FR2483809A1 - METHOD AND INSTALLATION FOR MANUFACTURING TUBES ON TUBE STRETCH BENCHES - Google Patents

Abstract

THE INVENTION RELATES TO A PLANT FOR MANUFACTURING TUBES ON STRETCH BENCHES. THE INSTALLATION INCLUDES A LAMINATOR WITH OBLIQUE CYLINDERS 13, A STAMPING DEVICE 19 AND A STRETCHING BENCH 16 WITH NON-DEGRADED ROD BUT WITH A ROUNDED EDGE, THE TWO RIBBONS 6, 7 OF THE STRETCHING BENCH ARE DESIGNED FOR A REDUCTION IN THE SECTION FROM 6 TO 12 IN TOTAL, RELATING TO THE SECTION OF ROUGH 1. ROD 2 IS EQUIPPED WITH A DRIVE WHICH ALLOWS THE ROD FORWARD SPEED TO BE INCREASED WHILE PASSING THROUGH THE TWO CAGES PREVIOUS. APPLICATION TO THE MANUFACTURING OF LARGE LENGTH TUBES.

Description

The invention relates to a method for manufacturing large tubes.

  length on tube drawing benches, in which ingots are rolled in an oblique roll mill to form open tube blanks, after which a diameter decrease at their anterior end is applied by stamping and then with a rod inserted in the tube blank, they are pushed through a plurality of reducing grooves arranged in series and thus, they are transformed into tubes by hot rolling in successive stages of deformation. A process of this kind is known

by DE-OS 1 452 255.

  The productivity of the known process depends, as in all rolling processes, on the duration of the different steps. The initial stamping of the anterior end of the tube blank takes appreciable time. In the known processes, it is necessary to tighten it to a significant extent, in a bottle neck or in another form,

  so that the necessary thrust force can be trans-

  roughing tube. However, a tightening

  notable requires a corresponding time and furthermore, -

  causes a relatively large loss at the end

  previous which is no longer usable thereafter.

  The object of the invention is to perfect a process of this kind in such a way that the initial stamping process can be abbreviated and that

  the end to be stamped can be decreased.

  Therefore, according to the invention, there is provided a method characterized in that the first two stages of deformation, one operates with a decrease in section which is each time 40 to 60% lower than the section decrease when of the next deformation step and that during the movement of the front end of the tube blank, the thrust speed of the first to the third step of the tube is increased.

  deformation by accelerating the tube blank.

  - 2 - One embodiment is characterized in that the section decrease in the first deformation step is 2 to 5%, that in the second deformation step it is 5 to 10% and that the phase Acceleration is complete when the anterior end of the draft

enters the third groove.

  For the implementation of the method, the invention proposes an installation comprising a rolling mill with oblique cylinders, a drawing device and a drawing bench with undegraded rod but with a rounded edge, characterized in that the two anterior grooves of the drafting bench are designed for a total sectional reduction of 6 to 12%, relative to the section of the blank, and that the rod is provided with a drive which makes it possible to increase the speed of the advancement of the stem

  during the passage through the two previous cages.

  According to a preferred embodiment, the installation is characterized in that the section decrease in the first groove is about 3%, in the second groove about 8% and that the speeds of advancement of the rod in the first groove are 1 to 2 m / s, in the second groove 2 to 3 m / s and in the third groove and the following,

4 to 6 m / s.

  Thanks to the invention, it can provide a very small initial stamping. It is therefore sufficient for a single crushing deformation performed by means of a suitable tool in the form of a cap, in itself known, to realize for

  the stem a sufficient stop. The duration of stamping time

  initial sage is thus reduced significantly. In addition, since less material is consumed for the initial stamping region, the loss due to the initial stamping operation is decreased as well.

is improved overall.

  The invention is based on the idea that in the drawing-bed rolling of blanks of open tubes initially stamped, the process of making a rigid connection between the anterior end of the rod and the region of Initial stamping can be further completed in the first two cages in which the splines also apply to the initial stamping region a slight additional tightening. As a result of the reduction in outer diameter and rolling on the rod in the first two stands, the initially stamped annular bottom is stabilized and furthermore, an assisted connection is made between the rod and the inner wall of the tube, so that we do not have to dread a breakthrough

of the stem.

