Method for controlling single crystal integrity of quadruple guide blade

Abstract

The invention relates to a method for controlling the integrity of a single crystal of a quadruple guide blade, and belongs to the technical field of precision casting of aviation turbine blades. The casting method of the quadruple single crystal guide blade comprises the processes of ceramic mold core preparation, wax mold module pressing and combination, shell mold preparation, directional solidification, depoling, stress relief annealing, vacuum heat treatment, single crystal integrity detection and the like. The wax mold module comprises a pouring system wax mold, a blade wax mold, a transition section and a spiral crystal selector; the blade wax mold is provided with a blind riser which is arranged on the large margin plate and is flush with the end face of the exhaust edge of the blade body extension section on the outer side of the large margin plate; one end of the blade wax mold is connected with the plate-shaped ingate, the other end is connected with the transition section, and the transition section is connected with the bottom plate through the spiral crystal selector. According to the method for controlling the integrity of the casting blade single crystals, the metallurgical defects of mixed crystals, recrystallization and the like of the quadruple integral casting single crystal turbine guide blade can be effectively reduced, the problem of the integrity of the blade single crystals is solved, and the qualified rate of the quadruple single crystal guide blade is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of precision casting of aviation turbine blades, and in particular relates to a method for controlling the integrity of a single crystal of a quadruple guide blade. Background Art

[0002] In the field of high-temperature alloys, nickel-based high-temperature alloys occupy a particularly important position. Compared with iron-based and cobalt-based alloys, nickel-based high-temperature alloys have better high-temperature properties, good oxidation resistance and corrosion resistance. It can be said that the development of nickel-based high-temperature alloys determines the development of aviation turbine engines and the development of the aviation industry. With the continuous increase in the turbine pre-turbine temperature and thrust-to-weight ratio of gas turbine engines, such as the design inlet temperature of aircraft engines with a thrust-to-weight ratio of 10, which has reached more than 1850K, this has put forward higher and higher requirements on turbine blade materials. Since single-crystal alloys eliminate grain boundaries and significantly reduce grain boundary strengthening elements that reduce the melting point, the initial melting temperature of the alloy is increased, and solid solution treatment can be performed in a higher temperature range. It has good long-term life, low creep rate, good thermal fatigue resistance and oxidation corrosion resistance. Its temperature bearing capacity is greatly improved compared with directional alloys and equiaxed crystal alloys, so it has been widely used in modern advanced aircraft engines, aerospace engines and hot end components of gas turbines. Turbine blades are one of the most critical hot end components of aircraft engines, bearing the highest temperature, the most complex stress, and the most severe environmental corrosion. Turbine blades are generally divided into turbine working blades and turbine guide blades. As a stator, the structure of turbine guide blades is relatively complex. In order to further improve turbine efficiency, reduce welding, and improve structural strength, it is a future development trend for multi-joint guide blades to gradually replace single-joint guide blades. The guide blades are mainly composed of upper edge plates, blade bodies, and lower edge plates. The edge plates are large in size and complex in structure. The blade bodies are thin and have a large thickness transition difference with the edge plates. The blades are precision cast without allowances, especially the four-joint guide blades. Their complex structure brings great challenges to the growth of single crystals, looseness control, recrystallization control, and size control of the guide blades. The blade preparation is difficult and the qualified rate is low.

[0003] In the early days, single-crystal guide blades were mainly single-joint structures, and single-joint blade split casting, combined processing, combined welding and other methods were used to prepare the multi-joint guide blade parts of the engine. However, with the improvement of engine efficiency and long-term service requirements, the turbine efficiency loss and safety and reliability problems caused by the split casting single-crystal guide blade method have attracted more and more attention. Therefore, the technical demand for single-crystal multi-joint guide blades has become increasingly strong, and the newly designed engine turbine guide blades have tended to be prepared by the multi-joint molding method. However, due to the complex structure and large volume of multi-joint guide blades, metallurgical defects such as impurities and recrystallization are easily caused during the single crystal preparation process, and the single crystal integrity detection scrap rate is high, especially for quadruple single crystal guide blades. Therefore, mastering the control method of the single crystal integrity of quadruple guide blades can effectively solve the metallurgical defects such as impurities and recrystallization of quadruple guide blades during the preparation process, and improve the pass rate of quadruple single crystal guide blades. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a wax mold combination of a quadruple guide blade and a casting method for single crystal integrity, which can effectively reduce metallurgical defects such as impurities and recrystallization of quadruple integrally cast single crystal turbine guide blades, solve the problem of blade single crystal integrity, and improve the pass rate of quadruple single crystal guide blades.

