LASER Beam Welding | LASER Cutting System

Laser Beam Welding:

Definition:

Laser beam welding is a welding process that uses a laser beam to melt and vaporizes a material. LASER (Light Amplification by Stimulated Emission of Radiation) beams are very high energy density electromagnetic beams which are highly coherent, monochromic and unidirectional.

01-laser beam machining process

Power of LASER:

For example, a LASER can give a power output of nearly 100 W/mm2 of beam cross section in short bursts. By focussing this beam on a spot (1 / 100) mm2 in size, the beam will be concentrated to a power density of 10 KW / mm2. This concentrated energy is so intense that it easily ionizes the atmospheric air to create sparks. With the beam focused from a high power laser, even the hardest material like “diamond can be melted in a fraction of a second. Temperatures of the order of 8000 deg Celsius have been produced in less than 0.5 milliseconds with lasers. This high energy can be used to melt and vaporize work piece material in a very short time and permit its fusion with another metal.

In addition to welding, LASER’s can be used for cutting, drilling, micromachining, surface heat treating and selective cladding of materials.

01-laser beam-xenon flash tube

Application areas:

1. Automotive industry

a. Gear parts such as Cog wheels, planet gears

b. Body making such as bottom plates, skins etc.

c. Engine components such as tapper housings, diesel engine pre-combustion chambers

01-automobile laser beam machining process

2. Aerospace industry

a. Engine components

b. Instrument cases

01-aeronautical laser machining process

3. Steel industry

a. Pipe production

b. Vehicle superstructures

c. Continuous metal strips

d. Tins

01-laser beam machining applications

4. Electronics industry

a. PCB’s

b. Accumulator cases

c. Transformer plates

d. Cathode ray tubes

5. Plant and Apparatus engineering

a. Seal welds at housings

b. Measurement probes

6. Medical industry

a. Heart pacemaker cases

b. Artificial hip joints

01-medical laser testing

Advantages of laser beam welding:

1. The laser beam can melt and vaporize any known material. Even non-metallic and refractory materials can be easily worked with.

2. It can easily weld or join dissimilar metals or metals which are difficult to weld by conventional methods

3. No flux are filler metals is needed

4. The ability to focus the beam at very narrow spots makes welding of extremely small components and deep welding possible

5. Heat affected zone is small. This is helpful in welding close to heat sensitive areas

6. Production rates are fairly high

7. The process can be easily automated

8. Welds can be made inside transparent glass or plastic housings

9. Areas not readily accessible can also be welded

10. Can cut holes as small as .005 mm with depth/diameter ratios of 50:1

 

Disadvantages of laser beam welding:

1. Cost of equipment is high

2. High reflectivity materials are difficult to work with.

3. Laser welding is limited to depths of approximately 1.5 mm and additional energy only tends to create gas voids and undercuts in the work

4. Materials such as magnesium tend to vaporize and produce severe surface voids.

5. Deep cut produce taper

Pressure Thermite Welding | Thermite Welding Process

Pressure Thermit Welding:

Pressure thermit welding is a process in which the heat produced by the thermit reaction is utilized only for heating the ends of the pieces to be joined, while the actual joint formation occurs by solid pressure welding.

History of Thermit welding:

In 1893 Hans Goldschmidt of Germany began to experiment with Alumino-thermic reactions. They are highly exothermic processes involving reactions of metallic oxides with Aluminium powders. This work led to a patent application for the Thermit process in 1895. due to the large amount of heat released by exothermic chemical reactions and the versatility of the thermit process, other applications were quickly found. By the end of the 19th Century, the Thermit process had been successfully used to make repairs to large cast and forged steel parts and in thermit welding of railways.

Two variations of the process are in use.

Process 1:

When welding pieces of small cross-section area like the ends of a pipe, the ends are first aligned properly. A mould is built around the section and heated. When the slag is poured into mould, the slag enters and forming the thin film around the ends. The metal follows next and displaces the slag. The film formed on the parts to be welded does not permit the thermit steel to fuse with the metal of the work but heats it to welding temperature. When the joint reaches the welding temperature the parts are drawn together forming a pressure butt joint. Specially designed clamps are used to apply pressure to bring the butting faces together for welding.

01-pressure_thermite_welding

Process 2:

In the other version used for thicker work pieces the ends are spaced to a small distance apart in a removable mould. The space between the ends of the work pieces is filled with thermit metal and the ignition started. The reactions products are allowed to stay in place till the parts to be joined reach the required temperature for solid welding. The mold and the reaction products are then removed and pressure applied to complete the solid weld.

Disadvantages:

The quality of weld produced by either method is, however, not very satisfactory and the cost is very high. The process is therefore not very commonly used in practice.