Directional solidification equipment and heat compensation method for same

Abstract

The invention discloses directional solidification equipment and a heat compensation method for the equipment. The equipment comprises a crucible; the heat conducting pad is arranged at the bottom of the crucible; each thermal compensation vertical pipe group comprises a plurality of thermal compensation vertical pipes which are parallel to the side wall of the crucible; the main liquid storage tank is attached to the heat conduction pad, and a buffer gas chamber is arranged below the main liquid storage tank; the number of the auxiliary liquid storage tanks is equal to that of the thermal compensation vertical pipe sets, the auxiliary liquid storage tanks are arranged on the side of the main liquid storage tank, and the top of each auxiliary liquid storage tank is communicated with the thermal compensation vertical pipes of one thermal compensation vertical pipe set; a gate valve type piston is arranged in each auxiliary liquid storage tank, and an inflatable diaphragm capsule is arranged above each gate valve type piston; the inflatable diaphragm capsule is connected with the buffer air chamber through an air pipe provided with a one-way air valve; each auxiliary liquid storage tank is communicated with the main liquid storage tank through a thermal compensation horizontal pipe; and the top of the main liquid storage tank is respectively communicated with all the thermal compensation vertical pipes. The heat compensation method can dynamically adjust the height of the liquid level in the heat compensation vertical pipe, so that the net heat exchange capacity of the side wall approaches zero.

Description

Technical Field

[0001] The present invention relates to the technical field of directional solidification, in particular to a directional solidification device and a heat compensation method used for the device. Background Art

[0002] The core of directional solidification technology lies in achieving directional phase transformation of the melt through precise control of the temperature field. Existing technologies generally employ a combination of passive insulation and active heat dissipation. For example, these methods use multiple layers of insulation or composite insulation structures to insulate the crucible's sidewalls and top, supplemented by forced heat dissipation from the crucible's bottom (e.g., air or liquid cooling) to create specific heat dissipation channels and a unidirectional temperature gradient, ultimately achieving the desired temperature field for directional solidification.

[0003] However, the thermal resistance of the insulation structure in the prior art fluctuates with directional solidification at different temperatures, resulting in unstable insulation performance. Furthermore, heat dissipation from the crucible bottom accounts for 70%-80% of the equipment's total energy consumption. The prior art does not dynamically compensate for this excess heat by feeding it back to the sidewalls, resulting in low energy efficiency.

[0004] In summary, the existing technology cannot achieve adaptive heat compensation throughout the solidification process, resulting in poor process stability and high energy consumption. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a directional solidification device and a heat compensation method for the device.

[0006] The present invention provides a directional solidification device, comprising: Crucible; A thermal pad disposed at the bottom of the crucible; A plurality of thermal compensation riser tube groups, each thermal compensation riser tube group including a plurality of thermal compensation riser tubes arranged parallel to the side wall of the crucible; The main liquid reservoir is fitted with the thermal pad, and a buffer air chamber is provided underneath; A plurality of auxiliary liquid storage tanks, the number of which is equal to the number of the thermal compensation riser groups and which are arranged on the side of the main liquid storage tank, wherein the top of each auxiliary liquid storage tank is connected to a plurality of thermal compensation risers of a thermal compensation riser group; Each auxiliary liquid storage tank is provided with a gate valve piston inside, and an inflatable membrane box is provided above the gate valve piston; The inflatable membrane box is connected to the buffer air chamber through an air pipe provided with a one-way air valve; Each auxiliary liquid storage tank is connected to the main liquid storage tank through a heat compensation horizontal pipe; The top of the main liquid storage tank is connected to all the thermal compensation risers respectively.

[0007] Optionally, the directional solidification equipment further includes: An insulating cover covering the top and sides of the crucible; The heat insulation layer covering the heat compensation riser is arranged between the crucible and the heat insulation cover.

[0008] The present invention also provides a heat compensation method for any of the above-mentioned directional solidification equipment, characterized in that it comprises the following steps: Evacuate the interior of the main liquid storage tank, auxiliary liquid storage tank, thermal compensation horizontal pipe and thermal compensation vertical pipe; The main liquid storage tank is filled with a heat-conducting liquid. During the directional solidification process, the heat emitted from the bottom of the crucible drives the heat-conducting liquid in the main liquid storage tank to expand. The temperature change at the bottom of the crucible is sensed by the inflatable membrane box, and the linkage mechanism between the inflatable membrane box and the gate valve piston is combined to make the heat-conducting liquid in the main liquid storage tank flow into the auxiliary liquid storage tank through the heat compensation horizontal pipe; During the directional solidification process, the morphological changes of the phase transition interface are monitored in real time; Based on the first formula of the phase change interface morphology and the heat exchange amount of the crucible side wall, temperature changes and morphology changes, the liquid level in the thermal compensation riser is dynamically adjusted to make the net heat exchange amount of the side wall approach zero and maintain the phase change interface level; The first formula is as follows: ; Here, the vertical symmetry axis of the melt is set as the y-axis, the melt width is set as W, the lower boundary of the region with a height of Δ where the phase change interface is located is set as the x-axis, and the height Δ is used as the calculation region. q is the heat flux density of the crucible side wall, and t is the temperature of the calculation region. To calculate the lower edge temperature of the region, is the upper edge temperature of the calculation area, s is the latent heat of solidification continuously released during the solidification process, λ is the thermal conductivity of the melt, , n is an odd number.

