BISMILLAH TECHNICAL TRAINING CENTER

What is TIG Welding?

TIG Welding is a manual welding process that requires the welder to use two hands to weld. What seperates 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 Names

Knowing alternative names and abbreviations for TIG welding is important for anyone who is interested in getting a job as a TIG welder. Many companies may use alternative names when placing ads in the classifieds. Sometimes they may use alternative name on a written test to test your knowledge of the welding process. Besides that the alternative name means something to the process. As of today TIG welding is the slang term that is widely accepted and used. TIG stands for Tungsten Inert Gas Welding.

TIG welding's proper name is Gas Tungsten Arc Welding or "GTAW". This is the name the American Welding Society and other welding organizations refer to this process on their welding procedures. GTAW is also the abbreviation that welding engineers use to specify the welding process that is to be used on blue prints. On top of that; when working on high pressure piping you could get sent home for a few days for not using proper terminology!

When TIG welding was introduced around the 1940’s Helium gas was the primary shielding gas used in process. The term Heliarc welding was the common phrase used back in the day and now is a registered trademark “GENUINE HELIARC”, from what I know, it now owned by ESAB welding equipment! Why would this matter when you are job hunting or working in a shop? Most old timers and veteran welder’s refer to TIG welding as Heliarc welding. I learned this very early on when I started to weld. I did not know Heliarc was also TIG welding! I thought when I went to welding school TIG welding was a new process I was going to learn. Wrong! Just like my former boss called the refrigerator the “ice box”, they are both the same thing. When someone reefers to TIG welding as heliarc, it’s pretty safe to assume either they have a lot of experience, or apprenticed under a journeyman welder who has been around.

Why Use Tungsten to Weld

Since the name includes the term “Tungsten” and tungsten is what makes TIG welding possible, it is good to know what tungsten is! Tungsten is a very hard, slightly radioactive, and brittle metal. Its uses are limited compared to other metals. In TIG welding the tungsten is made into a non consumable electrode that is used to create the arc for TIG welding. Typical other uses for tungsten are in light bulbs, heating elements, and rocket engines. Basically any place that requires a very high melting point or the need to pass electricity at a high temperature is needed. In the case of TIG welding the tungsten metal properties allows an arc to maintain a temperature up to 11,000 degrees fahrenheit. A high melting point and excellent electrical conductivity keeps the tungsten electrode from burning up! The unique properties of tungsten allow welding with a hotter arc then the actual melting point of the tungsten. The tensile strength of tungsten is an extremely high up to 500,000 lbs per square inch! Comparing it to commonly used steel with 36,000 lbs of tensile strength per square inch, tungsten is very strong! Although the metal is very strong it is also brittle! It is not hard to break a tungsten electrode with just a tap of a hammer.

How TIG Welding Works

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 fill the 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 perflow and postflow feature. The preflow feature gives the shielding gas a pre flow time to shield the weld area before the arc is started. The postflow 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 Stick welding uses two polarity types when welding using Direct Current and they are:

• D/C Direct Current Electrode (-) Negative. This means the electrode or welding handle is the negative side of the circuit and the electricity flows from the TIG torch to the metal.
• D/C Direct Current Electrode (+) Positive. This means that the electrode or welding handle is the positive side of the circuit and the electricity flows from the metal to the TIG torch.

The difference the polarity makes has to do with how much heat is applied to the electrode. D/C electrode (-) negative concentrates about 2/3 of the heat onto the metal welded. This produces a deep penetration weld. D/C electrode (+) positive concentrates about 2/3 of the heat onto the electrode. This produces a shallow weld that is more suitable for sheet metal and at the same time gives the arc characteristics a cleansing action. To better understand the flow of D/C current you need to think of it in terms of water flowing. If you take a pitcher of water and pour it into a glass, the glass receiving the water gets most of the friction. So in this case the pitcher is the (-) negative side (loosing water) and the glass is the (+) positive side (gaining water). Basically the side is gaining water is the side with the most friction. In comparison to welding, this is the side most of the heat is concentrated on. That's exactly how D/C power works!

