Manufacturing method of H2S-resistant low-temperature pipeline pipe

Abstract

The invention relates to the technical field of pipeline preparation, and discloses a manufacturing method of an anti-H2S low-temperature pipeline pipe, which comprises the following steps: S1, pipe blank preparation, S2, heating and rolling, S3, online normalizing treatment, S4, precise component regulation and control, S5, inclusion optimization, and S6, comprehensive experimental detection. The manufactured pipeline can stably work in a low-temperature and H2S-containing severe environment, through chemical component design including strict control over the content of all elements, the pipeline pipe has good comprehensive performance, in the aspect of impact energy, the average impact energy reaches 155 J at the temperature of-56 DEG C and far exceeds the general standard, the impact resistance of the pipeline pipe at the low temperature is effectively enhanced, and the service life of the pipeline pipe is prolonged. And cracks caused by low-temperature embrittlement are avoided. Meanwhile, the HIC and SSC test results are excellent, and the excellent hydrogen sulfide corrosion resistance is shown. Therefore, the pipeline pipe can be widely applied to the fields of low-temperature and H2S environment petroleum and natural gas transportation and the like, and the application range of the pipeline pipe is greatly expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline preparation, and specifically provides a manufacturing method for an H2S-resistant low-temperature pipeline pipe. Background Art

[0002] In the fields of energy transportation such as oil and natural gas, pipeline pipes are key infrastructure materials. With the increasingly complex energy extraction environment, the demand for pipeline pipes that can adapt to low temperatures and resist hydrogen sulfide (H2S) corrosion is constantly increasing. Low-temperature acid-resistant pipeline pipes are a type of pipe designed to meet the requirements of these special environments. They need to maintain good mechanical properties under low-temperature conditions and have the ability to resist hydrogen sulfide corrosion to ensure the safety and stability of energy transportation.

[0003] In the prior art, products of the Gr.6 steel grade under the specification standard of seamless and welded steel pipes for low-temperature equipment ASTM A333 / A333M are mainly used to meet the usage requirements in low-temperature environments. During production, the composition of the steel is adjusted according to this standard and manufactured through a series of conventional rolling, heat treatment and other processes. It focuses on the low-temperature impact energy, requiring that the average impact energy ≥ 18 J and the single minimum 14 J at -45 °C (adjusted according to the wall thickness). For products of steel grades such as BNS in the API 5L pipeline pipe standard, they focus on meeting the usage requirements in acidic environments. The production process is designed around acid resistance and achieved by adjusting chemical compositions and optimizing manufacturing processes.

[0004] The prior art has obvious limitations. Although products of the Gr.6 steel grade under the ASTM A333 / A333M standard can meet certain low-temperature impact energy requirements, they do not have acid resistance at all. In an acidic environment containing H2S, they are extremely prone to corrosion, resulting in pipe damage and unable to guarantee the safety and stability of energy transportation. For products of steel grades such as BNS in the API 5L standard, although they meet the usage requirements in acidic environments, they cannot maintain good mechanical properties in environments with low temperatures reaching -45 °C and lower, and are prone to low-temperature embrittlement, affecting the strength and toughness of the pipes, and also bringing huge hidden dangers to energy transportation. Neither of these two types of products can meet the requirements for low-temperature acid-resistant pipeline pipes in the current complex energy extraction and transportation environments. In view of this, we propose a manufacturing method for an H2S-resistant low-temperature pipeline pipe. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a manufacturing method for an H2S-resistant low-temperature pipeline pipe, which solves the problem that the current products cannot meet the requirements for low-temperature acid-resistant pipeline pipes in the current complex energy extraction and transportation environments.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A manufacturing method for an H2S-resistant low-temperature pipeline pipe, comprising the following steps:

[0007] S1: Tube blank preparation step

[0008] Steel is made in a converter or an electric furnace, and then continuously cast into a tube blank after secondary refining, vacuum degassing, and Ca treatment outside the furnace;

[0009] S2: Heating and rolling step

[0010] The tube blank is heated in a rotary hearth furnace at 1250 - 1270 °C and rolled through the PQF continuous rolling process;

[0011] S3: Online normalizing treatment step

[0012] When the temperature of the rolled tube reaches 500 - 550 °C before entering the re-heating furnace, it enters the re-heating furnace. The temperature of the re-heating furnace is set at 940 ± 20 °C and heated according to the heating time (minutes) = K × S + 10 - 15 (holding time), where S is the wall thickness of the rough tube in mm, K is the soaking coefficient with a value of 2 minutes / mm. When the wall thickness of the rough tube S ≤ 5 mm, the holding time is 10 minutes, and the rest is 15 minutes. The final rolling temperature after stretch reducing ≥ 860 °C;

[0013] S4: Precise composition control step

[0014] In the secondary refining process of tube blank preparation, the composition of the molten steel is accurately analyzed. According to the analysis results, the contents of basic elements such as carbon, silicon, and manganese are fine-tuned and accurately controlled within the specified range; at the same time, the addition amounts of trace elements such as V, Nb, and Ti are accurately controlled and added in a specific ratio to control the ratio of V, Nb, and Ti within a certain range; in addition, the contents of Al and N are strictly controlled to ensure that Al:N is between 2.5 - 3:1;

