Temperature control method for manufacturing thick-walled seamless pipe and temperature control device thereof

Abstract

The application provides a temperature control method for thick-wall seamless pipes, which comprises a heating step and a cooling step. In the heating step, the outer wall of the thick-wall seamless pipe is heated by a high-temperature flame. According to the measured temperature value of the thick-wall seamless pipe, the local temperature difference is calculated. According to the relationship between the local temperature difference and the maximum tolerable local temperature difference, it is determined whether to start the induction coil or continue the high-temperature flame heating, and the heating of the pipe is completed. In the cooling step, according to the temperature value of the thick-wall seamless pipe, the local maximum temperature difference is calculated. The size relationship between the local maximum temperature difference and the maximum tolerable local temperature difference is compared to determine whether the cooling step is normal, so that the cooling of the thick-wall seamless pipe is completed. The temperature control device of the application is based on electromagnetic induction auxiliary heating under the control of infrared temperature measurement. The intervention time of electromagnetic induction heating is determined by temperature. Different magnetic field penetration depths are coped with, and the frequency and power size are adjusted, so that the local temperature difference in the pipe in the heating and cooling steps is controlled within the material bearing range.

Description

Technical Field

[0001] This invention relates to the field of pipe heating, and more particularly to a temperature control method for thick-walled seamless pipes. More specifically, this invention relates to heating and cooling technology for thick-walled seamless pipes, which achieves temperature distribution control of the thick-walled seamless pipe by adding an electromagnetic induction coil, so that the local temperature difference inside the pipe is controlled within the material's tolerance range during the heating and cooling steps. Background Technology

[0002] Thick-walled seamless pipes are widely used in various harsh environments due to their superior performance, high safety factor, and high manufacturing cost in the field of metal piping. Thick-walled seamless pipes operating in high-pressure environments typically have a high diameter-to-diameter ratio (over 30%). They require heating or cooling before and after heat treatment or reaming, but the large wall thickness makes it difficult to control the temperature propagation rate, easily leading to significant internal thermal stress and cracking.

[0003] In existing technologies, the heating and cooling of seamless pipes often employs slow heating and furnace cooling methods. While these methods are economical, for thick-walled workpieces, the heating and cooling rates need to be controlled within a certain range. Exceeding this range results in excessive temperature differences between the outer and inner surfaces, easily causing thermal stress and leading to pipe cracking. Furthermore, under natural cooling conditions, the cooling rate can easily be too rapid, causing a rapid drop in the outer wall temperature and potentially generating significant residual stress in certain areas. Insufficient heating also affects the production efficiency of thick-walled seamless pipes. Traditional furnace heating has the advantage of low cost, while induction heating can achieve precise penetration heating to different depths by adjusting the frequency; however, induction heating is expensive. In the field of thick-walled pipe production, using hybrid energy sources to achieve high efficiency and energy saving offers unique advantages. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a temperature control method and apparatus for thick-walled seamless tubes. By symmetrically arranging a left-side induction coil group and a right-side induction coil group on both sides of the thick-walled seamless tube, the magnetic field penetration and Curie temperature characteristics of the material are utilized to precisely heat the thick-walled seamless tube, changing the heat diffusion mode inside the tube, shortening the heating time, and reducing thermal stress. The cooling state of the thick-walled seamless tube is monitored in real time by a temperature monitoring infrared camera to determine whether the temperature difference is too large and the maximum temperature gradient occurs. At the same time, a suitable frequency can be determined to enable precise local heating of the induction coil group, reduce the temperature difference, and reduce the generation of residual stress.

[0005] This invention provides a temperature control method for manufacturing thick-walled seamless tubes, comprising a heating step and a cooling step.

[0006] The implementation of the heating step S1 includes the following sub-steps:

[0007] S11. Based on the material properties of the thick-walled seamless tube to be manufactured and the production needs, determine the final heating temperature T, the upper limit of the temperature difference X1, and the temperature drop difference X2.

[0008] S12. Heat the outer wall of the thick-walled seamless tube with a high-temperature flame, and record the inner wall temperature value T1 and the outer wall temperature value T2 of the thick-walled seamless tube as measured by the inner wall temperature monitoring infrared camera. If either the inner wall temperature value T1 or the outer wall temperature value T2 fails to reach the final temperature T, then continue to step S13.

[0009] S13. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube measured in step S12, calculate the local temperature difference of the thick-walled seamless tube. If the local temperature difference If the temperature difference is less than the upper limit X1, continue heating the outer wall of the thick-walled seamless tube with a high-temperature flame until the local temperature difference is reached. Greater than the upper limit of temperature difference X1; when the local temperature difference When the temperature difference exceeds the upper limit X1, the high-temperature flame heating of the outer wall of the thick-walled seamless tube is stopped, and the left and right induction coil groups symmetrically arranged on both sides of the thick-walled seamless tube are brought together towards the thick-walled seamless tube until they are concentric with the thick-walled seamless tube, and step S14 is performed.

[0010] S14. Start the left induction coil group and the right induction coil group respectively, and heat the thick-walled seamless tube with frequency H1 and power W1, and record the inner wall temperature value T1 of the thick-walled seamless tube measured by the inner wall temperature monitoring infrared camera and the outer wall temperature value T2 of the thick-walled seamless tube measured by the outer wall temperature monitoring infrared camera.

