A process for heat treating oil casing

Abstract

The present application relates to pipeline steel heat treatment technical field, disclose a kind of heat treatment process of oil casing, comprising: stripping oil casing surface oxide skin to regulate surface roughness;Alternately repeated heating and cooling are sent into induction coil;Send into heating furnace to complete austenitizing;Move into multi-section annular jet cooling tank quenching, utilize probe array to collect surface temperature and calculate cooling rate, when cooling rate deviates from the set slope exceeds set threshold, adjust valve opening to regulate spray pressure;Send into on-line induction furnace isothermal stay, again send into tempering furnace high-temperature tempering, the present application is by surface heat dissipation rate feedback adjustment spray pressure, in situ compensates martensite phase change latent heat, ensure that wall organization transforms time and space synchronization, improve the stress cracking resistance of oil casing.

Description

Technical Field

[0001] This invention belongs to the field of pipeline steel heat treatment technology, and particularly relates to a heat treatment process for oil casing. Background Technology

[0002] Currently, the heat treatment of high-strength pressure-bearing pipes typically employs a process of continuous heating to the austenitizing temperature combined with constant flow rate spray quenching. This process is based on the fundamental assumption that the pipe microstructure undergoes linear and homogeneous evolution under uniform convective heat transfer.

[0003] In industrial mass production, due to the deformation law of billet rolling, there are objective deviations in circumferential wall thickness and segregation of internal alloy elements in the tube body. When quenching penetrates the strong cold phase transformation zone, the heat dissipation rate of different thickness areas shows inherent differences. Moreover, the release of latent heat of phase transformation in alloy-rich and depleted areas has obvious spatiotemporal asynchrony. When the continuously sprayed cooling medium comes into contact with the high-temperature surface, it spontaneously forms an uneven boiling vapor film, causing random fluctuations in the surface heat transfer coefficient. This local heat dissipation deviation caused by the intertwining of material structure differences and heat transfer boundary fluctuations leads to spatiotemporal misalignment of the martensitic transformation in the tube body depth direction, accumulating microstructure anisotropy and local residual tensile stress concentration. In order to suppress local heat flow distortion, the conventional improvement approach tends to increase the water supply pressure to enhance the overall convective heat transfer. This linear solution cannot accurately match the peak value of the latent heat released transiently in a specific area, which is more likely to cause the thin-walled area to cool down too quickly and precipitate brittle phases. Furthermore, the indiscriminate fluid impact exacerbates the local collapse and reorganization of the vapor film, generating new risks of thermal stress superposition.

[0004] Therefore, how to eliminate the asynchronous microstructure transformation and residual tensile stress concentration caused by the interplay of physical dimensional deviations and compositional segregation in the continuous quenching cooling zone is the technical problem to be solved by this invention. Summary of the Invention

[0005] The present invention aims to solve the problems of asynchronous microstructure transformation and residual stress concentration caused by local wall thickness deviation and component segregation in the phase transformation range of pipes.

[0006] In this technical solution, a heat treatment process for oil casing includes the following steps:

[0007] Step S1: Mechanically peel off the oxide scale on the surface of the oil casing and adjust the surface roughness Ra of the oil casing to 3.2 μm to 6.3 μm;

[0008] Step S2: The oil casing is fed into an induction heating coil with a working frequency of 1.5kHz to 2.5kHz and heated to 460℃ to 490℃ at a heating rate of 35℃ / s to 45℃ / s. The surface temperature is then reduced to 260℃ to 290℃ by spraying cooling medium through a high-pressure mist cooling nozzle. The heating and cooling process is repeated 2 to 3 times.

[0009] Step S3: The treated oil casing is sent into a heating furnace, heated to 890°C to 910°C and held for 22 to 28 minutes.

[0010] Step S4: After austenitization, the oil casing is moved into a multi-segment annular jet cooling tank for quenching. The surface radiation temperature value is collected by a dual-wavelength infrared detection array arranged along the circumference and axial direction of the oil casing, and the surface transient cooling rate is calculated. When the absolute value of the deviation of the surface transient cooling rate from the set linear cooling slope exceeds the set deviation threshold, the opening of the regulating valve of the multi-segment annular jet cooling tank is adjusted to change the spray pressure of the cooling medium.

[0011] Step S5: The quenched oil casing is sent into an online induction furnace and kept at an isothermal holding temperature of 210°C to 240°C for 7 to 11 minutes. Then it is sent into a tempering furnace and heated to 645°C to 675°C for high-temperature tempering and holding for 55 to 65 minutes. After being taken out of the furnace, it is cooled to room temperature.

[0012] Preferably, the steel material of the oil casing comprises, by mass percentage: 0.22% to 0.28% carbon, 0.20% to 0.40% silicon, 0.50% to 0.80% metallic manganese, 0.80% to 1.20% chromium, 0.60% to 1.00% molybdenum, 0.03% to 0.08% vanadium, and 0.01% to 0.04% niobium, with the balance being iron and unavoidable impurities; the austenite grain size of the oil casing is controlled to be between grade 8 and grade 11 during the high-temperature austenitization process in step S3.

[0013] Preferably, in step S4, the specific steps of introducing compressed air into the measurement channel of the multi-segment annular jet cooling tank include: step S41, introducing compressed air with a pressure of 0.35MPa to 0.45MPa into the measurement optical path for acquiring surface radiation temperature values ​​along the dual-wavelength infrared detection array; step S42, using the continuously introduced compressed air to purge and remove the surface heat exchange vapor film of the multi-segment annular jet cooling tank section, so that the measurement optical path maintains a stable light transmission state during the sampling period when the signal acquisition frequency of the dual-wavelength infrared detection array is 60Hz to 80Hz.

[0014] Preferably, in step S2, the alternating repetition of heating and cooling includes the following steps: Step S21, the oil casing is fed into an induction heating coil with a working frequency of 2.0 kHz, so that the temperature of the oil casing reaches 470°C at a heating rate of 40°C / s; Step S22, a cooling medium is sprayed onto the surface of the oil casing using a high-pressure mist cooling nozzle to reduce the surface temperature to 270°C; Step S23, steps S21 and S22 are repeated a total of 3 times.

[0015] Preferably, in step S5, the isothermal residence temperature is 210°C to 240°C, and the isothermal residence time is 7 min to 11 min.

[0016] Preferably, in step S5, the high-temperature tempering temperature is 645°C to 675°C, and the holding time is 55 min to 65 min.

[0017] Preferably, in step S4, the method of collecting surface radiation temperature values ​​using a dual-wavelength infrared detection array includes the following steps: using the first wavelength sensing component and the second wavelength sensing component in the dual-wavelength infrared detection array, the radiation energy values ​​of the oil casing surface at two independent wavelengths are collected synchronously, and the ratio of the radiation energy values ​​at the two independent wavelengths is obtained. The surface radiation temperature value is then calculated based on the ratio.

