Forgings

Forging is a hot-working process, heat being necessary to render the metal plastic in order that it may be more easily shaped. The oldest form of forging is hand forging as carried out by the 

When large quantities of accurately shaped products are required, these are produced by a process known as closed-die forging or drop forging. With this method, the hot metal is placed between two halves of a die each containing a cavity such that when the metal is squeezed into the cavity a completed forging of the required shape is produced. Fig. 16.12. The metal is subjected to repeated blows, usually from a mechanical press, to ensure proper flow of the metal to fill the die cavity. A number of stages 

Forging is used in the production of parts which have to withstand heavy or unpredictable loads, such as levers, cams, gears, connecting rods and axle shafts. Mechanical properties are improved by forging, as a result of the flow of metal being controlled so that the direction of grain flow 

The process of drop forging is normally restricted to larger batch quantities, due to die costs. 

Upset forging increases the diameter of a workpiece by compressing its length. It is a 

One of the two halves of the die is attached to the moving part of the press, the other to the anvil. The cavity contained in the die is designed 

This process is used in the highspeed volume production of screws, bolts and other fasteners, engine valves and a multitude of similar headed parts. 

Presses can be mechanical, hydraulic or drop hammer type. 

Closed die forging series of die impressions used to generate shape. 

Open die forging hot material deformed between a flat or shaped punch and die. Sections can be flat, square, round or polygon. Shape and dimensions largely controlled by operator. 

Roll forging reduction of section thickness of a doughnut-shaped preform to increase its diameter. Similar to ring rolling (see 3.2), but uses impact forces from hammers. 

Upset forging heated metal stock gripped by dies and end pressed into desired shape, i.e. increasing the diameter by reducing height. 

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The experimental investigations are carried out in order to get an idea about the variations of the visibility of the indications during practical inspections. The specimen where a test piece with spare eroded artificial defects (Width 25 pm depth d = 30, 60, 120 pm) and other specimen with natural cracks, a forged steering lever and a weld. As an example, in Fig 4 the steering lever with 2 cracks can be seen and below the dependance on the visibilty of a weak indication and a part of the bright indications on the field strenght H. 

Fig. 5 Indications of natural defects in a forged steering lever...

Different kinds of castings and moulded products or forged materials etc. 

In the limit of low densities, A2.4.15 shows that the zeroth-order approximation forg(r) has the fonn... 

After aluminium, iron is the most abundant metal and the fourth most abundant of all the elements it occurs chiefly as oxides (for example haematite (FCjO,), magnetite (lodestonej (FC3O4) and as iron pyrites FeSj- Free iron is found in meteorites, and it is probable that primitive man used this source of iron for tools and weapons. The extraction of iron began several thousand years ago, and it is still the most important metal in everyday life because of its abundance and cheapness, and its ability to be cast, drawn and forged for a variety of uses. 

Pig-iron or cast iron contains impurities, chiefly carbon (up to 5 ). free or combined as iron carbides. These impurities, some of which form interstitial compounds (p. I I3i with the iron, make it hard and brittle, and it melts fairly sharply at temperatures between 1400 and 1500 K pure iron becomes soft before it melts (at 1812 K). Hence cast iron cannot be forged or welded. 

As early as 2500 bce m India indigo was used to dye cloth a deep blue The early Phoenicians discovered that a purple dye of great value Tyrian purple could be extracted from a Mediterranean sea snail The beauty of the color and its scarcity made purple the color of royalty The availability of dyestuffs underwent an abrupt change m 1856 when William Henry Perkin an 18 year old student accidentally discovered a simple way to prepare a deep purple dye which he called mauveme from extracts of coal tar This led to a search for other synthetic dyes and forged a permanent link between industry and chemical research... 

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