[0011] S15. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube measured in step S14, calculate the local induced temperature difference of the thick-walled seamless tube. If the local induced temperature difference If the temperature difference exceeds the upper limit X1, then continue heating the thick-walled seamless tube using the left and right induction coil sets. If the local temperature difference... If the temperature drop difference is less than 2 times, then the left and right induction coil groups will be turned off.

[0012] S16. Based on step S15, determine whether the thick-walled seamless tube to be manufactured meets the final temperature T. If the final temperature has not been reached, continue to step S12 for heating; if the final temperature is met, the heating step is completed.

[0013] The implementation of the cooling step S2 includes the following sub-steps:

[0014] S21. Determine the initial temperature T3 of the thick-walled seamless tube to be manufactured, set the final cooling temperature T4 of the thick-walled seamless tube to be manufactured, and set the maximum value of the local maximum temperature difference ∆T of the thick-walled seamless tube to be manufactured to X3.

[0015] S22. Start cooling in the set environment;

[0016] S23. Based on the inner wall temperature value T1 of the thick-walled seamless tube measured by the inner wall temperature monitoring infrared camera and the outer wall temperature value T2 of the thick-walled seamless tube measured by the outer wall temperature monitoring infrared camera, calculate the local maximum temperature difference ∆T of the thick-walled seamless tube.

[0017] S24. Based on the local maximum temperature difference ∆T of the thick-walled seamless tube obtained in step S23, compare the local maximum temperature difference ∆T with the maximum value X3. If the local maximum temperature difference ∆T is greater than the maximum value X3, it is considered that the thick-walled seamless tube is cooling too fast under the set environment. Then, start the left induction coil group and the right induction coil group. The induction coil group heats with power W2 and frequency H2 until the local maximum temperature difference ∆T is less than the maximum value X3. If the local maximum temperature difference ∆T is less than the maximum value X3, it is considered that the cooling rate of the thick-walled seamless tube is normal. Then, continue cooling under the set environment.

[0018] S25. Continuously monitor the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube using a temperature monitoring infrared camera. If either the inner wall temperature T1 or the outer wall temperature T2 fails to reach the final cooling temperature T4, return to step S22. When both the inner wall temperature T1 and the outer wall temperature T2 are lower than the final cooling temperature T4, cooling is complete.

[0019] Preferably, the material properties of the thick-walled seamless tube include the outer diameter, inner diameter, resistivity, relative permeability, and Curie temperature of the thick-walled seamless tube.

[0020] Preferably, in sub-step S14 of the heating step, the determination process of the frequency H1 and the power W1 is as follows:

[0021] S141. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube measured in step S12, plot the temperature T-wall thickness S-function relationship curve of the thick-walled seamless tube. The specific expression is as follows:

[0022]

[0023] Where T1 is the inner wall temperature of the thick-walled seamless tube, T2 is the outer wall temperature of the thick-walled seamless tube, R1 is the outer wall radius of the thick-walled seamless tube, and R2 is the inner wall radius of the thick-walled seamless tube.

[0024] S142. Based on the relative permeability and resistivity of the thick-walled seamless tube, determine the maximum heating depth corresponding to each electromagnetic frequency of the thick-walled seamless tube, and plot the frequency H-heating depth S curve expression of the thick-walled seamless tube as follows:

[0025]

[0026] Where p is the resistivity of the thick-walled seamless tube. The magnetic permeability of the thick-walled seamless tube;

[0027] S143. Based on the temperature T-wall thickness S function relationship curve of the thick-walled seamless tube obtained in step S141, determine the heating depth s1 corresponding to the point where the temperature gradient ∆T along the radial direction of the thick-walled seamless tube is the maximum and is lower than the Curie temperature of the thick-walled seamless tube, and obtain the heating depth of the induction coil group.

[0028] S144. Based on the heating depth s1 obtained in step S143 and the corresponding temperature value, determine the power W1 of the induction coil group, and then substitute s1 into the frequency H-heating depth S curve obtained in step S142 to obtain the current frequency H1 in the coil at this time.

[0029] Preferably, the temperature-wall thickness depth function curve of the thick-walled seamless tube is plotted according to the steady-state logarithmic thermal conductivity curve of a circular tube.

[0030] Preferably, the upper limit of the temperature difference X1 and the temperature drop difference X2 of induction heating are set according to the material properties of the thick-walled seamless tube.

[0031] Preferably, in sub-step S24 of the cooling step, the determination process of the frequency H2 and the power W2 is as follows:

[0032] S241. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube measured in step S23, plot the temperature-wall thickness depth function relationship curve of the thick-walled seamless tube.

[0033] S242. Based on the relative permeability and resistivity of the thick-walled seamless tube, determine the maximum heating depth corresponding to each electromagnetic frequency of the thick-walled seamless tube, and plot the frequency-heating depth curve of the thick-walled seamless tube.

[0034] S243. Based on the temperature-wall thickness depth function relationship curve of the thick-walled seamless tube obtained in step S241, determine the heating depth s2 corresponding to the point where the temperature gradient ∆T along the radial direction of the thick-walled seamless tube is the maximum and is lower than the Curie temperature of the thick-walled seamless tube, and obtain the heating depth of the induction coil group.

[0035] S244. Based on the heating depth s2 obtained in step S243, substitute it into the frequency-heating depth obtained in S242 to determine the frequency H2; determine the power W2 of the induction coil group through the temperature values ​​T1 and T2.

[0036] Preferably, the power W1 of the induction coil group is proportional to the inner wall temperature T1 and the outer wall temperature T2, respectively; in the cooling step, the power W2 of the induction coil group is proportional to the inner wall temperature T1 and the outer wall temperature T2, respectively.