[0009] Optionally, when the heat loss of the crucible side wall increases, the phase change interface becomes concave, the volume of the inflatable membrane box becomes smaller, and the gate valve piston is driven to rise, so that the liquid level in the thermal compensation riser is increased to enhance heat preservation and suppress the concave phase change interface; When there is excess heat on the side wall of the crucible, the phase change interface bulges upward, the volume of the inflatable membrane box increases, driving the gate valve piston to lower, lowering the liquid level in the thermal compensation riser to reduce insulation and suppress the bulge of the phase change interface.

[0010] Optionally, the first formula is obtained based on the temperature field formula and the boundary condition formula in the calculation area, and includes at least the following steps: Transform the temperature field formula and the boundary condition formula to obtain the first temperature field formula, the second temperature field formula, the third temperature field formula, the first boundary condition formula, the second boundary condition formula, and the third boundary condition formula; The temperature field formula is: ; The boundary condition formula is: ;in, is the temperature distribution function at the bottom edge of the calculation area, is the temperature distribution function along the upper edge of the calculation area; Based on the first temperature field formula and the first boundary condition formula, the second temperature field formula and the second boundary condition formula, and the third temperature field formula and the third boundary condition formula, they are solved respectively to obtain the first formula.

[0011] Optionally, solving the first temperature field formula and the first boundary condition formula, the second temperature field formula and the second boundary condition formula, and the third temperature field formula and the third boundary condition formula respectively to obtain the first formula includes at least the following steps: Based on the first formula of temperature field and the first formula of boundary condition, the second formula is obtained by solving; The first formula of temperature field is: ; The first formula of the boundary condition is: ; Based on the second formula of temperature field and the second formula of boundary condition, the third formula is obtained; The second temperature field formula is: ; The second boundary condition formula is: ; Based on the third formula of temperature field and the third formula of boundary condition, the fourth formula is obtained; The third formula of temperature field is: ; The third boundary condition formula is: ; Based on the second formula, the third formula, the fourth formula, the boundary condition formula, and the sum of the first temperature field formula, the second temperature field formula, and the third temperature field formula, the first formula is solved.

[0012] Optionally, solving the second formula based on the first temperature field formula and the first boundary condition formula includes the following steps: make , then u satisfies the fifth formula: ; And the boundary conditions satisfy the sixth formula: ; Through Fourier expansion, the analytical solution of u is obtained as: ; According to u and the analytical solution, the second formula is obtained as follows: .

[0013] Optionally, based on the second temperature field formula and the second boundary condition formula, the separation of variables method is used to solve the third formula as follows: ; in, is the periodic constant factor.

[0014] Optionally, based on the third temperature field formula and the third boundary condition formula, the fourth formula is obtained by using the separation of variables method as follows: .

[0015] Optionally, solving the first formula based on the second formula, the third formula, the fourth formula, the boundary condition formula, and the sum of the first temperature field formula, the second temperature field formula, and the third temperature field formula includes the following steps: Based on the sum of the first temperature field formula, the second temperature field formula, and the third temperature field formula, the following formula is obtained: ; Based on the second, third, and fourth formulas, the boundary condition formula is transformed to obtain the fifth formula as follows: ; Based on the second formula, the third formula, the fourth formula, the fifth formula, and the sum of the first temperature field formula, the second temperature field formula, and the third temperature field formula, the separation of variables method is used to solve the problem and obtain the first formula.

[0016] Compared with the existing technology, the present invention provides multiple auxiliary liquid storage tanks and corresponding controlled thermal compensation riser groups, combined with a linkage mechanism, to achieve real-time compensation for heat loss on the crucible side wall, thereby solving the problem in the existing technology that the insulation structure is fixed and cannot be adjusted in real time; the directional solidification equipment described in the present invention can effectively transfer the heat emitted from the bottom of the crucible to the side wall for insulation and control of the phase change interface morphology, thereby recovering and reusing the originally wasted heat energy and improving energy utilization efficiency.

[0017] Compared with the prior art, the present invention further reduces heat loss and improves the insulation effect of the entire directional solidification process by providing insulation covers on the top and sides of the crucible and providing an insulation layer between the crucible and the insulation cover; it helps to reduce the energy that must be input to maintain the required temperature, thereby reducing overall energy consumption.

[0018] Compared with the existing technology, the present invention dynamically adjusts the liquid level height in the thermal compensation riser based on the first formula of the phase change interface morphology and the heat exchange amount of the crucible side wall, so as to accurately control the morphology of the phase change interface and maintain its level, thereby improving the solidification quality; by real-time monitoring of the morphological changes of the phase change interface and dynamic adjustment, the stability of the directional solidification process is improved and defects caused by temperature fluctuations are reduced.

[0019] Compared with the prior art, when the heat loss of the crucible side wall increases or there is excess heat, the device of the present invention can automatically adjust the liquid level in the heat compensation riser to strengthen or reduce insulation, thereby realizing automatic control of the solidification process and improving the automation level of the process.

[0020] Compared with the prior art, the first formula of the present invention is obtained based on the temperature field formula and the boundary condition formula in the calculation area, which provides accurate theoretical support for heat compensation and makes heat compensation more scientific and accurate.

[0021] Compared with the prior art, the present invention obtains the first formula through a multi-step precise solution process, thereby further improving the accuracy and reliability of heat compensation.

[0022] Compared with the prior art, the analytical solution obtained by the present invention through Fourier expansion provides precise control parameters for heat compensation, thereby being able to more accurately control the morphology of the phase change interface.

