A precision casting sand mold gradient solidification synergistic regulation system and method

Abstract

The application discloses a precision casting sand mold gradient solidification collaborative regulation system and method, relates to the technical field of precision casting solidification process control, and comprises a basic parameter acquisition module, a target path generation module, a time slice partition module, a variable thermal resistance regulation module, a sound-heat coupling acquisition module, a solidification front inversion module, a feeding channel evaluation module, a solidification deviation judgment module and a collaborative control module. The system acquires a casting three-dimensional model, material solidification temperature intervals, wall thickness distribution, thermal node positions, riser positions, pouring temperature, sand mold thermal conductivity parameters and cooling boundary conditions. The application maps the casting wall thickness distribution, thermal node positions and riser feeding directions into a target gradient solidification path, changes the sand mold regulation target from single-point temperature reduction or local temperature preservation into whole-process solidification path control along the feeding direction, and improves the executability of complex precision casting solidification sequence design.

Description

Technical Field

[0001] This invention relates to the field of precision casting solidification process control, and more specifically, to a precision casting sand mold gradient solidification coordinated control system and method. Background Technology

[0002] In the sand casting process of precision castings, abrupt changes in casting wall thickness, concentrated hot spots, and limited riser feeding distance can easily lead to uncontrolled solidification front advancement, resulting in shrinkage cavities, porosity, or localized undercooling defects. In the prior art, CN1526495A discloses a casting method and apparatus for directional solidification, which determines the dynamic positions of the solid phase, crystallization zone, and liquid phase zone through local cooling, local heat preservation, and sensor data acquisition. However, it mainly relies on local temperature control of the mold and does not establish an equal solidification time plate control zone or a variable thermal resistance switching mechanism for adjacent areas of the sand mold. CN219064710U discloses a temperature measuring device for sand castings, which obtains the temperature at specific locations inside the sand mold through a support, protective sleeve, and thermocouple. However, its monitoring object is still mainly single-point temperature, making it difficult to invert the width of the mushy zone, the direction of the solidification front, and the connectivity of the feeding channel. CN106825422A discloses a method for inspecting the feeding efficiency of risers and the quality of heat-insulating risers in cast steel parts. This is a post-solidification verification method and cannot be controlled online during the solidification process. Therefore, a collaborative control scheme for sand mold solidification that can combine the target gradient solidification path, acoustic-thermal coupling inversion, survival evaluation of the feeding channel, and variable thermal resistance zonal regulation is needed. Summary of the Invention

[0003] The purpose of this invention is to provide a precision casting sand mold gradient solidification coordinated control system and method, which solves the problems in the existing precision casting sand mold casting process, such as sudden changes in casting wall thickness, concentrated heat points, and limited riser feeding distance, which easily lead to uncontrolled solidification front advancement direction, resulting in shrinkage cavities, porosity, or localized undercooling defects.

[0004] This invention achieves the above objectives through the following technical solution: a precision casting sand mold gradient solidification coordinated control system, the system comprising:

[0005] The module includes a basic parameter acquisition module, a target path generation module, a time slice partitioning module, a variable thermal resistance control module, an acoustic-thermal coupling acquisition module, a solidification front inversion module, a feeding channel evaluation module, a solidification deviation judgment module, and a collaborative control module.

[0006] The basic parameter acquisition module is used to acquire the three-dimensional model of the casting, the solidification temperature range of the material, the wall thickness distribution, the location of the hot spot, the location of the riser, the pouring temperature, as well as the heat transfer parameters of the sand mold and the cooling boundary conditions.

[0007] The target path generation module is used to generate a target gradient solidification path that progresses from the far-end region to the hot-node region and then to the riser region based on the wall thickness distribution, hot-node location, and riser location.

[0008] The time slice partitioning module is used to divide the sand mold and the area adjacent to the casting into multiple equal solidification time slice control zones according to the target gradient solidification path, and to configure the target solidification time window and target thermal resistance state for each equal solidification time slice control zone.

[0009] The variable thermal resistance control module is located in the equal solidification time control zone and is used to switch between the high thermal resistance state, low thermal resistance state and thermal resistance transition state of the corresponding zone.

[0010] The acoustic-thermal coupling acquisition module is used to acquire multi-source state signals during the solidification process of the casting; the multi-source state signals include at least temperature signals, heat flow signals, acoustic signals and vibration signals.

[0011] The solidification front inversion module is used to determine the solidification front state based on the multi-source state signal;

[0012] The feeding channel evaluation module is used to evaluate the feeding channel status between the riser and the hot spot area;

[0013] The solidification deviation determination module is used to output the solidification deviation type;

[0014] The collaborative control module is used to control the variable thermal resistance adjustment module to perform cooling, heat preservation, and thermal resistance switching according to the solidification deviation type.

[0015] Furthermore, the target path generation module includes:

[0016] Region identification unit, solidification sequence calculation unit, and feeding direction constraint unit;

[0017] The region identification unit is used to identify thin-walled regions, thick-walled regions, geometric transition regions, and hot spot regions based on the three-dimensional model of the casting and the wall thickness distribution.

[0018] The solidification sequence calculation unit is used to determine the theoretical solidification sequence of each region based on the material solidification temperature range, wall thickness distribution, and sand mold thermal conductivity parameters.

[0019] The feeding direction constraint unit is used to determine the feeding direction based on the riser position and the hot spot position, and to set the region far from the riser and with a shorter theoretical solidification time as the priority solidification region, the hot spot region as the intermediate solidification region, and the region close to the riser as the post-solidification region, thereby generating the target gradient solidification path.

[0020] Furthermore, the time-slice partitioning module includes:

[0021] Path projection unit, time slice merging unit, and thermal resistance target configuration unit;

[0022] The path projection unit is used to project the target gradient solidification path onto the sand mold adjacent area outside the sand mold-casting interface.

[0023] The time slice merging unit is used to group adjacent areas of sand molds with theoretical solidification times in the same solidification time interval into the same equal solidification time slice control area.

[0024] The thermal resistance target configuration unit is used to configure low thermal resistance heat dissipation target, high thermal resistance heat preservation target, or thermal resistance transition target for each equal solidification time plate control zone based on the target solidification time window difference between adjacent equal solidification time plate control zones.

[0025] Furthermore, the variable thermal resistance control module includes:

[0026] Thermally conductive components, thermally insulating components, phase change insulation layers, cooling interfaces, thermal insulation interfaces, and thermal resistance switching actuators;

[0027] The thermally conductive component is used to form a low thermal resistance heat dissipation channel;

[0028] The thermal insulation component is used to form a high thermal resistance insulation channel;

[0029] The phase change barrier layer is disposed between the heat-conducting component and the heat-insulating component to form a thermal resistance transition state within the material solidification temperature range;

[0030] The thermal resistance transition state is formed by the phase change barrier layer maintaining an approximately isothermal heat transfer path through the absorption or release of latent heat of phase change within its phase change temperature range. The phase change temperature is set within the temperature range below the liquidus temperature of the material and above the solidus temperature.

[0031] The cooling interface is used to connect the cooling medium;

[0032] The insulation interface is used to connect a heating medium or an insulation medium;

[0033] The thermal resistance switching actuator is used to drive the heat-conducting component, heat-insulating component, or phase change barrier layer into the corresponding heat transfer position according to the control command output by the collaborative control module.

[0034] Furthermore, the acoustic-thermal coupling acquisition module includes:

[0035] Temperature acquisition unit, heat flow acquisition unit, sound wave transmission and reception unit, and vibration acquisition unit;

[0036] The temperature acquisition unit is arranged in the area adjacent to the inner wall of the sand mold, the outer wall area of ​​the sand mold, or the neck area of ​​the riser, and is used to acquire temperature signals.

[0037] The heat flow acquisition unit is arranged on the heat transfer path in the equal solidification time control zone and is used to acquire heat flow signals.

[0038] The acoustic wave transmitting and receiving unit includes an acoustic wave transmitting end and an acoustic wave receiving end, used to collect acoustic wave propagation time signals and acoustic wave attenuation signals;

[0039] The acoustic wave transmitting and receiving unit includes multiple sets of acoustic wave transmitting ends and acoustic wave receiving ends arranged around the periphery of the sand mold. Multiple intersecting acoustic paths are formed between adjacent transmitting ends and receiving ends to collect acoustic wave propagation time signals and acoustic wave attenuation signals on different acoustic paths.

[0040] The acoustic wave transmitter and receiver are set on the metal waveguide medium inside the sand mold. The acoustic wave is transmitted to the area adjacent to the casting through the metal waveguide medium to avoid directly passing through the highly attenuated sand mold body.

[0041] The acoustic wave transmitting and receiving unit calibrates the unloaded acoustic characteristics of the sand mold before casting to form a reference benchmark, and uses the difference between the measured signal and the reference benchmark as the inversion input.

