A casting process and equipment for long and eccentric sleeve metal castings

Abstract

The application discloses a kind of long eccentric sleeve metal castings pouring process and equipment, it is related to metal casting pouring technical field, the core dynamic support and positioning include: before starting servo adjusting type multi-point support arm, 2 groups are set to each side 8 groups of support arm, distribution is in core upstream and downstream and symmetrical position;Real-time displacement amount of core is detected using non-contact laser displacement sensor, data is transmitted to PLC system in real time;When detecting that core displacement deviation exceeds ±0.05mm, PLC automatically adjusts support arm lifting and clamping, realizes core locking positioning.The application realizes real-time online locking core center position function by designing dynamic core support positioning, solves the problem of core deviation and fracture, improves the size precision of casting.

Description

Technical Field

[0001] This invention relates to the field of metal casting technology, specifically to a casting process and equipment for a slender eccentric sleeve metal casting. Background Technology

[0002] Slender, eccentric sleeve casting cores are prone to displacement or breakage during resin sand casting due to buoyancy and thermal stress of the molten metal, resulting in defects such as uneven wall thickness, shrinkage cavities, porosity, and sand adhesion. Traditional processes rely heavily on passive chills and local risers for feeding, which cannot achieve overall sequential solidification and online closed-loop control, resulting in low yield and significant manual intervention.

[0003] Patent CN109676117B discloses a metal mold casting inverting pouring device and its pouring method. The above patent reduces casting defects and greatly improves the yield.

[0004] The aforementioned patent employs a reverse pouring process, which allows molten metal to smoothly enter the mold cavity from the bottom. This reduces turbulence in the molten metal, helps to block slag, and removes gas from the mold cavity. However, the slender core is susceptible to buoyancy and thermal stress during the molten metal filling process, which can lead to core displacement or breakage, resulting in uneven casting wall thickness and out-of-tolerance dimensions.

[0005] Therefore, this application proposes a casting process and equipment for slender eccentric sleeve metal castings that can lock the core center position online in real time. Summary of the Invention

[0006] The purpose of this invention is to provide a casting process and equipment for slender eccentric sleeve metal castings, so as to solve the technical problems mentioned in the background art, such as uneven wall thickness, shrinkage cavities, porosity and sand adhesion caused by the displacement or fracture of molten metal due to buoyancy and thermal stress.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a casting process for a slender eccentric sleeve metal casting, comprising sand mold and core preparation, dynamic core support and positioning, vacuum-assisted bottom pouring, electromagnetic stirring-assisted filling, dual-zone temperature field control, intelligent closed-loop control, and cooling demolding and post-treatment, wherein the dynamic core support and positioning includes:

[0008] Before closing the mold, start the servo-adjustable multi-point support arm. There are 2 sets of support arms on each side, for a total of 8 sets, distributed in the upstream and downstream and symmetrical parts of the core.

[0009] The real-time displacement of the core is detected by a non-contact laser displacement sensor, and the data is transmitted to the PLC system in real time.

[0010] When the detected core displacement deviation exceeds ±0.05mm, the PLC automatically adjusts the lifting and clamping of the support arm to achieve core locking and positioning.

[0011] Preferably, the preparation of the sand mold and core includes the following steps:

[0012] The outer sand box is made of resin sand. The sand mixing process controls the sand mold compressive strength to be ≥2MPa and the sand temperature to be controlled between 15℃ and 35℃.

[0013] The core is a slender eccentric structure made of resin sand, with a length-to-outer-mold ratio of 0.6 to 0.95. An internal ceramic-metal composite skeleton is embedded. The skeleton is composed of a nickel-chromium alloy shell covering a high-strength ceramic rod. The ceramic in the ceramic-metal composite skeleton is zirconia ceramic, and the metal cladding layer is a nickel-chromium alloy with a thickness of 0.5 to 1.0 mm. The core length is 1 / 5 to 1 / 8 of the total length of the casting.

[0014] Preferably, the vacuum-assisted bottom-pouring casting includes:

[0015] After the mold is sealed, the cavity is maintained at a negative pressure of 0.05MPa to 0.08MPa through the vacuum vent located on the top plate of the mold.

[0016] The molten metal is filled from bottom to top through multiple ingates located at the bottom of the casting. The ingates have a diameter of 10~12mm and are distributed in radially symmetrical positions. The filling speed is controlled at 0.7~1.0m / s to suppress turbulence.

[0017] The molten metal used for casting is QT500-7 ductile iron, the casting temperature is controlled at 1430±15℃, and the casting time is ≤40s.

[0018] Preferably, the electromagnetic stirring-assisted filling includes:

[0019] A frequency-adjustable electromagnetic induction coil with 5 to 10 turns is arranged around the mold, with an induced current of 0.5 to 2 kA and a frequency of 10 to 30 Hz.

[0020] During the casting process, an electric current is applied to create a micro-perturbation magnetic field, which acts on the molten metal in the mold cavity, improving the uniformity of filling and promoting the escape of microbubbles.

