Piercing press making axial hole in hot steel ingots - where hydraulic limit-stops restrict downward stroke of piercing mandrel

摘要

The press has a crosshead driven vertically and carrying the piercing mandrel. The downward stroke of the crosshead is limited by hydraulically adjusted thrust pads. Pref. the thrust pads consist of four hydraulic cylinders located at the corners of a rectangle, each hydraulic cylinder contg. a piston with a piston rod pushed downwards via a coil spring located round each rod. The rods form the thrust pads or stops. Hydraulic cylinders are pref. fed with hydraulic fluid via four pipes connected together so the pressure in all four hydraulic cylinders is the same, and the height of the rods is the same. The hydraulic circuit pref. includes a pump feeding a constant vol. into the pipes, and also solenoid valves controlling and reversing the flow of hydraulic fluid. Used to obtain a pierced hole with very accurate length in the ingot so the desired thickness is left between the base of the hole and bottom end of the ingot.