JP2022013983A - Manufacturing method of steel pipe and manufacturing apparatus of steel pipe - Google Patents

Abstract

To provide a manufacturing method of a steel pipe which can prevent the quality deterioration due to twisting of a joint pipe after welding and a manufacturing apparatus of the steel pipe.SOLUTION: A manufacturing method of a steel pipe comprises: a heating step of heating an edge portion of band steel; a welding step of molding a tubular joint pipe by holding the band steel with at least one pair of pressure rolls, making the edge portions of the band steel face each other and welding the edge portions; a cooling step of cooling a seam portion of the joint pipe; a thermal image acquisition step of acquiring a thermal image by imaging the joint pipe; a twisting detection step of detecting twisting in the peripheral direction at the position of the seam portion based on the thermal image acquired in the thermal image acquisition step; and a correction step of correcting the twisting by displacing one of the pair of pressure rolls in the welding step in the thrust direction with respect to the other on the basis of the twisting detected in the detection step.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a steel pipe formed by welding an edge portion of a strip of steel and an apparatus for manufacturing a steel pipe.

When manufacturing a steel pipe, the edge of the heated steel strip is heated to a high temperature by high-frequency current, etc., and then welded to the edges at both ends by pressure bonding, etc., while forming into a cylinder with a molding roll. Is given. The part where the edge parts are joined is called the seam part, and the part other than the seam part is called the mother pipe part. The cylindrically molded joint pipe is molded to have the outer diameter of the product by drawing and rolling.

When rolling the joint pipe while keeping the seam part, which is heated intensively and hot before joining, in a high temperature state during drawing rolling, the temperature difference between the mother pipe part and the seam part causes the circumferential direction. Deformation resistance difference occurs, and the rolling finish dimensional accuracy deteriorates. Therefore, in order to reduce the temperature difference in the circumferential direction of the joint pipe before rolling, forced cooling is performed on the seam portion by a cooling mechanism after welding, and the temperature of the seam portion is lowered to lower the temperature of the seam portion and the base metal. The temperature difference between the part and the part is eliminated. The seam portion of the joint pipe is conveyed to the cooling mechanism in a state of being positioned at a predetermined position, and the cooling water is sprayed to the predetermined position of the joint pipe in the cooling mechanism.

Here, the joint pipe may be twisted in the circumferential direction due to the influence of molding or drawing rolling, and the portion to be forcibly cooled may be separated from the seam portion due to the twisting. As described above, in order to reduce the temperature deviation in the circumferential direction of the joint pipe and obtain a high-quality rolled finish, it is necessary to detect the position of the seam portion and correct the twist. Therefore, it has been conventionally proposed to detect the position of the seam portion based on the temperature of the joint pipe (see, for example, Patent Document 1). Patent Document 1 discloses a method in which a temperature distribution in the circumferential direction is measured by a scanning radiation thermometer to detect the position of a seam portion in the circumferential direction, and twisting is controlled by a twist correction device in a subsequent stage.

Japanese Unexamined Patent Publication No. 11-277147

However, in the method of Patent Document 1, twist correction is performed by feeding forward the measurement result of the radiation thermometer to the twist correction device in the subsequent stage. Therefore, when twisting occurs during welding, the seam portion may not be cooled normally, and the rolled finish may not be good due to uneven thickness generated due to uneven heat in the circumferential direction.

Therefore, an object of the present invention is to provide a steel pipe manufacturing method and a steel pipe manufacturing apparatus capable of preventing quality deterioration due to twisting of the joined pipe after welding.

