Manufacturing process for riser joint of offshore oil and gas platform

Abstract

The invention discloses a manufacturing process of a riser joint of an offshore oil and gas platform, which relates to the technical field of preparation and comprises the following steps: selecting a forge piece with specific components, smelting through an electric furnace or an oxidation converter, forging, performing isothermal annealing, performing final heat treatment and performing mechanical property test; the isothermal annealing temperature monitoring method comprises the following steps: monitoring the temperature in a furnace cooling stage, and calculating an isothermal tradeoff value to determine an isothermal analysis point; constructing an isothermal gradient field, analyzing temperature change, constructing an equivalent cooling temperature curve, and comparing the equivalent cooling temperature curve with a supercooled austenite continuous cooling transformation curve; if the curve change trends are inconsistent, whether the current temperature is in a bainite stage is judged, and if not, the regulation margin is judged; if the regulation margin is insufficient, the approach time difference is calculated, the temperature is regulated in stages, and the process stability is improved.

Description

Technical Field

[0001] The invention relates to the technical field of preparation, and in particular to a manufacturing process for a riser joint of an offshore oil and gas platform. Background Art

[0002] In the development of marine oil and gas resources, riser joints are core components connecting floating platforms and seabed wellheads. As deep-sea oil and gas development expands into ultra-deepwater areas, riser joints need to withstand alternating loads, high temperature and high pressure environments, and long-term service requirements under complex sea conditions, which puts higher demands on the manufacturing process.

[0003] The existing technology lacks control over the selection and processing of raw materials. The chemical composition of the materials required for the riser joints is not strictly limited, resulting in unstable impurity content inside the forgings. If multiple upsetting and drawing processes are used during the forging process to optimize the forging ratio and eliminate casting defects such as looseness, segregation, and columnar crystals, the internal structure of the forgings will be uniform, which will help improve the quality and reliability of the casting products.

[0004] In the isothermal annealing process, the existing technology lacks temperature monitoring and control. In the furnace cooling stage, it is impossible to determine the temperature abnormal area and it is difficult to timely and effectively control the temperature in the furnace. This may lead to the formation of granular bainite in some areas of the forging, which in turn affects the microstructure transformation of the forging. If the isothermal analysis point is determined by calculating the isothermal trade-off value, the isothermal gradient field is constructed, the temperature changes of each part are monitored, the temperature gradient is accurately grasped, and the process parameters are controlled to ensure that each part undergoes phase transformation at a suitable temperature, promote uniform transformation of the microstructure, stabilize the impact toughness of the forging, reduce the inhomogeneity of the impact specimen, and improve the product quality stability and reliability.

[0005] To this end, the present invention provides a process for manufacturing a riser joint of an offshore oil and gas platform. Summary of the invention

[0006] The object of the present invention is to provide a manufacturing process for an offshore oil and gas platform riser joint, so as to solve the problem that the above-mentioned prior art lacks temperature monitoring and regulation during isothermal annealing, and in the furnace cooling stage, it is impossible to determine the temperature abnormal area, and it is difficult to timely and effectively regulate the temperature in the furnace; this leads to the formation of granular bainite in some areas of the forging, thereby affecting the microstructural transformation of the forging.

[0007] In a first aspect, the present invention provides a process for manufacturing a riser joint of an offshore oil and gas platform, comprising the following steps: S1. Determine the raw material composition of the riser joint; S2, forging processing; S3, preliminary heat treatment using isothermal annealing; S4, final heat treatment; S5. Sampling and mechanical properties testing.

[0008] In a second aspect, the present invention provides a temperature monitoring method for isothermal annealing, which is used to implement temperature monitoring in the isothermal annealing stage, comprising the following steps: Step 1: numerically analyze the temperature of different monitoring points during the furnace cooling stage to obtain an isothermal trade-off value, and determine the isothermal analysis point based on the isothermal trade-off value; Step 2: Based on the isothermal analysis points, determine the temperature gradient in the isothermal analysis area and construct the isothermal gradient field; Step 3: Analyze different gradient descent paths of the temperature gradient field, extract the temperature analysis path, determine the equivalent cooling temperature curve of the temperature analysis path, and perform consistency analysis with the continuous cooling transformation curve of supercooled austenite to determine whether the curve shows a consistent change trend; Step 4: If not, determine whether the temperature of the current equivalent cooling temperature curve is in the bainite stage; if not, determine whether the current furnace temperature control margin is sufficient; Step 5: If the current temperature control margin is insufficient, the temperature of the isothermal analysis area is controlled in stages.

