SU902889A2 - Welding unit of mill for producing welded straight-seam tubes - Google Patents

Description

(54) WELDING KNOT MILL FOR THE PRODUCTION OF WELDED

Straight, PIPE

one

The invention relates to the production of conduit pipes and can be used in the manufacture of pipes of any gauge from various grades of steel.

According to the main author. St. No. 707643 is a well-known welding unit of the mill for the manufacture of welded straight seam pipes, which includes welded guide and round bead rolls, as well as stabilizing rolls mounted behind the bead rolls that can be moved in a plane perpendicular to the axis of the pipe, while the first pair of stabilizing rolls are mounted behind the bead rolls at a distance of 2-10 pipe diameters, and the middle parts of the calibrating surface of the stabilizing rolls are made with a radius of 1.1-2.5 of the radius of the calibrating surface of the bevelling roller one.

The disadvantage of the welding unit is that the working surface of the seam pressurizing rolls forms a round caliber, which does not provide either a stable filling of the latter with a tubular billet, or a good quality edge compaction, which further ensures the quality application of the welded joint. Working surfaces

The stabilizing rollers are made with a constantly increasing ovalization towards the larger vertical axis.

Thus, these disadvantages do not allow to improve the quality and speed of welding.

The aim of the invention is to increase the welding speed and quality of the pipes produced.

The goal is achieved by the fact that in the welding unit of the mill for the manufacture of welded straight pipe, a closed caliber formed by the squeeze rolls is an oval with a small vertical axis equal to 0.8-0.95 of the diameter of the finished pipe, and the caliber formed by stabilizing rollers , an oval, the small vertical axis of which is smaller than the corresponding axis of the caliber formed by the pick-up rollers by 5-10 ° / o.

Such constructive performance of the welded assembly provides the most favorable filling of the tube billet of the welding caliber, which allows adjusting the nature of the contact between edges, which depends on the radius of the upper part of the welding caliber. i.e., precise alignment of edges, their stable (without corrugation) position in the weld zone. In addition, constructive execution of the gauge of stabilizing rolls with a small shaft axis, smaller than the minor axis of the oval of the gauge of the suture-shaped rolls by 5-10 ° / o, allows adjusting the edge tension, or rather creating tension that compensates for the thermal broadening of the edges and significantly reduces pipe buckling blanks. Moreover, according to the experimental data obtained during the molding with the use of this device, it can be said that when the difference in the values of the small axes of the said ovals is less than 5%, the effect of stretching the edges is too small. When the difference of this size, exceeding 10 ° / o, there are subsequently difficulties in obtaining a round pipe from a pipe with prominent ovality on traditional gauge walls. For a good calibration in this case, it would be necessary to create additional expensive devices, which would significantly reduce the technical and economic effect of using the proposed device as a whole. All of the above characteristics of the present invention flow from the creation of a welding unit, which in the area of the preforming of the welding gauge provides a well-formed pipe billet. In the deformation zone, from the beginning of the contact of the rolls with the billet until the edges are completely joined, elastic and plastic bending of the cold billet occurs. From the point of view of the formation of hot cracks in the joint, the dangerous contour stresses at the pipe exit from the deformation zone will be the greater, the greater the calibration ovality. A theoretical analysis of the stress-strain state in the welding caliber leads to the conclusion that one of the main factors affecting the quality of the weld is the nature of the contact edges, which depends on the radius of the upper part of the welding gauge. To obtain the necessary contact of edges, two-radial oval calibers are used. By varying the ratio between the calibrating radii of the welding rolls (by increasing or decreasing the hem of the edges), the process of formation of the seam and the amount of internal burr can be controlled. The use of servo roller coils forming a closed caliber in the form of an oval with a small vertical axis equal to (0.8-0.95) the diameter of the finished pipe, as the results of experiments have shown, will allow to carry out the deformation process with the highest quality and thereby improve the quality of the produced pipes and the welding speed . The value of the small vertical axis was chosen (0.8-0.95) of the diameter of the finished pipe from the analysis of experimental data. The value, greater than 0.95 of the diameter of the finished pipe, is almost close to the traditional round gauges of the seam bending rolls, with the loss of the deforming advantages mentioned above. The magnitude of the small vertical axis, less than 0.8 of the finished pipe, is associated with subsequent and technological difficulties. In order to finally obtain a round pipe with a constant length of electric mill pipe welding, the oval billet had to be gradually calibrated into a circle immediately behind the welding-welding unit. Since the molten weld metal did not have time to completely recrystallize, the resulting stress reduction caused a pipe with cracks in the weld. ,,,, FIG. 1 shows the proposed welding unit; in fig. 2 shows section A-A in FIG. one; in fig. 3 shows a section BB in FIG. 1. The welding assembly of an electric pipe-welding mill contains weld rollers 1, into which a finally formed tube billet enters from a pipe-forming mill. Moreover, the shredding rollers designed to compress the molten edges in order to weld them form a closed caliber in the form of an oval with a small vertical axis equal to (0.8-0.95) the diameter of the finished pipe. The pairs of stabilizing rolls 2 are made vertical with the possibility of moving relative to each other in a plane perpendicular to the welded tubular billet, and also form a closed gauge in the form of an oval. the small axis of which is smaller than the corresponding axis of the caliber formed by the shaking rollers by 5-10%. The proposed device works as follows. From the tube forming mill, the finally formed tubular billet is directed to the gauge formed by the seam-like rolls 1, where it is gradually calibrated and welded. The stabilizing rollers 2, mounted at a certain distance L from the shocking compressors, alter the compression of the welded tubular billet, allow to adjust the exact convergence of edges, their stable position in the welding zone, to eliminate the spiral twisting and straining of the welded tubular billet. The use of this device provides the necessary tension in the edges, which eliminates the thermal broadening of the latter, and also leads to the creation of a falling trajectory of the edges, and

Means and to the minimum. tubular billet.

In addition, the fixation of the strip in the strip-forming and stabilizing rollers, forming gauges in the form of an oval with a small vertical axis, ensures its steady state over the cross section and the absence of helical twisting in the dynamics of strip movement along the entire tube welded mill.

Claims (1)

Invention Formula Welding unit of the mill for the manufacture of welded conduit pipes according to ed. St. No. 707643, characterized in that, for the purpose of increase the welding speed and quality of the pipes produced, the closed caliber formed by the squeeze rolls is an oval with a small vertical axis equal to 0.8-0.95 of the diameter of the finished pipe, and the caliber formed by stabilizing rollers is an oval with a small vertical axis which is smaller corresponding to the axis of the caliber formed by the sjoboobzhimny rolls, at 5-10 ° / o. Sources of information taken into account during the examination 1. USSR author's certificate No. 707643, cl. B 21 C 37/08, 1977 (prototype) f1 / g y f /.