A Textbook of Arc Welding
Ever since 17th century, after the industrial revolution, technology has made our lives comfortable. Man started using iron and steel and since then they play a crucial role in our day to day lives. We are simply surrounded by metals. It in the place we live, the things we do or use to accomplish our work. Thus it has aided in almost all sectors of our lives.
One of the strongest methods of joining any metal is through fusion with the help of arc welding. Technically speaking, electric current allows the electric arc to melt 2 metal pieces, a filter material is used which enables the pieces to mix and as it cools it solidifies into one piece.
GMAV commonly known as gas melting arc welding and also referred to as MIG (Metal Inert Gas) welding can be described as a semi-automatic or fully automatic arc welding process. It comprises of a welding gun which is filled with continuous wire electrode and shielding gas. The filler electrode material comes as spools of wire.
Initially GMAV was developed only for aluminum welding and other non-ferrous metals. Later it was used for welding steel which minimized the time taken for welding process. In short GMAV has revolutionized the art of welding and it provides greater degree of consistency and faster production rates.
Some of its advantages are; higher rate of filler metal deposition, narrow weld bead, minimum distortion, provides easier clean and precise welds. The demerits of GMAV are its complexity, quite expensive and tedious installation or setting up procedures.
The welding gun consists of a control switch, contact tip, power cable, gas nozzle, an electrode and a gas hose. Initially the operator switches on the controls with the help of the control switch. He then initiates the wire feed of the equipment, the electric power supply, and the shielding gas flow. This causes the electric arc to be struck. The contact tip is made up of copper. Though you have a variety of materials for contact tip in today's market, usually copper is preferred. At times this tip is chemically treated to minimize spatter.
The gas nozzle evenly directs the shielding gas over the welding zone. For high current welding operations larger nozzles are preferred. This enables greater shielding gas flow. A water hose is used in such high electric operations as the equipment sustains lot of heat and it has to be minimized for maintenance purposes and increasing the equipment's life time. Repairing costs will also inflict a burden for the industry. Usually the rate of feed for the machine is maintained constantly. However there are some highly technical advanced machines in today's market which varies the wire feed rate in response to arc length and the voltage supply.
Most applications uses constant voltage supply and changes in arc length creates a lot of heat and current extracted for the process. Thus arc lengths are also maintained constantly depending upon the voltage supply. Alternating current (AC) is seldom used and electrodes are positively charged. This polarity is altered when special-emissive coated electrodes are used.
An electrode selection is highly influenced by composition of the metal, the process and design and material surface design.
If all of the above factors are chosen perfectly, we can produce high quality welds at cheaper cost.