JP3624680B2 - Method for cooling inner and outer surfaces of steel pipe and inner and outer surface cooling device - Google Patents

Description

【００４５】
【発明の効果】
本発明にれば、鋼管出側端部付近に発生する焼入れ後の鋼管外径の不均一を抑制することができる。
【図面の簡単な説明】
【図１】本発明の方法および装置を示す図であり、図１（ａ）は、処理工程を示すブロック図であり、図１（ｂ）は、方法および装置の概要を示す概念図である。
【図２】内面冷却水の出側における水温と経過時間との関係を示すグラフである。
【図３】内面冷却水の鋼管入側、中間部および出側における鋼管内面温度と鋼管内面熱伝達率との関係を示すグラフである。
【図４】内面冷却を３秒先行して焼き入れた場合と焼き入れない場合における鋼管入側端からの距離と外径との関係を示すグラフである。
【図５】内面冷却の先行時間を変化させたときの鋼管入側端からの距離と外径との関係を示すグラフである。
【図６】外面冷却の先行時間を変化させたときの鋼管入側端からの距離と外径との関係を示すグラフである。
【図７】冷却開始時間と径小率Ｋとの関係示すグラフである。
【図８】出側鋼管端から２ｍ の範囲で、外面冷却を先行させたときの鋼管入側端からの距離と外径との関係を示すグラフである。
【図９】内面冷却を３秒先行させたときの鋼管寸法（肉厚、外径）と焼入れ後の径小率Ｋとの関係を示すグラフである。
【図１０】内面３秒先行冷却、外面１秒先行冷却および外面２秒先行冷却時の鋼管寸法（肉厚×外径）と径小率Ｋとの関係を示すグラフである。
【図１１】外径１７７．８ｍｍ、肉厚１０ｍｍの鋼管について内面３秒先行冷却および外面１秒先行冷却における径小率Ｋと焼き曲がり量との関係を比較したグラフである。
【図１２】鋼管出側端部の外面冷却装置の構成を示す概念図である。
【符号の説明】
１：加熱炉、 ２：冷却装置、
３：高架水槽 ４：外面冷却装置、
５：内面冷却装置、 ６：流下水遮断樋、
７：回転装置、 ８：鋼管出側端部の外面冷却装置、
９：搬送ローラ、 １０：冷却水制御装置、
１１：流調弁、 １２：鋼管、
１３：冷却装置架台、 １４：貯水タンク
１５：給水口、 １６：ポンプ、
１７：スプレーノズル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for cooling the inner and outer surfaces of a steel pipe and an inner and outer surface cooling device for suppressing non-uniformity of the outer diameter that occurs in the axial direction of the steel pipe when heat treating the steel pipe.
[0002]
[Prior art]
As a method for cooling the inner and outer surfaces of a steel pipe, Japanese Patent Application Laid-Open No. 58-141332 discloses a method of forcibly cooling the inner and outer surfaces of a steel pipe simultaneously by supplying cooling water from a nozzle provided in the water tank while immersing the steel pipe in a water tank and rotating it. A method is disclosed.
[0003]
However, this method is not suitable for cooling a long pipe because an apparatus such as a water tank becomes large-scale when the inner and outer surfaces of the steel pipe are simultaneously cooled. Moreover, even if the outer surface cooling can be performed almost simultaneously in the axial direction of the steel pipe by immersion and rotating cooling, the inner surface cooling becomes uneven in the axial direction of the steel pipe due to the difference in the penetration time of the cooling water. There is a problem of being big.
[0004]
Moreover, the disclosed content of the publication is intended to improve the bending, and does not achieve the higher goal of improving the non-uniformity of the outer diameter of the steel pipe.
[0005]
Japanese Patent Laid-Open No. 58-52426 discloses a method of cooling the outer surface of a steel pipe that flows down the entire length of the rotating steel pipe as a cooling method of the steel pipe, and Japanese Patent Publication No. 2-8008 discloses a steel pipe. The methods of simultaneously cooling the inner and outer surfaces while rotating the steel pipe and reciprocating the steel pipe in the axial direction are disclosed, but all of them are methods developed for the purpose of preventing the steel pipe from being bent. The objective of improving the non-uniformity of the steel pipe outer diameter in the axial direction of the steel pipe after quenching is not achieved.