[0021] Preferably, the dual-zone temperature field control includes:

[0022] Arrange adjustable chills with a thickness of 10~30mm in the thick parts of the casting, and adjust the insertion depth to control the local cooling rate ≤30℃ / min;

[0023] An annular resistance heating jacket is installed in the riser area at the top of the casting to maintain the surface temperature at 500℃~600℃ and prolong the riser solidification time.

[0024] A K-type thermocouple array is arranged along the longitudinal direction of the casting, with one measuring point every 20~50mm, and the sampling frequency is ≥1Hz.

[0025] Preferably, the intelligent closed-loop control includes:

[0026] All displacement and temperature signals are compared with the preset solidification curve through the PLC system;

[0027] When the system detects a temperature deviation > ±5℃ or a displacement > ±0.05mm, the PLC system issues an adjustment command to control the chill insertion depth, heating jacket output power, and support arm position, thereby achieving closed-loop regulation throughout the entire process.

[0028] Preferably, the cooling demolding and post-processing includes:

[0029] After pouring, the indoor pressure is restored to normal, and the cavity is maintained for cooling time of ≥36 hours to ensure complete solidification;

[0030] After cooling, the castings are unpacked and demolded, and then subjected to shot blasting, grinding, dimensional re-inspection, and ultrasonic testing.

[0031] Preferably, the support arm is made of aluminum alloy coated with heat-resistant ceramic material, and has a flexible coupling for connection with a linear guide rail. The vacuum pumping device adopts a dual-channel pump group structure with a pressure feedback valve to dynamically maintain the pumping pressure within a preset range of ±5%. The electromagnetic induction coil is wrapped with high-temperature ceramic insulating material and has an embedded thermal resistance temperature control module to ensure that the coil surface temperature does not exceed 80°C. The PLC chill insertion depth is connected by an HMI and has a real-time data upload function to the cloud, uploading the solidification curve and displacement trajectory to the server for subsequent data modeling and optimization. The internal shrinkage cavity volume fraction of the casting is controlled below 0.1%, the core offset is controlled within ±0.02mm, and the casting density is ≥7.15g / cm³. 3 .

[0032] Preferably, the casting equipment includes:

[0033] The sand mold fixing and box assembly platform is equipped with a dual-guide rail precision positioning mechanism;

[0034] The dynamic core support system includes multiple servo-adjustable ceramic-metal support arms, a non-contact laser displacement sensor group, and a linkage positioning algorithm module;

[0035] The vacuum-assisted bottom injection system includes a mold evacuation pipeline, a two-stage vacuum pump unit, and a distributed bottom injection gate system;

[0036] The electromagnetic stirring module includes a multi-turn coil, a power control box, and a cooling protection system;

[0037] The temperature field control system includes a distributed lifting chill, a resistance heating jacket, and a K-type thermocouple array sensing module;

[0038] The main control system uses a PLC controller and is equipped with an HMI touch terminal, real-time monitoring software, and a process database.

[0039] Preferably, the main control system comprises:

[0040] Displacement control unit: Receives data from the laser sensor and controls the movement of the support arm with an accuracy of ≤±0.02mm;

[0041] Temperature control unit: Receives thermocouple temperature curves and controls the chill insertion depth error to ≤±1mm and the heating jacket temperature error to ≤±5℃;

[0042] Process self-learning function: Automatically optimizes the cooling rhythm by comparing the historical successful freezing curve with the current curve.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] 1. This invention, through the design of a dynamic core support positioning, achieves real-time online locking of the core center position, solving the problems of core offset and breakage, and improving the dimensional accuracy of castings;

[0045] 2. This invention, through the design of vacuum-assisted bottom-pouring casting and electromagnetic stirring-assisted filling, achieves turbulent filling, promotes degassing, solves the problems of shrinkage cavities, porosity and sand adhesion, improves the density of castings, and reduces shrinkage cavities and porosity.

[0046] 3. This invention achieves sequential solidification through a dual-zone temperature field control design, solving the problems of local shrinkage porosity and uneven solidification, causing shrinkage cavities to move to the riser and improving the density of the casting;

[0047] 4. This invention, through the design of intelligent closed-loop control, realizes the function of automatic adjustment and optimization of parameters throughout the process, solves the problems of reliance on manual experience and large process fluctuations, and improves the casting yield. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the casting process for the slender eccentric sleeve metal casting of the present invention. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] Please see Figure 1The present invention provides an embodiment of a casting process for a slender eccentric sleeve metal casting, comprising sand mold and core preparation, dynamic support and positioning of the core, vacuum-assisted bottom pouring, electromagnetic stirring-assisted filling, dual-zone temperature field control, intelligent closed-loop control, and cooling demolding and post-treatment. The sand mold and core preparation includes the following steps:

[0051] The outer sand box is made of resin sand. The sand mixing process controls the sand mold compressive strength to be ≥2MPa and the sand temperature to be controlled between 15℃ and 35℃.

[0052] The core is a slender eccentric structure made of resin sand, with a length-to-outer-mold ratio of 0.6 to 0.95. An internal ceramic-metal composite skeleton is embedded. The skeleton is composed of a nickel-chromium alloy shell covering a high-strength ceramic rod. The ceramic in the ceramic-metal composite skeleton is zirconium oxide ceramic, and the metal cladding layer is a nickel-chromium alloy with a thickness of 0.5 to 1.0 mm. The core length is 1 / 5 to 1 / 8 of the total length of the casting.

