FR2600562A1 - PROCESS AND INSTALLATION FOR MANUFACTURING SOLDER FREE TUBES - Google Patents

Abstract

A.PROCESS AND INSTALLATION FOR THE MANUFACTURING OF SEAMLESS PIPES; B.PROCESS CHARACTERIZED IN THAT THE STRETCHING IS CARRIED OUT DIRECTLY AFTER THE DRILLING IN THE SAME HOT, THE ROLLED PRODUCT BEING STRETCHED IN THE SAME ROLLER CAGE 6, BUT HOWEVER IN A DIRECTION OF PASSAGE OPPOSED TO THAT OF THE DRILLING; C. THE INVENTION RELATES TO A PROCESS FOR THE MANUFACTURING OF SEAMLESS TUBES AND TO THE IMPLEMENTATION OF THIS PROCESS.

Description

1. "Method and installation for the manufacture of tubes

seamless ".

  The invention relates to a method for the manufacture of seamless tubes, wherein an ingot heated to the rolling temperature is pierced in a piercing mill stand to obtain a hollow block, subsequently drawn to obtain a tube blank, and finally laminated to obtain the finished tube, In the vast majority of cases, loers of the manufacture of seamless tubes, the three process steps mentioned above are implemented, and this using three different devices. Drilling is frequently carried out in an oblique roller mill stand since it delivers a hollow block with a reduced tolerance to the thickness of the walls and a relatively long length. The drawing is often carried out in a second oblique cylinder rolling mill stand, in the form of an Assel 20 rolling mill stand or a Diescher rolling mill stand. The tube blank thus obtained during drawing is; after intermediate heating, rolled to obtain a finished tube in a calibrating rolling train or in a train

  rolling-reduction rolling mill inserted afterwards.

  It is already known (Zeitschrift BKXNDER, BLECHE, 2. ROHRE, 14 (1973) 4 pages 150 and 151), with the same oblique cylinder rolling mill cage, piercing blecs to obtain hollow blocks and stretching the hollow blocks for get blanks of tubes. In this known method, however, a number of hollow blocks are first produced by drilling, then the roll cage is converted to an oblique cylinder to go from piercing to drawing, and is taken up by drawing treatment of

  hollow blocks previously manufactured to obtain blanks of tubes.

  Since the drilling of several successive blocks requires a very long time and the conversion of the obliquely rolled roll stand to go from drilling to drawing also requires a certain time, it is not possible in this known process, The hollow blocks must thus be preheated again before drawing, which is not economical and requires

  of time, and this, in addition, requires to provide and operate a suitable oven.

  In addition, both during drilling and during drawing, the rolling product is respectively moved through the roll stand from the feed chute of the inlet side blocks to the outlet side where it is ejected. laterally. A transport device is then used to return the hollow blocks of the outlet side towards the entrance side of the cage.

  rolling mill with oblique cylinder, which entails the corresponding investments.

  In addition, a mandrel rod is introduced into the inlet side of the hollow block at the beginning of the drawing process, until its anterior front surface is pressed against the bottom of the hollow block hole. The mandrel rod then pushes, in the manner of a swivel bench, the hollow block into the region of the rolls of the roll cage. rolling mill with oblique cylinder, where the stretching process takes place. Accordingly, in this known method, a hollow block is used which is not completely drilled, but which has a bottom acting as a stop for the mandrel rod. Therefore, it is necessary to prematurely interrupt the drilling process in the oblique roller mill stand to maintain a bottom portion or the hollow block must be made with a drill press. These two methods have the disadvantage that a large fraction of the material must be riblonné because, after stretching, it is necessary to eliminate this bottom part and to rip it. For the reasons mentioned above, the known process is difficult, time consuming, not economical, and can in any case be used only for a low production capacity, so that this process does not require is not imposed in practice. The purpose of the invention is to realize the process initially mentioned, in a simpler, technically better and more economical way, and to create an installation which, for relatively small investments, allows the implementation of the method according to

to the invention.

  This object is achieved according to the invention in that the drawing takes place directly after drilling in the same hot, the rolling product being stretched in the same piercing mill stand, however

  in a direction of passage opposite to that of the piercing.