TIG Torch Types

When it comes to TIG welding there are two options for choosing a TIG tourch! The first is an air cooled torch which is the least expensive and most practical. The down side is the air cooled TIG torch is it heats up quite a bit and much of the heat the arc produces is wasted. I literally am able to weld ten minutes with an air cooled torch before the handle gets too hot to hold! The second is a water cooled torch. This is the most efficient type of torch but it requires a water cooler and additional maintenance. Much like maintaining a radiator of a car.

Remote Start vs. Manual Start

Once a TIG torch is chosen there are two options on how to start the arc, manual start vs. remote start. First there is the simple way of manually starting the arc. Just like a Stick welding once the TIG welding machine is turned on, so is TIG torch. The arc is started by manually striking the metal with the tungsten. The second option is remote start. Remote start features come in two different forms. The first being a switch that is on the torch and the second is foot pedal operated.

Hand operated remote starts are very simple. All they are is a button that is taped onto the TIG torch that is simply pressed with a finger once you are ready to start to weld. What happens is the hand operated remote start cable is connected to the TIG welding power supply and it activates the high frequency start feature. It makes starting the arc easier and keeps the tungsten from getting contaminated.

Foot operated or foot pedal remote starts are a bit more complicated. They control the high frequency start and at the same time control the amperage. Just like the gas pedal in your car, the further down you push the more power you get. Foot operated remote starts are mostly suited for shop work where the welder is able to sit. It is very difficult to weld standing with a foot pedal remote start. The upside to a foot pedal remote start is you have full control over the heat that you are welding with.

TIG Welding Shielding Gasses

Shielding gasses for TIG welding are used to protect the weld area from any air that will contaminate the weld. The two most commonly used gasses to TIG weld are:

Argon / Ar (typically used) Helium / He

Since Argon and Helium are Nobel inert gasses they do not change the characteristics of the weld joint. What you weld with, is what you get. In some rare cases there are three types of mixture used. The first is Argon and hydrogen and the second is Argon and Nitrogen. The third mixture is Argon and Helium and that is typically used on thicker metals to get deeper weld penetration. In most cases pure Argon will cover almost all welding needs.

Tungsten Electrode Types

As the name states “Tungsten Inert Gas Welding” tungsten is the main ingredient in the electrode. What changes is there are very small percentages of other metals added to help create the desired arc characteristics. The common metals added to Tungsten are Cerium, Lanthanum, and Zirconium. In the real world the following Tungsten mixtures are the most widely used:

• Pure Tungsten, EWP
• 1/4 % to 1/2% Zirconium Tungsten, EWLa-1
• 1% Thorium Tungsten, EWPTh-1
• 2% Thorium Tungsten, EWPTh-2

Pure Tungsten is used with A/C alternating current for welding aluminum and magnesium only. It comes with a green colored tip with an AWS (American Welding Society) classification code of “EWP” on the package.

Zirconium Tungsten has similar properties to pure Tungsten. Zirconium Tungsten comes in a mixture form ranging from ¼% Zirconium Oxide up to 1/2% Zirconium Oxide and the rest is Tungsten. It is typically used with A/C alternating current for welding of aluminum and magnesium. It comes with a brown colored tip and an AWS classification of EWLa-1 on the package.

Thoriated Tungsten is typically used with direct current and the polarity is (DCEN) electrode negative. The added Thorium Oxide helps the electrode carry more current at a lower tempeture while making arc starting a bit easier. Thoriated Tungsten is used for welding most metals besides aluminum and magnesium. Some of the metals it works well on are carbon steel, stainless steel, chromium alloys, nickel, and most other ferrous metals. The percentages of Thorium Oxide added typically range from 1% to 2%. 1% Thoriated Tungsten comes with a yellow colored tip and has an AWS classification of EWTh-1 on the package. 2% Thoriated Tungsten comes with a red collored tip and has an AWS classification of EWTh-2 on the package.