[0042] The vibration acquisition unit is installed on the outer wall of the sand mold or the sand mold support structure, and is used to acquire vibration response signals during the solidification process.

[0043] Furthermore, the solidification front inversion module includes:

[0044] Thermal state calculation unit, acoustic state calculation unit, stiffness state calculation unit, and leading edge fusion inversion unit;

[0045] The thermal state calculation unit is used to calculate the transient heat transfer state of the area adjacent to the sand mold based on the temperature signal and the heat flow signal.

[0046] The acoustic state calculation unit uses ultrasonic travel time tomography to divide the interior of the casting into a grid. It establishes travel time equations based on the propagation time of sound waves along multiple intersecting sound paths, and solves the sound velocity field using algebraic reconstruction or filtered back projection iteration. The sound velocity field is then converted into a solid fraction field based on a pre-calibrated solid fraction-sound velocity mapping relationship. A preset solid fraction isosurface is used as the solidification front position, and the width of the solid fraction transition zone is used as the width of the mushy region.

[0047] The stiffness state calculation unit uses the pre-calibrated solidified layer thickness-natural frequency relationship curve to inversely solve the solidified layer thickness from the measured vibration response frequency, as an auxiliary correction signal.

[0048] The front fusion inversion unit determines the propulsion speed based on the change of the solidification front position at continuous sampling time, and estimates the propulsion direction of the solidification front using the multi-path arrival time difference. Using the transient heat transfer field output by the thermal state calculation unit as the prior field, the prior field is corrected by the measured information output by the acoustic state calculation unit and the stiffness state calculation unit using the data assimilation method. The unit outputs the solidification front position, propulsion speed, propulsion direction, mushy region width, and the remaining liquid phase state of the hot spot region.

[0049] Furthermore, the compensation channel evaluation module includes:

[0050] The unit includes a path compression extraction unit, a channel status calculation unit, and a survival output unit.

[0051] The feeding path extraction unit is used to determine the feeding path from the riser to the hot spot region based on the riser location, the hot spot location, and the target gradient solidification path.

[0052] The channel state calculation unit is used to determine the feeding path state based on the continuity of the mushy region, the riser neck temperature, the remaining liquid phase state in the hot spot region, the direction of solidification front advancement, and the risk of feeding path closure.

[0053] The survival rate output unit is used to output a low survival rate state when the continuity of the mushy region decreases, the riser neck temperature is lower than the target insulation temperature, the remaining liquid phase in the hot spot region is insufficient, the solidification front advance direction deviates from the target gradient solidification path, or the risk of the feeding path closure increases.

[0054] The compensation channel evaluation module also introduces a continuous judgment mechanism: when the survival rate of the compensation channel is lower than the preset survival rate threshold, the control action is not executed immediately, but a continuous timer is started. Only when the survival rate of the compensation channel is lower than the preset survival rate threshold for a period of time exceeding the preset continuous judgment time window is the compensation channel judged to have a risk of inactivation and the control action is triggered. When the survival rate of the compensation channel recovers to above the preset survival rate threshold and is maintained for a period of time exceeding the preset recovery confirmation time window, the survival rate of the compensation channel is judged to have recovered, and the control intensity is gradually reduced.

[0055] Furthermore, the solidification deviation determination module includes:

[0056] Path deviation judgment unit, time deviation judgment unit, and compensation risk judgment unit;

[0057] The path deviation determination unit is used to compare the consistency between the actual solidification front advancement direction and the target gradient solidification path direction.

[0058] The time deviation determination unit is used to compare the actual solidification time of each solidification time control zone with the target solidification time window.

[0059] The compensation risk determination unit is used to compare the survival rate of the compensation channel with a preset survival threshold.

[0060] The solidification deviation types include delayed solidification in the distal region, premature solidification in the thin-walled region, premature solidification of the riser neck, closure of the feeding path, and deviation of the solidification front from the target gradient solidification path.

[0061] Furthermore, the collaborative control module includes:

[0062] Cooling control unit, heat preservation control unit, thermal resistance switching control unit, and linkage correction unit;

[0063] The cooling control unit is used to control the corresponding equal solidification time plate adjustment area to connect the cooling interface when the solidification is delayed in the remote area, and to control the thermal resistance switching actuator to make the heat-conducting component enter the low thermal resistance heat dissipation position.

[0064] The thermal insulation control unit is used to control the corresponding equal solidification time plate adjustment area to connect the thermal insulation interface when there is a risk of premature solidification in the thin-walled area, and to control the thermal resistance switching actuator to make the thermal insulation component enter the high thermal resistance insulation position.

[0065] The thermal resistance switching control unit is used to switch the area of ​​the riser neck or the area of ​​the feeding path to a high thermal resistance state when there is a risk of premature solidification in the riser neck or feeding path.

[0066] The linkage correction unit is used to simultaneously adjust the cooling intensity, heat preservation intensity, and thermal resistance state of two or more adjacent equal solidification time slice control zones when the solidification front deviates from the target gradient solidification path, and to perform coordinated compensation of the cooling intensity, heat preservation intensity, and thermal resistance state based on the heat transfer coupling relationship between adjacent control zones.

[0067] A method for coordinated control of gradient solidification in precision casting sand molds, applied to the aforementioned coordinated control system for gradient solidification in precision casting sand molds, the method comprising:

[0068] Obtain the three-dimensional model of the casting, the solidification temperature range of the material, the wall thickness distribution, the location of the hot spot, the location of the riser, the pouring temperature, as well as the heat transfer parameters of the sand mold and the cooling boundary conditions;

[0069] Based on the wall thickness distribution, hot spot location, and riser location, a target gradient solidification path is generated that progresses from the far-end region to the hot spot region and then to the riser region.

[0070] Based on the target gradient solidification path, the sand mold and the area adjacent to the casting are divided into multiple equal solidification time control zones, and the target solidification time window and target thermal resistance state of each equal solidification time control zone are determined.

[0071] A variable thermal resistance control module is configured in each solidification time control zone, so that the corresponding zone can switch between high thermal resistance state, low thermal resistance state and thermal resistance transition state.

[0072] Collect multi-source state signals during the solidification process of the casting; the multi-source state signals include at least temperature signals, heat flow signals, sound wave signals, and vibration signals;

[0073] The solidification front state is determined based on the multi-source state signal;

[0074] Evaluate the state of the feeding channel between the riser and the hot spot;

[0075] The type of solidification deviation is determined based on the state of the feeding channel, the target solidification time window, and the target gradient solidification path.

[0076] According to the solidification deviation type, the corresponding solidification time control zone is used to perform cooling, heat preservation, low thermal resistance switching, high thermal resistance switching, or multi-zone linkage correction until the casting completes solidification and forms a gradient solidification state that progresses along the target gradient solidification path.

[0077] The beneficial effects of this invention are as follows:

[0078] 1. By mapping the casting wall thickness distribution, hot spot location, and riser feeding direction to a unified target gradient solidification path, the sand mold control target is transformed from single-point cooling or local heat preservation to full-process solidification path control along the feeding direction, which improves the feasibility of solidification sequence design for complex precision castings.

[0079] 2. By setting equal solidification time control zones, the sand mold and the area adjacent to the casting are divided into zones according to the target solidification time window. This gives clear time constraints to the cooling, heat preservation and thermal resistance adjustment of each zone, avoids mutual interference between different control zones, and is conducive to forming a continuous and stable gradient solidification state.

[0080] 3. By introducing a variable thermal resistance control module, the local area of ​​the sand mold can switch between a high thermal resistance state and a low thermal resistance state. Combined with the cooling interface, the insulation interface and the phase change isolation layer, the local heat transfer state can be actively adjusted, overcoming the problem that the thermal boundary of the traditional sand mold is difficult to dynamically adjust once it is set.

[0081] 4. By collecting temperature, heat flow, sound wave propagation time, sound wave attenuation and vibration response signals, the solidification front position, propagation speed, propagation direction, width of the mushy zone and the state of the remaining liquid phase are comprehensively inverted. Compared with single temperature monitoring, it can more accurately identify the solidification state inside the casting.

[0082] 5. By calculating the survival rate of the feeding channel and using it together with the solidification front deviation as the control basis, it is possible to identify the risks of premature solidification of the riser neck, closure of the feeding path, delayed solidification in the far-end area, and premature solidification in the thin-walled area in advance. This enables closed-loop coordinated correction of cooling, heat preservation, and thermal resistance, thereby reducing the probability of shrinkage cavities and porosity defects.

