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While welding is a job that typically requires a fair amount of time to be spent using your hands, it’s a job that also requires one to know bit of technical information. A term that you will see quite often is welding current and it will always be labeled on machines as AC or DC. These letters are acronyms which detail whether the machine’s polarity is alternating current or direct current. Many wonder why this tends to matter so much? Well, in this article we will detail the reasons why it pays to understand just exactly what these terms mean.
What exactly is “Polarity”?
The electricity that your welding machine generates can only have either a positive or negative pole. This negative or positive charge is what welders mean when they refer to polarity. Polarity is an important topic to pay attention to because it affects both the quality and strength of certain types of welds. If you use the wrong polarity in a certain welding process you will likely create a fair amount of splatter, not have enough control over your arc, and not penetrate the base material well enough.
Reverse and straight polarity
Reverse and straight polarity refer to the electrode positive and electrode negative polarity. Currents with an electric positive or reverse polarity tend to have a better penetration in the base material. On the other hand, electrode negative or straight polarity currents tend to have a faster melt-off and a faster deposition rate. Also keep in mind that the weld can also be affected by the types of shielding gas that you use.
What exactly is an “alternating” or “direct” current?
An alternating current is one that alternates the direction it flows in and changes its polarity about 120 times a second using a 60 hertz current. On the other hand, a direct current is one that has a constant polarity. You will find these terms labeled on both electrodes and machines with an “ac” or “dc” respectively.
How can using a Direct Current and an Alternating Current differ when welding?
Certain types of welding usually require a certain type of current because of the level of penetration that they need. For example, you will usually see a direct current being used for submerged arc welding. Now, with submerged arc welding we will see direct current electrodes being placed in both the DCEP and DCEN categories. DCEN stands for Direct Current Electrode Negative and is usually used for Submerged arc welding due to the lack of deposition and increased burn off rate it provides. In the case of TIG welding, you will typically find it using a DC negative as well. This is because the negative heat helps the tungsten shielding gas from overheating the torch.
