CN111906245A - Method for preparing ceramic core by molding combined coating - Google Patents
Method for preparing ceramic core by molding combined coating Download PDFInfo
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- CN111906245A CN111906245A CN202010750904.1A CN202010750904A CN111906245A CN 111906245 A CN111906245 A CN 111906245A CN 202010750904 A CN202010750904 A CN 202010750904A CN 111906245 A CN111906245 A CN 111906245A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
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- B22C3/00—Selection of compositions for coating the surfaces of moulds, cores, or patterns
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- B22C9/00—Moulds or cores; Moulding processes
- B22C9/10—Cores; Manufacture or installation of cores
Abstract
The invention aims to provide a preparation process of a ceramic core and a high-temperature alloy cavity structure casting, wherein the preparation process of the ceramic core comprises the following steps: dividing the inner cavity into a left half cavity structure and a right half cavity structure at the maximum section of the inner cavity of the casting, preparing a left half core wax mould and a right half core wax mould which are completely consistent with the inner cavity structure of the casting in shape and size, wherein the inner shape and size corresponding to the concave parts of the left half core wax mould and the right half core wax mould are completely consistent with the outer shape and size of the ceramic core; preparing a left half mold core and a right half mold core by adopting a precision casting process, drying the half mold cores, dewaxing and roasting, trimming the maximum sections of the left half mold core and the right half mold core after sintering, and reserving negative tolerances on a left trimming surface and a right trimming surface respectively; combining the left half-die ceramic core and the right half-die ceramic core into an integral ceramic core by adopting an adhesive, and then drying for 4-8 hours to obtain the ceramic core for the high-temperature alloy casting. The method can improve the comprehensive performance of the ceramic core, simplify the preparation process and procedure, ensure the matching of the core and the mould shell and reduce the casting cost.
Description
Technical Field
The invention belongs to the technical field of high-temperature alloy precision casting, and particularly provides a preparation method of a ceramic core.
Background
High-temperature alloy precision castings are widely applied to the fields of power generation, power industry and the like, the castings generally have complex inner cavity structures, can not be directly prepared by adopting the traditional precision casting process, generally need to adopt a ceramic core to form the inner cavity structures, then adopt a chemical method to remove the core, and finally form the cavity of the castings.
At present, most ceramic cores are alumina-based or silica-based materials, powder particles are fine (larger than 200 meshes), the ceramic cores are prepared by adopting powder mixing, slurry preparation, injection molding and sintering processes, the process is complicated and long, and certain process difficulty and defects exist, such as easy deformation of the cores in the injection molding and sintering processes, large shrinkage of the cores after sintering, and the like, which cause size out-of-tolerance or disqualification. In addition, in the use process, the ceramic core and the mould shell have larger performance difference, so that the core is bent or broken and the like, and the cost rejection rate of castings is obviously improved. For a casting with a structure with a plurality of small through hole sections and a large concave cavity, the accurate forming of an inner cavity cannot be guaranteed by a common precision casting process. The technology for forming the core by the normal coating, sanding and the like adopted in the literature (coating cored precision casting hollow blade casting, pages 11-13, special casting and non-ferrous alloy, first period 1994) has certain limitations, such as only preparing the core with a non-narrow inner cavity, requiring that the cooling channel in the casting is in a straight-through shape and has no circuitous and tortuous, and the length of the inner cavity is shorter than 100mm, otherwise, the technology cannot ensure that the core is coated on the central part. At the same time, the corundum type core is very difficult to remove after casting. The process of the above document does not allow the production of castings having a plurality of small through-hole cross-sections and a large concave-interior cavity structure. The use of injection molding processes to produce ceramic cores is inefficient, costly, and performance-limiting, and it is therefore necessary to develop a new process for producing such structural castings.
Disclosure of Invention
The invention aims to provide a novel preparation process of a ceramic core and a high-temperature alloy cavity structure casting, which aims to improve the comprehensive performance of the ceramic core (especially the core with a plurality of small through hole sections and a large concave cavity structure), simplify the preparation process and process, ensure the matching of the core and a mould shell and reduce the casting cost.
