RU2786428C1 - Cooling device for seamless steel pipes - Google Patents

Abstract

FIELD: cooling devices.

SUBSTANCE: invention relates to cooling devices, which can be used in the manufacture of seamless metal pipes. A cooling device for cooling of a seamless rolled metal pipe contains a nozzle assembly with nozzles made with the possibility of supply of a cooling medium to an outer peripheral surface of the pipe during its transportation along a supply direction on a cooling section of the cooling device, wherein the nozzle assembly contains a passage, through which the pipe can be extracted from the cooling section in a radial direction of the pipe.

EFFECT: invention is aimed at an increase in operational reliability of seamless rolled pipes.

17 cl, 4 dwg

Description

Technical field

The invention relates to a cooling device for cooling a seamless rolled pipe, preferably a steel pipe, with a nozzle assembly for supplying a cooling medium to the outer peripheral surface of the pipe.

State of the art

In the manufacture of seamless steel pipes, a stretch-reducing or sizing rolling mill is used, containing a plurality of rolling stands located one behind the other in the pipe feed direction. Billet tubes coming from the previous unit are loaded in a hot-rolled state into a sizing or stretch-reducing rolling mill. In the case of steel pipes, the temperature of the pipe at the inlet, as a rule, lies in the range from 900°C to 1000°C. If the pipe after the previous unit has a temperature too low for rolling, then it is additionally heated in an intermediate furnace.

When exiting the rolling mill, the temperature of the material is still above the austenitization point (critical temperature Ar3), depending on the material grade, approximately above a temperature of 820 to 840°C. The pipes are cooled, as a rule, in air by means of natural convection. Thus, a normalized structure is produced, i.e. the pipe has a moderately fine-grained structure, typically substantially free of deformation textures that adversely affect mechanical properties.

High quality pipes, such as those for oil and gas production or structural pipes, require improved mechanical properties, in particular increased strength, combined with high toughness and weldability. It is known that in order to improve the mechanical properties, rolled and cooled pipes can be improved on special heat treatment lines. At the same time, in the first tempering step, the pipes are heated again to the austenitizing temperature, and then quickly cooled in quenching devices, resulting in the formation of high-strength transformation phases such as martensite, and finally heated again to eliminate internal self-stresses.

Such additional heat treatment is technologically complex and energy intensive. Therefore, methods have been developed in which the residual heat of the rolling process is also used for heat treatment. To this end, after sizing or stretch-reduction rolling, the tube is cooled very quickly, and cooling rates that are significantly increased compared to a normal rolling mill cooler must be achieved. The required cooling rates are achieved by means of special cooling sections, which are not part of the usual equipment of pipe mills for the production of seamless pipes. They rapidly cool the tube immediately after exiting the rolling mill by supplying it with a cooling medium such as water or a water-air mixture from outside.

Thus, EP 2682485 B1 describes a method and apparatus for the production of seamless steel pipes with a continuous cooling section located after the last rolling stand, containing a plurality of distribution rings arranged concentrically around the rolled material. The distribution rings have three or more nozzles for spraying the coolant onto the pipe to be cooled.

According to the prior art, the distribution rings surround the cooled pipe concentrically with respect to its central axis. In order to cool the pipe sufficiently rapidly during transport from the rolling mill, a plurality of such distribution rings must be provided. The disadvantage of this solution is that, in the event of a fault in which the tube remains lying on the outlet side of the rolling mill, it is not possible to easily remove the tube from the transport section, since it is surrounded by distribution rings. Instead, the pipe must be cut into small pieces of pipe, which are then manually removed from the cooling section.

According to another technical solution known from WO 2016/035103 A1, the cooled pipe is lifted into the cooling device from below. In this case, to achieve uniform cooling during cooling, the pipe must rotate around its own axis. However, in the case of a continuous cooling section, it is not possible to bring the tube into rotation directly behind the rolling mill, since at the beginning of the tapping process, i.e. at the beginning of cooling, it is still connected to the rolling mill at the rear end. In addition, pipe lengths behind the rolling mill are generally much longer than pipes in heat treatment lines, since pipes in heat treatment lines are already cut to finished product lengths of, for example, 8 to 14 m, while tube billets at the exit of the rolling mill are not yet separated and have a length of up to 100 m. Such long cooling sections are technically complex and hardly economical to operate.

