A TIG welder is one of the most precise welding tools you can use for the job and is also capable of good brazing. A TIG welder can be used for both welding and brazing metalworking activities, provided the operator knows how to use it properly.
So how do you use a TIG welder to braze? Using a TIG welder to braze is similar to using a TIG welder for basic welding operations, except that you also perform these additional steps for a braze:
- Placing tack filler
- Pulse welder for control
- Avoid melting the base metal
TIG brazing may be a very useful brazing technique, but TIG welders are among the most difficult welders to use in the shop. Read on to find out more about TIG welders, brazing, and how you can use one to pull it off.
What Is Brazing?
Brazing and welding are similar metalworking techniques in that they both involve the use of filler metal to form a seam between two joined metal pieces. Still, they are different in one major way: welding involves fusing the filler metal with the base metal to synthesize the two while brazing patches filler metal between the two joined pieces like molten glue.
Both brazing and welding require the use of shielding gas, such as argon. Welding is suitable for metals with similar melting points, while brazing is primarily used to join dissimilar metals.
Luckily, both can be accomplished with a TIG welder, by far the most versatile of welding methods over stick and MIG welding.
Advantages and Disadvantages of TIG Brazing
TIG welders are among some of the most sophisticated pieces of equipment in metalworking and come with a load of benefits, but also have some drawbacks as well. Here are some of the advantages and disadvantages of brazing with a TIG welder:
- High quality, precise brazing jobs
- Aesthetically pleasing bead
- Works well on thinner metals
- Suitable for working on motorcycle frames or other automotive sheet metal
- TIG brazing/welding allows you to work on any metal that will conduct electricity, including more exotic metals such as titanium
- Difficult to control all three aspects of the process simultaneously (controlling gas shield flow, welder travel, and filler feed at the same time requires massive dexterity and focus)
- TIG welding and brazing is not forgiving of beginner mistakes and can lead to very ugly or unstable welds without practice
- TIG welding and brazing is a slower process that requires more skill to master than other forms of welding
While the quality advantages of working with a TIG welding torch are readily apparent, those metalworkers intending to use one for brazing will have to overcome a fairly steep learning curve to develop really good-looking, sturdy beads.
Fundamental Elements of Welding and Brazing
Welding and brazing share the same fundamental elements, which are all present in the setup of a TIG welder:
- Heat source: The heat source is what allows a filler wire to be melted for a TIG braze, and obviously, very high temperatures are used to melt metals such as tungsten and steel, so caution should always be used around a welding or brazing operation.
- Shielding gas: In most cases, a pure inert gas is used to shield the welder from oxidizing elements in the atmosphere. This is often pure argon, but an argon-helium mixture is sometimes used as well in certain welding scenarios.
- Welding torch: The welding torch is formed by the tungsten electrode, the collet body, the welding cup, the back cap, and o-ring. Many also incorporate a valve to increase flow control of the inert gas shield.
- Filler wire: The type of filler wire used will be determined by the specific brazing job being done. A common type of filler wire for TIG brazing is silicon bronze.
Anatomy of a TIG Welding Torch
To use a TIG welding torch for brazing, it helps to know a little bit about how a TIG welding torch is set up. Here are the basic parts of a TIG welding torch:
- Air-cooled torch: This is where you’ll heat the filler wire from.
- Tungsten electrode: The electrode protrudes from the end of the welding torch and is the point of heat contact for the filler wire (in brazing it is important to keep this heat off the base metal)
- Collet/collet body: This is the part of the TIG torch that holds the tungsten electrode in place, and also serves as a base for the welding cup to sit on.
- Welding cup: The welding cup is the cupped piece on the end of the welding torch that helps to keep the argon shielding gas contained around the weld pool; this helps reduce oxidation and contamination of the weld or braze operation.
Now that you know the parts of the TIG welding torch let’s put it together.
Assembling a TIG Welder for Brazing
There are several steps you need to undertake to assemble a TIG welding torch to begin a brazing operation. Here is the process of assembling a TIG welding torch:
- Put the tungsten in the collet. Be sure during this process not to over-tighten or strip the soft, fine copper alloy threads within the welding torch. It’s important to be gentle with your tools to increase their longevity.
