Rail transit cable double-layer co-extrusion insulation irradiation cross-linking agent dose control process

Abstract

The application discloses a kind of track traffic cable double-layer co-extrusion insulation irradiation crosslinking dose control processes, it is related to track traffic vehicle cable manufacturing technical field.The dose-gel content response curve of inner and outer layer insulation material is fitted respectively, and the effective dose interval of each layer is determined;According to the interlayer dose ratio coefficient determined by electron beam layering energy deposition distribution, the irradiation dose correlation model is established, and the optimal conveying speed and optimal beam intensity are solved in the intersection feasible region with inner and outer layer effective dose interval as constraint;According to the optimal process parameters, the core line is implemented single electron beam irradiation;After irradiation, the inner and outer layer insulation of core line is stripped respectively, and the gel content is independently determined, and the gel content of inner and outer layer is continuously satisfied as the effective parameter determination condition of respective target window.The gel content of inner and outer layer is controlled in respective target window in single irradiation, and the problem that existing unified dose process cannot consider the low-temperature flexibility of inner layer and the flame-retardant performance requirement of outer layer is solved.

Description

Technical Field

[0001] This application relates to the field of cable manufacturing technology for rail transit vehicles, specifically a process for controlling the dosage of irradiation crosslinking of double-layer co-extruded insulation for rail transit cables. Background Technology

[0002] Power cables and control cables for rail transit vehicles generally employ a double-layer co-extruded insulation structure. The inner insulation material (hereinafter referred to as the inner layer material) provides oil resistance and low-temperature resistance, and is typically an M-grade or F-grade modified polyolefin; the outer insulation material (hereinafter referred to as the outer layer material) provides flame retardancy and fire protection, and is typically a halogen-free, low-smoke flame-retardant polyolefin. Due to their different chemical compositions, the efficiency of radiation-induced free radical generation, the rate of cross-linking reaction, and the degree of side reactions (such as oxidative degradation) all exhibit significant differences. Specifically, the inner layer material is more sensitive to electron beam radiation, and its gel content response curve with increasing dose has a steeper slope; the outer layer material, due to its large content of flame-retardant fillers (such as aluminum hydroxide and magnesium hydroxide), has relatively lower radiation sensitivity and requires a higher dose to achieve the target degree of cross-linking.

[0003] Current irradiation crosslinking processes apply a uniform electron beam dose to double-layer co-extruded insulated core wires, failing to consider the optimal crosslinking degree windows for both inner and outer layer materials. If the optimal dose for the outer flame-retardant material is used as the benchmark, the inner oil-resistant and cold-resistant material, due to its higher radiation sensitivity, undergoes excessive crosslinking, resulting in excessively high inter-chain network density, a significant decrease in material elongation, an increase in low-temperature embrittlement temperature, and deterioration in low-temperature flexibility, posing a risk of insulation layer cracking in the low-temperature operating environment of rail transit vehicles. Conversely, if the optimal dose for the inner layer material is used as the benchmark, the outer flame-retardant material suffers from insufficient crosslinking, an incomplete three-dimensional network structure, reduced high-temperature stability of the flame-retardant char layer, and decreased flame spread suppression capability, failing to meet the highest fire resistance requirements for rail transit vehicle cables in "Railway Applications—Fire Protection for Rail Vehicles—Part 2: Fire Requirements for Materials and Components" (EN 45545-2). Furthermore, current processes lack a mechanism for detecting and providing feedback on the layered gel content of the double-layer structure, leading to significant batch-to-batch deviations in gel content and unstable product qualification rates. Summary of the Invention

[0004] The purpose of this application is to provide a dose control process for irradiation crosslinking of double-layer co-extruded insulation in rail transit cables to solve the problems mentioned in the background art.

[0005] In a first aspect, one embodiment of this application provides a dose control process for irradiation crosslinking of double-layer co-extruded insulation in rail transit cables. This process includes: subjecting the inner and outer insulation materials to multi-dose gradient irradiation and measuring the gel content point-by-point; fitting dose-gel content response curves for the inner and outer insulation materials respectively; determining the effective dose range for the inner layer corresponding to the target gel content window and the effective dose range for the outer layer corresponding to the target gel content window of the inner insulation material based on the two response curves; and determining the interlayer dose ratio coefficient between the irradiated dose of the outer insulation and the irradiated dose of the inner insulation based on the layered energy deposition distribution of the electron beam in the double-layer insulation structure, in order to transmit... A correlation model for the irradiated dose of each layer was established using velocity and beam intensity as process parameters. The effective dose range of the inner layer and the effective dose range of the outer layer were used as constraints. The optimal transmission velocity and optimal beam intensity were solved within the feasible region of the intersection of the two constraints. The double-layer co-extruded insulated core wire was subjected to single electron beam irradiation according to the optimal transmission velocity and optimal beam intensity. After irradiation, the core wire was sampled, and the outer and inner insulation layers at the sampling locations were peeled off separately and the gel content was measured independently. The measured gel content of the outer layer was compared with the target gel content window of the outer layer, and the measured gel content of the inner layer was compared with the target gel content window of the inner layer. The condition that the gel content of both the inner and outer layers continuously met their respective target gel content windows was used as the effective criterion for the optimal transmission velocity and optimal beam intensity.

[0006] In conjunction with the first aspect, in some implementations of the first aspect, the process further includes: when the measured gel content of the inner layer or the measured gel content of the outer layer deviates from their respective target gel content windows, the gel content deviation of each layer is back-calculated into the required dose correction amount for each layer using the dose-gel content response curves of the inner and outer insulating materials; when the dose correction directions of the inner and outer layers are consistent, the overall dose level is corrected by adjusting the transmission speed, and it is verified that the adjusted irradiated doses of the inner and outer layers both fall within their respective effective dose ranges, thus obtaining the updated transmission speed and beam intensity; when the dose correction directions of the inner and outer layers are opposite, the actual value of the interlayer dose ratio coefficient is back-calculated based on the measured gel content of the inner and outer layers, and the optimal transmission speed and optimal beam intensity are re-solved after replacing the interlayer dose ratio coefficient with the actual value, thus obtaining the updated transmission speed and beam intensity; irradiation is re-implemented with the updated transmission speed and beam intensity, and the layered gel content is detected, and the process is iterated until the gel content of both the inner and outer layers continuously meets their respective target gel content windows.

[0007] In conjunction with the first aspect, in certain implementations of the first aspect, the inner and outer insulating materials are subjected to multi-dose gradient irradiation, and the gel content is measured point by point. The dose-gel content response curves of the inner and outer insulating materials are then fitted to obtain the dose-gel content response curves of the inner and outer insulating materials, respectively. This includes: preparing calibration strips independently for the inner and outer insulating materials, with the extrusion process conditions of the two sets of calibration strips consistent with the actual production line; subjecting the two sets of calibration strips to multi-dose gradient irradiation in batches, and measuring the gel content at each irradiation dose point by point according to the dose gradient to obtain the measured data points of the inner and outer insulating materials; and using the irradiation dose as the independent variable and the gel content as the dependent variable, performing curve fitting on the measured data points of the inner and outer insulating materials to obtain the dose-gel content response curves of the inner and outer insulating materials, respectively.