  This process according to the invention is therefore distinguished from known processes in that the rolling mill roll stand operates in a reversible manner for drilling and for drawing and the two passes follow each other for a short period of time. time interval. In the first passage, the block is pierced, while in the second passage in the opposite direction, the same block is stretched shortly thereafter on the same oblique cylinder mill, to obtain a tube blank. As a result, there is no noticeable cooling between drilling and drawing, thereby avoiding intermediate heating. In addition, no transport device is required to transport the rolled product from the outlet side to the inlet side around the roll cage. In addition, guiding of the mandrel rod is simplified because a mandrel rod and a thrust bearing are only used

  at the outlet side of the rolling mill roll stand.

  The stroke of this rod is in this case, shorter because this rod does not need to be extracted from the hollow block, but on the contrary, it is equalized by the mandrel rod 15 during the second pass. Finally, the output guide for the hollow block during drilling is at the same time also, during drawing, a good entry guide, in which the hollow block can easily rotate and is not twisted while being stressed. by a high couple. Another advantage is that, at the beginning of drilling and drawing, respectively, the maximum load then occurring for the roll stand and the rolled product is decreased, since there is a gradual acceleration in from the stopping state of the rolls, or from a reduced rotational speed of the rolls to the normal operating speed of rotation. The state of stopping of the rolls or the reduced speed of rotation of the rolls results, without additional control, from the reversible operation of the rolling mill in accordance with the invention, operation in which, because of the inversion of the of rotation of the rolls, they must be accelerated from the stopping position both at the beginning of the piercing and at the beginning of the piercing.

beginning of stretching.

  During drilling and drawing, the mandrel rod 5 remains inside the hollow block or the tube blank, which prevents air, and especially oxygen from the air, from entering. inside the hollow block

  or the tube blank and oxidize the inner wall.

  In addition, it is possible, in the case of the method according to the invention, to maintain at a particularly reduced level the clearance between the mandrel rod and the inner wall of the hollow block or the tube blank, and this because the mandrel rod does not need to be threaded again. The reduced importance of this game, also maintains the residual amount of air and oxygen that can still penetrate in this case, at a very low level, so that no significant oxidation of the wall occurs internal. As a result, the rolling engagement of oxide particles in the inner wall, which thus remains remarkably smoother, is also avoided during etching. Although in general the hollow block, for producing the tube blank, is drawn after drilling on a mandrel rod placed therein, to obtain a thinner wall, for greater drawing of the product. In rolling, it is quite advantageous in a series of cases, to stretch the hollow block after drilling hollow pass, that is to say without tools placed inside. Although a tube blank with a thicker wall is obtained, this wall thickness is within particularly narrow tolerances, which clearly improves the quality of the finished tubes. It is particularly advisable to laminate for finishing, after drilling and drawing, the tube blank in a calibrating rolling mill or in a stretch-reducing rolling mill without intermediate heating. This is made possible by the process according to the invention, because in its case, drilling and drawing succeed each other very rapidly.

  and that it operates with a single internal tool that takes heat once on the product in rolling.

  As a result, the first rolling heating is sufficient not only for drilling and drawing, but also for sizing rolling or rolling.

stretching and reduction.

  On the other hand, it is also possible for the tube blank, after drilling and drawing, to be further stretched in a reversible roll stand in one or more steps, interspersed later, of the process. In this way, the following drawing equipment is relieved and tube blanks with particularly thin walls are obtained. For these process steps subsequently inserted, for the purpose of drawing, it is possible, for example, to use mandrel or

no pilgrim.

  The invention further relates to an installation for carrying out the process according to the invention. This plant comprises an oblique-cylinder rolling mill stand, or piercing mill, which is equipped on the inlet side with a guide chute for the ingots and a pusher, and on the outlet side, with a rolling mandrel on one side. rotatable mandrel shank, capable of moving axially, and mounted in a thrust bearing a calibrating rolling mill or stretch-reducer being interposed following the piercing mill stand, installation characterized in that the drive, as well as the position of the cylinders and possibly that of the guides of the piercing mill stand can, after each passage, be adjusted at will on the drilling or on the drawing and respectively on the other direction of passage of the rolling product, while in the neighborhood of

  In the delivery channel of the ingots, there is provided a device for evacuating the drawn tube blank.

