JP5851136B2 - Cooling device and cooling method for metal tube after heating - Google Patents

Description

The present invention relates to a cooling device for rapidly cooling a heated metal tube with a cooling liquid in a heat treatment step of the metal tube or a metal tube manufacturing step by welding, and a method for cooling the heated metal tube using the cooling device. About.

Steel pipes, aluminum alloy pipes, titanium alloy pipes, zirconium alloy pipes and the like are manufactured by a method such as cold working, hot working, or continuous welding pipe making. In these methods, after cutting to a certain length after pipe making, or continuously after the pipe making machine, the metal pipe is placed at a predetermined temperature, for example, about 950 ° C. or more in the case of a steel pipe, in order to obtain desired characteristics. Then, a heat treatment such as quenching that rapidly cools after heating or a residual strain removing process is performed. In the continuous welding pipe manufacturing method, the cooled metal pipe is cut into a product dimension length by a traveling cutting machine after the dimensional accuracy is increased by a finish forming roll.

As a method of rapidly cooling a metal pipe after heating, generally, a plurality of hole-shaped spray nozzles having injection holes of a certain hole size are provided on the outer periphery of the metal pipe in order to perform highly efficient cooling in a short time. There is used a method in which a cooling liquid is sprayed by using a gas and is cooled within a few seconds to a few dozen seconds by heat conduction to near the temperature of the cooling liquid (for example, Patent Documents 1 to 7). Then, the hole-shaped spray nozzle and the metal tube can be relatively moved in the central axis direction of the metal tube, or the hole-shaped spray nozzle and the metal tube can be relatively rotated around the center axis of the metal tube. Has also been done. In addition, a double structure of the outer cylinder and the inner cylinder is used, and cooling water is gradually discharged from the outlets of two or more ring-shaped nozzles into the inner cylinder through which the steel pipe is passed. There is also known an apparatus that cools the metal tube by immersing it in the water (Patent Document 8). In this apparatus, the size of the outlet is constant, and can the supply water pressure be increased to increase the amount of cooling water? Need to increase the number of outlets.

2 to 4 are schematic perspective views showing a conventional cooling method using a hole-shaped spray nozzle array. FIG.
Is a method of cooling using the cooling device 1 in which hole spray nozzles are arranged at substantially constant intervals on the outer periphery of the metal tube 2. FIG. 3 shows a cooling method using the cooling device 1 in which a plurality of sets of hole-shaped spray nozzle arrays are arranged in the direction of the central axis of the metal tube 2. FIG. 4 shows a method of cooling the cooling device 1 having a plurality of hole spray nozzle arrays arranged in the circumferential direction of the metal tube 2. However, in the hole-shaped spray nozzle array as shown in FIGS. 2 and 3, the cooling liquid collides with the outer surface of the metal tube in a spot shape, resulting in uneven cooling capacity and unevenness on the surface of the metal tube. As shown in FIG. 4, in the method of rotating the hole-shaped spray nozzle row, the unevenness of the cooling capacity is reduced, but there is a drive system such as a motor around the cooling device, which is not preferable for maintenance, and there is room for improvement. Remains.

As in the conventional cooling method, the pattern until the coolant sprayed from the many hole-shaped spray nozzles discretely arranged on the outer periphery of the metal tube collides with the outer surface of the metal tube is discrete, and cooling is caused by interference. This causes a non-uniformity and a time difference, and causes deformation and uneven surface properties in the metal tube, which is not preferable. Although ideas such as increasing the number of hole-shaped spray nozzles or moving the hole-shaped spray nozzle and the metal tube relative to each other can be considered, there is a limit in principle in any case.

The hole spray nozzle of the conventional example controls the injection amount of the coolant by changing the pressure applied to the coolant flowing through the nozzle having a constant hole size, but the control range is limited to a narrow range. In addition, when using industrial water that is practically used as a cooling liquid, the nozzle hole may be clogged with foreign matter mixed in the industrial water, resulting in an unintended injection pattern of the cooling water, making maintenance difficult to remove the clogging. Met.

