Casting defect control method for complex thin-wall special-shaped heat-resistant cast steel member
Through the combination of investment, bidirectional composite stir casting technology and specific shell structure, the casting defects of complex thin-walled special-shaped heat-resistant steel components are solved, and high-quality casting molding is achieved.
Patent Information
- Application Number
- CN202510632419.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-16
- Publication Date
- 2025-08-12
AI Technical Summary
The existing casting process is difficult to effectively control the defects such as shrinkage, shrinkage holes, cold partitions, insufficient pouring and thermal cracks of complex thin-walled special-shaped heat-resistant steel components, resulting in low yield.
The investment and bidirectional composite stirring casting technology is adopted, combined with the mold shell structure of specific surface layer, transition layer and back layer. Through the composite stirring of rotation and revolution, the grain shearing is refined during the solidification process of liquid steel, ensuring the deformation resistance and interface bonding strength of the mold shell, and avoiding the occurrence of casting defects.
The defects such as shrinkage, shrinkage, insufficient pouring in traditional casting have been significantly eliminated, and the molding quality and yield of complex thin-walled special-shaped heat-resistant steel components have been improved.
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Figure CN120460680A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of metal casting, and in particular to a method for controlling casting defects of a complex thin-walled special-shaped heat-resistant cast steel component. Background Art
[0002] The exhaust pipe is a three-way structure with a U-shaped connection. The manifold emerges from the root of the U. The minimum angle at the root of the U is approximately 65 degrees, and the wall thickness is approximately 3 to 3.5 mm. As can be seen, the exhaust pipe is a complex, thin-walled, irregularly shaped, and asymmetrical structure. Currently, exhaust pipes are primarily cast from heat-resistant steel, which offers advantages such as good heat resistance and fatigue resistance and is widely used in the exhaust systems of high-performance engines. However, factors such as the complex thin-walled and special-shaped structure of the exhaust pipe and the poor fluidity of high-alloy heat-resistant cast steel make the casting of the exhaust pipe more difficult. There are three main difficulties: First, the asymmetric structure of the exhaust pipe causes a large difference in heat between the main pipe and the manifold after casting. Under the conditions of natural solidification, it is difficult to achieve sequential solidification, resulting in solidification defects; second, due to the limitations of the spatial layout of the exhaust system, the main pipe has to complete a 180° turn in a short distance, and the corner is too steep, which is not conducive to the molding of molten steel, causing the liquid-solid interface to shrink and thermal stress to concentrate, which in turn leads to problems such as cracking of the exhaust pipe; third, high-alloy heat-resistant steel itself has poor casting fluidity. Casting in a thin-walled, long-process special-shaped cavity is prone to problems such as cold shut and insufficient pouring, and it is difficult to compensate for the shrinkage of the molten steel, which is prone to defects such as shrinkage and shrinkage holes.
[0003] In summary, in the process of casting complex thin-walled special-shaped heat-resistant steel components such as automobile exhaust pipes using existing casting processes such as sand casting and investment casting, casting defects occur due to the above reasons, making the casting quality of complex thin-walled special-shaped heat-resistant steel components difficult to control and the yield of finished products low. Summary of the Invention
[0004] In response to the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components. The method utilizes a combination of investment casting and two-way composite stirring casting technology to make the resulting complex thin-walled special-shaped heat-resistant steel components have a dense structure and will not have defects such as shrinkage, shrinkage cavities, cold shut, insufficient pouring, and thermal cracks.
[0005] The purpose of the present invention is achieved through the following technical solutions: A method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components, comprising: Step S1, wax mold manufacturing: design and manufacture a metal wax mold according to the structure of a complex thin-walled special-shaped heat-resistant steel component; Step S2, wax pattern making: melting the wax-based pattern material and injecting the wax-based pattern material into the metal wax pattern mold to form a wax pattern; Step S3, shell production: coating the wax mold with boron nitride, drying, and then coating, sanding, and drying in sequence, repeatedly obtaining a shell structure consisting of a surface layer, a transition layer, a back layer, and a sealing layer; then, heating and melting the wax mold assembly to obtain a shell; Step S4, vacuum melting: The shell is installed in the mold, and the charge, mold, runner, and crucible are baked; the charge is then loaded into the crucible, the furnace is closed and vacuumed, the charge is melted, and after the charge is completely melted, alloying elements are added and dissolved into the charge to form molten steel; Step S5, casting and molding: pouring molten steel into the shell cavity in the mold, and simultaneously starting the stirring device to make the mold rotate and revolve in a composite stirring manner; after the molten steel is completely solidified, removing the shell from the mold; Step S6, sand removal: using a combination of mechanical vibration and sand blowing to remove the mold shell on the surface of the casting to obtain a thin-walled special-shaped heat-resistant cast steel component.
[0006] Based on further optimization of the above scheme, the melting temperature of the wax-based mold material in step S2 is 70-100° C.; the pressure of injecting the wax-based mold material is 0.5-0.9 MPa.
[0007] Based on further optimization of the above solution, the thickness of the surface layer is 0.07-0.12 mm, the thickness of the transition layer is 1.5-2.0 mm, the thickness of the back layer is 1.5-3.0 mm, and the thickness of the sealing layer is 0.3-0.5 mm.
