CN108941457B - Preparation method of shell of guide blade casting made of K438 high-temperature alloy - Google Patents

Abstract

The invention relates to a preparation method of a shell of a K438 high-temperature alloy guide vane casting, which comprises a shell surface layer and a multilayer shell back layer, wherein the shell surface layer is formed by solidifying and combining shell surface layer slurry and a surface layer sand spraying material, the particle size of zircon powder for preparing the slurry in the shell surface layer slurry is 300-1250 meshes, and the aggregate of the surface layer sand spraying layer is zircon powder with the particle size of 100-150 meshes; the back layer of the shell is formed by solidifying and combining back layer slurry and back layer sanding material, the grain size of fused quartz powder and fused quartz sand for preparing the slurry in the back layer slurry is 100-1250 meshes, and the aggregate of the back layer sanding layer is quartz sand with the grain size of 10-50 meshes; the surface layer slurry of the shell uses zircon powder, the back layer slurry uses fused quartz with extremely small expansion coefficient, the obtained shell has small thermal expansion coefficient, and the particle size of the used powder is strictly controlled so as to reduce the difference of the thermal expansion coefficient between the surface layer and the back layer of the shell.

Description

Preparation method of shell of guide blade casting made of K438 high-temperature alloy

Technical Field

The invention relates to the technical field of investment casting, in particular to a preparation method of a shell of a guide blade casting made of K438 high-temperature alloy.

Background

With the improvement of energy utilization efficiency, more and more parts are designed based on a complex pneumatic principle or fluid dynamics, the shapes of the parts are complex, and the requirements on integrity and precision are higher. Investment casting enables the precision casting of extremely complex shaped parts in its entirety and thus is the primary or even the only method of producing complex metal components. Because the investment precision casting process has the characteristics of long flow, multiple working procedures, complex influence factors and the like, the obtaining of the near-net-shaped casting is not easy. In a plurality of processes of investment casting, three key processes have large influence on the size and deformation of a casting, namely wax mold preparation, shell preparation and casting solidification. The dimensional deformation of the wax mold is easy to control, the shrinkage deformation of the casting is greatly influenced by the interaction of metal and the shell in the casting pouring and cooling processes, on one hand, the shell is subjected to thermal shock and mechanical shock of the metal, and on the other hand, the metal is cooled and solidified through the heat dissipation of the shell. Therefore, the low strength of the shell and the softening deformation are important causes for the deformation of the casting. After the metal is poured, the larger the thermal expansion rate of the shell is, the larger the solidification shrinkage deformation of the casting is.

The large thin-wall complex annular high-temperature alloy casting is a common key part of an aeroengine, a gas turbine and the like, and has the advantages of large size, complex structure, high requirements on metallurgical quality and dimensional precision, and casting temperature of the alloy castings of 1400-1600 ℃, so that the casting shell quality in the investment casting process is greatly required. But the existing shell-making process has the defects of large casting shrinkage rate, unsatisfactory casting forming effect and the like. The more complex the casting structure, the more the shrinkage from the wax pattern to the metal is affected by structural factors and, in general, no mathematically resolved solution exists. Therefore, different shrinkage rates of each part of a casting during mold design can lead the mold design to be abnormally complex, thereby causing the defect that the dimensional precision is difficult to control; meanwhile, the surface of the shell is rough due to the fact that the roasting temperature or the heat preservation time is short in the using process of the shell, particularly in the field of manufacturing of large-scale thin-wall high-temperature alloy castings, the surface quality of the castings is affected, and the castings are difficult to clean.

Therefore, the shell preparation process of the large thin-wall complex annular high-temperature alloy casting needs to be improved so as to meet the requirement of the casting. The thermal stress and the shell strength of the casting are not high in the pouring process, and the high-temperature softening of the shell is a main reason for large shrinkage and deformation of the casting. Therefore, the shell with small thermal expansion coefficient and large deformation resistance is very important for aviation thin-wall castings.

Disclosure of Invention

The invention aims to provide a shell with near-zero shrinkage based on fused quartz and a preparation method thereof.

The technical scheme includes that the shell with the nearly zero shrinkage rate based on fused quartz comprises a shell surface layer tightly attached to the surface of a prefabricated wax film and a multi-layer shell back layer tightly attached to the outer side of the shell surface layer, wherein the shell surface layer is formed by solidifying and combining shell surface layer slurry and a surface layer sanding material, the components of the shell surface layer slurry comprise silica sol, zircon powder, cobalt aluminate, a wetting agent, a defoaming agent and a reinforcing agent, and aggregate of the surface layer sanding layer is zircon powder; the back molding layer is formed by solidifying and combining back molding layer slurry and back sanding material, the back molding layer slurry comprises silica sol, fused quartz powder, fused quartz sand, a wetting agent, a defoaming agent, distilled water and a reinforcing agent, and aggregate of the back sanding layer is quartz sand; the shell has a small coefficient of thermal expansion because zircon powder is used as a surface layer slurry and fused quartz having an extremely small coefficient of expansion is used as a back layer slurry.

