Nickel-based corrosion-resistant alloy pipe end surfacing automation temperature control system and temperature control method

Abstract

The present application relates to the field of corrosion-resistant alloy cladding heat management of steel pipe ends, and particularly relates to a nickel-based corrosion-resistant alloy pipe end cladding automatic temperature control system for controllable cooling of cladded pipes during the cladding process, characterized in that the system comprises a pressing unit, a heat exchange unit, a control unit, a sensing unit and a pipe placement table. The heat exchange unit and the sensing unit are installed on the pressing unit and are connected to the control unit under control. The control unit obtains state information of the cladded pipe from the sensing unit, then generates control information and sends it to the heat exchange unit, so as to adjust the temperature of the cladded pipe. The pressing unit is installed on the pipe placement table and presses the heat exchange unit and the sensing unit to the cladded pipe, so as to ensure reliable state information and working efficiency of the heat exchange unit. The present application also comprises a method. The present application combines heat pipe heat conduction technology, temperature sensor technology and automatic control technology, so that the cladding processing time is reduced by more than half and the efficiency is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of thermal management of corrosion-resistant alloy overlay welding on steel pipe fittings, and in particular to an automated temperature control system and method for nickel-based corrosion-resistant alloy overlay welding on pipe fittings. Background Technology

[0002] Fusion-bonded epoxy powder coating is the mainstream technology for pipeline system protection. However, during on-site welding and installation of fusion-bonded epoxy powder-coated pipes, the protective integrity of the welded joints is an issue. To address this problem, some manufacturers have adopted a technique of overlaying corrosion-resistant alloy sections onto the pipe ends. However, excessively high interpass temperatures during welding alter the crystallization process of the molten pool, resulting in coarse grains and significant compositional segregation, which severely deteriorates the performance of the weld overlay. Therefore, pipe end welding suffers from low efficiency due to input temperature control issues. For example, after each layer is welded, the workpiece must be allowed to cool to a comfortable temperature before welding the next layer, and the interpass temperature must be strictly controlled, generally below 100 degrees Celsius. Currently, the main solution to the temperature input problem in pipe end welding is air cooling, but this is inefficient. If water cooling is used, the rapid cooling of the welded area creates a large temperature gradient with the substrate, leading to a significant increase in residual tensile stress at the interface, which may then cause cracks in the weld overlay. In addition, direct water cooling may cause hydrogen atoms in the water to penetrate into the high-temperature weld metal, and after cooling, they may accumulate and cause HIC hydrogen-induced cracks. Summary of the Invention

[0003] The purpose of this invention is to provide an automated temperature control system and method for overlay welding of nickel-based corrosion-resistant alloy pipe ends, which mainly solves the problems existing in the prior art.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is to provide an automated temperature control system for overlay welding of nickel-based corrosion-resistant alloy pipe ends, used to controllably cool the overlay welded pipe fittings during the overlay welding process. The system is characterized by comprising a clamping unit, a heat exchange unit, a control unit, a sensing unit, and a pipe fitting placement platform.

[0005] The heat exchange unit and the sensing unit are mounted on the clamping unit and are controlled and connected to the control unit. The control unit obtains the status information of the weld overlay pipe fitting from the sensing unit, then generates control information and sends it to the heat exchange unit to adjust the temperature of the weld overlay pipe fitting. The clamping unit is mounted on the pipe fitting placement platform to press the heat exchange unit and the sensing unit tightly against the weld overlay pipe fitting, ensuring that the sensing unit reads the correct status information and also ensuring the working efficiency of the heat exchange unit.

[0006] Furthermore, the clamping unit includes a thermal contactor and a clamping cylinder;

[0007] The clamping cylinder is fixed on the pipe fitting placement platform, and the thermal contactor is connected to the movable end of the clamping cylinder. The thermal contactor is connected to the heat exchange unit and contacts the weld overlay pipe fitting. Its contact surface is arc-shaped, and the radius of the arc is the same as the outer diameter of the weld overlay pipe fitting. When the clamping cylinder is activated and pressed against the weld overlay pipe fitting, the thermal contactor fully adheres to the outer surface of the weld overlay pipe fitting, conducting and absorbing the heat of the weld overlay pipe fitting.

[0008] Furthermore, the heat exchange unit includes a gravity heat pipe and a cooling fan;

[0009] The gravity heat pipe is connected to the compression unit and is filled with circulating working fluid. It absorbs the heat of the welded pipe through the compression unit. The cooling fan is installed near the gravity heat pipe to dissipate heat from it. Both the gravity heat pipe and the cooling fan are connected to the control unit, which adjusts the circulation speed and fan speed.

