What is the working principle of arc welding? What are the types of equipment required and the advantages and disadvantages of the process? How many Types of Welding methods?
Answer: Working principle of arc welding | Types of Welding methods
The heat required for the melting and joining of plates is obtained due to the electrical arc. This phenomenon is called arc welding. When the power supply is given and the optimum gap is maintained between the cathode and anode, the negatively charged electrons are generated at the cathode and it moves towards the anode at a very high speed, because of this kinetic energy of electrons is converted into heat energy. The amount of heat generated at the anode is much higher than the cathode because of the 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: The cable carries the current to the desired place and cable connectors are essential for connections.
4. Earthing clamps: These are used to close the 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 ultraviolet and infra-red rays. For this purpose, a 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 grasp ability.
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, the welding process can be divided into
seven major 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.