WELDING
is a process in which two or more parts are joined permanently at their touching
surfaces by a suitable application of heat and/or pressure.
It is classified into two groups
1). Fusion welding: In this process, base metal is melted by means of heat.
Oxyfuel Gas Welding (OFW)this process is also known as oxy-acetylene welding. heat is supplied by the combustion of acetylene in a stream of oxygen.Both gases are supplied to the torch through flexible hoses .Heat from this torch is lower and far less concetrated than than from an electric arc.
Resistance welding. Resistance welding is a group of welding process in which coalescence is produced by the heat obtained from the resistance of the work to the flow of electric current in a circuit of which the work is a part and by the appication of pressure.
Electron- beam welding (EBW). Electron beam welding is defined as a fusion welding process wherein coales.
Arc welding and similar processes
It consists of combination of different welding processes wherein coalescence is produced by heating with an electric arc, (mostly without the applicatiodn of pressure)andde with or without the use of filler metals depending upon the base plate thickness.
Shielded-Metal Arc (SMAW) or Stick Welding
This is an arc welding process wherein coalescence is produced by heating the workpiece
with an electric arc setup between a flux-coated electrode and the workpiece
Submerged Arc Welding (SAW)
This is another type of arc welding process, in which coalescence is produced by heating the
workpiece with an electric arc setup between the bare electrode and the work piece.
Flux-Cored Arc Welding (FCAW)
This process is similar to the shielded-arc stick welding process with the main difference
being the flux is inside the welding rod
Gas-Metal Arc Welding (GMAW)
In this process an inert gas such as argon, helium, carbon dioxide or a mixture of them are
used to prevent atmospheric contamination of the weld. The shielding gas is allowed to flow
through the weld gun.
Gas-Tungsten Arc Welding (GTAW)
This process is also known as tungsten–inert gas (TIG) welding. This is similar to the GasMetal
Arc Welding process. Difference being the electrode is non consumable and does not
provide filler metal in this case.
Plasma Arc Welding (PAW)
This process is similar to TIG. A non-consumable electrode is used in this process. Arc
plasma is a temporary state of gas. The gas gets ionized after the passage of electric current and becomes a conductor of electricity.
Electron-Beam Welding (EBW)
Electron beam welding is defined as a fusion welding process wherein coalescence is produced by the heat obtained from a concentrated beam of high velocity electron. When high velocity electrons strike the workpiece, kinetic energy is transformed into thermal energy causing localized heating and melting of the weld metal.
2). Solid -state welding: In this process, joining of parts take place by applications pressure alone or a combination of heat and pressure.
1. Diffusion bonding (DB): Parts are pressed together at an elevated temperature below
the melting point for a period of time.
2. Friction Welding (FRW)
In friction welding (solid state welding process) coalescence is produced by utilizing the heat obtained from the mechanically induced rotating motion between the rubbing surfaces. When the temperature at the interface of the two parts is sufficiently high, the rotation is stopped and increased axial force is applied. This fuses the two parts together
3. Ultrasonic welding (USW) for metals: This process utilizes transverse oscillation of one part against the other to develop sufficient frictional heat for fusion to occur.