[0015] S5: Inclusion optimization step

[0016] During the Ca treatment process, a dynamic monitoring system is used to continuously track the changes of inclusions in the molten steel. According to the real-time state of the molten steel, the addition amount and addition timing of Ca are accurately controlled, and the addition amount of Ca is accurately adjusted within a certain range and added when the molten steel temperature is in a specific range; at the same time, through electromagnetic stirring technology, the inclusions are promoted to fully react and float, and the stirring time is controlled within a certain time range, and the stirring intensity is set within a specific intensity range;

[0017] S6: Comprehensive experimental testing

[0018] The comprehensive performance of the prepared pipeline is detected, and the detection contents include impact resistance, tensile properties, hardness, grain size, HIC, and SSC.

[0019] Preferably, in the step of preparing the tube blank, during Ca treatment, a spectral analyzer is used to real-time detect the sulfur and oxygen contents of the molten steel, and the amount of Ca added is calculated by an automated control system in combination with the molten steel temperature data. The calculation process is based on a multi-parameter regression algorithm model established, comprehensively considering parameters including sulfur and oxygen contents, molten steel temperature, and molten steel volume, and precisely controlling the amount of Ca added within the numerical range.

[0020] Preferably, in the step of preparing the tube blank, electromagnetic stirring technology is adopted during the continuous casting process. At least two groups of electromagnetic stirring devices are arranged in the continuous casting mold. One group is arranged at the upper part of the mold, and the other group is arranged at the lower part of the mold. The current intensity and frequency of the two groups of electromagnetic stirring devices are respectively adjusted by a controller. The current intensity of the upper electromagnetic stirring device is controlled within the range of 300 - 500 A, and the frequency is set in the interval of 2 - 4 Hz. The current intensity of the lower electromagnetic stirring device is controlled within the range of 400 - 600 A, and the frequency is set in the interval of 3 - 5 Hz.

[0021] Preferably, in the step of hot rolling with heating, the rolling speed and tension are real-time monitored and adjusted during the PQF continuous rolling process. Pressure sensors and speed sensors are installed on each stand of the continuous rolling mill to real-time collect the rolling pressure and tube speed data. The collected data is analyzed and processed by an automated control system. When the pressure or speed fluctuates, the system automatically adjusts the rotational speed of the continuous rolling mill motor and the spacing between the rolls. The adjustment accuracy is controlled within the range of ±0.05 mm to ensure that the rolling speed is stable in the interval of 2.5 - 4.5 m / s and the tension is stable in the interval of 5 - 15 kN.

[0022] Preferably, in the step of hot rolling with heating, zoning temperature control technology is adopted during the heating in the ring furnace. The ring furnace is divided into three zones: a preheating zone, a heating zone, and a soaking zone. Each zone is equipped with an independent infrared temperature measurement device and temperature control device. The infrared temperature measurement equipment conducts infrared temperature measurement and monitoring on each area inside the ring furnace, and at the same time draws a real-time temperature change curve, and compares the detected temperature change curve with the preset temperature change curve. The control system adjusts the heating power of the reheating furnace in real-time through the PID control algorithm according to the temperature data. Among them, the proportional coefficient Kp is set to 0.5 - 1.5, the integral coefficient Ki is set to 0.01 - 0.1, and the differential coefficient Kd is set to 0.05 - 0.2.

[0023] Preferably, in the step of online normalizing treatment, a temperature gradient is set in the reheating furnace. In the length direction of the reheating furnace, it is divided into three temperature sections from the inlet to the outlet. The temperature of the first section is set at 920 - 930 °C, the temperature of the second section is set at 940 ± 20 °C, and the temperature of the third section is set at 930 - 940 °C. The temperature fluctuation of each temperature section is controlled within ±5 °C. Among them, the power of the heating elements in the first section is 40 - 50% of the total power, the second section is 50 - 60%, and the third section is 30 - 40%.

[0024] Preferably, the various experimental designs in the comprehensive experimental detection are as follows:

[0025] Charpy impact energy detection: Using the Charpy impact test method, at a test temperature of -56°C, at least 3 standard impact specimens are prepared from the pipeline pipe for impact testing. Record the Charpy impact energy values of each specimen and calculate the average Charpy impact energy;

[0026] Tensile property detection: At a test temperature of 21°C, prepare tensile specimens according to relevant standards, and use a tensile testing machine to conduct tensile tests on the specimens to determine the yield strength Rp0.2, tensile strength, and elongation of the pipeline pipe;

[0027] Hardness detection: Using a Vickers hardness tester, with a test force of 10 kg, conduct hardness tests on at least 3 different positions on the surface of the pipeline pipe, and record the HV(10) hardness values of each test point;

[0028] Grain size detection: Cut a metallographic specimen from the pipeline pipe. After treatments such as grinding, polishing, and etching, use a metallographic microscope to observe the metallographic structure, and determine the grain size grade of the pipeline pipe according to the standard rating method;

[0029] HIC detection: Fabricate the pipeline pipe into a standard specimen, and conduct a hydrogen-induced cracking (HIC) test in a specific solution environment with an initial test pH value of 2.6. After the test, measure the pH value of the solution, and use metallographic analysis or other appropriate methods to determine the crack sensitivity ratio (CSR), crack length ratio (CLR), and crack thickness ratio (CTR) of the specimen;

[0030] SSC detection: Process the pipeline pipe into specimens that meet the requirements, and conduct a sulfide stress corrosion cracking test in a solution with an initial test pH value of 0. After the test, check whether the specimens are fractured and record the test results.

