Method for adjusting directional solidification parameters of large-module nickel-based single crystal blade

Abstract

The invention discloses a method for adjusting directional solidification parameters of a large-module nickel-based single crystal blade, which comprises the following steps of: preparing a large-module nickel-based single crystal blade wax mold module, and embedding a ceramic tube on a nickel-based single crystal blade wax mold at a specific position; preparing a large-module nickel-based single crystal blade ceramic shell, and inserting a thermocouple into a ceramic tube; the large-module nickel-based single crystal blade ceramic shell and the mother alloy ingot are placed in a heater and a crucible of a vacuum induction melting furnace respectively, and a directional solidification test is carried out to determine temperature field distribution of a margin plate switching part in the chord length direction; designing the adjusted temperature of the heater and the drawing rate of the large-module nickel-based single crystal blade ceramic shell; and a large-module nickel-based single crystal blade ceramic shell is prepared again, a ceramic tube is not buried any more, and directional solidification is carried out by adopting the adjusted technological parameters. According to the method, the defects of mixed crystals, small-angle crystal boundaries and the like at the adapter part of the margin plate can be reduced, and the structure uniformity and consistency of the large-module single-crystal blade are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of directional solidification of nickel-based single crystal blades, and in particular relates to a method for adjusting directional solidification parameters of a large-module nickel-based single crystal blade. Background Art

[0002] As we all know, nickel-based single-crystal high-temperature alloys are the preferred materials for aircraft engine turbine blades. The casting qualification rate and structural stability of single-crystal blades are one of the key factors affecting the development cost of aircraft engines. The preparation of traditional single-crystal blades adopts a small module method. The number of single-crystal blades that can be prepared by each module is limited, resulting in a large amount of waste of master alloys and auxiliary materials, limiting the efficiency improvement of the single-crystal blade preparation process, and increasing the development cost and cycle of single-crystal blades. In recent years, the use of large modules to prepare single-crystal blades has received increasing attention in the field of nickel-based high-temperature alloys. The use of large modules to prepare single-crystal blades can significantly improve the preparation efficiency of single-crystal blades, save raw materials and auxiliary materials, and effectively reduce the manufacturing cost of single-crystal blades after the qualification rate of single-crystal blade preparation using the large module method is improved.

[0003] However, the large-module method for preparing single-crystal blades has problems such as uneven temperature field caused by the module structure and too high isothermal slopes at key locations such as the edge plate transition area. The use of constant process parameters such as heater temperature and pulling rate will cause single-crystal blades to easily produce defects such as stray crystals and small-angle grain boundaries at locations such as the transition area, thereby reducing the single crystal integrity of the single crystal blades and limiting the improvement of the qualified rate of large-module single crystal blades. Therefore, it is urgent to develop a method for adjusting the directional solidification parameters of large-module nickel-based single crystal blades. The temperature field distribution at locations such as the edge plate transition area can be determined by experimental temperature measurement methods, and the directional solidification parameters of the single crystal blades can be adjusted to achieve the purpose of achieving the consistency of the nickel-based single crystal high-temperature alloy structure and the integrity of the single crystal.

[0004] The invention patent with application publication number CN103752808A discloses a method for realizing variable pulling rate of casting mold in directional solidification casting. The method first measures the time-temperature curve of high temperature alloy casting in directional solidification casting by infrared thermometer, and then obtains the instantaneous growth rate of high temperature alloy casting in the directional crystal growth direction; then obtains the pulling rate required for high temperature alloy casting at a certain coordinate in the directional crystal growth direction according to the relationship between the pulling rate and the instantaneous growth rate; finally, according to the obtained pulling rate required for high temperature alloy casting at a certain coordinate in the directional crystal growth direction, the pulling rate of the casting mold is adjusted in real time. This technical solution uses infrared temperature measurement method for temperature measurement, and its temperature measurement has great limitations. In addition, large module single crystal blades are affected by the complex structure of the blade itself and the complex module layout. It is difficult to use infrared temperature measurement method to measure the alloy temperature at specific key positions, and it cannot be used to adjust the pulling rate and heater temperature of large module single crystal blades. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade, and the adjustment method comprises the following steps in chronological order:

[0006] Step 1: according to the design requirements, several nickel-based single crystal blade wax molds are pressed, and the pouring cup, runner, nickel-based single crystal blade wax mold, seed crystal and chassis are sequentially assembled from top to bottom into a nickel-based single crystal blade wax mold module, which is composed of several layers of nickel-based single crystal blade wax molds arranged longitudinally and several layers of nickel-based single crystal blade wax molds arranged radially, that is, a large-module nickel-based single crystal blade wax mold module; in the large-module nickel-based single crystal blade wax mold module, ceramic tubes are buried on the nickel-based single crystal blade wax molds on the same radius in the lowest layer;

