A product is said to be wrought if it is manipulated in the solid state from a cast shape. The choice of manipulation process depends upon the material to be manipulated, the shape required, the accuracy required and the quantity involved.
Working produces grain fibre, by orientation of grains, elongation of impurities, resulting in directional properties.
Wrought forms can be:
(i) Long-length forms, like drawn bar, rolled sections, sheet, plate, tube, wire and extruded sections.
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(ii) Individual component forms like forging of connecting rod, crankshaft, etc.
i. Bars:
Bars in several cross-sections, like round, square, rectangular, and hexagonal are the common rolling mill’s products. Mild steel, medium carbon steel and alloy steel are commonly supplied in the form of black bar (black surface occurs due to oxidation of steel by atmosphere during hot rolling). The corners are generally rounded in case of black bars. Bars are sometimes cut off to smaller lengths to produce billets, suitable for forging.
ii. Bright-Drawn Bars:
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These are produced by drawing bars through shaped dies. These have smooth surface and are of accurate size. Such a bar is used on capstan, turret or automatic lathes. The drawing operation work-hardens the surface of bright-drawn bar, the depth of hardening being proportional to the severity of the drawing. Work-hardening is not desirable if the bar is to be heated for joining purposes. To avoid distortion, such bars should be subjected to bright annealing.
iii. Rolled Sections:
These include angles, channels, joists are used for constructional work.
iv. Sheet:
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Hot-rolled and cold-rolled sheet is available in a range of metals and alloys, and over a wide range of sizes. Tin-coated steel sheet is used for food canning and fancy goods. The finish is rust-proof and can be easily soldered. Galvanised sheet is commonly used. It can’t be worked or heated for bending etc.
v. Plate:
Mild steel plate is hot-rolled to a thickness between 3 mm and 50 mm. Plates are used in ship work, boilers, heavy tanks and vessels etc.
vi. Tube:
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It is produced by solid drawing for heavy duty jobs, seam welded and close jointed.
vii. Wire:
It is usually cold-drawn through dies. Cold drawing work hardens the material and as such wire should be annealed if it is to be bent at a later stage.
viii. Extruded Sections:
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Simple as well as complicated sections are extruded.