Test coil heat treatment system and process

Abstract

The invention discloses a test coil heat treatment system and process, and the system comprises a vertical gas furnace which is used for accommodating and heating a test coil; the crucible is arranged in the vertical gas furnace and is used for directly carrying out heat treatment on the test coil; the argon protection control system is connected with the vertical gas furnace and the built-in crucible, provides high-purity argon to replace gas, maintains micro-charging and micro-discharging in the heat treatment process, and controls the temperature in the vertical gas furnace so as to meet the heat treatment of the coil; the argon supply system is used for supplying argon to the vertical gas furnace and the built-in crucible; and the monitoring and control system is used for monitoring and controlling the temperature, the pressure and the flow in the heat treatment process in real time. The temperature control system and the thermocouple are used in cooperation, accurate temperature control over the coil in different stages can be achieved, the heat treatment quality is improved, the argon protection system provides a stable protection atmosphere for the coil through the preheating coil and the flow control valve, oxidation and impurity pollution are effectively prevented, and the corrosion resistance and the electrical performance of the coil are improved.

Description

Technical Field

[0001] The invention relates to a test coil heat treatment system and process. Background Art

[0002] A coil usually refers to a ring-shaped wire winding. The most common coil applications include motors, inductors, transformers, and loop antennas. Test coils are mainly used for winding structures of heat-treated parts.

[0003] In the traditional test coil heat treatment process, there are usually problems such as inaccurate temperature control, poor temperature uniformity in the furnace, and high impurity content in the heat treatment environment. These problems may lead to unstable heat treatment effects on coil materials and affect the final performance of the coil. In addition, traditional heat treatment systems often lack effective argon protection and precise gas replacement mechanisms, making the coil susceptible to oxidation and contamination during the heat treatment process. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions: a test coil heat treatment system, comprising:

[0005] A vertical gas furnace to contain and heat the test coils;

[0006] Crucible, placed inside the vertical gas furnace, used to directly heat treat the test coil;

[0007] Argon protection control system, connected to the vertical gas furnace and built-in crucible, provides high-purity argon to replace gas and maintain micro-filling and micro-discharging during heat treatment, and controls the temperature in the vertical gas furnace to meet the heat treatment of the coil;

[0008] Argon gas supply system, used to supply argon gas to the vertical gas furnace and built-in crucible;

[0009] Monitoring and control systems are used to monitor and control temperature, pressure and flow in real time during heat treatment.

[0010] As a preferred technical solution of the present invention, the temperature control system includes a thermocouple and a temperature controller. The thermocouple is arranged at different positions of the coil to monitor the temperature of the coil in real time. The temperature controller receives the signal of the thermocouple and controls the heating element to achieve precise temperature control. The heating element is connected to the gas supply pipeline, and the gas supply pipeline transports the gas to the combustion chamber of the vertical gas furnace.

[0011] As a preferred technical solution of the present invention, the argon protection control system includes a liquid argon tank, a heat exchanger, an argon pipeline, an automatic valve and a pressure gauge. The argon pipeline connects the liquid argon tank and the heat exchanger as well as the heat exchanger and the vertical gas furnace. The automatic valve is used to control the flow rate of argon. The pressure gauge is used to monitor the pressure of argon. The argon pipeline is further connected to a crucible in the vertical gas furnace to realize the circulation of argon.

[0012] As a preferred technical solution of the present invention, the argon gas in the argon tank is divided into slightly positive pressure argon gas and high pressure argon gas through an automatic valve, the slightly positive pressure argon gas is passed into the crucible, and the high pressure argon gas is passed into the heat treatment coil.

[0013] As a preferred technical solution of the present invention, it also includes a hybrid heating system, which includes a natural gas heating system and an electric heating system. The electric heating system includes an electric heater and an electric heating pipeline arranged outside the vertical gas furnace. The electric heating system is used to heat the slightly positive pressure argon gas.

[0014] As a preferred technical solution of the present invention, the natural gas heating system includes a burner arranged on a vertical gas furnace. The natural gas is burned through the burner, and the generated gas forms a vortex that runs through the entire furnace body in the vertical gas furnace. The gas vortex is used to insulate the crucible in the vertical gas furnace and preheat the high-pressure argon gas.

[0015] As a preferred technical solution of the present invention, the monitoring and control system includes a sampling unit, a gas pretreatment system, a gas analyzer and a control unit. The sampling unit includes a pipeline stainless steel flange sampler, which filters the sample gas and transports it to the gas controller. The gas pretreatment system is used to process the gas sample collected by the sampling unit. The gas analyzer is used to analyze the processed gas sample. The control unit is used to receive data from the gas analyzer and control the entire heat treatment process. The control unit is connected to each sampling unit, the gas pretreatment system and the gas analyzer through a data line.

[0016] As a preferred technical solution of the present invention, the vertical gas furnace and the crucible are both made of composite steel plates, the crucible is completely sealed, and is evacuated by a vacuum system.

[0017] As a preferred technical solution of the present invention, the vacuum tube system includes a vacuum unit and a vacuum gauge for evacuating the crucible and the coil, and the vacuum unit includes a Roots pump and a screw pump;

[0018] Among them, a pneumatic butterfly valve is configured, a water-cooling jacket is configured on the pipeline between the pneumatic butterfly valve and the Roots pump, the vacuum unit and the vertical gas furnace are connected through a stainless steel pipeline, and a bypass pipeline and a pneumatic baffle valve are also configured. The bypass pipeline is connected to the coil evacuation pipeline.

[0019] A test coil heat treatment process, the specific steps are as follows:

[0020] S1. Preparation: Fix the test coil with a fixture to ensure the outer dimensions of the winding and prevent deformation during the heat treatment. Preheat the test coil and the anti-deformation tooling. The size of the anti-deformation tooling is slightly larger than the size of the test coil. Ensure that the tooling is suitable for the formal coil and the test coil. Then place the test coil in the built-in crucible of the vertical gas furnace. The crucible is designed for directly heat treating the test coil.

