CN110421144B - Pressure-regulating precision casting method for high-temperature alloy floating wall tile under action of external electromagnetic field - Google Patents
Pressure-regulating precision casting method for high-temperature alloy floating wall tile under action of external electromagnetic field Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
- B22C7/02—Lost patterns
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D18/00—Pressure casting; Vacuum casting
- B22D18/04—Low pressure casting, i.e. making use of pressures up to a few bars to fill the mould
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D18/00—Pressure casting; Vacuum casting
- B22D18/08—Controlling, supervising, e.g. for safety reasons
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/02—Use of electric or magnetic effects
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C19/00—Alloys based on nickel or cobalt
- C22C19/03—Alloys based on nickel or cobalt based on nickel
- C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
- C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
- C22C19/057—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being less 10%
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Abstract
The invention provides a pressure regulating precision casting method of a high-temperature alloy floating wall tile under the action of an external electromagnetic field, which comprises the following steps: printing by adopting a 3D printing technology to obtain a wax mold of the pouring system; carrying out atomization polishing and grinding on the wax mould, and removing surface layer grains of the wax mould; preparing a multi-layer shell on a wax mould; then demolding the shell; the high-temperature alloy melt is poured into a shell of a shell by adopting vacuum antigravity pressure regulation to form a casting, an alternating electromagnetic field is added in the casting process of the casting, so that the electromagnetic volume force in the filling and solidification processes plays a role in stirring the high-temperature alloy melt, forced convection is generated to change the temperature field and the concentration field of the high-temperature alloy melt, and crystal grains are refined. The invention is matched with a pressure-regulating casting device, and an alternating electromagnetic field is applied in the process of filling and solidifying the casting, so that the effect of electromagnetic stirring forced convection is realized, the metallurgical quality of the casting is improved, the internal defects are reduced, and the density is improved.
Description
Technical Field
The invention relates to the field of precision casting methods, in particular to a pressure regulating precision casting method of a high-temperature alloy floating wall tile under the action of an external electromagnetic field.
Background
With the vigorous development of the aviation industry in China, the design of aviation castings tends to be high in quality, light in weight, precise, thin in wall and complex. The pressure-regulating casting process is a new antigravity precise forming method, it integrates the advantages of vacuum suction casting, low-pressure casting and counter-pressure casting techniques, and is a common method for producing high-quality complex thin-wall casting.
The thrust-weight ratio is the most important performance index of the performance of the aircraft engine, and the improvement of the working temperature of the floating wall of the combustion chamber of the engine is an important measure for improving the thrust-weight ratio. Since the floating wall tiles are typically thin-walled, high dimensional accuracy, complex-shaped high temperature alloy castings, they are typically produced using conventional gravity investment casting or countergravity investment casting processes to achieve shape and dimensional accuracy control requirements. However, even if the antigravity casting process is adopted, the effects of improving the casting segregation and refining the crystal grains are limited, and the metallurgical quality and the product yield of the floating wall casting are still low.
Through search, the Chinese patent with the publication number of 103302242A discloses a typical pressure-regulating casting method for high-temperature alloy floating wall tiles, and the mold filling capacity and the density of a solidification structure of liquid metal melt are improved by regulating process parameters such as vacuum degree, mold filling pressure, pressurization speed, crystallization pressure, pressure maintaining time and the like. However, the improvement effect of the composition segregation of the alloy liquid is very limited only by adjusting the process parameters, and particularly, the center segregation of the casting is difficult to eliminate and the dendritic crystal wall is difficult to break or break to refine the crystal grains by adopting the gas pressure to control the mold filling and solidification processes.
It has been found through search that chinese patent publication No. 105583366 a discloses a precision casting method for floating wall tiles that improves the fluidity of the liquid metal by raising the preheating temperature of the shell. However, the above patent has the disadvantages that the resistance of the shell wall to the scouring and flowing of the high-temperature molten metal is lowered due to the increase of the temperature of the shell, impurities are easily introduced into the liquid metal, and the supercooling of the shell wall to the liquid metal grains is weakened, thereby reducing the grain refining effect.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a pressure regulating and precision casting method of a high-temperature alloy floating wall tile under the action of an external electromagnetic field.