[0083] 6. Based on the Chvorinov solidification time rule and gradient solidification principle, the solidification sequence is actively arranged along the feeding direction, and the liquid phase feeding path between the riser and the hot spot is guaranteed in real time by the short-plate constraint of the feeding channel survival. From the perspective of heat transfer and feeding mechanism, the hot spot area is guaranteed to obtain effective liquid phase feeding in the later stage of solidification, thereby reducing the probability of shrinkage cavities, shrinkage porosity and local undercooling defects at the mechanism level. Attached Figure Description

[0084] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0085] Figure 1 This is a schematic diagram of the overall system structure of the present invention;

[0086] Figure 2 This is a schematic diagram illustrating the target gradient solidification path and the division of the equal solidification time plate control zone in this invention.

[0087] Figure 3 This is a schematic diagram of the variable thermal resistance control module structure of the present invention;

[0088] Figure 4 This is a schematic diagram of the acoustic-thermal coupling acquisition and solidification front feedback of the present invention;

[0089] Figure 5 This is a flowchart of the collaborative control method of the present invention. Detailed Implementation

[0090] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0091] Example 1:

[0092] Please see Figures 1-5This invention provides a precision casting sand mold gradient solidification collaborative control system. This system is suitable for closed-loop control of the solidification front advancement direction, hot spot zone feeding state, and local heat transfer boundary of precision castings during sand casting. The system includes a basic parameter acquisition module, a target path generation module, a time slice partitioning module, a variable thermal resistance control module, an acoustic-thermal coupling acquisition module, a solidification front inversion module, a feeding channel evaluation module, a solidification deviation judgment module, and a collaborative control module.

[0093] In this embodiment, the system is suitable for systems with external dimensions of [missing information]. to Minimum wall thickness is to Maximum wall thickness is to Precision castings. The casting material can be cast steel, aluminum alloy, or high-temperature alloy. Before system operation, the liquidus temperature and solidus temperature are input according to the casting material. Taking cast steel as an example, the liquidus temperature is... to Solidus temperature is taken to The casting temperature is taken above the liquidus temperature. to The thermal conductivity of the sand mold is taken as... to The initial temperature of the sand mold is taken as to The external environment heat transfer coefficient is taken as to The above parameters were determined by the material handbook, casting process card, thermal conductivity test results of sand mold samples, and the initial boundary conditions of the casting simulation software.

[0094] The basic parameter acquisition module is used to acquire the 3D model of the precision casting, the material solidification temperature range, wall thickness distribution, hot spot location, riser location, pouring temperature, sand mold thermal conductivity parameters, and cooling boundary conditions. The 3D model of the casting uses... Format or The format import is used to characterize the spatial geometry of the casting; the material solidification temperature range is used to determine the liquidus temperature, solidus temperature, and pasty region temperature range; the wall thickness distribution is used to identify the heat dissipation differences in different areas of the casting; the hot spot location is used to determine the high-temperature retention areas that are prone to shrinkage cavities or porosity; the riser location is used to determine the source and direction of feeding; the sand mold thermal conductivity parameters and cooling boundary conditions are used to determine the initial heat transfer capacity of the sand mold. The pouring temperature is used to determine the initial superheat during pouring and the solidification initiation time, and together with other parameters, constitutes the initial boundary conditions for solidification control.

[0095] During the 3D model processing, the basic parameter acquisition module divides the 3D model of the casting into several spatial regions, and the optimal side length of the mesh unit is selected. to For minimum wall thickness less than In thin-walled regions, the side length of mesh elements should not exceed one-third of the minimum wall thickness to reduce the identification error of hot spots in thin-walled regions. The location of hot spots is determined by both the wall thickness modulus and the degree of local volume concentration, with priority given to hot spot regions having a wall thickness modulus greater than that of adjacent regions. The wall thickness modulus is determined by the local volume of the casting and the effective heat dissipation area of ​​that local region.

[0096] The target path generation module generates a target gradient solidification path that progresses from the far-end region to the hot-node region and then to the riser region, based on wall thickness distribution, hot spot location, and riser location. To ensure dimensional consistency in the solidification time calculations for each region, the system uniformly converts the length parameter to [value missing]. Convert the time parameters to a unified value. Convert the temperature parameters to a uniform value. The thermal resistance parameter is uniformly converted to The reference solidification time for each casting region is determined according to the following formula:

[0097]

[0098] In the formula, Indicates the first The reference solidification time for each casting region, in units of ; This represents the reference solidification time obtained from the simulation of the reference specimen or first piece, in units of... ; Indicates the first The wall thickness modulus of each casting region, in units of ; The wall thickness modulus of the reference region, in units of The median of the wall thickness modulus for all regions is preferred. Indicates the first The equivalent thermal resistance of the sand mold heat transfer path for each region, in units of ; This represents the equivalent thermal resistance of the sand mold heat transfer path in the reference region, in units of... .because and All are dimensionless ratios, therefore Units and Consistent, all are . Instead of using empirical constants, the solidification time is determined by actual measurement of solidification time on test bars of the same material or by the solidification endpoint time of a reference area in casting simulation. The square relationship is determined based on Chvorinov's solidification time rule, which states that the solidification time of a casting is proportional to the square of the wall thickness modulus. The thermal resistance ratio is used to correct for the influence of differences in sand mold heat dissipation conditions on the solidification time.

[0099] After obtaining the reference solidification time for each region, the target path generation module generates the target gradient solidification path through the region identification unit, solidification sequence calculation unit, and feeding direction constraint unit. The region identification unit identifies thin-walled regions, thick-walled regions, geometric transition regions, and hot spots based on the three-dimensional model of the casting and the wall thickness distribution; the solidification sequence calculation unit determines the theoretical solidification order of each region according to the material solidification temperature range, wall thickness distribution, and thermal conductivity parameters of the sand mold; the feeding direction constraint unit determines the feeding direction according to the riser position and hot spot position, and sets the region far from the riser and with a shorter reference solidification time as the priority solidification region, the hot spot region as the intermediate solidification region, and the region close to the riser and connected to the hot spot region as the later solidification region, thus forming the target gradient solidification path that progresses from the far-end region to the hot spot region and then to the riser region.

[0100] The target gradient solidification path is not simply determined by geometric distance, but simultaneously satisfies both the feeding direction constraint and the solidification time increment constraint. When a region is far from the riser, but its baseline solidification time is greater than that of the hot spot region, the system marks this region as a solidification lag risk area and prioritizes low thermal resistance heat dissipation targets in subsequent time slice partitions. This method avoids solidification lag in far-end thick-walled regions that could disrupt the feeding direction.

[0101] The time-slice partitioning module is used to divide the sand mold and the area adjacent to the casting into multiple equal-solidification time-slice control zones based on the target gradient solidification path, and to configure the target solidification time window and target thermal resistance state for each equal-solidification time-slice control zone. The time-slice partitioning module includes a path projection unit, a time-slice merging unit, and a thermal resistance target configuration unit. The path projection unit projects the target gradient solidification path onto the sand mold's adjacent area outside the sand mold-casting interface; the time-slice merging unit merges sand mold adjacent areas with theoretical solidification times within the same solidification time interval into the same equal-solidification time-slice control zone; the thermal resistance target configuration unit configures low thermal resistance heat dissipation targets, high thermal resistance heat preservation targets, or thermal resistance transition targets for each equal-solidification time-slice control zone based on the difference in target solidification time windows between adjacent equal-solidification time-slice control zones.

[0102] The target solidification time window for each equal solidification time control zone is determined centered on the reference solidification time of the corresponding zone. For zones with ordinary wall thickness, the target solidification time window is preferably selected as a fraction of the reference solidification time. The target solidification time window for the hot spot region is preferably taken as the reference solidification time. To improve the feeding control accuracy in the hot spot region; the target solidification time window for the riser neck region is preferably selected from the reference solidification time. To reduce the risk of premature closure of the feeding channel. When the reference solidification time is less than At that time, the allowable deviation shall not be less than To avoid misjudgments in thin-walled areas due to sampling intervals or sensor response lag, the above proportions are determined by comparing the temperature curves of at least three trial castings of similar castings with the solidification simulation results. When there are fewer than three trial castings, the initial values ​​are first determined using simulation results, and then corrected based on the inspection results after the first piece is produced.

