“Process of joining two similar or dissimilar metals by heat or by pressure or by both using a filler metal to achieve a defect less joint having the physical properties similar to that of parent metal”.
Dissimilar metal means:-
- Those that are chemically different (steel,Cu, Al, etc).
- Those that are metallurgically different (MS, SS, etc).
*Dissimilar metal imparts galvanic cell corrosion Commonly welded base metals:-
–Ferrous-[WI, CI, C-steel (low, med, high), alloy steel, SS]
–Non-ferrous-(Al, Cu ,Mg, Ni, Zn & their alloys)
You may also define welding as –
Welding is a method of joining metals in which heat and/or pressure are applied to the area of contact between the two components; a filler metal may be added into the joint depending on the welding process.
Welding methods can roughly be classified into pressure processes, fusion processes, and brazing and soldering by the mechanism of joining metals.
In the pressure processes, the joint is made by applying pressure to the area of contact of the two components, which may or may not be heated to a molten state. In fusion processes, two components are joined by heating the area of contact to a molten state, and no pressure is applied.
In brazing and soldering, a filler metal having a lower melting point than that of the base metal is melted with a gas torch or in a furnace and is applied to the area of contact.
The molten filler metal wets the surfaces of the base metal and is drawn into or held in the joint by the capillary action without fusing the base metals