[0006]
[Problems to be solved by the invention]
In the manufacturing process of steel pipes, there is usually an outer diameter straightening device such as a sizer or straightener after the quenching device, which can remove the non-uniformity of the outer diameter to some extent, but excessive correction is a product due to the effect of processing It is necessary to suppress as much as possible the non-uniformity of the outer diameter of the steel pipe after quenching.
[0007]
The object of the present invention is to end the steel pipe end on the opposite side (outside of the internal cooling water) from the supply of the internal cooling water when quenching long steel pipes of various diameters and thicknesses made of carbon steel or low alloy steel. An object of the present invention is to provide a cooling method and a cooling device for the inner and outer surfaces of a steel pipe that suppress unevenness of the outer diameter of the steel pipe after quenching that occurs near the portion.
[0008]
[Means for Solving the Problems]
While rotating the heated steel pipe around the central axis, the outer surface of the steel pipe is simultaneously cooled by a single or a plurality of plate-shaped water curtains provided in parallel to the axial direction of the steel pipe, and from the inner surface cooling device installed at the end of the steel pipe In the cooling method of supplying cooling water to cool the inner surface of the pipe, from the viewpoint of suppressing the bending of the pipe caused by the nonuniformity of the steel pipe in the circumferential direction of the outer surface, the inner surface cooling is usually small in the circumferential direction of the cooling. Start at the same time as the start of external cooling or earlier. Here, the start timing of the outer surface cooling refers to the timing when the plate-shaped water curtain collides with the steel pipe, and the start timing of the inner surface cooling refers to the cooling water supplied from the cooling device entering the pipe from the end of the cooling device. The time when. In this case, it can be expected to suppress the non-uniformity in the circumferential direction of the cooling, but the non-uniformity in the axial direction of the steel pipe due to the cooling capacity of the inner surface and the non-uniformity in the outer diameter in the axial direction of the steel pipe due to this. It becomes a problem.
[0009]
Below, the non-uniformity in the axial direction of the steel pipe in the cooling capacity of the inner surface and the non-uniformity in the outer diameter in the axial direction of the steel pipe resulting from this will be described.
When cooling the inner surface of a heated steel pipe by supplying cooling water from a cooling device installed at the end of the steel pipe (on the steel pipe entry side), the temperature of the cooling water rises as the cooling water advances into the steel pipe. In addition to the rise in the temperature of the internal cooling water, the end of the steel pipe is opened at the pipe end opposite to the pipe supply side (steel pipe outlet side), so the pressure of the cooling water decreases, and the cooling capacity is reduced accordingly. It decreases in the axial direction. This decrease in cooling capacity becomes more pronounced as the steel pipe becomes longer.
[0010]
FIG. 2 is a time change from the start of cooling of the cooling water temperature on the inner surface of the steel pipe outlet side.
As shown in the figure, on the outlet side of the cooling water on the inner surface, the temperature of the cooling water on the inner surface rises to a maximum of about 60 ° C. At this time, the temperature of the cooling water on the inlet side is 22 ° C.
[0011]
FIG. 3 shows the results of measuring the heat transfer coefficient on the inner surface of the steel pipe at the steel pipe entry side, intermediate portion, and exit side.
As shown in the figure, the cooling capacity decreases as the temperature of the cooling water on the inner surface rises. Due to the decrease in the cooling capacity, the outer diameter of the steel pipe after cooling gradually decreases in accordance with the traveling direction of the cooling water on the inner surface, and the outer diameter becomes particularly small at the aforementioned open end where the cooling capacity is significantly decreased. Normally, these non-uniformities in the outer diameter are removed by an outer diameter straightening device such as a hot straightener after quenching or tempering, but depending on the steel type, outer diameter, and wall thickness of the steel pipe, the outer diameter tolerance is not sufficiently removed. However, even if the outer diameter non-uniformity can be removed to the extent that it is within the tolerance, the mechanical performance received during the correction may deteriorate the performance of the product.