  The breakthrough of the stem constitutes an appreciable risk in another kind of drawbars operating with a degraded rod, because first of all the degraded portion projecting from the anterior end of the rod must assume the advancement of the rod. tube blank and therefore, as known from German Offenlegungsschrift No. 2,812,778, it is necessary to design the anterior grooves for a lesser

decrease of section.

  An advantageous embodiment is characterized in that the installation comprises an axially acting embossing device for stamping the tube blank and which ensures a decrease in outside diameter whose taper angle is 22 to 280. that the right-angled frontal surface of the shank has a rounded edge having a radius of 8 to 12 minutes and that the difference between the inside diameter of the tube blank and the diameter of the shank is 4 to 6% of the diameter of the

rod.

  The invention provides a significant improvement in tube manufacturing processes of the species defined above. Thanks to the possibility of producing long hollow bodies with relatively thin walls in an oblique-roll mill, it is possible, if necessary, to transfer to the rolling mill with oblique cylinders a portion of the sectional reduction which is usual in the drawing bench. It thus becomes possible to manufacture blanks having a significantly larger diameter, for the same force limit of thrust. The force limit to be applied is called the force to be applied via the mandrel rod and which must not be exceeded when the pierced part is deformed simultaneously in

  several flutes of drawing bench. In the installations

  design, the maximum thrust force is limited to around 100 t, taking into account the forces that appear in rack-and-pinion

of the stem.

  The advantages of the process according to the invention, namely the possibility of using thick-walled blanks of sufficient length, also including the economical manufacture of large-sized tubes with relatively thick walls for oil deposits, as well as the possible increase in the maximum diameter of the blanks, from about 170 mm to about 255 mm, for the same thrust force, open wide possibilities for the application of a tube manufacturing process whose steps are drilling at the rolling mill. oblique, then stamping and finally-rolling in a drawing bench. However, if necessary,

  can still provide, in the following, a pulling mill-

  reducer for the subsequent processing of rolled tubes. The invention teaches that the maximum thrust force to be transmitted occurs at the earliest when the end of the blank has passed the third groove of the drawing bench. Therefore, contrary to the opinion of the professional environment, it is not necessary to give the front end of the blank, in the stamping device, a shape such that the thrust limit force can be transmitted as soon as possible. the beginning, but according to the invention, it suffices that a thrust force of the first groove, limited by the slightest reduction in section and the initially low thrust speed, can be transmitted. Thus, thanks to the invention, part of the stamping process is in some way transferred to the first stands of the drawbench and in the first stands, it is constituted, for the front surface of the mandrel rod, a surface of application whose resistance increases by one groove

  to the other to the same extent as the pushing force.

  Meanwhile, the accuracy of this idea has been confirmed

  through in-depth experiences in practical work.

  The slight, preferably tapered, forming of the tube blank, called stamping, is provided by axial compression in a single step, right next to and parallel to the drawbench. The tightening and stamping time is much lower than the minimum cycle of the drawing bench. During the tightening period, the mandrel rod can be introduced into the hollow ingot, positioned and then withdrawn and transferred to the drawbench. The combination of low deformation

  initially during stamping and the corresponding calibration

  laying in the flutes 1 to 3 of the drawbench is an important teaching of the invention. Thus, the initial light stamping described is not sufficient to transfer the thrust forces that already occur in the first grooves during the conventional calibration bench drawing. On the other hand, the initial stamping suitable for conventional calibrations can not be realized from

  the simple way described, not fast enough.

  The initial light stamping according to the invention further means relatively reduced axial forces during stamping and these forces can be absorbed without difficulty by a jaw mandrel. This results in lower heat losses as a result of shorter cycles in the clamping device. In addition, the wide open end of the blank substantially decreases the force peak that occurs during penetration into the groove. Thus, no doubt, the longevity of the bearings, which is critical in all installations

  drawing bench, is favorably influenced.

  Exemplary embodiments of the invention are shown in the accompanying drawings in which: Figure 1 shows a front end of blank in the jaws of the stamping device; Figure 2 shows the partially stamped tube blank; Figures 3 to 6 show successive steps of the method in the drawing bench; Figure 7 is a schematic section of the first reduction groove; Figure 8 is a section of the second groove

reductive -

  Figure 9 is a tube mill facility.

  FIG. 1 shows in half-section a blank of tube 1, clamped on all sides in the mandrel 3 of a

  stamping device, immediately after stamping

  wise. The anterior end of the tube blank 1 is conically tightened, the taper angle α to be 22 to 280. The length of the constricted end, i.e. of reduced diameter, is designated by LK and the primitive form of the tube blank 1 is indicated

by a dash 21.