[0037] Preferably, in the heating step, the heating depth s1 is proportional to the power W1 of the induction coil group; and in the cooling step, the heating depth s2 is proportional to the power W2 of the induction coil group.

[0038] A second aspect of the present invention provides a temperature control device for a temperature control method in manufacturing thick-walled seamless tubes, comprising a left induction coil group, a right induction coil group, a support, an inner wall temperature monitoring infrared camera, and an outer wall temperature monitoring infrared camera. The left and right induction coil groups are symmetrically distributed on both sides of the thick-walled seamless tube. The inner wall temperature monitoring infrared camera is located at one end of the thick-walled seamless tube, and the outer wall temperature monitoring infrared camera is located at the upper end of the thick-walled seamless tube. The thick-walled seamless tube is fixed on the support.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] 1. In the heating step of thick-walled seamless tubes, the present invention uses a resistance furnace or flame heating method to ensure that the heat conduction process proceeds from the outer surface to the inside, resulting in a certain temperature gradient in the thickness direction; by using an induction coil, the magnetic field penetration and Curie temperature characteristics of the material are utilized to achieve precise heating of the parts with large internal temperature gradients, thereby changing the temperature diffusion mode, shortening the heating time, and reducing thermal stress.

[0041] 2. In the cooling process of thick-walled seamless pipes, the natural cooling process also generates a large temperature gradient along the pipe wall thickness, with the inner wall temperature higher than the outer wall temperature. Due to uneven deformation of the internal material during the cooling process, significant residual stress is generated, and excessively rapid cooling can directly lead to pipe rupture. However, the cooling process of this invention can monitor and control the pipe cooling status in real time. Using a temperature monitoring infrared camera, it can determine whether the temperature difference is too large and the maximum temperature gradient occurs. Simultaneously, it can determine an appropriate frequency to enable precise localized heating of the induction coil assembly, thus mitigating the temperature difference. Attached Figure Description

[0042] Figure 1 This is a flowchart of the temperature control method for manufacturing thick-walled seamless tubes according to the present invention;

[0043] Figure 2 This is a temperature distribution along the wall thickness in the heating step of the temperature control method for manufacturing thick-walled seamless tubes according to the present invention;

[0044] Figure 3 The current frequency corresponding to the required heating depth of the induction coil assembly in the temperature control method of the present invention for manufacturing thick-walled seamless tubes;

[0045] Figure 4 This is a diagram showing the distribution of magnetic field strength along the wall thickness in the temperature control method for manufacturing thick-walled seamless tubes according to the present invention.

[0046] Figure 5 This is a structural diagram of the temperature control device for manufacturing thick-walled seamless tubes according to the present invention;

[0047] Figure 6a and 6b The figures show the changes in resistivity and permeability of the thick-walled seamless tube in the temperature control method for manufacturing thick-walled seamless tubes according to the present invention.

[0048] Key reference numerals:

[0049] Left induction coil group 1, right induction coil group 2, thick-walled seamless tube 3, bracket 4, inner wall temperature monitoring infrared camera 5, outer wall temperature monitoring infrared camera 6. Detailed Implementation

[0050] To fully describe the technical content, structural features, objectives, and effects of this invention, a detailed description will be provided below in conjunction with the accompanying drawings.

[0051] like Figure 2 As shown, when heating large forgings and castings, the heating and cooling time can be hundreds of hours. The internal temperature distribution can be equivalently represented by steady-state heat transfer, and the temperature distribution along the wall thickness can be obtained using a logarithmic law. The temperature development along the wall thickness can be understood as from A→B→C. If only external methods such as flame heating are used, the curve will have a larger slope, resulting in excessively large local temperature gradients. Therefore, the temperature control method of this invention for manufacturing thick-walled seamless tubes achieves control of the thick-walled temperature distribution by incorporating an induction coil group, such as... Figure 1 As shown, the temperature control method includes a heating step and a cooling step. In the process of producing large-diameter thick-walled pipes, the pipes need to be heated or cooled in processes such as piercing, rolling, and tempering. By setting the temperature control method and temperature control device proposed in this invention, production efficiency can be significantly improved.

[0052] The heating process combines the characteristics of high-temperature flame heating and induction coil assembly to achieve uniform heating of the thick-walled seamless tube 3. First, surface heating is performed using methods such as high-temperature flame heating. During this heating step, as the material temperature increases, the corresponding magnetic permeability decreases, and demagnetization occurs after exceeding the Curie temperature. Since an infrared camera monitors the inner and outer wall temperatures of the thick-walled seamless tube 3 in real time, induction heating is applied to the tube as the temperature rises. The magnetic field distribution along the wall thickness direction is as follows: Figure 4 As shown in Figure a, at the initial low temperature, the magnetic field preferentially concentrates in the surface region (curve a). As time progresses and the surface temperature increases, the magnetic field generates extreme values ​​(b→c) internally. This is used as the basis for determining the intervention time of the induction heating coil group and the adjustment of the induction coil group's frequency and power. During this process, two heating methods are used alternately to precisely control the radial temperature transfer rate of the pipe, while simultaneously improving heating efficiency.

[0053] The implementation of heating step S1 includes the following sub-steps:

[0054] S11. Based on the material properties of the thick-walled seamless tube 3 to be manufactured, and according to production needs, determine the final heating temperature T, the upper limit of the temperature difference X1, and the temperature drop difference X2.