[0012]
FIG. 4 shows an outer diameter distribution when a steel pipe having an outer diameter of 244.5 mm, a wall thickness of 11 mm, and a length of 24000 mm is cooled by inner and outer surfaces with the inner surface cooling advanced for 3 seconds.
As shown in the figure, the outer diameter after quenching is considerably smaller at the outlet side than the outer diameter after pipe making. When such non-uniformity of the outer diameter occurs, it is a problem that a few meters at the exit end must be cut after quenching, and must be solved from the viewpoint of yield improvement.
[0013]
As a result of repeating experiments and theoretical analysis on the case of cooling the inner and outer surfaces of a long steel pipe having a length of 20 m to 30 m, the present inventor obtained the following knowledge.
(A) By controlling the timing for starting the inner surface cooling and the timing for starting the outer surface cooling, the outer surface cooling is preceded by the inner surface cooling, so that the non-uniformity of the outer diameter in the axial direction of the steel pipe can be suppressed. There is an optimum value for the time difference that causes cooling to precede internal cooling, depending on the outer diameter and thickness of the steel pipe to be cooled.
[0014]
(B) Although depending on the material of the steel pipe, even when the outer surface cooling is preceded by the inner surface cooling for a steel pipe having an outer diameter of 200 mm or more and a wall thickness of 10 mm or more, the bending to be concerned is the conventional cooling condition. However, it does not become large.
[0015]
(C) FIG. 5 is an outer diameter distribution after quenching in the axial direction of the steel pipe when the inner and outer surfaces are cooled while rotating a steel pipe having an outer diameter of 244.5 mm, a wall thickness of 11 mm, and a length of 24,000 mm from 850 ° C. . Here, the outer surface is cooled with a flow rate of 1.5 m ³ / (m · min) with two rows of plate-like water curtains, and the inner surface is cooled at a flow rate of 3000 T / H or more from the inlet side by a cooling water supply nozzle. The start is 0, 1, 3, 5 seconds ahead of the start of external cooling. The steel pipe rotation speed is 80 rpm.
[0016]
FIG. 6 shows the outer diameter distribution after cooling when cooling of the outer surface is preceded by cooling of the inner surface for 1, 2, 3, and 4 seconds, respectively, and the other cooling conditions are the same as those in FIG.
As shown in FIGS. 5 and 6, it can be seen that the outer diameter non-uniformity in the axial direction of the steel pipe is greatly suppressed by starting the outer surface cooling for about 1 to 2 seconds prior to the inner surface cooling.
[0017]
FIG. 7 is a graph obtained by rearranging the results of FIGS. 5 and 6, and is a graph showing the relationship between the cooling start time and the small diameter ratio K. There is an optimal time difference in the cooling start time difference between the inner and outer surfaces. . The minus on the horizontal axis indicates the time (seconds) to precede the inner surface cooling. Here, the small diameter ratio K is an index representing the non-uniformity of the outer diameter in the axial direction of the steel pipe, and the following (1) It is defined as an expression.
K (%) = (maximum outer diameter−minimum outer diameter) / (maximum outer diameter) × 100 (1)
(D) FIG. 8 shows that the outer surface of the steel pipe in the range of 2 m 2 from the outlet side of the steel pipe is cooled for 0.5 second to 2 seconds prior to the simultaneous cooling process on the inner and outer surfaces shown in FIG. It is the outer diameter distribution of the axial direction of the steel pipe after hardening when it cools simultaneously.
[0018]
As shown in the figure, non-uniformity of the outer diameter in the axial direction of the steel pipe is greatly suppressed by cooling the outer surface of the exit side for about 0.5 to 2 seconds, and the effect is that the overall length of the outer surface is reduced. It becomes larger than the case of pre-cooling.
[0019]
(E) FIG. 9 shows the small diameter ratio K in the case where the inner surface cooling is preceded by the outer surface cooling for 3 seconds with respect to the steel pipes having various dimensions.