Therefore, in the conventional example, it is required to improve the maintainability of removing the clogging of the foreign matter in the injection range of the injection portion of the hole-shaped spray nozzle and the wide control range of the flow rate and flow rate of the coolant. In addition, when the metal pipe to be cooled is held in the horizontal direction, there is a difference in the influence of gravity depending on which direction of the coolant is injected from the top and bottom on the outer periphery of the metal pipe, but by selecting the injection conditions It is important to secure a wide control range of the flow rate and flow rate of the coolant from the viewpoint that the influence should be minimized in practical use.

When multiple hole spray nozzles are used in a spatially distributed manner on the outer periphery of the metal tube, the entire circumference of the metal tube is harmonized with the spatial arrangement of the nozzles (nozzle row) and the spray pattern of each nozzle. However, since the spray from one nozzle forms a water stream with a solid angle, the work of reconciling the spatial arrangement and the spray pattern is complicated and difficult. Further, the theoretical limit that the coolant is supplied discretely from a finite number of supply units cannot be exceeded, and cooling unevenness still occurs.

JP 53-117610 A JP 59-140331 A Japanese Patent Laid-Open No. 06-073455 JP 2001-246408 A JP 2008-261018 A JP 2008-296271 A JP 2010-242153 A Japanese Utility Model Publication No. 04-069445

In a method of heating and quenching while continuously manufacturing a metal tube and conveying the metal tube, or a method of heating and quenching with a metal tube of a certain length standing still, the metal tube is a high frequency induction heating device For example, a method in which a cooling liquid is sprayed on the outer periphery of the metal tube and then rapidly cooled after being heated to a uniform temperature symmetrical with respect to the central axis by the above method is generally employed. In these methods, when a metal tube after heating is quenched by injecting a cooling liquid from a cooling device, the deformation of the metal tube due to the difference in heat treatment history of each part caused by uneven cooling of each part of the metal pipe And the occurrence of surface irregularities is a problem. The non-uniform cooling is caused by the non-uniform amount of water and water pressure sprayed at each part, and the injection position that should be on a perfect circle in the circumferential direction of the metal pipe is disturbed by the part in the axial direction of the metal pipe. Arise.
Therefore, it is necessary to quench the metal tube uniformly and symmetrically with respect to its central axis. When the metal tube is arranged in the horizontal direction, the sprayed coolant has different gravity effects on the upper, lower and side surfaces of the metal tube, so the metal tube is arranged in the vertical direction. Compared to, uniform cooling of the entire circumference of the metal tube becomes more difficult.

If the metal tube cannot be cooled rapidly and symmetrically to the central axis, the metal tube partially contracts and deforms due to the difference in the mechanical properties of the metal that occurs in the circumferential direction due to the heat treatment temperature history dependence. Product quality and operational problems such as deterioration of roundness, unevenness of the tube surface, bending in the long direction and occurrence of meandering occur. In addition, the state of the oxide generated on the surface of the metal tube from heating to cooling becomes non-uniform, and in the subsequent pickling step, the surface property of the metal tube after the removal of the oxide is uneven It becomes.

Furthermore, in the method in which the metal tube is heated by the heating device while being transported in the horizontal direction at a constant speed, and then rapidly cooled by the cooling device and heat-treated, the cooling liquid is placed on the hot metal tube by the cooling device disposed immediately after the heating device. If the spray is sprayed, the coolant may unintentionally flow back to the heat source side of the heating device depending on the spraying conditions, possibly damaging the heat source, and it is necessary to prevent the back flow to the heat source side by an appropriate method.

When trying to rapidly cool a metal tube symmetrically about its central axis, the cooling method by discrete arrangement of hole-shaped spray nozzles has the above-mentioned problems to be solved. The present invention solves the above-mentioned problems by spraying a coolant in the form of a liquid film. In the following description, a case where cooling water such as typical industrial water is used as the cooling liquid will be described. However, the cooling liquid may be a cooling medium such as oil other than water.

