Directional solidification method

Abstract

The invention discloses a directional solidification method in the technical field of pouring, which comprises the following steps: placing a casting part of a casting mold shell in a sleeve during pouring, placing a cooling material in the sleeve, melting and gathering the cooling material at the bottom end of the sleeve in the pouring process, and then solidifying the cooling material; the cooling material is arranged on the upper surface of the water cooling disc to completely fit 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 pouring procedure, high-area heat exchange between the water cooling disc and the casting mold shell is achieved through the cooling material, the temperature gradient can be better formed on the casting part of the casting mold shell, the oriented growth effect of casting grains is better, and the casting quality is improved. And meanwhile, the device can adapt to castings of different shapes and sizes, can be directly applied to equipment used by a traditional high-speed solidification method in a sleeving mode, and is low in improvement cost and learning cost.

Description

Technical Field

[0001] The invention relates to the technical field of casting, in particular to a directional solidification method. Background Art

[0002] The working environment of the hot end parts of aircraft engines is harsh, especially the working blades, which are in service for a long time under high temperature and high pressure. The high temperature performance of the parts is higher than that of the cold end parts. The turbine blades formed by directional solidification have better temperature resistance than equiaxial blades.

[0003] The commonly used directional solidification methods for manufacturing directional blades today are liquid metal cooling (LMC) and high speed solidification (HRS). By forming a temperature gradient in a single direction during the solidification process of liquid metal, the grains grow along a fixed direction, and finally a directional blade is formed.

[0004] The traditional HRS method achieves directional solidification by placing the product on a water-cooled crystallizer, and the heat of the module is taken away by conduction to the water-cooled crystallizer. However, the blades are long and the contact area between the mold shell and the water-cooled crystallizer is too small during solidification. In the later stage of solidification, the heat conduction distance of the module becomes longer, and the heat conduction efficiency is low, which will lead to poor directional effect. The current solution to this problem is usually to set a radiation cooling device under the module heater, and assist the overall heat dissipation by radiation in the later stage of directional pulling. However, due to the different module structures, the radiation heat dissipation conditions at different positions are inconsistent, which will still lead to a decrease in temperature gradient and poor directional effect.

[0005] Based on this, the present invention designs a directional solidification method to solve the above problems. Summary of the invention

[0006] To achieve the above object, the present invention provides the following technical solution: a directional solidification method, during pouring, a casting part of a casting mold shell is enclosed by a sleeve, and a cooling material is placed in the sleeve, comprising the following steps:

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

[0008] The sleeve is tubular, and the vertical projection of the sleeve completely falls into the vertical projection of the water cooling plate, 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 empty part of the sleeve other than the casting mold shell with cooling material, or placing cooling material on a water cooling plate, and then placing the casting mold shell and the sleeve 1 on the water cooling plate so that the cooling material is in the inner cavity of the sleeve;

[0010] 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;

[0011] S3, sending the casting mold shell and sleeve into the pouring furnace through the water cooling plate for pouring;

[0012] 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.

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

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

[0015] As a further solution of the present invention, in step S2, when filling the vacant part of the sleeve that is not the casting mold shell with cooling material, 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 stuck in the gap of the casting part in the casting mold shell.

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

[0017] S31, extending the casting mold shell from the bottom of the casting furnace into the casting furnace through the water cooling plate;

[0018] S32, heating the casting material to a preset temperature to melt the casting material;

[0019] S32, heating the pouring furnace to make the temperature in the pouring furnace reach the preheating temperature to melt the cooled material;

[0020] S33, high temperature liquid casting material is poured into the casting mold shell from the pouring cup at the top of the casting mold shell;

[0021] S34, the water cooling plate descends to drive the casting mold shell downward to leave the casting furnace through the opening at the bottom of the casting furnace.

[0022] As a further solution of the present invention, the casting mold shell 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 top opening of the sleeve.

[0023] As a further solution of the present invention, the bottom surface of the sleeve 1 and the bottom end of the casting part 23 in the casting mold shell are on the same plane.

[0024] The present invention has the following beneficial effects:

[0025] The present invention places the casting part of the casting mold shell in a sleeve during pouring, and places cooling material in the sleeve. During the pouring process, the cooling material will first melt and gather at the bottom end of the sleeve and then solidify, so as to completely fit on the upper surface of the water-cooled plate and wrap the casting part of the casting mold shell. In the later cooling process of the pouring procedure, high-area heat exchange of the water-cooled plate and the casting mold shell is achieved through the cooling material, and a temperature gradient can be better formed in the casting part of the casting mold shell, so that the directional growth effect of the casting grains is better, and the comprehensive performance of the final casting is improved. At the same time, it can adapt to castings of different shapes and sizes, and can be directly applied to the equipment used in the traditional high-speed solidification method, with low improvement cost and low learning cost.

[0026] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting a part of this application are used to provide a further understanding 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:

[0028] Figure 1 It is a flow chart of the present invention.

[0029] Figure 2 It is a schematic diagram of the installation of the sleeve 1 and the casting mold shell 2 in the present invention.

[0030] Figure 3 It is a schematic diagram of filling the cooling material in the present invention.

[0031] Figure 4 It is a structural schematic diagram of the pouring procedure in the present invention.

[0032] Legend:

[0033] 1. Sleeve; 2. Casting mold shell; 21. Pouring cup; 22. Runner; 23. Casting part; 3. Pouring furnace; 4. Water cooling plate. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0035] See also Figure 1-4 The present invention provides a technical solution: a directional solidification method, comprising the following steps:

[0036] S1, preparing a casting mold shell 2 and a sleeve 1;

[0037] The sleeve 1 is tubular, and the vertical projection of the sleeve 1 completely falls into the vertical projection of the water cooling plate 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;

[0038] 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;

[0039] 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;

[0040] S3, sending the casting mold shell 2 and the sleeve 1 into the pouring furnace 3 through the water cooling plate 4 for pouring;

[0041] 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.

[0042] At present, the material of aircraft engine blades is mostly nickel-based high-temperature alloy, whose solid solution temperature is about 1000°C. During the pouring process, the nickel-based high-temperature alloy needs to be heated to about 1500°C, and the casting mold shell 2 also needs to be preheated to 1500°C. Therefore, aluminum can be selected as the cooling material. The melting point of aluminum is 660°C, which is much lower than the melting point of the 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.

[0043] The casting mold shell 2 includes a pouring cup 21, a runner 22 and a casting part 23. The pouring cup 21 is connected to the inner cavities of all casting parts 23 through the runner 22 below. 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.

[0044] By placing the casting part 23 of the casting mold shell 2 in the sleeve 1, during the pouring process, the sleeve 1 and the casting mold shell 2 are placed on the water-cooling plate 4, and the water-cooling plate 4 will seal the bottom of the sleeve 1, thereby, the vacant part of the sleeve 1 other than the casting mold shell 2 can be filled with cooling material or the cooling material can be placed on the water-cooling plate 4, and then the sleeve 1 and the casting mold shell 2 are placed on the water-cooling plate 4, so that the cooling material is covered in the sleeve 1, and 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 located in the sleeve 1, and the cooling material enter the pouring furnace 3 driven by the water-cooling plate 4. Since the melting point of the cooling material is lower than the preheating temperature, the cooling material in the sleeve 1 will first be melted into liquid by high temperature during preheating, and will flow and gather on the water-cooling plate 4 under the action of gravity, which is equivalent to The casting part 23 of the casting mold shell 2 is immersed in the liquid cooling material. After the pouring is completed, the water cooling plate 4, the sleeve 1 and the casting mold shell 2 leave the pouring furnace 3 for cooling. At this time, the liquid cooling material gathered at the bottom of the sleeve 1 and in contact with the water cooling plate 4 will be rapidly cooled and solidified from bottom to top, and the casting part 23 of the casting mold shell 2 will be wrapped in the cooling material. Since the cooling material will flow downward under the action of gravity when it is in a liquid state, the cooling material will contact the upper surface of the entire water cooling plate 4. The solidified cooling material will also wrap the casting part 23 of the casting mold shell 2. In 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 plate 4. Then, the thermal conductivity between the water cooling plate 4 and the casting mold shell 2 will be greatly improved, thereby realizing efficient directional heat conduction in the later stage of the solidification process.

[0045] By setting the sleeve 1 to be sleeved on the outside of the casting part 23 of the casting mold shell 2, and putting solid cooling material into the sleeve 1 before pouring, the cooling material can be poured together with the sleeve 1 and the casting mold shell 2. The cooling material in the solid state is easy to place and fix, and has stronger controllability. However, the contact area between the solid cooling material and the water cooling plate 4 and the casting part 23 of the casting mold shell 2 is small, and the heat conduction efficiency is low. There is a temperature rise preheating process in the pouring process. The temperature rise process in the pouring process makes the cooling material melt into a liquid state. The liquid cooling material will be downwardly collected on the water cooling plate 4 under the action of gravity and the casting of the casting mold shell 2 The liquid cooling material is fluid and can adapt to castings of different shapes and sizes, thereby increasing the contact area between the cooling material and the water-cooled plate 4 and the casting part 23 of the casting mold shell 2. In this way, in the subsequent cooling process, the heat of the casting part 23 of the casting mold shell 2 can be transferred to the water-cooled plate 4 through the cooling material, which greatly improves 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 shell 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 shell 2, so that the directional growth effect of the casting grains is better, and the comprehensive performance of the final casting is improved.

[0046] This method improves the cooling effect of the water cooling plate 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 the temperature gradient is better formed on the casting material. The comprehensive performance of the final casting is more excellent. It can be directly applied to the equipment used in the traditional high-speed solidification method, with low improvement cost and low learning cost.

[0047] During the manufacturing process of the sleeve 1, it is impossible for the bottom surface of the sleeve 1 to be completely flat. Therefore, when the sleeve 1 is placed on the water-cooling plate 4, the sleeve 1 cannot completely fit the upper surface of the water-cooling plate 4, and there will be a gap between the sleeve 1 and the upper surface of the water-cooling plate 4. When the cooling material melts and gathers on the upper surface of the water-cooling plate 4, due to the low temperature of the water-cooling plate 4 itself, the liquid cooling material will be rapidly cooled when it contacts the water-cooling plate 4, so that the cooling material in direct contact with the upper surface of the water-cooling plate 4 will solidify quickly, so that after the cooling material is melted, the cooling material at the bottom that contacts the water-cooling plate 4 is always in a solid state, thereby preventing the liquid cooling material from leaking out of the gap between the sleeve 1 and the water-cooling plate 4, ensuring that no leakage occurs, thereby ensuring work safety.

[0048] After cooling is completed, the solidified cooling material needs to be separated from the casting mold shell 2 first before the subsequent removal process of the casting mold shell 2 can be carried out. Since the melting point of the cooling material is lower than the melting point of the casting material, the cooling material can be heated to the melting point, and the entire casting mold shell 2 can be placed in a box-type induction cooker for heating. Heating the casting is a conventional technical means in the field and will not be elaborated here. The cooling material is melted by heating and then leaves the sleeve 1 from the bottom end of the sleeve 1 and is separated from the casting mold shell 2. The separation operation is simple and convenient.

[0049] Specifically, in step S3, the pouring process of the casting mold shell 2 is as follows:

[0050] S31, extending the casting mold shell 2 and the sleeve 1 from the bottom of the casting furnace 3 into the casting furnace 3 through the water cooling plate 4, at which time the sleeve 1 already contains cooling material;

[0051] S32, heating the casting material to a preset temperature to melt the casting material, and the heating of the casting material is performed outside the pouring furnace 3;

[0052] S32, heating the pouring furnace 3 to make the temperature in the pouring furnace 3 reach the preheating temperature to ensure the stability and quality of the mold shell during the pouring process. A heater is provided in the pouring furnace 3. The temperature in the pouring furnace 3 can be increased by the operation of the heater, and the casting mold shell 2 located in the pouring furnace 3 is heated to the pouring temperature. In the process of heating in the pouring furnace 3, the cooling material will first reach the melting point and melt, and then gather to the bottom of the sleeve 1 under the action of gravity and contact with the water cooling plate 4. The cooling material in contact with the water cooling plate 4 always remains in a solid state due to the effect of bottom quenching to form a bottom closure, thereby preventing the liquid cooling material from leaking out of the gap between the sleeve 1 and the water cooling plate 4;

[0053] S33, high temperature liquid casting material is poured into the casting mold shell 2 from the pouring cup 21 at the top of the casting mold shell 2;

[0054] S34, the water cooling plate 4 descends and drives the casting mold shell 2 downward to leave the casting furnace 3 through the opening at the bottom of the casting furnace 3. At this time, the entire casting mold shell 2 begins to cool down. Since the bottom of the casting mold shell 2 is in contact with the water cooling plate 4, the closer the bottom of the entire casting mold shell 2 is to the water cooling plate 4, the faster the cooling speed is, so as to form a temperature gradient in the casting part 23 of the casting mold shell 2.

[0055] Specifically, in some examples, the casting mold shell 2 and the sleeve 1 are manufactured in one piece, and the steps of preparing the casting mold shell 2 and the sleeve 1 are as follows:

[0056] S11, preparing a casting wax mold, the casting wax molds are combined to form a wax mold module, the outer side of the wax mold module encloses the sleeve 1 wax mold, and the top of the sleeve 1 wax mold is fixed to the runner 22;

[0057] S12, coating the sleeve 1 wax model and the wax model module with slurry and sanding to a suitable thickness, and then removing the wax material to obtain the casting mold shell 2 with the sleeve 1.

[0058] In this example, the bottom surface of the sleeve 1 and the bottom end of the casting part 23 in the casting mold shell 2 are on the same plane, so that the casting part 23 of the casting mold shell 2 and the bottom end of the sleeve 1 can both contact the water cooling plate 4. The contact between the casting part 23 of the casting mold shell 2 and the water cooling plate 4 can increase the heat conduction area, and the contact between the bottom end of the sleeve 1 and the water cooling plate 4 can prevent a large gap between the sleeve 1 and the top surface of the water cooling plate 4, ensuring that the cooling material will not leak.

[0059] Specifically, in some examples, the sleeve 1 and the casting mold shell 2 are manufactured separately. After the wax mold is manufactured separately, it is separately coated with slurry and sanded to form. During pouring, the casting part 23 of the casting mold shell 2 is placed in the sleeve 1, so that the sleeve 1 can be reused, which reduces the difficulty of manufacturing the casting mold shell 2 and also saves production costs.

[0060] Specifically, in step S2, when the cooling material is filled into the vacant part of the sleeve 1 other than the casting mold shell 2, the width of the cooling material matches the gap of the casting part 23 in the casting mold shell 2 so that the cooling material can be stuck in the gap of the casting part 23 in the casting mold shell 2.

[0061] Specifically, Figure 2 As shown, 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 in the sleeve 1, the runner 22 of the casting mold shell 2 will cover the top surface of the sleeve 1 to close the top opening of the sleeve 1 to prevent the cooling material from volatilizing to the furnace wall of the casting furnace 3.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A directional solidification method, characterized in that: During pouring, a casting part (23) of a casting mold shell (2) is enclosed by a sleeve (1), and a cooling material is placed in the sleeve (1), comprising the following steps: S1, preparing a casting mold shell (2) and a 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 plate (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 empty part of the sleeve (1) other than the casting mold shell (2) with cooling material, so that the cooling material is in the inner cavity of the sleeve (1) and performs a casting process together with the casting mold shell (2); 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; S3, sending the casting mold shell (2) and the sleeve (1) into the pouring furnace (3) through the water cooling plate (4) for pouring; S4, heating the casting mold shell (2), 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 (2).

2. A directional solidification method according to claim 1, characterized in that: In step S2, when the cooling material is filled into the sleeve (1), the cooling material can be directly stuck in the gap of the casting part (23) of the casting mold shell (2), or the cooling material can be directly placed on the water cooling plate (4).

3. A directional solidification method according to claim 1, characterized in that: The sleeve (1) and the casting mold shell (2) are manufactured in one piece.

4. A directional solidification method according to claim 1, characterized in that: The sleeve (1) and the casting mold shell (2) are manufactured separately.

5. A directional solidification method according to claim 1, characterized in that: In step S2, when the cooling material is filled into the vacant part of the sleeve (1) that is not the casting mold shell (2), the width of the cooling material matches the gap of the casting part (23) in the casting mold shell (2), so that the cooling material can be stuck in the gap of the casting part (23) in the casting mold shell (2).

6. A directional solidification method according to claim 1, characterized in that: In step S3, the pouring process of the casting mold shell (2) is as follows: S31, extending the casting mold shell (2) from the bottom of the casting furnace (3) into the casting furnace (3) through the water cooling plate (4); S32, heating the casting material to a preset temperature to melt the casting material; S32, heating the casting furnace (3) to increase the temperature inside the casting furnace (3) to a preheating temperature to melt the cooled material; S33, high-temperature liquid casting material is poured into the casting mold shell (2) through the pouring cup (21) at the top of the casting mold shell (2); S34, the water cooling plate (4) descends to drive the casting mold shell (2) downward and leave the casting furnace (3) through the opening at the bottom of the casting furnace (3).

7. A directional solidification method according to claim 1, characterized in that: The casting mold shell (2) comprises a pouring cup (21), a runner (22) and a casting part (23) from top to bottom, wherein 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).

8. A directional solidification method according to claim 3, characterized in that: The bottom surface of the sleeve (1) and the bottom end of the casting part (23) in the casting mold shell (2) are located on the same plane.

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