A method for closed-loop control of manufacturing process parameters for composite steel pipes

Abstract

The application belongs to the technical field of industrial control, and particularly discloses a composite steel pipe manufacturing process parameter closed-loop control method, which comprises the following steps: acquiring temperature variation sequences, heating power, rolling pressure and composite steel pipe wall thickness parameters of the outer layer carbon steel, and further determining temperature variation characteristic sequences of the inner layer stainless steel to construct an interface thermal expansion difference driving quantity; performing time correlation analysis on the interface thermal expansion difference driving quantity and the rolling pressure variation sequences to construct a dynamic response lag characteristic quantity; determining whether there is a defect risk caused by material thermal expansion mismatch at the interface between the outer layer carbon steel and the inner layer stainless steel based on the interface thermal expansion difference driving quantity and the dynamic response lag characteristic quantity; and when it is determined that there is a defect risk, performing pre-compensation control on the interface area through linkage adjustment of the heating power and the rolling pressure; and the method has the following advantages: interface mismatch identification and pre-compensation are realized, and the bonding quality of the composite steel pipe is improved.

Description

Technical Field

[0001] This invention relates to the field of industrial control technology, and more specifically, to a closed-loop control method for process parameters in the manufacturing of composite steel pipes. Background Technology

[0002] Composite steel pipes, especially bimetallic composite steel pipes formed by combining an outer layer of carbon steel and an inner layer of stainless steel, have been widely used in petrochemical, energy transmission and high-temperature and high-pressure fluid pipelines due to their combination of the high strength of carbon steel and the corrosion resistance of stainless steel.

[0003] In existing technologies, such composite steel pipes are typically manufactured through hot rolling, hot expansion, or composite extrusion. During manufacturing, process parameters such as heating temperature, rolling pressure, and forming rhythm must be controlled to ensure the quality of the interface bonding. However, relying solely on outer layer temperature or overall pressure for control is insufficient to accurately reflect the true bonding state of the interface area. In particular, it is difficult to identify asynchronous interface deformation caused by differences in material thermal expansion, thus hindering effective prediction and early intervention for these hidden defects. This can easily lead to localized unbonded or delamination phenomena in the composite steel pipe after forming, affecting product quality and reliability.

[0004] Therefore, a closed-loop control method for process parameters in the manufacturing of composite steel pipes is proposed. Summary of the Invention

[0005] This invention aims to provide a closed-loop control method for process parameters in the manufacturing of composite steel pipes, in order to solve or improve the above-mentioned technical problems where the asynchronous interface deformation and lag caused by the difference in thermal expansion of materials are accurately characterized based on the outer layer temperature or overall pressure, thus making it impossible to effectively predict and control the risk of local non-bonding or delamination at the interface of composite steel pipes.

[0006] In view of this, the first aspect of the present invention is to provide a closed-loop control method for process parameters in the manufacturing of composite steel pipes.

[0007] The first aspect of the present invention provides a closed-loop control method for process parameters in the manufacturing of a composite steel pipe, used for closed-loop control of the manufacturing process parameters of a bimetallic composite steel pipe formed by an outer carbon steel layer and an inner stainless steel layer in an industrial control system, and includes the following steps: acquiring the temperature change sequence, heating power, rolling pressure, and composite steel pipe wall thickness parameters of the outer carbon steel layer during the manufacturing process; determining the temperature change characterization sequence of the inner stainless steel layer based on the temperature change sequence of the outer carbon steel layer, the heating power, the composite steel pipe wall thickness parameters, and the material heat transfer characteristics of the outer carbon steel layer and the inner stainless steel layer; and determining the temperature change characterization sequence of the inner stainless steel layer based on the temperature change sequence and the temperature change... Characterizing the sequence and the thermal expansion characteristics of the outer carbon steel and inner stainless steel, an interfacial thermal expansion difference driving quantity is constructed; the interfacial thermal expansion difference driving quantity and the rolling pressure change sequence are subjected to time correlation analysis to construct a dynamic response hysteresis characteristic quantity; based on the interfacial thermal expansion difference driving quantity and the dynamic response hysteresis characteristic quantity, it is determined whether there is a defect risk caused by material thermal expansion mismatch at the interface where the outer carbon steel and inner stainless steel are bonded; when the defect risk is determined to exist, the heating power and the rolling pressure are linked to perform pre-compensation control on the interface area to make the deformation behavior of the outer carbon steel and inner stainless steel tend to be synchronized.

