Important comments about TIG welding:
TIG (tungsten inert gas) welding is the process commonly referred to as
"Heliarc" -- which is a copyrighted name owned by the Linde Corporation,
who developed the process using helium as the shielding gas. Argon is
more popular, as it shields better . . . although helium is useful in some
cases, due to different heat effects compared to argon. By the way,
Linde also makes nice TIG welding machines. I used to own one. And I
am a HUGE fan of TIG welding. I absolutely love it, and have been doing
it (as well as other welding processes) for decades.
The difference between TIG welding and others is that since in this
process, the tungsten (so it won't melt) electrode is non-consumable,
any filler material must be fed into the weld puddle by hand. The heat
input is controlled independently of this, generally by a foot-operated
pedal.
Which brings me to my more important comments. . .
In "stick" welding, where the welding rod gets consumed, and in
MIG welding, where the wire electrode gets consumed, the filler
material automatically flows into the weld puddle -- and this flow
is generally enough to prevent cracking of the weld as it cools.
But in TIG welding, you could pour too much heat and too little
filler material into the weld. This typically can cause the weld to
crack, and a cracked weld is like NO WELD! This is because a crack
can spread very easily under a small amount of force, due to stress
concentration. A familiar example of this? Bite a potato chip bag
and it will tear quite easily.
When TIG welding, except in special (rare) circumstances, it's
important to add enough filler material to provide strength and
prevent cracking. (That's the brief lesson . . . more details on
this are available, if you care to ask.)