Cooling device for seamless steel pipes

Abstract

Cooling device (1) for cooling a seamless, rolled tube (R) made of a metal, preferably steel, which has a nozzle arrangement (10) with one or more nozzles (14) which are arranged to apply a cooling medium (K), preferably water or a water mixture, to the outer circumferential surface of the tube (R) while the tube (R) is transported along a conveying direction (F) through a cooling section of the cooling device (1), wherein the nozzle arrangement (10) has an access (Z) through which the tube (R) can be removed from the cooling section in a radial direction of the tube (R), preferably upwards.

Description

Technical field

[0001] The invention relates to a cooling device for cooling a seamless, rolled pipe, preferably a steel pipe, with a nozzle arrangement for applying a cooling medium to the outer circumferential surface of the pipe. Background of the invention

[0002] The production of seamless steel tubes utilizes a stretch-reducing mill or a sizing mill, which comprises several rolling stands arranged in series along the tube's conveying direction. The raw tubes, emerging from a pre-mill, are fed into the sizing or stretch-reducing mill while still hot from the rolling process. Operating temperatures for steel tubes typically range between 900°C and 1,000°C. If the tube's temperature after the pre-mill is too low for rolling, it is reheated in an intermediate furnace.

[0003] Upon exiting the rolling mill, the material temperature is still above the austenitizing point (Ar3 transformation point), typically between 820 and 840°C, depending on the material grade. The pipes are generally cooled in air by natural convection. This results in a normally rolled microstructure, meaning the pipe is moderately fine-grained and largely free of deformation textures that could negatively affect its mechanical properties.

[0004] For higher-grade pipes, such as those used in oil and gas production or structural applications, improved mechanical properties are required, particularly higher strength combined with high toughness and weldability. To improve these mechanical properties, it is known to temper the rolled and cooled pipes in special heat treatment lines. In a first tempering step, the pipes are reheated to the austenitizing temperature, then rapidly cooled in quenching units, forming high-strength transformation phases such as martensite, and finally reheated to eliminate internal residual stresses.

[0005] This additional heat treatment is process-complex and energy-intensive. For this reason, methods have been developed that utilize the residual heat from the rolling process for heat treatment. To this end, the tube is cooled very rapidly after dimension or stretch reduction rolling, achieving cooling rates significantly higher than those of a standard cooling bed. The required cooling rates are achieved by special cooling sections not typically found in seamless tube rolling mills. These sections accelerate the cooling of the tube immediately after it exits the mill by externally applying a cooling medium, such as water or a water / air mixture.

[0006] EP 2 682 485 B1 describes a method and apparatus for the production of seamless steel tubes with a continuous cooling section downstream of the last rolling stand, which has a plurality of distributor rings arranged concentrically around the rolled material. The distributor rings have three or more nozzles for spraying the cooling medium onto the tube to be cooled.

[0007] According to this state of the art, the distributor rings enclose the pipe to be cooled concentrically around its central axis. A large number of such distributor rings are required to cool the pipe sufficiently quickly during transport from the rolling mill. A disadvantage is that in the event of a malfunction, where the pipe remains on the exit side of the rolling mill, it is not easily possible to lift the pipe out of the transport section, as it is enclosed by the distributor rings. Instead, the pipe must be cut into small pieces, which then have to be manually removed from the cooling section.

[0008] According to another technical solution, known from WO 2016 / 035 103 A1, the pipe to be cooled is lifted into a cooling device from below. In this case, the pipe must be rotated around its own axis during cooling to achieve uniform cooling. However, in a continuous cooling section immediately downstream of a rolling mill, it is not possible to rotate the pipe, as its rear end is still connected to the rolling mill at the beginning of the exit process, i.e., at the start of cooling. Furthermore, the pipe lengths downstream of the rolling mill are usually significantly greater than in the heat treatment lines, since in the latter the pipes are already cut to finished lengths of, for example, 8 to 14 m, whereas the pipe strands at the end of the rolling mill are still undivided and up to 100 m long. Such long cooling sections are technically complex and hardly economical to operate. Description of the invention

[0009] One object of the invention is to improve the continuous cooling of seamless, rolled metal tubes, preferably steel, and in particular their operational reliability.