[0055] Specifically, the material properties of the thick-walled seamless tube 3 include its outer diameter, inner diameter, resistivity, relative permeability, and Curie temperature. The upper limit of the temperature difference X1 and the temperature drop-off difference X2 for induction heating are set according to the material properties of the thick-walled seamless tube 3. Different materials have different stress sensitivities. A temperature difference exceeding the upper limit X1 can easily generate significant thermal stress, increasing the risk of pipe breakage. A temperature drop below the drop-off difference X2 indicates that the temperature difference has been reduced through induction heating, and flame heating can be used again.

[0056] S12. Heat the outer wall of the thick-walled seamless tube 3 with a high-temperature flame, and record the inner wall temperature value T1 of the thick-walled seamless tube 3 measured by the inner wall temperature monitoring infrared camera 5 and the outer wall temperature value T2 of the thick-walled seamless tube 3 measured by the outer wall temperature monitoring infrared camera 6. If both the inner wall temperature value T1 and the outer wall temperature value T2 reach the final temperature T, the heating ends. If either the inner wall temperature value T1 or the outer wall temperature value T2 does not reach the final temperature T, continue to step S13.

[0057] S13. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube 3 measured in step S12, calculate the local temperature difference of the thick-walled seamless tube 3. If the local temperature difference If the temperature difference is less than the upper limit X1, then continue heating the outer wall of the thick-walled seamless tube 3 using a high-temperature flame; if the local temperature difference... If the temperature difference exceeds the upper limit X1, the high-temperature flame heating of the outer wall of the thick-walled seamless tube 3 is stopped, and the left induction coil group 1 and the right induction coil group 2, which are symmetrically arranged on both sides of the thick-walled seamless tube 3, are brought together towards the thick-walled seamless tube 3 until they are concentric with the thick-walled seamless tube 3, and step S14 is performed.

[0058] S14. Start the left induction coil group 1 and the right induction coil group 2 respectively, and heat the thick-walled seamless tube 3 with frequency H1 and power W1. Record the inner wall temperature value T1 of the thick-walled seamless tube 3 measured by the inner wall temperature monitoring infrared camera 5 and the outer wall temperature value T2 of the thick-walled seamless tube 3 measured by the outer wall temperature monitoring infrared camera 6.

[0059] Furthermore, the process for determining the heating frequency H1 and power W1 of the left induction coil group 1 and the right induction coil group 2 is as follows:

[0060] S141. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube 3 measured in step S12, plot the temperature-wall thickness depth function curve of the thick-walled seamless tube 3. The specific expression is as follows:

[0061]

[0062] Wherein, T1 is the inner wall temperature of the thick-walled seamless tube 3, T2 is the outer wall temperature of the thick-walled seamless tube 3, R1 is the outer wall radius of the thick-walled seamless tube 3, and R2 is the inner wall radius of the thick-walled seamless tube 3.

[0063] Specifically, the temperature-wall thickness depth function curve of the thick-walled seamless tube 3 is plotted according to the distribution of the steady-state logarithmic thermal conductivity curve of the circular tube.

[0064] S142. Based on the relative permeability and resistivity of the thick-walled seamless tube 3, determine the maximum heating depth corresponding to each electromagnetic frequency of the thick-walled seamless tube 3, and plot the frequency-heating depth curve of the thick-walled seamless tube 3. The expression for the frequency H-heating depth S curve of the thick-walled seamless tube is as follows:

[0065]

[0066] Where p is the resistivity of the thick-walled seamless tube 3. denoted as 3, which is the magnetic permeability of the thick-walled seamless tube.

[0067] S143. Based on the temperature-wall thickness depth function relationship curve of the thick-walled seamless tube 3 obtained in step S141, determine the heating depth s1 corresponding to the point where the temperature gradient ∆T along the radial direction of the thick-walled seamless tube 3 is maximum and lower than the Curie temperature of the thick-walled seamless tube 3, and obtain the heating depth of the induction coil group.

[0068] S144. Based on the heating depth s1 obtained in step S143 and the corresponding temperature value, determine the power W1 of the induction coil group. The greater the inner wall temperature T1 and the outer wall temperature T2, the greater the power W1 of the induction coil group and the deeper the heating depth s1.

[0069] Specifically, the current frequency of the induction coil group is related to the ability of the magnetic field to penetrate the interior of an object. Within a certain range, the lower the frequency, the easier it is to generate a magnetic field in a deeper part. The stronger the magnetic field, the stronger the induced current, the faster the heat generation, and the higher the heating efficiency. Therefore, as the heating process progresses, if it is necessary to use an induction coil group for heating, the depth to be heated must be obtained through certain means.

[0070] S15. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube 3 measured in step S14, calculate the local temperature difference of the thick-walled seamless tube 3. If the local temperature difference If the temperature difference exceeds the upper limit X1, then continue heating the thick-walled seamless tube 3 using the left induction coil group 1 and the right induction coil group 2. If the local temperature difference... If the temperature drops to a level of X2, then the left induction coil group 1 and the right induction coil group 2 will be turned off.

[0071] S16. Based on step S15, determine whether the thick-walled seamless tube 3 to be manufactured meets the final temperature T. If the final temperature is not reached, continue to step S2 for heating. If the final temperature is met, the heating step is completed.