[0103] A variable thermal resistance control module is installed in each solidification time slice control zone to switch the corresponding region between a high thermal resistance state, a low thermal resistance state, and a thermal resistance transition state. The variable thermal resistance control module includes a heat-conducting component, a heat-insulating component, a phase change barrier layer, a cooling interface, a thermal insulation interface, and a thermal resistance switching actuator. The heat-conducting component forms a low thermal resistance heat dissipation channel and can be made of copper alloy plate, graphite heat-conducting block, or metal chill, with an equivalent thermal conductivity of not less than [value missing]. Thermal insulation components are used to form high thermal resistance insulation channels and can be made of ceramic fiber boards, microporous insulation boards, or high-temperature resistant insulation sand cores, with an equivalent thermal conductivity not exceeding [a certain value]. The phase change barrier layer is placed between the heat-conducting component and the heat-insulating component, and its phase change temperature is set below the liquidus temperature of the material. to It is used to create a thermal resistance transition state during the transition of the casting from the liquid phase to the paste region; the cooling interface is used to connect compressed air, atomized water cooling, or circulating cooling medium, with an inlet temperature of [temperature missing]. to The insulation interface is used to connect electric heating elements, hot air channels, or insulation jackets. The insulation control temperature is preferably higher than the solidus temperature of the material. to The thermal resistance switching actuator is used to drive the heat-conducting component, heat-insulating component, or phase change barrier layer into the corresponding heat transfer position according to the control command output by the collaborative control module.

[0104] The thermal resistance transition state is formed by the phase change barrier layer absorbing or releasing latent heat of phase change within its phase change temperature range to keep the heat transfer path approximately isothermal. When the solidification front of the casting advances to this region, the phase change barrier layer absorbs or releases latent heat near the phase change temperature, keeping the temperature of the heat transfer path near the phase change point. This creates an equivalent thermal resistance transition state between the low thermal resistance heat dissipation channel formed by the heat-conducting component and the high thermal resistance heat preservation channel formed by the heat insulation component, thus preventing the gradient solidification sequence from being disturbed by abrupt changes in thermal resistance in this region.

[0105] The acoustic-thermal coupling acquisition module is used to acquire temperature signals, heat flow signals, sound wave propagation time signals, sound wave attenuation signals, and vibration response signals during casting and solidification. The module includes a temperature acquisition unit, a heat flow acquisition unit, a sound wave transmitting and receiving unit, and a vibration acquisition unit. The temperature acquisition unit is located near the inner wall of the sand mold, on the outer wall of the sand mold, or in the riser neck area, with a sampling period of [missing information]. to Temperature measurement error not greater than The heat flux acquisition unit is arranged on the heat transfer path in the equal solidification time control zone, and the sampling period is [missing information]. to The heat flow measurement range is to The acoustic wave transmitting and receiving unit includes an acoustic wave transmitting end and an acoustic wave receiving end, each... to To complete one test, the preferred sound wave frequency is... to The time resolution of sound wave propagation is not less than The vibration acquisition unit is installed on the outer wall of the sand mold or on the sand mold support structure, and the sampling frequency is [missing information]. to It is used to extract the change in response frequency caused by the change in structural stiffness during solidification.

[0106] Furthermore, to overcome the engineering difficulties of acoustic and vibration sensing under sand mold enclosure, the acoustic-thermal coupling acquisition module's acoustic wave transmitter and receiver are arranged around the perimeter of the sand mold, forming multiple intersecting acoustic paths for acquiring acoustic wave propagation time and attenuation signals along different paths. The acoustic wave transmitter and receiver are positioned on a metal waveguide medium (such as chills or copper alloy heat-conducting plates) within the sand mold. After propagating along the metal waveguide medium into the vicinity of the casting, the acoustic waves are reflected or transmitted through the casting-sand mold interface and received, thus preventing the acoustic waves from directly penetrating the highly attenuated sand mold body. The acoustic wave frequency... Within the frequency range selected by the acoustic wave transmitting and receiving unit, a lower frequency band is preferred, and the transmission energy is increased. Pulse compression or multiple average correlation extraction methods are used to compensate for the attenuation of the sand mold itself on the acoustic waves. Before casting, the acoustic characteristics of the sand mold under no-load are calibrated as a reference benchmark. During solidification, the difference between the measured signal and the reference benchmark is used as the input of the solidification front inversion module to deduct the influence of the sand mold's own attenuation and the reflection of the fixed interface. The reference benchmark is used as the source of the reference signal value in the dimensionless normalization processing of the acoustic-thermal coupling acquisition module and is updated based on the measured results after the first trial casting.

[0107] To avoid calculation errors caused by the direct use of signals with different dimensions in the judgment, the acoustic-thermal coupling acquisition module performs dimensionless normalization processing on the temperature signal, heat flow signal, sound wave propagation time signal, sound wave attenuation signal, and vibration response signal before inputting them into the solidification front inversion module, according to the following formula:

[0108]

[0109] In the formula, Indicates the first Each solidification time control zone is in The first moment The normalization deviation of the signal is a dimensionless quantity. Indicates the measured signal value; This represents the reference signal value for the same control zone under the target solidification path; Indicates the first The calibration scale for this type of signal. Signal types include temperature, heat flux, sound wave propagation time, sound wave attenuation, and vibration response. The determination rule is: the temperature signal is taken as follows. to heat flow signal acquisition to The sound wave propagation time signal is taken to Sound wave attenuation signal to The vibration response signal is taken as twice the root mean square value of the unloaded vibration before the first piece is poured. Through the above normalization process, signals of different dimensions are converted into dimensionless deviation values, thereby ensuring the consistency of parameter dimensions in the subsequent solidification front inversion process.

[0110] The solidification front inversion module is used to invert the position, propagation velocity, propagation direction, width of the mushy zone, and residual liquid phase state of the hot spot region of the solidification front based on the normalized acoustic-thermal coupling signal. The solidification front inversion module includes a thermal state calculation unit, an acoustic state calculation unit, a stiffness state calculation unit, and a front fusion inversion unit. The thermal state calculation unit calculates the transient heat transfer state of the sand mold's adjacent area based on temperature and heat flow signals; the acoustic state calculation unit calculates the sound velocity change state based on the sound wave propagation time signal and the mushy zone distribution state based on the sound wave attenuation signal; the stiffness state calculation unit calculates the structural stiffness change state based on the vibration response signal; and the front fusion inversion unit spatially matches the transient heat transfer state, sound velocity change state, mushy zone distribution state, and structural stiffness change state, outputting the real-time state of the solidification front inside the casting.

[0111] Furthermore, the solidification front inversion module determines the solidification front state as follows: The acoustic state calculation unit uses ultrasonic travel-time tomography to divide the casting interior into several grids. Based on the propagation time of sound waves along multiple intersecting sound paths, a travel-time equation is established. Algebraic reconstruction or filtered back-projection is used to iteratively solve the sound velocity field. The sound velocity field is then converted into a solid fraction field based on a pre-calibrated solid fraction-sound velocity mapping relationship. A preset solid fraction isosurface is used as the solidification front position, and the width of the solid fraction transition zone is used as the width of the mushy region. The front fusion inversion unit determines the propagation speed based on the change in the solidification front position over continuous sampling time, and uses... The solidification front advance direction is estimated using multiple arrival time differences. The stiffness state calculation unit uses a pre-calibrated solidified layer thickness-natural frequency relationship curve to inversely solve the solidified layer thickness from the measured vibration response frequency, serving as an auxiliary correction signal for cross-validation of the solidification front state. The front fusion inversion unit uses the transient heat transfer field output by the thermal state calculation unit as the prior field, employing ensemble Kalman filtering or Bayesian update data assimilation methods to correct the prior field with measured information output by the acoustic state calculation unit and the stiffness state calculation unit, outputting the solidification front position, advance velocity, advance direction, mushy zone width, and remaining liquid phase state in the hot spot zone. The solid fraction-sound velocity mapping relationship and the solidified layer thickness-natural frequency relationship curve are calibrated through solidification tests or finite element modal analysis of specimens of the same material, and corrected based on the results of X-ray inspection, low-magnification inspection, or cross-sectional inspection after the first casting. The vibration response signal participates in the solidification front state inversion as an auxiliary correction signal, without independently determining the position and direction of the solidification front, thus avoiding underdetermined errors from single vibration inversion. This application is the first to integrate multi-source acoustic vibration information with a priori heat transfer field data for online inversion of the solidification front in sand casting. Combined with variable thermal resistance zonal control to form a closed loop, it can identify the internal solidification state of the casting online and dynamically adjust the thermal boundary of the sand mold. This allows tomographic imaging and data assimilation methods to work together in the sand mold solidification scenario, overcoming the shortcomings of existing technologies that rely on single-point temperature monitoring to identify the internal solidification state of the casting online and cannot dynamically adjust the thermal boundary of the sand mold accordingly.

