JPH1121628A - Method and equipment for cooling steel tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and equipment for controlling the cooling of the steel tube capable of uniformly controlling the cooling stop temperature in the longitudinal direction and in the circumferential direction of the steel tube, and improving the quality and the yield of the steel tube. SOLUTION: In a cooling method of a steel tube, the steel tube is cooled by flowing down >=2 row of plate-like cooling water curtain 5 putting a highest part 1a of the steel tube between them when viewed in the axial direction of the horizontally placed steel tube 1, and the cooling is started and stopped at the same position in the circumferential direction of the steel tube, for example, at the position 1b. A cooling equipment of the steel tube is provided with a means 2 to turn the steel tube 1 in a horizontal condition, two rows of nozzles 3a, 3b to flow down the plate-like cooling water curtain which are provided putting the highest part 1a of the steel tube between them, a cooling water shut-off plate 4 to stop the flow-down of the plate-like cooling water 5 over the steel tube 1, and an integrated number of revolution counting device 15 of the steel tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for cooling a steel pipe in a steel pipe manufacturing process, and more particularly to a method and an apparatus for cooling a steel pipe suitable for uniformly controlling a cooling stop temperature.

[0002]

2. Description of the Related Art A typical example of a heat treatment method in a steel pipe manufacturing process is a quenching treatment for rapidly cooling a heated steel pipe to around room temperature, forcibly cooling the heated steel pipe to a specific temperature range, and then allowing it to cool naturally. Controlled cooling, etc.

[0003] In the case of quenching, in order to obtain a quenched structure, cooling to a low temperature of about 200 ° C or less may be performed as soon as possible. However, in the case of controlled cooling, it is necessary to cool from around 850 ° C., for example, and to stop the cooling in a specific temperature range such as around 500 ° C. to 600 ° C. Therefore, a cooling method is used in which the cooling is easily stopped as compared with the quenching process. For example, JP
Japanese Patent Application Laid-Open No. 9-23819 discloses a method of performing spray cooling from the outer surface of a steel pipe while rotating the steel pipe.
For example, there is a method described in Japanese Patent Application Laid-Open No. 2-63618 in which a plate-like laminar flow is caused to flow down on the outer surface of a steel pipe while rotating the steel pipe.

[0004] In particular, the cooling method described in Japanese Patent Application Laid-Open No. 62-63618 aims to accurately control the cooling stop temperature and cooling rate by cooling while measuring the inner surface temperature. ing.

In the controlled cooling, in order to improve the quality and yield of the steel pipe, it is necessary to end the cooling at a uniform temperature not only in the pipe longitudinal direction but also in the circumferential direction.

However, in the spray cooling method disclosed in Japanese Patent Application Laid-Open No. 59-23819, it is necessary to take measures against interference of spray nozzles in order to uniformly cool in the longitudinal direction. However, there is a problem that the equipment becomes large. Further, in order to uniformly cool in the circumferential direction, it is necessary to spray cooling water uniformly in the circumferential direction, and for that purpose, it is necessary to change the spray distance of the cooling water according to the size of the steel pipe. However, there was a problem that the equipment became large. In addition, spray cooling method,
Nozzle clogging is likely to occur, and there is also a problem of equipment maintenance.

Further, in the method described in Japanese Patent Application Laid-Open No. 62-63618, since the laminar flow in the form of a plate flowing down to the upper part of the steel pipe is one line, the water film on the upper part of the steel pipe is unstable, Since the width of the cooling part due to the water film changes in the longitudinal direction of the steel pipe, there is a problem that temperature variation is likely to occur in the longitudinal direction of the steel pipe. In addition, the control of the variation in the temperature in the circumferential direction was difficult because the water film on the upper part of the steel pipe was unstable.