[0010] Furthermore, the gravity heat pipe includes an evaporation tank, a first steam section, a second steam section, a third steam section, a condensation section, a liquid storage section, a liquid return section, and a regulating valve;

[0011] The evaporation tank is located at the lowest plane; the first steam section is vertically arranged and connected to the evaporation tank; the second steam section is horizontally arranged, with one end connected to the top of the first steam section and the other end connected to the bottom of the third steam section; the top of the third steam section is connected to the condensation section; the liquid storage section is arranged below the condensation section; the liquid storage section is connected to the top of the return liquid section through the regulating valve; the top of the return liquid section is also connected to the bottom of the third steam section, and the bottom of the return liquid section is connected to the evaporation tank; the regulating valve is connected to the control unit, which adjusts the opening size to regulate the circulation speed.

[0012] Furthermore, in the gravity heat pipe, the return liquid section, the third vapor section, the condensation section, and the storage liquid section constitute an intermediate evaporation loop, which is used to bypass part of the circulating working fluid when the temperature of the return liquid section is too high, so that it does not pass through the evaporation tank, thereby accelerating the heat transfer process; when the circulating working fluid in liquid form flows out of the storage liquid section, part of the circulating working fluid evaporates directly in the return liquid section, and then passes through the third vapor section, enters the condensation section, and falls back to the storage liquid section after condensation.

[0013] Furthermore, in the gravity heat pipe, the third steam section, the return liquid section, the evaporation tank, the first steam section, and the second steam section constitute an intermediate condensation loop. This loop is used to allow part of the circulating working fluid to bypass the heat transfer process of the condensation section when the temperature of the circulating working fluid is low. Part of the circulating working fluid in vapor form condenses in the third steam section, and the condensed liquid form of the circulating working fluid falls downward into the return liquid section, thereby bypassing the condensation section and flowing directly into the evaporation tank. After absorbing heat, it evaporates again and then returns to the third steam section through the first steam section and the second steam section.

[0014] Furthermore, the control unit includes a programmable logic controller (PLC) and an alarm; the PLC is externally connected to the heat exchange unit and the sensing unit, and internally connected to the alarm; the PLC reads the status information from the sensing unit, manipulates the alarm to operate according to the status information, and simultaneously generates control information and sends it to the heat exchange unit.

[0015] Furthermore, the sensing unit is a temperature sensor connected to the control unit, which collects the real-time temperature of the weld overlay pipe fitting, generates the status information, and sends it to the control unit.

[0016] This invention also discloses a temperature control method using the aforementioned automated temperature control system for nickel-based corrosion-resistant alloy pipe end overlay welding, characterized by comprising the steps of...

[0017] Step S100: Set adjustment parameters on the control unit;

[0018] Step S200: Place the weld overlay pipe fitting with the weld overlay end facing downwards onto the pipe fitting placement platform; then use the clamping unit to hold the weld overlay pipe fitting, so that the heat exchange unit and the weld overlay pipe fitting form thermal contact;

[0019] In step S300, the control unit generates control information based on the adjustment parameters and the status information read from the sensing unit, and sends it to the heat exchange unit to controllably cool the weld overlay pipe fitting.

[0020] In step S400, the control unit continuously reads the status information. When the temperature of the weld overlay pipe reaches a preset value, it jumps to step S500; otherwise, it proceeds to step S300.

[0021] In step S500, the control unit stops the heat exchange unit and issues a warning message using an alarm device to indicate that the cooling operation is complete.

[0022] Step S600: Release the clamping unit, and the heat conduction unit disengages from the weld overlay fitting; remove the weld overlay fitting.

[0023] Further, in step S300, the controllable cooling includes multiple cooling cycles corresponding to different temperature ranges; each cooling cycle also includes a switching threshold, dividing the cooling cycle into a cooling cycle and a heat preservation cycle; in a cooling cycle, when the status information indicates that the temperature of the welded pipe is higher than the switching threshold, the control unit uses proportional-integral-derivative control to accelerate the transfer of heat from the welded pipe by adjusting the opening of the regulating valve of the gravity heat pipe in the heat exchange unit and adjusting the fan speed of the cooling fan in the heat exchange unit; when the status information indicates that the temperature of the welded pipe is less than or equal to the switching threshold, the control unit closes the regulating valve to enter the heat preservation cycle, i.e., the natural cooling state; after the welded pipe naturally cools down and leaves the temperature range of the current cooling cycle, it enters the next cooling cycle.

