Page 18 - Curriculum Visions Dynamic Book

(Below) Railway tracks are produced by rolling steel.
(Above) Steel is more easily plastically deformed when it is about 1,200°C. During rolling, the steel is compressed into thinner or narrower pieces usually about an eighth of its original thickness. The large crystals in the usually brittle cast steel are converted into many smaller, longer crystals that make the steel tougher and more ductile.
Rolling
(Right) By passing a sheet or rod through a series of rollers, the steel can be shaped into a more complex form.
Rolling is either performed by pushing or pulling the metal through a series of rollers, each making the sheet thinner, or by passing it back and forth through the same rollers whose gap is continually narrowed.
Beams, such as I-beams (or girders) used in buildings and in the track for railways, are made by rolling the metal while controlling how it can spread out.
Hot rolling is easier but leaves the metal no stronger. Cold rolling is harder but makes the metal stronger, more brittle, and with a smoother finish.
The shape of over 90% of metal (including
metal that has been through the continuous
cast process) is changed by rolling it into a bar or a sheet. This is done in a workshop called a rolling mill. Sheet is the most easily used form of the common metals such as iron, aluminium, and copper.
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