Generally speaking, the axial resistance of the head and guide plate is increased, and the roll is dragged into the friction. The factors that reduce friction will promote the increase of sliding. The factors that affect the axial sliding coefficient are as follows:

(1) The effect of welding steel pipe rolling speed and elongation coefficient. Generally, the increase of elongation coefficient will cause the increase of axial sliding, that is, the value of axial sliding coefficient decreases. The effect of welding steel pipe rolling speed should be analyzed in detail. One way to improve the piercing speed is to increase the roll speed and the other is to increase the feeding Angle. Increasing the roll speed will lead to an increase in slip, that is, the axial speed efficiency is reduced, on the contrary, the motor capacity is significantly increased, so the best way is to increase the feed Angle, which is one of the effective measures to improve the piercing speed in recent years. The results show that the slip decreases with the increase of the feed Angle, that is, the slip coefficient increases.

(2) The influence of welded steel pipe billet diameter. With the increase of the diameter of welded steel pipe billet, the axial slip increases, which may be caused by the decrease of D/d2 ratio and the decrease of roll pulling force. In addition, the head used for perforating large diameter welded steel pipe billet is short, and the slope of the head bus is large, which leads to the increase of the axial resistance of the head.

(3) The influence of the friction coefficient between the metal and the roll. The factors that affect the coefficient of friction will have a direct or indirect effect on the slip, such as the roller surface is too smooth, the slip will increase, and sometimes even rolling.

(4) The effect of perforation temperature. The friction coefficient can be increased by slightly lowering the temperature of welded steel tube billet during perforation, and the axial slip can be reduced. However, increasing the perforation temperature actually reduces the slip, because the resistance of the head to prevent the axial flow of the metal is reduced.

The slippage can be reduced by properly increasing the reduction amount, because the drag force is increased. The axial resistance of the guide to the metal can be reduced by increasing the spacing of the guide properly, thus reducing the slip. In addition, steel type and capillary size also affect the axial slip coefficient.

How to improve the axial sliding coefficient?

Practice has proved that increasing the feeding Angle; Reduce roll speed; Increase roll diameter; Reduce the Angle of the inlet roller facing the welding steel pipe rolling line; The axial sliding coefficient of cross rolling can be improved by reducing the elongation coefficient. If the piercing machine properly increases the front diameter shrinkage of the top head; Using top lubricants; or the active rotating guide plate instead of the guide plate can also achieve good results. Under the condition of ensuring normal perforation, the straight column of the ejector rod should also have enough rigidity to reduce the swing of the ejector head in the deformation zone during perforation and increase the axial operation resistance.