1. UNIT-2 CASTING AND WELDING

2. LASER BEAM WELDING
Light energy is converted into heat energy. Hence, light energy is produced from the laser source like ruby rod in the form of monochromatic light
Due to electrical discharge from the capacitors, the flash tube converts the electrical energy into light flashes
When ruby rod is exposed to the intense light flash, the chromium atoms of the crystal excited & pumped to a high energy level beam
This high energy level is immediately reduced to intermediate & drop to original state with the evolution of red fluorescent light.
When this light energy is impacted to the work piece, it will convert into heat energy.

3. The various laser forms are
1. Liquid laser
2. Gas laser
3. Ruby laser
4. Semi conductor laser

4. Advantages
It is used in glass & plastics
Even very small holes can also be welded
Accuracy is greater
There is no heat loss
Neat & clear surface finish can be obtained
Disadvantages
Welding process is slow
Limited depth of weld can be done
It is not suitable for large production

5. Applications: Thin metals about 0.5 to 1.5mm thick can be welded
It is very much useful in electronic components welding
It is used in aircraft components joining
It is very much useful in joining metal alloys

6. PLASMA ARC WELDING
Special form of GTAW in which a constricted plasma arc is directed at weld area
Tungsten electrode is contained in a nozzle that focuses a high velocity stream of inert gas (argon) into arc region to form a high velocity, intensely hot plasma arc stream
Temperatures is PAW reach 28,000°C (50,000°F), due to constriction of arc, producing a plasma jet of small diameter and very high energy density

8. Advantages Disadvantages Penetration is uniform Arc stability is good
High accuracy weld can be produced
High speed weld can be obtained
Disadvantages
Huge noise occurs during welding
It is limited to high thickness applications
Ultraviolet radiation can affect human body
Gas consumption is high