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FERROUS METALS

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They are first cast into simple shapes, ingot

Later ingots are given a preliminary shapingby being rolled or forged into billets. Finally, desired shapes are obtained frombillets by: Forging Rolling Extrusion

Drawing

Shaping Structural Steel

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FORGING

Place a billet in a die and apply

pressure with a suitably shapedpunch.

As the metal is forced into position, it is stressed

above the proportional limit and refinement ingrain boundaries or goes into strain hardening.Thick plates, sheetings and objects of irregular

shape are produced by forging.

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ROLLING

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Hot Rolling: If the temperature of themetal is above its critical temperaturewhich causes recrystallization of thecrystallic structure. Properties will not beaffected greatly.

Cold Rolling: If the temperature is belowthe critical temperature the initial crystallic

structure will be maintained but theproperties will change. The strength isincreased but the ductility is decreased.

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EXTRUSION

Applying sufficient pressure to thematerial by forcing it through a die whichhas the required constant cross-section(I-beams, channel section)

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DRAWING

A rolled rod is pulled through a diehaving an opening smaller than the original

cross-section of the rod. Wires and somerods are prepared by this method.

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FACTORS THAT AFFECTPROPERTIES OF STEELS

Carbon contentHeat treatment and shaping method

Presence of harmful elementsPresence of alloying materials.

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Carbon Content

For steel C ~0.05-2% usually

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Carbon Content

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Cold Drawn & Cold Rolled Nomicrostructural changes. Changes are

plastic deformations in the form ofelongation of grains.Hot Rolled Microstructural changes

Drawn & Annealed Initial stresses arereleaved.

Heat Treatment andShaping Methods

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Heat Treatment andShaping Methods

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Alloying Elements

Alloying elements are added to steel: Higher strength with ductility

Higher resistance to corrosion Higher resistance to heat

Chromium & Nickel are the most important

alloying elements. Stainless Steel has~20% Chromium & 8% Nickel.