JPS59190328A - Method and device for cooling metallic pipe - Google Patents

Abstract

PURPOSE:To cool uniformly and efficiently a metallic pipe and to prevent bending deformation due to cooling by applying a liquid cooling medium with high velocity on the metallic pipe of a high temp. in the internal axial direction thereof, providing an obstructive body on the releasing side of the cooling medium thereby applying fluid resistance thereto. CONSTITUTION:A high temp. steel pipe 1 is disposed on a turning roll in an adequate water tank, and a movable weir 15 is adjusted to lower a water level (b) down to the level of the steel pipe or below. High pressure water P1 is ejected from the inside pipe 9 of a double-pipe nozzle and low pressure water P2 from an outside pipe 10 to pass the cooling water with high velocity in the pipe 1 in the axial direction thereof. An obstructive body 21 is provided on the outlet side of the pipe 1 to apply adequate fluid resistance to the cooling water in the pipe 1. The cooling water is then filled fully in the pipe 1 without space from the front to the rear end thereof and the pipe 1 is uniformly and quickly cooled. If the free end of the pipe 1 is long, the parts within 500mm. respectively from the ends thereof are preferably restrained by pinch rolls, etc. to prevent oscillation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for cooling metal pipes, particularly steel pipes, in a heat treatment process and the like. The present invention is a cooling method that should be collectively referred to as the in-pipe flow cooling method, and is particularly suitable for preventing deformation of small-diameter, thin-walled pipes due to heat treatment and cooling. The pipe internal flow cooling method is a method in which a relatively high-speed cooling liquid flows from one end of a pipe to cool the pipe from its inner surface.

Conventionally, for heat treatment cooling of small-diameter, thin-walled pipes, the so-called external cooling method, in which a cooling liquid is sprayed from the outside surface, or the method of immersion cooling in a water tank have been adopted industrially. There are disadvantages such as large and frequent bending, which increases the amount of work in the subsequent finishing process and causes high costs.

In addition to being able to extremely prevent bending including end bending, the in-pipe flow cooling method of the present invention dramatically improves the degree of filling of the cooling liquid at the tube end inlet. The basic feature is that quenching defects at the edges can be completely prevented.

As described above, the present invention is primarily intended to provide an effective and economical method and industrial means for preventing bending and deformation of small-diameter tubes during the cooling process. In the following detailed description of the present invention, heat treatment cooling of steel pipes and immersion type inner and outer surface cooling methods will be used as examples to compare and contrast.

The features of this immersion-type internal surface cooling device are that the inner and outer surfaces of the steel pipe are cooled at the same time, and consideration is given to preventing bending and poor roundness. If not, the structure will be as shown in FIGS. 1 and 2. That is, the heated steel pipe 1 is transferred into the water tank 3 by the carry-in conveyor 2. The cooling water level in the water tank is at position a (the position where the steel pipe is completely immersed), the high-temperature steel pipe transported to the water tank 3 is submerged in water, and the nuclide is rotated by the turning roll 4 installed in the sow tank. Pinch roll 5
be restrained at. At the same time, high-pressure water is ejected from the inner nozzle 6 in the axial direction of the steel pipe to cool the inner surface of the steel pipe. Also,
Low-pressure water is ejected from the outer surface nozzle 7 to stir and cool the outer surface of the steel pipe.

After the required cooling time according to the wall thickness of the steel pipe, the rotation of the turning rolls 4 is stopped, the pinch rolls 5 are opened, and the steel pipe is carried out of the tank by the carry-out conveyor 8 to complete the quenching.

The immersion type internal and external cooling method uses the following methods to cool from the internal and external surfaces.
Even in extremely thick steel pipes, an extremely stable hardened martensitic l-i weave can be obtained without adding large amounts of special alloy components to improve hardenability, so it is advantageous in terms of cost. be.

On the other hand, according to the experimental results conducted by the present inventors regarding the deformation of steel pipes due to cooling, (1) Roundness, or flattening deformation, tends to increase as the steel pipe size becomes smaller (outer diameter/wall thickness → smaller). This is mostly due to non-uniform cooling of the outer surface.

In addition, non-uniform exfoliation of scale during the cooling process is also a cause of non-uniform cooling of the outer surface.