[0010] The problem is solved by a cooling device having the features of claim 1 and a device having the features of claim 15. Advantageous further developments follow from the dependent claims, the following description of the invention and the description of preferred embodiments.

[0011] The cooling device according to the invention serves to cool a seamless, rolled tube. The tube is a metal tube, preferably a steel tube. However, all alloys are included whose mechanical properties, such as strength, tensile strength, toughness, weldability, etc., can be improved by heat treatment. In particular, the tube is made of a high-quality alloy suitable for use in oil and gas production or for structural pipes.

[0012] The cooling device comprises a nozzle arrangement with one or more nozzles configured to apply a cooling medium, preferably water or a water mixture, to the outer circumferential surface of the pipe as it is conveyed along a conveying direction through a cooling section of the device. The term "water mixture" refers to a water-based cooling medium containing one or more additives. These additives may include dissolved solids, liquids, or gases. For example, the cooling medium could be a water / air mixture. The term "cooling section" refers to the portion of the cooling device along the conveying direction where the pipe is exposed to the cooling medium. The cooling device provides continuous cooling, as the pipe is cooled during conveying or transport through the cooling section.

[0013] According to the invention, the nozzle assembly has an access point through which the pipe can be removed from the cooling section in the radial direction of the pipe, i.e., perpendicular to the longitudinal extent of the pipe. In other words, the nozzle assembly does not completely enclose the pipe circumferentially, but is open or can be opened on one side. The access point is dimensioned such that the pipe can be removed laterally or radially from the cooling section. Preferably, the access point is positioned so that the pipe can be removed upwards (in the direction of gravity). Furthermore, the access point preferably extends in a straight line parallel to the pipe axis to simplify any removal of the pipe from the cooling section. It should be noted that several access points can also be provided.

[0014] The nozzle arrangement therefore does not include any closed-ring structures. Instead, at least one access point is provided, allowing the pipe to be removed radially from the cooling section in the event of a malfunction, such as a breakdown. The working space in the area of ​​the access point is not obstructed by lines, pipes, or the like. This creates a cooling section that, on the one hand, can be short enough to accommodate intact pipe sections of, for example, up to 100 m in length, and, on the other hand, allows the pipes to be removed laterally without having to cut them into smaller sections within the cooling device beforehand. Furthermore, this access facilitates any maintenance and cleaning work on the cooling device.

[0015] The cooling device is particularly advantageous for the rapid cooling of the tube immediately downstream of a rolling mill, such as a stretch-reducing mill or a sizing mill. The term "immediately downstream" here means that the tube enters the cooling section of the cooling device while its rear end is still integrated into the rolling mill. It should be noted that the terms "upstream" and "downstream" are relative to the conveying direction of the tube.

[0016] To ensure uniform cooling along the pipe circumference despite the absence of concentric distributor rings, the nozzles can be designed, arranged, and aligned so that the amount of coolant sprayed is essentially constant around the pipe circumference. In other words, the coolant flow rate per nozzle and the spray direction can be adjusted to achieve, or at least approximate, symmetrical and concentric cooling.

[0017] Preferably, the nozzle arrangement comprises one or more nozzle arms, each with at least one distribution pipe and one or more nozzle lances connected to and extending from it, each with one or more nozzles. By providing nozzle arms, the supply of cooling medium to the nozzles can be ensured in a structurally simple manner, without the supply lines having to completely encircle the pipe. The nozzle lances can be of different lengths to spray the cooling medium as evenly as possible over the entire circumference of the pipe. In the case of straight distribution pipes, the nozzle lances can be longer at the edges than in the center of the respective distribution pipe, so that the nozzles are located at least approximately on an imaginary partial ring.

[0018] Preferably, the cooling device further comprises a fluid system configured to supply the distribution pipes with the cooling medium, whereby several distribution pipes can be grouped into a single fluid unit, which is operated by a common pump and / or switched by a common valve system. Such a modular grouping of the fluid supply simplifies the design, and at the same time allows the nozzles to be operated section by section with different pressures, flow rates, etc., thereby optimizing the cooling of the pipe.

[0019] Preferably, the distribution pipes are designed to convey the cooling medium in the cross-sectional plane of the pipe and / or along the conveying direction, thereby creating a structurally simple access that extends in a straight line parallel to the pipe axis.