[0023] Compared with the prior art, the present invention solves the first formula based on the second formula, the third formula, the fourth formula and the fifth formula, integrates the influence of multiple factors, and improves the accuracy of controlling the phase change interface morphology. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 This is a simplified structural diagram of an embodiment of a directional solidification device according to the present invention; Figure 2 A simplified flow chart of an embodiment of a heat compensation method for directional solidification equipment according to the present invention; Figure 3 A schematic diagram of a phase change interface in an embodiment of a heat compensation method for directional solidification equipment according to the present invention; Figure 4 A schematic diagram drawn according to a first formula of an embodiment of a heat compensation method for a directional solidification device of the present invention; Figure 5 A schematic diagram of the initial stage of solidification of an embodiment of a heat compensation method for directional solidification equipment according to the present invention; Figure 6 Schematic diagram of a heat compensation standpipe filled with heat-conducting liquid in an embodiment of a heat compensation method for directional solidification equipment according to the present invention; Figure 7 This is a schematic diagram of the structure of eight independent thermal compensation risers in accordance with an embodiment of the directional solidification apparatus of the present invention; Figure 8 This is a schematic diagram showing the principle of a heat compensation process when the phase change interface is concave in an embodiment of a heat compensation method for directional solidification equipment of the present invention; Figure 9 This is another principle schematic diagram of the heat compensation process when the phase change interface is concave in one embodiment of the heat compensation method for directional solidification equipment of the present invention; Figure 10 This is a schematic diagram showing the principle of the heat compensation process when the phase change interface is convex in an embodiment of the heat compensation method for directional solidification equipment of the present invention; Figure 11 This is another principle diagram of the heat compensation process when the phase change interface is convex in one embodiment of the heat compensation method for directional solidification equipment of the present invention; Figure 12 A schematic diagram showing the principle of a phase change interface level in an embodiment of a heat compensation method for a directional solidification device according to the present invention; Figure 13 This is another principle schematic diagram of the phase change interface level in one embodiment of the heat compensation method for directional solidification equipment of the present invention.

[0025] Figure numerals: 10, crucible; 20, thermal pad; 30, thermal compensation riser; 40, main liquid storage tank; 50, buffer gas chamber; 60, auxiliary liquid storage tank, 61, inflatable membrane box, 62, gate valve piston; 70, air pipe, 71, one-way air valve; 80, thermal insulation cover; 90, thermal insulation layer. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] like Figure 1 As shown, the present invention provides a directional solidification device, comprising: Crucible 10; A thermal pad 20 disposed at the bottom of the crucible 10; Multiple thermal compensation riser groups, each thermal compensation riser group includes multiple thermal compensation risers 30 arranged parallel to the side wall of the crucible 10; The main liquid storage tank 40 is in contact with the thermal pad 20 and has a buffer air chamber 50 below it; A plurality of auxiliary liquid storage tanks 60, the number of which is equal to the number of the thermal compensation riser groups and which are arranged on the side of the main liquid storage tank 40, wherein the top of each auxiliary liquid storage tank 60 is connected to the plurality of thermal compensation risers 30 of a thermal compensation riser group; Each auxiliary liquid storage tank 60 is provided with a gate valve piston 62 inside, and an inflatable membrane box 61 is provided above the gate valve piston 62; The inflatable membrane box 61 is connected to the buffer air chamber 50 through an air pipe 70 provided with a one-way air valve 71; Each auxiliary liquid storage tank 60 is connected to the main liquid storage tank 40 through a heat compensation horizontal pipe; The top of the main liquid storage tank 40 is communicated with all the thermal compensation risers 30 respectively.

[0028] The present invention provides a plurality of auxiliary liquid storage tanks 60 and correspondingly controlled thermal compensation riser groups, combined with a linkage mechanism, to achieve real-time compensation for heat loss on the side wall of the crucible 10, thereby solving the problem in the prior art that the insulation structure is fixed and cannot be adjusted in real time; the directional solidification equipment described in the present invention can effectively transfer the heat emitted from the bottom of the crucible 10 to the side wall for insulation and control of the phase change interface morphology, thereby recovering and reusing the originally wasted heat energy and improving energy utilization efficiency.

[0029] Preferably, the directional solidification equipment further comprises: a heat-insulating cover 80 covering the top of the crucible 10; The heat insulation layer 90 covering the heat compensation standpipe 30 is disposed between the crucible 10 and the heat insulation cover 80 .

[0030] The present invention further reduces heat loss and improves the insulation effect of the entire directional solidification process by arranging a heat-insulating cover 80 on the top and sides of the crucible 10 and an insulating layer 90 between the crucible 10 and the heat-insulating cover 80; it helps to reduce the energy that must be input to maintain the required temperature, thereby reducing overall energy consumption.

[0031] like Figure 2 As shown, the present invention also provides a heat compensation method for any of the above-mentioned directional solidification equipment, characterized in that it includes the following steps: Evacuate the interior of the main liquid storage tank 40, the auxiliary liquid storage tank 60, the thermal compensation horizontal pipe and the thermal compensation vertical pipe 30; Fill the main liquid storage tank 40 with heat-conducting liquid. During the directional solidification process, the heat emitted from the bottom of the crucible 10 drives the heat-conducting liquid in the main liquid storage tank 40 to expand. The temperature change at the bottom of the crucible 10 is sensed by the inflatable membrane box 61. Combined with the linkage mechanism of the inflatable membrane box 61 and the gate valve piston 62, the heat-conducting liquid in the main liquid storage tank 40 flows into the auxiliary liquid storage tank 60 through the heat compensation horizontal pipe. During the directional solidification process, the morphological changes of the phase transition interface are monitored in real time; Based on the first formula of the phase change interface morphology and the heat exchange amount of the side wall of the crucible 10, the temperature change and the morphology change, the liquid level in the thermal compensation riser 30 is dynamically adjusted to make the net heat exchange amount of the side wall approach zero and maintain the phase change interface level; The first formula is as follows: ; Among them, since the phase change interface only occupies a small layer area in the melt, by virtue of symmetry, the vertical symmetry axis of the melt is set as the y-axis, the melt width is set as W, the lower boundary of the small thin layer area with a height of Δ where the phase change interface is located is set as the x-axis, and the height Δ is used as the calculation area (refer to Figure 3 ), because the height of Δ is extremely small, the latent heat released by the solidification of the melt at the phase change interface is evenly distributed in the entire calculation area; q is the heat flux density of the side wall of the crucible 10, t is the temperature of the calculation area, To calculate the lower edge temperature of the region, is the upper edge temperature of the calculation area, s is the latent heat of solidification continuously released during the solidification process, λ is the thermal conductivity of the melt, , n is an odd number.