[0031] Preferably, the dimensional tolerance of the impact specimens prepared in the Charpy impact energy detection is controlled within ±0.1 mm. During the tensile property detection, the force value accuracy of the tensile testing machine is controlled within ±1% FS, and the displacement measurement accuracy is controlled within ±0.05 mm. During the hardness detection, the distance between adjacent test points is not less than 3 mm. During the grain size detection, the magnification of the metallographic microscope is 500 times.

[0032] Preferably, in the test solution for HIC detection, in addition to controlling the initial pH value, the Cl- concentration in the solution is also controlled within 1000 - 1200 mg / L, and the test duration is 96 hours. During the SSC detection, a four-point bending method is used to apply stress to the specimens, and the stress loading rate is controlled within 0.5 - 1 MPa / s.

[0033] A H2S resistant low-temperature pipeline pipe, wherein the chemical composition of the H2S resistant low-temperature pipeline pipe, measured by weight percentage, meets the following requirements: C: 0.10-0.14, Si: 0.15-0.35, Mn: 0.95-1.15, P≤0.015, S≤0.003, Ni≤0.20, Cr≤0.20, Mo≤0.10, Cu≤0.20, V≤0.05, Alt: 0.015-0.040, Nb≤0.015, Ti≤0.015, and the content ratio of Al to N meets Al:N≥2:1.

[0034] The present invention provides a method for manufacturing H2S resistant low temperature pipeline pipe. It has the following beneficial effects:

[0035] 1. The pipeline manufactured by the present invention can work stably in a harsh environment with low temperature and H2S. Through chemical composition design, including strict control of the content of each element, the pipeline has good comprehensive performance. In terms of impact energy, the average impact energy reaches 155J at -56°C, which is far beyond the general standard, effectively enhancing the impact resistance of the pipeline at low temperature and avoiding rupture due to low temperature embrittlement. At the same time, the HIC and SSC test results are excellent, indicating that it has excellent resistance to hydrogen sulfide corrosion. This makes the pipeline widely used in the fields of petroleum and natural gas transportation in low temperature and H2S environment, greatly expanding the application range of the pipeline.

[0036] 2. The present invention significantly improves the quality, efficiency and cost-effectiveness of line pipe manufacturing through multi-algorithm collaborative control. Kalman filtering and fuzzy adaptive PID achieve high-precision adjustment of rolling speed ±0.05mm, ensure the stability of process parameters (speed 2.5-4.5m / s, tension 5-15kN), and improve the impact performance of pipes (-56℃ impact energy 155J) and dimensional accuracy. The online normalizing process shortens the production cycle, the precise control of composition (Al:N≥2:1) refines the grains, and the optimization of inclusion morphology improves purity. The zoned temperature control technology reduces energy consumption, and the closed-loop monitoring system reduces equipment loss and scrap rate, comprehensively reducing production costs by more than 15%, and enhancing production stability and product reliability.

[0037] 3. The PQF continuous rolling process and online normalizing heat treatment process adopted in the present invention have significant advantages. The PQF continuous rolling process cooperates with precise heating temperature control to ensure the rolling quality of the pipe. Compared with offline normalizing, the online normalizing process reduces production costs, shortens production time, and improves production efficiency. Moreover, vacuum degassing and Ca treatment of tube billet manufacturing not only cleans the molten steel and reduces nozzle blockage, but also improves the anisotropy of the steel and improves the purity of the steel. The final manufactured line pipe has a grain size of 9, uniform hardness, good tensile properties, and an all-round improvement in product quality, which enhances the competitiveness of the product in the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the flow chart of the manufacturing method of the anti-H2S low-temperature pipeline pipe;

[0039] Figure 2 This is the schematic diagram of the PID regulation control steps of the present invention. Specific embodiments

[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the specification of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0041] Embodiment:

[0042] Please refer to the attached Figure 1 - attached Figure 2 , the embodiment of the present invention provides a manufacturing method of an anti-H2S low-temperature pipeline pipe, including the following steps:

[0043] S1: Tube blank preparation step

[0044] Use a converter or an electric furnace to smelt steel, and continuously cast into a tube blank after secondary refining, vacuum degassing, and Ca treatment;

[0045] S2: Heating and rolling step

[0046] Heat the tube blank in a rotary hearth furnace at 1250 - 1270 °C and roll it through the PQF continuous rolling process;

[0047] S3: Online normalizing treatment step

[0048] When the temperature of the rolled tube reaches 500 - 550 °C before entering the reheating furnace, it enters the reheating furnace. The temperature of the reheating furnace is set at 940 ± 20 °C, and it is heated according to the heating time (minutes) = K × S + 10 - 15 (holding time), where S is the wall thickness of the rough tube in mm, K is the heat penetration coefficient and its value is 2 minutes / mm. When the wall thickness S of the rough tube ≤ 5 mm, the holding time is 10 minutes, and the rest is 15 minutes. The final rolling temperature after stretch reducing ≥ 860 °C;

[0049] S4: Component precise regulation step

[0050] In the secondary refining process of tube blank preparation, the composition of the molten steel is accurately analyzed. According to the analysis results, the contents of basic elements such as carbon, silicon, and manganese are finely adjusted to accurately control them within the specified range. At the same time, the addition amounts of trace elements such as V, Nb, and Ti are accurately controlled and added in a specific ratio to control the ratio of V, Nb, and Ti within a certain range. In addition, the contents of Al and N are strictly controlled to ensure that Al:N is between 2.5 - 3:1.