The cooling device of the present invention is a cooling device that cools the heated metal tube by injecting cooling water onto the outer surface of the metal tube from an injection port arranged concentrically with the metal tube on the outer periphery of the metal tube.
This cooling device includes a first member and a second member, and has a cooling water passage and an annular slit nozzle inclined in a truncated cone shape connected to the cooling water passage.
The slit nozzle is composed of an annular slit opening formed by the leading edge of the slit inner edge and the outer edge of the slit, and has an injection port for injecting the coolant in the form of a liquid film obliquely on the outer surface of the metal tube. Yes.
Further, the inner edge of the slit can protrude in the cooling liquid injection direction by a length L from the outer edge of the slit, and the length L and the slit interval d of the slit opening are set between the first member and the second member. It can be adjusted by relative movement.
The frustoconical inclination leading to the inner edge of the slit is when the injection port is arranged concentrically with the metal tube.
It is preferably 30 ° to 60 ° expressed by an angle θ with respect to the central axis of the metal tube.

As one aspect of the cooling device, the first member is an inner annular body, the second member is an outer annular body, and a cooling water flow path is provided inside the outer annular body. An annular slit nozzle is formed between the tip-side inner surface of the outer annular body and the tip-side outer surface of the inner annular body. The inner annular body and the outer annular body are relatively movable in the central axis direction of the metal tube.

Using the cooling device, the metal pipe is run in the forward direction with the injection direction of the cooling water injected from the injection port, or the cooling device is moved in the direction opposite to the injection direction with respect to the stationary metal pipe. And
The metal tube after heating can be cooled. In this method, the length L can be adjusted so that the cooling liquid is stably ejected in the form of a liquid film, and the liquid film collides on the same circle of the outer circumference of the metal tube.

In the above cooling method, the angle of the cooling water that collides with the collision position on the same circular circumference of the outer surface of the metal tube is preferably as close to θ or as close to θ as possible.
By adjusting the slit interval so as to maintain the angle, the cooling water in the form of a water film colliding with the metal tube can flow in contact with the metal tube in the form of a water film.

If the slit interval is excessively large or the pressure of the cooling water to be injected is excessively small, the ejection speed becomes insufficient, the influence of gravity is large, and the angle of collision with the outer surface of the metal tube is θ. It will deviate from the ideal state, and the collision position of the water film will deviate from the same circle on the upper, side and lower surfaces of the metal tube, causing defects in the quality of the metal tube such as bending. Become. In order to prevent this, it is necessary to eject the cooling water at a sufficient speed and flow rate so that the water film does not collapse due to gravity.

As a result of the injection angle θ applied to the water film-like cooling water, the cooling water becomes a water film-like flow with a uniform thickness along the outer surface of the metal tube, the cooling becomes uniform, and the cooling water contacts the outer surface of the metal tube. Cooling efficiency by keeping the time long can be increased, and the occurrence of bending of the metal tube due to insufficient cooling can be suppressed. Furthermore, when this cooling device is provided at the rear stage of the heating device and the metal tube is run, the sprayed water splash or water flow is directed on the upper side of the outer surface of the metal tube toward the heating equipment upstream of the metal tube. Backflow can be reduced and equipment damage can also be reduced.

Moreover, in the said cooling method, it is preferable to use the cooling device which made the value which remove | divided the cross-sectional area of the said cooling water flow path by the area of the said slit opening part 2-5. As a result, the cooling water can be stably fed in the circumferential direction inside the annular slit, so that the cooling water can be jetted with a more uniform flow rate and pressure symmetrically to the central axis of the metal tube.

When the cooling device having the annular slit nozzle structure of the present invention is used, the cooling water is sprayed in a uniform amount all at the same time on all the same circles on the outer circumference of the heated metal tube. Is cooled uniformly and symmetrically around its central axis, so that the entire circumference of the metal tube can be uniformly cooled, and the occurrence of a temperature difference in the circumferential direction of the metal tube due to cooling using a conventional spray nozzle is reduced. Distortion / deformation, bending, and meandering of the metal tube due to uneven cooling in the circumferential direction of the metal tube are alleviated, and unevenness in surface properties that appears after removal of the oxide film formed on the surface of the metal tube by heating is also improved.