[0008] Based on further optimization of the above scheme, the surface layer is mainly composed of silica sol and zircon powder, with additives of nano aerogel, carbon fiber, and yttrium oxide, and is sprinkled with 100 / 120 sieve zircon sand; the transition layer is mainly composed of silica sol and mullite powder, with additives of nano aerogel and magnesium borate whiskers, and is sprinkled with 30 / 60 sieve mullite sand; the back layer is mainly composed of silica sol and mullite powder, with additives of nano aerogel and cobalt aluminate, and is sprinkled with 16 / 30 sieve mullite sand; the sealing layer is mainly composed of silica sol and mullite powder, with additives of nano aerogel and nano clay.
[0009] Based on further optimization of the above scheme, the content of nano-aerogel in the surface layer, transition layer, back layer and sealing layer shows a decreasing trend, and the particle size is 10 to 50 μm.
[0010] Based on further optimization of the above scheme, the mass ratio of silica sol to zircon powder in the surface layer is 1.38-1.42:1.48-1.52, the weight percentage of nano aerogel is 0.48%-0.52%, the weight percentage of carbon fiber is 0.05%-0.15%, and the weight percentage of yttrium oxide is 0.15%-0.25%.
[0011] Based on further optimization of the above scheme, the mass ratio of silica sol to mullite powder in the transition layer is 1.68-1.72:1.98-2.02, the weight percentage of nano aerogel is 0.43%-0.47%, and the weight percentage of magnesium borate is 0.05%-0.15%.
[0012] Based on further optimization of the above scheme, the mass ratio of silica sol to mullite powder in the back layer is 1.28-1.32:1.48-1.52, the weight percentage of nano aerogel is 0.38%-0.42%, and the weight percentage of cobalt aluminate is 0.25%-0.35%.
[0013] Based on further optimization of the above scheme, the mass ratio of silica sol to mullite powder in the sealing layer is 1.38-1.42:1.58-1.62, the weight percentage of nano aerogel is 0.33%-0.37%, and the weight percentage of nano clay is 0.15%-0.25%.
[0014] Based on further optimization of the above scheme, the drying time of the surface layer is 4 to 6 hours, the drying time of the transition layer is 8 to 10 hours, the drying time of the back layer is 12 to 14 hours, and the drying time of the sealing layer is 14 to 16 hours; the drying temperature of the surface layer, transition layer, back layer, and sealing layer is 22 to 28°C, and the relative humidity of the air is maintained at 40% to 60%.
[0015] Based on further optimization of the above solution, the thickness of the boron nitride layer is 150 to 250 μm.
[0016] Based on the further optimization of the above scheme, in step S3, the specific steps of heating and melting the wax mold module to obtain the mold shell are: placing the mold shell with the wax film into a steam dewaxing kettle, closing the dewaxing kettle, passing steam to make the pressure reach 0.4~0.6MPa and the temperature reach 170~190℃, and maintaining it for 15~30min to allow the wax film to fully melt and flow out of the mold shell; then, placing the dewaxed mold shell in a high-temperature furnace, raising the temperature from room temperature to 300~500℃, keeping it warm for 1~2h, continuing to raise the temperature to 900~1100℃, keeping it warm for 2~4h, cooling to room temperature, and taking out the mold shell.
[0017] Based on further optimization of the above solution, in step S4, the furnace is vacuumed to 7-10 Pa.
[0018] Based on further optimization of the above scheme, in step S5, the rotation speed is 30 to 50 rpm, the ratio of revolution to rotation speed is 1:-0.8 to-0.55, and the composite stirring time is 30 to 50 min.
[0019] The following are the technical effects of the solution of the present invention: The present invention adopts the casting technology of investment casting and bidirectional composite stirring. Through the bidirectional composite stirring action of rotation and revolution, the grains are sheared and refined, and the components are evenly distributed during the solidification of the molten steel, thereby effectively eliminating the thermal cracks of complex thin-walled special-shaped heat-resistant steel components. At the same time, the present invention utilizes the shell structure composition of a specific surface layer, transition layer, back layer, and sealing layer. First, a transition gradient of the thermal expansion coefficient is formed to avoid the shell from delamination and falling off due to excessive stress during the pouring of molten steel and composite stirring, thereby improving the shell's deformation resistance and ensuring the normal progress of casting. Second, the shell is prevented from generating thermal shock cracks and crack propagation during the pouring of molten steel and composite stirring, thereby avoiding the problems of the shell being difficult to fall off due to the penetration cracks of molten steel and the occurrence of defective products in complex thin-walled special-shaped heat-resistant steel components. Third, the interface bonding strength between the layers is effectively improved, the shell is integrated, thereby ensuring the stability during the pouring of molten steel and composite stirring, and avoiding the problems of shell deformation and failure caused by thermal-anti-shear oscillation. By combining the specific shell structure of the present invention with the investment casting + bidirectional composite stirring casting technology, defects such as shrinkage, shrinkage cavities, and insufficient pouring caused by traditional investment casting are significantly eliminated, thereby improving the molding quality of the final casting. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a structural schematic diagram of a bidirectional composite stirring investment casting device in an embodiment of the present invention.
[0021] Figure 2 Schematic diagram of the casting structure after bidirectional composite stirring investment casting in an embodiment of the present invention.
[0022] Figure 3 This is the microstructure of the casting after bidirectional composite stirring investment casting in an embodiment of the present invention.
