The terms welding is define the joining of two or more surface (usually metals, but not always) under the influence of heat, so the product shall be nearly homogeneous union as possible. This is the main definition of welding.
In all welding joint processes heat is applied to or produced at the joint and heated surfaces are brought into close contact, as result the joint surfaces to grow together into single body.
Now we will see what happen during this growing up together process. It is we all known that the matter is made of molecules which in turn into atom. The atoms of molecules are become active when the temperature of material reaches absolute zero (-
Electric Resistance Welding
It is called plastic or pressure welding process where coalescence is produced by heat by electric current flow through the electrode. There no need any electrode and joint is produced between two consecutive bodies. The pressure is needed to made welding perfectly. The types of resistance welding are-
This welding is called fusion welding joint process. The joint of metals are heated by a mixture of combustible fuel gas (Acetylene, propane, butane or hydrogen) and oxygen. There are four types of gas welding -
In this welding process heat is produced by electric arc or spark. A closed loop of electric circuit with a small air gap and electric current is flow through it which causes electric spark. Due to spark or arc a huge quantity of heat is produced which about temperature from 32000C to 40000C. Many types of arc welding describe below 1. Carbon arc welding, 2. TIG welding, 3. MIG welding, 4. Submerged arc welding, 5. Shielded metal arc welding, 6. Plasma arc welding, 7. Flux cored arc welding, 8. Electro slag welding.
The solid state welding describe as the coalescence is produced at temperature essentially below the melting point of base metal to joint. This welding is performed under applied pressure and there are no use of additional filler metal.