TIG Welding 101: Everything you Need to Know

By Jayden Mark

When it comes production work, construction and high grade components, TIG welding is the standard method for welding together components. What is TIG welding, how does it work, and what makes it good at these tasks?

What is TIG Welding?

Tungsten Inert Gas (TIG) welding, also called gas tungsten arc welding (GTAW) or Heliarc welding, was originally invented to weld together magnesium parts used in aircraft.

In TIG welding, an arc of electricity between a tungsten electrode and the metal generates heat, while filler wire is fed into this hot area by hand to form a welding pool. The welding gun sprays the area with an inert gas, protecting the weld pool and electrode from oxygen contamination. The resulting weld is slag free and has the same corrosion resistance as the surrounding metal.

What is a TIG Welder?

A TIG welder is similar to a stick welder. Both welding machines use the same type of power supply, and some stick welding machines can be set up for TIG welding. The welder only controls the amperage, while voltage varies depending on the length of the welding arc.

Using a regular welding amperage, the electrode must come in direct contact with the metal to start the arc. However, most TIG welders made today have a high frequency start mode. This creates a high amperage pulse when the electrode comes close to metal, starting the arc without requiring direct contact. This makes it easier to start the arc, and reduces wear on the electrode.

Like MIG welders, TIG welders spray the area around the electrode with an inert gas to prevent oxygen contamination. To reduce contamination further, TIG welders have pre-flow and post-flow modes. These flow the shielding gas before the arc strikes and after it stops to shield the weld pool as it forms and as it cools.

TIG welding can use an AC, DC negative or DC positive connection. DC negative welding concentrates the heat on the metal, resulting in a deep weld. DC positive welding concentrates the heat on the electrode, creating a shallow weld that works well on thin metals and is better at self cleaning. AC current welds in short bursts, reducing the heat around the weld. The change in polarity also helps with self cleaning of the weld pool. The welding happens during negative current flow, while positive flow cleans the weld. The machine can vary the pulses, letting the user choose between faster welding or more cleaning. Most AC welding is done at 65-70% negative current. AC current is used to make clean welds on aluminum and magnesium.

Electrodes

Electrodes come in three main formulas: Pure tungsten, zirconium tungsten and thoriated tungsten.

Pure tungsten goes under the American Welding Society (AWS) classification EWP. Zirconium tungsten (AWS EWLa-1) electrodes are available in blends containing 0.25 to 0.5% zirconium oxide. The zirconium helps them maintain a ball tip, and reduces contamination and splitting. Pure tungsten and zirconium tungsten electrodes are used for AC welding on magnesium and aluminum.

Thoriated tungsten typically uses electrode negative electricity. Adding thorium oxide helps the electrode flow more current at low temperatures for easier arc starting. This electrode is compatible with most metals, aside from aluminum and magnesium. This includes carbon steel, stainless steel, chromium alloy and nickel. AWS EWTh-1 electrodes contain 1% thorium oxide, while EWTh-2 electrodes contains 2% thorium oxide.

Electrodes come in widths from 0.04 inches up to ¼ inch. Larger electrodes can handle more amperage, making them suitable for welding thick metal.

Shaping Electrodes

Electrodes come with a square cut end. Grinding or melting the tip into different shapes changes how they weld.

Pointed tips are used to weld ferrous metals with DC negative current. This concentrates the heat on the metal next to the electrode. Electrodes can be ground to a point with a grinding wheel or a tungsten sharpener. Tungsten sharpeners work like pencil sharpeners, shaving off the end with a series of angled blades.

Rounded and tapered ball electrodes are used on non-ferrous metals, including aluminum and magnesium. The rounded tip spreads out the heat for better control of metal temperatures. Rounded tips are used with alternating current. The tip is formed by setting the generator to DC electrode positive and shutting off the shielding gas. Welding on a piece of copper or other clean metal concentrates heat on the electrode, melting it. This rounds off the corners. From there, the generator can be switched to AC mode and the shielding gas turned on to weld metal.

Shielding Gas and TIG Cups

TIG welding is sometimes called Heliarc welding because the process originally used helium as the shielding gas. Today, most welding jobs use argon as the main shielding gas. Adding other gases improves different characteristics of the weld:

Helium increases penetration and makes the weld pool flow faster.
Oxygen and carbon dioxide help keep the arc stable.
Hydrogen offers similar characteristics to helium, but it only works with a few metals. It’s usually found in blends used for stainless steel welding.
Nitrogen is added to gas used on nitrogen-containing alloys to create stronger weld deposits.