[0023] Figure 4 Schematic diagram of the defects caused by traditional investment casting of complex thin-walled special-shaped heat-resistant cast steel components.
[0024] Among them, 10, casting mold; 20, mold shell; 30, gate; 40, turntable. DETAILED DESCRIPTION
[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.
[0026] Example 1: A method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components, comprising: Step S1, wax mold manufacturing: design and manufacture a metal wax mold according to the structure of the complex thin-walled special-shaped heat-resistant steel component (in order to facilitate the subsequent demolding of the wax mold from the metal wax mold, the metal wax mold adopts a splicing structure and each splicing part can be cut in half to facilitate the removal of the wax mold; at the same time, the wax molds of each splicing part can be removed from the corresponding metal wax mold separately and then assembled to form a wax mold as a whole).
[0027] Step S2, wax pattern making: melt the wax-based mold material at a temperature of 70°C, and inject the wax-based mold material into the metal wax mold at an injection pressure of 0.5 MPa to form a wax mold (after injection and cooling, the wax mold assembly is separated from the metal wax mold, and a wax film module is formed by splicing and assembling multiple wax mold assemblies. The wax film module has the same structure as the complex thin-walled special-shaped heat-resistant steel component that actually needs to be prepared).
[0028] Step S3, manufacturing the mold shell 20: First, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated with boron nitride, and the thickness of the boron nitride layer is 150 μm; Then, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated, sanded, and dried in sequence, and this process is repeated multiple times to obtain a mold shell 20 structure consisting of a surface layer, a transition layer, a back layer, and a sealing layer; the surface layer is 0.07 mm thick, the transition layer is 1.5 mm thick, the back layer is 1.5 mm thick, and the sealing layer is 0.3 mm thick; Specifically, the surface layer is primarily composed of silica sol and zircon powder in a mass ratio of 1.38:1.48. Nano-aerogel, carbon fiber, and yttrium oxide are added as additives. The nano-aerogel is 0.48% by weight with a particle size of 10μm, the carbon fiber is 0.05% by weight, and the yttrium oxide is 0.15% by weight. Zircon sand with a 100 / 120 sieve is sprinkled. Drying time is 4 hours, the drying temperature is 28°C, and the relative humidity is maintained at 40%. The transition layer is primarily composed of silica sol and mullite powder in a mass ratio of 1.68:1.98. Nano-aerogel and magnesium borate whiskers are added as additives. The nano-aerogel is 0.43% by weight with a particle size of 10μm, the magnesium borate is 0.05% by weight, and mullite sand with a 30 / 60 sieve is sprinkled. Drying time is 8 hours, the drying temperature is 26°C, and the relative humidity is maintained at 40%. The backing layer is primarily composed of silica sol and mullite powder in a mass ratio of 1.28:1.48. Nanoaerogel and cobalt aluminate additives are added. The nanoaerogel is 0.38% by weight with a particle size of 10 μm, and the cobalt aluminate is 0.25% by weight. Mullite sand with a 16 / 30 sieve is sprinkled on top. The drying time is 12 hours, the drying temperature is 26°C, and the relative humidity is maintained at 40%. The sealing layer is primarily composed of silica sol and mullite powder in a mass ratio of 1.38:1.58. Nanoaerogel and nanoclay additives are added. The nanoaerogel is 0.33% by weight with a particle size of 10 μm, and the nanoclay is 0.15% by weight. The drying time is 14 hours, the drying temperature is 26°C, and the relative humidity is maintained at 40%.
[0029] Place the mold shell 20 with the wax film in a steam dewaxing kettle, close the dewaxing kettle, introduce steam to make the pressure reach 0.4MPa and the temperature reach 170℃, maintain for 30min, so that the wax film is fully melted and flows out of the mold shell 20; then, place the dewaxed mold shell 20 in a high-temperature furnace, raise the temperature from room temperature to 300℃, keep it warm for 2h, continue to raise the temperature to 900℃, keep it warm for 4h, cool to room temperature, and take out the mold shell 20.
[0030] Step S4, vacuum melting: The shell 20 is installed in the mold 10, and the charge, mold 10, runner, and crucible are baked; then the charge is loaded into the crucible, the furnace is closed, and the vacuum is evacuated to 7 Pa. The charge is melted, and after the charge is completely melted, the alloying element material is added at a melting temperature of 1350°C (the melting temperature can be between 1350°C and 1450°C, preferably 1350°C in this embodiment) to dissolve the alloying element into the charge to form molten steel.
[0031] Step S5, casting molding: Figure 1As shown: a bidirectional composite stirring investment casting device comprises a turntable 40, a mold 10 and a shell 20, wherein a rotating seat is provided on the outer ring of the end face of the turntable 40, and the bottom surface of the mold 10 is fixedly connected to the end face of the rotating seat (ensuring synchronous rotation between the mold 10 and the rotating seat), the shell 20 is installed in the mold 10 and a gate 30 connected to its molding cavity is provided on the outer side of the shell 20, and the molten steel is poured into the molding cavity of the shell 20 through the gate 30, the pouring temperature is 1520 ℃ (the pouring temperature can be between 1520 and 1600 ℃, and 1520 ℃ is preferred in this embodiment), the pouring speed is 25 kg / s (the pouring speed can be between 25 and 30 kg / s, and 25 kg / s is preferred in this embodiment), and the stirring device is turned on simultaneously to make the mold 10 perform composite stirring of rotation and revolution, the rotation speed (i.e., the rotation speed of the rotating seat, Figure 1 As shown in the figure, the rotation speed of the turntable 40 is 30 rpm ... Figure 1 The ratio of the rotation speed (clockwise as shown in the figure looking from top to bottom) to the rotation speed is 1:-0.55, and the composite stirring time is 50 minutes; after the molten steel is completely solidified, the shell 20 is taken out from the mold 10.
