Welding uses heat to join separate materials into one unit.
Basic heat and hammer welding has been around for hundreds, even thousands of years. The sections of the two pieces of metal that were to be joined would be melted in a hot fire and then the welder would apply pressure via heavy hammer blows to join the two items.
Heat and hammer, or forge welding was used until the early twentieth century when gas and electric heat began to be used. These had the advantage of producing greater heat than a simple fire could produce. Further the heat can be directed through devices that allow for precision and thus much smaller welds.
Different types of welding processes are available.
There are several different types of welding processes used today. The one thing they all have in common is they apply a heat source to the material to be welded as part of the process. Some methods also use a flux material to help protect the weld from contamination, others achieve this by the use of a gas. A welding method may be chosen by how precise it can be, the material it can be used to weld and the expense. Some of the most common welding types are S.M.A.W., G.M.A.W., T.G.A.W.,
Shielded metal arc welding (S.M.A.W.) is one of the most common kinds of welding. An electrode covered with a flux material is heated by electric heat and as it burns, two things happen simultaneously. First, the target area becomes heated melting the materials to be welded, second the flux produces a slag and gases which protect the area from contamination. This method is also known as stick welding. It is versatile and easy to learn.
Gas Metal Arc Welding is also very popular and is used extensively in industry and manufacturing. It is sometimes called MIG or MAG welding for metal inert gas or metal active gas welding. In this method a welding tool feeds a wire electrode and a gas into the weld area. The heated wire melts the target materials and the gas helps keep the area from being contaminated. The relatively short time it takes to complete a job and the different ways it can be used explain the popularity of MIG welding.
TIG welding, formally known as Tungsten Gas Arc Welding or T.G.A.W. uses tungsten for the consumable electrode. It is possible to achieve more control with this type of welding, compared to other methods, but is also harder to learn.
There are other welding methods but these three are some of the best known and widely used. Other welding methods include Flux cored arc welding. (F.C.A.W.) This method feeds a wire and uses a flux material but, in contrast with stick welding, the wire is hollow and the flux is contained within the wire. Electroslag welding is useful for welding relatively thick pieces of material and for items that need to be in a vertical position. S.A.W. or submerged arc welding, on the other hand is usually used on horizontal pieces. In this method an electrode is fed underneath a sheet of flux material which is coating the materials to be welded.
Welding can also, of course, be done with the use of an acetylene torch but this is primarily for home use and even there is mostly used for relatively simple repairs.
Welding has a wide range of applications and it can be expected that this will not change in the near future. This makes it a good skill to learn either as a career choice or fall back skill for someone entering the work force or needing a career change.