A directional solidification method

Abstract

The application discloses a directional solidification method in the field of casting technology, which comprises the following steps: placing the casting part of the casting mold shell in a sleeve during casting, and placing cooling material in the sleeve, wherein the cooling material is first melted and gathered at the bottom end of the sleeve during the casting process, and then solidified to completely adhere to the upper surface of the water cooling disc and wrap the casting part of the casting mold shell, in the later cooling process of the casting process, the high area heat exchange of the water cooling disc and the casting mold shell is realized through the cooling material, the temperature gradient of the casting part of the casting mold shell can be better formed, the directional growth effect of the casting grain is better, and the comprehensive performance of the final casting is improved, meanwhile, the directional solidification method can be adapted to castings with different shapes and sizes, can be directly applied to the equipment used in the traditional high-speed solidification method, and the improvement cost is low and the learning cost is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of casting technology, in particular to a directional solidification method. BACKGROUND

[0002] The working environment of the hot end part of an aero-engine is harsh, especially the working blade which serves in high temperature and high pressure conditions for a long time. The high temperature performance of the part is higher than that of the cold end part. The turbine blade formed by directional solidification has better temperature resistance than the equiaxed blade.

[0003] The commonly used directional solidification methods for manufacturing directional blades today are liquid metal cooling (LMC) and high speed solidification (HRS). A single direction temperature gradient is formed in the liquid metal solidification process, so that the grain growth is carried out along the fixed direction, and finally the directional blade is formed.

[0004] The traditional HRS method places the product on the water-cooled crystallizer. The heat of the mold is taken away by conduction to the water-cooled crystallizer, so as to realize directional solidification. However, the blade is long and the contact area between the mold shell and the water-cooled crystallizer is too small during solidification. The heat conduction distance of the mold is longer in the late solidification stage, and the heat conduction efficiency is low, which may cause poor directional effect. At present, the way to solve this problem is to set a radiation cooling device below the mold heater. The radiation method is used to assist the overall heat dissipation in the late directional drawing. However, due to the different structures of the mold, the radiation heat dissipation conditions at different positions are inconsistent, which may still cause the temperature gradient to decrease and the directional effect to be poor.

[0005] Therefore, the present application designs a directional solidification method to solve the above problems. SUMMARY

[0006] To achieve the above purpose, the present application provides the following technical scheme: a directional solidification method, which surrounds the casting part of the casting mold shell by a sleeve during casting, and puts cooling materials in the sleeve, comprising the following steps:

[0007] S1, preparing a casting mold shell and a sleeve;

[0008] The sleeve is tubular, the vertical projection of the sleeve completely falls into the vertical projection of the water-cooled disc, and the vertical projection of the casting part of the casting mold shell completely falls into the vertical projection of the inner cavity of the sleeve;

[0009] S2, filling the cooling materials in the non-casting mold shell vacancy part of the sleeve, or placing the cooling materials on the water-cooled disc, and then placing the casting mold shell and the sleeve 1 on the water-cooled disc, so that the cooling materials are in the inner cavity of the sleeve;

[0010] The melting point of the cooling materials is lower than the melting point of the casting materials and the preheating temperature in the casting process;

[0011] S3, the casting mold shell and sleeve are sent into the pouring furnace by the water cooling disc for pouring;

[0012] S4, the casting mold shell is heated, the heating temperature is higher than the melting point of the cooling material and lower than the melting point of the casting material, so that the cooling material is melted and separated from the casting mold shell.

[0013] As a further scheme of the present application, the sleeve is integrally manufactured with the casting mold shell.

[0014] As a further scheme of the present application, the sleeve and the casting mold shell are separately manufactured.

[0015] As a further scheme of the present application, in step S2, when the cooling material is filled into the sleeve in the empty part of the casting mold shell, the width of the cooling material matches the gap of the casting part in the casting mold shell, so that the cooling material can be clamped in the gap of the casting part in the casting mold shell.

