PRODUCTION OF METALS 

The term metal production refers to all of the

processes involved in the conversion of a raw

material, such as a metallic ore , to a final form in

which the metal can be used for some commercial

or industrial purpose. In some instances, metal

production involves relatively few steps since the

metal already occurs in an elemental form in

nature. Such is the case with gold, silver, platinum,

and other so-called noble metals. These metals

normally occur in nature uncombined with other

elements and can therefore be put to some

commercial use with comparatively little additional

treatment.

In the majority of cases, however, metals occur in

nature as compounds, such as the oxide or the

sulfide, and must first be converted to their

elemental state. They may then be treated in a

wide variety of ways in order to make them usable

for specific practical applications.

Metal Manufacturing Processes

Casting Processes : Metal casting processes

involve pouring molten metal into a mold cavity

where, once solid, the metal take on the shape of

the cavity. They can be divided into two categories

based on the type of mold:

Expendable Mold Casting: where the mold must be

destroyed in order to remove the part

Permanent Mold Casting: for which the mold is

fabricated out of a ductile material and can be

used repeatedly.

Powder Metallurgy: In powder metallurgy a metal

powder is compacted into the desired shape and

heated to cause the particles to bond into a rigid

mass.

Deformation Processes : Deformation processes

include metal forming and sheet metalworking

processes. These processes use plastic

deformation resulting from the use of a tool that

applies stresses to the piece which exceed the

yield stress of the metal. There are two types of

deformation processes:

Bulk Processes: Bulk deformation processes are

characterized by large deformations and shape

changes and by the fact that the surface area to

volume ratio is relatively small. Bulk processes

include rolling, forging, extrusion and wire and bar

drawing.

Sheet Metalworking: Sheet metalworking

processes are performed on metal sheets, strips

and coils having a high surface area to volume

ratio. These operations use a punch and die to

form the workpiece. Bending, drawing and shearing

are types of sheet metalworking processes.

Material Removal Processes : These processes

remove extra material from the workpiece in order

to achieve the desired shape and include:

Machining Operations: These are cutting

operations using cutting tools that are harder than

the metal of the product. They include turning,  drilling, milling, shaping, planing, broaching and

sawing.

Abrasive Machining: In these methods material is

removed by abrasive particles that normally form a

bonded wheel. Grinding, honing and lapping are

included in this category.

Nontraditional Processes: These methods use

lasers, electron beams, chemical erosion, electric

discharge and electrochemical energy instead of

traditional cutting and grinding tools.

Joining and Assembly Processes: In these

operations multiple parts are connected either

permanently or semipermanently to form a new

entity.

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