Disclosure of the essence of the invention

The object of the invention is to improve the continuous cooling of seamless rolled pipes made of metal, preferably steel, in particular to increase their operational reliability.

This problem is solved by a cooling device with the features of paragraph 1 and a device with the features of paragraph 15 of the claims. Advantageous improved embodiments follow from the dependent claims, the following description of the invention and the description of preferred embodiments.

The cooling device according to the invention is intended for cooling a seamless rolled pipe. The pipe is a metal pipe, preferably a steel pipe. However, it covers all alloys whose mechanical properties, such as, for example, strength, tensile strength, toughness, weldability, etc., can be improved by heat treatment. In particular, the pipe is made of a high quality alloy suitable for oil and gas applications or structural pipes.

The cooling device comprises a nozzle assembly with one or more nozzles configured to supply a cooling medium, preferably water or an aqueous mixture, to the outer peripheral surface of the pipe, while the pipe is transported along the supply direction in the cooling section of the cooling device. The term "water mixture" means a water-based cooling medium containing one or more additives. Additives may contain dissolved solids, liquids or also gases. Thus, the cooling medium may be, for example, a water-air mixture. In this case, the term "cooling section" means that section of the cooling device along the direction of supply, in which the cooling medium is supplied to the pipe. The cooling device provides continuous cooling, since the pipe is cooled during supply or, respectively, transport in the cooling section.

According to the invention, the nozzle assembly comprises a passage through which the pipe can be withdrawn from the cooling section in the radial direction of the pipe, i.e. perpendicular to the longitudinal length of the pipe. In other words, in the circumferential direction, the nozzle assembly does not completely surround the pipe, on one side it is open or can be opened. In this case, said passage has such dimensions that the pipe can be removed from the cooling section in the lateral or, respectively, the radial direction. Preferably, the passage is located in such a way that the pipe can be withdrawn upwards (when viewed in the direction of gravity). In addition, in order to simplify the possible removal of the pipe from the cooling section, the passage preferably runs in a straight line, parallel to the axis of the pipe. It should be pointed out that a plurality of passageways may also be provided.

Accordingly, the nozzle assembly does not contain closed annular structures. Instead, at least one passage is provided by which, in the event of a malfunction, such as an accident, the pipe can be removed from the cooling section in the radial direction. The working space in the aisle area is not obstructed by lines, pipes, etc. In this way, a cooling section is created which, on the one hand, can be short enough to process not yet separated tubular blanks, for example, up to 100 m long, and from which, on the other hand, the pipes can be removed laterally without the need for prior separation. them in the cooling device to shorter pipe lengths. In addition, said passage facilitates possible maintenance and repair work in the cooling device.

The cooling device is particularly preferably configured to rapidly cool the tube directly downstream of the rolling mill, for example a stretch-reduction mill or a sizing mill. The term "directly behind" here means that the pipe enters the cooling section of the cooling device, while at the rear end it is still connected to the rolling mill. It should be pointed out that the terms "before" and "behind" should be considered in relation to the direction of pipe feed.

In order to provide uniform cooling along the pipe perimeter despite the omission of concentric distribution rings, the nozzles can be configured, positioned and oriented such that the amount of coolant sprayed along the pipe perimeter is substantially constant. In other words, the flow rate of the cooling medium per nozzle and the direction of the jet can be adjusted in such a way that symmetrical and concentric cooling is achieved or at least approximately achieved.

To this end, the nozzle assembly preferably comprises one or more nozzle mounting brackets, each of which contains at least one distribution tube and one or more nozzle tubes connected to the distribution tube and extending from the distribution tube, each of which contains one or more nozzles. By providing brackets for fastening the nozzles, the supply of the nozzles with the cooling medium can be ensured in a structurally simple manner, without the need to completely encircle the pipe with supply conduits in the circumferential direction. Tubes with nozzles can be of various lengths for uniform spraying of the cooling medium, if possible, around the entire perimeter of the pipe. In the case of straight distributor pipes, the nozzle tubes at the edge portions can be longer than at the center of the respective distributor pipe, with the result that the nozzles are at least approximately on one imaginary incomplete ring.

The cooling device preferably also includes a hydraulic system configured to supply the distribution pipes with a cooling medium, wherein the plurality of distribution pipes can be combined into a hydraulic unit served by a common pump and/or switched by a common valve system. Due to this integration of the fluid supply in a modular way, it can be simplified in terms of design, at the same time the nozzles in the sections can be operated with different pressures, volumetric flow rates, etc., thereby optimizing the cooling of the pipe.