[0005] The present invention adopts the following technical solution:

[0006] A wax mold module for a quadruple single crystal guide blade, comprising a casting system wax mold, a blade wax mold 9, a transition section 4 and a spiral crystal selector 5; the casting system wax mold comprises: a cylindrical ingode 1, a plate ingode 2, a base plate 6, a pouring cup 7, a cross runner 8 and a center injection pipe 11; the pouring cup 7, the cross runner 8 and the base plate 6 are connected by the center injection pipe 11; the cross runner 8 is connected to the plate ingode 2 through the cylindrical ingode 1;

[0007] The blade wax model 9 comprises: a ceramic core 3, a blind riser 10, a large edge plate 12, and a small edge plate 13; the blind riser 10 is arranged on the large edge plate 12, and one side of the blind riser 10 is connected with the exhaust edge 15 of the blade body extension section outside the large edge plate in a flush manner; the ceramic core 3 is arranged in the blade inner cavity of the blade wax model 9; the large edge plate 12 is located at the outer edge of the blade wax model 9, and the small edge plate 13 is located at the inner edge of the blade wax model 9;

[0008] One end of the blade wax mold 9 is connected to the plate-shaped ingrate 2, and the other end is connected to the transition section 4; the transition section 4 is connected to the bottom plate 6 through the spiral crystal selector 5;

[0009] Further, the spiral end of the spiral crystal selector 5 is connected to the transition section 4, and the starting end of the spiral crystal selector 5 is connected perpendicularly to the bottom plate 6;

[0010] Among them, the large edge plate is the outer edge part of the blade. It smoothly connects with the blade body to form a channel. The large edge plate plays an important supporting role in the assembly process of the blade to ensure the smoothness of the airway. In addition, the large edge plate needs to have good heat resistance and structural strength in the high temperature and high stress environment of the blade to ensure the stability and reliability of the engine. The small edge plate is the inner edge part of the blade. It is connected to the inner ring and plays a role of limiting and supporting in the assembly of the blade. The design and manufacture of the small edge plate also need to consider its performance requirements in high temperature and high pressure environments to ensure the overall performance and safety of the blade.

[0011] A method for casting a quadruple single crystal guide blade comprises the following steps:

[0012] (1) Preparation of the wax mold assembly, including: a wax mold for a pressing and pouring system, a transition section 4 and a spiral crystal selector 5;

[0013] Prepare a ceramic core 3, place the ceramic core 3 in the cavity of the blade wax mold and press it, connect the blind riser 10 with the exhaust edge 15 of the blade body extension section on the outer side of the large edge plate on the blade wax mold 9 to keep the end surface flush, and connect the other side of the blind riser 10 with the large edge plate 12;

[0014] Assemble the casting system wax mold, the blade wax mold 9, the transition section 4 and the spiral crystal selector 5 to obtain a wax mold module, including: connecting the pouring cup 7, the cross runner 8 and the bottom plate 6 through the center injection pipe 11, connecting the cross runner 8 with multiple cylindrical ingates 1, and connecting the cylindrical ingates 1 with the plate-like ingates 2, and assembling them into a casting system wax mold; connecting one end of the blade wax mold 9 to the plate-like ingates 2, and the other end to the transition section 4, the transition section 4 to the bottom plate 6 through the spiral crystal selector 5, and the spiral end of the spiral crystal selector 5 is connected to the transition section 4, and the starting end of the spiral crystal selector 5 is connected perpendicularly to the bottom plate 6;

[0015] (2) coating the wax mold module with paint and then dewaxing and baking to obtain a shell mold;

[0016] (3) melting and pouring the shell mold, and cutting it from the wax mold assembly to obtain a quadruple single crystal guide vane casting containing a ceramic core;

[0017] (4) removing the ceramic core from the quadruple single crystal guide blade casting containing the ceramic core to obtain the quadruple single crystal guide blade casting;

[0018] (5) performing stress relief annealing on the quadruple single crystal guide vane casting;

[0019] (6) The quadruple single crystal guide vane casting is subjected to vacuum heat treatment.