  7. As cages with oblique cylinders, various embodiments may be taken into consideration, but especially Assel rolling mill cages and Diescher rolling mill cages. In the latter case, the speed of the Diescher disks is about four times to twenty

  times higher during stretching than during

  It has been recognized that in the case of such cages with oblique cylinders, it is quite possible to provide the adjustment devices for cylinder positions, and possibly also guides, such as for example Diescher discs, so that these can be positioned in seconds to go from drilling to drawing, or from drawing to drilling. Above all, radial placement and / or erection must be changed. Angular position of the axes of rotation of the rolls to adjust the roll cage to oblique cylinder on the other process of transformation. The rotational speeds of rotation and the direction of rotation of the drive can, if necessary, also be modified in a few seconds. It is necessary in this respect to make some construction modifications with respect to known rolling mill roll stands, but these modifications are likely to be made. If the adjusting devices for the positioning of the rolls are provided so that they can also operate under the rolling force, that is, while the rolling stock is being introduced, the

  The cylinders are then able, even without pushing devices, to attract at the beginning of the next rolling passage the rolled product into the sizing opening.

  In a preferred embodiment of the invention, the acute positioning angles, delimited by the longitudinal axis of the rolling product and, respectively, an axis of rotation of rolls, the rolls during drilling and drawing, have a high top that is placed on 8. this entry, equipped with ingots feed chute, piercing mill cage. the definition of the input and output sides, always referring in the documents only to the drilling process. With these provisions, it is obtained that the rolling stock passes, during drilling, by a rolling caliber with - referred to the direction of passage - the axes of rotation of the cylinders extending in a divergent manner, while at the time of the drilling. drawing, this product passes through a rolling die with convergently converging cylinder rotation axes. This reduces, during drilling, an undesirable twist of the product in laninage, and promotes its flaring. During drawing, the then convergent position of the axes of rotation of the rollers ensures a limitation of the flare and thus also advantageously prevents, in the case of thin walls of the rolling product, the formation of angular ends. of the tube blank. To obtain these advantages, it is not necessary in the case of reversible rolling according to the invention, to give any other inclination to the axes of rotation of the rolls, because the passage from the divergent disposition to the convergent arrangement, results only the inversion of the direction of passage of the rolling product. It is thus always sufficient, after a passage of the rolled product, to modify the importance of the angle of adjustment of the rolls. It is advisable to size the adjustment angle between 1 and about 20, with the highest number of degrees being set during drilling. It is furthermore advantageous to have the drive motors for the rollers on the side of the thrust bearing for the rod.

chuck.

  It is advantageous that, as a device for evacuating the drawn tube blank, a rotatable guide tube, coaxial with the axis of passage of the rolling product, is interposed following the delivery chute 9. .

  ingots on the opposite side to the piercing mill stand. Such a guide tube is already the subject of an older patent application (DE-OS 35 33 119) whose application is also proposed here.

  It is then recommended to provide that at the beginning of the stretching, the speed-controlled mandrel rod is introduced through the rolling caliber and penetrates into the entry zone of the guide tube, where it is

  maintained with the thrust bearing at least until the inlet of the tube blank into the guide tube.

  This means that the mandrel rod at the beginning of the stretching process, by a controlled displacement of the thrust bearing, is moved forwards through the zone of the rolls into the guide tube, and is maintained only in this position, so that the beginning of the drawn tube blank is also guided correctly in the area of the block feed chute, and is introduced from

  safely in the inlet of the guide tube.

  As soon as this is the case, the mandrel rod can already be removed by a stretching process progressively towards the exit side, but this can also be done afterwards.

  the completion of the stretching process.

  In an advantageous embodiment of the invention, there is provided as a pusher device 25 for the hollow blocks at the beginning of the drawing, a stem shank with an external diameter greater than that of the hollow blocks, this shank being mounted in the thrust bearing and driving the mandrel rod with which it is coaxially coupled. The introduction of the hollow blocks into the zone of the cylinder is thus carried out during drawing without additional construction expense, thanks to the existing stem shank anyway and thus relieves the highly stressed area on this side of the cage rolling mill with oblique cylinder. Given the large outer diameter of the stem shank, a radial plT opposing a folding

outward is superfluous.