The invention provides a pressure regulating precision casting method of a high-temperature alloy floating wall tile under the action of an external electromagnetic field, which comprises the following steps:
printing by adopting a 3D printing technology to obtain a wax mold of the pouring system;
carrying out atomization polishing and grinding on the wax mould, and removing surface layer grains of the wax mould;
preparing a multi-layered shell on the wax pattern;
demolding the shell;
the high-temperature alloy melt is poured into the shell of the shell by adopting vacuum antigravity pressure regulation to form a casting, an alternating electromagnetic field is added in the casting process of the casting, so that the electromagnetic volume force in the filling and solidification processes plays a role in stirring the high-temperature alloy melt, forced convection is generated to change the temperature field and the concentration field of the high-temperature alloy melt, and crystal grains are refined.
Further: the method is carried out according to the following steps:
s1: designing a reasonable gating system and a reasonable casting process scheme for the floating wall tile by combining a casting process design principle and a casting simulation CAE technology;
s2: printing by adopting a 3D printing technology to obtain a three-dimensional photosensitive resin wax pattern of the pouring system;
s3: carrying out atomization polishing and grinding on the wax mould, removing surface layer grains and ensuring the surface quality of the wax mould;
s4: repeatedly soaking the resin wax pattern with slurry, spraying sand powder and drying by means of a mechanical arm of an automatic shell making device to obtain a multi-layer precision casting shell;
s5: roasting the shell to remove resin in the shell, and cleaning the shell to remove residual impurities;
s6: preheating the shell and the lift tube; placing a high-temperature alloy ingot in a crucible of a lower tank of a pressure-regulating casting device, and smelting the high-temperature alloy ingot under the negative pressure of-30 KPa to-50 KPa of vacuum degree;
s7: the shell and the liquid lifting pipe are arranged in the pressure-regulating casting device, the shell and the liquid lifting pipe are fixed by adopting a sand box and a weight, and an upper tank body and a lower tank body of the pressure-regulating casting device are sealed;
s8: an electromagnetic generator is arranged on the outer layer of the sand box, and is started to adjust alternating current in the induction coil;
s9: and starting the gas circuit control system according to a preset pressure difference curve, sequentially completing the processes of vacuumizing, mold filling, boosting, pressure maintaining and pressure relief of the casting, closing the electromagnetic generator after the high-temperature alloy liquid flows back to the crucible from the liquid lifting pipe, and cooling the casting to room temperature.
Preferably, in S4, a multi-layer precision casting shell is prepared, wherein the thickness of each layer of the shell is 8-10 mm.
Preferably, in S6, the preheating shell and the lift tube include: the outer wall of the shell is wrapped with a layer of refractory cotton which plays a role in heat preservation and heat insulation, the inner wall and the outer wall of the lift pipe are coated with a layer of alumina powder film for oxidation resistance, the shell and the lift pipe are placed into a resistance heating furnace together, heating is carried out at a constant heating speed, and heat preservation is carried out after the shell and the lift pipe are heated to a certain temperature.
Preferably, in S7, the flask and the weight are used to fix the shell and the lift tube, that is, the shell and the lift tube are quickly transferred to a middle partition plate of the pressure-regulating casting device, the middle partition plate divides the pressure-regulating casting device into an upper tank body and a lower tank body, the shell is reversely buckled on the lift tube, and the lift tube passes through the middle partition plate and is communicated with a crucible of the lower tank body of the pressure-regulating casting device; and isolating a gap between a lower tank and a middle partition plate of the pressure-regulating casting device by using a weight and a sealing ring, covering the shell reversely buckled on the lift pipe by using a sand box of which the outer layer is wound with an induction coil of an electromagnetic generator, filling the inner layer of the sand box with molding sand, fixing the sand box and the middle partition plate together, and sealing the upper tank body and the lower tank body of the pressure-regulating casting device.