[0008] The beneficial effects of this invention compared to the prior art are as follows:

[0009] By acquiring the temperature change sequence, heating power, rolling pressure, and composite steel pipe wall thickness parameters of the outer carbon steel layer during the manufacturing process of the composite steel pipe, and determining the temperature change characterization sequence of the inner stainless steel layer based on the temperature change sequence, heating power, composite steel pipe wall thickness parameters, and the material heat transfer characteristics of the outer carbon steel layer and the inner stainless steel layer, the thermal state of the inner and outer layers of the bimetallic composite steel pipe can be effectively characterized when the inner stainless steel layer is inconvenient to measure directly. This allows for the establishment of the temperature evolution relationship between the outer carbon steel layer and the inner stainless steel layer during the manufacturing process.

[0010] By constructing the interfacial thermal expansion difference driving quantity based on the temperature change sequence and the temperature change characterization sequence, as well as the thermal expansion characteristics of the outer carbon steel and the inner stainless steel, and by performing time correlation analysis on the interfacial thermal expansion difference driving quantity and the rolling pressure change sequence to construct a dynamic response hysteresis characteristic quantity, it is possible to simultaneously analyze the state of the bonding interface between the outer carbon steel and the inner stainless steel from two dimensions: the amplitude of interfacial thermal expansion mismatch and the dynamic response time sequence. This improves the accuracy of predicting the risk of hidden defects such as local non-bonding, insufficient bonding, or delamination caused by material thermal expansion mismatch.

[0011] When the aforementioned defect risk is determined, the heating power and rolling pressure are linked and adjusted to perform pre-compensation control on the interface area, so that the deformation behavior of the outer carbon steel and the inner stainless steel tends to be synchronized. This allows the heat input adjustment and forming pressure adjustment to be specifically corrected around the interface risk state, thereby reducing the degree of interface thermal expansion mismatch, reducing the probability of local non-bonding or delamination, and ultimately improving the interface bonding quality, manufacturing stability and product reliability of the composite steel pipe.

[0012] Additional aspects and advantages of embodiments of the invention will become apparent in the following description or may be learned by practice of embodiments of the invention. Attached Figure Description

[0013] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0014] Figure 1 This is a flowchart illustrating an incomplete method of the present invention;

[0015] Figure 2 This is a schematic diagram showing the temperature change relationship between the outer carbon steel layer and the inner stainless steel layer of the present invention.

[0016] Figure 3 This is a schematic diagram illustrating the analysis of the interfacial thermal expansion difference driving force of the present invention.

[0017] Figure 4 This is a schematic diagram illustrating the dynamic response hysteresis determination of the present invention;

[0018] Figure 5 This is a schematic diagram of the interface between the outer carbon steel layer and the inner stainless steel layer of the present invention. Detailed Implementation

[0019] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0020] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0021] Please see Figures 1-5 The following describes a closed-loop control method for process parameters in the manufacturing of composite steel pipes according to some embodiments of the present invention.

[0022] The physical meaning of some parameters in all the formulas below in this application;

[0023] An embodiment of the first aspect of the present invention provides a closed-loop control method for process parameters in the manufacturing of composite steel pipes. In some embodiments of the present invention, such as... Figures 1-5 As shown, a method for closed-loop control of manufacturing process parameters of a bimetallic composite steel pipe formed by an outer layer of carbon steel and an inner layer of stainless steel in an industrial control system includes:

[0024] S101, obtain the temperature change sequence of the outer carbon steel, heating power, rolling pressure and composite steel pipe wall thickness parameters during the manufacturing process of composite steel pipe.

[0025] Here, obtaining the temperature change sequence of the outer carbon steel is to characterize the thermal state of the outer carbon steel during heating and rolling, enabling subsequent analysis of the temperature evolution trend of the outer layer of the composite steel pipe based on the actual heating condition of the outer carbon steel. Obtaining the heating power reflects the intensity of heat energy input to the composite steel pipe during manufacturing, as heating power directly affects the heating rate of the outer carbon steel and the heat transfer process to the inner stainless steel, thus providing a thermal input basis for determining the temperature change characterization sequence of the inner stainless steel. Obtaining the rolling pressure characterizes the external pressure state experienced by the composite steel pipe during forming. Since rolling pressure not only affects the tightness of the fit between the outer carbon steel and the inner stainless steel but also the plastic deformation process of the interface region, it provides a mechanical basis for subsequent analysis of the interface response state and its changing trend. Obtaining the composite steel pipe wall thickness parameter characterizes the structural dimensional characteristics of the outer carbon steel and the inner stainless steel in the radial direction, as wall thickness directly affects the heat transfer path and efficiency between the outer carbon steel and the inner stainless steel, and further affects the temperature distribution and thermal expansion behavior differences between the two layers after heating.

[0026] S102, based on the temperature change sequence of the outer carbon steel, the heating power, the wall thickness parameters of the composite steel pipe, and the material heat transfer characteristics of the outer carbon steel and the inner stainless steel, determine the temperature change characterization sequence of the inner stainless steel.