Tungsten Electrode Diameters

As with all electrodes there are choices in electrode diameters. With TIG welding the electrode size is not the most critical component of the process. As long as the electrode used stays within it amperage rating. What matters the most is the shape of the tip and that determines the arc characteristics. For most uses any size between 1/16 to 1/8 of an inch electrode diameter will do. The more common sizes on the market are:

• .04
• 1/16
• 3/32
• 1/8
• 5/32
• 3/16
• 1/4

Shaping Tungsten Electrodes

Since Tungsten comes in a rod form with a square cut end it needs to be shaped. Some of the tip shapes used in these electrodes are pointed, rounded, and tapered with a ball end.

Pointed Tungsten Electrodes

A pointed tip is typically used in welding ferrous metals like steel. The current used is DCEN (direct current electrode negative). What this does is allow the current to flow from the electrode to the metal. This allows the electrode to concentrate the arc tempeture onto the metal. The pointed tip in this case will keep its shape by maintaining a higher arc tempeture then the electrodes melting point. If the polarity were reversed the tungsten would likely start melting. Shaping of a pointed electrode is typically done on a grinding wheel or Tungsten electrode sharpener. When using a grinding wheel it is best to use a fine grit wheel that is only to be used for sharpening Tungsten electrodes. There is a down side to using a grinding wheel. Since Tungsten is slightly radioactive you really do not want to inhale any of the particles! To sharpen the electrode point it upward while slowly and lightly rolling it on the grinding wheel between your fingers to obtain a round point. Oh yeah, don’t wear gloves while doing this! The last thing you need is a glove to be pulled into the grinding wheel! If you have a Tungsten electrode sharpener it is much like a pencil sharpener. Much easier and safer!

Rounded and Tapered Ball End Tungsten Electrodes

Rounded or tapered ball end electrodes typically used for welding non-ferrous metals like aluminum and magnesium. The current used to weld these metals is A/C (alternating current). The rounded or tapered ball ended electrode helps by spreading the arc over a wider area of the electrode. To get a round or ball shaped end to an electrode, this it is done using DCEP (direct current electrode positive). To get this shape the Argon gas should be turned on and if possible start an arc on a piece of copper. What will happen is the tungsten will begin to melt once the amperage is high enough and then start to create a droplet at the end of the electrode. Once you get the proper size ball at the end of the electrode, stop the arc. After the shape is obtained turn the power supply back to A/C. In the case a piece of copper is not available simple use the cleanest piece of metal you can find to the job.

In some other cases a rounded or tapered ball end electrodes can be used for welding sheet metals with DCEP (direct current electrode positive). What this does is concentrate 2/3 of the heat on the tungsten electrode and prevent blowing holes in the sheet metal. The one thing to avoid when TIG welding with DCEP is too much current. Otherwise the tungsten will burn up!

TIG Cup Sizes

Cup sizes come with a standard coding system. The coding system is pretty simple! For example a # 5 cup is 5/16 of an inch or a #9 cup is 9/16 of an inch size. The number used on the cup is like X/16. Whatever numbers used on the cup size always assume it the first number of an inch broken down into 16’ths of an inch.

Filler Wire Designation

Just like any other welding process the filler wire for TIG welding has a designation coding system. Since TIG welding does not use any flux, the designations are pretty simple. In most cases you can use MIG welding wire. The only difference between MIG welding wire and TIG welding wire is the way they are packaged. Typically TIG welding wire comes in 36” lengths. A common welding wire for mild steel is ER70S-2. The designation code is as follows:

• ER- An electrode or filler rod that is used in either a wire feed or TIG welding.
• 70- A minimum of 70,000 pounds of tensile strength per square inch of weld.
• S -Solid wire.
• 2- The amount of deoxidizing agent and cleansing agent on the electrode.

TIG welding wires come in many sizes and these are the more common diameters:

• 1/16
• 3/32
• 1/8
• 5/32
• 3/16

Joint Set-Up

Joint set-up is extremely critical when it comes to TIG welding. There cannot be any rust, oxidation, mill scale, paint, oil, or anything that does not belong there except for the bare metal. All joints must be cleaned with a grinder or in the case of some metals like aluminum a chemical cleaner is used. One of my first jobs was welding aluminum in a factory and every piece to be welded got an acid bath before welding. TIG welding in my opinion produces the best weld quality but that weld quality depends a lot on a clean joint.