[0021] S2, preheating, gas replacement in the furnace and winding, use preheating coil to preheat argon, and adjust the inlet flow and pressure through the flow control valve, start the argon protection system, fill the furnace with high-purity argon, perform gas replacement, and establish an oxygen-free or low-oxygen atmosphere;

[0022] S3, heating up, controlling the heating element in the vertical gas furnace through the temperature control system, heating up according to a predetermined temperature curve until the temperature of the first insulation stage of the heat treatment is reached;

[0023] S4, heat preservation, keep the coil at 210 degrees Celsius for 50 hours, then keep it at 340 degrees Celsius for 25 hours, then keep it at 450 degrees Celsius for 25 hours, and finally keep it at 575 degrees Celsius for 100 hours. The temperature control accuracy of each stage is better than ±1.0 degrees Celsius;

[0024] S5, maintaining the coil at 650 degrees Celsius for 100 hours to complete the final heat treatment stage;

[0025] S6. Use monitoring and control systems to monitor the temperature, pressure, flow and other parameters of the coil in real time to ensure the stability and uniformity of the heat treatment process;

[0026] S7. Record the key parameters during the heat treatment process, including furnace temperature, coil temperature, inlet pressure, outlet pressure, furnace pressure, furnace inlet flow, coil inlet flow, oxygen content, water content and hydrocarbon content;

[0027] S8. Ensure that the heat treatment system can operate stably and continuously for 45 days. After completion, conduct a quality inspection on the appearance and internal structure of the coil to ensure that the heat treatment effect meets the design requirements.

[0028] Compared with the prior art, the beneficial effects that the present invention can achieve are: through the coordinated use of the temperature control system and the thermocouple, precise temperature control of the coil at different stages can be achieved, thereby improving the quality of heat treatment; the argon protection system provides a stable protective atmosphere for the coil through the preheating coil and the flow control valve, effectively preventing oxidation and impurity pollution, and improving the corrosion resistance and electrical properties of the coil; the monitoring and control system can monitor and record the key parameters in the heat treatment process of the coil in real time, providing important data support for process optimization and quality traceability; the heat treatment process can adapt to coils of different materials and sizes, has good adaptability and flexibility, and can meet the personalized needs of different customers. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the overall structure of the present invention from a first viewing angle;

[0030] Figure 2 The stress and deformation diagram of the crucible in the cold state of the present invention;

[0031] Figure 3 is a stress and deformation diagram inside the crucible at high temperature of the present invention;

[0032] Figure 4 It is the temperature distribution cloud diagram of the present invention;

[0033] Figure 5 is a flow field distribution diagram in the crucible of the present invention;

[0034] Figure 6 It is the temperature isobar distribution diagram of the present invention.

[0035] Among them: 1. Vertical gas furnace; 2. Crucible; 3. Thermocouple; 4. Argon tank; 5. Argon pipeline; 6. Automatic valve; 7. Pressure gauge; 8. Heat exchanger; 9. Electric heating pipeline; 10. Burner. DETAILED DESCRIPTION

[0036] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments, but the following embodiments are only preferred embodiments of the present invention, not all. Based on the embodiments in the implementation mode, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention. The experimental methods in the following embodiments, unless otherwise specified, are conventional methods, and the materials, reagents, etc. used in the following embodiments, unless otherwise specified, can be obtained from commercial channels.

[0037] Example:

[0038] This embodiment proposes a test coil heat treatment system, including a vertical gas furnace 1, which is placed in a nuclear vessel plant. The furnace body is cylindrical in shape. The inner wall diameter of the vertical gas furnace 1 is 12 meters, and it is divided into 4 sections. The height of the furnace is 12 meters, and the height of the furnace is more than 8 meters. The maximum heat treatment temperature is 900 degrees Celsius, and the temperature control range is ±7 degrees Celsius. The dimensions are: Material: SA387 12CL2+TP410S composite steel plate, the heat treatment process meets the maximum temperature of 690 degrees Celsius, and the insulation time is 4 hours. Used to accommodate and heat the test coil; Crucible 2, placed inside the vertical gas furnace 1, is used to directly heat treat the test coil; Crucible 2 is made of high-temperature resistant stainless steel and is completely sealed. After discharging, it needs to be evacuated and replaced with argon, and the concentration of argon and other gases such as oxygen and water are monitored. When the concentration content does not meet the standard, argon is supplemented and replaced, and the positive pressure of argon is always maintained in the crucible 2. The argon protection control system is connected to the vertical gas furnace 1 and the built-in crucible 2 to provide high-purity argon to replace the gas and maintain micro-filling and micro-discharging during the heat treatment process, and control the temperature in the vertical gas furnace 1 to meet the heat treatment of specific coils; Argon gas supply system, used to provide argon to the vertical gas furnace 1 and the built-in crucible 2; Monitoring and control system, used to monitor and control the temperature, pressure and flow rate during the heat treatment process in real time;

