PURPOSE: To detect a phase transformation, where a superplastic phenomenon is shown and plastic deformation is possible, to perform the plastic working immediately, by measuring continuously changes of the structure state of a work which is heated and detecting a point where the measured value is changed rapidly.
CONSTITUTION: A work 1 consisting of metallic materials has one end fixed to a fixed material 3 through a chuck 2 and the other connected to a piston 6 of a pulling device 5. The work 1 is heated through chucks 2 and 4 by the power supply from a heating power source 8, and the heating power is controlled by a power control circuit 9. The change of the structure state of the work 1 is detected by measuring the magnetic permeability by a magnetic sensor 10. The magnetic permeability is measured continuously, and heating is stopped at the time point when a rapid change is detected, and pressure oil is charged to the pulling device 5 from a port 7 to move the piston 6 in the direction of an arrow, and the chuck 4 is pulled in the direction of an arrow to subject the work 1 to the pulling work.
SAITOU MAKOTO
NAGASAKA HIROYASU
