METHOD FOR DECIDING GENERATION OF PERFORATION IN MATERIAL TO BE ROLLED IN MANDREL MILL

PURPOSE:To decide the presence or absence of the perforation generated in a material to be rolled during rolling by sending a signal from a comparator to a decision circuit to emit an alarm when the fluctuation level of load exceeds the fluctuation level of the load set in the comparator. CONSTITUTION:The material to be rolled does not exist in the perforated part and, therefore, the rolling load drops sharply if the material 24 which is the blank pipe under rolling is perforated by excessive tension and when this perfo rated part is rolled. Then, the generation of the perforation can be confirmed if the sharp drop of the rolling load is recognized and, therefore, the load fluctua tion level to the extent of the fluctuation level of the load at the time of rolling of the perforated part is set in the comparator 3. The load signal from a load detector 1 disposed in a roll chock is sent through a gate 2 to this comparator 3 which compares the signal with the set value. The generation of the perfora tion is decided and the alarm is emitted if the fluctuation level of the rolling load is larger than the set value.