[0032] The present invention dynamically adjusts the liquid level height in the thermal compensation riser 30 based on a first formula of the phase change interface morphology and the heat exchange amount of the crucible 10 side wall, thereby accurately controlling the morphology of the phase change interface and maintaining its level, thereby improving the solidification quality; by real-time monitoring of the morphological changes of the phase change interface and dynamic adjustment, the stability of the directional solidification process is improved and defects caused by temperature fluctuations are reduced.

[0033] The present invention can be used for directional solidification purification of polysilicon or directional solidification of titanium aluminum alloy precision casting or aluminum alloy precision casting. On the premise of meeting the basic temperature field of directional solidification, it also has the ability to dynamically adjust the phase change interface morphology, reduce thermal stress and prevent ingot cracking.

[0034] For example, in the actual application of the present invention in the directional solidification purification of polysilicon or the precision casting process of titanium-aluminum alloy, the bottom main liquid storage tank 40, the auxiliary liquid storage tank 60, the inflatable membrane box 61, the thermal compensation horizontal tube and the thermal compensation vertical tube 30 are all made of nickel alloy (Inconel600), the inflatable membrane box 61 is filled with argon, and a Galinstan liquid metal alloy composed of 68.5% Ga (gallium) + 21.5% In (indium) + 10% Sn (tin) (melting point is 6°C, boiling point >1400°C) is used as the thermal compensation liquid working fluid.

[0035] For example, in the directional solidification process of aluminum alloy precision casting in the present invention, the bottom main liquid storage tank 40, the auxiliary liquid storage tank 60, the inflatable membrane box 61, the thermal compensation horizontal tube and the thermal compensation vertical tube 30 are all made of titanium alloy, the inflatable membrane box 61 is filled with nitrogen, and high-temperature silicone oil is used as the thermal compensation liquid working medium.

[0036] The design concept of the present invention is that since heat loss and dissipation during directional solidification of the melt is unavoidable, it is better to "direct" this heat to the sidewalls of crucible 10 for full utilization, effectively providing side insulation and control. At the same time, the overall temperature field of the melt is maintained above the phase transition temperature, preventing premature solidification.

[0037] Therefore, the present invention utilizes the heat dissipated from the bottom of the crucible 10 during directional solidification to drive the auxiliary liquid reservoir 60 and the inflatable membrane 61. When the heat-conducting liquid in the main liquid reservoir 40 expands due to heat, it enters the auxiliary liquid reservoir 60 through the horizontal heat compensation pipe. The inflatable membrane 61 senses the temperature changes around the bottom of the crucible 10 and actuates the gate valve piston 62 in the auxiliary liquid reservoir 60, controlling the liquid level in the vertical heat compensation pipe 30. Heat from the bottom of the crucible 10 is then transferred from the liquid to the sidewalls of the crucible 10.

[0038] The present invention not only achieves sidewall insulation but also adjusts the morphology of the phase change interface by varying the liquid level within the thermal compensation riser 30 on the sidewall of the crucible 10, achieving the process goal of varying the thermal insulation and heat dissipation intensity of the melt. Compared to traditional thermal insulation and heat dissipation solutions, the present invention dynamically adjusts the thermal insulation and heat dissipation intensity during the directional solidification process, automatically corrects the phase change interface morphology, and offers simple, reliable, and low-cost control equipment.

[0039] In this embodiment, when the heat loss from the side wall of the crucible 10 increases, the phase change interface becomes concave, the volume of the inflatable membrane box 61 decreases, and the gate valve piston 62 is driven to rise, thereby raising the liquid level in the thermal compensation riser 30 to enhance heat preservation and suppress the concave phase change interface. When the side wall of the crucible 10 has excess heat, the phase change interface bulges upward, the volume of the inflatable membrane box 61 increases, and the gate valve piston 62 is driven to descend, so that the liquid level in the thermal compensation riser 30 is lowered to reduce heat preservation and suppress the bulge of the phase change interface.

[0040] When the heat loss of the side wall of the crucible 10 increases or there is excess heat, the device can automatically adjust the liquid level in the thermal compensation riser 30 to strengthen or reduce insulation, thereby achieving automatic control of the solidification process and improving the automation level of the process.

[0041] In this embodiment, the first formula is obtained based on the temperature field formula and the boundary condition formula in the calculation area, and includes at least the following steps: Transform the temperature field formula and the boundary condition formula to obtain the first temperature field formula, the second temperature field formula, the third temperature field formula, the first boundary condition formula, the second boundary condition formula, and the third boundary condition formula; Since the solidification temperature of directional solidification is constant, the thermal properties of the region remain consistent regardless of the height of Δ during the entire solidification process. The directional solidification process also continuously releases latent heat of solidification, and the temperature field satisfies the Poisson equation with an internal heat source (i.e., the temperature field formula), specifically: ; The boundary condition formula is: ;in, is the temperature distribution function at the bottom edge of the calculation area, is the temperature distribution function along the upper edge of the calculation area; Based on the first temperature field formula and the first boundary condition formula, the second temperature field formula and the second boundary condition formula, and the third temperature field formula and the third boundary condition formula, they are solved respectively to obtain the first formula.