[0051] S5: Inclusion optimization step

[0052] During the Ca treatment process, a dynamic monitoring system is used to continuously track the changes in inclusions in the molten steel. According to the real-time state of the molten steel, the addition amount and addition timing of Ca are accurately controlled. The addition amount of Ca is accurately adjusted within a certain range and Ca is added when the temperature of the molten steel is within a specific range. At the same time, through electromagnetic stirring technology, the inclusions are promoted to fully react and float. The stirring time is controlled within a certain time range and the stirring intensity is set within a specific intensity range.

[0053] S6: Comprehensive experimental detection

[0054] The comprehensive performance of the prepared pipeline is detected. The detection contents include impact resistance, tensile properties, hardness, grain size, HIC, and SSC.

[0055] In the tube blank preparation step, during the Ca treatment, a spectroscopic analyzer is used to continuously detect the sulfur and oxygen contents of the molten steel. The addition amount of Ca is calculated through an automated control system combined with the molten steel temperature data. The calculation process is based on a multi-parameter regression algorithm model established, comprehensively considering parameters such as sulfur and oxygen contents, molten steel temperature, and molten steel volume, to accurately control the addition amount of Ca within the numerical range.

[0056] In the tube blank preparation step, electromagnetic stirring technology is used in the continuous casting process. At least two sets of electromagnetic stirring devices are set in the continuous casting mold. One set is set at the upper part of the mold and the other set is set at the lower part of the mold. The current intensity and frequency of the two sets of electromagnetic stirring devices are respectively adjusted through a controller. The current intensity of the upper electromagnetic stirring device is controlled within the range of 300 - 500A and the frequency is set within the range of 2 - 4Hz. The current intensity of the lower electromagnetic stirring device is controlled within the range of 400 - 600A and the frequency is set within the range of 3 - 5Hz.

[0057] In the described hot rolling step, the rolling speed and tension are monitored and adjusted in real time during the PQF tandem rolling process. Pressure sensors and speed sensors are installed on each stand of the tandem mill to collect rolling pressure and pipe speed data in real time. The collected data is analyzed and processed by an automated control system. When fluctuations occur in pressure or speed, the system automatically adjusts the rotational speed of the tandem mill motor and the spacing between the rolls, with the adjustment accuracy controlled within the range of ±0.05 mm, ensuring that the rolling speed is stable in the range of 2.5 - 4.5 m / s and the tension is stable in the range of 5 - 15 kN. The following algorithm steps are established during the process:

[0058] Step 1: Data acquisition and preprocessing

[0059] 1.1 Sensor data acquisition Key parameters during the rolling process are collected in real time through pressure sensors and speed sensors installed on each stand of the tandem mill:

[0060] Pressure sensor: Measures the rolling force P i (Unit: MPa), reflecting the metal deformation resistance;

[0061] Speed sensor: Measures the pipe outlet speed v i (Unit: m / s), directly affecting production efficiency and dimensional accuracy;

[0062] Sampling frequency: f = 100 Hz (sampling period T = 0.01 s), ensuring data real-time.

[0063] 1.2 Kalman filtering algorithm Since there is noise interference in the sensor signals, the Kalman filter is needed to improve data reliability. The established state space model:

[0064]

[0065] Where:

[0066] is the state vector, including pressure, pressure change rate, speed, and speed change rate.

[0067] z k =[P measured ,v measured T is the observation vector, i.e., the actual measurement value of the sensor.

[0068] F is the state transition matrix, describing the dynamic characteristics of the system (such as the inertia of pressure and speed).

[0069] H is the observation matrix, establishing the relationship between the state and the measurement value.

[0070] w k and v k are the process noise and observation noise respectively, following a Gaussian distribution.​

[0071] Kalman filter recurrence formula:

[0072] Prediction stage: Estimate the current state based on the previous state estimate. Where Q is the process noise covariance, reflecting model uncertainty.

[0073] Update stage: Correct the prediction result by combining the current measurement value. Where K k is the Kalman gain, weighing the credibility of the predicted value and the measured value; R is the observation noise covariance.

[0074] Parameter selection:

[0075] Q = diag(0.01, 0.001, 0.01, 0.001): A small value indicates low process noise and a more deterministic system dynamics.