Furthermore, the grain diameter of zircon powder for preparing slurry in the shell surface layer slurry is 300 meshes to 1250 meshes, and aggregate of the surface layer sand-spreading layer is zircon powder with the grain diameter of 100 meshes to 150 meshes; fused quartz powder and fused quartz sand used for preparing slurry in the shell back layer slurry have the particle sizes of 100 meshes to 1250 meshes, and aggregate of the back layer sand-scattering layer is quartz sand with the particle size of 10 meshes to 50 meshes; the grain diameters of the powder for the surface layer slurry, the powder for the surface layer sand-hanging layer aggregate, the powder for the back layer slurry and the powder for the back layer sand-hanging layer aggregate are strictly controlled so as to reduce the difference of the thermal expansion coefficients between the surface layer and the back layer of the shell, and the obtained shell is more uniform.

Further, the formula of the shell surface layer slurry comprises the following components in percentage by mass: 15-20% of silica sol, 5-10% of cobalt aluminate, 0-0.5% of wetting agent, 0-0.5% of defoaming agent, 0.5-1.0% of distilled water, 0.5-1.0% of reinforcing agent and the balance of zircon powder; the formula of the shell-back layer slurry comprises the following components in percentage by mass: 20-40% of silica sol, 5-15% of fused quartz sand with the grain size of 100 meshes-300 meshes, 0-0.5% of wetting agent, 0-0.5% of defoaming agent and the balance of fused quartz powder with the grain size of 300 meshes-1250 meshes; 5% -15% of fused quartz with the particle size close to that of the aggregate of the sand layer scattered on the shell surface layer is added into the back layer slurry, so that the shell surface layer and the back layer are easy to bond, and the phenomenon that the prepared shell is uneven due to the fact that the particle size difference of the powder is too large is avoided.

Further, the reinforcing agent is a mixture of styrene-butadiene latex, acrylic acid and acrylate, wherein the styrene-butadiene latex accounts for 40-70% by mass, the acrylic acid accounts for 25-59% by mass, and the acrylate accounts for 1-10% by mass; after the reinforcing agent is added, the cracking risk of the shell during dewaxing can be reduced, the room temperature strength of the shell is improved, the porosity of the shell during high-temperature roasting is increased, the high-temperature air permeability of the shell is improved, the cracking risk of the quartz phase-change shell after primary roasting is reduced, the shell washing procedure after primary roasting of the shell can be increased, the inclusion risk of a casting is reduced, and the shell recycling is facilitated.

Further, the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, wherein the mass percent of the polyoxyethylene ether is 60-80%, and the mass percent of the carboxymethyl cellulose is 20-40%; the wetting agent is mixed with distilled water and then added into the slurry, so that the permeability and the leveling property of the slurry can be improved.

Further, the defoaming agent is at least one of n-butyl alcohol, n-octyl alcohol, polydimethylsiloxane or ethylene glycol butyl ether phosphate.

The preparation method of the shell with the near-zero shrinkage rate comprises the following steps:

A. and (4) drying the surface of the wax mould module after oil removal treatment.

B. Preparing shell surface layer slurry, adding 15-20% of silica sol, 5-10% of cobalt aluminate, 0.5% of wetting agent, 0-0.5% of defoaming agent, 0.5-1.0% of distilled water, 0.5-1.0% of reinforcing agent and the balance of zircon powder, mixing, stirring until the silica sol and the powder are well combined together, enabling the viscosity of the slurry to reach 20-25s and the pH value to be larger than 8, and obtaining the surface layer slurry.

C. Coating the surface layer slurry on a wax mold, spraying zircon powder with the particle diameter of 100-150 meshes, sanding, ensuring that the zircon powder on the surface of the shell is uniformly and comprehensively covered, drying for 2-24 hours at the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 2-4 hours to prepare the shell surface layer.

D. Preparing back layer slurry, adding silica sol which accounts for 20-40% of the weight of the slurry, adding fused quartz sand which accounts for 5-15% of the weight of the slurry and has a particle size of 100 meshes-300 meshes, adding a wetting agent which accounts for 0-0.5% of the weight, adding a defoaming agent which accounts for 0-0.5% of the weight, and mixing the rest fused quartz powder which has a particle size of 300 meshes-1250 meshes, stirring until the silica sol and the powder are well combined together, and enabling the viscosity of the slurry to reach 10-20s and the pH value to be greater than 7 to obtain the back layer slurry.

