MYPIBLOGs

Welding is the process of joining together two pieces of metal so that bonding takes place at their original boundary surfaces. When two parts to be joined are melted together, heat or pressure or both is applied and with or without added metal for formation of metallic bond.

1. NEED FOR WELDING

With ever increasing demand for both high production rates and high precision, fully mechanized or automated welding processes have taken a prominent place in the welding field. The rate at which automation is being introduced into welding process is astonishing and it may be expected that by the end of this century more automated machines than men in welding fabrication units will be found. In addition, computers play critical role in running the automated welding processes and the commands given by the computer will be taken from the programs, which in turn, need algorithms of the welding variables in the form of mathematical equations. 

2.METAL JOINING METHODS

The art of joining metals is about 3000 years old. The origin of welding is probably to be traced to the shaping of metals. In industry every worker is working for changing the shape of metals by different methods and machines. Welding is a metal joining method. The following methods are used for joining metals:

(i) Soldering

This joint is made on thin metals using solder as a joining medium. The melting point of solder is less than the metals to be joined. The joint can be opened by heating upto the solder melting temperature (below 400°C).

(ii) Brazing

The joint is similar to soldering but has more strength. The joining medium used is brass, which has a higher melting temperature than solder. The joint can also be opened by heating upto the melting point of brass (850-950°C).

(iii) Welding

A metal joining method in which the joining edges are heated and fused together with or without filler metal to form a permanent (homogeneous) bond is known as welding. Or in other words, “Welding is a process of joining two or more pieces of thesame or dissimilar materials to achieve complete coalescence.

Types of welding

Oxy acetylene(Gas welding)

Oxygen/Acetylene welding, or “Gas Welding”, is a process which relies on combustion of oxygen and acetylene. When mixed together in correct proportions within a hand-held torch or blowpipe, a hot flame is produced with a temperature of about 3200°C. The chemical action of the oxy/acetylene flame can be adjusted by changing the ratio of the volume of oxygen to acetylene, using the valves on the torch or blowpipe.

Equipment

Oxy/acetylene equipment is portable and easy to use. It comprises oxygen and acetylene gases stored under pressure in steel cylinders. The cylinders should be fitted with regulators, to control the pressure and flow of gases. Flexible hoses are used to connect the regulators to the torch or blowpipe. Specially designed safety devices, called flame traps or “Flashback Arrestors” are fitted between the hoses and the regulators. Flashback arrestors prevent flames generated by a 'flashback' from reaching the cylinders 

Laser welding(newer welding)