PRODUCTION OF PIERCING MANDREL FOR ROLLING SEAMLESS STEEL TUBE

摘要

PURPOSE: To prolong the service life of a mandrel bar by diffusedly penetrating the surface of the mandrel with a low-melting point metal, carrying out a heat treatment and thereby securing the adhesion of scales. ;CONSTITUTION: On the wear surface of a mandrel which is formed in a piercing shape rolling seamless steel tube and which comes into contact with a rolling material, a low-melting point metal consisting of Cu, Zu, Al or an alloy of these is diffusedly penetrated, and the surface intercrystalline part is embrittled. With this pretreatment the mandrel having embrittlement in the surface intercrystalline part is processed, either by a quenching and tempering heat treatment or by a high-temp. rapid heating at the initial stage of a tube rolling, provided with fine hexagonal surface cracking formed on the embrittled intercrystalline part, and the adhesion of scales is secured. In addition, a lubricity at the time of the tube rolling is developed, and wear and rough surface are suppressed.;COPYRIGHT: (C)1994,JPO