The technical scheme of the invention is as follows:
a method for preparing a ceramic core by molding combined coating is characterized by comprising the following specific preparation steps:
1) preparing a left half-core wax mould and a right half-core wax mould:
the inner cavity of the casting to be prepared comprises a plurality of through holes and an inwards concave inner cavity, the inner cavity is divided into a left half cavity structure and a right half cavity structure at the maximum section of the inner cavity of the casting, and a left half core wax mould and a right half core wax mould which are completely consistent with the inner cavity structure shape and size of the casting are prepared, wherein the inner shape size corresponding to the concave parts of the left half core wax mould and the right half core wax mould is completely consistent with the outer shape structure size of the ceramic core;
2) preparing a left half model core and a right half model core:
preparing core slurry, preparing a left half mold core and a right half mold core by adopting a precision casting process, drying the half mold cores, dewaxing and roasting, trimming the maximum cross sections of the left half mold core and the right half mold core after sintering, and reserving negative tolerances h1 and h2 on the left trimming surface and the right trimming surface respectively;
3) preparing an integral ceramic core:
combining the left half-die ceramic core and the right half-die ceramic core into an integral ceramic core by adopting an adhesive, wherein the thickness H of the adhesive layer is the sum of left and right negative tolerance numerical values, and H is H1+ H2, and then drying in the air for 4-8 hours to obtain the ceramic core for the high-temperature alloy casting.
As a preferred technical scheme:
the inner cavity of the casting contains a plurality of through holes, wherein the aperture of each through hole
Or the side length a is not less than 2mm and not more than the diameter of the inner concave cavity
Or the minimum of the side length b; the height of the through-hole (i.e., the radial distance between both ends of the through-hole) L1 is not less than 2 mm. Diameter of the inner concave cavity
Or the minimum value of the side length b is 5mm, the maximum value is 100mm, and the height L of the inner cavity of the casting is 20-300 mm.
In the step 1), the left half-core wax mould and the right half-core wax mould are prepared by adopting an injection molding process, wherein the injection pressure is 3-5 atmospheric pressures, the injection time is 10-60 seconds, and the pressure maintaining time is 10-60 seconds.
In the step 2), the preparation process of the left and right half mold cores comprises the following steps:
the coating is prepared from mixed powder of quartz glass powder and zircon powder and silica sol, wherein the mass ratio of the quartz glass powder to the zircon powder is (60-90%): (10-40%), the mass ratio of the mixed powder to the silica sol is (75-80%): (20-25%), the granularity of the quartz glass powder is 400-400 meshes, the granularity of the zircon powder is 200-400 meshes, the concentration of the silica sol is 30-35%, and the radius of the silica sol is 5-10 nm;
the sanding material is quartz sand with the granularity of 24-80 meshes; the first layer is a coating layer, and the drying time is 4-8 hours at room temperature; the second layer of coating is sanded by 80 meshes, and the drying time is 4-8 hours; the third layer of coating is sanded by 60 meshes, and the drying time is 4-8 hours; the fourth layer of coating is sanded by 60 meshes, and the drying time is 4-8 hours; a fifth layer of coating is sanded for 24 to 36 meshes, and the drying time is 4 to 8 hours; drying the sixth coating layer for 4-8 hours;
drying and then carrying out dewaxing treatment, wherein steam dewaxing is adopted for dewaxing, the steam pressure is 6-8 atmospheric pressures, and the time is 5-15 seconds; and roasting at 850-1050 ℃ for 4-6 hours after dewaxing.
In the step 2), the value ranges of the left and right trimming surfaces reserved with negative tolerances h1 and h2 are 0.2-0.5 mm.
The adhesive in the step 3) is completely consistent with the coating components used for preparing the core.
The invention also provides a preparation method of the high-temperature alloy casting, which is characterized in that the integral ceramic core is prepared by the method, the integral ceramic core is dried and then is subjected to wax pattern molding after being detected to be qualified, and then the mould shell is prepared by a precision casting shell-making process; casting or directional solidification is carried out after the mould shell is sintered, then shell cleaning is carried out, and a high-temperature alloy casting with an inner cavity structure is obtained after a chemical decoring procedure.
As a preferred technical scheme:
and (3) placing the combined ceramic core into a mold for casting wax mold molding, wherein the wax mold is formed by injection molding, the injection pressure is 3-5 atmospheric pressures, the injection time is 10-60 seconds, and the pressure maintaining time is 10-60 seconds.
