Foundry

 

 

Founding, or casting, is the process of forming metal objects by melting metal and pouring it into molds. A foundry is a commercial esta�blishment for founding or producing castings. Significant in these defini�tions is the use of liquid metal to cast the shape of the object directly, producing cast metal. Wrought metal products differ from cast metal products in that the metal has received mechanical working treatments such as forging, rolling, or extruding. Practically all metal is initially cast. Castings obtain their shape principally when molten metal solidifies in the desired form. Wrought objects, however, are cast as ingots and then plastically worked to approximately the desired shape. Since man�s present civilization has arisen in a large part from the development of methods of putting metals into shapes that will do his work, all these processes are significant.

The strength of the foundry industry rests in the fundamental nature of casting as a process for causing metals to take shapes that will serve the needs of man. Other methods of shaping exist, each with its own spe�cific merits. Machining, forging, welding, stamping, hot working, etc., provide other means of shaping metals into objects which have use. Each of the foregoing has applications in which it is unexcelled and others for which it is unsuited. Rarely is an engineering product completed which does not use several or all of the fundamental metal-processing methods. The foundry industry is thus built on one of the truly basic methods available for shaping metals to useful ends.

Certain advantages are inherent in the metal-casting process. These may form the basis for choosing casting as a process to be preferred over shaping process in a particular case.

Some of the reasons for the success of the casting process follow:

The most intricate of shapes, both external and internal, may be cast. As a result, many other operations such as machining, forging, and welding may be minimized or eliminated.

Because of their metallurgical nature, some metals can only, be cast to shape since they cannot be hot-worked into bars, rods, plates, or other shapes from ingot form as a preliminary to other processing. The highly useful and low-cost cast irons, which exceed all other metals in tonnage cast, illustrate this fact.

Construction may be simplified. Objects may be cast in a single subject to vibration and/or fatigue. The transmission mechanism is built of heat-treated high-strength alloy steel, and it should be frequently examined for the start of fatigue cracks, for which purpose the engine must be disassembled. Strict attention to this liability has almost eliminated failures of machine parts in airplanes, even though the factor of safety is as low as 1 /4.