[0076] R = diag(0.1, 0.05): Reflects that the noise of the pressure sensor is greater than that of the speed sensor

[0077] Step 2: Deviation calculation and analysis

[0078] 2.1 Deviation between the set value and the actual value

[0079] Calculate the deviation between the current measurement value and the target value as the control basis:

[0080] Pressure deviation:

[0081] Speed deviation:

[0082] Deviation change rate: Δe P (k) = e P (k) - e P (k - 1) Δe v (k) = e v (k) - e v (k - 1) The deviation change rate reflects the system dynamics trend and is used to predict future deviations.

[0083] 2.2 Deviation threshold judgment

[0084] To avoid frequent adjustments, set the trigger threshold:

[0085] If |e P (k)| > δ P or |e v (k)| > δ v , then start the PID controller to adjust the parameters.

[0086] Threshold setting: δ P = 0.5 MPa, δ v = 0.1 m / s, determined based on process stability requirements.

[0087] Step 3: Fuzzy adaptive PID parameter tuning

[0088] Traditional PID parameters are fixed and difficult to adapt to the non - linear changes in the rolling process. In this case, a fuzzy logic is established to dynamically adjust PID parameters:

[0089] 3.1 Fuzzification of input variables

[0090] Map the deviation e and the deviation change rate Δe to the fuzzy set:

[0091] Fuzzy set: {NB, NM, NS, ZO, PS, PM, PB} (Negative Big, Negative Medium, Negative Small, Zero, Positive Small, Positive Medium, Positive Big).

[0092] Membership function (taking the triangle as an example): For example, when x = 0, it completely belongs to the "Zero" set (membership degree is 1).

[0093] 3.2 Fuzzy rule base

[0094] Design rules based on experience, such as:

[0095] Rule 1: If e is Negative Big and Δe is Negative Big, then increase the proportional coefficient Kp and decrease the integral coefficient Ki.

[0096] Rule 2: If e is Zero and Δe is Positive Small, then slightly adjust Kp and appropriately increase Ki

[0097] 3.3 Fuzzy inference and defuzzification

[0098] Mamdani inference method: Combine the conclusions of each rule through the "AND" operation to obtain the fuzzy set of the output variable;

[0099] Centroid method for defuzzification:

[0100]

[0101] Calculate the centroid of the fuzzy set to obtain the accurate parameter adjustment amount ΔK p 、ΔK i 、ΔK d .

[0102] 3.4 PID parameter update

[0103] Based on the fuzzy inference result, dynamically adjust PID parameters:

[0104] Initial parameter: K p0= 1.0, K i0 = 0.05, K d0 = 0.1 (empirical value);

[0105] Update formula:

[0106] K p = K p0 + ΔK p

[0107] K i = K i0 + ΔK i

[0108] K d = K d0 + ΔK d

[0109] Step 4: Incremental PID controller calculation

[0110] Use the incremental PID algorithm to calculate the control quantity and avoid the problem of integral saturation:

[0111] 4.1 Calculation of speed control quantity

[0112] Incremental PID formula:

[0113] Δu v (k) = K p [e v (k) - e v (k - 1)] + K i e v (k) + K d [e v (k) - 2e v (k - 1) +

[0114] e v (k - 2)];

[0115] Proportional term: K p [e v (k) - e v (k - 1)], reflecting the current deviation change and providing a quick response;

[0116] Integral term: K i e v (k), eliminating the steady-state error;

[0117] Derivative term: K d [e v (k) - 2e v (k - 1) + e v (k - 2)], predicting the trend of deviation change and suppressing oscillation;

[0118] Control quantity update: u v (k) = u v (k - 1) + Δu v (k);

[0119] 4.2 Calculation of roll gap control quantity. Similarly, calculate the roll gap adjustment quantity corresponding to the pressure:

[0120] Δu s (k) = K p [e P (k) - e P (k - 1)] + K i e P (k) + K d [e P (k) - 2e P (k - 1) +

[0121] e P (k - 2)];

[0122] u s (k) = u s (k - 1) + Δu s (k)

[0123] Step 5: Multivariable coupling feedforward compensation

[0124] During the rolling process, the speed change will cause tension fluctuations (speed - tension coupling), and feedforward compensation is required:

[0125] 5.1 Speed - tension coupling model

[0126] Transfer function relationship: T(s) = G FT (s) · v(s) + G TT (s) · T ref (s)

[0127] Where:

[0128] The influence of speed on tension (K FT = -0.8 kN / (m / s), the negative sign indicates that the increase in speed will reduce the tension).

[0129] The dynamic characteristics of tension itself (K TT = 0.9, T TT = 0.3 s).

[0130] 5.2 Feedforward compensation calculation

[0131] After discretization:

[0132] Reduce system oscillation by compensating in advance for the influence of speed changes on tension

[0133] 5.3 Synthesis of the final control quantity

[0134] Motor speed control quantity: u motor (k) = u v (k) + u FF (k)

[0135] Roll gap control quantity: u roll (k) = u s (k)

[0136] Step 6: Actuator control and accuracy assurance

[0137] 6.1 Motor speed control Convert the control quantity into the actual motor speed: ω(k) = ω0 + K ω ·u motor (k)

[0138] Where:

[0139] ω0 = 1500 rpm (reference speed)

[0140] K ω = 20 rpm / (kN) (gain coefficient).

