JP2017185545A - Method and system for production of seamless hot-rolled tube as well as rolled centrifugally cast tube and use of hollow block produced by means of centrifugal casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To elongate sensitive hollow blocks or tubes in a hot-forming elongator while maintaining, if possible, the internal structure that is present or that forms immediately after casting, thereby making it possible that, in the case of suitable method management, even thin-walled tubes or tubes rolled from centrifugally cast hollow blocks are made available to a sufficiently operationally reliable extent, with the result that, for the first time, it is possible for rolled centrifugally cast composite material tubes to be made available and for composite material hollow blocks produced using centrifugal casting to be utilized for the production of a seamless tube.SOLUTION: Provided is a method of producing a seamless hot-rolled tube (70), comprising: elongating a cast hollow block in a hot-forming elongator (20) with an elongation of 10 or less, with one of the following included: (i) circumventing a cross-roll piercing step or interposing a cross-roll piercing step at an elongation below 1.5 and (ii) utilizing at least part of the casting heat.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a seamless hot rolled tube and a system for producing a seamless hot rolled tube comprising a hollow block casting unit and a stretcher following the hollow block casting unit. Furthermore, the present invention relates to the use of a rolled centrifugal cast tube and a hollow block produced by centrifugal casting.

  A method and system for producing a seamless tube is presented in the overview in US Pat. No. 6,057,049, for example, first a hollow block is obtained using an extrusion process, and then the hollow block is a three-roll cross roll. Via a piercer and other cross-roll piercers, it is passed through a stretcher (such as a pilger mill, plug mill, push bench, or continuous mill) and subsequently or also after-treated by a reeler. Via a reheating furnace, it passes through a calibration unit (such as a becking mill, sizing mill, or stretch reduction system). In this regard, the workpiece to be treated can be hot-rolled or cold-rolled in each case.

  From Patent Document 2 or Patent Document 3 having the same priority, a hollow block is obtained using an extrusion method, and the hollow block is pre-stretched by a hot pilger rolling mill, and finally rolled by a stretcher, that is, a continuous rolling mill. It is known to do.

  Also, for example, V.I. M.M. Non-Patent Document 1 by PARSIN et al. Describes that seamless tubes can be produced by hollow blocks obtained by centrifugal casting or extrusion, these blocks being stretched after removal of the scale, then rolled again, Here again, the publication first passes through a cross-roll drilling machine called a "piercing machine".

  In this context, it has been shown that these processes cannot be applied to particularly delicate hollow blocks or tubes, for example, hollow blocks manufactured using relatively thin wall tubes or centrifugal casting. This is because, as already confirmed by, for example, PARSHIN et al., Many surface defects occur in the final rolled tube. This is especially true for rolled centrifugal cast composite tubes that cannot be manufactured reliably. Here, patent document 4 or patent document 5 suggests the manufacture of a known centrifugal cast tube by pilger rolling.

East German Patent No. 68215 British Patent No. 1298323 German Patent Application No. 1906961 German Patent Invention No. 502155 German Patent Invention No. 1602116

V. M.M. PARSHIN et al., “Production of Hollow Continuous-Cast Billet for Seamless Pipe”, ISSN 0967-0912, Steel in Translation, 2012, Vol. 42, no. 12, pp 825-829 (c) Allerton Press, Inc. , 2012

  It is an object of the present invention to provide a method and apparatus for manufacturing seamless hot rolled tubes that gently handle workpieces, and the use of corresponding tubes and corresponding hollow blocks.

  The object of the present invention is achieved by the use of a system and method for producing seamless hot rolled and rolled centrifugal cast tubes and the use of hollow blocks produced by centrifugal casting, having the features of the independent claims. Further advantageous embodiments independent of these, if applicable, can be found in the dependent claims and the following description.

  In this regard, the present invention provides that a delicate hollow block or tube, if possible, is stretched with a thermoforming stretcher while maintaining the internal structure that exists or occurs immediately after casting, so that process control is appropriate. In some cases, the starting point is the basic recognition that even thin-walled tubes or tubes rolled from centrifugally cast hollow blocks can be provided with sufficient functional reliability. Therefore, this also makes it possible for the first time to provide a rolled centrifugal cast composite tube and to utilize composite hollow blocks produced by centrifugal casting for the production of seamless centrifugal cast composite tubes.