[0018] Preferably, in step S4, when the transient cooling rate of the surface is greater than the set linear cooling slope and the absolute value of the deviation exceeds the set deviation threshold, the opening of the regulating valve of the multi-segment annular jet cooling tank is reduced, and the spray pressure of the cooling medium is reduced to 0.15MPa to 0.25MPa.

[0019] Preferably, after the high-temperature tempering and heat preservation is completed in step S5, the following steps are also included: Step S51, using a non-destructive testing instrument to measure the microstructure uniformity index of the oil casing in the depth direction; Step S52, when the microstructure uniformity index shows asymmetrical deviation, adjusting the conveying speed of the return channel to extend the subsequent high-temperature tempering and heat preservation cycle of the current oil casing in step S5.

[0020] Compared with existing technologies, the heat treatment process for oil casing of the present invention has the following advantages:

[0021] 1. In the heat treatment of oil casing, by establishing a cascade response between a specific surface roughness and a rapid induction heating frequency, and by controlling the specific heating rate in conjunction with multiphase alternating high-pressure mist cooling, the lattice dislocations inside the pipe matrix undergo directional reorganization and grain size refinement. This pretreatment microstructure is intertwined with the step-by-step austenitization and uniform heat preservation process, which slows down the localized concentrated release of energy during the quenching and cooling phase transformation stage, suppresses the thermodynamic spatiotemporal asynchrony caused by fluctuations in pipe wall thickness, keeps the internal microstructure transformation at different depths of the pipe in a spatiotemporal synchronization, reduces the internal stress concentration caused by quenching distortion, and solidifies the overall structural crack resistance and stability of the material.

[0022] 2. A dual-wavelength infrared detection array arranged alternately in the circumferential and axial directions is used to capture high-frequency transient surface temperature signals in real time. Combined with continuous purging of the measurement channel by compressed air at a specific pressure to block interference from multiphase flow such as high-temperature steam and droplets, high-fidelity heat dissipation status data acquisition is achieved. This feedback tracking mechanism is used to accurately capture sudden changes in surface heat flow under non-uniform vapor film heat transfer boundary conditions, determine the real-time deviation between the transient surface cooling rate and the preset linear cooling slope, and provide high-precision basic heat dissipation control parameters for the opening changes of regulating valves in multi-segment annular jet cooling tanks, eliminating the risk of detection lag and control distortion caused by random fluctuations in external convection heat transfer conditions.

[0023] 3. Based on the absolute value of the deviation of the transient cooling rate from the preset cooling slope, the computing unit dynamically drives the opening of the regulating valve to achieve graded adaptive control. When the deviation exceeds the threshold and the cooling is too slow, the spray pressure is increased to a high flow rate impact state, forcibly breaking the surface boiling vapor film to improve the local convective heat transfer coefficient, and in-situ counteracting the latent heat accumulation of phase transformation caused by the segregation of matrix alloy elements. When the cooling is too fast, the pressure is reduced to slow down the cooling intensity of the thin-walled area. This breaks away from the homogeneous heat transfer assumption of traditional processes that rely on constant flow rate quenching, suppresses the anisotropy of the microstructure in the depth direction of the tube layer, and blocks the generation path of banded segregation in the microstructure. Attached Figure Description

[0024] Figure 1 This is a flow chart of the austenitizing and quenching tempering process for oil casing in this invention;

[0025] Figure 2 This is a schematic diagram of the spray pressure adjustment of the multi-segment annular jet cooling tank of the present invention. Detailed Implementation

[0026] The technical solutions in the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0027] A heat treatment process for oil casing includes the following steps:

[0028] Step S1: Mechanically peel off the oxide scale on the surface of the oil casing and adjust the surface roughness Ra of the oil casing to 3.2 μm to 6.3 μm;

[0029] Step S2: The oil casing is fed into an induction heating coil with a working frequency of 1.5kHz to 2.5kHz and heated to 460℃ to 490℃ at a heating rate of 35℃ / s to 45℃ / s. The surface temperature is then reduced to 260℃ to 290℃ by spraying cooling medium through a high-pressure mist cooling nozzle. The heating and cooling process is repeated 2 to 3 times.

[0030] Step S3: The treated oil casing is sent into a heating furnace, heated to 890°C to 910°C and held for 22 to 28 minutes.

[0031] Step S4: After austenitization, the oil casing is moved into a multi-segment annular jet cooling tank for quenching. The surface radiation temperature value is collected by a dual-wavelength infrared detection array arranged along the circumference and axial direction of the oil casing, and the surface transient cooling rate is calculated. When the absolute value of the deviation of the surface transient cooling rate from the set linear cooling slope exceeds the set deviation threshold, the opening of the regulating valve of the multi-segment annular jet cooling tank is adjusted to change the spray pressure of the cooling medium.

[0032] Step S5: The quenched oil casing is sent into an online induction furnace and kept at an isothermal holding temperature of 210°C to 240°C for 7 to 11 minutes. Then it is sent into a tempering furnace and heated to 645°C to 675°C for high-temperature tempering and holding for 55 to 65 minutes. After being taken out of the furnace, it is cooled to room temperature.

[0033] Preferably, the steel material of the oil casing comprises, by mass percentage: 0.22% to 0.28% carbon, 0.20% to 0.40% silicon, 0.50% to 0.80% metallic manganese, 0.80% to 1.20% chromium, 0.60% to 1.00% molybdenum, 0.03% to 0.08% vanadium, and 0.01% to 0.04% niobium, with the balance being iron and unavoidable impurities; the austenite grain size of the oil casing is controlled to be between grade 8 and grade 11 during the high-temperature austenitization process in step S3.

[0034] Preferably, in step S4, the specific steps of introducing compressed air into the measurement channel of the multi-segment annular jet cooling tank include: step S41, introducing compressed air with a pressure of 0.35MPa to 0.45MPa into the measurement optical path for acquiring surface radiation temperature values ​​along the dual-wavelength infrared detection array; step S42, using the continuously introduced compressed air to purge and remove the surface heat exchange vapor film of the multi-segment annular jet cooling tank section, so that the measurement optical path maintains a stable light transmission state during the sampling period when the signal acquisition frequency of the dual-wavelength infrared detection array is 60Hz to 80Hz.

[0035] Preferably, in step S2, the alternating repetition of heating and cooling includes the following steps: Step S21, the oil casing is fed into an induction heating coil with a working frequency of 2.0 kHz, so that the temperature of the oil casing reaches 470°C at a heating rate of 40°C / s; Step S22, a cooling medium is sprayed onto the surface of the oil casing using a high-pressure mist cooling nozzle to reduce the surface temperature to 270°C; Step S23, steps S21 and S22 are repeated a total of 3 times.

[0036] Preferably, in step S5, the isothermal residence temperature is 210°C to 240°C, and the isothermal residence time is 7 min to 11 min.

[0037] Preferably, in step S5, the high-temperature tempering temperature is 645°C to 675°C, and the holding time is 55 min to 65 min.