[0027] Here, the temperature change sequence of the outer carbon steel serves as the external temperature basis for heat transfer analysis, characterizing the actual heating state of the outer carbon steel during the manufacturing process and its changes over time, thus providing a temperature starting point for heat transfer from the outer layer to the inner layer; heating power is used as a characterizing parameter of heat input intensity to reflect the magnitude and trend of heat energy input to the composite steel pipe during the manufacturing process, thereby determining the driving conditions for the continuous conduction of heat into the interior of the composite steel pipe.

[0028] Furthermore, the structural dimensional relationship between the outer carbon steel layer and the inner stainless steel layer in the radial direction is characterized by the composite steel pipe wall thickness parameter, so that the heat transfer path length and the degree of attenuation during the transfer process can be reflected. In addition, combined with the heat transfer characteristics of the outer carbon steel layer and the inner stainless steel layer, the differences in thermal conductivity, heat storage capacity and temperature response speed of the two layers are comprehensively analyzed, so that the heat transfer process from the outer carbon steel layer to the inner stainless steel layer can be characterized according to the actual heat transfer law of the bimetallic composite steel pipe, rather than being treated as the heat transfer mode of a single homogeneous material.

[0029] Specifically, the step of determining the temperature change characterization sequence of the inner stainless steel layer includes: constructing a radial temperature field model based on the transient heat transfer relationship between the outer carbon steel layer and the inner stainless steel layer in the radial direction; and the radial temperature field model includes:

[0030]

[0031] In the formula, This refers to the density of the corresponding layer material; This refers to the specific heat capacity of the corresponding layer material; The thermal conductivity of the corresponding layer material; This is the temperature distribution function of the corresponding layer material; The outer layer is made of carbon steel; The inner layer is made of stainless steel; The radial coordinate of the composite steel pipe is taken from the inner radius to the outer radius.

[0032] For the specific description above, in the case of a long, straight circular tube where the temperature mainly changes radially, a one-dimensional radial transient heat conduction equation can be used. The classical heat conduction derivation gives: for constant physical properties and without a bulk heat source, the one-dimensional unsteady-state heat conduction in cylindrical coordinates satisfies:

[0033]

[0034] For the double-layer material (outer layer carbon steel o, inner layer 304i), the above radial temperature field model is satisfied in their respective regions.

[0035] Applying a continuity condition at the interface r=rm, we obtain the interface continuity condition satisfied by the radial temperature field model:

[0036] The boundary of the outer surface r=ro can explicitly introduce the heating power as a heat flux boundary:

[0037]

[0038] The equivalent input heat flux density on the outer surface is given, and the interface continuity condition satisfied by the radial temperature field model is obtained.

[0039] Specifically, the radial temperature field model satisfies the following interface continuity condition:

[0040]

[0041] In the formula, The radius of the interface between the outer carbon steel layer and the inner stainless steel layer; The temperature distribution function of the outer carbon steel layer; The temperature distribution function of the inner stainless steel layer; The thermal conductivity of the outer carbon steel layer; The thermal conductivity of the inner stainless steel layer;

[0042]

[0043] In the formula, The equivalent input heat flux density of the outer surface; For effective heating efficiency; This refers to the heating power. The effective heat exchange area for heating.

[0044] S103, based on the temperature change sequence and the temperature change characterization sequence, as well as the thermal expansion characteristics of the outer carbon steel and the inner stainless steel, construct the interface thermal expansion difference driving quantity.

[0045] Here, the temperature change sequence characterizes the actual temperature change state of the outer carbon steel during the manufacturing process, and the temperature change characterization sequence characterizes the corresponding temperature change state of the inner stainless steel during the same manufacturing process, thus allowing the heating difference between the outer carbon steel and the inner stainless steel at the same moment to be correlated. Furthermore, combining the respective thermal expansion characteristics of the outer carbon steel and the inner stainless steel, the thermal expansion behavior of the two materials under the current temperature conditions is correlated. Due to the difference in thermal expansion characteristics between the outer carbon steel and the inner stainless steel, even under similar heating environments, they will exhibit different thermal deformation trends, leading to inconsistent deformation at the bonding interface. By quantifying this driving factor, an interface thermal expansion difference driving quantity can be constructed, which reflects the relative deformation trend of the outer carbon steel and the inner stainless steel at the interface due to temperature and thermal expansion differences.

[0046] Specifically, the step of constructing the interfacial thermal expansion difference driving amount includes:

[0047] The average temperatures of the outer carbon steel layer and the inner stainless steel layer are determined separately; based on the average temperatures of the outer carbon steel layer and the inner stainless steel layer and the aforementioned thermal expansion characteristics, the interfacial thermal expansion difference driving amount is constructed.

