CN114535506A - Method for controlling solidification of investment casting magnesium alloy casting and investment casting method - Google Patents
Method for controlling solidification of investment casting magnesium alloy casting and investment casting method Download PDFInfo
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- CN114535506A CN114535506A CN202210441182.0A CN202210441182A CN114535506A CN 114535506 A CN114535506 A CN 114535506A CN 202210441182 A CN202210441182 A CN 202210441182A CN 114535506 A CN114535506 A CN 114535506A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
- B22C9/04—Use of lost patterns
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C3/00—Selection of compositions for coating the surfaces of moulds, cores, or patterns
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/08—Features with respect to supply of molten metal, e.g. ingates, circular gates, skim gates
- B22C9/082—Sprues, pouring cups
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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
- B22D27/04—Influencing the temperature of the metal, e.g. by heating or cooling the mould
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
The invention relates to the technical field of casting processes, in particular to a method for controlling solidification of an investment casting magnesium alloy casting and an investment casting method. The method for controlling solidification of the investment casting magnesium alloy casting comprises the following steps: A. adding a material with a heat conductivity coefficient less than 0.002W/(m.K) at a transition layer position of a formwork corresponding to the thin-wall part of the casting; the thickness of the thin-wall part of the casting is less than 5 mm; B. adopting a silicon carbide cooling element at the position of the mould shell corresponding to the thick-wall part of the casting; the thickness of the thick-wall part of the casting is more than 20 mm; C. coating ceramic glaze on the outer surfaces of the dead head and part of the pouring gate; the coating thickness of the ceramic glaze is 0.2-0.3 mm; D. and pouring the alloy into a mold shell, and performing oil quenching on the mold shell when the temperature of the mold shell is 500-550 ℃ after pouring. The method is beneficial to improving the structure uniformity, the mechanical property and the like of the magnesium alloy casting.
Description
Technical Field
The invention relates to the technical field of casting processes, in particular to a method for controlling solidification of an investment casting magnesium alloy casting and an investment casting method.
Background
Magnesium alloy has been widely used in recent years as a structural material because of its low specific gravity, high specific strength, high specific stiffness, good thermal conductivity, good electrical conductivity, good machinability, excellent vibration damping properties and electromagnetic shielding properties, and easy machine-shaping and recycling. The investment casting process is one of the main preparation modes of magnesium alloy castings. The magnesium alloy casting with high size precision, smooth surface and complex shape can be cast by adopting an investment casting process.
Investment casting is a near-net-shape production process, which comprises the preparation of a wax film, the coating of refractory materials, dewaxing, smelting, pouring, demoulding and the post-treatment. The traditional investment casting method generally controls the solidification balance mainly by the size of a dead head; the position with large riser and thick wall of the casting is solidified slowly, and the position with thin wall of the casting is solidified quickly; the solidification speed mainly depends on controlling the integral temperature of the shuttering and the temperature of the poured alloy liquid. For magnesium alloy, the magnesium alloy has the characteristics of small hot melting, low density and high heat loss; therefore, when the magnesium alloy casting is prepared according to the traditional investment casting process, the problems of cold shut and insufficient casting are easily generated at the thin-wall part of the magnesium alloy casting, and the problems of thick structure, low mechanical property, serious looseness, poor feeding effect of a riser and the like are easily generated at the wall thickness part of the magnesium alloy casting.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The invention aims to provide a method for controlling solidification of an investment casting magnesium alloy casting, which is used for completely or partially solving the problems of cold shut, insufficient pouring, poor feeding effect of a riser, large casting structure, low mechanical property, serious looseness and the like caused by different casting solidification speeds in the magnesium alloy investment casting process in the prior art.
The second purpose of the invention is to provide a magnesium alloy investment casting method, which comprises the method for controlling solidification of the investment casting magnesium alloy casting, and the magnesium alloy casting prepared by the method has the characteristics of compact and uniform structure, excellent mechanical property and the like.