[0024] In view of the above technical features, this invention utilizes the high thermal conductivity of heat pipes (their theoretical thermal conductivity is 10,000 to 100,000 W / m·K, which is 250 times that of copper and 500 times that of aluminum). By designing a heat pipe heat conduction technology with controllable operating efficiency and combining it with temperature sensor technology and PLC control technology, this invention improves and solves the low efficiency problem caused by interlayer temperature control in the welding of nickel-based corrosion-resistant alloy pipe ends. Compared with existing technologies, this invention has significant advantages: the processing time of a single weld joint with two layers of welding is reduced by more than half, and efficiency is greatly improved. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a preferred embodiment of the automated temperature control system for overlay welding of nickel-based corrosion-resistant alloy pipe ends according to the present invention;

[0026] Figure 2 This is a system block diagram of a preferred embodiment of the automated temperature control system for nickel-based corrosion-resistant alloy pipe end overlay welding of the present invention;

[0027] Figure 3 This is a schematic diagram of the heat exchange unit in a preferred embodiment of the automated temperature control system for overlay welding of nickel-based corrosion-resistant alloy pipe ends according to the present invention;

[0028] Figure 4 This is a schematic diagram of the arrangement of the heat exchange unit and the clamping unit in a preferred embodiment of the automated temperature control system for overlay welding of nickel-based corrosion-resistant alloy pipe ends according to the present invention.

[0029] Figure 5This is a flowchart of a preferred embodiment of the temperature control method of the present invention using an automated temperature control system for overlay welding of nickel-based corrosion-resistant alloy pipe ends.

[0030] In the diagram: 100-Clamping unit, 200-Heat exchange unit, 300-Control unit, 400-Sensing unit, 500-Pipe placement platform, 600-Weld overlay pipe fitting;

[0031] 101 - Thermal contactor, 102 - Clamping cylinder 102;

[0032] 210-Gravity heat pipe, 220-Heat dissipation fan; 211-Evaporation tank, 212-First steam section, 213-Second steam section, 214-Third steam section, 215-Condensation section, 216-Liquid storage section, 217-Liquid return section, 218 Regulating valve;

[0033] 301 - Programmable Logic Controller; 302 - Alarm Device;

[0034] 601 - Weld overlay area. Detailed Implementation

[0035] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0036] This embodiment takes the end-welding of API 5L X60 steel seamless straight pipe fittings commonly used in offshore oil engineering as an example. The fitting has an outer diameter of 406.4 mm, a wall thickness of 12.7 mm, and a length of 500 mm. Inconel 625 nickel-based alloy welding wire is used as the welding material. The welding parameters are: the length of the corrosion-resistant alloy section is 100 mm on each side, the thickness of the corrosion-resistant alloy weld layer is 4 mm ± 0.5 mm, and the number of weld layers is 2. The welding type is argon arc welding, and the welding machine model is FIT-VCS1400-1200-12000 argon arc welding machine. Temperature gradient of the fitting after welding: The temperature gradient of the fitting after welding was simulated using ANSYS software. After air cooling for ten minutes, the temperature in the high-temperature zone (0 to 100 mm) is 600 to 800 °C, with a temperature gradient of 2-3 °C / mm.

[0037] Please see Figures 1 to 4This invention discloses an automated temperature control system for nickel-based corrosion-resistant alloy pipe end overlay welding. As shown in the figure, a preferred embodiment includes a clamping unit 100, a heat exchange unit 200, a control unit 300, a sensing unit 400, and a pipe fitting placement platform 500. The core of the entire system is the control unit 300, which is connected to the heat exchange unit 200 and the sensing unit 400. It acquires the status information of the overlay pipe fitting 600 from the sensing unit 400, then generates control information and sends it to the heat exchange unit 200. By changing the operating mode of the heat exchange unit 200, the temperature of the overlay pipe fitting 600 is adjusted, achieving controllable cooling. Both the heat exchange unit 200 and the sensing unit 400 are mounted on the clamping unit 100. Driven by the clamping unit 100, they are pressed against the overlay pipe fitting 600. Pressure contact reduces the thermal resistance between the clamping unit 200 and the overlay pipe fitting 600, ensuring the working efficiency of the heat exchange unit 200, improving heat conduction efficiency, making temperature control more precise, and ensuring that the sensing unit 400 reads the correct status information. The clamping unit 100, the heat exchange unit 200, and the sensing unit 400 are all arranged in pairs symmetrically and are located at both ends of the circular diameter of the cross-section of the weld overlay pipe fitting 600.

