Bipolar zigzag directional solidification casting heating device and using method

Abstract

The invention discloses a bipolar zigzag directional solidification casting heating device and a use method, the bipolar zigzag directional solidification casting heating device comprises: a heat insulation assembly defining a heat preservation cavity; the heating assembly is arranged in the heat preservation cavity and used for conducting radiation heating on the in-line casting module stretching into the heat preservation cavity; the heating assembly is divided into an upper heating group and a lower heating group along the height direction, and each heating group comprises a left electrode heating assembly and a right electrode heating assembly which are oppositely arranged and electrically isolated from each other, so that four closed electric heating loops which are electrically isolated from each other are formed; heating plates in the left side electrode heating assembly and the right side electrode heating assembly are staggered in a zigzag shape, so that the contours of the heating plates on the left side and the right side are opposite and form a plurality of rhombic heating spaces for accommodating single castings; the temperature control assembly is provided with temperature measuring points corresponding to the four closed electric heating loops respectively and used for collecting temperature feedback signals of the loops and conducting independent closed-loop adjustment on heating currents of the loops; and the conductive assembly is electrically connected with the heating assembly and is used for accessing an external power supply. The invention aims to enable the heating structure to realize uniform heating in multiple direction dimensions, realize relatively symmetrical intense radiation heat exchange in all directions, improve the uniformity of a temperature field, and reduce the risk of occurrence of defects such as mixed crystals and freckles.

Description

Technical Field

[0001] This invention relates to the field of metal casting technology, specifically to a bipolar serrated directional solidification casting heating device and its usage method. Background Technology

[0002] Currently, high-rate solidification (HRS) is the primary method used in industrial production to manufacture single-crystal turbine blades. In this technology, the heater structure of the vacuum directional solidification furnace is cylindrical or annular. To achieve efficient preparation of single-crystal blades, the ceramic mold shells used for casting high-temperature alloy single-crystal blades also need to be assembled into annular blade mold shell groups for single-casting. However, due to the shielding of radiation between the annular mold shell groups, the side of the mold shell facing away from the heater cannot obtain the same direct radiant heating conditions as the side facing the heater. This leads to internal heat transfer lag during the directional solidification process, resulting in severe bending and tilting of the isotherm at the solid-liquid interface in the lateral dimension. Compared to the side facing the heater, the heat transfer lag zone on the side facing away from the heater causes a wider pasty zone, worsening solidification conditions and increasing the risk of defects such as impurities and freckles forming at this location.

[0003] To address these issues, existing solutions have proposed parallel heater structures. By arranging modules in a single row or in parallel, each casting receives relatively symmetrical heating conditions on both sides, effectively mitigating the adverse effects of the "shadowing effect" of the ring heater in traditional HRS equipment. However, this parallel heater only ensures relatively symmetrical heating conditions on the sides of the casting directly facing the heater. The corresponding sides between castings cannot be directly heated by the heater's radiation, making it difficult to guarantee consistent heating conditions and potentially leading to tilting of the isotherms at the solid-liquid interface.

[0004] Therefore, a directional solidification casting heating device is still needed to enable the heating structure to achieve uniform heating in multiple directional dimensions, realize relatively symmetrical strong radiative heat transfer in each direction, improve the uniformity of the temperature field, and reduce the risk of defects. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a bipolar sawtooth-shaped directional solidification casting heating device and its usage method. The purpose is to enable the heating structure to achieve uniform heating in multiple directional dimensions, realize relatively symmetrical strong radiation heat transfer in each direction, improve the uniformity of the temperature field, and reduce the risk of defects such as impurities and freckles.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: According to a first aspect of the present invention, a bipolar serrated directional solidification casting heating device is provided, comprising: Thermal insulation components are installed to form an insulated cavity; A heating component is disposed within the insulation cavity and is used to radiate heat to the inline casting module extending into the insulation cavity. The heating assembly is divided into an upper heating group and a lower heating group along the height direction. Each heating group includes a left electrode heating assembly and a right electrode heating assembly that are arranged opposite to each other and electrically isolated from each other, thereby forming four closed electric heating circuits that are electrically isolated from each other. The heating plates in the left and right electrode heating assemblies are arranged in a sawtooth pattern, so that the outlines of the heating plates on the left and right sides are opposite and form multiple rhomboid heating spaces for accommodating a single casting. The temperature control component has temperature measuring points corresponding to the four closed electric heating circuits, which are used to collect temperature feedback signals of each circuit and independently adjust the heating current of each circuit in a closed loop. A conductive component, electrically connected to the heating component, is used to connect to an external power source.

[0007] In one possible implementation of the first aspect, the heating plates are arranged in pairs within a single electrode heating assembly, perpendicular to each other and staggered.

[0008] In one possible implementation of the first aspect, the temperature control component includes four sets of platinum-rhodium thermocouples, which are respectively set at the temperature measuring points of the four closed electric heating circuits, and the heating current of the corresponding circuit is independently adjusted based on the signal of each thermocouple using a PID control algorithm.

[0009] In one possible implementation of the first aspect, the heating component is mounted on the heat insulation component via a graphite electrode; the graphite electrode passes through the sidewall of the heat insulation component, with one end electrically connected to the heating plate and the other end electrically connected to the conductive component; the graphite electrode is provided with threads and an adjusting nut that mates with them, and the installation position of the heating component in the heat insulation cavity can be adjusted by adjusting the locking position of the adjusting nut and the clamping position of the graphite electrode on the conductive component.