Purging

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 Nitrogen or 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 144. There are a 144 cubic inches in a cubic foot. In this case a 1442 cubic square inches divided into 144 leaves you with about 10 cubic feet of volume. To purge the pipe with one air exchange you need to run the filler gas at 10 CFH for one hour. To speed it up to let’s say 15 minutes simple run the filler gas at 40 CFH for 15 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 guidlines for machine set-up are as follows:

• 1/16 Tungsten - Require an amperage rage between 50 to 100 amps. The recomendated 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 recomendated 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

When TIG welding smaller diameter aluminum tubing many people like to use a high production button. The purpose for the button is to bump the weld. What that means is basically spot welding around the pipe or tubing. This technique is typically used to weld anodized aluminum pipe. In the yacht industry many boats have tuna or marlin towers installed before they are sold. These towers are made of brushed or anodized aluminum to keep the pipe protected from the salt water. The anodized pipe has a coating that makes it very difficult to weld. Welding anodized aluminum requires two steps. The first step is to spot weld around the pipe and add filler wire. This weld is less then acceptable looking because the anodized coating has not melted properly. The second step is to spot or bump weld around the same weld without adding filler wire. What this does is melt the anodized coating into the weld better. After that the weld is painted with weld paint to protect it.

TIG Welding Exotic Metals and Alloys

TIG can weld almost any metal. This is possible because the main gasses used are noble inert gasses and their properties do not alter the weld properties. Most other welding processes use some type of flux or chemical additives to the filler metal. With TIG welding it is pure heat that creates the weld joint and that allows any metal that can be melted to be joined as long as the filler wire is compatible. Some of the exotic metals that are commonly welded are:

Copper Nickel “CUNI” and Copper Nickel Alloys

TIG welding copper and copper nickel alloys are typically done with pure Argon and sometimes Argon / Helium (75% Ar /25% He) gas mixture. In most cases the tungsten type used will be 2% Cerium with an orange color and an AWS classification of EWCe-2. In other cases 2% Thorium tungsten can be used. The most common welding current and polarity is DCEN (direct current electrode negative).

Many people who weld CUNI say it has a muddy feel to it. That is only true if you use too much heat and in that case the metal will turn very dark. When done right the weld will look very close to stainless steel with almost the same copper color to it. The best way to describe the feel and look of the puddle is a combination between stainless steel and aluminum. The puddle acts like stainless steel but is more fluid with a hint of shine or tin feel like welding aluminum. The catch with welding copper nickel and copper nickel alloys is that cold lap and roll are a common problem. Many time the weld looks like it has penetrated properly but in some places it is actually lacking penetration. It is very hard to detect cold roll and lap with copper nickel unless a die penetration test is done.

When it comes to open root welds on copper nickel there is a different technique used. What is done is you need to keyhole the root open on the joint! Not a joke! You strike your arc and then create a keyhole followed by dipping the filler wire into it. You just keep repeating this till the root is finished. It may sound difficult but the filler wire puts in a very smooth root with good penetration on the backside!

Magnesium

Magnesium is typically welded with pure Argon gas. The type of tungsten used is typically Zirconiated tungsten with an AWS designation of EWZr. In most cases the current will be A/C (alternating current) requiring a high frequency start.

Titanium

Welding titanium uses Argon gas and many times requires an Argon bath to be welded in. In many cases the gas coverage that the TIG torch gives is not enough. Titanium can be welded using 2% Thorium Tungsten with an AWS classification of EWPTh-2 and with DCEN (direct current electrode negative).

TIG Welding of Dissimilar Metals

One of the less common welding practices is welding of dissimilar metals. TIG welding has a lot of options when it comes to welding dissimilar metals. Most of these options depend on the design of the filler wire. In a few cases there are two steps to welding dissimilar metals but in the end theses metals can be joined. Some of the combinations of dissimilar metals that can be TIG welded are:

• Copper to Everdur
• Copper Nickel to Everdur
• Copper and Everdur to Steel
• Copper to Stainless Steel
• Hastelloy Alloy C to Steel
• Nickel to Steel
• Stainless Steel to Cast Iron
• Stainless Steel to Inconel
• Stainless Steel to Low Alloy or Carbon Steel

TIG Welding Techniques

When it comes to TIG welding techniques many of the standard patters still apply. What really changes is the way the filler rod is added and the fact that you need to use both hands at the same time. When adding the filler rod the filler rod should always be kept in the shielded gas area to avoid contaminating the filler wire. Most of the other changes have to do with how the arc is started. With a high frequency start, the starting of an arc is not an issue. With manual or scratch start there can be some trouble. The main problem with scratch start is that the tungsten may contaminate the weld and loose its shape in the process. The way most TIG welds are done is with a side to side motion of the TIG torch. As long as your amperage is set properly and you see the weld puddle wash into the sides of the weld you should be fine. Just like any other welding process there is not a single pattern or way to make a good weld. TIG welding works well in all positions on almost any metal. The only differences between a flat, horizontal, vertical and an overhead weld is how you mentally approach the task. Most of it comes down to a positive mind set and practicing! The end result is you want a smooth uniform bead that has washed into the joint properly.

Forehand vs. Backhand

When it comes to forehand vs’ backhanded welding it does not make much of a difference. Since TIG welding uses a filler metal added by hand, the arc is what determines the weld penetration. As long as the puddle washes into the metal smoothly it makes no difference how you travel. With other welding processes the angle of the travel is unforgiving! TIG welding on the other hand is very forgiving when it comes to torch angle and travel direction as long as the gas coverage is good.

Freehand

The freehand technique for TIG welding is exactly that, freehand. It’s pretty simple, just start a puddle and start adding filler metal with the other hand. Keep repeating!

Walking the Cup

Walking the cup is a welding technique that gives the welder much more control then free hand welding! When comparing freehand welding to walking the cup there is a huge difference in weld quality and appearance! A weld that was done by walking the cup is almost robot like with the bead pattern very uniform and consistent. This is because the cup of the TIG torch is always leaning on the weld joint and the arc length is kept the same. Arc length is the key when it comes to TIG welding bead appearance. To walk the cup you need to place the TIG torch cup on the weld joint and set the tungsten so that it is just above the weld joint. Then simply walk the cup and add or hold your filler wire in the joint. The cup gets its forward travel speed by moving the TIG torch handle in a way that creates a forward travel motion. There are many ways to walk the cup but the ultimately it keeps the welder’s hands steady by providing a something to lean on at all times with a consistent arc length!

TIG Welding Pipe and How to Walk the Cup

Walking the cup is a welding technique that is almost exclusive to TIG welding pipe! This technique is the industry standard for TIG welding pipe. Many companies that hire TIG welders won’t even consider someone if they do not weld pipe by using the walking the cup technique. My personal experience is that every interview I had for TIG welding pipe was about do I know how to walk the cup.

There are three ways to walk the cup:

• Ratcheting the Cup
• Wobbling the Cup
• Sliding the Cup

Ratcheting the Cup

The first is the ratchet technique; it is just like turning a ratchet on a bolt. Ratcheting the cup is typically used anywhere there is a flat area to lean the TIG torch cup on. This is done by placing the cup on the pipe and turning the handle just like a ratchet on a bolt. The forward motion is created by having a slight twitch of the wrist at the end of each ratchet reversal. This is the hardest technique for walking the cup but also the best when it comes to weld quality. The reason behind this is the arc length is kept extremely close to the puddle while maintaining a consistent height at all times.

Wobbling the Cup

The second way to walk the cup is to wobble the cup side to side like moving a heavy barrel that is standing. This is typically used with a larger cup sizes and is best used on a flat surface or directly over another weld. This method is a lot easier the ratcheting the cup but also not as precise! This is because the arc length is always changing from the wobble of the cup. It still beats free hand welding and I use still use it in tight spots where I need to weld left handed with a mirror. Wobbling the cup is a good start to learning to walk the cup. Once wobbling the cup is mastered it’s time to take it to the next level by mastering ratcheting the cup. This is where you will learn to perfect TIG welding pipe.

