A manufacturing process for riser joints of offshore oil and gas platforms

Abstract

The present invention discloses a manufacturing process for a riser joint of an offshore oil and gas platform, relating to the technical field of preparation, including: the manufacturing process selects forgings with specific components, smelts them through an electric furnace or an oxygen converter, and conducts forging, isothermal annealing, final heat treatment, and mechanical property testing; the method for monitoring the isothermal annealing temperature includes: monitoring the temperature in the furnace cooling stage, calculating the isothermal trade-off value to determine the isothermal analysis point; constructing an isothermal gradient field, analyzing the temperature change, constructing an equivalent cooling temperature curve, and comparing it with the continuous cooling transformation curve of supercooled austenite; if the trend of the curve changes inconsistently, judge whether the current temperature is in the bainite stage, and if not, judge the regulation margin; if the regulation margin is insufficient, calculate the approximate time difference, regulate the temperature in stages, and improve the stability of the process.

Description

Technical Field

[0001] The present invention relates to the field of manufacturing technologies, and particularly to a manufacturing process for riser joints of offshore oil and gas platforms. Background Art

[0002] In the development of offshore oil and gas resources, riser joints, as core components connecting floating platforms and subsea wellheads, need to withstand alternating loads, high-temperature and high-pressure environments under complex sea conditions, and long-term service requirements as deep-sea oil and gas development expands into ultra-deep water areas, posing higher requirements for manufacturing processes.

[0003] The existing technology lacks control in the selection and treatment of raw materials, and does not strictly limit the chemical composition of the materials required for riser joints, resulting in unstable impurity content inside the forged parts. If, during the forging process, multiple upsetting and drawing processes are used to optimize the forging ratio and eliminate casting defects such as porosity, segregation, and columnar crystals, making the internal structure of the forged parts uniform, it is beneficial to improve the quality and reliability of the cast products.

[0004] During the isothermal annealing process of the existing technology, there is a lack of monitoring and control of temperature. In the furnace cooling stage, it is impossible to determine the temperature abnormal area, and it is difficult to timely and effectively control the furnace temperature; this may cause granular bainite to form in some areas of the forged parts, thereby affecting the microstructure transformation of the forged parts. If the isothermal balance value is calculated to determine the isothermal analysis point, an isothermal gradient field is constructed, the temperature changes of each part are monitored, the temperature gradient is accurately grasped, the process parameters are adjusted, and each part undergoes phase transformation at an appropriate temperature, promoting uniform microstructure transformation, stabilizing the impact toughness of the forged parts, reducing the non-uniformity of impact specimens, and improving the quality stability and reliability of the products.

[0005] Therefore, the present invention provides a manufacturing process for riser joints of offshore oil and gas platforms. Summary of the Invention

[0006] The purpose of the present invention is to provide a manufacturing process for riser joints of offshore oil and gas platforms to solve the problems in the existing technology during the isothermal annealing process, such as the lack of monitoring and control of temperature, the inability to determine the temperature abnormal area in the furnace cooling stage, and the difficulty in timely and effectively controlling the furnace temperature; this may cause granular bainite to form in some areas of the forged parts, thereby affecting the microstructure transformation of the forged parts.

[0007] In a first aspect, the present invention provides a manufacturing process for riser joints of offshore oil and gas platforms, including the following steps:

[0008] S1. Determine the raw material composition of the riser joint;

[0009] S2. Forging processing;

[0010] S3. Adopt preliminary heat treatment of isothermal annealing;

[0011] S4, Final heat treatment;

[0012] S5, Sampling and mechanical property testing.

[0013] In a second aspect, the present invention provides a temperature monitoring method for isothermal annealing, which is used to realize the temperature monitoring in the isothermal annealing stage, and includes the following steps:

[0014] Step 1: Numerically analyze the temperatures of different monitoring points in the furnace cooling stage to obtain an isothermal trade-off value, and based on the isothermal trade-off value, determine the isothermal analysis point;

[0015] Step 2: Based on the isothermal analysis point, determine the temperature gradient in the isothermal analysis area and construct an isothermal gradient field;

[0016] 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 a consistency analysis with the continuous cooling transformation curve of undercooled austenite to judge whether the curves show a consistent change trend;

[0017] Step 4: If they are inconsistent, judge whether the temperature of the current equivalent cooling temperature curve is in the bainite stage. If not, judge whether the regulation margin of the current furnace temperature is sufficient;

[0018] Step 5: If the current temperature regulation margin is insufficient, regulate the temperature in the isothermal analysis area in stages.