[0020] In order to obtain a single crystal complete quadruple single crystal guide blade casting, the method further includes step (7) of performing a single crystal integrity test to obtain a single crystal complete quadruple single crystal guide blade casting.

[0021] Furthermore, the step (1) of preparing the ceramic core 3 is to use a ceramic core mold of a quadruple single crystal guide vane to prepare a ceramic core with a target inner cavity structure and a qualified size, preferably a silicon-based ceramic core, such as a SiO2 ceramic core. The ceramic core wax mold is used to make a hollow blade wax mold, which is a process for forming a complex inner cavity structure during precision casting.

[0022] Furthermore, in step (1), the wax material for pressing the blade wax mold 9 containing the ceramic core 3, the wax mold for pressing the casting system, the transition section 4 and the spiral crystal selector 5 can be medium-temperature wax or low-temperature wax; the holding time after pressing is 40-60s.

[0023] Furthermore, in step (2), the wax mold module is coated with paint and then dewaxed and roasted, wherein: the number of coating layers is 6-8 layers; the coating is a corundum system coating without adding mineralizer and without reinforcement, which can reduce the shell strength, increase the shell yield, and avoid the formation of recrystallization and impurity crystals during the casting process. The wax mold module after coating is steam dewaxed, the dewaxing pressure is 8.5-9.5bar, and the dewaxing time is 10-20min; the dewaxed shell is roasted, the roasting temperature is 900-950℃, the heating rate is 5-10℃ / min, and the insulation time is 1-3h.

[0024] Furthermore, in step (3), the shell mold temperature for melting and pouring the shell mold is 1500-1530°C, the pouring temperature is 1500-1530°C, and the shell mold pulling rate is 3-5mm / min.

[0025] Furthermore, step (4) is to perform core removal on the ceramic core of the quadruple single crystal guide blade casting containing the ceramic core to obtain the quadruple single crystal guide blade casting, including: using a high temperature, high pressure and low concentration core removal liquid to remove the ceramic core in the inner cavity of the quadruple single crystal guide blade casting, thereby reducing the damage to the outer surface and inner cavity of the blade caused by core removal.

[0026] The core removal liquid is a potassium hydroxide solution or a sodium hydroxide solution with a concentration of 30-40%, a temperature of 100-150° C., and a pressure of 5-10 bar.

[0027] In a specific embodiment, the core removal liquid is a potassium hydroxide solution with a concentration of 40%, a temperature of 150° C., and a pressure of 5 bar.

[0028] Furthermore, the stress relief annealing of the quadruple single crystal guide blade casting in step (5) is as follows: the blade casting is subjected to multi-stage heating and insulation with a partial pressure of argon gas greater than or equal to 80 Pa, and then cooled with the furnace, and the vacuum degree is ≤10 -2 Pa; the heating rate of the heating is 2-10°C / min, the target temperature of the heating is 980-1260°C, and the insulation time is 100-600min.

[0029] In a specific embodiment, the blade casting is heated and kept in three stages while maintaining an argon partial pressure greater than or equal to 80 Pa, and then cooled to 300°C with the furnace; the three stages of heating and keeping are: heating from room temperature to 980°C at a heating rate of 10°C / min, and keeping warm for 600 minutes, then heating to 1100°C at a heating rate of 5°C / min, and keeping warm for 600 minutes, and then heating to 1260°C at a heating rate of 5°C / min, and keeping warm for 120 minutes.

[0030] Among them, the quadruple single crystal guide blade casting is subjected to stress relief annealing, the purpose of which is to eliminate the thermal stress and structural stress generated during the casting process and avoid recrystallization in subsequent heat treatment.