[0032] Step S6, sand removal: After natural cooling, the mold shell 20 on the surface of the casting is removed by a combination of mechanical vibration and sand blowing to obtain a thin-walled special-shaped heat-resistant cast steel component.
[0033] Example 2: A method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components, comprising: Step S1, wax mold manufacturing: design and manufacture a metal wax mold according to the structure of the complex thin-walled special-shaped heat-resistant steel component (in order to facilitate the subsequent demolding of the wax mold from the metal wax mold, the metal wax mold adopts a splicing structure and each splicing part can be cut in half to facilitate the removal of the wax mold; at the same time, the wax molds of each splicing part can be removed from the corresponding metal wax mold separately and then assembled to form a wax mold as a whole).
[0034] Step S2, wax pattern making: melt the wax-based mold material at a temperature of 85°C, and inject the wax-based mold material into the metal wax mold at an injection pressure of 0.7 MPa to form a wax mold (after injection and cooling, the wax mold assembly is separated from the metal wax mold, and a wax film module is formed by splicing and assembling multiple wax mold assemblies. The wax film module has the same structure as the complex thin-walled special-shaped heat-resistant steel component that actually needs to be prepared).
[0035] Step S3, manufacturing the mold shell 20: First, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated with boron nitride, and the thickness of the boron nitride layer is 200 μm; Then, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated, sanded, and dried in sequence, and this process is repeated multiple times to obtain a mold shell 20 structure consisting of a surface layer, a transition layer, a back layer, and a sealing layer; the surface layer is 0.1 mm thick, the transition layer is 1.7 mm thick, the back layer is 2.2 mm thick, and the sealing layer is 0.4 mm thick; Specifically, the surface layer is primarily composed of silica sol and zircon powder in a mass ratio of 1.4:1.5. Nano-aerogel, carbon fiber, and yttrium oxide are added as additives. The nano-aerogel is 0.5% by weight with a particle size of 30 μm, the carbon fiber is 0.1% by weight, and the yttrium oxide is 0.2% by weight. Zircon sand with a 100 / 120 sieve is sprinkled. The drying time is 5 hours, the drying temperature is 25°C, and the relative humidity is maintained at 50%. The transition layer is primarily composed of silica sol and mullite powder in a mass ratio of 1.7:2. Nano-aerogel and magnesium borate whiskers are added as additives. The nano-aerogel is 0.45% by weight with a particle size of 30 μm, the magnesium borate is 0.1% by weight, and mullite sand with a 30 / 60 sieve is sprinkled. The drying time is 9 hours, the drying temperature is 24°C, and the relative humidity is maintained at 50%. The backing layer is primarily composed of silica sol and mullite powder in a mass ratio of 1.3:1.5. Nanoaerogel and cobalt aluminate additives are added. The nanoaerogel is 0.4% by weight with a particle size of 30 μm, and the cobalt aluminate is 0.3% by weight. Mullite sand with a 16 / 30 sieve is sprinkled. The drying time is 13 hours, the drying temperature is 24°C, and the relative humidity is maintained at 50%. The sealing layer is primarily composed of silica sol and mullite powder in a mass ratio of 1.4:1.6. Nanoaerogel and nanoclay additives are added. The nanoaerogel is 0.35% by weight with a particle size of 30 μm, and the nanoclay is 0.2% by weight. The drying time is 15 hours, the drying temperature is 24°C, and the relative humidity is maintained at 50%.
[0036] Place the mold shell 20 with the wax film in a steam dewaxing kettle, close the dewaxing kettle, introduce steam to make the pressure reach 0.5 MPa and the temperature reach 180°C, maintain for 22 minutes, so that the wax film is fully melted and flows out of the mold shell 20; then, place the dewaxed mold shell 20 in a high-temperature furnace, raise the temperature from room temperature to 400°C, keep it warm for 1.5 hours, continue to raise the temperature to 1000°C, keep it warm for 3 hours, cool to room temperature, and take out the mold shell 20.
[0037] Step S4, vacuum melting: The shell 20 is installed in the mold 10, and the charge, mold 10, runner, and crucible are baked; then the charge is loaded into the crucible, the furnace is closed, and the vacuum is evacuated to 8.5 Pa. The charge is melted. After the charge is completely melted, the alloying element material is added at a melting temperature of 1400°C (the melting temperature can be between 1350°C and 1450°C, preferably 1400°C in this embodiment) to dissolve the alloying element into the charge to form molten steel.