In order to achieve the above purpose of the present invention, the following technical solutions are adopted:
the invention provides a method for controlling solidification of investment casting magnesium alloy castings, which comprises the following steps:
A. adding a material with a heat conductivity coefficient less than 0.002W/(m.K) at a position of a transition layer of a formwork corresponding to the thin-wall part of the casting; the thickness of the thin-wall part of the casting is less than 5 mm;
B. adopting a silicon carbide cooling element at the position of the mould shell corresponding to the thick-wall part of the casting; the thickness of the thick-wall part of the casting is more than 20 mm;
C. coating ceramic glaze on the outer surfaces of a riser and a part of a pouring channel of the formwork; the coating thickness of the ceramic glaze is 0.2-0.3 mm;
D. and pouring the alloy into the formwork, and after pouring is finished, performing oil quenching on the whole formwork when the temperature of the formwork is 500-550 ℃.
Furthermore, the thermal conductivity coefficient of the ceramic glaze is 0.04-0.06W/(m.K).
Further, the ceramic glaze comprises, by weight, 55-65 parts of lead oxide, 3-5 parts of borax, 30-35 parts of silicon dioxide and 2-5 parts of aluminum oxide.
Further, the ceramic glaze is SAMYO SCG-607.
Further, the oil quenching time is 5-30 min.
Further, the oil-quenched quenching oil comprises U8132.
Further, the material with the thermal conductivity coefficient less than 0.002W/(m.K) comprises one or more of perlite, vermiculite, vitrified micro bubbles and heat preservation cotton.
Further, the silicon carbide cooling element is prepared from the following raw materials in parts by weight: 70-80 parts of silicon carbide, 5-10 parts of potassium fluoride and 15-20 parts of wax material.
Further, the partial pouring channel is one or more of a main pouring channel, an auxiliary feeding channel, a filling pouring channel and a feeding pouring channel when the casting is poured.
The invention also provides a method for investment casting of magnesium alloy, which comprises the method for controlling solidification of investment casting magnesium alloy castings.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a method for controlling solidification of an investment casting magnesium alloy casting, which increases thermal equilibrium gradient by using heating and heat-insulating materials at a riser and a pouring gate part needing feeding, so that feeding performance is maximized; furthermore, a material with a very low heat conductivity coefficient is added at the position of the mould shell corresponding to the transition layer of the thin-wall part of the magnesium alloy casting, so that the mould filling problem of the thin-wall part of the casting is solved, and the defects of cold shut and insufficient casting of the casting are avoided; silicon carbide cooling elements are used on the thick-wall part of the magnesium alloy casting and the part needing quick cooling, so that the cooling speed is controlled, and the thick-wall quick cooling of the casting is facilitated; after the casting is poured, the whole casting is cooled by oil, the oil can permeate the formwork, the heat conduction is fast, and the casting is fast cooled; the surface of the casting feeding and riser part is coated with a layer of enamel material, so that the enamel material cannot penetrate into a formwork, and has lower heat conduction compared with other parts, thereby playing a good feeding role; the solidification speed of different parts of the casting can be controlled by the method, so that the prepared magnesium alloy casting has the characteristics of compact structure, small grain size, excellent mechanical property and the like.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following detailed description, but those skilled in the art will understand that the following described examples are some, not all, of the examples of the present invention, and are only used for illustrating the present invention, and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The method for controlling solidification of investment casting magnesium alloy castings and the investment casting method according to embodiments of the present invention will be specifically described below.
In some embodiments of the invention there is provided a method of controlling solidification of an investment cast magnesium alloy casting comprising the steps of:
A. adding a material with a heat conductivity coefficient less than 0.002W/(m.K) at a transition layer position of a formwork corresponding to the thin-wall part of the casting; the thickness of the thin-wall part of the casting is less than 5 mm;
B. adopting a silicon carbide cooling element at the position of the mould shell corresponding to the thick-wall part of the casting; the thickness of the thick-wall part of the casting is more than 20 mm;
C. coating ceramic glaze on the outer surfaces of a riser and a part of a pouring channel of the formwork; the coating thickness of the ceramic glaze is 0.2-0.3 mm;
D. and pouring the alloy into the formwork, and performing oil quenching on the whole formwork when the temperature of the formwork is 500-550 ℃ after pouring.