[0010] In one possible implementation of the first aspect, the conductive component includes a conductive block body and a clamping mechanism; the conductive block body has a cooling channel inside; and the graphite electrode is adjustablely mounted in the clamping mechanism.

[0011] In one possible implementation of the first aspect, the conductive component further includes an inlet flange having a cooling medium inlet and a cooling medium outlet communicating with the cooling channel, wherein the cooling medium inlet is located below and the cooling medium outlet is located above.

[0012] In one possible implementation of the first aspect, the thermal insulation component is composed of multiple rigid carbon felts.

[0013] In one possible implementation of the first aspect, the heating plate is made of carbon fiber material.

[0014] According to a second aspect of the present invention, a method for directional solidification casting using the aforementioned bipolar serrated directional solidification casting heating apparatus is provided, comprising: The casting modules arranged in a straight line are placed in the heat-insulating cavity, so that each casting is located in the central area of ​​a diamond-shaped heating space; Adjust the position of the heating component according to the width of the casting module so that the heating plate and the casting module reach the preset radiation distance; The heating component is powered by the conductive component, and the four closed electric heating circuits are independently PID controlled by the temperature control component to raise the temperature of the insulation cavity to the target temperature or at the target heating rate. Molten metal is poured into the preheated casting mold and then pulled out to complete directional solidification.

[0015] In one possible implementation of the second aspect, the step of adjusting the position of the heating component includes: loosening the adjusting nut, adjusting the extension length of the graphite electrode in the clamping mechanism, and then re-tightening the adjusting nut.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: This invention provides a bipolar sawtooth-shaped directional solidification casting heating device. Through a bipolar sawtooth heating space layout, the heating plates are designed with staggered sawtooth patterns on both sides, so that each casting is naturally surrounded by a near-rhomboid heating space center. This significantly shortens the radiation distance from the casting to the nearest heating plate surface in all four main diagonal directions. Based on the fundamental principle that radiative heat transfer intensity is inversely proportional to the square of the distance, the casting can simultaneously receive strong radiative heating of similar intensity in these four directions. This fundamentally changes the uneven heating caused by traditional annular and parallel heaters, resulting in more symmetrical and uniform heating conditions in the circumferential direction of the casting cross-section. In the actual directional solidification process, multi-directional balanced strong radiative heating can significantly reduce the transverse temperature difference inside the casting, causing the isotherms at the solid-liquid interface to tend to be straight in the horizontal direction. This effectively suppresses interface tilting and abnormal widening of the mushy region caused by heat transfer lag, thereby reducing the risk of defects such as impurities and freckles.

[0017] The heating components are electrically isolated in both vertical and horizontal directions, forming four completely independent, electrically isolated closed heating loops: upper left, upper right, lower left, and lower right. Each loop is equipped with an independent temperature measurement and closed-loop control system. This allows the device to not only consider horizontal uniformity but also actively control the temperature gradient in the vertical direction. In actual operation, due to differences in furnace structure, heat loss, or the modules themselves, the thermal state of the upper and lower, left and right areas of the insulation cavity may not be consistent. Through independent PID control of the four loops, these non-uniformities can be compensated for in real time. For example, heating power can be increased individually in areas with large heat loss, while areas that may overheat can be suppressed. By controlling the temperature independently in each zone, the control dimension of the temperature field is elevated from overall coarse control to local adjustment, enhancing the adaptability of the entire heating system to complex operating conditions and thus improving the stability of the directional solidification process.

[0018] By employing a topology that allows for multi-directional, close-range heating of the casting, this invention enables more direct and efficient transfer of radiant heat to the casting module at the same total heating power, reducing ineffective spatial radiation losses. The diamond-shaped surrounding network of heating plates maximizes the effective radiation angle to the casting surface within the limited equipment space. Simultaneously, the four independent circuits allow the temperature control system to respond more quickly to local temperature fluctuations, adjusting the current output promptly, which helps maintain the dynamic balance of the thermal field and shortens the temperature stabilization time during the process cycle. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the overall structure of a bipolar sawtooth-shaped directional solidification casting heating device according to the present invention. Figure 2 This is a schematic diagram of the temperature control component in a bipolar sawtooth-shaped directional solidification casting heating device of the present invention; Figure 3 This is a schematic diagram of a single electrode heating component in a bipolar sawtooth-shaped directional solidification casting heating device of the present invention. Figure 4 This is a schematic diagram of the conductive component structure in a bipolar sawtooth-shaped directional solidification casting heating device of the present invention. Figure 5 This is a top view of a bipolar sawtooth-shaped directional solidification casting heating device according to the present invention; Figure 6An isometric assembly drawing of a heating component in a bipolar sawtooth-shaped directional solidification casting heating device; Figure 7 This is a schematic diagram illustrating the calculation of the radiation angle coefficient between micro-element surfaces; Figure 8 The diagrams show a comparison of the heating principles of three heating devices for castings: (a) is a diagram of the heating process of a traditional ring heating device, (b) is a diagram of the heating process of a parallel heating device, and (c) is a diagram of the heating process of a bipolar sawtooth directional solidification casting heating device. Figure 9 The temperature field distribution of the casting during directional solidification of the casting is shown in the parallel heating device and the bipolar sawtooth directional solidification casting heating device. (a) is a schematic diagram of the casting temperature field of the casting using the bipolar sawtooth directional solidification casting heating device of the present invention; (b) is a schematic diagram of the casting temperature field of the casting using the parallel heating device of the prior art. Figure 10 The average temperature difference between the left and right temperature measuring points of the stepped casting during the directional solidification of the casting is shown in the parallel heating device and the bipolar sawtooth directional solidification casting heating device, as the pulling time changes. Figure 11 A comparison of the temperature fields of the conductive components with and without cooling water during heating in a bipolar sawtooth directional solidification casting heating device is shown. (a) Temperature field distribution of the single-polar heating component with cooling water, (b) Temperature field distribution of the conductive component with cooling water, (c) Temperature field distribution of the single-polar heating component without cooling water, and (d) Temperature field distribution of the conductive component without cooling water. In the diagram: 101, thermal insulation component; 102, temperature control component; 103, heating component; 104, conductive component; 201, platinum-rhodium thermocouple; 202, ceramic protective tube; 301, carbon fiber heating plate; 302, graphite connecting strip; 303, graphite screw; 304, adjusting nut; 305, graphite electrode; 401, conductive block body; 402, cooling channel; 403, clamping mechanism; 404, external channel; 405, electrical flange. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions 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, 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.

