The tubes are then pickled, phosphate coated and lubricated to facilitate the next process of tube drawing. Depending on the finished size required, the tubes are subjected to single, double or triple drawing. After every draw the tubes are annealed at a temperature of 750 0C. The tubes are then straightened and cleaned before being cut to the exact length required. The finished tubes are tested for quality-dimensional inspection, hydrostatic pressure testing, eddy current flaw detection as required- and are marked and coated with rust preventive oil before being bundled and dispatched.
A brief description of various major processes and equipment involved in the manufacture of seamless pipes and tubes is as follows.