[0007] Step 2: Use a rubber plug to seal the mouth of the ceramic tube, and then apply several layers of shell and a layer of sealing slurry on the outer surface of the large-module nickel-based single crystal blade wax mold module, dry each layer after coating, and then dewax and bake the shell to obtain a large-module nickel-based single crystal blade ceramic shell;

[0008] Step 3: remove the rubber plug from the orifice of the ceramic tube, then insert the thermocouple into the orifice of the ceramic tube, and seal the orifice of the ceramic tube with refractory slurry to fix the thermocouple in the ceramic tube;

[0009] Step 4: placing the large module nickel-based single crystal blade ceramic shell and the master alloy ingot in the heater and crucible of the vacuum induction melting furnace respectively, evacuating the vacuum induction melting furnace to a certain vacuum degree, heating the heater to the insulation temperature of the large module nickel-based single crystal blade ceramic shell, heating the crucible to make the master alloy ingot go through the melting, smelting and refining processes in sequence, and then cooling the master alloy liquid to the pouring temperature. The pouring temperature of the master alloy liquid is the insulation temperature of the large module nickel-based single crystal blade ceramic shell;

[0010] Step 5: pouring the master alloy liquid into the large module nickel-based single crystal blade ceramic shell, standing for a certain period of time, and then pulling the large module nickel-based single crystal blade ceramic shell downward at a certain pulling rate. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to be flush with the lower surface of the baffle below the heater, stop pulling and stand for a certain period of time, and record the temperature values ​​measured by each thermocouple at this time; keeping the heater temperature and the pulling rate unchanged, continue to pull the large module nickel-based single crystal blade ceramic shell downward, and when the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to a certain distance from the lower surface of the baffle below the heater, stop pulling and stand for a certain period of time, and record the temperature values ​​measured by each thermocouple at this time;

[0011] Step 6: Adjust the heater temperature and the pulling rate according to the temperature values ​​measured by each thermocouple, and calculate the adjusted heater temperature, the temperature parameters of the nickel-based single crystal blade, the adjusted pulling rate of the nickel-based single crystal blade, and the adjusted pulling rate of the large-module nickel-based single crystal blade ceramic shell;

[0012] Step 7: re-prepare the large-module nickel-based single crystal blade ceramic shell according to the operations of steps 1 to 3, but no ceramic tube is buried on the nickel-based single crystal blade wax mold; heat the re-prepared large-module nickel-based single crystal blade ceramic shell and the master alloy ingot according to the operation of step 4, and the heater temperature is the original heater temperature;

[0013] Step eight: pour the master alloy liquid into the newly prepared large-module nickel-based single crystal blade ceramic shell, let it stand for a certain period of time, and then pull the large-module nickel-based single crystal blade ceramic shell downward at the original pulling rate. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to be flush with the lower surface of the baffle under the heater, change the original heater temperature to the adjusted heater temperature, and change the original pulling rate to the adjusted pulling rate; continue to pull at a uniform speed with the adjusted heater temperature and the adjusted pulling rate. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to a certain distance from the lower surface of the baffle under the heater, change the adjusted heater temperature to the original heater temperature, and adjust the adjusted pulling rate to the original pulling rate; the heater temperature adjustment process and pulling rate adjustment process of the large-module nickel-based single crystal blade ceramic shell of other layers are the same as those of the bottom layer. Until the pulling is completed, take out the large-module nickel-based single crystal blade ceramic shell, and knock off the shell to obtain the large-module nickel-based single crystal blade.

[0014] Preferably, in step one, the longitudinally arranged nickel-based single crystal blade wax mold has at least two layers, and the radially arranged nickel-based single crystal blade wax mold has at least two layers; three ceramic tubes are buried in the nickel-based single crystal blade wax mold, and the three ceramic tubes are buried at equal distances in the transition part between the blade body and the edge plate of the nickel-based single crystal blade, and the ceramic tubes form an angle of 45° with the upper surface of the edge plate of the nickel-based single crystal blade.

[0015] In any of the above schemes, preferably, in step 2, the mold shell is coated alternately with corundum powder slurry and corundum sand, and the sealing slurry layer is coated with corundum powder slurry, with a total of 6.5-8.5 layers coated.

[0016] In any of the above schemes, preferably, in step 4, the vacuum degree in the vacuum induction melting furnace is 4-6 Pa, and the temperature of the heater is 1520-1540°C.