[0072] The cooling step involves calculating the maximum local temperature difference ∆T of the thick-walled seamless tube 3 based on the inner wall temperature monitoring infrared camera 5 and the outer wall temperature monitoring infrared camera 6, and comparing it with a set maximum value to control it to be less than a certain range. For example, this ensures that the local temperature difference inside the tube during the cooling step is controlled within the material's tolerance range.

[0073] The specific implementation steps of cooling step S2 are as follows:

[0074] S21. Determine the initial temperature T3 of the thick-walled seamless tube 3 to be manufactured, set the final cooling temperature T4 of the thick-walled seamless tube 3 to be manufactured, and set the maximum value of the local maximum temperature difference ∆T of the thick-walled seamless tube 3 to be manufactured to X3.

[0075] S22, Start cooling in the set environment.

[0076] S23. Based on the inner wall temperature value T1 of the thick-walled seamless tube 3 measured by the inner wall temperature monitoring infrared camera 5 and the outer wall temperature value T2 of the thick-walled seamless tube 3 measured by the outer wall temperature monitoring infrared camera 6, calculate the local maximum temperature difference ∆T of the thick-walled seamless tube 3.

[0077] S24. Based on the local maximum temperature difference ∆T of the thick-walled seamless tube 3 obtained in step S23, compare the local maximum temperature difference ∆T with the maximum value X3. If the local maximum temperature difference ∆T is greater than the maximum value X3, it is considered that the cooling rate of the thick-walled seamless tube 3 is too fast under the set environment, and the left induction coil group 1 and the right induction coil group 2 are started. The induction coil groups are heated with power W2 and frequency H2 until the local maximum temperature difference ∆T is less than the maximum value X3, and then step S2 is performed. If the local maximum temperature difference ∆T is less than the maximum value X3, it is considered that the cooling rate of the thick-walled seamless tube 3 is normal, and cooling continues under the set environment.

[0078] Furthermore, the process for determining the frequency H2 and power W2 of the left induction coil group 1 and the right induction coil group 2 is as follows:

[0079] S241. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube 3 measured in step S23, as well as the material properties of the thick-walled seamless tube 3, plot the temperature-wall thickness-depth function relationship curve of the thick-walled seamless tube 3.

[0080] S242. Based on the relative permeability and resistivity of the thick-walled seamless tube 3, determine the maximum heating depth corresponding to each electromagnetic frequency of the thick-walled seamless tube 3, and plot the frequency-heating depth curve of the thick-walled seamless tube 3 to obtain the frequency H2 of the induction coil group.

[0081] S243. Based on the temperature-wall thickness depth function relationship curve of the thick-walled seamless tube 3 obtained in step S241, determine the heating depth s2 corresponding to the point where the temperature gradient ∆T along the radial direction of the thick-walled seamless tube is the maximum and is lower than the Curie temperature of the thick-walled seamless tube, and obtain the heating depth of the induction coil group.

[0082] S244. Based on the heating depth s2 obtained in step S243 and the corresponding temperature value, determine the power W2 of the induction coil group. The greater the inner wall temperature value T1 and the outer wall temperature value T2, the greater the power W2 of the induction coil group and the deeper the heating depth s2.

[0083] S25. Use a temperature monitoring infrared camera to continuously detect the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube. If either the inner wall temperature T1 or the outer wall temperature T2 fails to reach the final cooling temperature T4, return to step S22. When both the inner wall temperature T1 and the outer wall temperature T2 are lower than the final cooling temperature T4, the cooling is complete.

[0084] In the heating step, the power W1 of the induction coil group is proportional to the inner wall temperature T1 and the outer wall temperature T2, respectively; the heating depth s1 is proportional to the power W1 of the induction coil group. In the cooling step, the power W2 of the induction coil group is proportional to the inner wall temperature T1 and the outer wall temperature T2, respectively; the heating depth s2 is proportional to the power W2 of the induction coil group.

[0085] Temperature control devices used in the manufacture of thick-walled seamless tubes, such as Figure 5 As shown, the system includes a left induction coil group 1, a right induction coil group 2, a bracket 4, an inner wall temperature monitoring infrared camera 5, and an outer wall temperature monitoring infrared camera 6. To ensure the induction coil groups quickly approach when heating the thick-walled seamless pipe 3 and quickly retreat after heating, a semi-circular design is used for the induction coil groups. The left induction coil group 1 and the right induction coil group 2 rotate in either clockwise or counterclockwise direction. The shape of the induction coil groups is designed according to the length of the thick-walled seamless pipe 3, or multiple coil groups can be connected in parallel. The left induction coil group 1 and the right induction coil group 2 are horizontally symmetrically distributed on both sides of the thick-walled seamless pipe 3. When heating, the center of the semi-circle of the induction coil group coincides with the center of the pipe to achieve uniform circumferential heating. The inner wall temperature monitoring infrared camera 5 is located at one end of the thick-walled seamless pipe 3, and the outer wall temperature monitoring infrared camera 6 is located at the upper end of the thick-walled seamless pipe 3. The thick-walled seamless pipe 3 is fixed to the bracket 4.

[0086] Temperature monitoring can be achieved using infrared temperature cameras or temperature measurement cameras; flame heating can be achieved using high-temperature gases (flames) produced by the combustion of coal, coke, heavy oil, diesel, coal gas or natural gas in a heating furnace, or in the form of electric resistance furnaces.

