TIG Welding is a manual welding process that requires the welder to use two hands to weld. What separates TIG welding from most other welding processes is the way the arc is created and how the filler metal is added! When TIG Welding one hand is used for holding the TIG torch that produces the arc and the other hand is to add the filler metal to the weld joint. Because two hands are required to weld; TIG welding is the most difficult of the processes to learn, but at the same time is the most versatile when it comes to different metals. This process is slow but when done right it produces the highest quality weld! TIG welding is mostly used for critical weld joints, welding metals other than common steel, and where precise, small welds are needed.

TIG welding requires three thing, heat, shielding, and filler metal. The heat is produced by electricity passing through the tungsten electrode by creating an arc to the metal. The shielding comes from a compressed bottle of gas that flows to the weld area to protect it from air. The filler metal is just a wire that is dipped by hand into the arc and melted. The way these three things come together is pretty simple. First the welder turns on the gas flow, many times by a valve on the TIG torch itself. The gas begins to flow and starts protecting the weld area from the air. The torch is held over the weld joint just far enough for the torch not to touch the metal. Then the welder presses a foot pedal and the TIG torches tungsten electrode starts an arc. Once the arc is started the two pieces of metal begin to melt by creating a puddle of metal. Once the puddle is established the welder with the other hand starts filling the joint by manually dipping a welding wire into the arc to fillthe joint. Ultimately this process creates a single piece of metal.

TIG Power Supplies

TIG welding power supplies are usually Stick welding power supplies. The main difference between SMAW welding power supply and TIG power supply are the bells and whistles TIG welding sometimes requires. A basic TIG torch can be added to a Stick welding power supply and it will weld fine. Both power supplies are constant amperage power supplies. Meaning they keep the amperage consistent and the heat settings are regulated in amperage. The voltage on these power supplies will vary depending on the length of the arc.

TIG power supplies many times come with a feature called a “high frequency start”. This eliminates the need to physical strike an arc. Once the TIG torch is activated the high frequency start feature will can literally create an arc across a one inch gap between the TIG torch and the metal! This is done by creating a brief moment of high voltage that has the pressure required to jump the distance. It is just like a Jacobs’s ladder used in science experiments. Once the arc is established the voltage drops and the amperage goes to what the machine is set at. This is very useful to keep the tungsten from getting contaminated and used up. The high frequency start feature helps the tungsten electrode live up to its designation as a non consumable electrode.

Some common feature for TIG welding power supplies are pre-flow and post-flow feature. The pre-flow feature gives the shielding gas a pre-flow time to shield the weld area before the arc is started. The post-flow feature keeps the gas flowing for a set time after the arc is stopped to keep the weld are protected until the weld cools.

Other features of TIG welding power supplies are frequency settings that help the characteristics of the welding arc. There are many ways to help the welding arc run smother. Some of the features do this by using frequency ranges and or pulses of electricity to achieve the desired arc type. The biggest benefits of these features are they give the arc a cleaning characteristic. These settings are not very commonly unless welding aluminum or magnesium.

How to Convert a Stick Welder into a TIG Welder

It is very common in the field to use a Stick welder to TIG weld pipe. This is what most big companies use to TIG weld carbon and stainless steel pipe. I think Stick welding power supplies do a better job then TIG welding power supplies when it comes to heavy wall pipe.

The actual conversion is very easy and only requires an air cooled TIG torch and a bottle of Argon. For most welding applications there will be three steps involved to start TIG welding:

•  First change the polarity to D/C Electrode (-) negative.
•  Second take a air cooled TIG torch and hook it up to the stinger or electrode holder.
•  Third take the gas supply hose and attach it to a regulator on a bottle of Argon.

That is all that needs to be done to convert a Stick Welder to a TIG welder!

TIG Welding Voltage Type and Welding Polarities

TIG welding just like Stick welding uses the same voltage types. The two Voltage types are:

•  D/C Direct Current like the current from a car battery that only flows in one direction. That is from the (-) negative side to the (+) positive side.
•  A/C Alternating Current like the current in your home. This current changes direction many times a second.