E. Coating the back layer slurry on the dried shell surface layer, spraying quartz sand with the grain diameter of 10-50 meshes, carrying out sand coating, drying at the room temperature of 21 +/-5 ℃ and the humidity of 35-75% for 2-24 hours, and carrying out air drying for 0.5-1 hour to prepare the shell 2 nd layer.

F. Repeating the step E for multiple times to finish the preparation of the multilayer shell-back layer; and (3) adjusting the viscosity of the back layer slurry to 15-18s in the last layer of the back layer, not hanging sand, and drying for not less than 15 hours at the room temperature of 21 +/-5 ℃ and the humidity of 35-75% to finish sealing slurry.

G. And (3) dewaxing by adopting steam, and then roasting the shell by adopting an electric furnace, wherein the roasting temperature is 900-1000 ℃, and the heat is preserved for 4-6 hours to obtain a shell finished product.

Further, the step E is repeated 8-12 times to obtain a shell having a more moderate thickness.

According to the near-zero shrinkage rate shell based on fused quartz, zircon powder is used as surface layer slurry of the shell, fused quartz with extremely small expansion coefficient is used as back layer slurry, the obtained shell has a small thermal expansion coefficient, and the particle diameters of powder for the surface layer slurry, powder for the surface layer sand-hanging layer aggregate, powder for the back layer slurry and powder for the back layer sand-hanging layer aggregate are strictly controlled so as to reduce the difference of the thermal expansion coefficients between the surface layer and the back layer of the shell, so that the obtained shell is more uniform; 5% -15% of fused quartz with the particle size close to that of the aggregate of the sand-scattering layer of the shell surface layer is added into the back layer slurry, so that the shell surface layer and the back layer are easy to bond, and the problem that the prepared shell is not uniform due to overlarge powder particle size difference is avoided; especially in the field of manufacturing large thin-wall high-temperature alloy castings, the deformation and uneven thickness of the thin wall of the casting can be well prevented; the expansion coefficient of a part of the shell from room temperature to casting pouring temperature is close to 0 by using the limited material, so that the size control is not limited by the complex structure of the casting, the size precision of the casting is ensured, the surface of the prepared shell is compact and smooth, the surface quality of the obtained casting is high, and the defects of looseness, slag inclusion, cracks and the like of the casting can be effectively reduced; after the reinforcing agent is added, the cracking risk of the shell during dewaxing can be reduced, the room temperature strength of the shell is improved, the porosity of the shell during high-temperature roasting is increased, the high-temperature air permeability of the shell is improved, the cracking risk of the quartz phase-change shell after primary roasting is reduced, the shell washing procedure after primary roasting of the shell can be increased, the inclusion risk of a casting is reduced, and the shell recycling is facilitated; the wetting agent is added to increase the permeability and the leveling property of the slurry.

Detailed Description

Example 1

The method for preparing the shell of the guide blade casting of the K438 high-temperature alloy specifically comprises the following steps:

A. carrying out oil removal treatment on the surface of the wax mould module and then drying;

B. preparing shell surface layer slurry, mixing according to the weight ratio of 15% of silica sol and 75% of zircon powder with the particle size of 300 meshes-1250 meshes, adding 7% of cobalt aluminate and 0.5% of wetting agent, wherein the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, and the mass ratio of the polyoxyethylene ether to the carboxymethyl cellulose in the wetting agent is 6: 4; adding n-butanol (other examples can be at least one of n-octanol, polydimethylsiloxane or ethylene glycol butyl ether phosphate) accounting for 0.5 weight percent as a defoaming agent, adding distilled water accounting for 1.0 weight percent, adding a reinforcing agent accounting for 1.0 weight percent, wherein the reinforcing agent is a mixture of butylbenzene latex, acrylic acid and acrylic ester, and the mass ratio of the butylbenzene latex, the acrylic acid and the acrylic ester is 4:5: 1; stirring until the silica sol and the powder are well combined together, enabling the viscosity of the slurry to reach 20-25s (measured by using a No. 5 Zea En cup), and adjusting the pH value to be not lower than 8 to obtain surface layer slurry;

C. coating the surface layer slurry on a wax mold, spraying zircon powder with the particle diameter of 100-150 meshes for sand hanging, ensuring that the zircon powder on the surface of the shell is uniformly and comprehensively covered, drying for 2-24 hours in an environment with the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 2-4 hours to prepare the shell surface layer;