[0017] In any of the above schemes, preferably, in step five, the master alloy liquid is poured into a large-module nickel-based single crystal blade ceramic shell, and after standing for 1-2 minutes, the large-module nickel-based single crystal blade ceramic shell is pulled downward at a pulling rate of 2.5-5 mm / s. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to be flush with the lower surface of the baffle under the heater, the pulling is stopped and the shell is left to stand for 10-15 seconds. At this time, the temperature values ​​measured by each thermocouple are recorded. If the nickel-based single crystal blades are numbered from the inner layer to the outer layer as 1#, 2#.......n#, the temperature values ​​measured by each thermocouple are T 1a , T 1b , T 1c , T 2a , T 2b , T 2c .......T na , T nb , T nc .

[0018] In any of the above schemes, preferably, in step 5, the heater temperature is maintained at 1520-1540°C and the pulling rate is 2.5-5mm / s, and the large module nickel-based single crystal blade ceramic shell is continuously pulled downward. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to 5-8mm from the lower surface of the baffle below the heater, the pulling is stopped and left to stand for 10-15s. At this time, the temperature value measured by each thermocouple is recorded as T 1a '、T 1b '、T 1c '、T 2a '、T 2b '、T 2c '.......T na '、T nb '、T nc '.

[0019] In any of the above solutions, preferably, in step 6, the adjusted heater temperature is Where: T1 is the original heater temperature, °C; T2 is the adjusted heater temperature, °C;

[0020] The temperature parameters of nickel-based single crystal blades are Where: M i is the temperature parameter of the i-th nickel-based single crystal blade, i.e., the intermediate parameter, °C;

[0021] The adjusted pulling rate of the nickel-based single crystal blade is V i2 =V1*(T ia '-T ic ') / M i , where: V1 is the original pulling rate, mm / s; V i2is the adjusted pulling rate of the i-th nickel-based single crystal blade, mm / s; M i is the temperature parameter of the i-th nickel-based single crystal blade, i.e., the intermediate parameter, °C;

[0022] The adjusted pulling rate of the large module nickel-based single crystal blade ceramic shell is Where: V2 is the adjusted pulling rate, mm / s; V i2 is the adjusted pulling rate of the i-th nickel-based single crystal blade, mm / s; n is a natural number.

[0023] In any of the above schemes, it is preferred that in step eight, the master alloy liquid is poured into a newly prepared large-module nickel-based single crystal blade ceramic shell and allowed to stand for 1-2 minutes; when the upper surface of the edge plate of the bottommost nickel-based single crystal blade is pulled to 5-8 mm from the lower surface of the baffle below the heater, the adjusted heater temperature is changed to the original heater temperature, and the adjusted pulling rate is adjusted to the original pulling rate.

[0024] In the present invention, the pressing of the nickel-based single crystal blade wax model, the preparation of the nickel-based single crystal blade ceramic shell (including slurry preparation, drying process, dewaxing process, roasting process, etc.), the melting and refining of the master alloy ingot, and the directional solidification process can all adopt traditional technologies, and no special requirements are made on the process parameters. The alloy pouring temperature, shell temperature and other parameters are selected according to the solidus and liquidus temperatures of the nickel-based single crystal alloy used.

[0025] The method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade of the present invention is applicable to the directional solidification process of preparing nickel-based single crystal high-temperature alloy blades using a large-module method. The temperature field distribution of the edge plate transition part of each single crystal blade of the large module along the chord length direction is determined by a directional solidification test method, and the temperature field change of the single crystal blade edge plate when it is pulled to the vicinity of the single crystal furnace baffle is obtained, and then the pulling rate and heater temperature at this position are adjusted. The method can be used to adjust the directional solidification process of the large-module single crystal blade in detail, reduce the probability of defects such as impurities and small-angle grain boundaries generated at the edge plate transition part due to uneven temperature, improve the casting qualification rate and stability of the large-module single crystal blade, improve the uniformity and consistency of the organization of the large-module single crystal blade, and then reduce the preparation cost of the single crystal blade. The present invention determines the temperature field distribution of the directional solidification process of the large-module single crystal alloy blade by the embedded thermocouple method, and adjusts the pulling rate and heater temperature based on this, so as to achieve the purpose of improving the uniformity of the temperature field of the single crystal alloy prepared by the large module and suppress the generation of defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of a wax mold module of a large-module nickel-based single crystal blade in a preferred embodiment of a method for adjusting directional solidification parameters of a large-module nickel-based single crystal blade of the present invention;

[0027] Figure 2 for Figure 1 A schematic diagram of the buried position of the ceramic tube on the nickel-based single crystal blade wax model in the embodiment shown;

[0028] Figure 3 for Figure 1 Microscopic morphology photos of the edge plate transition part in the embodiment shown, wherein: (a) is a photo of the eutectic morphology of the transition part before the directional solidification parameters are adjusted, and (b) is a photo of the eutectic morphology of the transition part after the directional solidification parameters are adjusted;

[0029] Figure 4 for Figure 1 The defect photos of the edge plate transition part in the embodiment shown, wherein: (a) is a photo of the transition part with stray crystals before the directional solidification parameters are adjusted, and (b) is a photo of the transition part without stray crystals after the directional solidification parameters are adjusted.