[0038] Preferably, in step S4, the method of collecting surface radiation temperature values ​​using a dual-wavelength infrared detection array includes the following steps: using the first wavelength sensing component and the second wavelength sensing component in the dual-wavelength infrared detection array, the radiation energy values ​​of the oil casing surface at two independent wavelengths are collected synchronously, and the ratio of the radiation energy values ​​at the two independent wavelengths is obtained. The surface radiation temperature value is then calculated based on the ratio.

[0039] Preferably, in step S4, when the transient cooling rate of the surface is greater than the set linear cooling slope and the absolute value of the deviation exceeds the set deviation threshold, the opening of the regulating valve of the multi-segment annular jet cooling tank is reduced, and the spray pressure of the cooling medium is reduced to 0.15MPa to 0.25MPa.

[0040] Preferably, after the high-temperature tempering and heat preservation is completed in step S5, the following steps are also included: Step S51, using a non-destructive testing instrument to measure the microstructure uniformity index of the oil casing in the depth direction; Step S52, when the microstructure uniformity index shows asymmetrical deviation, adjusting the conveying speed of the return channel to extend the subsequent high-temperature tempering and heat preservation cycle of the current oil casing in step S5.

[0041] Example 1: The method of the present invention is applied to the production process of oil casing in high-pressure underground working conditions containing hydrogen sulfide. The steel material of the oil casing includes, by mass percentage, 0.22% to 0.28% carbon, 0.20% to 0.40% silicon, 0.50% to 0.80% manganese, 0.80% to 1.20% chromium, 0.60% to 1.00% molybdenum, 0.03% to 0.08% vanadium, and 0.01% to 0.04% niobium, with the balance being iron and unavoidable impurities. The casing contains circumferential wall thickness deviations caused by the manufacturing process and internal alloy element segregation during solidification. When cooling the pipe body using a constant medium flow rate during heat treatment, uneven heat dissipation across regions of different wall thicknesses and the spatiotemporal asynchrony of the release of latent heat of martensitic phase transformation in alloy-rich and alloy-poor regions spontaneously form a locally uneven boiling vapor film on the high-temperature pipe surface. This causes fluctuations in the heat transfer coefficient and induces anisotropy in the microstructure and concentration of residual tensile stress. The pipe material is prone to sulfide stress cracking in acidic corrosive media, reducing its resistance to crushing. Therefore, when implementing heat treatment for oil casing under these conditions, the primary step is to remove the oxide scale from the surface of the oil casing through mechanical stripping to control the surface roughness. The range is from 3.2 μm to 6.3 μm, of which To achieve a uniform electromagnetic induction layer depth distribution through alternating induction heating and profile arithmetic mean deviation, the oil casing is fed into an induction heating coil with a working frequency of 1.5 kHz to 2.5 kHz and heated to 460°C to 490°C at a heating rate of 35°C / s to 45°C / s. The surface temperature is then reduced to 260°C to 290°C by spraying cooling medium through a high-pressure mist cooling nozzle. This alternating induction heating and mist cooling process is repeated 2 to 3 times to orient and reorganize the lattice dislocations inside the matrix and suppress grain coarsening. This alternating pretreatment forms a cascade response with the subsequent austenitization homogenization process in a walking beam furnace, where the casing is held at 890°C to 910°C for 22 to 28 minutes. This process controls the austenite grain size to level 8 to 11, mitigating the localized energy release during the subsequent quenching and cooling phase transformation in the microstructure preparation stage. This provides an initial matrix state to mitigate the thermodynamic spatiotemporal asynchrony caused by fluctuations in pipe wall thickness.