As shown in the figure, even if the outer diameters of the steel pipes to be cooled are different, the small diameter ratio K may increase at a certain thickness, and the thickness of the steel pipe dimensions at which the small diameter ratio K increases at each outer diameter. The effect on the small diameter ratio K was investigated when the start time of cooling of the entire outer surface was preceded by 1 to 2 seconds before the start time of inner surface cooling.
[0020]
FIG. 10 shows the influence on the small diameter ratio K when the internal cooling which is the conventional cooling method is preceded by 3 seconds and when the cooling start timing of the entire outer surface is preceded by 1 to 2 seconds from the start timing of the internal cooling. Is a comparison.
[0021]
As shown in the figure, when the outer surface cooling is preceded by 1 second for a steel pipe having an outer diameter of about 250 mm, the smaller diameter ratio K is reduced when the outer surface cooling is preceded by 2 seconds for a steel pipe having a larger outer diameter. It can be seen that the non-uniformity of the outer diameter of the steel pipe in the axial direction can be suppressed. Further, in a steel pipe having an outer diameter of 150 mm or less and a wall thickness of about 10 mm, even if the inner surface cooling is preceded, the small diameter ratio is originally small, and it is not necessary to precede the outer surface cooling.
[0022]
(F) Further, with these five types of dimensions, the outer diameter 177 of which the most feared to bend out of the four dimensions excluding the outer diameter φ139.7 mm × thickness t10 mm, which does not require the outer surface precedent cooling, is provided. The amount of bending after cooling per 10 m 2 of the steel pipe when the inner surface cooling was preceded by 3 seconds and the outer surface cooling was preceded by 1 second was investigated for the one having a thickness of .8 mm and a thickness of 10 mm.
[0023]
FIG. 11 shows the results of the above investigation.
As shown in the figure, even if the outer surface cooling is preceded, the bending amount can be within an allowable range. Here, the allowable amount of bending is set to 10 mm or less per 10 m 2 which does not cause a problem in conveying the steel pipe.
[0024]
This invention is made | formed based on the above knowledge, and the summary is as showing to following (1)-(3).
(1) While cooling the heated steel pipe around the central axis, cooling water is supplied from an outer surface cooling device provided in parallel to the axial direction of the steel pipe to simultaneously cool the outer surface of the steel pipe in the axial direction. In the cooling method of the inner and outer surfaces of the steel pipe, in which cooling water is supplied to the inner surface of the steel pipe from the inner surface cooling device installed on the inner surface, the outer surface cooling is started before the inner surface cooling. Method.
[0025]
(2) While cooling the heated steel pipe around the central axis, cooling water is supplied from an outer surface cooling device provided in parallel to the axial direction of the steel pipe to simultaneously cool the outer surface of the steel pipe in the axial direction. In the cooling method of the inner and outer surfaces of the steel pipe that cools the inner surface by supplying cooling water to the inner surface of the steel pipe from the inner surface cooling device installed in the inner surface, the inner surface cooling water is supplied to the outer surface of the steel pipe prior to simultaneously cooling the inner and outer surfaces over the entire length. A method for cooling the inner and outer surfaces of a steel pipe, characterized in that cooling is performed in a range of 5/100 to 15/100 of the total length of the steel pipe from the opposite end.
[0026]
(3) A device for rotating the steel pipe around the central axis, an outer surface cooling device provided parallel to the axial direction of the steel pipe, an inner surface cooling device installed from the end of the steel pipe toward the inner surface of the steel pipe, and the axial direction of the steel pipe A steel pipe inner / outer surface cooling device comprising an outer surface cooling device at a steel pipe outlet end portion that is movable in a direction parallel to the plurality of cooling devices.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
The configuration of the present invention is shown in FIGS. FIG. 1A shows a basic flow of the processing steps, and FIG. 1B shows an outline of the cooling device 2.