- Place the back cap. Again, the welding torch will have fine copper alloy screw threads on the back cap, so do not over-tighten. Tightening by hand is fine; there is no need to bring tightening tools like pliers into this process.
- Lock in with the collet. Both the collet and back cap should fit snugly onto either end of the welding torch. Note that there is also an O-ring in the assembly to prevent shielding gas from escaping out the backside of the torch, and direct it into the welding cup instead.
- Install the welding cup. Thread the welding cup onto the welding torch’s front end until it seats into the insulator on the torch.
At this point, the TIG torch should be fully assembled and ready for use in a brazing operation.
How to Set Up the Shield
Along with the welding torch itself, there is some setup involved in the inert gas shield aspect of the TIG rig. Here are the steps necessary to get your gas shield ready for welding or brazing:
- Turn on the gas slowly (the ball in the flowmeter gauge can crack the tubing if the pressure is turned on too quickly).
- Set airflow between 15-20 cubic feet per hour.
- Set to 125 DC amps.
- Test the pedal to ensure that it’s working properly.
- Provide 7-8 seconds of inert gas post-flow. This is to protect red-hot tungsten while it is cooling down and avoid oxidation.
- Leave post-flow over material after the arc is out.
Problems Assembling a TIG Welder
There are a few common issues that metalworkers who are not familiar with a TIG setup often run into when assembling their TIG welder.
- Can’t keep tungsten tightened into the collet: This is typically the result of threading the back cap down without seating the tungsten electrode and collet in the torch first. It’s a widespread novice mistake, and welding instructors see it all the time.
This looseness cannot be solved by tightening down the back cap or welding cup, which is the first impulse of many novice metalworkers. It can only be fixed by loosening the back cap, properly seating the tungsten in the collet, and then re-tightening the back cap afterward.
- Can’t understand measurements on the welding cup: Welding cups come marked with a single whole number (for example, 9). This number signifies the width of the welding cup by sixteenths of an inch, so a welding cup marked “9” is 9/16ths of an inch in diameter.
How Far Should Tungsten Stick Out of the Welding Cup?
The reason the measurement marking on the welding cup is essential is that that measurement (ex. 9/16ths of an inch) is also the maximum length of tungsten you’ll want protruding from the end of your TIG torch.
This standard will give you maximum control over the torch while also increasing the quality of your resulting weld or braze.
What Kind of Tungsten to Use in a TIG Welder for Brazing?
Suitable tungsten to use in a TIG torch is a 3/32” tungsten, sharpened to a 30-degree point. This sharpened tungsten will give you the most reliable arc strikes with a low burn-off point so that your electrodes last longer.
This is a significant advantage considering that tungsten is relatively expensive to stock in the shop as a rare metal resource.
How to Hold a TIG Welder for Brazing
When brazing, it is important to remember that any welding or brazing is a forward process; for TIG welders, especially, you should always use a “push angle” rather than pull the tungsten through the weld pool.
With TIG welders, dragging the tungsten rather than pushing it makes the weld susceptible to the Venturi effect, and can increase the porosity of the joint. This leads to an ugly and unstable braze or weld.
Instead, the welder should push the TIG torch forward at a very slight angle (10-15 degrees vertical angle). Righthanded metalworkers should push from right to left, while lefthanded metalworkers should push from left to right.
To initiate the arc on the TIG welder, compress the foot pedal all the way. Some TIG torches may require a tap or scratch start to initiate the arc, but many do not.
Tips for a Successful TIG Braze
There are a few concepts you can learn to make brazing with a TIG torch more successful. Here are some of the key points to keep in mind:
- Consistent travel speed: The travel speed of the TIG torch is what determines the width of the bead. If you don’t keep the travel speed of the torch consistent, you will end up with welds and brazes that look inconsistent.
- Quicker speed: A faster travel speed equals a more narrow bead, and moving too fast with the torch may decrease the integrity of the weld because there is less filler spread overall along the seam.