[0022] Before describing the specific implementation methods, in conjunction with Figure 7 As shown, the design concept of this invention is briefly explained based on the principle of radiative heat transfer. The intensity of radiative heat transfer is directly proportional to the radiation angle coefficient, which can be expressed as:

[0023] in, This is the reference distance between radiating surface elements. and Let be the angle between the normal to the surface element and the connecting line.

[0024] It can be seen that, when the radiation area and orientation are constant, the intensity of radiation heat transfer is approximately inversely proportional to the square of the distance. The smaller the distance, the larger the angle coefficient and the stronger the radiation heat transfer.

[0025] like Figure 8 As shown in (a), in a conventional annular heating device, for a certain casting, except for a few areas close to the heating surface in a certain direction (such as the W direction), the distances from the heating surface in the other three directions are... Both are very large, which means that the casting can only achieve a small radiation distance and a high radiation angle factor in about 1 / 4 of the directions. X The area with strong heat exchange surface accounts for only 25%, resulting in low overall heat exchange efficiency, poor temperature gradient, and very uneven temperature field.

[0026] like Figure 8 As shown in (b), the parallel heating device, by changing the assembly method of the casting and arranging heating surfaces on both sides of the casting, allows the casting to obtain a relatively small radiation distance in both directions facing the heater. For the casting at the end of the module, approximately 1 / 4 of the heat transfer radius is removed in the direction (E direction). r Medium, corresponding to approximately 3 / 4 of the heat transfer radius in the directions (N, W, S). r Very small, angle factor X The surface area is relatively large, allowing for strong radiative heat transfer. However, for the castings in the middle of the module, only about 2 / 4 of the directions (N and S directions) can achieve strong radiative heat transfer. Therefore, the strong heat transfer surface of the parallel heating device accounts for 50-75%, resulting in strong overall heat transfer efficiency and relatively proper temperature control. However, there are still some areas where the temperature field is not uniform (such as the ends of the module).

[0027] like Figure 8 As shown in (c), the present invention constructs a bipolar sawtooth heating space to increase the radiation distance of the casting in the four orthogonal diagonal directions. All are significantly reduced, thus reducing the angle coefficient. X It achieves high values ​​in multiple directions, theoretically realizing a near 100% strong heat exchange surface ratio, fundamentally improving heating uniformity.

[0028] like Figure 1 , Figure 5 and Figure 6As shown, this invention provides a bipolar sawtooth-shaped directional solidification casting heating device for heating and holding a linearly assembled casting module within a vacuum directional solidification furnace. By improving the heating space topology, it solves the problems of uneven heating, heat transfer lag, and temperature field asymmetry in the casting, thereby reducing the risk of defects such as impurities and freckles. The device mainly includes a heat insulation component 101, a temperature control component 102, a heating component 103, and a conductive component 104, wherein: The heat insulation component 101 is arranged to form a heat-insulating cavity.

[0029] Heating assembly 103 is disposed in the heat preservation cavity and is used to radiate heat to the inline casting module extending into the heat preservation cavity. The heating assembly 103 is divided into an upper heating group and a lower heating group along the height direction. Each heating group includes a left electrode heating assembly and a right electrode heating assembly that are arranged opposite to each other and electrically isolated from each other, thereby forming four electrically isolated closed electric heating circuits. The heating plates 301 in the left electrode heating assembly and the right electrode heating assembly are arranged in a sawtooth pattern, so that the outlines of the heating plates 301 on the left and right sides are opposite to each other and form multiple rhomboid heating spaces for accommodating a single casting.

[0030] The temperature control component 102 has temperature measuring points corresponding to the four closed electric heating circuits, which are used to collect temperature feedback signals of each circuit and independently adjust the heating current of each circuit in a closed loop.