[0038] Step S5, casting molding: Figure 1 As shown: a bidirectional composite stirring investment casting device comprises a turntable 40, a mold 10 and a shell 20, wherein a rotating seat is provided on the outer ring of the end face of the turntable 40, and the bottom surface of the mold 10 is fixedly connected to the end face of the rotating seat (ensuring synchronous rotation between the mold 10 and the rotating seat), the shell 20 is installed in the mold 10 and a gate 30 connected to its molding cavity is provided on the outer side of the shell 20, and the molten steel is poured into the molding cavity of the shell 20 through the gate 30, the pouring temperature is 1560°C (the pouring temperature can be between 1520 and 1600°C, and 1560°C is preferred in this embodiment), the pouring speed is 27kg / s (the pouring speed can be between 25 and 30kg / s, and 27g / s is preferred in this embodiment), and the stirring device is turned on simultaneously to make the mold 10 perform composite stirring of rotation and revolution, the rotation speed (i.e., the rotation speed of the rotating seat, Figure 1 As shown in the figure, the rotation speed of the turntable 40 is 40 rpm ... Figure 1 The ratio of the rotation speed (clockwise as shown in the figure looking from top to bottom) to the rotation speed is 1:-0.67, and the composite stirring time is 40 minutes; after the molten steel is completely solidified, the shell 20 is taken out from the mold 10.
[0039] Step S6, sand removal: After natural cooling, the mold shell 20 on the surface of the casting is removed by a combination of mechanical vibration and sand blowing to obtain a thin-walled special-shaped heat-resistant cast steel component.
[0040] Figure 2 and Figure 3 The overall appearance and microstructure of the thin-walled special-shaped heat-resistant cast steel component prepared in this embodiment clearly show that the overall appearance of the cast steel component prepared in this embodiment has no obvious defects such as cracks, shrinkage, shrinkage holes, cold shut, insufficient pouring, etc., and the microstructure is dense and evenly distributed.
[0041] Example 3: A method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components, comprising: Step S1, wax mold manufacturing: design and manufacture a metal wax mold according to the structure of the complex thin-walled special-shaped heat-resistant steel component (in order to facilitate the subsequent demolding of the wax mold from the metal wax mold, the metal wax mold adopts a splicing structure and each splicing part can be cut in half to facilitate the removal of the wax mold; at the same time, the wax molds of each splicing part can be removed from the corresponding metal wax mold separately and then assembled to form a wax mold as a whole).
[0042] Step S2, wax pattern making: melt the wax-based mold material at a temperature of 100°C, and inject the wax-based mold material into the metal wax mold at an injection pressure of 0.9 MPa to form a wax mold (after injection and cooling, the wax mold assembly is separated from the metal wax mold, and a wax film module is formed by splicing and assembling multiple wax mold assemblies. The wax film module has the same structure as the complex thin-walled special-shaped heat-resistant steel component that actually needs to be prepared).
[0043] Step S3, manufacturing the mold shell 20: First, the surface of the wax mold (i.e., the inner and outer surfaces of the wax mold) is coated with boron nitride, and the thickness of the boron nitride layer is 250 μm; Then, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated, sanded, and dried in sequence, and this process is repeated multiple times to obtain a mold shell 20 structure consisting of a surface layer, a transition layer, a back layer, and a sealing layer; the surface layer is 0.12 mm thick, the transition layer is 2.0 mm thick, the back layer is 3.0 mm thick, and the sealing layer is 0.5 mm thick; Specifically, the surface layer is primarily composed of silica sol and zircon powder in a mass ratio of 1.42:1.52. Nano-aerogel, carbon fiber, and yttrium oxide are added as additives. The nano-aerogel is 0.52% by weight with a particle size of 50 μm, the carbon fiber is 0.15% by weight, and the yttrium oxide is 0.25% by weight. Zircon sand with a 100 / 120 sieve is sprinkled. Drying time is 6 hours, the drying temperature is 23°C, and the relative humidity is maintained at 60%. The transition layer is primarily composed of silica sol and mullite powder in a mass ratio of 1.72:2.02. Nano-aerogel and magnesium borate whiskers are added as additives. The nano-aerogel is 0.47% by weight with a particle size of 50 μm, the magnesium borate is 0.15% by weight, and mullite sand with a 30 / 60 sieve is sprinkled. Drying time is 10 hours, the drying temperature is 22°C, and the relative humidity is maintained at 60%. The backing layer is primarily composed of silica sol and mullite powder in a mass ratio of 1.32:1.52. Nanoaerogel and cobalt aluminate additives are added. The nanoaerogel is 0.42% by weight with a particle size of 50 μm, and the cobalt aluminate is 0.35% by weight. Mullite sand with a 16 / 30 sieve is sprinkled on top. The drying time is 14 hours, the drying temperature is 22°C, and the relative humidity is maintained at 60%. The sealing layer is primarily composed of silica sol and mullite powder in a mass ratio of 1.42:1.62. Nanoaerogel and nanoclay additives are added. The nanoaerogel is 0.37% by weight with a particle size of 50 μm, and the nanoclay is 0.25% by weight. The drying time is 16 hours, the drying temperature is 22°C, and the relative humidity is maintained at 60%.
[0044] Place the mold shell 20 with the wax film into a steam dewaxing kettle, close the dewaxing kettle, introduce steam to make the pressure reach 0.6MPa and the temperature reach 190℃, maintain for 15 minutes, so that the wax film is fully melted and flows out of the mold shell 20; then, place the dewaxed mold shell 20 in a high-temperature furnace, raise the temperature from room temperature to 500℃, keep it warm for 1 hour, continue to raise the temperature to 1100℃, keep it warm for 2 hours, cool to room temperature, and take out the mold shell 20.
