The welding pipe sizing process of high frequency welded pipe equipment includes empty rolling, micro-tension rolling, active rolling and passive rolling, the maximum rolling force and the maximum linear speed are not the same point, the small hole type accepts large pipes and traces. 6 features such as reducing rolling.

(1) Micro-reducing rolling. Whether it is round-to-round sizing rolling, or round-to-round or different-to-different shaping rolling, the reduction rate is generally very small. For welded pipes with an outer diameter in the range of φ15~200mm, the total diameter reduction usually only accounts for 1.2%~0.65% of the outer diameter D of the finished pipe. The pass reduction rate and average pass reduction rate are shown in the table below. This feature has guiding significance for sizing roll pass design, sizing allowance setting and actual operation, and provides a basis for formulating sizing process parameters.

(2)Rolling on an empty stomach.Welded pipe sizing belongs to the category of hollow cold rolling, which is to use sizing rollers to roll open welded pipes, and only need to apply a small rolling force to achieve changes in the shape and size of the welded pipe. Longitudinal length. This feature requires that the rolling force applied by the sizing pass should not be large, otherwise it will easily lead to a sudden reduction in the size of the cross-section of the welded pipe, distortion of the shape, and failure to achieve the process goal.

(3)Micro tension rolling. High frequency welded pipe equipment is inseparable from longitudinal tension in the whole process of manufacturing welded pipe and rolling. The longitudinal tension of the sizing section is closely related to the forming section and the welding section. After the specification of the welded pipe is determined, the main factors affecting the sizing tension are the line speed and rolling force of the sizing flat roll pass. Determined by the micro-reduction characteristics of the welded pipe sizing process and the characteristics of open rolling, the rolling force applied by the sizing roller to the welded pipe cannot be large, and the resulting friction force cannot be compared with that of solid rolling. This feature requires that the linear speed of the sizing flat roll must be slightly faster than that of the forming flat roll, so as to obtain more friction required by the sizing process.

(4)Active rolling and passive rolling coexist. In addition to the reduction and deformation of the sizing flat roll during rolling, another important function is to provide the driving force for the operation of the welded pipe, while the force of the sizing vertical roll hinders the operation of the welded pipe. This feature requires that when adjusting the sizing level and vertical roll, not only the size adjustment, but also the adjustment of the rolling force of the flat roll and the rolling force of the vertical roll, to ensure that the rolling force of the flat roll is greater than that of the vertical roll. This is a basic principle that must be followed when adjusting the sizing level and vertical roller.

(5)The maximum rolling force of the sizing flat roll pass is contrary to the maximum linear speed. Taking the sizing round hole type as an example, in the normal production process, care should be taken to prevent the size of the round tube from exceeding the upper and lower dimensions in the vertical and horizontal directions.

(6) The small hole type accepts large welded pipes. According to the sizing process and the sizing principle, the geometric size of the welded pipe before entering the next sizing roller pass is always larger than the size of the pass. In actual operation, in order to avoid friction with the maximum linear speed A and B of the hole pattern when the welded pipe enters the hole pattern, the size of the corresponding welded pipe part is always adjusted to be slightly smaller than the hole pattern size. This contradiction between the theoretical design of the round hole shape and the actual adjustment of the welded pipe to an ellipse directly leads to two unfavorable consequences: one is to increase the friction between the edge of the front pass and the welded pipe, which accelerates the wear of the edge of the pass; The upper part corresponding to the edge of the hole is prone to pressure injury. Although this abrasion and crushing is sometimes minor, it is not necessary. This inspires people to improve the design ideas of the existing round (including some special-shaped pipes) pass, so that the theory is closer to reality, so as to eliminate the adverse effects of the pass on the welded pipe and the pass itself, and prolong the use of the roll pass. life.

These characteristics of the welded pipe sizing process are the basis for the high frequency welded pipe equipment to formulate the welded pipe sizing process and establish the adjustment principle.

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