JPH0349970B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) This invention is applicable to upset steel pipes used as steel pipes for oil and natural gas extraction, and large diameter, extra-thick wall steel pipes used in offshore structures for deep sea oil wells and gas wells. The present invention relates to a cooling device for a metal tube having a step in a portion having different radial dimensions in the axial direction, for example, a tube end portion. (Prior Art) The following describes a case where a steel pipe having different radial dimensions in the axial direction, such as a steel pipe having a step in the outer diameter, is heat treated. For steel pipes with an outer diameter of 16 inches (406.4 mm) or less, which are called small-diameter or medium-diameter steel pipes, threads are cut at the end of the pipe to connect the steel pipe in the axial direction, so the wall thickness at that part must be made thicker than the other parts. In order to increase the size of the pipe, hot upset processing is often performed to create a step at the end of the pipe. There are two types of upset processing for steel pipes: outer upset, which increases the thickness on the outer surface of the steel pipe, and inner upset, which increases the wall thickness on the inner circumferential surface of the steel pipe, but this invention mainly targets the process of increasing the thickness on the outer surface. This is an outer upset steel pipe with increased thickness. Such a steel pipe has parts with different radial dimensions in the axial direction, for example, a step at the pipe end,
When cooling is performed using the so-called diagonal forward injection external surface cooling method, which is conventionally performed and injects the cooling medium from a nozzle group at a predetermined angle to the pipe axis while directing the cooling medium toward the center of the pipe cross section, the cooling medium flows over the pipe outer circumferential surface. It flows along the axial direction and jumps near the step, resulting in a portion of the steel pipe that is not cooled. As a result, poor quenching occurs in the steel pipe, resulting in a fatal defect in product quality. In addition, when a steel pipe with a step on its outer diameter in the axial direction is heated or cooled by a conventional method of heating and cooling while being conveyed by a conveying device with a fixed pass line, the thick step portion and other stationary portions are heated or cooled. Due to differences in radial dimensions, the center of the induction heating coil or cooling tunnel header may be misaligned with the steel pipe axis, or
Since the axis of the steel pipe is inclined, problems arise such as uneven heating and uneven cooling (uneven quenching) of the steel pipe, which in turn leads to poor shape. As stated in the following (objectives of the invention), the main aim of the present invention is to develop large diameter steel pipes for deep sea marine structures, such as tension leg platforms.
Traditionally, Tether Pipe, etc. for Leg Platform) were manufactured by forging, then heat treatment (quenching, tempering), and then machining, or by heat treating thick plates, forming pipes, welding, and machining. Therefore, there were many problems in terms of materials, quality, and cost. As mentioned above, as a manufacturing method for this type of steel pipe, the method of final heat treatment after pipe making and welding was unknown and did not exist. (Purpose of the Invention) Since there is a current or future demand for the supply of heat-treated upset steel pipes and large diameter steel pipes for offshore structures that have a step in the outer diameter in the axial direction,
The present invention was made with the object of providing a cooling device for metal tubes that does not cause the above-mentioned problems even when the tube ends have a step difference of 80 mm to 100 mm. (Structure and operation of the invention) The gist of the invention lies in the cooling cooling device described below. A device for cooling a metal tube having portions with different radial dimensions in the axial direction while conveying the metal tube in the axial direction; A plurality of metal tube support rollers equipped with a hydraulic lifting mechanism for changing the position of the surface in the radial direction, or a metal tube support surface that corresponds to a change in radial dimension due to axial displacement of the metal tube. a plurality of metal tube support rollers that are provided with a fluid pressure lifting mechanism for changing the position of the metal tube in the radial direction and are displaced in the tube axis direction by a drive device as the metal tube moves; heating the metal tube; an induction heating device for: a plurality of headers extending in the axial direction of a metal tube; a group of nozzles for injecting a cooling medium from the headers onto the outer circumferential surface of the metal tube; a metal tube cooling device having a nozzle angle adjuster that simultaneously changes the angle between the cooling medium injection direction and the metal tube radial direction by the same angle in a plane perpendicular or almost perpendicular to Metal tube cooling device with. The present invention will be explained in detail below. First, one of the problems with the prior art is that when a metal tube is transported (displaced) in the axial direction, the induction heating coil is The problem is that the center of the cross section of the heating means or the tunnel type external cooling device is misaligned with the tube axis, or the metal tube axis is tilted. First, in order to solve this problem, the inventor