[0053] The sand mold fixing and box assembly platform is equipped with a dual-guide rail precision positioning mechanism;

[0054] The support arm is made of aluminum alloy coated with heat-resistant ceramic and is connected to a linear slide rail via a flexible coupling.

[0055] Furthermore, the sand used for sand molding is high-quality resin sand with a recycling rate of ≥90%, and the amount of new sand added is ≤10%; the resin ratio is 1%~1.2%, and the p-toluenesulfonic acid curing agent accounts for 55%~60% of the resin mass; the sand mixing process is as follows: 80% recycled sand and 20% new sand are added to a continuous sand mixer first, and after adding the resin and curing agent, the mixture is mixed for 60 seconds and then allowed to stand for 30 seconds; the sand temperature and strength are as follows: the sand temperature is controlled at 15℃~35℃ in winter and the same in summer; sampling and testing are conducted, and the compressive strength of the sand mold is ≥2MPa;

[0056] Core geometry: The ratio of the total core length to the outer mold length is 0.6~0.95, and the eccentricity ±δ is determined according to the design value; Skeleton structure: A composite skeleton composed of a zirconia ceramic rod and a nickel-chromium alloy shell with a thickness of 0.5mm~1.0mm is pre-embedded in the core body; Curing and inspection: After the core is made, it is left to cure naturally for 24 hours. Sampling and testing show that the dimensional deviation is ≤±0.05mm and the surface strength is ≥1.8MPa;

[0057] Sand mold fixing and box clamping: The mold platform is equipped with a double guide rail precision positioning mechanism. The guide rail spacing is customized according to the width of the mold shape. The guide rail is equipped with a linear encoder, and the positioning accuracy is ≤0.02mm. When closing the box, the sand mold is closed by the synchronous jacks on the left and right sides of the platform to keep the box closing pressure uniform. The box closing force is controlled within the range of 5kN~8kN. The completed core and composite skeleton are placed into the positioning groove of the lower sand box and aligned using the platform guide rails. After the upper sand box is closed to the contact state, the core compensation eccentricity δ is ≤±0.02mm by manually adjusting the screw. After determining the position, the platform quick device is tightened to prevent the whole body from moving during subsequent support and pouring processes.

[0058] Please see Figure 1 The present invention provides an embodiment of a casting process for a slender eccentric sleeve metal casting, wherein the dynamic support and positioning of the core includes:

[0059] Before closing the mold, start the servo-adjustable multi-point support arm. There are 2 sets of support arms on each side, for a total of 8 sets, distributed in the upstream and downstream and symmetrical parts of the core.

[0060] The real-time displacement of the core is detected by a non-contact laser displacement sensor, and the data is transmitted to the PLC system in real time.

[0061] When the detected core displacement deviation exceeds ±0.05mm, the PLC automatically adjusts the lifting and clamping of the support arm to achieve core locking and positioning.

[0062] The dynamic core support system includes multiple servo-adjustable ceramic-metal support arms, a non-contact laser displacement sensor group, and a linkage positioning algorithm module;

[0063] Furthermore, before closing the mold, the PLC sends a "zeroing" command to each servo drive, causing the eight support arms to retract to their initial position 10mm away from the core surface. After zeroing, the PLC verifies that the position error of each arm is ≤0.1mm before proceeding to the next step. The PLC controls each support arm to move forward at a speed of 10mm / s according to a preset curve, contacting the core surface and applying an initial preload of 100N. The preload sensor samples in real time to ensure that the uniformity error of the preload between the eight arms is ≤±5N. After preloading is completed, the PLC displays the actual preload value of each arm on the HMI interface, which can be manually confirmed or automatically corrected.

[0064] Each laser displacement sensor is mounted on the support arm mounting base, with a measurement range of 0-5mm. After the mold box is closed and pre-tightened, the PLC triggers "zero-point calibration," recording the original readings of 8 measuring points as baselines. The PLC compares the calibrated readings with the stored baseline values; the difference must be ≤ ±0.02mm before pouring preparation can begin. If the difference exceeds the limit, the system prompts "sensor abnormality" and automatically performs recalibration or alarms. The laser displacement sensor outputs the core center offset Δx in real time. i(i=1...8), the PLC sets the deviation threshold Δx-max=±0.05mm; whenever any Δx i If the error exceeds ±0.05mm, the PLC immediately calculates the required compensation force ΔF = K·(Δx) i -sgn(Δx) i (0.05mm), where K=200N / mm, the PLC adjusts the servo driver of the corresponding support arm according to the ΔF command, adjusting the clamping force and displacement until Δx i All Δx recovered to within ±0.02mm. i Once stabilized, the PLC locks the current arm position and continues monitoring for the next sample.

[0065] To address the core offset trend, the algorithm performs a weighted average of the feedback signals from the eight arms. If the absolute value of the weighted offset result is greater than 0.03 mm, all support arms are finely adjusted simultaneously to ensure overall center correction.