[0009] In a third aspect, the present invention provides a temperature monitoring system for isothermal annealing, which is used to implement a temperature monitoring method for isothermal annealing, and includes the following modules: Single analysis module: used to perform numerical analysis on the temperature of different monitoring points during the furnace cooling stage, obtain isothermal trade-off values, and determine isothermal analysis points based on the isothermal trade-off values; Regional analysis module: Based on the isothermal analysis points, determine the temperature gradient of the isothermal analysis area and construct the isothermal gradient field; Trend analysis module: used to analyze different gradient descent paths of the temperature gradient field, extract the temperature analysis path, determine the equivalent cooling temperature curve of the temperature analysis path, and perform consistency analysis with the continuous cooling transformation curve of supercooled austenite to determine whether the curve shows a consistent change trend; Margin determination module: if not, it is used to determine whether the temperature of the current equivalent cooling temperature curve is in the bainite stage. If not, it is used to determine whether the control margin of the current furnace temperature is sufficient. Temperature control module: If the current temperature control margin is insufficient, it is used to control the temperature of the isothermal analysis area in stages.

[0010] Beneficial effects of the present invention: 1. The limitation of raw material composition, such as the specific chemical composition requirements of A694F65 forgings, lays the foundation for product performance. Multiple upsetting and drawing during the forging process make the internal structure of the forging uniform, enhancing the stability and reliability of the material; isothermal annealing treatment promotes the uniform transformation of the microstructure into ferrite and pearlite, reducing the possibility of granular bainite, and the final heat treatment further optimizes the material performance, which is conducive to improving the load-bearing capacity and service life of the riser joint.

[0011] 2. The isothermal annealing temperature monitoring method monitors and controls the temperature from both time and space dimensions. By calculating the isothermal trade-off value to determine the isothermal analysis point, the temperature abnormality area can be located to provide a basis for process optimization; an isothermal gradient field is constructed to monitor the temperature change of the forging in real time, grasp the temperature gradient, and then control the process temperature so that the forging can undergo phase change under appropriate temperature conditions, promote uniform transformation of the microstructure, reduce the non-uniformity of the impact specimen performance, and improve product quality stability and reliability.

[0012] 3. Carry out consistency analysis on the equivalent cooling temperature curve and the continuous cooling transformation curve of supercooled austenite, and judge the temperature state in combination with the phase change judgment conditions to timely discover potential phase change risks. When the temperature control margin is insufficient, the temperature of the isothermal analysis area is controlled in stages, and the control target value of each stage is calculated, so that the temperature control equipment in the furnace can control the temperature, reduce the phase change anomalies caused by abnormal temperature, improve the reliability and stability of the entire manufacturing process, reduce the scrap rate, and improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0014] Figure 1 This is a flow chart of a manufacturing process of a riser joint for an offshore oil and gas platform provided by the present invention; Figure 2 It is a flow chart of a temperature monitoring method for isothermal annealing provided by the present invention; Figure 3 It is a module diagram of a temperature monitoring system for isothermal annealing provided by the present invention. DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention. Embodiment 1

[0016] like Figure 1 As shown, an embodiment of the present invention provides a manufacturing process for an offshore oil and gas platform riser joint, comprising the following steps: S1. Determine the raw material composition of the riser joint; Specifically, the chemical composition of the raw material A694F65 forging of the riser joint is: C: 0.11%; Si: 0.15%; Mn: 1.15%; P: 0.014%; S: 0.0021%; Ni: 0.41%; Cr: 0.2%; Al: 0.041%; Ti: 0.03%; Mo: 0.08%; Cu: 0.33%; V: 0.089%; N: 0.01%; CE: 0.40%; Among them, CE=C+Mn / 6+(Cr+Mo+V) / 5+(Cu+Ni) / 15; The smelting is carried out by using electric furnace smelting or oxidation converter, double slag process, air degassing and refining furnace refining; It should be noted that CE is the abbreviation of Carbon Equivalent, which is an indicator used to measure the influence of carbon and other alloying elements in steel materials on the weldability and hardening tendency of materials; S2, forging processing; The forging heating temperature is controlled at 1160℃, and step heating is adopted when heating. When the temperature reaches 880℃, it is kept for 0.5 hours, and then raised to the forging heating temperature and kept warm; The forging process involves two upsetting and two drawing steps to ensure that the forging ratio is not less than the preset forging ratio; Preferably, the forging ratio is 4; It should be noted that multiple upsetting and drawing processes are helpful to eliminate or reduce casting defects such as looseness, segregation, columnar crystals, etc., so that the internal structure of the forging is uniform. After forging, air cooling is used for cooling; S3, preliminary heat treatment using isothermal annealing; The forgings are austenitized at 920°C, and the holding time is calculated as 30min / 25.4mm; After the forging is austenitized, the temperature is lowered to 640℃ with the furnace, kept at this temperature for 2 hours, and finally air-cooled to room temperature; It should be noted that isothermal annealing can make the microstructure of A694F65 forgings uniformly transformed into ferrite + pearlite, avoid the production of granular bainite, prepare for subsequent quenching and tempering heat treatment, and reduce the inhomogeneity of impact specimens; S4, final heat treatment; The final heat treatment includes quenching and tempering. In the quenching process, the holding temperature is set to 880℃, the holding time is calculated as 30min / 25.4mm, and water cooling is adopted. The cooling medium temperature is controlled at 30℃. During the tempering process, the holding temperature is set to 622°C, and the holding time is also calculated according to 30min / 25.4mm. After tempering, air cooling is used; S5, sampling and mechanical properties testing; Sampling is carried out according to DNV-ST-F101 standard, and mechanical property tests are performed on forgings; It should be noted that the purpose of mechanical property testing of forgings is to ensure that product quality meets the use requirements of riser joints on offshore oil and gas platforms. Embodiment 2