[0031] The conductive component 104 is electrically connected to the heating component 103 and is used to connect to an external power source.

[0032] It should be noted that the in-line casting module includes at least two castings arranged in a straight line and a gating system communicating with the at least two castings.

[0033] Specifically, the insulation component 101 is surrounded by multiple rigid carbon felts, forming an insulated cavity with openings at the top and bottom. Its function is to create a high-temperature environment and reduce heat loss. The rigid carbon felt has high refractoriness and low thermal conductivity, which can limit the conduction and radiation loss of heat to the external structure of the furnace to the greatest extent, and efficiently confine the heat energy inside the cavity for heating the casting module.

[0034] The heating assembly 103, which generates thermal radiation, is entirely housed within the insulation cavity. The heating assembly 103 employs a bipolar sawtooth topology. First, along the height direction (vertical direction) of the cavity, the entire heating assembly is divided into an upper heating zone and a lower heating zone. Second, within each height zone (e.g., the upper zone), there are two electrically isolated electrode heating assemblies arranged opposite each other: a left-side electrode heating assembly and a right-side electrode heating assembly. Therefore, the entire heating assembly constitutes four electrically isolated closed electric heating loops: the upper zone left electrode, the upper zone right electrode, the lower zone left electrode, and the lower zone right electrode. These four loops can be independently powered and controlled.

[0035] Each side's electrode heating assembly consists of multiple specific heating plates 301. Preferably, the heating plates 301 are woven from carbon fiber. Their arrangement is not a simple planar array, but rather a zigzag staggered pattern. Specifically, the heating plates 301 on the left and right sides are arranged with their outlines opposite each other, thus forming multiple open diamond-shaped heating spaces between them. During the design, each casting in the in-line casting module and its connected gating system should be correspondingly surrounded by the central area of ​​the diamond-shaped heating spaces. This layout minimizes the distance from the casting to the nearest heating plate along the four orthogonal diagonal directions (southeast, southwest, northeast, and northwest), thereby achieving close and strong radiative heat transfer conditions and greatly reducing the geometric obstruction and "shadowing effect" in traditional heating methods.

[0036] The temperature control component 102 is used to achieve independent temperature control. The temperature control component 102 has four temperature measuring points, each corresponding to one of the four independent electric heating circuits. By installing temperature sensors at appropriate locations in each circuit, temperature feedback signals from each area can be collected in real time. Based on the temperature feedback signals, the control system can independently adjust the heating current of the four circuits using PID closed-loop regulation. This zoned independent temperature control method effectively compensates for local temperature differences caused by furnace structure, uneven heat loss, or module differences, thereby ensuring a high degree of uniformity of the horizontal temperature field within the entire insulation cavity and facilitating the control of the longitudinal temperature gradient.

[0037] The conductive component 104 is the interface for power input. It is electrically connected to the heating component 103 via the graphite electrode 305 and is used to introduce a large external current power supply into the high-temperature insulation cavity.

[0038] In one implementation, the heating plates 301 are arranged in pairs within a single electrode heating assembly, perpendicular to each other and staggered.

[0039] Specifically, such as Figure 3As shown, when constructing a single electrode heating assembly, such as the upper left assembly, the multiple heating plates 301 contained therein are assembled in pairs according to specific rules. Each pair of heating plates is fixed at a mutually perpendicular angle, for example, one plate mainly faces the left-right direction, and the other plate mainly faces the front-back direction.

[0040] In one implementation, the temperature control component 102 includes four sets of platinum-rhodium thermocouples 201, which are respectively set at the temperature measuring points of the four closed electric heating circuits, and the heating current of the corresponding circuit is independently adjusted based on the signal of each thermocouple using a PID control algorithm.

[0041] Specifically, four sets of platinum-rhodium thermocouples 201 are selected as temperature sensing elements, such as Figure 2 As shown, each platinum-rhodium thermocouple 201 is protected by a ceramic sheath 202. The measuring ends of the four thermocouples are respectively arranged at the temperature measuring points of four closed electric heating circuits.

[0042] Four independent PID control loops, each receiving a temperature feedback signal from a corresponding platinum-rhodium thermocouple 201, compare the signal with the set target temperature or heating curve. The PID algorithm calculates the required control quantity in real time and outputs a signal to adjust the heating current of the corresponding loop. With this configuration, the temperatures of the four heating zones (upper left, upper right, lower left, and lower right) can be set and controlled completely independently, thereby achieving temperature field regulation of the insulation cavity.

[0043] In one feasible approach, such as Figure 3 As shown, the heating component 103 is mounted on the heat insulation component 101 via a graphite electrode 305. The graphite electrode 305 passes through the side wall of the heat insulation component 101, with one end electrically connected to the heating plate 301 and the other end electrically connected to the conductive component 104. The graphite electrode 305 is provided with threads and an adjusting nut 304 that mates with it. By adjusting the locking position of the adjusting nut 304 and the clamping position of the graphite electrode 305 on the conductive component 104, the installation position of the heating component 103 in the heat insulation cavity can be adjusted.

