The Electric Arc
As the name itself suggests, electric arc welding utilizes electric energy to initiate and sustain an arc which is the source of intense heat sufficient to melt the materials to be joined and help them fuse together. But how is this arc generated and what are the underlying principles in that?
Well if you remember having turned a heavy electric appliance ON or OFF, you might have notice that some sparks fly from the place where the actual electric contact behind the switch takes place. This is something similar to what happens in electric arc welding and should help you to understand it more clearly.
Current travels from point A to point B only if there is a certain potential difference between the two points which should be sufficient to overcome the electric resistance between the two points. If you are not clear about this concept let me tell you some examples from every day life. Suppose it is a holiday and you are sitting comfortably in you bedroom and relaxing, and I tell you to go out in the scorching heat (or biting cold) to the market to buy a loaf of bread, what would you do? I for one would surely grumble and would want some extra money for a chocolate as an incentive which generates sufficient drive or desire within me to want to go out instead of relaxing. The size of the chocolate which I would want would depend on the amount of resistance I have to overcome from my mind which would depend on outside temperature, distance of shop and so forth. In the same way, current, which is nothing but a movement of electrons, needs a certain drive to make them move from one place to another which is supplied in the form of a potential difference. This potential difference (chocolate in our case) would depend on the resistance which in turn depends on the material characteristics, distance to be covered by the current and so forth.
Now if we want to generate an arc or flow of current through air which happens to be a good insulator meaning that it offers high electric resistance to current, we certainly need a good amount of potential difference between the two points across which the arc has to be maintained, namely the electrode used for welding and the work piece material. But then welding is done by human beings (of course Robots are also used nowadays which we will study in a different article about robot welding – keep a lookout for that as well), therefore safety is also a prime concern in welding. Hence we cannot use very high voltages as well hence an optimum value has to be agreed upon which is necessary for the arc and safe for humans as well.
I think it is quite sufficient if you ponder over this article for the moment and giving it time to digest. In the next article named as part 2 which the same title, we would move ahead on the issues and go a bit deeper on the same.