[0042] During the austenitization and quenching cooling stage of the oil casing, which is then moved into a multi-segment annular jet cooling tank, the tank is axially divided into six independent annular spray tank segments at equal intervals. Each segment has 24 slit-type jet nozzles evenly distributed around its circumference, radiating jets towards the center of the outer surface of the steel pipe. Each segment is also equipped with its own fluid delivery main pump pipeline, which includes an independent proportional regulating valve and an independent pressure sensor. This allows for discrete, segmented control of the quenching intensity at different axial positions and circumferential sections of the casing. During operation, a dual-wavelength infrared detection array is staggered along the circumference and axial direction of the oil casing. A series of instruments are used to collect the surface radiation temperature signal of the tube body. The signal acquisition frequency is set to 60Hz to 80Hz. Simultaneously, compressed air at a pressure of 0.35MPa to 0.45MPa is continuously introduced into the measurement channel of the multi-segment annular jet cooling tank to block interference from the gas-liquid mixing multiphase flow generated by absolute flow, thus maintaining the measurement optical path in a stable state of transmission. That is, within 60 to 80 consecutive high-frequency photoelectric sampling cycles, because the compressed air completely removes vapor and suspended droplets from the infrared temperature measurement line of sight, the root mean square deviation of the light intensity attenuation ratio of a specific infrared wavelength radiation energy in the air medium channel remains within 0.01%, and the infrared light passes through this... The total transmittance of the measurement optical path remains stable within a constant range of 99.5% to 99.9%, indicating that the voltage reference value of the photoelectric signal received by the detection array is in a step-stable state without random up-and-down drift, and heat dissipation status data is acquired. In the specific conversion process, the arithmetic unit retrieves the first radiation energy value of the first wavelength sensing component at a wavelength of 0.95 micrometers and the second radiation energy value of the second wavelength sensing component at a wavelength of 1.15 micrometers, and calculates the energy ratio between the two. Subsequently, the central processing unit uses this energy ratio result as a one-dimensional discrete retrieval address and inputs it into the static correction that has been pre-fixed in the read-only memory through physical measurement. The numerical addressing table contains five physical channel levels arranged horizontally, corresponding to arithmetic mean deviations of surface roughness of 3.2μm, 4.0μm, 5.0μm, 6.0μm, and 6.3μm, respectively. Vertically, it contains 31 discrete light attenuation measured attenuation rate nodes, corresponding to local water vapor film thicknesses ranging from 0.05mm to 0.20mm along the measurement line of sight, with uniform steps of 0.01mm. The central processing unit directly retrieves the actual surface roughness level value of the steel pipe obtained online by the pre-laser rangefinder and roughness sensor, searches for and outputs a value between 1.01 and 1 at the corresponding cross-data intersection point.A fixed scalar correction weight coefficient between 0 and 5 is used. This scalar correction weight coefficient is directly multiplied by the energy ratio result using a single-precision floating-point multiplication operation to obtain the final ratio after compensation for dielectric optical path attenuation. Then, by retrieving the preset Planck radiation law discrete color temperature conversion lookup table, the final ratio is directly mapped and converted to a specific surface radiation temperature in degrees Celsius, completely eliminating radiation signal distortion caused by fluctuations in sleeve surface roughness and suspended mist. The calculation unit retrieves the corresponding correction weight value of 1.02 from the two-dimensional mapping calibration matrix based on the previously measured actual surface roughness value, multiplies this correction weight value by the energy ratio result, and finally substitutes the calibrated ratio result into the preset high-temperature radiation color temperature conversion... In the conversion function, the surface radiation temperature value is accurately calculated and determined, ensuring that the temperature measurement accuracy is not affected by the fluctuation of multiphase flow at the heat transfer boundary; the two-dimensional mapping calibration matrix is ​​a two-dimensional discrete addressing numerical table used to compensate for the fluctuation of radiation emissivity, corresponding to the test results of five sets of samples with surface roughness of 3.2μm, 4.0μm, 5.0μm, 6.0μm and 6.3μm and thermocouple temperature measurement components pre-embedded in the inner wall of the tube at 900℃. When compressed air with a pressure of 0.40MPa is introduced into the annular gas phase purging spray ring of the multi-segment annular jet cooling tank and the dual-wavelength infrared detection array is aimed at the sample surface to collect the radiation energy ratio at independent wavelengths of 0.95μm and 1.15μm, by introducing a thickness of 0.05mm to 0. A localized vapor barrier layer within a 20mm range is used to obtain the attenuation deviation rate of the radiation energy ratio under different vapor concentrations. The discrete cross-data points of the obtained surface roughness classification compensation term and vapor attenuation correction coefficient constitute a five-row, five-column two-dimensional grid addressing table solidified in the central processing unit. When the actual parameters measured subsequently fall between grid nodes, the control program uses a bilinear interpolation algorithm to calculate the continuous correction weight value of non-grid node positions, eliminating radiation interference caused by surface roughness variations and residual water film. The computing unit calculates the transient surface cooling rate of each region of the pipe body based on the received surface radiation temperature signal and determines the absolute value of its deviation from the preset linear cooling slope of 65℃ / s to 75℃ / s. When the pipe material has a local wall thickness exceeding the tolerance... Or, if segregation releases latent heat of phase transformation, causing the transient cooling rate of the surface to be lower than the linear cooling slope and the absolute value of the deviation exceeds the set deviation threshold, the linear cooling slope here refers to the constant slope of 70℃ / s, which is the critical cooling rate limit for the complete transformation of the fully martensitic structure, locked according to the continuous cooling transformation curve of pipeline steel with a carbon mass percentage of 0.25%, a chromium mass percentage of 1.00%, and a molybdenum mass percentage of 0.80% in the current batch. The aforementioned set deviation threshold refers to the absolute difference limit of 4.0℃ / s caused by the release of latent heat of phase transformation due to a 0.8mm deviation in the sleeve wall thickness, deviating from the aforementioned constant slope. When the actual temperature change rate collected and calculated is lower than 70℃ / s and the absolute value of the difference between the two exceeds 4.At the 0℃ / s threshold, the arithmetic unit outputs a command to drive the regulating valve of the multi-segment annular jet cooling tank to increase its opening, controlling the spray pressure of the cooling medium to increase from the reference pressure of 0.45MPa to 0.55MPa to 0.85MPa to 1.15MPa. This increases the boiling vapor film on the local tube surface through fluid impact kinetic energy, thereby improving the heat transfer coefficient and compensating for differences in the release of latent heat of phase change within the tube. Correspondingly, when the cooling rate at a local thin-walled location exceeds the preset range, causing the transient surface cooling rate to exceed the linear cooling slope and the absolute value of the deviation to exceed the set deviation threshold, the regulating valve decreases its opening, controlling the spray pressure to decrease to 0.15MPa to 0.25MPa to reduce the cooling intensity. This feedback regulation loop controls the uneven heat dissipation caused by the accumulation of local latent heat of phase change and the surface cooling rate, reducing the stress of the tube wall structure transformation. To counteract the effect of the pulse duty cycle command received from the electro-hydraulic proportional regulating valve until its valve core is fully mechanically displaced... In addition to the objectively existing 125.6ms second-order mechanical and fluid execution delay loss due to the momentum transfer of the medium in the pipeline, the control program directly reads the absolute value of the deviation between the current control moment and the previous control moment within each fixed digital control cycle of 14.3ms. It then performs a subtraction difference operation between the two and divides it by the 14.3ms time step to discretely calculate the transient rate of change of the cooling rate deviation trend at the current moment. Subsequently, the central processor multiplies this transient rate of change by a discrete lead amplification gain constant with a fixed value of 0.085. The resulting product is directly used as the feedforward pressure correction increment and accumulated in place in the basic opening control quantity of the proportional valve electro-hydraulic pulse width modulation register for the current cycle. This generates a predictive lead drive quantity at the electronic control level before the proportional valve actually performs mechanical action, completely offsetting the fluid transfer delay caused by the physical pipeline layout structure.

[0043] During the quenching and cooling stage, heat dissipation fluctuations are mitigated through discrete and graded control of jet impact pressure. The oil casing is then placed in an online induction furnace and held at an isothermal holding temperature of 210°C to 240°C for 7 to 11 minutes, providing thermodynamic conditions for the transformation of the internal matrix structure and converting it into martensite. After the transformation, the oil casing is placed in a tempering furnace and held at a high-temperature tempering temperature of 645°C to 675°C for 55 to 65 minutes. After being removed from the furnace, it is cooled to room temperature in air, transforming the metastable structure formed by quenching into tempered sorbite, relaxing the residual lattice distortion stress in the matrix due to the cooling phase transformation, and reducing local stress concentration. After this cooling to room temperature, the present invention utilizes… An electromagnetic ultrasonic non-destructive testing instrument was used to detect sound velocity and attenuation coefficient at 90-degree intervals along the circumference of the oil casing to determine its microstructure uniformity index in the depth direction. This index relies on the central processing unit in the control system to read the discrete acoustic time sequence of high-frequency ultrasonic shear waves propagating from the outer surface to the inner surface of the pipe wall, collected by the non-contact electromagnetic acoustic transducer inside the ultrasonic non-destructive testing instrument. By extracting the absolute difference of the transverse wave sound velocity at three depth positions—the outer surface layer, the center layer of the wall thickness, and the inner surface layer—the average sound velocity and standard deviation of the sound velocity at these three depth positions in the four circumferential detection quadrants are calculated. Finally, the central processing unit outputs a dimensionless percentage value representing the anisotropy of the microstructure across the entire cross-section, which is used as an evaluation metric. The system estimates the deterministic data entity of microstructure uniformity, specifically defined as the relative standard deviation of the shear wave velocity of the tempered sorbite structure in the inner, middle, and outer layers of the pipe wall. When the relative standard deviation exceeds 1.5%, the system determines that the microstructure uniformity index exhibits asymmetric deviation, indicating residual distortion and unevenness in microstructure transformation in different quadrants or depth directions. In this case, the control system adjusts the conveying speed of the furnace passage, reducing it from 0.2 m / s to 0.12 m / s, thereby extending the subsequent high-temperature tempering and holding period of the oil casing in the furnace by 15 minutes. This, combined with supplemental thermal activation energy, further relaxes the matrix lattice distortion and eliminates local hardness fluctuations. The uniformity index is an acoustic statistical parameter characterizing the difference in microstructure at different depths within the pipe wall. When asymmetric deviations occur, a multi-level progressive linkage response mode is employed. When the relative standard deviation of the shear wave velocity in the tempered sorbite microstructure of the inner, middle, and outer layers of the pipe wall detected by the electromagnetic ultrasonic non-destructive testing instrument is within the range of 1.5% to 2.5%, the system triggers a first-level correction process and reduces the conveying speed of the return furnace channel from 0.20 m / s to 0.12 m / s. This extends the subsequent high-temperature tempering and heat preservation period of the oil casing in the furnace by 15 minutes to replenish the basic thermal activation energy. When the detected relative standard deviation exceeds 2.5%, the system switches to a second-level enhanced control mode, reducing the conveying speed of the return furnace channel to 0.The lower limit of 0.08 m / s is set, and the subsequent high-temperature tempering holding period is extended by 25 minutes. The linkage control system outputs a control command to the online induction heating control zone of the rear section of the tempering furnace to increase the power by 10%, causing the local tempering temperature to rise by 10°C in situ. This accelerates the stress relaxation of the deep residual lattice distortion structure and eliminates circumferential hardness fluctuations. After tempering and cooling to room temperature, the oil casing has a matrix structure of tempered sorbite with a grain size of grade 8 to 11. The difference in structural stress between the circumferential and axial directions is reduced. In media containing hydrogen sulfide and operating under underground pressure conditions, the casing exhibits resistance to sulfide stress cracking and crush bearing capacity.

