There are four basic noncutting removal processes: 1 in chemical milling the metal is removed by the etching reaction of chemical solutions on the metal; although usually applied to metals, it can also be used on plastics and glass, 2 electrochemical machining uses the principle of metal plating in reverse, as the workpiece, instead of being built up by the plating process, is eaten away in a controlled manner by the action of the electrical current, 3 electrodischarge machining and grinding erodes or cuts the metal by high-energy sparks or electrical discharges, 4 laser machining cuts metallic or refractory materials with an intense beam of light from a laser.
The first group includes metallic coating, such as electroplating; organic finishing, such as painting; and porcelain enameling. A bonding or filler material, the same as or different from the materials being joined, may or may not be used.
First, the crude ore is processed to increase the concentration of the desired metal; this is called beneficiation. Start Your Free Trial Today The processes used to convert raw materials into finished products perform one or both of two major functions: first, they form the material into the desired shape; second, they alter or improve the properties of the material.
The term as used here includes weldingbrazingsolderingand adhesive and chemical bonding. Although some thermal treatments are applicable to most families of materials, they are most widely used on metals.
Materials in their solid state are formed into desired shapes by the application of a force or pressure. A finishing operation is sometimes needed.