Electric Arc Welding - The Welding Circuit
This is the Second Part of a 2-part article series. To start at the beginning, please read Electric Arc Welding – A Useful Technique for Strong Welds (Part 1).
The Welding Circuit
The word circuit must be familiar even if you are not an electric geek, but from other sources as well such as motor sports. The term refers to the complete path or route along which any activity such as a racing event takes place. Now if you know about electronics, the current consists of the flow of electrons which rush from one polarity to the other {Of course don’t confuse the AC and DC stuff – just refer to some study material for this clarification for if I start to explain it here, I will go much off track} and the track which they follow is known as the electrical circuit, which may vary depending on the type of appliance and application just as the racing track would depend on factors whether it is a bike race, car race, rally and so on.
The basic welding circuit consists of a transformer which is powered from the electric source and converts the typical high voltage - low current electricity into high current – low voltage electricity as explained previously. The two terminals of the output from the transformer are connected to the work-piece and the welding electrode respectively. This has been pictorially depicted in the image accompanying this page.
The transformer has controls where you can increase or decrease the current depending on the type of weld and the material to be joined together which you don’t need to bother at this stage.
The work piece is connected one of the terminals of the transformer which is “earthed”. The work piece in the figure has been shown in the form of two pieces of metal which are to be joined along their length which is depicted in the form of a small gap between the two pieces
The electrode is connected to the other end of the transformer through the electrode holder which is made up of an insulating material to avoid any possibility of an electric shock to the person carrying out the welding.
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?
If we were to simply touch the electrode to the work piece the electric circuit would complete itself which would mean that current would start to flow across the path as depicted by the wires. But then just ask yourself whether it would achieve any purpose and the answer to that would be a big NO! So how do we actually carry out the process? What we do is that we simply strike the electrode against the work piece and quickly pull it back by a very short distance of the order of millimeters. This recreates what happens when you put OFF a heavy appliance in your home – a spark is generated which jumps across the two sides to complete the circuit. This spark or arc generates intense heat which is sufficient to melt the metals involved while depositing additional material from the electrode and this solidifies to complete the welding.