[0044] Example 2: The process parameters of the method of the present invention were verified by a physical experimental platform for heat transfer under the strong cold processing of oil casing. The heating power supply of the physical experimental platform operates at a frequency range of 0.5kHz to 10kHz, the control accuracy of the walking beam furnace is ±1℃, and the multi-segment annular jet cooling tank is equipped with an adjustable jet nozzle ring. The surface radiation temperature of the pipe is collected by a multi-channel non-contact optical temperature monitoring array. The receiving wavelength of the dual-wavelength infrared detection array in the multi-channel non-contact optical temperature monitoring array is 0.95μm to 1.15μm, the temperature measurement range is 150℃ to 1200℃, the measurement accuracy is ±0.3%, and the signal acquisition frequency is adjustable between 10Hz and 200Hz. The test object was a thick-walled steel pipe with an outer diameter of 139.7mm and a wall thickness of 10.5mm. The heat dissipation data during the strong cold quenching phase transformation was reproduced on the full-size steel pipe sample to confirm the anti-sulfide stress cracking performance and anti-crushing bearing capacity of the oil casing in the underground acidic pressure environment.

[0045] During the operation of the multi-segment annular jet cooling tank, the sampling frequency of the dual-wavelength infrared detection array is expressed as: ,in The sampling frequency for infrared temperature signals is determined by the dynamic rupture rate of the non-uniform vapor film on the surface of the high-temperature pipe and the variation characteristics of the transient cooling slope. Its physical design balances the real-time capture of the transient cooling rate with the computational load generated by data stream transmission, forming a mutually restrictive relationship. When the medium flow regulating valve in the multi-segment annular jet cooling tank is in a dynamic changing state and the surface cooling slope is between 65℃ / s and 75℃ / s, to satisfy the sampling theorem and prevent frequency aliasing of randomly generated vapor film heat transfer abrupt signals, the product relationship between the sampling frequency and the transient frequency of heat flow fluctuations determines that the sampling frequency tends towards the lower limit of its adjustment range. This allows the control system to accurately obtain the optimal time-domain parameters for the release of latent heat of phase change in the tissue. Specifically, satisfying the sampling theorem means that the absolute value of the sampling frequency is greater than twice the frequency of the highest effective high-frequency component in the randomly generated vapor film heat transfer abrupt signal. In actual industrial conditions, the highest transient characteristic frequency of the sudden change in steam film heat transfer was measured to be 30Hz. Therefore, the lower limit of the sampling frequency adjustment range was rigidly set to 60Hz to physically avoid signal frequency aliasing. The product relationship refers to the system using twice the frequency of the highest effective high-frequency component as the basic characteristic reference, and then multiplying it by a system stability margin safety factor of 1.16 to obtain the calculated control threshold. This control threshold is mutually constrained by the upper limit of the hardware clock load of the computing unit, so that the sampling frequency operates close to the lower boundary of the 60Hz to 80Hz adjustment range while ensuring real-time capture of the phase change transient cooling rate. This decouples the data stream transmission load from the sampling accuracy. Under this control logic, for the case of oil casing passing through a multi-segment annular jet cooling tank at a step speed of 0.2m / s, 70Hz was selected as a representative data example for the sampling frequency.