[0066] Please see Figure 1 The present invention provides an embodiment of a casting process for a slender eccentric sleeve metal casting, wherein the vacuum-assisted bottom-pouring casting includes:

[0067] After the mold is sealed, the cavity is maintained at a negative pressure of 0.05MPa to 0.08MPa through the vacuum vent located on the top plate of the mold.

[0068] The molten metal is filled from bottom to top through multiple ingates located at the bottom of the casting. The ingates have a diameter of 10~12mm and are distributed in radially symmetrical positions. The filling speed is controlled at 0.7~1.0m / s to suppress turbulence.

[0069] The molten metal used for pouring is QT500-7 ductile iron, the pouring temperature is controlled at 1430±15℃, and the pouring time is ≤40s.

[0070] The vacuum-assisted bottom injection system includes a mold evacuation pipeline, a two-stage vacuum pump unit, and a distributed bottom injection gate system;

[0071] The vacuum pumping device adopts a dual-channel pump set structure and is equipped with a pressure feedback valve to dynamically maintain the pumping pressure within a preset range of ±5%.

[0072] Next, the upper and lower sand boxes are closed, aligned with the double guide rail precision positioning mechanism and locked. Two φ20mm vacuum extraction ports are reserved on the top plate of the mold and connected to the two-stage vacuum pump group located in the side cabinet of the equipment. All flange sealing rings are checked to ensure that there are no air leaks after the boxes are closed. Two two-stage rotary vane pumps, A and B, are connected in series. Pump A has a pumping speed of 100L / min and pump B has a pumping speed of 60L / min. An automatic pressure feedback valve and an electronic pressure sensor are installed in the extraction pipeline. The sensor has a range of 0-0.1MPa and an accuracy of 0.001MPa. The vacuum pipeline uses a 16mm inner diameter high-temperature resistant flexible hose and is arranged as short and straight as possible to reduce leakage and dead zone volume.

[0073] After the mold is closed, the PLC issues a "vacuum" command, starting pumps A and B to work in parallel. The vacuum line pressure rapidly drops to a negative pressure of 0.1MPa over approximately 8 seconds. When the pressure reaches the preset value of 0.08MPa, the PLC slightly opens the B pump channel through the pressure feedback valve to maintain a stable negative pressure of 0.05MPa~0.08MPa. This negative pressure is maintained for at least 30 minutes after the pouring is completed, with pressure fluctuations within ±5%. QT500-7 ductile iron is smelted, with a carbon equivalent of 4.2% and a sulfur content ≤0.02%. Magnesium oxide coating is used for pretreatment, and the temperature is adjusted to 1430±15℃. The holding furnace is equipped with thermocouple monitoring, with temperature fluctuations ≤±5℃. A 150mm thermocouple is installed before the riser and gating gate. 3 The preheated core has four radially symmetrical ingates at the bottom, with an inner diameter of 12mm and a length customized according to the bottom thickness of the casting. The ingate surface is coated with a magnesium oxide heat-insulating coating. The PLC synchronously controls the opening of the pouring valve. The molten metal fills the cavity from bottom to top through the four ingates at a single-sided flow rate of 0.8m / s and an overall filling speed of 0.8m / s to 1.0m / s. The entire filling process, from the opening of the pouring port to the closing of the last riser, is controlled within 35s and does not exceed 40s. A 1kA / 20Hz electromagnetic induction coil is started synchronously with the pouring. The micro-perturbation field continues until the last molten metal from the ingate enters the cavity and then stops. Stirring promotes the discharge of gas to the bottom and further reduces the formation of porosity.

[0074] After pouring, continue vacuuming for 30 minutes to further reduce the residual air pressure in the cavity and promote the discharge of microbubbles inside the molten metal. The laser displacement and thermocouple system continue to monitor the core and temperature. No additional action of the support arm is required. After 30 minutes, the PLC commands to gradually shut down the vacuum pump and open the pressure relief valve, so that the pressure in the mold cavity slowly rises to atmospheric pressure within 60 seconds to avoid core drift caused by sudden pressure. After the pressure relief is completed, wait 5 minutes before retracting the support arm and opening the mold.

[0075] Please see Figure 1 The present invention provides an embodiment of a casting process for a slender eccentric sleeve metal casting, wherein the electromagnetic stirring-assisted filling includes:

[0076] A frequency-adjustable electromagnetic induction coil with 5 to 10 turns is arranged around the mold, with an induced current of 0.5 to 2 kA and a frequency of 10 to 30 Hz.

[0077] During the casting process, an electric current is applied to create a micro-perturbation magnetic field, which acts on the molten metal in the mold cavity, improving the uniformity of filling and promoting the escape of microbubbles.

[0078] The electromagnetic stirring module includes a multi-turn coil, a power control box, and a cooling protection system;

[0079] The electromagnetic induction coil is clad with high-temperature ceramic insulating material and has an embedded thermal resistance temperature control module to ensure that the coil surface temperature does not exceed 80°C.

[0080] Furthermore, a frequency-adjustable electromagnetic induction coil is evenly wound 7 turns along the longitudinal direction of the sand mold outside the mold. The coil width covers 50% of the outer perimeter of the mold, and the height matches the height of the cavity and is slightly higher than the riser by 20mm. The coil conductor is made of φ6mm heat-resistant copper-aluminum composite wire, and is wrapped with a 0.5mm thick high-temperature ceramic insulation material. A miniature PT100 thermal resistance sensing unit is embedded between every 3rd and 5th turns to monitor the coil surface temperature in real time. A high-temperature resistant fiber mesh is then covered on the outside of the insulation layer to improve mechanical strength and prevent accidental collision damage.

