Pouring process and equipment for thin and long eccentric bushing metal casting

Abstract

The invention discloses a casting process and equipment for a thin and long eccentric bushing metal casting, and relates to the technical field of casting of metal castings, and dynamic supporting and positioning of a mold core comprise the steps that servo adjusting type multi-point supporting arms are started before mold closing, and eight sets of supporting arms are arranged on each side and are distributed on the upstream and downstream of the mold core and the symmetrical positions of the upstream and downstream of the mold core; a non-contact laser displacement sensor is used for detecting the real-time displacement amount of the mold core, and data are transmitted to a PLC system in real time; and when it is detected that the displacement deviation of the mold core exceeds + / -0.05 mm, the PLC automatically adjusts the supporting arm to ascend, descend and clamp the mold core, and locking and positioning of the mold core are achieved. Dynamic mold core supporting and positioning are designed, the function of locking the center position of the mold core online in real time is achieved, the problems of core deviation and breakage are solved, and the size precision of a casting is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal casting pouring, and specifically to a pouring process and equipment for a slender eccentric sleeve metal casting. Background Art

[0002] In the resin sand pouring of the core of a slender eccentric sleeve casting, the core is prone to shift or break due to the buoyancy and thermal stress of the molten metal, resulting in defects such as uneven wall thickness, shrinkage cavity, gas hole, and sand sticking. Traditional processes mostly rely on passive chill blocks and local risers for feeding, and cannot achieve overall sequential solidification and on-line closed-loop control, with low yield and much manual intervention.

[0003] Patent CN109676117B discloses an anti-inversion pouring device and pouring method for a metal mold casting, and the above patent realizes reducing casting defects and greatly improving the finished product rate.

[0004] The above patent adopts an anti-inversion pouring process, which can make the molten metal smoothly enter the cavity from the lower part, reducing the turbulence of the molten metal and playing the roles of slag blocking and exhausting the gas in the cavity. However, in the process of molten metal filling, the slender core is prone to be affected by buoyancy and thermal stress, resulting in core offset or fracture, and causing uneven wall thickness and out-of-tolerance dimensions of the casting.

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

[0006] The purpose of the present invention is to provide a pouring process and equipment for a slender eccentric sleeve metal casting, so as to solve the technical problems of offset or fracture caused by the buoyancy and thermal stress of the molten metal, resulting in defects such as uneven wall thickness, shrinkage cavity, gas hole, and sand sticking as mentioned in the above background art.

[0007] To achieve the above purpose, the present invention provides the following technical solution: A pouring process for a slender eccentric sleeve metal casting, including sand mold and core preparation, dynamic support and positioning of the core, vacuum-assisted bottom pouring, electromagnetic stirring-assisted filling, two-zone temperature field control, intelligent closed-loop control, and cooling and demolding and post-treatment. The dynamic support and positioning of the core includes: Before closing the mold, start the servo-regulated multi-point support arms, with 2 groups on each side, a total of 8 groups of support arms, distributed at the upstream and downstream and symmetric parts of the core; Use a non-contact laser displacement sensor to detect the real-time displacement of the core, and transmit the data to the PLC system in real time; When it is detected that the displacement deviation of the core exceeds ±0.05 mm, the PLC automatically adjusts the lifting and clamping of the support arms to achieve locking and positioning of the core.

[0008] Preferably, the sand mold and core preparation includes the following steps: The outer mold sand box is made of resin sand, and the sand mixing process controls the sand mold compressive strength to ≥2MPa, and the sand temperature is controlled at 15℃~35℃; The core is a slender eccentric structure made of resin sand, with a length-to-outer mold ratio of 0.6~0.95. A ceramic-metal composite skeleton is embedded inside, and the skeleton is composed of a high-strength ceramic rod covered with a nickel-chromium alloy shell. The ceramic in the ceramic-metal composite skeleton is zirconia ceramic, and the metal coating is a nickel-chromium alloy with a thickness of 0.5~1.0mm. The core head length is 1 / 5~1 / 8 of the total length of the casting.

[0009] Preferably, the vacuum-assisted bottom pouring comprises: After the box is closed and sealed, the cavity is maintained at a negative pressure of 0.05MPa~0.08MPa through the vacuum exhaust port set on the top plate of the mold; The molten metal is filled from bottom to top through multiple ingates at the bottom of the casting. The diameter of the ingates is 10-12 mm and they are distributed in radially symmetrical positions. The filling speed is controlled at 0.7-1.0 m / s to suppress turbulence. QT500-7 ductile iron is used for pouring molten metal, the pouring temperature is controlled at 1430±15℃, and the pouring time is ≤40s.

[0010] Preferably, the electromagnetic stirring assisted filling comprises: Arrange 5~10 turns of adjustable frequency electromagnetic induction coil around the casting mold, with an induced current of 0.5~2kA and a frequency of 10~30Hz; During the pouring process, electricity is turned on to form a micro-perturbation magnetic field, which acts on the molten metal in the mold cavity, improves the filling uniformity and promotes the escape of microbubbles.