  10. According to another embodiment of the invention, the portion of the cylinders ensuring the flare during drilling, is provided to ensure the smoothing of the rolling product during the drawing. This middle part of the cylinders remains relatively spared during drilling, so that it is still usable even after a very long running time for drawing, in which very high requirements are imposed on the accuracy and quality of the drilling. surface of the product in rolling. In addition, the part of the rollers ensuring reduction during drilling,

  is intended to ensure the rounding of the tube blank during drawing and vice versa.

  In addition, it is possible to provide that the direction of passage of the rolling product is capable of being modified by modifying the advance angle of the rolls. In this way, it is possible to avoid reversal of the direction of rotation of the drive of the cylinders, inversion during which there are important moments of inertia, by virtue of which braking and re-starting of the engine. drive in the opposite direction of rotation, are expensive and time consuming. A modification of the advance angle of the rolls makes it possible to operate without modifying the direction of rotation of the rolls according to the

  reversible rolling method according to the invention.

  It is advantageous to provide that the speed of passage of the rolling product is lower during drilling than during stretching. The largest torque required for drilling results in a lower appropriate pass rate, about the same power demand of the drive as pulling requiring

  lower torque for a higher corresponding pass rate. In the ideal case, it is thus possible to use for drilling and drawing, the same power training installed.

  Lastly, it is expedient to provide that, in advance of the calibrating rolling mill or of the stretch-reducing rolling mill, a cut-off device is provided to free the ends of the tube blank. This is recommended because the end tips of the tube blanks after drilling and drawing are of irregular conformation, which can lead to mishaps.

during finishing rolling.

  The invention is shown in the accompanying drawings, with reference to an exemplary embodiment. FIG. 1 shows in plan an installation according to the invention; FIG. 2 shows an oblique cylinder during drilling,

  Figure 3 shows an oblique cylinder during drawing.

  In FIG. 1, an ingot heated to the rolling temperature and coming from a furnace, not shown,

  arrives on a roller path 1 and on a transverse conveyor 2, in a delivery channel ingots 3.

  A pusher 4 pushes the ingot in the axial direction out of the feed chute of the ingots 3 between the rolls 5 of an oblique cylinder rolling mill cage 6. At the output side of this cage, a mandrel rod 7 with a rolling mandrel 7a extends into the region of the rolls 5, this mandrel rod 7 being guided radially by a guide 8 of the mandrel rod - and the hollow block, and being guided and maintained in the axial direction by a stem shank 18 as well as a thrust bearing 9. The shank shank 18 has an outer diameter which is greater than that of the hollow blocks 15. It also acts as a pushing device for the hollow blocks 15

at the beginning of stretching.

  During drilling, the block is laminated to the mandrel rod 7, a lubricating agent and / or a deoxidizing agent being advantageously introduced through

  12. mediate the mandrel rod 7 and optionally also, through the rolling mandrel 7a, in the

  internal drilling 7 of the rolling block 15a, - see Figure 2.

  When drawing immediately after the hollow block thus obtained and which surrounds the mandrel rod 7, this hollow block is stretched by the same cylinders 5 to obtain a tube blank being then moved back in the opposite direction relative to the delivery chute of the blocks 3. The mandrel rod 7, with or without its rolling mandrel 7a, somewhat larger in diameter, and possibly removed, is then moved in the axial direction towards the discharge chute. supply of the blocks 3 by a damentally controlled movement of the thrust bearing 9. This continues until the rolling mandrel 7a is in the inlet zone of the first section 10a of the guide tube 10. rolling mandrel 7a remains at least in the inlet zone of the section 10a of the guide tube, until the front part of the tube blank has penetrated therein. Then, the barrel 7 with the rolling mandrel 7a can be slowly withdrawn by means of the thrust bearing 9 and the stem shank 18. This is already possible during the drawing, but only to the extent that the mandrel 7a is still on the side of the rolls 5 facing the feed chute of the blocks 3. Only after completion of the drawing process the mandrel rod 7 and the shank 18 are removed in the position shown in Figure 1, in which the process of

drilling for the next ingot.