[0039] The argon protection control system includes a liquid argon tank, a heat exchanger 8, an argon pipeline 5, an automatic valve 6 and a pressure gauge 7. The argon pipeline 5 connects the liquid argon tank and the heat exchanger 8 and the heat exchanger 8 and the vertical gas furnace 1. The automatic valve 6 is used to control the flow rate of argon, and the pressure gauge 7 is used to monitor the pressure of argon. The argon pipeline 5 is further connected to the crucible 2 in the vertical gas furnace 1 to realize the circulation of argon. The intake pipelines for gas replacement in the furnace and the winding need to install preheating coils in the furnace. The intake flow and pressure in the winding are adjustable, and the appropriate intake pressure is preset according to the flow resistance of the conductor. For the reserved inlet and outlet pipeline interfaces of the furnace, the pipe diameter, quantity and position should refer to the numerical simulation analysis results of the temperature uniformity design scheme. The argon in the argon tank 4 is divided into slightly positive pressure argon and high pressure argon through the automatic valve 6. The slightly positive pressure argon is passed into the crucible 2, and the high pressure argon is passed into the heat treatment coil. According to the different functions of the two argon gas paths, the argon gas heating part is divided into two parts, and both paths are passed into their respective preheaters. The hot heater is a spiral tube installed outside the crucible 2, and the spiral tube is placed in a vertical furnace. The high-temperature combustion gas in the vertical furnace first preheats the argon gas so that the argon gas outlet temperature reaches the required temperature. The preheated argon gas is compensated by micro-positive pressure and high-voltage electric heating compensators, respectively, to achieve the purpose of precise temperature control and rapid response. The argon gas is discharged through the coil and the crucible 2, and the argon gas is tested according to the requirements after cooling. The coil must meet the requirements of heat treatment time, temperature curve, temperature uniformity and gas impurity content at the same time. It also includes a mixed heating system, which includes a natural gas heating system and an electric heating system. The electric heating system includes an electric heater arranged outside the vertical gas furnace 1 and an electric heating pipeline 9. The electric heating system is used to heat the micro-positive pressure argon gas.

[0040] The natural gas heating system includes a burner 10 arranged on the vertical gas furnace 1. Natural gas is burned through the burner 10, and the generated gas forms a vortex that runs through the entire furnace body in the vertical gas furnace 1. The gas vortex is used to keep the crucible 2 in the vertical gas furnace 1 warm and preheat the high-pressure argon gas. Two layers of 8 320kw gas burners 10 are arranged in a staggered manner in the upper and lower layers to ensure the temperature uniformity in the furnace. For example, the required temperature in the crucible 2 is 650 degrees Celsius, and the burner 10 is used to increase the furnace temperature to 640±5 degrees Celsius).

[0041] The monitoring and control system includes a sampling unit, a gas pretreatment system, a gas analyzer and a control unit. The sampling unit includes a pipeline stainless steel flange sampler, which filters the sample gas and transports it to the gas controller. The gas pretreatment system is used to process the gas sample collected by the sampling unit. The gas analyzer is used to analyze the processed gas sample. The control unit is used to receive the data of the gas analyzer and control the entire heat treatment process. The control unit is connected to each sampling unit, the gas pretreatment system and the gas analyzer through a data line. The vertical gas furnace 1 and the crucible 2 are made of composite steel plates. The crucible 2 is completely sealed and evacuated by a vacuum system. During the heat treatment process, in order to ensure the outer dimensions of the winding, a clamp is required to fix the sub-coil. Before the formal heat treatment, the test coil and the anti-deformation tooling are now heat treated. The anti-deformation tooling is suitable for the formal coil and the test coil, and the size is slightly larger than the first size. The coil is made of ITER-grade Nb3Sn wire, and is kept at 210 degrees Celsius for 50 hours + 340 degrees Celsius for 25 hours + 450 degrees Celsius for 25 hours + 575 degrees Celsius for 100 hours + 650 degrees Celsius for 100 hours + cooled to 500 degrees Celsius and then cooled with the furnace. (2) The heating rate of the effective temperature uniformity zone of the furnace (including the winding) is 5 degrees Celsius / h (from room temperature to 650 degrees Celsius); the maximum cooling rate of the effective temperature uniformity zone of the furnace (including the winding) is not more than 5 degrees Celsius / h (from 650 degrees Celsius to 500 degrees Celsius). The temperature uniformity of the furnace of the heat treatment system must meet the following requirements: Heating stage: when the furnace temperature is <450 degrees Celsius, the winding temperature uniformity △T≤±25 degrees Celsius; when the furnace temperature is ≥450 degrees Celsius, the winding temperature uniformity △T≤±20 degrees Celsius; Insulation stage: 210 degrees Celsius, 340 degrees Celsius, 450 degrees Celsius, and 650 degrees Celsius are stable, and the winding temperature uniformity △T≤±5 degrees Celsius. The heating rate of the effective temperature uniformity zone (including the winding) of the heat treatment system furnace is continuously adjustable between 0 degrees Celsius / h and 20 degrees Celsius / h; the maximum heating temperature of the furnace body is 750 degrees Celsius; the temperature control accuracy is better than ±1.0 degrees Celsius; the heating elements of the heat treatment furnace are reasonably arranged, and a redundant set of heating elements must be provided; the heating system must consider the additional heating load caused by the support platform, anti-deformation tooling, and auxiliary components; the arrangement of thermocouples 3: coils 1, 6, and 7 are arranged with a group of thermocouples 3 at most every 1.5m, 2m, and 1.3m, respectively, and each group of sub-coils is arranged with about 100 thermocouples 3, and two sub-coils are heat treated each time. The winding will be heat treated under controlled atmosphere conditions protected by argon gas. During the heat treatment process, the impurity gas content in the winding and the furnace should be detected in real time to ensure that the impurity gas content meets the technical requirements shown in the following table.

[0042]

[0043] The vacuum tube system includes a vacuum unit and a vacuum gauge for evacuating the crucible and the coil. The vacuum unit includes a Roots pump and a screw pump; a pneumatic butterfly valve is configured, and a water-cooling jacket is configured on the pipeline between the pneumatic butterfly valve and the Roots pump. The vacuum unit is connected to the vertical gas furnace through a stainless steel pipeline. A bypass pipeline and a pneumatic baffle valve are also configured. The bypass pipeline is connected to the coil evacuation pipeline. The vacuum unit is composed of a Shanghai Sunshine ZJY-2500A Roots pump as the main pump, and a ZJY-600A Roots pump and a Shanghai Gaopeng GP300-4 screw pump as the front stage unit. The unit is equipped with a DN200 pneumatic butterfly valve as the main pumping valve, and a water-cooling jacket is configured on the pipeline between the main valve and the Roots pump. The vacuum unit is connected to the furnace body through a stainless steel pipeline. Three pumps are assembled on a rack, and every two pumps are connected by a bellows, which can block vibration and facilitate installation. A muffler filter is provided at the outlet of the screw pump. The unit is equipped with a DN40 bypass pipeline and a DN40 pneumatic flapper valve, which is connected to the coil evacuation pipeline for coil evacuation. The system is equipped with a Chengdu Zhenghua ZDR-II dual-channel resistance vacuum gauge and two ZJ-52T metal vacuum gauges, one for measuring the furnace and the other for measuring the vacuum degree of the coil. The vacuum system is equipped with a complete interlocking mechanism to achieve sequential startup and shutdown. All valves are immediately closed in the event of an unexpected power outage.

