Welding is a fabrication process that joins materials. Usually metals or thermoplastics, by using high heat to melt the parts together. And allowing them to cool causing fusion. It is from lower temperature metal-joining techniques such as soldering. Which do not melt the base metal. In addition to melting the base metal, a filler material is usually added to the joint to form a pool of molten material (the weld pool). That cools to form a joint that, based on weld configuration (butt, full penetration, fillet, etc.). It can be stronger than the base material (parent metal). It technique used for joining metallic parts usually through the application of heat.
Pressure may also be used with heat or by itself to produce a weld. It also requires a form of shield to protect the filler metals or melted metals from being contaminated.
One of the most common types of arc welding is shielded metal arc welding; it is also known as manual metal arc weld or stick welding. Electric current is used to strike an arc between the base material and electrode rod, which is made of typically steel and is covered with a flux that protects the weld area from oxidation and contamination by producing carbon dioxide (CO2) gas during the welding process. The electrode core itself acts as filler material, making a separate filler.
Weld times are slow. Since the electrode must be replaced and the flux must be cleaned away after welding. Furthermore, the process is limited to materials, though special electrodes have made possible the welding of cast iron, stainless steel, aluminum, and other metals.
Many common welding procedures involve an open electric arc , the risk of burns and fire is possible; this is why it is classified as a hot work process. To prevent injury, welders should wear personal protective equipment in the form of heavy leather gloves. And protective long sleeve jackets to avoid heat and flames.
Clothing such as polyester should not be worn since it may burn or can cause injury. The brightness of the weld area called arc eye or flash burns in which ultraviolet light causes inflammation of the cornea and can burn the retinas of the eyes. Goggles and welding helmets are worn to prevent this exposure. To protect bystanders, the welded area should be surrounded by translucent welded curtains. These curtains, made of a polyvinyl chloride plastic film, shielded outside the welded area from the UV light of the electric arc. But it cannot be replace the filter glass used in helmets.