[0141] 6.2 Roll gap control Convert the control quantity into roll gap adjustment: Δd(k) = K d ·u roll (k)

[0142] Where: K d = 0.05 mm / (MPa), ensuring an adjustment accuracy of ±0.05 mm.

[0143] 6.3 Accuracy assurance measures Achieve high-precision control using a hydraulic servo system:

[0144] Position closed-loop PID control:

[0145]

[0146] Where:

[0147] e d (k) = d set (k) - d actual (k);

[0148] K p□ = 5 (high proportional gain ensures response speed)

[0149] K i□ = 0.2;

[0150] Kd□ = 0.1.

[0151] Step 7: Closed-loop control and monitoring

[0152] 7.1 Control period

[0153] System control period T c = 0.02 s (50 Hz), balancing real-time performance and computing resources.

[0154] 7.2 Monitoring metrics

[0155] Rolling pressure fluctuation range: ΔP ≤ 0.3 MPa (ensuring dimensional accuracy).

[0156] Speed fluctuation range: Δv ≤ 0.05 m / s (avoiding steel pulling or piling).

[0157] Tension fluctuation range: ΔT ≤ 1 kN (preventing pipe fracture)

[0158] 7.3 Stability criterion

[0159] Use Lyapunov stability theory to verify the system stability:

[0160] Construct the Lyapunov function: V(x) = x T Px > 0

[0161] If its derivative satisfies:

[0162] Then the system is asymptotically stable, where A and B are the system state matrices, and P is a positive definite symmetric matrix.

[0163] In the said hot rolling step, during the heating in the rotary hearth furnace, the zone temperature control technology is adopted. The rotary hearth furnace is divided into three zones: the preheating zone, the heating zone, and the soaking zone. Each zone is equipped with an independent infrared temperature measuring device and a temperature control device. The infrared temperature measuring equipment monitors the internal temperature of each zone of the rotary hearth furnace by infrared temperature measurement, and at the same time draws the real-time temperature change curve, and compares the detected temperature change curve with the preset temperature change curve. The control system adjusts the heating power of the reheating furnace in real time through the PID control algorithm according to the temperature data. Among them, the proportional coefficient Kp is set to 0.5 - 1.5, the integral coefficient Ki is set to 0.01 - 0.1, and the differential coefficient Kd is set to 0.05 - 0.2.

[0164] In the online normalizing treatment step, a temperature gradient is set in the reheating furnace. Along the length direction of the reheating furnace, it is divided into three temperature sections from the inlet to the outlet. The temperature of the first section is set at 920 - 930 °C, the temperature of the second section is set at 940 ± 20 °C, and the temperature of the third section is set at 930 - 940 °C. The temperature fluctuation of each temperature section is controlled within ±5 °C. Among them, the power of the heating elements in the first section is 40 - 50% of the total power, the second section is 50 - 60%, and the third section is 30 - 40%.

[0165] The various experimental designs in the comprehensive experimental detection are as follows:

[0166] Impact energy detection: Using the Charpy impact test method, at a test temperature of -56 °C, at least 3 standard impact specimens are prepared from the pipeline pipe for impact tests, the impact energy values of each specimen are recorded, and the average impact energy is calculated;

[0167] Tensile property detection: At a test temperature of 21 °C, tensile specimens are prepared according to relevant standards, and a tensile testing machine is used to conduct tensile tests on the specimens to measure the yield strength Rp0.2, tensile strength, and elongation rate of the pipeline pipe;

[0168] Hardness detection: Using a Vickers hardness tester, with a test force of 10 kg, the hardness of at least 3 different positions on the surface of the pipeline pipe is tested, and the HV(10) hardness values of each test point are recorded;

[0169] Grain size detection: A metallographic specimen is intercepted from the pipeline pipe. After being ground, polished, corroded, etc., a metallographic microscope is used to observe the metallographic structure, and the grain size grade of the pipeline pipe is determined according to the standard rating method;

[0170] HIC detection: The pipeline pipe is made into a standard specimen, and a hydrogen-induced cracking (HIC) test is carried out in a specific solution environment with an initial test pH value of 2.6. After the test, the pH value of the solution is measured, and the crack sensitivity rate (CSR), crack length rate (CLR), and crack thickness rate (CTR) of the specimen are measured using metallographic analysis or other suitable methods;

[0171] SSC detection: The pipeline pipe is processed into a specimen that meets the requirements, and a sulfide stress corrosion cracking test is carried out in a solution with an initial test pH value of 0. After the test, the specimen is checked for fracture, and the test results are recorded.

[0172] In the impact energy detection, the dimensional tolerance of the prepared impact specimens is controlled within ±0.1 mm. In the tensile property detection, the force value accuracy of the tensile testing machine is controlled within ±1% FS, and the displacement measurement accuracy is controlled within ±0.05 mm. In the hardness detection, the distance between adjacent test points is not less than 3 mm. In the grain size detection, the magnification of the metallographic microscope is 500 times.