The present invention has the following configurations in order to solve these problems.
[1] A pipe-shaped joint pipe is formed by a heating step of heating the edge portion of the strip and welding by sandwiching the strip using at least one pair of rolling rolls and welding the edge portions of the strip so as to face each other. A method for manufacturing a steel pipe, comprising a welding step for forming and a cooling step for cooling the seam portion of the joined pipe.
A thermal image acquisition step of imaging the junction tube to acquire a thermal image,
A twist detection step of detecting a twist in the circumferential direction of the position of the seam portion based on the thermal image acquired in the thermal image acquisition step, and a twist detection step.
Based on the twist detected by the detection step, one of the pair of rolling rolls in the welding step is displaced with respect to the other in the thrust direction to correct the twist.
A method for manufacturing a steel pipe having.
[2] In the twist detection step, the position of the seam portion of the joint pipe is detected based on the temperature difference of each part of the joint pipe in the thermal image, and the position of the seam portion detected is used as described above. The method for manufacturing a steel pipe according to [1], which detects a twist in the circumferential direction of the position of the seam portion.
[3] The method for manufacturing a steel pipe according to [2], wherein the position of the highest temperature among the temperatures of the joined pipe is detected as the position of the seam portion.
[4] In the straightening step, the twist amount of the seam portion is controlled by controlling the position of the rolling roll in the roll axis direction in the welding step according to the twist amount of the seam portion [1] to [3]. ]. The method for manufacturing a steel pipe according to any one of.
[5] A heating mechanism that heats the edge of the steel strip,
A welding mechanism for forming a pipe-shaped joint pipe by sandwiching the strip with at least one pair of rolling rolls and welding the edges of the strip with the edges facing each other.
A cooling mechanism that cools the seam portion of the joint pipe,
A twist detection device that detects a twist in the circumferential direction of the seam portion of the joint pipe, and a twist detection device.
Equipped with
The twist detection device is
A thermal image acquisition unit that captures an image of the junction tube and acquires a thermal image,
A twist detection unit that detects a twist in the circumferential direction of the position of the seam portion based on the thermal image acquired by the thermal image acquisition unit, and a twist detection unit.
Have,
The welding mechanism is a steel pipe manufacturing apparatus that corrects the twist by displaces one of the pair of rolling rolls in the thrust direction with respect to the other based on the twist detected by the twist detection device.

According to the present invention, by correcting the twist of the joint pipe detected from the thermal image in the welding process, insufficient cooling to the seam portion due to the twist of the mother pipe portion is suppressed, and deterioration of the quality of the steel pipe is prevented. can do.

It is a schematic diagram which shows the preferable embodiment of the steel pipe manufacturing apparatus of this invention. It is a schematic diagram which shows an example of a pair of rolling rolls located in the vertical direction in the welding mechanism of FIG. It is a photograph which shows an example of the thermal image acquired by the thermal image acquisition part of FIG. It is a graph which shows the temperature distribution in the circumferential direction in the thermal image of FIG. It is a photograph which shows another example of the thermal image acquired by the thermal image acquisition part of FIG. It is a graph which shows the temperature distribution in the circumferential direction in the thermal image of FIG. It is a schematic diagram which shows an example of the welding mechanism of FIG.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a schematic view showing a preferred embodiment of the steel pipe manufacturing apparatus of the present invention. The steel pipe manufacturing apparatus 1 of FIG. 1 is, for example, a manufacturing line for manufacturing a steel pipe from a strip steel SS by hot rolling, and has a heating mechanism 2 for heating the strip steel SS and a bent edge of the heated strip steel SS. It has a welding mechanism 3 for welding each other to form a joint pipe P, and a cooling mechanism 4 for cooling the seam portion SW of the joint pipe P. Further, the steel pipe manufacturing apparatus 1 of FIG. 1 has a drawing rolling mechanism (sizing mechanism) 5 that draws the joined pipe P cooled by the cooling mechanism 4 to a set outer diameter.

The heating mechanism 2 includes a preheating furnace 2a that heats the entire strip steel SS, and an edge heating section 2b that further heats the edge portions at both ends of the strip steel SS heated in the preheating furnace 2a. The edge heating portion 2b heats the edge portions at both ends of the strip steel SS by, for example, induction heating. The heating method is not limited to heating by electromagnetic induction, and known techniques such as ultrasonic waves can be used. The welding mechanism 3 welds by pressing and welding (forging) the edge portions of the strip steel SS so as to face each other, whereby a pipe-shaped joint pipe P is formed. The welding mechanism 3 includes a plurality of squeeze rolls (rolling rolls) that sandwich the strip steel SS heated from the vertical direction and the horizontal direction and roll the strip steel SS into a cylindrical shape so as to abut the edges at both ends.