[0112] Specifically, the preferred location for the solidification front is a spatial boundary where the temperature is between the liquidus and solidus temperatures, the acoustic attenuation changes abruptly, and the vibration response stiffness begins to increase. To determine whether the solidification front deviates from the target gradient solidification path, the solidification front inversion module generates an actual propagation vector based on the positional changes of the actual solidification front at continuous sampling times. This vector is then compared with the target direction vector of the target gradient solidification path in the current region, and directional consistency is calculated using the following formula:

[0113]

[0114] In the formula, Indicates the first The angle between the actual solidification front advancement direction and the target gradient solidification path direction at the time of sampling, in units of... ; This represents the actual propagation vector from the solidification front position at the previous sampling time to the solidification front position at the current sampling time, in units of... ; This represents the target direction vector of the target gradient solidification path in the current region, in units of... ; Represents the dot product of two vectors; and Let represent the magnitudes of the two vectors respectively. Since the dimensions of the numerator and denominator are both 1 / 2... ,therefore It is a dimensionless quantity. The preferred deviation threshold is For thin-walled regions, take For thick-walled hot spot regions This threshold is determined by the fluctuation range of the solidification front direction corresponding to the no-shrinkage result in the casting simulation, and is corrected by the defect detection results after the first trial casting.

[0115] The feeding channel evaluation module is used to calculate the survival rate of feeding channels between the riser and the hot spot region. The module includes a feeding path extraction unit, a channel status calculation unit, and a survival rate output unit. The feeding path extraction unit determines the feeding path from the riser to the hot spot region based on the riser location, hot spot location, and target gradient solidification path. The channel status calculation unit determines the feeding path status based on the continuity of the mushy zone, the riser neck temperature, the remaining liquid phase state in the hot spot region, the direction of solidification front advancement, and the risk of feeding path closure. The survival rate output unit outputs the survival rate of the feeding channel.

[0116] To avoid the averaging effect masking localized failures in the patching process due to the simple weighting of multiple indicators, this embodiment uses a short-board constraint method to determine the survival rate of the patching channels, as detailed below:

[0117]

[0118] In the formula, express The survival rate of the constantly replenished channel is a dimensionless quantity between 0 and 1. Indicates the continuity coefficient of the pasty region; This indicates the riser neck temperature retention coefficient; Indicates the residual liquid phase coefficient in the hot spot region; Indicates the solidification direction consistency coefficient; This represents the coefficient for unclosed feeding paths. All coefficients are normalized to between 0 and 1, where 1 indicates that the corresponding state meets the feeding requirements, and 0 indicates that the corresponding state does not meet the feeding requirements. The minimum value is used as the survival rate of the feeding channel, meaning that if any critical link fails, the feeding channel is considered to be at risk of deactivation. This avoids the use of weighted averages to mask problems such as premature solidification of the riser neck, breakage of the mushy zone, or partial closure of the feeding path.

[0119] To avoid control oscillations caused by misjudgment of the survival rate of the compensation channel due to instantaneous noise or signal fluctuations in the sensor, this embodiment introduces a continuous judgment mechanism for determining the survival rate of the compensation channel: when the survival rate of the compensation channel... Below the preset survival threshold At that time, the system does not immediately execute the control action, but instead starts a continuous timer; only when consistently below The time exceeds the duration determination time window Only then does the system determine that the compensation channel is at risk of inactivation and trigger control actions. The preferred time is 15s to 30s, with the specific value determined based on the target solidification time window width of each solidification time control zone. For thin-walled regions... Take 15 seconds for the hot spot region. Take 30 seconds. Restore to The above conditions must be maintained continuously for a period exceeding the recovery confirmation time window. At that point, the system determines that the survival rate has been restored and gradually reduces the intensity of regulation. The optimal time is 30s to 60s.

[0120] Among them, the continuity coefficient of the mushy region The riser neck temperature retention coefficient is determined by the continuity of the pasty zone between the riser and the hot spot. A coefficient of 0.8 to 1.0 is used for continuity, 0.4 to 0.7 for a tendency to break, and 0 to 0.3 for complete breakage. The riser neck temperature is determined by its position relative to the solidus temperature; when the riser neck temperature is higher than the solidus temperature... The values ​​above are taken as 0.8 to 1.0, when the temperature is above the solidus temperature. to When the temperature is above the solidus temperature, the value is taken as 0.5 to 0.8. Within the specified range, take 0.3 to 0.5; below the solidus temperature, take 0 to 0.3. Residual liquid phase coefficient in the hot zone. The proportion of the remaining liquid phase in the hot spot region is determined, and the proportion of the remaining liquid phase is not less than [amount missing]. When the concentration is taken as 0.7 to 1.0, the proportion of the remaining liquid phase is... to When the concentration is 0.4 to 0.7, the proportion of the remaining liquid phase is lower than... The value is taken as 0 to 0.4. Solidification direction consistency coefficient. The angle is determined based on the formula. When the angle is not greater than the threshold, it is taken as 0.8 to 1.0; when the angle exceeds the threshold but does not exceed 1.5 times the threshold, it is taken as 0.4 to 0.8; and when the angle exceeds 1.5 times the threshold, it is taken as 0 to 0.4. (Unclosed coefficient of the compensation path) The value is determined based on whether there is a solid phase barrier in the compensation path. When it is not closed, the value is 0.8 to 1.0; when it is locally narrowed, the value is 0.4 to 0.8; and when a solid phase barrier is formed, the value is 0 to 0.4.

[0121] Channel survival threshold The preferred value is 0.65. The rule for determining this threshold is: first, obtain the value when no shrinkage cavities or porosity are generated through casting simulation. The variation curve is then corrected using the results of radiographic testing, low-magnification inspection, or cross-sectional inspection of at least three trial castings. Below 0.65 and lasting longer At this point, the system determines that the feeding channel is at risk of deactivation. This applies when the hot spot volume is larger than the total casting volume. castings, Increased to 0.70; for thin-walled regions with a proportion greater than castings, Increased to 0.72; for riser feeding distance less than And castings with shorter feeding paths, It can be reduced to 0.60. The above adjustment rules are used to adapt to the feeding safety margin requirements of different casting structures.

[0122] The solidification deviation determination module outputs the solidification deviation type based on the solidification front state and the survival rate of the feeding channel. The module includes a path deviation determination unit, a time deviation determination unit, and a feeding risk determination unit. The path deviation determination unit compares the actual solidification front advancement direction with the direction of the target gradient solidification path; the time deviation determination unit compares the actual solidification time of each solidification time slice control zone with the target solidification time window; and the feeding risk determination unit compares the survival rate of the feeding channel with a preset survival threshold.

[0123] When the actual solidification time of a certain remote solidification time control zone is later than the upper limit of the target solidification time window, and the temperature drop rate in that zone is lower than the reference drop rate... When the solidification deviation judgment module determines that the solidification is delayed in the far-end region, and the actual solidification time of the thin-walled region is earlier than the lower limit of the target solidification time window, and there is still a liquid phase feeding requirement between this region and the hot spot region, it is determined that the thin-walled region is solidified prematurely. When the riser neck temperature is lower than the solidus temperature... If the riser neck solidifies prematurely within the safe range and the survival rate of the feeding channel is lower than the preset survival rate threshold, it is considered a risk of premature solidification. If the continuity coefficient of the mushy region is lower than 0.4 or the unclosed coefficient of the feeding path is lower than 0.4, it is considered a risk of closure of the feeding path. If the angle between the actual solidification front advancement direction and the target gradient solidification path direction exceeds the threshold of the corresponding region and continues for two sampling cycles, it is considered that the solidification front deviates from the target gradient solidification path.

[0124] The collaborative control module controls the variable thermal resistance adjustment module to perform cooling, heat preservation, and thermal resistance switching based on the solidification deviation type. The collaborative control module includes a cooling control unit, a heat preservation control unit, a thermal resistance switching control unit, and a linkage correction unit. When solidification lags in the remote region, the cooling control unit controls the corresponding equal solidification time slice control zone to connect the cooling interface and controls the thermal resistance switching actuator to move the heat-conducting component to a low thermal resistance heat dissipation position. At this time, the cooling medium flow rate is... to The control objective is to increase the rate of temperature decrease in the corresponding region to the reference rate of temperature decrease. to When there is a risk of premature solidification in the thin-walled area, the insulation control unit controls the corresponding solidification time adjustment zone to connect the insulation interface and controls the thermal resistance switching actuator to put the insulation component into a high thermal resistance insulation position, with the insulation temperature set above the solidus temperature. to The control objective is to bring the actual solidification time of the thin-walled region back within the target solidification time window. When there is a risk of premature solidification at the riser neck or feeding path, the thermal resistance switching control unit switches the riser neck region or feeding path region to a high thermal resistance state and adjusts the heating or insulation intensity to restore the survival rate of the feeding channel to above the preset survival threshold. When the solidification front deviates from the target gradient solidification path, the linkage correction unit simultaneously adjusts the cooling intensity, insulation intensity, and thermal resistance state of two or more adjacent equal solidification time slice control zones to restore the angle between the actual solidification front advancement direction and the target gradient solidification path direction to within the threshold within two consecutive sampling cycles.