[0031] Furthermore, in step (6), the quadruple single crystal guide vane casting is subjected to vacuum heat treatment, including vacuum solution heat treatment, vacuum primary aging heat treatment and vacuum secondary aging treatment;

[0032] The vacuum solution heat treatment is to maintain an argon partial pressure of 80 Pa or more and a vacuum degree of 10 -2 Pa, the blade casting is heated and kept in multiple stages at a heating rate of 2-10°C / min and a target temperature of 800-1315°C, and then cooled by argon gas; the number of heating and keeping stages is 2-5 stages (for example, 3 stages), and the keeping time is 20-240min.

[0033] In a specific embodiment, the vacuum solution heat treatment is to maintain an argon partial pressure of 80 Pa or more and a vacuum degree of 10 -2 Pa, the blade casting is heated from room temperature to 800℃ at a heating rate of 10℃ / min, and then kept warm for 20min, then heated to 1290℃ at a heating rate of 10℃ / min, and then kept warm for 60min, then heated to 1300℃ at a heating rate of 2℃ / min, and then kept warm for 60min, then heated to 1310℃ at a heating rate of 2℃ / min, and then kept warm for 60min, finally heated to 1315℃ at a heating rate of 2℃ / min, and then kept warm for 240min. After the insulation, argon gas greater than or equal to 2.5bar is filled for strong cooling, and it is cooled to below 300℃ and taken out of the furnace.

[0034] The vacuum primary aging heat treatment is to maintain an argon partial pressure of greater than or equal to 80Pa and a vacuum degree of ≤10-2 Pa, the blade casting is heated and kept in multiple stages at a heating rate of 5-10°C / min and a target temperature of 800-1120°C, and then cooled by argon gas; the number of heating and keeping stages is 2-3 stages (for example, 2 stages), and the keeping time is 20-240min.

[0035] In a specific embodiment, the vacuum primary aging heat treatment is to maintain an argon partial pressure of greater than or equal to 80 Pa and a vacuum degree of ≤10 -2 Pa, the blade casting is heated to 800℃ at a heating rate of 10℃ / min and then kept warm for 20min, then heated to 1120℃ at a heating rate of 5℃ / min and then kept warm for 240min. After the insulation, argon gas greater than or equal to 2.5bar is filled for strong cooling, and it is cooled to below 300℃ and taken out of the furnace.

[0036] The vacuum secondary aging treatment is to maintain an argon partial pressure of 80 Pa or more and a vacuum degree of 10 -2 Pa, heating and maintaining the blade casting at a target temperature of 800-900°C at a heating rate of 5-10°C / min, and then cooling with argon gas; the holding time is 1200-1440min;

[0037] In a specific embodiment, the vacuum secondary aging treatment is to maintain an argon partial pressure of greater than or equal to 80 Pa and a vacuum degree of ≤10 -2 Pa, the blade casting is heated to 870℃ at a heating rate of 10℃ / min and then kept warm for 1440min. After the insulation is completed, argon gas ≥2.5bar is filled for strong cooling, and the blade casting is cooled to below 300℃ and taken out of the furnace.

[0038] Furthermore, the single crystal integrity test is performed in step (7) to obtain a single crystal complete quadruple single crystal guide blade casting, including using a corrosive agent to corrode the quadruple single crystal guide blade casting after vacuum heat treatment, and obtaining a single crystal complete quadruple single crystal guide blade after the test; the composition of the corrosive agent is FeCl3:HCl:HNO3:H2O=(80±20)g / L:(200±25)g / L:(10±5)g / L:1L.

[0039] Among them, the detection basis is to observe that the quadruple single crystal guide blade casting composed of a single crystal grain is a single crystal complete quadruple single crystal guide blade; among them, the impure crystals and recrystallization after corrosion will have a large contrast difference with the main body of the single crystal blade, which is easier to identify, so there is no limit on the tools used for detection and observation.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The ceramic core of the present invention adopts silicon-based ceramic material, has moderate strength, and can avoid the problem of recrystallization in the inner cavity of the quadruple single crystal guide blade.

[0042] The present invention welds a blind riser to the exhaust edge of the blade body extension section outside the large edge plate of the blade wax model to keep the end faces of the two flush, and the other side of the blind riser is connected to the large edge plate, which slows down the cooling speed of the blade body extension section, reduces the temperature difference between it and the large edge plate and the exhaust edge of the blade body extension section outside the large edge plate, reduces the lateral temperature gradient, reduces the corresponding thermal stress, and at the same time increases the exhaust edge of the blade body extension section outside the large edge plate to reduce its structural stress, thereby avoiding the independent nucleation and growth of miscellaneous crystals in the blade body extension section outside the large edge plate and at the exhaust edge of the blade body extension section outside the large edge plate, and also avoids recrystallization.