When displacing a steel pipe with a step in the axial direction, we devised a means to prevent the axial center of the metal pipe from shifting in the radial direction. FIG. 1 shows an example of this. In FIG. 1, reference numeral 1 is a steel pipe, and the head and tail end portions have steps with a wall thickness larger on the outer peripheral surface side than on other portions. 2 is a stationary part of the steel pipe 1. 3
4 is an induction heating device, and 4 is a cooling device, which in this embodiment is a circumferential injection cooling device, which will be described later. 5 is a fluid pressure mechanism, for example a hydraulic cylinder. Reference numeral 6 denotes a metal tube support roller, which allows the fluid pressure mechanism 5 to deform the radial position of the metal tube, in this embodiment, the vertical position, discretely or continuously. 7 is a wheel for moving the support roller,
It functions to displace the metal tube support roller 6 in the axial direction of the metal tube by a drive device such as a chain (not shown). 8 is a floor surface, and 18 is a metal tube position detection device. In FIG. 1, in order to move (displace) the metal tube 1 in the axial direction, the rotation of the metal tube support roller 6 is stopped and the metal tube 1 is moved axially by the axial displacement of the metal tube 1 using a walking beam method. Alternatively, the metal tube support rollers 6 may be rotationally driven to convey the metal tube 1 in the axial direction. By rotating the metal tube support roller 6,
When displacing the metal tube 1 in the axial direction, the metal tube support roller 6 does not displace the metal tube 1 in the axial direction, and the metal tube position detection device 18 detects the head end position of the metal tube 1. At the same time, an arithmetic unit (not shown) tracks the axial position of the metal tube 1 based on the axial movement speed of the metal tube 1 and the detection result of the head end position, and based on this, the metal tube support roller 6 tracks the axial position of the metal tube 1. The radial position of 1 is the fluid pressure mechanism 5.
to prevent the metal tube axis from changing in the radial direction due to the movement of the stepped portion. Further, a combination of both of the above methods may be used. In addition, when the metal tube support roller 6 is stopped and the metal tube is conveyed in the axial direction by displacement in the tube axis direction using a walking beam method, each metal tube support device 31 moves as the metal tube 1 moves. ,3
2, 33, 34, 35, and 36, the position of the support roller 6 in the radial direction of the metal tube is displaced by the liquid pressure elevating mechanism 5 in correspondence with the stepped portion and the straight tube portion of the metal tube, and at the same time, for example, as shown in FIG. 35 or 36 of the metal tube support devices shown in FIG. 3 is constructed by moving the stepped portion or the straight tube portion in the tube axis direction with wheels 7 as the metal tube moves while supporting the stepped portion or the straight tube portion with support rollers. To prevent fluctuations in the radial direction of a metal tube axis due to movement of a stepped portion. Further, in this case, along with the movement of the metal tube, the other metal tube support devices 31, 32, and 34 are also moved in the tube axis direction by the wheels 7 within a movable range. In this invention, such a device prevents fluctuations in the radial direction of the metal tube axis due to axial movement (displacement) of the metal tube having portions with different outer diameters in the axial direction. Do it like this. Next, the second problem with the prior art is the so-called diagonal forward injection outer surface cooling method, in which the cooling medium is injected from a nozzle group at a predetermined angle to the tube axis and directed toward the center of the cross section of the metal tube. When the steel pipe is cooled, the problem is that the cooling medium flows along the outer peripheral surface of the pipe in the axial direction and jumps near the step, resulting in a portion of the steel pipe that is not cooled. This conventional diagonal forward injection external cooling method utilizes the fact that a refrigerant is injected, and after colliding with the outer peripheral surface of a metal tube, the refrigerant flows in the axial direction on the outer peripheral surface of the metal tube, increasing the heat transfer area. , aiming to increase the amount of heat removed. Therefore, the refrigerant separates from the tube surface at the stepped portion, and new refrigerant supplied from the outside is prevented from reaching the outer circumferential surface of the tube due to this separated refrigerant. With such a mechanism, poor cooling and, in turn, poor quenching occurred from the stepped portion to the end of the tube. The third problem with the prior art is that, for example, the cooling device for steel pipe quenching disclosed in JP-A-55-8473 adopts a method in which cooling fluid is supplied to each header from one common annular chamber. Because of this, it is not possible to ensure uniform cooling in the circumferential direction.