Preferably, in S6, the material of the superalloy ingot is an M951 alloy, and is composed of, by mass, 0.05% of C, 9.00% of Cr, 5.00% of Co, 3.50% of W, 3.00% of Mo, 2.20% of Nb, 5.90% of Al, 0.02% of Y, 0.024% of B, and the balance Ni.
Preferably, in S8, the magnitude of the alternating current is 10A.
Preferably, in S9, the crystallization pressure is 200KPa to 300KPa, and the pressure holding time is 5min to 25 min. The crystallization pressure and the pressure maintaining time have obvious influence on the density and the secondary dendrite spacing of the casting. The crystallization pressure is the difference between the pressure of the lower tank and the pressure of the upper tank in the pressure curve in the crystallization pressure maintaining section. The crystallization pressure and the pressure maintaining time have obvious influence on the density and the secondary dendrite spacing of the casting.
Compared with the prior art, the invention has at least one of the following beneficial effects:
the method creatively combines the antigravity casting with the external electromagnetic field, applies the alternating electromagnetic field in the metal mold filling and solidifying processes, plays roles of forced convection, segregation inhibition, grain refinement and the like, improves the surface quality and the internal quality of the casting, refines the grains, and improves the service performance of the casting. The control of the liquid metal filling and solidification process is the key of an important way for improving the structure and the mechanical property of the casting.
The method of the invention adopts a vacuum antigravity pressure-regulating casting mode, which can effectively prevent the pollution of the melt and the introduction of gas inclusions, thereby reducing the oxide inclusions and air holes in the casting.
Furthermore, the method can ensure that the liquid level of the casting in the mold filling process is stable by controlling parameters such as the mold filling pressurization speed, the mold filling pressure and the like, and reduces the splashing of liquid drops and the erosion to the inner wall of the mold shell, thereby reducing the slag entrapment; effective feeding in the casting solidification process can be ensured by controlling the crusting pressure, the crystallization pressurization and the pressure maintaining time, and the density of the casting is improved; the segregation in the casting solidification process can be effectively inhibited through the additional alternating electromagnetic field, the looseness and the shrinkage cavity are reduced, the crystal grains are refined, and the mechanical property of the casting is improved.
Furthermore, the method of the invention adopts the sand box coupled with the electromagnetic generator to act, and is matched with the pressure-regulating casting device, and the alternating electromagnetic field is applied in the casting mold filling and solidifying processes, thereby realizing the effect of electromagnetic stirring forced convection, improving the metallurgical quality of the casting, reducing the internal defects, improving the density, further refining the grain size of the solidification structure, effectively reducing the generation of the solidification segregation of the casting, ensuring that the appearance profile of the casting is clearer and the surface quality is high.
Furthermore, the method of the invention has the advantages that the good pressure-regulating casting device and the vacuum degree before sealing and mold filling effectively avoid the generation of air holes and oxidized inclusions; the pressure difference between the upper tank body and the lower tank body is favorable for improving the driving force of casting feeding and melt flowing, sequential solidification is realized, and the defects of shrinkage porosity, shrinkage cavity, insufficient pouring and the like are reduced.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic view of a pressure-regulated casting apparatus according to a preferred embodiment of the present invention;
FIG. 2 is a melting process curve of an IGBT intermediate frequency furnace in a preferred embodiment of the invention;
FIG. 3 is a pressure regulating casting process curve in a preferred embodiment of the present invention;
FIG. 4 is a view of a floating wall component in a preferred embodiment of the present invention;
the scores in the figure are indicated as: the device comprises an upper tank body 1, a lower tank body 2, a middle partition plate 3, a sand box 4, molding sand 5, heat-preservation asbestos 6, an electromagnetic generator 7, a liquid lifting pipe 8, a high-temperature alloy melt 9, a crucible 10, a base 11, an air path control system 12 and a shell 13.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
The high-temperature alloy floating wall tile is an important heat dissipation component of a high-temperature combustion chamber of an aeroengine. The following embodiment of the invention provides a pressure regulating precision casting method of a high-temperature alloy floating wall tile under the action of an external electromagnetic field, which comprises the steps of printing by adopting a 3D printing technology to obtain a wax mold of a pouring system; carrying out atomization polishing and grinding on the wax mould, and removing surface layer grains of the wax mould; preparing a multi-layered shell 13 on a wax pattern; then demolding the shell 13; the high-temperature alloy melt 9 is poured into a shell of a shell 13 by adopting vacuum antigravity pressure regulation to form a casting, an alternating electromagnetic field is added in the casting process of the casting, and during the specific implementation, an electromagnetic generator 7 is arranged outside an upper tank sand box 4 on a vacuum pressure regulation casting device controlled by air pressure, so that the alternating electromagnetic field is added in the casting process of the casting, the electromagnetic volume force in the filling and solidification process plays an electromagnetic stirring role on the high-temperature alloy melt 9, the forced convection is generated to change the temperature field and the concentration field of the high-temperature alloy melt 9, the casting segregation is reduced, and the crystal grains are refined.
