Lets start with basic:-
What is Welding?
Welding is the process of joining metal parts by application of heat and it is most widely used in fabrication. This process done with or without application of pressure and addition of filler material.
It is the ability or join ability of material to weld with similar materials without cracking. Many metal and thermoplastics can be welded together to fabricate a final material but some are easier to weld than others.
Factors affecting weldability:-
- Thermal conductivity
- Melting point
- Thermal expansion
- Surface condition
- Change in microstructure
Different type of welding:-
Types of welding process
Gas welding is the process of welding in which metal parts are weld using different gases with oxygen. Below are the different type of gas welding.
- It’s very common welding process .A mixture of oxygen and acetylene is used to join metal parts. Mixture of oxygen and acetylene burns as an intense /focussed flame, having temperature more than 3500 degree centigrade.
- When this flam come in contact with metal parts ,it melts the surface of metal and form molten pool and allowing welding to take place.
- This welding is also used for brazing, bronze welding ,forging/shaping metal and cutting.
- Its very simple type of welding process. where heat or flame is produce from mixture of acetylene and air .
- Joints are weld without the application of pressure and with or without use of filler metals.
- Maximum temperature is 2400 degree centigrade. This welding used where soft solder is required like copper plumbing.
- Mixture of hydrogen and oxygen gas is used for welding ,temperature of flame is more than 2500 degree centigrade.
In resistance welding electric current is used to join metallic parts.There are different forms of resistance welding, including spot welding, seam welding, projection welding, and butt welding.
The heat generated in Resistance welding is expressed by the equation:-
Where E = heat energy,
t=time that the current
Commonly used resistance welding are spot, seam ,butt and projection welding.
- In this welding two or more metal sheets are placed between electrode ,and electric current is supplied for a definite time and force is exerted on work piece .
- One work piece is place with the moving electrode and one work piece place with fixed electrode. Both work piece are held under pressure and heavy current is passed between the electrodes for preset time.
- Due to high current, the area of metals in contact shall be rapidly raised to welding temperature. The pressure between electrodes, squeezes the hot metal together thus completing the weld.
- Seam welding is similar to spot welding except that it uses disc shaped electrode .A current is passed through roller to the material in contact with them.
- Mechanical pressure is applied by roller on workpiece using gas-tight or liquid-tight.
- It is modification of spot welding, and in this Projections are provided on the surface of one of the work piece which offer resistance during passage of current and thus generating heat at those points and weld occur.
- Its a welding technique use to join two components together and this process done by a gradual preheating of the two components, and then placing them together under certain pressure.
Under this welding AC current or Dc currents is supply to create electric arc between an metal sticks(electrode) and the base material to melt the material at that point and metal is cool result in a binding of the metals.
Carbon arc welding
Its very common welding process in which joining of metals is produce by heating with arc between a carbon electrodes and the work piece. The arc heat and melts the work piece edges, forming a joint.
Metal arc welding
This welding is also known as shielded metal arc welding; it involves striking an arc between a covered metal electrode and a work piece .The work piece are made part of an electric circuit known as welding circuit.
Plasma arc welding
Plasma arc welding is similar to gas tungsten arc welding, in this heat or electric arc is generated between a non –consumable tungsten electrode and work piece.
Difference between plasma arc welding and gas tungsten arc welding is positioning of electrode within the body of the torch.
Gas metal arc welding
In this electric arc is established between a consumable wire electrode and work piece and weld area is shielded by an effectively inert atmosphere of argon, helium, carbon dioxide or various gas mixture. This process is also called as inert gas welding.
Gas tungsten arc
In this welding process arc is formed between a non consumable tungsten electrode and the work piece and gas is fed through the torch to shield the electrode and molten weld pool.
Electron bean welding
- It is a fusion welding process in which a beam of high velocity electron is applied on material to join. As the kinetic energy of electrons is transformed into heat, melting of work piece occur and welding of metal take place successfully.
- Welding process is done in condition of a vacuum to prevent dispersion of electron beam
Laser beam welding
- This welding process used to join multiple work piece of metal (mostly in automobile industry).
- This process is similar to electron beam welding; in this process high energy beam is used.
- Laser beam provides a concentrated heat source, allowing narrow deep welds with high welding rates.
Solid state welding
In this welding process no external source of heat is used for joining, joining of metal take place in solid state. In this welding process filler metal is not used and welding does not involve molten states of base material.
It is part of solid state welding process that generate heat through mechanical friction between a moving work piece and stationary work piece .That heat is used to join two work piece by applying external pressure at the surface of work piece.
The friction is applied until the plastic forming temperature is achieved and temperature is around 900-1300 degree centigrade. Under this temperature external force is applied until the both work piece make a permanent joint.
It is a welding process in which heat is generated using ultrasonic waves or vibration. In this high frequency electrical energy is converted into high-frequency mechanical motion.
Frequency range is above the normal hearing range and it is about 20000 to 30000 Hz.
It is a solid state welding process that creates fusion of surface to be joined by applying pressure at high temperature.
Under this welding process filler material may or may not be use, if used they may be in the form of electroplated surface and heat required for melting the work piece is obtained by resistance ,induction or furnace .
For joining most refractory metals, a protective inert atmosphere is used and for general material atmosphere and vacuum furnace are used.
It is a solid state welding process in which welding is done by accelerating one of the work piece at extremely high velocity through the use of chemical explosives.
Explosive welding allows highly dissimilar metals such as aluminium, alloy steel, carbon steel, alloys of copper, stainless steel all can be welded one another.