The casting mould shell is prepared by adopting a precision casting process:
the coating is prepared from zircon powder and silica sol, and the mass ratio of the zircon powder to the silica sol is (75-80%): (20-25%), zircon powder of 320 meshes, silica sol concentration of 30-35% and colloidal particle radius of 5-10 nm; the sanding material is quartz sand with the granularity of 24-80 meshes; the first layer is a coating layer, and the drying time is 4-8 hours at room temperature; the second layer of coating is sanded by 80 meshes, and the drying time is 4-8 hours; the third layer of coating is sanded by 60 meshes, and the drying time is 4-8 hours; the fourth layer of coating is sanded by 60 meshes, and the drying time is 4-8 hours; a fifth layer of coating is sanded for 24 to 36 meshes, and the drying time is 4 to 8 hours; drying the sixth coating layer for 4-8 hours; drying and then carrying out dewaxing treatment, wherein steam dewaxing is adopted for dewaxing, the steam pressure is 6-8 atmospheric pressures, and the time is 5-15 seconds; and roasting at 850-1050 ℃ for 4-6 hours after dewaxing.
The method is suitable for the following alloy materials:
if the alloy material is common casting high-temperature alloy such as K438, K418, K452 and the like, the casting pouring temperature is 1480 and 1550 ℃, and the pouring time is 10-50 seconds;
for example, the alloy material is oriented or single crystal high temperature alloy such as DZ125, DD403, DD6, DD10, DD33, etc., the casting pouring temperature is 1500-.
In the invention, the casting needs to be subjected to depoling treatment after the shell is cleaned, a depoling medium is an aqueous solution of sodium hydroxide or potassium hydroxide, the concentration is 30-45%, the temperature is 160-190 ℃, the pressure is 0.3-0.8MPa, and the time is 8-20 hours, then acid neutralization cleaning is carried out, and finally the casting is obtained after drying.
The invention has the following beneficial effects:
1. the invention divides the inner cavity into a left half cavity structure and a right half cavity structure at the maximum cross section of the inner cavity of the casting containing a plurality of small through holes, respectively prepares wax molds which are completely opposite to the appearance structures of the two half cavities, then adopts a coating shell making process to prepare a half cavity ceramic core, and then adopts an adhesive to combine the left half cavity ceramic core and the right half cavity ceramic core into an integral ceramic core, thereby effectively solving the problem that the accurate molding of the inner cavity can not be ensured for the casting with a plurality of small through hole cross sections and a large concave cavity structure in the prior art.
2. The method is simple, efficient and low in cost, and ensures the removability, the dimensional stability and the performance matching of the ceramic core and the formwork.
Drawings
FIG. 1 is a schematic view of a casting construction.
FIG. 2 is a schematic diagram of the process of the present invention.
Fig. 3 right half core wax pattern.
Fig. 4 right half core.
FIG. 5 shows a cross-sectional cavity of the casting.
Reference numerals: 1. the casting comprises a casting body 2, a casting inner cavity, 3, a left half-core wax mould, 4, a right half-core wax mould, 5, a left half-core, 6, a right half-core, 7, an integral core, 8, a casting wax mould, 9, a mould shell, 10 and a mould shell after dewaxing.
Detailed Description
Example 1
1) The casting inner cavity comprises a plurality of through holes, the diameter of each through hole is 2mm, the height of each through hole (namely the radial distance between two ends of each through hole) is 2mm, the maximum diameter size of the concave inner cavity is 50mm, and the height of the casting inner cavity is 150 mm. And (3) parting at the maximum section of the inner cavity structure of the casting to prepare left and right half-core wax molds (see figure 3) which are completely consistent with the shape and the size of the inner cavity structure of the casting, wherein the inner shape and the size corresponding to the concave parts of the left and right wax molds are completely consistent with the shape and the size of the ceramic core. The injection molding is adopted for preparation, the injection pressure is 3 atmospheric pressures, the injection time is 10 seconds, and the pressure maintaining time is 10 seconds.
2) Preparing a core slurry coating, wherein the coating is prepared from mixed powder of quartz glass powder and zircon powder and silica sol, and the mass ratio of the quartz glass powder to the zircon powder is 70%: 30 percent, and the mass ratio of the mixed powder to the silica sol is 75 percent: 25 percent, the granularity of quartz glass powder is 400 meshes, the granularity of zircon powder is 200 meshes, the concentration of silica sol is 35 percent, and the radius of colloidal particles is 5 nm; preparing a left half mold core and a right half mold core by adopting a precision casting process, wherein the sanding material is quartz sand; the first layer is a coating layer, and the drying time is 4 hours at room temperature; a second layer of coating is sanded by 80 meshes, and the drying time is 4 hours; the third layer of coating is sanded by 60 meshes, and the drying time is 4 hours; the fourth layer of coating is sanded by 60 meshes, and the drying time is 4 hours; the fifth layer of coating is sanded by 36 meshes, and the drying time is 4 hours; drying the sixth coating layer for 4 hours; drying and then carrying out dewaxing treatment, wherein steam dewaxing is adopted for dewaxing, and the steam pressure is 6 atmospheric pressures for 5 seconds; roasting the mold core after dewaxing, wherein the roasting temperature is 950 ℃, and the roasting time is 4 hours; and (4) trimming the left and right half model cores, and reserving negative tolerance of 0.5mm at the maximum sections of the left and right half model cores respectively.