In the method, the electromagnetic volume force in the filling and solidification processes plays a role in stirring the high-temperature alloy melt 9, specifically, the electromagnetic stirring reduces the temperature gradient of the melt and the component supercooling at a liquid/solid interface, effectively reduces or eliminates center segregation, promotes non-spontaneous nucleation, and thereby refines the solidification structure. Meanwhile, the electromagnetic stirring enables the melted crystal grains to enter into the interdendritic region more easily, so that the defects of looseness and shrinkage cavity of the casting are further reduced.
In another embodiment, a pressure regulating precision casting method of a high-temperature alloy floating wall tile with an external electromagnetic effect is further described by combining a pressure regulating casting device, and the adopted material is M951 alloy. The M951 high-temperature alloy is a nickel-based casting high-temperature alloy, has good oxidation resistance and fatigue resistance, and also has the advantages of low density, good casting performance and the like.
Referring to fig. 1, in the embodiment of the present invention, a pressure-regulating casting device with an external electromagnetic field may be used, which is disclosed in the prior art, and the specific structural features of the pressure-regulating casting device may be referred to in chinese patent publication No. 102717051 a. The embodiment is improved on the pressure regulating casting device, namely, an electromagnetic generator 7 is arranged outside the sand box 4 of the upper tank body 1 of the pressure regulating casting device. Based on the structural characteristics of the pressure-regulating casting device, the pressure-regulating casting device with the action of the external electromagnetic field in the embodiment comprises a tank body, an air circuit system, a base 11, a crucible 10, an electromagnetic generator 7 and the like, wherein the tank body is positioned above the base 11, a middle partition plate 3 is arranged in the tank body, a cavity is divided into an upper tank body 1 and a lower tank body 2 by the middle partition plate 3, the electromagnetic generator 7 is arranged outside a sand box 4 of the upper tank body 1, the crucible 10 is positioned in the lower tank body 2, and the air circuit system is respectively communicated with the upper tank body 1 and the lower tank body 2. Due to the existence of the electromagnetic generator 7, in addition to the pressure difference effect of the upper tank body 1 and the lower tank body 2, the alloy liquid is additionally subjected to the electromagnetic stirring effect generated by the induction coil in the process of filling and solidifying in the mould shell 13. The mechanical nature of the electromagnetic field acting on the micro-scale is an electromagnetic force, namely Lorentz force. In the negative pressure mold filling process, the alloy liquid is subjected to the effect of forced convection, the component difference of different positions in the alloy liquid is weakened, the heat dissipation of the alloy liquid to the casting shell 13 is accelerated, and in the positive pressure solidification process, the component supercooling of a liquid/solid interface is reduced, the center segregation of the casting is effectively reduced, the dendritic crystal arms are broken or broken, and the crystal grains are refined.
By adopting the device shown in the figure 1, the pressure regulating precision casting method of the high-temperature alloy floating wall tile under the action of the external electromagnetic field in the embodiment of the invention comprises the following specific steps:
s1: designing a floating wall pouring scheme: and (3) combining a casting process design principle and a casting simulation CAE technology, designing a reasonable pouring scheme for the floating wall and simulating and optimizing pouring process parameters.