[0017] like Figure 1 As shown, an embodiment of the present invention provides a manufacturing process for an offshore oil and gas platform riser joint, comprising the following steps: S1. Determine the raw material composition of the riser joint; Specifically, the chemical composition of the raw material A694F65 forging of the riser joint is: C: 0.14%; Si: 0.25%; Mn: 1.20%; P: 0.015%; S: 0.0028%; Ni: 0.47%; Cr: 0.23%; Al: 0.046%; Ti: 0.035%; Mo: 0.09%; Cu: 0.34%; V: 0.095%; N: 0.011%; CE: 0.41%, where CE = C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15; The smelting is carried out by using electric furnace smelting or oxidation converter, double slag process, air degassing and refining furnace refining; S2, forging processing; The forging heating temperature is controlled at 1180℃, and step heating is adopted when heating. When the temperature reaches 900℃, it is kept at this temperature for 0.75 hours, and then it is raised to the forging heating temperature and kept at this temperature. The forging process involves two upsetting and two drawing steps to ensure that the forging ratio is not less than the preset forging ratio; Preferably, the forging ratio is 4; The forgings were austenitized at 930°C, and the holding time was calculated as 45min / 25.4mm; After the forging is austenitized, the temperature is lowered to 650℃ with the furnace, kept at this temperature for 2.5 hours, and finally air-cooled to room temperature; S4, final heat treatment; The final heat treatment includes quenching and tempering. In the quenching process, the holding temperature is set to 890℃, the holding time is calculated as 50min / 25.4mm, and water cooling is adopted. The cooling medium temperature is controlled at 35℃. During the tempering process, the holding temperature is set to 630°C, the holding time is calculated as 45min / 25.4mm, and air cooling is used after tempering; S5, sampling and mechanical properties testing; Sampling is carried out according to DNV-ST-F101 standard, and mechanical property tests are performed on forgings; It should be noted that the purpose of mechanical property testing of forgings is to ensure that product quality meets the use requirements of riser joints on offshore oil and gas platforms. Embodiment 3

[0018] like Figure 1 As shown, an embodiment of the present invention provides a manufacturing process for an offshore oil and gas platform riser joint, comprising the following steps: S1. Determine the raw material composition of the riser joint; Specifically, the chemical composition of the raw material A694F65 forging of the riser joint is: C: 0.17%; Si: 0.35%; Mn: 1.30%; P: 0.020%; S: 0.003%; Ni: 0.50%; Cr: 0.25%; Al: 0.05%; Ti: 0.04%; Mo: 0.10%; Cu: 0.35%; V: 0.10%; N: 0.012%; CE: 0.43%; The smelting is carried out by using electric furnace smelting or oxidation converter, double slag process, air degassing and refining furnace refining; S2, forging processing; The forging heating temperature is controlled at 1200℃, and step heating is adopted when heating. When the temperature reaches 920℃, it is kept at this temperature for 1 hour, and then it is raised to the forging heating temperature and kept at this temperature. The forging process involves two upsetting and two drawing steps to ensure that the forging ratio is not less than the preset forging ratio; Preferably, the forging ratio is 4; S3, preliminary heat treatment using isothermal annealing; The forgings were austenitized at 940°C, and the holding time was calculated as 60min / 25.4mm; After the forging is austenitized, the temperature is lowered to 660℃ with the furnace, kept at this temperature for 3 hours, and finally air-cooled to room temperature; S4, final heat treatment; The final heat treatment includes quenching and tempering. In the quenching process, the holding temperature is set to 900°C, the holding time is calculated as 60min / 25.4mm, and water cooling is adopted. The cooling medium temperature is controlled at 40°C. During the tempering process, the holding temperature is set to 638°C, the holding time is calculated as 60min / 25.4mm, and air cooling is used after tempering; S5, sampling and mechanical properties testing; Sampling is carried out according to DNV-ST-F101 standard, and mechanical property tests are performed on forgings; It should be noted that the purpose of mechanical property testing of forgings is to ensure that product quality meets the use requirements of riser joints on offshore oil and gas platforms. Embodiment 4