[0011] Preferably, the dual-zone temperature field control includes: Arrange a 10-30mm thick chiller at the thickest part of the casting, and adjust the insertion depth to control the local cooling rate to ≤30℃ / min; An annular resistance heating sleeve is installed in the riser area at the top of the casting to maintain the surface temperature at 500℃~600℃ and extend the solidification time of the riser; A K-type thermocouple array is arranged along the longitudinal direction of the casting, with a measuring point every 20~50mm and a sampling rate of ≥1Hz.

[0012] Preferably, 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 that the temperature deviation is greater than ±5°C or the displacement is greater than ±0.05mm, the PLC system issues an adjustment command to control the insertion depth of the chiller, the output power of the heating sleeve and the position of the support arm, thus achieving closed-loop regulation of the entire process.

[0013] Preferably, the cooling and demolding and post-treatment include: After pouring, the normal pressure is restored in the chamber, and the cavity cooling time is maintained ≥ 36 hours to ensure complete solidification; After cooling, the mold is opened for demolding, and shot peening, grinding, dimensional re-inspection, and ultrasonic flaw detection are performed on the surface of the casting.

[0014] Preferably, the support arm is made of aluminum alloy coated with a heat-resistant ceramic coating, is connected to the flexible coupling and the linear slide rail, the vacuum pumping device adopts a dual-channel pump group structure, is equipped with a pressure feedback valve, and realizes that the pumping pressure is dynamically maintained within a preset range of ±5%. The electromagnetic induction coil cladding is a high-temperature ceramic insulating material, and a thermal resistance temperature control module is embedded to ensure that the surface temperature of the coil does not exceed 80°C. The insertion depth of the PLC chill is connected by the HMI and has the function of real-time data cloud upload. The solidification curve and displacement trajectory are uploaded to the server for subsequent data modeling optimization. The shrinkage cavity volume fraction inside the casting is controlled below 0.1%, the core offset is controlled within ±0.02 mm, and the density of the casting ≥ 7.15 g / cm 3 .

[0015] Preferably, the pouring equipment includes: A sand mold fixing and closing platform with a double-rail precision positioning mechanism; A dynamic core support system, including multiple servo-adjustable ceramic-metal support arms, a non-contact laser displacement sensor group, and a linkage positioning algorithm module; A vacuum-assisted bottom gating system, including a mold suction pipeline, a two-stage vacuum pump group, and a distributed bottom gating system; An electromagnetic stirring module, including a multi-turn coil, a power control box, and a cooling protection system; A temperature field regulation system, including distributed lifting chills, resistance heating sleeves, and a K-type thermocouple array sensing module; The main control system uses a PLC controller and is configured with an HMI touch terminal, real-time monitoring software, and a process database.