[0043] During the wax mold assembly process, the starting end of the spiral crystal selector is kept perpendicular to the bottom plate to ensure that the single crystal grows along the

[001] direction and reduce the deviation of the blade along the

[001] direction. During the wax mold assembly process, the side of the large edge plate is kept parallel to the center injection pipe, which can minimize the lateral temperature gradient of the casting during solidification and avoid the nucleation and growth of stray crystals.

[0044] The present invention adopts vacuum stress relief annealing below the recrystallization temperature of the quadruple single crystal guide blades, thereby reducing or eliminating the thermal stress and structural stress generated during the casting process of the complex structure of the quadruple single crystal guide blades, and avoiding the quadruple single crystal guide blades from being scrapped due to recrystallization during the high-temperature vacuum solution heat treatment process.

[0045] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the specific embodiments pointed out in the description. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is an overall schematic diagram of the wax model assembly of the quadruple single crystal guide vane of the present invention;

[0047] Figure 2 It is a partial schematic diagram of the wax model assembly of the quadruple single crystal guide vanes of the present invention;

[0048] Figure 3 for Figure 2 Left view of

[0049] Figure 4 It is a partial schematic diagram of the dark riser of the wax model assembly of the quadruple single crystal guide blade of the present invention;

[0050] Figure numerals: cylindrical ingates 1, plate ingates 2, ceramic core 3, transition section 4, spiral crystal selector 5, base plate 6, pouring cup 7, cross runner 8, blade wax mold 9, blind riser 10, center injection pipe 11, large edge plate 12, small edge plate 13, blade body extension section outside the large edge plate 14, exhaust edge of the blade body extension section outside the large edge plate 15. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical scheme and advantages of the present invention clearer, the implementation scheme of the present application will be described in detail below in conjunction with specific examples. The technical terms and scientific terms used in the present invention have the meanings generally understood by those of ordinary skill in the art to which the present invention belongs, without other definitions. Without departing from the concept of the present invention, those skilled in the art may make various improvements and changes to the specific implementation methods of the present invention specification, which all belong to the protection scope of the present invention. The raw materials used in the present invention are all commercially available unless otherwise specified.

[0052] like Figure 1-3 As shown, this embodiment takes a wax mold assembly of a quadruple single crystal guide blade as an example, the wax mold assembly includes a casting system wax mold, a blade wax mold 9, a transition section 4 and a spiral crystal selector 5; the casting system wax mold includes: a cylindrical ingode 1, a plate ingode 2, a base plate 6, a pouring cup 7, a cross runner 8 and a center injection pipe 11; the pouring cup 7, the cross runner 8 and the base plate 6 are connected by the center injection pipe 11; the cross runner 8 is connected to the plate ingode 2 through the cylindrical ingode 1;

[0053] The blade wax model 9 includes: a ceramic core 3, a blind riser 10, a large edge plate 12, and a small edge plate 13; the large edge plate 12 is located at the outer edge of the blade wax model 9, and the small edge plate 13 is located at the inner edge of the blade wax model 9; the large edge plate 12 includes a large edge plate outer blade body extension section 14 and a large edge plate outer blade body extension section exhaust edge 15; Figure 4 As shown, the blind riser 10 is arranged on the large edge plate 12 and one side of the blind riser 10 is connected to the exhaust edge 15 of the blade extension section outside the large edge plate in a flush manner; the ceramic core 3 is arranged in the blade inner cavity of the blade wax mold 9;

[0054] One end of the blade wax mold 9 is connected to the plate-shaped ingrate 2, and the other end is connected to the transition section 4; the transition section 4 is connected to the bottom plate 6 through the spiral crystal selector 5;

[0055] The spiral end of the spiral crystal selector 5 is connected to the transition section 4 , and the starting end of the spiral crystal selector 5 is connected perpendicularly to the bottom plate 6 .

