TIG generally runs the inverter harder than DC. A machine may show 60% at 180A on DC and only 45% at 180A on AC.
Always check both columns in the chart. Many marketing pages only list DC, which makes the machine look better than it is.
Can I reset a thermal overload faster?
Only by cooling the machine down. Point a fan at the case, open the vents, and get it out of direct sunlight. Don't wrap wet towels around it.
That's an electrical shock hazard. The thermostat will reset when the internal components drop below the trip temperature.
Does pulse welding improve my duty cycle?
It can, because pulsing lowers the average amperage. The machine spends less time at full output. But peak amperage still counts.
If you're running a hot pulse with a high peak, you're still close to the limit. Check the chart rather than assume pulse saves you.
How long should I wait between weld passes?
Long enough to stay under your rated weld time. If the rating is 60%, you need at least four minutes of rest in every 10-minute window. Wait until the cooling fan slows down before starting the next pass.
In a warm shop, add an extra minute.
What is a good duty cycle for home use?
40% to 60% at your typical working amperage is plenty. That's four to six minutes of weld time per cycle. If you mostly do short tacks, 20% is workable.
If you fabricate all day, look for 100% at the amperage you actually use.
Final Recommendation / Decision Guide
Duty cycle is a budget, not a spec sheet trophy. Match it to the work you actually do. Short beads and light metal?
A 40% machine will serve you well. Long passes, thick steel, or production work? Buy 100% at your normal operating amperage.
If a machine keeps tripping, don't blame the welder. Lower the amps, shorten the passes, rotate between joints, and give the fan room to breathe. When you buy, read the chart instead of the front sticker.
That one habit will save you more frustration than any other piece of advice.