The perspective view which shows notionally the aspect of the cooling by the cooling device of this invention in contrast with the conventional method shown in FIGS. The schematic perspective view which shows the cooling mode (Example 1) by the hole-shaped spray nozzle row | line | column of a prior art example. The schematic perspective view which shows the cooling mode (Example 2) by the hole-shaped spray nozzle row | line | column of a prior art example. The schematic perspective view which shows the cooling mode (Example 3) by the hole-shaped spray nozzle row | line | column of a prior art example. The longitudinal cross-sectional view which shows the one aspect | mode of the cooling device of this invention. In the cooling device of this invention, explanatory drawing about the slit space | interval of a slit opening part. In the cooling apparatus of this invention, explanatory drawing of the length L which a slit inner edge protrudes in the injection direction of a cooling water rather than a slit outer edge. The cooling device of this invention WHEREIN: Explanatory drawing of ratio of the cross-sectional area of a cooling water flow path, and the opening area of a slit. The schematic side view which shows typically the Example which applied the cooling device of this invention to the heat processing equipment provided in a part of continuous welding pipe manufacturing machine.

As one aspect of the cooling device of the present invention, the first member is an inner annular body, the second member is an outer annular body, a cooling water flow path is provided inside the outer annular body, An embodiment will be described in which an annular slit nozzle is formed between the front-end-side outer surfaces of the inner annular body so that the inner annular body and the outer annular body can be moved relatively in the central axis direction of the metal tube.

As shown in FIG. 1, the cooling device 1 of the present invention comprises an annular body, and a metal tube 2 as in the conventional method.
The cooling water flow W is formed as a water film so as to be squeezed from the annular slit nozzle with respect to the central axis of the metal tube 2 and is sprayed obliquely on the outer surface of the metal tube 2.
The metal tube 2 is rapidly cooled after being heated to a uniform temperature symmetrical to its central axis by a high frequency induction heating device or the like (not shown). In the method of using the cooling device of the present invention, when the metal tube is used without traveling, the cooling device is moved in the direction opposite to the traveling direction of the metal tube shown in FIG. Spray cooling water.

FIG. 5 shows an embodiment in which the cooling device of the present invention is arranged concentrically with a metal tube that runs in the horizontal direction. As shown in FIG. 5, the cooling device 1 includes an inner annular body 3 and a screw structure 1 on the outer side.
1 and the outer annular body 4 fitted by a slide structure or the like.
The outer annular body 4 has a cooling water passage 5 and a slit 6 connected to the cooling water passage 5 inside.

The cooling water flow path 5 formed inside the outer annular body 4 may be provided in an annular shape around the entire circumference of the outer annular body 4, but may be provided only in part. A cooling water supply port 7 is provided from the cooling water flow path 5 to the outside of the outer annular body 4 and connected to a cooling water supply pipe (not shown), and the cooling water whose water pressure is adjusted is supplied.

The inner surface of the outer annular body 4 and the outer surface of the inner annular body 3 are inclined in a truncated cone shape so as to form a slit 6 connected to the cooling water flow path 5. An annular opening 10 is formed by the outer edge 9. The slit 6 may have a space gradually narrowed toward the opening 10 in the same manner as a normal tapered nozzle. Cooling water is injected from the annular opening 10 into the atmosphere. As shown in FIGS. 6A and 6B, the slit in which the cooling water is jetted by relatively moving the inner annular body 3 forming the slit inner edge 8 and the outer annular body 4 forming the slit outer edge 9. By adjusting the slit interval d of the opening, it is possible to control the injection amount and the injection speed of the cooling water per unit time.

The inner annular body 3 and the outer annular body 4 are fitted so as to be relatively rotatable by the screw structure 11 at a position opposite to the annular opening 10. The slit interval can be adjusted by this relative rotation. And the annular clearance 12 for adjusting the slit space | interval d of a slit opening part by making the inner side annular body 3 and the outer side annular body 4 relatively movable in the center-axis direction of both is provided between both. For adjustment of the slit distance d, other relative position adjusters such as a slide mechanism may be used instead of the screw structure. The slit interval d is a uniform value over the entire circumference of the annular slit nozzle. An O-ring 13 is provided as a watertight seal at an intermediate portion between the cooling water flow path 5 and the clearance 12. The axial lengths of the inner annular body 3 and the outer annular body 4 may be about 200 mm, for example. The inner annular body 3 and the outer annular body 4 can be manufactured by cutting a steel material or the like.