[0056] During the wax mold assembly process, the starting end of the spiral crystal selector remains perpendicular to the base plate to ensure that the single crystal grows along the

[001] direction and reduce the deviation of the blade along the

[001] direction.

[0057] During the wax pattern assembly process, the side of the large edge plate is kept parallel to the center injection pipe, which can minimize the lateral temperature gradient of the casting during solidification and avoid the nucleation and growth of stray crystals.

[0058] This embodiment takes a casting method for the integrity of a quadruple single crystal guide blade as an example, and includes the following steps:

[0059] (1) Preparation of wax model module, including:

[0060] A. Press and cast the wax mold of the casting system, the transition section 4 and the spiral crystal selector 5. Use KC4013C wax to press the spiral crystal selector 5. The wax mold pressure holding time is 30 seconds. Use KC4013C wax to press the wax mold of the casting system and the transition section 4. The wax mold pressure holding time is 40 seconds.

[0061] B. Using a ceramic core mold of a quadruple single crystal guide vane to prepare a SiO2 ceramic core 3 with a qualified size;

[0062] C. Use F28 wax to place the ceramic core 3 in the cavity of the blade wax mold and press the blade wax mold 9. Keep the pressure for 60 seconds. Remove the split seams of the wax mold and make the transition smooth. Use an X-ray online detection system to check each ceramic core in the blade wax mold to ensure that each ceramic core has no defects such as cracks and corner loss. Weld the blind riser 10 to the exhaust edge 15 of the blade extension section on the outer side of the large edge plate on the blade wax mold 9 with the end faces flush. The other side of the blind riser 10 is connected to the large edge plate 12, as shown in the figure. Figure 4 As shown;

[0063] D. Assemble the casting system wax mold, the blade wax mold 9, the transition section 4 and the spiral crystal selector 5 to obtain a wax mold module, including: assembling and connecting the pouring cup 7, the cross runner 8 and the base plate 6 through the center injection pipe 11, adjusting the distance between the cross runner 8 and the base plate 6 to an appropriate height and locking them; connecting a plurality of cylindrical ingates 1 on the cross runner 8, and connecting the plate-like ingates 2 on the cylindrical ingates 1 to form a casting system wax mold; connecting one end of the blade wax mold 9 to the plate-like ingates 2, and connecting the other end to the transition section 4, connecting the transition section 4 to the base plate 6 through the spiral crystal selector 5, and the spiral end of the spiral crystal selector 5 is connected to the transition section 4, and the starting end of the spiral crystal selector 5 is connected perpendicular to the base plate 6.

[0064] E. Transfer the wax mold module to the automatic cleaning line for cleaning and degreasing. After natural drying, transfer it to the shell making line to prepare the shell mold.

[0065] (2) coating the wax mold module with paint and then dewaxing and baking to obtain a shell mold;

[0066] The coating is a corundum system coating without adding a mineralizer and without reinforcement, which can reduce the shell strength, increase the shell yieldability, and avoid the generation of recrystallization and impurity crystals during the casting process; the coating is a solution prepared by GRJ-30 silica sol and W20 corundum powder, corundum powder: silica sol=5:1 (mass ratio), and the sand hanging material is corundum sand.

[0067] The number of coating layers is 7. After the 1st and 2nd layer of paint, the sanding is 80 mesh corundum sand. After the 3rd layer of paint, the sanding is 30-60 mesh corundum sand. After the 4th to 6th layers of paint, the sanding is 16-30 mesh corundum sand. The 7th layer is only painted without sanding.

[0068] The wax mold module after coating is placed in a steam dewaxing kettle for dewaxing, the dewaxing pressure is 9 bar, and the dewaxing time is 15 minutes. After dewaxing, the shell is placed in a baking furnace for baking, the baking temperature is 900℃, the heating rate is 2.5℃ / min, and the heat preservation is 2h. After the heat preservation is completed, the power is turned off and the temperature is lowered to below 100℃ before it can be taken out of the furnace. At this point, the shell preparation is completed.