[0008] In conjunction with the first aspect, in certain implementations of the first aspect, the effective dose range of the inner layer corresponding to the target gel content window of the inner layer insulation material and the effective dose range of the outer layer corresponding to the target gel content window of the outer layer insulation material are determined based on two response curves, including: determining the target gel content window of the inner layer insulation material based on the low-temperature flexibility requirements of the inner layer insulation material, determining the target gel content window of the outer layer insulation material based on the flame retardant performance requirements of the outer layer insulation material, and wherein the lower limit of the target gel content window of the outer layer insulation material is higher than the lower limit of the target gel content window of the inner layer insulation material; using the inverse function of the dose-gel content response curve of the inner layer insulation material, solving for the irradiation dose range corresponding to the gel content falling within the target gel content window of the inner layer insulation material, to obtain the effective dose range of the inner layer; using the inverse function of the dose-gel content response curve of the outer layer insulation material, solving for the irradiation dose range corresponding to the gel content falling within the target gel content window of the outer layer insulation material, to obtain the effective dose range of the outer layer.

[0009] In conjunction with the first aspect, in certain implementations of the first aspect, the interlayer dose ratio coefficient between the irradiated dose of the outer layer insulation and the irradiated dose of the inner layer insulation is determined based on the layered energy deposition distribution of the electron beam in the double-layer insulation structure. A correlation model for the irradiated dose of each layer is established using transmission speed and beam current intensity as process parameters. This includes: using particle transport simulation to calculate the energy deposition distribution of the electron beam in the thickness direction of the double-layer insulation structure; taking the ratio of the energy deposition value at the midpoint depth of the outer layer insulation to the energy deposition value at the midpoint depth of the inner layer insulation to obtain the interlayer dose ratio coefficient; establishing a correlation model for the irradiated dose of the outer layer insulation proportional to the ratio of beam current intensity to transmission speed; and using the interlayer dose ratio coefficient to express the irradiated dose of the inner layer insulation as the irradiated dose of the outer layer insulation divided by the interlayer dose ratio coefficient, so that the irradiated doses of both the inner and outer layers are uniquely determined by the same set of transmission speed and beam current intensity.

[0010] In conjunction with the first aspect, in some implementations of the first aspect, the effective dose range of the inner layer and the effective dose range of the outer layer are used as constraints. The optimal transmission speed and optimal beam intensity are solved within the feasible region of the intersection of the two constraints. This includes: using an association model to transform the effective dose range of the inner layer and the effective dose range of the outer layer into constraint ranges for the ratio of beam intensity to transmission speed, and taking the intersection of the two constraint ranges as the feasible region; if the feasible region is empty, it is determined that there are no process parameters that simultaneously satisfy the gel content targets of the inner and outer layers under the current combination of double-layer insulation wall thickness and accelerator energy. After adjusting the wall thickness design or accelerator energy, the interlayer dose ratio coefficient is re-determined and the feasible region is solved again; if the feasible region is not empty, the ratio of beam intensity to transmission speed that minimizes the sum of the deviation of the inner layer insulation gel content from the center value of the inner layer target gel content window and the deviation of the outer layer insulation gel content from the center value of the outer layer target gel content window is taken within the feasible region. The optimal transmission speed and optimal beam intensity are calculated in conjunction with the maximum transmission speed allowed by the equipment.

[0011] In conjunction with the first aspect, in certain implementations of the first aspect, the optimal transmission speed and optimal beam intensity are determined by the continuous satisfaction of the inner and outer layer gel contents within their respective target gel content windows. This includes: determining the sampling location for the same batch of irradiated core wires at a frequency of sampling one sample per fixed length, and adding forced sampling points at core wire locations where the transmission speed or beam intensity exceeds their respective deviation thresholds during irradiation; taking core wire samples at each sampling location, cutting along the longitudinal direction of the outer insulation to completely peel off the outer insulation to obtain the outer layer test sample, and then peeling the inner insulation from the conductor to obtain the inner layer test sample; measuring the gel content of the outer layer test sample and the inner layer test sample respectively, comparing the measured gel content of the outer layer with the outer layer target gel content window, and comparing the measured gel content of the inner layer with the inner layer target gel content window; and using the condition that the measured gel content of the inner layer and the measured gel content of the outer layer at three or more consecutive sampling locations of non-forced sampling points in the same batch fall within their respective target gel content windows as the optimal transmission speed and optimal beam intensity determination condition, otherwise triggering parameter iterative correction.

[0012] In conjunction with the first aspect, in certain implementations of the first aspect, the dose-gel content response curves of the inner and outer insulating materials are used to back-calculate the gel content deviation of each layer into the required dose correction for each layer. This includes: calculating the inner layer deviation between the measured gel content of the inner layer and the center value of the target gel content window, and the outer layer deviation between the measured gel content of the outer layer and the center value of the target gel content window; using the inverse function of the dose-gel content response curve of the inner insulating material, the inner layer deviation is back-calculated into the required dose correction for the inner layer; using the inverse function of the dose-gel content response curve of the outer insulating material, the outer layer deviation is back-calculated into the required dose correction for the outer layer; when the inner or outer layer deviation is positive, it indicates that the corresponding layer is over-crosslinked and the irradiated dose needs to be reduced; when it is negative, it indicates that the corresponding layer is under-crosslinked and the irradiated dose needs to be increased.

[0013] In conjunction with the first aspect, in certain implementations of the first aspect, irradiation is re-implemented with updated transmission speed and beam current intensity, and the layered gel content is detected. This process is iterated until the gel content of both the inner and outer layers continuously meets their respective target gel content windows. This includes: re-implementing a single electron beam irradiation on subsequent batches of core wires with updated transmission speed and beam current intensity, sampling the irradiated core wires, and independently measuring the gel content of the outer and inner insulation layers at the sampling locations after peeling them off. The measured gel content of the outer layer is compared with the target gel content window of the outer layer, and the measured gel content of the inner layer is compared with the target gel content window of the inner layer. If the gel content of both the inner and outer layers continuously meets their respective target gel content windows, then the updated transmission speed and beam current intensity are incorporated into the current double-layer insulation wall thickness specification process. The parameter database serves as the baseline parameter for subsequent batches. If the gel content of the inner and outer layers still deviates, the gel content deviation of each layer is recalculated using the dose-gel content response curves of the inner and outer insulation materials to obtain the required dose correction for each layer. The updated transmission speed and beam intensity are then determined based on the dose correction directions of the inner and outer layers for the next iteration. If the gel content of the inner and outer layers still cannot continuously meet their respective target gel content windows after more than three iterations, it is determined that the material radiation response is abnormal. The inner and outer insulation materials of the current batch are then recalibrated with multi-dose gradient irradiation, and the dose-gel content response curves of the inner and outer insulation materials are refitted.