That is, in the method described in Japanese Patent Application Laid-Open No. 62-63618, there is a high possibility that the temperature will vary in both the longitudinal direction and the circumferential direction of the steel pipe. In addition, when cooling steel pipes that tend to bend, such as small-diameter thin-walled steel pipes, it is necessary to install protective holding rolls, etc., because this temperature variation may cause the steel pipe to bend and damage the equipment. However, there has been a problem that the whole equipment becomes large-scale and maintenance is required when bending occurs.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is suitable for uniformly controlling the cooling stop temperature in the longitudinal direction and the circumferential direction of a steel pipe. An object of the present invention is to provide a cooling method and a cooling device for a steel pipe.

[0010]

According to the method for cooling a steel pipe of the present invention, a plate-shaped cooling water parallel to the pipe axis is caused to flow down from above onto a steel pipe which is placed horizontally and rotates. A method of cooling a steel pipe, characterized in that two or more rows of the plate-shaped cooling water flow down so as to sandwich the top of the steel pipe, and that cooling is stopped at a cooling start position in a circumferential direction of the steel pipe. .

Further, the steel pipe cooling device of the present invention comprises a means for rotating the steel pipe in a horizontal state, and a plate-like means which is above the rotating steel pipe and is parallel to the pipe axis so as to sandwich the uppermost part of the steel pipe. It is characterized by comprising: two or more rows of nozzles for causing the cooling water to flow down, a cooling water cutoff plate for stopping the plate-shaped cooling water from flowing down to the steel pipe, and a rotation speed integrating means for integrating the rotation speed of the steel pipe. And

The "plate shape" refers to a curtain-like mode in which cooling water flowing down is continuous in the pipe axis direction, and a curtain-like form in which cooling water flowing down is provided at predetermined intervals in the pipe axis direction. Both aspects are included.

When cooling water is caused to flow down from the upper part of the rotating steel pipe by the slit-shaped nozzle, the cooling water flows down in a plate shape, as if the steel pipe were wrapped with cloth. This is called a slit laminar flow (hereinafter referred to as a laminar flow).

The present inventors have proposed in Japanese Patent Application Laid-Open No. 7-310126 a method of cooling a steel pipe by flowing two or more rows of plate-shaped cooling water. According to this method, the plate-shaped cooling water (lamina flow) is provided in two or more rows,
Even if the flow rate of cooling water is increased, there is no scattering,
Since a stable water film is formed at a portion sandwiched by laminar flows of rows or more, the heat transfer coefficient at this portion can be increased. As a result, the cooling capacity of the cooling water can be improved.

The present inventor has paid attention to this method, and has controlled the cooling method of cooling the upper part of the steel pipe between two or more rows of laminar flows so that the outer surface of each part of the steel pipe passes at the same time. The present inventors have found that it is effective to apply the present invention, and have completed the present invention.

That is, in the method for cooling a steel pipe according to the present invention, two or more rows of plate-shaped cooling water flow down so as to sandwich the uppermost part of the horizontally placed steel pipe. Therefore, a water film region having a high heat transfer coefficient can be stably formed in the upper part of the steel pipe with a uniform width in the longitudinal direction. As a result, not only can the cooling be performed efficiently and stably, but also the cooling can be performed uniformly in the longitudinal direction of the steel pipe. Further, a water film region having a high heat transfer coefficient is formed stably at a predetermined width on the upper part of the steel pipe, and the start and stop of the cooling are performed at the same position in the circumferential direction of the steel pipe, so that any position on the outer surface of the steel pipe is adjusted to this position. Since it passes through the water film area for the same time, uniform cooling can be performed in the circumferential direction.

Further, the steel pipe cooling device of the present invention includes a cooling water cut-off plate for stopping the plate-shaped cooling water from flowing down to the steel pipe, and an integrated rotation speed measuring device for integrating the rotation speed of the steel pipe. I have. The decimal part of the rotation speed obtained by the integrated rotation speed measuring device indicates the rotation position of the steel pipe. Therefore, the number of rotations of the steel pipe is integrated, and when the steel pipe has been rotated a predetermined integer number of times, the cooling water cutoff plate can be operated such that the start and stop of cooling are at the same position in the circumferential direction of the steel pipe. .