[0016] Preferably, the main control system has: A displacement control unit: receives laser sensor data and controls the movement accuracy of the support arm ≤ ±0.02 mm; A temperature regulation unit: receives the thermocouple temperature curve and controls the insertion depth error of the chill ≤ ±1 mm and the temperature error of the heating sleeve ≤ ±5°C; A process self-learning function: compares the historical solidification success curve with the current curve and automatically optimizes the cooling rhythm.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. The present invention is designed with dynamic core support positioning to achieve real-time online locking of the core center position, thereby solving the problems of core offset and breakage and improving the dimensional accuracy of the casting; 2. The present invention realizes turbulence-free filling and promotes degassing by designing vacuum-assisted bottom pouring and electromagnetic stirring-assisted filling, thereby solving the problems of shrinkage cavities, pores and sand sticking, improving the density of castings and reducing shrinkage porosity; 3. The present invention realizes sequential solidification by designing a dual-zone temperature field control, solves the problems of local shrinkage and uneven solidification, moves the shrinkage cavity to the riser, and improves the density of the casting; 4. The present invention is designed with intelligent closed-loop control to achieve full-process automatic adjustment parameter optimization function, solve the problems of manual experience dependence and large process fluctuations, and improve the casting yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The figure is a schematic diagram of the pouring process of the slender eccentric sleeve metal casting of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] See also Figure 1 The present invention provides an embodiment: a casting process for a slender eccentric sleeve metal casting, including sand mold and core preparation, core dynamic support and positioning, vacuum-assisted bottom pouring, electromagnetic stirring-assisted filling, dual-zone temperature field control, intelligent closed-loop control, cooling demolding and post-processing, wherein the sand mold and core preparation includes the following steps: The outer mold sand box is made of resin sand, and the sand mixing process controls the sand mold compressive strength to ≥2MPa, and the sand temperature is controlled at 15℃~35℃; The core is a thin and long eccentric structure made of resin sand, with a length-to-outer mold ratio of 0.6~0.95. A ceramic-metal composite skeleton is embedded inside. The skeleton is composed of a high-strength ceramic rod covered with a nickel-chromium alloy shell. The ceramic in the ceramic-metal composite skeleton is zirconia ceramic, and the metal coating is a nickel-chromium alloy with a thickness of 0.5~1.0mm. The core head length is 1 / 5~1 / 8 of the total length of the casting; The sand mold fixing and box closing platform is equipped with a double-guide precision positioning mechanism; The support arm is made of aluminum alloy coated with a heat-resistant ceramic coating and is connected to the linear guide rail by a flexible coupling; Furthermore, for the sand used in the sand mold: High-quality resin sand with a recycling rate of ≥ 90% is adopted, and the addition amount of new sand is ≤ 10%; Resin ratio: The resin content is 1% - 1.2%, and the p-toluenesulfonic acid curing agent accounts for 55% - 60% of the resin mass; Sand mixing process: First, 80% of the recycled sand and 20% of the new sand are added to a continuous sand mixer. After adding the resin and the curing agent, they are mixed for 60 s and then left standing for 30 s; Sand temperature and strength: In winter, the sand temperature is controlled at 15°C - 35°C, and the same in summer; Sampling and testing, the compressive strength of the sand mold is ≥ 2 MPa; Core geometric dimensions: The ratio of the total length of the core to the length of the outer mold 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 tightly coated with a nickel-chromium alloy shell with a thickness of 0.5 mm - 1.0 mm is embedded in the core body; Curing and inspection: After the core is made, it is left to cure naturally for 24 h. Sampling and testing shows that the dimensional deviation is ≤ ±0.05 mm and the surface strength is ≥ 1.8 MPa; Sand mold fixing and mold closing clamping: The mold platform is equipped with a double-rail precision positioning mechanism. The rail spacing is customized according to the width of the casting shape. The rails are equipped with linear encoding rulers, and the positioning accuracy is ≤ 0.02 mm; When closing the mold, the sand mold is closed by the synchronous jacks on the left and right sides of the platform to keep the mold closing pressure uniform, and the mold closing force is controlled within the range of 5 kN - 8 kN; The completed core together with the composite skeleton is placed into the positioning groove of the lower sand box, aligned using the platform rails. After the upper sand box is closed to the contact state, through manual fine-tuning of the screw, the core compensates for the eccentricity δ ≤ ±0.02 mm. After determining the position, the quick device of the platform is tightened to prevent overall movement during subsequent support and pouring processes.

[0021] Please refer to Figure 1 , an embodiment provided by the present invention: A pouring process for a slender eccentric sleeve metal casting, wherein the dynamic support and positioning of the core includes: Before closing the mold, start the servo-regulated multi-point support arms. A total of 8 groups of support arms are arranged in 2 groups on each side, distributed at the upstream, downstream, and symmetric parts of the core; Use a non-contact laser displacement sensor to detect the real-time displacement of the core, and transmit the data to the PLC system in real time; When it is detected that the displacement deviation of the core exceeds ±0.05 mm, the PLC automatically adjusts the lifting and clamping of the support arms to achieve locking and positioning of the core; The dynamic core support system includes multiple servo-regulated ceramic-metal support arms, a non-contact laser displacement sensor group, and a linkage positioning algorithm module; Further, before closing the mold, the PLC sends a "zeroing" instruction to each servo drive, retracting the 8 groups of support arms to the initial position 10 mm away from the core surface. After zeroing is completed, the PLC verifies that the error of each arm position is ≤ 0.1 mm before proceeding to the next step. The PLC controls each group of support arms to move forward at a speed of 10 mm / s according to a preset curve, contact the core surface, and apply an initial pre-tightening force of 100 N. The pre-tightening force sensor samples in real time to ensure that the uniformity error of the pre-tightening force among the eight arms is ≤ ±5 N. After pre-tightening, the PLC displays the actual pre-tightening force value of each arm on the HMI interface for manual confirmation or automatic correction; Each laser displacement sensor is installed on the support arm fixing seat, with a measurement range of 0 - 5 mm. After closing the mold and pre-tightening, the PLC triggers "zero calibration", records the original readings of 8 measurement points as the baseline. The PLC compares the calibrated readings with the stored reference values, and the difference ≤ ±0.02 mm is required to start the pouring preparation. If there is an overlimit, the system prompts "sensor abnormality" and automatically performs re-calibration or alarms; the laser displacement sensor outputs the core center offset Δx i (i = 1...8), and the PLC sets the deviation threshold Δx-max = ±0.05 mm; whenever any Δx i exceeds ±0.05 mm, the PLC immediately calculates the required compensation force ΔF = K·(Δx i - sgn(Δx i )·0.05 mm), where K = 200 N / mm. The PLC adjusts the servo drive of the corresponding support arm according to the ΔF instruction, adjusts the clamping force and displacement until Δx i returns to within ±0.02 mm. After all Δx i are stable, the PLC locks the current arm position and continues to monitor the next sample; Regarding the core offset trend, the algorithm performs weighted averaging on the feedback signals of the 8 arms. If the absolute value of the weighted offset result > 0.03 mm, all support arms are simultaneously fine-tuned to ensure overall center correction.

