1. The strength of the foundry industry rests in the fundamental nature of casting as a process for causing metals take shapes that will serve the needs of man.
2. Engineering metals are used in industry in the form of alloys be¬cause the properties of alloys much better than the properties of pure metals.
3. Alloy cast irons are coming into extensive use although they are more expensive than iron.
4. Non-ferrous metals are generally more expensive per pound than the ferrous metals, and are used only when some characteristic not by iron or steel is essential or desirable in application.
5. In many cases, the engineer requires steel with a tensile strength, yield point, hardness, response to heat treatment, etc., that cannot obtained with plain carbon steels.
6. The furnace that is used for separating iron from the other elements combined with it in the iron is called a blast furnace.
7. The Bessemer converter, in which the process takes place, is a pear-shaped tilting vessel made of steel plates and lined with heat-resisting and clay.
8. Beneath the furnace there are two large chambers containing a checkerboard arrangement of firebricks through which air or gas freely.
9. Thus, the pre¬sence of oxides, compounds of oxygen with other elements, or other impurities undesirable in fine steels can be materially reduced. Sulphur is almost completely eliminated in the basic furnace.
10.High grade tool steels and some alloy steels are still made by the crucible process, although the electric furnace is now capable of steel equal in quality to crucible steel.