As shown in FIG. 5, the diameter D <b> 2 of the slit inner edge 8 is naturally larger than the diameter D <b> 1 of the outer surface of the metal tube 2 because it is necessary to pass the metal tube 2. The difference between the diameters D1 and D2 is preferably 40mm-10
About 0 mm. In FIG. 5, the diameter D3 of the position of the end opposite to the position of the slit inner edge 8 is made larger than D2, but this is to facilitate insertion of the metal tube into the cooling device from the upstream side. Yes, D2 and D3 may be the same size.

As shown in FIG. 5, the cooling water is applied to the outer surface of the metal tube 2 in such a direction as to converge toward the center axis of the metal tube 2 at a spray angle of an angle θ with respect to the center axis of the metal tube. It is sprayed in the form of a water film in the atmosphere. At this time, the injection water pressure and the slit interval d are adjusted so that the angle of the cooling water that collides with the collision position ab on the circumference of the outer surface of the metal tube 2 is maintained as much as possible. The collision position a-b on the circumference is desirable for uniform cooling as it is on or close to a perfect circle formed in a cross section perpendicular to the central axis of the metal tube. The collision position ab changes in the direction of the central axis of the metal tube according to the value of θ and the difference between D1 and D2.

The cooling water W in the form of a water film that has collided with the collision position a-b on the same circumference of the perfect circle flows for a certain length along the entire circumference of the metal tube 2, and partly evaporates. Some leave downwards. Thus, even when the metal pipe 2 is positioned in the horizontal direction by spraying the cooling water at the spray angle of the angle θ, many heat exchanges are performed at the collision position on any of the upper side, the side surface, and the lower side. Instead of detaching from the surface of the metal tube immediately after the operation is performed, the water film continues to contact the entire circumference of the metal tube for a certain length while maintaining a certain thickness, increasing the chance of contacting the cooling water. Thus, the uniform cooling capacity of the entire circumference of the metal tube can be enhanced in a non-immersed state in the cooling water. Further, the amount of the splash-like cooling water A that scatters on the upper side of the outer surface of the metal tube 2 in the direction opposite to the traveling direction is reduced.

The spray angle θ of the water-film-like cooling water is preferably in the range of about 30 ° to 60 °. With such an angle, the flow of the cooling water after reaching the metal tube is changed in the direction of the central axis of the metal tube. Can be guided in parallel. The spraying angle θ is selected appropriately depending on the type of the metal tube to be cooled, the heating temperature of the metal tube, the desired cooling rate, the amount of cooling water, and the like. When the spraying angle θ is smaller than 30 °, the arrival of the water flow to the metal pipe varies, and the surface of the metal pipe is likely to be uneven or bent. In addition, when the spray angle θ is larger than 60 °, the water flow reaches the metal tube better, but a reverse flow to the heating device such as a high-frequency induction heating device also occurs, and the cooling start point is set to the collision position of the cooling water. It cannot be determined with certainty, the cooling state fluctuates, and the surface of the metal tube is uneven or bent.

Thus, the conventional hole-shaped spray nozzle array is formed by spraying water film-like cooling water, which is jetted so as to be conically constricted from the annular opening 10 toward the central axis of the metal pipe 2, onto the metal pipe 2. The surface of the obtained metal tube product can reduce fluctuations in the spraying state of the cooling water, such as when sprayed in droplets using the, stabilize the cooling state, and reduce the occurrence of uneven cooling capacity. Quality can be improved.

For example, in the case of solution heat treatment of a stainless steel pipe, a steel pipe traveling at a line speed of about 1 to 3 m / min is heated to about 1100 ° C. with a heating device and then cooled to about 40 ° C. or less with a cooling device at a cooling rate of 50 ° C./second. Although it is necessary to rapidly cool as described above, even in such an on-line pipe making method, the metal pipe can be rapidly cooled symmetrically and uniformly with respect to its central axis.