[0019] like Figure 2 As shown, a manufacturing process for an offshore oil and gas platform riser joint also includes a temperature monitoring method for isothermal annealing to achieve temperature control in the isothermal annealing stage, including the following steps: Step 1: numerically analyze the temperature of different monitoring points during the furnace cooling stage to obtain an isothermal trade-off value, and determine the isothermal analysis point based on the isothermal trade-off value; In some embodiments, during the furnace cooling stage, different monitoring points are divided in the furnace and the forgings, and thermocouples are installed at the monitoring points to measure the temperature in the furnace and the forgings; It should be noted that the furnace cooling stage is the most sensitive stage for isothermal annealing temperature control and is the most likely to produce granular bainite; During the monitoring period, the temperature data of the monitoring point is obtained to determine whether the temperature of the monitoring point is within the preset temperature expectation; If the temperature at the monitoring point is not within the preset temperature expectation, a temperature warning signal is generated to adjust the temperature in the furnace so that the temperature at the monitoring point is within the temperature expectation; It should be noted that the temperature expectations are set by professionals in this field based on experience; If the temperature of the monitoring point is within the preset temperature expectation, calculate the time-temperature change rate at different monitoring moments within the monitoring period; By formula: Get the temperature change rate at different monitoring times, where represents temperature, t represents time, is the number of the monitoring moment; It should be noted that the time-temperature change rate is the temperature change rate of the monitoring point analyzed from the time dimension; Based on the temperature change rate at different monitoring times of the monitoring point, a temperature change sequence is constructed, and the mean absolute deviation MAD and the instantaneous maximum deviation MaxΔT of the temperature change sequence are calculated; By formula: Get the mean absolute deviation MAD of the temperature change sequence, where n is the total number of monitoring moments in the temperature change sequence, is the average value of the temperature change series; By formula: Get the maximum instantaneous deviation MaxΔT of the temperature change sequence; The isothermal trade-off value of the monitoring point is obtained by weighted calculation based on the mean absolute deviation and the instantaneous maximum deviation, where the weights of the mean absolute deviation and the instantaneous maximum deviation are 1.25 and 0.86, respectively; Obtain the isothermal trade-off values ​​of all monitoring points, sort them according to the numerical values ​​of the isothermal trade-off values, and determine the monitoring point with the largest isothermal trade-off value as the isothermal analysis point; It should be noted that the role of determining the isothermal analysis point is: Function 1: Locate the abnormal temperature area: Select the monitoring point with the largest isothermal trade-off value as the isothermal analysis point, which means that the temperature fluctuation in the area where the monitoring point is located is the most drastic, which is conducive to determining the abnormal temperature area; Function 2: As the basis for optimizing the process, if the isothermal analysis point is located at the edge of the furnace, it is necessary to adjust the heater power distribution or the gas circulation path; if it is located on the surface of the forging, it is necessary to check the placement of the forging or the surface oxidation state.