[0048] And the amount of thermal expansion difference at the interface satisfies the following formula:

[0049]

[0050] In the formula, This is the amount driven by the difference in interfacial thermal expansion. The coefficient of linear expansion of the outer carbon steel layer; The coefficient of linear expansion of the inner stainless steel layer; This refers to the average temperature of the outer carbon steel layer; This represents the average temperature of the inner stainless steel layer. This is a reference temperature.

[0051] Regarding the specific description above, a direct driver of the risk of interfacial delamination / lack of bonding is the incompatibility of free deformation between the two layers due to differences in temperature rise and linear expansion coefficients. Using a linear elastic small-strain approximation, and taking the reference temperature Tref as a baseline, the "free thermal strain" of the two layers near the interface is defined.

[0052]

[0053] in o(t), i(t) is recommended to take the average temperature of each layer thickness to reflect the overall expansion trend, and the discrete summation is implemented online:

[0054]

[0055] Based on this, the aforementioned interfacial thermal expansion difference driving quantity is defined.

[0056] The average temperature of the outer carbon steel layer and the average temperature of the inner stainless steel layer respectively satisfy the following:

[0057]

[0058] In the formula, The thickness of the outer carbon steel layer; The thickness of the inner stainless steel layer; The outer radius of the composite steel pipe; The inner radius of the composite steel pipe; This is the radial temperature field function.

[0059] S104, perform time correlation analysis on the interface thermal expansion difference driving amount and the rolling pressure change sequence to construct dynamic response hysteresis characteristic quantity; based on the interface thermal expansion difference driving amount and the dynamic response hysteresis characteristic quantity, determine whether there is a defect risk caused by material thermal expansion mismatch at the interface where the outer carbon steel and inner stainless steel are bonded.

[0060] Here, the interfacial thermal expansion difference driving quantity is used to characterize the relative deformation trend of the interface between the outer carbon steel and the inner stainless steel due to the difference in thermal expansion characteristics during heating. The rolling pressure change sequence is used to characterize the change of the external forming action applied to the composite steel pipe during manufacturing over time. By performing time correlation analysis on the interfacial thermal expansion difference driving quantity and the rolling pressure change sequence, the interfacial thermal deformation trend and the external pressure action process can be correlated in the time dimension, thereby identifying whether there are asynchronous responses, lags, or mismatches between the two. Based on this, a dynamic response lag characteristic quantity is constructed to further characterize the comprehensive response state of the interfacial region to the thermal expansion difference and rolling pressure change, so that the interface... The analysis can not only examine the static thermal expansion difference but also reflect the dynamic temporal changes to indicate whether there is a delayed response or abnormal changes in the interface bonding state. Because the difference in thermal expansion characteristics between the outer carbon steel and the inner stainless steel can cause a mismatch trend at the interface, and when this mismatch trend and the rolling pressure cannot be effectively matched in time, the interface area is more prone to localized insufficient bonding, localized stress concentration, or unstable interface bonding. By comprehensively considering the interface thermal expansion difference driving quantity and the dynamic response hysteresis characteristic quantity, a more targeted judgment can be made on the interface state of the outer carbon steel and inner stainless steel bonding, thereby identifying whether there is a risk of defects caused by material thermal expansion mismatch at the interface.

[0061] Specifically, the steps for constructing the dynamic response hysteresis characteristic include:

[0062] The interfacial thermal expansion difference driving quantity sequence is used as the first time series, and the rolling pressure fluctuation sequence is used as the second time series. The discrete cross-correlation function is calculated within the sliding window.

[0063] The dynamic response lag characteristics are determined based on the number of lag steps after the discrete cross-correlation function reaches its maximum value.

[0064] The discrete cross-correlation function includes:

[0065]

[0066] In the formula, The discrete cross-correlation value between the first and second time series is used to characterize the number of lag steps. ; This represents the interfacial thermal expansion difference driving quantity corresponding to the kth sampling time. This represents the change in rolling pressure at the k-th sampling time. This is the average value of the sequence of interface thermal expansion difference driving quantities within the current sliding window; This is the average value of the rolling pressure change sequence within the current sliding window; To indicate the length of the sliding window; This refers to the data within the sliding window.

[0067] Regarding the specific description above, the instantaneous amplitude of Δε alone is insufficient to characterize the hidden risk of phase mismatch in thermal and mechanical coupling: during the forming process, there is a dynamic response delay between temperature field changes and pressure / rolling force adjustments. If the response lag increases, the interface may experience a higher tendency to shear / strip in a short period of time.