FIG. 2 is a schematic view showing an example of a pair of rolling rolls located in the vertical direction in the welding mechanism of FIG. The pair of rolling rolls 3a and 3b of FIG. 2 sandwich the strip steel SS from the vertical direction to form the strip steel SS into a cylindrical shape. At this time, the welding mechanism 3 is formed so that the edges of both ends of the strip steel SS abut at the center of the pipe on the lower side of the joint pipe P, and the center of the pipe on the lower side of the joint pipe P is set as the reference position Def at both ends. The seam portion SW is formed by crimping the edge portion. Although the case where the reference position Pref is set to the lower position of the pipe center is illustrated, it can be set to any position in the circumferential direction such as the upper side of the pipe center. The pair of rolling rolls 3a and 3b are controlled so that their relative positions can be moved in the thrust direction (that is, the roll axis direction of the rolling rolls 3a and 3b), and the positions of the rolling rolls 3a and 3b in the roll axis direction are controlled. By controlling and changing the relative position, it is possible to control the force applied in the circumferential direction of the joint pipe P.

The cooling mechanism 4 of FIG. 1 is composed of, for example, a gas-water mist nozzle injection device, and injects cooling water into the seam portion SW of the joint pipe P to cool the joint pipe P. As described above, the joint pipe P has a seam portion SW formed at the reference position Pref, and is conveyed from the welding mechanism 3 to the cooling mechanism 4 in that state. The cooling mechanism 4 injects cooling water to the seam portion SW located at the reference position Pref to cool the seam portion SW.

Here, when the joint pipe P is conveyed from the welding mechanism 3 to the cooling mechanism 4, the joint pipe P may be twisted in the circumferential direction. As described above, since the cooling mechanism 4 injects cooling water on the premise that the seam portion SW is positioned at the reference position Pref, the seam portion SW is not cooled by the cooling water when the joint pipe P is twisted. Then, when rolling is performed by the drawing rolling mechanism 5 in the subsequent stage, the quality of the steel pipe is deteriorated due to uneven thickness or the like. Therefore, in the steel pipe manufacturing apparatus 1 of FIG. 1, a twist detecting device 10 for detecting the twist of the seam portion SW of the joint pipe P is provided between the cooling mechanism 4 and the drawing rolling mechanism 5, and the twist detecting device 10 is provided. The detection result in is fed back to the welding mechanism 3.

The twist detection device 10 of FIG. 1 detects a twist in the circumferential direction of the seam portion SW of the joint pipe P, and is installed, for example, on the downstream side of the cooling mechanism 4. The twist detection device 10 includes a thermal image acquisition unit 11 and a twist detection unit 12. The thermal image acquisition unit 11 includes a thermography camera that captures the junction tube P and acquires the thermal image TP. The thermal image acquisition unit 11 is installed at a position where, for example, the junction tube P being transported is imaged from below so that the seam unit SW is included in the thermal image TP.

FIG. 3 is a photograph showing an example of a thermal image acquired by the thermal image acquisition unit, and FIG. 4 is a graph showing a temperature distribution in the circumferential direction in the thermal image of FIG. 3 and 4 illustrate a case where the position of the seam portion SW is twisted by a twist amount θ with respect to the reference position Pref during transportation from the welding mechanism 3 to the cooling mechanism 4. Therefore, the seam portion SW is not normally cooled in the cooling mechanism 4, and the temperature increases as the seam portion SW approaches from the mother pipe portion, and the seam portion SW is the most in the circumferential direction of the joint pipe P. The temperature rises.

The twist detection unit 12 of FIG. 1 comprises a control device such as a computer, and detects a twist in the circumferential direction of the junction pipe P based on the thermal image TP acquired by the thermal image acquisition unit 11. At this time, the twist detection unit 12 detects the position of the seam portion SW of the junction pipe P based on the temperature difference of each portion of the junction pipe P in the thermal image TP, and uses the detected position of the seam portion SW. Detects a twist in the circumferential direction of the position of the seam portion SW.