[0044] Figure 2 The stress and deformation distribution diagram of the crucible in the cold state shows that when the crucible is in the cold state, the average stress of most parts is 20MPa, but there is a high stress area at the manhole connection, which can reach up to 59.875MPa. The top of the crucible has only 1.2mm deformation, and the deformation of other parts can be ignored. Figure 3 The stress and deformation distribution diagram of the crucible at high temperature shows that when the crucible is burned to 650 degrees Celsius, most parts are subjected to a stress of 3.62MPa, but there is a high stress area at the bottom of the boiler, which can reach up to 32.508MPa. At this time, the crucible as a whole has an average deformation of 45.6mm, and the deformation of the furnace top is up to 58.2mm.

[0045] The crucible needs to meet certain temperature and temperature uniformity. Based on the maximum required heating, the calculation is performed and the symmetrical 1 / 4 is selected as the calculation model. The number of grids is 33.74 million. The model tooling is made of stainless steel, with a specific heat capacity of 502.5 J / (kg.K) and a thermal conductivity of 16.3 W / (mK). The specific heat capacity of the coil is 381 J / (kg.K) and a thermal conductivity of 22 W / (mK). The constant pressure specific heat capacity of argon is 520.6 J / (kg.K), the thermal conductivity is 0.0308 W / (mK), and the viscosity is 0.039×10 - 3The wall temperature was set to 645°C, the argon gas flow rate was 500L / min (15g / s), and the argon gas inlet temperature was 670°C. The distribution of the coil and the flow field were studied. Figure 4 As shown in the figure, it is a temperature distribution cloud map. It can be obtained that the overall temperature of the coil is between 649.2℃ and 651.5℃, and the highest and lowest temperature difference of the coil is 2.3℃. Due to the reduction of the argon flow rate, the inlet temperature of the argon needs to be increased. When it is 500L / min, the temperature uniformity can meet the temperature requirements and temperature uniformity requirements. The actual situation is better than the simulated conditions because the constant temperature argon is also introduced into the coil, making the temperature uniformity better. The temperature uniformity design of this nozzle is analyzed, as shown in the figure. Figure 5 As shown in the figure, due to the vortex structure formed in the crucible, the temperature distribution is more uniform, and a more uniform flow field is formed around the coil. Figure 6 The figure shows the distribution of isotherms in the crucible. The temperature pressure gradient around the coil is low, which can make the temperature more uniform. The wall temperature is set to 645℃, and the argon gas uses a small flow rate of 500L / min (15g / s. The reason for setting this flow rate is that the argon gas after the coil heat treatment is used as the protective gas in the crucible. The maximum flow rate in the coil is 15g / s). When the argon inlet temperature is selected at 670℃, the uniformity requirement is met. The overall temperature of the coil is between 649.2℃ and 651.5℃, and the highest and lowest temperature difference of the coil is 2.3℃.

[0046] Furthermore, the heat exchange pipe is made of heat-resistant steel S30409, and the allowable stress of the pipe material (750°C) is:

[0047] [σ]1=25(MPa)

[0048] Minimum wall thickness:

[0049] Where, the pipe pressure P c =1.5MPa, if the inner tube diameter is d i =34mm, considering safety redundancy, spiral radius and bracket strength, the stainless steel pipe is selected from standard The following calculation is based on a 3mm thick heat exchange tube.

[0050] The strength check of the container crucible uses S30409 stainless steel. The temperature of argon is heated from 20℃ to 650℃, and the calculated qualitative parameters (1.5MPa, 335℃) are:

[0051] Gas density: ρ0 = 13 kg / m 3

[0052] Specific heat capacity: C p0 =520.5J / (kg·K)

[0053] Viscosity: μ0 = 0.039 × 10 -3 Pa·s

[0054] Thermal conductivity: λ0=0.04W / (m·K)

[0055] The argon flow rate is set to be less than 0.03kg / s, which is the maximum argon flow rate. Designed according to the maximum argon flow rate, when the argon flow rate is less than this flow rate, the heat exchange fully meets the requirements. According to the actual test situation, the flow rate can be gradually reduced until it is less than a certain minimum flow rate. If the concentration of argon impurities exceeds the standard or the coil temperature non-uniformity does not meet the requirements, then this flow rate is the minimum argon flow rate. The heat exchange spiral tube adopts standard S30409 heat-resistant stainless steel pipe. According to the maximum working condition design, the maximum flow rate of argon is about 0.03kg / s. The inlet temperature of argon is 20℃, the outlet temperature of argon is 650℃, and the temperature rise ΔT2=630℃. The centerline diameter of the spiral tube is D c =9m, the inner diameter of the furnace shell is D L =11m, the diameter of the outer wall of the crucible is D g =7.54m. Pipeline parameters, inner diameter of inner pipe: d i =0.034m, inner tube outer diameter: d o =0.04m, spiral tube center diameter: D c =9m, spiral tube pitch, equivalent to thread pitch: H1 = 0.2m, twice the distance between the inner diameter of the shell and the center line of the spiral tube: J = 5m, diameter of the micro-positive pressure tube: ds = 0.089m, flow area in a single tube: S0 = πd i 2 / 4=0.000907m 2