[0019] In a third aspect, the present invention provides a temperature monitoring system for isothermal annealing, which is used to realize a temperature monitoring method for isothermal annealing, and includes the following modules:

[0020] Single analysis module: It is used to numerically analyze the temperatures of different monitoring points in the furnace cooling stage to obtain an isothermal trade-off value, and based on the isothermal trade-off value, determine the isothermal analysis point;

[0021] Area analysis module: Based on the isothermal analysis point, determine the temperature gradient in the isothermal analysis area and construct an isothermal gradient field;

[0022] Trend analysis module: It is 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 a consistency analysis with the continuous cooling transformation curve of undercooled austenite to judge whether the curves show a consistent change trend;

[0023] Margin determination module: If they are inconsistent, it is used to judge whether the temperature of the current equivalent cooling temperature curve is in the bainite stage. If not, judge whether the regulation margin of the current furnace temperature is sufficient;

[0024] Temperature control module: If the current temperature regulation margin is insufficient, it is used to regulate the temperature of the isothermal analysis area in stages.

[0025] Advantages of the present invention:

[0026] 1. By defining the raw material composition, such as the specific chemical composition requirements of A694F65 forgings, it lays a foundation for the product performance. During the forging process, multiple upsetting and drawing operations are carried out to make the internal structure of the forgings uniform, enhancing the stability and reliability of the material; the isothermal annealing treatment promotes the uniform transformation of the microstructure into ferrite and pearlite, reducing the possibility of granular bainite generation, and the final heat treatment further optimizes the material performance, which is beneficial to improving the bearing capacity and service life of the riser joint.

[0027] 2. The isothermal annealing temperature monitoring method monitors and regulates the temperature from two dimensions of time and space. By calculating the isothermal trade-off value to determine the isothermal analysis point, it can locate the temperature abnormal area, providing a basis for optimizing the process; constructing an isothermal gradient field to monitor the temperature change of the forgings in real time, mastering the temperature gradient, and then regulating the process temperature, enabling the forgings to undergo phase transformation under suitable temperature conditions, promoting the uniform transformation of the microstructure, reducing the non-uniformity of the impact specimen performance, and improving the quality stability and reliability of the product.

[0028] 3. Conduct a consistency analysis of the equivalent cooling temperature curve and the continuous cooling transformation curve of undercooled austenite, and combine the phase transformation judgment conditions to judge the temperature state, timely discover potential phase transformation risks. When the temperature regulation margin is insufficient, regulate the temperature of the isothermal analysis area in stages, calculate the regulation target value for each stage, and enable the furnace temperature control equipment to regulate the temperature, reducing the phase transformation abnormality caused by temperature abnormality, enhancing the reliability and stability of the entire manufacturing process, reducing the scrap rate, and improving the production efficiency. Description of the drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 is a flowchart of a manufacturing process for a riser joint of an offshore oil and gas platform provided by the present invention;

[0031] Figure 2 is a flowchart of a temperature monitoring method for isothermal annealing provided by the present invention;

[0032] Figure 3 is a module diagram of a temperature monitoring system for isothermal annealing provided by the present invention. Detailed implementation manners

[0033] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Embodiment 1

[0034] As Figure 1 shown, a manufacturing process for a riser joint of an offshore oil and gas platform provided by an embodiment of the present invention includes the following steps:

[0035] S1. Determine the raw material components of the riser joint;

[0036] Specifically, the chemical components of the raw material A694F65 forging of the riser joint are: 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%;

[0037] Among them, CE = C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15;

[0038] Use electric furnace smelting or oxidation converter, double slag process, and vacuum degassing for refining furnace refining for smelting;

[0039] It should be noted that CE is the abbreviation of Carbon Equivalent, which is an index used to measure the influence of carbon and other alloying elements on the weldability and hardening tendency of steel materials;

[0040] S2. Forging processing;

[0041] Control the forging heating temperature at 1160°C. Use stepped heating during heating. When the temperature rises to 880°C, hold for 0.5 hours, and then raise it to the forging heating temperature and hold;

[0042] The forging process goes through two upsetting and two drawing processes to ensure that the forging ratio is not less than the preset forging ratio;

[0043] Preferably, the forging ratio is 4;

[0044] It should be noted that through multiple upsetting and drawing operations, it is beneficial to eliminate or reduce casting defects such as porosity, segregation, and columnar crystals, making the internal structure of the forging uniform. After forging and forming, it is cooled by air cooling;