[0022] Please refer to Figure 1 , an embodiment provided by the present invention: a pouring process for a slender eccentric sleeve metal casting, and the vacuum-assisted bottom gating pouring includes: After closing the mold and sealing, through the vacuum extraction port provided on the mold top plate, the cavity is maintained in a negative pressure state of 0.05 MPa to 0.08 MPa; The molten metal fills the mold from bottom to top through multiple ingates provided at the bottom of the casting. The diameter of the ingates is 10 - 12 mm, distributed at radially symmetric positions, and the filling speed is controlled at 0.7 - 1.0 m / s to suppress turbulence; The molten metal for pouring is QT500 - 7 ductile iron, the pouring temperature is controlled at 1430 ± 15 °C, and the pouring time ≤ 40 s; Vacuum-assisted bottom-pouring system, including a mold evacuation pipeline, a two-stage vacuum pump set, and a distributed bottom-pouring gate system; The vacuum evacuation device adopts a dual-channel pump set structure and is equipped with a pressure feedback valve to dynamically maintain the evacuation pressure within the preset range of ±5%; Furthermore, close the upper and lower sand boxes, align them with the double-rail precision positioning mechanism and lock them. Reserve two φ20mm vacuum evacuation ports on the mold top plate and connect them to the two-stage vacuum pump set located in the equipment side cabinet. Check that all flange surface gaskets are intact to ensure no air leakage points after the mold is closed. Use two two-stage rotary vane pumps, A and B, in series combination. The pumping speed of pump A is 100L / min, and the pumping speed of pump B is 60L / min. An automatic pressure feedback valve and an electronic pressure sensor are installed in the evacuation pipeline. The range of the sensor is 0 - 0.1MPa, and the accuracy is 0.001MPa. The vacuum pipeline uses a high-temperature resistant hose with an inner diameter of 16mm, and the layout is as short and straight as possible to reduce leakage and dead volume; After the mold is closed, the PLC issues a "vacuum evacuation" command to start the parallel operation of pump A and pump B. The pressure in the vacuum pipeline quickly drops to a negative pressure of 0.1MPa, about 8s. When the pressure reaches the preset value of 0.08MPa, the PLC slightly opens the channel of pump B through the pressure feedback valve to maintain a stable negative pressure of 0.05MPa - 0.08MPa. The negative pressure maintenance time lasts at least 30min after the pouring is completed. During this period, the pressure fluctuation is within ±5%; Melting QT500 - 7 ductile iron, sampling and detecting the carbon equivalent of 4.2%, the sulfur content is less than dnegyu0.02%, pre-treating with magnesia coating, adjusting the temperature to 1430 ± 15°C, monitoring with a thermocouple in the holding furnace, the temperature fluctuation ≤ ±5°C, and installing a 150mm 3 preheated cored wire at the front of the riser. Four radially symmetric ingates with an inner diameter of 12mm are arranged at the bottom, and the length is customized according to the bottom thickness of the casting. The surface of the ingate is sprayed with a magnesia heat-insulating coating. The PLC synchronously controls the opening of the pouring valve, and the molten metal fills the cavity from bottom to top through the four ingates at the bottom. The unilateral flow rate is 0.8m / s, and the overall filling speed is 0.8m / s - 1.0m / s. The entire filling process is controlled within 35s from the opening of the pouring port to the closing of the last riser, not exceeding 40s; Start a 1kA / 20Hz electromagnetic induction coil synchronously with the pouring, and stop the micro-perturbation field when the last molten metal in the ingate enters the cavity. Stirring can promote the discharge of gas to the bottom and further reduce the generation of pores; Continue to evacuate the vacuum for 30min after the pouring is completed to further reduce the residual air pressure in the cavity and promote the discharge of micro-bubbles inside the molten metal. The laser displacement and thermocouple system continue to monitor the core and temperature without additional actions of the support arm. After 30min, the PLC commands to gradually close the vacuum pump and open the pressure relief valve to slowly raise the pressure in the mold cavity to atmospheric pressure within 60s to avoid the core drifting caused by sudden pressure. Wait for 5min after the pressure relief is completed before retracting the support arm and opening the mold.