Preferably, the distribution pipes are designed to supply the cooling medium in the plane of the pipe cross-section and/or along the direction of supply, whereby a passage can be created in a simple structural manner, running straight and parallel to the axis of the pipe.

Preferably, the cooling section has a shorter length than the pipe, said length being, for example, about 8 to 16 m. Thus, a compact cooling device is created, whereby improvement of the pipes by heat treatment can be carried out at reasonable construction costs.

Preferably, the position and/or orientation and/or volume flow of one or more nozzles of the nozzle assembly can be adjustable, whereby the cooling effect can be flexibly adapted, for example, depending on product and/or process parameters.

Preferably, the nozzles of the nozzle assembly are designed in such a way that a plurality of spray planes can be formed, which can be adjusted or respectively moved, for example along the feed direction. Thus, each spray plane may comprise, for example, two nozzle holders, each containing a plurality of nozzle tubes. By appropriately arranging the spray planes, the cooling effect can be flexibly adjusted, for example depending on product and/or process parameters.

Preferably, the cooling device is adapted to cool the pipe to a final temperature below the Ar3 critical temperature, in order thereby to form high-strength transformation phases such as martensite. To this end, the pipe is preferably cooled to a temperature of 450°C to 600°C. In this case, the outlet temperature, i.e. the temperature at which the pipe leaves, for example, the rolling mill is, for example, from 820°C to 840°C.

Preferably, the cooling device is configured to perform local control or quasi-continuous control of the pressure and/or flow of the cooling medium, preferably depending on the product and/or based on measurement data, experience data and/or a process model. In this case, the controllability refers to areas along the cooling section, whereby the heat transfer coefficients can be flexibly adjusted in the feed direction. Each of the adjustable sections may contain one or more spray planes, nozzle brackets, etc., however, it can also be upgraded down to the structural level of the individual nozzles. This is what is meant by the term "quasi-continuous".

The cooling section is preferably divided in such a way that in the first section the nozzle assembly is configured to spray at high pressure, preferably more than 10 bar, and in the next (in the feed direction) section at a lower pressure. Thus, in a high-pressure region, for example, heat transfer coefficients of more than 10,000 W/(m ² K) can be achieved, which makes it possible to achieve rapid cooling of the pipe.

Preferably, the cooling device is configured to operate intermittently such that one or more nozzles, respectively, when the pipe enters the cooling section, i. e. when passing the front end of the pipe, are made with the possibility of connection, and when the pipe exits the cooling section, i.e. at the passage of the rear end of the pipe, shutdown, and preferably one or more sensors are located in the cooling section or behind the cooling section, made with the possibility of recognizing the ends of the pipe. Thus, the coolant can be prevented from entering the pipe.

Preferably, the cooling device also includes a shroud completely or partially surrounding the nozzle assembly and/or one or more pneumatic scrapers. Due to the housing, pollution of the environment by the cooling medium is prevented, in particular, the pollution of the environment by sprayed water and water vapor can thus be reduced. Pneumatic scrapers can be used for a similar purpose in order to prevent the entry of coolant into devices that are particularly endangered, such as, for example, radiometric measurements of wall thickness or other parameters in front of the cooling section and/or behind the cooling section.

Preferably, the pipe feed direction along the cooling section is inclined with respect to the horizontal, i. e. it is lowered or raised, whereby the installation space at the transition from the rolling mill to the possible cooler can be shortened.

The above object is also achieved by an apparatus comprising a rolling mill, preferably a stretch-reduction mill or a sizing mill, and a cooling apparatus as described above. In the feed direction, the cooling device is behind the rolling mill and is configured to cool the pipe rolled by the rolling mill.

The features, technical effects, advantages and exemplary embodiments described with respect to a cooling device are similarly valid for said device.

In particular, the cooling device is located directly behind the rolling mill, which makes it possible to also use the residual heat of the rolling process to improve the pipe by means of heat treatment according to the principle of synergy.

Preferably, the rolling mill comprises one or more cooling elements configured to reduce the temperature of the pipe in the rolling mill below the Ar3 critical temperature, preferably about 30° below the Ar3 critical temperature. Thus, the cooling effect can be enhanced. Thus, according to this embodiment, the lowering of the inlet temperature or the rolling temperature takes place already in the rolling mill, so that a lower than usual final rolling temperature can be applied.

