JPS6059286B2 - Metal tube cooling method and device - Google Patents

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 side of the 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 drawbacks such as large and frequent bending, which increases the amount of work in the subsequent finishing process.
It was also a cause of high costs. The in-pipe flow cooling method of the present invention not only greatly prevents bending including end bending, but also dramatically improves the degree of cooling liquid filling at the tube end inlet, and completely prevents quenching defects at the tube end inlet. There are basic characteristics to what you can do.

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 characteristics of this immersion-type inner and outer cooling device are that it cools the inner and outer surfaces of the steel pipe almost simultaneously, and that it takes care to prevent bending and poor roundness. , the structure is as shown in FIGS. 1 and 2. That is, the heated steel pipe 1 is sent into the water tank 3 while being transferred 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, is rotated by the turning roll 4 installed approximately in the center of the tank, and is restrained by the pinch roll 5. Ru. 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. Further, low pressure water is jetted out 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, a very stable hardened martensitic structure 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) circularity, or flattening deformation, tends to increase as the steel pipe size increases (outer diameter/wall thickness→larger). 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 one of the causes 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.

However, even now, the problem of bending (particularly end bending) deformation of small-diameter steel pipes remains an important technical problem from a practical standpoint. The size that is particularly difficult to prevent from bending and deforming is 80? There are small diameter steel pipes with the following outer diameters.

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. 8077!77 where bending is particularly likely to occur!
The following small diameter sizes can be sufficiently hardened by cooling on one side, except for special upset vibes.

Moreover, some upset 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 an 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 above-mentioned reasons, so we experimentally investigated the tube internal flow cooling method. did.

The results of the inventors' pipe internal flow quenching cooling experiment are shown in Figure 3, and as is clear from this, the bending caused by cooling only the pipe internal flow is extremely small, and this method prevents bending. It was confirmed that the effect was extremely significant.

In the case of cooling only the flow inside the pipe, the number of Ray nozzles is 1CP to 10.
7, the uniformity of cooling in the circumferential direction is extremely high, and since there are no obstacles in the longitudinal direction of the pipe, uniform cooling can be achieved in both the circumferential and longitudinal directions. Furthermore,
As a result of investigating the scale thickness and residual scale distribution 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 that it sometimes remained in an abattomatous shape. It was confirmed that there was almost no difference, and that it was uniform. On the other hand, the outer surface is often not peeled off uniformly during the cooling process, and scale remains attached to the outer surface, resulting in an "avatar-like" appearance.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 Directional non-uniformity always exists.

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 in small-diameter, thin-walled steel pipes, and roundness defects tend to occur 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 (lσ~107), and uniform flow cooling within the pipe can be achieved without rotating the steel pipe. This kind of characteristic tube flow cooling can be applied on an industrial scale. The relationship 6 is shown, but as can be seen from the figure, depending on the hole diameter of the inner nozzle 6 and the size of the steel pipe, or the geometric relationship between the two, the shape of the end face of the steel pipe may change. There may be cases where the C part is not cooled or the cooling is insufficient, for example,
Quenching will be defective.

In FIG. 4, it seems that this problem can be solved by making the hole diameter of the nozzle 6 equal to or slightly larger than the inner diameter of the steel pipe 1, but according to experiments conducted by the present inventors, especially when the free end is long, During the cooling process, the steel pipe undergoes 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 bending of the end and other problems. It was found that deformation easily occurs.

Therefore, it is necessary to restrain the end of the steel pipe on the cooling water inlet side, and the position is 50Trr from the pipe end! n or less, it is necessary to suppress "゜oscillation movement," and the nozzle hole diameter must be smaller than the inner diameter of the steel pipe.The length of the heat-treated steel pipe changes significantly, so the length of the heat-treated steel pipe can be changed arbitrarily. It is also necessary to construct a method for always restraining the position within 500wn from both pipe ends, suppressing the swinging movement, and preventing the pipe ends from bending.

In the conventionally disclosed method of installing a plurality of restraint devices fixed to a cooling device, it is necessary to arrange a large number of restraint devices at intervals of 500 frames or less. This is because if you do not do this, if the pipe length changes arbitrarily, the free length of the pipe end will be 500
This is because it is within m. This method requires a large number of restraint devices, resulting in a complex structure and a very expensive cooling device, making it impractical. Therefore, the inventors of the present application,
The latter method as illustrated in FIG. 7 is provided.

