SK278793B6 - The rolling-mill train for drafting of hollow bodies with the use of a mandrel - Google Patents

Abstract

The rolling-mill train used for drafting of hollow bodies with the use of a mandrel contains at least one main forming bench (1) having a universal arrangement closed to the horizontal rolls (2) being to be set, together with vertical rolls (4, 5) and it also contains the duo finisher (6) located after the main forming bench (1) or the bench (12) with the same driving, being located before the main forming bench (1).

Description

The rolling line for drawing hollow bodies on the mandrel comprises at least one main forming stand (1) with a universal arrangement of adjustable horizontal cylinders (2,3) and vertical cylinders (4, 5) and a duo finishing stand (6) downstream of the main forming stand (1). 1), and possibly also a driving stand (12), placed upstream of the main forming stand (1).

Technical field

The invention relates to a rolling mill for drawing hollow bodies on a mandrel.

BACKGROUND OF THE INVENTION

The production of seamless steel tubes is usually carried out in three forming stages, which are punching in a punching machine, stretching in the main rolling stage, passage through the finishing rolls in a calibration reducing mill or in a reducing extension mill. A number of rolling methods have proven to be the main stage of the line, e.g. automatic rolling and pilgrim rolling. Recently, continuous rolling on a rolling bar has become particularly important. Here, the rolling material is transformed in a series of five to eight successive rolling stands either by a free-running or guided mandrel. The rolling mills are usually duo rolling mills whose rolling gaps are offset by 90 [deg.] To each other in order to achieve as even a deformation of the wall thickness as possible by this alternating arrangement. The number of rolling stands is predetermined by the desired elongation in the main forming stage and the formation of a rolling calibration, wherein the rolling calibration itself again depends on the number of rolls of the rolling stand.

In the duo rolling mill rolling method, the rolling gauge distinguishes between the calibration base and the two lateral calibration sides. While at the calibration base the wall of the rolled material is pressed directly and thus deformed, there is a considerable indefinite deformation in the calibration flanks. Depending on the design of the gauge, even in this region of the wall, the wall may weaken, squeeze, or even create unevenness in poor calibration, as long as the material flows between the cylinder bodies due to the gauge overfill.

In order to eliminate this undesirable effect, it has been attempted to create that portion of the gauge that presses on the rolled material so that no material, when overfilled, can flow into the rolling nip and no high relative velocities between the rolled material and the rolls can result in friction in the calibration flanks. It was also necessary to improve poor gripping conditions at a high enclosure angle. To this end, more or less the calibration sides were more open.

In careful consideration of the rolling process, it must also be assumed that there is more or less great play before rolling between the rolling mandrel and the hollow body - the hollow block. This play is necessary in order to allow the roll bar to be inserted undisturbed and also to avoid close contact between the roll bar and the hollow block so that the hollow block is not cooled too much.

Before the wall of the hollow block itself is reduced, this play is forced out during rolling. Thereby, the hollow block is shaped into an oval shape because the wall of the rolled metal extends towards the calibration flanks, i. j. in the direction of the roll gap. Once the wall of the hollow block enters between the caliber and the rolling mandrel and deformation begins, the directly printed area in the calibration base is elongated. Depending on the magnitude of the indirect effect of elongation in the directly printed area, i. j. in the calibration base, the wall of the hollow block in the calibration flanks may be enlarged or weakened.

Thus, in the mill stand known in duo calibration, the wall thickness reduction in the calibration base and hence the elongation per mill stand is limited due to the allowed surrounding angle. In order to achieve sufficient elongation and to manage the indispensability of forming the rolled material in the calibration flanks, a greater number of rolling stands is required, which is disadvantageous in view of the high investment and operating costs.

SUMMARY OF THE INVENTION

The object of the present invention is to keep the number of rolling stands as small as possible and to achieve the greatest possible elongation with a smaller number of rolling stands.

