Another tig question

By dumfarmer Date 12-11-2002 16:38

Well I solved some of my early problems by finding out I was trying to weld with mig gas instead of argon. My question, I have gas welding experience on aircraft etc. I find myself tig welding much the same way. The weld is cleaner but looks almost the same. The tig welds I've seen look like a neat series of overlapping puddles with very little weld buildup. I don't feel comfortable with so little buildup, especially on aircraft tubing. I'm practicing on 1/16" mild steel. What do you guys think. Thanks Larry

By Lawrence (*****)

Date 12-11-2002 18:50

Fact of the matter is:

Speaking in general terms, Aircraft componants do not have a large reinforcement requirement in groove welds or fillets. Large amounts of reinforcement (lets say more than the thickness of the material welded in groove welds and 1.5 times the thickness of the thinner member in fillets, this applies to steels under 0.090 thickness ) are often viewed as unacceptable for many reasons. Unrestricted airflow is one reason, another would be vibration, variences in thickness must always be considered and minimized in thin materials subject to cyclic stresses of heat, cold and vibration.

With proper preperation, filler material selection, heat input and stress relief when required, thin GTA welds require very little reinforcement above the thickness of the parent material and are often blended flush.

Aluminum in most cases has greater allowences for reinforcement or buildup.

Undercut, insufficent filler or lack of fusion are on the opposit side of the issue and are equally important in design and post weld inspection and are never acceptable.

Your 1/16 inch mild steel is great for practice! Section your work and inspect for insufficient filler, practice will help you determine the balence between too much and too little heat/filler.

Specific guidlines for each metal group may be found in Mil-Std. 1595a and the ASM Materials Guide Vol 6.

Lawrence Bower
Welding Instructor
United Airlines

By dumfarmer Date 12-12-2002 15:29

Lawrence, Thank you very much for the good info. Eventually I hope to use tig to rebuild a wrecked Taylor Cub that I have. Sure hope things work out for you with United. Larry

By welder_guy2001 (***)

Date 12-13-2002 06:05

it depends on what you're welding. lawrence laid out the parameters for aircraft. but if you're gonna be welding on something structural the fillet weld legs should be at least the thickness of the thinnest piece being welded together. ie: 1/4" welded to 1/2" steel needs a 1/4" fillet. and groove welds on structural members are usually filled to 1/16" over the thickness of the base metal. for 1/16" sheetmetal, a groove weld filled to the thickness of the sheet should be enough.