[0030] Notes in the figure: 1- pouring cup, 2- pouring channel, 3- nickel-based single crystal blade wax mold, 4- seed crystal, 5- chassis, 6- ceramic tube, 301- blade body, 302- edge plate, 303- tenon, 304- transition part. DETAILED DESCRIPTION

[0031] In order to further understand the content of the present invention, the present invention will be described in detail below in conjunction with specific embodiments.

[0032] Embodiment 1:

[0033] According to a preferred embodiment of the method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade of the present invention, the adjustment method comprises the following steps in chronological order:

[0034] Step 1: according to the design requirements, several nickel-based single crystal blade wax molds are pressed, and the pouring cup 1, the runner 2, the nickel-based single crystal blade wax mold 3, the seed crystal 4 and the chassis 5 are combined from top to bottom to form a nickel-based single crystal blade wax mold module, which is composed of several layers of nickel-based single crystal blade wax molds 3 arranged longitudinally and several layers of nickel-based single crystal blade wax molds 3 arranged radially, that is, a large module nickel-based single crystal blade wax mold module; in the large module nickel-based single crystal blade wax mold module, ceramic tubes 6 are buried on the nickel-based single crystal blade wax molds on the same radius in the bottom layer, and the specific structure is as follows Figure 1 As shown;

[0035] Step 2: Use a rubber plug to seal the mouth of the ceramic tube, and then apply several layers of shell and a layer of sealing slurry on the outer surface of the large-module nickel-based single crystal blade wax mold module, dry each layer after coating, and then dewax and bake the shell to obtain a large-module nickel-based single crystal blade ceramic shell;

[0036] Step 3: remove the rubber plug from the orifice of the ceramic tube, then insert the thermocouple into the orifice of the ceramic tube, and seal the orifice of the ceramic tube with refractory slurry to fix the thermocouple in the ceramic tube;

[0037] Step 4: placing the large module nickel-based single crystal blade ceramic shell and the master alloy ingot in the heater and crucible of the vacuum induction melting furnace respectively, evacuating the vacuum induction melting furnace to a certain vacuum degree, heating the heater to the insulation temperature of the large module nickel-based single crystal blade ceramic shell, heating the crucible to make the master alloy ingot go through the melting, smelting and refining processes in sequence, and then cooling the master alloy liquid to the pouring temperature. The pouring temperature of the master alloy liquid is the insulation temperature of the large module nickel-based single crystal blade ceramic shell;

[0038] Step 5: pouring the master alloy liquid into the large module nickel-based single crystal blade ceramic shell, standing for a certain period of time, and then pulling the large module nickel-based single crystal blade ceramic shell downward at a certain pulling rate. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to be flush with the lower surface of the baffle below the heater, stop pulling and stand for a certain period of time, and record the temperature values ​​measured by each thermocouple at this time; keeping the heater temperature and the pulling rate unchanged, continue to pull the large module nickel-based single crystal blade ceramic shell downward, and when the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to a certain distance from the lower surface of the baffle below the heater, stop pulling and stand for a certain period of time, and record the temperature values ​​measured by each thermocouple at this time;

[0039] Step 6: Adjust the heater temperature and the pulling rate according to the temperature values ​​measured by each thermocouple, and calculate the adjusted heater temperature, the temperature parameters of the nickel-based single crystal blade, the adjusted pulling rate of the nickel-based single crystal blade, and the adjusted pulling rate of the large-module nickel-based single crystal blade ceramic shell;

[0040] Step 7: re-prepare the large-module nickel-based single crystal blade ceramic shell according to the operations of steps 1 to 3, but no ceramic tube is buried on the nickel-based single crystal blade wax mold; heat the re-prepared large-module nickel-based single crystal blade ceramic shell and the master alloy ingot according to the operation of step 4, and the heater temperature is the original heater temperature;

