1.0 Introduction
In every fabrication process involving metals and non-metals, there is always a need to join two metal parts which gives rise to welding machine.
Actually, welding is a metal-joining process. It may be defined as the art of joining two metal parts by means of heat or pressure or both in such away that the resultant joint is equivalent in composition and characteristics to the metals used.
Welding machines has two sides the electrical side (primary side) and the welding side (secondary side).
Generally, welding processes fall into two categories namely:
- Fusion welding
- Non-fusion welding.
Fusion welding involves melting the parent metal while non-fusion welding does not involve melting of the parent metal. Examples of fusion welding include; carbon arc welding, metal arc welding electron beam welding, electro slag welding which utilizes electric energy.
Examples of non-fusion welding includes forge welding and gas non-fusion welding which use chemical energy, explosive welding, friction welding and ultrasonic etc.
This uses mechanical energy resistance welding which uses electrical energy. Proper selection of the welding process depends on the kind of metals to be joined. Cost involves nature of products to be fabricated and the production techniques adopted.
Electricity plays a vital role in welding process as it is used for generating heat at the point to welding in order to melt the material which will subsequently fuse and form the actual weld joint.
There are many ways of producing this heat but the two most common methods are;
- Resistance welding and arc welding.
Resistance welding is fundamentally heat and squeeze process. The term resistance welding denotes a group processes in which welding heat is produced by the resistance offered to the passage of electric current through the two metal pieces being welded. These processes differ from the fusion processes in the sense that no extra metal by H = 12Rt/s
Obviously, amount of heat produced depends on;
- Square of the current
- The time of current
- The resistance offered.
As seen, in simple resistance welding, high-amperage is necessary for adequate weld. Usually, R is contact resistance between the two metals being welded together.
The current is passed for a suitable length of time controlled by a timer. In arc welding, electricity is conducted in the form of an arc which is established between the two metallic surfaces. It is the most used welding process because it can be used in all welding positions with mild alloy, heat and corrosion resistance steels and with some copper nickels base alloys.
The process is used in ship building, structural and general engineering.
It is a low capital cost process, which uses portable equipment and can be supplied to a wide range of joint and type.
In arc welding, two forms of electrical energy are used; these are Alternating Current (A.C) and Direct Current (D.C).
This material contains electrical diagrams, circuits, illustrations and more (Very detailed).
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