D. preparing back layer slurry, mixing 40% of silica sol, 50% of fused quartz powder with the particle size of 300 meshes-1250 meshes and 9% of fused quartz sand with the particle size of 100 meshes-300 meshes according to the weight ratio, adding a wetting agent accounting for 0.5% of the weight ratio, wherein the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, and the mass percentage of the polyoxyethylene ether to the carboxymethyl cellulose is 7: 3; adding n-butanol (as other examples, at least one of n-octanol, polydimethylsiloxane and ethylene glycol monobutyl ether phosphate) 0.5 wt%, stirring until the silica sol and the powder are well combined together, and making the viscosity of the slurry reach 10-20s (measured by using No. 5 Zehn cup), and adjusting pH value to be not less than 7 to obtain back layer slurry;

E. coating the back layer slurry on the dried shell surface layer, spraying quartz sand with the grain diameter of 10-50 meshes for sand hanging, drying for 2-24 hours at the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 0.5-1 hour to prepare a shell layer 2;

F. e, repeating the step E for multiple times to finish the preparation of the shell layers from the 3 rd layer to the 11 th layer; then adjusting the viscosity of the back layer slurry to 15-18s (measured by using a No. 5 Zea cup), preparing the last layer of the back layer of the shell, not hanging sand, drying for 20 hours in an environment with the room temperature of 21 +/-5 ℃ and the humidity of 35-75 percent, and finishing sealing slurry;

G. and (3) dewaxing by adopting steam, and roasting the shell by adopting an electric furnace at the roasting temperature of 900 ℃ for 4-6 hours to obtain the shell finished product.

The dimensions of the critical parts of the guide vane manufactured by using the shell are measured, and the measured values are shown in table 1.

TABLE 1 guide vane size test results

Size part	Design size (mm)	Tolerance requirement (mm)	Measured dimensions (mm)	Actual tolerance (mm)
					Thickness of exhaust edge	1.12	±0.25	1.15	±0.05
Throat canal	28.57	±0.25	28.63	±0.08
					Size of channel	191	±0.25	189.94	±0.1

According to the measurement results, the size precision of the key part of the guide blade manufactured by the shell of the invention can meet the standard of CT-4, the size precision of the casting is ensured, the surface of the manufactured shell is compact and smooth, the surface quality of the obtained casting is high, and the defects of casting looseness, slag inclusion, cracks and the like can be effectively reduced. For the shell needing to be roasted secondarily, a shell washing procedure is added after primary roasting, and the cleaned shell is roasted secondarily, so that the recycling of the shell is realized, and the inclusion risk and the casting cost of the casting are reduced.

Example 2

The shell for preparing the ring sleeve casting of the K4169 high-temperature alloy specifically comprises the following steps:

A. carrying out oil removal treatment on the surface of the wax mould module and then drying;

B. preparing shell surface layer slurry, mixing according to the weight ratio of 20% of silica sol and 70% of zircon powder with the particle size of 300 meshes-1250 meshes, adding 7% of cobalt aluminate and 0.5% of wetting agent, wherein the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, and the mass percentage of the polyoxyethylene ether to the carboxymethyl cellulose is 6: 4; adding n-butanol (other examples can be at least one of n-octanol, polydimethylsiloxane or ethylene glycol butyl ether phosphate) accounting for 0.5% by weight as a defoaming agent, adding distilled water accounting for 1.0% by weight, adding a reinforcing agent accounting for 1.0% by weight, wherein the reinforcing agent is a mixture of butylbenzene latex, acrylic acid and acrylic ester, and the mass percentage of the butylbenzene latex, the acrylic acid and the acrylic ester is 6:3: 1; stirring until the silica sol and the powder are well combined together, enabling the viscosity of the slurry to reach 20-25s (measured by using a No. 5 Zea En cup), and adjusting the pH value to be not lower than 8 to obtain surface layer slurry;

C. coating the surface layer slurry on a wax mold, spraying zircon powder with the particle diameter of 100-150 meshes for sand hanging, ensuring that the zircon powder on the surface of the shell is uniformly and comprehensively covered, drying for 2-24 hours at the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 2-4 hours to prepare the shell surface layer;

D. preparing back layer slurry, mixing 20% of silica sol, 64% of fused quartz powder with the particle size of 300 meshes-1250 meshes and 15% of fused quartz sand with the particle size of 100 meshes-300 meshes, adding a wetting agent accounting for 0.5% of the weight ratio, wherein the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, and the mass percentage of the polyoxyethylene ether to the carboxymethyl cellulose is 6: 4; adding n-butanol (as other examples, at least one of n-octanol, polydimethylsiloxane and ethylene glycol monobutyl ether phosphate) 0.5 wt%, stirring until the silica sol and the powder are well combined together, and making the viscosity of the slurry reach 10-20s (measured by using No. 5 Zehn cup), and adjusting pH value to be not less than 7 to obtain back layer slurry;

