Antioxidant composition, particle size, chemical stability, physical stability and the number of blowing, blowing pressure, time all have strict requirements, mainly to solve the problem of large extension of the tube rolling mill, the mandrel and the rolling Relative movement between pieces is large.
The working conditions of the mandrel are worse, and the mandrel is more prone to wear and scratches. When the lubrication condition is not good, it is prone to a rolling accident or the stripping machine cannot smoothly extract the waste tube from the mandrel at the end of rolling.
The constrained mandrel continuous tube rolling mill did not have an air reducer at the beginning. Instead, a tube blank of one specification corresponds to a pass. This is mainly because the relative movement ratio of the mandrel and the inner surface of the rolling material during rolling is floating. The working conditions of the core rod are more severe, and the core rod is easier to wear and scratch. The capillary tube is not allowed to move longitudinally before entering the tube rolling mill in the process of the limiting mandrel. The secondary oxidation of the inner surface of the capillary must be effectively prevented to ensure the quality of the seamless steel pipe. Therefore, it is impossible to arrange an air reduction machine between the piercing machine and the tube rolling mill like a floating mandrel. If the tandem arrangement of semi-floating mandrels is adopted, the increase in the length of the mandrel will slow down the rolling rhythm (due to the backward movement of the mandrel at the end of rolling), which will affect the production capacity of the unit, which is also uneconomical. In the past ten years, the limited-movement mandrel unit has also been constantly absorbing the strengths of other units. An overhead reducer (two-roller, three-roller, and four-roller types are available) is arranged in tandem on the inlet side of the tube mill to eliminate the capillary The gap between the surface and the mandrel and the head and tail diameter deviation of the outer diameter of the capillary make the rolling more stable, thereby improving the service life of the roll and ensuring the geometric dimensional accuracy of the seamless steel pipe and the quality of the inner and outer surfaces.