The magnesium alloy is an alloy formed by adding other elements into magnesium as a base, has the characteristics of low specific gravity, high specific strength, high specific rigidity, good thermal conductivity, good electrical conductivity, good machinability, excellent vibration damping property, electromagnetic shielding property and the like, and is more and more widely applied in recent years. However, in the process of casting the magnesium alloy casting by using the investment, because the magnesium alloy has the characteristics of small hot melting, low density and high heat loss, the solidification speeds of different positions of the magnesium alloy casting are different by using the traditional investment casting process, so that the problems of cold shut, insufficient casting, poor riser feeding effect, large and thick casting structure, low mechanical property, serious looseness and the like are easily caused.
According to the method for controlling solidification of the investment casting magnesium alloy casting, the material with very low heat conductivity coefficient is added at the position of the formwork corresponding to the transition layer of the thin-wall part of the casting, so that the thin-wall mold filling problem is solved, and the defects of cold shut and insufficient pouring of the magnesium alloy casting are avoided.
According to the method for controlling solidification of the investment casting magnesium alloy casting, the silicon carbide cooling element is adopted at the position of the formwork corresponding to the thick-wall part of the casting, so that the thick part of the casting can be rapidly cooled, and the problems of shrinkage cavity, looseness and the like caused by slow solidification speed of the thick part of the casting are effectively avoided.
According to the method for controlling solidification of the investment casting magnesium alloy casting, the heating and heat-insulating material is used on the riser and the outer surface of the pouring channel needing to be fed, namely, the enamel material is coated on the riser and the outer surface of the pouring channel needing to be fed, compared with other parts, the method is slow in heat conduction, increases the heat balance gradient, maximizes the feeding performance, plays a good feeding role, and is beneficial to improving the filling performance and the loosening performance.
According to the method for controlling solidification of the investment casting magnesium alloy casting, after the magnesium alloy casting is poured, oil is integrally used for cooling, the oil can permeate the formwork, heat conduction is fast, fast cooling of the casting is facilitated, and the prepared magnesium alloy casting has the characteristics of compact structure, small grain size, excellent mechanical property and the like.
In some embodiments of the invention, the ceramic glaze is typically, but not by way of limitation, applied at a thickness of 0.2mm, 0.21mm, 0.22mm, 0.23mm, 0.24mm, 0.25mm, 0.26mm, 0.27mm, 0.28mm, 0.29mm and 0.3mm, for example.
In some embodiments of the invention, the ceramic glaze has a thermal conductivity of 0.04-0.06W/(m.K); preferably, the ceramic glaze has a thermal conductivity of 0.05W/(m.K).
In some embodiments of the invention, the ceramic glaze comprises 55-65 parts by weight of lead oxide, 3-5 parts by weight of borax, 30-35 parts by weight of silicon dioxide and 2-5 parts by weight of aluminum oxide; preferably, the ceramic glaze comprises 60 parts of lead oxide, 4 parts of borax, 33 parts of silicon dioxide and 3 parts of aluminum oxide in parts by weight.
In some embodiments of the invention, the ceramic glaze is SAMYO SCG-607; SAMYO SCG-607 can be uniformly attached to the surface of the formwork, and has the characteristics of good coating property and low melting point (about 550 ℃).
According to the invention, the enamel material is coated on the outer surfaces of the riser and the pouring gate needing feeding, and is relatively compact, so that quenching oil can be prevented from permeating into a formwork, and the riser has a good feeding effect.
In some embodiments of the invention, the ceramic glaze is applied by brushing.
In some embodiments of the present invention, the oil quenching time is 5 to 30 min.
The oil quenching time is not strictly limited, and is in direct proportion to the casting weight of the magnesium liquid: the time T (S) = pouring weight/10, namely every ten kilograms of weight is taken out according to the cooling time of one minute or according to the cooling of the oil temperature to be below 150 ℃, and the oil inlet temperature is generally 500 ℃ and 550 ℃.