[0173] In the test solution for HIC detection, in addition to controlling the initial pH value, the Cl⁻ concentration in the solution needs to be controlled at 1000 - 1200 mg / L, and the test time lasts for 96 hours. When performing SSC detection, a four-point bending method is used to apply stress to the specimen, and the stress loading rate is controlled at 0.5 - 1 MPa / s. The experimental data obtained in the experiment are as follows:

[0174] ① Impact energy

[0175] Test temperature °C Impact energy 1 (J) Impact energy 2 (J) Impact energy 3 (J) Average impact energy (J) -56 150 161 154 155

[0176] ② Tensile properties

[0177]

[0178] ③ Hardness

[0179]

[0180] ④ Grain size: Grade 9

[0181] ⑤ HIC

[0182] pH value at the beginning of the test pH value at the end of the test CSR CLR CTR 2.6 3.6 0 0 0

[0183] ⑥ SSC

[0184]

[0185] An H₂S-resistant low-temperature pipeline pipe, in which the chemical components of the H₂S-resistant low-temperature pipeline pipe are calculated by weight percentage and satisfy: C: 0.10 - 0.14, Si: 0.15 - 0.35, Mn: 0.95 - 1.15, P ≤ 0.015, S ≤ 0.003, Ni ≤ 0.20, Cr ≤ 0.20, Mo ≤ 0.10, Cu ≤ 0.20, V ≤ 0.05, Alt: 0.015 - 0.040, Nb ≤ 0.015, Ti ≤ 0.015, and the content ratio of Al to N satisfies Al:N ≥ 2:1.

[0186] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A manufacturing method of an H2S-resistant low-temperature pipeline pipe, characterized in that, It includes the following steps: S1: Tube blank preparation step Steel is made in a converter or an electric furnace, and then continuous casting is carried out after ladle furnace refining, vacuum degassing, and Ca treatment to obtain a tube blank; S2: Heating and rolling step The tube blank is heated in a rotary hearth furnace at 1250 - 1270 °C and rolled through the PQF continuous rolling process; S3: Online normalizing treatment step When the temperature of the rolled tube reaches 500 - 550 °C before entering the reheating furnace, it enters the reheating furnace. The temperature of the reheating furnace is set at 940 ± 20 °C, and heating is carried out according to the heating time (minutes) = K × S + 10 - 15 (holding time), where S is the wall thickness of the semi-finished tube in mm, K is the heat penetration coefficient with a value of 2 minutes / mm. When the wall thickness of the semi-finished tube S ≤ 5 mm, the holding time is 10 minutes, and the rest is 15 minutes. The final rolling temperature after stretch reducing is ≥ 860 °C; S4: Precise composition control step In the ladle furnace refining stage of tube blank preparation, the composition of the molten steel is accurately analyzed. According to the analysis results, the contents of basic elements such as carbon, silicon, and manganese are finely adjusted and accurately controlled within the specified range. At the same time, the addition amounts of trace elements such as V, Nb, and Ti are precisely controlled and added in a specific ratio to control the ratio of V, Nb, and Ti within a certain range. In addition, the contents of Al and N are strictly controlled to ensure that Al:N is between 2.5 - 3:1; S5: Inclusion optimization step During the Ca treatment process, a dynamic monitoring system is used to real-time track the changes of inclusions in the molten steel. According to the real-time state of the molten steel, the addition amount and addition timing of Ca are accurately controlled, and the addition amount of Ca is precisely adjusted within a certain range and Ca is added when the molten steel temperature is in a specific interval. At the same time, through electromagnetic stirring technology, the inclusions are promoted to fully react and float, and the stirring time is controlled within a certain time range, and the stirring intensity is set within a specific intensity range; S6: Comprehensive experimental detection Comprehensive performance detection is carried out on the prepared pipeline, and the detection contents include impact resistance, tensile performance, hardness, grain size, HIC, and SSC.

2. The manufacturing method of an H2S-resistant low-temperature pipeline pipe according to claim 1, characterized in that, In the tube blank preparation step, during Ca treatment, a spectral analyzer is used to real-time detect the sulfur and oxygen contents of the molten steel, and the addition amount of Ca is calculated through an automatic control system combined with the molten steel temperature data. The calculation process is based on a multi-parameter regression algorithm model established, comprehensively considering parameters including sulfur and oxygen contents, molten steel temperature, and molten steel volume, and the addition amount of Ca is accurately controlled within the numerical range.

3. The manufacturing method of an H2S-resistant low-temperature pipeline pipe according to claim 1, characterized in that, In the tube blank preparation step, electromagnetic stirring technology is used during continuous casting. At least two groups of electromagnetic stirring devices are set in the continuous casting mold, one group is set at the upper part of the mold, and the other group is set at the lower part of the mold; the current intensity and frequency of the two groups of electromagnetic stirring devices are respectively adjusted through a controller. The current intensity of the upper electromagnetic stirring device is controlled within the range of 300 - 500 A, and the frequency is set within the range of 2 - 4 Hz. The current intensity of the lower electromagnetic stirring device is controlled within the range of 400 - 600 A, and the frequency is set within the range of 3 - 5 Hz.

