Risk Assessment of Lung Cancer



Risk Assessment of Lung Cancer

Founding, or metal casting, involves the pouring of molten metal into the hollow inside of a heat-resistant mould which is the outside or negative shape of the pattern of the desired metal object. The mould may contain a core to determine the dimensions of any internal cavity in the final casting. Foundry work comprises:

making a pattern of the desired article

making the mould and cores and assembling the mould

melting and refining the metal

pouring the metal into the mould

cooling the metal casting

removing the mould and core from the metal casting

removing extra metal from the finished casting. (Dautry 2008)

The basic principles of foundry technology have changed little in thousands of years. However, processes have become more mechanized and automatic. Wooden patterns have been replaced by metal and plastic, new substances have been developed for producing cores and moulds, and a wide range of alloys are used. The most prominent foundry process is sand moulding of iron.

On the basis of the designer's drawings, a pattern conforming to the external shape of the finished metal casting is constructed. In the same way, a corebox is made that will produce suitable cores to dictate the internal configuration of the final article. Sand casting is the most widely used method, but other techniques are available. These include: permanent mould casting, using moulds of iron or steel; die casting, in which the molten metal, often a light alloy, is forced into a metal mould under pressures of 70 to 7,000; and investment casting, where a wax pattern is made of each casting to be produced and is covered with refractory which will form the mould into which the metal is poured. The “lost foam” process uses polystyrene foam patterns in sand to make aluminium castings. (Ludwiczek 2003)

Metals or alloys are melted and prepared in a furnace which may be of the cupola, rotary, reverberatory, crucible, electric arc, channel or coreless induction type (see table 82.5). Relevant metallurgical or chemical analyses are performed. Molten metal is poured into the assembled mould either via a ladle or directly from the furnace. When the metal has cooled, the mould and core material are removed (shakeout, stripping or knockout) and the casting is cleaned and dressed (despruing, shot-blasting or hydro-blasting and other abrasive techniques). Certain castings may require welding, heat treatment or painting before the finished article will meet the specifications of the buyer. (Donovan 2009)

Types of foundry furnaces 

Furnace

Description

Cupola furnace

A cupola furnace is a tall, vertical furnace, open at the top with hinged doors at the bottom. It is charged from the top with alternate layers of coke, limestone and metal; the molten metal is removed at the bottom. Special hazards include carbon monoxide and heat.

Electric arc furnace

The furnace is charged with ingots, scrap, alloy metals and fluxing agents. An arc is produced between three electrodes and the metal charge, melting the metal. A slag with fluxes covers the surface ...