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Thin titanium sheet is unforgiving, but the welder is rarely the only problem. You need stable DC TIG output, a clean gas system, reliable high-frequency starting, and enough shielding to protect both sides of the joint. A weld can look acceptable on the torch side while the back of the sheet has turned gray, blue, or chalky from oxidation.

For most fabrication work, the best choice is a dedicated DC TIG machine with adjustable pulse, a good foot pedal, pre-flow and post-flow controls, and a torch that can accept a large gas lens. In a purged setup, the machine does not need unusual titanium-specific functions. It needs consistent low-amperage control and an operator who can keep oxygen away from hot metal.

What to Look For in a TIG Welder

Choose a machine that can run DC electrode negative (DCEN), start with HF rather than scratch-start, and regulate amperage smoothly below 20 amps. Thin titanium sheet often calls for roughly 15 to 45 amps, depending on thickness, joint design, fit-up, and travel speed. A welder rated at 200 amps is useful, but its low-end behavior matters more than its maximum output.

Pulse control is valuable, though not mandatory. A starting range of 0.5 to 2 pulses per second, with peak current around 35 to 50 percent above background current, can reduce heat input. Keep the pulse controls simple at first; excessive pulsing can create uneven bead spacing and make arc length harder to manage.

Pre-flow and post-flow are essential. Use enough pre-flow to purge the torch and cup—often 0.5 to 1 second—and post-flow long enough to keep the tungsten and weld hot spot shielded as they cool. Around 6 to 12 seconds is a practical starting range for small sheet welds. A remote amperage control is also worth paying for because it lets you reduce current at the end of a weld without snapping the arc off.

Which Welder Type Makes Sense?

A compact DC inverter is usually the sensible buy. An AC/DC machine is worthwhile if you also weld aluminum or want more refined arc controls, but AC is not required for titanium. A low-cost machine is fine when the sheet is relatively thick, the work is occasional, and you are prepared to replace a basic torch, gas lens, or pedal. For repeatable aerospace-style seams, the cheapest package often becomes expensive after upgrades and wasted material.

Compare DC TIG welders with HF start and pulse by their minimum rated amperage, control range, and included accessories rather than advertised peak amps.

Building the Purged Setup

Use high-purity argon for torch shielding and a separate purge line for the back of the joint. A flow-through purge box or a custom chamber is better than simply flooding the room behind the sheet. Titanium absorbs oxygen, nitrogen, and hydrogen when hot, so the entire underside of the molten pool and the cooling weld must remain protected.

Begin with a slow purge, commonly 5 to 15 cubic feet per hour (CFH), depending on chamber volume and leaks. Excessive flow can create turbulence and pull room air into the enclosure. Add a diffuser or porous outlet so the purge gas moves gently. If the setup is critical, verify oxygen concentration with an oxygen analyzer; waiting for a fixed number of minutes is less reliable than measuring the actual atmosphere.

A trailing shield on the torch is still useful even with a back purge. Use a large cup and gas lens, and extend coverage behind the arc far enough to protect the cooling bead. Torch flow commonly falls in the 15 to 25 CFH range, but cup size, drafts, and nozzle design change the requirement. Keep the torch close and the arc length short—about 1/16 inch is a useful target for thin sheet.

For buying options, look at TIG gas lens kits with large cups and a long trailing shield. These are often a more useful upgrade than buying a higher-amperage power source.

Practical Starting Settings

For 0.020-inch titanium sheet, begin around 15 to 25 amps. For 0.040-inch sheet, 25 to 45 amps is a reasonable starting range. Use a sharp 1.5 or 2.4 mm tungsten, ground lengthwise to a consistent point, with a small truncated tip if preferred. Use DCEN, no filler for autogenous seams when fit-up allows, and add filler only when the joint requires it.

Do not use steel brushes, dirty files, or shop rags contaminated with oil. Degrease the titanium with a suitable solvent, then use dedicated stainless brushes or abrasive materials reserved for titanium. Handle cleaned parts with clean gloves. Even fingerprints can contribute to discoloration and porosity in a sensitive joint.

Make a short tack sequence, then inspect the tack welds before closing the seam. Keep the sheet tightly fitted; gaps force more heat and filler into the joint. Travel steadily and do not pause on the sheet edges. If the weld pool becomes wide, dull, or sluggish, stop and find the cause rather than continuing.

Common Failure Modes

Bright silver, straw, or very light gold can be acceptable depending on the application and procedure. Dark blue, gray, white, or powdery weld metal usually indicates inadequate shielding, contamination, excessive heat, or a trailing shield that is too short. Do not grind away severe discoloration and assume the weld is sound; oxidation can extend below the visible surface.

Porosity commonly comes from leaks, wet hoses, contaminated filler, poor purging, or turbulence caused by excessive gas flow. A wandering arc can result from a contaminated tungsten or magnetic effects near fixtures. Crater cracking often comes from ending the weld abruptly, so use downslope or reduce current manually while maintaining shielding.

For a dependable package, prioritize a stable 200-amp DC TIG welder with a quality torch and pedal over raw output. Add a water-cooled torch only when long welds or repeated production work make torch heat uncomfortable. For occasional thin-sheet repairs, an air-cooled torch is cheaper, simpler, and entirely adequate.