| 摘要 |
PURPOSE:To improve working efficiency for various kinds of materials to be worked, by measuring the change of supersonic characteristics of the material, and performing plastic working at the temp. which exceeds the temp. measured at that point of time. CONSTITUTION:A material 1 to be worked is heated by applying electric current from an electric-heating source 6, and together, the change of supersonic characteristics accompanying the temp. rise is measured by a supersonic flaw detector 13. When the sudden change of supersonic characteristics caused by the sudden change of a structural state of the material 1 is detected, a prescribed heat energy is given by the source 6 to rise the temp. of it by a prescribed temp., by setting the temp. detected, at that point of time with a temp. detector 12, as a standard temp. The material 1 is, then, made to be in the optimum working temp. i.e. in a structural state of the highest degree of plasticity. Then cooling gas is blown against the material 1 from each air nozzle to make the material 1 possess a temp. pattern through its axial direction in order to make the material 1 possess a gradient in the degree of plasticity. Next, respective parts of the material 1 are stretched through the axial direction in different elongation ratios respectively, corresponding to a small diametral part and to the degrees of plasticity at respective parts, so as to form a taper rod of which diameter changes in its axial direction. |
