Welding Tips and Tricks

I have a question about 'POLARITY'.

Most common carbon steel must be welded with DCEP in SMAW and MIG.

What happen with DCEN ?

On the contrary in TIG welding DCEN is used..

I heard that the electron makes it high temperature by hitting the material connected with positive pole.

But I don't know why opposite polarity is used in SMAW and TIG.

As the aluminum is welded with DCEP in MIG, is it available to weld aluminum with DCEP in TIG ?

How about including this into 'TIG welding basics overview' in YouTube ?

Generally speaking, in an electric circuit power flows from negative to positive. In an EN scenario electricity flows from the torch to the weld metal, and opposite for EP.

Heat concentrates on the positive end of that exchange, which is why TIG DCEN on steel gives good penetration. TIG DCEP is do-able but requires a large tungsten electrode because in that context heat concentrates in the electrode (the "positive" side of the arc). On my very first ever TIG outing I reversed the leads and tried DCEP on steel: smoked the tungsten, not a good start.

You can think of AC TIG welding on aluminum, for instance, as an alternating mix of DCEN and DCEP: the A/C sine wave moves through a "hill" above the line and a "valley" below the line.

DCEN on aluminum is possible, and I for one will be interested to see the video mentioned here:
http://forum.weldingtipsandtricks.com/v ... 521#p38521

Gas shielded GMAW is DCEP while FCAW is typically DCEN. I *believe* that polarities vary in SMAW, to some extent at least, to exploit differences in the way flux coatings react during the weld process, but I'm sure I'll get corrected on that one.

Welcome to the forum!

Stick can be run AC, DC+, or DC- depending on the situation.

Here is a chart for the result: (stick welding)

Couldn't find it online so I scanned this page from my text book. Should help.

MNDave, the chart you posted is specific to stick electrodes, correct? It is opposite the polarity characteristics of TIG.

tig polarity
http://image.minitruckinweb.com/f/tech/ ... larity.jpg

Artie F. Emm wrote:MNDave, the chart you posted is specific to stick electrodes, correct? It is opposite the polarity characteristics of TIG.

Yes, the chart is for stick welding.