[0045] Step S4, vacuum melting: The shell 20 is installed in the mold 10, and the charge, mold 10, runner, and crucible are baked; then the charge is placed in the crucible, the furnace is closed, and the vacuum is evacuated to 10 Pa. The charge is melted, and after the charge is completely melted, the alloying element material is added at a melting temperature of 1450°C (the melting temperature can be between 1350°C and 1450°C, preferably 1450°C in this embodiment) to dissolve the alloying element into the charge to form molten steel.
[0046] Step S5, casting molding: Figure 1As shown: a bidirectional composite stirring investment casting device comprises a turntable 40, a mold 10 and a shell 20, wherein a rotating seat is provided on the outer ring of the end face of the turntable 40, and the bottom surface of the mold 10 is fixedly connected to the end face of the rotating seat (ensuring synchronous rotation between the mold 10 and the rotating seat), the shell 20 is installed in the mold 10 and a gate 30 connected to its molding cavity is provided on the outer side of the shell 20, and the molten steel is poured into the molding cavity of the shell 20 through the gate 30, the pouring temperature is 1600°C (the pouring temperature can be between 1520 and 1600°C, and 1600°C is preferred in this embodiment), the pouring speed is 30kg / s (the pouring speed can be between 25 and 30kg / s, and 30kg / s is preferred in this embodiment), and the stirring device is turned on synchronously to make the mold 10 perform composite stirring of self-rotation and revolution, the self-rotation speed (i.e., the rotation speed of the rotating seat, Figure 1 As shown in the figure, the rotation speed of the turntable 40 is 50 rpm ... Figure 1 The ratio of the rotation speed (clockwise as shown in the figure looking from top to bottom) to the rotation speed is 1:-0.8, and the composite stirring time is 30 minutes; after the molten steel is completely solidified, the shell 20 is taken out from the mold 10.
[0047] Step S6, sand removal: After natural cooling, the mold shell 20 on the surface of the casting is removed by a combination of mechanical vibration and sand blowing to obtain a thin-walled special-shaped heat-resistant cast steel component.
[0048] Example 4: As a preferred specific implementation method, based on the schemes of Examples 1 to 3, after obtaining the thin-walled special-shaped heat-resistant cast steel components, it is necessary to clean the sand, oil, impurities, etc. on the inner and outer surfaces of the cast steel components through mechanical cleaning and chemical cleaning.
[0049] Comparative Example 1: An investment casting method for a cast steel component, comprising: Step S1, wax mold manufacturing: the same as step S1 in Example 2.
[0050] Step S2, wax mold preparation: the same as step S2 in Example 2.
[0051] Step S3, shell production: First, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated with boron nitride, and the boron nitride layer has a thickness of 200 μm; Then, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated, sanded, and dried repeatedly to obtain a shell structure consisting of a surface layer, a transition layer, a back layer, and a sealing layer; the thickness of the surface layer is 0.1mm, the thickness of the transition layer is 1.7mm, the thickness of the back layer is 2.2mm, and the thickness of the sealing layer is 0.4mm; Specifically, the surface layer is primarily composed of silica sol and zircon powder in a 1:1 mass ratio. Nano-aerogel, carbon fiber, and yttrium oxide are added as additives. The nano-aerogel is 0.5% by weight with a particle size of 30 μm, the carbon fiber is 0.1% by weight, and the yttrium oxide is 0.2% by weight. Zircon sand with a 100 / 120 sieve is sprinkled. The drying time is 5 hours, the drying temperature is 25°C, and the relative humidity is maintained at 50%. The transition layer is primarily composed of silica sol and mullite powder in a 1:1 mass ratio. Nano-aerogel and magnesium borate whiskers are added as additives. The nano-aerogel is 0.45% by weight with a particle size of 30 μm, the magnesium borate is 0.1% by weight, and mullite sand with a 30 / 60 sieve is sprinkled. The drying time is 9 hours, the drying temperature is 24°C, and the relative humidity is maintained at 50%. The backing layer is primarily composed of silica sol and mullite powder in a 1:1 mass ratio. Nanoaerogel and cobalt aluminate additives are added. The nanoaerogel is 0.4% by weight with a particle size of 30 μm, and the cobalt aluminate is 0.3% by weight. Mullite sand with a 16 / 30 sieve is sprinkled. The drying time is 13 hours, the drying temperature is 24°C, and the relative humidity is maintained at 50%. The sealing layer is primarily composed of silica sol and mullite powder in a 1:1 mass ratio. Nanoaerogel and nanoclay additives are added. The nanoaerogel is 0.35% by weight with a particle size of 30 μm, and the nanoclay is 0.2% by weight. The drying time is 15 hours, the drying temperature is 24°C, and the relative humidity is maintained at 50%.
[0052] Place the mold shell with wax film into the steam dewaxing kettle, close the dewaxing kettle, introduce steam to make the pressure reach 0.5MPa and the temperature reach 180℃, maintain for 22 minutes, so that the wax film is fully melted and flows out of the mold shell; then, place the dewaxed mold shell in a high-temperature furnace, raise the temperature from room temperature to 400℃, keep it warm for 1.5 hours, continue to raise the temperature to 1000℃, keep it warm for 3 hours, cool to room temperature, and take out the mold shell.