[0045] S3. Perform preliminary heat treatment by isothermal annealing;

[0046] Austenitize the forging at 920 °C, and the holding time is calculated according to 30 min / 25.4 mm;

[0047] After the forging is austenitized, cool it in the furnace to 640 °C, hold for 2 hours, and finally air cool to room temperature;

[0048] It should be noted that isothermal annealing can uniformly transform the microstructure of A694F65 forgings into ferrite + pearlite, avoid the formation of granular bainite, prepare for subsequent quenching and tempering heat treatment, and reduce the non-uniformity of impact specimens;

[0049] S4. Final heat treatment;

[0050] The final heat treatment includes quenching and tempering. Among them, during the quenching process, the holding temperature is set at 880 °C, the holding time is calculated according to 30 min / 25.4 mm, and it is cooled by water cooling, and the temperature of the cooling medium is controlled at 30 °C;

[0051] During the tempering process, the holding temperature is set at 622 °C, the holding time is also calculated according to 30 min / 25.4 mm, and it is cooled by air cooling after tempering;

[0052] S5. Sampling and mechanical property testing;

[0053] Sampling is carried out according to the DNV-ST-F101 standard, and mechanical property testing is performed on the forging;

[0054] It should be noted that the purpose of performing mechanical property testing on the forging is to ensure that the product quality meets the usage requirements of the riser joint for offshore oil and gas platforms. Example Two

[0055] As Figure 1 shown, a manufacturing process for a riser joint of an offshore oil and gas platform provided by an embodiment of the present invention includes the following steps:

[0056] S1. Determine the raw material composition of the riser joint;

[0057] Specifically, the chemical composition of the raw material A694F65 forging of the riser joint is as follows: 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;

[0058] Smelting is carried out by using an electric furnace smelting or an oxygen converter, a double slag process, and a vacuum degassing for refining furnace refining;

[0059] S2. Forging processing;

[0060] The forging heating temperature is controlled at 1180°C. Stepwise heating is adopted during heating. When the temperature rises to 900°C, it is kept warm for 0.75 hours, and then it is raised to the forging heating temperature and kept warm;

[0061] The forging process goes through two upsetting and two drawing processes to ensure that the forging ratio is not less than the preset forging ratio;

[0062] Preferably, the forging ratio is 4;

[0063] The forging is austenitized at 930°C, and the holding time is calculated according to 45 min / 25.4 mm;

[0064] After the forging is austenitized, it is cooled in the furnace to 650°C, kept warm for 2.5 hours, and finally air-cooled to room temperature;

[0065] S4. Final heat treatment;

[0066] The final heat treatment includes quenching and tempering. Among them, during the quenching process, the holding temperature is set at 890°C, the holding time is calculated according to 50 min / 25.4 mm, and water cooling is used for cooling, and the temperature of the cooling medium is controlled at 35°C;

[0067] During the tempering process, the holding temperature is set at 630°C, the holding time is calculated according to 45 min / 25.4 mm, and air cooling is used for cooling after tempering;

[0068] S5. Sampling and mechanical property testing;

[0069] Sampling is carried out according to the DNV-ST-F101 standard, and mechanical property testing is performed on the forging;

[0070] It should be noted that the purpose of performing mechanical property testing on the forging is to ensure that the product quality meets the usage requirements of the riser joint for offshore oil and gas platforms. Example 3

[0071] As shown Figure 1 in the figure, a manufacturing process for a riser joint of an offshore oil and gas platform provided by an embodiment of the present invention includes the following steps:

[0072] S1. Determine the raw material composition of the riser joint;

[0073] 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%;

[0074] Use electric furnace smelting or oxidation converter, double slag process, and vacuum degassing for refining furnace refining for smelting;

[0075] S2. Forging processing;

[0076] Control the forging heating temperature at 1200°C, and use stepped heating during heating. When the temperature rises to 920°C, hold for 1 hour, and then raise it to the forging heating temperature and hold;

[0077] The forging process undergoes two upsetting and two drawing processes to ensure that the forging ratio is not less than the preset forging ratio;

[0078] Preferably, the forging ratio is 4;

[0079] S3. Adopt preliminary heat treatment of isothermal annealing;

[0080] Austenitize the forging at 940°C, and calculate the holding time according to 60 min / 25.4 mm;

[0081] After the forging is austenitized, cool it in the furnace to 660°C, hold for 3 hours, and finally air cool to room temperature;

[0082] S4. Final heat treatment;