[0081] Equipped with a 600V / 3kA adjustable DC power supply and inverter module, the output current is adjustable from 0.5kA to 2kA and the frequency is adjustable from 10Hz to 30Hz. The control box has a built-in soft start function, and the output current rises from 0 to the target current in a linear manner within 2 seconds to avoid instantaneous strong impact on the core. The thermal resistance temperature control module has a sampling frequency of 1Hz. When the coil surface temperature is ≥80℃, the PLC automatically reduces the current to a safe value of 0.5kA and alarms. If the temperature continues to rise, it will automatically cut off the power and switch to bypass cooling mode. It can only be restarted after the temperature drops below 50℃.

[0082] Five seconds before vacuum bottom injection begins, the PLC sends a "preheat" command to the power control box, increasing the current to 0.5kA / 10Hz to preheat the coil and stabilize the winding temperature. Once the vacuum negative pressure reaches 0.06MPa and the core is positioned, the pouring valve opens, and the PLC immediately increases the current to 1kA / 20Hz, switching to "stirring mode": Initial stage (0~10s): The current is maintained at 1kA / 20Hz to promote the flow of molten metal into the cavity and suppress initial turbulence; Middle stage (10~25s): The current can be adjusted to 1.5kA / 25Hz, and the current is finely adjusted by ±0.2kA according to the temperature gradient and flow rate curve fed back by the thermocouple; Final stage (25s until filling is complete): The current is gradually reduced to 0.8kA / 15Hz to allow auxiliary gas to escape and stabilize the surface of the molten metal; After pouring is completed, the final current is maintained for 2 seconds to ensure that the last participating liquid is fully stirred, and then the power is slowly cut off.

[0083] The outer layer of the coil is equipped with an aluminum alloy heat sink, which improves the passive heat dissipation rate by 30%. A small air-cooled high-temperature fan is installed at the bottom and on both sides of the bracket. It is linked with the thermal switch and automatically turns on when the coil surface temperature is >70℃. During the normal casting cycle, the fan keeps blowing air at a low speed. If the coil surface temperature is >75℃, the fan switches to high speed and the air-cooling pipeline is activated at the same time to compensate for cooling until the temperature is <65℃.

[0084] Please see Figure 1 The present invention provides an embodiment of a casting process for a slender eccentric sleeve metal casting, wherein the dual-zone temperature field control includes:

[0085] Arrange adjustable chills with a thickness of 10~30mm in the thick parts of the casting, and adjust the insertion depth to control the local cooling rate ≤30℃ / min;

[0086] An annular resistance heating jacket is installed in the riser area at the top of the casting to maintain the surface temperature at 500℃~600℃ and prolong the riser solidification time.

[0087] A K-type thermocouple array is arranged along the longitudinal direction of the casting, with one measuring point every 20~50mm, and the sampling frequency is ≥1Hz;

[0088] The temperature field control system includes a distributed lifting chill, a resistance heating jacket, and a K-type thermocouple array sensing module;

[0089] The PLC chill insertion depth is connected via HMI and features real-time data upload to the cloud. Solidification curves and displacement trajectories are uploaded to the server for subsequent data modeling and optimization. The internal shrinkage cavity volume fraction of the casting is controlled below 0.1%, core offset is controlled within ±0.02mm, and the casting density is ≥7.15g / cm³. 3；

[0090] Furthermore, a set of liftable chills is arranged on each side of the thicker parts of the casting, such as the flange connection section. Each set contains two parallel chills made of high thermal conductivity cast iron, with an insertion depth of 0-30mm, driven by a servo motor via a lead screw. A ring-shaped resistance heating sleeve surrounds the riser, with an inner diameter designed to be 1.5D based on the riser diameter D. The sleeve is made of steel pipe lined with a ceramic insulation layer, and the heating wire is made of Ni-Cr alloy wire with a rated power of 3kW. With a PID controller, the temperature is maintained in real-time at 500℃~600℃. K-type heating... The thermocouple array is evenly distributed along the longitudinal direction of the casting, with a measuring point every 40mm. The thermocouples are fixed to the outside of the sand mold and are in contact with the cavity through a high-temperature ceramic sleeve. The sampling frequency is 1Hz. The PLC is responsible for reading 10 temperature signals and core displacement signals, running a dual-zone temperature control algorithm. The initial insertion depth of the chill and the target temperature of the heating jacket can be manually set on the HMI interface, and the temperature curve and insertion depth change are displayed in real time. The system has a data upload function to the cloud, pushing the latest 10-point temperature-time curve and displacement trajectory to the server every 60s.

