Category: Casting And Welding

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:

This process lies between gravity die casting and high-pressure die casting. In a low-pressure casting process, the molten metal is forced upward by gas or air pressure into a graphite or metal mould. The mould is located just above the furnace. It may take half a minute to fill up the mould, so any entrapped…

Cold-chamber die casting is used for relatively high melting point non-ferrous alloys such as aluminium, magnesium, and brass which require higher pressure and temperature for melting. These metals are not melted in a self-contained pot as in hot-chamber die casting due to short life of pot (Figure 20.21). Therefore, the metal is melted in an…

A hot-chamber die casting machine is shown in Figure 20.20. This machine is used with alloys of low melting points because of the difficulties encountered such as increased corrosion of the machine parts at high temperatures. Since many metals have an affinity for iron, only those casting alloys are used that do not attack the immersed…

There are two types of high pressure die casting.