Cracking The Tig Welding Secret This Year

Description

TIG welding is a manual type of welding where the welder has to use both of his hands for a proper weld. Here the welder uses one of his hands to hold the TIG hot torch and the other to add the filler metal to the weld.

Hence, TIG welding is considered one of the most difficult of all the welding processes out there. It is also versatile and professional when compared to welding various metals. This process is done extremely slowly for good quality and precise, small welds.

TIG basically stands for ‘Tungsten Inert Gas’ welding and is also well-known as ‘Gas Tungsten Arc Welding’ (GTAW). This named was coined by the ‘American Welding Society’.

History

TIG welding was first introduced in the 1940s where Helium gas was the only shielding gas used back then. It was termed ‘Heliarc’ in those days. This has got a registered trademark now that is, “Genuine Heliarc” which is now owned by ESAB equipment.

Why Tungsten?

Tungsten is very hard, slightly radioactive, and is a brittle metal. It is very little used. Here, we convert the tungsten into a non-consumable electrode to do TIG welding.

You can find this element is used in light bulbs, heating elements, and rocket engines. This is radically used in regions where very high temperature is used and you also need to pass electricity continuously.

In TIG welding, as tungsten is the main metal used here, it allows heating temperatures about 11,000-degree Fahrenheit. As told earlier, tungsten has a high melting point and good conductivity which makes welding ease.

The tensile strength of tungsten is 50,000 lbs. per square inch. Being all this tough and rigid, it is brittle though, and can be broken with a heavy tap using a hammer.

How does it work?

You need three basic necessities to fulfill a TIG weld which is heat, shielding gas, and filler metal. The heat in the electrode is formed by passing electricity via the electrode and creating an arc to the metal.

The shielding gas is supplied for protection from a compressed bottle of gas and it flows to the welding area/zone. The filler metal is just a wire that is dipped into the arc and melted by just placing it using one’s hands.

    Steps:

    • It is recommended to check for proper gas flow based on the nozzle selected and the dimensions of the metal.
    • Now, adjust the amperage and type of current flowing through the welding machine based on the technique of TIG welding performed.
    • Then, you can turn the welder ‘ON’ and place the foot control in the area which is comfortable for you.
    • Press the foot control and strike the arc gently.
    • A puddle will be formed now, and then add the filler rod to the leading edge.
    • Make sure that you do not contaminate the tungsten electrode and hence move the TIG welding torch back to the puddle when the filler metal is added.
    • It is always recommended to clean all the metallic surfaces and joints respectively. It involves processes like scraping, grinding, brushing, and wire brush treatment. The material used for the wire brush must be the same as that of the welding metal.
    • You should not use metals over ¼ inches thickness of any metal except for magnesium and aluminum. Similarly, metal has less than 3/16 inches does not need any edge preparation.
    • But if the thickness of metal used is over 3/16 inches, then ground or machined edges can help in proper bead penetration.

 

TIG Process Joints

  • Square-Butt Joint:

    The tungsten electrode must be moved along the centerline of metal to be welded. The recommended angles for TIG welding square-butt joint are:

    • 20-30-degree electrode angle
    • 90-degree work angle
    • 60-70-degree dray angle

    Hold the tungsten electrode about 1/8 inches above the base metal and strike the arc. Once you see the weld puddle formation, add filler to the higher edge of the puddle, and then move the end forward as much as possible.

  • T-Joints & Lap Joints:

  • Flat Position Welding:

    • Tack welding the base metal for every 3 inches is necessary if you are welding in a flat position and have lap and T-joints. Moreover, joints are to be made in a flat position only.
    • The work angle for the torch is either a 60-70 degree drag angle or else a 10-20-degree work angle.
    • You must point the electrode along the horizontal edge to weld instead of the vertical edge. You may strike the arc now for the formation of the weld puddle.
    • A “C” shaped weld puddle will be formed and this signifies that both the edges of the metal are melting together.
    • Once again hold the electrode about 1/8 inches above the base metal and move it close to the weld puddle once you see that the puddle has been formed. Now add the filler rod to the weld puddle.
    • Repeat this TIG process and move the bead forward. If you reach the end of the weld, move the electrode towards the rear of the puddle once again to fill it with filler rod and withdraw it from the weld zone.
    • Slowly lift the TIG welding torch to ensure the shielding gas to be formed over it and provides protection to the weld.
    Horizontal Position Welding:
    • Horizontal welding position has all the steps similar to the flat position welding. The only changes are in its drag angles.
    • The drag angle of the torch should be:
      • 60-75-degrees
    • The work angle must be:
      • 15-30-degrees
    • To prevent molten metal remains from drooping and sagging, make sure to have a small puddle and add the filler rod at the upper edge of the puddle.