S2: 3D printing a wax pattern: and printing by adopting a photocuring 3D printing (SLA) technology to obtain the three-dimensional photosensitive resin wax pattern of the pouring system.
S3: atomizing and polishing the wax mold: and carrying out atomization polishing and grinding on the wax mould so as to remove surface layer grains and ensure the surface quality of the wax mould.
S4: preparing a shell 13: the resin wax mold is repeatedly soaked with slurry, sprayed with sand powder and dried by a manipulator of the automatic shell making device for many times, and then the multi-layer precision casting shell 13 with the thickness of 10mm is prepared.
S5: roasting and cleaning the shell 13: the shell 13 is placed in a high-temperature roasting furnace to remove most of the photosensitive resin in the shell, and the shell 13 is washed and cleaned to remove residual impurities.
S6: preheating shell 13 and lift tube 8: the outer wall of the shell 13 is wrapped with a layer of heat preservation asbestos 6 which plays a role in heat preservation and heat insulation, the inner wall and the outer wall of the lift pipe 8 are coated with a layer of alumina powder film for oxidation resistance, the shell 13 and the lift pipe 8 are put into a resistance heating furnace together, the temperature is heated to 1000 ℃ at a constant heating rate of 5 ℃/min, and the heat is preserved for 1 h.
S6: melting M951 alloy ingot: sealing an upper tank body 1 and a lower tank body 2 of the pressure regulating casting device, starting a gas path control system 12 of the pressure regulating casting device to perform vacuum pumping operation, keeping the vacuum degree of the lower tank body 2 of the pressure regulating casting device between-30 KPa and-50 KPa, turning on an IGBT medium frequency induction power supply, and melting and heating the M951 alloy ingot to 1580 ℃ by adopting a common heating process.
Referring to fig. 2, in the present embodiment, the medium frequency induction power source directly acts on the crucible 10 of the lower tank, and the maximum mass of the alloy liquid contained in the crucible 10 is 10kg, which is the melting process curve of the medium frequency furnace adopted in the present embodiment in combination with experimental experience. The smelting of the high-temperature alloy requires large power, the larger the heating power of the intermediate frequency furnace is, the longer the overheating time of the alloy liquid is, and the more serious the burning loss of the alloy elements is. Usually, the alloy liquid is heated to be completely melted and has a certain superheat degree by gradually increasing the power of the intermediate frequency furnace, and meanwhile, the process that the casting shell 13 and the riser tube 8 are transferred and fixed into the pressure-regulating casting device is considered, so that heat loss exists, and the heating power of 25Kw and 30Kw is prolonged to 10min from 5min to make up for the heat loss in the process.
S7: stationary mold shell 13 and lift tube 8: and (3) quickly transferring the shell 13 and the lift pipe 8 from the resistance heating furnace to the middle partition plate 3 of the pressure-regulating casting device, wherein the shell 13 is reversely buckled on the lift pipe 8, and the lift pipe 8 passes through the middle partition plate 3 and is communicated with the crucible 10 of the lower tank body 2 of the pressure-regulating casting device. The gap between the upper tank body 1 and the lower tank body 2 of the pressure-regulating casting device is well adjusted by using a weight and a sealing ring, a shell 13 reversely buckled on a lift pipe 8 is covered by a sand box 4 of which the outer layer is wound with an induction coil of an electromagnetic generator 7, the inner layer of the sand box 4 is filled with molding sand 5, the sand box 4 and a locking ring of the middle tank body 3 are fixed together by using a buckle plate and a locking bolt, and then the upper tank body 1 and the lower tank body 2 of the pressure-regulating casting device are sealed. The good pressure-regulating casting device and the vacuum degree before sealed mold filling effectively avoid the generation of air holes and oxidized inclusions; the pressure difference between the upper tank body 1 and the lower tank body 2 is beneficial to improving the driving force of casting feeding and melt flowing, realizing sequential solidification, and reducing the defects of shrinkage porosity, shrinkage cavity, insufficient pouring and the like.