TIG welding just like when welding using Direct Current and they are:

Purging is a common term when it comes to TIG welding pipe. What purging does is replace the air in a pipe with a gas that will not react with the root of the weld. Purging prevents weld oxidation or in pipe welder slag “sugar”. When interviewing for pipe TIG welding jobs a common question asked is “How do you prevent sugar”? In other cases when welding, a box can be filled with Argon to weld in it. Argon is heavier then air so it will fill a box or shape just like water. Argon can also be dangerous when the proper ventilation is not used. If you are in a sealed room and you have a bottle of Argon leaking, it will fill the room from bottom up, just like water would. Unlike water you cannot see or smell it. Once the Argon fills the room you will be breathing and suffocating at the same time, while not even knowing it! Pretty scary! Typically Argon is used to TIG weld but since it is very expensive it is not used by itself to purge pipe. What most people use to purge a pipe is Nitrogenor Co2 gas.

Pipe Purging

Purging pipe typically requires the use of math. In some cases like in shipyards they have charts that say what pipe size, length, CFH (cubic feet an hour of gas flow) is needed, and the time required purging the pipe. The other way is the canary method. Simply put a canary into the pipe and when the bird kicks the bucket you can be sure the pipe is purged of oxygen. I strongly advise against that method!

How to Purge Pipe

Before purging the pipe the open area of the pipe need to be sealed off. That also includes the weld area. This is done by taping to area and when it is welded the tape is pulled away in small sections. Once the area is sealed off you need to put a vent hole at one end of the pipe opposite of the side you have a tube filling the pipe. The location of the vent hole will vary depending on if you are using Helium or Argon. If you are using an Argon based filler gas you will want the vent whole at the top of the pipe because Argon is heavier then the air. If you are using a Helium based filler gas you will want the vent whole at the bottom of the pipe because Helium is lighter then the air.

The best way to purge a pipe is to take the inside diameter and the length of the pipe in inches. Once you have those dimensions you simply figure out how many square cubic inches are needed to be filled, followed by converting them into cubic feet. This is done by taking the inside diameter multiplied by itself and then multiplying it by (.7854) then that answer is multiplied by the length. For example a pipe with an inside diameter of 6 inches would be done like this. 6 X 6 = 36, then 36 X .7854 = 28.2744, followed by multiplying that number by the length in inches. In simple terms the inside diameter of this pipe has 28.2744 cubic inches per inch of pipe. If the pipe is about 51 inches long you will have about 1442 cubic square inches of volume on the inside. This was done by multiplying 28.2744 X 51 inches of pipe length. One you have the cubic inches simply divide them into 1728. There are a 1728 cubic inches in a cubic foot. In this case a 1442 cubic square inches divided into 144 leaves you with about .83 cubic feet of volume. To purge the pipe with one air exchange you need to run the filler gas at 10 CFH for about 5 minutes. To speed it up simple run the filler gas at 50 CFH for 1 minutes. Since gas flow is measured by CFH (cubic feet per hour) all you have to do is time the flow rate to the cubic feet of filler gas needed.

This is the way I figure out how to purge a pipe. I have read a few books that say how to figure out the inside volume of a pipe and I just don’t get what they are saying. Why can’t they just keep it simply!

TIG Welding Machine Set-Up

When setting up a TIG welder there are two main settings. They are amperage and gas flow. Amperage settings vary depending on the type and thickness of the metal to be welded. Gas flow rates also vary depending on draft conditions, cup size, and sometimes the position of the weld. The gas flow rate could range from 5 CFH to 60 CFH for a large cup and drafty conditions. When choosing the gas to weld it is almost always assumed that you will be using pure Argon.