The reason for this is that it has already been clarified in the field of heat transfer engineering that heat transfer differs depending on the position of the heat transfer surface in space.
This is because it is necessary to appropriately adjust and control the ejection conditions of each header on the bottom and side surfaces. Conventionally, this point was completely ignored, resulting in poor shape and uneven baking after cooling. The inventor of the present application solved this problem and made it possible to achieve extremely uniform cooling in the circumferential direction. In order to solve this problem, the inventor devised the following cooling means. That is, as shown in Figure 2, the cooling medium is injected from a number of nozzles in a direction perpendicular to the axial direction of the metal tube and at an appropriate angle to the radial direction, creating a cooling medium tunnel in the space. (Hereinafter, the method of cooling a cylindrical object using a tunnel-shaped ring of cooling medium will be abbreviated as the circumferential injection cooling method.), and the thick part of the steel pipe with steps is
In order for the cooling medium to pass through the tunnel-shaped ring portion described above, the nozzle is designed and arranged to have a shape and dimensions that match the desired inner diameter and thickness of the ring ring, and the cooling medium is injected. Set direction. In addition, if the step on the outer periphery of the steel pipe is extremely large and the outer diameter of the thick wall portion is larger than the outer diameter of the ring ring of the cooling medium, during transportation and cooling of the target steel pipe,
The injection angle of the coolant is automatically changed based on the tracking result of the axial position of the steel pipe by the calculation device, and the ring size of the coolant is changed. In any case, according to the present invention, changing the ring size of the cooling medium according to the outer diameter size of the steel pipe passing through the cooling device at that time changes the injection angle of the cooling medium from the nozzle. This can be easily done. The inner diameter, outer diameter, and thickness of the cooling medium annular tunnel need to be designed in advance so as to match the cross-sectional dimensions of the metal tube having steps. The above description can be expressed mathematically as follows. (Refer to Figure 3) Let the wall thickness and outer diameter of the straight pipe part of the steel pipe with a step be ts and Ds, respectively, and the wall thickness and outer diameter of the pipe end part be t _E and D _E , respectively, and the refrigerant annular tunnel. If the inner and outer diameters are di and do, respectively, it is desirable that the outer surface of the steel pipe to be cooled be within the outer diameter of the annular tunnel, so do≧Ds or D _E (1) Collision with the outer periphery of the steel pipe to be cooled Since the refrigerant flows somewhat along the outer periphery of the steel pipe, equation (1) is not an absolute condition, but from the viewpoint of uniformity of cooling, etc., it is desirable to set the condition of equation (1). Also, since the inner diameter of the annular tunnel must be smaller than the outer diameter of the straight pipe section, di<Ds (2) Next, the amount of refrigerant to be supplied into the tunnel-shaped cooling zone with a length of 1 m is Qm ³ / min/m, and assuming that the water volume distribution within the cross section of the annular tunnel is uniform, di
The refrigerant in the annular layers of ~Ds and di~ _DE will be supplied to the straight pipe section and the pipe end surface, respectively. The average water density of the outer surface of the straight pipe part and the pipe end part is Q _S , Q _E
If m ³ /min・m ² , then Q _S =Q (D _S ² −di ² )/πD _S (do ² −di ² ) (3) Q _E =Q(D _E ² −di ² /πD _E ( do ² − di ² ) (4) If do and di do not need to be changed between the straight pipe section and the pipe end, and Q is constant, the ratio of the two is D _E /Q _S = D _S /D _E ×D _E ² −di ² /D _S ² −di ² (5) Especially when the difference in level is extremely large, due to the interaction between the geometric dimensions and shape of the steel pipe to be cooled and the dimensions of the annular tunnel, If the straight pipe part and the pipe end part are cooled with the same annular tunnel dimensions, the condition of formula (1) or (2) may not be satisfied in one of the parts.In this case, , in each part (1)
The injection direction of the refrigerant may be set so that the conditions of equation (2) and (2) are satisfied, and the optimum average water flow density is just right for cooling. In addition, the steel pipe shape and size range to be heat treated with the same cooling equipment are