E. coating the back layer slurry on the dried shell surface layer, spraying quartz sand with the grain diameter of 10-50 meshes for sand hanging, drying for 2-24 hours at the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 0.5-1 hour to prepare a shell layer 2;

F. e, repeating the step E for multiple times to finish the preparation of the shell back layers from the 3 rd layer to the 9 th layer; then adjusting the viscosity of the back layer slurry to 15-18s (measured by using a No. 5 Zea cup), preparing the last layer of the back layer of the shell, not hanging sand, drying for 20 hours in an environment with the room temperature of 21 +/-5 ℃ and the humidity of 35-75 percent, and finishing sealing slurry;

G. and (3) dewaxing by adopting steam, and roasting the shell by adopting an electric furnace, wherein the roasting temperature is 1000 ℃, and the heat preservation is carried out for 4-6 hours to obtain the shell finished product.

The dimensions of the key parts of the ring sleeve casting made of the shell are measured, and the measured values are shown in table 2.

TABLE 2 measurement results of Ring casing casting size

Size part	Design size (mm)	Tolerance requirement (mm)	Measured dimensions (mm)	Actual tolerance (mm)
					Outer diameter of outer ring	348	±0.25	347.78	±0.1
Outer ring inner diameter	300	±0.25	299.96	±0.1
					Wall thickness of outer ring	2	±0.05	1.98	±0.02

According to the measurement results, the size precision of the key part of the ring sleeve casting prepared from the shell can meet the standard of CT-4, the size precision of the casting is ensured, the surface of the prepared shell is compact and smooth, the surface quality of the obtained casting is high, and the defects of casting looseness, slag inclusion, cracks and the like can be effectively reduced. For the shell needing to be roasted secondarily, a shell washing procedure is added after primary roasting, and the cleaned shell is roasted secondarily, so that the recycling of the shell is realized, and the inclusion risk and the casting cost of the casting are reduced.

Example 3

The shell for preparing the K403 high-temperature alloy nozzle ring casting specifically comprises the following steps:

A. carrying out oil removal treatment on the surface of the wax mould module and then drying;

B. preparing shell surface layer slurry, mixing according to the weight ratio of 15% of silica sol and 73% of zircon powder with the particle size of 300 meshes-1250 meshes, adding 10% of cobalt aluminate in weight ratio, and adding 0.25% of wetting agent in weight ratio, wherein the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, and the mass percentage of the polyoxyethylene ether to the carboxymethyl cellulose is 8: 2; adding n-butanol (other examples can be at least one of n-octanol, polydimethylsiloxane or ethylene glycol butyl ether phosphate) accounting for 0.25 wt% as a defoaming agent, adding distilled water accounting for 1 wt%, adding a reinforcing agent accounting for 0.5 wt%, wherein the reinforcing agent is a mixture of styrene-butadiene latex, acrylic acid and acrylic ester, and the mass ratio of the styrene-butadiene latex, the acrylic acid and the acrylic ester is 7:2.5: 0.5; stirring until the silica sol and the powder are well combined together, enabling the viscosity of the slurry to reach 20-25s (measured by using a No. 5 Zea En cup), and adjusting the pH value to be not lower than 8 to obtain surface layer slurry;

C. coating the surface layer slurry on a wax mold, spraying zircon powder with the particle diameter of 100-150 meshes for sand hanging, ensuring that the zircon powder on the surface of the shell is uniformly and comprehensively covered, drying for 2-24 hours in an environment with the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 2-4 hours to prepare the shell surface layer;

D. preparing back layer slurry, mixing 30% of silica sol, 64% of fused quartz powder with the particle size of 300 meshes-1250 meshes and 5% of fused quartz sand with the particle size of 100 meshes-300 meshes, adding a wetting agent accounting for 0.5% of the weight ratio, wherein the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, and the mass percentage of the polyoxyethylene ether to the carboxymethyl cellulose is 8: 2; adding n-butanol (as other examples, at least one of n-octanol, polydimethylsiloxane and ethylene glycol monobutyl ether phosphate) 0.5 wt%, stirring until the silica sol and the powder are well combined together, and making the viscosity of the slurry reach 10-20s (measured by using No. 5 Zehn cup), and adjusting pH value to be not less than 7 to obtain back layer slurry;