  Therefore, a method for manufacturing a seamless hot-rolled tube characterized in that a cast hollow block is stretched in a thermoforming stretcher having an elongation of 10 or less without a cross-roll perforating step, and method management is also possible. It was also possible to confirm that each workpiece was handled gently while remaining appropriate.

  Obviously, cross roll drilling appears to intervene in the material structure of the cast hollow block so hard that the corresponding quality of the workpiece thus provided can no longer be guaranteed. Here, the actual stretching is performed by thermoforming with a stretcher. This is also true for the Pilger rolling process, as described, for example, in US Pat. For example, the pilger rolling process is performed upstream of the stretcher itself, and the pilger rolling process has an elongation greater than 11 to sufficiently pre-stretch the workpiece for the stretcher itself.

  Several experiments have shown that it is not necessary to eliminate the cross-roll drilling step unless the material structure intervention that occurs during cross-roll drilling is not too severe. In this regard, to produce a seamless hot-rolled tube characterized in that for a thermoforming stretcher having an elongation of 10 or less, a cast hollow block is stretched with an elongation of less than 1.5 with a cross roll punch. This method also handles each workpiece gently.

  Such intervention of the cross-roll drilling step appears to be particularly practical when an eccentricity of more than 4% can be seen in the cast hollow block, and this eccentricity can be correspondingly reduced by the cross-roll drilling step. . If necessary, such intervention can be performed with an eccentricity of more than 3.8%, in particular with an eccentricity of more than 3.6%.

  In this context, the term “elongation” represents the ratio of the entry and exit cross-sections of each workpiece as it passes through the corresponding rolling mill or during the corresponding rolling method step.

  A method for producing a seamless hot rolled tube, characterized in that the cast hollow block is stretched using at least part of the casting heat in a thermoforming stretcher having an elongation of 10 or less, Handle the workpiece gently enough. This means that if at least part of the casting heat is utilized, the time that elapses between the casting process for producing the cast hollow block and the thermoforming stretcher, the corresponding crystallization process on the workpiece or these This is likely due to the fact that the complex forming process on the workpieces of this type cannot be selected as long as possible. On the other hand, stretching with a thermoform stretcher appears to act gently or accurately on each workpiece.

  A system for producing a seamless hot-rolled tube comprising a hollow block casting unit and a stretcher disposed downstream of the hollow block casting unit, and a transport segment between the hollow block casting unit and the stretcher However, the system is also characterized in that it is short enough so that part of the casting heat is utilized for stretching in the stretcher, and the conveying segment between the hollow block casting unit and the stretcher is interrupted by a furnace, Appropriately gentle to the workpiece. In this regard, it should be understood that the corresponding benefits may be destroyed by the action of harmful methods such as, for example, an artificial cooling process, without the system losing its suitability to act on the workpiece reasonably.

  In this regard, each transport segment may also include the necessary intermediate steps, such as possible separation processes, or even the intervention of a cross-roll punch as already described above, if the elongation is sufficiently low. Please understand that you can.

  With regard to the elongation rate in possible cross-roll perforators, it is possible to achieve a gentler handling of the workpiece with a low elongation rate, in particular with an elongation of less than 1.4 or even with an elongation of less than 1.3. Emphasize what you can do.

  After stretching with the stretcher, the hollow block or the workpiece produced from the hollow block by stretching is preferably calibrated with a calibration unit. In this way, it is possible to guarantee the dimensional accuracy of the tube produced in particular as described above. Therefore, it is advantageous in the manufacturing system if the calibration unit follows the expander.

  In particular, a sizing mill or a stretch reduction mill can be used as a calibration unit. These are well known from the current state of the art.

  In general, as is already well known from the current state of the art, calibration is performed without internal tools at the calibration unit.

  It is therefore advantageous for the workpiece to pass through the stretcher only once, in particular not through further stretchers. Maintaining the casting heat at the workpiece until it passes through the second stretcher is very complex.