(2) The bending deformation tends to increase as the steel pipe size becomes smaller (smaller diameter, thinner wall), and, like poor roundness, it is mainly caused by non-uniform cooling of the outer surface.

This has been confirmed.

In order to achieve uniform external cooling in (1) and (2) above,
Many industrial methods and means have been proposed in the past and have made considerable progress. -1 However, even now, the problem of bending (particularly end-face bending) deformation of small-diameter steel pipes remains an important technical problem from a practical standpoint.

Particularly difficult to prevent bending and deformation is a small diameter steel pipe with an outer diameter of 80 mm or less. The present invention primarily aims to provide an industrial method and means for preventing bending deformation during the cooling process of this small diameter size.

Thin wall thicknesses of 80 mm or less, where bending is particularly likely to occur, can be sufficiently hardened with single-sided cooling, except for special upcent pipes. Furthermore, some ampsent tubes whose end wall thickness has been increased have a wall thickness that exceeds the limit of single-sided cooling, but this can be handled by adding auxiliary means to be described later.

For single-sided cooling, the tube internal flow cooling method in the atmosphere and the external surface cooling method are considered, but the latter method has a limit in reducing quench bending due to the reasons mentioned above, so we experimentally investigated the tube internal flow cooling method. .

The results of the inventors' in-pipe quenching cooling experiment are shown in Figure 3, and as is clear from this, the bending caused by cooling only the in-pipe flow is extremely small, and the bending prevention effect of this method is extremely effective. It was confirmed that this was significant. In the case of cooling only through the flow inside the pipe, it is a turbulent flow with a Ray nozzle number of 105 to 107, so the uniformity of cooling in the circumferential direction is extremely high.
Since there are no obstacles in the longitudinal direction of the tube, uniform cooling is possible in both the circumferential and longitudinal directions. Furthermore, as a result of investigating the distribution of residual scale on the inner and outer surfaces of steel pipes subjected to immersion cooling on the inner and outer surfaces, it was found that the scale thickness on the inner surface was thinner than that on the outer surface, and remained in an ``avatar-like'' shape. It was confirmed that the scale was uniform with almost no peeling.On the other hand, scale was not peeled off uniformly on the outer surface during the cooling process, and scale remained attached to it in many cases, forming an N'' avatar shape. In such cases, there is generally a noticeable tendency for the steel pipe to bend significantly.

In general, in underwater external cooling in the immersion type internal and external cooling method and in ordinary external cooling methods, unavoidable circumferential and longitudinal There is always some non-uniformity. Due to non-uniform cooling caused by the above two factors, it has been confirmed that methods that utilize cooling from the outer surface tend to cause bending and poor roundness.

In particular, bending tends to occur more easily in small-diameter, thin-walled steel pipes, and poor roundness tends to occur more easily in large-diameter, thin-walled steel pipes.

For the above reasons, to prevent bending of small diameter thin walls,
It can be said that the tube flow cooling method in the atmosphere is an extremely superior method industrially.

In the case of internal flow cooling, as shown in FIG. 3, there was almost no effect of steel pipe rotation on bending. The reason for this is that sufficient turbulence can be obtained due to the large Ray nozzle number (]05 to 107), and uniform flow cooling within the pipe can be achieved without rotating the steel pipe.

There are several serious problems in realizing such characteristic pipe flow cooling on an industrial scale.

FIG. 4 shows the relationship between the end surface of the steel pipe 1 and the inner nozzle 6 during cooling. As can be seen from the figure, the inner nozzle 6
Depending on the hole diameter, the size of the steel pipe, or the geometrical relationship between the two, the 0 part of the # pipe end face may not be cooled, or the cooling may be insufficient, resulting in, for example, poor quenching.

In Fig. 4, this problem seems likely to be solved by making the hole diameter of the nozzle 6 equal to or slightly larger than the inner diameter of the steel pipe, but according to the experiments of the present inventors, especially when the free end is long, During the cooling process, the steel pipe makes a complex oscillating motion, so the high-pressure water ejected from the nozzle with a large hole misses its target and splashes onto the outside surface of the steel pipe to be cooled, causing end face warping and other deformations. Therefore, it is necessary to restrain the end of the steel pipe on the cooling water inlet side, and the position must be 50,071 m or less from the end of the pipe to allow one swinging motion.
It is necessary to suppress this and the nozzle hole diameter to be smaller than the inner diameter of the steel pipe.