The TIG cup surrounds the electrode, directing shielding gas around the weld. Cups are numbered based on 1/16 inch measurements. For example, a #5 cup has a 5/16 inch opening. Cup size should match the electrode size. A 1/6 inch tungsten tip needs a #4-6 cup, while most larger tips need a #6-8 cup. Bigger cups are needed for applications that require large amounts of shielding gas, including drafty work areas.

Filler Wire

TIG welding uses the same type of wire as MIG welding. This wire is usually sold in 36 inch segments. These wires use a standard code to indicate their characteristics, starting with “ER” for “electrode wire.” Different codes are used for different types of wires.

Carbon Steel:

A number indicating the minimum tensile strength in thousands of pounds.
The type of wire. “S” is solid wire, while “T” is flux core. Flux core is not used in TIG welding.
A number indicating the amount of deoxidizing and cleaning agents in the wire.

For example, let’s say you have some ER70S6 wire. This is electrode wire with tensile strength of 70,000 lbs, a solid core, and a large amount of deoxidizing and cleaning agents.

Stainless Steel:

Three numbers indicating the steel grade
“L” for low carbon electrode

ER309L is the most common stainless steel wire. It works on both stainless steel and carbon steel.

Aluminum:

The wire series, indicated with one digit
The amount of silicone in the wire, indicated with three digits

ER4043 is made for 4000 series aluminum.

While you can use MIG wire off of a spool, it’s safer to use TIG wire for welding jobs. The wire may be identical, but TIG wire has the code stamped into each wire segment, so you can’t mix it up. Weld with the wrong wire, and you can ruin the piece you’re working on. TIG filler wire is available in thicknesses from 1/16 to 3/16 inches.

Preparing Pieces for TIG Welding

TIG welding can produce high quality welds, but only on pieces that are clean. Surfaces need to be ground down or wiped down with cleaners to remove anything on top of the metal, including oils, paint, oxidation and rust.

To get the best results when TIG welding, all surfaces need to be shielded from oxygen. Otherwise, the weld will produce fine slag called “sugar” on the side opposite of the weld. Flat pieces can be placed in a bath of argon. Since argon is heavier than air, it stays in the confines of the work container, shielding all sides of the metal being welded. Pipes are purged by pumping them full of an inert gas.

Purging Pipes

Purging pumps helium, argon, nitrogen or carbon dioxide into the pipe at a rate that is fast enough to displace oxygen and prevents air from leaking inside.

This process starts by taping over any holes or gaps in the pipe, including the area to be welded. Two holes are made in the tape. One hole is for the shielding gas hose, while the other hose lets the gas pass out of the pipe. When using heavier than air gasses, the hose goes at the bottom of the piece and the vent hole at the top to trap the gas. With lighter than air gasses, the hose is the top and the vent hole at the bottom.

The amount of gas needed varies depending on the flow rate of the gas, the pipe size and the thickness of the metal. There are charts with pre-calculated estimates, as well as formulas that can be used to calculate the gas needed. You can also use an oxygen monitoring tool, which uses a probe to measure how much oxygen is inside the pipe.

Once the pipe is filled with shielding gas, it can be welded. The tape over the welding area is slowly peeled back during the weld to minimize gas loss.

Setting up a TIG Welder

TIG welders have two main settings: amperage and gas flow rate. Like other types of welding, increasing amperage adds more heat, helping the electrode penetrate thick metal. Larger electrodes need more power. Typically, a 1/6 inch tungsten electrode uses 50-100 amps, while a 1/8 inch electrode needs 100 to 250 amps.

Gas flow rate varies depending on the cup size and amount of draft in the area. More gas is needed to keep the weld covered in windy conditions. This can be anywhere from a few Cubic Feet per Hour (CFH) to 50-60 CFH. Most jobs fall in the 10-25 CFH range.

Welding Technique

All TIG welding uses the same basic technique, with most of the changes revolving around the wire, current flow and gas used. The torch determines penetration, while the movement of the rod controls the flow. That means the angle and movement of the electrode doesn’t matter as much as other types of welding. That said, there are some unique challenges with different types of metal:

Welding most types of steel is straight forward, except stainless steel. It needs more shielding gas, and it’s prone to warping.
Melted aluminum doesn’t look much different from solid aluminum. This makes it easy to overheat, blowing through the metal and leaving holes.
Anodizing is hard to weld through. However, it’s possible to get a clean weld by making two passes. The first pass melts the filler rod, while the second pass uses “bump” welding. This uses the electrode to reheat the filler and anodizing, forming a smoother surface.
Copper nickel alloys flow faster than steel when melted, but it’s difficult to get good penetration.
Titanium must be fully shielded to weld, requiring the use of an argon bath.