[0028]
(1) The invention described in claim 1 is an outer surface provided in parallel with the axial direction of the steel pipe while rotating the heated steel pipe 12 carried out of the heating furnace 1 around the central axis using the rotating device 7. The inner and outer surfaces of the steel pipe that cools the inner surface by supplying cooling water from the cooling device 4 to simultaneously cool the outer surface of the steel pipe in the axial direction and supplying the cooling water to the inner surface of the steel pipe from the inner surface cooling device 5 installed at the end of the steel pipe. In this cooling method, the outer surface cooling is started before the inner surface cooling.
[0029]
(2) The invention described in claim 2 is provided in parallel to the axial direction of the steel pipe while rotating the heated steel pipe 12 carried out of the heating furnace 1 around the central axis using the steel pipe rotating device 7. Cooling of the inner and outer surfaces of the steel pipe which supplies cooling water from the outer surface cooling device 4 to cool the outer surface of the steel pipe at the same time and supplies cooling water to the inner surface of the steel pipe from the inner surface cooling device 5 installed at the end of the steel pipe In the method, prior to cooling the inner and outer surfaces over the entire length, the outer surface of the steel pipe ranges from 5/100 to 15/100 length of the entire length of the steel pipe from the end opposite to the inner surface where cooling water is supplied. In this method, cooling is performed using the outer surface cooling device 8 at the end of the steel pipe.
[0030]
(3) The invention described in claim 3 includes a steel pipe rotating device 7 for rotating the steel pipe around the central axis, an outer surface cooling device 4 provided parallel to the axial direction of the steel pipe, and an end of the steel pipe from the end of the steel pipe to the inner surface of the steel pipe. This is a cooling device comprising an inner surface cooling device 5 installed toward the end, and an end external cooling device 8 on the steel tube outlet side that is movable in a direction parallel to the axial direction of the steel pipe and has a plurality of cooling devices.
[0031]
The outer surface cooling device 4 may be any device that can supply cooling water uniformly and simultaneously to the outer surface of the steel pipe in the axial direction of the steel pipe, and the inner surface cooling device 5 also cools the inner surface of the steel pipe from the end of the steel pipe to the inner surface of the steel pipe. Any device capable of supplying water may be used.
[0032]
For example, the outer surface cooling device may be a device that supplies plate-shaped cooling water from above the steel pipe along a plane including the tube axis, and a slit nozzle is suitable as the nozzle that supplies the plate-shaped cooling water. . In order to ensure a stable flow, the inner surface cooling device is preferably provided with a nozzle having a straight pipeline as long as possible, and a rectifying plate or the like may be provided at the nozzle tip. Furthermore, in order to ensure the water pressure in the pipe, an inner surface cooling device that can grip the steel pipe from the outer periphery and seal the end of the steel pipe is preferable.
The rotational speed of the steel pipe is desirably 80 rpm or more from the viewpoint of suppressing the bending amount, and is preferably 110 rpm or less in consideration of the apparatus cost.
[0033]
In addition to the above-mentioned device, the end of the steel pipe that can be cooled independently in the range of 5/100 to 15/100 of the total length of the steel pipe at the end of the steel pipe at the inner cooling water discharge side of any steel pipe length An external cooling device 8 is required. The reason why the range of 5/100 to 15/100 of the total length of the steel pipe is less than 5/100 is sufficient to achieve the original purpose of assisting cooling in the range where the inner surface cooling capacity is reduced. This is because if it exceeds 15/100, cooling is assisted to the extent that the inner surface cooling capacity is not reduced, resulting in excessive cooling, increasing the outer diameter, and non-uniformity of the outer diameter becomes a problem. .
A preferred range is from 8/100 to 12/100.
[0034]
The steel pipe exit side end outer surface cooling device 8 includes a plurality of spray nozzles 17 disposed at intervals of several tens of centimeters on a transport roller 9 movable in parallel to the axial direction of the steel pipe, and the length of the steel pipe 12 to be cooled. It is only necessary to move it according to the circumstances so that the range of 5/100 to 15/100 of the total length of the steel pipe can be cooled. The apparatus described above is preferable.