[0083] The final heat treatment includes quenching and tempering. Among them, during the quenching process, the holding temperature is set at 900°C, the holding time is calculated according to 60 min / 25.4 mm, and water cooling is used for cooling, and the temperature of the cooling medium is controlled at 40°C;

[0084] During the tempering process, the holding temperature is set at 638°C, the holding time is calculated according to 60 min / 25.4 mm, and air cooling is used for cooling after tempering;

[0085] S5. Sampling and mechanical property testing;

[0086] Sampling is carried out in accordance with the DNV-ST-F101 standard, and the mechanical properties of the forgings are tested;

[0087] It should be noted that the purpose of testing the mechanical properties of the forgings is to ensure that the product quality meets the usage requirements of the riser joints for offshore oil and gas platforms. Example 4

[0088] As Figure 2 shown, a manufacturing process for riser joints of offshore oil and gas platforms further includes a temperature monitoring method for isothermal annealing to achieve temperature control in the isothermal annealing stage, including the following steps:

[0089] Step 1: Numerically analyze the temperatures of different monitoring points in the furnace cooling stage to obtain an isothermal trade-off value, and based on the isothermal trade-off value, determine the isothermal analysis points;

[0090] In some embodiments, in 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 temperatures in the furnace and the forgings;

[0091] It should be noted that the furnace cooling stage is the most sensitive link in the temperature control of isothermal annealing and is the most likely to generate granular bainite;

[0092] During the monitoring period, obtain the temperature data of the monitoring points and determine whether the temperatures of the monitoring points are within the preset temperature expectations;

[0093] If the temperature of the monitoring point is not within the preset temperature expectations, generate a temperature warning signal and adjust the temperature in the furnace to make the temperature of the monitoring point within the temperature expectations;

[0094] It should be noted that the temperature expectations are set by those skilled in the art based on experience;

[0095] If the temperature of the monitoring point is within the preset temperature expectations, calculate the temperature-time change rate at different monitoring times during the monitoring period;

[0096] Through the formula: Obtain the temperature-time change rate at different monitoring times, where represents the temperature, t represents the time, is the number of the monitoring time;

[0097] It should be noted that the temperature-time change rate is to analyze the temperature change rate of the monitoring point from the time dimension;

[0098] Based on the temperature-time change rates of different monitoring times of the monitoring point, construct a temperature change sequence, and calculate the mean absolute deviation MAD and the instantaneous maximum deviation MaxΔT of the temperature change sequence;

[0099] Through the formula: Obtain 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 sequence;

[0100] Through the formula: Obtain the instantaneous maximum deviation MaxΔT of the temperature change sequence;

[0101] Based on the mean absolute deviation and the instantaneous maximum deviation, through weighted calculation, obtain the isothermal trade-off value of the monitoring point, where the weights of the mean absolute deviation and the instantaneous maximum deviation are 1.25 and 0.86 respectively;

[0102] Obtain the isothermal trade-off values of all monitoring points, sort them according to the numerical size of the isothermal trade-off values, and determine the monitoring point with the largest numerical value of the isothermal trade-off value as the isothermal analysis point;

[0103] It should be noted that the role of determining the isothermal analysis point is as follows:

[0104] Role 1. Locate the temperature anomaly area: Select the monitoring point with the largest numerical value of the isothermal trade-off value as the isothermal analysis point, which represents that the temperature fluctuation in the area where the monitoring point is located is the most intense, and is conducive to determining the temperature anomaly area;

[0105] Role 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 position of the forging or the surface oxidation state.

[0106] Step 2. Based on the isothermal analysis point, determine the temperature gradient of the isothermal analysis area and construct an isothermal gradient field;

[0107] Obtain the position of the isothermal analysis point. If the position of the isothermal analysis point is on the surface of the forging or inside the forging, take the isothermal analysis point as the origin and obtain the monitoring points within the preset monitoring radius;

[0108] It should be noted that the preset monitoring radius is determined by professional technicians in this field based on past processing experience;

[0109] Based on the monitoring points within the preset radius, construct an isothermal analysis area;

[0110] Construct the temperature gradient field of the isothermal analysis area through the three-dimensional unsteady heat conduction differential equation;

[0111] Specifically, the equation is: , where is the density of the forging, k x 、k y 、k z are the thermal conductivity coefficients 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, Cp Specific heat capacity of the forging material

[0112] It should be noted that k x 、k y 、k z are set by professionals in the field. In the forging heat preservation scenario, if there is no additional internal heat source, Q = 0;