That is, prior to cooling the steel pipe, the steel pipe is placed at one of a plurality of delivery reference positions determined to correspond to each of a plurality of fixed restraint devices fixed to the main body of the cooling device, depending on the length of the steel pipe. Align one end of the tube. The other end of the steel pipe is fitted into a pipe end restraint device movable in the pipe axis direction. The carry-in reference position for this operation is the position where the movable tube end restraint device moves and the restraint positions of both tube ends are set during cooling.
It is selected so that it is within 50 mm from each tube end. With this method, the number of restraint devices fixed to the cooling device that restrain the middle part of the steel pipe can be reduced, and even if the pipe length changes arbitrarily, it is possible to always restrain the area within 500 m from both ends of the pipe. becomes. The moving distance of one movable restraint device is approximately equal to the interval between the intermediate restraint devices. The inventors of the present invention have conducted various experiments to solve the problem of the degree of filling of cooling water 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 found that this problem can be solved by installing a coolant suction promotion mechanism at the inlet end of the tube.

The suction promotion mechanism draws a relatively low-speed liquid cooling medium flowing around the outer periphery of a relatively high-speed flow into the front surface of the inlet of the metal tube to be cooled.
The flow path is narrowed, and this throttle interferes with the flow of the relatively high-speed liquid cooling medium ejected from the inner pipe, allowing the low-speed liquid to be well drawn into the pipe and allowing the coolant to be cooled. It spreads at the inlet of the metal pipe, and the degree of filling of the cooling medium is improved. The structure shown in FIG. 5, which can accommodate any steel pipe outer diameter, is simple and preferred 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 promoting 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 1
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 steel pipe inlet, and the inlet is sufficiently filled with cooling water, solving the problem of poor cooling at the pipe end. In addition, by adjusting the balance between the jetting pressure of low-pressure water and high-pressure water,
It has been found that this method also has the effect of preventing high-pressure water from colliding with the end of the pipe and scattering around. The inner diameter of the outer ring tube of the double tube nozzle (=outer diameter of the outer tube) is larger than the inner diameter of the steel tube to be cooled, and is suitably up to about 1.4 times the maximum inner diameter of the group of steel tubes to be cooled.

This is because if the inner diameter of the outer ring pipe is less than the inner diameter of the steel pipe to be cooled, the cooling water may not be completely filled at the steel pipe inlet.
This is because if it is 1.4 times or more, the amount of low-pressure coolant will increase unnecessarily. The hole diameter of the nozzle for spouting the high-pressure cooling liquid is made smaller than the inner diameter of the steel pipes to be cooled, but is allowed to be about 213 to 1 h, which is the minimum inner diameter of the group of steel pipes to be cooled.

This eliminates the need to replace nozzles for each steel pipe size within the range of small-diameter steel pipes, which has many operational advantages. If the hole diameter is smaller than this, the average in-pipe flow velocity of the cooling liquid 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 10 and is sucked into the inner surface of the end of the steel pipe by a hydrodynamic action with the suction promotion mechanism, thereby ensuring that the inlet is filled with cooling liquid and increasing the cooling rate and uniformity of cooling at the end. To ensure sex. It is.

As shown in the figure, the suction promotion mechanism is comprised of a ratchet-shaped suction promotion plate 11 in contact with the steel pipe 1, and a mechanism consisting of a cylinder 12, a piston 13, and a spring 14 for holding the suction promotion plate 11 so as to be freely displaceable in the axial direction. The cylinder 12 portion is integrally provided at the axial end of the outer ring tube 10.
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, lowering the water level in the water tank 3 to below position b (the level position where the steel pipe is exposed to the atmosphere), and double-layering the inner nozzle. It is shown as a pipe, and in the figure, high pressure water is supplied to P1 and low pressure water is supplied to P2. 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. Furthermore, lowering the water level a to b can be easily done by moving the movable weir 15 at the end of the water tank 3 up and down using the drive device 16 and the 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 facility exclusively for small diameters. However, the steel pipe sizes normally manufactured on one production line have a certain outer diameter range, approximately 2007177! Steel pipes with an outer diameter of more than 200mm are medium diameter lines. Considering that the following items are processed in a small diameter line, the same general equipment can be used in combination with an immersion type internal and external cooling device without the need to newly install internal flow cooling equipment specifically for the small diameter and thin wall size. This means that 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 upset tubes with thickened tube ends, by providing a tube end outer surface cooling device only for the upset section, bending can be prevented in the same way as in the case of only the internal flow described above. The feature of the device is that the tube end outer surface cooling device is appropriately arranged for various tube lengths in order to obtain the effect of improving the cooling capacity of the thickened portion.

That is, a tube end external cooling device is installed at each reference position of the tube end and is selectively used, and at the other end of the tube, there is a double tube inner nozzle and a set of tube holding devices that are movable.
It is characterized by being equipped with a pair of tube end outer surface cooling devices, and with the invention of this device, there is less bending deformation of the upset tube, and stable hardening performance can be obtained at the upset portion. . Moreover, it becomes possible to deal with upset pipes of arbitrary pipe lengths, which has many industrial advantages. An embodiment of the present invention will be described with reference to FIG. 7. A plurality of pipe end outer surface cooling devices 18 are provided for each of the steel pipe import standards E, f, g, and h.