[0016] As a further scheme of the present application, in step S3, the pouring process of the casting mold shell is as follows:

[0017] S31, the casting mold shell is extended into the pouring furnace from the bottom of the pouring furnace by the water cooling disc;

[0018] S32, the casting material is heated to a preset temperature, so that the casting material is melted, the pouring furnace is heated to a preset temperature, so that the temperature in the pouring furnace reaches the preheating temperature to melt the cooling material;

[0019] S33, the high-temperature liquid casting material is poured into the casting mold shell from the top pouring cup of the casting mold shell;

[0020] S34, the water cooling disc is lowered to drive the casting mold shell to leave the pouring furnace from the opening at the bottom of the pouring furnace.

[0021] As a further scheme of the present application, the casting mold shell sequentially includes a pouring cup, a runner and a casting part from top to bottom, the runner is plate-shaped, and the shape and size of the runner match the shape and size of the opening at the top of the sleeve.

[0022] As a further scheme of the present application, the bottom surface of the sleeve 1 is on the same plane as the bottom end of the casting part 23 in the casting mold shell.

[0023] The present application has the following advantages:

[0024] The application places the casting part of the casting mold shell in the sleeve during pouring, and places cooling material in the sleeve, which will melt and gather at the bottom end of the sleeve during pouring, and then solidify to completely adhere to the upper surface of the water cooling disc and wrap the casting part of the casting mold shell, so that the water cooling disc and the casting mold shell can realize high area heat exchange through the cooling material during the late cooling process of the pouring process, so that the temperature gradient of the casting part of the casting mold shell can be better formed, the directional growth effect of the casting grain is better, the comprehensive performance of the final casting is improved, and different shapes and sizes of castings can be adapted, which can be directly applied to the equipment used in the traditional high-speed solidification method, and the improvement cost is low and the learning cost is low.

[0025] In addition to the purposes, features and advantages described above, the application has other purposes, features and advantages. The application will be further described below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application, and are incorporated in and constitute a part of this application. The embodiments of the application illustrated in the drawings, and their description thereto, are presented to explain the application and are not intended to limit the application. In the drawings:

[0027] Figure 1 Flowchart of the application.

[0028] Figure 2 Installation schematic diagram of the sleeve 1 and the casting mold shell 2 in the application.

[0029] Figure 3 Filling schematic diagram of the cooling material in the application.

[0030] Figure 4 Structural schematic diagram of the pouring process in the application.

[0031] Legend:

[0032] 1, sleeve; 2, casting mold shell; 21, sprue cup; 22, runner; 23, casting part; 3, pouring furnace; 4, water cooling disc. DETAILED DESCRIPTION

[0033] The embodiments of the application will be described in detail below with reference to the drawings, but the application can be implemented in various different ways as defined and covered below.

[0034] Please refer to Figures 1-4 The application provides a technical solution: a directional solidification method, comprising the following steps:

[0035] S1, preparing a casting mold shell 2 and a sleeve 1;

[0036] The sleeve 1 is tubular, and the vertical projection of the sleeve 1 completely falls within the vertical projection of the water-cooling plate 4, and the vertical projection of the casting portion 23 of the casting mold shell 2 completely falls within the vertical projection of the inner cavity of the sleeve 1;

[0037] S2, filling the empty part of the sleeve 1 other than the casting mold shell 2 with cooling material, or placing cooling material on the water cooling plate 4, and then placing the casting mold shell 2 and the sleeve 1 on the water cooling plate 4 so that the cooling material is in the inner cavity of the sleeve 1;

[0038] The melting point of the cooling material is lower than the melting point of the casting material and the preheating temperature during the pouring process;

[0039] S3, the casting mold shell 2 and the sleeve 1 are sent into the pouring furnace 3 through the water cooling plate 4 for pouring;

[0040] S4, heating the casting mold shell, wherein the heating temperature is higher than the melting point of the cooling material and lower than the melting point of the casting material, so that the cooling material melts and separates from the casting mold shell.

[0041] Currently, the material of aircraft engine blades is mostly nickel-based high-temperature alloy, whose solid solution temperature is about 1000℃. During the pouring process, the nickel-based high-temperature alloy needs to be heated to about 1500℃, and the casting mold shell 2 also needs to be preheated to 1500℃. Therefore, aluminum can be selected as the cooling material. The melting point of aluminum is 660℃, which is much lower than the melting point of nickel-based high-temperature alloy and the preheating temperature during pouring, and the thermal conductivity of aluminum is higher than the ceramic of the casting mold shell 2.

