Brief introduction of tube piercing mill

Tube piercing mill

Pipe piercing is one of the most important deformation process in the production of hot-rolled seamless steel pipe. Its task is to make the solid billet rolled into a hollow capillary.According to the structure of the piercing mill the deformation characteristics of the punch process, the existing method of piercing can be divided into: skew rolling punch, pushing perforation and pressure perforation, and most widely used is the skew rolling perforation. The shapes of the skew rolling piercer roll are as roller piercer type, cone roll piercing type and disc type, among of which, roller piercer roll is used in bar mill, and cone roll piercing used in the large size of the roll, and disc punch used relatively less. Regardless of the roll shape, in order to ensure the implementation of the tube billet biting and perforation of cone all are under the help of the perforation (roll inlet cone), roll-off cone (exit roll cone) and roll rolling belt (excess between the entrance and exit cone part).

Piercer roll mostly adopts the combination of roller and roller set structure. In this way, after the roll scraps, the roll shaft can continue to reuse to reduce the tool cost. Small punch roller materials more choose 45 or 40 Cr with tempering treatment. Large piercer roll shaft more adopts 42 CrMo with tempering treatment. In terms of roller materials, at present, each manufacturer varies, some manufacturer selects the forging 45, 55, and other high quality carbon structural steel.Some manufacturer chooses 50 Mn, 65 Mn, 70 Mn and 70 Mn2Mo, 60 CrMnMo alloy steel casting or forging steel. Hardness range requirements vary also, some require HB180-220, some require HB220-260. In order to increase the bite, large piercing mill roll commonly adds reticular pattern with depth of 0.8~1.2 mm on the inlet cone.

According to recent situations at home and abroad, the selection of piercer roll casting with medium carbon alloy steel material 50 Mn, 60 CrMnMo is proper, one is it has good strength and wear resistance, secondary it is applicable to all kinds of rolling steel pipe. Control the hardness in the range of HB200-240 is more reasonable.