[0069] (3) Melting and pouring the shell mold, cutting it from the wax mold assembly to obtain a four-piece single crystal guide vane casting containing a ceramic core, including:

[0070] The shell is placed in a single crystal furnace. The alloy used is DD412 second-generation single crystal alloy. The shell temperature is 1510°C, the pouring temperature is 1510°C, and the shell pulling rate is 3mm / min. After the pulling is completed, the casting is taken out of the single crystal furnace. After the blade is cleaned from the furnace, it is cut from the module to obtain a quadruple single crystal guide blade casting.

[0071] (4) De-coring the ceramic core of a quadruple single crystal guide blade casting containing a ceramic core to obtain a quadruple single crystal guide blade casting, including: removing the ceramic core in the inner cavity of the quadruple single crystal guide blade casting using a high temperature, high pressure and low concentration de-coring liquid to reduce the damage to the outer surface and inner cavity of the blade caused by de-coring. The de-coring liquid is a potassium hydroxide solution with a concentration of 40%, a temperature of 150° C. and a pressure of 5 bar.

[0072] (5) performing stress relief annealing on the quadruple single crystal guide vane casting;

[0073] Due to the complex structure of the quadruple single crystal guide vane, there are large casting stresses during the casting process. If high-temperature solid solution heat treatment is directly performed, recrystallization will occur on the outer surface and inner cavity of the casting, destroying the integrity of the blade single crystal and causing it to be scrapped.

[0074] The stress relief annealing of the quadruple single crystal guide blade casting in step (5) is as follows: maintaining an argon partial pressure of greater than or equal to 80 Pa, heating the blade casting from room temperature to 980°C at a heating rate of 10°C / min, and then keeping it warm for 600 minutes, then heating it to 1100°C at a heating rate of 5°C / min, and then keeping it warm for 600 minutes, then heating it to 1260°C at a heating rate of 5°C / min, and then keeping it warm for 120 minutes, and finally turning off the power supply, allowing the blade precision casting to cool with the furnace, and taking it out of the furnace when the furnace temperature cools to 300°C.

[0075] Among them, the quadruple single crystal guide blade casting is subjected to stress relief annealing, the purpose of which is to eliminate the thermal stress and structural stress generated during the casting process and avoid recrystallization in subsequent heat treatment.

[0076] (6) performing vacuum heat treatment on the quadruple single crystal guide vane casting, including vacuum solution heat treatment, vacuum primary aging heat treatment and vacuum secondary aging treatment;

[0077] The vacuum solution heat treatment is to maintain an argon partial pressure of 80 Pa or more and a vacuum degree of 10 -2 Pa, the blade casting is heated from room temperature to 800℃ at a heating rate of 10℃ / min, and then kept warm for 20min, then heated to 1290℃ at a heating rate of 10℃ / min, and then kept warm for 60min, then heated to 1300℃ at a heating rate of 2℃ / min, and then kept warm for 60min, then heated to 1310℃ at a heating rate of 2℃ / min, and then kept warm for 60min, finally heated to 1315℃ at a heating rate of 2℃ / min, and then kept warm for 240min. After the insulation, argon gas greater than or equal to 2.5bar is filled for strong cooling, and it is cooled to below 300℃ and taken out of the furnace.

[0078] The vacuum primary aging heat treatment is to maintain an argon partial pressure of greater than or equal to 80Pa and a vacuum degree of ≤10 -2 Pa, the blade casting is heated to 800℃ at a heating rate of 10℃ / min and then kept warm for 20min, then heated to 1120℃ at a heating rate of 5℃ / min and then kept warm for 240min. After the insulation, argon gas greater than or equal to 2.5bar is filled for strong cooling, and it is cooled to below 300℃ and taken out of the furnace.

[0079] The vacuum secondary aging treatment is to maintain an argon partial pressure of 80 Pa or more and a vacuum degree of 10 -2 Pa, the blade casting is heated to 870℃ at a heating rate of 10℃ / min and then kept warm for 1440min. After the insulation is completed, argon gas ≥2.5bar is filled for strong cooling, and the blade casting is cooled to below 300℃ and taken out of the furnace.

[0080] (7) Performing a single crystal integrity test to obtain a single crystal complete quadruple single crystal guide blade, comprising using a corrosive agent to corrode the quadruple single crystal guide blade casting after vacuum heat treatment, and obtaining a single crystal complete quadruple single crystal guide blade after the test; the composition of the corrosive agent is FeCl3:HCl:HNO3:H2O=(80±20)g / L:(200±25)g / L:(10±5)g / L:1L.