[0041] Step eight: pour the master alloy liquid into the newly prepared large-module nickel-based single crystal blade ceramic shell, let it stand for a certain period of time, and then pull the large-module nickel-based single crystal blade ceramic shell downward at the original pulling rate. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to be flush with the lower surface of the baffle under the heater, change the original heater temperature to the adjusted heater temperature, and change the original pulling rate to the adjusted pulling rate; continue to pull at a uniform speed with the adjusted heater temperature and the adjusted pulling rate. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to a certain distance from the lower surface of the baffle under the heater, change the adjusted heater temperature to the original heater temperature, and adjust the adjusted pulling rate to the original pulling rate; the heater temperature adjustment process and pulling rate adjustment process of the large-module nickel-based single crystal blade ceramic shell of other layers are the same as those of the bottom layer. Until the pulling is completed, take out the large-module nickel-based single crystal blade ceramic shell, and knock off the shell to obtain the large-module nickel-based single crystal blade.

[0042] In step 1, the nickel-based single crystal blade wax model 3 is composed of a blade body 301, an edge plate 302 and a tenon 303. The transition connection position between the blade body 301 and the edge plate 302 is a transition part 304. The specific structure is as follows: Figure 2 As shown; the longitudinally arranged nickel-based single crystal blade wax mold is three-layered, and the radially arranged nickel-based single crystal blade wax mold is three-layered; three ceramic tubes are buried on the nickel-based single crystal blade wax mold, and the three ceramic tubes are buried at equal distances at the transition part between the blade body and the edge plate of the nickel-based single crystal blade, and the ceramic tubes form an angle of 45° with the upper surface of the edge plate of the nickel-based single crystal blade.

[0043] In step 2, the mold shell is coated with corundum powder slurry and corundum sand alternately, and the sealing slurry layer is coated with corundum powder slurry, with a total of 7.5 layers coated.

[0044] In step 4, the vacuum degree in the vacuum induction melting furnace is 5 Pa, and the heater temperature is 1530°C.

[0045] In step five, the master alloy liquid is poured into the large-module nickel-based single crystal blade ceramic shell. After standing for 1.5 minutes, the large-module nickel-based single crystal blade ceramic shell is pulled downward at a pulling rate of 3.5 mm / s. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to be flush with the lower surface of the baffle under the heater, the pulling is stopped and the temperature is left to stand for 10-15 seconds. At this time, the temperature values ​​measured by each thermocouple are recorded. If the nickel-based single crystal blades are numbered from the inner layer to the outer layer as 1#, 2#,...n#, the temperature values ​​measured by each thermocouple are T 1a , T 1b , T 1c , T 2a , T 2b , T 2c.......T na 、T nb 、T nc .

[0046] Keep the heater temperature at 1530℃ and the pulling rate at 3.5mm / s, and continue to pull down the large module nickel-based single crystal blade ceramic shell. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to 7mm from the lower surface of the baffle below the heater, stop pulling and let it stand for 12s. At this time, record the temperature value measured by each thermocouple as T 1a '、T 1b '、T 1c '、T 2a '、T 2b '、T 2c '.......T na '、T nb '、T nc '.

[0047] In step 6, the adjusted heater temperature is Where: T1 is the original heater temperature, °C; T2 is the adjusted heater temperature, °C.

[0048] The temperature parameters of nickel-based single crystal blades are Where: M i is the temperature parameter of the i-th nickel-based single crystal blade, that is, the intermediate parameter, ℃.

[0049] The adjusted pulling rate of the nickel-based single crystal blade is V i2 =V1*(T ia '-T ic ') / M i , where: V1 is the original pulling rate, mm / s; V i2 is the adjusted pulling rate of the i-th nickel-based single crystal blade, mm / s; M i is the temperature parameter of the i-th nickel-based single crystal blade, that is, the intermediate parameter, ℃.

[0050] The adjusted pulling rate of the large module nickel-based single crystal blade ceramic shell is Where: V2 is the adjusted pulling rate, mm / s; V i2 is the adjusted pulling rate of the i-th nickel-based single crystal blade, mm / s; n is a natural number.

[0051] In step eight, the master alloy liquid is poured into the newly prepared large-module nickel-based single crystal blade ceramic shell and left to stand for 1.5 minutes; when the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to 7 mm from the lower surface of the baffle below the heater, the adjusted heater temperature is changed to the original heater temperature, and the adjusted pulling rate is adjusted to the original pulling rate.