The "same position" for starting and stopping the cooling at the same position in the circumferential direction of the steel pipe depends on the width of the water film region formed on the upper part of the steel pipe, but is ± 0.5 radian.
In the case where the number of rotations is represented by the number of rotations, it means that the number of rotations is within a range of integer times ± 0.08 times.

Further, in the present invention, it is only required that a water film region having a high heat transfer rate can be stably formed in the upper part of the steel pipe with a uniform width in the longitudinal direction. It may be an odd row.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1A and 1B are schematic diagrams illustrating an example of a steel pipe cooling device according to the present invention, wherein FIG. 1A is a front view and FIG. 1B is a side view.

The steel pipe 1 is driven to rotate by a turning roller 2. Above the top (top) 1a of the steel pipe, two rows of slit nozzles 3a and 3b for letting plate-shaped cooling water flow down are arranged. A shutter 4 for damping the cooling water and a gutter 6 for discharging the cooling water damped by the shutter 4 are provided.

Also, a shutter rotation drive controller 12 for controlling the opening and closing of the shutter 4, a touching roller 16 for measuring the rotation speed of the steel pipe, and an integrated rotation for integrating the rotation speed of the steel pipe from the rotation speed of the touching roller 16 Number measuring device 1
5 and a central controller 13 for controlling the entire apparatus.

The central controller 13 performs the following operation. Based on a cooling instruction including a cooling time from the console 11, a target integrated rotation speed of the steel pipe is calculated from the cooling time. It instructs the shutter rotation drive controller 12 to start cooling, and instructs the integrated rotation speed measuring device 15 to measure the rotation speed of the steel pipe. When the rotation speed of the steel pipe reaches the target integrated rotation speed, the shutter rotation drive controller 12 is instructed to stop cooling. Also,
The central controller 13 is a turning roller drive controller 1
The rotation speed of the turning roller 2 is controlled via the control unit 4.

FIGS. 2A and 2B are schematic views showing the state of the steel pipe cooling device when the shutter is opened and closed. FIG. 2A is a front view showing the shutter open state, and FIG. 2B is a front view showing the shutter closed state. FIG.

When the shutter 4 shown in FIG. 2A is open, two rows of plate-like laminar flows from the slit nozzles 3a and 3b cause a water film region 21 having a high heat transfer coefficient to be formed above the steel pipe 1. Are formed stably, and the steel pipe 1 is cooled.

When the shutter 4 is closed as shown in FIG. 2B, the cooling water is stopped by the shutter 4 and the stopped cooling water is discharged by the gutter 6.

An example of the method for cooling a steel pipe according to the present invention will be described with reference to FIGS.

The state where the shutter 4 is closed (FIG. 2B).
Then, the high-temperature steel pipe 1 is conveyed onto the turning roller 2,
Is placed.

When the shutter 4 is opened, the cooling of the high-temperature steel pipe 1 is started. Cooling water volume and tube rotation speed
It is set in advance based on the surface temperature of the high-temperature steel pipe before the start of cooling (FIG. 2A).

When the rotation speed of the steel pipe 1 reaches the target integrated rotation speed, a signal from the shutter rotation drive controller 12
The shutter 4 rotates, the cooling water 5 is dammed, and the cooling is instantly terminated.

A stable stagnant water area 21 is formed near the top 1a of the outer surface of the steel pipe by two or more laminar flows, and cooling is started and stopped at the same position in the circumferential direction of the steel pipe, for example, position 1b. Since any position in the circumferential direction passes through the stagnant water region for the same time, uneven cooling can be suppressed.

The time delay from the start of cooling to the shutter rotation drive controller 12 to the actual start of cooling and the time delay from the instruction to stop cooling to the actual stop of cooling are set in advance. By estimating and controlling in consideration of these, the cooling start position and the cooling end position of the steel pipe can be accurately matched.