Sliding the Cup

Sliding the cup is just that! The cup slides and you literally push it to guide the tungsten to where it needs to be. Sliding the cup is done anywhere that is too odd of a surface to walk the cup. More commonly sliding the cup is used in the grove of a heavy wall pipe. You have a large bevel with a cup size that fits between the joint. Simply set your tungsten to the right height and start sliding the cup from side to side and forward to spread your filler wire. Sliding the cup is also used for putting in the root and hot pass on a heavy wall pipe. This technique is never mentioned in welding books but is typically learned in the field. Sliding the cup is also used when a pipe is almost filled and ready for the cap. In this case, the surface the cup is leaning on is not flat enough to walk the cup and not deep enough in the grove to slide the cup. Compromise is what is needed! You do whatever it takes to fill the joint. Most of the time half the motion of the cup is sliding and the other half is walking it. It’s a little tricky but just takes some time to get used to.

TIG Welding Pipe with an Open Root

When it comes to TIG welding pipe with an open root the joint preparation is more than half the battle! The bevel must be Clean and Even all the way around the pipe. The mill scale should be ground back at least 1 inch on the inside and outside of the pipe. The bevel should have a feathered edge and the gap should range between 1/16” to 1/8 of an inch depending on the size of the filler wire being used. For most students practicing in school the gap can be set by using a TIG wire bent into a V. Simple place the TIG wire on the bevel and then place the other coupon on top of it. Make sure the pipes are aligned properly. The main thing is you want the gap to be even all the way around the pipe and just small enough to put your filler wire into the grove without it being able to slip inside the pipe.

Tacking the Pipe

Tacking the pipe is done by placing the filler wire into the grove and going over it with the TIG torch. If you will be using a 1/8 filler wire you will set the gap with a 1/8 filler wire. To tack the pipe you want to find a spot that the filler wire can’t slip through the grove. Then simply tack the pipe. Once the first tack is in you need to puller the spacer out a little very quickly. What will happen is the tack will shrink and then you put in another tack on the opposite side of the pipe. Once the first two tacks are in you will need to pull the spacer out. Now check the gap all the way around the pipe and make sure it is even. If not make some adjustments. Ideally you want the tacks to be about ¾ of an inch long.

The technique used to tack the pipe is almost a shake of the TIG torch. You place the filler wire into the grove and run over it while making sure you fuse both sides of the bevel. When you get to the end of the tack stop your arc and do not pull out your filler wire! Wait a second for the tack to cool and then break off the filler wire from the tack. This is done to avoid creating a keyhole that would later create a lump in the root when you try to tie in the root into the tack. Once all of the tacks are in you should feather the tacks before putting in the root. If the tacks are not perfect don’t worry because you will go over them when you put in the root. When you go over them on the root pass they will smooth out and be barely noticeable. After each tack make sure you cut off the end of you filler wire to get rid of any contamination.

After each tack make sure you cut off the end of you filler wire to get rid of any contamination. A contaminated filler rod will cause problems with the weld and at the same time make the tack or weld difficult to do. When it comes to TIG welding the trick is to have everything clean. That means the joint, filler wire and the tungsten must all be extremely clean. The picture of the tungsten electrode below is a perfect example of a contaminated electrode that needs reshaping!

Pipe Welding Techniques for an Open Root

When it comes to the techniques used for TIG welding an open root there are two ways to do it. It comes down to where you learned to weld. In America the southern states weld different then the northern states. The northern states just lay the filler rod in the bevel and walk over it. That’s me the Yankee! In the southern states, mostly on the Gulf of Mexico, they use a smaller diameter wire then the root opening. What they do is feed the wire from the opposite side of the pipe by leaning it on a tack. The filler wire is literally being feed from the inside of the pipe! It’s not easy but knowing how to do that is really good if your pipe has a bad fit-up. Personally just running over the wire works for me and is a lot easier then feeding the filler rod!

The welding technique used will depend on the thickness of the pipe. On thin wall pipe you can either ratchet or wobble the cup. This is because you will have a shallow bevel that you can walk on with the cup. If it is heavy wall pipe you will want a cup size that is small enough to fit between the groves and slide easily.