E. coating the back layer slurry on the dried shell surface layer, spraying quartz sand with the grain diameter of 10-50 meshes for sand hanging, drying for 2-24 hours at the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 0.5-1 hour to prepare a shell layer 2;

F. e, repeating the step E for multiple times to finish the preparation of the shell back layers from the 3 rd layer to the 9 th layer; then adjusting the viscosity of the back layer slurry to 15-18s (measured by using a No. 5 Zea cup), preparing the last layer of the back layer of the shell, not hanging sand, drying for 20 hours in an environment with the room temperature of 21 +/-5 ℃ and the humidity of 35-75 percent, and finishing sealing slurry;

G. and (3) dewaxing by adopting steam, and roasting the shell by adopting an electric furnace, wherein the roasting temperature is 1000 ℃, and the heat preservation is carried out for 4-6 hours to obtain the shell finished product.

The dimensions of the key parts of the nozzle ring casting made from the shell are measured, and the measured values are shown in table 3.

TABLE 3 nozzle ring casting size detection table

Size part	Design size (mm)	Tolerance requirement (mm)	Measured dimensions (mm)	Actual tolerance (mm)
					Thickness of exhaust edge	1.41	±0.07	1.39	±0.05
Throat canal	20.45	±0.2	20.4	±0.08
					Size of channel	98	±0.3	98.05	±0. 1

According to the measurement results, the dimensional accuracy of the key part of the nozzle ring casting prepared from the shell can meet the standard of CT-4, the dimensional accuracy of the casting is ensured, the surface of the prepared shell is compact and smooth, the surface quality of the obtained casting is high, and the defects of casting looseness, slag inclusion, cracks and the like can be effectively reduced. For the shell needing to be roasted secondarily, a shell washing procedure is added after primary roasting, and the cleaned shell is roasted secondarily, so that the recycling of the shell is realized, and the inclusion risk and the casting cost of the casting are reduced.

Example 4

On the basis of embodiment 3, the shell of the nozzle ring casting of the K403 high-temperature alloy is prepared by adjusting the mixture ratio of partial components, and the method specifically comprises the following steps:

A. carrying out oil removal treatment on the surface of the wax mould module and then drying;

B. preparing shell surface layer slurry, mixing according to the weight ratio of 20% of silica sol and 67% of zircon powder with the particle size of 300 meshes-1250 meshes, adding 10% of cobalt aluminate in weight ratio, and adding 0.5% of wetting agent in weight ratio, wherein the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, and the mass percentage of the polyoxyethylene ether to the carboxymethyl cellulose is 7: 3; adding n-butanol (other examples can be at least one of n-octanol, polydimethylsiloxane or ethylene glycol butyl ether phosphate) accounting for 0.5 wt% as a defoaming agent, adding distilled water accounting for 1 wt%, adding a reinforcing agent accounting for 1 wt%, wherein the reinforcing agent is a mixture of styrene-butadiene latex, acrylic acid and acrylate, and the mass ratio of the styrene-butadiene latex, the acrylic acid and the acrylate is 40:59: 1; stirring until the silica sol and the powder are well combined together, enabling the viscosity of the slurry to reach 20-25s (measured by using a No. 5 Zea En cup), and adjusting the pH value to be not lower than 8 to obtain surface layer slurry;

C. coating the surface layer slurry on a wax mold, spraying zircon powder with the particle diameter of 100-150 meshes for sand hanging, ensuring that the zircon powder on the surface of the shell is uniformly and comprehensively covered, drying for 2-24 hours in an environment with the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 2-4 hours to prepare the shell surface layer;

D. preparing back layer slurry, mixing 20% of silica sol, 65% of fused quartz powder with the particle size of 300 meshes-1250 meshes and 14% of fused quartz sand with the particle size of 100 meshes-300 meshes, adding a wetting agent accounting for 0.5% of the weight ratio, wherein the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, and the mass percentage of the polyoxyethylene ether to the carboxymethyl cellulose is 7: 3; adding n-butanol (as other examples, at least one of n-octanol, polydimethylsiloxane and ethylene glycol monobutyl ether phosphate) 0.5 wt%, stirring until the silica sol and the powder are well combined together, and making the viscosity of the slurry reach 10-20s (measured by using No. 5 Zehn cup), and adjusting pH value to be not less than 7 to obtain back layer slurry;

E. coating the back layer slurry on the dried shell surface layer, spraying quartz sand with the grain diameter of 10-50 meshes for sand hanging, drying for 2-24 hours at the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 0.5-1 hour to prepare a shell layer 2;

F. e, repeating the step E for multiple times to finish the preparation of the shell back layers from the 3 rd layer to the 9 th layer; then adjusting the viscosity of the back layer slurry to 15-18s (measured by using a No. 5 Zea cup), preparing the last layer of the back layer of the shell, not hanging sand, drying for 20 hours in an environment with the room temperature of 21 +/-5 ℃ and the humidity of 35-75 percent, and finishing sealing slurry;

G. and (3) dewaxing by adopting steam, and roasting the shell by adopting an electric furnace, wherein the roasting temperature is 1000 ℃, and the heat preservation is carried out for 4-6 hours to obtain the shell finished product.

