Abstract: In rapidly cooling a large diameter metal pipe for quenching purposes, the essential requirements for ensuring uniform cooling of the pipe, namely, the jet velocity and the dip angle and transverse angle of jets of the cooling water directed against the surface of the pipe from a large number of spray nozzles contained in each of a first and second ring header encircling the pipe, and the distance between the circumferential line defined on the pipe by connecting the points of impingement onto the pipe surface of the water jets sprayed in the direction of the second header from the spray nozzles of the first header and the similar circumferential line defined on the pipe by connecting the points of impingement onto the pipe surface of the water jets sprayed in the direction of the first header from the spray nozzles of the rear second header, are specified with numerical values.

Abstract: A cooling method and apparatus wherein in the process of continuously hardening a metal pipe by heating the metal pipe as it passes through a heating unit and then cooling the inner surface of the metal pipe, an annular cooling nozzle having a large number of nozzle openings is placed in the metal pipe, and the spray direction of jets of cooling medium from the nozzle openings is selected so as to maintain a dip angle of between 30.degree. and 70.degree. and a transversal angle of between 30.degree. and 90.degree. and either cooling water or a mixture of cooling water and compressed air is sprayed with a jet velocity of greater than 5 meters per second onto a large number of points on the circumference of the inner wall of the metal pipe.

Abstract: A method of quenching a large-diameter thin-walled metal pipe includes the steps of moving the metal pipe through a heating zone and passing the pipe through a cooling zone following passage of the pipe through the heating zone. The cooling zone includes a plurality of nozzles for spraying a cooling liquid onto the pipe from the nozzles, so as to quench the pipe. The process steps further include detecting the amount of strain on the outer periphery of the quenched pipe at the rear end of the cooling zone, as seen in the direction of movement of the pipe, so as to obtain a deviation of a detected value from a preset value, and adjusting the amount of cooling liquid sprayed onto the pipe from the nozzles in accordance with the amount of deviation from the preset value, so that the adjusted cooling water spray controls the deviation of pipe emerging from the cooling zone, for example, reduces the eccentricity of a circular pipe.