[0113] Through the formula: Approximately measure the change rate of potential temperature in the x-axis direction, where x is the x-axis coordinate of the isothermal analysis point, is the distance in the x-axis direction between the isothermal analysis point and other monitoring points within the isothermal analysis area;

[0114] Through the formula: Approximately measure the change rate of potential temperature in the y-axis direction, where y is the y-axis coordinate of the isothermal analysis point, is the distance in the y-axis direction between the isothermal analysis point and other monitoring points within the isothermal analysis area;

[0115] Through the formula: Approximately measure the change rate 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 within the isothermal analysis area;

[0116] It should be noted that the change rate of potential temperature measures the temperature change rate of the monitoring point from the distance dimension. The functions of constructing the temperature gradient field are as follows:

[0117] Function 1: Facilitate the uniform transformation of the microstructure. Constructing the temperature gradient field can monitor the temperature changes of each part of the forging in the austenitizing, furnace cooling, and subsequent heat preservation stages in real time. If the temperature gradient is unreasonable, the phase transformation processes in different regions of the forging will be inconsistent, which may lead to the formation of granular bainite in some regions. By accurately mastering the temperature gradient, the process parameters can be adjusted to ensure that each part undergoes phase transformation under appropriate temperature-time conditions, promote the uniform transformation of the microstructure, and stabilize the impact toughness of the forging;

[0118] Function 2: Reduce the non-uniformity of impact specimens. Constructing the temperature gradient field can evaluate the overall temperature state of the forging, find areas where temperature anomalies may exist, and take measures in advance to adjust. Maintaining uniform temperature during isothermal annealing can reduce the non-uniformity of the performance of impact specimens, improve the stability and reliability of product quality, and meet the requirements of engineering applications for the consistency of material properties.

[0119] The technical solution of this embodiment is as follows: perform numerical analysis on the temperatures of different monitoring points during the furnace cooling stage to obtain the isothermal trade-off value. Based on the isothermal trade-off value, determine the isothermal analysis point, monitor and control the temperature from two dimensions of time and space. By calculating the isothermal trade-off value to determine the isothermal analysis point, it is possible to locate the temperature abnormal area and provide a basis for optimizing the process; based on the isothermal analysis point, determine the temperature gradient of the isothermal analysis area and construct an isothermal gradient field, which is beneficial to providing a data basis for subsequent temperature gradient analysis. Embodiment Five

[0120] As Figure 2 shown, a temperature monitoring method for isothermal annealing further includes the following steps:

[0121] Step Three: 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 undercooled austenite to judge whether the curves show a consistent change trend;

[0122] In some embodiments, based on the temperature gradient field of the isothermal analysis area, use the gradient descent algorithm to identify the gradient descent path;

[0123] 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 positions of the path points to approach the local low-temperature area to obtain the gradient descent path;

[0124] Obtain multiple gradient descent paths of the temperature gradient field, and extract the change rate of the temperature gradient for each gradient descent path within the monitoring period;

[0125] Calculate the mean value of the time-temperature change rates at both ends of the gradient descent path to obtain the path time-temperature change rate;

[0126] Perform dimensionless processing on the path time-temperature change rate and the change rate of the temperature gradient, and then perform summation processing to obtain the path change value;

[0127] It should be noted that the path change value reflects the comprehensive severity of the temperature change during the isothermal annealing process 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 transformation processes of the forgings;

[0128] Obtain the path change values of multiple gradient descent paths, perform sorting analysis, and determine the gradient descent path with the largest numerical value in the path change values as the gradient analysis path;

[0129] Perform integral operation on the time-temperature change rate within the gradient analysis path to construct an equivalent cooling temperature curve;

[0130] In some embodiments, based on the historical data of material processing, a continuous cooling transformation (CCT) curve of undercooled austenite is plotted;

[0131] Obtain the continuous cooling transformation curve of undercooled austenite. Based on the equivalent cooling temperature curve, perform a consistency analysis on the continuous cooling transformation curve of undercooled austenite and the equivalent cooling temperature curve to determine whether the change trends of the equivalent cooling temperature curve and the continuous cooling transformation curve of undercooled austenite are consistent;

[0132] Sample the temperature axes of the continuous cooling transformation curve of undercooled austenite and the equivalent cooling temperature curve according to the defined conditions to obtain sampling points;

[0133] Specifically, by obtaining the historical manufacturing process data of the riser joint, calculate the frequency of generating the historical temperature warning signal;

[0134] Multiply the frequency of generating the historical temperature warning signal by the time length of the continuous cooling transformation curve of undercooled austenite or the equivalent cooling temperature curve to obtain the number of sampling points;

