Gas Metal Arc Welding

Gas metal arc welding uses an arc between a continuous filler metal (consumable) electrode and the weld pool. Shielding is provided by an externally supplied shielding gas. This process is also known as MIG welding or MAG welding.  MIG (Metal Inert Gas) welding means the use of an inert (i.e. non active) gas. MAG (Metal Active Gas) welding requires the use of an active gas (i.e. carbon dioxide and oxygen). CO₂ is a more commonly used shortening of MAG welding gas.

The process consists of a DC arc burning between a thin bare metal wire electrode and the workpiece. The arc and weld area are enveloped in a protective gas shield. The wire electrode is fed from a spool, through a welding torch which is connected to the positive terminal into the weld zone. MIG/MAG welding is the most widely used process in the world today. It is a versatile method which offers a lot of advantages. The technique is easy to use and there is no need for slag-cleaning. Another advantage is the extremely high productivity that MIG/MAG welding makes possible.

MIG/MAG welding is used on all thicknesses of steels, aluminium, nickel, stainless steels etc. The MAG process is suitable both for steel and unalloyed, low-alloy and high-alloy based materials. The MIG process, on the other hand, is used for welding aluminium and copper materials.

TIG Welding

In TIG welding an arc is created between a nonconsumable tungsten electrode and the metal being welded. The arc produces the heat needed to melt the work. The shielding gas keeps oxygen in the air away from the molten weld pool and the hot tungsten. Gas is fed through the torch in order to shield the electrode and the molten weld pool. The shielding gas used is pure argon. There may or may not be filler metal added to the molten weld pool during the process. Tungsten is used for the electrode because of its high melting temperature and good electrical characteristics. 

The main advantage of TIG welding is the wide range of materials that it can weld. TIG welding is used to a great extent for welding different kinds of alloys of aluminium and stainless steel, specially when quality is of great importance. This technique is mainly used in aeronautical constructions and in the chemical and the nuclear power industry. 

Flux Cored Arc Welding

Flux cored arc welding (FCAW) is an electric arc welding process that uses an arc between a continuously fed flux-filled electrode and the weld pool. The process is used with shielded gas from a flux contained within the tubular electrode with or without additional shielding from an externally supplied gas.

The FCAW process utilizes the heat of an arc between a continuously fed consumable flux cored electrode and the work. The heat of the arc melts the surface of the base metal and the end of the electrode. The metal melted off the electrode is transferred across the arc to the work piece, where it becomes the deposited weld metal. Shielding is obtained from the disintegration of ingredients contained within the flux cored electrode. Additional shielding is obtained from an envelope of gas supplied through a nozzle to the arc area. Ingredients within the electrode produce gas for shielding and also provide deoxidizers, ionizers, purifying agents and, in some cases, alloying elements.

Submerged Arc Welding

Submerged arc welding (SAW) is an arc welding process that fuses together the parts to be welded by heating them with one or more electric arcs between one or more bare electrodes and the work piece. The submerged arc welding process utilizes the heat of an arc between a continuously fed electrode and the work. The heat of the arc melts the surface of the base metal and the end of the electrode. The metal melted off the electrode is transferred through the arc to the workpiece, where it becomes the deposited weld metal. 

Shielding is obtained from a blanket of granular flux, which is laid directly over the weld area. The flux close to the arc melts and intermixes with the molten weld metal and helps purify and fortify it. The flux forms a glasslike slag that is lighter in weight than the deposited weld metal and floats on the surface as a protective cover. The weld is submerged under this layer of flux and slag- hence the name submerged arc welding.

Plasma Arc Welding

In plasma arc welding, a shielded arc is struck between a non consumable electrode and the torch body, and this arc transforms an inert gas into plasma. A plasma is a gas which is heated to an extremely high temperature and ionized so that it becomes electrically conductive. Similar to GTAW (TIG), the plasma arc welding process uses this plasma to transfer an electric arc to a work piece. The metal to be welded is melted by the intense heat of the arc and fuses together. In the plasma welding torch a tungsten electrode is located within a copper nozzle having a small opening at the tip. A pilot arc is initiated between the torch electrode and nozzle tip. This arc is then transferred to the metal to be welded. Shielding gas is obtained from the hot ionized gas issuing from the orifice. Auxiliary inert shielding gas or a mixture of inert gases is normally used.

By forcing the plasma gas and arc through a constricted orifice, the torch delivers a high concentration of heat to a small area. With high performance welding equipment, the plasma process produces exceptionally high quality welds. Like gas tungsten arc welding, the plasma arc welding process can be used to weld most commercial metals, and it can be used for a wide variety of metal thicknesses.