[0042] For the temperature field formula, the left edge of the calculation area x=0 is located in the center of the crucible 10. Due to the central symmetry, it can be considered as adiabatic here, that is, x=W / 2 is located at the right edge of the calculation area. There may be heat exchange with the outside world, that is, there is a heat flux density q, and we can get: When q>0, the direction of heat flux is along the positive x-axis, that is, the heat loss at the right edge of the calculation area; When q < 0, the direction of the heat flux is along the negative x-axis, that is, the right edge of the calculation area obtains heat; When q=0, there is no heat exchange and the edge of the calculation area is perfectly adiabatic.

[0043] The most important parameter of the directional solidification process is the net heat exchange amount of the side wall of the crucible 10, which determines the morphology of the phase change interface, and keeping the phase change interface horizontal is the key to the success of directional solidification. Therefore, it is necessary to establish a mathematical model to explore the mathematical relationship between the side wall heat exchange, the bottom heat dissipation intensity and the phase change interface morphology, to provide a theoretical basis for the present invention, and also to facilitate quantitative control of the phase change interface morphology. The first formula of the present invention is obtained based on the temperature field formula and the boundary condition formula in the calculation area, which provides accurate theoretical support for heat compensation, making heat compensation more scientific and accurate.

[0044] Since the temperature field formula contains non-homogeneous boundary conditions, it is difficult to solve it directly. Therefore, in this embodiment, based on the first temperature field formula and the first boundary condition formula, the second temperature field formula and the second boundary condition formula, and the third temperature field formula and the third boundary condition formula, respectively, solving them to obtain the first formula includes at least the following steps: Based on the first formula of temperature field and the first formula of boundary condition, the second formula is obtained by solving; The first formula of temperature field is: ; The first formula of the boundary condition is: ; Based on the second formula of temperature field and the second formula of boundary condition, the third formula is obtained; The second temperature field formula is: ; The second boundary condition formula is: ; Based on the third formula of temperature field and the third formula of boundary condition, the fourth formula is obtained; The third formula of temperature field is: ; The third boundary condition formula is: ; Based on the second formula, the third formula, the fourth formula, the boundary condition formula, and the sum of the first temperature field formula, the second temperature field formula, and the third temperature field formula, the first formula is solved.

[0045] The present invention obtains the first formula through a multi-step accurate solution process, thereby further improving the accuracy and reliability of heat compensation.

[0046] In this embodiment, based on the first temperature field formula and the first boundary condition formula, solving the second formula includes the following steps: make , then u satisfies the fifth formula: ; And the boundary conditions satisfy the sixth formula: ; Through Fourier expansion, the analytical solution of u is obtained as: .

[0047] The analytical solution obtained by the Fourier expansion of the present invention provides precise control parameters for heat compensation, thereby being able to more accurately control the morphology of the phase change interface.

[0048] In this embodiment, based on the second temperature field formula and the second boundary condition formula, the third formula is obtained by using the separation of variables method as follows: ; Here, m is a positive integer greater than or equal to 2.

[0049] In this embodiment, based on the third temperature field formula and the third boundary condition formula, the fourth formula is obtained by using the separation of variables method as follows: .

[0050] In this embodiment, based on the second formula, the third formula, the fourth formula, the boundary condition formula, and the sum of the first temperature field formula, the second temperature field formula, and the third temperature field formula, solving the first formula includes the following steps: Based on the sum of the first temperature field formula, the second temperature field formula, and the third temperature field formula, the following formula is obtained: ; Based on the second, third and fourth formulas, let t Δ(x) (represent and ) is a constant, and the boundary condition formula is transformed to obtain the fifth formula as follows: ; Based on the second, third, fourth, and fifth formulas, as well as the sum of the first, second, and third temperature field formulas, the separation of variables method is used to solve the problem and obtain the first formula: .

[0051] The present invention solves the first formula based on the second formula, the third formula, the fourth formula, the boundary condition formula, and the sum of the first temperature field formula, the second temperature field formula, and the third temperature field formula, thereby integrating the influence of multiple factors and improving the accuracy of controlling the phase change interface morphology.

[0052] By plotting the first formula (ref. Figure 4 ) It can be seen that the heat flux density q at the edge of the crucible 10 affects the phase change interface: the greater the heat loss value of the side wall of the crucible 10 (q is a positive value), the more concave the phase change interface is; the greater the heat gain value of the side wall of the crucible 10 (q is a negative value), the more convex the phase change interface is; the side wall of the crucible 10 is ideally insulated (q is 0), and the phase change interface remains horizontal.

[0053] Therefore, it has been theoretically proven that by changing the insulation properties of the sidewalls of the crucible 10 through the thermal compensation riser 30 of this solution, and thereby adjusting the heat exchange intensity, the morphology of the phase change interface can be controlled. When directional solidification is used for precision casting or crystal growth purification, if the sidewalls lose heat, the phase change interface becomes concave, solidification thermal stress concentrates, reducing the purity of the ingot and even risking ingot cracking. When the sidewalls gain heat, the phase change interface becomes convex, the direction of crystal (grain) growth tilts during solidification, and the arrangement of dendrites becomes uncontrolled. When there is no heat exchange on the sidewalls, the phase change interface becomes horizontal, and the solidification quality is optimal at this time. Since the solidification process is a comprehensive result of heat conduction, convection, and heat radiation, maintaining the horizontality of the phase change interface at each stage of solidification is the key to successful solidification and is also the difficulty and focus of the process.