3) The thickness of the bonding layer is controlled to be 1mm by utilizing a tool, the left half mold core and the right half mold core (shown in figure 4) are combined into an integral ceramic core by adopting an adhesive, the adhesive and the coating used for preparing the core have the same components, and then the integral ceramic core is dried in air for 4 hours.
4) After drying, putting the qualified integral ceramic core into a mould for casting wax mould molding, wherein the wax mould is formed by injection molding, the injection pressure is 3 atmospheric pressures, the injection time is 10 seconds, and the pressure maintaining time is 30 seconds; then preparing a mould shell through a precision casting shell manufacturing process; the coating is prepared from zircon powder and silica sol, and the mass ratio of the zircon powder to the silica sol is 75%: 25 percent, 320 meshes of zircon powder, 35 percent of silica sol concentration and 5nm of colloidal particle radius; the sanding material is quartz sand; the first layer is a coating layer, and the drying time is 4 hours at room temperature; a second layer of coating is sanded by 80 meshes, and the drying time is 4 hours; the third layer of coating is sanded by 60 meshes, and the drying time is 4 hours; the fourth layer of coating is sanded by 60 meshes, and the drying time is 4 hours; the fifth layer of coating is sanded by 36 meshes, and the drying time is 4 hours; drying the sixth coating layer for 4 hours; and (3) carrying out dewaxing treatment after drying, wherein steam dewaxing is adopted for dewaxing, and the steam pressure is 6 atmospheric pressures for 10 seconds.
5) Roasting at 950 ℃ for 4 hours after dewaxing; casting pouring is carried out after the mould shell is sintered, the casting pouring temperature is 1500 ℃, the pouring time is 10 seconds, and the alloy material is K438 cast high-temperature alloy; and (3) cleaning the shell after pouring, performing core removal treatment after the casting is cleaned, wherein the core removal medium is an aqueous solution of sodium hydroxide, the concentration of the aqueous solution is 30%, the temperature is 190 ℃, the pressure is 0.6MPa, the time is 12 hours, then performing acid neutralization cleaning, and finally drying to obtain the casting, wherein the formed inner cavity is shown in figure 5.
Example 2
1) The casting inner cavity comprises a plurality of through holes, the diameter of each through hole is 10mm, the height of each through hole is 12mm, the maximum diameter of the concave inner cavity is 50mm, and the height of the casting inner cavity is 300 mm. And parting the maximum section of the inner cavity structure of the casting to prepare a left half core wax mould and a right half core wax mould which are completely consistent with the shape and the size of the inner cavity structure of the casting, wherein the inner shape and the size corresponding to the concave parts of the left wax mould and the right wax mould are completely consistent with the shape and the size of the ceramic core. The injection molding is adopted for preparation, the injection pressure is 3 atmospheric pressures, the injection time is 10 seconds, and the dwell time is 20 seconds.
2) Preparing a core slurry coating, wherein the coating is prepared from mixed powder of quartz glass powder and zircon powder and silica sol, and the mass ratio of the quartz glass powder to the zircon powder is 90%: 10 percent, and the mass ratio of the mixed powder to the silica sol is 80 percent: 20 percent, the granularity of quartz glass powder is 600 meshes, the granularity of zircon powder is 400 meshes, the concentration of silica sol is 35 percent, and the radius of colloidal particles is 10 nm; preparing a left half mold core and a right half mold core by adopting a precision casting process, wherein a sanding material is quartz sand, a first layer is a coating layer, and the drying time is 6 hours at room temperature; a second layer of coating is sanded by 80 meshes, and the drying time is 6 hours; the third layer of coating is sanded by 60 meshes, and the drying time is 6 hours; the fourth layer of coating is sanded by 60 meshes, and the drying time is 8 hours; a fifth layer of coating is sanded by 24 meshes, and the drying time is 8 hours; drying the sixth coating layer for 8 hours; drying and then carrying out dewaxing treatment, wherein steam dewaxing is adopted for dewaxing, the steam pressure is 8 atmospheric pressures, and the time is 5 seconds; roasting the core after dewaxing, wherein the roasting temperature is 1050 ℃ and the roasting time is 6 hours; and (4) trimming the left and right half model cores, and reserving negative tolerance of 0.2mm and 0.5mm at the maximum cross sections of the left and right half model cores respectively.