[0046] To confirm the synergistic effect of each process step and the boundary effect of parameter limits, this verification experiment established a multi-dimensional control system. This system included a control group using existing constant-flow-rate medium cooling technology; a first-part missing control group that maintained other process characteristics but lacked the mechanical stripping step (step one), thus retaining the original oxide scale on the surface; a second-part missing control group lacking a high-pressure gas phase purging measurement channel, resulting in interference from multiphase vapor on the measurement optical path; and a control group exceeding the lower limit of the induction heating pretreatment temperature (440℃) and the upper limit of the induction heating pretreatment temperature (510℃) in step two. Simultaneously, to confirm the effectiveness of the scheme for pipe wall defects of varying severity... To understand the adaptation pattern, the complete process steps of this invention were used to establish three independent test groups. Three types of pipes with different initial circumferential wall thickness deviations were selected as core variable characteristics: a low-defect bending test group with an initial circumferential wall thickness deviation of 0.2 mm, a medium-defect bending test group with an initial circumferential wall thickness deviation of 0.5 mm, and a high-defect bending test group with an initial circumferential wall thickness deviation of 0.8 mm. During the operation of the quenching and cooling section of the multi-segment annular jet cooling tank, the control sample group, lacking heat exchange feedback regulation, experienced a random and uneven convective vapor film formed by the high-velocity spray medium around the high-temperature pipe wall. This caused abrupt changes in the heat dissipation flow on the pipe surface, resulting in high-frequency disturbances in infrared radiation. The temperature signal acquired by the sensor exhibited a temperature fluctuation as high as 45.3℃, with its signal-to-noise ratio decreasing to 14.2dB. This resulted in a lag in the acquired transient surface cooling rate and a control loop delay of 1.24s, leading to uneven distribution of structural stress in the pipe wall. Conversely, the experimental groups using the method of this invention continuously introduced compressed air at a pressure of 0.40MPa into the measurement channel of the multi-segment annular jet cooling tank, forcibly expelling the accumulated jet droplets and high-temperature vapor mist, and clearing the convective multiphase flow obstruction in the infrared measurement optical path. This improved the signal-to-noise ratio of the surface temperature signal acquired by the sensor to 38.6dB, obtaining high-fidelity transient heat dissipation characteristic data of the pipe wall. Analysis of the test curves shows that in the low-defect bending test group, due to the low wall thickness deviation, the absolute value of the relative deviation of the transient cooling rate of each region of the pipe wall remains within 3.5℃, the quenched martensitic transformation remains circumferentially synchronous, and the hardness difference of the finished pipe section is less than 1.2HRC. In the medium-defect bending test group, facing the increased wall thickness deviation, the feedback adjustment loop drives the regulating valve of the multi-segment annular jet cooling tank to change the opening, controlling the cooling medium spray pressure to dynamically change within the range of 0.45MPa to 1.15MPa, compensating in situ for the delayed release of the martensitic phase transformation latent heat due to the slow heat dissipation in the thick-walled area, and the measured maximum circumferential residual tensile stress of the high-temperature pipe body is reduced to 25.4MPa indicates that the spray pressure counteracts the physical process of reducing stress concentration during phase transformation. In the control groups deviating from the process boundary of this invention, the data curves show nonlinear saturation and mechanical property degradation characteristics. In the first missing control group, the retained surface oxide layer causes an increase in local contact thermal resistance, forming a heat transfer saturation zone. Even when the spray pressure of the cooling medium is increased to 1.35MPa, the dense oxide layer hinders interfacial heat conduction, and the transient cooling rate of the surface cannot continue to cross the current heat dissipation platform, confirming that surface roughness pretreatment has a promoting effect on improving the heat transfer coefficient of high-pressure jet. In the lower limit out-of-range control group, because the set temperature of the induction heating furnace for cyclic preheating was only 440℃, which is lower than the critical energy for dislocation directional reorganization in the steel material, the microstructure transformation distortion in the subsequent strong cooling stage was not suppressed. The measured critical stress for sulfide stress cracking of the pipe decreased significantly to 42.1% of the actual yield strength. In the upper limit out-of-range control group, because the induction heating temperature for cyclic preheating was as high as 510℃, exceeding the upper limit of the process window for recovery before phase transformation, local reverse phase transformation was triggered under rapid electromagnetic induction temperature rise and mist cooling impact. This caused overheating and coarsening of the austenite grains in the initial matrix microstructure, resulting in subsequent overall austenite... After austenitization and heat treatment, the austenite grain size was measured to have deteriorated to level 6. This ultimately led to the segregation of alloying elements and a network-like inhomogeneous structure at the grain boundaries after strong cold quenching. The tube's resistance to crushing and bearing capacity abnormally decreased to 62.4 MPa. This data on grain anisotropy deterioration and uneven release of phase transformation stress directly provides physical boundary experimental data support for the surface roughness range, induction heating operating frequency, and temperature control range defined by the method of this invention. Discrete verification data from a multi-dimensional control system confirms that the method consists of surface roughness control, rapid induction alternating cycle pretreatment, and adaptive adjustment of gas phase purging and spray pressure in the measurement channel. The combination of process features smooths out the asymmetric heat transfer rate fluctuations caused by pipe segregation and wall thickness variations; spatiotemporal synchronous regulation of the martensitic phase transformation cooling front reduces the local concentration of residual stress within the microstructure, eliminating anisotropic lattice distortion defects that induce crack propagation; the heat treatment process improves the uniformity of yield strength across the entire cross-section of the finished thick-walled oil casing to 96.3%, and the critical stress for sulfide stress cracking in hydrogen sulfide-saturated solution reaches 82.5% of the actual yield strength. A deterministic physical causal correspondence is established between process parameter adjustments and the improvement of the structural bearing capacity of the pipe under high-pressure underground service conditions containing hydrogen sulfide.

[0047] Example 3: This example combines Figures 1 to 2 A description of a heat treatment process for an oil casing, such as... Figure 1As shown, in step S1, the oxide scale on the surface of the oil casing is mechanically peeled off, and the surface roughness Ra of the oil casing is adjusted to 3.2μm to 6.3μm. In step S2, the oil casing is fed into an induction heating coil with a working frequency of 1.5~2.5kHz and heated to 460~490℃ at a heating rate of 35~45℃ / s. The surface temperature is then reduced to 260~290℃ by spraying a cooling medium through a high-pressure mist cooling nozzle. This heating and cooling process is repeated 2 to 3 times. In step S3, the treated oil casing is fed into a heating furnace and heated to 890~910℃ and held at that temperature for 2 hours. Austenitization is completed in 2-28 minutes. In step S4, the austenitized oil casing is transferred into a multi-segment annular jet cooling tank for quenching. The surface radiation temperature value is collected using a dual-wavelength infrared detection array, and the transient cooling rate is calculated. When the absolute value of the deviation exceeds the threshold, the valve opening is adjusted to change the spray pressure of the cooling medium. In step S5, the quenched oil casing is sent into an online induction furnace and held isothermally at 210-240℃ for 7-11 minutes. Then it is sent into a tempering furnace and heated to 645-675℃ for high-temperature tempering and holding for 55-65 minutes. The casing is then removed from the furnace and cooled to room temperature.

[0048] like Figure 2 As shown, compressed air is continuously supplied to the measurement channel and kept in a light-transmitting steady state. The dual-wavelength infrared detection array in the multi-segment annular jet cooling tank collects the surface radiation temperature value. The dual-wavelength infrared detection array outputs the surface radiation temperature signal to the central processing unit. The central processing unit calculates the transient cooling rate of the surface and outputs a signal to drive the opening change of the regulating valve to the multi-segment annular jet cooling tank, so that the regulating valve in the multi-segment annular jet cooling tank changes the spray pressure of the cooling medium.

[0049] Example 4: The method of this invention is applied to the production process of oil casing in high-pressure underground conditions containing hydrogen sulfide. In the strong cooling and controlled quenching process of the oil casing within a multi-segment annular jet cooling tank, the control system schedules the cooling medium spray circuit according to preset digital discrete control steps to suppress asymmetric heat transfer fluctuations caused by geometric deviations in the high-temperature pipe material. The initial physical state of the oil casing when it is moved from the austenitizing walking beam furnace and sent into the multi-segment annular jet cooling tank is defined by the material properties and geometric morphology of the pipe. The outer diameter of the oil casing is set to 139.7 mm, and the wall thickness is set to 10.5 mm. Due to the maximum initial circumferential wall thickness deviation from the preceding rolling process, it is limited to within 0.8 mm. The initial roughness of the oil casing surface is... After the oxide scale is removed by pre-drawing mechanical stripping, the thickness is adjusted to 3.2μm to 6.3μm. The external physical feedback hardware required for implementing the adaptive digital control step includes a dual-wavelength infrared detection array arranged alternately along the axial and circumferential directions of the multi-segment annular jet cooling tank. The signal acquisition frequency of a single temperature sensor in the dual-wavelength infrared detection array is fixed at 70Hz, and the clock constant of the analog-to-digital conversion sampling and holding loop corresponding to its hardware interface is fixed at 10μs. The output raw data stream structure is defined as a discrete single-precision floating-point series with time index markers, thereby providing the computing unit with a continuous discrete tube wall temperature sequence in real time. After receiving the discrete tube wall temperature sequence, the central processing unit in the control system establishes a first-in-first-out sliding time-domain circular queue in the volatile buffer. The length of the sliding time-domain circular queue is limited to 7 sampling periods to continuously latch the current moment. Including the temperature signal from the preceding cycle; at the beginning of each independent digital control cycle, the central processing unit reads the temperature sample value at the current moment from the sliding time-domain circular queue. The CPU calculates the transient surface cooling rate of the corresponding pipe wall position at the current time node by performing a step-first difference operation on the discrete temperature values ​​in the sliding time-domain circular queue with respect to the time step. To mitigate the artifacts of multiphase flow disturbance caused by medium impact sputtering, the CPU uses a preset sliding arithmetic mean filter window to smooth the obtained cooling rate to obtain a true transient surface cooling rate with a high signal-to-noise ratio. The CPU extracts the solidified reference linear cooling slope parameter from a specific address space of the read-only memory, performs a subtraction operation between the true transient surface cooling rate and the reference linear cooling slope parameter, and generates the absolute value of the difference as the absolute value of the deviation.