[0020] Preferably, the cooling section is shorter than the pipe; for example, it is approximately 8 to 16 m long. In this way, a compact cooling device is created, making it possible to heat-treat the pipes with reasonable construction effort.

[0021] Preferably, the position and / or orientation and / or volume flow rate of one or more nozzles of the nozzle arrangement is adjustable, allowing the cooling effect to be flexibly adapted, for example depending on product and / or process parameters.

[0022] Preferably, the nozzles of the nozzle assembly are configured to form multiple spray planes, which can be adjusted or moved along the conveying direction. Each spray plane can, for example, have two nozzle arms, each with several nozzle lances. By appropriately positioning the spray planes, the cooling effect can be flexibly adjusted, for example, depending on product and / or process parameters.

[0023] Preferably, the cooling device is configured to cool the tube to a final temperature below the Ar3 transformation point, thereby forming high-strength transformation phases such as martensite. Preferably, the tube is cooled to approximately 450°C to 600°C for this purpose. The initial temperature, i.e., the temperature at which the tube leaves the rolling mill, is, for example, 820°C to 840°C.

[0024] Preferably, the cooling device is configured to perform section-by-section or quasi-continuous control of the pressure and / or flow rates of the cooling medium, preferably depending on the product and / or based on measured values, empirical data, and / or a process model. The controllability here refers to sections along the cooling path, allowing the heat transfer coefficients to be flexibly adjusted in the conveying direction. The controllable sections can each comprise one or more spray levels, nozzle arms, etc.; however, they can also be refined down to the structural level of individual nozzles. This is what is meant by the term "quasi-continuous."

[0025] Preferably, the cooling section is divided such that in a first section the nozzle arrangement is configured for high-pressure spraying, preferably at pressures greater than 10 bar, and in a subsequent section in the conveying direction for lower pressures. In this way, heat transfer coefficients of, for example, more than 10,000 W / (m²) are achieved in the high-pressure section. 2 K) achievable, thereby enabling a sudden cooling of the pipe.

[0026] Preferably, the cooling device is configured for discontinuous operation such that one or more nozzles can be switched on when the pipe enters the cooling section (i.e., when the front end of the pipe passes through) and switched off when the pipe exits the cooling section (i.e., when the rear end of the pipe passes through), with one or more sensors preferably arranged within or behind the cooling section to detect the pipe ends. This prevents cooling medium from entering the pipe.

[0027] Preferably, the cooling device further comprises an enclosure that completely or partially surrounds the nozzle assembly and / or one or more compressed air wipers. An enclosure prevents contamination of the surroundings with the cooling medium, in particular reducing the amount of spray water and water vapor in the environment. Compressed air wipers can be used for a similar purpose, to prevent the cooling medium from entering particularly vulnerable areas, such as radiometric wall thickness gauges or other measuring points upstream and / or downstream of the cooling section.

[0028] Preferably, the conveying direction of the pipe along the cooling section is inclined relative to the horizontal, i.e., it falls or rises, which can shorten the installation space at the transition from the rolling mill to any cooling bed.

[0029] The aforementioned problem is further solved by a device comprising a rolling mill, preferably a stretch-reducing rolling mill or a sizing rolling mill, and a cooling device as described above. The cooling device is located downstream of the rolling mill in the conveying direction and is designed to cool the tube rolled by the rolling mill.

[0030] The features, technical effects, advantages and embodiments described in relation to the cooling device apply analogously to this device.

[0031] In particular, the cooling device is located directly behind the rolling mill, whereby the residual heat from the rolling process is used synergistically for the heat treatment of the tube.

[0032] Preferably, the rolling mill has one or more cooling elements designed to reduce the temperature of the tube in the mill below the Ar3 transformation point, preferably by approximately 30°C below the Ar3 transformation point. This enhances the cooling effect. According to this embodiment, the operating or rolling temperature is thus reduced within the mill itself, allowing for a lower final rolling temperature than is normally used.