[0023] Please refer toFigure 1 , an embodiment provided by the present invention: a casting process for a slender eccentric sleeve metal casting, wherein the electromagnetic stirring-assisted filling includes: Arrange 5 to 10 turns of adjustable-frequency electromagnetic induction coils around the mold, with an induced current of 0.5 to 2 kA and a frequency of 10 to 30 Hz; During the pouring process, an electric current is applied to form a perturbed magnetic field, which acts on the molten metal in the cavity to improve the filling uniformity and promote the escape of microbubbles; The electromagnetic stirring module includes a multi-turn coil, a power control box, and a cooling protection system; The cladding of the electromagnetic induction coil is made of high-temperature ceramic insulating material, with a built-in thermal resistance temperature control module to ensure that the surface temperature of the coil does not exceed 80 °C; Furthermore, wind 7 turns of adjustable-frequency electromagnetic induction coils uniformly along the longitudinal direction of the mold outside the sand mold. The width of the coil covers 50% of the outer periphery of the mold, and the height matches the height of the cavity and is slightly 20 mm higher than the riser part. The coil conductor uses φ6 mm heat-resistant copper-aluminum composite wire, with a layer of 0.5 mm thick high-temperature ceramic insulating material wrapped outside. Embedded a micro PT100 thermal resistance sensing unit between the 3rd and 5th turns for real-time monitoring of the coil surface temperature. Then cover a layer of high-temperature resistant fiber grid cloth outside the insulation layer to improve mechanical strength and prevent accidental collision damage; Configure a 600V / 3kA adjustable DC power supply and an inverter module, with an output current adjustable from 0.5 kA to 2 kA and a frequency adjustable from 10 Hz to 30 Hz. The control box has a built-in soft start function, and the output current rises linearly from 0 to the target current within 2 s to avoid instantaneous strong impact on the core. The sampling frequency of the thermal resistance temperature control module is 1 Hz. When the coil surface temperature ≥ 80 °C, the PLC automatically reduces the current to the safe value of 0.5 kA and alarms. If the temperature still rises, it will automatically cut off the power and switch to the bypass cooling mode, and can only be restarted after the temperature drops below 50 °C; 5 s before the start of vacuum bottom pouring, the PLC sends a "preheating" command to the power control box to raise the current to 0.5 kA / 10 Hz to preheat the coil and stabilize the winding temperature. After the vacuum negative pressure reaches 0.06 MPa and the core positioning is completed, the pouring valve is opened, and the PLC immediately raises the current to 1 kA / 20 Hz and switches to the "stirring mode": Initial stage (0 - 10 s): The current remains at 1 kA / 20 Hz to promote the molten metal to flow into the cavity and suppress the initial turbulence; Middle stage (10 - 25 s): The current can be adjusted to 1.5 kA / 25 Hz, and the current is finely adjusted by ±0.2 kA according to the temperature gradient and flow rate curve feedback by the thermocouple; Final stage (25 s to filling completion): The current gradually drops to 0.8 kA / 15 Hz to assist the escape of gas and stabilize the surface of the molten metal; After pouring, keep the final stage current for 2 s to ensure that the last part of the liquid is fully stirred, and then slowly cut off the power; An aluminum alloy heat sink is assembled on the outer layer of the coil, and the passive heat dissipation rate is increased by 30%. A small air-cooled high-temperature fan is assembled at the bottom and both sides of the bracket respectively, which is linked with a thermal switch. When the surface temperature of the coil > 70 °C, it will be automatically turned on. During the normal casting cycle, the fan keeps blowing at a low speed. If the surface temperature of the coil > 75 °C, the fan switches to high speed and at the same time starts the air-cooled pipeline to compensate for the temperature drop until the temperature < 65 °C.

