Function of steel pipe centering device
The centering device is mainly used to prevent the speed jitter of the ejector during the high-speed rotation of the piercing process, maintain the stability of the piercing process, and prevent the serious eccentricity of the capillary or the bending of the ejector. Generally, there are 3-4 centring devices. With the increase of capillary length, there are 5-7 centring devices.
Generally, each centering device is composed of three centring rollers with 120 ° to each other. Two upper and lower centring rolls. The action of the centering device during piercing is described below.
(1) When the tube blank is bited into the blank and close to the centering device, the centering roll of the stand timely holds the ejector rod and rotates with the ejector rod (follower roll), so as to keep the axis of the ejector rod on the rolling line and avoid excessive swing.
(2) When the front end of the capillary is close to a certain centering device, the three centering rollers open a small distance (i.e. capillary position) at the same time to make the capillary enter between the three centering rollers and rotate forward. At this time, the centering device can guide the capillary and prevent the capillary from swinging excessively. The opening distance (capillary position) of centring roll should be adjusted according to the capillary diameter. Generally, the outer diameter of the capillary plus the capillary runout (8 ~ 12 mm) should be selected for the distance (diameter) of three centring rolls.
(3) When the piercing process is completed, the upper centering roller is lifted up a large distance (open position). At this time, the lifting roller table placed between the centering rollers rises to drag the capillary, and the rotary roller table can transport the capillary.
The driving of centering roller was first completed by cylinder, which was mainly used in small units. The modern maximum unit is usually driven by hydraulic cylinder and realizes automatic control.
