About Welding Process and Its Theory
Welding is the method in which metals are joined together by melting them and using a filler to join the parts. To weld, a combination of heat and pressure is used. The earliest form of welding is called forge welding and dates back to 2000 B.C. In this, the metals are heated and hammered to fuse them. Nowadays this is only practiced by blacksmiths. There are various methods that are followed after the advent of electricity. Now different sources of energy are used for welding purposes - gas flame, electric current, laser, electronic beam, friction and ultra sound. Some of them are Arc welding, Gas welding and Resistance welding.
The method that is mostly used is arc welding. This is also called stick welding. In this, inexpensive equipment is used and a continuous supply of AC or DC is required with constant voltage. Welding is done by an electric arc between the electrode and the base materials. At the point of welding, the metal is melted. Shielding gas protects the area. The work is done speedily. It has a high concentration of heat and so the distortion is less. Some of the processes are - shielded metal arc, gas tungsten arc, gas metal arc and submerged arc.
Gas welding is generally used for repair work and welding of materials that cannot withstand high temperatures. This includes repairing pipes and tubes, welding plastics, making jewelry etc.
Resistance welding needs costly equipment and it cannot be used in all situations. In this method additional sheets of metal are used to encase the pieces that have to be fused together.
The latest method is laser welding or energy beam welding. It is very fast and the accuracy is perfect, but it is too expensive for all purposes. Electron beams are also used. This is greatly automotive and aerospace industry.
Welding can be done only on certain metals. When it comes to alloys, it is difficult to know its composition and hence can create a problem when it is welded. Stainless steel tends to crack and distort when fused.
In many manufacturing units, welding has become automated and robots are used in many areas. Welding is not only done indoors in manufacturing units, it can be done outdoors too. It can be done underwater, where ships and pipelines underwater have to be repaired. Its use in space is also being researched.
It is very essential to be very careful while welding. A welder requires a good welding gear which includes a welding helmet, welding gloves and a heavy jacket. The eyes can be damaged if you do not protect your eyes when you see the arc. The fumes from welding can also be highly toxic. You can also get electric shock, burns, and overexposure to ultra violet rays. So, extreme care should be taken by the welder, while welding. One should have welding hoods, eye protection, face protection, welding gloves, first aid kit, hearing protection, respiratory protection and any other protective gear that will be of help to the welder.
The difference in the different types of welding is the different types of energy that is used to generate heat and the method that is used to weld the metals. With modern technology, there are many newer and safer methods that are used.