[0014] In conjunction with the first aspect, in certain implementations of the first aspect, a single electron beam irradiation is performed on the double-layer co-extruded insulated core wire according to the optimal transmission speed and optimal beam current intensity. This includes: before irradiation, online measurement of the outer and inner insulation wall thicknesses of the currently produced core wire; if the deviation between the measured values ​​of the outer or inner insulation wall thickness and the specified values ​​exceeds the allowable range, recalculating the interlayer dose ratio coefficient based on the measured values ​​of the outer and inner insulation wall thicknesses, and resolving the optimal transmission speed and optimal beam current intensity using the updated interlayer dose ratio coefficient; during the irradiation process, the transmission speed and beam current intensity are collected in real time. The actual values ​​are calculated and the deviations from the optimal transmission speed and optimal beam intensity are calculated separately. When the deviation of the transmission speed or the deviation of the beam intensity exceeds their respective deviation thresholds, the corresponding core wire position is marked. The marked position is included in the mandatory sampling range in the layered gel content detection after irradiation. For core wires with a total wall thickness of double insulation that exceeds the allowable thickness for single irradiation dose uniformity, the cumulative irradiated dose of the inner and outer layers is symmetrically superimposed by irradiating both sides once. The interlayer dose ratio coefficient is recalculated based on the layered irradiated dose after the two irradiations are superimposed. The optimal transmission speed and optimal beam intensity are then resolved based on the updated interlayer dose ratio coefficient.

[0015] Compared with the prior art, the beneficial effects of this application are:

[0016] 1. This application establishes separate dose-gel content response curves for the inner and outer insulation materials, and performs dual-constraint optimization by using the effective dose range of the inner and outer layers as constraints. In a single electron beam irradiation, the gel content of the inner and outer insulation layers is controlled within their respective target gel content windows. This overcomes the inherent defects of existing uniform dose processes that irradiate double-layer co-extruded insulated core wires with a single dose, which cannot simultaneously meet the low-temperature flexibility requirements of the inner layer and the flame-retardant performance requirements of the outer layer. This enables the product to simultaneously meet the low-temperature flexibility requirements and fire resistance requirements of rail transit vehicle cables.

[0017] 2. This application independently measures the gel content after peeling off the outer and inner insulation layers of the irradiated core wire. The deviation of the measured gel content of each layer is calculated by using the inverse function of the response curve of each layer to obtain the required dose correction amount for each layer. Based on the dose correction direction of the inner and outer layers, the application adopts the overall dose adjustment or interlayer dose ratio coefficient correction strategy to perform parameter iterative correction. This effectively compensates for the influence of material batch fluctuations on radiation sensitivity and overcomes the problems of existing processes lacking a layer detection and feedback mechanism for double-layer structures, large batch-to-batch gel content deviations, and unstable product qualification rates. Attached Figure Description

[0018] Figure 1 A schematic diagram of the process for controlling the irradiation crosslinking dosage of double-layer co-extruded insulation for rail transit cables provided in an embodiment of this application; Figure 2 This is a schematic diagram of the process for controlling the irradiation crosslinking dosage of double-layer co-extruded insulation for rail transit cables, provided in another embodiment of this application. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] Figure 1 This is a schematic flowchart illustrating the irradiation crosslinking dosage control process for double-layer co-extruded insulation of rail transit cables, as provided in one embodiment of this application. Figure 1 As shown in the figure, an embodiment of this application provides a radiation crosslinking dosage control process for double-layer co-extruded insulation of rail transit cables, which includes the following steps: Step 101: Perform multi-dose gradient irradiation on the inner and outer insulating materials respectively and measure the gel content point by point. Fit the dose-gel content response curve of the inner insulating material and the dose-gel content response curve of the outer insulating material respectively. Based on the two response curves, determine the effective dose range of the inner layer corresponding to the target gel content window of the inner insulating material and the effective dose range of the outer layer corresponding to the target gel content window of the outer insulating material respectively.

[0021] It should be understood that the inner insulation material refers to the material used in the inner insulation layer that is close to the conductor in the double co-extruded insulation structure. It is responsible for oil resistance and low temperature resistance, and is usually a modified polyolefin.

[0022] The outer insulation material refers to the material used in the outer insulation layer of a double-layer co-extruded insulation structure. It undertakes the function of flame retardancy and fire prevention and is usually a halogen-free, low-smoke flame-retardant polyolefin.

[0023] Multi-dose gradient irradiation refers to a calibration experiment method in which different irradiation doses are applied sequentially at fixed steps within a set dose range to obtain full-dose range data of the material's radiation response.

[0024] Gel content refers to the percentage of the mass of the cross-linked network that is insoluble in solvent after irradiation cross-linking, which is a quantitative indicator of the degree of cross-linking.

[0025] The dose-gel content response curve is a quantitative relationship curve obtained by fitting the irradiation dose as the independent variable and the gel content as the dependent variable, which reflects the radiation crosslinking sensitivity of a specific material.

[0026] The target gel content window refers to the acceptable range of gel content determined according to the performance requirements of each layer of insulation material. The inner layer is determined based on the low-temperature flexibility requirements, and the outer layer is determined based on the flame retardant performance requirements.

[0027] The effective dose range refers to the irradiation dose range that makes the gel content of the corresponding layer of insulating material fall within the target gel content window, and is obtained by solving the inverse function of the response curve.

[0028] Step 102: Determine the interlayer dose ratio coefficient between the irradiated dose of the outer insulation layer and the irradiated dose of the inner insulation layer based on the layered energy deposition distribution of the electron beam in the double-layer insulation structure. Establish a correlation model of the irradiated dose of each layer using transmission speed and beam current intensity as process parameters. Simultaneously use the effective dose range of the inner layer and the effective dose range of the outer layer as constraints, and solve for the optimal transmission speed and optimal beam current intensity within the feasible region of the intersection of the two constraints.

[0029] It should be understood that the layered energy deposition distribution refers to the spatial distribution of energy deposited at various depths when an electron beam penetrates along the thickness direction of a double-layer insulating structure, which is obtained by particle transport simulation calculation.

[0030] The interlayer dose ratio coefficient refers to the ratio of the irradiated dose at the midpoint depth of the outer insulation layer to the irradiated dose at the midpoint depth of the inner insulation layer. It quantitatively characterizes the difference in dose between the inner and outer layers caused by the different penetration depths of the electron beam in a double-layer structure.

[0031] The correlation model refers to a quantitative model that uses transmission speed and beam intensity as process parameters and expresses the radiation dose of the inner and outer layers as the same set of process parameter functions through the interlayer dose ratio coefficient.

[0032] Transmission speed refers to the linear velocity of the core wire as it passes through the electron beam irradiation area. Its magnitude determines the residence time of the core wire in the beam region, which in turn affects the irradiated dose.

[0033] Beam intensity refers to the beam current value output by an electron beam accelerator. Its magnitude determines the energy deposited in the material per unit time, and thus affects the irradiation dose.