S8, starting the electromagnetic generator 7: the electromagnetic generator 7 located on the outer layer of the flask 4 is turned on, and the effective value of the alternating current in the induction coil is adjusted to 10A.
And S9, starting the gas circuit control system 12 according to a preset pressure difference curve, sequentially completing the processes of vacuumizing, filling, boosting, maintaining pressure and releasing pressure of the casting, closing the electromagnetic generator 7 after the molten metal flows back to the crucible 10 from the liquid lifting pipe 8, and cooling the casting to room temperature. As a preferred embodiment, the crystallization pressure in S9 is 250KPa, and the dwell time is 20 min. The crystallization pressure is the difference between the pressure of the lower tank and the pressure of the upper tank in the pressure curve in the crystallization pressure maintaining section. The crystallization pressure and the pressure maintaining time have obvious influence on the density and the secondary dendrite spacing of the casting.
Referring to FIG. 3, the pressure regulating gas circuit control system 12 is activated to simultaneously evacuate the upper and lower vessels of the pressure casting apparatus to a set value, typically-50 KPa, based on the vacuum requirement of the M951 alloy pressure regulating casting. At the moment, the pressure regulating casting control system can be automatically triggered to sequentially complete liquid lifting, mold filling, crusting pressurization, crusting pressure maintaining, crystallization pressurization, synchronous pressurization, crystallization pressure maintaining, intercommunication and exhaust. From the liquid raising stage to the crystallization pressurizing stage, the pressure of the upper tank is constant and equal to the set value of the vacuumizing end stage, while the pressure of the lower tank is continuously increased in the process, but the pressure of the upper tank and the pressure of the lower tank are always kept at negative pressure in the process. Specifically, the lower tank pressure-increasing speed and pressure in the liquid-raising stage of the lift tank are set so as to ensure that the flow state of the molten metal in the liquid-charging process of the lift pipe 8 is a laminar flow state. The setting of the tank mold filling pressure in the casting mold filling process is determined by combining the shape complexity, the shape height, the wall thickness and the thermophysical parameters of the alloy liquid, and the mold filling and pressurizing speed is selected to ensure the smooth mold filling of the alloy liquid in the casting. And in the whole process of liquid lifting and filling, the electromagnetic generator 7 plays a role of forced convection on the alloy liquid. The forced convection action reduces the temperature difference and the component difference of different positions in the alloy liquid, accelerates the heat dissipation of the alloy liquid to the casting shell 13 and increases the supercooling degree of the alloy liquid at the casting shell 13. Therefore, when the mold filling is complete, the molten metal in contact with the casting shell 13 can be crystallized and solidified at the earliest time, the lower tank is continuously subjected to crusting and pressurizing, and the crusting and pressure maintaining are carried out for a period of time, so that a fine and compact solidified shell layer can be formed near the casting shell 13. But at the moment, the alloy liquid from the solidification shell to the interior of the casting is not completely solidified, and the lower tank still needs to be further crystallized and pressurized, which is beneficial to better feeding of the casting in the solidification process. Then keeping the difference value (namely crystallization pressure) between the lower tank pressure and the upper tank pressure unchanged, synchronously boosting the pressure of the upper tank body 1 and the lower tank body 2 to a positive pressure state, and then keeping the upper tank pressure and the lower tank pressure at the moment for crystallization. The surface quality of the casting can be ensured by maintaining the crystallization and pressure for a period of time under positive pressure until the alloy liquid is completely solidified, and the electromagnetic stirring in the solidification process reduces the component supercooling of a liquid/solid interface, thereby effectively reducing the center segregation of the casting. In addition, the electromagnetic stirring not only makes the melted crystal grains enter into the interdendritic region more easily to reduce the loose defect, but also can break or break the dendrite arms to promote the non-spontaneous nucleation and refine the crystal grains. And finally, communicating the pressures of the upper tank body 1 and the lower tank body 2 and exhausting.
The floating wall tile prepared by the embodiment has the advantages of complex and ultrathin structure and high precision. Referring to fig. 4, tile with wall thickness of about 1.5mm and 150mm × 50mm is distributed with 5 large circular holes, 9 large bosses, 90 small through holes and hundreds of air holes with diameter less than 1 mm.
