Patent ID: 6575009
Filing Date: 2003-06-10
Classification: B21K,B62D,Y10T

Abstract:
A process for producing an article with toothed portions, such as a pipe shaped rack bar, comprising the steps of:a) providing a die having, at its inner surface, toothed portions; b) holding a blank pipe in the die; c) providing a mandrel having a tapered operating head; d) inserting, repeatedly, the mandrel into an axial space of the blank pipe, so that the operating head of the mandrel causes the material to be flown radially outwardly toward the inner surface of the die, thereby generating toothed portions on the blank pipe corresponding to the toothed portions of the die; e) maintaining during the repeated insertions of the mandrel, an increased temperature of the work generated substantially solely by a heat due to the execution of the insertion of the mandrel to the blank pipe, which temperature is substantially in a range where a so-called work-softening phenomenon is obtained; f) preventing, during the repeated insertions of the mandrel, the metal from being subjected to an age-hardening, and; g) canceling, during the repeated insertions of the mandrel, a deviated flow of a metal flow toward the die.