3) The thickness of the bonding layer is controlled to be 0.7mm by utilizing a tool, the left half mold core and the right half mold core are combined into an integral ceramic core by adopting an adhesive, the adhesive and the coating used for preparing the ceramic core have the same components completely, and then the ceramic core is dried in the air for 4 hours.
4) After drying, putting the qualified integral ceramic core into a mould to carry out wax mould molding on the casting, wherein the wax mould is formed by injection, the injection pressure is 5 atmospheric pressures, the injection time is 20 seconds, and the pressure maintaining time is 60 seconds; then preparing a mould shell through a precision casting shell manufacturing process; the coating is prepared from zircon powder and silica sol, and the mass ratio of the zircon powder to the silica sol is 80%: 20 percent, 320 meshes of zircon powder, 35 percent of silica sol concentration and 10nm of colloidal particle radius; the sanding material is quartz sand; the first layer is a coating layer, and the drying time is 8 hours at room temperature; a second layer of coating is sanded by 80 meshes, and the drying time is 8 hours; the third layer of coating is sanded by 60 meshes, and the drying time is 8 hours; the fourth layer of coating is sanded by 60 meshes, and the drying time is 8 hours; a fifth layer of coating is sanded by 24 meshes, and the drying time is 8 hours; drying the sixth coating layer for 8 hours; and (3) drying and then carrying out dewaxing treatment, wherein steam dewaxing is adopted for dewaxing, and the steam pressure is 8 atmospheric pressures for 5 seconds.
5) Roasting at 1050 ℃ for 6 hours after dewaxing; casting pouring is carried out after the mould shell is sintered, the casting pouring temperature is 1520 ℃, the pouring time is 10 seconds, and the alloy material is K418 cast high-temperature alloy; and (3) cleaning the shell after pouring, performing core removal treatment after the casting is cleaned, wherein the core removal medium is an aqueous solution of potassium hydroxide, the concentration of the aqueous solution is 30%, the temperature of the aqueous solution is 180 ℃, the pressure of the aqueous solution is 0.6MPa, the time of the aqueous solution is 20 hours, then performing acid neutralization cleaning, and finally drying to obtain the casting.
Example 3
1) The inner cavity of the casting comprises a plurality of through holes, the side length of each through hole is 20mm, the height of each through hole is 20mm, the maximum diameter of the inner concave cavity is 100mm, and the height of the inner cavity of the casting is 100 mm. And parting the maximum section of the inner cavity structure of the casting to prepare left and right half-core wax molds which are completely consistent with the shape and the size of the inner cavity structure of the casting, wherein the inner shape and the size corresponding to the concave parts of the left and right wax molds are completely consistent with the outer shape and the size of the ceramic core. The injection molding is adopted for preparation, the injection pressure is 5 atmospheric pressures, the injection time is 60 seconds, and the pressure maintaining time is 60 seconds.
2) Preparing a core slurry coating, wherein the coating is prepared from mixed powder of quartz glass powder and zircon powder and silica sol, and the mass ratio of the quartz glass powder to the zircon powder is 60%: 40%, and the mass ratio of the mixed powder to the silica sol is 75%: 25 percent, the granularity of quartz glass powder is 400 meshes, the granularity of zircon powder is 300 meshes, the concentration of silica sol is 30 percent, and the radius of colloidal particles is 5 nm; preparing a left half mold core and a right half mold core by adopting a precision casting process, wherein the sanding material is quartz sand; the first layer is a coating layer, and the drying time is 4 hours at room temperature; a second layer of coating is sanded by 80 meshes, and the drying time is 4 hours; the third layer of coating is sanded by 60 meshes, and the drying time is 4 hours; the fourth layer of coating is sanded by 60 meshes, and the drying time is 4 hours; the fifth layer of coating is sanded by 24 meshes, and the drying time is 4 hours; drying the sixth coating layer for 8 hours; drying and then carrying out dewaxing treatment, wherein steam dewaxing is adopted for dewaxing, the steam pressure is 6 atmospheric pressures, and the time is 15 seconds; roasting the mold core after dewaxing, wherein the roasting temperature is 850 ℃, and the roasting time is 6 hours; and (4) trimming the left and right half model cores, and reserving negative tolerance of 0.5mm at the maximum sections of the left and right half model cores respectively.