TIG welding can bond dissimilar metals. Generally, this uses the methods that work for the metal that is the most difficult to weld. For example, if you’re welding stainless steel to carbon steel, you would need to use a stainless steel-compatible electrode and gas.

What to Look for When Buying a TIG Welder

The cheapest welders are DC only, so they only weld carbon steel or stainless steel. They have a set preflow and post flow, which should fit most ferrous metal welding. You also won’t find high frequency starting on these models. These models can often be set up for both TIG and stick welding.

Professional models can generate both AC and DC power. All aspects can be altered to fit the job, including pre-flow, post-flow, gas flow rate, amperage and polarity.

There are TIG welders designed to run on either 120 or 240 volts, and some can run on both voltages. Machines using 120 volts can’t weld anything more than 1/8 inch thick. Keep in mind that peak amperage on a 120 volt welder can only be reached with a 20 amp socket. These sockets always have one T-shaped hole. Standard household outlets, which have two slot-shaped holes, top out at 15 amps. If you want to use a TIG welder at full power in your shop or garage, you need to add a full 20 amp circuit, including a circuit breaker, wiring and outlet.

Foot pedals offer the most precise amperage control, while using the trigger on the torch will send a set amount of current through the metal and electrode. Rocker foot pedals offer the most precise control. Professional models use the trigger to activate different modes, including high frequency starts and steady current.

Digital models offer functions that make it easier to do difficult weld jobs. Pulse mode varies amperage automatically, which helps with self cleaning and helps prevent warping on thin metal. These welders also save your preferred settings, making it easy to switch between metals.

Professional welders usually come with a torch that has a bendable tip. This makes it easier to get the electrode into tight spaces.

Welders have a duty cycle, which is how long you can weld before it overheats. For example, a machine with a 50% duty cycle can weld for 5 minutes out of every 10. The other five minutes are needed for cooling. Real world performance may be lower or higher. For most hobbyist uses, duty cycle isn’t a problem, because projects are small, and frequent repositioning is required. For production, a high duty cycle is useful because adjustments are minimal once you have your piece set up in a jig.

TIG torches can be air or water cooled. Air cooled torches are cheaper, but the handle can heat up after a few minutes of welding. Water cooled torches transfer heat out of the torch using coolant, so they can be held for hours during long welding jobs.

What are the Advantages of TIG Welding?

TIG welding is compatible with almost every metal and alloy in use today.
The electrode and gun are thin, letting them get in areas that can’t be reached with other welding techniques.
This type of welding has low amperage requirements, so it won’t blow through thin sheets of metal.
Amperage can be changed during the weld with a thumb or foot controller, while separating the electrode and wire allows fine control of the weld pool. This makes TIG welding ideal for curves and intricate designs, as well as transitioning between thin and thick components.

What are the Disadvantages of TIG Welding?

The space between the arc and the base metal is small, and it can be difficult to coordinate the wire and electrode while controlling amperage. This makes TIG welding one of the most difficult types of welding to learn.
TIG welding requires both hands, so the pieces being joined together must be held in place by a jig. Hand feeding also takes more time than the automatic wire feed used in MIG welding. If other methods will work for the job, they’re usually easier and faster than TIG welding.
TIG welding requires a blanket of inert gas to prevent slag formation. This makes it a poor choice for outdoor work, where wind can make it difficult to maintain gas coverage.
Because it requires clean surfaces, it’s not a good choice for welding used, painted or corroded parts.

Where is TIG welding Used?

Aerospace - Welds on planes and spacecraft need to be strong and precise, making TIG welding an ideal choice. These craft frequently use nonferous metals, particularly aluminum and titanium, that are easier to bond usin
Automotive - TIG welding creates corrosion-resistant welds, which are desirable on areas that experience salt corrosion, particularly the fenders and frame.
Art - While MIG welding is popular for its low learning curve, artists often prefer TIG welding for its cleaner, slag-free lines.
Structural Welding - Since TIG welding works with a range of metals and can penetrate thick pieces, it’s an ideal process for fusing structural components, including those made from aluminum and stainless steel.
Pipe Welding - Welders frequently need to join pipes made of different materials together. They also need a welding method that gets good penetration on thick pipes.
Fabrication - TIG welding works with all kinds of metals, and can even join dissimilar metals. This makes TIG welding the most popular fusing method next to MIG welding in fabrication shops. TIG welding is also popular with race car builders, since they frequently deal with aluminum and exotic materials.

Jayden Mark

Jayden Mark has gained a wealth of knowledge about safety protocols in industries while working in a steel mill as well as a welder in the construction industry. He is the content editor for comfortworkboots.com where he shares his insights and expertize in his related field.