The embodiment combines the advantages of pressure-regulating casting and electromagnetic field in casting application, and plays an important role in further improving the molding quality of the casting and improving the structure and performance of the casting.
The above is an example of the present invention, and the present invention may also have other implementation manners, such as changing the design structure of the voltage regulating casting device coupled electromagnetic generator 7, and changing the parameters in the coupled electromagnetic generator 7, such as current, voltage, frequency, etc.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.
Claims (5)
1. A pressure regulating precision casting method of a high-temperature alloy floating wall tile under the action of an external electromagnetic field is characterized by comprising the following steps: the method comprises the following steps:
printing by adopting a 3D printing technology to obtain a wax mold of the pouring system;
carrying out atomization polishing and grinding on the wax mould, and removing surface layer grains of the wax mould;
preparing a multi-layer shell on the wax mold;
demolding the shell;
pouring the high-temperature alloy melt into the shell of the shell by adopting vacuum antigravity pressure regulation to form a casting, and adding an alternating electromagnetic field in the casting process of the casting to ensure that the electromagnetic volume force in the filling and solidifying processes plays a role in stirring the high-temperature alloy melt, so that forced convection is generated to change the temperature field and the concentration field of the high-temperature alloy melt, and crystal grains are refined;
the method is carried out according to the following steps:
s1: designing a gating system and a casting process scheme for the floating wall tile by combining a casting process design principle and a casting simulation CAE technology;
s2: printing by adopting a 3D printing technology to obtain a three-dimensional photosensitive resin wax pattern of the pouring system;
s3: carrying out atomization polishing and grinding on the wax mould, removing surface layer grains and ensuring the surface quality of the wax mould;
s4: repeatedly soaking the resin wax pattern with slurry, spraying sand powder and drying by means of a mechanical arm of an automatic shell making device to obtain a multi-layer precision casting shell;
s5: roasting the shell to remove resin in the shell, and cleaning the shell to remove residual impurities;
s6: preheating the shell and the lift tube; placing a high-temperature alloy ingot into a crucible of a lower tank body of a pressure-regulating casting device, and smelting the high-temperature alloy ingot under the negative pressure of-30 KPa to-50 KPa of vacuum degree;
s7: placing the shell and the liquid lifting pipe in the pressure-regulating casting device, fixing the shell and the liquid lifting pipe by adopting a sand box and a weight, and sealing an upper tank body and a lower tank body of the pressure-regulating casting device;
s8: arranging an electromagnetic generator on the outer layer of the sand box, starting the electromagnetic generator, and adjusting alternating current in an induction coil;
s9: starting a gas circuit control system according to a preset pressure difference curve, sequentially completing the processes of vacuumizing, mold filling, boosting, pressure maintaining and pressure relief of the casting, closing the electromagnetic generator after the high-temperature alloy liquid flows back to the crucible from the liquid lifting pipe, and cooling the casting to room temperature;
s6, the preheating shell and the lift tube include:
coating a layer of refractory cotton with heat preservation and insulation effects on the outer wall of the shell, and coating a layer of alumina powder film for oxidation resistance on the inner wall and the outer wall of the lift tube;
putting the shell and the lift pipe into a resistance heating furnace, heating at a constant heating speed, heating to a preset temperature, and preserving heat;
s7, fixing the shell and the lift tube by a sand box and a weight, comprising:
the shell and the liquid lifting pipe are quickly transferred to a middle partition plate of the pressure-regulating casting device, the middle partition plate divides the pressure-regulating casting device into an upper tank body and a lower tank body, the shell is reversely buckled on the liquid lifting pipe, and the liquid lifting pipe penetrates through the middle partition plate and is communicated with the crucible of the lower tank body of the pressure-regulating casting device;
isolating a gap between the lower tank body and the middle partition plate of the pressure-regulating casting device by using the weight and the sealing ring, covering the shell reversely buckled on the lift pipe by using the sand box of which the outer layer is wound with the induction coil of the electromagnetic generator, filling the inner layer of the sand box with molding sand, fixing the sand box and the middle partition plate together, and then sealing the upper tank body and the lower tank body of the pressure-regulating casting device;