[0038] A clamping unit 100, mounted on a pipe fitting placement platform 500, includes a thermal contactor 101 and a clamping cylinder 102. It is used to fix and clamp the weld overlay pipe fitting 600, while simultaneously pressing the heat exchange unit 200 and the sensing unit 400 against the weld overlay pipe fitting 600. The clamping cylinder 102 is directly fixed to the pipe fitting placement platform 500, with the thermal contactor 101 mounted on its movable end. One side of the thermal contactor 101 contacts the weld overlay pipe fitting 600, and its contact surface is arc-shaped. The radius of this arc is the same as the outer diameter of the weld overlay pipe fitting 600. The thermal contactor 101 is also connected to the heat exchange unit 200. Thus, when the clamping cylinder 102 actuates, pressing the thermal contactor 101 against the weld overlay pipe fitting 600, the thermal contactor 101 can fully adhere to the outer surface of the weld overlay pipe fitting 600, absorbing heat from the weld overlay pipe fitting 600 and conducting it to the heat exchange unit 200. In this embodiment, the thermal contactor 101 is made of copper, with an arc shape, an arc of 90 degrees, a thickness of 50 mm, and an axial length of 300 mm. A total of four thermal contactors 101 are used, arranged in pairs, facing each other. Furthermore, due to the heat resistance limitations of the interface thermally conductive material, the position of the thermal contactor 101 is moved 200 mm upwards from the weld overlay portion 601, meaning the weld overlay pipe fitting 600 and the thermal contactor 101 are 200 to 500 mm from the weld overlay pipe end.

[0039] The heat exchange unit 200 includes a gravity heat pipe 210 and a cooling fan 220. The gravity heat pipe 210 has a vacuum-sealed structure and is connected to a heat contactor 101 on the compression unit 100. It is filled with a circulating working fluid, which conducts and absorbs heat from the welded pipe fitting 600 through the heat contactor 101. It consists of an evaporation tank 211, a first steam section 212, a second steam section 213, a third steam section 214, a condensation section 215, a liquid storage section 216, a liquid return section 217, and a regulating valve 218. The cooling fan 220 is installed near the condensation section 215 of the gravity heat pipe 210 to dissipate heat and cool the circulating working fluid in the gravity heat pipe 210. Both the regulating valve 218 and the cooling fan 220 in the gravity heat pipe 210 are controlled by a control unit 300. The control unit 300 sets the opening of the regulating valve 218 to adjust the circulation speed of the circulating working fluid and can also directly adjust the fan speed of the cooling fan 220.

[0040] In the gravity heat pipe 210, the evaporation tank 211 is arc-shaped and located at the lowest plane. A first steam section 212 is vertically connected to the evaporation tank 211. Both the evaporation tank 211 and the first steam section 212 are located within the heat contactor 101. The arc of the evaporation tank 211 is concentric with the arc of the heat contactor 101, and the first steam section 212 is perpendicular to the arc surface of the evaporation tank 211. At the top of the first steam section 212, one end of a horizontally arranged second steam section 213 is connected. The other end of the second steam section 213 is connected to the bottom of a vertically arranged third steam section 214. The top of the third steam section 214 is connected to a condensation section 215. A liquid storage section 216 is located below the condensation section 215. The inner diameter of the liquid storage section 216 is larger than the inner diameters of the evaporation tank 211, the first steam section 212, the second steam section 213, the third steam section 214, and the return liquid section 217. When the regulating valve 218 is closed and all the circulating working fluid in the evaporation tank 211 has completely evaporated, the circulating working fluid in the gravity heat pipe 210 is entirely located in the storage section 216. The storage section 216 is connected to the top of the return section 217 via the regulating valve 218, and the top of the return section 217 is also directly connected to the bottom of the third steam section 214. The bottom of the return section 217 is connected to the evaporation tank 211. In this embodiment, the gravity heat pipe 210 is made of 304 stainless steel, and the circulating working fluid is tertiary distilled water. The inner diameter of the storage section 216 is 100 mm, the effective length of the storage section 216 is 200 mm, and the effective volume of the storage section 216 is 1570 ml. The inner diameter of the first steam section 212, the second steam section 213, the third steam section 214 and the return liquid section 217 is 20mm. The width of the evaporation tank 211 is 25mm and the depth is 40mm, that is, the volume of the evaporation tank 211 is 338ml.