  As already explained above, the method and system described above gently handle the workpiece to be processed in each case. These methods and systems are particularly useful in the manufacture of seamless hot rolled metal tubes, especially when the seamless hot rolled metal tubes have a diameter of less than 7 inches and / or a wall thickness of clearly less than 100 mm. Is suitable. In particular, the method and system described above are suitable for rolling composite hollow blocks made by centrifugal casting, and thus seamless hot rolled tubes in the form of hot rolled centrifugal cast composite tubes. Is provided.

  Thus, unlike the view known from the state of the art, it makes available composite hollow blocks produced by hollow casting to produce seamless pipes on the one hand and rolled centrifugal cast composite pipes on the other hand. It is possible for the first time. Accordingly, a rolled centrifugal cast pipe characterized in that the rolled centrifugal cast pipe is a hot rolled centrifugal cast composite pipe, and a composite hollow block produced by centrifugal casting for producing a seamless hot rolled pipe The seamless hot rolled tube is then manufactured to form a hot rolled centrifugal cast composite tube.

  That is, the systems and methods described above have been shown to be particularly suitable for rolling multi-layer tubes, particularly multi-layer metal tubes. This is especially true for multilayer tubes or composite tubes in which the associated composite hollow block is provided using centrifugal casting. It is true that the production of composite pipes by centrifugal casting is known. However, it is also possible for the first time to roll such a tube, in particular this immediately after casting, without having to use a more complicated procedure, in particular between the rolling process and casting.

  Therefore, it is advantageous when composite hollow blocks manufactured by centrifugal casting are used for the manufacture of seamless hot rolled centrifugal cast composite tubes. Therefore, it is also advantageous when the rolled centrifugal cast tube is a rolled or hot rolled centrifugal cast composite tube. At this time, it can also be said that the corresponding centrifugal cast pipe has bimetal characteristics.

  If necessary, the hollow block can be heated with a stretcher prior to stretching. This is particularly advantageous if for some reason it does not apply to stretch with a thermoforming stretcher using at least a portion of the casting heat. In particular, however, this can also be done to support the thermoforming stretching process.

  On the other hand, in order to take advantage of at least part of the casting heat (which also naturally saves energy), the conveying segment between the hollow block casting unit and the stretcher is interrupted at best by a furnace and / or cutting unit. Please understand that. In this way, treatments that can lead to a time delay between the casting process and the hot forming and stretching process can ensure that only what is absolutely necessary is performed. Of course, the shortest possible transport segment, ie the transport segment through which the workpiece passes quickly, serves this purpose.

  If the cast hollow block is very long and cannot be stretched by a single length in the stretcher, a cutting unit may be required between the hollow block casting unit and the stretcher. Time loss can be minimized when the cutting unit is properly designed and operates very quickly, and in some cases when actually operating with a cast hollow block. It is also conceivable to operate two or more stretchers adjacent to each other to avoid time loss that can be caused by having to wait until a piece of the split hollow block has been stretched.

  Preferably, the transport segment between the hollow block casting unit and the stretcher is operated without interruption and has a locking system to and from the furnace, where in this connection the necessary cutting unit Is not considered an interruption as long as the delay caused by it is short enough. This makes it possible to supply the cast hollow block to the stretcher as quickly as possible. A workpiece that may be present, such as a cut portion of a hollow block, can then be moved from the transport segment by the locking system and temporarily contained in the furnace. At an appropriate time, the workpiece can be moved out of the furnace and returned to the transport segment, where the workpiece can then reach the thermoforming stretcher directly. This system structure allows for the maximum utilization of at least part of the casting heat if the corresponding method steps are appropriately coordinated with each other.

  In addition to passing the hollow block through the stretcher in the arrangement described above, the transport segment in the arrangement described above is consequently interrupted by the furnace. Thus, it is believed that every hollow block passes through the furnace, but some of them can pass through the furnace at very high speeds if necessary. In the latter situation, the transport segment to the stretcher that passes through the furnace can be omitted.

