Radiant Energy Welding
The Radiant energy welding process is a group of welding processes wherein heat is obtained by focusing an energy beam on the workpiece.
The radiant welding process can be classified as follows:
- Electron Beam welding process
- Laser Beam welding process
Electron Beam Welding
The electron beam process is relatively new in the welding industry. The discovery of the electron beam is nearly 300 years old, but its widespread use occurred during World War II when ultra-high purity welds required to connect reactive and refractory metals.
Electron beam welding is a fusion welding process wherein heat is obtained (by changing the kinetic energy of electrons to thermal energy) from a focused beam composed primarily of high-velocity electrons.
Principle of Operation
The process of electron beam welding in a high vacuum can be classified into the following sequence:
Joint preparation and cleaning
A joint for electron beam welding ordinarily has closely fitted, abutting square groove faces to enable the narrow electron beam to fuse parent metal on both sides of the joint in making a weld. For this purpose commonly the joint gap of about 0.050 or0.075 mm maximum used for making narrow welds. A suitable root opening is provided if filler metal is to be added during welding. Mechanical or chemical methods of cleaning may be carried out a few minutes before welding is started.
Types of Joints for
Butt joint, Corner Joints, T joints, Lap joints, and Edge joints can melt through electron beam welding.
Fixturing and Demagnetization of the workpiece
Residual magnetism in the workpiece and fixtures may be the cause of the deflection of the electron beam, all made of magnetic materials, disintegrating, before welding, placing them in a fifty-cycle inductor region, and removing them slowly.
Laser Beam Welding
Laser beam welding is a process of Radiant energy welding wherein the heat is generated from the application of a sequential beam of light, impinging over the surface to be joined.
In the laser welding process, the concentrated beam is generated from the emission of light, applied to the workpiece. Thus the light energy is converted into thermal energy and the workpiece gets the heat required to thaw, thereby completing the welding process.
As shown in the diagram, the laser welding system consists of a (cylindrical shape) ruby crystal, mounted with a flush tube, which contains an inert gas called xenon. Ruby is aluminum oxide with chromium dispersed throughout it, forming about 1/2000 of the crystal, which is less than a natural ruby contains. The end of the crystal is silvered to form mirrors internally, while one end has a tiny hole in the silver layer, through which the laser beam emerges.
The flash tube, around the outside of the crystal, is designed for the operation of a rate of thousands of flashes per second. It converts electrical energy into light energy..
The main work of the capacitor bank unit is to store the electrical energy by charging a high voltage power supply. It energizes the flash tube by an appropriate triggering system. Xenon transforms a high proportion of the electrical energy into white light flashes when the capacitors discharge. The duration of flashes is around 1/1000 second.
As the ruby is exposed to the intense light flashes, the chromium amounts of the crystal are excited and pumped to a high energy level. These chromium atoms immediately drop to an intermediate energy level with the evolution of heat and eventually drop back to their original state with the evolution of a discrete quantity of radiation in the form of red fluorescent light.