  The thus-drawn tube blank is moved through the guide tube sections 10a, 10b, 10c by means of drive rollers 11 to a calibrated rolling mill or to a reduction tenter rolling mill. train, the tube blank is rolled to obtain the finished tube. In front of the calibrating rolling train 13 or of the reducing rolling mill 12, there is provided a cutting device 13 by which it is possible to free a piece of the ends of the tube blank, in case this This is necessary because of dimensional deviations or irregularities and shaping at the ends of the tube blank. The cylinders 5 of the rolling mill stand with oblique rollers 6 are driven in a known manner by the motors 14 and by means of long drive shafts. These shafts and the motors 14 can also be arranged on the other side, facing the thrust bearing 9 of the oblique roller mill stand 6, so that the apex of the angle of adjustment delimited by the axes rotation of the cylinders, is on the entrance side, at

  approximately in the vicinity of the delivery channel ingots 3.

  The cylinders 5 are then oppositely adjusted, as shown in Figure 1, obliquely to the longitudinal axis of the rolling product. To modify the direction of passage, it is first of all possible to modify the direction of rotation of the motors 14. Moreover, it is possible to modify only the angle of advance of the cylinders 5. This angle of advance is not visible in the accompanying drawings. This is the angle between the plane of the figure and the axis of rotation of the cylinder 5. The axes of rotation of the cylinders 5 are not parallel, in the case of rolling mill cages, the ground of the factory or the plane of Figure 1I but inclined relative to them by a few degrees. If this inclination is changed in the opposite direction, the direction of transport of the rolls 5 and hence the direction of passage of the rolled product is also changed.

  Figure 2 shows, on a larger scale, a cylinder 5 which is shown, during drilling, with a different inclination direction than that in Figure 1.

  14. The mandrel rod 7 then pushes the rolling mill 7a into the ingot 15 and makes an internal bore 16. It is clearly seen that between the mandrel rod 7 and the inner wall 17 of the internal bore 16 there is a narrow annular space, in which there is little air and barely oxygen. The cylinder 5 has an anterior portion 5a which serves to attract the ingot 15 into the "caliber". A portion 5b, more strongly conical, connected thereto causes a reduction in the transverse section of the ingot, and there follows a shoulder 5c of the cylinder and a cylindrical portion 5d which

  are used for drilling and flaring of the rolling product.

  The last section 5e of the cylinder 5 ensures the rounding

of the hollow block 15a thus created.

  The same cylinder 5 is shown in FIG. 3 during drawing of the hollow block 15a to obtain a tube blank 15b. The rolling mandrel 7a is pushed through the calibration aperture constituted by the cylinders 15, the cylindrical portion 5b of the cylinders 5, which is used for drilling the flaring, is used in the drawing shown in FIG. 3 for smoothing and calibrating in thickness of the wall of the tube blank, in cooperation with the mandrel rod 7. The section 5e of the cylinders which lor; Drilling, was used only for the rounding, is used in drawing according to Figure 3, for the reduction of the thickness of the wall and simultaneously to attract the hollow block 15a in the caliber. The latter function is assumed during the drilling by the section 5a of the cylinders, which wears relatively intensely because of the usual irregularities of the ingot 15, the acceleration in rotation to

  bring, rolling work and different speeds.

  As can be seen clearly in FIG. 3, this portion 5a of the cylinder no longer comes into contact with the blank 35 of finished tube 15b, so that irregularities caused by these wear phenomena can occur. of the section 5a of the cylinder, are not to be feared. The position of the rollers in FIG. 3 has changed substantially with respect to that of FIG. 2 in that the adjustment angle α has become almost zero and a corresponding radial positioning has taken place which essentially determines

  the thickness of the wall of the tube blank 15b.

  It should be noted, however, that both during drilling and during drawing, other positions of the rolls may be used, and that other forms of rolls may also be used.