[0056] Equivalent diameter:

[0057] Flow area of ​​outer annular gap of coil:

[0058] Argon gas absorption capacity:

[0059] Heat transfer coefficient in the tube: Prandtl number of heat conducting medium: Pr0=(C p0 μ0) / λ0=0.64

[0060] Flow velocity of the heat transfer medium in the inner tube during heating:

[0061] Reynolds number of heat conducting medium during heating: Re0=(d i v0ρ0) / μ0=28787

[0062] Inner surface heat transfer coefficient during heating: α 01 =0.023λ0Re0 0.8 Pr0 0.4 / d i =85.6

[0063] Heat transfer coefficient of spiral tube to enhance heat transfer during heating:

[0064] Heat transfer coefficient outside the tube: The exhaust flow rate of the furnace gas is: At 650℃, the flue gas density is ρ1=0.38kg / m 3 , then the mass flow rate is: Then the viscosity of the flue gas at 650℃ μ1=38.8×10 - 6 Pa·s, thermal conductivity λ1=0.078W / (m·K), constant pressure specific heat capacity C p1 =1220J / (kg·K).

[0065] Annular gap fluid flow velocity:

[0066] Reynolds number of the fluid in the outer tube annulus: Re1=(D c +J-2d o )v1ρ1 / μ1=2726.6

[0067] Prandtl number when heating: Pr1=(C p1 μ1) / λ1=0.61

[0068] The estimated wall temperature during heating is t w =250℃, the temperature difference between the wall temperature and the infinite distance is: ΔT2=|t w -T1|=400℃

[0069] Grashof constant: Gr1 = βgΔT2(D c +J) 3 ρ1 2 / μ1 2 =1.13×10 12

[0070] Among them, the expansion coefficient of the inner tube is: β = 0.0011m / ℃, the acceleration of gravity is: g = 9.8m 2 / s. Turbulent natural convection determination coefficient:

[0071] Rayleigh number: Ra=Gr1Pr1=6.93×10 11

[0072] The combustion flue gas is calculated as turbulent flow, Nusselt number:

[0073] Nu 01 =0.27Re1 0.63 Pr1 0.36 (Pr1 / Pr w ) 0.25 =34.47

[0074] Among them, the Prandtl number of the fluid at the average wall temperature is: Pr w =0.65.

[0075] Nusselt number: Nu1=εNu 01 =24.13

[0076] Among them, the single tube row correction coefficient ε=0.7.

[0077] Heat transfer coefficient outside the tube: α1=λ1Nu1 / d o =47.05

[0078] Wall temperature calculation: Among them, the thermal resistance value of the dirt on the outside of the tube is: r1 = 0.000352m 2 ℃ / W, thermal resistance of dirt inside the tube r2=0.000176m 2 ·℃ / W. Therefore, the estimated wall temperature of 250℃ is not much different from the calculated result and the error can be ignored.

[0079] Overall heat transfer coefficient for heating: Among them, the thermal conductivity of the tube wall (250℃)λ w = = 18.25W / (m·℃) Inner tube wall thickness: d b =0.003m.

[0080] Average temperature difference:

[0081] Heat exchange area during heating:

[0082] Select the maximum heat exchange area for pipeline design, the required pipe length is:

[0083] Parameters and specifications of spiral tube:

[0084] The length of each spiral tube: L0=((πD c ) 2 +H1) 0.5 =28.3(m)

[0085] Minimum number of turns of spiral tube: N = L S / L0=1

[0086] Since the temperature of argon gas is low after vaporization, winter experiments may cause the air heat exchanger to have a poor effect. Each set of spiral tubes can be set to be wound 3 times. Total height of spiral tube: H z =NH1=0.6(m).

[0087] Actual heat exchange area: S s =πd o L s =7.536m 2

[0088] Heat exchange area margin: Y = (S s -S) / S=166.5%

[0089] Flow loss verification: In order to solve the pressure difference loss in the spiral tube, first calculate the friction coefficient in the spiral tube: f = f0 (1 + 0.075Re0 0.25 (d i / d o ) 0.5 )=0.0797

[0090] When the relative roughness is 0.005, according to the Moody diagram, the friction coefficient of the straight tube is f0=0.042, and the pressure difference loss in the tube is greater during heating.

[0091] Inner tube fluid pressure difference loss: ΔP = fL s ρ0v0 2 / (2d o )=7094(Pa)

[0092] In engineering calculations, the local head loss is calculated as 10-15% of the loss along the way, and the total loss of the spiral tube heat exchanger is 8158Pa.

[0093] The heat exchange pipe is made of heat-resistant steel S30409. The allowable stress of the pipe material (700℃):

[0094] [σ]1=27(MPa) (34)

[0095] Minimum wall thickness:

[0096] Where, the pipe pressure P c =0.002MPa, the pipe material is standard DN80 seamless steel pipe, the inner pipe diameter is d i =82mm, considering safety redundancy, spiral radius and bracket strength, the stainless steel pipe is selected from standard The following calculation is based on a 3.5mm thick heat exchange tube. Strength check of the container crucible: the diameter of the container pot is 7.5 meters and the height is 3.5 meters. The container crucible is cylindrical and made of S30409 stainless steel. The wall thickness of the container pot is at least 0.3mm. Considering a certain safety margin, the following calculation is based on a thickness of 8mm. Strength check of the crucible head: assuming the weld coefficient Φ = 0.85, the thickness of the elliptical head is calculated as follows:

[0097]

[0098] Considering the strength and processability, the wall thickness of the elliptical head of the crucible is selected to be 8mm.