  Therefore, preferably the furnace acts as a shock absorber. Also, if the casting heat in each hollow block is not sufficient to guarantee the thermoforming stretching process, a furnace can be utilized for reheating if necessary. The furnace can also be used for temperature equilibration if necessary if process related issues arise in this regard. The furnace is particularly aimed for temperature stabilization when the hollow block exits the hollow block casting unit at a temperature that varies for some reason. This can cause the portion of the hollow block cast first to have a longer cooling time than the portion of the hollow block cast last. Furthermore, it can therefore be useful to temper the individual parts of the hollow block in a furnace used as a shock absorber after the hollow block has been separated into several parts by a cutting unit. This is done until a single hollow block portion can be further processed. This is because, under certain circumstances, this period can be different for each single hollow block portion.

  It is therefore advantageous if the hollow block is tempered in a furnace used as a shock absorber before stretching. In particular, this can occur when the casting heat is still in the hollow block and the hollow block is not cooled before the stretcher, and thus the crystallization process corresponds to the post-cast condition.

  In general, it should be understood that a furnace can also be utilized to heat the contained cast hollow block if for some reason at least a portion of the cast heat is not utilized.

  As the hollow block casting unit, any casting unit suitable for the production of hollow blocks can be used. In particular, for ergonomic reasons, hollow extrusion units are possible, some of which can be configured to actually operate continuously, in which case saw or other cutting Must have a unit. In particular, a centrifugal casting unit can also be used as the hollow block casting unit, where both the discontinuous centrifugal casting unit and the continuous centrifugal casting unit can be used either vertically or horizontally or in a composite form. it can. Thus, in the case of continuous casting units, it is advantageous if they are followed by a cutting unit. Here, it is clear that the cutting unit can be used in combination with other casting units.

  Thus, with respect to method management, it should be understood that the cast hollow block can be cast in the above-described orientation and continuously or discontinuously, particularly by extrusion or centrifugal casting. It should be understood that other casting methods can be used for corresponding advantages if desired.

  In principle, any unit that can be stretched by subjecting a cast hollow block to stretching is suitable as a stretcher. In particular, pilger mills or longitudinal mills such as push benches, plug mills or continuous mills can be used for this purpose. In general, the stretcher works with an internal tool to allow it to produce sufficient dimensional accuracy and a suitable stretch reduction process.

  Accordingly, the stretcher of the presented configuration is a rolling unit in which the inner diameter of each rolling tube is determined, or a rolling unit in which the inner surface of each rolling tube is finally subjected to a rolling force by an internal work tool.

  Particularly preferably, a longitudinal rolling mill is used as the stretcher. This is because in this case a particularly gentle rolling process takes place. In this connection, it is emphasized that the Pilger mill cannot be called a longitudinal mill by itself, since the Pilger process should actually be classified as a forging process.

  The use of a push bench as a longitudinal rolling mill has proved particularly favorable and advantageous with regard to its action on the respective hollow block. This is especially true when the push bench has rolls that operate in a molding manner, particularly when the rolls have a plurality of rolls that operate in a molding manner disposed on a plurality of frames, and when it is preferable to eliminate a fixed lock ring or the like. apply.

  Preferably, a stretcher, or in particular a longitudinal rolling mill, in particular a push bench, causes an elongation of 2 or more. In this way, the stretcher can take on the deformation performed by the cross roll drilling step or by the cross roll drilling step which has a relatively strong effect in part or possibly entirely. At this time, therefore, there is not necessarily a need for intervention for correction, especially in subsequent processing steps, such as a calibration unit.

  In order to act gently on the hollow block to be stretched, it is advantageous in each case that the stretcher, or in particular the cross-roll perforator, in particular the push bench, has an elongation of 10 or less.

  It should be understood that the features of the solutions described above and in the claims can also be combined where applicable, thus allowing their advantages to be implemented in combination.

  Advantageously, the stretcher stretches the hollow block with an elongation of 8 or less that is gentle on the workpiece, especially when the workpiece is a composite. Thus, in particular, the cast hollow block is advantageously stretched with a thermoforming stretcher having an elongation of 7 or less.

  Further advantages, objects, and properties of the present invention are illustrated using the following description of exemplary embodiments. These exemplary embodiments are also shown in particular in the accompanying drawings.