[0041] In the gravity heat pipe 210, the circulating working fluid comprises a complete cycle and two sub-cycles. In the complete cycle, the circulating working fluid in the evaporation tank 211 is heated by the heat contactor 101 and becomes gaseous, entering the second steam end 213 through the first steam section 212. Specifically, as it rises along the first steam section 212, it continues to absorb heat from the heat contactor 101, thereby removing more heat. The gaseous circulating working fluid continues along the second steam end 213 and the third steam section 214 into the condensation section 215. In the condensation section 215, the circulating working fluid releases heat and becomes liquid again, descending into the liquid storage section 216. The cooling rate of the circulating working fluid can be adjusted by changing the rotation speed of the cooling fan 220 installed outside the condensation section 215. The liquid circulating working fluid in the liquid storage section 216 passes through the regulating valve 218 and then re-enters the evaporation tank 211 through the return section 217 to absorb heat.

[0042] When the temperature of the circulating working fluid in the gravity heat pipe 210 is low, the circulation process forms a first type of sub-cycle through the intermediate condensation loop. The intermediate condensation loop consists of an evaporation tank 211, a first steam section 212, a second steam section 213, a third steam section 214, and a return liquid section 217. In the first type of sub-cycle, part of the circulating working fluid in vapor form is cooled in the third steam section 214. Because its initial temperature is low enough, its temperature in the third steam section 214 has dropped to a point sufficient for condensation, so part of the circulating working fluid has become liquid in the third steam section 214. The condensed liquid circulating working fluid falls directly into the return liquid section 217, thus bypassing the condensation section 215 and returning directly to the evaporation tank 211 to re-enter the endothermic evaporation cycle.

[0043] When the temperature of the circulating working fluid in the gravity heat pipe 210 is too high, the circulation process forms a second type of sub-circulation through the intermediate evaporation circuit. The intermediate evaporation circuit consists of a third steam section 214, a condensation section 215, a storage section 216, and a return section 217. It is used to bypass the evaporation tank 211 and introduce part of the circulating working fluid back into the condensation section 215 for cooling, thereby rapidly reducing the temperature of the circulating working fluid, improving the overall heat exchange efficiency, and accelerating the cooling of the circulating working fluid. In the second type of sub-circulation, the liquid circulating working fluid flowing out of the storage section 216 flows through the return section 217. If the temperature of the return section 217 is too high, part of the circulating working fluid reaches the evaporation temperature in the return section 217, turns into steam, rises into the third steam section 214, and then enters the condensation section 215 again for cooling. After condensation, it falls back into the storage section 216.

[0044] The control unit 300 includes a programmable logic controller (PLC) 301 and an alarm 302. The PLC 301 is the core of the control logic; it connects externally to the regulating valve 218 and cooling fan 220 in the heat exchange unit 200, as well as the sensing unit 400, and internally to the alarm 302. The PLC 301 reads status information from the sensing unit 400 as input, then generates control information based on the status information and sends it to the heat exchange unit 200 to control the operating status of the regulating valve 218 and cooling fan 220. Simultaneously, the PLC 301 also manipulates the alarm based on the status information to indicate the status of the cooling process of the welded pipe fitting 600, such as issuing a warning when the set temperature is reached or when a system abnormality occurs.

[0045] The sensing unit 400 is a temperature sensor installed in the thermal contactor 101. It collects the real-time temperature of the weld overlay pipe fitting 600 and generates status information to report to the control unit 100.

[0046] Please see Figure 5 The present invention also discloses a temperature control method using the above-mentioned automated temperature control system for nickel-based corrosion-resistant alloy pipe end overlay welding. A preferred embodiment includes the following steps:

[0047] Step S1: Set the adjustment parameters.

[0048] Different cooling strategies are employed for different types of weld overlay pipe fittings. Therefore, before work begins, adjustment parameters are set on the control unit according to the type of weld overlay pipe fitting. In this embodiment, the adjustment parameters include the expected cooling rate.

[0049] Step S2: Install and fix the weld overlay pipe fittings.

[0050] Place the weld overlay pipe fitting onto the fitting placement platform with the weld overlay end facing downwards. Then, apply an interfacial heat-conducting material to the contact surface between the weld overlay pipe fitting and the heat contactor. Finally, activate the clamping unit, and the clamping cylinder will clamp the weld overlay pipe fitting, while simultaneously causing the heat contactor to adhere to the outer surface of the weld overlay pipe fitting, thereby establishing thermal contact between the heat exchange unit and the weld overlay pipe fitting.