The inventors of the present invention have conducted various experiments to solve the problem of the degree of cooling water filling at the inlet of the steel pipe and the uneven cooling of the outer surface of the pipe end, and as a result, the double pipe nozzle and steel pipe shown in Fig. 5 have been developed. We have determined that this problem can be solved by installing a coolant suction promotion mechanism at the inlet end of the tube. The suction promoting mechanism has a simple structure as shown in FIG. 5, which can be adapted to any steel pipe outer diameter, and is preferable from a practical standpoint. A piston-type sliding system using air or water pressure was adopted as a method for tracking variations in the position of the tube ends.

By installing the suction promotion mechanism, it is possible to not only improve the degree of filling of the inlet with cooling water but also to prevent the cooling water from scattering on the outer surface of the steel pipe near the pipe end.

High pressure water is supplied from the inner pipe 9 of the double pipe nozzle, and the outer ring pipe i
Low-pressure water is ejected from the annular space formed between the inner tube 9 and the inner tube 9. In this way, low-pressure water is drawn into the steel pipe by the suction effect of high-pressure water at the inlet of the steel pipe, and the inlet is sufficiently filled with cooling water, solving the problem of poor cooling at the end of the pipe. It has also been found that by adjusting the balance between the ejection pressures of low-pressure water and high-pressure water, it is possible to prevent the high-pressure water from colliding with the pipe ends and scattering around.

The inner diameter of the outer ring tube of the double-pipe nozzle (-the inner diameter of the outer tube) is 1.5 mm smaller than the inner diameter of the steel tube to be cooled. It is appropriate that the diameter be up to 1.4 times the maximum inner diameter of the group of steel pipes to be cooled. This is because if the inner diameter of the outer ring tube is less than the inner diameter of the steel tube to be cooled, the cooling water may not be completely filled at the inlet of the steel tube, and if it is 14 times or more, the amount of low-pressure cooling liquid will increase unnecessarily.

The hole diameter of the nozzle that spouts high-pressure cooling liquid is made smaller than the inner diameter of the steel pipes to be cooled, but
/3 to 1/2 is acceptable.

Therefore, within the range of small diameter steel pipes, there is no need to replace the nozzle for each steel pipe size, which has great operational advantages. If the hole diameter is smaller than this, the average tube-side flow velocity of the coolant will be slow, which may cause the water temperature to rise too much at the rear end of the steel pipe, resulting in insufficient cooling capacity. Furthermore, in order to increase the average flow velocity in the pipe, problems arise such as the need for an extremely high-pressure pump, which is economically disadvantageous.

As mentioned above, one of the basic features of the present invention is that, as shown in FIG. Low-pressure water is ejected from the pipe and is sucked into the inner surface of the end of the steel pipe through a hydrodynamic action with the suction promotion mechanism, ensuring that the inlet is filled with cooling liquid and improving the cooling rate and uniformity of cooling at the end. It is to be ensured. As shown in the figure, the suction promotion mechanism includes a trumpet-shaped suction promotion plate 11 in contact with the steel pipe 1, a cylinder 12 and a piston 13 for holding the trumpet-shaped suction promotion plate 11 so as to be freely displaceable in the axial direction.
and a mechanism consisting of a spring 14.

The cylinder 12 portion is integrally provided at the axial end of the outer ring tube ]0.

The tube flow cooling method is the most effective cooling method for quenching and cooling small diameter steel pipes. However, if the rear end of the steel pipe is freely open, especially in the case of a steel pipe with a relatively large diameter among small diameters, a gap may occur near the rear end of the steel pipe, and the inside of the pipe may not be filled with cooling water. , quenching defects occur.

In order to fill the rear end of the pipe with cooling water, it would be much better to further increase the flow velocity in the pipe, but this would require a very large high-pressure pump to increase the flow velocity in the pipe, resulting in high costs. invite

As a result of various experimental studies on ways to achieve uniform and complete quenching by filling cooling water up to the rear end of the pipe, we found that there are obstacles behind the front and rear ends that create flow resistance. It was discovered that by installing a pipe, the cooling water can be filled to the rear end of the pipe without increasing the flow velocity excessively, and uniform and complete quenching can be achieved.