[0099] Under normal temperature, considering that the crucible is vacuumed, the pressure is 0.1MPa, and the allowable stress of stainless steel parts is 137MPa, the cylinder wall thickness of the crucible is at least 2.7mm, and the crucible head is at least 3.2mm. The wall thickness of the heat exchange tube is at least 0.03mm, and the selected standards meet the requirements. Summary: Heat exchange tube selection Seamless stainless steel pipe, crucible cylinder wall thickness 10mm, crucible upper cover 20mm, lower cover 40mm thick, material selected S30409, crucible cylinder has reinforcing ribs, crucible upper and lower covers have well-shaped reinforcing ribs.

[0100] When the temperature of argon is heated from 20°C to 650°C, the calculated qualitative parameters (1atm, 335°C) are: Gas density: ρ0 = 0.87kg / m 3 , specific heat capacity: C p0 =520.5J / (kg·K)Viscosity:μ0=0.039×10 -3 Pa·s, thermal conductivity: λ0=0.0308W / (m·K) Set the argon flow rate to be less than 1000L / min. At room temperature and pressure, the argon flow rate is less than 0.029735kg / s, which is the maximum argon flow rate. Designed according to the maximum argon flow rate, when the argon flow rate is less than this flow rate, the heat exchange fully meets the requirements. According to the actual test situation, the flow rate can be gradually reduced until it is less than a certain minimum flow rate. The concentration of argon impurities exceeds the standard, or the coil temperature non-uniformity does not meet the requirements, then this flow rate is the minimum argon flow rate.

[0101] According to the previous analysis, the heat exchange spiral tube adopts standard S30409 heat-resistant stainless steel pipe. According to the maximum working condition design, the maximum flow rate of argon is about 0.1kg / s. The inlet temperature of argon is 20℃, the outlet temperature of argon is 650℃, and the temperature rise ΔT2=630℃. The centerline diameter of the spiral tube is D c =8.5m, the inner diameter of the furnace shell is D L =11m, the diameter of the outer wall of the crucible is D g=7.52m, inner diameter of inner tube: d i =0.082m, inner tube outer diameter: d o =0.089m, spiral tube center diameter: D c =8.5m, the distance between the spiral pipe and the spiral pipe is equivalent to the thread pitch: H1 = 0.5m, the distance between the inner wall diameter of the shell and the center line of the spiral pipe is twice: J = 5m

[0102] Flow area in a single tube: S0 = πd i 2 / 4=0.00528m 2

[0103] Equivalent diameter: Flow area of ​​outer annular gap of coil: Argon gas absorption capacity: Heat transfer coefficient in tube:

[0104] Prandtl number of heat conducting medium: Pr0=(C p0 μ0) / λ0=0.64

[0105] Flow velocity of the heat transfer medium in the inner tube during heating: Reynolds number of heat conducting medium during heating: Re0=(d i v0ρ0) / μ0=39877

[0106] Inner surface heat transfer coefficient during heating: α 01 =0.023λ0Re0 0.8 Pr0 0.4 / d i =34.6

[0107] Heat transfer coefficient of spiral tube to enhance heat transfer during heating: Heat transfer coefficient outside the tube:

[0108] The exhaust flow rate of furnace gas is: At 650℃, the flue gas density is ρ1=0.38kg / m 3 , then the mass flow rate is: The flue gas parameters are as follows:

[0109] Temperature (℃) Density (kg / m 3 )Specific heat capacity at constant pressure [kJ / (kg·K)] Thermal conductivity × 10 2 (W / (m·K)) dynamic viscosity × 10^(-6)(Pa·s) kinematic viscosity × 10^(-6)(m 2 / s), then the viscosity of the flue gas at 650℃ μ1=38.8×10 -6 Pa·s, thermal conductivity λ1=0.078W / (m·K), constant pressure specific heat capacity C p1=1220J / (kg·K). Annular fluid flow velocity: Reynolds number of the fluid in the outer tube annulus: Re1=(D c +J-2d o )v1ρ1 / μ1=2613

[0110] Prandtl number when heating: Pr1=(C p1 μ1) / λ1=0.62

[0111] The estimated wall temperature during heating is t w =250℃, the temperature difference between the wall temperature and the infinite distance is: ΔT2=|t w -T1|=410℃

[0112] Grashof constant: Gr1 = βgΔT2(D c +J) 3 ρ1 2 / μ1 2 =9.3×10 11

[0113] Among them, the expansion coefficient of the inner tube is: β = 0.0011m / ℃, the acceleration of gravity is: g = 9.8m 2 / s. Turbulent natural convection determination coefficient:

[0114] Rayleigh number: Ra=Gr1Pr1=5.79×10 11

[0115] The combustion flue gas is calculated as turbulent flow, Nusselt number:

[0116] Nu 01 =0.27Re1 0.63 Pr1 0.36 (Pr1 / Pr w ) 0.25 =31.73

[0117] Among them, the Prandtl number of the fluid at the average wall temperature is: Pr w =0.66.

[0118] Nusselt number: Nu1=εNu 01 =22.2, where the single tube row correction coefficient ε=0.7.

[0119] Heat transfer coefficient outside the tube: α1=λ1Nu1 / d o =19.5.

[0120] Wall temperature calculation: Among them, the thermal resistance value of the dirt on the outside of the tube is: r1 = 0.000352m 2 ℃ / W, thermal resistance of dirt inside the tube r2=0.000176m2 ·℃ / W. Therefore, the estimated wall temperature of 250℃ is not much different from the calculated result and the error can be ignored.

[0121] Overall heat transfer coefficient for heating: Among them, the thermal conductivity of the tube wall (250℃)λ w = = 18.6W / (m·℃) Inner tube wall thickness: d b =0.0035m. Average temperature difference: Heat exchange area during heating: Select the maximum heat exchange area for pipeline design, the required pipe length is: Parameters and specifications of spiral tube:

[0122] The length of each spiral tube: L0=((πD c ) 2 +H1) 0.5 =26.7(m)

[0123] Number of turns of the spiral tube: N = L S / L0=2.6

[0124] The spiral tube can be set to be wound at least 5 times.