[0087] The following describes in further detail a temperature control method and device for thick-walled seamless tubes according to the present invention, with reference to embodiments:

[0088] In this specific embodiment, the thick-walled seamless tube 3 has a diameter of 400 mm, an inner diameter of 200 mm, is made of N80 steel, and has a Curie temperature of 750°C. The changes in resistivity and permeability are as follows: Figure 6a , 6b As shown.

[0089] In the initial state, the thick-walled seamless tube 3 is fixed on the bracket 4. After installation, a certain space is reserved around the thick-walled seamless tube 3. The left induction coil group 1 and the right induction coil group 2 are adjusted to be horizontally aligned with the thick-walled seamless tube 3 and away from it. The specific process of heating the thick-walled seamless tube 3 at this time is as follows:

[0090] S11. Based on the material properties of the thick-walled seamless tube 3 to be manufactured, the upper limit of the temperature difference X1 of the high-temperature flame is set to 8°C / mm and the temperature drop difference X2 is set to 4°C / mm. Based on production needs, the required temperature for this heat treatment is determined to be 1000°C.

[0091] S12. Heat the outer wall of the thick-walled seamless tube 3 with a high-temperature flame, and record the inner wall temperature value T1 of the thick-walled seamless tube 3 measured by the inner wall temperature monitoring infrared camera 5 and the outer wall temperature value T2 of the thick-walled seamless tube 3 measured by the outer wall temperature monitoring infrared camera 6. At this time, neither the inner wall temperature value T1 nor the outer wall temperature value T2 has reached the final temperature of 1000°C, so continue to step S13.

[0092] In this step, the flame can be heated using coal, coke, or heavy oil.

[0093] S13. After heating for 120 minutes, based on the inner wall temperature of 800°C and the outer wall temperature of 400°C of the thick-walled seamless tube 3 measured in step S12, calculate the local temperature difference of the thick-walled seamless tube 3. At this time, the local temperature difference If the temperature difference exceeds 8°C / mm, stop heating the outer wall of the thick-walled seamless tube 3 with the high-temperature flame, and move the left induction coil group 1 and the right induction coil group 2, which are symmetrically arranged on both sides of the thick-walled seamless tube 3, towards the thick-walled seamless tube 3 until they are concentric with the thick-walled seamless tube 3, and proceed to step S14.

[0094] S14. Start the left induction coil group 1 and the right induction coil group 2 respectively, and heat the thick-walled seamless tube 3 at a frequency of 5079Hz and a power of 500KW. Record the inner wall temperature value T1 of the thick-walled seamless tube 3 measured by the inner wall temperature monitoring infrared camera 5 and the outer wall temperature value T2 of the thick-walled seamless tube 3 measured by the outer wall temperature monitoring infrared camera 6.

[0095] Furthermore, the process for determining the heating frequency H1 and power W1 of the left induction coil group 1 and the right induction coil group 2 is as follows:

[0096] S141. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless pipe 3 measured in step S12, as well as the inner and outer diameters of the pipe, plot the temperature T-wall thickness S-function relationship curve of the thick-walled seamless pipe 3 according to the steady-state logarithmic heat conduction curve distribution of a circular pipe. The specific expression is as follows:

[0097]

[0098] Wherein, T1 is the inner wall temperature of the thick-walled seamless tube 3, T2 is the outer wall temperature of the thick-walled seamless tube 3, R1 is the outer wall radius of the thick-walled seamless tube 3, and R2 is the inner wall radius of the thick-walled seamless tube 3.

[0099] S142, such as Figure 3 Based on the relative permeability and resistivity of the thick-walled seamless tube 3, the maximum heating depth corresponding to each electromagnetic frequency of the thick-walled seamless tube 3 is determined, and the frequency H-heating depth S curve expression of the thick-walled seamless tube is plotted as follows:

[0100]

[0101] Where p is the resistivity of the thick-walled seamless tube 3. denoted as 3, which is the magnetic permeability of the thick-walled seamless tube.

[0102] S143. Based on the temperature-wall thickness depth function curve of the thick-walled seamless tube 3 obtained in step S141, determine the heating depth corresponding to the point where the temperature gradient along the radial direction of the thick-walled seamless tube 3 is 8°C / mm and is lower than the Curie temperature of the thick-walled seamless tube 3, and obtain the heating depth of the induction coil group. Find the depth corresponding to the maximum temperature difference through the curve, and subtract the thickness before the Curie temperature point to obtain the heating depth of 15.1mm.

[0103] S144. Based on the heating depth of 15.1 mm obtained in step S143 and the corresponding temperature of 600°C, the power of the induction coil group is determined to be 500 kW. Substituting the heating depth of 15.1 mm into S142, the frequency of the induction coil group is obtained as 5079 Hz. For N80 steel, the heating depth varies at different temperatures; the frequency is determined based on the current temperature and depth. The frequency H-heating depth S curve for a thick-walled seamless tube at 600°C is shown below. Figure 3 As shown.

[0104] S15. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube 3 measured in step S14, calculate the local temperature difference of the thick-walled seamless tube 3 after continuing heating for 3 minutes. At this time, the local temperature difference If the temperature drops to a level of X2, then the left induction coil group 1 and the right induction coil group 2 will be turned off.