[0024] Please refer to Figure 1 , an embodiment provided by the present invention: a casting process for a slender eccentric sleeve metal casting, and the dual-zone temperature field control includes: Liftable chillers with a thickness of 10 - 30 mm are arranged at the thick and large parts of the casting, and the insertion depth is adjusted to control the local cooling rate ≤ 30 °C / min; An annular resistance heating sleeve is arranged in the riser area at the top of the casting to maintain the surface temperature at 500 °C - 600 °C and extend the solidification time of the riser; A K-type thermocouple array is arranged longitudinally along the casting, with a measuring point arranged every 20 - 50 mm, and the sampling rate ≥ 1 Hz; The temperature field control system includes a distributed liftable chiller, a resistance heating sleeve, and a sensing module of the K-type thermocouple array; The PLC controls the insertion depth of the chiller through the HMI connection, and has the function of real-time data cloud upload. The solidification curve and displacement trajectory are uploaded to the server for subsequent data modeling and optimization. The shrinkage cavity volume fraction inside the casting is controlled below 0.1%, the core offset is controlled within ±0.02 mm, and the casting density ≥ 7.15 g / cm 3； Furthermore, a set of liftable chillers is arranged on each side of the left and right of the thick and large part at the back of the casting, such as the flange connection section. Each set contains two parallel chillers. The chiller material is high thermal conductivity cast iron, and the insertable depth is 0 - 30 mm, which is driven by a servo motor through a lead screw; the annular resistance heating sleeve surrounds the riser. The inner diameter is designed as 1.5D according to the riser diameter D. The sleeve shell uses a steel pipe lined with a ceramic insulation layer, and the heating wire uses Ni-Cr alloy wire, with a rated power of 3 kW. With a PID controller, the temperature is maintained at 500 °C - 600 °C in real time; the K-type thermocouple array is evenly distributed longitudinally along the casting, with a measuring point set every 40 mm. The thermocouple is fixed on the outside of the sand mold and is in contact with the cavity surface through a high-temperature ceramic sleeve. The sampling frequency is 1 Hz; the PLC is responsible for reading 10 temperature signals and core displacement signals, running the dual-zone temperature control algorithm. The initial insert depth of the chiller and the target temperature of the heating sleeve can be manually set on the HMI interface, and the temperature curve and insert depth change are displayed in real time. The system has the function of data cloud upload, and the latest 10-point temperature-time curve and displacement trajectory are pushed to the server every 60 s; After the mold assembling is completed and the core is locked, the PLC commands the ring heating sleeve to preheat at a power of 1 kW for 5 minutes to raise the temperature of the riser area to 400 °C. At the same time, the chill is retracted to the initial position, and the thermocouple calibrates the "zero-time temperature" according to the points and records the baseline. After the vacuum bottom pouring is started and the riser temperature has reached 500 °C, the PLC synchronously sets the initial insertion depth of the chill to 20 mm, and the system starts to record the temperature of each point and the core displacement Δx. The PLC calculates the temperature slope of the thermocouple near the flange section in real time: Rcool = -ΔT / Δt, where ΔT is the temperature difference and Δt is the time difference; If Rcool > 30 °C / min, the insertion depth of the chill is retracted by 1 mm each time; If Rcool < 20 °C / min, the insertion depth of the chill is increased by 1 mm each time; The PLC compares the temperature of the thermocouple in the riser area with the target of 550 °C. If the deviation > ±20 °C, the power of the heating sleeve is adjusted by ±10%. When the riser temperature drops below 300 °C and the flange area temperature drops below 550 °C, the PLC commands the chill to reset and the heating sleeve to cut off the power, waits for natural cooling to room temperature under normal pressure, releases the core support, and performs post-treatment after opening the mold and demolding.

[0025] Please refer to Figure 1 , an embodiment provided by the present invention: a pouring process for a slender eccentric sleeve metal casting, and 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 that the temperature deviation > ±5 °C or the displacement > ±0.05 mm, the PLC system issues an adjustment instruction to control the insertion depth of the chill, the output power of the heating sleeve, and the position of the support arm, realizing the whole-process closed-loop adjustment; The main control system uses a PLC controller and is configured with an HMI touch terminal, real-time monitoring software, and a process database; The main control system has: Displacement control unit: receives the data of the laser sensor and controls the movement accuracy of the support arm ≤ ±0.02 mm; Temperature adjustment unit: receives the thermocouple temperature curve and controls the insertion depth error of the chill ≤ ±1 mm and the heating sleeve temperature error ≤ ±5 °C; Process self-learning function: compares the historical successful solidification curve with the current curve to automatically optimize the cooling rhythm; Further, start the PLC main control system, log in to the process personnel account through the HMI, and 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 closing is completed and the core is locked, the PLC sequentially reads the initial readings of 8 laser displacement sensors and 10 K-type thermocouples, establishes baseline data, and the HMI displays the baseline values of each measuring point and the preset upper / lower limits. After manual confirmation, enter the pouring stage; Data sampling: Laser displacement: Sampling frequency 1 Hz, collect Δx1~Δx8; Thermocouple data: Sampling frequency 1 Hz, collect T1~T 10 , the PLC filters the original data, performs moving window averaging 3 times, and then sends it to the closed-loop comparison module. After each sampling, the PLC will use the current temperature vector T i (t) and the preset solidification curve T i -ref(t) to make the difference ΔT i =T i -T i -ref; at the same time, calculate the maximum displacement deviation Δx - max = max(|Δx1...Δx8|); Temperature deviation response: If any ΔTi > +5°C, the PLC issues a "cooling" instruction to control the corresponding chill depth to be increased by 2 mm; if any ΔTi < –5°C, the PLC issues a "warming" instruction to reduce the chill depth by 2 mm or increase the heating jacket power by 5%; Displacement deviation response: If Δx_max > 0.05 mm, the PLC issues a "support arm pressurization" instruction, and the corresponding arm increases the clamping force ΔF = 200 N / mm×(Δx_max – 0.05 mm) until Δx_max ≤ 0.02 mm; if Δx_max < 0.02 mm, the PLC can instruct the support arm to be loosened by 5 N to reduce the risk of over-clamping; all adjustment instructions enter the PLC instruction queue and follow the "temperature priority → displacement priority" strategy: temperature deviation processing takes precedence; displacement deviation processing follows; after each round of adjustment, the PLC waits for 5 s before performing the next sampling comparison to avoid instruction conflicts; The displacement control unit receives the laser sensor data and controls the servo support arm through the PID algorithm to achieve a motion accuracy ≤ 0.02 mm, with a step-back protection: if the displacement is still not corrected after 3 consecutive instructions, it will automatically alarm and pause the pouring; the temperature adjustment unit receives the thermocouple signal, drives the chill and controls the heating jacket through a two-way four-cylinder. The chill insertion depth error ≤ ±1 mm, and the heating jacket temperature error ≤ ±5°C. When switching between the chill and the heating jacket, it has a soft switching function, that is, it smoothly transitions within 2 s to avoid thermal shock; After the pouring of this batch is completed, the PLC packs all sampling points, including the temperature curve, displacement trajectory, and adjustment instruction timestamps, and uploads them to the process database. The server-side runs a data analysis model to compare the historical successful curve with the current curve, and automatically adjusts the preset solidification curve parameters for the next batch, such as the initial insertion depth of chill blocks and response thresholds. The optimization results are sent to the PLC through the HMI and automatically loaded at the next startup.