[0052] In this embodiment, the microscopic morphology of the edge plate transition part is shown in FIG. Figure 3 As shown in the figure, (a) is a photo of the eutectic morphology of the transition part before the directional solidification parameters are adjusted, and (b) is a photo of the eutectic morphology of the transition part after the directional solidification parameters are adjusted; the defect photo of the edge plate transition part is shown in Figure 4 As shown in the figure, (a) is a photo of the transition part with stray crystals before the directional solidification parameters are adjusted, and (b) is a photo of the transition part without stray crystals after the directional solidification parameters are adjusted. It can be seen from the figure that after the process parameters of directional solidification are adjusted, the eutectic of the cast nickel-based single crystal blade at the edge plate transition part is significantly reduced, and there is no stray crystal defect.

[0053] In this embodiment, the pressing of the nickel-based single crystal blade wax model, the preparation of the nickel-based single crystal blade ceramic shell (including slurry preparation, drying process, dewaxing process, roasting process, etc.), the melting and refining of the master alloy ingot, and the directional solidification process can all be carried out using conventional technologies, and no special requirements are made on the process parameters. The alloy pouring temperature, shell temperature and other parameters are selected according to the solidus and liquidus temperatures of the nickel-based single crystal alloy used.

[0054] The method for adjusting the directional solidification parameters of the large-module nickel-based single crystal blade of this embodiment is applicable to the directional solidification process of preparing nickel-based single crystal high-temperature alloy blades using the large-module method. The temperature field distribution of the edge plate transition part of each single crystal blade of the large module along the chord length direction is determined by the method of directional solidification test, and the temperature field change of the single crystal blade edge plate when it is pulled to the vicinity of the single crystal furnace baffle is obtained, and then the pulling rate and heater temperature at this position are adjusted. This method can be used to adjust the directional solidification process of the large-module single crystal blade in detail, reduce the probability of defects such as impurities and small-angle grain boundaries due to uneven temperature at the edge plate transition part, improve the casting qualification rate and stability of the large-module single crystal blade, improve the uniformity and consistency of the organization of the large-module single crystal blade, and then reduce the preparation cost of the single crystal blade. In this embodiment, the temperature field distribution of the directional solidification process of the large-module single crystal alloy blade is determined by the embedded thermocouple method, and the pulling rate and heater temperature are adjusted based on this, so as to achieve the purpose of improving the uniformity of the temperature field of the single crystal alloy prepared by the large module and suppress the generation of defects.

[0055] Embodiment 2:

[0056] According to another preferred embodiment of the method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade of the present invention, its process flow, technical principles and beneficial effects are basically the same as those of the first embodiment, except that:

[0057] In step 2, the mold shell is coated with corundum powder slurry and corundum sand alternately, and the sealing slurry layer is coated with corundum powder slurry, and a total of 6.5 layers are coated.

[0058] In step 4, the vacuum degree in the vacuum induction melting furnace is 4 Pa, and the heater temperature is 1520°C.

[0059] In step five, the master alloy liquid is poured into the large module nickel-based single crystal blade ceramic shell. After standing for 1 minute, the large module nickel-based single crystal blade ceramic shell is pulled downward at a pulling rate of 2.5 mm / s. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to be flush with the lower surface of the baffle under the heater, the pulling is stopped and the shell is allowed to stand for 10 seconds. The heater temperature is maintained at 1520°C and the pulling rate is 2.5 mm / s, and the large module nickel-based single crystal blade ceramic shell is continued to be pulled downward. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to 5 mm from the lower surface of the baffle under the heater, the pulling is stopped and the shell is allowed to stand for 10 seconds.

[0060] In step eight, the master alloy liquid is poured into the newly prepared large-module nickel-based single crystal blade ceramic shell and allowed to stand for 1 minute; when the upper surface of the edge plate of the bottommost nickel-based single crystal blade is pulled to 5 mm from the lower surface of the baffle below the heater, the adjusted heater temperature is changed to the original heater temperature, and the adjusted pulling rate is adjusted to the original pulling rate.

[0061] Embodiment three:

[0062] According to another preferred embodiment of the method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade of the present invention, its process flow, technical principles and beneficial effects are basically the same as those of the first embodiment, except that:

[0063] In step 2, the mold shell is coated alternately with corundum powder slurry and corundum sand, and the sealing slurry layer is coated with corundum powder slurry, with a total of 8.5 layers coated.

[0064] In step 4, the vacuum degree in the vacuum induction melting furnace is 6 Pa, and the temperature of the heater is 1540°C.

[0065] In step five, the master alloy liquid is poured into the large module nickel-based single crystal blade ceramic shell. After standing for 1 minute, the large module nickel-based single crystal blade ceramic shell is pulled downward at a pulling rate of 5 mm / s. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to be flush with the lower surface of the baffle under the heater, the pulling is stopped and the shell is allowed to stand for 15 seconds. The heater temperature is maintained at 1540°C and the pulling rate is 5 mm / s, and the large module nickel-based single crystal blade ceramic shell is continued to be pulled downward. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to 8 mm from the lower surface of the baffle under the heater, the pulling is stopped and the shell is allowed to stand for 15 seconds.