Di and do designs are essential. In the cooling device of the present invention, the direction of refrigerant injection can be easily adjusted by using a header angle adjustment device to easily adjust the injection direction of refrigerant from a plurality of headers parallel to the tube axis arranged in the circumferential direction. , since it has a controllable mechanism, it can be controlled in accordance with the cooling location while the steel pipe to be cooled is moving. Since steel pipes with relatively large steps, which are the main object of the present invention, generally have thick walls, the conveyance speed of the steel pipes is relatively slow, and the cooling device of the present invention has the advantage that automatic control is easy. Uniformity of cooling,
No problems arise in terms of cooling capacity. If the difference in level is large, a cooling device consisting of short headers is arranged in multiple stages, and the nozzle jet direction of the header of each cooling device is optimized to the outer diameter and shape of the cooling part of the steel pipe. Automatic control from time to time can achieve even more uniform cooling, especially before and after the stepped portion. FIG. 2 shows an apparatus for carrying out the circumferential injection cooling method of this invention. In FIG. 2, reference numeral 1 is a metal tube that has portions (steps) with different radial dimensions, that is, outer diameters, in the axial direction. 9A, 9B, and 9C are intermediate receiver tanks that supply the header 10 with a cooling medium, such as water. Intermediate receiver tanks 9A, 9B, and 9C each have an independent route, and the coolant pressure difference between nozzles due to the gravity difference caused by the difference in distance from the floor surface of the many headers 10 and the transmission in space are eliminated. In order to eliminate differences in heat transfer due to the orientation of the hot surface, each intermediate receiver tank is equipped with a pressure control mechanism so that the pressure of the cooling medium can be set independently. 10 is a header, and intermediate receiver tanks 9A, 9
The cooling medium is supplied from either B or 9C, and is injected from the nozzle 10A in a tangential direction with respect to the cooling medium ring to be formed. Reference numeral 11 denotes an injection direction angle adjustment device, which ultimately displaces the injection direction adjustment ring 30 in the circumferential direction, although the power transmission path is omitted in FIG. The frame of the pin-jointed header is displaced in the circumferential direction of the header 10, and the angle formed by the nozzle 10A with the radial direction of the metal tube 1 is changed to change the injection direction of the cooling medium. Reference numerals 12 and 13 are lifting devices that vertically change the cross-sectional center position of the entire cooling device shown in FIG. 6 is a metal tube support roller. 15 is a coolant pipe port, and 16 is a coolant pipe, for which flexible hoses are used in this embodiment. The circumferential injection cooling device shown in FIG. 2 described above is the cooling device 4 in FIG. 1. In the embodiment shown in Fig. 2, the header group is divided into a plurality of blocks by an intermediate receiver tank, but there is some variation in the amount of cooling medium injected from each header without dividing the header. They also interfere with each other and become uniform. FIGS. 3a and 3b show the state in which the steel pipe passes through the coolant ring formed by the circumferential injection cooling device and the coolant ring tunnel shown in FIG. 2. In FIG. 3a, 17 is a ring-shaped tunnel for cooling medium formed in the space. In the state shown in Fig. 3b, that is, the steel pipe is passing through the ring-shaped tunnel of the cooling medium, the cooling water (cooling medium) has a thickness from the inner diameter di of the cooling medium ring to the outer diameter D of the steel pipe. , applied to the outer peripheral surface of the steel pipe, from the outer diameter do of the ring of the cooling medium to the outer diameter D of the steel pipe
Cooling water with a thickness of For example, when cooling a steel pipe that has thick walled parts at the head and tail ends of the pipe that are thicker on the outer circumferential side than the other parts, the hardening or cooling process from the stepped part to the pipe end is prevented. The reason why the uniformity is eliminated is that since the injection direction of the refrigerant is substantially perpendicular to the tube axis, the above-mentioned refrigerant scattering phenomenon does not occur, and new refrigerant is always supplied to the cooling surface. In the cooling device of the present invention, not only a single liquid refrigerant but also a mixed refrigerant of air and water may be used as the refrigerant. As mentioned above, steel pipes with relatively large steps generally have thick walls, so if the inside and outside surfaces are cooled simultaneously,