In some embodiments of the invention, the oil quenched quench oil comprises U8132.
According to the method for controlling solidification of the investment casting magnesium alloy casting, the cast mould shell is subjected to oil quenching, and the mould shell can be rapidly cooled in quenching oil, so that finer magnesium alloy grains can be obtained.
In some embodiments of the invention, the material having a thermal conductivity of less than 0.002W/(m · K) comprises one or more of perlite, vermiculite, vitrified micro bubbles and thermal insulating cotton.
In some embodiments of the present invention, a silicon carbide cooling element is prepared from the following raw materials in parts by weight: 70-80 parts of silicon carbide, 5-10 parts of potassium fluoride and 15-20 parts of wax material.
In some embodiments of the present invention, the silicon carbide cooling element is prepared from the following raw materials in parts by weight:
75 parts of silicon carbide, 7 parts of potassium fluoride, 17 parts of paraffin and 1 part of beeswax.
In some embodiments of the present invention, a method of making a silicon carbide cooling element comprises the steps of:
a. grinding 75 parts of silicon carbide (250 meshes) and 7 parts of powdery potassium fluoride in a ball mill for 5 hours to obtain mixed powder, melting wax materials (17 parts of paraffin and 1 part of beeswax) into wax liquid at 110 ℃, slowly adding the mixed powder into the wax liquid, and stirring in the adding process until a pasty mixture is obtained; and (3) putting the paste mixture into a core pressing machine, and pressing to obtain a green blank.
b. And cooling the green blank for 24h, then loading into a pot, coating the green blank with 300-mesh aluminum oxide, and roasting at 1100 ℃ for 8h to obtain a blank.
c. And sequentially carrying out high-temperature strengthening treatment and low-temperature strengthening treatment on the blank to obtain the silicon carbide cooling element.
In some embodiments of the present invention, in a method of manufacturing a silicon carbide cooling element, the high temperature strengthening treatment comprises: completely soaking the blank obtained after roasting in silica sol for 20min until no bubbling occurs, taking out, drying at 25 ℃ for 24h, and then drying at 400 ℃ for 2 h; the low-temperature strengthening treatment comprises the following steps: and completely soaking the blank subjected to the high-temperature strengthening treatment in phenolic resin for 20min until no bubbling occurs, taking out, drying at 25 ℃ for 24h, and then drying at 120 ℃ for 2 h.
In some embodiments of the invention, employing the silicon carbide cooling element comprises bonding the silicon carbide cooling element to a formwork location corresponding to the thick wall portion of the casting; preferably, the bonding comprises bonding with a bonding wax.
In some embodiments of the invention, the partial runners are one or more of a main runner, a secondary feeding runner, a filling runner, and a feeding runner; the type of the partial pouring channel can be selected according to specific practical conditions.
The method for controlling solidification of the investment casting magnesium alloy casting balances the integral solidification speed of the magnesium alloy casting by regulating and controlling the solidification speed of different positions of the magnesium alloy casting, so that the prepared magnesium alloy casting has compact structure and good uniformity, the size of crystal grains is less than 40 mu m, and the magnesium alloy casting has excellent mechanical property.
In some embodiments of the present invention, the magnesium alloy is any one of magnesium aluminum alloy, magnesium zinc alloy and magnesium zirconium alloy, but is not limited thereto, and the rest may be magnesium alloy.
Also provided in some embodiments of the invention is a method of investment casting a magnesium alloy, including the above-described method of controlling solidification of an investment cast magnesium alloy casting.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
The method for controlling solidification of the investment casting magnesium alloy casting provided by the embodiment comprises the following steps:
A. perlite (with the grain diameter of 20 +/-5 meshes) is added at the position of a transition layer of a formwork corresponding to the part of the casting thin wall with the thickness of less than 5 mm;
B. adhering the silicon carbide cooling element to the position of the mould shell (the wax film outer wall of the mould shell) corresponding to the thick wall part of the casting with the thickness of more than 20mm by adopting adhesive wax;
C. coating a layer of ceramic glaze SAMYO SCG-607 with the thickness of 0.25mm on the outer surfaces of a riser and a feeding runner;
D. pouring the alloy into a mould shell, and after pouring, putting the whole mould shell into quenching oil U8132 for oil quenching when the temperature of the mould shell is 500 ℃, wherein the time for oil quenching is 5 min.