[0125] Example 2:

[0126] This embodiment provides a method for coordinated control of gradient solidification in sand molds for precision castings, implemented using the system of Embodiment 1. Taking a precision steel support casting as an example, the casting's external dimensions are... Minimum wall thickness is The maximum wall thickness is The hot spot is located at the intersection of two reinforcing ribs, and the riser is positioned above the hot spot. The material's liquidus temperature is taken as... Solidus temperature is taken The pouring temperature is taken The thermal conductivity of the sand mold is taken as The environmental heat transfer coefficient is taken as .

[0127] It should be noted that all process parameters, control thresholds and solidification time data in this embodiment are exemplary values ​​for the cast steel precision bracket casting structure. In actual implementation, those skilled in the art can adjust them according to the casting material, structural dimensions and sand mold heat dissipation conditions. This embodiment should not be construed as a limitation on the scope of protection of this invention.

[0128] The system first uses a basic parameter acquisition module to read the 3D model of the casting and extract wall thickness distribution, hot spot location, riser location, and sand mold thermal conductivity parameters. The target path generation module calculates the wall thickness modulus for each region based on the 3D model and uses a formula to determine the reference solidification time for each region. The calculation results show that the reference solidification time for the far-end thin-walled region is... to The reference solidification time for the geometric transition region is to The reference solidification time for the hot spot region is to The target holding time in the riser neck region is no less than the solidification endpoint time in the hot spot region. Therefore, the system generates a target gradient solidification path from the distal thin-walled region to the geometric transition region, then to the hot spot region, and finally towards the riser neck.

[0129] Subsequently, the time-slot partitioning module divides the adjacent area of ​​the sand mold into four equal-solidification time-slot control zones. The first control zone corresponds to the distal thin-walled region (i.e., as shown in the image). Figure 2 The target solidification time window is shown in the far-end region. to The target thermal resistance state is a low thermal resistance heat dissipation state; the second control region corresponds to the geometric transition region (i.e., as shown in the figure). Figure 2 The transition zone shown), the target solidification time window is to The target thermal resistance state is the thermal resistance transition state; the third control zone corresponds to the thermal node zone, and the target solidification time window is... to The target thermal resistance state is an adjustable heat dissipation state (e.g.) Figure 2 As shown); the fourth control zone corresponds to the riser neck and the feeding path region (i.e., as shown). Figure 2 The riser region shown is a target thermal resistance state, which is a high thermal resistance insulation state, and its insulation duration covers the late solidification stage of the hot spot region.

[0130] After pouring begins, the acoustic-thermal coupling acquisition module collects temperature signals, heat flow signals, sound wave propagation time signals, sound wave attenuation signals, and vibration response signals according to a set cycle, and performs dimensionless normalization processing using formulas. The solidification front inversion module determines the position of the solidification front based on the normalized acoustic-thermal coupling signals and calculates the angle between the actual solidification front direction and the target gradient solidification path direction using formulas. When the first control zone is in The target mushy region boundary has not yet been reached, and the rate of temperature decrease is lower than the reference rate of decrease. When the solidification deviation judgment module determines that the solidification of the far-end region is lagging, the collaborative control module opens the cooling interface of the first control zone and puts the heat-conducting component into a low thermal resistance heat dissipation position, thereby accelerating the heat dissipation of the far-end thin-walled region and bringing it back into the target solidification time window.

[0131] During the mid-solidation phase, when the acoustic attenuation signal in the second control zone indicates premature expansion of the mushy region and a narrowing trend in the feeding channel between the thin-walled region and the hot spot region, the solidification deviation judgment module determines that there is a risk of excessively rapid solidification in the geometric transition region. The collaborative control module controls the second control zone to enter a thermal resistance transition state, allowing the phase change barrier layer to enter the heat transfer path, thereby reducing the risk of narrowing of the feeding channel caused by excessively rapid solidification in this region. When the riser neck temperature in the fourth control zone approaches or exceeds the solidus temperature... When the safety lower limit is reached, the collaborative control module activates the insulation interface to maintain the riser neck area at a safe level. This maintains the feeding capacity between the riser and the hot spot.

[0132] During the later stages of solidification, the feeding channel evaluation module uses a formula to calculate the survival rate of the feeding channels. When the survival rate of the feeding channels is lower than... And continue to exceed When the solidification deviation judgment module determines that the feeding channel has a risk of deactivation, the collaborative control module prioritizes high thermal resistance insulation control for the riser neck area and the area where the feeding path is located. When the survival rate of the feeding channel recovers to above 0.70 and remains continuously thereafter... Subsequently, the collaborative control module reduces the insulation power to maintain the continuity of the feeding path and avoid excessive delay in solidification in the riser area.

[0133] Through the aforementioned cyclical control, the system continuously performs signal acquisition, front-edge inversion, survival evaluation, deviation judgment, and coordinated control during the casting solidification process until the casting completes solidification. Ultimately, the solidification front of the casting advances in the order of the first, second, third, and fourth control zones, and the hot spot zone maintains effective feeding conditions in the later stages of solidification, thereby reducing the probability of shrinkage cavities, porosity, and localized undercooling defects.

[0134] Example 3:

[0135] This embodiment provides another method for coordinated control of gradient solidification in sand castings using the system of Embodiment 1. Taking a thin-walled aluminum alloy pump body casting as an example, the casting's external dimensions are... Minimum wall thickness is The maximum wall thickness is The casting features an internal structure with annular flow channels and reinforcing ribs. The hot spot is located at the junction of the pump body flange root and the reinforcing ribs. The riser is positioned above the hot spot area and connects to it via the riser neck. The casting material is aluminum alloy, and the liquidus temperature is [missing value]. Solidus temperature is taken The pouring temperature is taken The thermal conductivity of the sand mold is taken as The initial temperature of the sand mold is taken as The environmental heat transfer coefficient is taken as .

[0136] It should be noted that all process parameters, control thresholds and solidification time data in this embodiment are exemplary values ​​for the aluminum alloy thin-walled pump body casting structure. In actual implementation, those skilled in the art can adjust them according to the casting material, structural dimensions and sand mold heat dissipation conditions. This embodiment should not be construed as a limitation on the scope of protection of this invention.

[0137] Before system operation, the basic parameter acquisition module imports the 3D model of the casting and divides the casting into five regions: the thin-walled region at the far end of the pump body, the annular flow channel transition region, the thick-walled region of the flange, the hot spot region, and the riser neck feeding region. The mesh cell side length is... The side length of the mesh cells in the far-end thin-walled region is taken as To improve the accuracy of solidification front identification in thin-walled regions, the system calculates the wall thickness modulus of each region based on the local volume and effective heat dissipation area, and uses a formula to determine the baseline solidification time for each region. The calculation results are as follows: the baseline solidification time for the distal thin-walled region is... to The reference solidification time for the annular flow channel transition zone is to The reference solidification time for the thick-walled zone of the flange is to The reference solidification time for the hot spot region is to The target insulation time for the riser neck shrinkage area shall not be less than .

[0138] Based on the aforementioned baseline solidification time and riser feeding direction, the target path generation module generates a target gradient solidification path from the distal thin-walled region to the annular flow channel transition region, then to the flange thick-walled region and hot spot region, and finally pointing to the riser neck feeding region. Since the flange thick-walled region and the hot spot region are adjacent and there is a liquid phase feeding requirement between them, the system sets the flange thick-walled region as the intermediate solidification region and the riser neck feeding region as the post-solidification region to ensure that the hot spot region can still obtain liquid phase feeding through the riser in the later stage of solidification.

[0139] The time-slot partitioning module divides the adjacent area of ​​the sand mold into 5 equal-setting-time-slot control zones. The first control zone corresponds to the far-end thin-walled region, with a target setting time window of [missing information]. to The target thermal resistance state is a low thermal resistance heat dissipation state; the second control zone corresponds to the annular flow channel transition zone, and the target solidification time window is... to The target thermal resistance state is the thermal resistance transition state; the third control zone corresponds to the flange thick-walled region, and the target solidification time window is... to The target thermal resistance state is an adjustable heat dissipation state; the fourth control zone corresponds to the thermal node zone, and the target solidification time window is... to The target thermal resistance state is a phased control state; the 5th control zone corresponds to the riser neck feeding zone, and the target thermal resistance state is a high thermal resistance insulation state, with a target insulation duration of [duration missing]. to Within the aforementioned target solidification time window, the thin-walled region is solidified according to the baseline solidification time. It is determined that the hot spot zone is set according to the baseline solidification time. It is determined that the riser neck feeding zone is set according to the reference solidification time. The determination was made, and adjustments were made based on the temperature curve of the first trial pour.