[0026] Please refer to Figure 1 , an embodiment provided by the present invention: a pouring process for a slender eccentric sleeve metal casting, wherein the cooling and demolding and post-treatment include: After pouring is completed, the normal pressure is restored indoors, and the cavity cooling time is maintained for ≥ 36 hours to ensure complete solidification; After cooling, the mold is opened for demolding, and shot peening, grinding, dimensional re-inspection, and ultrasonic flaw detection are performed on the surface of the casting; Furthermore, after pouring is completed, the PLC controls the pressure relief valve to slowly raise the cavity pressure from -0.06 MPa negative pressure to atmospheric pressure within 60 s, avoiding stress concentration in the core or sand mold structure caused by sudden pressure changes. The automotive workshop environment is maintained at 20 ± 5 °C and relative humidity ≤ 60%. Natural cooling is carried out for 36 h. The central temperature during the cooling process is monitored by the fifth thermocouple measuring point, i.e., the middle part of the casting. It is required that the central temperature drops from 900 °C to 400 °C within 24 h and drops to < 200 °C within 36 h. Vibration and movement of the closing platform are strictly prohibited during cooling to prevent sand mold deformation or casting stress damage; After cooling is completed, the PLC issues a "support arm reset" instruction, and all support arms retract to the initial position at a speed of 10 mm / s. The reset error ≤ ±0.1 mm. Manually or automatically operate the quick lock structure of the platform, and the guide rail slides smoothly to open the upper sand box. During operation, keep the buffer and limit stop blocks intact, and the box-opening speed ≤ 5 mm / s to ensure that the sand mold separates slowly; The workpiece is clamped by the robotic arm, and the fixture pressure ≤ 500 N to avoid surface indentation, and it is placed on a refractory bench for standby; A crawler-type gantry shot peening machine is used. The size of the shot peening chamber is customized according to the shape of the casting. The shot peening medium is G10 grade carbon steel shot, with an average diameter of 0.7 mm, a hardness of HRC45, a shot peening pressure of 0.4 MPa, and a shot peening distance of 150 mm. The casting is taken out after circulating in the chamber for 2 weeks, and residual sand grains and scale are thoroughly removed.

[0027] Working principle: A closed-loop system composed of a servo-adjustable multi-point support arm and a non-contact laser displacement sensor is used to detect and correct the core offset in real time, keeping the core stable and non-displaced throughout the process; After closing the mold, the cavity is evacuated to a negative pressure of 0.05 MPa to 0.08 MPa, and then QT500-7 ductile iron is bottom-poured through a radially symmetric internal runner from bottom to top. At the same time, an electromagnetic field of 0.5 - 2 kA and 10 - 30 Hz is applied to suppress turbulence and promote gas escape; Insert liftable chill blocks into the thick and large parts of the casting flange, wrap resistance heating sleeves at the riser outlet, and arrange K-type thermocouples longitudinally. The PLC compares the temperature and displacement signals with the preset curve, and automatically adjusts the insertion depth of the chill blocks, the power of the heating sleeves, and the position of the support arms to achieve a full-process closed loop.

[0028] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present invention. Any reference signs in the claims should not be construed as limiting the claims concerned.

Claims

1. A pouring process for a slender eccentric sleeve metal casting, including sand mold and core preparation, dynamic support and positioning of the core, vacuum-assisted bottom pouring, electromagnetic stirring-assisted filling, two-zone temperature field control, intelligent closed-loop control, and cooling and demolding and post-treatment, characterized in that: The core dynamic support and positioning includes: Before closing the box, the servo-adjustable multi-point support arms are started. Two groups of support arms are set on each side, totaling 8 groups, distributed upstream and downstream and symmetrically at the core; The non-contact laser displacement sensor is used to detect the real-time displacement of the core, and the data is transmitted to the PLC system in real time; When it is detected that the core displacement deviation exceeds ±0.05mm, the PLC automatically adjusts the lifting and clamping of the support arm to achieve core locking and positioning.