[0135] It should be noted that the number of sampling points is rounded;

[0136] Based on the number of sampling points, divide the temperature axes of the continuous cooling transformation curve of undercooled austenite and the equivalent cooling temperature curve to determine the interval length of the sampling points;

[0137] Based on the interval length of the sampling points, divide the temperature axes of the continuous cooling transformation curve of undercooled austenite and the equivalent cooling temperature curve into multiple sampling points;

[0138] Calculate the Euclidean distance of the corresponding sampling points of the continuous cooling transformation curve of undercooled austenite and the equivalent cooling temperature curve;

[0139] Obtain the mean value of the Euclidean distances of all sampling points as the curve difference coefficient;

[0140] If the curve difference coefficient is lower than the preset curve difference coefficient threshold, it is considered whether the change trends of the cooling temperature curve and the continuous cooling transformation curve of undercooled austenite are consistent. Otherwise, they are inconsistent;

[0141] It should be noted that the function of judging whether the change trends of the curves are consistent is as follows:

[0142] Function 1. Discriminate the phase transformation process: By comparing the change trends of the two curves, the phase transformation process of the forging during isothermal annealing can be discriminated;

[0143] Function 2. Evaluate the temperature control effect: A consistent curve change trend indicates that the current temperature control strategy can enable the forging to undergo phase transformation under appropriate temperature-time conditions, and the temperature control is effective. Inconsistency, on the other hand, reflects problems in temperature control, such as excessive temperature fluctuations and unreasonable cooling rates, reminding the operator to adjust the temperature control parameters in a timely manner and optimize the temperature control strategy.

[0144] Step 4. If inconsistent, determine whether the temperature of the current equivalent cooling temperature curve is in the bainite stage. If not, determine whether the regulation margin of the current furnace temperature is sufficient;

[0145] If inconsistent, and the temperature of the current equivalent cooling temperature curve is lower than the temperature of the continuous cooling transformation curve of supercooled austenite;

[0146] Obtain the temperature of the current equivalent cooling temperature curve, calculate the temperature-time change rate, and determine whether the temperature of the current equivalent cooling temperature curve is in the bainite stage according to the phase transformation judgment conditions;

[0147] Specifically, from the historical manufacturing process data, obtain the temperature range for bainite formation, the critical temperature-time range allowed for bainite phase transformation, and the shortest residence time required for full bainite transformation;

[0148] Among them, the critical temperature-time range refers to the lowest to the highest temperature-time change rate allowed for bainite phase transformation;

[0149] Phase transformation judgment condition 1. Determine whether the temperature of the current equivalent cooling temperature curve is within the temperature range for bainite formation;

[0150] Phase transformation judgment condition 2. Determine whether the temperature-time change rate of the current equivalent cooling temperature curve meets the critical temperature-time range allowed for bainite phase transformation;

[0151] Phase transformation judgment condition 3. If the phase transformation determination condition 1 is met, calculate the phase transformation time and determine whether the phase transformation time reaches the shortest residence time required for full bainite transformation;

[0152] The phase transformation time refers to the time length from the time when the phase transformation determination condition 1 is met to the current time;

[0153] It should be noted that if the temperature of the current equivalent cooling temperature curve does not meet all the phase transformation judgment conditions, it is considered that the temperature of the current equivalent cooling temperature curve is not in the bainite stage;

[0154] If the temperature of the current equivalent cooling temperature curve is in the bainite stage, generate a phase transformation warning signal and regulate the temperature in the furnace to deviate from the phase transformation judgment conditions;

[0155] It should be noted that deviating from the phase transformation judgment conditions means deviating from the temperature range for bainite formation;

[0156] If the temperature of the current equivalent cooling temperature curve is not in the bainite stage and the phase transformation judgment condition 1 is not reached, obtain the maximum value of the instantaneous temperature change rate of the current equivalent temperature curve;

[0157] Perform weighted calculation on the maximum value of the instantaneous temperature change rate of the current equivalent temperature curve and the isothermal trade-off value to obtain the temperature-time proximity rate;

[0158] 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;

[0159] Based on the temperature-time proximity rate, calculate the proximity time between the temperature of the current equivalent cooling temperature curve and the critical temperature-time range;

[0160] Obtain the standard response time of the furnace temperature control equipment from the historical manufacturing process data;

[0161] It should be noted that the standard response time is the temperature regulation time benchmark set based on process specifications, equipment performance, and material characteristics in industrial production, used to evaluate the response timeliness of the regulation to temperature changes. The temperature control equipment includes: heating control unit, gas flow rate control unit, etc.;