[0034] The feasible region refers to the parameter space corresponding to the intersection of the constraint ranges of the inner and outer effective dose ranges after both are simultaneously transformed into constraints on the ratio of beam intensity to transmission speed.

[0035] The optimal transmission speed and optimal beam intensity refer to the optimal pair of process parameters within the feasible region that simultaneously bring the gel content of the inner and outer layers as close as possible to the center value of their respective target gel content windows while also taking into account production efficiency.

[0036] Step 103: Perform a single electron beam irradiation on the double-layer co-extruded insulated core wire at the optimal transmission speed and optimal beam current intensity.

[0037] It should be understood that double-layer co-extruded insulated core wire refers to a cable core wire with a double-layer insulation structure formed by simultaneously coating the inner and outer insulation materials onto the outer surface of the conductor through a co-extrusion process.

[0038] Single electron beam irradiation refers to applying an electron beam to the core wire only once in the same irradiation process. By precisely controlling the optimal process parameters, the target cross-linking degree of the inner and outer layers can be achieved simultaneously, which is different from the multi-stage irradiation process.

[0039] Step 104: Sample the core wire after irradiation, peel off the outer and inner insulation layers at the sampling locations and measure the gel content independently, compare the measured gel content of the outer layer with the target gel content window, and compare the measured gel content of the inner layer with the target gel content window. The condition that the gel content of both the inner and outer layers continuously meets their respective target gel content windows is used as an effective criterion for determining the optimal transmission speed and optimal beam intensity.

[0040] It should be understood that separate peeling refers to peeling the outer insulation layer and the inner insulation layer separately and sequentially after longitudinal slicing, so that the two test samples do not mix, thereby enabling independent determination of the gel content of each layer.

[0041] The measured gel content of the outer layer and the measured gel content of the inner layer refer to the measured gel content obtained by independently determining the gel content of the outer layer test sample and the inner layer test sample according to the xylene extraction method specified in GB / T 18950.

[0042] Continuous satisfaction means that the gel content of the inner and outer layers of three or more consecutive sampling locations at non-mandatory sampling points in the same batch all fall within their respective target gel content windows, in order to eliminate the interference of occasional sample deviations on the determination of parameter validity.

[0043] This embodiment establishes dose-gel content response curves for both inner and outer layer materials and solves for optimal process parameters using a dual-constraint optimization method. In a single electron beam irradiation, it simultaneously achieves the target crosslinking degree required for both the low-temperature flexibility of the inner layer and the flame retardant performance of the outer layer in the double-layer co-extruded insulation. The effectiveness of the parameters is verified by layered gel content detection, thus solving the problem that existing uniform dose processes cannot simultaneously take into account the optimal crosslinking degree window for both inner and outer layer materials.

[0044] Figure 2 This is a schematic flowchart illustrating the irradiation crosslinking dosage control process for double-layer co-extruded insulation of rail transit cables, provided as another embodiment of this application. Figure 2 As shown in the figure, the irradiation crosslinking dosage control process for double-layer co-extruded insulation of rail transit cables provided in one embodiment of this application further includes the following steps: Step 201: When the measured gel content of the inner layer or the measured gel content of the outer layer deviates from their respective target gel content windows, the gel content deviation of each layer is back-calculated into the required dose correction amount for each layer using the dose-gel content response curve of the inner layer insulation material and the dose-gel content response curve of the outer layer insulation material.

[0045] Specifically, when the measured gel content of the inner layer or the measured gel content of the outer layer deviates from their respective target gel content windows, the inner layer deviation between the measured gel content of the inner layer and the center value of the inner layer target gel content window is calculated respectively. And the outer layer deviation between the measured gel content of the outer layer and the center value of the target gel content window of the outer layer. When the inner or outer layer deviation is positive, it indicates that the corresponding layer is over-crosslinked and the radiation dose needs to be reduced; when it is negative, it indicates that the corresponding layer is under-crosslinked and the radiation dose needs to be increased. The inverse function of the dose-gel content response curve of the inner layer insulation material is used. The inner layer deviation is then converted into the required dose correction for the inner layer. The inverse function of the dose-gel content response curve of the outer insulating material was used. The outer layer deviation is then converted into the required dose correction for the outer layer. The specific calculation formula is as follows: ; ; in, This represents the center value of the inner layer target gel content window. This represents the center value of the outer layer target gel content window. This represents the measured gel content of the inner layer. This represents the measured gel content of the outer layer.

[0046] Step 202: When the inner and outer layer dose correction directions are consistent, the overall dose level is corrected by adjusting the transmission speed, and it is verified that the adjusted inner and outer layer irradiation doses fall within their respective effective dose ranges, thus obtaining the updated transmission speed and beam intensity.

[0047] Specifically, when the dosage correction directions of the inner and outer layers are consistent, that is... and The same sign indicates that the overall dose of the inner and outer layers is too high or too low. The overall dose level is corrected by adjusting the transmission speed to maintain the beam intensity. Unchanged, transmission speed correction amount Calculate using the following formula: ; in, For optimal transmission speed, , For the optimal pair of process parameters, For device constants, The design radiation dose for the outer insulation in step 102; the updated transmission speed. With the updated transmission speed and original beam intensity Calculate the radiation dose to the inner layer and verify whether it falls within the effective dose range for the inner layer. If the verification passes, then... and The updated transmission speed and beam intensity are used as the basis for the updated calculation. If the verification fails, the double-constraint optimization is re-executed with the updated interlayer dose ratio coefficient to obtain the updated transmission speed and beam intensity.

[0048] Step 203: When the inner and outer layer dose correction directions are opposite, the actual value of the interlayer dose ratio coefficient is calculated based on the measured gel content of the inner and outer layers. The actual value is used to replace the interlayer dose ratio coefficient, and the optimal transmission speed and optimal beam intensity are solved again to obtain the updated transmission speed and beam intensity.

[0049] Specifically, when the dosage correction directions of the inner and outer layers are opposite, that is... and The opposite sign indicates a discrepancy between the actual value of the interlayer dose ratio coefficient (the ratio of the irradiated dose of the outer insulation layer to the irradiated dose of the inner insulation layer) and the calculated value used when establishing the correlation model. Simply adjusting the transmission speed or beam intensity cannot simultaneously improve the discrepancy between the two layers. Based on the measured gel content of the inner and outer layers, the actual irradiated doses of each layer are calculated using the inverse function of their respective dose-gel content response curves. The ratio of these two values ​​yields the actual value of the interlayer dose ratio coefficient. : ; by Replace the interlayer dose ratio coefficient in the correlation model, re-execute the double-constraint optimization to solve for the optimal transmission velocity and optimal beam intensity, obtain the updated transmission velocity and beam intensity, and then... Update the process parameter database to the current specification, and use the value as the interlayer dose ratio coefficient for subsequent batches.

[0050] Step 204: Irradiate again with the updated delivery speed and beam intensity and detect the layered gel content. Repeat this process until the gel content of both the inner and outer layers continuously meets their respective target gel content windows.