[0054] According to the first formula, the most critical parameters in the directional solidification process are the heat exchange conditions on the sidewalls of the crucible 10 and the heat dissipation intensity at the bottom, which determine the phase change interface morphology and solidification quality. Traditional directional solidification equipment relies primarily on passive thermal insulation materials. Even with active mechanical structures (such as the lifting heat shield directional solidification method), their thermal insulation capacity lacks adjustment margin and flexibility when operating conditions change, and the morphology of the phase change interface cannot be monitored and corrected in real time during the solidification process. The present invention incorporates a thermal compensation riser 30 and designs an automatic control structure that links the inflatable membrane 61 to the liquid storage tank. Using simple control logic based on the thermal expansion of the liquid and the thermal expansion and contraction of the gas within the inflatable membrane 61, the flow of the liquid working medium within the tube is driven, allowing real-time adjustment of the liquid level within the thermal compensation riser 30. This achieves the process requirements of dynamic thermal insulation of the crucible 10 sidewalls and control of the phase change interface morphology as the solidification progresses. Furthermore, the present invention eliminates the need for multiple embedded sensors, complex circuits, and control chips for closed-loop control, further reducing overall costs.

[0055] It should be noted that, in the present invention, one auxiliary liquid storage tank 60 controls one corresponding thermal compensation riser group. However, there is no specific requirement for the number of thermal compensation risers 30 included in each thermal compensation riser group. Different thermal compensation riser groups can include the same or different numbers of thermal compensation risers 30. However, the number of auxiliary liquid storage tanks 60 is determined based on the accuracy of temperature field control during the directional solidification process.

[0056] For example, if the phase change interface morphology needs to be controlled more precisely, a larger number of auxiliary liquid storage tanks 60 are required, and the number of thermal compensation risers 30 included in the thermal compensation riser group controlled by each auxiliary liquid storage tank 60 is smaller.

[0057] The thickness and number of thermal compensation risers 30 are primarily limited by three factors: processing difficulty, processing cost, and fluid flow resistance. Theoretically, the thinner and more numerous the thermal compensation risers 30, the better the temperature field control accuracy. However, in practice, as processing difficulty, cost, and fluid flow resistance increase, thinner and more numerous thermal compensation risers 30 may not necessarily achieve the desired effect (for example, if the fluid flows too slowly, the control effect will be poor).

[0058] Therefore, the number of auxiliary liquid storage tanks 60 provided is generally 8-16, and each auxiliary liquid storage tank 60 controls a corresponding thermal compensation riser group comprising 4-8 thermal compensation risers 30. It is understood that the auxiliary liquid storage tank 60 is positioned closest to the location of the thermal compensation riser group it controls.

[0059] It should be noted that the above description is merely an illustrative description and does not constitute an improper limitation to the present invention.

[0060] Furthermore, the principle of the heat supplement method of the present invention is described with reference to the accompanying drawings to facilitate understanding of the present invention.

[0061] After the interiors of the main liquid storage tank 40 , the auxiliary liquid storage tank 60 , the heat compensation horizontal pipe and the heat compensation vertical pipe 30 are evacuated, the main liquid storage tank 40 is filled with heat-conducting liquid (working medium).

[0062] In the initial stage of solidification, the heat-conducting liquid is stored in the main liquid storage tank 40 (see Figure 5 Because the main liquid reservoir 40 and the horizontal thermal compensation tube are in close contact with the thermal pad 20 at the bottom of the crucible 10, the thermally conductive liquid in the main liquid reservoir 40 expands upon heating, passing through the auxiliary liquid reservoir 60 and into the thermal compensation riser 30. Consequently, some of the heat dissipated from the bottom of the crucible 10 is transferred by the thermally conductive liquid to the thermal compensation riser 30. This effectively "guides" the heat dissipated from the bottom of the crucible 10 to the sidewalls of the crucible 10, which require insulation, thus providing active auxiliary insulation for the sidewalls. Simultaneously, the thermal compensation riser 30 in the vacuum section also provides passive insulation.

[0063] After solidification begins, as heat dissipates from the bottom of the crucible 10, the thermally conductive liquid in the main reservoir 40 expands. Furthermore, the bottom buffer chamber 50 begins to expand and squeeze the main reservoir 40, causing the thermally conductive liquid in the main reservoir 40 to gradually enter the auxiliary reservoir 60 through the thermal compensation horizontal pipe. During initial solidification, the bottom heat dissipation temperature is higher. Because the inflatable bellows 61 is tightly attached to the bottom of the crucible 10, its initial temperature is higher than that of the buffer chamber 50 at the bottom of the main reservoir 40. Consequently, the air pressure inside the inflatable bellows 61 is higher. When the pressure difference is sufficient to open the one-way air valve 71 between them, the inflatable bellows 61 shrinks slightly, causing the gate valve piston 62 in the auxiliary reservoir 60 to rise, causing the volume of the auxiliary reservoir 60 to increase slightly, allowing it to accommodate more liquid and slowing the rapid rise of the liquid level in the thermal compensation riser 30. Therefore, during the initial solidification phase, this design effectively controls the phase transition interface imbalance caused by excessive directional solidification rates. As solidification proceeds, the liquid level in the thermal compensation riser 30 rises along the phase change interface, and the solidified portion (solid phase) is kept warm and annealed to reduce thermal stress and prevent cracking. Until the solidification process is completed, the thermal compensation riser 30 is filled with heat-conducting liquid (please refer to Figure 6 ), to keep the ingot warm as a whole.