[0081] Among them, the detection basis is to observe that the quadruple single crystal guide blade casting composed of a single crystal grain is a single crystal complete quadruple single crystal guide blade; among them, the impure crystals and recrystallization after corrosion will have a large contrast difference with the main body of the single crystal blade, which is easier to identify, so there is no limit on the tools used for detection and observation.

[0082] The single crystal integrity detection passing rate of the quadruple single crystal guide blade cast by the present invention is above 95%.

[0083] The method for controlling the single crystal integrity of the quadruple integrally cast single crystal guide blade casting of the present invention can effectively reduce metallurgical defects such as blade impurities and recrystallization, solve the problem of blade single crystal integrity, and improve the qualified rate of blades.

[0084] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A wax mold assembly of a quadruple single crystal guide vane, characterized in that: Including casting system wax mold, blade wax mold, transition section and spiral crystal selector; The wax mold of the pouring system comprises: a cylindrical ingode, a plate-shaped ingode, a base plate, a pouring cup, a cross runner and a center injection pipe; the pouring cup, the cross runner and the base plate are connected by the center injection pipe; the cross runner is connected to the plate-shaped ingode through the cylindrical ingode; The blade wax model comprises: a ceramic core, a blind riser, a large edge plate, and a small edge plate; the blind riser is arranged on the large edge plate, and one side of the blind riser is connected with the exhaust edge of the blade extension section outside the large edge plate to keep the end surface flush; the ceramic core is arranged in the blade inner cavity of the blade wax model; One end of the blade wax mold is connected to the plate-shaped ingrown channel, and the other end is connected to the transition section; the transition section is connected to the bottom plate through a spiral crystal selector.

2. A wax mold assembly of a quadruple single crystal guide vane according to claim 1, characterized in that: The spiral end of the spiral crystal selector is connected to the transition section, and the starting end of the spiral crystal selector is connected perpendicularly to the bottom plate.

3. A method for casting a quadruple single crystal guide vane, characterized in that: The following steps are involved: (1) The preparation of a wax mold assembly as claimed in any one of claims 1 to 2, wherein the ceramic core is placed in the mold cavity of the blade wax mold and pressed; (2) coating the wax mold module with paint and then dewaxing and baking to obtain a shell mold; (3) melting and pouring the shell mold, and cutting it from the wax mold assembly to obtain a four-joint guide vane casting containing a ceramic core; (4) removing the ceramic core from the quadruple guide blade casting containing the ceramic core to obtain the quadruple guide blade casting; (5) performing stress relief annealing on the quadruple guide vane casting; (6) The quadruple guide vane casting is subjected to vacuum heat treatment.

4. The casting method according to claim 3, characterized in that: The ceramic core is a silicon-based ceramic core.

5. The casting method according to claim 3, characterized in that: The coating layer number of the coating paint is 6-8 layers.

6. The casting method according to claim 3, characterized in that: The dewaxing pressure is 8.5-9.5 bar, and the dewaxing time is 10-20 min.

7. The casting method according to claim 3, characterized in that: The calcination temperature is 900-950° C., the calcination heating rate is 5-10° C. / min, and the calcination holding time is 1-3 h.

8. The casting method according to claim 3, characterized in that: The shell mold temperature for melting and pouring the shell mold is 1500-1530° C., the pouring temperature is 1500-1530° C., and the shell mold pulling rate is 3-5 mm / min.

9. The casting method according to claim 3, characterized in that: The stress relief annealing of the quadruple guide blade casting is as follows: maintaining an argon partial pressure of 80 Pa or more, heating and insulating the blade casting in multiple stages, and then cooling it with the furnace, with a vacuum degree of ≤10 -2 Pa; the heating rate of the heating is 2-10°C / min, the target temperature of the heating is 980-1260°C, and the insulation time is 100-600min.

10. The casting method according to claim 3, characterized in that: The vacuum heat treatment of the quadruple guide blade casting includes vacuum solution heat treatment, vacuum primary aging heat treatment and vacuum secondary aging treatment.

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