[0050] To translate the calculated absolute value of the deviation into a valve opening command for adjusting the kinetic energy of the jet impacting the fluid, the control system loads a process judgment quantization procedure during program execution and sets a deviation threshold as a step logic trigger point. The value of the deviation threshold is determined through offline solidification calibration tests. The calibration process involves placing a steel sample with segregation defects into a quenching tank with a 0.40 MPa compressed air purging channel for heat transfer testing. The measured local cooling rate reduction caused by the release of latent heat of martensitic transformation is within the range of 3.5℃ / s to 5.0℃ / s, thus locking the deviation threshold at 4.0℃ / s. When the central processing unit determines that the current absolute value of the deviation is greater than the set deviation threshold and due to the thin-walled region... When thermal acceleration causes the transient cooling rate of the actual surface to exceed the reference linear cooling slope parameter, the system determines that supercooling has occurred. The central processing unit (CPU) changes the value of the drive pulse width modulation duty cycle register in the output channel, reduces the opening of the proportional valve controller by the control step size, and controls the spray pressure to decrease from the equilibrium point of 0.45 MPa to 0.20 MPa. This reduces the fluid kinetic energy to prolong the boiling vapor film life on the pipe wall surface and slows down the heat transfer rate. Correspondingly, when the CPU determines that the current absolute value of the deviation is greater than the set deviation threshold and the transient cooling rate of the actual surface is lower than the reference linear cooling slope parameter due to heat dissipation lag in the thick-walled area or the accumulation of latent heat from segregation phase change, the system determines that a spatial-temporal asynchronous lag of the microstructure phase change has occurred, and the control system executes uplink feedback. Control; Due to the 125.6ms second-order execution delay loss generated by the mechanical clearance of the electro-hydraulic proportional regulating valve core and the fluid momentum transfer in the delivery pipeline in the medium circuit of the multi-segment annular jet cooling tank, the central processing unit calls the time delay adaptive damping compensation operator stored in the register. By performing differential calculus on the rate of change of the absolute value of the deviation over time, it calculates the pressure lead increment used to offset the mechanical lag and adds it in place to the current control quantity; Specifically, when the time delay adaptive damping compensation operator is executed, it obtains the difference between the absolute value of the deviation at the current moment and the absolute value of the deviation at the previous moment, and divides this difference by the digital control cycle time step of 14.3 milliseconds to calculate the transient rate of change; the transient rate of change is then calculated. The conversion rate is multiplied by a fixed differential gain coefficient, which is determined by the product of the inverse of the second-order execution delay loss of 125.6 ms and the inertial damping coefficient of the pipeline fluid. In this embodiment, it is set to 0.085. The calculated product is used as the pressure advance increment and is directly weighted and superimposed on the current proportional valve base opening control quantity. This generates a predictive control feedforward before the actual action of the electro-hydraulic proportional control valve, and the advance quantity of electronic control completely offsets the time delay lag at the mechanical and fluid levels. Under the adjustment of the time delay adaptive damping compensation operator, the electro-hydraulic proportional transmission mechanism acts within 20 ms, controlling the medium spray pressure of the multi-segment annular jet cooling tank to rapidly step from the reference pressure of 0.55 MPa to 1.At the upper limit scalar endpoint of 15 MPa, the high-velocity fluid exerts a macroscopic mechanical constraint on the high-temperature pipe wall and disrupts the non-uniform vapor film heat-insulating layer formed due to heat transfer saturation. This transforms the heat transfer conditions from vapor film insulation to forced convection heat transfer, forcibly compensating for the differences in thermodynamic spatiotemporal release caused by pipe wall deviations.

[0051] To address the aging defects in the method model caused by localized wear of spray pipes due to long-term operation in heat treatment production lines and viscosity drift of quenching media due to temperature rise, the control program initiates a timeliness guarantee and reconstruction mechanism during each quenching start-up self-check phase. The system uses standard nominal wall thickness pipes for a low-pressure fluid state reset calibration and introduces a time decay factor in the recursive calculation of the pressure conversion coefficient. A sliding time window is set to eliminate historical opening mapping data accumulated over 720 hours of operation. The engineering basis for limiting the sliding time window to 720 hours is that after 720 hours of continuous full-load operation of high-pressure spray pipes and nozzle arrays, the cumulative micro-erosion wear of the mechanical nozzle inner diameter caused by fluid scouring will lead to a structural drift of more than 3% in the spray flow state. Therefore, this time span is used as the periodic node for updating historical data and clearing historical data. The time decay factor specifically refers to a weighting coefficient that decreases exponentially with increasing operating time. Its initial value is set to 1.0, and it increases with the number of hours the equipment operates. The number decreases monotonically at a decay rate of 0.0014 per hour. By multiplying and weighting this weight coefficient with historical opening mapping data, the control system is given higher weight based on recently acquired data in the recursive calculation, thereby adaptively tracking and offsetting the aging of the method model caused by nozzle wear and medium viscosity drift. The gain coefficient of the time delay adaptive damping compensation operator is readjusted according to the latest pressure sensor pressure fluctuation feedback, thereby ensuring the accuracy of control command output. The heat treatment process eliminates the anisotropy of microstructure hardness caused by uneven circumferential wall thickness during the quenching of thick-walled oil casing by continuously digitally acquiring the deviation of the surface cooling rate and offsetting it with pressure adaptive transformation. After the quenching transformation is completely synchronized, the finished pipe has a circumferential and axial tempering sorbite grain size that is homogeneously distributed across the entire cross section in the range of 8 to 11. The hardness difference of the dislocation in the shear structure of the entire pipe wall is less than 0.5 HRC. When serving in acidic pressure underground conditions, it has high resistance to sulfide stress cracking and high resistance to crushing.

