Steelmaking

Different metals require different combinations of operations and processes, but typically the production of a metal involves two major steps. The first is the production of an impure metal from ore minerals, commonly, oxides or sulfides. Steelmaking is the second step in producing steel from iron ore. In this stage, impurities such as sulfur, phosphorus, and excess carbon are removed from the raw iron, and alloying elements such as manganese, nickel, chromium and vanadium are added to produce the exact steel required. The refining of the impure metal is performed by selective oxidation of impurities or by electrolysis. Because the production of metals employs many chemical reactions, metallurgy has been closely connected with inorganic chemistry.

The materials used in modern steelmaking are:

• The iron produced in a blast furnace, either as molten iron or as pig iron.

• Scrap steel.

• Alloying elements.

The original methods of producing steel were labor-intensive and highly skilled arts. An important aspect of the industrial revolution was the development of large-scale methods of producing forgeable metal .The paddling furnace was initially a means of producing wrought iron, but was later applied to steel production. The Bessemer converter was the first successful mass steelmaking process, followed by the open hearth furnace

Unconventional machine tools

Unconventional machine tools include plasma-arc, laser-beam, electro discharge, electrochemical, ultrasonic, and electron-beam machines.

Plasma Arc Plasma-arc machining (PAM) employs a high-velocity jet of high-temperature gas (see Plasma) to melt and displace material in its path. The materials cut by PAM are generally those that are difficult to cut by any other means, such as stainless steels and aluminum alloys.

Laser Laser-beam machining (LBM) is accomplished by precisely manipulating a beam of coherent light (see Laser) to vaporize unwanted material. LBM is particularly suited to making accurately placed holes. The LBM process can make holes in refractory metals and ceramics and in very thin materials without warping the workpiece. Extremely fine wires can also be welded using LBM equipment.

Electro discharge Electro discharge machining (EDM), also known as spark erosion, employs electrical energy to remove metal from the workpiece without touching it. A pulsating high- frequency electric current is applied between the tool point and the work piece, causing sparks to jump the gap and vaporize small areas of the workpiece. Because no cutting forces are involved, light, delicate operations can be performed on thin work pieces. EDM can produce shapes unobtainable by any conventional machining process.