The preparation method of the silicon carbide cooling element comprises the following steps:
a. grinding 75 parts of silicon carbide (250 meshes) and 7 parts of powdery potassium fluoride in a ball mill for 5 hours to obtain mixed powder, melting wax materials (17 parts of paraffin and 1 part of beeswax) into wax liquid at 110 ℃, slowly adding the mixed powder into the wax liquid, and stirring in the adding process until a pasty mixture is obtained; and (3) putting the paste mixture into a core pressing machine, and pressing into a green body.
b. And cooling the green blank for 24h, then loading into a pot, coating the green blank with 300-mesh aluminum oxide, and roasting at 1100 ℃ for 8h to obtain a blank.
c. Carrying out high-temperature strengthening treatment and low-temperature strengthening treatment on the blank to obtain a silicon carbide cooling element; wherein, the high-temperature strengthening treatment comprises the following steps: completely soaking the blank obtained after roasting in silica sol for 20min until no bubbling occurs, taking out, drying at 25 ℃ for 24h, and then drying at 400 ℃ for 2 h; the low-temperature strengthening treatment comprises the following steps: and (3) completely soaking the blank subjected to the high-temperature strengthening treatment in phenolic resin for 20min until no bubbling occurs, taking out, drying at 25 ℃ for 24h, and then drying at 120 ℃ for 2 h.
Example 2
The method for controlling solidification of an investment casting magnesium alloy casting provided by the present embodiment is as follows with reference to example 1, except that: in the step C, a layer of ceramic glaze SAMYO SCG-607 with the thickness of 0.2mm is coated on the outer surfaces of a riser and a feeding runner; and D, pouring the alloy into the formwork, and after the pouring is finished, putting the whole formwork into quenching oil U8132 for oil quenching when the temperature of the formwork is 550 ℃, wherein the oil quenching time is 30 min.
Example 3
The method of controlling solidification of an investment cast magnesium alloy casting provided in this example is as in example 1, except that: and step C, brushing a layer of ceramic glaze DZTMY-1 with the thickness of 0.25mm on the outer surfaces of the riser and the feeding runner.
Comparative example 1
The method for controlling solidification of an investment casting magnesium alloy casting provided by the comparative example is as in example 1, except that in step C, a layer of ceramic glaze SAMYO SCG-607 with the thickness of 0.1mm is coated on the outer surfaces of a riser and a feeding runner.
Comparative example 2
The method for controlling solidification of the investment casting magnesium alloy casting provided by the comparative example comprises the following steps:
A. perlite (with the grain diameter of 20 +/-5 meshes) is added at the position of a transition layer of a formwork corresponding to the part of the casting thin wall with the thickness of less than 5 mm;
B. adhering the silicon carbide cooling element to the position of the formwork (the outer wall of the wax film of the formwork) corresponding to the part with the thickness of more than 20mm of the casting by using adhesive wax;
C. and pouring the alloy into a mould shell, and after pouring, putting the whole mould shell into quenching oil U8132 for oil quenching when the temperature of the mould shell is 550 ℃, wherein the time for oil quenching is 5 min.
Comparative example 3
The method for controlling solidification of the investment casting magnesium alloy casting provided by the comparative example comprises the following steps:
A. coating a layer of ceramic glaze SAMYO SCG-607 with the thickness of 0.25mm on the outer surfaces of a riser and a feeding runner;
B. pouring the alloy into a mould shell, and after pouring, putting the whole mould shell into quenching oil U8132 for oil quenching when the temperature of the mould shell is 500 ℃, wherein the time for oil quenching is 5 min.
Comparative example 4
The method for controlling solidification of an investment casting magnesium alloy casting provided by the comparative example is as in example 1, except that in step D, the alloy is poured into a mold shell, and after pouring is completed, air cooling is performed to room temperature.