[0051] In this embodiment, the interfacial thermal conductive material is crucial for the heat transfer efficiency between the welded pipe fitting and the thermal contactor. Therefore, JB103-400 type high-temperature resistant thermal conductive silicone grease is selected, with an operating temperature range of -50 to 400 degrees Celsius and a thermal conductivity of 3.0 W / mK. The pressure between the thermal contactor and the welded pipe fitting is maintained at 1 MPa.

[0052] Step S3: Controllably cool the weld overlay pipe fittings according to the adjustment parameters.

[0053] The control unit generates control information based on pre-configured adjustment parameters and status information read from the sensing unit, and sends it to the heat exchange unit. The heat exchange unit then controls the cooling of the welded pipe fitting. For example, it reads the expected cooling rate from the adjustment parameters, calculates the actual cooling rate using the status information, compares the difference between the expected and actual cooling rates, and uses proportional-integral-derivative (PID) control to generate control information. This adjusts the circulation speed of the working fluid and the fan speed of the cooling fan until they are consistent. Furthermore, due to contact thermal resistance and conduction hysteresis, there is a certain temperature difference between the actual temperature of the welded area of ​​the welded pipe fitting and the temperature collected by the sensing unit. Therefore, the temperature value collected in the status information is adjusted upwards by 10 to 30 degrees Celsius as a correction.

[0054] Specifically, the controllable cooling process comprises multiple cooling cycles, each corresponding to a different temperature range. Within each cooling cycle, a switching threshold is defined, dividing the cycle into a cooling cycle and a holding cycle. In a single cooling cycle, the welded pipe fitting is first rapidly cooled using the cooling cycle, followed by a holding cycle that allows it to cool naturally until its temperature leaves the temperature range corresponding to the current cooling cycle.

[0055] When the status information indicates that the temperature of the welded pipe fitting is higher than the switching threshold, the control unit uses proportional-integral-derivative (PID) control to adjust the opening of the regulating valve and the speed of the cooling fan, thereby accelerating the transfer of heat from the welded pipe fitting and achieving rapid cooling. When the status information indicates that the temperature of the welded pipe fitting is less than or equal to the switching threshold, the heat preservation cycle begins. At this time, the control unit closes the regulating valve and stops the main circulation of the working fluid, allowing the welded pipe fitting to enter a natural cooling state.

[0056] In this embodiment, the cooling process for the weld overlay pipe fitting is divided into five cooling cycles, covering a temperature range from above 550 degrees Celsius to 100 degrees Celsius. The weld overlay pipe fitting begins its cooling process in different cooling cycles based on its actual temperature.

[0057] process Starting temperature (degrees Celsius) Set cooling rate (degrees Celsius per second) Purpose Time (seconds) Cooling cycle 1 A1 point to 550℃ 30 austenite to pearlite Insulation cycle 1 550℃ Austenite completely transforms into pearlite 300 Cooling cycle 2 550 to 450℃ 10 Slow cooling to avoid stress concentration Insulation cycle 2 450℃ Stress relief 300 Cooling cycle 3 450 to 350℃ 10 Slow cooling to avoid stress concentration Insulation cycle 3 350℃ Stress relief 300 Cooling cycle 4 350 to 250℃ 10 Slow cooling to avoid stress concentration Insulation cycle 4 250℃ Stress relief 300 Cooling cycle 5 250 to 100℃ 10 Slow cooling to avoid stress concentration Insulation period 5 100℃ Stress relief 300

[0058] The control strategies employed by the control unit for the five cooling cycles, as well as the cooling and holding cycles within each cooling cycle, are shown in the table below. Here, ti represents the real-time temperature collected by the sensing unit.

[0059] Procedure number Process maintenance conditions (degrees Celsius) Cooling speed adjustment Proceed to the next step (ti is in degrees Celsius). Timing method Cooling cycle 1 ti ≥ 550℃ Cooling + PID regulation if <550℃ Insulation cycle 1 540℃<ti<550℃ Heat pipe off Heat preservation time = 300 seconds Timer timing Cooling cycle 2 450℃≤ti<550℃ Cooling + PID regulation if <450℃ Insulation cycle 2 440℃<ti<450℃ Heat pipe off Heat preservation time = 300 seconds Timer timing Cooling cycle 3 350℃≤ti<450℃ Cooling + PID regulation if <350℃ Insulation cycle 3 340℃<ti<350℃ Heat pipe off Heat preservation time = 300 seconds Timer timing Cooling cycle 4 250℃≤ti<350℃ Cooling + PID regulation if <250℃ Insulation cycle 4 240℃<ti<250℃ Heat pipe off Heat preservation time = 300 seconds Timer timing Cooling cycle 5 100℃≤ti<250℃ Cooling + PID regulation ti = 100℃ Insulation period 5 90℃<ti<100℃ Heat pipe off Heat preservation time = 300 seconds Timer timing

[0060] Step S4: Determine whether the cooling process is complete.