[0051] Specifically, subsequent batches of core wires are subjected to a single electron beam irradiation with the updated transmission speed and beam current intensity. Samples are taken from the irradiated core wires, and the outer and inner insulation layers at the sampling locations are peeled off separately, with the gel content measured independently. The measured gel content of the outer layer is compared with the target gel content window, and the measured gel content of the inner layer is compared with the target gel content window. If the gel content of both the inner and outer layers continuously meets their respective target gel content windows, the updated transmission speed and beam current intensity are written into the current double-insulation wall thickness specification's process parameter database as the benchmark parameters for subsequent batches. If there are still deviations in the gel content of the inner and outer layers, step 201 is repeated. The deviation of gel content in each layer is used to back-calculate the required dose correction for each layer using the dose-gel content response curves of the inner and outer insulating materials. The updated transmission speed and beam intensity are then determined based on the dose correction directions of the inner and outer layers, and the next iteration is performed. If the gel content of the inner and outer layers still cannot continuously meet their respective target gel content windows after more than three iterations, it is determined that the material radiation response is abnormal. The inner and outer insulating materials of the current batch are then recalibrated with multi-dose gradient irradiation, and the dose-gel content response curves of the inner and outer insulating materials are refitted.

[0052] Furthermore, calibration samples were prepared independently using inner and outer insulation materials respectively. The extrusion temperature profiles, screw speeds, and die pressures of the two sets of calibration samples were kept consistent with those of the actual production line to ensure that the material morphology of the calibration samples was the same as that of the insulation layer material of the actual produced core wire. The two sets of calibration samples had to be prepared independently in batches, rather than being irradiated together, to avoid the mutual shielding of the beam by the materials in the superimposed state affecting the accuracy of the actual received dose of each layer.

[0053] Two sets of calibration strips were subjected to multi-dose gradient irradiation in batches. The gel content was measured point by point at each irradiation dose according to the dose gradient, obtaining the measured data points of the inner insulation material and the outer insulation material. The gel content was determined according to the xylene extraction method specified in GB / T 18950, with the irradiation dose as the criterion. (kGy) represents the abscissa and gel content. (%) is used as the vertical axis, and the measured values ​​of gel content of inner and outer insulating materials at each dosage point are recorded point by point.

[0054] Using irradiation dose as the independent variable and gel content as the dependent variable, curve fitting was performed on the measured data points of the inner and outer insulation materials, respectively. The fitting adopted the Sigmoid function form to obtain the dose-gel content response curves of the inner and outer insulation materials. The specific expressions are as follows: ; ; in, , The gel content saturation values ​​(%) of the inner and outer insulating materials are respectively. , For each of the response curves, the growth rate coefficient is... This reflects the fundamental difference that the inner layer insulation material is more sensitive to radiation than the outer layer insulation material. , The dose (kGy) corresponding to the half-maximum gel content of each response curve is given; all the above parameters are determined by nonlinear least squares fitting of the measured data points.

[0055] Furthermore, the target gel content window for the inner layer insulation material is determined based on the low-temperature flexibility requirements of the inner layer insulation material, and the target gel content window for the outer layer insulation material is determined based on the flame retardant performance requirements of the outer layer insulation material. The lower limit of the target gel content window for the outer layer insulation material is higher than the lower limit of the target gel content window for the inner layer insulation material. The upper limit of the target gel content window for the inner layer insulation material is set based on the following: when the gel content exceeds this limit, the cross-linking network density of the inner modified polyolefin is too high, the degree of restriction on chain segment movement exceeds the range tolerable by low-temperature flexibility, and the low-temperature elongation at break begins to decrease significantly. The lower limit of the target gel content window for the outer layer insulation material is set based on the following: when the gel content is below this limit, the high-temperature mechanical stability of the char layer formed by the outer halogen-free flame retardant material under combustion conditions is insufficient, the char layer is prone to cracking and falling off at high temperatures, affecting the flame retardant persistence and failing to meet the fire resistance requirements of rail transit vehicle cables.

[0056] Using the inverse function of the dose-gel content response curve of the inner insulating material The irradiation dose range corresponding to the gel content falling within the target gel content window of the inner insulating material is determined. The target gel content window for the inner material is set to 70%–80%, and the corresponding effective dose range is: ; in, , These represent the lower and upper limits of the target gel content window for the inner insulating material, respectively.

[0057] Using the inverse function of the dose-gel content response curve of the outer insulating material The irradiation dose range corresponding to the gel content falling within the target gel content window of the outer insulating material is determined. The target gel content window for the outer material is set to 75%–85%, and the corresponding effective dose range is as follows: ; in, , These represent the lower and upper limits of the target gel content window for the outer insulating material, respectively.

[0058] Furthermore, particle transport simulations were used to calculate the energy deposition distribution of the electron beam along the thickness of the double-layer insulation structure. The ratio of the energy deposition value at the midpoint depth of the outer insulation layer to that at the midpoint depth of the inner insulation layer was used to obtain the interlayer dose ratio coefficient. Specifically: ; The outer insulation layer receives the irradiation first and has slightly higher energy deposition, while the inner insulation layer, being located deeper, has slightly lower energy deposition. Interlayer dose ratio coefficient The typical value range is 1.05 to 1.30, and the greater the thickness of the outer insulation wall, the higher the value. The larger the value, the more significant the shielding effect of the outer insulation layer on the inner insulation layer; for different combinations of outer insulation wall thickness and accelerator energy, a pre-established... The value lookup table is obtained through interpolation during actual process calculations.

[0059] A correlation model for the radiation dose received by the outer insulation layer is established, which is proportional to the ratio of beam current intensity to transmission speed. Specifically: ; in, For device constants ( The comprehensive effect of the inherent parameters of the equipment and materials, such as accelerator energy, beam cross-sectional area and material density, is determined by the equipment calibration experiment. The beam current intensity is (mA). The transmission speed (m / min) is used; and the interlayer dose ratio coefficient is utilized. The radiation dose to the inner insulation layer is expressed as the radiation dose to the outer insulation layer divided by the interlayer dose ratio coefficient, specifically: ; Therefore, the radiation dose received by the outer insulation layer and the radiation dose of the inner insulation All use the same set of transmission speeds and beam intensity and known quantities , The only certainty is the interlayer dose ratio coefficient between the two. coupling.

[0060] Furthermore, using a correlation model, the inner and outer effective dose ranges are transformed into constraint ranges for the ratio of beam intensity to transmission velocity, respectively. Then, according to the outer layer radiation dose correlation model The range of the outer constraint can be obtained as follows: ; Inner layer radiation dose correlation model The range of inner constraints can be obtained as follows: ; The feasible region is the intersection of the two constraints. ; If the feasible region is empty, meaning the lower limit of the above intersection is greater than the upper limit, then it is determined that there are no process parameters that can simultaneously meet the gel content targets of the inner and outer layers under the current combination of double-layer insulation wall thickness and accelerator energy. The wall thickness design or accelerator energy needs to be adjusted. After adjustment, the interlayer dose ratio coefficient is recalculated using particle transport simulation with the updated outer and inner insulation wall thicknesses. and with the updated inter-layer dose ratio coefficient Resolve the above feasible region until the feasible region is non-empty.