[0053] Step S4, vacuum melting: the same as step S4 in Example 2.
[0054] Step S5, casting molding: the same as step S5 in Example 2.
[0055] Step S6, sand falling: the same as step S6 in Example 2.
[0056] Comparative Example 2: An investment casting method for a cast steel component, comprising: Step S1, wax mold manufacturing: the same as step S1 in Example 2.
[0057] Step S2, wax mold preparation: the same as step S2 in Example 2.
[0058] Step S3, shell production: First, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated with boron nitride, and the boron nitride layer has a thickness of 200 μm; Then, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated, sanded, and dried repeatedly to obtain a shell structure consisting of a surface layer, a transition layer, a back layer, and a sealing layer; the thickness of the surface layer is 0.1mm, the thickness of the transition layer is 1.7mm, the thickness of the back layer is 2.2mm, and the thickness of the sealing layer is 0.4mm; Specifically, the surface layer is primarily composed of silica sol and zircon powder, with a mass ratio of 1.4:1.5. Nanoaerogel and carbon fiber additives are added, with the nanoaerogel comprising 0.5% by weight and a particle size of 30 μm, and the carbon fiber comprising 0.1% by weight. Zircon sand with a 100 / 120 sieve is sprinkled. The drying time is 5 hours, the drying temperature is 25°C, and the relative humidity is maintained at 50%. The transition layer, backing layer, and sealing layer are consistent with those in Example 2.
[0059] Place the mold shell with wax film into the steam dewaxing kettle, close the dewaxing kettle, introduce steam to make the pressure reach 0.5MPa and the temperature reach 180℃, maintain for 22 minutes, so that the wax film is fully melted and flows out of the mold shell; then, place the dewaxed mold shell in a high-temperature furnace, raise the temperature from room temperature to 400℃, keep it warm for 1.5 hours, continue to raise the temperature to 1000℃, keep it warm for 3 hours, cool to room temperature, and take out the mold shell.
[0060] Step S4, vacuum melting: the same as step S4 in Example 2.
[0061] Step S5, casting molding: the same as step S5 in Example 2.
[0062] Step S6, sand falling: the same as step S6 in Example 2.
[0063] Comparative Example 3: An investment casting method for a cast steel component, comprising: Step S1, wax mold manufacturing: the same as step S1 in Example 2.
[0064] Step S2, wax mold preparation: the same as step S2 in Example 2.
[0065] Step S3, shell production: First, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated with boron nitride, and the boron nitride layer has a thickness of 200 μm; Then, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated, sanded, and dried repeatedly to obtain a shell structure consisting of a surface layer, a transition layer, a back layer, and a sealing layer; the thickness of the surface layer is 0.1mm, the thickness of the transition layer is 1.7mm, the thickness of the back layer is 2.2mm, and the thickness of the sealing layer is 0.4mm; Specifically, the transition layer is primarily composed of silica sol and mullite powder in a mass ratio of 1.7:2. A nano-aerogel additive is added, with a weight percentage of 0.45% and a particle size of 30 μm. 30 / 60 sieve mullite sand is sprinkled. The drying time is 9 hours, the drying temperature is 24°C, and the relative humidity is maintained at 50%. The surface layer, backing layer, and sealing layer are consistent with those in Example 2.
[0066] Place the mold shell with wax film into the steam dewaxing kettle, close the dewaxing kettle, introduce steam to make the pressure reach 0.5MPa and the temperature reach 180℃, maintain for 22 minutes, so that the wax film is fully melted and flows out of the mold shell; then, place the dewaxed mold shell in a high-temperature furnace, raise the temperature from room temperature to 400℃, keep it warm for 1.5 hours, continue to raise the temperature to 1000℃, keep it warm for 3 hours, cool to room temperature, and take out the mold shell.
[0067] Step S4, vacuum melting: the same as step S4 in Example 2.
[0068] Step S5, casting molding: the same as step S5 in Example 2.
[0069] Step S6, sand falling: the same as step S6 in Example 2.
[0070] Comparative Example 4: An investment casting method for a cast steel component, comprising: Step S1, wax mold manufacturing: the same as step S1 in Example 2.
[0071] Step S2, wax mold preparation: the same as step S2 in Example 2.
[0072] Step S3, shell production: First, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated with boron nitride, and the boron nitride layer has a thickness of 200 μm; Then, the wax mold surface (i.e., the inner and outer surfaces of the wax mold) is coated, sanded, and dried repeatedly to obtain a shell structure consisting of a surface layer, a transition layer, a back layer, and a sealing layer; the thickness of the surface layer is 0.1mm, the thickness of the transition layer is 1.7mm, the thickness of the back layer is 2.2mm, and the thickness of the sealing layer is 0.4mm; Specifically, the surface layer, transition layer, and back layer were consistent with those in Example 2. The sealing layer was primarily composed of silica sol and mullite powder in a mass ratio of 1.4:1.6, with nano-aerogel additives added. The nano-aerogel had a weight percentage of 0.35% and a particle size of 30 μm. The drying time was 15 hours, the drying temperature was 24°C, and the relative humidity was maintained at 50%.