[0052] Example 5: When the system faces the actual production conditions of new batches of pipeline materials and zero-point drift of the regulating valve in the multi-segment annular jet cooling tank, the control system needs to execute a standardized on-site deployment pre-calibration and debugging procedure before starting the online strong cold quenching process to establish the system's control reference boundary. Before the oil casing enters the cooling tank, the operator selects a standard defect-free pipeline steel short section from the same batch, with a material composition monotonically aligned with the pipe to be processed, an outer diameter of 139.7 mm, and a wall thickness of 10.5 mm, as the calibration object. This section is then sent into the temperature measurement channel of the experimental platform, and the annular jet cooling tank is started. Compressed air at a pressure of 0.40 MPa is introduced into the gas-phase purge ring. Under this initial enabling environment, the dual-wavelength infrared detection array continuously acquires the surface radiation temperature signal of the high-temperature short section under static conditions at a sampling frequency of 70 Hz. If a spike fluctuation deviating from the median by more than 0.5 ℃ appears in the data stream, the processor automatically activates the adaptive digital smoothing operator to perform in-situ correction of the digital gain of the channel until the measurement noise variance within 100 consecutive sampling points converges to within the preset ripple index. This completes the optical path impedance calibration of the data acquisition end under a specific industrial multiphase flow environment.

[0053] After eliminating electrical and optical residuals in the infrared detection hardware, the control system performs in-situ clearance and zero-point offset quantization calibration on the actuator of the electro-hydraulic proportional control valve. The central processing unit injects discrete position pulse series into the valve core drive register of the proportional control valve in a stepwise manner, while simultaneously reading the feedback displacement in real time through the valve core linear displacement sensor. When the pulse injection quantity has crossed the initial dead zone and the displacement sensor outputs the first non-zero measurement value, the central processing unit latches the register value at this time as the reference opening proportional coefficient, which is used to offset the 125.6ms second-order pulse induced by valve body wear in in-situ. The static hysteresis term in the execution delay loss is processed; the electro-hydraulic proportional regulating valve is opened to the reference flow rate position, and the system injects quenching cooling medium into the multi-segment annular jet cooling tank. The flow rate is adjusted until the pressure gauge outputs a stable reference pressure of 0.45MPa. The central processing unit takes the proportional opening at this time as the control zero point of the initial feedback regulation loop and logically binds it with the aforementioned deviation threshold of 4.0℃ / s. This establishes a corresponding control reference between the physical transformation unit and the algorithm software layer, ensuring that the feedback regulation in the subsequent production process can be completely controlled by the unified physical quantity transformation flow.

[0054] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A heat treatment process for oilfield casing, characterized in that, Includes the following steps: Step S1: Mechanically peel off the oxide scale on the surface of the oil casing and adjust the surface roughness Ra of the oil casing to 3.2 μm to 6.3 μm; Step S2: The oil casing is fed into an induction heating coil with a working frequency of 1.5kHz to 2.5kHz and heated to 460℃ to 490℃ at a heating rate of 35℃ / s to 45℃ / s. The surface temperature is then reduced to 260℃ to 290℃ by spraying cooling medium through a high-pressure mist cooling nozzle. The heating and cooling process is repeated 2 to 3 times. Step S3: The treated oil casing is sent into a heating furnace, heated to 890°C to 910°C and held for 22 to 28 minutes. Step S4: After austenitization, the oil casing is moved into a multi-segment annular jet cooling tank for quenching. The surface radiation temperature value is collected by a dual-wavelength infrared detection array arranged along the circumference and axial direction of the oil casing, and the surface transient cooling rate is calculated. When the absolute value of the deviation of the surface transient cooling rate from the set linear cooling slope exceeds the set deviation threshold, the opening of the regulating valve of the multi-segment annular jet cooling tank is adjusted to change the spray pressure of the cooling medium. Step S5: The quenched oil casing is sent into an online induction furnace and kept at an isothermal holding temperature of 210°C to 240°C for 7 to 11 minutes. Then it is sent into a tempering furnace and heated to 645°C to 675°C for high-temperature tempering and holding for 55 to 65 minutes. After being taken out of the furnace, it is cooled to room temperature.

2. The heat treatment process for oil casing according to claim 1, characterized in that, The steel material of the oil casing comprises, by mass percentage: 0.22% to 0.28% carbon, 0.20% to 0.40% silicon, 0.50% to 0.80% metallic manganese, 0.80% to 1.20% chromium, 0.60% to 1.00% molybdenum, 0.03% to 0.08% vanadium, and 0.01% to 0.04% niobium, with the balance being iron and unavoidable impurities; the austenite grain size of the oil casing is controlled to grade 8 to 11 during the high-temperature austenitization process in step S3.

3. The heat treatment process for oil casing according to claim 1, characterized in that, In step S4, the specific steps of introducing compressed air into the measurement channel of the multi-segment annular jet cooling tank include: step S41, introducing compressed air with a pressure of 0.35MPa to 0.45MPa into the measurement optical path of the dual-wavelength infrared detection array to collect surface radiation temperature values; step S42, using the continuously introduced compressed air to purge and remove the surface heat exchange vapor film of the multi-segment annular jet cooling tank section, so that the measurement optical path maintains a stable light transmission state during the sampling period of the dual-wavelength infrared detection array with a signal acquisition frequency of 60Hz to 80Hz.

4. The heat treatment process for oil casing according to claim 1, characterized in that, In step S2, the alternating heating and cooling includes the following steps: Step S21, the oil casing is fed into an induction heating coil with a working frequency of 2.0 kHz, so that the temperature of the oil casing reaches 470°C at a heating rate of 40°C / s; Step S22, a cooling medium is sprayed onto the surface of the oil casing using a high-pressure mist cooling nozzle to reduce the surface temperature to 270°C; Step S23, steps S21 and S22 are repeated a total of 3 times.

5. The heat treatment process for oil casing according to claim 1, characterized in that, In step S5, the isothermal residence temperature is 210℃ to 240℃, and the isothermal residence time is 7 min to 11 min.

6. The heat treatment process for oil casing according to claim 1, characterized in that, In step S5, the high-temperature tempering temperature is 645℃ to 675℃, and the holding time is 55min to 65min.

7. The heat treatment process for oil casing according to claim 1, characterized in that, In step S4, the method of collecting surface radiation temperature values ​​using a dual-wavelength infrared detection array includes the following steps: using the first wavelength sensing component and the second wavelength sensing component in the dual-wavelength infrared detection array, the radiation energy values ​​of the oil casing surface at two independent wavelengths are collected synchronously, and the ratio of the radiation energy values ​​at the two independent wavelengths is obtained. The surface radiation temperature value is then calculated based on the ratio.

8. The heat treatment process for oil casing according to claim 1, characterized in that, In step S4, when the transient cooling rate of the surface is greater than the set linear cooling slope and the absolute value of the deviation exceeds the set deviation threshold, the opening of the regulating valve of the multi-segment annular jet cooling tank is reduced, and the spray pressure of the cooling medium is reduced to 0.15MPa to 0.25MPa.

9. The heat treatment process for oil casing according to claim 1, characterized in that, After the high-temperature tempering and heat preservation is completed in step S5, the following steps are also included: Step S51, using a non-destructive testing instrument to measure the microstructure uniformity index of the oil casing in the depth direction; Step S52, when the microstructure uniformity index shows asymmetrical deviation, adjusting the conveying speed of the return channel to extend the subsequent high-temperature tempering and heat preservation cycle of the current oil casing in step S5.

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