One embodiment of the invention is shown in FIG. 1O. 21 in FIG. 10 is an obstacle for providing flow resistance to the flow inside the pipe. It can be seen that due to the presence of the obstacle 21, the cooling water is filled to the rear end. The bold dotted line in the figure indicates the water level within the front and rear ends when no obstruction is attached, and it can be seen that a void is formed.

In addition, when such an obstacle is attached, measures are required to prevent the cooling water discharged from the steel pipe to be cooled from scattering.

Next, embodiments and application examples of the present invention will be explained. Figure 6 shows the immersion type internal and external cooling device shown in Figures 1 and 2.
The water level in the water tank 3 is lowered below position b (the level position where the steel pipe is exposed to the atmosphere), and the internal nozzle is double piped. In the figure, P1 shows high-pressure water and P2 shows low-pressure water. is supplied. In the embodiment shown in FIG. 6, since the underwater external nozzle 7 in FIG. 1 was stopped, the low-pressure water supplied to P2 was switched and used. Further, lowering the water level a to b can be easily done by moving a movable weir 15 up and down at the end of the water tank 3 using a drive device 6 and a screw jack 17. Although the embodiment shown in FIG. 6 is an immersion type inner and outer cooling device, it does not need to be used also as an immersion type inner and outer cooling device, and can also be implemented as a cooling equipment exclusively for small diameters.

However, usually the steel pipe sizes produced on one production line have a certain outer diameter range, approximately 200 m
Considering that steel pipes with an outer diameter of rn or more are processed in a medium-diameter line, and steel pipes with an outer diameter of 200m7n or less are processed in a small-diameter line, it is possible to use immersion type inner and outer cooling without the need to newly install internal flow cooling equipment for the small diameter and thin wall size. By making it possible to use it also as a device,
With the same equipment, heat treatment and cooling can be performed economically over a wide range of outer diameters and wall thicknesses. In other words, by equipping the same immersion-type internal and external cooling device with the ability to heat-treat and cool both small-diameter, thin-walled pipes and large-diameter, thick-walled pipes, it is necessary to newly install heat treatment and cooling equipment exclusively for small-diameter, thin-walled pipes. It has great industrial advantages, such as saving space for heating furnaces and installation space, and being advantageous in terms of layout.

Another embodiment of the present invention is that even for amplifier set tubes with thickened tube ends, by providing a tube end outer surface cooling device only for the amplifier set portion, bending can be prevented in the same way as in the case of only the internal flow described above. This device is designed to improve the cooling capacity of the thickened portion, and the feature of the device is that the tube end outer surface cooling device is appropriately arranged for various tube lengths. In other words, for the tube end external cooling device installed at each reference position of the tube end and selectively used, and the other end of the tube, two
It is characterized by being equipped with a pair of tube end outer surface cooling devices that are movable together with a double tube type inner nozzle and a set of tube holding devices.With the invention of this device, there is little bending deformation of upset tubes, and , stable hardening performance was obtained in the amplifier set section. In addition, it becomes possible to deal with amplifier cent tubes of arbitrary tube lengths, which is a great industrial advantage.

An embodiment according to the present invention will be described with reference to FIG. 7. The tube end outer surface cooling device 18 has a steel tube carrying-in standard e.

Provide multiple locations for each f, g+h. Amp set tube 1
9e shows a case where the length is relatively short; in this case, the carry-in reference position e is used and the tube end outer surface cooling device 18e is used. Upset pipe], the tube end on the left side in FIG. 7 of 9e changes in position by the dimensional difference between the carry-in standards e to f, so the tube end outer surface cooling device 18i needs to be moved. In this embodiment, an inner pipe 9 of an inner nozzle, an outer ring pipe 10, a set of turning rolls 4, and a vinyl roll 5 are used.
(!: Common KS! End outer surface cooling device) 81 was attached to the movable trolley 20.

Figure 8 shows the case where the amplifier set tube length is medium.
For upcent tube 19 g, tube end outer surface cooling device 1
．． Use 8g. FIG. 9 shows a case where the amplifier set tube is long, and a tube end outer surface cooling device 18h is used for the amplifier set tube 19h.