[0020] Step 2: Based on the isothermal analysis points, determine the temperature gradient in the isothermal analysis area and construct the isothermal gradient field; Obtain the position of the isothermal analysis point. If the isothermal analysis point is located on the surface of the forging or inside the forging, take the isothermal analysis point as the origin and obtain the monitoring point within the preset monitoring radius. It should be noted that the preset monitoring radius is determined by professionals in this field based on previous processing experience; Based on the monitoring points within the preset radius, an isothermal analysis area is constructed; The temperature gradient field in the isothermal analysis area is constructed through the three-dimensional unsteady heat conduction differential equation; Specifically, the equation is: ,in is the density of the forging, k x , k y , k z are the thermal conductivity of the forging in the x, y, and z directions, respectively; Q is the heat generated in the furnace per unit volume per unit time; C p Specific heat capacity of forging material; It should be noted that k x , k y , k z It is set by professional technicians in this field. In the forging insulation scenario, if there is no additional internal heating source, Q=0; By formula: Approximately measures the rate of change of potential temperature in the x-axis direction, where x is the x-axis coordinate of the isothermal analysis point, is the distance between the isothermal analysis point and other monitoring points in the isothermal analysis area in the x-axis direction; By formula: Approximately measures the rate of change of potential temperature in the y-axis direction, where y is the y-axis coordinate of the isothermal analysis point, is the distance between the isothermal analysis point and other monitoring points in the isothermal analysis area in the y-axis direction; By formula: Approximately measures the rate of change of potential temperature in the z-axis direction, where z is the z-axis coordinate of the isothermal analysis point, is the distance in the z-axis direction between the isothermal analysis point and other monitoring points in the isothermal analysis area; It should be noted that the potential temperature change rate is the temperature change rate of the monitoring point measured from the distance dimension, where the role of constructing the temperature gradient field is: Function 1: It is conducive to the uniform transformation of microstructure. The construction of temperature gradient field can monitor the temperature changes of various parts of forgings in real time during austenitization, furnace cooling and subsequent insulation stages. If the temperature gradient is unreasonable, the phase transformation process of different regions of the forging will be inconsistent, which may lead to the formation of granular bainite in some areas. By accurately controlling the temperature gradient, the process parameters can be adjusted to ensure that each part undergoes phase transformation under appropriate temperature-time conditions, promote uniform transformation of microstructure, and stabilize the impact toughness of forgings; Function 2: Reduce the non-uniformity of impact specimens. Constructing a temperature gradient field can evaluate the overall temperature state of the forging, identify areas where temperature anomalies may exist, and take measures to adjust in advance. Maintain uniform temperature during isothermal annealing, thereby reducing the non-uniformity of impact specimen performance, improving product quality stability and reliability, and meeting the requirements of engineering applications for material performance consistency.

[0021] The technical solution of this embodiment is: numerically analyze the temperatures at different monitoring points during the furnace cooling stage to obtain isothermal trade-off values, determine isothermal analysis points based on the isothermal trade-off values, monitor and control the temperature from both time and space dimensions, and determine isothermal analysis points by calculating the isothermal trade-off values, so as to locate abnormal temperature areas and provide a basis for optimizing the process; determine the temperature gradient of the isothermal analysis area based on the isothermal analysis points, and construct an isothermal gradient field, which is conducive to providing a data basis for subsequent temperature gradient analysis. Embodiment 5

[0022] like Figure 2 As shown, a temperature monitoring method for isothermal annealing also includes the following steps: Step 3: Analyze different gradient descent paths of the temperature gradient field, extract the temperature analysis path, determine the equivalent cooling temperature curve of the temperature analysis path, and perform consistency analysis with the continuous cooling transformation curve of supercooled austenite to determine whether the curve shows a consistent change trend; In some embodiments, a gradient descent path is identified using a gradient descent algorithm based on the temperature gradient field in the isothermal analysis region; It should be noted that the gradient descent algorithm calculates the negative gradient direction of the temperature change, that is, the path with the fastest temperature drop, and iteratively adjusts the position of the path point to approach the local low temperature area to obtain the gradient descent path; Obtain multiple gradient descent paths of the temperature gradient field, and extract the rate of change of the temperature gradient of each gradient descent path during the monitoring period; Calculate the average of the time-temperature change rate of the two endpoints of the gradient descent path to obtain the path time-temperature change rate; The path temperature change rate and the temperature gradient change rate are dimensionless processed and then summed to obtain the path change value; It should be noted that the path change value reflects the comprehensive severity of temperature change during isothermal annealing from the time and space dimensions. The larger the value, the more significant the path temperature fluctuation in the isothermal analysis area, which may lead to inconsistent phase change process of the forging. Obtain path change values ​​of multiple gradient descent paths, perform sorting analysis, and determine the gradient descent path with the largest path change value as the gradient analysis path; Integrate the time-temperature change rate within the gradient analysis path to construct an equivalent cooling temperature curve; In some embodiments, a continuous cooling transformation (CCT) curve of supercooled austenite is drawn using historical data of material processing; Obtaining a supercooled austenite continuous cooling transformation curve, and based on the equivalent cooling temperature curve, performing consistency analysis on the supercooled austenite continuous cooling transformation curve and the equivalent cooling temperature curve to determine whether the change trends of the equivalent cooling temperature curve and the supercooled austenite continuous cooling transformation curve are consistent; According to the limited conditions, the temperature axes of the supercooled austenite continuous cooling transformation curve and the equivalent cooling temperature curve are sampled to obtain sampling points; Specifically, by acquiring historical manufacturing process data of the riser joint, the frequency of generation of historical temperature warning signals is calculated; The number of sampling points is obtained by multiplying the frequency of the historical temperature warning signal generation by the time length of the supercooled austenite continuous cooling transformation curve or the equivalent cooling temperature curve; It should be noted that the number of sampling points has been rounded off; Based on the number of sampling points, the temperature axis of the supercooled austenite continuous cooling transformation curve and the equivalent cooling temperature curve is divided to determine the interval length of the sampling points; Based on the interval length of the sampling points, the temperature axis of the supercooled austenite continuous cooling transformation curve and the equivalent cooling temperature curve is divided into multiple sampling points; Calculate the Euclidean distance of the corresponding sampling points of the supercooled austenite continuous cooling transformation curve and the equivalent cooling temperature curve; Get the mean of the Euclidean distances of all sampling points as the curve difference coefficient; If the curve difference coefficient is lower than the preset curve difference coefficient threshold, it is considered that the cooling temperature curve is consistent with the change trend of the supercooled austenite continuous cooling transformation curve, otherwise, it is inconsistent; It should be noted that the role of judging whether the changing trend of the curve is consistent is: Function 1. Determine the phase change process: By comparing the change trends of the two curves, the phase change process of the forging during isothermal annealing can be determined; Function 2: Evaluate the temperature control effect: Consistent curve change trend indicates that the current temperature control strategy can make the forgings undergo phase transformation under appropriate temperature-time conditions, and the temperature control is effective. Inconsistency reflects that there are problems with temperature control, such as excessive temperature fluctuations, unreasonable cooling rates, etc., reminding operators to adjust temperature control parameters in a timely manner and optimize temperature control strategies.