[0066] In step eight, the master alloy liquid is poured into the newly prepared large-module nickel-based single crystal blade ceramic shell and left to stand for 2 minutes; when the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to 8 mm from the lower surface of the baffle below the heater, the adjusted heater temperature is changed to the original heater temperature, and the adjusted pulling rate is adjusted to the original pulling rate.

[0067] Special note: The technical solution of the present invention involves many parameters, and the synergistic effects between the various parameters need to be comprehensively considered to obtain the beneficial effects and significant progress of the present invention. Moreover, the value ranges of the various parameters in the technical solution are obtained after a large number of experiments. For each parameter and the combination of each parameter, the inventor has recorded a large amount of experimental data. Due to space limitations, the specific experimental data will not be disclosed here.

[0068] It is not difficult for those skilled in the art to understand that the method for adjusting the directional solidification parameters of the large-module nickel-based single crystal blade of the present invention includes any combination of the invention content and the specific implementation method of the above-mentioned invention specification and the various parts shown in the drawings. Due to the limited space and to make the specification concise, the various schemes composed of these combinations are not described one by one. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade, characterized in that: The adjustment method comprises the following steps in order: Step 1: according to the design requirements, several nickel-based single crystal blade wax molds are pressed, and the pouring cup, runner, nickel-based single crystal blade wax mold, seed crystal and chassis are assembled from top to bottom to form a nickel-based single crystal blade wax mold module, which is composed of several layers of nickel-based single crystal blade wax molds arranged longitudinally and several layers of nickel-based single crystal blade wax molds arranged radially, that is, a large module nickel-based single crystal blade wax mold module; In the large-module nickel-based single crystal blade wax mold module, ceramic tubes are embedded in the nickel-based single crystal blade wax molds located on the same radius in the lowest layer; Step 2: Use a rubber plug to seal the mouth of the ceramic tube, and then apply several layers of shell and a layer of sealing slurry on the outer surface of the large-module nickel-based single crystal blade wax mold module, dry each layer after coating, and then dewax and bake the shell to obtain a large-module nickel-based single crystal blade ceramic shell; Step 3: remove the rubber plug from the orifice of the ceramic tube, then insert the thermocouple into the orifice of the ceramic tube, and seal the orifice of the ceramic tube with refractory slurry to fix the thermocouple in the ceramic tube; Step 4: placing the large module nickel-based single crystal blade ceramic shell and the master alloy ingot in the heater and crucible of the vacuum induction melting furnace respectively, evacuating the vacuum induction melting furnace to a certain vacuum degree, heating the heater to the insulation temperature of the large module nickel-based single crystal blade ceramic shell, heating the crucible to make the master alloy ingot go through the melting, smelting and refining processes in sequence, and then cooling the master alloy liquid to the pouring temperature. The pouring temperature of the master alloy liquid is the insulation temperature of the large module nickel-based single crystal blade ceramic shell; Step 5: pouring the master alloy liquid into the large module nickel-based single crystal blade ceramic shell, standing for a certain period of time, and then pulling the large module nickel-based single crystal blade ceramic shell downward at a certain pulling rate. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to be flush with the lower surface of the baffle below the heater, stop pulling and stand for a certain period of time, and record the temperature values ​​measured by each thermocouple at this time; keeping the heater temperature and the pulling rate unchanged, continue to pull the large module nickel-based single crystal blade ceramic shell downward, and when the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to a certain distance from the lower surface of the baffle below the heater, stop pulling and stand for a certain period of time, and record the temperature values ​​measured by each thermocouple at this time; Step 6: Adjust the heater temperature and the pulling rate according to the temperature values ​​measured by each thermocouple, and calculate the adjusted heater temperature, the temperature parameters of the nickel-based single crystal blade, the adjusted pulling rate of the nickel-based single crystal blade, and the adjusted pulling rate of the large-module nickel-based single crystal blade ceramic shell; Step 7: re-prepare the large-module nickel-based single crystal blade ceramic shell according to the operations of steps 1 to 3, but no ceramic tube is buried on the nickel-based single crystal blade wax mold; heat the re-prepared large-module nickel-based single crystal blade ceramic shell and the master alloy ingot according to the operation of step 4, and the heater temperature is the original heater temperature; Step eight: pour the master alloy liquid into the newly prepared large-module nickel-based single crystal blade ceramic shell, let it stand for a certain period of time, and then pull the large-module nickel-based single crystal blade ceramic shell downward at the original pulling rate. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to be flush with the lower surface of the baffle under the heater, change the original heater temperature to the adjusted heater temperature, and change the original pulling rate to the adjusted pulling rate; continue to pull at a uniform speed with the adjusted heater temperature and the adjusted pulling rate. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to a certain distance from the lower surface of the baffle under the heater, change the adjusted heater temperature to the original heater temperature, and adjust the adjusted pulling rate to the original pulling rate; the heater temperature adjustment process and pulling rate adjustment process of the large-module nickel-based single crystal blade ceramic shell of other layers are the same as those of the bottom layer. Until the pulling is completed, take out the large-module nickel-based single crystal blade ceramic shell, and knock off the shell to obtain the large-module nickel-based single crystal blade.