Specifically, the twist detection unit 12 detects the position with the highest temperature in the thermal image TP as the position of the seam unit SW. The temperature of the mother pipe may be set to, for example, the heating temperature of the steel strip SS set in the preheating furnace 2a, or the mother pipe may be specified by edge detection or the like from the thermal image TP to detect the temperature. You may try to do it. As shown in FIGS. 3 and 4, when the twist generated between the welding mechanism 3 and the cooling mechanism 4 is detected, the temperature of the seam portion SW becomes the highest. Utilizing this, the twist detection unit 12 detects the position where the temperature is the highest as the position of the seam unit SW. Next, as shown in FIGS. 3 and 4, since the lower side of the center of the pipe is set as the reference position Def, the twist detection unit 12 is based on the deviation between the detected seam portion SW position and the reference position Def. And detect the twist in the circumferential direction. If the position of the seam portion SW and the reference position Def deviate from each other, the twist detection unit 12 may determine that twisting has occurred, or the position of the seam portion SW and the reference position Def may deviate from each other. If is larger than the set amount, it may be determined that twisting has occurred, and if it is less than or equal to the set amount, it may be determined that the twist is within the allowable range.

Although the case where the twist detection unit 12 detects the twist when the seam portion SW as shown in FIGS. 3 and 4 is not cooled by the cooling mechanism 4 is exemplified, the case where the twist occurs after passing through the cooling mechanism 4. There is. FIG. 5 is a schematic diagram showing another example of the thermal image acquired by the thermal image acquisition unit of FIG. 1, and FIG. 6 is a graph showing the temperature distribution in the circumferential direction in the thermal image of FIG. 5 and 6 illustrate a case where the position of the seam portion SW is twisted by the twist amount θ with respect to the reference position Pref during transportation from the cooling mechanism 4 to the drawing rolling mechanism 5. When the seam portion SW is cooled by the cooling mechanism 4, as shown in FIGS. 5 and 6, the temperature of the seam portion SW cooled by the cooling mechanism 4 is higher than that of the mother pipe portion heated by the preheating furnace 2a. Is the lowest, so the temperature is the lowest in the seam portion SW.

Here, even if the twist is as shown in FIGS. 5 and 6, the twist detection unit 12 detects the position of the seam portion SW having a temperature lower than the temperature of the mother pipe portion, thereby cooling by the cooling mechanism 4. Later twists can be detected. Then, as in the case of FIGS. 3 and 4 described above, the twist detection unit 12 detects the twist of the joint pipe P based on the position of the seam portion SW and the reference position Ref.

Here, since the strip steel SS or the joint pipe P welded by the welding mechanism 3 and the joint pipe P after cooling by the cooling mechanism 4 are not yet cut and are in a connected state, cooling is completed. The twist of the joint pipe P is transmitted to the twist to the joint pipe P before cooling, and even if the seam portion SW can be cooled at present, the welding mechanism 3 may be twisted in the future. Therefore, the twist detection unit 12 also detects the twist after cooling and feeds it back to the welding mechanism 3, so that it is possible to prevent the quality deterioration of the steel pipe due to insufficient cooling to the seam portion SW. In the above embodiment, the case of detecting the twist in both the cases of FIGS. 3 and 4 and the case of FIGS. 5 and 6 is illustrated, but only one of them may be detected.

Further, the case where the twist detection unit 12 detects the highest temperature position or the lowest temperature position in the thermal image TP as the position of the seam unit SW is illustrated, but the present invention is not limited to this, and the seam unit SW is not limited to this. Anything can be used as long as it can detect the amount of twist to the position where it is cooled by the cooling mechanism 4. That is, the cooling mechanism 4 injects cooling water into a certain range in the circumferential direction of the joining pipe P, and the seam portion SW may be located within this cooling range. Therefore, for example, a certain range including the maximum temperature or the minimum temperature in the thermal image TP may be detected as the position of the seam portion SW. Alternatively, a region such as the maximum temperature region or the minimum temperature region may be detected as the position of the seam portion SW according to the temperature resolution of the thermal image TP.

The twist amount θ detected by the twist detection unit 12 in FIG. 1 is fed back to the welding mechanism 3. Then, the welding control unit 3c of the welding mechanism 3 moves the rolling roll 3a of FIG. 2 in the thrust direction with respect to the rolling roll 3b based on the twist amount θ, and controls the force applied in the circumferential direction of the joint pipe P. Then, the joint pipe P is rotationally moved in the circumferential direction to correct the twist. The welding control unit 3c stores in advance a relational expression showing the relationship between the thrust movement amount x of the rolling rolls 3a and 3b and the twist amount θ, and the thrust movement amount x is derived from the twist amount θ using the relational expression. Then, the thrust movement of the rolling rolls 3a and 3b is controlled.