[0091] After the mold box is closed and the core is locked, the PLC commands the annular heating jacket to preheat at 1kW for 5 minutes, raising the temperature in the riser area to 400℃. Simultaneously, the chill is retracted to its initial position, and the thermocouples are calibrated at their designated points to achieve the "zero-temperature" and the baseline is recorded. After vacuum injection is initiated, the riser temperature reaches 500℃. The PLC simultaneously sets the initial chill insertion depth to 20mm, and the system begins recording the temperature at each point and the core displacement Δx. The PLC calculates the temperature slope of the thermocouples near the flange section in real time.

[0092] Rcool = -ΔT / Δt, where ΔT is the temperature difference and Δt is the time difference;

[0093] If Rcool > 30℃ / min, the chill insertion depth will be reduced by 1mm each time;

[0094] If Rcool < 20℃ / min, the chill insertion depth is increased by 1mm each time;

[0095] The PLC compares the temperature of the thermocouple in the riser area with the target 550℃. If the deviation is greater than ±20℃, the heating jacket power is adjusted by ±10%. When the riser temperature drops below 300℃ and the flange area temperature drops below 550℃, the PLC commands the chiller to reset and the heating jacket to be de-energized. The system waits for the temperature to cool naturally to room temperature under normal pressure, then the core support is removed, and the mold is unpacked and demolded for post-processing.

[0096] Please see Figure 1 The present invention provides an embodiment of a casting process for a slender eccentric sleeve metal casting, wherein the intelligent closed-loop control includes:

[0097] All displacement and temperature signals are compared with the preset solidification curve through the PLC system;

[0098] When the system detects a temperature deviation > ±5℃ or a displacement > ±0.05mm, the PLC system issues an adjustment command to control the chill insertion depth, heating jacket output power, and support arm position, thereby achieving closed-loop regulation throughout the entire process.

[0099] The main control system uses a PLC controller and is equipped with an HMI touch terminal, real-time monitoring software, and a process database.

[0100] The main control system has the following features:

[0101] Displacement control unit: Receives data from the laser sensor and controls the movement of the support arm with an accuracy of ≤±0.02mm;

[0102] Temperature control unit: Receives thermocouple temperature curves and controls the chill insertion depth error to ≤±1mm and the heating jacket temperature error to ≤±5℃;

[0103] Process self-learning function: Automatically optimizes the cooling rhythm by comparing the historical successful freezing curve with the current curve;

[0104] Next, the PLC main control system is started, and the process personnel's account is logged in through the HMI. The HMI automatically loads the preset "temperature-time solidification curve" and "core displacement threshold curve" of this batch of castings from the process database. After the mold is closed and the core is locked, the PLC reads the initial readings of 8 laser displacement sensors and 10 K-type thermocouples in sequence to establish baseline data. The HMI displays the baseline values ​​of each measuring point and the preset upper / lower limits. After manual confirmation, the pouring stage begins.

[0105] Data sampling: Laser displacement: sampling frequency 1Hz, acquiring Δx1~Δx8; Thermocouple data: sampling frequency 1Hz, acquiring T1~T 10 The PLC filters the raw data, averages it three times using a sliding window, and then sends it to the closed-loop comparison module. After each sampling, the PLC sends the current temperature vector T. i (t) and the preset solidification curve T i -ref(t) is used to calculate the difference ΔT i =T i -T i -ref; Simultaneously calculate the maximum displacement deviation Δx - max = max(|Δx1...Δx8|);

[0106] Temperature deviation response: If any ΔTᵢ > +5℃, the PLC issues a "cooling" command, controlling the corresponding chill insertion depth to increase by 2mm; if any ΔTᵢ < -5℃, the PLC issues a "warming" command, reducing the chill insertion depth by 2mm or increasing the heating jacket power by 5%.

[0107] Displacement deviation response: If Δx_max > 0.05mm, the PLC issues a "support arm pressurization" command, increasing the clamping force of the corresponding arm by ΔF = 200N / mm × (Δx_max – 0.05mm) until Δx_max ≤ 0.02mm; if Δx_max < 0.02mm, the PLC can command to release the support arm by 5N to reduce the risk of over-clamping; all adjustment commands enter the PLC command queue, following the "temperature priority → displacement priority" strategy: temperature deviation processing is performed first; displacement deviation processing is performed second; after each round of adjustment, the PLC waits 5 seconds before performing the next sampling comparison to avoid command conflicts;

[0108] The displacement control unit receives data from the laser sensor and controls the servo support arm through a PID algorithm to achieve a motion accuracy of ≤0.02mm. It has step-back protection: if the displacement is not corrected after 3 consecutive commands, it will automatically alarm and stop pouring. The temperature regulation unit receives thermocouple signals and drives the chill and PID control the heating jacket through a bidirectional four-cylinder drive. The chill insertion depth error is ≤±1mm and the heating jacket temperature error is ≤±5℃. When switching between the chill and the heating jacket, it has a soft switching function, that is, a smooth transition within 2 seconds to avoid thermal shock.

[0109] After this batch of casting is completed, the PLC packages all sampling points, including temperature curves, displacement trajectories, and adjustment command timestamps, and uploads them to the process database. The server runs the data analysis model, compares the historical successful curves with the current curve, and automatically adjusts the preset solidification curve parameters for the next batch, such as the initial insertion depth of the chill and the response threshold. The optimization results are sent to the PLC through the HMI and are automatically loaded on the next startup.