[0068] This scheme defines hysteresis characteristics that can be calculated online: First, construct two time series: the expansion difference series -xk=Δεk and the pressure / rolling force fluctuation series -yk=ΔFk; and calculate the discrete cross-correlation within a sliding window Nw:

[0069]

[0070] The time delay estimation takes the lag corresponding to the peak of the cross-correlation:

[0071]

[0072] The idea that the peak value of cross-correlation corresponds to the time delay estimation is explicitly described in the theory of time delay estimation / cross-correlation: the peak value of the correlation function corresponds to the time delay point. If the noise is large or there are multiple peaks, generalized cross-correlation (GCC) can be used to make the peak value sharper, and the weighting function can be selected according to different noise / reflection conditions.

[0073] To facilitate threshold standardization, a normalized hysteresis feature quantity is defined:

[0074]

[0075] Online applications can then undergo EWMA smoothing:

[0076]

[0077] The meaning of the EWMA recursive formula and λ is given in the NIST Engineering Statistics Handbook.

[0078] Specifically, determining whether there is a risk of defects at the interface between the outer carbon steel layer and the inner stainless steel layer caused by material thermal expansion mismatch includes:

[0079] When the absolute value of the interfacial thermal expansion difference driving amount is greater than the thermal expansion difference threshold, it is determined that there is a risk of interfacial thermal expansion mismatch.

[0080] When the dynamic response hysteresis characteristic is greater than the hysteresis threshold, it is determined that there is a risk of interface response hysteresis.

[0081] When the risk of interface thermal expansion mismatch and / or the risk of interface response hysteresis exist, it is determined that the interface has a defect risk.

[0082] Regarding the specific description above, by comparing the absolute value of the interfacial thermal expansion difference driving amount with the thermal expansion difference threshold, the relative deformation intensity caused by the difference in thermal expansion characteristics between the outer carbon steel and the inner stainless steel at the interface can be quantitatively judged. When the absolute value of the interfacial thermal expansion difference driving amount is greater than the thermal expansion difference threshold, it indicates that the thermal expansion difference at the interface has exceeded the preset allowable range. At this time, inconsistency in interface deformation is more likely to occur between the outer carbon steel and the inner stainless steel, thus determining that there is a risk of interfacial thermal expansion mismatch. Simultaneously, by comparing the dynamic response hysteresis characteristic quantity with the hysteresis threshold, the relative deformation intensity caused by the difference in thermal expansion in the interface region can be quantitatively judged. The timing response state relative to the rolling pressure change under different actions is judged. When the dynamic response hysteresis characteristic is greater than the hysteresis threshold, it indicates that the interface region has a significant hysteresis in response to the current thermal deformation trend and forming pressure. At this time, the interface bonding process is prone to mismatch between the pressure and the interface deformation state, so it is determined that there is a risk of interface response hysteresis. Furthermore, when there is a risk of interface thermal expansion mismatch and / or a risk of interface response hysteresis, it indicates that the interface region has already shown abnormalities in the thermal expansion difference amplitude and / or dynamic response timing. Thus, it can be comprehensively judged that there is a defect risk in the interface of the outer carbon steel and inner stainless steel bonding.

[0083] S105, when the risk of the aforementioned defect is determined, the interface area is pre-compensated by adjusting the heating power and the rolling pressure in a coordinated manner, so that the deformation behavior of the outer carbon steel and the inner stainless steel tends to be synchronized.

[0084] Here, given that the interface has been determined to have a risk of defects caused by material thermal expansion mismatch, it indicates that there is already a mismatch between the heating and stress states of the outer carbon steel and the inner stainless steel in the current manufacturing process. If the original process parameters are maintained at this time, the interface area is more likely to further develop problems such as insufficient local bonding, local deformation imbalance, or unstable interface bonding. Therefore, it is necessary to adjust the heating power and rolling pressure in a coordinated manner to simultaneously correct the heat input conditions and forming conditions of the interface area. The adjustment of the heating power is to change the heat transfer process from the outer carbon steel to the inner stainless steel, thereby suppressing the temperature difference between the outer carbon steel and the inner stainless steel and reducing the thermal expansion difference caused by the temperature difference. Adjusting the rolling pressure alters the intensity of the external forming action acting on the composite steel pipe, re-matching the bonding and plastic deformation states of the outer carbon steel and inner stainless steel at the interface. This reduces interface anomalies caused by uneven stress or mismatched action sequences. Furthermore, by coordinating the adjustment of the heating power and rolling pressure, the thermal and mechanical effects are no longer isolated but rather targeted pre-compensation control is implemented around identified defect risks in the interface region. This ensures that the heat transfer, thermal expansion, and pressure forming processes coordinate in terms of time and effect, gradually synchronizing the deformation behavior of the outer carbon steel and inner stainless steel at the interface, thereby reducing the degree of interface thermal expansion mismatch and the probability of interface defect formation.