The case where the upset pipe 19e is relatively short is shown, and in this case, the carry-in reference position e is used and the tube end outer surface cooling device 18e is used. Regarding the left side tube end of the upset tube 19e in FIG.
needs to be moved. In this embodiment, a method is adopted in which the tube end outer surface cooling device 181 is attached to the moving carriage 20 together with the inner tube 9 of the inner nozzle, the outer ring tube 10, and a set of turning rolls and male pinch rolls 5. FIG. 8 shows a case where the upset pipe length is medium, and the upset pipe 19
18 g of the tube end outer surface cooling device is used for 18 g. 9th
Although the figure shows a case where the length of the upset tube is long, a tube end outer surface cooling device 18h is used for the upset 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 cooling curves, especially in small-diameter thin-walled pipes. As described in detail, it can be applied with many industrial advantages.

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. In addition, in the description of the present invention, in the immersion type internal and external cooling device,
Although we have described an embodiment in which a double-pipe inner nozzle is used when implementing the pipe flow cooling method, in this case, the purpose can be achieved without necessarily using a double-pipe inner nozzle (including a suction promotion mechanism). Ru.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the immersion type internal and external cooling device, Figure 2 is a vertical cross-sectional view of the immersion type internal and external cooling device, Figure 3 is a graph showing the bending prevention effect by cooling only the flow inside the pipe, and Figure 4 is an explanatory diagram of the flow of cooling water inside the inner cooling nozzle and the pipe end,
Fig. 5 is an explanatory diagram showing how the pipe end is filled with cooling liquid by the double pipe inner nozzle and suction mechanism according to the present invention, and Fig. 6 is an immersion type inner and outer cooling device according to an embodiment of the present invention. Figures 7 and 8 are vertical sectional views of the device showing that it can also be used in combination with
9 and 9 are diagrams showing the arrangement of the tube end outer surface cooling device for the upset portion of the upset tube according to the present invention. 1... Steel pipe, 2... Carrying conveyor, 3... Water tank,
4... Turning roll, 5... Pinch roll, 6
...Inner surface nozzle, 7...Underwater outer surface nozzle, 8...
Unloading conveyor, 9... Inner pipe, 10... Outer ring pipe, 11
... Suction promotion plate (mechanism), 12 ... Cylinder, 1
3... Zestone, 14... Spring, 15... Movable weir, 16... Drive device, 17... Screw jack, 18... Pipe end outer surface cooling device, 19... Upset pipe, 20...Moving trolley.

Claims (1)