Voltage Type

TIG welding has the same voltage configuration as Stick welding.
There are two basic types of voltages available which are:

  • Direct Current (DC): This current flows only along one direction i.e., from negative to the positive terminal.
  • Alternating Current (AC): This current can change its direction as many times as it wants. Once it can flow from the negative to the positive terminal and then vice-versa.

Welding Polarities

  • Direct Current Negative Electrode: This means that the welding electrode is connected to the negative side of the circuit and the flow of electricity is from the TIG torch to the metal. A DC negative electrode produces about 2/3 of the heat onto the welded metal.
  • Direct Current Positive Electrode: The electrode, in this case, is connected to the positive side of the circuit and the flow of electricity is from the base metal to the TIG torch. A DC positive electrode on the other hand concentrates about 2/3 of the heat onto the electrode itself.

Torch Types

    Air-Cooled TIG Torch:

      The air-cooled TIG torch is the cheapest type of TIG welding torch available in the market. It heats a lot during the work and most of the heat the arc produces is wasted.

    Water-cooled Tig Torch:

      It is similar to an air-cooled TIG torch but the difference here is that it has a water cooler that has a radiator fitted in it to spray water over it to cool it down.

TIG Welding Stainless Steel

Stainless steel and steel are pretty much similar and hence they have similar welding techniques. It uses the same tungsten electrode and argon gas as shielding gas.

Welding using stainless steel produces more shielding gas coverage. The problem with stainless steel is that if too much heat is applied, then they warp too much or else have the tendency to be not braced properly.

  • If the stainless-steel weld has a copper color to it, then it has been welded properly.
  • If it is gray or black in color, then you are moving the welding torch too slowly.
  • Joint preparation is very important for welding stainless -steel as if it is not clean enough, then the filler rod will not stick strong enough with the weld.
  • This results in poor weld output.
  • This happens in multi-pass welds too.
  • If one bead is done in the first pass, then before the second pass, you will have to clean the weld and metal before doing the second pass.

 

 

Common Mistakes

    Poor gas coverage:

      When you have improper shielding gas supply or else no shielding gas supplied to the weld for protection, then rapid contamination might occur. This is because too much or too little gas is present around the weld.

      Major mistakes here are:
      • Improper checking of gas cylinder label. Using a gas cylinder with the wrong type of gas.
      • The poor gas flow rate as it was not measured.
      • A standard collet body instead of a gas lens is used.
      • Fitting and hoses through which shielding gas is supplied are not checked for leaks and breakage.

    Wrong Current:

      This is a mistake that is mostly made by beginners who have a huge enthusiasm to weld instantly. They use the wrong current flow while beginning the welding process. They even forget whether to use AV or DC current for the metal and the electrode.

      • Using Alternating Current (AC) is ideal for TIG welding and it is essential for a welder to know the type of current that he needs to use for a particular welding type.
      • Welding using Direct Current (DC) will be difficult to eliminate aluminum oxide layer formed over the weld which is toxic and causes deterioration and damage to the weld.
      • It also mixes with the filler metal contaminating the entire workpiece.
      • The positive electrode portion removes all the aluminum oxide while the negative electrode melts away the base metal.
      • Some welders tend to use even wrong temperature settings while doing TIG welding.

    Weld Grittiness:

      If you weld at abnormally high temperatures, it might lead to the formation of a rough and gritty nature of appearance on the welded portion.

      It also weakens the metal. Using the 5356-filler metal is better than the 4043 one as it does not get defective in long usage.

      Further, if moisture, grease, oil, and other toxins are not removed from the surface of the weld, then it also leads to contamination.

    Combination:

      Welders must know the right combinations for welding T-joints and fillet joints. The mistakes they make usually with these joints are welding them by:
      • Improper fitting and also keeping the torch far away from the joints.
      • Improper feeding of filler rod.
      • Welding as fast as they can without any slow processes.
      • Increased arc length and in turn losing directional force and control over the electrode.

    Lacking fusion:

      The fusion of joints and the weld near the root of the base metal might not occur properly is the welding torch is held too far away, fit-up is not tight, and if the filler rod is not filled properly.

      An increase in the arc length is also another factor in this. Transformer-based welding machines also cause this issue as the arc in them keeps on moving between the joint sides.

 

 

    Lack of Cleanliness:

      When it comes to manual welding, cleaning is the first and foremost process to be done with the welding equipment, metal, and electrodes. This is because a dirty base metal or electrode might cause a lot of imperfections, distortions, cracks, and damage.

    Discoloration:

      This is one such error made by the welder which cannot be reverted back nor regretted about later on. Overheating stainless steel causes the steel to discolor and look very ugly after the weld is completed. It further reduces the corrosion resistance of the steel.

    Oxidation:

      Stainless steel available in the market is generally manufactured with a corrosion-resistant coating on top of it and because of this, it is resistant to oxidation. Using shielding gas (argon) to protect the weld can help in preventing any sort of oxidation on the weld as well as the steel.