[0061] If the feasible region is not empty, then the optimal ratio of beam intensity to transmission speed is selected within the feasible region. , The goal is to minimize the sum of the deviations of the inner layer insulation gel content from the center of the inner layer target gel content window and the deviations of the outer layer insulation gel content from the center of the outer layer target gel content window. Specifically: ; in, This represents the center value of the inner layer target gel content window. The value is the center value of the outer layer target gel content window; within the equipment's allowable range, the highest allowable transfer speed is preferred. As the optimal transmission speed The optimal beam intensity is obtained by combining x. Output optimal transmission speed and optimal beam intensity As an execution parameter for irradiation processing.

[0062] Furthermore, for the same batch of irradiated core wires, the sampling location is determined according to the basic frequency of sampling one sample per fixed length; and the actual values ​​of transmission speed and beam intensity are collected in real time during the irradiation process. When the deviation of transmission speed or beam intensity exceeds its respective deviation threshold, the corresponding core wire position is marked, and a forced sampling point is added at the marked position; forced sampling points are also added at the beginning and end of the batch to cover the transient fluctuation area of ​​parameters that may exist during the irradiation start-up and shutdown phases; the final sampling location list is generated by combining the above rules, and the precise core wire length coordinates of each sample are recorded.

[0063] For each sampling location, take a core wire sample of no less than 100 mm in length. First, use a special wire stripping tool to longitudinally cut along the outer insulation layer, controlling the cutting depth to within 90% of the outer insulation wall thickness to avoid damaging the inner insulation layer. Then, completely peel off the outer insulation layer along the cut line and collect it as the outer layer test sample. Next, peel the inner insulation layer off the conductor and collect it as the inner layer test sample. Weigh the two sets of test samples separately, with a total mass of no less than 200 mg for each set, to meet the sample quantity requirements for gel content determination.

[0064] The gel content of the outer and inner layer test samples was determined by the xylene extraction method specified in GB / T 18950, respectively, and the measured gel content of the outer layer was obtained. and the measured gel content of the inner layer The measured gel content of the outer layer is compared with the target gel content window of the outer layer, and the measured gel content of the inner layer is compared with the target gel content window of the inner layer. The determination of the sample corresponding to the forced sampling point is the same as that of the regular sampling point. If the gel content of both the inner and outer layers of the sample at the forced sampling point is within their respective target gel content windows, the core wire at that position is judged to be qualified. If it is not qualified, the core wire segment is isolated.

[0065] The optimal transmission speed and optimal beam intensity are determined to be valid if the measured gel content of the inner layer and the measured gel content of the outer layer at three or more consecutive sampling locations of non-mandatory sampling points in the same batch all fall within their respective target gel content windows. If the above determination conditions are met, the current optimal transmission speed and optimal beam intensity are confirmed to be valid, and all core wires corresponding to the non-mandatory sampling points in this batch are judged to be qualified; otherwise, parameter iterative correction is triggered.

[0066] Furthermore, the measured gel content of the inner layer was calculated separately. Center value of inner layer target gel content window Inner layer deviation and the measured gel content of the outer layer Center value of outer target gel content window outer layer deviation Specifically: ; ; Using the inverse function of the dose-gel content response curve of the inner insulating material The inner layer deviation is then converted into the required dose correction for the inner layer. Specifically: ; Using the inverse function of the dose-gel content response curve of the outer insulating material The outer layer deviation is then converted into the required dose correction for the outer layer. Specifically: ; Inner layer deviation Or outer layer deviation When the value is positive, it indicates that the corresponding layer is over-crosslinked and the radiation dose needs to be reduced; the corresponding dose correction amount is... Negative value; inner layer deviation Or outer layer deviation A negative value indicates insufficient cross-linking of the corresponding layer, requiring an increase in the irradiation dose; the corresponding dose correction amount is... It is a positive value; the dosage correction amount required for the inner layer is as described above. and the required dose correction for the outer layer The directional relationship serves as the basis for determining the subsequent parameter correction strategy.

[0067] Furthermore, subsequent batches of core wires are subjected to a single electron beam irradiation with the updated transmission speed and beam intensity. After irradiation, the core wires are sampled according to the aforementioned sampling method. The outer and inner insulation layers at the sampling locations are stripped separately, and the gel content is measured independently. The measured gel content of the outer layer is compared with the target gel content window of the outer layer, and the measured gel content of the inner layer is compared with the target gel content window of the inner layer. The qualification judgment rule is consistent with the above, and the condition for parameter stability is that the measured gel content of the inner layer and the measured gel content of the outer layer at three or more consecutive sampling locations of non-mandatory sampling points in the same batch all fall within their respective target gel content windows.

[0068] If the gel content of both the inner and outer layers continuously meets their respective target gel content windows, the updated delivery speed and beam intensity will be written into the process parameter database of the current double-layer insulation wall thickness specification. The updated delivery speed and beam intensity will replace the original optimal delivery speed and optimal beam intensity as the benchmark parameters for subsequent batches of irradiation processing of this specification.

[0069] If the gel content of the inner and outer layers still deviates, the gel content deviation of each layer is recalculated using the inverse function of the dose-gel content response curve of the inner layer insulation material and the inverse function of the dose-gel content response curve of the outer layer insulation material to obtain the required dose correction amount for each layer in this iteration. and the required dose correction for the outer layer ;like and If the signals are the same, the overall dose level is corrected by adjusting the transmission speed, while maintaining the beam intensity. It is then verified that the adjusted doses to both the inner and outer layers fall within their respective effective dose ranges, thus obtaining the updated transmission speed and beam intensity for this iteration. If... and If the signs are different, the actual value of the interlayer dose ratio coefficient is calculated based on the measured gel content of the inner and outer layers. The actual value is used to replace the interlayer dose ratio coefficient, and the double-constraint optimization solution is re-executed to obtain the transmission speed and beam intensity after this iteration. The transmission speed and beam intensity after this iteration are used to enter the next round of irradiation and detection iteration.

[0070] If the gel content of the inner and outer layers still cannot continuously meet their respective target gel content windows after more than three iterations, it is determined that the material radiation response is abnormal. That is, the radiation sensitivity of the inner or outer insulation material of the current batch has deviated from the dose-gel content response curve obtained by the original calibration, and the parameter iteration correction mechanism has failed. At this time, the inner and outer insulation materials of the current batch are recalibrated by multi-dose gradient irradiation according to the aforementioned calibration procedure. The gel content is measured point by point according to the dose gradient. The dose-gel content response curves of the inner and outer insulation materials are refitted. The original calibration curve in the process parameter database is replaced with the recalibrated response curve. The dual-constraint optimization is re-executed to solve for the optimal transmission speed and the optimal beam intensity.