[0064] During directional solidification, if the phase change interface is unbalanced (such as overall or local concave and convex), the present invention can automatically adjust and correct the phase change interface. Figure 7 As shown, 8 groups of independent thermal compensation tubes can be controlled by their own inflatable membrane boxes 61 and auxiliary liquid storage tanks 60. Taking the thermal compensation tubes at the corners as an example, the specific control principle and steps of phase change interface correction are as follows: When the phase change interface is concave, according to the analysis of the first formula, the side wall of the crucible 10 loses heat, especially the heat loss at the corners of the side wall of the crucible 10 is particularly significant. Therefore, the heat dissipation intensity at the bottom corners of the crucible 10 is reduced, making the volume of the inflatable membrane box 61 smaller (thinner), driving the gate valve piston 62 in the auxiliary liquid storage tank 60 to rise (refer to Figure 8 ), the flow resistance is reduced, causing the liquid level in the sidewall thermal compensation riser 30 to rise, strengthening the thermal compensation there. Since the air pressure in the inflatable membrane box 61 is lower than that in the buffer air chamber 50 at this time, but the air pipe 70 between the buffer air chamber 50 and the inflatable membrane box 61 is equipped with a one-way air valve 71, the one-way air valve 71 is closed, and the gas in the buffer air chamber 50 cannot enter the inflatable membrane box 61. Therefore, the position of the gate valve piston 62 in the main liquid storage tank 40 remains basically unchanged, causing the liquid level in the other thermal compensation risers 30 to be lower than the liquid level in the risers at the corners of the crucible 10, thereby generating a height difference throughout the thermal compensation riser 30, forming a concave sidewall insulation pattern similar to a concave phase change interface (refer to Figure 9 ), compensates for the heat loss from the side wall of the crucible 10, and restores the phase change interface from concave to horizontal.

[0065] When the sidewalls of the crucible 10 receive heat, the phase change interface convexes. To correct the convex interface morphology, it is necessary to reduce the insulation strength of the sidewalls of the crucible 10 at the interface height. As the inflatable membrane box 61 expands due to heat, the gate valve piston 62 in the auxiliary liquid storage tank 60 descends, throttling the flow, increasing the flow resistance, and correspondingly lowering the liquid level in the thermal compensation riser 30, reducing the sidewall heat compensation (see Figure 10 ), accelerating the solidification of the melt at the sidewalls and restoring the phase change interface to a horizontal level. During this process, since the air pressure in the inflatable bellows 61 is higher than that in the buffer air chamber 50, the pressure difference pushes open the spring of the one-way air valve 71 between the two. The valve opens, and the inflatable bellows 61 provides gas compensation to the buffer air chamber 50, further increasing the volume of the buffer air chamber 50. This squeezes the bottom of the main liquid storage tank 40, causing the liquid level in the other thermal compensation risers 30 to rise slightly, forming a thermal insulation pattern with a significantly convex liquid level as a whole (see Figure 2). Figure 11 ), which can effectively modify the phase change interface.

[0066] When there is no heat exchange on the side wall of the crucible 10, the phase change interface is horizontal and the directional solidification effect is the best. At this time, the air pressure in the buffer chamber 50 and each inflatable membrane box 61 is basically equal, and the inflatable membrane box 61 and the gate valve piston 62 move slowly and synchronously with the solidification process (refer to Figure 12 ), the liquid level in all heat compensation risers 30 rises slowly along with the phase change interface, achieving the process effect of dynamic insulation (reference Figure 13 ).

[0067] According to the first formula of the present invention, the thickness, density, and grouping of the sidewall thermal compensation risers 30 can be designed for different directionally solidified materials, thereby increasing the application flexibility of the method of the present invention. The above parameter changes under different solidification conditions are summarized in Table 1.

[0068] Table 1 Summary of parameter changes under different solidification conditions

[0069] It should be noted that, in actual applications, the thermal compensation riser is thinner and has a higher density than that shown in the figure. For the convenience of explanation and illustration, the drawings shown in the present invention appropriately enlarge and simplify the thermal compensation riser. This is only for illustrative purposes and does not constitute an improper limitation to the present invention.

[0070] It should be noted that in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0071] While the foregoing description shows and describes preferred embodiments of the present invention, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments, and can be modified within the scope of the present invention by the teachings herein or by techniques or knowledge in the relevant art. Modifications and variations made by those skilled in the art without departing from the spirit and scope of the present invention are intended to be within the scope of the appended claims.

Claims

1. A directional solidification device, characterized in that: include: Crucible; A thermal pad disposed at the bottom of the crucible; A plurality of thermal compensation riser tube groups, each thermal compensation riser tube group including a plurality of thermal compensation riser tubes arranged parallel to the side wall of the crucible; The main liquid reservoir is fitted with the thermal pad, and a buffer air chamber is provided underneath; A plurality of auxiliary liquid storage tanks, the number of which is equal to the number of the thermal compensation riser groups and which are arranged on the side of the main liquid storage tank, wherein the top of each auxiliary liquid storage tank is connected to a plurality of thermal compensation risers of a thermal compensation riser group; Each auxiliary liquid storage tank is provided with a gate valve piston inside, and an inflatable membrane box is provided above the gate valve piston; The inflatable membrane box is connected to the buffer air chamber through an air pipe provided with a one-way air valve; Each auxiliary liquid storage tank is connected to the main liquid storage tank through a heat compensation horizontal pipe; The top of the main liquid storage tank is connected to all the thermal compensation risers respectively.