The metal pipes that are subject to cooling devices vary widely in material, pipe diameter, wall thickness, heat treatment conditions, etc., so cooling is required to obtain a cooling state according to the characteristics and processing speed of metal pipe products including heat capacity. It is desirable to be able to adjust the capacity. The system for spraying cooling water can cope with the change in the cooling condition if the pressure and flow rate can be adjusted respectively. In the cooling device of the present invention, since the slit interval is a uniform value around the entire circumference of the annular slit nozzle, the slit interval is adjusted so that it is sprayed symmetrically and uniformly on the central axis of the metal tube. A desired cooling effect is obtained.

As shown in FIG. 6, the slit interval d can be changed according to the cooling condition by relatively moving the inner annular body 3 and the outer annular body 4 in the central axis direction of both. FIG. 6 (A)
FIG. 6B shows a state where the relative distance is increased to reduce the slit interval d, and FIG. 6B shows a state where the slit interval d is increased.

When observing the injection section in a cross section in the injection direction of the cooling water, if the cooling water is in a state where both sides of the water film are constrained at the position where the cooling water finally leaves the slit opening, When the cooling water is released from the ends of both sides constrained from the difference between the pressure of the air and the atmospheric pressure of the separation destination toward the outside of the restriction, the cooling water bends outward in the injection direction at the time of separation. Or, many splashes occur, the collision position of the upper, lower, and side surfaces of the metal tube deviates from the same circle, the spray pattern spreads over a wide range, and the splashes are scattered. There is a bug.

However, if the slit inner edge 8 is slightly protruded in the cooling water injection direction from the position of the slit outer edge 9, the flow of the cooling water forms a water film with a uniform thickness, which increases the effect of suppressing the disturbance of the injection water flow. . FIG. 7 is a diagram for explaining the length L of the slit inner edge 8 protruding from the slit outer edge 9 (hereinafter referred to as “projection length L of the slit inner edge”) as viewed in the cross section in the cooling water injection direction. For example, when a nozzle having a slit opening interval constant of 1 mm and a projection length L of the inner edge of the slit as a parameter is produced, the stability of water sprayed into the atmosphere is such that the length L is 5 m.
When it becomes m or more, the flow of the cooling water forms a water film, and the turbulence of the sprayed water flow can be suppressed. The length L is sufficient if it is about 30 mm at the longest, but in principle, D1 = D shown in FIG.
This is possible up to 2. However, a clearance sufficient to avoid contact between the outer surface of the metal tube 2 and the slit inner edge 8 is necessary.

The protruding length L of the slit inner edge can be determined according to the slit opening interval d, the jet water pressure, the type of the cooling medium, the difference between the diameter D1 of the slit inner edge 8 and the diameter D2 of the outer surface of the metal tube 2, and the like.
As a result, the cooling water can be sprayed onto the exact same circumference of the outer surface of the metal tube 2 only by adjusting the length L by relatively moving the inner annular body 3 and the outer annular body 4. It becomes like this.

The cooling device needs to be able to cope with a case where a metal tube product having a large heat capacity passes at a high speed and a case where a metal tube product having a small heat capacity passes at a low speed. In the former case, it is necessary to increase the cooling capacity. In general, when the upper limit of the flow rate is determined from the supply capacity of the cooling water, the slit distance d is increased in order to increase the contact surface area of the high temperature object and the cooling water while using the cooling water having a constant flow rate within the limit. It is good to squeeze out at high speed.

When there is a margin in the flow rate and rapid cooling is required, the flow rate is increased while maintaining the cooling water ejection speed. Further, the flow rate may be reduced from the viewpoint of economy and from the viewpoint of reducing the load of processing work such as recovery of cooling water.