Additional advantages and features of the present invention will become apparent from the following description of the preferred embodiments. The features described therein can be implemented individually or in combination with one or more of the above features, if these features do not contradict each other. The following is a description of preferred embodiments with reference to the accompanying drawings.

Brief description of the drawings

Fig. 1 is a schematic sectional view of a nozzle assembly of a continuous cooling section with a hydraulic assembly connected to it, according to one embodiment.

Fig. 2 is a plan view of the nozzle assembly of FIG. one.

Fig. 3 is a schematic sectional view of a nozzle assembly of a continuous cooling section according to another embodiment.

Fig. 4 is a plan view of the nozzle assembly of FIG. 3 with a hydraulic unit connected to it.

Implementation of the invention

The preferred embodiments are described below with the aid of the drawings. Here, the same, similar or identically functioning elements are designated in the various drawings by identical reference symbols and, in order to avoid redundancy, the detailed description of these elements is partially omitted.

Fig. 1 is a schematic sectional view of a continuous cooling section nozzle assembly 10 with a hydraulic assembly 20 connected to it, according to one embodiment. In FIG. 2, the nozzle assembly 10 is shown in plan view.

The nozzle assembly 10 is part of the cooling device 1, which is preferably located as a continuous cooling section immediately after the seamless tube rolling mill R. Here, the term "directly" means that the tube R enters the continuous cooling section, while at the rear end (when viewed in the feed direction, cf. Fig. 2) it is still connected to the rolling mill.

The pipe R is made of metal, preferably steel, the metal being in particular high quality alloys suitable for oil and gas applications or structural pipes.

The aforementioned rolling mill, not shown in the drawings, is preferably a stretch-reducing rolling mill or a sizing mill having a plurality of rolling stands arranged one behind the other in the supply direction F of the tube R. to the rolling mill. The inlet temperature lies, for example, in the range from 900°C to 1000°C. When leaving the rolling mill, the pipe R preferably has a temperature of more than 820°C to 840°C.

Nozzle assembly 10 comprises one or more nozzle mounting brackets 11, each containing at least one distribution tube 12 and one or more nozzle tubes 13 connected to the distribution tube and extending from the distribution tube, each containing one or more nozzles 14. The distribution pipes 12 are supplied by a hydraulic system with a cooling medium K, preferably water or an aqueous mixture, which then flows through the pipes 13 with nozzles to the nozzles 14 and from them is supplied or sprayed, respectively, into the pipe R.

The nozzle mounting brackets 11 with their distribution tubes 12 and nozzle tubes 13 can be arranged in planes which are referred to herein as "spray planes" S. In this exemplary embodiment, each spray plane S comprises, for example, two nozzle mounting brackets 11, each of which contains a distribution pipe 12 and five tubes 13 connected to it with nozzles. However, there are no restrictions in this regard. Moreover, the number and arrangement of nozzle mounting brackets 11, nozzle tubes 13, and nozzles 14 can be freely selected, provided that uniform cooling of the pipe R is ensured, and the nozzle assembly 10, as explained below, does not contain closed annular structures.

In the section in Fig. 2 shows only two spray planes S. However, in order to provide a sufficient cooling effect, as a rule, the number of spray planes S located along the supply path of the pipe R is larger. Cooling area, i.e. the section of the supply path on which the coolant K is supplied to the pipe R, depending on the number, position and orientation of the nozzles 14, the flow rate of the coolant K, etc., can be relatively short and range, for example, from 8 to 16 m.

The nozzle assembly 10 may be configured such that the spray planes S or part of the spray planes can be adjusted by moving along the feed direction F. To this end, the brackets 11 for attaching the nozzles, or part of said brackets, can be moved. Alternatively or additionally, the nozzle tubes 13 or part of said tubes can be positioned rotatably by means that, for example, the respective nozzle holders 11 can be mounted rotatably around their own axis. In addition, it is not necessary for the nozzle assembly 10 to form a plurality of well-defined spray planes.

Thus, the tubes 13 with their nozzles 14, for example, can be positioned and/or oriented in such a way that, when viewed in the feed direction F, the coolant K is supplied to the tube R substantially uniformly.

A plurality of distribution pipes 12 may be combined into a hydraulic assembly 20 served by one common pump 21 and/or switched by a common valve system.

