Basics of TIG Welding.

Posted by rohini patel on July 2nd, 2018

You only need one kind.

Unless you want to complicate your life, make up your mind to use only one type of TIG Electrodes. When you have 2 or 3 different kinds of tungsten in your box and you accidentally grind the color code off, how are you going to know what you have? Back in the day welders would mainly use either pure tungsten for welding aluminum or 2% thoriated for welding steels.

Even with only 2 different kinds of tungsten, they still got mixed up when the color got ground off.

Even though there has been a lot of talk over the last 10 years or so about thoriated electrodes being hazardous because thorium is slightly radioactive, welders still use them a lot.

What exactly is DCEN aka Straight Polarity used for in TIG welding?

Welding current flows from negative to positive.

So when the electrode is negative, that means the current is flowing from the tungsten electrode into the metal being welded.

That is why TIG is so precise and why on steels, stainless steels, inconel, titanium, etc, a small precise puddle is easy to establish quickly.

What about DCEP aka Reverse polarity

Opposite from electrode negative, the current flows from the metal up through the electrode and that causes the electrode to get really hot really quick. It makes tigging on dcep very limited.I say limited because there are actually a small handful of applications where dcep is used for tig welding. One example is on magnesium castings. There is an old TIG report from Union Carbide where DCEP as well as using a 50/50 mix of argon/helium actually provided good results on magnesium castings like aircraft gearboxes.

This was the process for GTAW mag until it was changed when tig welders with square wave technology and AC balance became the norm.

Is Alternating current actually a mix of positive and negative current?

For the purpose of knowing the effects of welding polarity on TIG, it sure helps to think of AC as a mixture of both good and bad aspects of DCEN and DCEP.

What is the AC balance setting?

What that means is that while there is no adjustment knob for AC balance, the machine automatically adjusts the ratio of EP and EN while you weld.

The level of oxidation on the surface of aluminum can affect the level of cathodic etching needed to break up the oxide film.

So this Lincoln TIG 175 senses the resistance and adjusts on the fly. Now personally, AC balance is a setting I like to be able to adjust manually, but results speak loudly and it ran a good bead on aluminum. I would guess from the band of etching on the edges of the aluminum beads I welded, that the machine default setting is around 65-70% EN.

2% lanthanated tungsten electrodes handle the amps better than most

The only problem with 2% lanthanated is that it does not break cleanly. You can’t just snap it with your fingers or 2 pairs of pliers. It bends and splits. You pretty much have to cut it with a grinder or at least score it with a grinder before you break it.

This is a pretty small price to pay for an all purpose TIG Electrodes that works on carbon steels, stainless steel, nickel alloys, aluminum, magnesium, titanium, cobalt, copper alloys, pot metal, and everything else

Ref: weldingtipsandtricks.com/tungsten-electrodes.html