The tubes must next be straightened. This is done in cross rolls as has been mentioned under the manufacture of lap-welded pipe, or in various other types of machines.
Cupping and Drawing Seamless Tubes from Plates
Much seamless tubing goes into automobile, bicycle, and various other products for which very high grade and perfect material is desirable. One of the many interesting applications of seamless tubing is its use in very fine sizes for hypodermic needles.
Seamless tubes are easily bent, swaged, upset, spun or otherwise changed in form, as the material is ductile and there are no welds to open.
Very large tubes are not made in the way just described. They are rather made by “cupping” flat, round steel plates through a die. A cup is then in several successive drawings put through smaller dies, under which treatment it grows longer each time and gets a thinner wall until it has become a long tube with the one end still closed. For open ended tubes this and the upper, open end are cut or trimmed off.
Cold-drawing here necessitates annealing to restore ductility just as it does elsewhere and each annealing operation is necessarily followed by pickling for removal of the scale formed.
By rapidly spinning large tubes in lathes or other machines and the application of pressure with the proper tools and lubrication, the walls of the tubes may be deformed. In this way the ends may be expanded, made smaller, or completely closed. By such “spinning” operations large tubes are made into articles of various shapes.
By this same “cupping” or hydraulic drawing of flat, well lubricated sheets of soft steel, seamless high-pressure gas cylinders, steel drums, barrels, and the like are made.