According to the embodiment of FIG. 1 and 2, the distribution pipes 12 supply the coolant K in the cross-sectional plane of the pipe R. Alternatively, the coolant K can also be supplied along the longitudinal axis of the pipe (ie the supply direction F), as shown in the exemplary embodiment of FIG. 3 and 4. Of course, the distribution pipes 12 can also be arranged in other ways, provided that the passage Z described below is provided.

It has already been pointed out above that the nozzle assembly 10 does not contain closed annular structures. Instead, the nozzle holders 11 are designed in such a way that they are open on at least one side, so that in the event of a malfunction (accident), the pipe R can be removed from the cooling section in the radial direction, preferably upwards. In other words, the nozzle assembly 10 along the feed direction F leaves an uncovered gap or passage Z, through which the pipe R can be withdrawn if necessary. To ensure unhindered removal of the pipe R from the cooling section, the size of the passage Z is greater than the diameter of the pipe R.

In this way, a cooling section is created, on the one hand, short enough to allow the processing of not yet separated tubular blanks, for example, up to 100 m long, and from which, on the other hand, the pipes R can be easily removed, for example, in the event of a malfunction , in particular without having to cut them beforehand in the spray planes S.

In order to ensure uniform cooling along the pipe perimeter, despite the omission of concentric distribution rings, the nozzles 14 can be configured, positioned and oriented such that the amount of coolant K sprayed along the pipe perimeter is substantially constant. In other words, the flow rate of the cooling medium K per nozzle 14 and the direction of the jet can be adjusted in such a way that symmetrical and concentric cooling is achieved or at least approximately achieved. In the case of straight distribution pipes 12, as shown in FIG. 1, for this purpose the tubes 13 with nozzles at the edge portions can be longer than at the center of the respective distribution tube 12, whereby the nozzles 14 are at least approximately on one imaginary incomplete ring.

The cooling device 1 described here cools the tubes R to a final temperature of approximately 450° C. to 600° C., whereby a particularly fine grain structure can be achieved. After being cooled by the cooling device 1, the pipe R can continue to be cooled to room temperature by air convection.

In combination with a rolling mill located in front, the billet tube is preferably first cooled to a temperature below the critical temperature Ar1 and then reheated to the rolling temperature. The pipe R is then rolled in the rolling mill and transferred or, respectively, transported to the cooling device 1 for subsequent rapid cooling.

According to a preferred embodiment, the cooling section is divided into a plurality of sections, with the nozzle assembly 10 being capable of spraying at high pressure, for example more than 10 bar, in the first section, and at a lower pressure in the next section in the feed direction. Thus, in a high-pressure region, for example, heat transfer coefficients of more than 10,000 W/(m ² K) can be achieved.

Alternatively or additionally, while observing in the flow direction F, a sectional or quasi-continuous control of the pressure and/or the flow rate of the coolant K can be realized depending on the product and/or on the basis of measurement data, experience data and/or a process model.

The cooling device 1 can be configured to operate intermittently in that the nozzle holders 11, for example, can be connected according to the passage of the front end of the pipe, and disconnected when the rear end of the pipe passes, whereby the ingress of the coolant K can be prevented. into the pipe R. For this purpose, one or more sensors can be located in the cooling section or behind the barrier section, configured to recognize the ends of the pipe.

Preferably, the cooling section is wholly or partially enclosed in a casing in order to prevent pollution of the environment by the cooling medium K, in particular to reduce pollution of the environment by sprayed water and steam. Pneumatic scrapers can be used for a similar purpose in order to prevent the coolant K from entering devices that are particularly endangered, such as, for example, radiometric measurements of wall thickness or other parameters upstream and/or downstream of the cooling section.

The feed direction F of the pipe R along the cooling section can be inclined relative to the horizontal (lowering or rising), whereby the installation space at the transition from the rolling mill to the possible cooler can be shortened. Additionally or alternatively, the cooling section can be integrated into the transition area to the refrigerator. Since the spray space is not blocked by the passage Z, the pipe R can be removed from the cooling section and transferred to the cooler.

To enhance the cooling effect, the cooling device 1 shown here is also suitable for combination with additional cooling elements in the rolling mill. According to one embodiment, the lowering of the inlet temperature or the rolling temperature takes place in the rolling mill, so that a lower than usual final rolling temperature can be applied. Thus, in the rolling mill, the tube R can be cooled to a temperature of about 30° C. below the critical temperature Ar3.

Where applicable, all individual features shown in the exemplary embodiments may be combined with each other and/or interchanged without departing from the scope of the invention.