[0042] The casting mold shell 2 includes a pouring cup 21, a runner 22 and a casting part 23. The inner cavity of all casting parts 23 is connected through the runner 22 below the pouring cup 21. During pouring, the liquid casting material is poured into the pouring cup 21 and transported to the inner cavity of each casting part 23 through the runner 22 connected to the lower end of the pouring cup 21.

[0043] By placing the casting part 23 of the casting mold shell 2 into the sleeve 1, during the pouring process, the sleeve 1 and the casting mold shell 2 are placed on the water cooling disc 4, the water cooling disc 4 will seal the bottom of the sleeve 1, thus, the empty part of the sleeve 1 without the casting mold shell 2 can be filled with cooling material or the cooling material is placed on the water cooling disc 4, then the sleeve 1 and the casting mold shell 2 are placed on the water cooling disc 4, so that the cooling material is covered in the sleeve 1, the melting point of the cooling material is lower than the melting point of the casting material and the preheating temperature during the pouring process, during the pouring process, the sleeve 1, the casting mold shell 2 in the sleeve 1 and the cooling material are driven by the water cooling disc 4 into the pouring furnace 3, because the melting point of the cooling material is lower than the preheating temperature, thus, the cooling material in the sleeve 1 will be melted into liquid at high temperature during preheating, and flows and gathers on the water cooling disc 4 under the action of gravity, at this time, it is equivalent to immerse the casting part 23 of the casting mold shell 2 in the liquid cooling material, after the pouring is completed, the water cooling disc 4, the sleeve 1 and the casting mold shell 2 are separated from the pouring furnace 3 for cooling, at this time, the liquid cooling material gathered at the bottom end of the sleeve 1 in contact with the water cooling disc 4 will be rapidly cooled and solidified from bottom to top, the casting part 23 of the casting mold shell 2 is wrapped in the cooling material, because the cooling material will flow downward under the action of gravity when it is in liquid state, thus, the cooling material will contact the upper surface of the entire water cooling disc 4, the solidified cooling material will also wrap the casting part 23 of the casting mold shell 2, during the later cooling process, the cooling material can be used as an intermediate medium to accelerate the heat exchange between the casting mold shell 2 and the water cooling disc 4, then the heat conduction efficiency between the water cooling disc 4 and the casting mold shell 2 will be greatly improved, so as to realize the high-efficiency directional heat conduction during the later solidification process;

[0044] The sleeve 1 is arranged outside the casting part 23 of the casting mold 2, and the solid cooling material is placed in the sleeve 1 before pouring, so that the cooling material can be poured together with the sleeve 1 and the casting mold 2. The cooling material in the solid state is easy to place, convenient to fix, and has higher controllability, but the contact area of the solid cooling material with the water cooling disc 4 and the casting part 23 of the casting mold 2 is smaller, and the heat conduction efficiency is lower. During the pouring process, there is a preheating process, and the cooling material is melted into a liquid state through the heating process in the pouring process. The liquid cooling material will gather on the water cooling disc 4 under the action of gravity and wrap the casting part 23 of the casting mold 2. The liquid cooling material has fluidity and can adapt to different shapes and sizes of castings, so that the contact area of the cooling material with the water cooling disc 4 and the casting part 23 of the casting mold 2 is increased. Thus, in the subsequent cooling process, the heat of the casting part 23 of the casting mold 2 can be conducted to the water cooling disc 4 through the cooling material, greatly improving the cooling efficiency in the later stage of the cooling process. At the same time, the cooling material wraps the casting part 23 of the casting mold 2 from bottom to top, so that the heat is transferred from top to bottom, which can better form a temperature gradient in the casting part 23 of the casting mold 2, and the directional growth effect of the casting grain is better, thereby improving the comprehensive performance of the final casting.

[0045] The method improves the cooling effect of the water cooling disc 4 in the current high-speed solidification method (HRS) on the casting material in the later stage of the cooling process without adding additional equipment. The cooling effect on the casting material is better, and a temperature gradient is better formed on the casting material, so that the comprehensive performance of the final casting is more excellent. The method can be directly applied to the equipment used in the traditional high-speed solidification method, and the improvement cost and learning cost are low.

