What is the working principle of arc welding? What are the equipments required and advantages and disadvantages of the process? How many Types of Welding methods?
Answer: Working principle of arc welding | Types of Welding methods
Heat required for melting and joining of plates, is obtained due to electrical arc. This phenomenon is called arc welding. When the power supply is given and optimum gap is maintained between cathode and anode, the negative charged electrons are generated at cathode and it moves towards anode at very high speed, due to this kinetic energy of electrons is converted into heat energy. The amount of heat generated at anode is much higher that the cathode because of very high velocity of electrons.
Generally it is used for the fabrication of pressure vessels, penstocks and boilers. Other application includes automobile industries.
The most commonly used equipment for arc welding are as follows :
1. AC or DC machines : Both direct current and alternating current are used for electric arc welding, each having its particular application. DC supply is generally obtained from generators driven by electric motors whereas AC supply transformers are used where electricity supply is available.
2. Electrode and electrode holders : Commonly used electrodes are of two types i.e. bare electrodes and coated electrodes. Bare electrodes are cheaper but weld produced through these are of poor quality. Coated electrodes are used in modern welding machines as they carry a core of bare metallic wire produced with a coating or covering on the outside surface.
3. Cables and connector : Cable carry the current to the desired place and cable connectors are essential for connections.
4. Earthing clamps : These are used to close electric circuit.
5. Chipping hammer : It is used to remove the slag from welded portions.
6. Wire brush : It is used for cleaning the weld after chipping.
7. Helmet : The face and the eyes of the operator must be protected from the arc which contains ultra‐violet and infra‐red rays. For this purpose, helmet or face shield is used.
The advantages of arc welding are :
1. Higher welding speed.
2. Greater deposition rates.
3. Less post welding cleaning.
4. Better weld pool graspability.
5. No loss of working hours brought in by changing terminals.
6. Positional welding offers no issues when contrasted with different procedures.
7. The procedure is effortlessly mechanized.
8. No flux is required.
9. Ultra‐low hydrogen process.
The disadvantages of arc welding are :
1. Higher introductory setup cost.
2. Higher upkeep costs because of additional electronic parts.
3. The setting of plant variables requires a high aptitude level.
4. Less productive where high obligation cycle prerequisites are vital.
5. Radiation impacts are more extreme.
Types of Welding methods
Ans. Based on the method of heat generation and application, welding process can be divided into
seven main categories :
1. Gas welding :
(a) Oxy‐acetylene gas welding (b) Air‐acetylene gas welding
(c) Oxy‐hydrogen gas welding.
2. Arc welding :
(a) Shielded metal arc welding (SMAW)
(b) Inert gas shielded metal arc welding (TIG/MIG)
(c) Atomic hydrogen welding (d) Submerged arc welding
(e) Plasma arc welding (f) Electro slag welding.
3. Resistance welding :
(a) Spot welding (b) Seam welding
(c) Projection welding (d) Percussion welding
(e) Flash butt welding.
4. Solid‐state welding :
(a) Friction welding (b) Explosive welding
(c) Roll welding (d) Ultrasonic welding
(e) Forge welding (f) Diffusion welding
(g) Hot pressure welding.
5. Radiant energy welding :
(a) Electron beam welding (b) Laser beam welding.
6. Exothermic welding :
(a) Thermite welding (b) Cad welding.
7. Related welding process :
(a) Soldering (b) Brazing.