It is a figure which shows the various deformation | transformation form regarding the manufacturing system and method for manufacturing a seamless hot-rolled tube. FIG. 2 is a schematic cross-sectional view through a centrifugally cast composite material tube.

  First, the manufacturing system for manufacturing a seamless hot-rolled tube schematically shown in FIG. 1 includes a hollow block casting unit 10, and after the hollow block casting unit 10, stretchers are provided via conveying segments 41 and 42. 20 continues. The stretcher 20 is followed by a calibration unit 30 via the transport segment 43 so that the stretcher 20 and the calibration unit 30 can provide hot rolled tubes from the casting block.

  In this regard, the transport segments 41, 42 are configured to be short so that casting heat can be utilized during stretching. Obviously, there is no cross roll drilling machine between the hollow block casting unit 10 and the stretcher 20, but if necessary, a cross roll drilling machine having a slight elongation of, for example, 1.2 to 1.4. Can also be placed here.

  A furnace 50 is provided in the transport segments 41, 42 between the hollow block casting unit 10 and the stretcher 20. Preferably, the furnace 50 is not located directly on the transport segments 41, 42 and is provided with a locking system by which the cast hollow block is taken out of the transport segments 41, 42 and returned to the transport segments 41, 42 again. Can do. Thus, the workpiece can bypass the furnace 50 and reach the stretcher 20 directly, which allows direct use of casting heat and is also preferable in terms of energy usage. The workpiece may be tempered in the furnace 50 or maintained at temperature. In an alternative embodiment, the locking system can be omitted, so that every hollow block passes through the furnace 50 and some workpieces with the appropriate temperature extend through the furnace 50 very quickly if necessary. Pass to vessel 20.

  In particular, a rotary hearth furnace 51, a reflection furnace 52, or an induction furnace 53 can be used as the furnace 50.

  If deemed necessary, a reheating furnace 54 can be provided in the transport segment 43 between the stretcher 20 and the calibration unit 30.

  Similarly, a cutting unit (not shown) can be provided in the transport segment 43.

  In particular, the hollow block casting unit 10 can be a horizontal discontinuous centrifugal casting unit 11 or a vertical continuous casting unit 12. In general, the discontinuous centrifugal casting unit 11, like the other discontinuous casting units, does not require a cutting unit to cut the cast hollow block if the subsequent system stage is properly aligned with the casting unit.

  In the vertical continuous centrifugal casting unit 12, as schematically shown, a saw is provided, and the cut piece is cut and transferred to the transport segment 41. It is also conceivable that the continuous centrifugal casting unit is tilted so as to allow the discharge of the hollow block. Again, if necessary, a cutting unit can be provided.

  Furthermore, a hollow extrusion unit 13 or a vertical hollow extrusion unit 14 can also be used as the hollow block casting unit 10. In general, these hollow extrusion units are followed by a cutting unit 60 after the transport segment 44. In this exemplary embodiment, this unit is provided as a saw 61, but it will be appreciated that other cutting units capable of cutting the hollow block at a sufficient rate can also be used.

  It should be understood that a horizontal continuous centrifugal casting unit can be used as the hollow block casting unit 10 if necessary, and a cutting unit 60 can be placed after the transport segment 44 downstream of the horizontal continuous centrifugal casting unit. .

  In particular, a longitudinal rolling mill 21 such as a push bench 22, a plug rolling mill 24, or a continuous rolling mill 25 is used as the stretcher 20. Similarly, a hot pilger mill 23 can be used as the stretcher 20.

  As the calibration unit 30, a sizing mill 31 or a stretch reduction mill 32 is an option.

  The production system and the corresponding production method presented above are particularly suitable as the hollow block casting unit 10 associated with the centrifugal casting units 11, 12. Centrifugal casting makes it possible to produce a multilayer or bimetallic centrifugal cast hollow block, which can be hot rolled with the production system 40 and corresponding methods. In this way, the tube 70 can be provided as a centrifugal cast tube 71, which has an outer material layer 73 and an inner material layer 74 made of different materials and having different material properties. Due to the manufacturing process, and in particular by the hot rolling process in the stretcher 20, a mixed layer 75 is formed between the outer material layer 73 and the inner material layer 74. Thus, the hot rolling process in the stretcher 20 results in a hot rolled centrifugal cast composite tube 72, which has bimetallic properties if the method is properly managed.