[0033] Further advantages and features of the present invention will become apparent from the following description of preferred embodiments. The features described therein can be implemented individually or in combination with one or more of the features set forth above, provided that the features do not contradict each other. The following description of the preferred embodiments is given with reference to the accompanying drawings. Brief description of the characters The Fig. Figure 1 is a schematic cross-sectional view of the nozzle arrangement of a flow-through cooling section with an attached fluid unit according to one embodiment; The Fig. 2 shows the nozzle arrangement of the Fig. 1 in a top view; The Fig. Figure 3 is a schematic cross-sectional view of the nozzle arrangement of a flow-through cooling section according to a further embodiment; The Fig. Figure 4 shows the nozzle arrangement according to the Fig. 3 with attached fluid unit in a top view. Detailed description of preferred embodiments

[0034] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the different figures are designated with identical reference numerals, and repeated descriptions of these elements are sometimes omitted to avoid redundancy.

[0035] The Fig. Figure 1 is a schematic cross-sectional view of the nozzle arrangement 10 of a flow-through cooling section with an attached fluid unit 20 according to one embodiment. Fig. Figure 2 shows the nozzle arrangement 10 in a top view.

[0036] The nozzle arrangement 10 is part of a cooling device 1, which is arranged as a continuous cooling section preferably directly downstream of a rolling mill for rolling seamless tubes R. The term "directly downstream" here means that the tube R enters the continuous cooling section while at the rear end, in the conveying direction F (see figure 1), it is located at the rear end. Fig. 2) of the pipe R, still integrated in the rolling mill.

[0037] The pipe R is made of a metal, preferably steel, in particular including high-quality alloys suitable for use in oil and gas production or for structural pipes.

[0038] The aforementioned rolling mill, not shown in the figures, is preferably a stretch-reducing mill or sizing mill comprising several rolling stands arranged one behind the other in the conveying direction F of the tube R. The parent tubes coming from a pre-unit are fed into the rolling mill in a mill-hot state. The operating temperatures are, for example, in the range between 900°C and 1,000°C. Upon exiting the rolling mill, the tube R preferably has a temperature of over 820°C to 840°C.

[0039] The nozzle arrangement 10 has one or more nozzle arms 11, each of which has at least one distribution pipe 12 and one or more nozzle lances 13 connected to and extending from it, each with one or more nozzles 14. The distribution pipes 12 are supplied via a fluid system with a cooling medium K, preferably water or a water mixture, which then flows via the nozzle lances 13 to the nozzles 14 and is discharged or sprayed by them onto the pipe R.

[0040] The nozzle arms 11 with their distribution pipes 12 and nozzle lances 13 can be arranged in planes, which are referred to herein as "spray planes" S. In the present embodiment, each spray plane S has, by way of example, two nozzle arms 11, each with a distribution pipe 12 and five nozzle lances 13 connected thereto. However, there is no such limitation. Rather, the number and arrangement of the nozzle arms 11, nozzle lances 13, and nozzles 14 can be freely selected, as long as uniform cooling of the pipe R is ensured and the nozzle arrangement 10, as described below, does not comprise any closed-ring structures.

[0041] In the excerpt of Fig. Figure 2 shows only two spray planes S. However, the number of spray planes S arranged along the conveying path of the pipe S is normally greater in order to achieve a sufficient cooling effect. The cooling section, i.e., the section of the conveying path in which the pipe R is exposed to the cooling medium K, can be relatively short, for example, 8 to 16 m, depending on the number, position, and orientation of the nozzles 14, the flow rate of the cooling medium K, etc.

[0042] The nozzle arrangement 10 can be configured such that the spray planes S, or a portion thereof, are adjustable along the conveying direction F. For this purpose, the nozzle arms 11, or a portion thereof, can be slidably mounted. Alternatively or additionally, the nozzle lances 13, or a portion thereof, can be pivotably mounted, for example, by allowing the corresponding nozzle arms 11 to rotate about their own axes. Furthermore, it is not absolutely necessary for the nozzle arrangement 10 to form several well-defined spray planes. For example, the nozzle lances 13 with their nozzles 14 can be positioned and / or aligned such that the pipe R, viewed in the conveying direction F, is supplied with the cooling medium K in a substantially uniform manner.

[0043] Several distribution pipes 12 can be combined to form a fluid unit 20, which is operated by a common pump 21 and / or switched by a common valve system.

[0044] According to the exemplary embodiment of the Fig. 1 and Fig. 2. The distribution pipes 12 convey the cooling medium K in the cross-sectional plane of the pipe R. Alternatively, the cooling medium K can also be conveyed along the longitudinal axis of the pipe (= conveying direction F), as in the embodiment shown in the Fig. 3 and Fig. Figure 4 is shown. Of course, the distribution pipes 12 can also be arranged in other ways, as long as the access Z shown below is ensured.