[0125] Total height of spiral tube H z =NH1=2.5(m)

[0126] Actual heat exchange area: S s =πd o L s =37.31m 2

[0127] Heat exchange area margin: Y = (S s -S) / S=76.3%.

[0128] The temperature rise process in the crucible requires argon heating. Assuming that the crucible wall temperature is 1°C lower than the average temperature in the furnace during the temperature rise period, C p =520J / (kgK), the thermal conductivity of the crucible is:

[0129] Thermal conductivity of cylinder wall λ w =16.2W / (mK), temperature 0-210℃;

[0130] Thermal conductivity of cylinder wall λ w =17.8W / (mK), temperature 210-340℃;

[0131] Thermal conductivity of cylinder wall λ w =19.4W / (mK), temperature 340-450℃;

[0132] Thermal conductivity of cylinder wall λw =21W / (mK), temperature 450-575℃;

[0133] Thermal conductivity of cylinder wall λ w =22.6W / (mK), temperature 575-650℃.

[0134] t w is the wall temperature, t f is the gas temperature, the heating rate of the furnace is 5℃ / h, assuming that the average gas temperature is 0.2℃ higher than the average crucible wall temperature, the crucible wall thickness δ1=20mm, the height is calculated as H=5000mm, the insulation cotton thickness δ2=0mm, at 0-210℃, the heat dissipation loss of the crucible is:

[0135] The same method can be used to obtain

[0136] At 210-340℃, the crucible heat loss L = 1023W;

[0137] At 340-450℃, the crucible heat loss L = 1028W;

[0138] At 450-575℃, the crucible heat loss L = 1031W;

[0139] At 575-650℃, the crucible heat dissipation loss L=1091W.

[0140] Assuming the temperature difference of argon is 20℃, calculate the argon flow rate according to this formula:

[0141]

[0142] At 0-210℃, a heating process of 42 hours is required, requiring 14821kg of argon;

[0143] At 210-340℃, a heating process of 26 hours is required, and 9203kg of argon is required;

[0144] At 340-450℃, a 24-hour heating process is required, requiring 8540kg of argon;

[0145] At 340-575℃, a heating process of 25 hours is required, and 8926kg of argon is required;

[0146] At 575-650℃, a heating process of 15 hours is required, and 5664kg of argon is required;

[0147] If the heating rate is 5℃ / h, the average temperature of the fuel gas is 0.2℃ higher than the average wall temperature of the crucible, and a total of 47136kg of argon is required during the heating stage. At 650℃, argon (20℃) is heated to 645℃ in the vertical heating furnace (it has the ability to heat to nearly 650℃ and the stable range is ±5℃), enters the electric heating compensation area, and then is heated to 650℃ through electric heating compensation, and then enters the crucible as a heat treatment protective gas for the coil, and then is discharged from the crucible to the external environment without recycling. According to the micro-positive pressure in the crucible, the maximum argon flow rate is designed because when the argon flow rate is less than this flow rate, the heat exchange conditions fully meet the requirements. After the construction, according to the actual test situation, the flow rate can be gradually reduced until it is less than a certain minimum flow rate. If the concentration of argon impurities exceeds the standard or the coil temperature non-uniformity does not meet the requirements, then this flow rate is the minimum argon flow rate. The minimum argon flow rate is related to the process, the arrangement of the nozzle in the crucible, the sealing degree of the crucible, the cleanliness of the workpiece, etc.

[0148] A method for using a test coil heat treatment system, the specific steps are as follows:

[0149] S1. Preparation: Fix the test coil with a fixture to ensure the outer dimensions of the winding and prevent deformation during the heat treatment. Preheat the test coil and the anti-deformation tooling. The size of the anti-deformation tooling is slightly larger than the size of the test coil. Ensure that the tooling is suitable for the formal coil and the test coil. Then place the test coil in the built-in crucible of the vertical gas furnace. The crucible is designed for directly heat treating the test coil.

[0150] S2, preheating, gas replacement in the furnace and winding, use preheating coil to preheat argon, and adjust the inlet flow and pressure through the flow control valve, start the argon protection system, fill the furnace with high-purity argon, perform gas replacement, and establish an oxygen-free or low-oxygen atmosphere;

[0151] S3, heating up, controlling the heating element in the vertical gas furnace through the temperature control system, heating up according to a predetermined temperature curve until the temperature of the first insulation stage of the heat treatment is reached;

[0152] S4, heat preservation, keep the coil at 210 degrees Celsius for 50 hours, then keep it at 340 degrees Celsius for 25 hours, then keep it at 450 degrees Celsius for 25 hours, and finally keep it at 575 degrees Celsius for 100 hours. The temperature control accuracy of each stage is better than ±1.0 degrees Celsius;

[0153] S5, maintaining the coil at 650 degrees Celsius for 100 hours to complete the final heat treatment stage;

[0154] S6. Use monitoring and control systems to monitor the temperature, pressure, flow and other parameters of the coil in real time to ensure the stability and uniformity of the heat treatment process;

[0155] S7. Record the key parameters during the heat treatment process, including furnace temperature, coil temperature, inlet pressure, outlet pressure, furnace pressure, furnace inlet flow, coil inlet flow, oxygen content, water content and hydrocarbon content;

[0156] S8. Ensure that the heat treatment system can operate stably and continuously for 45 days. After completion, conduct a quality inspection on the appearance and internal structure of the coil to ensure that the heat treatment effect meets the design requirements.

[0157] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0158] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above implementation regulations. The above implementation regulations and descriptions are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A test coil heat treatment system, characterized in that: include: A vertical gas furnace (1) for accommodating and heating the test coil; A crucible (2) is placed inside the vertical gas furnace (1) and is used to directly perform heat treatment on the test coil; An argon protection control system is connected to the vertical gas furnace (1) and the built-in crucible (2), provides high-purity argon gas to replace the gas and maintain micro-filling and micro-discharging during the heat treatment process, and controls the temperature in the vertical gas furnace (1) to meet the heat treatment requirements of the coil; An argon gas supply system, used for supplying argon gas to the vertical gas furnace (1) and the built-in crucible (2); Monitoring and control systems are used to monitor and control temperature, pressure and flow in real time during heat treatment.