Test example 1
The manufacturing process of ZM6 magnesium alloy intermediate casing shell castings 1#, 2#, 3#, 4#, 5#, 6# and 7# for the aircraft engine is as follows:
the preparation method of the casting 1# comprises the method for controlling solidification of an investment casting magnesium alloy casting in the embodiment 1, and the preparation method specifically comprises the following steps: 1. preparing a material for preparing a mould shell, pressing a wax piece, adopting bonding wax to bond a silicon carbide cooling element to the position of the mould shell corresponding to the part of the casting with the thickness larger than 20mm (the silicon carbide cooling element is the silicon carbide cooling element in the embodiment 1), combining a pouring system, coating, adding perlite (the grain diameter is 20 +/-5 meshes) to the position of a transition layer of the mould shell corresponding to the part of the casting with the thin wall thickness smaller than 5mm, dewaxing and roasting to obtain the mould shell; 2. coating a layer of ceramic glaze SAMYO SCG-607 with the thickness of 0.25mm on the outer surfaces of a riser and a feeding runner of the formwork; 3. preheating the mould shell (heating the mould shell to 650 ℃ and then cooling to 350 ℃); 4. alloy smelting and casting; 5. after the pouring is finished, when the temperature of the formwork is 500 ℃, putting the whole formwork into quenching oil U8132 for oil quenching, wherein the oil quenching time is 5 min; 6. taking out the casting, removing the formwork, separating the casting system, and carrying out fine modification and heat treatment on the casting to obtain a casting No. 1.
The method for producing casting # 2 includes the method for controlling solidification of an investment casting magnesium alloy casting of example 2, and the specific production method thereof refers to the production method of casting # 1 described above, except that: step 2, brushing a layer of ceramic glaze SAMYO SCG-607 with the thickness of 0.2mm on the outer surfaces of a riser and a feeding runner of the formwork; and 5, after the pouring is finished, when the temperature of the formwork is 550 ℃, putting the whole formwork into quenching oil U8132 for oil quenching, wherein the oil quenching time is 30 min.
The method for producing casting # 3 included the method for controlling solidification of an investment casting magnesium alloy casting of example 3, and the specific production method thereof was referenced to the production method of casting # 1 described above, except that: and 2, brushing a layer of ceramic glaze DZTMY-1 with the thickness of 0.25mm on the outer surfaces of a riser and a feeding runner of the formwork.
The method for producing casting 4# includes the method for controlling solidification of investment casting magnesium alloy casting of comparative example 1, and the specific production method thereof refers to the production method of casting 1# described above, except that: and 2, brushing a layer of ceramic glaze SAMYO SCG-607 with the thickness of 0.1mm on the outer surfaces of a riser and a feeding runner of the formwork.
The preparation method of the casting 5# comprises the method for controlling solidification of the investment casting magnesium alloy casting of the comparative example 2, and the specific preparation method comprises the following steps: 1. preparing a material for preparing a mould shell, pressing a wax piece, adopting bonding wax to bond a silicon carbide cooling element to the position of the mould shell corresponding to the part of the casting with the thickness larger than 20mm (the silicon carbide cooling element is the silicon carbide cooling element in the embodiment 1), combining a pouring system, coating, adding perlite (the grain diameter is 20 +/-5 meshes) to the position of a transition layer of the mould shell corresponding to the part of the casting with the thin wall thickness smaller than 5mm, dewaxing and roasting to obtain the mould shell; 2. preheating the mould shell (heating the mould shell to 650 ℃ and then cooling to 350 ℃); 3. alloy smelting and casting; 4. after the pouring is finished, when the temperature of the formwork is 550 ℃, putting the whole formwork into quenching oil U8132 for oil quenching, wherein the oil quenching time is 5 min; 5. taking out the casting, removing the mould shell, separating the pouring system, and carrying out fine modification and heat treatment on the casting to obtain a casting 5 #.