[0105] S16. Based on step S15, determine whether the thick-walled seamless tube 3 to be manufactured meets the final temperature T. At this time, neither the inner wall temperature T1 nor the outer wall temperature T2 of the thick-walled seamless tube has reached the final temperature of 1000°C. Then, continue with step S2 for heating. After heating for 160 minutes, the inner wall temperature is monitored to be 800°C and the outer wall temperature is 1000°C. Calculate the local temperature difference. Is T1 higher than the temperature difference value of 8°C / mm, at which point is the local temperature difference... If the temperature difference exceeds 8°C / mm, stop heating the outer wall of the thick-walled seamless tube 3 with the high-temperature flame. Then, move the left induction coil group 1 and the right induction coil group 2, which are symmetrically arranged on both sides of the thick-walled seamless tube 3, towards the thick-walled seamless tube 3 until they are concentric. Heat the thick-walled seamless tube 3 at a frequency of 3000Hz and a power of 800KW. The heating process is continuously monitored, and the local temperature difference is recorded. After 60 minutes, T1 drops back to the range of X2, and heating stops. At this point, the inner wall temperature T1 is lower than the final temperature of 1000°C, so flame heating is switched on. After 3 hours, T1 and T2 reach 1000°C, and heating is complete.

[0106] In a preferred embodiment of the present invention, the cooling step is illustrated below:

[0107] The initial temperature of the S21 pipe is 1000°C at T3, and it is cooled to room temperature at T4 of 25°C. The pipe radius is 400mm and the thickness is 200mm. The material is N80 steel. It is required that the local temperature difference in the radial direction during the cooling process is always less than X3, which is 8°C / mm.

[0108] S21, Argon gas is introduced into the environment for air cooling.

[0109] S22, Infrared camera 5 for monitoring inner wall temperature measures inner wall temperature T1, infrared camera 6 for monitoring outer wall temperature measures outer wall temperature T2, and calculates local temperature difference ∆T.

[0110] S23. During the cooling process, continuously compare the value of ∆T with 8°C / mm. If ∆T is greater than 8°C / mm, it indicates that the cooling is too fast.

[0111] S24, the induction coil is heated by passing a frequency H2 and a current W2, and after induction heating, ∆T drops to 2°C / mm.

[0112] S25, continuously monitor the temperature using an infrared camera and calculate whether ∆T is less than 8°C / mm. If it is less than X3, proceed to the next step.

[0113] S26, determine whether T1 and T2 have both reached 25°C. If not, proceed to the next step.

[0114] S27, continue cooling the pipes via air cooling, and calculate whether ∆T exceeds X3.

[0115] S28, cooling ends when both T1 and T2 are below 25°C and ∆T does not exceed the upper limit X3.

[0116] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A temperature control method for manufacturing thick-walled seamless tubes, characterized in that, It includes a heating step and a cooling step. The implementation of the heating step S1 includes the following sub-steps: S11. Based on the material properties of the thick-walled seamless tube to be manufactured and the production needs, determine the final heating temperature T, the upper limit of the temperature difference X1, and the temperature drop difference X2. S12. Heat the outer wall of the thick-walled seamless tube with a high-temperature flame, and record the inner wall temperature value T1 and the outer wall temperature value T2 of the thick-walled seamless tube as measured by the inner wall temperature monitoring infrared camera. If either the inner wall temperature value T1 or the outer wall temperature value T2 fails to reach the final temperature T, then continue to step S13. S13. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube measured in step S12, calculate the local temperature difference of the thick-walled seamless tube. If the local temperature difference If the temperature difference is less than the upper limit X1, continue heating the outer wall of the thick-walled seamless tube with a high-temperature flame until the local temperature difference is reached. Greater than the upper limit of temperature difference X1; when the local temperature difference When the temperature difference exceeds the upper limit X1, the high-temperature flame heating of the outer wall of the thick-walled seamless tube is stopped, and the left and right induction coil groups symmetrically arranged on both sides of the thick-walled seamless tube are brought together towards the thick-walled seamless tube until they are concentric with the thick-walled seamless tube, and step S14 is performed. S14. Start the left induction coil group and the right induction coil group respectively, and heat the thick-walled seamless tube with frequency H1 and power W1, and record the inner wall temperature value T1 of the thick-walled seamless tube measured by the inner wall temperature monitoring infrared camera and the outer wall temperature value T2 of the thick-walled seamless tube measured by the outer wall temperature monitoring infrared camera. S15. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube measured in step S14, calculate the local induced temperature difference of the thick-walled seamless tube. If the local induced temperature difference If the temperature difference exceeds the upper limit X1, then continue heating the thick-walled seamless tube using the left and right induction coil sets. If the local temperature difference... If the temperature drop difference is less than 2 times, then the left and right induction coil groups will be turned off. S16. Based on step S15, determine whether the thick-walled seamless tube to be manufactured meets the final temperature T. If the final temperature has not been reached, continue to step S12 for heating; if the final temperature is met, the heating step is completed. The implementation of the cooling step S2 includes the following sub-steps: S21. Determine the initial temperature T3 of the thick-walled seamless tube to be manufactured, set the final cooling temperature T4 of the thick-walled seamless tube to be manufactured, and set the maximum value of the local maximum temperature difference ∆T of the thick-walled seamless tube to be manufactured to X3. S22. Start cooling in the set environment; S23. Based on the inner wall temperature value T1 of the thick-walled seamless tube measured by the inner wall temperature monitoring infrared camera and the outer wall temperature value T2 of the thick-walled seamless tube measured by the outer wall temperature monitoring infrared camera, calculate the local maximum temperature difference ∆T of the thick-walled seamless tube. S24. Based on the local maximum temperature difference ∆T of the thick-walled seamless tube obtained in step S23, compare the local maximum temperature difference ∆T with the maximum value X3. If the local maximum temperature difference ∆T is greater than the maximum value X3, it is considered that the thick-walled seamless tube is cooling too fast under the set environment. Then, start the left induction coil group and the right induction coil group. The induction coil group heats with power W2 and frequency H2 until the local maximum temperature difference ∆T is less than the maximum value X3. If the local maximum temperature difference ∆T is less than the maximum value X3, it is considered that the cooling rate of the thick-walled seamless tube is normal. Then, continue cooling under the set environment. S25. Use a temperature monitoring infrared camera to continuously detect the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube. If either the inner wall temperature T1 or the outer wall temperature T2 fails to reach the final cooling temperature T4, return to step S22. When both the inner wall temperature T1 and the outer wall temperature T2 are lower than the final cooling temperature T4, the cooling is complete.