[0162] Compare the proximity time with the preset standard response time. If the proximity time is lower than the preset standard response time, the regulation margin of the current temperature is insufficient; otherwise, the regulation margin is within the expected range;

[0163] It should be noted that the function of judging whether the regulation margin is sufficient is as follows:

[0164] Function 1. Identify temperature regulation risks: By judging the regulation margin, potential temperature regulation risks can be detected in a timely manner. If the regulation margin is insufficient, it means that the temperature of the current equivalent cooling temperature curve may quickly approach or enter an undesired phase transformation region, and the existing temperature regulation system cannot respond and adjust in a timely manner;

[0165] Function 2. Optimize process temperature control: Judging the regulation margin provides a basis for optimizing process temperature control. When it is determined that the regulation margin is insufficient, adjust the process temperature parameters according to the actual situation, and on the basis of the proximity time difference, optimize the temperature regulation of the subsequent isothermal analysis region in stages, and reasonably allocate the regulation target values of each stage, so that the furnace temperature control equipment can regulate the temperature more reasonably, which helps to stabilize and improve the process, and improve the stability and controllability of the process.

[0166] The technical solution of this embodiment is as follows: 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 conduct a consistency analysis with the continuous cooling transformation curve of supercooled austenite to judge whether the curves show a consistent change trend. If not, judge whether the temperature of the current equivalent cooling temperature curve is in the bainite stage. If not, judge whether the regulation margin of the current furnace temperature is sufficient, which is conducive to timely discovering potential phase transformation risks. Example Six

[0167] As Figure 2 shown, an isothermal annealing temperature monitoring method further includes the following steps:

[0168] Step Five: If the current temperature regulation margin is insufficient, regulate the temperature in the isothermal analysis area in stages;

[0169] If the current temperature regulation margin is insufficient, calculate the difference between the approaching time and the preset standard response time to obtain the approaching time difference;

[0170] Based on the approaching time difference, divide the temperature regulation in the isothermal analysis area into multiple stages and calculate the regulation target value for each stage;

[0171] The temperature control device in the furnace regulates the temperature in the furnace according to the regulation target value of each stage;

[0172] Specifically, obtain the temperature difference between the current equivalent cooling temperature curve and the temperature of the continuous cooling transformation curve of cold austenite;

[0173] Based on the number of each stage, divide the temperature difference to obtain the regulation target value for each stage;

[0174] Based on the target value of the regulation amount for each stage, regulate the temperature in the isothermal analysis area through the temperature control device in the furnace;

[0175] It should be noted that the function of conducting staged regulation is as follows:

[0176] Function One: Improve the accuracy of temperature control: During the manufacturing process, the temperature requirements in different stages are extremely strict. Staged regulation can set the regulation target value for each stage based on real-time temperature data and the gap from the standard, meeting the process requirements for temperature.

[0177] Function Two: Reduce the possibility of abnormal phase transformation: Staged regulation can effectively avoid this situation. By monitoring the relationship between the equivalent cooling temperature curve and the continuous cooling transformation curve of supercooled austenite, regulate the temperature to ensure that the phase transformation process proceeds as expected and improve the reliability of the product. Example Seven

[0178] As Figure 3 shown, an isothermal annealing temperature monitoring system for implementing an isothermal annealing temperature monitoring method includes the following modules:

[0179] Single analysis module: used to numerically analyze the temperatures of different monitoring points during the furnace cooling stage to obtain an isothermal trade-off value, and based on the isothermal trade-off value, determine the isothermal analysis point;

[0180] Region analysis module: based on the isothermal analysis point, determine the temperature gradient of the isothermal analysis region and construct an isothermal gradient field;

[0181] 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 undercooled austenite to judge whether the curves show a consistent change trend;

[0182] Margin determination module: if inconsistent, used to judge whether the temperature of the current equivalent cooling temperature curve is in the bainite stage, and if not, judge whether the regulation margin of the current furnace temperature is sufficient;

[0183] Temperature control module: if the current temperature regulation margin is insufficient, used to regulate the temperature of the isothermal analysis region in stages.

