- Slides: 12
WHAT IS WELDING ? welding is a metal joining process which produces permanent joint by heating the metals upto suitable temperature with or without application of filler material.
If filler metal is same as base metal it is called homogeneous welding. If filler metal is different from base metal it is called heterogeneous welding. If no filler metal is used then it is called autogeneous welding.
Almost all metals and alloys, and some ceramics can be welded, with or without filler. Still other advantages of welding are (1) There are processes that can be performed manually, semi-automatically, or completely automatically which can be done by welding (2) some processes can be made portable for implementation in the field for erection of large structures on site or for maintenance and repair of such structures and equipment; (3) continuous welds provide tightness (so welding is the process of choice for fabricating pressure vessels) (4) welding (better than most other joining processes) can be performed remotely in hazardous environments (e. g. , underwater, in areas of radiation, in outer space) using robots
Base metal The metal to be joined or cut is called the base metal Root It is the point at which the two metal pieces are to be joined by welding Weld pass A single movement of the welding electrode along the length of the joint which results in a bead is called weld pass. Weld bead Bead is the metal added during a single pass of welding. Weld
Penetration It is the depth upto which the weld metal combines with the base metal when measured from the top surface. Puddle The portion of the weld joint that is melted by the heat of the welding is called puddle. Deposition rate The rate at which the weld metal is deposited per unit time is called deposited rate (kg/h), HAZ
Four types of welding positions: Flat Welding Position (either 1 F or 1 G) Horizontal Welding Position (either 2 F or 2 G) Vertical Welding Position (either 3 F or 3 G) Overhead Welding Position (either 4 F or 4 G)
Flat welding Position Vertical Welding Position The flat position is one in which the welding is performed from the upper side of the joint and the face of the weld is approximately horizontal. In vertical position, the plane of the work-piece is vertical and the weld is deposited upon a vertical surface. Horizontal Welding Position The overhead position is probably even more difficult to weld than the vertical position. Here the pull of gravity against the molten metal is much greater In horizontal position, the plane of the work piece is vertical and the deposited weld head is horizontal. Overhead Welding Position