[0046] During the manufacturing process of the sleeve 1, the bottom surface of the sleeve 1 cannot be completely flat. Therefore, when the sleeve 1 is placed on the water cooling disc 4, the sleeve 1 cannot completely fit the upper surface of the water cooling disc 4, and a gap will exist between the sleeve 1 and the upper surface of the water cooling disc 4. When the cooling material melts and gathers on the upper surface of the water cooling disc 4, the liquid cooling material will rapidly cool and solidify when it contacts the water cooling disc 4 due to the low temperature of the water cooling disc 4, so that the cooling material at the lowest part of the cooling material after melting is always in a solid state. Therefore, it can prevent the liquid cooling material from leaking out of the gap between the sleeve 1 and the water cooling disc 4, ensure that there is no liquid leakage, and ensure work safety.

[0047] After the cooling is completed, the solidified cooling material needs to be separated from the casting mold shell 2 first, and then the subsequent disassembly process of the casting mold shell 2 can be carried out. Since the melting point of the cooling material is lower than that of the casting material, the cooling material can be heated to the melting point. The entire casting mold shell 2 can be placed in a box-type electromagnetic oven for heating. Heating the casting is a conventional technical means in the art, and will not be described here. After the cooling material is melted by heating and leaves the sleeve 1 from the bottom end of the sleeve 1, the cooling material is separated from the casting mold shell 2. The separation operation is simple and convenient.

[0048] Specifically, in step S3, the pouring process of the casting mold shell 2 is as follows:

[0049] S31, the casting mold shell 2 and the sleeve 1 are inserted into the pouring furnace 3 from the bottom of the pouring furnace 3 through the water-cooled disc 4. At this time, the sleeve 1 already contains cooling material;

[0050] S32, the casting material is heated to a preset temperature to melt the casting material. The heating of the casting material is carried out outside the pouring furnace 3. The pouring furnace 3 is heated to ensure the stability and quality of the mold shell during pouring. The pouring furnace 3 is provided with a heater. The temperature in the pouring furnace 3 can be raised by the heater, and the casting mold shell 2 located in the pouring furnace 3 is heated to the pouring temperature. During the heating process in the pouring furnace 3, the cooling material will first reach the melting point and melt. Then, under the action of gravity, it will gather at the bottom of the sleeve 1 and contact the water-cooled disc 4. The cooling material in contact with the water-cooled disc 4 remains solid due to the bottom chilling effect, forming a bottom seal to prevent liquid cooling material from leaking out of the gap between the sleeve 1 and the water-cooled disc 4;

[0051] S33, the high-temperature liquid casting material is poured into the casting mold shell 2 from the top pouring cup 21 of the casting mold shell 2;

[0052] S34, the water-cooled disc 4 is lowered to drive the casting mold shell 2 to leave the pouring furnace 3 from the opening at the bottom of the pouring furnace 3. At this time, the entire casting mold shell 2 starts to cool down. Since the bottom of the casting mold shell 2 is in contact with the water-cooled disc 4, the cooling speed of the entire casting mold shell 2 increases as it gets closer to the water-cooled disc 4, so as to form a temperature gradient in the casting part 23 of the casting mold shell 2.

[0053] Specifically, in some examples, the casting mold shell 2 and the sleeve 1 are integrally manufactured. The steps for preparing the casting mold shell 2 and the sleeve 1 are as follows:

[0054] S11, prepare a casting wax mold. The casting wax mold is combined to form a wax mold module. The outside of the wax mold module encloses a sleeve 1 wax mold. The top end of the sleeve 1 wax mold is fixed with a pouring channel 22;

[0055] S12, coating the wax mold and wax mold module of the sleeve 1 with slurry and sanding to the appropriate thickness, and then removing the wax to obtain the casting mold shell 2 with the sleeve 1.

[0056] In the present example, the bottom surface of the sleeve 1 is in the same plane as the bottom end of the casting part 23 of the casting mold shell 2, so that the casting part 23 of the casting mold shell 2 and the bottom end of the sleeve 1 can both be in contact with the water-cooled disc 4. The contact between the casting part 23 of the casting mold shell 2 and the water-cooled disc 4 can increase the heat conduction area, and the contact between the bottom end of the sleeve 1 and the water-cooled disc 4 can prevent a large gap between the sleeve 1 and the top surface of the water-cooled disc 4, ensuring that the cooling material does not leak.