[0044] Specifically, multiple heating plates 301 in the heating assembly 103 are electrically connected in series via graphite connecting strips 302 and fastened together using graphite screws 303. The graphite electrode 305 has external threads machined on its rod, passing through a pre-drilled circular hole in the side wall of the insulation assembly 101 from the inside. Its inner end connects to the electrical connection point of the heating assembly 103, while its outer end extends to the outside of the insulation cavity. An adjusting nut 304 is screwed onto the rod of the graphite electrode 305 on the outside of the insulation assembly 101. When the adjusting nut 304 is tightened, its end face presses against the outer wall surface of the insulation assembly 101, thereby fixing the graphite electrode 305 and the entire side of the heating assembly 103 suspended and supported by it. It should be noted that the mating surfaces of the adjusting nut 304, the graphite electrode 305, and the insulation assembly 101 are all coated with an insulating layer to prevent the rigid carbon felt in the insulation assembly 101 from becoming conductive.

[0045] When the width of the inline casting module changes, the radiation distance between the heater and the casting may also change. Compared to annular heaters, which can achieve geometric position compensation within a certain range by changing the module assembly method, parallel heaters are difficult to compensate for radiation distance differences by adjusting the module assembly method. If the device lacks a structure to adjust the heating spacing without replacing the heating element, the radiation distance difference is not easily eliminated, which may lead to problems such as reduced local radiative heat transfer intensity, reduced temperature gradient, and widening of the mushy region, thereby further increasing the risk of defects occurring during directional solidification. The heating component 103 of this invention has an adjustable spacing, which can adapt to inline casting modules of different widths.

[0046] The process of adjusting the spacing is as follows: When it is necessary to change the spacing between the left and right heating plates 301 to accommodate a wider or narrower inline casting module, first loosen the adjusting nuts 304 on both sides. At this time, the heating assembly 103 acts as a single unit that can slide along the mounting holes on the side wall of the insulation assembly 101. The operator can push or pull the heating assembly 103 as a whole to change its lateral position within the insulation cavity. At the same time, the length of the graphite electrode 305 extending from the clamping part of the conductive assembly 104 also changes accordingly. Determine the new installation position based on the maximum external dimensions of the casting module and the required minimum radiation distance. After adjustment, retighten the adjusting nuts 304 to lock the heating assembly 103 in the new position. This structure enables continuous adjustment of the heating space width without replacing any heating plates 301.

[0047] In one possible implementation, the conductive component 104 includes a conductive block body 401 and a clamping mechanism 403; the conductive block body 401 has a cooling channel 402 inside; and the graphite electrode 305 is adjustablely mounted in the clamping mechanism 403.

[0048] Specifically, such as Figure 4 As shown, the main body of the conductive component 104 is a conductive block body 401, preferably made of copper with high conductivity. To ensure controllable temperature rise under high current, a meandering internal cooling channel 402 is directly machined inside the conductive block body 401 and connected to the external channel 404. During operation, circulating cooling water needs to be introduced into the cooling channel 402 to force-cool the conductive component 104, thereby reducing its operating temperature and suppressing heat transfer to the external power supply.

[0049] To connect and secure the graphite electrode 305 extending from the heating assembly, the conductive block body 401 is equipped with a dedicated clamping mechanism 403. For example, this clamping mechanism 403 can be a conductive clamping block assembly with fastening bolts. The outer end of the graphite electrode 305 is placed within the clamping jaws of the clamping mechanism 403, and mechanical fixation is achieved by tightening the bolts. As mentioned earlier, when adjusting the position of the heating assembly 103, the specific position of the graphite electrode 305 clamped in the clamping mechanism 403 can be adjusted synchronously, and final tightening is performed after adjustment.

[0050] In one feasible approach, such as Figure 4 As shown, the conductive component 104 also includes a current-leading flange 405, which has a cooling medium inlet and a cooling medium outlet communicating with the cooling channel 402, wherein the cooling medium inlet is located at the bottom and the cooling medium outlet is located at the top.

[0051] In other words, the power-in flange 405 serves as both a power terminal and a cooling pipe interface. A cooling medium inlet and outlet, communicating with the internal cooling channel 402, are machined on the power-in flange 405, arranged in a bottom-in, top-out flow direction. That is, the cooling medium inlet is located at the bottom of the power-in flange 405, and the cooling medium outlet is located at the top. During operation, cooling water flows in from the bottom inlet, passes through the cooling channel 402 inside the conductive block body 401, and then flows out from the top outlet. This arrangement facilitates the water flow to fill the channel, ensuring uniform and efficient cooling and achieving the best temperature reduction effect.

[0052] Preferably, the heating plate 301 is made of carbon fiber material. Carbon fiber material has excellent resistance stability, high radiation emissivity and a higher heating rate than graphite when energized in a high temperature vacuum environment.

[0053] This embodiment provides a method for directional solidification casting using the bipolar serrated directional solidification casting heating device described in any of the above embodiments. The specific steps are as follows: Step 1: Install the casting module (including the ceramic mold shell and its internal cavity) prepared using the in-line molding method onto the pull-out device of the directional solidification furnace. Operate the pull-out device to send the casting module into the heating device cavity from below. Adjust the horizontal position of the module to ensure that each casting in the module and the middle runner are located in the center area of ​​the corresponding diamond-shaped heating space.