[0045] It has already been pointed out that the nozzle assembly 10 does not comprise any closed-ring structures. Rather, the nozzle arms 11 are open at least on one side to allow the pipe R to be removed from the cooling section in the event of a malfunction (breakdown) in a radial direction, preferably upwards. In other words, the nozzle assembly 10 leaves an unobstructed gap or access Z along the conveying direction F through which the pipe R can be removed if necessary. The working space in the area of ​​access Z is not obstructed by lines, pipes, or the like. The dimension of access Z is larger than the diameter of the pipe R to ensure unobstructed removal of the pipe R from the cooling section.

[0046] This creates a cooling section that is short enough to process undivided pipe sections of, for example, up to 100 m in length, and from which, for example, the pipes R can be easily removed in the event of a malfunction, especially without having to cut them beforehand at the spray levels S.

[0047] To ensure uniform cooling along the pipe circumference despite the absence of concentric distributor rings, the nozzles 14 can be designed, arranged, and aligned such that the amount of sprayed cooling medium K is essentially constant along the pipe circumference. In other words, the flow rate of the cooling medium K per nozzle 14 and the spray direction can be adjusted to achieve, or at least approximate, symmetrical and concentric cooling. In the case of straight distributor pipes 12, as in the Fig.As shown in Figure 1, for this purpose the nozzle lances 13 can be longer at the outer sections than in the center of the corresponding distributor pipe 12, whereby the nozzles 14 are located at least approximately on an imaginary partial ring.

[0048] The cooling device 1 described herein is suitable for cooling the tubes R to final temperatures of approximately 450°C to 600°C, thereby achieving a particularly fine-grained structure. Following cooling by the cooling device 1, the tube R can be further cooled to room temperature by air convection.

[0049] In conjunction with an upstream rolling section, the parent tube is preferably first cooled to temperatures below the Ar1 transformation point and then reheated to rolling temperature. The tube R is then rolled in the rolling mill and transferred or transported to the cooling device 1 for subsequent rapid cooling.

[0050] According to an advantageous embodiment, the cooling section is divided into several sections, wherein in a first section the nozzle arrangement 10 is configured for high-pressure spraying, for example at pressures of more than 10 bar, and in a subsequent section in the conveying direction F for lower pressures. In this way, heat transfer coefficients of, for example, more than 10,000 W / (m²) are achieved in the high-pressure range. 2 K) achievable.

[0051] Alternatively or additionally, a section-by-section or quasi-continuous control of the pressure and / or flow rates of the cooling medium K, viewed in the conveying direction F, can be implemented depending on the product and / or based on measured values, empirical values ​​and / or a process model.

[0052] The cooling device 1 can be configured for discontinuous operation by switching on nozzle arms 11, for example, as fluid passes through the front end of the pipe and switching them off as fluid passes through the rear end, thus preventing cooling medium K from entering the pipe R. For this purpose, one or more sensors designed to detect the pipe ends can be arranged inside or behind the cooling section.

[0053] Preferably, the cooling section is located completely or partially within an enclosure to prevent contamination of the surroundings with cooling medium K, and in particular to reduce the impact of spray water and water vapor on the environment. Compressed air wipers can be used for a similar purpose to prevent the cooling medium K from entering particularly vulnerable equipment, such as radiometric wall thickness gauges or other measuring points upstream and / or downstream of the cooling section.

[0054] The conveying direction F of the pipe R along the cooling section can be inclined (upward or downward), which reduces the installation space required at the transition from the rolling mill to any cooling bed. Additionally or alternatively, the cooling section can be integrated into the transition area to the cooling bed. Since the spray chamber is not closed due to access Z, the pipe R can be lifted out of the cooling section and transferred to the cooling bed.

[0055] The cooling device 1 described herein is also suitable for combination with additional cooling elements in the rolling mill to enhance the cooling effect. According to one embodiment, the operating or rolling temperature is lowered in the rolling mill, so that a lower final rolling temperature than is normally used is applied. In this way, the pipe R can be subcooled in the rolling mill to a temperature of approximately 30°C below the Ar3 transformation point.