Before starting to weld you need to cut your filler wire on an angle to match the feathered tacks. Then place the wire on the feathered tack and strike an arc in the middle of the tack. Wait for the tack to start melting and slowly walk the cup toward the filler rod. When you get close to the filler wire you will want to keep the wire pressed into the root and slowly approach it. Move slowly enough that the filler wire becomes fluid and sucks itself into the tack. At this point the travel speed is picked up and you keep walking the cup. When walking the cup do not wash the root too far onto the sides of the bevel. If you do you will get suck back or a concave root surface. Once the weld is ready to tie into the next tack, start to slow your travel speed down. Approach the tack slowly while pressing the filler rod into the tack. Once the filler wire reaches the tack start to press and lift the filler wire to at least a 45 degrees or more when tying into the tack. If you do not lift the filler wire and create a steep angle you will likely create a hole before the tack is tied in properly. Breaking the arc off of the tack needs to be done by quickly increasing your travel speed and long arcing off. This is done to prevent a fisheye. The finished root pass should be smooth all around. The tie-ins should be barely noticeable and the root surface should be flat to convex. A flat root surface is not a big deal because it will push in more on the hot pass.

Trouble Shooting an Open Root TIG Weld

When it comes to open root TIG welds there are some common problems but all of them are easy to fix. TIG welding is a very forgiving process! Here are some common problems with open root welds and there solutions:

Concave Root Surface or Suck Back

Increase your travel speed Lower the amperage Don’t wash to far onto the bevel Increase the TIG torch angle

Filler wire is to large Shielding gas flow is to low Increase the angle of the filler wire

Pipe Welding Techniques for the Hot Pass and Filler Passes

When it comes to the hot pass and filler passes they are just like to root pass but require a higher heat setting. For example if you are welding a 2” schedule 160 pipe the root pass will require about 90 amps and the hot pass will require 125 amps. On heavy wall pipe the technique used is sliding the cup. On thin wall pipe the technique used is walking the cup. This is because the bevel is shallow enough to allow the cup to walk on the edges of the bevel.

The general rule for these passes is keeping them under 3/4 of an inch wide. After that, start doing multiple passes. The hot pass is also where you will be able to push the root pass in to fix a flat or concave root surface. On the hot and filler passes you want to wash into the bevel very well. Unlike the root pass where you a focusing on pushing the filler wire into to grove here the main focus is on washing the filler wire onto the sides of the bevel. The fill pass does get tricky if you are almost done filling a heavy wall pipe. This is an area that will require compromise when it comes to the welding technique used. It typically takes half the motion of sliding the cup and the other half walking the cup.

When selecting a cup size for heavy wall pipe it is very common to use multiple cups depending on the thickness of the grove. Most times you start with a smaller cup and work your way up to larger cup sizes depending on how much if the grove is filled. The idea is to use a large enough cup that will slide in the grove above the weld without touching the weld. Once the pipe is almost filled up you go back to a smaller cup so that you can build a shelf of weld and start the transition to walking the cup.

Pipe Welding Techniques for the Cap

Welding the cap on a pipe is no different than walking the cup on any other surface. Ideally you want to ratchet the cup but if you are not there yet just wobble the cup. The cap weld does have some common problems that are easily solved. The most common problem with the cap is undercut. Undercut is typically solved by cleaning the weld area before each pass with a sanding disk or file. What happens is each pass that you weld creates a heat affected zone. What needs to be cleaned is the surface of the pipe that is going to be welded. This area typically has a blue tint to it that shows you the heat affected area. Just remove the surface metal with a file or fine sanding disk! This applies to all restarts and stringer beads. After that the weld should flow smoothly again. When it comes to TIG welding pipe or anything else the key to good weld quality is cleanliness!

TIG Welder Trouble Shooting

When TIG welding there is some common problems and weld defects. Most of these problems are easy to solve when you know what to look for. Some of the common problems include:

Weld Porosity

Weld Porosity can be caused by many factors. Some of the common causes of weld porosity are:

• Arc length is too long. Shorten your arc length.
• The joint is not cleaned properly. Clean with grinder or wire brush.
• 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.