[0071] Furthermore, before irradiation, the thickness of the outer and inner insulation layers of the current production core wire is measured online using an online diameter measuring instrument. If the measured value of the outer or inner insulation layer thickness deviates from the specified value beyond the allowable range, the interlayer dose ratio coefficient is recalculated using particle transport simulation based on the measured values ​​of the outer and inner insulation layer thicknesses. The double-constraint optimization solution is then re-executed with the updated interlayer dose ratio coefficient, and the optimal transmission speed and optimal beam intensity are updated before irradiation can be initiated. If the deviation between the measured wall thickness and the specified value is within the allowable range, irradiation is initiated directly according to the optimal transmission speed and optimal beam intensity stored in the process parameter database.

[0072] During irradiation, the actual values ​​of transmission velocity and beam intensity are collected in real time at a sampling frequency of not less than 10Hz, and the deviation between the actual transmission velocity and the optimal transmission velocity is calculated. and the deviation between the actual beam intensity and the optimal beam intensity : ; ; When the transmission speed deviates Or beam intensity deviation When the deviation exceeds their respective thresholds, it is preferable to... or The system automatically alarms and marks the core wire position corresponding to that moment. All core wire segments corresponding to that moment are included in the marking range during the alarm duration. The marked position is included in the mandatory sampling range for the layered gel content detection after irradiation and is recorded separately in the batch quality file. For specifications with insufficient process window margin, the deviation threshold is further tightened based on the standard value to ensure the dosage control accuracy under that specification.

[0073] For core wires with a total wall thickness exceeding the allowable thickness for dose uniformity in a single irradiation, a method of irradiating both sides once is adopted. This allows the core wire to be rotated 180° by a guiding device during transmission and then pass through the beam region again, ensuring that the cumulative irradiated doses of the inner and outer layers are symmetrically superimposed, thereby reducing the degree of dose non-uniformity between the inner and outer layers caused by the electron beam energy deposition distribution pattern. For the case of double-sided irradiation, the interlayer dose ratio coefficient is recalculated based on the ratio of the cumulative irradiated doses of each layer after the two irradiations are superimposed. The ratio of the total irradiated dose of the outer layer to the total irradiated dose of the inner layer after the superposition of the doses of each layer in the two irradiations is taken as the updated interlayer dose ratio coefficient. The optimal transmission speed and optimal beam intensity are then re-solved using the updated interlayer dose ratio coefficient and the dual-constraint optimization is performed again.

[0074] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A dosage control process for irradiation crosslinking of double-layer co-extruded insulation in rail transit cables, characterized in that, include: The inner and outer insulating materials were subjected to multi-dose gradient irradiation and the gel content was measured point by point. The dose-gel content response curves of the inner and outer insulating materials were obtained by fitting the two response curves respectively. Based on the two response curves, the effective dose range of the inner layer corresponding to the target gel content window of the inner insulating material and the effective dose range of the outer layer corresponding to the target gel content window of the outer insulating material were determined respectively. Based on the layered energy deposition distribution of the electron beam in the double-layer insulation structure, the interlayer dose ratio coefficient between the irradiated dose of the outer layer insulation and the irradiated dose of the inner layer insulation is determined. The correlation model of the irradiated dose of each layer is established with the transmission speed and beam current intensity as process parameters. The effective dose range of the inner layer and the effective dose range of the outer layer are used as constraints. The optimal transmission speed and the optimal beam current intensity are solved in the feasible region of the intersection of the two constraints. The double-layer co-extruded insulated core wire is subjected to single electron beam irradiation at the optimal transmission speed and the optimal beam current intensity. After irradiation, the core wire is sampled, and the outer and inner insulation layers at the sampling locations are peeled off separately and the gel content is measured independently. The measured gel content of the outer layer is compared with the target gel content window of the outer layer, and the measured gel content of the inner layer is compared with the target gel content window of the inner layer. The condition that the gel content of both the inner and outer layers continuously meets their respective target gel content windows is used as the effective judgment condition for the optimal transmission speed and the optimal beam intensity. When the measured gel content of the inner layer or the measured gel content of the outer layer deviates from the respective target gel content window, the gel content deviation of each layer is back-calculated into the required dose correction amount for each layer using the dose-gel content response curve of the inner layer insulation material and the dose-gel content response curve of the outer layer insulation material. When the inner and outer layer dose correction directions are consistent, the overall dose level is corrected by adjusting the transmission speed, and it is verified that the adjusted inner and outer layer irradiation doses fall within their respective effective dose ranges, thus obtaining the updated transmission speed and beam intensity. When the inner and outer layer dose correction directions are opposite, the actual value of the interlayer dose ratio coefficient is back-calculated based on the measured gel content of the inner and outer layers. The actual value is used to replace the interlayer dose ratio coefficient, and the optimal transmission speed and optimal beam intensity are re-solved to obtain the updated transmission speed and beam intensity. Irradiation is re-implemented with the updated transmission speed and beam intensity, and the layered gel content is detected. This process is repeated until the gel content of both the inner and outer layers continuously meets their respective target gel content windows.

2. The process according to claim 1, characterized in that, The process involves subjecting the inner and outer insulation materials to multi-dose gradient irradiation and measuring the gel content point-by-point, respectively. Dose-gel content response curves for the inner and outer insulation materials are then fitted to obtain the respective curves. Calibration strips were prepared independently using inner and outer insulation materials, and the extrusion process conditions of the two sets of calibration strips were kept consistent with those of the actual production line. The two sets of calibration strips were subjected to multi-dose gradient irradiation in batches, and the gel content was measured point by point under each irradiation dose according to the dose gradient to obtain the measured data points of the inner layer insulation material and the measured data points of the outer layer insulation material. Using irradiation dose as the independent variable and gel content as the dependent variable, curve fitting was performed on the measured data points of the inner insulating material and the measured data points of the outer insulating material to obtain the dose-gel content response curves of the inner insulating material and the outer insulating material.

3. The process according to claim 2, characterized in that, The step of determining the effective dose range of the inner layer corresponding to the target gel content window of the inner layer insulation material and the effective dose range of the outer layer insulation material corresponding to the target gel content window of the outer layer insulation material based on the two response curves includes: The target gel content window of the inner layer insulation material is determined based on the low-temperature flexibility requirements of the inner layer insulation material, and the target gel content window of the outer layer insulation material is determined based on the flame retardant performance requirements of the outer layer insulation material. The lower limit of the target gel content window of the outer layer insulation material is higher than the lower limit of the target gel content window of the inner layer insulation material. By using the inverse function of the dose-gel content response curve of the inner insulating material, the irradiation dose range corresponding to the gel content falling within the target gel content window of the inner insulating material is solved, thus obtaining the effective dose range of the inner layer. By using the inverse function of the dose-gel content response curve of the outer insulating material, the irradiation dose range corresponding to the gel content falling within the target gel content window of the outer insulating material is calculated, thus obtaining the effective dose range of the outer layer.

