Re: Welding DC+ vs DC- vs AC ... please explain !

Posted by T_Bone on August 25, 2006 at 15:37:33 from (4.240.90.119):

In Reply to: Welding DC+ vs DC- vs AC ... please explain ! posted by Alberta Mike on August 24, 2006 at 15:16:07:

Hi Mike,

Great info has already been posted on the subject so I'll take the discussion in a different direction.

Welding is a process of heating the base metal to where it can accept drolets of molten metal from the electrode to join metal.

AC, DCEN and DCEP are used to control those droplets of molten metal.

The flow of electrons in DC welding circuits is from negitive to positive and is called straight polarity.

When we reverse the welding leads then electron flow is from positive to negitive also called reverse polarity.

When AC current is used for welding, you get a base metal cleaning action that cleans on the alternating phase of the current, anotherwords the current cylces up and down thru the frequency and the base metal is cleaned and filler metal is deposited in both directions. This works well in the flat position and when the base metal hasn't been prep'd as it should be and where the molten droplets has a chance too fast freeze to the base metal.

When DCEN is used for welding the most of the cleaning action stops as far as the frequency is concerned as DC current only flows along the surface of a line and doesn't alternate thru the base metal like the AC current did.

Since electron flow is from negitive to positive then the molten droplets flow too the base metal from the electrode causing a very fast deposit of the droplets. The slang term is known as fast freeze between weldors. If the droplets fast freeze to the base metal then the base metal is cooler while welding thus is a good choice for sheet metal welding or filling poor joint fit up.

When DCEP is used for welding electron flow is from base metal to the electrode and most of the heat build up is on the base metal. What this does is allows for greater molten puddle control for the weldor when using the correct electrodes. Transfer of the molten droplets is slightly slower than using DCEN or AC.

This will cover the basics of some of the differences but in reality there's alot more to using AC, DCEN or DCEP than what's been written here, so I will add too this at a latter time.

T_Bone

Replies:

• Re: Welding DC+ vs DC- vs AC ... please explain ! Rick Castle 18:22:18 03/03/07 (0)

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