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

95. A ceramic-metal composite skeleton is embedded inside, and the skeleton is composed of a high-strength ceramic rod covered with a nickel-chromium alloy shell. The ceramic in the ceramic-metal composite skeleton is zirconia ceramic, and the metal coating is a nickel-chromium alloy with a thickness of 0.5~1.0mm. The core head length is 1 / 5~1 / 8 of the total length of the casting.

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

4. The casting process of a slender eccentric sleeve metal casting according to claim 1, characterized in that: The electromagnetic stirring assisted filling comprises: Arrange 5~10 turns of adjustable frequency electromagnetic induction coil around the casting mold, with an induced current of 0.5~2kA and a frequency of 10~30Hz; During the pouring process, electricity is turned on to form a micro-perturbation magnetic field, which acts on the molten metal in the mold cavity, improves the filling uniformity and promotes the escape of microbubbles.

5. The casting process of a slender eccentric sleeve metal casting according to claim 1, characterized in that: The dual-zone temperature field control includes: Arrange a 10-30mm thick chiller at the thickest part of the casting, and adjust the insertion depth to control the local cooling rate to ≤30℃ / min; An annular resistance heating sleeve is installed in the riser area at the top of the casting to maintain the surface temperature at 500℃~600℃ and extend the solidification time of the riser; A K-type thermocouple array is arranged along the longitudinal direction of the casting, with a measuring point every 20~50mm and a sampling rate of ≥1Hz.

6. The casting process of a slender eccentric sleeve metal casting according to claim 1, characterized in that: 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 that the temperature deviation is greater than ±5°C or the displacement is greater than ±0.05mm, the PLC system issues an adjustment command to control the insertion depth of the chiller, the output power of the heating sleeve and the position of the support arm, thus achieving closed-loop regulation of the entire process.

7. The casting process of a slender eccentric sleeve metal casting according to claim 1, characterized in that: The cooling, demoulding and post-processing include: After pouring is completed, the indoor pressure returns to normal, and the cavity cooling time is maintained for ≥36 hours to ensure complete solidification; After cooling, the casting is unpacked and demolded, and the surface is shot blasted, polished, re-inspected and ultrasonically inspected.

8. The casting process of a slender eccentric sleeve metal casting according to claim 2, characterized in that: The support arm is made of aluminum alloy coated with a heat-resistant ceramic coating, and is connected to the linear slide rail through a flexible coupling. The vacuum pumping device adopts a dual-channel pump group structure and is equipped with a pressure feedback valve to dynamically maintain the pumping pressure within the preset range of ±5%. The electromagnetic induction coil cladding is made of a high-temperature ceramic insulating material and is embedded with a thermal resistance temperature control module to ensure that the surface temperature of the coil does not exceed 80°C. The insertion depth of the PLC chill is connected by the HMI and has the function of real-time data cloud uploading, uploading the solidification curve and displacement trajectory to the server for subsequent data modeling optimization. The volume fraction of shrinkage cavities inside the casting is controlled below 0.1%, the core offset is controlled within ±0.02 mm, and the density of the casting is ≥7.15 g / cm 3 .

9. A pouring device for a slender eccentric sleeve metal casting, applicable to the pouring process of a slender eccentric sleeve metal casting according to any one of claims 1-8, characterized in that: The pouring equipment comprises: The sand mold fixing and box closing platform is equipped with a double-guide precision positioning mechanism; Dynamic core support system, including multiple servo-adjustable ceramic-metal support arms, non-contact laser displacement sensor groups, and linkage positioning algorithm modules; Vacuum-assisted bottom pouring system, including a mold exhaust pipeline, a two-stage vacuum pump group, and a decentralized bottom pouring gate system; Electromagnetic stirring module, including multi-turn coils, a power control box, and a cooling protection system; Temperature field control system, including distributed lifting chill blocks, resistance heating sleeves, and a K-type thermocouple array sensing module; The main control system uses a PLC controller and is configured with an HMI touch terminal, real-time monitoring software, and a process database.

10. The pouring device for a slender eccentric sleeve metal casting according to claim 9, characterized in that: The main control system has: Displacement control unit: Receives laser sensor data and controls the movement accuracy of the support arm ≤ ±0.02 mm; Temperature adjustment unit: Receives the thermocouple temperature curve and controls the insertion depth error of the chill block ≤ ±1 mm, and the temperature error of the heating sleeve ≤ ±5 °C; Process self-learning function: Compares the historical solidification success curve with the current curve to automatically optimize the cooling rhythm.

Images