A high cooling rate can be obtained, and it is advantageous in terms of materials and material design as well as in terms of cost, and the quality is stable. To cool the inner surface of the steel pipe, the apparatus shown in FIGS. 4a and 4b is used. In Figures 4a and b, 19
20 is an inner cooling head, 20 is a hollow bar for supplying refrigerant,
21 is the support leg of the cooling head and hollow bar, 22
2 is a jetting refrigerant, and 23 is a rotating guide vane. These inner surface cooling methods cannot be applied unless the axial center of the steel pipe to be cooled remains unchanged, but by using the above-mentioned conveying means with a constant axial center, it has become possible for the first time to put it into practical use as an inner surface cooling method for metal pipes with steps. Ta. In the method for cooling the inner and outer surfaces of a steel pipe with a step at the pipe end proposed by the present inventor, the steel pipe is transported by the method described above so that the axis always remains unchanged with respect to space, and the outer surface is subjected to the above-mentioned circumferential injection. It is also possible to simultaneously cool the inner and outer surfaces of the steel pipe by applying a cooling method and simultaneously spray cooling the inner surface of the steel pipe. In this way, cooling a steel pipe from the inside and outside not only allows a high cooling rate even for a steel pipe with a large wall thickness, but also reduces the temperature variation in the wall thickness direction of the steel pipe. Because I can,
When cooling steel pipes, it is possible to achieve high precision and expand the range of possible temperature/time relationships. (Examples) Example 1 Heating and quenching were performed using the conveying device and induction heating device shown in FIG. 1 and the circumferential injection cooling device shown in FIG. 2. The heating temperature was 930°C and the cooling start temperature was 870°C. For comparison, a diagonal forward injection cooling device was installed in the cooling device section shown in FIG. 1, and similar quenching was performed. The dimensions and shape of the test steel pipe are as shown in Table 1.
The refrigerant was industrial water (water temperature 23°C).

[Table] The advantages and disadvantages of both cooling methods were compared based on the quenching hardness of the upset part, and the results are shown in Table 2.

【table】

[Table] From Table 2, it can be seen that in the conventional diagonal forward injection cooling method, the quenching of the upset part is incomplete, whereas in the circumferential injection cooling method of the present invention, complete quenching is achieved. The cooling method solved the problem of poor quenching at the tube ends. Example 2 A quenching experiment was carried out by inserting the quenching head for inner surface cooling shown in FIG. 4 into the same heating and cooling equipment row as in Embodiment 1 from the tip of the steel pipe to be cooled. The quench head was a slit nozzle type quench head. In this embodiment, the floor surface 8 in Fig. 1 is tilted at 1.5 degrees with respect to the horizontal plane, so that the cooling water for the inner surface spray can be easily discharged to the tip side of the steel pipe to be cooled, and the induction heating device can be easily discharged. to prevent it from flowing backwards. A circumferential injection cooling device similar to that shown in FIG. 2 with 24 headers was used. In this example, as shown in Table 3, both the outer diameter and step difference of the steel pipe are very large, so in the injection direction set for hardening the pipe end, the inner diameter and outer diameter of the annular tunnel formed in the space are Since it is large, the average water density becomes small when the straight pipe part is quenched, so the inner diameter of the annular tunnel was reduced by about 60 mm when the straight pipe part was quenched. The method is to determine the position of the shoulder of the step,
Calculated from the reference position passing time and conveyance speed,
The injection direction in the circumferential direction was controlled in stages from the position 2/3 of the way through the cooling device shown in the figure.

[Table] In this example, the conveyance speed of the cooled steel pipe is 0.3
m/min, and the cooling start temperature was 800°C (>Ar ₃ ). As a hardened head for internal spraying, the type shown in Fig. 4b was found to be good. The reason for this is that the cooling water supplied from the slit nozzle comes into wide contact with the inner surface of the steel pipe to be cooled by the swirling guide vanes, expanding the heat transfer area and increasing the amount of heat removed. Table 4 shows the hardness distribution in the wall thickness direction after quenching and cooling, separated into the tube end portion and the straight tube portion.