[0110] Please see Figure 1 The present invention provides an embodiment of a casting process for a slender eccentric sleeve metal casting, wherein the cooling, demolding, and post-treatment include:

[0111] After pouring, the indoor pressure is restored to normal, and the cavity is maintained for cooling time of ≥36 hours to ensure complete solidification;

[0112] After cooling, the casting is unpacked and demolded, and then the surface of the casting is shot-blasted, ground, dimensionally inspected, and ultrasonically tested.

[0113] Furthermore, after casting, the PLC controls the pressure relief valve to slowly increase the cavity pressure from 0.06MPa negative pressure to atmospheric pressure within 60 seconds to avoid stress concentration in the core or sand mold structure caused by sudden pressure changes. The automotive workshop environment is maintained at 20±5℃ and relative humidity ≤60%, and the casting is allowed to cool naturally for 36 hours. During the cooling process, the core temperature is monitored by the fifth measuring point of the thermocouple, i.e., the middle of the casting. It is required that the core temperature drop from 900℃ to 400℃ within 24 hours and to <200℃ within 36 hours. Vibration and movement of the mold closing platform are strictly prohibited during the cooling period to prevent sand mold deformation or stress damage to the casting.

[0114] After cooling is complete, the PLC issues a "support arm reset" command. All support arms retract to their initial positions at a speed of 10mm / s, with a reset error of ≤±0.1mm. The platform quick-lock mechanism is manually or automatically activated, and the guide rail slides smoothly to open the upper sand box. During operation, the buffer and limit blocks must be kept intact. The opening speed should be ≤5mm / s to ensure that the sand mold separates slowly. The workpiece is held by the robotic arm with a clamping pressure of ≤500N to avoid surface indentations and is placed on a fire-resistant frame for later use.

[0115] The machine uses a tracked gantry shot blasting machine. The size of the shot blasting chamber is customized according to the shape of the casting. The shot blasting medium is G10 grade carbon steel shot with an average diameter of 0.7mm and a hardness of HRC45. The shot blasting pressure is 0.4MPa and the shot blasting distance is 150mm. The casting is taken out after circulating in the chamber for 2 weeks, and residual sand and oxide scale are thoroughly removed.

[0116] Working principle: A closed-loop system is formed by a servo-adjustable multi-point support arm and a non-contact laser displacement sensor to detect and correct core offset in real time, keeping the core stable and without displacement throughout the entire process;

[0117] After the mold is closed, the cavity is drawn to a negative pressure of 0.05MPa~0.08MPa, and then QT500-7 ductile iron is poured from bottom to top through the radially symmetrical inner gating. At the same time, an electromagnetic field of 0.5-2kA and 10-30Hz is introduced to suppress turbulence and promote gas escape.

[0118] A liftable chill is inserted into the thick part of the casting flange, a resistance heating jacket is wrapped around the riser, and K-type thermocouples are arranged longitudinally. The PLC automatically adjusts the chill insertion depth, heating jacket power and support arm position according to the temperature and displacement signals compared with the preset curve, realizing a closed loop throughout the process.

[0119] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A casting process for a slender eccentric sleeve metal casting, comprising sand mold and core preparation, dynamic core support and positioning, vacuum-assisted bottom pouring, electromagnetic stirring-assisted filling, dual-zone temperature field control, intelligent closed-loop control, and cooling demolding and post-treatment, characterized in that: The dynamic support and positioning of the core includes: Before closing the mold, start the servo-adjustable multi-point support arm. There are 2 sets of support arms on each side, for a total of 8 sets, distributed in the upstream and downstream and symmetrical parts of the core. The real-time displacement of the core is detected by a non-contact laser displacement sensor, and the data is transmitted to the PLC system in real time. When the detected core displacement deviation exceeds ±0.05mm, the PLC automatically adjusts the lifting and clamping of the support arm to achieve core locking and positioning. The dual-zone temperature field control includes: Arrange adjustable chills with a thickness of 10~30mm in the thick parts of the casting, and adjust the insertion depth to control the local cooling rate ≤30℃ / min; An annular resistance heating jacket is installed in the riser area at the top of the casting to maintain the surface temperature at 500℃~600℃ and prolong the riser solidification time. A K-type thermocouple array is arranged along the longitudinal direction of the casting, with one measuring point every 20~50mm, and the sampling frequency is ≥1Hz; The intelligent closed-loop control includes: All displacement and temperature signals are compared with the preset solidification curve through the PLC system; When the system detects a temperature deviation > ±5℃ or a displacement > ±0.05mm, the PLC system issues an adjustment command to control the chill insertion depth, heating jacket output power, and support arm position, thereby achieving closed-loop regulation throughout the entire process. The support arm is made of aluminum alloy coated with heat-resistant ceramic and is connected to a linear slide rail via a flexible coupling. Each laser displacement sensor is mounted on the support arm mounting base, with a measurement range of 0-5mm. After the mold box is closed and pre-tightened, the PLC triggers "zero-point calibration," recording the original readings of 8 measuring points as a baseline. The PLC compares the calibrated readings with the stored baseline value. The casting preparation can only begin if the difference is ≤ ±0.02mm. If the difference exceeds the limit, the system prompts "sensor abnormality" and automatically performs recalibration or an alarm. The laser displacement sensor outputs the core center offset Δx in real time. i (i=1...8), the PLC sets the deviation threshold Δx-max=±0.05mm; whenever any Δx i If the error exceeds ±0.05mm, the PLC immediately calculates the required compensation force ΔF = K·(Δx) i -sgn(Δx) i (0.05mm), where K=200N / mm, the PLC adjusts the servo driver of the corresponding support arm according to the ΔF command, adjusting the clamping force and displacement until Δx i All Δx recovered to within ±0.02mm. i Once stabilized, the PLC locks the current arm position and continues monitoring for the next sample.

