Fusion Welding

We have already studied, that welding is a precise, reliable, cost-effective and a highly technical method for joining materials in manufacturing industries.  Welding requires to generate heat using electricity, gases, base materials (that may be pre -heated), welding rods / filler materials, etc.   All types of welding can be divided basically in to 2 varieties :

1. Fusion Welding
2. Non Fusion Welding

In this article, we will study about various types of Fusion welding.

Fusion Welding – Is the process of melting and joining two metals at a suitable temperature, with heat & mostly with filler. The metal parts are locally heated to melt along the joint. Heating is carried out by oxy fuel flame or electric Arc.

Types of Fusion Welding:

1. SMAW/MMAW
2. GTAW/TIG
3. GMAW (MIG/MAG)
4. FCAW
5. SAW
6. PAW
7. OFGW

1. SMAW/MMAW – Shielded metal arc welding (SMAW), also known as manual metal arc welding (MMA or MMAW), flux shielded arc welding or informally as stick welding, is a manual arc welding process that uses a consumable electrode covered with a flux to lay the weld. It is used to form an electric arc between the electrode and the metals to be joined & hence the name.
2. GTAW/TIG – Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding. It is a Fusion Welding Process in which arc is generated between Tungsten Rod & the work, that uses a non-consumable tungsten electrode to produce the weld. The weld area and electrode are protected from oxidation or other atmospheric contamination by an inert shielding gas (argon or helium). Filler Wire is separately added to Weld Pool to act as a fusing metal. Welding Torch & Tungsten Rod are cooled by flow of argon / cooling water.
3. GMAW (MIG/MAG) – Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) is a welding process in which an electric arc is created between a consumable MIG wire electrode and the work piece metal. This electric arc heats the work piece metals, causing them to fuse (melt and join). Along with the wire electrode, a shielding gas feeds through the welding gun, which shields the process from atmospheric contamination. The only truly inert gases used in welding are argon and helium but for many applications gases containing chemically active constituents may also be used. In these cases the process is referred to as M.A.G. (Metal Active Gas).
4. FCAW – Flux-cored arc welding (FCAW or FCA) is a semi-automatic or automatic arc welding process. FCAW requires a continuously-fed consumable tubular electrode containing a flux and a constant-voltage or, less commonly, a constant-current welding power supply. An externally supplied shielding gas is sometimes used, but often the flux itself is relied upon to generate the necessary protection from the atmosphere, producing both gaseous protection and liquid slag protecting the weld. The process is widely used in construction because of its high welding speed and portability.
5. SAW – Submerged-arc welding (SAW) is a common arc welding & semi automatic process that involves the formation of an arc between a continuously fed electrode and the work piece. A blanket of powdered flux generates a protective gas shield and a slag (and may also be used to add alloying elements to the weld pool) which protects the weld zone.

6. PAW – Plasma arc welding (PAW) is an arc welding process similar to gas tungsten arc welding (GTAW). The electric arc is formed between an electrode (which is usually but not always made of sintered tungsten) and the work piece. The key difference from GTAW is that in PAW, the electrode is positioned within the body of the torch, so the plasma arc is separated from the shielding gas envelope. The plasma is then forced through a fine-bore copper nozzle which constricts the arc and the plasma exits the orifice at high velocities (approaching the speed of sound) and a temperature approaching 28,000 °C (50,000 °F) or higher.
7. OFGW – Oxy-Fuel Gas Welding includes those welding operations which use the combustion of a fuel gas and oxygen to provide sufficient heat for fusion welding. Fusion welding, with or without filler metal, in which the heat for welding is produced by the combustion of a fuel gas or gasses with an admixture of oxygen. Gas welding in which the fuel gas is acetylene. Other fuel gases are also used with oxygen (i.e. butane, hydrogen, and propane).