The cooling water channel 5 in the cooling device 1 preferably has a sufficiently large channel cross-sectional area. Since cooling water is jetted from the annular opening 10 of the slit 6, it is ideal that the cooling water is supplied from the cooling water supply port 7 to the slit 6. If an attempt is made to supply cooling water, the external structure becomes complicated. As shown in FIG. 5, the supply of cooling water from the outside to the cooling device 1 is practically at one place or several places. If there is only a small cross-sectional flow path from the positionally biased cooling water supply port 7 to the slit 6, the injection from the annular opening 10 is also biased, and an ideal annular water film Cannot be obtained. The reason for this is that, in a flow path having a small cross-sectional area, the flow velocity increases and the influence of flow resistance increases, and cooling water is supplied from the difference in flow resistance from the cooling water supply port 7 to each part of the annular opening 10. Bias,
Further, the cooling water reaches the annular opening 10 while moving in the circumferential direction of the annular slit at a high speed inside the slit 6, a circumferential component is added to the injection angle, and, for example, about two cooling water supply ports 7 are provided. In the plurality of cases, it is considered that the collision of the water flow also occurs in the annular opening portions that are equidistant from the respective cooling water supply ports.

One way to correct this problem is to increase the number of cooling water supply ports 7, but there is a limit to the increase in the number of cooling water supplies, and it is necessary to balance the supply of cooling water from each supply section. There are difficulties. Further, as one of the correction methods for adjusting the injection angle from the opening 10, there is a method of providing a rectifying plate inside the slit 6. However, the flow resistance is increased, and the injection amount for each position of the opening 10 is increased. Aggravate the negative effects of increasing differences.

These difficulties are caused by providing the cooling water flow path 5 having a large cross-sectional area and the cross-sectional area and the slit 6.
This can be solved by adjusting the ratio of the opening areas. In the nozzle shape shown in FIG. 8, if the ratio of the opening area of the slit 6 (the total area of the slit opening portion viewed from the extension line of the inner edge of the slit) and the cross-sectional area of the cooling water channel 5 is set to a certain level or more, cooling at the time of injection is performed. The shape of water is stable, and cooling water can be sprayed more uniformly. The value obtained by dividing the channel cross-sectional area by the area of the slit opening is 2.
It is preferable that the cross-sectional area of the flow path is sufficiently large with respect to the amount of cooling water jetted from the nozzle. Even if it is too large, the effect is reduced, so it is sufficient that it is about 5 times at most. Thus, the flow resistance is minimized by suppressing the flow velocity in the circumferential direction in the cooling device 1, and sufficient cooling water is held in the cooling water flowing portion into the slit 6, and the pressure is evenly applied thereto. The cooling water flow path 5 can have a function of a flow velocity equalizing chamber.

As schematically shown in FIG. 9, the cooling device 1 of the present invention was applied to a process of heating and cooling in a continuous welding pipe making machine for a stainless steel pipe 2. Outer diameter D1 = continuously formed and welded at a constant speed
A stainless steel pipe (SUS304) with a diameter of 34.0 mm and a wall thickness of 3.0 t is approximately 11 symmetrically and symmetrically about the central axis of the steel pipe.
The heat was uniformly applied by the high-frequency heating coil 14 so as to be 50 ° C. and conveyed by the drive roll 15. For the heated steel pipe being transported at a line speed of 2.0 m / min, the cooling water is supplied to the outer surface of the steel pipe using a cooling device as shown in FIG. 5 (inner annular body diameter D2 = 75 mm, axial length = 210 mm). And cooled to about 40 ° C. At the last position of the continuous welding pipe making line, it was cut to a length of about 4 m with a traveling cutting machine. The area of the flow path / the area of the slit opening is 2, the slit opening interval d = 1 mm.
The injection angle θ is 45 °, and the protruding length L of the inner edge of the slit is 0, 1, 3, 5, 10, 20,
It changed into 30 mm and implemented. The water pressure supplied to the nozzle is 0.2 MPa, and the amount of water jetted is 200 L /
It was set to min. The results are shown in Table 1.

When the length L was about 5 mm or more, the water film of the cooling water became a layer having a uniform thickness, and the effect of suppressing the disturbance of the water film sprayed on the outer surface of the steel pipe was high. Thereby, it was possible to easily spray the cooling water surely on the same circular circumference of the outer surface of the metal tube.