This object is achieved by a rolling line for drawing hollow bodies on a mandrel, which comprises at least one main molding table 20 cu with a universal arrangement of adjustable horizontal cylinders and vertical cylinders and a duo finishing mill downstream of the main molding mill and possibly also a driving machine. stool, placed in front of the main forming stool.

With such a rolling mill, excellent rolling quality and large elongation on a single rolling mill can be achieved at low installation costs.

An advantageous embodiment of the invention is characterized in that the two opposing horizontal rolls of the main molding mill are driven.

A further advantageous embodiment of the invention consists in that the horizontal rolls have a larger diameter than the non-driven vertical rolls of the main forming stand. With such an embodiment, gripping conditions between the driven rollers can be improved.

Another preferred embodiment is that each of the horizontal cylinders overlaps a portion of the circumference of the rolled material that is greater than 90 °. The relatively small shape irregularities in the calibration flanks that arise in this cylinder arrangement are compensated for by the corresponding widening of the caliber. Said bulges may be removed in a subsequent rolling mill with two driven rollers, the angle of which they surround the rolled metal is greater than 90 °.

Another advantageous embodiment consists in that the axes of the non-driven vertical cylinders lie in the rolling direction behind the plane defined by the axes of the horizontal cylinders. This arrangement is suitable for improving the gripping conditions of the driven rollers of the main molding mill. Due to the principle of a driven pair of rollers, these rollers will be subjected to the additional driving forces required to pass the rolled metal between the non-driven rollers. Especially in the case of a large reduction in the thickness of the ste55, the impact impact is too early, i. j. at a time when the gripping conditions of the driven mill stand are not yet effective. In this case, the engagement impact can be avoided, as mentioned, so that the axes of the non-driven rollers are arranged offset in the rolling direction 60 not beyond the axes of the driven rollers.

Preferably, the axes of the driven output rollers duo of the finishing mill are arranged perpendicular to the axis of the horizontal rollers of the main forming mill, the output rollers overlapping a portion of the circumference of the rolled material 65 that is larger than the portion covered by the vertical rollers. This arrangement compensates for the unevenness created in the rolling gap region of the main molding mill in the next duo of the finishing mill.

Another preferred embodiment of the invention is that the drive stand is designed as a hollow block reshaping device in at least one longitudinal median plane that extends offset relative to the median plane running through the calibration base of the horizontal cylinders.

With this embodiment, the same conditions are created for the entry of the second block into the universal mill, which are set by calibration in the next mill. There is a surprising advantage that it is possible to increase the elongation in the main molding mill, so that reduction to only one rolling mill is possible. This object can be achieved according to the invention in that the hollow block of material, e.g. The oval is treated in the drive stand before the continuous tube stand as described in DE-P 39 14 016 A1. It is recommended to select the degree of deformation so that the inner wall of the hollow block in the region of the cylinder flanks of the driven rollers of the universal mill stand abuts the roll bar.

Surprisingly, according to the present invention, a rolling mill is provided for stretching hollow bodies on a mandrel, i.e. a rolling mill with a high elongation, so that a large number of continuous rolling stands can be disposed of in succession, but the desired task of the invention can be achieved costs.

BRIEF DESCRIPTION OF THE DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in more detail with reference to the drawings, in which: FIG. 1 is a view of a rolling mill according to the invention and FIG. 2 is a cross-sectional view of the main forming stand of FIG. First

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 shows the main forming stand 1, which is formed in a universal rolling arrangement. In the illustrated embodiment, the horizontal-vertical arrangement is selected. However, it is also possible to provide rollers inclined by 45 ° in a known manner. In FIG. 1 also shows the horizontal rollers 2, 3 and the vertical roll 4, 5 of the main forming stand 1. From this figure it is equally clear that the main forming stand 1 is arranged on a base plate 11 on which the output duo of the finishing stand 6 is also arranged. The latter is provided with output cylinders 14, which are driven by the output drive motor 15 above the duo finishing mill 6.