[0035]
FIG. 12 is a conceptual diagram showing the configuration of the steel pipe outlet side cooling device 8 in more detail.
As shown in FIG. 12, the operation method for cooling the outer surface of the end of the steel pipe is such that a necessary amount of water is injected from the water supply port 15 into the water storage tank 14 before the steel pipe 12 is transferred to the cooling device. At the same time as being transported into the cooling device, the cooling device mount 13 is moved by the transport roller 9 and the spray nozzle 17 is stopped at a position where it can cool about 5/100 to 15/100 of the length of the steel pipe, and the rotation of the steel pipe When the rotation of the steel pipe rotated by the apparatus 7 reaches a steady state, the water pressurized by the pump 16 is opened to the flow control valve 11 and supplied to the spray nozzle 17, and cooling water is injected to make the steel pipe 12 1. From the spray nozzle 17 and then the outer surface cooling and the inner surface cooling are started simultaneously.
[0036]
The inner surface cooling and the outer surface cooling are performed by opening and closing the sewage blocking bar 6 and the flow control valve 11, respectively, according to the preset timing preset in the cooling water control apparatus 10 shown in FIG.
[0037]
The preceding time for cooling the outer surface will be described below.
The leading time of the outer surface cooling is preferably about 1 second when the flow rate of the internal cooling water is 3000 T / H or more, the outer diameter of the steel pipe is 250 mm or less, and about 2 seconds when the outer diameter of the steel pipe is more than that.
[0038]
In order to properly cool the inner surface, a flow rate of 3000 T / H or more is required.
The leading time of the outer surface cooling at the steel pipe outlet side end may be the same as above as long as it has a cooling capability comparable to that of the normal outer surface cooling as in the steel pipe outlet side cooling device 8 shown above. About 0.5 to 2 seconds is preferable.
[0039]
【Example】
A steel pipe heated to 950 ° C. in a heating furnace is conveyed to a cooling device, and after the steel pipe is placed at a predetermined position in the cooling device, the steel pipe is rotated at a rotational speed of 80 rpm by a steel pipe rotating device. Cooling was started when the rotation of the motor reached a steady state.
[0040]
At this time, the outer surface cooling was performed by flowing water from the slit nozzle, and the inner surface cooling was performed by passing water from the spray nozzle.
The inner surface cooling water amount was set to 3300-4400 T / H, and the outer surface cooling water amount was set to 1.5 m ³ / (m · min).
[0041]
Similarly, after the heated and transported steel pipe reaches steady rotation at 80 rpm, the steel pipe outlet end outer surface cooling device which has already been moved to the steel pipe outlet end 0.5 second in the range of one tenth of the steel pipe length. The outer surface of the outgoing side end was cooled for 2 seconds from the start, and the inner side cooling and the outer side cooling were started simultaneously with the cooling stop of the outer side of the outgoing side end. As the outlet end outer surface cooling device, the device shown in FIG. 12 was used.
[0042]
Table 1 shows cooling conditions and evaluation results.
The unit of the amount of cooling water on the outer surface is m ³ / (m · min), and 1 min. Per 1 m of the length of the steel pipe. When the cooling water amount per unit is m ³ and the leading time of the outer surface cooling is negative, the leading time of the inner surface cooling is indicated.
[0043]
As shown in Table 1, when the outer surface cooling is preceded, the small diameter ratio becomes 0.30% or less, but when the cooling of the steel pipe outlet side end is preceded, it becomes 0.10% or less, which is further improved. It was. When the internal cooling was preceded, the small diameter ratio deteriorated by exceeding 0.30%.
[0044]
[Table 1]

[0045]
【The invention's effect】
According to the present invention, it is possible to suppress non-uniformity of the outer diameter of the steel pipe after quenching that occurs in the vicinity of the steel pipe outlet end.
[Brief description of the drawings]
FIG. 1 is a diagram showing a method and apparatus of the present invention, FIG. 1 (a) is a block diagram showing processing steps, and FIG. 1 (b) is a conceptual diagram showing an outline of the method and apparatus. .