[0056] Where applicable, all individual features set out in the exemplary embodiments can be combined and / or exchanged without leaving the scope of the invention. Reference symbol list 1 cooling device 10 nozzle arrangement 11 Nozzle arm 12 distribution pipe 13 Nozzle lance 14 nozzle 20 fluid units 21 Pump R pipe F Conveyor direction K Cooling medium S spray plane Z Access

Claims

Cooling device (1) for cooling a seamless, rolled tube (R) made of a metal, preferably steel, which has a nozzle arrangement (10) with one or more nozzles (14) which are arranged to apply a cooling medium (K), preferably water or a water mixture, to the outer circumferential surface of the tube (R) while the tube (R) is transported along a conveying direction (F) through a cooling section of the cooling device (1), wherein the nozzle arrangement (10) has an access (Z) through which the tube (R) can be removed from the cooling section in a radial direction of the tube (R), preferably upwards. Cooling device (1) according to claim 1, characterized in that the nozzle arrangement (10) has one or more nozzle arms (11), each having at least one distributor pipe (12) and one or more nozzle lances (13) connected thereto and extending therefrom, each with one or more nozzles (14). Cooling device (1) according to claim 2, characterized in that it further comprises a fluid system which is arranged to supply the distribution pipes (12) with the cooling medium (K), wherein preferably several distribution pipes (12) are grouped together to form a fluid unit (20) which is operated by a common pump (21) and / or switched by a common valve system. Cooling device (1) according to claim 2 or 3, characterized in that the distribution pipes (12) are arranged to convey the cooling medium (K) in the cross-sectional plane of the pipe (R) and / or along the conveying direction (F). Cooling device (1) according to one of the preceding claims, characterized in that the cooling section is shorter than the pipe (R), preferably 8 to 16 m long. Cooling device (1) according to one of the preceding claims, characterized in that the position and / or orientation and / or the volume flow rate of one or more nozzles (14) of the nozzle arrangement (10) is adjustable. Cooling device (1) according to one of the preceding claims, characterized in that the nozzles (14) of the nozzle arrangement (10) are arranged such that several spray planes (S) are formed, which are preferably adjustable along the conveying direction (F). Cooling device (1) according to one of the preceding claims, characterized in that it is configured to cool the tube (R) to a final temperature below the Ar3 conversion point, preferably to about 450°C to 600°C. Cooling device (1) according to one of the preceding claims, characterized in that it is configured to perform a section-wise or quasi-continuous control of pressure and / or flow rates of the cooling medium (K), preferably depending on the product and / or based on measured values, empirical values ​​and / or a process model. Cooling device (1) according to one of the preceding claims, characterized in that the cooling section is divided into several sections, wherein in a first section the nozzle arrangement (10) is set up for high-pressure spraying, preferably with pressures of more than 10 bar, and in a subsequent section in the conveying direction (F) for lower pressures. Cooling device (1) according to one of the preceding claims, characterized in that it is configured for discontinuous operation such that one or more nozzles (14) can be switched on with the inlet of the pipe (R) into the cooling section and switched off with the outlet of the pipe (R) from the cooling section, wherein preferably one or more sensors, which are configured to detect the pipe ends, are arranged inside or behind the cooling section. Cooling device (1) according to one of the preceding claims, characterized in that it further comprises a housing which completely or partially surrounds the nozzle arrangement (10) and / or has one or more compressed air wipers. Cooling device (1) according to one of the preceding claims, characterized in that the conveying direction (F) of the pipe (R) along the cooling section is inclined relative to the horizontal. Cooling device (1) according to one of the preceding claims, characterized in that it is arranged directly behind a rolling mill for rolling the tube (R), so that the tube (R) enters the cooling section while it is still connected in the rolling mill at the rear end. Device comprising a rolling mill, preferably a stretch-reducing rolling mill or a sizing rolling mill, and a cooling device (1) according to one of the preceding claims, which is located behind the rolling mill in the conveying direction (F) and is designed to cool the tube (R) rolled by the rolling mill. Device according to claim 15, characterized in that the rolling mill has one or more cooling elements which are arranged to reduce the temperature of the tube (R) in the rolling mill below the Ar3 conversion point, preferably by about 30° below the Ar3 conversion point.

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