[Claims] 1. A method for cooling a high-temperature metal tube, the method comprising: a plurality of fixed restraints fixed to a cooling device main body according to the length of the metal tube to restrain displacement of the tube in the radial direction. Aligning one end of the metal tube with one of a plurality of metal tube import standards determined to correspond to each of the devices, move the metal tube in a direction perpendicular to its axial direction and transport it into the cooling device main body, and A plurality of fixed restraint devices are actuated to restrain the radial displacement of the tube at a position within 500 mm from one end of the tube and at predetermined intervals in the axial direction, and at the same time to restrain the radial displacement of the tube internal flow injection nozzle and the tube. A movable cart carrying a restraining means for restraining the pipe is moved in the axial direction of the pipe, and stopped at a position where the restraining means is within 500 mm from the other end of the pipe in the axial direction. 1. A method for cooling a metal tube, characterized in that the metal tube is cooled by injecting a liquid cooling medium from an intra-pipe flow injection nozzle under a condition in which displacement of the tube radial direction at the axial end is restrained. 2. A method for cooling a high-temperature metal tube, which corresponds to each of a plurality of fixed restraint devices fixed to a cooling device main body according to the length of the metal tube and restraining displacement of the tube in the radial direction. Aligning one end of the metal tube with one of the plurality of metal tube carrying standards determined as above, the metal tube is moved in a direction perpendicular to its axial direction and carried into the cooling device main body, and the plurality of fixed restraint devices are moved. actuate to restrain the radial displacement of the tube at a position within 500 mm from one end of the tube and at a predetermined interval in the axial direction, and also to restrain the radial position of the internal flow injection nozzle and the tube. The loaded mobile cart is moved in the axial direction of the tube, and stopped at a position where the restraining means is within 500 mm from the other end of the tube in the axial direction, and the restraining means causes the tube at the axial end of the tube to be stopped. A relatively high-speed liquid cooling medium is ejected from the inner tube of the inner tube flow injection nozzle with a double tube structure while radial displacement is restrained, and a liquid cooling medium is formed between the outer circumferential surface of the inner tube and the outer circumferential surface of the outer tube. 1. A method for cooling a metal tube, characterized in that the metal tube is cooled by jetting out a relatively low-velocity liquid cooling medium from an annular space in which the metal tube is cooled. 3 A device for cooling a metal tube by applying a high-speed liquid cooling medium in the axial direction of the tube, which is fixed to the main body of the cooling device at a predetermined interval in the length direction of the tube, and restrains displacement of the tube in the radial direction. a plurality of fixed restraint devices, and a plurality of fixed restraint devices located at a predetermined distance from the cooling device main body in a direction perpendicular to the tube axis direction and within 500 mm in the tube axis direction so as to correspond to each of the fixed restraint devices. A number of import standards are established to specify the metal pipe, and are selected and used depending on the length of the metal pipe, as well as the following double pipe nozzle and the restriction of radial displacement of the pipe within 500 mm from the axial end of the pipe. A movable trolley mounted on the movable trolley is equipped with a restraining means and is movable in the tube axis direction. a double tube nozzle configured to eject a relatively low-velocity liquid cooling medium from an annular space formed between the outer circumferential surface of the outer tube and the outer circumferential surface of the outer tube; an axial end of the outer tube of the double tube nozzle; Suction promotion plate (truncated conical tube) that connects the axial end of the metal tube to be cooled
It consists of a cylindrical part that integrally holds this suction promotion plate and is slidable in the axial direction with respect to the outer tube of the double-pipe nozzle, and a cylinder and a piston for displacing this in the axial direction and holding it in a predetermined position. A metal tube cooling device consisting of a suction promotion mechanism. 4. A method for cooling a high-temperature metal tube, which corresponds to each of a plurality of fixed restraint devices fixed to a cooling device main body according to the length of the metal tube and restraining displacement of the tube in the radial direction. Aligning one end of the metal tube with one of the plurality of metal tube carrying standards determined as above, the metal tube is moved in a direction perpendicular to its axial direction and carried into the cooling device main body, and the plurality of fixed restraint devices are moved. actuate to restrain the radial displacement of the tube at a position within 500 mm from one end of the tube and at a predetermined interval in the axial direction, and also to restrain the radial position of the internal flow injection nozzle and the tube. The loaded mobile cart is moved in the axial direction of the tube, and stopped at a position where the restraining means is within 500 mm from the other end of the tube in the axial direction, and the restraining means causes the tube at the axial end of the tube to be stopped. While the radial displacement is restrained, a relatively high-speed liquid cooling medium is ejected from the inner tube of the inner tube flow injection nozzle with a double tube structure, and the liquid coolant is jetted out at a relatively high speed between the outer circumferential surface of the inner tube and the outer circumferential surface of the outer tube. A relatively low-velocity liquid cooling medium is ejected from the formed annular space to cool the metal tube, and the liquid cooling medium is applied to the outer circumferential surface of a portion of the metal tube that is thicker than other portions. A method for cooling a metal tube, characterized in that the metal tube is cooled by using a metal tube. 5 A device for cooling a metal tube by applying a high-speed liquid cooling medium in the axial direction of the tube, which is fixed to the main body of the cooling device at a predetermined interval in the tube length direction to restrain displacement of the tube in the radial direction. a plurality of fixed restraint devices, and a plurality of fixed restraint devices located at a predetermined distance from the cooling device main body in a direction perpendicular to the tube axis direction and within 500 mm in the tube axis direction so as to correspond to each of the fixed restraint devices. A number of import standards are established to specify the metal tube, and are selected and used depending on the length of the metal tube, as well as the following double tube nozzle and the restriction of radial displacement of the tube within 500 mm from the axial end of the tube. A movable trolley mounted on the movable trolley is equipped with a restraining means and is movable in the tube axis direction. a double tube nozzle configured to eject relatively low-velocity liquid cooling medium from an annular space formed between the outer circumferential surface of the outer tube and the outer circumferential surface of the outer tube; and an axial end of the outer tube of the double tube nozzle. A suction promoting plate (a truncated conical tube) connects the axial end of the metal tube to be cooled, and the suction promoting plate is held integrally and slides in the axial direction with the outer tube of the double tube nozzle. A suction promoting mechanism consisting of a freely movable cylindrical part, a cylinder and a piston for displacing the cylindrical part in the axial direction and holding it in a predetermined position, and a suction promoting mechanism that is arranged at a predetermined interval in the axial direction of the metal tube, A plurality of external cooling devices are provided that inject a liquid cooling medium onto the outer circumferential surface of the thicker part than the other parts, and a plurality of external cooling devices are provided that inject a liquid cooling medium onto the outer circumferential surface of the thick part at one end in the axial direction of the metal tube. A metal tube cooling device equipped with a freely displaceable external cooling device.