The dimensions of the key parts of the nozzle ring casting prepared by adopting the shell are measured, and the measured values are shown in table 4.

TABLE 4 nozzle ring casting size detection table

Size part	Design size (mm)	Tolerance requirement (mm)	Measured dimensions (mm)	Actual tolerance (mm)
					Thickness of exhaust edge	1.41	±0.07	1.40	±0.05
Throat canal	20.45	±0.2	20.48	±0.08
					Size of channel	98	±0.3	98.02	±0. 1

According to the measurement results, the size precision of the key part can meet the standard of CT-4.

Example 5

On the basis of embodiment 1, the shell of the guide blade casting of the K438 high-temperature alloy is prepared by adjusting the proportion of partial components, and the method specifically comprises the following steps:

A. carrying out oil removal treatment on the surface of the wax mould module and then drying;

B. preparing shell surface layer slurry, mixing 18% of silica sol and 75% of zircon powder with the particle size of 300-1250 meshes according to the weight ratio, adding 5% of cobalt aluminate according to the weight ratio, and adding 0.5% of wetting agent according to the weight ratio, wherein the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, and the mass ratio of the polyoxyethylene ether to the carboxymethyl cellulose in the wetting agent is 6: 4; adding n-butanol (other examples can be at least one of n-octanol, polydimethylsiloxane or ethylene glycol butyl ether phosphate) accounting for 0.5% by weight as a defoaming agent, adding distilled water accounting for 0.5% by weight, adding a reinforcing agent accounting for 0.5% by weight, wherein the reinforcing agent is a mixture of butylbenzene latex, acrylic acid and acrylic ester, and the mass ratio of the butylbenzene latex to the acrylic acid to the acrylic ester is 40:55: 5; stirring until the silica sol and the powder are well combined together, enabling the viscosity of the slurry to reach 20-25s (measured by using a No. 5 Zea En cup), and adjusting the pH value to be not lower than 8 to obtain surface layer slurry;

C. coating the surface layer slurry on a wax mold, spraying zircon powder with the particle diameter of 100-150 meshes for sand hanging, ensuring that the zircon powder on the surface of the shell is uniformly and comprehensively covered, drying for 2-24 hours in an environment with the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 2-4 hours to prepare the shell surface layer;

D. preparing back layer slurry, mixing 30% of silica sol, 55% of fused quartz powder with the particle size of 300 meshes-1250 meshes and 14% of fused quartz sand with the particle size of 100 meshes-300 meshes according to the weight ratio, adding a wetting agent accounting for 0.5% of the weight ratio, wherein the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, and the mass percentage of the polyoxyethylene ether to the carboxymethyl cellulose is 6: 4; adding n-butanol (as other examples, at least one of n-octanol, polydimethylsiloxane and ethylene glycol monobutyl ether phosphate) 0.5 wt%, stirring until the silica sol and the powder are well combined together, and making the viscosity of the slurry reach 10-20s (measured by using No. 5 Zehn cup), and adjusting pH value to be not less than 7 to obtain back layer slurry;

E. coating the back layer slurry on the dried shell surface layer, spraying quartz sand with the grain diameter of 10-50 meshes for sand hanging, drying for 2-24 hours at the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 0.5-1 hour to prepare a shell layer 2;

F. e, repeating the step E for multiple times to finish the preparation of the shell layers from the 3 rd layer to the 11 th layer; then adjusting the viscosity of the back layer slurry to 15-18s (measured by using a No. 5 Zea cup), preparing the last layer of the back layer of the shell, not hanging sand, drying for 20 hours in an environment with the room temperature of 21 +/-5 ℃ and the humidity of 355-75 percent, and finishing sealing slurry;

G. and (3) dewaxing by adopting steam, and roasting the shell by adopting an electric furnace at the roasting temperature of 900 ℃ for 4-6 hours to obtain the shell finished product.

The dimensions of the critical parts of the guide vane manufactured by using the shell are measured, and the measured values are shown in table 1.