In this example, the number of revolutions of the steel pipe is obtained from the number of revolutions of the touching roller 16. When the slip of the steel pipe 1 on the turning roller 2 is small,
The rotation speed of the steel pipe may be obtained from the rotation speed of the turning roller 2. Needless to say, other methods may be used.

[0035]

Embodiments of the present invention will be described below.

The cooling device for the steel pipe used in the embodiment of the present invention is the device shown in FIGS.

A carbon steel pipe (0.2% by weight C) having an outer diameter of 244.5 mm, a thickness of 8.94 mm, and a length of 20 m was subjected to controlled cooling from 850 ° C. to 550 ° C. The variability was investigated. The measurement of temperature variation was performed by embedding a sheath thermocouple inside the thickness.

The number of slit nozzles is two, and the interval is
It was 100 mm. That is, the top (top) 1 of the steel pipe
a 50 m from the top (top) 1a
m. The amount of cooling water in the two rows was 1 m ³ / min · m. The cooling rate is about 30 ° C / sec. The cooling time is
About 10 seconds. That is, the rotation speed is 30 rpm, 40 rpm
With respect to m and 60 rpm, cooling was performed with the target integrated rotation speeds of the steel pipes set at 5, 7, and 10, respectively.

As a comparative example, the same controlled cooling was carried out by using only one row of slit nozzles and allowing cooling water to flow down to the top (top) of the steel pipe. Cooling water volume is 1m ³ /min.m
And The cooling rate is about 20 ° C / sec. Cooling time is 14
The speed was kept constant in seconds, and the control by the rotation speed of the steel pipe was not performed.

The results are shown in Table 1.

[0041]

[Table 1]

Table 1 shows the variation in temperature after cooling.

Compared with the conventional single-row laminar cooling based on the cooling time, the method of the present invention based on the number of revolutions can reduce the variation in the temperature in the circumferential and longitudinal directions of the tube.

[0044]

According to the method and the apparatus for cooling a steel pipe of the present invention, the cooling stop temperature can be controlled uniformly in the longitudinal direction and the circumferential direction of the steel pipe. As a result, steel pipe quality and yield can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating an example of a steel pipe cooling device according to the present invention, wherein (a) is a front view and (b) is a side view.

FIGS. 2A and 2B are schematic views showing a state of the steel pipe cooling device shown in FIG. 1 when a shutter is opened and closed, where FIG. 2A is a front view showing a shutter open state, and FIG. 2B is a front view showing a shutter closed state; FIG.

[Brief description of reference numerals]

 Reference Signs List 1 steel pipe 1a top (top) of steel pipe 1b position 2 turning roller 3a, 3b slit nozzle 4 shutter 5 cooling water 6 gutter 11 console 12 shutter rotation drive controller 13 central controller 14 turning roller drive controller 15 integrated rotation number measurement Apparatus 16 Touching roller 21 Stable water film area with high heat transfer coefficient

Claims (2)

[Claims] 1. A method of cooling a steel pipe by flowing plate-shaped cooling water parallel to the pipe axis from above onto a steel pipe that is placed horizontally and rotating on the surface of the steel pipe. A cooling method for a steel pipe, characterized by flowing down two or more rows of the plate-shaped cooling water so as to sandwich the cooling water and stopping cooling at a cooling start position in a circumferential direction of the steel pipe. 2. A means for rotating a steel pipe in a horizontal state, and at least two rows for flowing plate-shaped cooling water above the rotating steel pipe and parallel to the pipe axis so as to sandwich the uppermost part of the steel pipe. A cooling device for a steel pipe, comprising: a nozzle, a cooling water blocking plate for stopping the plate-shaped cooling water from flowing down to the steel pipe, and a rotation number integrating means for integrating the rotation number of the steel pipe.