Last time, we talked about reverse polarity. Hopefully, that is somewhat understood. Now the talk will be dealing with electrical straight polarity.
As we can see, the electrode is attached to the negative terminal on the power source and the work (metal to be welded) is attached to the positive terminal. This is the basic setup for DCEN. So what exactly is going on and why do we need to know about this?
Electrons flow naturally from negative to positive and that has an effect in terms of heat when it relates to welding.
So we get more heat and penetration on the work when we are in DCEN as opposed to DCEP. In SMAW (stick welding) this effect might not be that apparent but with GTAW (tig) it is a different story.
When we tig weld everything except aluminum and magnesium, we will be using direct current. With direct current, we have two choices. Reverse polarity or Straight polarity. Which polarity is the best choice? Straight of course. Why? Because we want to keep our tungsten tip sharp and pointed, not balled like the one in the picture (bottom right).
How does the tip remain sharp? Well if you look at the chart above, you will see that since the electrons are leaving the electrode and making contact with the work (DCEN) and 70 % of the heat is taking place at the work, the tungsten can maintain its pointed shape.
When the electrons leave the work and make contact with the electrode (DCEP) and 70 % of the heat is taking place at the electrode, the tungsten can’t maintain its pointed shape and starts to ball up.
What electrical polarity would I need to choose for Alternating current?
To be continued….