3) The thickness of the bonding layer is controlled to be 1mm by utilizing a tool, the left half mold core and the right half mold core are combined into an integral ceramic core by adopting an adhesive, the adhesive and the coating used for preparing the cores are completely consistent in composition, and then the integral ceramic core is dried in the air for 8 hours.
4) After drying, putting the qualified integral ceramic core into a mould for wax mould molding of a casting, wherein the wax mould is formed by injection, the injection pressure is 3 atmospheric pressures, the injection time is 60 seconds, and the pressure maintaining time is 60 seconds; then preparing a mould shell through a precision casting shell manufacturing process; the coating is prepared from zircon powder and silica sol, and the mass ratio of the zircon powder to the silica sol is 75%: 25 percent, 320 meshes of zircon powder, 35 percent of silica sol concentration and 10nm of colloidal particle radius; the sanding material is quartz sand; the first layer is a coating layer, and the drying time is 8 hours at room temperature; a second layer of coating is sanded by 80 meshes, and the drying time is 8 hours; the third layer of coating is sanded by 60 meshes, and the drying time is 8 hours; the fourth layer of coating is sanded by 60 meshes, and the drying time is 8 hours; a fifth layer of coating is sanded by 36 meshes, and the drying time is 8 hours; drying the sixth coating layer for 8 hours; and (3) drying and then carrying out dewaxing treatment, wherein steam dewaxing is adopted for dewaxing, and the steam pressure is 8 atmospheric pressures for 15 seconds.
5) Roasting at 1050 ℃ for 4 hours after dewaxing; the pouring temperature of the directional alloy casting is 1500 ℃, the drawing speed is 1mm/min, and the alloy is DD403 single crystal high-temperature alloy; and (3) removing the shell after directional solidification, performing core removal treatment after the shell of the casting is removed, wherein a core removal medium is an aqueous solution of potassium hydroxide, the concentration of the aqueous solution is 40%, the temperature of the aqueous solution is 190 ℃, the pressure of the aqueous solution is 0.8MPa, the time of the aqueous solution is 8 hours, then performing acid neutralization cleaning, and finally drying to obtain the casting.
Example 4
1) The inner cavity of the casting comprises a plurality of through holes, the side length of each through hole is 2mm, the height of each through hole is 6mm, the maximum diameter of the inner concave cavity is 20mm, and the height of the inner cavity of the casting is 20 mm. And parting the maximum section of the inner cavity structure of the casting to prepare a left half core wax mould and a right half core wax mould which are completely consistent with the shape and the size of the inner cavity structure of the casting, wherein the inner shape and the size corresponding to the concave parts of the left wax mould and the right wax mould are completely consistent with the shape and the size of the ceramic core. The injection molding is adopted for preparation, the injection pressure is 4 atmospheric pressures, the injection time is 20 seconds, and the dwell time is 20 seconds.
2) Preparing a core slurry coating, wherein the coating is prepared from mixed powder of quartz glass powder and zircon powder and silica sol, and the mass ratio of the quartz glass powder to the zircon powder is 90%: 10 percent, and the mass ratio of the mixed powder to the silica sol is 80 percent: 20 percent, the granularity of quartz glass powder is 400 meshes, the granularity of zircon powder is 200 meshes, the concentration of silica sol is 30 percent, and the radius of colloidal particles is 5 nm; preparing a left half mold core and a right half mold core by adopting a precision casting process, wherein a sanding material is quartz sand, a first layer is a coating layer, and the drying time is 6 hours at room temperature; a second layer of coating is sanded by 80 meshes, and the drying time is 6 hours; the third layer of coating is sanded by 60 meshes, and the drying time is 6 hours; the fourth layer of coating is sanded by 60 meshes, and the drying time is 6 hours; a fifth layer of coating is sanded by 36 meshes, and the drying time is 8 hours; drying the sixth coating layer for 8 hours; drying and then carrying out dewaxing treatment, wherein steam dewaxing is adopted for dewaxing, the steam pressure is 8 atmospheric pressures, and the time is 5 seconds; roasting the mold core after dewaxing, wherein the roasting temperature is 850 ℃, and the roasting time is 5 hours; and (4) trimming the half mold cores of the left mold core and the right mold core, and reserving negative tolerance of 0.4mm at the maximum sections of the left mold core and the right mold core respectively.
3) The thickness of the bonding layer is controlled to be 0.8mm by utilizing a tool, the left half mold core and the right half mold core are combined into an integral ceramic core by adopting an adhesive, the adhesive and the coating used for preparing the cores are completely consistent in composition, and then the integral ceramic core is dried in the air for 8 hours.