TABLE 5 guide vane size test results

Size part	Design size (mm)	Tolerance requirement (mm)	Measured dimensions (mm)	Actual tolerance (mm)
					Thickness of exhaust edge	1.12	±0.25	1.14	±0.05
Throat canal	28.57	±0.25	28.60	±0.08
					Size of channel	191	±0.25	189.98	±0.1

According to the measurement results, the size precision of the key part can meet the standard of CT-4.

According to the near-zero shrinkage rate shell based on fused quartz, the main component of the back layer material is fused quartz, and the ceramic shell has a small thermal expansion coefficient in the shell roasting and melt pouring processes, so that deformation and uneven thickness of a casting at a thin wall part can be well prevented; the expansion coefficient of a part of the shell from room temperature to casting pouring temperature is close to 0 by using the limited material, so that the size control is not limited by the complex structure of the casting, the size precision of the casting is ensured, the surface of the prepared shell is compact and smooth, the surface quality of the obtained casting is high, and the defects of casting loosening, slag inclusion, cracks and the like can be effectively reduced. After the reinforcing agent is added, the cracking risk of the shell during dewaxing can be reduced, the room temperature strength of the shell is improved, the porosity of the shell during high-temperature roasting is increased, the high-temperature air permeability of the shell is improved, the cracking risk of the quartz phase-change shell after primary roasting is reduced, the shell washing procedure after primary roasting of the shell can be increased, the inclusion risk of a casting is reduced, and the shell recycling is facilitated.

It should be understood that the above examples are only for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And such obvious variations or modifications which fall within the spirit of the invention are intended to be covered by the scope of the present invention.

Claims (1)

1. A preparation method of a shell of a K438 high-temperature alloy guide vane casting is characterized by comprising the following steps:

A. carrying out oil removal treatment on the surface of the wax mould module and then drying;

B. preparing shell surface layer slurry, wherein the weight percentage of the shell surface layer slurry is as follows: 15% of silica sol and 75% of zircon powder with the particle size of 300 meshes-1250 meshes are mixed according to the weight ratio, 7% of cobalt aluminate and 0.5% of wetting agent are added, the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, and the mass ratio of the polyoxyethylene ether concentrate to the carboxymethyl cellulose in the wetting agent is 6: 4; adding n-butanol accounting for 0.5 percent of the weight ratio as a defoaming agent, adding distilled water accounting for 1.0 percent of the weight ratio, and adding a reinforcing agent accounting for 1.0 percent of the weight ratio, wherein the reinforcing agent is a mixture of styrene-butadiene latex, acrylic acid and acrylic ester, and the mass ratio of the styrene-butadiene latex to the acrylic acid to the acrylic ester is 4:5: 1; stirring until the silica sol and the powder are well combined together, enabling the viscosity of the slurry to reach 20-25s, and adjusting the pH value to be not less than 8 to obtain surface layer slurry;

C. coating the surface layer slurry on a wax mold, spraying zircon powder with the particle diameter of 100-150 meshes for sand hanging, ensuring that the zircon powder on the surface of the shell is uniformly and comprehensively covered, drying for 2-24 hours in an environment with the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 2-4 hours to prepare the shell surface layer;

D. preparing back layer slurry, wherein the back layer slurry comprises the following components in percentage by weight: mixing 40% of silica sol, 50% of fused quartz powder with the particle size of 300 meshes-1250 meshes and 9% of fused quartz sand with the particle size of 100 meshes-300 meshes in weight ratio, adding 0.5% of wetting agent, wherein the wetting agent is a mixture of polyoxyethylene ether concentrate and carboxymethyl cellulose, and the mass percentage of the polyoxyethylene ether concentrate to the carboxymethyl cellulose is 7: 3; adding n-butanol accounting for 0.5 percent of the weight ratio, stirring until the silica sol and the powder are well combined together, enabling the viscosity of the slurry to reach 10-20s, and adjusting the pH value to be not less than 7 to obtain back layer slurry;

E. coating the back layer slurry on the dried shell surface layer, spraying quartz sand with the grain diameter of 10-50 meshes for sand hanging, drying for 2-24 hours at the room temperature of 21 +/-5 ℃ and the humidity of 35-75%, and air-drying for 0.5-1 hour to prepare a shell layer 2;

F. e, repeating the step E for multiple times to finish the preparation of the shell layers from the 3 rd layer to the 11 th layer; then adjusting the viscosity of the back layer slurry to 15-18s, preparing the last layer of the shell back layer, not hanging sand, and drying for 20 hours in an environment with the room temperature of 21 +/-5 ℃ and the humidity of 35-75% to finish sealing slurry;

G. and (3) dewaxing by adopting steam, and roasting the shell by adopting an electric furnace at the roasting temperature of 900 ℃ for 4-6 hours to obtain the shell finished product.