[0085] Specifically, the aforementioned pre-compensation control of the interface region through the coordinated adjustment of the heating power and the rolling pressure includes:

[0086] When the driving amount of the interface thermal expansion difference is too large, adjust the heating power distribution; when the dynamic response hysteresis characteristic increases, increase the rolling pressure.

[0087] Based on the interface thermal expansion difference driving amount and the dynamic response hysteresis characteristic amount, a feedforward compensation amount is constructed, and the control amount used to constrain the adjustment of heating power and the increase of rolling pressure is updated.

[0088] Regarding the specific description above, when the interfacial thermal expansion difference driving amount is too large, it indicates that the thermal expansion difference between the outer carbon steel and the inner stainless steel under the current heating state is relatively obvious. At this time, by adjusting the heating power distribution, the way heat input acts in the composite steel pipe manufacturing process can be changed, so that the process of heat transfer from the outer carbon steel to the inner stainless steel can be specifically corrected, thereby suppressing the further expansion of the temperature change difference between the outer carbon steel and the inner stainless steel, and reducing the relative deformation trend caused by the thermal expansion difference at the interface.

[0089] When the dynamic response hysteresis characteristic increases, it indicates that the interface region has a more obvious time lag in response to the current thermal expansion difference and forming effect. At this time, by increasing the rolling pressure, the bonding and forming effect between the outer carbon steel and the inner stainless steel at the interface position can be enhanced, so that the interface region can respond faster to the current deformation trend under stronger external pressure, thereby improving the dynamic matching state of the interface region under the combined influence of thermal and mechanical effects.

[0090] Furthermore, constructing a feedforward compensation quantity based on the interfacial thermal expansion difference driving quantity and the dynamic response hysteresis characteristic quantity is to generate a compensation basis for correcting subsequent process parameters in advance, based on the identified interfacial thermal deformation trend and dynamic response state, before the defect risk becomes more apparent. This ensures that the adjustment of heating power and the increase of rolling pressure are no longer executed in isolation, but are targeted and linked control around the current risk state of the interface. By using the feedforward compensation quantity to update the control quantity used to constrain the adjustment of heating power and the increase of rolling pressure, the magnitude, direction, and timing of the changes in heating power and rolling pressure can be kept consistent with the actual risk state of the interface region. This allows the interface region to receive advance compensation at both the thermal input condition and forming action condition levels, ultimately causing the deformation behavior of the outer carbon steel and the inner stainless steel to tend to be synchronized and reducing the probability of interface defect formation.

[0091] Furthermore, the closed-loop control method for process parameters in composite steel pipe manufacturing also includes:

[0092] The composite steel pipe is divided into multiple control zones along the circumference to obtain the temperature change sequence of the outer carbon steel corresponding to each control zone, and to perform linkage adjustment through the control zones respectively.

[0093] Based on the above further description, the control input is:

[0094]

[0095] The control objective is to minimize interface risk within constraints: keep |Δεk| within the threshold and as close as possible to the reference Δεref, typically set to 0 or the process offset value. This also ensures that Lk does not exceed Lth and avoids continuous increases, controlling the actuator amplitude and rate of change.

[0096]

[0097] Specifically, the feedforward compensation is as follows: using the predictions of the thermal model in the next Np steps, the temperature discrete model is used to predict... o, i, get k and L k. Define the excess quantity:

[0098]

[0099] Given a linear feedforward:

[0100]

[0101] When the thermal expansion difference or hysteresis exceeds the limit, the external heating power and / or forming pressure are increased in advance to enhance the interface contact and diffusion conditions and to counteract the phase misalignment of heat and force.

[0102] Furthermore, the control input vector is updated as follows:

[0103]

[0104] In the formula, This is a feedforward compensation quantity constructed based on the interface thermal expansion difference driving quantity and the dynamic response hysteresis characteristic quantity; This is a feedback regulation quantity constructed based on the interfacial thermal expansion difference driving quantity; This is a saturation function that limits the control input vector based on heating power constraints and rolling pressure constraints. This is the control variable for the next sample.

[0105] The present invention provides a closed-loop control method for process parameters in composite steel pipe manufacturing. By acquiring the temperature change sequence of the outer carbon steel, heating power, rolling pressure and composite steel pipe wall thickness parameters during the manufacturing process, the basic data correlation relationship of the composite steel pipe manufacturing process can be established from three levels: heat input conditions, forming stress conditions and structural dimension conditions.

[0106] By determining the temperature change sequence of the outer carbon steel, heating power, composite steel pipe wall thickness parameters, and material heat transfer characteristics of the outer carbon steel and inner stainless steel, the temperature change characterization sequence of the inner stainless steel is determined. This allows for effective characterization of the heating state of the inner stainless steel during the manufacturing process, even when direct measurement of the inner stainless steel is inconvenient. Thus, the temperature evolution relationship between the inner and outer layers of the bimetallic composite steel pipe can be established.