[0061] The control unit reads the status information. When the temperature of the welded pipe reaches the preset value, it jumps to step S5 to complete the cooling operation; otherwise, it proceeds to step S3 to continue the cooling operation.

[0062] Step S5: Cooling operation completed.

[0063] The control unit stops the heat exchange unit and issues a warning message using an alarm to indicate that the cooling operation is complete.

[0064] Step S6: Remove the weld overlay pipe fitting.

[0065] The clamping unit is released, the clamping cylinder is released, and the weld overlay fitting is released, thus severing the thermal contact between the heat conduction unit and the weld overlay fitting. The weld overlay fitting is then removed.

[0066] The following describes the evaluation of the actual cooling effect in this embodiment. After the first layer of welding is applied to the pipe end of the weld overlay fitting, the fitting is air-cooled for 10 minutes, then placed on the fitting placement platform. The hydraulic system is activated, and the heat contactors connected to the gravity heat pipes are pressed against the weld overlay fitting in pairs horizontally. Before pressing, JB103-400 type high-temperature resistant thermally conductive silicone grease is applied to the contact surface of the heat contactors to eliminate air at the contact surface and improve thermal conductivity.

[0067] After the system was turned on, the temperature sensor displayed a real-time temperature of 420 degrees Celsius. Referring to the table above, cooling cycle 3 covers temperatures from 350 degrees Celsius to 450 degrees Celsius; therefore, 420 degrees Celsius corresponds to cooling cycle 3. Thus, under the control of the control unit, the system entered cooling cycle 3 (the third cooling cycle) and sequentially executed cooling cycle 3, holding cycle 3, cooling cycle 4, holding cycle 4, cooling cycle 5, and holding cycle 5. The total process took 47 minutes, and the measured temperature of the welded area after completion was 96 degrees Celsius.

[0068] After the cooling process was completed, crack detection and microstructure analysis were performed on the weld overlay pipe fittings. No cracks were found. The microstructure of the heat-affected zone was mainly pearlite and a small amount of ferrite, with no martensite detected. No obvious Nb or Mo element segregation or Laves brittle phases were found in the weld overlay.

[0069] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An automated temperature control system for overlay welding of nickel-based corrosion-resistant alloy pipe ends, used for controllable cooling of the welded pipe fittings during the overlay welding process, characterized in that... It includes a pressing unit, a heat exchange unit, a control unit, a sensing unit, and a pipe placement platform; The heat exchange unit and the sensing unit are mounted on the clamping unit and are controlled to be connected to the control unit. The control unit obtains the status information of the weld overlay pipe fitting from the sensing unit, then generates control information and sends it to the heat exchange unit to adjust the temperature of the weld overlay pipe fitting. The clamping unit is mounted on the pipe fitting placement platform to press the heat exchange unit and the sensing unit tightly against the weld overlay pipe fitting, ensuring that the sensing unit reads the correct status information and also ensuring the working efficiency of the heat exchange unit. The clamping unit includes a thermal contactor and a clamping cylinder; The clamping cylinder is fixed on the pipe fitting placement platform, and the thermal contactor is connected to the movable end of the clamping cylinder. The thermal contactor is connected to the heat exchange unit and contacts the weld overlay pipe fitting. Its contact surface is arc-shaped, and the radius of the arc is the same as the outer diameter of the weld overlay pipe fitting. When the clamping cylinder is activated and pressed against the weld overlay pipe fitting, the thermal contactor fully adheres to the outer surface of the weld overlay pipe fitting, conducting and absorbing the heat of the weld overlay pipe fitting. The heat exchange unit includes a gravity heat pipe and a cooling fan; The gravity heat pipe is connected to the compression unit and is filled with circulating working fluid. It absorbs the heat of the welded pipe through the compression unit. The cooling fan is installed near the gravity heat pipe to dissipate heat from it. Both the gravity heat pipe and the cooling fan are connected to the control unit, which adjusts the circulation speed and fan speed. The gravity heat pipe includes an evaporation tank, a first steam section, a second steam section, a third steam section, a condensation section, a liquid storage section, a liquid return section, and a regulating valve; The evaporation tank is located at the lowest plane; the first steam section is vertically arranged and connected to the evaporation tank; the second steam section is horizontally arranged, with one end connected to the top of the first steam section and the other end connected to the bottom of the third steam section; the top of the third steam section is connected to the condensation section; the liquid storage section is arranged below the condensation section; the liquid storage section is connected to the top of the return liquid section through the regulating valve; the top of the return liquid section is also connected to the bottom of the third steam section, and the bottom of the return liquid section is connected to the evaporation tank; the regulating valve is connected to the control unit, which adjusts the opening size to regulate the circulation speed.