[0023] Step 4: If not, determine whether the temperature of the current equivalent cooling temperature curve is in the bainite stage; if not, determine whether the current furnace temperature control margin is sufficient; If they are inconsistent, and the temperature of the current equivalent cooling temperature curve is lower than the temperature of the supercooled austenite continuous cooling transformation curve; Obtain the temperature of the current equivalent cooling temperature curve, calculate the temperature change rate, and determine whether the temperature of the current equivalent cooling temperature curve is in the bainite stage according to the phase change judgment condition; Specifically, the temperature range for bainite formation, the critical temperature range allowed for bainite phase transformation, and the minimum residence time required for full transformation of bainite are obtained from historical manufacturing process data; Among them, the critical temperature range refers to the lowest to highest temperature change rate allowed for bainite phase transformation; Phase transformation judgment condition 1: judge whether the temperature of the current equivalent cooling temperature curve is within the temperature range of bainite formation; Phase transformation judgment condition 2: determine whether the temperature change rate of the current equivalent cooling temperature curve meets the critical temperature range allowed by the bainite phase transformation; Phase transformation judgment condition 3: If phase transformation judgment condition 1 is met, calculate the phase transformation time to determine whether the phase transformation time reaches the shortest residence time required for the full transformation of bainite; Phase change time refers to the length of time from the time when phase change judgment condition 1 is met to the current time; It should be noted that if the temperature of the current equivalent cooling temperature curve does not meet all the phase change judgment conditions, it is considered that the temperature of the current equivalent cooling temperature curve is not in the bainite stage; If the temperature of the current equivalent cooling temperature curve is in the bainite stage, a phase change warning signal is generated, and the temperature in the furnace is regulated to make the temperature deviate from the phase change judgment condition; It should be noted that the temperature deviation from the phase transformation judgment condition refers to the temperature range that deviates from the bainite formation; If the temperature of the current equivalent cooling temperature curve is not in the bainite stage and the phase change judgment condition 1 is not met, the maximum value of the instantaneous temperature change rate of the current equivalent temperature curve is obtained; The maximum value of the instantaneous time-temperature change rate of the current equivalent temperature curve and the isothermal trade-off value are weighted to obtain the time-temperature approach rate; Among them, the weights of the maximum value of the instantaneous temperature change rate and the isothermal trade-off value are 0.86 and 0.43, respectively; Based on the time-temperature approach rate, calculate the approach time between the temperature of the current equivalent cooling temperature curve and the critical time-temperature range; Obtain the standard response time of the furnace temperature control equipment from historical manufacturing process data; It should be noted that the standard response time is a temperature control time benchmark set based on process specifications, equipment performance, and material properties in industrial production. It is used to judge the timeliness of the response of the control to temperature changes. The temperature control equipment includes: heating control unit, gas flow rate control unit, etc. Compare the approach time with the preset standard response time. If the approach time is lower than the preset standard response time, the control margin of the current temperature is insufficient. Otherwise, the control margin is within the expected range. It should be noted that the role of judging whether the regulatory margin is sufficient is: Function 1: Identify temperature control risks: By judging the control margin, potential temperature control risks can be discovered in time. If the control margin is insufficient, it means that the temperature of the current equivalent cooling temperature curve may quickly approach or enter the undesirable phase change area, and the existing temperature control system cannot respond and adjust in time; Function 2: Optimize process temperature control: Determine the control margin to provide a basis for optimizing process temperature control. When it is determined that the control margin is insufficient, adjust the process temperature parameters according to the actual situation. On the basis of approximate time difference, optimize the temperature control of subsequent isothermal analysis areas in stages, reasonably allocate the control target value of each stage, and enable the temperature control equipment in the furnace to control the temperature more reasonably, which helps to stabilize and improve the process and improve the stability and controllability of the process.

