Cold - Rolling of Metal in Manufacturing

Bars of all shapes, rods, sheets, and strips are commonly finished by cold-rolling. Foil is made of the softer metals in this way. Two main reasons for cold - rolling metals are to get smooth bright surface finish and improved physical properties. If the object is only to give a clean, smooth finish to the metal, only a superficial amount of rolling will be needed. On the other hand, where it is desirable that the tensile strength, stiffness, and hardness be increased substantially , and that the section thickness be appreciably reduced, then higher roll pressures and deeper kneading are necessary. Cold-rolling also improves machinability by conferring the property of brittleness, a condition which is conductive to smooth tool finishes and well-broken chips.

As a preliminary step to the cold-rolling operation, sheets, strips etc. of hot-rolled steel are immersed in an acid solution to remove the scale and washed in water and then dried. The cleaned steel is passed repeatedly through set of rolls thereby producing a slight reduction in each pass until the required thickness is obtained.

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