4. The manufacturing method of an H2S-resistant low-temperature pipeline pipe according to claim 1, characterized in that, In the described hot rolling step, the rolling speed and tension are monitored and adjusted in real time during the PQF tandem rolling process. Pressure sensors and speed sensors are installed on each stand of the tandem rolling mill to collect the rolling pressure and pipe speed data in real time. The collected data is analyzed and processed by an automated control system. When fluctuations occur in the pressure or speed, the system automatically adjusts the rotational speed of the tandem rolling mill motor and the distance between the rolls. The adjustment accuracy is controlled within the range of ±0.05 mm to ensure that the rolling speed is stable in the range of 2.5 - 4.5 m / s and the tension is stable in the range of 5 - 15 kN.

5. The manufacturing method of an H2S-resistant low-temperature pipeline pipe according to claim 1, wherein In the described hot rolling step, the zoning temperature control technology is adopted during the heating in the rotary hearth furnace. The rotary hearth furnace is divided into three zones: the preheating zone, the heating zone, and the soaking zone. Independent infrared temperature measuring devices and temperature control devices are installed in each zone. The infrared temperature measuring equipment monitors the internal temperature of each zone of the rotary hearth furnace by infrared temperature measurement, and at the same time draws a real-time temperature change curve, and compares the detected temperature change curve with the preset temperature change curve. The control system adjusts the heating power of the reheating furnace in real time according to the temperature data through the PID control algorithm. Among them, the proportional coefficient Kp is set to 0.5 - 1.5, the integral coefficient Ki is set to 0.01 - 0.1, and the differential coefficient Kd is set to 0.05 - 0.

2.

6. The manufacturing method of an H2S-resistant low-temperature pipeline pipe according to claim 5, characterized in that, In the described online normalizing treatment step, a temperature gradient is set in the reheating furnace. In the length direction of the reheating furnace, it is divided into three temperature sections from the inlet to the outlet. The temperature of the first section is set at 920 - 930 °C, the temperature of the second section is set at 940 ± 20 °C, and the temperature of the third section is set at 930 - 940 °C. The temperature fluctuation of each temperature section is controlled within ±5 °C. Among them, the power of the heating elements in the first section is 40 - 50% of the total power, the second section is 50 - 60%, and the third section is 30 - 40%.

7. The manufacturing method of an H2S-resistant low-temperature pipeline pipe according to claim 1, characterized in that, The designs of each experiment in the described comprehensive experimental detection are as follows: Impact energy detection: Using the Charpy impact test method, at a test temperature of -56 °C, at least 3 standard impact specimens are prepared from the line pipe for impact tests, and the impact energy value of each specimen is recorded, and the average impact energy is calculated; Tensile property detection: At a test temperature of 21 °C, tensile specimens are prepared according to relevant standards, and a tensile testing machine is used to conduct tensile tests on the specimens to measure the yield strength Rp0.2, tensile strength, and elongation of the line pipe; Hardness detection: Using a Vickers hardness tester, with a test force of 10 kg, the hardness of at least 3 different positions on the surface of the line pipe is tested, and the HV(10) hardness value of each test point is recorded; Grain size detection: A metallographic specimen is cut from the line pipe. After being polished, polished, and etched, a metallographic microscope is used to observe the metallographic structure, and the grain size grade of the line pipe is determined according to the standard rating method; HIC detection: The line pipe is made into a standard specimen, and a hydrogen-induced cracking (HIC) test is carried out in a specific solution environment with an initial pH value of 2.

6. After the test, the pH value of the solution is measured, and the crack sensitivity rate (CSR), crack length rate (CLR), and crack thickness rate (CTR) of the specimen are measured by metallographic analysis or other appropriate methods; SSC test: Process the line pipe into specimens that meet the requirements, conduct sulfide stress corrosion cracking tests in a solution with an initial pH value of 0 at the beginning of the test. After the test, check whether the specimens are fractured and record the test results.

8. The manufacturing method of an H2S-resistant low-temperature pipeline pipe according to claim 7, characterized in that, In the preparation of impact specimens for the impact energy test, the dimensional tolerance is controlled within ±0.1 mm. During the tensile property test, the force value accuracy of the tensile testing machine is controlled within ±1% FS, and the displacement measurement accuracy is controlled within ±0.05 mm. During the hardness test, the distance between adjacent test points is not less than 3 mm. During the grain size test, the magnification of the metallurgical microscope is 500 times.

9. The manufacturing method of an H2S-resistant low-temperature pipeline pipe according to claim 7, characterized in that, In the test solution for the HIC test, in addition to controlling the initial pH value, the Cl- concentration in the solution also needs to be controlled within 1000 - 1200 mg / L, and the test duration is 96 hours. During the SSC test, stress is applied to the specimens using the four-point bending method, and the stress loading rate is controlled within 0.5 - 1 MPa / s.

10. A low-temperature pipeline pipe resistant to H2S according to claim 1, characterized in that, For the chemical composition of the anti-H2S low-temperature line pipe, by weight percentage, it meets the following requirements: C: 0.10 - 0.14, Si: 0.15 - 0.35, Mn: 0.95 - 1.15, P ≤ 0.015, S ≤ 0.003, Ni ≤ 0.20, Cr ≤ 0.20, Mo ≤ 0.10, Cu ≤ 0.20, V ≤ 0.05, Alt: 0.015 - 0.040, Nb ≤ 0.015, Ti ≤ 0.015, and the content ratio of Al to N meets Al:N ≥ 2:1.

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