FIG. 2 is a graph showing the relationship between the water temperature and the elapsed time on the outlet side of the inner surface cooling water.
FIG. 3 is a graph showing the relationship between the steel pipe inner surface temperature and the steel pipe inner surface heat transfer coefficient at the steel pipe inlet side, intermediate portion and outlet side of the inner cooling water.
FIG. 4 is a graph showing the relationship between the distance from the steel pipe entry side end and the outer diameter when the inner surface cooling is quenched for 3 seconds and when it is not quenched.
FIG. 5 is a graph showing the relationship between the distance from the steel pipe entry side end and the outer diameter when the leading time for inner surface cooling is changed.
FIG. 6 is a graph showing the relationship between the distance from the steel pipe entry side end and the outer diameter when the leading time of outer surface cooling is changed.
FIG. 7 is a graph showing the relationship between the cooling start time and the small diameter ratio K.
FIG. 8 is a graph showing the relationship between the distance from the steel pipe inlet side end and the outer diameter when the outer surface cooling is preceded in the range of 2 m 2 from the outlet side steel pipe end.
FIG. 9 is a graph showing the relationship between the steel pipe dimensions (thickness, outer diameter) and the small diameter ratio K after quenching when internal cooling is preceded by 3 seconds.
FIG. 10 is a graph showing a relationship between a steel pipe size (wall thickness × outer diameter) and a small diameter ratio K at the time of inner surface 3 seconds pre-cooling, outer surface 1 second pre-cooling, and outer surface 2 seconds pre-cooling.
FIG. 11 is a graph comparing the relationship between the small diameter ratio K and the amount of bending in a steel pipe having an outer diameter of 177.8 mm and a wall thickness of 10 mm in an inner surface pre-cooling of 3 seconds and an outer surface of pre-cooling of 1 second.
FIG. 12 is a conceptual diagram showing a configuration of an outer surface cooling device at a steel pipe outlet end portion.
[Explanation of symbols]
1: heating furnace, 2: cooling device,
3: Elevated water tank 4: Outer surface cooling device,
5: Inner surface cooling device, 6: Flowing water cutoff tank,
7: Rotating device, 8: Outer surface cooling device for steel pipe outlet side end,
9: Conveying roller, 10: Cooling water control device,
11: Flow control valve, 12: Steel pipe,
13: Cooling device mount, 14: Water storage tank 15: Water supply port, 16: Pump,
17: Spray nozzle

Claims (3)

While rotating the heated steel pipe around the central axis, cooling water was supplied from an outer surface cooling device provided in parallel to the axial direction of the steel pipe to simultaneously cool the outer surface of the steel pipe in the axial direction and installed at the end of the steel pipe. A method for cooling the inner and outer surfaces of a steel pipe, wherein cooling water is supplied from the inner surface cooling device to the inner surface of the steel pipe to cool the inner surface, wherein the outer surface cooling is started before the inner surface cooling. While rotating the heated steel pipe around the central axis, cooling water was supplied from an outer surface cooling device provided in parallel to the axial direction of the steel pipe to simultaneously cool the outer surface of the steel pipe in the axial direction and installed at the end of the steel pipe. In the cooling method of the inner and outer surfaces of the steel pipe that cools the inner surface by supplying cooling water to the inner surface of the steel pipe from the inner surface cooling device, the inner surface cooling water is supplied to the outer surface of the steel pipe prior to simultaneously cooling the inner and outer surfaces over the entire length. And cooling the inner and outer surfaces of the steel pipe, wherein the cooling is performed in a range of 5/100 to 15/100 of the total length of the steel pipe from the opposite end. A device for rotating the steel pipe around the central axis, an outer surface cooling device provided parallel to the axial direction of the steel pipe, an inner surface cooling device installed from the end of the steel pipe toward the inner surface of the steel pipe, and parallel to the axial direction of the steel pipe A steel pipe inner / outer surface cooling device comprising an outer surface cooling device at a steel pipe outlet end portion that is movable in a direction and has a plurality of cooling devices.

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