[0140] In this embodiment, the first control zone is configured with a copper alloy heat-conducting component with an equivalent thermal conductivity of [value missing]. It is connected to a compressed air cooling interface, and the inlet temperature of the cooling medium is... The initial flow rate is The second control zone is equipped with a phase change isolation layer, and the phase change temperature is... This is used to create a thermal resistance transition state when the aluminum alloy transitions from the liquid phase to the paste-like region. The third control zone is equipped with graphite heat-conducting blocks and ceramic fiber insulation plates, capable of switching between low thermal resistance heat dissipation and high thermal resistance heat preservation states according to control commands. The fourth control zone is equipped with local cooling and insulation interfaces for staged adjustment based on the remaining liquid phase state in the hot spot region. The fifth control zone is equipped with an electrically heated insulation jacket, with the insulation control temperature set to [temperature value missing]. to This temperature is higher than the solidus temperature of the material. to It is used to delay the premature solidification of the riser neck.

[0141] After the pouring begins, the acoustic-thermal coupling acquisition module simultaneously acquires temperature signals, heat flow signals, sound wave propagation time signals, sound wave attenuation signals, and vibration response signals. The temperature sampling period is [missing information]. The heat flow sampling period is taken The sound wave detection period is taken The frequency of the sound wave is taken Vibration sampling frequency is taken The system uses a formula to perform dimensionless normalization on various signals, with the temperature signal calibration scale being [missing value]. The calibration scale for heat flow signals is taken as follows The calibration scale for sound wave propagation time signals is taken as follows The calibration scale for acoustic wave attenuation signal is taken as follows The calibration scale for the vibration response signal is twice the root mean square value of the unloaded vibration before casting. After normalization, all signals are converted into dimensionless deviation values ​​for use in the solidification front state inversion.

[0142] In the early stage of solidification, when the first control zone is in When the rate of temperature decrease is lower than the reference rate of temperature decrease When the acoustic attenuation signal does not exhibit the boundary characteristics of a mushy region, the solidification deviation determination module determines that there is solidification hysteresis in the distal thin-walled region. The collaborative control module controls the heat-conducting component of the first control zone to move to a low thermal resistance heat dissipation position and changes the compressed air cooling flow rate from... Increase to This restores the rate of temperature decrease in the distal thin-walled region to the reference rate of decrease. Once the actual solidification time in the first control zone enters the target solidification time window, the system will reduce the cooling flow rate to [a certain value]. This is to avoid cracking due to excessive cooling in thin-walled areas.

[0143] During the middle stage of solidification, when the acoustic attenuation signal in the second control zone shows a continuous expansion of the mushy region, and the angle between the actual solidification front direction and the target gradient solidification path reaches... At that time, the system determines that the region is close to the directional deviation threshold according to the formula. Since the second control zone is the annular flow channel transition zone, the system adopts the corresponding thin-walled region. A threshold is used for judgment; if the included angle exceeds a certain threshold for two consecutive sampling periods... Subsequently, the collaborative control module causes the phase change barrier layer to enter the heat transfer path and reduces the cooling intensity of the adjacent first control zone, while appropriately increasing the heat dissipation intensity of the third control zone, so that the solidification front advances back toward the flange thick-walled area and the hot spot area.

[0144] During the later stages of solidification, the feeding channel evaluation module calculates the survival rate of the feeding channels according to a formula. The system determines in real time the continuity coefficient of the mushy zone, the riser neck temperature retention coefficient, the residual liquid phase coefficient of the hot spot zone, the solidification direction consistency coefficient, and the feeding path unsealing coefficient, and takes the minimum value among these as the survival rate of the feeding channel. When the residual liquid phase ratio in the hot spot zone of the 4th control zone drops to... The temperature at the neck of the riser in the fifth control zone is When no solid phase interruption occurs in the feeding path, the system calculates the feeding channel survival rate to be 0.68, which is higher than the preset survival rate threshold of 0.65, maintaining the current insulation state. When the riser neck temperature continues to decrease to... Furthermore, the survival rate of the compensation channel decreased to 0.62 and remained above that level. When the system determines that the feed channel is at risk of deactivation, the collaborative control module activates the electric heating insulation jacket in the 5th control zone and raises the insulation temperature to [a certain value]. At the same time, the fourth control zone is switched to a high thermal resistance state to prevent the remaining liquid phase in the hot spot zone from losing its feeding conditions too early.

[0145] When the survival rate of the compensation channel recovers to above 0.70 and remains thereafter Subsequently, the collaborative control module reduces the insulation power of the 5th control zone, maintaining the riser neck at... to The system gradually restores the adjustable heat dissipation state of the fourth control zone, allowing the hot spot region to enter a stable solidification stage after the feeding process is completed. Throughout the solidification process, the system continuously performs acoustic-thermal coupling signal acquisition, solidification front inversion, feeding channel survival evaluation, solidification deviation judgment, and coordinated control until the fifth control zone completes solidification.

[0146] Through the control process of this embodiment, the solidification sequence of the casting progresses from the first control zone, the second control zone, the third control zone, the fourth control zone to the fifth control zone, and the angle between the actual solidification front direction and the target gradient solidification path is controlled within a certain range. to Within this range, the survival rate of the feeding channels remains no less than 0.65 during the later stages of solidification in the hot spot region. Compared with aluminum alloy pump body castings of the same structure that do not employ this synergistic control system, this embodiment can reduce the probability of shrinkage cavities, porosity, and localized undercooling in the annular flow channel in the hot spot region, and improve the internal density and dimensional stability of the casting.

[0147] The above embodiments provide a detailed description of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A precision casting sand mold gradient solidification coordinated control system, characterized in that, The system includes: The module includes a basic parameter acquisition module, a target path generation module, a time slice partitioning module, a variable thermal resistance control module, an acoustic-thermal coupling acquisition module, a solidification front inversion module, a feeding channel evaluation module, a solidification deviation judgment module, and a collaborative control module. The basic parameter acquisition module is used to acquire the three-dimensional model of the casting, the solidification temperature range of the material, the wall thickness distribution, the location of the hot spot, the location of the riser, the pouring temperature, as well as the heat transfer parameters of the sand mold and the cooling boundary conditions. The target path generation module is used to generate a target gradient solidification path that progresses from the far-end region to the hot-node region and then to the riser region based on the wall thickness distribution, hot-node location, and riser location. The time slice partitioning module is used to divide the sand mold and the area adjacent to the casting into multiple equal solidification time slice control zones according to the target gradient solidification path, and to configure the target solidification time window and target thermal resistance state for each equal solidification time slice control zone. The variable thermal resistance control module is located in the equal solidification time control zone and is used to switch between the high thermal resistance state, low thermal resistance state and thermal resistance transition state of the corresponding zone. The acoustic-thermal coupling acquisition module is used to acquire multi-source state signals during the solidification process of the casting; the multi-source state signals include at least temperature signals, heat flow signals, acoustic signals and vibration signals. The solidification front inversion module is used to determine the solidification front state based on the multi-source state signal; The feeding channel evaluation module is used to evaluate the feeding channel status between the riser and the hot spot area; The solidification deviation determination module is used to output the solidification deviation type; The collaborative control module is used to control the variable thermal resistance adjustment module to perform cooling, heat preservation, and thermal resistance switching according to the solidification deviation type.

2. The precision casting sand mold gradient solidification coordinated control system according to claim 1, characterized in that, The target path generation module includes: Region identification unit, solidification sequence calculation unit, and feeding direction constraint unit; The region identification unit is used to identify thin-walled regions, thick-walled regions, geometric transition regions, and hot spot regions based on the three-dimensional model of the casting and the wall thickness distribution. The solidification sequence calculation unit is used to determine the theoretical solidification sequence of each region based on the material solidification temperature range, wall thickness distribution, and sand mold thermal conductivity parameters. The feeding direction constraint unit is used to determine the feeding direction based on the riser position and the hot spot position, and to set the region far from the riser and with a shorter theoretical solidification time as the priority solidification region, the hot spot region as the intermediate solidification region, and the region close to the riser as the post-solidification region, thereby generating the target gradient solidification path.

3. The precision casting sand mold gradient solidification coordinated control system according to claim 2, characterized in that, The time slice partitioning module includes: Path projection unit, time slice merging unit, and thermal resistance target configuration unit; The path projection unit is used to project the target gradient solidification path onto the sand mold adjacent area outside the sand mold-casting interface. The time slice merging unit is used to group adjacent areas of sand molds with theoretical solidification times in the same solidification time interval into the same equal solidification time slice control area. The thermal resistance target configuration unit is used to configure low thermal resistance heat dissipation target, high thermal resistance heat preservation target, or thermal resistance transition target for each equal solidification time plate control zone based on the target solidification time window difference between adjacent equal solidification time plate control zones.