  With respect to specific method management, the exemplary embodiment ensures that the stretcher operates at a stretch rate of 2-10.

DESCRIPTION OF SYMBOLS 10 Hollow block casting unit 11 Horizontal discontinuous centrifugal casting unit 12 Vertical continuous centrifugal casting unit 13 Horizontal extrusion unit 14 Horizontal hollow extrusion unit 20 Stretcher 21 Longitudinal rolling mill 22 Push bench 23 Hot pilger rolling mill 24 Plug rolling Machine 25 Continuous rolling mill 30 Calibration unit 31 Sizing mill 32 Stretch reduction rolling mill 40 Manufacturing system for manufacturing seamless hot-rolled tube 70 41 Conveying segment 42 Conveying segment 43 Conveying segment 44 Conveying segment 50 Furnace 51 Rotary hearth furnace 52 Reflective furnace 53 Induction furnace 54 Reheating furnace 60 Cutting unit 61 Saw 70 Pipe 71 Centrifugal casting pipe 72 Hot rolled centrifugal casting composite pipe 73 Outer material layer 74 Inner material layer 75 Mixed layer

Claims (14)

A method for producing a seamless hot rolled tube (70), comprising:
(I) without performing a cross roll drilling step at an elongation of less than 1.5, or via a cross roll drilling step, and / or (ii) utilizing at least part of the casting heat,
A method wherein the cast hollow block is stretched with a thermoforming stretcher (20) having an elongation of 10 or less.   The method according to claim 1, characterized in that the hollow block is heated before stretching in the stretcher (20) and / or tempered in a furnace (50) as a shock absorber.   3. A method according to claim 1 or 2, characterized in that, after stretching, the hollow block is calibrated with a calibration unit (30).   The cast hollow block is stretched with a thermoforming stretcher (20) at an elongation of 8 or less, in particular at an elongation of 7 or less. Manufacturing method.   A system (40) for producing a seamless hot-rolled tube (70) comprising a hollow block casting unit (10) and an expander (20) disposed downstream of the hollow block casting unit, The transport segments (41, 43, 44) between the hollow block casting unit (10) and the stretcher (20) can utilize part of the casting heat for stretching in the stretcher (20). The system (40), characterized in that it is sufficiently short so that the transport segment between the hollow block casting unit (10) and the stretcher (20) is interrupted by a furnace (50).   6. The transport segment (41, 43, 44) between the hollow block casting unit (10) and the stretcher (20) is interrupted by a cutting unit (60). Manufacturing system (40).   The transport segment (41, 43, 44) between the hollow block casting unit (10) and the stretcher (20) is operated without interruption and locked into and out of the furnace (50). 7. Manufacturing system (40) according to claim 5 or 6, characterized in that it has a system.   6. Manufacturing system (40) according to claim 5, characterized in that the furnace (50) serves as a shock absorber and / or is used for reheating or for the temperature equilibration.   The manufacturing system (40) according to any one of claims 5 to 8, characterized in that the hollow block casting unit (10) is a centrifugal casting unit (11, 12).   10. The stretcher (20) is followed by a calibration unit (30), preferably as a sizing mill (31) and / or a stretch reduction unit (32). The manufacturing system (40) described in 1.   11. Method or system (40) according to any one of the preceding claims, characterized in that the stretcher (20) is a longitudinal rolling mill (21), in particular a push bench (22). .   12. Manufacturing method or system (40) according to claim 11, characterized in that the longitudinal rolling mill (21), in particular the push bench (22), has an elongation of 2 or more and 8 or less.   A rolled centrifugal cast pipe (71), characterized in that the rolled centrifugal cast pipe (71) is a hot rolled centrifugal cast composite pipe (72).   Use of a composite hollow block produced by centrifugal casting to produce a seamless hot rolled centrifugal cast composite tube (72).