[0054] Step 2: Based on the maximum width dimension of the currently used inline casting module and the ideal radiation distance required by the process, determine the target spacing between the left and right heating plates 301. The operator loosens all adjusting nuts 304 and moves the heating component 103 to the predetermined installation position by pushing the heating assembly or adjusting the graphite electrode 305, thereby changing its depth through the sidewall of the heat insulation component and its clamping length in the clamping mechanism 403 and meeting the radiation distance requirements. Finally, all adjusting nuts 304 are tightened again to complete the fixing.

[0055] Step 3: Connect the cooling water circuit and introduce circulating cooling water into the cooling channel 402 of the conductive component 104, with the lower end serving as the cooling water inlet and the upper end as the cooling water outlet. Set appropriate inlet temperature and flow rate to achieve water cooling of the conductive component. Connect the device to an external high-current power supply to supply power to the four independent heating circuits through the conductive component 104 and graphite electrode 305.

[0056] Step 4: Set the target temperature or target heating rate in the control system, and configure the control parameters and current constraint parameters for each PID loop. Control parameters include proportional gain, integral gain, and derivative gain; current constraint parameters include initial current, maximum current, and minimum current. Start the temperature control program, and the system begins operation. Four sets of thermocouples collect temperature data in real time, and four independent PID control loops calculate and adjust the heating current of their respective loops to ensure the insulation cavity heats up quickly and evenly and stabilizes at the set temperature.

[0057] Step 5: After the casting module has been fully preheated and reached the required pouring temperature, pour molten high-temperature alloy metal into the pouring cup at the top of the module. Once the cavity is filled with molten metal, maintain the temperature for a certain period. Then, activate the pulling device to smoothly pull the casting module upwards from the high-temperature zone at a constant pulling rate. Under the influence of a strong axial temperature gradient, the metal undergoes directional solidification from top to bottom, ultimately yielding a high-quality casting with consistent microstructure and orientation.

[0058] This invention employs a bipolar sawtooth-shaped solidification casting heating device. By arranging the heating surfaces in a sawtooth pattern within a limited space, each casting is surrounded by four symmetrically arranged heating plates in a symmetrical rhomboid heating space. The radiation distance in the four orthogonal directions of southeast, southwest, northeast, and northwest is [not specified]. r Minimize all angle coefficients as much as possible.X The heat transfer efficiency is very high, and theoretically, similar strong radiative heat transfer conditions can be obtained in all four main directions, resulting in a very high overall heat transfer efficiency. The proportion of strong heat transfer surface is close to 100%, and the temperature gradient control capability is very strong. As a result, there is basically no heat transfer lag during the directional solidification process of the casting, and the temperature field is more uniform and flat in all horizontal directions, which helps to reduce the curvature and inclination of the isotherms at the solid-liquid interface and suppress the widening of the mushy region.

[0059] This invention addresses the challenges of directional solidification processes, which primarily rely on radiative heat transfer and are often limited by equipment space. It proposes a heating space topology and heater profile design for multi-cast inline modules, maximizing radiation viewing angles and heat transfer capacity within a confined space to enhance overall temperature field uniformity and temperature gradient control. This invention overcomes the limitations of previous solutions in terms of geometric obstruction or arrangement, raising the theoretical upper limit of temperature uniformity and heat transfer capacity while reducing the likelihood of defects caused by uneven temperature fields or poor gradient control.

[0060] This invention divides the heating component into four electrically isolated closed electric heating circuits: upper left pole, upper right pole, lower left pole, and lower right pole. Each circuit is equipped with a temperature measuring point and a PID temperature control circuit, allowing the heating current of each closed electric heating circuit to be adjusted independently. This enables zoned temperature control of the upper and lower height ranges and the left and right poles, which helps to improve the temperature control capability of the casting in all directions and further improve the uniformity of the temperature field.

[0061] This invention employs a graphite electrode thread and adjusting nut structure that passes through the sidewall of the heat insulation component, along with an adjustable clamping position of the graphite electrode on the conductive component. This allows the spacing between the heating component and the inline casting module to be adjusted without replacing the heating plate. This enables it to adapt to casting modules of different widths within a certain range, facilitating compensation for differences in radiation distance, improving local radiative heat transfer conditions, increasing heat transfer efficiency and temperature gradient, while reducing the frequency of heating component replacements and device changeover costs. In other words, the bipolar sawtooth heating space creates two sets of symmetries in the temperature field—left-right and front-back—ensuring that the casting receives similar radiative heating conditions in all four directions. This reduces the shadowing effect of traditional annular and parallel heating devices, increases the coverage area of ​​strong radiative heat transfer, and reduces heat transfer hysteresis. Furthermore, the adjustable spacing of the heating components adapts to modules of different widths, thereby improving temperature uniformity and gradient control capabilities, and reducing the risk of defects.