2. The method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade according to claim 1 is characterized in that: In step one, the longitudinally arranged nickel-based single crystal blade wax mold has at least two layers, and the radially arranged nickel-based single crystal blade wax mold has at least two layers; three ceramic tubes are buried on the nickel-based single crystal blade wax mold, and the three ceramic tubes are buried at equal distances at the transition position between the blade body and the edge plate of the nickel-based single crystal blade, and the ceramic tubes form an angle of 45° with the upper surface of the edge plate of the nickel-based single crystal blade.

3. The method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade according to claim 2, characterized in that: In step 2, the mold shell is coated alternately with corundum powder slurry and corundum sand, and the sealing slurry layer is coated with corundum powder slurry, with a total of 6.5-8.5 layers coated.

4. The method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade according to claim 3 is characterized in that: In step 4, the vacuum degree in the vacuum induction melting furnace is 4-6 Pa, and the heater temperature is 1520-1540°C.

5. The method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade according to claim 4, characterized in that: In step five, the master alloy liquid is poured into the large-module nickel-based single crystal blade ceramic shell. After standing for 1-2 minutes, the large-module nickel-based single crystal blade ceramic shell is pulled downward at a pulling rate of 2.5-5 mm / s. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to be flush with the lower surface of the baffle under the heater, the pulling is stopped and the temperature is left to stand for 10-15 seconds. At this time, the temperature values ​​measured by each thermocouple are recorded. If the nickel-based single crystal blades are numbered from the inner layer to the outer layer as 1#, 2#.......n#, the temperature values ​​measured by each thermocouple are T 1a , T 1b , T 1c , T 2a , T 2b , T 2c .......T na , T nb , T nc .

6. The method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade according to claim 5, characterized in that: In step 5, the heater temperature is maintained at 1520-1540°C and the pulling rate is maintained at 2.5-5 mm / s, and the large module nickel-based single crystal blade ceramic shell is continuously pulled downward. When the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to 5-8 mm from the lower surface of the baffle below the heater, the pulling is stopped and left to stand for 10-15 seconds. At this time, the temperature value measured by each thermocouple is recorded as T 1a '、T 1b '、T 1c '、T 2a '、T 2b '、T 2c '.......T na '、T nb '、T nc '.

7. The method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade according to claim 6, characterized in that: In step 6, the adjusted heater temperature is Where: T1 is the original heater temperature, °C; T2 is the adjusted heater temperature, °C; The temperature parameters of nickel-based single crystal blades are Where: M i is the temperature parameter of the i-th nickel-based single crystal blade, i.e., the intermediate parameter, °C; The adjusted pulling rate of the nickel-based single crystal blade is V i2 =V1*(T ia '-T ic ') / M i , where: V1 is the original pulling rate, mm / s; V i2 is the adjusted pulling rate of the i-th nickel-based single crystal blade, mm / s; M i is the temperature parameter of the i-th nickel-based single crystal blade, i.e., the intermediate parameter, °C; The adjusted pulling rate of the large module nickel-based single crystal blade ceramic shell is Where: V2 is the adjusted pulling rate, mm / s; V i2 is the adjusted pulling rate of the i-th nickel-based single crystal blade, mm / s; n is a natural number.

8. The method for adjusting the directional solidification parameters of a large-module nickel-based single crystal blade according to claim 7, characterized in that: In step eight, the master alloy liquid is poured into the newly prepared large-module nickel-based single crystal blade ceramic shell and allowed to stand for 1-2 minutes; when the upper surface of the edge plate of the bottom nickel-based single crystal blade is pulled to 5-8 mm from the lower surface of the baffle below the heater, the adjusted heater temperature is changed to the original heater temperature, and the adjusted pulling rate is adjusted to the original pulling rate.

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