[0073] Place the mold shell with wax film into the steam dewaxing kettle, close the dewaxing kettle, introduce steam to make the pressure reach 0.5MPa and the temperature reach 180℃, maintain for 22 minutes, so that the wax film is fully melted and flows out of the mold shell; then, place the dewaxed mold shell in a high-temperature furnace, raise the temperature from room temperature to 400℃, keep it warm for 1.5 hours, continue to raise the temperature to 1000℃, keep it warm for 3 hours, cool to room temperature, and take out the mold shell.
[0074] Step S4, vacuum melting: the same as step S4 in Example 2.
[0075] Step S5, casting molding: the same as step S5 in Example 2.
[0076] Step S6, sand falling: the same as step S6 in Example 2.
[0077] The overall appearance structure and microstructure of the cast steel components obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were observed, and the results are shown in the following table:
[0078] It can be seen from the results in the above table that: due to the adjustment of the materials of the shell surface layer, transition layer, back layer, and sealing layer in Comparative Examples 1 to Comparative Examples 4, they are subjected to high temperature and cyclic shear force during the pouring and two-way composite mixing process, and the shells have defects such as deformation, delamination, collapse, and thermal cracks, which in turn lead to deformation, defects, and other problems in the final castings, which do not meet the design requirements.
Claims
1. A method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components, characterized by: include: Step S1, wax mold manufacturing: design and manufacture a metal wax mold according to the structure of a complex thin-walled special-shaped heat-resistant steel component; Step S2, wax pattern making: melting the wax-based pattern material and injecting the wax-based pattern material into the metal wax pattern mold to form a wax pattern; Step S3, shell production: coating the wax mold with boron nitride, and then drying it, coating, sanding, and drying it in sequence, repeatedly obtaining a shell structure consisting of a surface layer, a transition layer, a back layer, and a sealing layer; Then, the wax mold set is heated and melted to obtain a shell; Step S4, vacuum melting: The shell is installed in the mold, and the charge, mold, runner, and crucible are baked; the charge is then loaded into the crucible, the furnace is closed and vacuumed, the charge is melted, and after the charge is completely melted, alloying elements are added and dissolved into the charge to form molten steel; Step S5, casting and molding: pouring molten steel into the shell cavity in the mold, and simultaneously starting the stirring device to make the mold rotate and revolve in a composite stirring manner; after the molten steel is completely solidified, removing the shell from the mold; Step S6, sand removal: using a combination of mechanical vibration and sand blowing to remove the mold shell on the surface of the casting to obtain a thin-walled special-shaped heat-resistant cast steel component.
2. The method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components according to claim 1, characterized in that: In step S2, the melting temperature of the wax-based mold material is 70-100° C.; the pressure of injecting the wax-based mold material is 0.5-0.9 MPa.
3. A method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components according to claim 1 or 2, characterized in that: The surface layer is mainly composed of silica sol and zircon powder, with nano aerogel, carbon fiber, and yttrium oxide additives added, and 100 / 120 sieve zircon sand is sprinkled; the transition layer is mainly composed of silica sol and mullite powder, with nano aerogel and magnesium borate whisker additives added, and 30 / 60 sieve mullite sand is sprinkled; the back layer is mainly composed of silica sol and mullite powder, with nano aerogel and cobalt aluminate additives added, and 16 / 30 sieve mullite sand is sprinkled; the sealing layer is mainly composed of silica sol and mullite powder, with nano aerogel and nano clay additives added.
4. A method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components according to claim 1 or 3, characterized in that: The content of nano aerogel in the surface layer, transition layer, back layer and sealing layer shows a decreasing trend, and the particle size is 10 to 50 μm.
5. A method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components according to claim 3 or 4, characterized in that: The mass ratio of silica sol to zircon powder in the surface layer is 1.38-1.42:1.48-1.52, the weight percentage of nano aerogel is 0.48%-0.52%, the weight percentage of carbon fiber is 0.05%-0.15%, and the weight percentage of yttrium oxide is 0.15%-0.25%.
6. A method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components according to claim 3 or 4, characterized in that: The mass ratio of silica sol to mullite powder in the transition layer is 1.68-1.72:1.98-2.02, the weight percentage of nano aerogel is 0.43%-0.47%, and the weight percentage of magnesium borate is 0.05%-0.15%.
7. The method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components according to claim 3, characterized in that: The mass ratio of the silica sol to the mullite powder in the back layer is 1.28-1.32:1.48-1.52, the weight percentage of the nano aerogel is 0.38%-0.42%, and the weight percentage of cobalt aluminate is 0.25%-0.35%.
8. The method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components according to claim 3, characterized in that: The mass ratio of silica sol to mullite powder in the sealing layer is 1.38-1.42:1.58-1.62, the weight percentage of nano aerogel is 0.33%-0.37%, and the weight percentage of nano clay is 0.15%-0.25%.
9. The method for controlling casting defects of complex thin-walled special-shaped heat-resistant cast steel components according to claim 1, characterized in that: The drying time of the surface layer is 4 to 6 hours, the drying time of the transition layer is 8 to 10 hours, the drying time of the back layer is 12 to 14 hours, and the drying time of the sealing layer is 14 to 16 hours; the drying temperature of the surface layer, transition layer, back layer and sealing layer is 22 to 28°C, and the relative humidity of the air is maintained at 40% to 60%.