Some basic guidelines for machine set-up are as follows:

• 1/16 Tungsten – Require an amperage rage between 50 to 100 amps. The recommended cup sizes are 4, 5, or 6. Gas flow rate should be between 5 to 15 CFH.
• 3/32 Tungsten – Require an amperage rage between 80 to 130 amps. The recomendated cup sizes are 6, 7, or 8. Gas flow rate should be between 8 to 20 CFH.
• 1/8 Tungsten – Require an amperage rage between 90 to 250 amps. The recommended cup sizes are 6, 7, or 8. Gas flow rate should be between 8 to 25 CFH.

Tig Welding Steel

Tig welding steel is very easy. The polarity typically used is DCEN (direct current electrode negative), Argon gas, and Thorium Tungsten. For welding steel and stainless steel the Tungsten needs to be shaped to a fine point.

TIG Welding Stainless Steel

Stainless steel welds almost like steel. It does not take a lot of extra practice, uses the same type of tungsten, and Argon gas. The one exception is that welding stainless steel requires good gas coverage. Steel is forgiving when it comes to Argon coverage. Stainless steel sometimes requires the weld to be submerged in an Argon bath or if it is an open root weld the inside of the joint must be purged with a filler gas. One of the problems of welding stainless steel is it has a tendency to warp if too much heat is applied or the pieces welded are not braced properly! Distortion can be controlled by staggering the welds and bracing the weld area frequently. When stainless steel is TIG welded properly it will have a copper color to it. If you find the weld to be a gray or dark color that means either you are moving to slow or your heat is to hot.

When TIG welding stainless steel, joint preparation is extremely important!  The joint must be absolutely free of anything except clean stainless steel. If this is not done you will find the filler wire will not flow into the joint. When welding on a less then clean stainless steel joint you will find the filler wire won’t want to stick to many parts of the joint. To avoid this it is best to hit the joint with a sanding disk or a file. This is true on multi pass welds too. If you put in one bead and then need to put in a second pass you also need to clean that area again before welding.

TIG Welding Aluminum

When TIG Welding aluminum there are a few steps needed to setup for it. First is the tungsten! The tungsten needs to be either pure Tungsten or Zirconium Tungsten. The tungsten also needs a ball shape at the end of it to spread the heat properly. The second is the current type and that is aluminum always welds with A/C (alternating current). Welding aluminum always requires a high frequency start from either a high production button or a foot pedal operated TIG torch. The main difference when welding aluminum verses other metals is how the puddle looks. Aluminum just has a shiny puddle that does not glow. It looks like tinfoil moving. When welding aluminum overheating of the metal must be avoided. It’s real easy to keep welding and all of a sudden the whole weld area just drops to the floor.

TIG Welding Anodized Aluminum

• Gas flow rate is too low or too high. In the event of the gas flow rate being too high the turbulence caused by the high flow rate will pull in air into the mix.
• The wrong cup size is being used. Change cup to proper size.
• Check for a draft coming into the weld area. If this is the case put up a barrier to stop the draft.
• The filler rod is oily, dirty, or corroded. Try a new filler rod.
• The shielding gas is contaminated. Change the gas.
• The wrong gas is being used. In most cases pure Argon is the proper gas type.
• The cup or is not tight enough. Check all TIG torch parts for tightness.
• The hose lines may not be tightened or have a leak. Check connections for tightness or use soapy water to find any leaks.

Tungsten Deteriorating or Unstable Arc

Tungsten deteriorating or an unstable arc is typically due to the following causes:

• Gas flow is too low. Raise gas flow rate.
• Arc length to long. Shorten arc length.
• Wrong gas being used. Change the gas.
• Tungsten is contaminated. Break and reshape the tungsten.
• Tungsten contacted the puddle. Clean tungsten and shorten stick-out.
• Tungsten electrode diameter is too big or small. Replace tungsten with proper size.
• Wrong polarity. Change polarity or voltage type.
• Amperage is too low. Raise amperage.
• Ground clamp is not contacting properly. Clean ground connection.
• Weld metal is not cleaned properly. Grind or wire brush weld joint.
• TIG torch connection is loose. Tighten TIG torch connection at power supply.