List of reference symbols

1 cooling device

10 nozzle assembly

11 nozzle bracket

12 distribution pipe

13 tube with nozzles

14 nozzle

20 hydraulic unit

21 pumps

R pipe

F feed direction

K coolant

S spray plane

Z pass.

Claims (19)

1. Cooling device (1) for cooling seamless rolled pipe (R) made of metal, containing a nozzle assembly (10) with nozzles (14) configured to supply a cooling medium (K) to the outer peripheral surface of the pipe (R) while the pipe (R) is transported along the supply direction (F) in the cooling section of the cooling device (1), and the nozzle assembly (10) contains a passage (Z) through which the pipe (R) can be removed from the cooling section in the radial direction of the pipe (R). 2. Cooling device (1) according to claim 1, characterized in that the nozzle assembly (10) contains one or more brackets (11) for attaching nozzles, each of which contains at least one distribution pipe (12) and one or more tubes (13) with nozzles connected to the distribution pipe (12) and extending from the distribution pipe (12), each of which contains one or more nozzles (14). 3. Cooling device (1) according to claim 2, characterized in that it also contains a hydraulic system configured to supply distribution pipes (12) with a cooling medium (K), moreover, a plurality of distribution pipes (12) are combined into a hydraulic assembly (20 ), served by a common pump (21) and/or switched by a common valve system. 4. Cooling device (1) according to claim 2 or 3, characterized in that the distribution pipes (12) are designed to supply the cooling medium (K) in the pipe cross-sectional plane (R) and/or along the supply direction (F). 5. Cooling device (1) according to any one of paragraphs. 1-4, characterized in that the cooling section has a length of 8 to 16 m. 6. Cooling device (1) according to any one of paragraphs. 1-5, characterized in that the position and/or orientation and/or volumetric flow rate of the nozzles (14) of the nozzle assembly (10) are adjustable. 7. Cooling device (1) according to any one of paragraphs. 1-6, characterized in that the nozzles (14) of the nozzle assembly (10) are configured to form a plurality of spray planes (S) adjustable along the feed direction (F). 8. Cooling device (1) according to any one of paragraphs. 1-7, characterized in that it is configured to cool the pipe (R) to a final temperature below the Ar3 critical temperature, preferably to a temperature of 450°C to 600°C. 9. Cooling device (1) according to any one of paragraphs. 1-8, characterized in that it is made with the possibility of implementing regulation in sections or quasi-continuous regulation of the pressure and/or flow of the cooling medium (K), preferably depending on the product and/or based on measurement data, experimental data and/or a process model . 10. Cooling device (1) according to any one of paragraphs. 1-9, characterized in that the cooling section is divided into a plurality of sections, and in the first section, the node (10) of the nozzles is made with the possibility of spraying under high pressure, with a pressure of more than 10 bar, and in the next section in the supply direction (F) - under lower pressure. 11. Cooling device (1) according to any one of paragraphs. 1-10, characterized in that it is made with the possibility of such periodic operation that the nozzles (14), respectively, at the entrance of the pipe (R) to the cooling section are made with the possibility of connection, and at the exit of the pipe (R) from the cooling section - disconnection, and one or more sensors are located in the cooling section or behind the cooling section, configured to recognize the ends of the pipe. 12. Cooling device (1) according to any one of paragraphs. 1-11, characterized in that it also contains a casing, completely or partially surrounding the assembly (10) of the nozzles, and/or one or more pneumatic scrapers. 13. Cooling device (1) according to any one of paragraphs. 1-12, characterized in that the feed direction (F) of the pipe (R) along the cooling section is inclined relative to the horizontal. 14. Cooling device (1) according to any one of paragraphs. 1-13, characterized in that the cooling medium (K) is water or an aqueous mixture, and the radial direction is the upward direction. 15. Device for processing seamless pipes containing a rolling mill and a cooling device according to any one of paragraphs. 1-14, downstream of the rolling mill in the feed direction (F) and configured to cool the pipe (R) rolled by the rolling mill. 16. Apparatus according to claim 15, characterized in that the rolling mill comprises one or more cooling elements configured to reduce the temperature of the pipe (R) in the rolling mill below the Ar3 critical temperature, preferably about 30° below the Ar3 critical temperature. 17. The device according to claim. 15 or 16, characterized in that the rolling mill is a reduction-stretch rolling mill or a sizing mill.

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