[0107] By constructing the interface thermal expansion difference driving quantity based on the temperature change sequence and temperature change characterization sequence, as well as the thermal expansion characteristics of the outer carbon steel and inner stainless steel, the relative deformation trend of the interface formed by the temperature change and thermal expansion difference of the inner and outer materials can be quantitatively characterized, so that the interface mismatch is no longer limited to the level of empirical judgment.

[0108] By performing time correlation analysis between the interfacial thermal expansion difference driving quantity and the rolling pressure change sequence, a dynamic response hysteresis characteristic quantity is constructed. Based on the interfacial thermal expansion difference driving quantity and the dynamic response hysteresis characteristic quantity, it is determined whether there is a defect risk caused by material thermal expansion mismatch at the interface between the outer carbon steel and the inner stainless steel. It can simultaneously identify the abnormal state of the interface from two dimensions: the amplitude of interfacial thermal deformation and the dynamic response time sequence, thereby improving the ability to predict hidden defects such as local non-bonding or delamination.

[0109] Furthermore, when a defect risk is identified, pre-compensation control is implemented in the interface region by linking the heating power and rolling pressure. When the interfacial thermal expansion difference driving amount is too large, the heating power distribution is adjusted; when the dynamic response lag characteristic amount increases, the rolling pressure is increased. At the same time, a feedforward compensation amount is constructed based on the interfacial thermal expansion difference driving amount and the dynamic response lag characteristic amount, and the control amount used to constrain the adjustment of heating power and the increase of rolling pressure is updated. This enables the heat input adjustment and forming force adjustment to be specifically corrected around the actual risk state of the interface, thereby synchronizing the deformation behavior of the outer carbon steel and the inner stainless steel, reducing the degree of interfacial thermal expansion mismatch and the probability of interfacial defect formation.

[0110] In any of the above embodiments, the external surface temperature can be measured using a fixed-point infrared thermometer / scanning infrared or thermal imager. The material emissivity needs to be set and reflection errors suppressed. Metal emissivity varies considerably depending on surface condition. For cold-rolled steel and stainless steel, the emissivity range in the 8–14 μm band can be referenced in the engineering table. It is recommended to measure vertically with an incident angle not exceeding 30° for low emissivity to optimize accuracy.

[0111] In any of the above embodiments, the inner layer temperature is usually not directly measurable. The inner surface of the stainless steel lining is in a high-temperature forming environment and rotates / moves, making it difficult to place contact sensors. Therefore, this solution uses an online estimation model and uses external surface temperature measurement to correct the model.

[0112] The above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit it. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this disclosure, and should all be included within the protection scope of this disclosure.

Claims

1. A closed-loop control method for process parameters in the manufacturing of composite steel pipes, characterized in that, This is used for closed-loop control of the manufacturing process parameters of bimetallic composite steel pipes formed by combining an outer layer of carbon steel and an inner layer of stainless steel in an industrial control system, and includes the following steps: Obtain the temperature change sequence, heating power, rolling pressure, and composite steel pipe wall thickness parameters of the outer carbon steel layer during the manufacturing process of composite steel pipe; Based on the temperature change sequence of the outer carbon steel, the heating power, the wall thickness parameters of the composite steel pipe, and the material heat transfer characteristics of the outer carbon steel and the inner stainless steel, the temperature change characterization sequence of the inner stainless steel is determined. Based on the temperature change sequence and the temperature change characterization sequence, as well as the thermal expansion characteristics of the outer carbon steel and the inner stainless steel, the interfacial thermal expansion difference driving force is constructed. A time correlation analysis was performed between the interfacial thermal expansion difference driving quantity and the rolling pressure change sequence to construct a dynamic response hysteresis characteristic quantity; Based on the interface thermal expansion difference driving amount and the dynamic response hysteresis characteristic amount, it is determined whether there is a defect risk caused by material thermal expansion mismatch at the interface where the outer carbon steel and inner stainless steel are bonded. When the risk of the aforementioned defect is determined, the interface area is pre-compensated by adjusting the heating power and the rolling pressure in a coordinated manner, so that the deformation behavior of the outer carbon steel and the inner stainless steel tends to be synchronized.

2. The closed-loop control method for process parameters in the manufacturing of composite steel pipes according to claim 1, characterized in that, The step of determining the temperature change characterization sequence of the inner stainless steel layer includes: constructing a radial temperature field model based on the transient heat transfer relationship between the outer carbon steel layer and the inner stainless steel layer in the radial direction; and the radial temperature field model includes: In the formula, This refers to the density of the corresponding layer material; This refers to the specific heat capacity of the corresponding layer material; The thermal conductivity of the corresponding layer material; This is the temperature distribution function of the corresponding layer material; The outer layer is made of carbon steel; The inner layer is made of stainless steel; The radial coordinate of the composite steel pipe is taken from the inner radius to the outer radius.

