Abstract: The invention is well adapted to the manufacture of water-cooled mandrels for use in a piercing mill. The method of the invention consists in that a cone-shaped cavity is formed in a blank by hot piercing, whereupon the blank thus formed is subjected to hot upset forging whereby it is reduced until its outer diameter at the end of the fitting section is in the range of from 0.9 to 1.02 times the diameter of the mandrel sizing band, the outer diameter of the mandrel working section and that of its nose being 0.9 to 1 times the diameters of the respective sections of the mandrel, the wall thickness in the area of the fitting section and that of the sizing band being from 0.7 to 1 times the thickness of the mandrel wall. Then, the fitting section is subjected to reduction effected concurrently with upset forging of the working section, this followed by final sizing of the mandrel setting cavity.

Abstract: A method comprises diffusion metal coating of pipes carried out in a vacuum chamber which contains metal evaporators. Prior to coating process a metal is fed into the interior of each pipe with the melting temperature thereof being substantially below that of the pipe metal. The metal coating of pipes is effected at a temperature above the melting temperature of the metal disposed within the pipes which are continuously rotating about their axes while axially advancing through the metal evaporator.