4) After drying, putting the qualified integral ceramic core into a mould to carry out wax mould molding on the casting, wherein the wax mould is formed by injection, the injection pressure is 5 atmospheric pressures, the injection time is 40 seconds, and the pressure maintaining time is 20 seconds; then preparing a mould shell through a precision casting shell manufacturing process; the coating is prepared from zircon powder and silica sol, and the mass ratio of the zircon powder to the silica sol is 75%: 25 percent, 320 meshes of zircon powder, 30 percent of silica sol concentration and 5nm of colloidal particle radius; the sanding material is quartz sand, the first layer is a coating layer, and the drying time is 8 hours at room temperature; a second layer of coating is sanded by 80 meshes, and the drying time is 8 hours; the third layer of coating is sanded by 60 meshes, and the drying time is 8 hours; the fourth layer of coating is sanded by 60 meshes, and the drying time is 8 hours; a fifth layer of coating is sanded by 36 meshes, and the drying time is 8 hours; drying the sixth coating layer for 8 hours; and (3) drying and then carrying out dewaxing treatment, wherein steam dewaxing is adopted for dewaxing, and the steam pressure is 8 atmospheric pressures for 15 seconds.
5) Roasting at 1050 ℃ for 4 hours after dewaxing; the pouring temperature of the directional alloy casting is 1500 ℃, the drawing speed is 6mm/min, and the alloy is DZ125 directional high-temperature alloy; and (3) removing the shell after directional solidification, performing core removal treatment after the shell of the casting is removed, wherein the core removal medium is an aqueous solution of sodium hydroxide, the concentration of the aqueous solution is 30%, the temperature is 190 ℃, the pressure is 0.5MPa, the time is 20 hours, then performing acid neutralization cleaning, and finally drying to obtain the casting.
The invention is not the best known technology.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (10)
1. A method for preparing a ceramic core by molding combined coating is characterized by comprising the following specific preparation steps:
1) preparing a left half-core wax mould and a right half-core wax mould:
the inner cavity of the casting to be prepared comprises a plurality of through holes and an inwards concave inner cavity, the inner cavity is divided into a left half cavity structure and a right half cavity structure at the maximum longitudinal section of the inner cavity of the casting, and a left half core wax mould and a right half core wax mould which are completely consistent with the inner cavity structure shape and size of the casting are prepared, wherein the inner shape size corresponding to the concave parts of the left half core wax mould and the right half core wax mould is completely consistent with the outer shape structure size of the ceramic core;
2) preparing a left half model core and a right half model core:
preparing core slurry, preparing a left half mold core and a right half mold core by adopting a precision casting process, drying the half mold cores, dewaxing and roasting, trimming the maximum cross sections of the left half mold core and the right half mold core after sintering, and reserving negative tolerances h1 and h2 on the left trimming surface and the right trimming surface respectively;
3) preparing an integral ceramic core:
combining the left half-die ceramic core and the right half-die ceramic core into an integral ceramic core by adopting an adhesive, wherein the thickness H of the adhesive layer is the sum of left and right negative tolerance numerical values, and H is H1+ H2, and then drying in the air for 4-8 hours to obtain the ceramic core for the high-temperature alloy casting.
2. The method for forming and preparing the combined coating of the ceramic core according to claim 1, wherein the method comprises the following steps: diameter of through hole of the casting
Or the side length a is not less than 2mm and not more than the diameter of the concave inner cavity
Or the minimum of the side length b.
3. The method for forming and preparing the combined coating of the ceramic core according to claim 1, wherein the method comprises the following steps: the diameter of the concave inner cavity of the casting
Or the minimum value of the side length b is 5mm, the maximum value is 100mm,the height L of the inner cavity of the casting is 20-300 mm.
4. The method for forming and preparing the combined coating of the ceramic core according to claim 1, wherein the method comprises the following steps: in the step 1), the left half-core wax mould and the right half-core wax mould are prepared by adopting an injection molding process, wherein the injection pressure is 3-5 atmospheric pressures, the injection time is 10-60 seconds, and the pressure maintaining time is 10-60 seconds.