[0062] Example 1: Two cross-shaped petal castings and two stepped castings are assembled into a casting module in a straight-line mold assembly and a corresponding ceramic mold shell is prepared. The ceramic mold shell is installed on the pull-out device of the directional solidification system and the ceramic mold shell of the casting module is extended into the heat preservation cavity and located between the heating components, so that the four castings and the corresponding positions of the intermediate gating are all in the central area of ​​each rhomboid heating space. The maximum external dimension of the inline casting module in the width direction is the width dimension of the cross-petal-shaped casting. The maximum width of the mold shell is 35mm, and the maximum dimension of the bottom runner is 32mm. Based on the above maximum external dimensions and combined with the assembly allowance, the minimum distance between the inner surfaces of the relatively arranged heating components is determined to be 36mm, and the minimum radiation distance between the heating plate and the outer surface of the mold shell is 20mm, thereby determining the installation position of the heating components in the insulation cavity. By adjusting the clamping position of the graphite electrode and the conductive component, and adjusting the locking position of the nut on the graphite electrode thread, the positioning and fixed installation of the heating components are achieved. Circulating cooling water is introduced into the cooling channel of the conductive component, with the lower end serving as the cooling water inlet and the upper end serving as the cooling water outlet. The inlet temperature and flow rate of the cooling water are set and controlled. In this embodiment, the cooling water inlet temperature is 20°C, the inlet flow rate is 0.85 m / s, and the corresponding flow rate is approximately 4 L / min, so as to achieve water cooling of the conductive component. The target temperature is set to 1800K, and PID control parameters and current constraint parameters are set. In this embodiment, considering the requirements for fast response and system stability, the control parameters are set as follows: proportional gain K. p =0.9A / K, Integral gain K i =0.5A / (K•s), differential gain K d =0.1s•A / K. Considering the power supply limitations and the current level under steady-state conditions, the current constraint parameters are set as follows: initial current 200A, maximum current 740A, minimum current 200A. Power is supplied to the heating component to preheat the mold shell. Temperature signals from the temperature measurement points corresponding to the four closed electric heating loops are collected, and the heating current of the corresponding closed electric heating loops is adjusted in closed loop using a PID algorithm. Under the conditions of this embodiment, the temperature can be quickly stabilized at the target temperature of around 1800K, and the steady-state current is about 450A. After the mold shell is preheated to the preset conditions, liquid high-temperature alloy is poured into the mold shell and held at that temperature for 100 seconds. Inside a bipolar sawtooth heating device, the casting mold is pulled upwards at a rate of 3 mm / min to achieve directional solidification. The temperature field during directional solidification is analyzed, and temperature measuring points are set at both ends of the stepped casting to calculate the temperature difference between the two ends. For comparison, identical casting molds are subjected to directional solidification using a parallel heating device under the same target temperature, pulling rate, and temperature measuring point arrangement. Figure 9 The diagram illustrates the temperature field distribution of the parallel heating device and the bipolar sawtooth heating device during the directional solidification of the casting in this embodiment. (a) is a schematic diagram of the casting temperature field of the bipolar sawtooth heating device of the present invention; (b) is a schematic diagram of the casting temperature field of the parallel heating device of the prior art. For the inner cross-shaped casting, in the bipolar sawtooth heating device of the present invention, since both sides have strong radiative heat exchange, the heat exchange is large and certain, and the casting temperature field always maintains a uniform and symmetrical distribution on both sides, with strong temperature uniformity. In contrast, the parallel heater of the prior art, since both sides have weak radiative heat exchange, the heat exchange is affected by multiple directions, making it difficult to ensure uniform heat exchange. The isotherms will show a certain degree of trend of the outer side being higher than the inner side, resulting in slightly poorer temperature uniformity. For the outer stepped casting, this phenomenon is even more obvious. In the bipolar sawtooth heating device of the present invention, the isotherms are initially straight and uniformly distributed. Although the isotherms show a slight trend of the outer side being higher than the inner side as the pulling time progresses, the overall inclination is much smaller than that of the parallel heater of the prior art. Figure 10 This diagram illustrates the variation of the average temperature difference between the left and right measuring points of the stepped casting during the directional solidification of the casting using a parallel heating device and a bipolar serrated directional solidification casting heating device in this embodiment. The comparative results show that, compared to the parallel heating device, the temperature difference between the left and right sides of the casting is significantly reduced when using the bipolar serrated heating device, and the average temperature difference between the measuring points at both ends of the stepped casting decreases by approximately 40-50 K. This indicates a significant reduction in the transverse temperature gradient of the casting and an improvement in the uniformity of the casting's temperature field.

[0063] Example 2: Without setting up a casting module, the single-pole heating component of the bipolar sawtooth heating device was energized and heated. In this embodiment, to verify the cooling effect of the internal cooling channel of the conductive component on the conductive component, the single-pole heating component of the bipolar sawtooth directional solidification casting heating device was energized and heated without setting up a casting module. The temperature field distribution of the conductive component electrically connected to the single-pole heating component was compared and analyzed under two working conditions: without cooling water and with cooling water.

[0064] Operating Condition 1: Cooling water is introduced, and a 200 A current is applied to the single-pole heating component. Circulating cooling water is introduced from the lower end of the cooling channel and discharged from the upper end. In this embodiment, the cooling water inlet temperature is 20 °C, the inlet flow velocity is 1 m / s, corresponding to a volumetric flow rate of approximately 4.7 L / min. Heating continues for 300 s. After heating is completed, the temperature field of the conductive component is analyzed. Figure 11 In the figure, (a) and (b) are the temperature fields of the conductive components when the bipolar sawtooth directional solidification casting heating device is heated and the cooling water is introduced. (a) is the temperature field distribution of the unipolar heating component and (b) is the temperature field distribution of the conductive component. The lowest temperature of the conductive component is about 293 K and the highest temperature is about 435 K.