4. The process according to claim 1, characterized in that, The method involves determining the interlayer dose ratio coefficient between the outer and inner insulation layers based on the layered energy deposition distribution of the electron beam in the double-layer insulation structure, and establishing a correlation model for the dose received by each layer using transmission speed and beam current intensity as process parameters. This includes: The energy deposition distribution of the electron beam in the thickness direction of the double-layer insulation structure is calculated by particle transport simulation. The ratio of the energy deposition value at the midpoint depth of the outer insulation layer to the energy deposition value at the midpoint depth of the inner insulation layer is taken to obtain the interlayer dose ratio coefficient. A correlation model for the radiation dose of the outer layer insulation is established by relating it to the ratio of beam intensity to transmission speed. The radiation dose of the inner layer insulation is expressed as the radiation dose of the outer layer insulation divided by the interlayer dose ratio coefficient using the interlayer dose ratio coefficient, so that the radiation doses of both the inner and outer layers are uniquely determined by the same set of transmission speeds and beam intensities.

5. The process according to claim 4, characterized in that, The step of solving for the optimal transmission speed and optimal beam intensity within the feasible region of the intersection of the inner and outer effective dose ranges as constraints includes: The inner effective dose range and the outer effective dose range are respectively transformed into constraint ranges on the ratio of beam intensity to transmission speed using the correlation model, and the intersection of the two constraint ranges is taken as the feasible region. If the feasible region is empty, it is determined that there are no process parameters that simultaneously meet the gel content targets of the inner and outer layers under the current combination of double-layer insulation wall thickness and accelerator energy. After adjusting the wall thickness design or accelerator energy, the interlayer dose ratio coefficient is re-determined and the feasible region is solved again. If the feasible region is not empty, then within the feasible region, the ratio of beam intensity to transmission speed that minimizes the sum of the inner layer insulating gel content deviation from the center value of the inner layer target gel content window and the outer layer insulating gel content deviation from the center value of the outer layer target gel content window is taken. The optimal transmission speed and optimal beam intensity are calculated in combination with the maximum transmission speed allowed by the equipment.

6. The process according to claim 1, characterized in that, The condition for determining the validity of the optimal transmission speed and the optimal beam intensity, which states that the gel content of both the inner and outer layers continuously meets the respective target gel content window, includes: For the same batch of irradiated core wires, the sampling location is determined according to the frequency of sampling one sample per fixed length, and forced sampling points are added at the core wire locations where the transmission speed or beam intensity exceeds their respective deviation thresholds during irradiation. For each sampling location, a core wire sample is taken, and after longitudinal cutting along the outer insulation layer, the outer insulation layer is completely peeled off to obtain the outer test sample. Then, the inner insulation layer is peeled off from the conductor to obtain the inner test sample. The gel content of the outer layer test sample and the inner layer test sample are measured respectively. The measured gel content of the outer layer is compared with the target gel content window of the outer layer, and the measured gel content of the inner layer is compared with the target gel content window of the inner layer. The optimal transmission speed and the optimal beam intensity are determined to be valid if the measured gel content of the inner layer and the measured gel content of the outer layer at three or more consecutive sampling locations in the same batch of non-mandatory sampling points all fall within their respective target gel content windows; otherwise, parameter iterative correction is triggered.

7. The process according to claim 1, characterized in that, The method of using the dose-gel content response curves of the inner insulating material and the outer insulating material to back-calculate the gel content deviation of each layer into the required dose correction for each layer includes: Calculate the inner layer deviation between the measured gel content of the inner layer and the center value of the target gel content window, and the outer layer deviation between the measured gel content of the outer layer and the center value of the target gel content window. Using the inverse function of the dose-gel content response curve of the inner insulating material, the inner layer deviation is inversely calculated into the required dose correction amount for the inner layer; Using the inverse function of the dose-gel content response curve of the outer insulating material, the deviation of the outer layer is back-calculated into the required dose correction amount for the outer layer; When the inner layer deviation or the outer layer deviation is positive, it indicates that the corresponding layer is over-crosslinked and the radiation dose needs to be reduced; when it is negative, it indicates that the corresponding layer is under-crosslinked and the radiation dose needs to be increased.

8. The process according to claim 1, characterized in that, The step of re-irradiating with the updated delivery speed and beam intensity and detecting the layered gel content, iterating cyclically until the gel content of both the inner and outer layers continuously meets the respective target gel content window, includes: The core wires of subsequent batches are subjected to a single electron beam irradiation with the updated transmission speed and beam intensity. After irradiation, the core wires are sampled. The outer and inner insulation layers at the sampling locations are peeled off separately and the gel content is measured independently. The measured gel content of the outer layer is compared with the target gel content window of the outer layer, and the measured gel content of the inner layer is compared with the target gel content window of the inner layer. If the gel content of both the inner and outer layers continuously meets the respective target gel content window, the updated transmission speed and beam intensity are written into the process parameter database of the current double-layer insulation wall thickness specification as the reference parameters for subsequent batches. If the gel content of the inner and outer layers still deviates, the gel content deviation of each layer is recalculated using the dose-gel content response curve of the inner layer insulation material and the dose-gel content response curve of the outer layer insulation material to obtain the required dose correction amount for each layer. The updated transmission speed and beam intensity are then re-determined based on the dose correction direction of the inner and outer layers for the next iteration. If the gel content of the inner and outer layers still cannot continuously meet the respective target gel content windows after more than three iterations, it is determined that the material radiation response is abnormal. The inner and outer insulating materials of the current batch are recalibrated by multi-dose gradient irradiation, and the dose-gel content response curves of the inner and outer insulating materials are refitted.

9. The process according to claim 5, characterized in that, The single electron beam irradiation of the double-layer co-extruded insulated core wire at the optimal transmission speed and the optimal beam current intensity includes: Before irradiation, the outer and inner insulation wall thicknesses of the current production core wire are measured online. If the measured values ​​of the outer or inner insulation wall thickness deviate from the specified values ​​beyond the allowable range, the interlayer dose ratio coefficient is recalculated based on the measured values ​​of the outer and inner insulation wall thicknesses, and the optimal transmission speed and the optimal beam intensity are resolved based on the updated interlayer dose ratio coefficient. During irradiation, the actual values ​​of the transmission speed and beam intensity are collected in real time and the deviations from the optimal transmission speed and the optimal beam intensity are calculated respectively. When the deviation of the transmission speed or the deviation of the beam intensity exceeds their respective deviation thresholds, the corresponding core wire position is marked. The marked position is included in the mandatory sampling range in the detection of the layered gel content after irradiation. For core wires with a total wall thickness exceeding the allowable thickness for uniformity of single irradiation dose, the cumulative irradiation dose of the inner and outer layers is symmetrically superimposed by irradiating both sides once each. The interlayer dose ratio coefficient is recalculated based on the layered irradiation dose after the two irradiations are superimposed. The optimal transmission speed and the optimal beam intensity are then recalculated based on the updated interlayer dose ratio coefficient.

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