Claims

1. A manufacturing process for a riser joint of an offshore oil and gas platform, characterized in that, It includes the following steps: Determine the raw material composition of the riser joint, forging process, preliminary heat treatment using isothermal annealing, final heat treatment, sampling, and mechanical property testing; Among them, the preliminary heat treatment using isothermal annealing specifically includes: Determine the temperature gradient of the isothermal analysis region and construct an isothermal gradient field; The determination method of the isothermal analysis region is: Conduct numerical analysis on the temperatures of different monitoring points during the furnace cooling stage, obtain the isothermal trade-off value, and determine the isothermal analysis point based on the isothermal trade-off value; Determine the isothermal analysis region based on the isothermal analysis point; The acquisition method of the isothermal trade-off value is: Obtain the temperature of the monitoring point, calculate the temperature change rate at different monitoring times during the monitoring period, and obtain the time-temperature change rate; Based on the temperature change rates at different monitoring times, construct a temperature change sequence, and calculate the mean absolute deviation and instantaneous maximum deviation of the temperature change sequence; Obtain the isothermal trade-off value of the monitoring point through weighted calculation based on the mean absolute deviation and instantaneous maximum deviation; Analyze different gradient descent paths of the temperature gradient field, determine the equivalent cooling temperature curve, and conduct consistency analysis with the continuous cooling transformation curve of supercooled austenite to judge whether the curves show a consistent change trend; Judge whether the temperature of the current equivalent cooling temperature curve is in the bainite stage. If not, judge whether the regulation margin of the current furnace temperature is sufficient; If the current temperature regulation margin is insufficient, regulate the temperature of the isothermal analysis region in stages.

2. The manufacturing process of a riser joint for an offshore oil and gas platform according to claim 1, characterized in that, The raw material composition is: The chemical composition of the raw material 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%, where CE = C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15.

3. The manufacturing process of a riser joint for an offshore oil and gas platform according to claim 1, wherein, The construction method of the isothermal gradient field is: Construct the temperature gradient field of the isothermal analysis region through the three-dimensional unsteady heat conduction differential equation.

4. The manufacturing process of a riser joint for an offshore oil and gas platform according to claim 1, characterized in that, The determination method of whether the curves show a consistent change trend is: Based on the temperature gradient field of the isothermal analysis region, use the gradient descent algorithm to identify the gradient descent path; Conduct quantitative analysis on the gradient descent path, determine the gradient analysis path, and construct the equivalent cooling temperature curve; Obtain the continuous cooling transformation curve of supercooled austenite, divide the sampling points of the equivalent cooling temperature curve and the continuous cooling transformation curve of supercooled austenite according to the specified conditions, and calculate the Euclidean distance of the sampling points; Obtain the mean value 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 curves show a consistent change trend.

5. The manufacturing process of a riser joint for an offshore oil and gas platform according to claim 4, characterized in that, The determination method of the gradient analysis path is: Extract the change rate of the temperature gradient of each gradient descent path during the monitoring period; Calculate the mean value of the time-temperature change rates at both ends of the gradient descent path to obtain the path time-temperature change rate; Sum up based on the change rates of the path time-temperature change rate and the temperature gradient, obtain the path change value, perform sorting analysis, and determine the gradient analysis path.

6. A manufacturing process for a riser joint of an offshore oil and gas platform according to claim 4, characterized in that, The limiting conditions are as follows: 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 sampling points; Based on the interval length of sampling points, divide the temperature axes of the continuous cooling transformation curve of undercooled austenite and the equivalent cooling temperature curve into multiple sampling points.

7. The manufacturing process of a riser joint for an offshore oil and gas platform according to claim 1, wherein The determination method for whether the regulation margin of the temperature in the front furnace is sufficient is as follows: Obtain the temperature of the current equivalent cooling temperature curve, calculate the time-temperature change rate, and judge whether the temperature of the current equivalent cooling temperature curve is in the bainite stage according to the phase transformation judgment condition; If not, obtain the maximum value of the instantaneous time-temperature change rate of the current equivalent temperature curve; Perform weighted calculation on the maximum value of the instantaneous time-temperature change rate of the current equivalent temperature curve and the isothermal trade-off value to obtain the time-temperature proximity rate; Based on the time-temperature proximity rate, calculate the proximity time between the temperature of the current equivalent cooling temperature curve and the preset critical time-temperature range; If the proximity time is lower than the preset standard response time, the regulation margin of the current temperature is insufficient.

8. A manufacturing process for a riser joint of an offshore oil and gas platform according to claim 1, characterized in that, The method of staged regulation is as follows: Calculate the proximity time difference between the proximity time and the preset standard response time, and divide the temperature regulation of the isothermal analysis area into multiple stages; Calculate the regulation target value for each stage, and regulate the temperature of the isothermal analysis area based on the regulation target value for each stage.

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