[0024] The technical solution of this embodiment is: analyze the different gradient descent paths of the temperature gradient field, extract the temperature analysis path, determine the equivalent cooling temperature curve of the temperature analysis path, and perform consistency analysis with the supercooled austenite continuous cooling transformation curve to determine whether the curve shows a consistent change trend. If not, determine whether the temperature of the current equivalent cooling temperature curve is in the bainite stage. If not, determine whether the current temperature control margin in the furnace is sufficient, which is conducive to timely discovery of potential phase change risks. Embodiment 6

[0025] like Figure 2 As shown, a temperature monitoring method for isothermal annealing also includes the following steps: Step 5: If the current temperature control margin is insufficient, the temperature of the isothermal analysis area is controlled in stages; If the current temperature control margin is insufficient, the difference between the approach time and the preset standard response time is calculated to obtain the approach time difference; Based on the approach time difference, the temperature control in the isothermal analysis area is divided into multiple stages, and the control target value of each stage is calculated; The temperature control equipment in the furnace regulates the temperature in the furnace according to the control target value of each stage; Specifically, the temperature difference between the current equivalent cooling temperature curve and the cold austenite continuous cooling transformation curve is obtained; Based on the number of each stage, the temperature difference is divided and processed to obtain the control target value of each stage; Based on the target value of the control amount at each stage, the temperature of the isothermal analysis area is controlled by the temperature control device in the furnace; It should be noted that the effects of phased regulation are: Function 1: Improve the accuracy of temperature control: In the manufacturing process, the temperature requirements at different stages are extremely strict. Phased control can set the control target value for each stage based on real-time temperature data and the gap with the standard to meet the temperature requirements of the process.

[0026] Function 2: Reduce the possibility of abnormal phase change: Phased control can effectively avoid this situation. By monitoring the relationship between the equivalent cooling temperature curve and the continuous cooling transformation curve of supercooled austenite, the temperature can be controlled to ensure that the phase change process proceeds as expected and improve product reliability. Embodiment 7

[0027] like Figure 3 As shown, a temperature monitoring system for isothermal annealing is used to implement a temperature monitoring method for isothermal annealing, including the following modules: Single analysis module: used to perform numerical analysis on the temperature of different monitoring points during the furnace cooling stage, obtain isothermal trade-off values, and determine isothermal analysis points based on the isothermal trade-off values; Regional analysis module: Based on the isothermal analysis points, determine the temperature gradient of the isothermal analysis area and construct the isothermal gradient field; Trend analysis module: used to analyze different gradient descent paths of the temperature gradient field, extract the temperature analysis path, determine the equivalent cooling temperature curve of the temperature analysis path, and perform consistency analysis with the continuous cooling transformation curve of supercooled austenite to determine whether the curve shows a consistent change trend; Margin determination module: if not, it is used to determine whether the temperature of the current equivalent cooling temperature curve is in the bainite stage. If not, it is used to determine whether the control margin of the current furnace temperature is sufficient. Temperature control module: If the current temperature control margin is insufficient, it is used to control the temperature of the isothermal analysis area in stages.

Claims

1. A manufacturing process for an offshore oil and gas platform riser joint, characterized in that: The following steps are involved: Determine the raw material composition, forging process, preliminary heat treatment using isothermal annealing, final heat treatment, sampling and mechanical property testing of riser joints; The preliminary heat treatment using isothermal annealing specifically includes: Determine the temperature gradient in the isothermal analysis area and construct the isothermal gradient field; Analyze different gradient descent paths of the temperature gradient field to determine the equivalent cooling temperature curve, and perform consistency analysis with the continuous cooling transformation curve of supercooled austenite to determine whether the curve shows a consistent change trend; Determine whether the temperature of the current equivalent cooling temperature curve is in the bainite stage. If not, determine whether the current furnace temperature control margin is sufficient. If the current temperature control margin is insufficient, the temperature of the isothermal analysis area is controlled in stages.

