Reheating furnaces.
Rolling stands.
Straightening and cooling tables.
Cut-off shears.
Coilers and decoilers for strips.
Roll-grinding machines.
A rolling stand consists of two or more rollers positioned one
above the other and in groups of two or more stands side by side.
The operation consists of passing a piece of metal between two or
more rollers, subjecting it to compression. The compression compacts
and lengthens or compacts and widens the particular piece of metal.
The action depends on the rollers' dimensions and the compression
applied.
In producing cold-rolled sheet and strip and cold-drawn rods and
bars of various dimensions, the oxide is removed from the hot-rolled
material by pickling; and the material is further reduced on cold-
rolling mills. Bars, sheets, and strips are cold-rolled to obtain a
desired surface finish, improve dimension tolerances, impart improved
physical properties, and make lighter gauges than can be made on hot-
strip mills.
Cold Drawing.
Cold drawing is used in making seamless tubing,
wire, streamlined tie rods, and other forms of stock.
Wire is made
from hot-rolled rods of various diameters. These rods are picked in
acid to remove scale, dipped in lime water, and then dried in a steam
room where they remain until ready for drawing.
The lime coating
adhering to the metal lubricates the rod during the drawing
operation.
The rod size used for drawing depends upon the diameter
desired in the finished wire.
To reduce the rod to the desired size wire, the rod is drawn cold
through a die.
One end of the rod is filed or hammered to a point
and slipped through the die opening. It is then gripped by the jaws
of the draw and pulled through the die. This series of operations is
done on a mechanism called a draw bench. To reduce the rod gradually
to the desired size, the wire is drawn through successively smaller
dies.
Because each of these drawings reduces the wire's ductility,
it must be annealed from time to time during the drawing operation.
Although cold working reduces the wire's ductility, it increases the
wire's tensile strength.
In making seamless steel aircraft tubing, the rod is cold
drawn through a ring-shaped die with a mandrel, metal bar,
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