2. The directional solidification equipment according to claim 1, characterized in that Also includes: An insulating cover covering the top and sides of the crucible; The heat insulation layer covering the heat compensation riser is arranged between the crucible and the heat insulation cover.

3. A heat compensation method for the directional solidification equipment according to claim 1 or 2, characterized in that: The following steps are involved: Evacuate the interior of the main liquid storage tank, auxiliary liquid storage tank, thermal compensation horizontal pipe and thermal compensation vertical pipe; The main liquid storage tank is filled with a heat-conducting liquid. During the directional solidification process, the heat emitted from the bottom of the crucible drives the heat-conducting liquid in the main liquid storage tank to expand. The temperature change at the bottom of the crucible is sensed by the inflatable membrane box, and the linkage mechanism between the inflatable membrane box and the gate valve piston is combined to make the heat-conducting liquid in the main liquid storage tank flow into the auxiliary liquid storage tank through the heat compensation horizontal pipe; During the directional solidification process, the morphological changes of the phase transition interface are monitored in real time; Based on the first formula of the phase change interface morphology and the heat exchange amount of the crucible side wall, temperature changes and morphology changes, the liquid level in the thermal compensation riser is dynamically adjusted to make the net heat exchange amount of the side wall approach zero and maintain the phase change interface level; The first formula is as follows: ； Here, the vertical symmetry axis of the melt is set as the y-axis, the melt width is set as W, the lower boundary of the region with a height of Δ where the phase change interface is located is set as the x-axis, and the height Δ is used as the calculation region. q is the heat flux density of the crucible side wall, and t is the temperature of the calculation region. To calculate the lower edge temperature of the region, is the upper edge temperature of the calculation area, s is the latent heat of solidification continuously released during the solidification process, λ is the thermal conductivity of the melt, , n is an odd number.

4. The heat compensation method for directional solidification equipment according to claim 3, characterized in that: When the heat loss of the crucible side wall increases, the phase change interface becomes concave, the volume of the inflatable membrane box becomes smaller, and the gate valve piston is driven to rise, so that the liquid level in the thermal compensation riser rises to strengthen the heat preservation and suppress the concave phase change interface. When there is excess heat on the side wall of the crucible, the phase change interface bulges upward, the volume of the inflatable membrane box increases, driving the gate valve piston to lower, lowering the liquid level in the thermal compensation riser to reduce insulation and suppress the bulge of the phase change interface.

5. The heat compensation method for directional solidification equipment according to claim 3, characterized in that: The first formula is obtained based on the temperature field formula and the boundary condition formula in the calculation area, and includes at least the following steps: Transform the temperature field formula and the boundary condition formula to obtain the first temperature field formula, the second temperature field formula, the third temperature field formula, the first boundary condition formula, the second boundary condition formula, and the third boundary condition formula; The temperature field formula is: ； The boundary condition formula is: ;in, is the temperature distribution function at the bottom edge of the calculation area, is the temperature distribution function along the upper edge of the calculation area; Based on the first temperature field formula and the first boundary condition formula, the second temperature field formula and the second boundary condition formula, and the third temperature field formula and the third boundary condition formula, they are solved respectively to obtain the first formula.

6. The heat compensation method for directional solidification equipment according to claim 5, characterized in that: Solving the first temperature field formula and the first boundary condition formula, the second temperature field formula and the second boundary condition formula, and the third temperature field formula and the third boundary condition formula respectively to obtain the first formula includes at least the following steps: Based on the first formula of temperature field and the first formula of boundary condition, the second formula is obtained by solving; The first formula of temperature field is: ； The first formula of the boundary condition is: ； Based on the second formula of temperature field and the second formula of boundary condition, the third formula is obtained; The second temperature field formula is: ； The second boundary condition formula is: ； Based on the third formula of temperature field and the third formula of boundary condition, the fourth formula is obtained; The third formula of temperature field is: ； The third boundary condition formula is: ； Based on the second formula, the third formula, the fourth formula, the boundary condition formula, and the sum of the first temperature field formula, the second temperature field formula, and the third temperature field formula, the first formula is solved.

7. The heat compensation method for directional solidification equipment according to claim 6, characterized in that: Based on the first temperature field formula and the first boundary condition formula, the second formula is obtained by solving the formula, including the following steps: make , then u satisfies the fifth formula: ； And the boundary conditions satisfy the sixth formula: ； Through Fourier expansion, the analytical solution of u is obtained as: ； According to u and the analytical solution, the second formula is obtained as follows: 。 8. The heat compensation method for directional solidification equipment according to claim 7, characterized in that: Based on the second formula of temperature field and the second formula of boundary condition, the third formula is solved by separation of variables method as follows: ； in, is the periodic constant factor.

9. The heat compensation method for directional solidification equipment according to claim 8, characterized in that: Based on the third formula of temperature field and the third formula of boundary condition, the fourth formula is solved by separation of variables method as follows: 。 10. The heat compensation method for directional solidification equipment according to claim 9, characterized in that: Based on the second formula, the third formula, the fourth formula, the boundary condition formula, and the sum of the first temperature field formula, the second temperature field formula, and the third temperature field formula, solving the first formula includes the following steps: Based on the sum of the first temperature field formula, the second temperature field formula, and the third temperature field formula, the following formula is obtained: ； Based on the second, third, and fourth formulas, the boundary condition formula is transformed to obtain the fifth formula as follows: ； Based on the second formula, the third formula, the fourth formula, the fifth formula, and the sum of the first temperature field formula, the second temperature field formula, and the third temperature field formula, the separation of variables method is used to solve the problem and obtain the first formula.

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