2. The temperature control method for manufacturing thick-walled seamless tubes according to claim 1, characterized in that, The material properties of the thick-walled seamless tube include its outer diameter, inner diameter, resistivity, relative permeability, and Curie temperature.

3. The temperature control method for manufacturing thick-walled seamless tubes according to claim 1 or 2, characterized in that, In sub-step S14 of the heating step, the determination process of the frequency H1 and the power W1 is as follows: S141. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube measured in step S12, plot the temperature T-wall thickness S-function relationship curve of the thick-walled seamless tube. The specific expression is as follows: ； Where T1 is the inner wall temperature of the thick-walled seamless tube, T2 is the outer wall temperature of the thick-walled seamless tube, R1 is the outer wall radius of the thick-walled seamless tube, and R2 is the inner wall radius of the thick-walled seamless tube. S142. Based on the relative permeability and resistivity of the thick-walled seamless tube, determine the maximum heating depth corresponding to each electromagnetic frequency of the thick-walled seamless tube, and plot the frequency H-heating depth S curve expression of the thick-walled seamless tube as follows: ； Where p is the resistivity of the thick-walled seamless tube. The magnetic permeability of the thick-walled seamless tube; S143. Based on the temperature T-wall thickness S function relationship curve of the thick-walled seamless tube obtained in step S141, determine the heating depth s1 corresponding to the point where the temperature gradient ∆T along the radial direction of the thick-walled seamless tube is the maximum and is lower than the Curie temperature of the thick-walled seamless tube, and obtain the heating depth of the induction coil group. S144. Based on the heating depth s1 obtained in step S143 and the corresponding temperature value, determine the power W1 of the induction coil group, and then substitute s1 into the frequency H-heating depth S curve obtained in step S142 to obtain the current frequency H1 in the coil at this time.

4. The temperature control method for manufacturing thick-walled seamless tubes according to claim 1, characterized in that, The temperature-wall thickness depth function curve of the thick-walled seamless tube is plotted according to the steady-state logarithmic thermal conductivity curve of a circular tube.

5. The temperature control method for manufacturing thick-walled seamless tubes according to claim 1, characterized in that, The upper limit of the temperature difference X1 and the temperature drop difference X2 of induction heating are set according to the material properties of the thick-walled seamless tube.

6. The temperature control method for manufacturing thick-walled seamless tubes according to claim 3, characterized in that, In sub-step S24 of the cooling step, the determination process of the frequency H2 and the power W2 is as follows: S241. Based on the inner wall temperature T1 and outer wall temperature T2 of the thick-walled seamless tube measured in step S23, plot the temperature-wall thickness depth function relationship curve of the thick-walled seamless tube. S242. Based on the relative permeability and resistivity of the thick-walled seamless tube, determine the maximum heating depth corresponding to each electromagnetic frequency of the thick-walled seamless tube, and plot the frequency-heating depth curve of the thick-walled seamless tube. S243. Based on the temperature-wall thickness depth function relationship curve of the thick-walled seamless tube obtained in step S241, determine the heating depth s2 corresponding to the point where the temperature gradient ∆T along the radial direction of the thick-walled seamless tube is the maximum and is lower than the Curie temperature of the thick-walled seamless tube, and obtain the heating depth of the induction coil group. S244. Based on the heating depth s2 obtained in step S243, substitute it into the frequency-heating depth obtained in S242 to determine the frequency H2; determine the power W2 of the induction coil group through the temperature values ​​T1 and T2.

7. The temperature control method for manufacturing thick-walled seamless tubes according to claim 6, characterized in that, In the heating step, the power W1 of the induction coil group is proportional to the inner wall temperature T1 and the outer wall temperature T2, respectively; in the cooling step, the power W2 of the induction coil group is proportional to the inner wall temperature T1 and the outer wall temperature T2, respectively.

8. The temperature control method for manufacturing thick-walled seamless tubes according to claim 7, characterized in that, In the heating step, the heating depth s1 is proportional to the power W1 of the induction coil group; in the cooling step, the heating depth s2 is proportional to the power W2 of the induction coil group.

9. A temperature control device for a temperature control method for manufacturing thick-walled seamless tubes according to any one of claims 1-8, characterized in that, It includes a left induction coil group, a right induction coil group, a bracket, an inner wall temperature monitoring infrared camera and an outer wall temperature monitoring infrared camera. The left and right induction coil groups are symmetrically distributed on both sides of the thick-walled seamless tube. The inner wall temperature monitoring infrared camera is located at one end of the thick-walled seamless tube, and the outer wall temperature monitoring infrared camera is located at the upper end of the thick-walled seamless tube. The thick-walled seamless tube is fixed on the bracket.

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