The method for producing casting 6# includes the method for controlling solidification of investment casting magnesium alloy casting of comparative example 3, and the specific production method thereof refers to the production method of casting 1# described above, except that: step 1, preparing a material for preparing a formwork, and pressing a wax piece, combining a casting system, coating and sanding, dewaxing and roasting to obtain the formwork.
The method for producing casting 7# includes the method for controlling solidification of investment casting magnesium alloy casting of comparative example 4, and the specific production method thereof refers to the production method of casting 1# described above, except that: and 5, after the pouring is finished, air cooling to room temperature.
The magnesium alloy castings 1#, 2#, 3#, 4#, 5#, 6# and 7# are subjected to metallurgical quality and mechanical property tests according to the HB7780 standard, so that the grain size, the porosity grade, the mechanical property (tensile strength) and the casting forming condition of the magnesium alloy castings are obtained, and the results are shown in Table 1. Wherein the loose grade is in accordance with HB7780-2005 standard; the mechanical property (tensile strength) and the grain size are obtained by measuring the position of the casting wall thickness of 50 mm.
TABLE 1
From table 1, it can be seen that the method for controlling solidification of investment casting magnesium alloy castings provided by the invention is beneficial to improving the filling performance, the structure compactness and the mechanical property of the castings, so that the prepared magnesium alloy castings have smaller grain size, more compact structures, good forming, excellent mechanical property and excellent metallurgical quality.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for controlling solidification of an investment casting magnesium alloy casting is characterized by comprising the following steps:
A. adding a material with a heat conductivity coefficient less than 0.002W/(m.K) at a transition layer position of a formwork corresponding to the thin-wall part of the casting; the thickness of the thin-wall part of the casting is less than 5 mm;
B. adopting a silicon carbide cooling element at the position of the mould shell corresponding to the thick-wall part of the casting; the thickness of the thick-wall part of the casting is more than 20 mm;
C. coating ceramic glaze on the outer surfaces of a riser and a part of a pouring channel of the formwork; the coating thickness of the ceramic glaze is 0.2-0.3 mm;
D. and pouring the alloy into the formwork, and after pouring is finished, performing oil quenching on the whole formwork when the temperature of the formwork is 500-550 ℃.
2. The method for controlling solidification of an investment casting magnesium alloy casting according to claim 1, wherein the ceramic glaze has a thermal conductivity of 0.04-0.06W/(m-K).
3. The method for controlling solidification of an investment casting magnesium alloy casting according to claim 1, wherein the ceramic glaze comprises 55-65 parts by weight of lead oxide, 3-5 parts by weight of borax, 30-35 parts by weight of silicon dioxide and 2-5 parts by weight of aluminum oxide.
4. The method of controlling solidification of an investment casting magnesium alloy casting according to claim 1, wherein the ceramic glaze is SAMYO SCG-607.
5. The method for controlling solidification of an investment casting magnesium alloy casting according to claim 1, wherein the oil quenching time is 5-30 min.
6. The method of controlling solidification of an investment casting magnesium alloy casting of claim 1, wherein the oil quenched quenching oil comprises U8132.
7. The method for controlling solidification of an investment casting magnesium alloy casting according to claim 1, wherein the material having a thermal conductivity less than 0.002W/(m-K) comprises one or more of perlite, vermiculite, vitrified micro bubbles and insulation wool.
8. The method for controlling solidification of an investment casting magnesium alloy casting according to claim 1, wherein the silicon carbide cooling element is prepared from the following raw materials in parts by weight: 70-80 parts of silicon carbide, 5-10 parts of potassium fluoride and 15-20 parts of wax material.
9. The method of controlling the solidification of an investment cast magnesium alloy casting according to claim 1 wherein the partial runner includes one or more of a main runner, an auxiliary feeding runner, a mold filling runner and a feeding runner in the pouring of the casting.
10. A method for investment casting of magnesium alloy, comprising the method for controlling solidification of investment casting magnesium alloy castings according to any one of claims 1 to 9.
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| CN202210441182.0A CN114535506B (en) | 2022-04-26 | 2022-04-26 | Method for controlling solidification of investment casting magnesium alloy casting and investment casting method |
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