2. The casting process for a slender eccentric sleeve metal casting according to claim 1, characterized in that: The preparation of the sand mold and core includes the following steps: The outer sand box is made of resin sand. The sand mixing process controls the sand mold compressive strength to be ≥2MPa and the sand temperature to be controlled between 15℃ and 35℃. The core is a slender eccentric structure made of resin sand, with a length-to-outer-mold ratio of 0.6 to 0.

95. An internal ceramic-metal composite skeleton is embedded. The skeleton is composed of a nickel-chromium alloy shell covering a high-strength ceramic rod. The ceramic in the ceramic-metal composite skeleton is zirconia ceramic, and the metal cladding layer is a nickel-chromium alloy with a thickness of 0.5 to 1.0 mm. The core length is 1 / 5 to 1 / 8 of the total length of the casting.

3. The casting process for a slender eccentric sleeve metal casting according to claim 1, characterized in that: The vacuum-assisted bottom-pouring casting includes: After the mold is sealed, the cavity is maintained at a negative pressure of 0.05MPa to 0.08MPa through the vacuum vent located on the top plate of the mold. The molten metal is filled from bottom to top through multiple ingates located at the bottom of the casting. The ingates have a diameter of 10~12mm and are distributed in radially symmetrical positions. The filling speed is controlled at 0.7~1.0m / s to suppress turbulence. The molten metal used for casting is QT500-7 ductile iron, the casting temperature is controlled at 1430±15℃, and the casting time is ≤40s.

4. The casting process for a slender eccentric sleeve metal casting according to claim 1, characterized in that: The electromagnetic stirring-assisted filling includes: A frequency-adjustable electromagnetic induction coil with 5 to 10 turns is arranged around the mold, with an induced current of 0.5 to 2 kA and a frequency of 10 to 30 Hz. During the casting process, an electric current is applied to create a micro-perturbation magnetic field, which acts on the molten metal in the mold cavity, improving the uniformity of filling and promoting the escape of microbubbles.

5. The casting process for a slender eccentric sleeve metal casting according to claim 1, characterized in that: The cooling, demolding, and post-processing include: After pouring, the indoor pressure is restored to normal, and the cavity is maintained for cooling time of ≥36 hours to ensure complete solidification; After cooling, the castings are unpacked and demolded, and then subjected to shot blasting, grinding, dimensional re-inspection, and ultrasonic testing.

6. The casting process for a slender eccentric sleeve metal casting according to claim 1, characterized in that: The vacuum pumping device adopts a dual-channel pump group structure with a pressure feedback valve to dynamically maintain the pumping pressure within a preset range of ±5%. The electromagnetic induction coil is wrapped with high-temperature ceramic insulating material and has an embedded thermal resistance temperature control module to ensure that the coil surface temperature does not exceed 80℃. The PLC chill insertion depth is connected by an HMI and has a real-time data upload function to the cloud, uploading the solidification curve and displacement trajectory to the server for subsequent data modeling and optimization. The internal shrinkage cavity volume fraction of the casting is controlled below 0.1%, the core offset is controlled within ±0.02mm, and the casting density is ≥7.15g / cm³. 3 .

7. A casting apparatus for a slender eccentric sleeve metal casting, applicable to the casting process of a slender eccentric sleeve metal casting as described in any one of claims 1-6, characterized in that: The casting equipment includes: The sand mold fixing and box assembly platform is equipped with a dual-guide rail precision positioning mechanism; The dynamic core support system includes multiple servo-adjustable ceramic-metal support arms, a non-contact laser displacement sensor group, and a linkage positioning algorithm module; The vacuum-assisted bottom injection system includes a mold evacuation pipeline, a two-stage vacuum pump unit, and a distributed bottom injection gate system; The electromagnetic stirring module includes a multi-turn coil, a power control box, and a cooling protection system; The temperature field control system includes a distributed lifting chill, a resistance heating jacket, and a K-type thermocouple array sensing module; The main control system uses a PLC controller and is equipped with an HMI touch terminal, real-time monitoring software, and a process database.

8. The casting equipment for a slender eccentric sleeve metal casting according to claim 7, characterized in that: The main control system has the following features: Displacement control unit: Receives data from the laser sensor and controls the movement of the support arm with an accuracy of ≤±0.02mm; Temperature control unit: Receives thermocouple temperature curves and controls the chill insertion depth error to ≤±1mm and the heating jacket temperature error to ≤±5℃; Process self-learning function: Automatically optimizes the cooling rhythm by comparing the historical successful freezing curve with the current curve.

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