2. The automated temperature control system for nickel-based corrosion-resistant alloy pipe end overlay welding according to claim 1, characterized in that, In the gravity heat pipe, the return liquid section, the third vapor section, the condensation section, and the storage liquid section constitute an intermediate evaporation loop. This loop is used to bypass part of the circulating working fluid when the temperature of the return liquid section is too high, preventing it from passing through the evaporation tank and accelerating the heat transfer process. When the liquid circulating working fluid flowing out of the storage liquid section passes through the return liquid section, part of the circulating working fluid evaporates directly in the return liquid section, then passes through the third vapor section, enters the condensation section, condenses, and falls back to the storage liquid section.

3. The automated temperature control system for nickel-based corrosion-resistant alloy pipe end overlay welding according to claim 1, characterized in that, In the gravity heat pipe, the third steam section, the return liquid section, the evaporation tank, the first steam section, and the second steam section constitute an intermediate condensation loop. This loop is used to allow part of the circulating working fluid to bypass the heat transfer process of the condensation section when the temperature of the circulating working fluid is low. Part of the circulating working fluid in vapor form condenses in the third steam section, and the condensed liquid form of the circulating working fluid falls downward into the return liquid section, thus bypassing the condensation section and flowing directly into the evaporation tank. After absorbing heat, it evaporates again and then returns to the third steam section through the first steam section and the second steam section.

4. The automated temperature control system for nickel-based corrosion-resistant alloy pipe end overlay welding according to claim 1, characterized in that, The control unit includes a programmable logic controller (PLC) and an alarm; the PLC is externally connected to the heat exchange unit and the sensing unit, and internally connected to the alarm; the PLC reads the status information from the sensing unit, manipulates the alarm to operate according to the status information, and generates control information to send to the heat exchange unit.

5. The automated temperature control system for nickel-based corrosion-resistant alloy pipe end overlay welding according to claim 1, characterized in that, The sensing unit is a temperature sensor connected to the control unit, which collects the real-time temperature of the weld overlay pipe fitting, generates the status information, and sends it to the control unit.

6. A temperature control method using the automated temperature control system for nickel-based corrosion-resistant alloy pipe end overlay welding as described in claim 1, characterized in that, Includes steps, Step S100: Set adjustment parameters on the control unit; Step S200: Place the weld overlay pipe fitting with the weld overlay end facing downwards onto the pipe fitting placement platform; then use the clamping unit to hold the weld overlay pipe fitting, so that the heat exchange unit and the weld overlay pipe fitting form thermal contact; In step S300, the control unit generates control information based on the adjustment parameters and the status information read from the sensing unit, and sends it to the heat exchange unit to controllably cool the weld overlay pipe fitting. In step S400, the control unit continuously reads the status information. When the temperature of the weld overlay pipe reaches a preset value, it jumps to step S500; otherwise, it proceeds to step S300. In step S500, the control unit stops the heat exchange unit and issues a warning message using an alarm device to indicate that the cooling operation is complete. Step S600: Release the clamping unit, and the heat exchange unit disengages from the weld overlay fitting; remove the weld overlay fitting.

7. The temperature control method according to claim 6, characterized in that, In step S300, the controllable cooling includes multiple cooling cycles corresponding to different temperature ranges. Each cooling cycle also includes a switching threshold, dividing the cooling cycle into a cooling cycle and a heat preservation cycle. In a cooling cycle, when the status information indicates that the temperature of the welded pipe is higher than the switching threshold, the control unit uses proportional-integral-derivative (PID) control to accelerate the transfer of heat from the welded pipe by adjusting the opening of the regulating valve of the gravity heat pipe in the heat exchange unit and adjusting the fan speed of the cooling fan in the heat exchange unit. When the status information indicates that the temperature of the welded pipe is less than or equal to the switching threshold, the control unit closes the regulating valve to enter the heat preservation cycle, i.e., the natural cooling state. Once the welded pipe has naturally cooled and left the temperature range of the current cooling cycle, it enters the next cooling cycle.

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