FIG. 7 is a graph showing the relationship between the thrust movement amount of the rolling roll and the twist amount of the joint pipe. As shown in FIG. 7, for example, the larger the twist amount θ, the larger the thrust movement amount x, and this relationship can be obtained in advance by an experiment (for example, x = −0.03θ + 0.05). Then, the welding control unit 3c controls the thrust movement amount x of the rolling rolls 3a and 3b based on the twist amount θ and the relational expression. Then, the joint pipe P is conveyed from the welding mechanism 3 to the cooling mechanism 4 in a state where the twist is corrected, and it is possible to prevent excessive or insufficient cooling of the seam portion SW due to the twist of the joint pipe P. As a result, in the drawing rolling mechanism 5, it is possible to suppress the uneven thickness due to the uneven heat in the circumferential direction of the joint pipe P and prevent the deterioration of quality.

Next, a preferred embodiment of the method for manufacturing a steel pipe of the present invention will be described with reference to FIG. First, the entire strip steel SS is preheated by the preheating furnace 2a, and the edge portion of the strip steel SS is heated by induction heating or the like in the edge heating portion 2b (heating step). After that, the heated strip steel SS is sandwiched between the plurality of rolling rolls 3a and 3b, and the edge portions at both ends of the strip steel strip SS are bent so as to face each other. A pipe-shaped joint pipe P is formed by crimping (forging) the opposing edge portions (welding process).

Then, the joining pipe P is conveyed to the cooling mechanism 4, and the seam portion SW of the joining pipe P is cooled in the cooling mechanism 4 (cooling step). The twist amount θ of the joint pipe P after cooling is detected by the twist detection device 10. At this time, the thermal image TP obtained by imaging the junction tube P is acquired (thermal image acquisition process, see FIGS. 3 to 6), and the twist of the position of the seam portion SW in the circumferential direction is detected based on the thermal image TP (see the thermal image acquisition process, FIGS. 3 to 6). Twist detection process). After that, the rolling rolls 3a and 3b of the welding mechanism 3 are displaced in the thrust direction based on the detected twist amount θ, and the twist is corrected (correction step). Then, the detected twist amount θ is fed back to the welding mechanism 3, and the welding mechanism 3 corrects the twist of the joint pipe P (correction step).

According to the above embodiment, when the seam portion SW is twisted, the twist amount θ is fed back to the welding mechanism 3, and the twist is corrected in the welding mechanism 3, so that the seam portion in the cooling mechanism 4 is twisted. It is possible to prevent the SW from not being cooled and to prevent quality deterioration such as generation of uneven thickness due to uneven heat. More specifically, for example, the uneven thickness ratio (unbalanced thickness ratio = maximum pipe thickness-minimum pipe thickness / average pipe thickness × 100) due to uneven heat in the circumferential direction of the joined pipe P is improved from 4.20 to 6.74. Results were obtained.

Further, when the position of the seam portion SW is detected based on the temperature measurement of the joint pipe P, it is detected based on the thermal image TP that continuously measures the circumferential temperature distribution of the joint pipe P molded into a tubular shape. As a result, it is possible to improve the detection accuracy of the position of the seam portion SW as compared with the conventional case where the scanning radiation thermometer whose temperature measurement is discontinuous is reciprocated in the arc direction.

Further, the position of the seam portion SW is determined from the thermal image TP by utilizing the fact that the joint pipe P after welding has the highest temperature in the seam portion SW and the joint pipe P after cooling has the lowest temperature in the seam portion SW. Since it is detected, the detection accuracy of the position of the seam portion SW can be improved.

Further, as shown in FIG. 2, the structure is such that the force applied in the circumferential direction of the mother pipe portion can be controlled by the thrust movement of the rolling rolls 3a and 3b, and at that time, the twist amount θ, the rolling roll 3a, By adjusting the thrust movement amount x of 3b according to the formula of FIG. 4, the twist detected from the thermal image TP can be corrected and controlled to an appropriate position. As a result, it becomes possible to prevent excessive or insufficient cooling of the seam portion SW due to twisting of the joint pipe P, and it is possible to suppress uneven thickness due to uneven heat in the circumferential direction of the joint pipe P.

