PIERCING METHOD AND PIERCING DEVICE

摘要

PROBLEM TO BE SOLVED: To manufacture a hollow extruded stock with high productivity and production efficiency by piercing a mandrel in a hollow hole of an aluminum alloy hollow billet to implement the piercing with the retracting drive force in the axial direction being smaller than the advancing drive force. SOLUTION: A pressure control device 50 adjusts a hydraulic pump for advancing to reduce the advancing speed when the advancing drive force of a mandrel 24 is brought close to the buckling limit value with the buckling limit value of the mandrel 24 as a reference for judgment, and the load applied to the mandrel 24 is reduced. Up to the speed changing point provided close to the position of generation of the estimated stick-slip vibration, the breakage of the mandrel is favorably prevented, the piercing time is shortened, and the productivity is improved by maintaining the advancing drive speed of the mandrel 24 to be high for a long time. The stick-slip vibration is suppressed by applying the retracting drive force smaller than the advancing drive force in the axial direction.