2. The test coil heat treatment system according to claim 1, characterized in that: The temperature control system comprises a thermocouple (3) and a temperature controller. The thermocouple (3) is arranged at different positions of the coil and is used to monitor the temperature of the coil in real time. The temperature controller receives a signal from the thermocouple (3) and controls a heating element to achieve precise temperature control. The heating element is connected to a gas supply pipeline, and the gas supply pipeline transports gas to a combustion chamber of the vertical gas furnace (1).

3. The test coil heat treatment system according to claim 1, characterized in that: The argon protection control system comprises a liquid argon tank, a heat exchanger (8), an argon gas pipeline (5), an automatic valve (6) and a pressure gauge (7); the argon gas pipeline (5) connects the liquid argon tank and the heat exchanger (8) and the heat exchanger (8) and the vertical gas furnace (1); the automatic valve (6) is used to control the flow of argon gas; the pressure gauge (7) is used to monitor the pressure of argon gas; the argon gas pipeline (5) is further connected to a crucible (2) in the vertical gas furnace (1) to realize the circulation of argon gas.

4. The test coil heat treatment system according to claim 3, characterized in that: The argon gas in the argon tank (4) is divided into slightly positive pressure argon gas and high pressure argon gas through an automatic valve (6). The slightly positive pressure argon gas is introduced into the crucible (2), and the high pressure argon gas is introduced into the heat treatment coil.

5. The test coil heat treatment system according to claim 4, characterized in that: It also includes a mixed heating system, which includes a natural gas heating system and an electric heating system. The electric heating system includes an electric heater arranged outside the vertical gas furnace (1) and an electric heating pipeline (9). The electric heating system is used to heat the slightly positive pressure argon gas.

6. The test coil heat treatment system according to claim 5, characterized in that: The natural gas heating system comprises a burner (10) arranged on a vertical gas furnace (1). Natural gas is burned by the burner (10), and the generated gas forms a vortex that runs through the entire furnace body in the vertical gas furnace (1). The gas vortex is used to keep the crucible (2) in the vertical gas furnace (1) warm and to preheat the high-pressure argon gas.

7. The test coil heat treatment system according to claim 1, characterized in that: The monitoring and control system includes a sampling unit, a gas pretreatment system, a gas analyzer and a control unit. The sampling unit includes a pipeline stainless steel flange sampler, which filters the sample gas and transports it to the gas controller. The gas pretreatment system is used to process the gas sample collected by the sampling unit. The gas analyzer is used to analyze the processed gas sample. The control unit is used to receive data from the gas analyzer and control the entire heat treatment process. The control unit is connected to each sampling unit, the gas pretreatment system and the gas analyzer through a data line.

8. The test coil heat treatment system according to claim 1, characterized in that: The vertical gas furnace (1) and the crucible (2) are both made of composite steel plates; the crucible (2) is completely sealed and evacuated by a vacuum system.

9. The test coil heat treatment system according to claim 8, characterized in that: The vacuum tube system comprises a vacuum unit and a vacuum gauge for evacuating the crucible (2) and the coil, and the vacuum unit comprises a Roots pump and a screw pump; A pneumatic butterfly valve is provided, a water-cooling jacket is provided on the pipeline between the pneumatic butterfly valve and the Roots pump, the vacuum unit and the vertical gas furnace (1) are connected via a stainless steel pipeline, a bypass pipeline and a pneumatic baffle valve are also provided, and the bypass pipeline is connected to the coil evacuation pipeline.

10. A test coil heat treatment process, characterized in that: The steps include: placing the test coil in the test coil heat treatment system according to any one of claims 1 to 9; S1. Preparation: Fix the test coil with a fixture to ensure the outer dimensions of the winding and prevent deformation during the heat treatment. Preheat the test coil and the anti-deformation tooling. The size of the anti-deformation tooling is slightly larger than the size of the test coil. Ensure that the tooling is suitable for the formal coil and the test coil. Then place the test coil in a built-in crucible (2) of a vertical gas furnace (1). The crucible (2) is designed to directly heat treat the test coil. S2, preheating, gas replacement in the furnace and winding, use preheating coil to preheat argon, and adjust the inlet flow and pressure through the flow control valve, start the argon protection system, fill the furnace with high-purity argon, perform gas replacement, and establish an oxygen-free or low-oxygen atmosphere; S3, heating up, controlling the heating element in the vertical gas furnace (1) through the temperature control system, heating up according to a predetermined temperature curve until the temperature of the first insulation stage of the heat treatment is reached; S4, heat preservation, keep the coil at 210 degrees Celsius for 50 hours, then keep it at 340 degrees Celsius for 25 hours, then keep it at 450 degrees Celsius for 25 hours, and finally keep it at 575 degrees Celsius for 100 hours. The temperature control accuracy of each stage is better than ±1.0 degrees Celsius; S5, maintaining the coil at 650 degrees Celsius for 100 hours to complete the final heat treatment stage; S6. Use monitoring and control systems to monitor the temperature, pressure, flow and other parameters of the coil in real time to ensure the stability and uniformity of the heat treatment process; S7. Record the key parameters during the heat treatment process, including furnace temperature, coil temperature, inlet pressure, outlet pressure, furnace pressure, furnace inlet flow, coil inlet flow, oxygen content, water content and hydrocarbon content; S8. Ensure that the heat treatment system can operate stably and continuously for 45 days. After completion, conduct a quality inspection on the appearance and internal structure of the coil to ensure that the heat treatment effect meets the design requirements.

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