  Another dash 22 indicates the rod 2 of the drawing bench, to be inserted in the tube blank 1. The tube blank 1 has an internal diameter DR, the rod 2 a diameter DS, it is rounded at its anterior edge , the radius r to be 8 to 12 mm. Moreover, the difference between the internal diameter DR of the tube blank 1 and the diameter DS of the rod represents 4 to

6% of the DS diameter of the stem.

  Figure 2 shows the front end, stamped

  initially, a tube blank 1.

  Figures 3 to 6 show deformation processes

  first three grooves 6, 7, 8 of the drawing bench.

  In Figure 3, the tube blank 1 has arrived, under the action of the rod 2, in contact with the first groove 6 and in Figure 2, it is completely introduced. When it abuts against the first groove 6, the rod 2 is generally pushed slightly further into the tube blank 1. The tube blank X is deformed by the first groove 6, so that the partially embossed end 4 moves inward with decrease of the minimum inside diameter designated by DK in FIG. 1. As a result, the carrier section between the rod 2 and the tube blank 1 increases so that an increased thrust force can be transmitted . In the second cage 7 (Figure 5), the carrier section is further strengthened and finally, in the third cage 8, it arrives at a shape that allows the transmission of the total force

thrust.

  Figures 7 and 8 show the splines 6 and 7 in section and it can be seen that given the use of three cylinder splines, the deformation is not uniform, seen on the circumference. The dotted polygon 23 is the contour of the inner edge of the application surface between the front surface of the rod 2 and the initially stamped end 4 of the tube blank 1. According to FIG. 7, the application surface direct is formed of three crescent-shaped portions 24 which, according to FIG. 8, have already changed into a

  approximately annular application surface 25.

  The tube rolling mill apparatus shown in FIG. 9 comprises an oblique roller mill 13, an oblique roller mill output 14, a transverse conveyor 15, a draw bench 16, and an output roll train 20. drawbench 16 comprises a rod carriage 17 provided with the rod 2, an adjustable rotational speed drive 18 for moving the rod carriage 17 and, in addition to the grooves 6, 7 and 8, further grooves 9, 10, 11 and 12. In addition, the installation comprises a stamping device 19

  which can slide transversely as a whole.

- 9-

Claims (4)

  1. A process for producing long tubes on tube drawing benches, in which ingots are rolled in an oblique-roll mill to form open tube blanks, after which a reduction is applied thereto. of diameter at their anterior end by stamping and then, with a rod inserted into the tube blank, are pushed through a plurality of reduction grooves arranged in series and thus, they are transformed into tubes by hot rolling in successive stages of deformation, characterized in that the first two deformation steps are carried out with a reduction in section which is each time 40 to 60% less than the reduction in section during the following deformation step and that during the movement of the anterior end of the tube blank, the thrust velocity of the first to the third deformation step is increased. accelerating the tube roughing.   2. A process according to claim 1, characterized in that the section decrease in the first deformation step is 2 to 5%, that in the second   deformation step it is 5 to 10% and that the.   acceleration phase is complete when the end   front of the burrow enters the third groove.   3.- tube manufacturing plant by the method according to claim 1, comprising an oblique roller mill 13, a stamping device 19 and a drawbench 16 rod non-degraded but rounded edge, characterized by the fact that the two front grooves 6, 7 of the drafting bench are designed for   a reduction of section of 6 to 12% in total, -   relative to the section of the blank 1 and that the rod 2 is provided with a drive which makes it possible to increase the forward speed of the rod during the passage through the two previous cages.   4. Installation according to claim 3, characterized in that the section decrease in the first groove 6 is about 3%, in the second groove 7 about 8% and the speeds of advancement of the rod in the first groove are 1 to 2 m / s, in the second groove of 2 to 3 m / s and in the third   flute and the following, from 4 to 6 m / s.   5.- Installation according to one of claims 3   and 4, characterized by the fact that it comprises an axially acting embossing device for stamping the tube blank and which ensures a decrease in the external diameter, the taper angle of which is 22 to 280, than the front surface. 22 at right angles to the rod 2 has a rounded edge having a radius of 8 to 12 mm and that the difference between the internal diameter DR of the tube blank and the diameter DS of the rod   represents 4 to 6% of the diameter of the stem.