[0065] Operating Condition 2: Without cooling water, a current of 200 A is applied to another single-pole heating component. Heating continues for 300 seconds without cooling water flowing through the conductive component's cooling channel. After heating, the temperature field of the conductive component is analyzed. Figure 11 In the figure, (c) and (d) represent the temperature field of the conductive component without cooling water when the bipolar sawtooth directional solidification casting heating device is heating. (c) represents the temperature field distribution of the unipolar heating component, and (d) represents the temperature field distribution of the conductive component. The lowest temperature of the conductive component is about 633 K, and the highest temperature is about 990 K.

[0066] Depend on Figure 11 (b) and Figure 11 As can be seen from (d) in the figure, under the same current of 200 A and the same heating time of 300 s, the introduction of circulating cooling water can significantly reduce the overall temperature level and the maximum temperature of the conductive component without affecting the overall temperature distribution of the heating component. This reduces the temperature rise of the conductive component and inhibits the transfer of heat to the external power supply terminal along the conductive path, which is beneficial to improving the reliability of the power supply connection.

[0067] In the description of this invention, it should be understood that the terms "upper", "lower", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0068] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0069] In this invention, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0070] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0071] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0072] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention.

Claims

1. A bipolar serrated directional solidification casting heating device, characterized in that, include: Thermal insulation component (101) is installed to form a thermal insulation cavity; A heating component (103) is disposed in the insulation cavity and is used to radiate heat to the inline casting module that extends into the insulation cavity. The heating component (103) is divided into an upper heating group and a lower heating group along the height direction. Each heating group includes a left electrode heating component and a right electrode heating component that are arranged opposite to each other and electrically isolated from each other, thereby forming four closed electric heating circuits that are electrically isolated from each other. The heating plates (301) in the left and right electrode heating assemblies are arranged in a sawtooth pattern, so that the outlines of the heating plates (301) on the left and right sides are opposite and form multiple rhomboid heating spaces for accommodating a single casting. The temperature control component (102) has temperature measuring points corresponding to the four closed electric heating circuits, which are used to collect the temperature feedback signals of each circuit and independently adjust the heating current of each circuit in a closed loop. The conductive component (104) is electrically connected to the heating component (103) and is used to connect to an external power source.

2. The bipolar serrated directional solidification casting heating device according to claim 1, characterized in that, The heating plates (301) are arranged in pairs within a single electrode heating assembly, perpendicular to each other and staggered.

3. The bipolar serrated directional solidification casting heating device according to claim 1, characterized in that, The temperature control component (102) includes four sets of platinum-rhodium thermocouples (201), which are respectively set at the temperature measurement points of the four closed electric heating circuits, and the heating current of the corresponding circuit is independently adjusted based on the signal of each thermocouple using a PID control algorithm.

4. The bipolar serrated directional solidification casting heating device according to claim 1, characterized in that, The heating component (103) is mounted on the heat insulation component (101) via a graphite electrode (305). The graphite electrode (305) passes through the side wall of the heat insulation component (101), with one end electrically connected to the heating plate (301) and the other end electrically connected to the conductive component (104). The graphite electrode (305) is provided with threads and an adjusting nut (304) that mates with it. By adjusting the locking position of the adjusting nut (304) and the clamping position of the graphite electrode (305) on the conductive component (104), the installation position of the heating component (103) in the heat insulation cavity can be adjusted.

5. The bipolar serrated directional solidification casting heating device according to claim 4, characterized in that, The conductive component (104) includes a conductive block body (401) and a clamping mechanism (403); a cooling channel (402) is provided inside the conductive block body (401); and the graphite electrode (305) is adjustablely installed in the clamping mechanism (403).

6. The bipolar serrated directional solidification casting heating device according to claim 5, characterized in that, The conductive component (104) further includes a current-leading flange (405), which has a cooling medium inlet and a cooling medium outlet communicating with the cooling channel (402), wherein the cooling medium inlet is located below and the cooling medium outlet is located above.

7. The bipolar serrated directional solidification casting heating device according to claim 1, characterized in that, The thermal insulation component (101) is composed of multiple rigid carbon felts.

8. The bipolar serrated directional solidification casting heating device according to claim 1, characterized in that, The heating plate (301) is made of carbon fiber material.

9. A method for directional solidification casting using the bipolar serrated directional solidification casting heating device as described in any one of claims 1-8, characterized in that, include: The casting modules arranged in a straight line are placed in the heat-insulating cavity, so that each casting is located in the central area of ​​a diamond-shaped heating space; Adjust the position of the heating component (103) according to the width of the casting module so that the heating plate (301) and the casting module reach a preset radiation distance; The heating component (103) is powered by the conductive component (104), and the four closed electric heating circuits are independently PID controlled by the temperature control component (102) so that the heat preservation cavity is heated to the target temperature or heated at the target heating rate. Molten metal is poured into the preheated casting mold and then pulled out to complete directional solidification.

10. The method according to claim 9, characterized in that, The steps for adjusting the position of the heating assembly (103) include: loosening the adjusting nut (304), adjusting the extension length of the graphite electrode (305) in the clamping mechanism (403), and then re-tightening the adjusting nut (304).

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