4. The precision casting sand mold gradient solidification coordinated control system according to claim 1, characterized in that, The variable thermal resistance control module includes: Thermally conductive components, thermally insulating components, phase change insulation layers, cooling interfaces, thermal insulation interfaces, and thermal resistance switching actuators; The thermally conductive component is used to form a low thermal resistance heat dissipation channel; The thermal insulation component is used to form a high thermal resistance insulation channel; The phase change barrier layer is disposed between the heat-conducting component and the heat-insulating component to form a thermal resistance transition state within the material solidification temperature range; The thermal resistance transition state is formed by the phase change barrier layer maintaining an approximately isothermal heat transfer path through the absorption or release of latent heat of phase change within its phase change temperature range. The phase change temperature is set within the temperature range below the liquidus temperature of the material and above the solidus temperature. The cooling interface is used to connect the cooling medium; The insulation interface is used to connect a heating medium or an insulation medium; The thermal resistance switching actuator is used to drive the heat-conducting component, heat-insulating component, or phase change barrier layer into the corresponding heat transfer position according to the control command output by the collaborative control module.

5. The precision casting sand mold gradient solidification coordinated control system according to claim 4, characterized in that, The acoustic-thermal coupling acquisition module includes: Temperature acquisition unit, heat flow acquisition unit, sound wave transmission and reception unit, and vibration acquisition unit; The temperature acquisition unit is arranged in the area adjacent to the inner wall of the sand mold, the outer wall area of ​​the sand mold, or the neck area of ​​the riser, and is used to acquire temperature signals. The heat flow acquisition unit is arranged on the heat transfer path in the equal solidification time control zone and is used to acquire heat flow signals. The acoustic wave transmitting and receiving unit includes an acoustic wave transmitting end and an acoustic wave receiving end, used to collect acoustic wave propagation time signals and acoustic wave attenuation signals; The acoustic wave transmitting and receiving unit includes multiple sets of acoustic wave transmitting ends and acoustic wave receiving ends arranged around the periphery of the sand mold. Multiple intersecting acoustic paths are formed between adjacent transmitting ends and receiving ends to collect acoustic wave propagation time signals and acoustic wave attenuation signals on different acoustic paths. The acoustic wave transmitter and receiver are set on the metal waveguide medium inside the sand mold. The acoustic wave is transmitted to the area adjacent to the casting through the metal waveguide medium to avoid directly passing through the highly attenuated sand mold body. The acoustic wave transmitting and receiving unit calibrates the unloaded acoustic characteristics of the sand mold before casting to form a reference benchmark, and uses the difference between the measured signal and the reference benchmark as the inversion input. The vibration acquisition unit is installed on the outer wall of the sand mold or the sand mold support structure, and is used to acquire vibration response signals during the solidification process.

6. The precision casting sand mold gradient solidification coordinated control system according to claim 5, characterized in that, The solidification front inversion module includes: Thermal state calculation unit, acoustic state calculation unit, stiffness state calculation unit, and leading edge fusion inversion unit; The thermal state calculation unit is used to calculate the transient heat transfer state of the area adjacent to the sand mold based on the temperature signal and the heat flow signal. The acoustic state calculation unit uses ultrasonic travel time tomography to divide the interior of the casting into a grid. It establishes travel time equations based on the propagation time of sound waves along multiple intersecting sound paths, and solves the sound velocity field using algebraic reconstruction or filtered back projection iteration. The sound velocity field is then converted into a solid fraction field based on a pre-calibrated solid fraction-sound velocity mapping relationship. A preset solid fraction isosurface is used as the solidification front position, and the width of the solid fraction transition zone is used as the width of the mushy region. The stiffness state calculation unit uses the pre-calibrated solidified layer thickness-natural frequency relationship curve to inversely solve the solidified layer thickness from the measured vibration response frequency, as an auxiliary correction signal. The front fusion inversion unit determines the propulsion speed based on the change of the solidification front position at continuous sampling time, and estimates the propulsion direction of the solidification front using the multi-path arrival time difference. Using the transient heat transfer field output by the thermal state calculation unit as the prior field, the prior field is corrected by the measured information output by the acoustic state calculation unit and the stiffness state calculation unit using the data assimilation method. The unit outputs the solidification front position, propulsion speed, propulsion direction, mushy region width, and the remaining liquid phase state of the hot spot region.

7. The precision casting sand mold gradient solidification coordinated control system according to claim 6, characterized in that, The compensation channel evaluation module includes: The unit includes a path compression extraction unit, a channel status calculation unit, and a survival output unit. The feeding path extraction unit is used to determine the feeding path from the riser to the hot spot region based on the riser location, the hot spot location, and the target gradient solidification path. The channel state calculation unit is used to determine the feeding path state based on the continuity of the mushy region, the riser neck temperature, the remaining liquid phase state in the hot spot region, the direction of solidification front advancement, and the risk of feeding path closure. The survival rate output unit is used to output a low survival rate state when the continuity of the mushy region decreases, the riser neck temperature is lower than the target insulation temperature, the remaining liquid phase in the hot spot region is insufficient, the solidification front advance direction deviates from the target gradient solidification path, or the risk of the feeding path being blocked increases. The survival output unit is also used to introduce a continuous determination mechanism: when the survival rate of the patching channel is lower than the preset survival threshold and continues to exceed the preset continuous determination time window, a low survival rate state is output; when the survival rate of the patching channel recovers to above the preset survival threshold and continues to exceed the preset recovery confirmation time window, a survival rate recovery state is output.

8. The precision casting sand mold gradient solidification coordinated control system according to claim 7, characterized in that, The solidification deviation determination module includes: Path deviation judgment unit, time deviation judgment unit, and compensation risk judgment unit; The path deviation determination unit is used to compare the consistency between the actual solidification front advancement direction and the target gradient solidification path direction. The time deviation determination unit is used to compare the actual solidification time of each solidification time control zone with the target solidification time window. The compensation risk determination unit is used to compare the survival rate of the compensation channel with a preset survival threshold. The solidification deviation types include delayed solidification in the distal region, premature solidification in the thin-walled region, premature solidification of the riser neck, closure of the feeding path, and deviation of the solidification front from the target gradient solidification path.

9. The precision casting sand mold gradient solidification coordinated control system according to claim 8, characterized in that, The collaborative control module includes: Cooling control unit, heat preservation control unit, thermal resistance switching control unit, and linkage correction unit; The cooling control unit is used to control the corresponding equal solidification time plate adjustment area to connect the cooling interface when the solidification is delayed in the remote area, and to control the thermal resistance switching actuator to make the heat-conducting component enter the low thermal resistance heat dissipation position. The thermal insulation control unit is used to control the corresponding equal solidification time plate adjustment area to connect the thermal insulation interface when there is a risk of premature solidification in the thin-walled area, and to control the thermal resistance switching actuator to make the thermal insulation component enter the high thermal resistance insulation position. The thermal resistance switching control unit is used to switch the area of ​​the riser neck or the area of ​​the feeding path to a high thermal resistance state when there is a risk of premature solidification in the riser neck or feeding path. The linkage correction unit is used to simultaneously adjust the cooling intensity, heat preservation intensity, and thermal resistance state of two or more adjacent equal solidification time slice control zones when the solidification front deviates from the target gradient solidification path, and to perform coordinated compensation of the cooling intensity, heat preservation intensity, and thermal resistance state based on the heat transfer coupling relationship between adjacent control zones.

10. A method for coordinated control of gradient solidification in precision casting sand molds, characterized in that, The method, applied to the precision casting sand mold gradient solidification coordinated control system according to any one of claims 1 to 9, comprises: Obtain the three-dimensional model of the casting, the solidification temperature range of the material, the wall thickness distribution, the location of the hot spot, the location of the riser, the pouring temperature, as well as the heat transfer parameters of the sand mold and the cooling boundary conditions; Based on the wall thickness distribution, hot spot location, and riser location, a target gradient solidification path is generated that progresses from the far-end region to the hot spot region and then to the riser region. Based on the target gradient solidification path, the sand mold and the area adjacent to the casting are divided into multiple equal solidification time control zones, and the target solidification time window and target thermal resistance state of each equal solidification time control zone are determined. A variable thermal resistance control module is configured in each solidification time control zone, so that the corresponding zone can switch between high thermal resistance state, low thermal resistance state and thermal resistance transition state. Collect multi-source state signals during the solidification process of the casting; the multi-source state signals include at least temperature signals, heat flow signals, sound wave signals, and vibration signals; The solidification front state is determined based on the multi-source state signal; Evaluate the state of the feeding channel between the riser and the hot spot; The type of solidification deviation is determined based on the state of the feeding channel, the target solidification time window, and the target gradient solidification path. According to the solidification deviation type, the corresponding solidification time control zone is used to perform cooling, heat preservation, low thermal resistance switching, high thermal resistance switching, or multi-zone linkage correction until the casting completes solidification and forms a gradient solidification state that progresses along the target gradient solidification path.

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