3. The closed-loop control method for process parameters in the manufacturing of composite steel pipes according to claim 2, characterized in that, The radial temperature field model satisfies the following interface continuity condition: In the formula, The radius of the interface between the outer carbon steel layer and the inner stainless steel layer; The temperature distribution function of the outer carbon steel layer; The temperature distribution function of the inner stainless steel layer; The thermal conductivity of the outer carbon steel layer; The thermal conductivity of the inner stainless steel layer; In the formula, The equivalent input heat flux density of the outer surface; For effective heating efficiency; This refers to the heating power. The effective heat exchange area for heating.

4. The closed-loop control method for process parameters in the manufacturing of composite steel pipes according to claim 1, characterized in that, The step of constructing the interfacial thermal expansion difference driving quantity includes: The average temperatures of the outer carbon steel layer and the inner stainless steel layer are determined separately; based on the average temperatures of the outer carbon steel layer and the inner stainless steel layer and the aforementioned thermal expansion characteristics, the interfacial thermal expansion difference driving amount is constructed.

5. The closed-loop control method for process parameters in the manufacturing of composite steel pipes according to claim 4, characterized in that, The driving force of the interfacial thermal expansion difference satisfies the following formula: In the formula, This is the amount driven by the difference in interfacial thermal expansion. The coefficient of linear expansion of the outer carbon steel layer; The coefficient of linear expansion of the inner stainless steel layer; This refers to the average temperature of the outer carbon steel layer; This represents the average temperature of the inner stainless steel layer. This is a reference temperature.

6. The closed-loop control method for process parameters in the manufacturing of composite steel pipes according to claim 5, characterized in that, The average temperature of the outer carbon steel layer and the average temperature of the inner stainless steel layer respectively satisfy the following: In the formula, The thickness of the outer carbon steel layer; The thickness of the inner stainless steel layer; The outer radius of the composite steel pipe; The inner radius of the composite steel pipe; This is the radial temperature field function.

7. The closed-loop control method for process parameters in the manufacturing of composite steel pipes according to claim 1, characterized in that, The steps for constructing the dynamic response hysteresis characteristic include: The interfacial thermal expansion difference driving quantity sequence is used as the first time series, and the rolling pressure fluctuation sequence is used as the second time series. The discrete cross-correlation function is calculated within the sliding window. The dynamic response lag characteristics are determined based on the number of lag steps after the discrete cross-correlation function reaches its maximum value. The discrete cross-correlation function includes: In the formula, The discrete cross-correlation value between the first and second time series is used to characterize the number of lag steps. ; This represents the interfacial thermal expansion difference driving quantity corresponding to the kth sampling time. This represents the change in rolling pressure at the k-th sampling time. This is the average value of the sequence of interface thermal expansion difference driving quantities within the current sliding window; This is the average value of the rolling pressure change sequence within the current sliding window; To indicate the length of the sliding window; This refers to the data within the sliding window.

8. The closed-loop control method for process parameters in the manufacturing of composite steel pipes according to claim 1, wherein determining whether there is a risk of defects caused by material thermal expansion mismatch at the interface between the outer carbon steel layer and the inner stainless steel layer includes: When the absolute value of the interface thermal expansion difference driving amount is greater than the thermal expansion difference threshold, it is determined that there is a risk of interface thermal expansion mismatch. When the dynamic response hysteresis characteristic is greater than the hysteresis threshold, it is determined that there is a risk of interface response hysteresis. When the risk of interface thermal expansion mismatch and / or the risk of interface response hysteresis exist, it is determined that the interface has a defect risk.

9. The closed-loop control method for process parameters in the manufacturing of composite steel pipes according to claim 8, characterized in that, The aforementioned method of implementing pre-compensation control of the interface region through the linkage adjustment of the heating power and the rolling pressure includes: When the interfacial thermal expansion difference driving amount is too large, adjust the heating power distribution; when the dynamic response hysteresis characteristic amount increases, increase the rolling pressure. Based on the interface thermal expansion difference driving amount and the dynamic response hysteresis characteristic amount, a feedforward compensation amount is constructed, and the control amount used to constrain the adjustment of heating power and the increase of rolling pressure is updated.

10. A closed-loop control method for process parameters in the manufacturing of composite steel pipes according to any one of claims 1-9, characterized in that, Also includes: The composite steel pipe is divided into multiple control zones along the circumference to obtain the temperature change sequence of the outer carbon steel corresponding to each control zone, and to perform linkage adjustment through the control zones respectively.

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