Table 2 shows the cooling results when the protrusion length L of the inner edge of the slit is 20 mm in Example 1 and the cooling results of cooling using the conventional hole spray nozzle shown in FIGS. 2 to 4 under the same water supply conditions. The quality of the obtained product is compared and shown.

The method of the present invention provides excellent quality for any of the occurrence of unevenness of the surface of the metal tube after cooling, the occurrence of unevenness in the circumferential direction of the surface of the metal tube, and the suppression of the occurrence of bending in the central axis direction of the metal tube. Showed that.

According to the present invention, in continuous pipe making by heat treatment such as quenching or welding, the whole circumference of the metal tube is more reliably ensured in the method of rapidly cooling the metal pipe after heating than the cooling method using the conventional hole spray nozzle array. Uniform and rapid cooling is possible, the occurrence of unevenness and bending of the surface of the metal tube can be prevented, and a uniform product surface with no uneven surface properties can be obtained.

DESCRIPTION OF SYMBOLS 1 Cooling device 2 Metal pipe 3 Inner ring body 4 Outer ring body 5 Cooling water flow path 6 Slit 7 Cooling water supply port 8 Slit inner edge 9 Slit outer edge 10 Annular opening 11 Screw structure 12 Clearance 13 O ring 14 High frequency heating coil 15 Drive Roll W Cooling water A Water droplet / splash a-b that flows back to the heating device side Colliding position of cooling water on the outer surface of the metal tube

Claims (6)

Cooling liquid is sprayed to the outer surface of the metal pipe from the injection port arranged concentrically with the metal pipe on the outer periphery of the metal pipe located in the horizontal direction, and the liquid film-like cooling liquid colliding with the metal pipe is liquidized on the metal pipe. In contact with the film
A cooling device for cooling the metal tube after heating by allowing it to flow ;
The cooling device is a combination of a first member and a second member, and has a cooling fluid channel and an annular slit nozzle inclined in a truncated cone shape connected to the cooling fluid channel,
The slit nozzle is composed of an annular slit opening formed by the leading edge of the slit inner edge and the outer edge of the slit, and has an injection port for injecting the coolant in a liquid film obliquely to the outer surface of the metal tube.
The frusto-conical inclination leading to the inner edge of the slit is represented by an angle θ with respect to the central axis of the metal tube.
° to 60 °,
The inner edge of the slit can protrude in the jet direction of the coolant by a length L from the outer edge of the slit,
The apparatus for cooling a metal tube after heating, wherein the protruding length L of the inner edge of the slit and the slit interval d of the slit opening can be adjusted by relative movement of the first member and the second member. The value obtained by dividing the cross-sectional area of the coolant flow path by the area of the slit opening is 2 to 5.
The metal pipe cooling device according to claim 1. The first member is an inner annular body, the second member is an outer annular body, and a coolant flow path is provided inside the outer annular body;
An annular slit nozzle is formed between the tip side inner surface of the outer annular body and the tip side outer surface of the inner annular body,
The apparatus for cooling a metal tube after heating according to claim 1, wherein the inner annular body and the outer annular body are relatively movable in the direction of the central axis of the metal tube. In the method of cooling the metal tube after heating using the cooling device according to any one of claims 1 to 3 , the cooling liquid is stably sprayed in a liquid film shape, and a round shape on the outer surface of the metal tube The protrusion length L of the inner edge of the slit is set to the slit interval d, the jet water pressure, the cooling medium so that the liquid film collides on the same circumference.
The method for cooling a metal tube after heating is characterized in that it is adjusted according to the difference between the diameter D1 of the inner edge of the slit and the diameter D2 of the outer surface of the metal tube. 5. The cooling method according to claim 4 , wherein the slit interval is adjusted so that the angle of the cooling liquid that collides with a collision position on the same circular circumference of the outer surface of the metal tube maintains the angle θ. A method for cooling a metal tube after heating. The cooling method according to claim 4 or 5, wherein the metal tube is centered by a high frequency induction heating device.
A method for cooling a metal tube after heating, wherein the metal tube is cooled after being heated to a uniform temperature symmetrical to an axis .

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