The embodiment of the present invention is not limited to the above embodiment, and various modifications can be made. For example, in FIG. 1, the case where the thermal image acquisition unit 11 is installed between the cooling mechanism 4 and the drawing rolling mechanism 5 is illustrated, but if twisting after welding is detected, the welding mechanism is used. It may be installed between 3 and the cooling mechanism 4.

Further, in FIG. 1, the thermal image acquisition unit 11 illustrates a case where one thermal image is acquired from one thermography, but two or more thermography is provided so as to acquire a plurality of thermal images. You may. In this case, it is preferable to shoot from different directions in the shooting direction by the plurality of thermography. For example, if thermography is provided on the top and bottom of the junction tube, even if the seam is twisted by 90 ° or more in the circumferential direction and deviates from the shooting field of view of one thermography, it can be reliably performed by another thermography. You will be able to shoot the seam part.

Further, in FIG. 1, the welding process exemplifies a case where the edge portion is induced and heated by the edge heating portion 2b and then the strip steel SS is formed into a tubular shape (forming) and crimped, but the welding process is not limited to this method. .. For example, after forming the strip steel SS so as to abut the edge portions by a forming mechanism, the edge portions may be heated by ultrasonic waves or the like and welded by ultrasonic crimping or the like. Even in this case, it is necessary to perform a cooling step after welding, and the joint pipe P may be twisted. Therefore, the present invention can be applied.

1 Steel pipe manufacturing equipment 2 Heating mechanism 2a Preheating furnace 2b Edge heating unit 3 Welding mechanism 3a, 3b Rolling roll 3c Welding control unit 4 Cooling mechanism 5 Stretching rolling mechanism 10 Twist detection device 11 Thermal image acquisition unit 12 Twist detection unit P Joining pipe Roll reference position SS strip steel SW seam part TP thermal image θ twist amount x thrust movement amount

Claims (5)

Welding to form a pipe-shaped joint pipe by heating the edge of the strip and welding the edges of the strip with at least one pair of rolling rolls sandwiching the strip so that the edges of the strip face each other. A method for manufacturing a steel pipe, comprising a step and a cooling step of cooling the seam portion of the joined pipe.
A thermal image acquisition step of imaging the junction tube to acquire a thermal image,
A twist detection step of detecting a twist in the circumferential direction of the position of the seam portion based on the thermal image acquired in the thermal image acquisition step, and a twist detection step.
Based on the twist detected by the detection step, one of the pair of rolling rolls in the welding step is displaced with respect to the other in the thrust direction to correct the twist.
A method for manufacturing a steel pipe having. In the twist detection step, the position of the seam portion of the joint pipe is detected based on the temperature difference of each portion of the joint pipe in the thermal image, and the position of the seam portion detected is used to detect the seam portion of the seam portion. The method for manufacturing a steel pipe according to claim 1, wherein the twist in the circumferential direction of the position is detected. The method for manufacturing a steel pipe according to claim 2, wherein the position of the highest temperature among the temperatures of the joined pipe is detected as the position of the seam portion. Any one of claims 1 to 3 that controls the twist amount of the seam portion by controlling the position of the rolling roll in the roll axis direction in the welding step according to the twist amount of the seam portion in the straightening step. The method for manufacturing a steel pipe according to the section. A heating mechanism that heats the edges of the steel strip,
A welding mechanism for forming a pipe-shaped joint pipe by sandwiching the strip with at least one pair of rolling rolls and welding the edges of the strip with the edges facing each other.
A cooling mechanism that cools the seam portion of the joint pipe,
A twist detection device that detects a twist in the circumferential direction of the seam portion of the joint pipe, and a twist detection device.
Equipped with
The twist detection device is
A thermal image acquisition unit that captures an image of the junction tube and acquires a thermal image,
A twist detection unit that detects a twist in the circumferential direction of the position of the seam portion based on the thermal image acquired by the thermal image acquisition unit, and a twist detection unit.
Have,
The welding mechanism is a steel pipe manufacturing apparatus that corrects the twist by displaces one of the pair of rolling rolls in the thrust direction with respect to the other based on the twist detected by the twist detection device.

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