starting a pressure regulating gas circuit control system, simultaneously vacuumizing an upper tank body and a lower tank body of a pressure regulating casting device to a set value according to the vacuum degree requirement of alloy pressure regulating casting, and automatically triggering the pressure regulating casting control system to sequentially finish liquid rising, mold filling, incrustation pressurization, incrustation pressure maintaining, crystallization pressurization, synchronous pressurization, crystallization pressure maintaining, intercommunication and exhaust;
specifically, the lower tank pressure-increasing speed and pressure-increasing pressure in the liquid-increasing stage of the liquid-increasing tank are set to ensure that the flowing state of molten metal in the liquid-increasing pipe mold-filling process is a laminar flow state, the size of the lower tank mold-filling pressure in the casting mold-filling process is determined by combining the shape complexity, the shape height, the wall thickness and the thermophysical parameters of the alloy liquid of the casting, and the mold-filling pressure-increasing speed is selected to ensure the stability of mold-filling of the alloy liquid in the casting; in the whole process of liquid lifting and filling, the electromagnetic generator plays a role of forced convection on the alloy liquid, the forced convection reduces the temperature difference and the component difference of different positions in the alloy liquid, accelerates the heat dissipation of the alloy liquid to the casting shell, and increases the supercooling degree of the alloy liquid at the casting shell, so that when the filling is complete, the metal liquid in contact with the casting shell can be crystallized and solidified at the earliest, the lower tank is continuously subjected to crust forming and pressurization and crust forming and pressure maintaining for a period of time, and a fine and compact solidified shell layer can be formed nearby the casting shell; at the moment, the alloy liquid from the solidification shell to the interior of the casting is not completely solidified, the lower tank still needs to be crystallized and pressurized further, so that the casting is favorably fed in the solidification process, then the difference value of the pressure of the lower tank and the pressure of the upper tank, namely the crystallization pressure, is kept unchanged, the upper tank and the lower tank are synchronously pressurized to a positive pressure state, then the pressure of the upper tank and the lower tank is kept for crystallization at the moment, the crystallization pressure is kept for a period of time under the positive pressure until the alloy liquid is completely solidified, the surface quality of the casting can be ensured, the electromagnetic stirring in the solidification process reduces the component supercooling of a liquid/solid interface, and the center segregation of the casting is effectively reduced.
2. The pressure-regulating precision casting method of the high-temperature alloy floating wall tile under the action of the external electromagnetic field according to claim 1, which is characterized in that: and S4, preparing a multi-layer precision casting shell, wherein the thickness of each layer of the shell is 8-10 mm.
3. The pressure-regulating precision casting method of the high-temperature alloy floating wall tile under the action of the external electromagnetic field according to claim 1, which is characterized in that: in S6, the high-temperature alloy ingot is made of M951 alloy and consists of the following elements in percentage by mass: 0.05% of C, 9.00% of Cr, 5.00% of Co, 3.50% of W, 3.00% of Mo, 2.20% of Nb, 5.90% of Al, 0.02% of Y, 0.024% of B and the balance of Ni.
4. The pressure-regulating precision casting method of the high-temperature alloy floating wall tile under the action of the external electromagnetic field according to claim 1, which is characterized in that: in S8, the magnitude of the alternating current is 10A.
5. The pressure-regulating precision casting method of the high-temperature alloy floating wall tile under the action of the external electromagnetic field according to claim 1, which is characterized in that: in S9, the crystallization pressure is 200 KPa-300 KPa, and the pressure holding time is 5 min-25 min.
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| CN113802030A (en) * | 2021-10-14 | 2021-12-17 | 上海交通大学 | Rare earth high-temperature alloy construction material and ultralimit precision casting method thereof |
| CN115815570A (en) * | 2023-02-15 | 2023-03-21 | 中北大学 | Vacuum electromagnetic low-pressure mold filling device and process for preparing heterogeneous composite structure by adopting same |
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