What I've learned about TIG

Background

Tungsten Inert Gas (TIG) creates clean welds free of slag but requires more preparation compared to stick or MIG welding processes.  It is useful for joining reactive metals used in aerospace, pipelines, and process piping in the food industry.  Because of the skill required, learning to TIG weld can pay well. 

Side note: TIG welding is not for the lazy.  If you are not willing to do what is necessary to produce good work, stick with MIG welding until you are ready to move on.

How to TIG weld successfully:

• Bring prior knowledge and welding skill 

  • Ideally, the best way to prepare yourself to learn TIG is to do some gas welding first.   

  • An understanding of arc length, travel speed, work angle, and travel angle. 

  • Be able to identify and correct weld defects.

  • A steady hand through practice

• Preparation is key - don't rush

  • TIG welding is not for the impatient.  Stick to MIG welding.

  • Always use clean and sharp tungsten.

  • Remove all mill scale from your work piece with an angle grinder.  Workpiece should be clean and shiny. 

  • Wipe down work piece AND filler rod with alcohol or acetone to remove oils.

• Setup

  • Use a current of 125 amps for 1/8" mild steel plate.

  • Generally, tungsten electrode stick out should be set to less than 1.5x cup diameter

  • Gas flow: Cup sizes 5-7 use ~13 CFH of Argon.   Higher flow rate isn't necessarily better because it can create a more turbulent stream that pulls air into the weld!  Gas flow needed also depends on electrode stick out.  If welding with a large cup and longer stick outs to get into a joint, flow rates of 20-30 may be needed to maintain shielding.  

• Technique

  • Once you establish the puddle, do NOT move until you apply enough heat to see the devil's eye.  If you don't know what this is, ask.

  • Watch your arc length!  Contact tip to work distance (CTWD) should be one electrode diameter.  If you long arc it, the puddle will not flow into the root on fillet welds.

  • Keep the hot end of the filler metal inside the gas shielding!  If you repeatedly pull it out too far, the heated end will oxidize and contaminate the weld.  

  • Keep a low filler metal angle to the work piece, approximately 15 degrees.  Higher angles risk pulling air inside the shielding.  

  • Tip: try to maintain a 90 degree angle between the torch and the filler metal

  • Do not touch the electrode to either the molten weld puddle or to the filler metal.  Doing so will immediately contaminate the tungsten and require and re-pointing to achieve a satisfactory weld.  Similarly, do not try to melt the filler metal with the arc.  

  • Don't run it full throttle, learn to ease up on the pedal to achieve the desired bead width.  Excessive heat makes it more difficult to control the puddle and also distorts the base metal.  While our machine might be set at 125 amps for most of our 1/8" thick plate welding, in many of my welds the machine is running maybe 65 amps.  Have someone look at your machine while you run a bead.

  • Since there is no flux used in TIG welding, maintain good gas shielding to protect puddle from oxidation.  

  • Practice a lot.  Seek feedback.  

When welding thin steel such as 1/8", use backing strips such as blocks of aluminum to absorb excess heat.  Fixture backing metals to ensure contact using clamps or vise grips.  These can also help keep air from contaminating the back side of your weld where there is no shielding.  Additionally, using pulse TIG rates such as 1.5 per second can help to improve control of workpiece heating.  Pulse TIG can also help from penetrating through edge joints to avoid pulling in oxides from back of the weld.

Use proper current so the weld penetrates into the base metal.  The use of backing metals may require more heat.   Examine each bead for defects and adjust accordingly.

 Aluminum TIG Tips:

Do not cross contaminate your workpiece by using grinding wheel or wire brushes previously used on steel.