[0057] Specifically, in some examples, the sleeve 1 and the casting mold shell 2 are both separately manufactured. After the wax mold is separately manufactured, the casting part 23 of the casting mold shell 2 is placed into the sleeve 1 during pouring, realizing the reusability of the sleeve 1, reducing the manufacturing difficulty of the casting mold shell 2, and saving production costs.

[0058] Specifically, in step S2, when the cooling material is filled into the non-casting-mold-shell-2 part of the sleeve 1, the width of the cooling material matches the gap of the casting part 23 of the casting mold shell 2, so that the cooling material can be clamped in the gap of the casting part 23 of the casting mold shell 2.

[0059] Specifically, as shown in Figure 2 In some examples, the runner 22 is plate-shaped, and the shape and size of the runner 22 match the shape and size of the top opening of the sleeve 1. After the casting part 23 of the casting mold shell 2 is placed into the sleeve 1, the runner 22 of the casting mold shell 2 covers the top surface of the sleeve 1 to close the top opening of the sleeve 1, preventing the cooling material from volatilizing onto the furnace wall of the pouring furnace 3.

[0060] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A directional solidification process characterized by, The step of filling the cooling material into the sleeve (1) and the step of pouring the casting material into the sleeve (1) and the casting mold shell (2) are as follows: S1, preparing the casting mold shell (2) and the sleeve (1); The sleeve (1) is tubular, and the vertical projection of the sleeve (1) completely falls into the vertical projection of the water cooling disc (4), and the vertical projection of the casting part (23) of the casting mold shell (2) completely falls into the vertical projection of the inner cavity of the sleeve (1); S2, filling the cooling material into the non-casting-mold-shell (2) part of the sleeve (1), so that the cooling material is in the inner cavity of the sleeve (1) and the casting mold shell (2) together during the pouring process; The melting point of the cooling material is lower than the melting point of the casting material and the preheating temperature during pouring; S3, sending the casting mold shell (2) and the sleeve (1) into the pouring furnace (3) through the water cooling disc (4) for pouring; S31, the casting mold shell (2) is inserted into the pouring furnace (3) from the bottom of the pouring furnace (3) through the water cooling disc (4); S32, the casting material is heated to a preset temperature, so that the casting material is melted, the pouring furnace (3) is heated, and the temperature in the pouring furnace (3) reaches the preheating temperature, so that the cooling material is melted; S33, the high-temperature liquid casting material is poured into the casting mold shell (2) from the top of the pouring cup (21) of the casting mold shell (2); S34, the water cooling disc (4) is lowered to drive the casting mold shell (2) to move downward and leave the pouring furnace (3) through the opening at the bottom of the pouring furnace (3); S4, heating the casting mold shell (2) to a temperature higher than the melting point of the cooling material and lower than the melting point of the casting material, so that the cooling material is melted and separated from the casting mold shell (2).

2. A directional solidification process according to claim 1, characterised in that: In step S2, the cooling material is clamped in the gap of the casting part (23) of the casting mold shell (2) or placed on the water cooling disc (4) when filling the cooling material into the sleeve (1).

3. A directional solidification process according to claim 1 wherein: The sleeve (1) is integrally manufactured with the casting mold shell (2).

4. A directional solidification process according to claim 1 wherein: The sleeve (1) and the casting mold shell (2) are separately manufactured.

5. A directional solidification process according to claim 1 wherein: In step S2, the width of the cooling material matches the gap of the casting part (23) in the casting mold shell (2) when filling the cooling material into the non-casting-mold-shell (2) part of the sleeve (1), so that the cooling material can be clamped in the gap of the casting part (23) in the casting mold shell (2).

6. The directional solidification method according to claim 1, wherein: The casting mold shell (2) sequentially includes a pouring cup (21), a runner (22), and a casting part (23) from top to bottom, the runner (22) is plate-shaped, and the shape and size of the runner (22) match the shape and size of the top opening of the sleeve (1).

7. A directional solidification process according to claim 3 wherein: The bottom surface of the sleeve (1) and the lowest end of the casting part (23) of the casting mold shell (2) are on the same plane.

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