In addition, a drive stand 12 is provided on the base plate 11 and is equipped with input rollers 13 driven by an input drive motor 15 '. These inlet rollers 13 are calibrated so as to deform the hollow block 7 in the longitudinal median plane, which extends through the horizontal calibration base of the inlet rollers 13. The hollow block 7 is rolled on the rod 8 and shaped slightly oval.

In particular, FIG. 1, the vertical rollers 4, 5 are mounted with respect to a plane running through the axes of the driven horizontal rollers 2, 3 offset by a value x towards the outlet side.

In FIG. 2 shows schematically the arrangement of the rollers 2, 3, 4, 5 of the main forming stand 1. The horizontal rollers 2, 3 are driven by spindles 9 which are connected via couplings 10 to the pins of the horizontal rollers 2, 3. The vertical rollers 4, 5 are carried freely , t. that they are not powered.

It will be appreciated that the driven horizontal rollers 2, 3 surround a portion of the tube greater than 90 °, while the non-driven vertical rollers 4, 5 surround a smaller portion. To accommodate relatively small shape unevennesses, it is possible to adjust the corresponding extension in the calibration sides. Within the scope of the invention, it is also possible, if desired, to provide a second main forming stand in a universal rolling arrangement.

Since the driven horizontal rollers 2, 3 are intended to retain the rolled material and pass it through the non-driven vertical rollers 4, 5, particularly good gripping conditions must be provided. As a rule, with particularly large wall thickness reductions, the initial impact occurs too early, i.e. when the gripping conditions of the driven rolling device are not yet fully effective. In order to alleviate the initial impact and to shift over time, the vertical rollers 4, 5 are offset by a value of x in the rolling direction, that is to say beyond the plane of the axes of the driven horizontal rollers 2, 3.

With the proposed rolling mill, with a small number of stands 1, 6, 12, preferably with only one main forming stand 1, a large thickness reduction can be achieved at the same wall thickness in order to achieve the best sales pipe at the lowest construction cost. In this case, the driving stand 12 may or may not improve the introduction into the main molding stand 1. The small residual shape irregularities which occur on the proposed rolling mill at the rolling gap between the driven horizontal rollers 2, 3 and the non-driven vertical rollers 4, 5 are received by the corresponding forming a roll gap in this area. These shape irregularities will be corrected in the next duo of the finishing mill 6 by an overlapping area of the output rollers 14 which is substantially greater than 90 ° of circumference.

Claims (7)

Rolling mill for drawing hollow bodies on a mandrel, characterized in that it comprises at least one main forming mill (1) with a universal arrangement of adjustable horizontal rollers (2, 3) and vertical rollers (4, 5) and a duo finishing mill (6) ), downstream of the main forming stand (1), and possibly also a driving stand (12), placed upstream of the main forming stand (1). Rolling mill according to claim 1, characterized in that two opposed horizontal rollers (2, 3) of the main forming stand (1) are provided with a drive. Rolling mill according to claim 1 or 2, characterized in that the horizontal rollers (2, 3) have a larger diameter than the non-driven vertical rollers (4, 5) of the main forming stand (1). Rolling mill according to one of Claims 1 to 3, characterized in that each of the horizontal rollers (2, 3) covers a part of the circumference of the rolled material that is greater than 90 °. A rolling mill according to any one of claims 1 to 5 4, characterized in that the axes of the non-driven vertical cylinders (4, 5) lie in the rolling direction behind the plane defined by the axes of the horizontal cylinders (2, 3). The rolling mill according to any one of claims 1 to 5 5, characterized in that the axes of the driven output rollers (14) of the duo finishing mill (6) are arranged perpendicular to the axis of the horizontal rollers (2, 3) of the main shaping mill (1), the output rollers (14) overlap which is larger than the part covered by the vertical cylinders (4, 5). Rolling mill according to any one of claims 1 to 7 5, characterized in that the drive stand (12) is configured as a device for reshaping the hollow block (7) in at least one longitudinal median plane 15 which extends offset relative to the median plane running through the calibration base of the horizontal cylinders (2, 3).