- Slower speed: Moving the TIG torch at a slower speed increases the size of the heat-affected zone around the bead and can lead to discoloring as well as porosity issues with the seam itself.
For best results, you should move the TIG torch at a consistent speed that is neither too quick nor too slow. Determining the proper speed for a consistent weld or braze is best accomplished through experience, so practice beads on scrap metal until you get a feel for how quickly the TIG torch should be moving across the base metal.
TIG Brazing Problems and How to Solve Them
Metalworkers run into several common issues in learning how to properly operate a TIG welder for either welding or brazing operations. Here are some of the most commonly-found problems people run into:
Problem – The arc is too long
the torch is held too far from the weld pool, this means the weld pool will not
be directly under the tungsten, increasing the chance of oxidation and
atmospheric contamination. This causes unsightly hazing of the metal and porosity
Solution: To combat this, keep the arc no further than 1/8th of an inch from the surface of the base metal. This distance should be kept consistent throughout the travel of the TIG torch for the best results.
Problem – Too much angle on the torch
Holding the welding torch at too severe of an angle (higher than 10-15 degrees vertical) causes oxidation. It can cause the welding cup to drag in the seam, reducing the consistency of torch travel and, consequently, consistency of the braze.
Solution: Keep the TIG torch held at a consistent 10-15 degree angle vertical to the surface of the base metal.
Problem – Contaminated tungsten
The tungsten is contaminated from being dipped into the weld pool or by direct contact with the filler wire.
Solution: Stop the braze in process, then re-sharpen, and clean the tungsten at a grinding bench before continuing operations. Do not attempt to weld or braze with contaminated tungsten to avoid quality problems with the result.
How to Add Filler Wire During a TIG Braze
One step in the metal-joining process that brazing shares with welding are the addition of filler metal (of various compositions) that is held to the weld pool to form a seam between two separate metal pieces.
In brazing, this filler material lays on top of the two pieces of base metal and acts as an adhesive force, rather than fusing with the base metals completely.
There are a few techniques for adding filler wire to a TIG braze properly. Follow this procedure to get the most out of your TIG brazing operation:
- Introduce filler wire on the leading edge of the weld pool. Each contact of the wire in the weld pool leaves a rounded mark in the weld or braze, and the end effect of this look is called “stacking dimes.” For a good-looking weld or braze, these contact marks should be consistent in size and spacing.
- Do not melt the filler wire with the arc and let it fall onto the base metal. Not only does this dramatically reduce control over the braze, but it also increases the likelihood of random drips of molten metal getting left willy-nilly around the seam, which looks terrible and is a waste of filler.
- Put on tacks at the corners. To quickly link two pieces of metal (such as in a fillet weld/braze), you can “tack” little bits of filler into the corners to join the two pieces of metal before continuing the seam. This keeps the two pieces steady enough that you can work without having to hold them yourself and keeps the job straight.
- Leave the filler wire in the weld pool. Some welding techniques require the filler wire to be dabbed into the front of the weld puddle, but for a solid braze, you want to use a lay wire technique and leave the wire always on the front edge of the weld pool.
- Avoid melting the base metal. The reason you want to use extra filler wire in a braze is and not dab it is because you are trying to avoid contact between the welding torch and the base metal. Ideally, the heat of the torch should be only affecting the filler metal and not the base.
- Use pulse functionality on your TIG welder for precision. Two pulses per second allow a high degree of control, and the pulse action of the torch helps to keep the weld pool cooler. This reduces overheating through to the base metal.
- Add the right amount of filler wire. Whatever diameter of wire you’re using, that’s roughly the amount of filler wire you should be pushing into the weld pool at any given time. Using more will lead to a bulky looking seam, and using less poses the risk of the TIG torch burning through the filler and into the base.
TIG Brazing is Complicated but Rewarding
Compared to some other types of welding and brazing, using a TIG torch is a little bit more complicated, and can prove daunting to novice metalworkers. It does take lots of practice and experience to do it consistently and correctly every time.
However, a TIG torch is one of the most versatile welding tools in a metal shop, and it is worth it to take the time to learn how to use one to be able to perform a wide array of precise welding and brazing jobs.