Author: haroonkhan

A weld is defined by the American Welding Society (AWS) as “a localized coalescence (the fusion or growing together of the grain structure of the materials being welded) of metals or nonmetals produced either by heating the materials to the required welding temperatures with or without the application of pressure, or by the application of…

The history of joining metals goes back several thousand years, with the earliest examples of welding from the Bronze Age and the Iron Age in Europe and the Middle East. Welding was used in the construction of the iron pillar in India, during the Ashoka empire. In ancient age, forge welding was in use but…

Wire Brushing: Wire brush of hardened steel wires, embedded in a wooden block, is extensively used for cleaning the casting surface. Tumbling: In this method, the castings to be cleaned are placed together with a number of small cast iron pieces called stars inside a large steel barrel. Both ends of the barrel are closed and the…

Casting defects are unwanted feature or irregularities in casting which make it of poor quality. These defects occur due to several reasons such as poor design of casting, excess moisture in mould, improper ramming of moulding sand, misalignment of cope and drag, etc. The various types of casting defects are shown in Figure 20.27. Figure 20.27 Casting…

The mould in this process is made up of a mixture of dried silica sand and phenolic resin formed into thin, half-mould shells, which are clamped together for pouring (Figure 20.26). The sand, free from clay, is first mixed with either urea or phenol formaldehyde; the mixture is put into a dump box or blowing…

This process was originally practiced by artisans in the 16th century forming the object in wax by hand. The wax object or pattern was then covered by a plaster investment (Figure 20.25). When this plaster became hard, the mould was heated in an oven, melting the wax and at the same time further drying hardening…

In this process, several mould cavities are located around the outer portion of a mould, and the metal is fed to these cavities. The mould cavities are fed through radial gates provided from a central pouring reservoir by the action of centrifugal force (Figure 20.24). Relatively low rotational speeds are required to produce sound castings…

Semi-centrifugal casting is used for the castings that are symmetrical about a central axis but complicated than true centrifugal castings. It is not necessary to have a central hole. A core will have to be employed if one is desired. The mould cavity is arranged within the mould so that its central axis will be vertical…

True centrifugal casting is used for pipe, liners, and symmetrical hollow body. They are cast by rotating the mould about its axis horizontally or vertically (Figure 20.22). The metal is held against the wall of the mould by centrifugal force and no core is used to form a cylindrical cavity inside the casting. The wall…

In this casting process, centrifugal force is used to feed the molten metal into the mould cavity, i.e., mould is rotated at high speeds (300–3,000 rpm). This process is more suitable for symmetrical shaped casting but other types of casting can also be produced. The centrifugal casting can be classified as follows: