Directional solidification device and directional solidification method

Abstract

The invention discloses a directional solidification device and a directional solidification method, and particularly relates to the technical field of forging equipment.The directional solidification device comprises a heat preserving furnace, a mold shell, a supporting mechanism, a heat insulation sleeve, a cooling pond and a cooling pond lifting mechanism, the supporting mechanism comprises a supporting disc and a supporting rod connected with the supporting disc, the mold shell is placed on the supporting disc and located in the heat preserving furnace, and the heat insulation sleeve is arranged on the supporting rod; the cooling pond lifting mechanism comprises a supporting plate and a supporting plate lifting rod connected with the supporting plate, cooling substances are contained in the cooling pond, the cooling pond is fixedly connected to the supporting plate, the supporting plate and the supporting rod are sleeved with the cooling pond, and the supporting rod can be connected with the cooling pond and the supporting plate in a sliding and sealing mode. The heat insulation sleeve is sleeved outside the cooling pond, and the supporting plate lifting rod is used for driving the supporting plate, the cooling pond and the heat insulation sleeve to ascend or descend. According to the method, the temperature gradient can be increased, the interval of primary dendritic crystals is increased, the dendritic crystal form is relatively regular, and the temperature bearing capacity of the single-crystal turbine blade is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of forging equipment, and particularly to a directional solidification device and a directional solidification method. Background Art

[0002] Directional solidification is a technique that enables metals or alloys to grow crystals along a specific direction during the solidification process. In the aerospace industry, directional solidification technology is used to manufacture high-temperature alloy blades, such as turbine engine blades. These blades need to work in high-temperature and high-stress environments. The columnar crystal or single-crystal structure obtained through directional solidification can significantly improve the high-temperature strength, creep resistance, and fatigue resistance of the blades, thus meeting the high-performance requirements of aeroengines.

[0003] Currently, vacuum induction directional solidification casting furnaces are commonly used at home and abroad to produce high-temperature alloy blades with single-crystal structures. During the preparation of single-crystal blades, the primary dendrite arm spacing of the single crystal determines the performance of the single crystal, and the primary dendrite arm spacing of the single crystal is determined by the temperature gradient of the single-crystal directional solidification furnace. When the temperature gradient is large, the supercooling degree distribution at the solidification front is relatively uniform, and the supercooling degree is small. In this case, the driving force for dendrite growth is relatively weak, and the dendrite growth rate is slow. At the same time, due to the "constraint" effect of the temperature gradient, dendrites are not prone to branching and disordered growth during the growth process, resulting in a relatively large primary dendrite arm spacing. On the contrary, when the temperature gradient is small, the supercooling degree at the solidification front is large and the distribution is uneven. This large supercooling degree provides a strong driving force for the rapid growth of dendrites, and the dendrite growth rate increases. Moreover, due to the small temperature gradient, the constraint effect on dendrite growth weakens, and dendrites are more likely to branch and grow irregularly, leading to a decrease in the primary dendrite arm spacing.

[0004] Therefore, in order to increase the temperature gradient of the single-crystal directional furnace, the single-crystal directional solidification furnace has gradually evolved from a water-cooled single-crystal directional solidification device (HRS) to a liquid metal-cooled directional solidification (LMC), as well as some other directional solidification technologies that improve the cooling intensity, such as liquid metal spraying (LMSC), static solid cooling directional solidification, and so on. However, these directional solidification technologies basically involve the downward movement of the central cooling disk, allowing the cold end of the directional solidification to gradually move away from the hot end (holding furnace), thus forming a unidirectional temperature gradient. The drawback of this technology is that the radiant heat at the hot end will heat the surface of the mold shell at the cold end, resulting in poor heat dissipation on the surface of the mold shell at the cold end and a small temperature gradient. Summary of the Invention

[0005] The objective of the present invention is to provide a directional solidification device and a directional solidification method to solve the problems existing in the above-mentioned prior art, which can increase the temperature gradient, increase the spacing of primary dendrites, make the dendrite morphology more regular, and improve the temperature-bearing capacity of single-crystal turbine blades.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a directional solidification device, including: a holding furnace, a mold shell, a support mechanism, a heat insulation sleeve, a cooling pool and a cooling pool lifting mechanism. The support mechanism includes a support plate and a support rod connected to the support plate. The mold shell is placed on the support plate. The mold shell is located in the holding furnace, and the top surface of the support plate is flush with the bottom opening of the holding furnace. The cooling pool lifting mechanism includes a support plate and a support plate lifting rod connected to the support plate. The cooling pool is filled with a cooling substance. The cooling pool is fixedly connected to the support plate. The cooling pool is sleeved outside the support plate and the support rod, and the support rod can be slidably and sealingly connected to the cooling pool and the support plate. The heat insulation sleeve is sleeved outside the cooling pool. The support plate lifting rod is used to drive the support plate, the cooling pool and the heat insulation sleeve to rise or fall.

[0008] Preferably, the height of the heat insulation sleeve is greater than the height of the mold shell.

[0009] Preferably, the outer diameter of the heat insulation sleeve is 5 mm smaller than the inner diameter of the holding furnace.

[0010] Preferably, it further includes a storage pool. The storage pool is fixedly installed on the support plate. The storage pool is used to store the cooling substance. The storage pool is connected and communicated with the cooling pool through a connecting pipe.

[0011] Preferably, a ceramic valve is provided on the connecting pipe.

[0012] Preferably, a heater is provided outside the storage pool. The heater is used to heat the storage pool. The cooling substance is metallic tin.

[0013] Preferably, the side wall of the cooling pool is a double-layer structure with a cavity, and cooling water can be introduced into the cavity.

[0014] Preferably, there is an annular gap between the inner side wall of the heat insulation sleeve and the outer side wall of the cooling pool. The annular gap is filled with ceramic fiber felt.

[0015] The present application also provides a directional solidification method for the above-mentioned directional solidification device, including the following steps:

[0016] Step 1: Place the mold shell on the support plate, move the support rod, and insert the mold shell into the holding furnace so that the top surface of the support plate is flush with the bottom of the holding furnace;

[0017] Step 2: Install the cooling pool outside the support rod and install the heat insulation sleeve outside the cooling pool;

[0018] Step 3: Start the pallet lifting rod to make the top of the cooling pool level with the bottom of the holding furnace, and at the same time enable the cooling substance in the cooling pool to submerge the support disk.

[0019] Step 4: Start heating the holding furnace. After waiting for the temperature in the holding furnace to reach 1500 °C and then insulating for 30 minutes, start the induction melting furnace to melt the single crystal alloy master alloy in the furnace. When the single crystal alloy master alloy in the induction melting furnace melts, adjust the pouring temperature to 1530 °C, and pour the 1530 °C single crystal alloy high-temperature melt into the mold shell.

[0020] Step 5: Start the pallet lifting rod to move upward. The pallet drives the cooling pool and the heat insulation sleeve to rise synchronously. The cooling substance in the cooling pool gradually submerges the lower part of the mold shell, thereby realizing the directional solidification of the single crystal alloy master alloy.

[0021] Preferably, in Step 5, the rising speed of the pallet lifting rod is 1 mm / min to 6 mm / min.

[0022] The present invention has achieved the following technical effects compared with the prior art:

[0023] The present invention provides a directional solidification device and a directional solidification method. The mold shell does not move. The pallet, cooling pool, and heat insulation sleeve are driven to rise or fall by the pallet lifting rod, which can ensure the stability of the single crystal growth process. By blocking heat transfer through the heat insulation sleeve, a thermal barrier is established between the high-temperature environment of the holding furnace and the low-temperature area of the cooling pool. At the same time, the cooling substance in the cooling pool submerges the cooling mold shell, and the two cooperate synchronously to improve the cooling intensity. Moreover, the external heat insulation and internal submergence are basically at the same height, which can ensure that the distance between the hot end and the cold end is basically close to zero, greatly increasing the temperature gradient, being conducive to obtaining a finer primary dendrite spacing, and improving the performance of single crystal blades. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0025] Figure 1 It is a schematic diagram of the directional solidification device.

[0026] In the figure: 1 - heat preservation furnace; 2 - mold shell; 3 - pouring cup; 4 - induction melting furnace; 5 - support plate; 6 - support rod; 7 - cooling pond; 8 - heat insulation sleeve; 9 - pallet; 10 - pallet lifting rod; 11 - storage pond; 12 - connecting pipe; 13 - ceramic valve; 14 - ceramic fiber felt; 15 - tin liquid. Detailed implementation mode

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] The purpose of the present invention is to provide a directional solidification device and a directional solidification method to solve the problems existing in the above-mentioned prior art, which can increase the temperature gradient, increase the spacing of primary dendrites, the dendrite morphology is relatively regular, and improve the temperature-bearing capacity of single-crystal turbine blades.

[0029] To make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation modes.

[0030] Embodiment 1

[0031] This embodiment provides a directional solidification device, such as Figure 1As shown in the figure, it includes: a holding furnace 1, a mold shell 2, a support mechanism, a heat insulation sleeve 8, a cooling pool 7, and a cooling pool 7 lifting mechanism. The support mechanism includes a support plate 5 and a support rod 6 connected to the support plate 5. The mold shell 2 is placed on the support plate 5. The mold shell 2 is located inside the holding furnace 1, and the top surface of the support plate 5 is flush with the bottom opening of the holding furnace 1. The cooling pool 7 lifting mechanism includes a support plate 9 and a support plate lifting rod 10 connected to the support plate 9. The cooling pool 7 is filled with a cooling substance. The cooling pool 7 is fixedly connected to the support plate 9. The cooling pool 7 is sleeved outside the support plate 5 and the support rod 6, and the support rod 6 can be slidably and sealedly connected to the cooling pool 7 and the support plate 9. The heat insulation sleeve 8 is sleeved outside the cooling pool 7. The support plate lifting rod 10 is used to drive the support plate 9, the cooling pool 7, and the heat insulation sleeve 8 to rise or fall. When the directional solidification device is in use, the mold shell 2 does not move. By driving the support plate 9, the cooling pool 7, and the heat insulation sleeve 8 to rise or fall through the support plate lifting rod 10, the stability of the single crystal growth process can be ensured; by blocking heat transfer through the heat insulation sleeve 8, a heat barrier is established between the high-temperature environment of the holding furnace 1 and the low-temperature area of the cooling pool 7, reducing the heat radiation and heat conduction from the holding furnace 1 to the cooling pool 7 direction, making the heat in the holding furnace 1 more concentrated in the high-temperature area of the film shell. At the same time, the cooling substance in the cooling pool 7 submerges the cooling mold shell 2, and the two cooperate synchronously to improve the cooling intensity. Moreover, the external heat insulation and internal submergence are basically at the same height, which can ensure that the distance between the hot end and the cold end is basically close to zero, greatly increasing the temperature gradient, being beneficial to obtaining a finer primary dendrite spacing, and improving the performance of the single crystal blade.

[0032] In a further preferred embodiment of the present embodiment, the height of the heat insulation sleeve 8 is greater than the height of the mold shell 2, ensuring the establishment of a stable heat barrier between the high-temperature environment of the holding furnace 1 and the low-temperature area of the cooling pool 7, reducing the heat radiation and heat conduction from the holding furnace 1 to the cooling pool 7 direction, and improving the heat insulation effect.

[0033] In a further preferred embodiment of the present embodiment, the outer diameter of the heat insulation sleeve 8 is 5 mm smaller than the inner diameter of the holding furnace 1, and the inner diameter of the heat insulation sleeve 8 is more than 20 mm larger than the outer diameter of the mold shell 2, ensuring that the heat insulation sleeve 8 can smoothly rise into the holding furnace 1 to insulate the mold shell 2.

[0034] In a further preferred embodiment of the present embodiment, the directional solidification device further includes a storage pool 11. The storage pool 11 is fixedly installed on the support plate 9. The storage pool 11 is used to store the cooling substance. The storage pool 11 is connected and communicated with the cooling pool 7 through a connecting pipe 12. A ceramic valve 13 is provided on the connecting pipe 12. The storage pool 11 and the cooling pool 7 are communicated, and the liquid level of the inner tin pool can be controlled through the liquid level of the storage pool 11.

[0035] In a further preferred embodiment of the present embodiment, a heater is provided outside the storage pool 11 for heating the storage pool 11. The cooling substance is metallic tin. When the single-crystal alloy master alloy in the induction melting furnace 4 is melted, the heater is started to melt the metallic tin in the storage pool 11 into molten tin 15.

[0036] In a further preferred embodiment of the present embodiment, the side wall of the cooling pool 7 is a double-layer structure with a cavity, and cooling water can be introduced into the cavity. When the cooling water flows in the cavity, it can efficiently absorb the heat transmitted from the side wall of the cooling pool 7 through convection, avoiding the accumulation of heat on the side wall of the cooling pool 7, thereby strictly controlling the solidification direction and preventing the instability of the solidification interface caused by local overheating or uneven cooling, ensuring the uniformity of the solidification of the single-crystal alloy master alloy.

[0037] In a further preferred embodiment of the present embodiment, there is an annular gap between the inner side wall of the heat insulation sleeve 8 and the outer side wall of the cooling pool 7. The annular gap is filled with ceramic fiber felt 14, and the annular gap is 10 mm - 20 mm. The annular gap between the heat insulation sleeve 8 and the cooling pool 7 is filled with the flexible heat insulation material ceramic fiber felt, which can not only allow thermal expansion but also reduce heat conduction.

[0038] Embodiment 2

[0039] The present embodiment provides a directional solidification method for the directional solidification device of Embodiment 1, including the following steps:

[0040] Step 1: Place the pouring cup 3 above the membrane shell, then place the membrane shell on the support plate 5, and insert the mold shell 2 into the heat preservation furnace 1. Ensure that the top surface of the support plate 5 is flush with the bottom of the heat preservation furnace 1;

[0041] Step 2: Install the cooling pool 7 outside the support rod 6 and install a heat insulation sleeve 8 outside the cooling pool 7;

[0042] Step 3: Start the support plate lifting rod 10 to make the top of the cooling pool 7 flush with the bottom of the heat preservation furnace 1, and at the same time make the cooling substance in the cooling pool 7 able to submerge the support plate 5;

[0043] Step 4: Start heating the heat preservation furnace 1. After waiting for the temperature in the heat preservation furnace 1 to reach 1500 °C and then keeping it warm for 30 minutes, start the induction melting furnace 4 to melt the single-crystal alloy master alloy in the furnace. After the single-crystal alloy master alloy in the induction melting furnace 4 is melted, adjust the pouring temperature to 1530 °C, and pour the 1530 °C single-crystal alloy high-temperature melt into the mold shell 2;

[0044] Step 5: Start the upward movement of the pallet lifting rod 10. The pallet 9 simultaneously drives the cooling pool 7 and the heat insulation sleeve 8 to rise synchronously. The cooling substance in the cooling pool 7 gradually submerges the lower part of the mold shell 2, thereby realizing the directional solidification of the single crystal alloy master alloy. By combining the heat insulation of the outer part of the film shell by the heat insulation sleeve 8 and the submerging and cooling of the tin liquid in the cooling pool 7, the cooling intensity is increased. At the same time, since the external heat insulation and the internal submerging are basically at the same height, the distance between the hot end and the cold end is basically close to zero, greatly increasing the temperature gradient, which is beneficial to obtaining a finer primary dendrite spacing and improving the performance of the single crystal blade.

[0045] In the preferred embodiment of the present embodiment, in Step 5, according to the needs of the directional solidification of the single crystal blade, the rising speed of the pallet lifting rod 10 is 1 mm / min to 6 mm / min to ensure the stability of solidification.

[0046] In the present invention, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A directional solidification device, characterized in that: Including: A holding furnace, a mold shell, a support mechanism, a heat insulation sleeve, a cooling pool, and a cooling pool lifting mechanism. The support mechanism includes a support plate and a support rod connected to the support plate. The mold shell is placed on the support plate. The mold shell is located inside the holding furnace, and the top surface of the support plate is flush with the bottom opening of the holding furnace. The cooling pool lifting mechanism includes a support plate and a support plate lifting rod connected to the support plate. The cooling pool is filled with a cooling substance. The cooling pool is fixedly connected to the support plate. The cooling pool is sleeved outside the support plate and the support rod, and the support rod can be slidably and sealedly connected to the cooling pool and the support plate. The heat insulation sleeve is sleeved outside the cooling pool. The support plate lifting rod is used to drive the support plate, the cooling pool, and the heat insulation sleeve to rise or fall.

2. The directional solidification device according to claim 1, characterized in that: The height of the heat insulation sleeve is greater than the height of the mold shell.

3. The directional solidification device according to claim 1, wherein: The outer diameter of the heat insulation sleeve is 5 mm smaller than the inner diameter of the holding furnace.

4. The directional solidification device according to claim 1, wherein: It further includes a storage pool. The storage pool is fixedly installed on the support plate. The storage pool is used to store the cooling substance. The storage pool is connected and communicated with the cooling pool through a connecting pipe.

5. The directional solidification device according to claim 4, characterized in that: A ceramic valve is provided on the connecting pipe.

6. The directional solidification apparatus according to claim 4, wherein: A heater is provided outside the storage pool. The heater is used to heat the storage pool. The cooling substance is metallic tin.

7. The directional solidification device according to claim 1, characterized in that: The side wall of the cooling pool is a double-layer structure with a cavity, and cooling water can be introduced into the cavity.

8. The directional solidification device according to claim 1, wherein: There is an annular gap between the inner side wall of the heat insulation sleeve and the outer side wall of the cooling pool. The annular gap is filled with ceramic fiber felt.

9. A directional solidification method for a directional solidification device according to any one of claims 1-8, characterized in that: Including the following steps: Step 1: Place the mold shell on the support plate, move the support rod, and extend the mold shell into the holding furnace so that the top surface of the support plate is flush with the bottom of the holding furnace. Step 2: Install the cooling pool outside the support rod and install the heat insulation sleeve outside the cooling pool. Step 3: Start the support plate lifting rod to make the top of the cooling pool flush with the bottom of the holding furnace, and at the same time make the cooling substance in the cooling pool able to submerge the support plate. Step 4: Start heating the holding furnace. When the temperature in the holding furnace reaches 1500 °C, keep it warm for 30 minutes, then start the induction melting furnace to melt the single crystal alloy master alloy in the furnace. When the single crystal alloy master alloy in the induction melting furnace melts, adjust the pouring temperature to 1530 °C, and pour the 1530 °C single crystal alloy high-temperature melt into the mold shell. Step 5: Start the support plate lifting rod to move upward. The support plate simultaneously drives the cooling pool and the heat insulation sleeve to rise synchronously. The cooling substance in the cooling pool gradually submerges the lower part of the mold shell, thereby realizing the directional solidification of the single crystal alloy master alloy.

10. The method for using the directional solidification device according to claim 9, characterized in that: In Step 5, the rising speed of the support plate lifting rod is 1 mm / min to 6 mm / min.

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