As explained above, according to the in-pipe flow cooling method using the double-pipe internal nozzle and the suction promotion mechanism of the present invention, and the device of the present invention, it is possible to almost prevent the cooling of narrow-diameter thin-walled pipes. In addition, as described in detail, many industrially advantageous applications are possible.

Note that the in-pipe flow cooling method of the present invention has a high heat treatment capacity (
In order to dramatically improve the number of steel pipes/hour), it is also possible to apply this method to a heat treatment device that cools multiple steel pipes at the same time. Furthermore, the double tube nozzle of the present invention can also be used as an inner jet nozzle for an immersion type inner and outer cooling device.

Furthermore, in the description of the present invention, an embodiment has been described in which a double-pipe internal nozzle is used when carrying out the intra-pipe flow cooling method in an immersion-type internal and external cooling device. The purpose can be achieved even without a suction promotion mechanism (including a suction promotion mechanism).

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an immersion type internal and external cooling device. FIG. 2 is a longitudinal sectional view of the immersion type internal and external cooling device. FIG. 3 is a graph showing the effect of preventing bending by cooling only the flow inside the pipe. FIG. 4 is an explanatory diagram of the internal cooling nozzle and the flow of cooling water within the pipe end. FIG. 5 is an explanatory view showing how the tube end is filled with cooling liquid by the double-tube inner nozzle and suction mechanism according to the present invention. FIG. 6 is a longitudinal cross-sectional view of an apparatus according to an embodiment of the present invention, showing that it can also be used as an immersion type internal and external cooling apparatus. Figures 7 and 8
9 and 9 are diagrams showing the arrangement of the tube end outer surface cooling device for the amplifier center portion of the amplifier set tube according to the present invention. FIG. 10 is an explanatory diagram of an embodiment in which the degree of filling of cooling water near the front and rear ends is improved by attaching obstacles near the front and rear end exits. DESCRIPTION OF SYMBOLS 1...Steel pipe, 2...Carry-in conveyor, 3...Water tank, 4...Turning roll, 5...Pinch roll, 6...Inner nozzle, 7...Underwater outer nozzle, 8... Unloading conveyor, 9...inner pipe, 10
... Outer ring pipe, 11... Suction promotion plate (mechanism), 12.
...Cylinder, 13...Piston, 14...
Spring, ]5... Movable weir, 16... Drive device, 17... Screw jack, 18... Tube end outside ml cooling device, 19... Upset tube, 20...
・Moving trolley, 21...Obstacle for adding flow resistance in a pipe Patent attorney representing the applicant Tomoyuki Yafuki (and 1 other person) Teitouri Neichi Masho (self-motivated) May 1980/? Mr. Kazuo Wakasugi, Commissioner of the Japanese Patent Office 1. Indication of the case Patent Application No. 60933 of 1982 2. Name of the invention Method and device for cooling metal tubes 3. Person making amendments Relationship to the case Applicant's address Otemachi, Chiyoda-ku, Tokyo 2-chome 6-3 name (
665) Nippon Steel Corporation 4, Agent Address: 704, 6-4-21 Akasaka, Minato-ku, Tokyo (
584) 7022 6. Contents of the amendment (1) "At the tube end inlet" on page 2, line 15 of the specification is corrected to "at the tube end inlet and outlet." (2) On page 12, line 14 of the circular, next to “I understand.” “If an obstacle is installed at the end of the pipe according to the present invention to provide flow resistance to the flow inside the pipe, the pipe diameter will become relatively large. If
The effects such as the fact that the flow velocity in the pipe can be kept relatively low are clear. ”
Insert.

Claims (1)

[Claims] 1. When cooling a high-temperature metal tube, a high-speed liquid cooling medium is applied in the axial direction inside the tube, and an obstacle is provided on the liquid cooling medium discharge side of the metal tube, so that the liquid cooling medium is A method for cooling a metal tube, characterized by imparting flow resistance. 2. A device for cooling a high-temperature metal tube, which is provided with means for freely rotating the metal tube and restraining displacement in the radial direction of the metal tube at locations within 500 mm from each axial end of the metal tube, and A metal pipe comprising: a liquid cooling medium supply means for applying a high-speed liquid cooling medium in the axial direction within the metal tube; and an obstacle that imparts flow resistance to the liquid cooling medium on the cooling medium discharge side of the metal tube. tube cooling system.