R E V E N D IC ATI 0N S

  1. A process for the manufacture of seamless tubes, wherein an ingot heated to the rolling temperature is pierced in a piercing machine cage to obtain a hollow block, subsequently drawn to obtain a tube blank and finally laminated to to obtain the finished tube, characterized in that the drawing takes place directly after the drilling in the same hot, the rolling product being drawn in the same piercing mill cage (6), but

  in a direction of passage opposite to that of the piercing.

  2. Method according to claim 1, characterized in that the hollow block (15a) is stretched after the

  drilling in hollow pass, that is to say without internal tool.

  3. A process according to any one of claims 1 or 2, characterized in that the tube blank

  (15b), after drilling and drawing, is rolled to finish in a calibrating rolling train or in a train

  rolling-reduction rolling mill, (12).

  4. A process according to any one of claims 1 or 2, characterized in that the tube blank (15b), after drilling and drawing in a reversible rolling mill (6), undergoes additional stretching in

  one or more steps of the process, interspersed following. 25 5.Installation for the implementation of the

  Process according to any one of Claims 1 to 4, with a piercing mill stand which is equipped, on the inlet side, with a guide chute for the ingots as well as a pusher, and on the outlet side with a mandrel. lami30 is swimming on a rotating mandrel rod, likely to

  axially moving, and mounted in a thrust bearing, a rolling mill calibrator or drag-pulling being interposed following the piercing mill stand, installation characterized in that the drive as well as the position of the rolls (5 ) and possibly that 17. the guides of the piercing mill stand (6) can after each passage be adjusted at will on the drilling or on the drawing and respectively on the other direction of passage of the rolling product (15) , while in the vicinity of the supply chute ingots (3),

  there is provided a device (10) for evacuating the drawn tube blank (15b).

  6.- Installation according to claim 5, characterized in that the acute positioning angles 10 (A), delimited by the longitudinal axis of the rolling product and respectively an axis of rotation of cylinders, cylinders (5) during the piercing and stretching have a top that is placed on the entrance side, equipped with the

  ingot delivery chute (3), piercing roll stand (6).

  7.- Installation according to claim 6, characterized in that the positioning angle (il) is dimensioned between one and about 200, the numbers

  highest degrees being implemented during drilling.

  8.- Installation according to claim 6, or 7, characterized in that the drive motors (14) for the cylinders (5) are arranged on the side of the bearing

  stopper (9) for the mandrel rod.

  9.- Insta llation according to any of the

  Claims 5 to 8, characterized in that as a device for evacuating the drawn tube blank (15b),

  a rotatable guide tube (10), coaxial with the axis of passage of the rolling product, is interposed following the delivery channel ingots (3) on the opposite side;

at the piercing mill stand (6).

  10. Installation according to claim 9, characterized in that at the beginning of the stretching, the speed-controlled mandrel rod (7) is introduced through the rolling caliber and penetrates into the zone 18_. the inlet of the guide tube (10), where it is held by means of the thrust bearing (9) at least up to the inlet

  the tube blank (15b) in the guide tube (10).

  11.- Installation according to any kills

  Claims 5 to 10, characterized in that it is

  provided as a pushing device for the hollow blocks (15a) at the beginning of the drawing, a rod shank (18) with an external diameter greater than that of the hollow blocks (15a), this shank being mounted in the thrust bearing ( 9) and 10 driving the mandrel rod (7) with which it is

coaxially coupled.

  12.- Installation according to any one of claims 5 to 11, characterized in that the part

  (5d) cylinders ensuring the flaring during drilling, 15 is provided to ensure the smoothing of the rolling product

(15) during stretching.

  13.- Installation according to any one of claims 5 to 12, characterized in that the part

  (5b) cylinders providing the reduction during drilling 20 is provided to ensure the rounding of the blank of

  tube (15h) during stretching and vice versa.

  14.- Installation according to any one of claims 5 to 13, characterized in that the meaning

  passage of the rolling product (15) is capable of being modified by changing the advance angle of the rolls (5).

  15.- Installation according to any one of claims 5 to 14, characterized in that the speed of passage of the rolling product is lower 30 during drilling than during stretching.

  16.- Installation according to any one of claims 5 to 15, characterized in that before

  calibrating rolling mill or rolling mill

  In a reducer (12), a trimming device (13) is provided for franking the ends of the tube blank.