2. The manufacturing process of an offshore oil and gas platform riser joint according to claim 1, characterized in that: The raw material components are: The chemical composition of the raw materials of the riser joint is: C≤0.18%; Si: 0.15%-0.35%; Mn≤1.30%; P≤0.020%; S≤0.003%; Ni≤0.50%; Cr≤0.25%; Al≤0.05%; Ti≤0.04%; Mo≤0.10%; Cu≤0.35%; V≤0.10%; N≤0.012%; CE≤0.43%, Among them, CE=C+Mn / 6+(Cr+Mo+V) / 5+(Cu+Ni) / 15.

3. The manufacturing process of an offshore oil and gas platform riser joint according to claim 1, characterized in that: The isothermal analysis region is determined as follows: Numerical analysis is performed on the temperature of different monitoring points during the furnace cooling stage to obtain the isothermal trade-off value, and the isothermal analysis point is determined based on the isothermal trade-off value; Based on the isothermal analysis points, the isothermal analysis region is determined.

4. The manufacturing process of an offshore oil and gas platform riser joint according to claim 3, characterized in that: The isothermal trade-off value is obtained as follows: Obtain the temperature of the monitoring point, calculate the temperature change rate at different monitoring times within the monitoring period, and obtain the time-temperature change rate; Based on the temperature change rate at different monitoring moments, a temperature change sequence is constructed, and the average absolute deviation and instantaneous maximum deviation of the temperature change sequence are calculated; The isothermal trade-off value of the monitoring point is obtained by weighted calculation based on the mean absolute deviation and the instantaneous maximum deviation.

5. The manufacturing process of an offshore oil and gas platform riser joint according to claim 1, characterized in that: The isothermal gradient field is constructed as follows: The temperature gradient field in the isothermal analysis area is constructed by the three-dimensional unsteady heat conduction differential equation.

6. The manufacturing process of an offshore oil and gas platform riser joint according to claim 1, characterized in that: The method for determining whether the curve presents a consistent change trend is as follows: Based on the temperature gradient field in the isothermal analysis area, a gradient descent algorithm is used to identify the gradient descent path; Quantitatively analyze the gradient descent path, determine the gradient analysis path, and construct the equivalent cooling temperature curve; Obtaining the continuous cooling transformation curve of supercooled austenite, dividing the sampling points of the equivalent cooling temperature curve and the continuous cooling transformation curve of supercooled austenite according to the limited conditions, and calculating the Euclidean distance of the sampling points; Get the mean of the Euclidean distances of all sampling points as the curve difference coefficient; If the curve difference coefficient is lower than the preset curve difference coefficient threshold, the curve shows a consistent change trend.

7. The manufacturing process of an offshore oil and gas platform riser joint according to claim 6, characterized in that: The gradient analysis path is determined as follows: Extract the rate of change of the temperature gradient of each gradient descent path during the monitoring period; Calculate the mean of the time-temperature change rate of the two endpoints of the gradient descent path to obtain the path time-temperature change rate; Based on the path time-temperature change rate and the temperature gradient change rate, the path change value is obtained and sorted and analyzed to determine the gradient analysis path.

8. The manufacturing process of an offshore oil and gas platform riser joint according to claim 6, characterized in that: The limiting conditions are: Obtain the frequency of historical temperature warning signal generation, perform numerical analysis based on the frequency of historical temperature warning signal generation, and determine the interval length of the sampling points; Based on the interval length of the sampling points, the temperature axis of the supercooled austenite continuous cooling transformation curve and the equivalent cooling temperature curve is divided into multiple sampling points.

9. The manufacturing process of an offshore oil and gas platform riser joint according to claim 1, characterized in that: The method for determining whether the control margin of the temperature in the fore furnace is sufficient is as follows: Obtain the temperature of the current equivalent cooling temperature curve, calculate the temperature change rate, and determine whether the temperature of the current equivalent cooling temperature curve is in the bainite stage according to the phase change judgment condition; If not, obtain the maximum value of the instantaneous temperature change rate of the current equivalent temperature curve; The maximum value of the instantaneous time-temperature change rate of the current equivalent temperature curve and the isothermal trade-off value are weighted to obtain the time-temperature approach rate; Based on the time-temperature approach rate, calculate the approach time between the temperature of the current equivalent cooling temperature curve and the preset critical time-temperature range; If the approach time is lower than the preset standard response time, the current temperature control margin is insufficient.

10. The manufacturing process of an offshore oil and gas platform riser joint according to claim 1, characterized in that: The staged control method is: Calculate the approach time difference between the approach time and the preset standard response time, and divide the temperature control of the isothermal analysis area into multiple stages; The control target value of each stage is calculated, and the temperature of the isothermal analysis area is controlled based on the control target value of each stage.

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