5. The method for preparing the ceramic core by combined coating molding according to claim 1, wherein in the step 2), the preparation process of the left and right half mold cores comprises the following steps:
the coating is prepared from mixed powder of quartz glass powder and zircon powder and silica sol, wherein the mass ratio of the quartz glass powder to the zircon powder is 60-90%: 10-40%, and the mass ratio of the mixed powder to the silica sol is 75-80%: 20-25%, the granularity of the quartz glass powder is 400-400 meshes, the granularity of the zircon powder is 200-400 meshes, the concentration of the silica sol is 30-35%, and the radius of the silica sol is 5-10 nm;
the sanding material is quartz sand with the granularity of 24-80 meshes; the first layer is a coating layer, and the drying time is 4-8 hours at room temperature; the second layer of coating is sanded by 80 meshes, and the drying time is 4-8 hours; the third layer of coating is sanded by 60 meshes, and the drying time is 4-8 hours; the fourth layer of coating is sanded by 60 meshes, and the drying time is 4-8 hours; a fifth layer of coating is sanded for 24 to 36 meshes, and the drying time is 4 to 8 hours; drying the sixth coating layer for 4-8 hours;
drying and then carrying out dewaxing treatment, wherein steam dewaxing is adopted for dewaxing, the steam pressure is 6-8 atmospheric pressures, and the time is 5-15 seconds; and roasting at 850-1050 ℃ for 4-6 hours after dewaxing.
6. The method for forming and preparing the combined coating of the ceramic core according to claim 1, wherein the method comprises the following steps: in the step 2), negative tolerances h1 and h2 are reserved on the left and right trimming surfaces, and the value range is 0.2-0.5 mm.
7. A method of forming a composite coating for a ceramic core as claimed in claim 1 or 5, wherein: the adhesive in the step 3) is completely consistent with the coating components used for preparing the core.
8. The preparation method of the high-temperature alloy casting is characterized by comprising the following specific steps of:
1) preparing a left half-core wax mould and a right half-core wax mould:
dividing the inner cavity into a left half cavity structure and a right half cavity structure at the maximum section of the inner cavity of the casting, and preparing a left half core wax mould and a right half core wax mould which are completely consistent with the inner cavity structure of the casting in shape and size, wherein the inner shape and size corresponding to the concave parts of the left half core wax mould and the right half core wax mould are completely consistent with the outer shape and size of the ceramic core;
2) preparing a left half model core and a right half model core:
preparing core slurry, preparing a left half mold core and a right half mold core by adopting a precision casting process, drying the half mold cores, dewaxing and roasting, trimming the maximum cross sections of the left half mold core and the right half mold core after sintering, and reserving negative tolerances h1 and h2 on the left trimming surface and the right trimming surface respectively;
3) preparing an integral ceramic core:
combining the left half-die ceramic core and the right half-die ceramic core into an integral ceramic core by adopting an adhesive, wherein the thickness H of the adhesive layer is the sum of left and right negative tolerance numerical values, and H is H1+ H2, and then drying in the air for 4-8 hours to obtain the ceramic core for the high-temperature alloy casting;
4) preparing a formwork:
drying the integral ceramic core, detecting to be qualified, carrying out wax mold forming, and preparing the mold shell by adopting a precision casting shell-making process;
5) preparing a high-temperature alloy casting:
casting or directional solidification is carried out after the mould shell is sintered, then shell cleaning is carried out, and a high-temperature alloy casting with an inner cavity structure is obtained after a chemical decoring procedure.
9. A method of making a superalloy casting according to claim 8, wherein: and 4) placing the combined ceramic core into a mold for casting wax mold molding, wherein the wax mold is formed by injection molding, the injection pressure is 3-5 atmospheric pressures, the injection time is 10-60 seconds, and the pressure maintaining time is 10-60 seconds.
10. A method of making a superalloy casting according to claim 8, wherein: in the step 4), the casting mould shell is prepared by adopting a precision casting process:
the coating is prepared from zircon powder and silica sol, and the mass ratio of the zircon powder to the silica sol is 75-80%: 20-25%, zircon powder of 320 meshes, silica sol concentration of 30-35% and colloidal particle radius of 5-10 nm; the sanding material is quartz sand with the granularity of 24-80 meshes; the first layer is a coating layer, and the drying time is 4-8 hours at room temperature; the second layer of coating is sanded by 80 meshes, and the drying time is 4-8 hours; the third layer of coating is sanded by 60 meshes, and the drying time is 4-8 hours; the fourth layer of coating is sanded by 60 meshes, and the drying time is 4-8 hours; a fifth layer of coating is sanded for 24 to 36 meshes, and the drying time is 4 to 8 hours; drying the sixth coating layer for 4-8 hours; drying and then carrying out dewaxing treatment, wherein steam dewaxing is adopted for dewaxing, the steam pressure is 6-8 atmospheric pressures, and the time is 5-15 seconds; and roasting at 850-1050 ℃ for 4-6 hours after dewaxing.
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