[Table] In the inner and outer surface cooling method of the present invention, the variation in hardness in the circumferential direction and longitudinal direction after quenching is as shown in Table 4. Considering unavoidable variations in material composition, structure, etc. It can be said that by the cooling method of the present invention, uniform quenching was achieved from the straight pipe section and the stepped section to the tube end. As described above, the cooling method of the present invention eliminated the quenching defects from the stepped portion to the tube end, achieved uniform quenching, and had good quenched shape (bend, roundness). Therefore, it has been demonstrated that the cooling method of the present invention is excellent as a method for cooling steel pipes having a large step at the pipe end, and can be put into practical use. (Effects of the Invention) As mentioned above, quenching or cooling of various types of steel pipes such as upset steel pipes having a step at the pipe end can be performed by
This was a difficult case as there were various problems in ensuring uniform material quality and other issues. This tendency is particularly noticeable in large-diameter, extra-thick steel pipes with large steps, and no cooling method has been put to practical use. The cooling method of the present invention enables uniform quenching and cooling over the entire length regardless of the degree of level difference, and has great industrial merits. In particular, as a heat treatment method for large-diameter, extremely thick-walled steel pipes with very large steps (due to threading) at the pipe ends used for constructing large offshore structures for deep-sea oil and gas wells, for which demand will increase in the future. It is optimal and the equipment cost is low. No heat treatment method has yet been proposed for large-diameter, extra-thick-walled steel pipes with this shape, and the industrial benefits for manufacturers and heat treaters of giant offshore structural steel pipes for deep-sea oil and gas wells are enormous. be. In the method for conveying a metal tube with a step according to the present invention, since the tube axis is always spatially constant, heating can be performed from the inner surface by inserting an induction heating coil into the tube from the rear end of the metal tube. Applications such as induction heating of the inner and outer surfaces of extremely thick parts are also possible.

[Brief explanation of drawings]

Figure 1 shows the support and
An explanatory diagram of the entire transport mechanism and heating and cooling device. FIG. 2 is an explanatory diagram of a circumferential injection device applied in the cooling method of the present invention. FIG. 3 is an explanatory diagram of an annular tunnel formed in a space in the circumferential injection cooling method. FIG. 3a explains the state and symbols when the metal tube to be cooled is not passing through. FIG. 3b shows the geometrical relationship between the metal tube and the annular tunnel through which the metal tube to be cooled passes. FIG. 4 is an embodiment B of the present invention.
An explanatory diagram of the quenching head for internal cooling used in . 1... Metal pipe with a step, 2... Straight pipe part of metal pipe,
3...Induction heating device, 4...Tangential injection cooling device, 5...Fluid pressure cylinder for height control, 6...
Support roll, 7... Wheel for forward and backward movement, 8... Floor surface, 9A, 9B, 9C... Intermediate receiver tank, 10... Header (for refrigerant injection), 11... Injection direction angle adjustment device, 12... Lifting device, 13...
... Lifting device, 15 ... Refrigerant pipe port, 16 ... Refrigerant pipe (to header), 17 ... Ring-shaped tunnel formed in space, 18 ... Pipe position detector, 19 ...
...Internal cooling head, 20...Hollow bar for refrigerant supply, 21...Support legs for cooling head and bar, 22
...Blowout refrigerant, 23...Swivel guide vane, 30...
Injection direction change frame.

Claims (1)

[Claims] 1 A device that cools a metal tube having portions with different radial dimensions in the axial direction while conveying it in the axial direction; A plurality of metal tube support rollers equipped with a hydraulic lifting mechanism for changing the position of the support surface in the radial direction, or a metal tube support that corresponds to a change in radial dimension due to axial displacement of the metal tube. A plurality of metal tube support rollers are provided with a fluid pressure lifting mechanism for changing the position of the surface in the radial direction and are displaced in the tube axis direction by a drive device as the metal tube moves; an induction heating device for heating; a plurality of headers extending in the axial direction of a metal tube; a nozzle group for injecting a cooling medium from the headers onto the outer peripheral surface of the metal tube; and an axis of the metal tube of the nozzles. a metal tube cooling device having a nozzle angle adjuster that simultaneously changes the angle formed between the cooling medium injection direction and the metal tube radial direction by the same angle in a plane perpendicular or almost perpendicular to the direction; A metal tube cooling device with steps.