Thermal control centrifugal coagulation device and coagulation method

Abstract

A heat control centrifugal solidification device and a solidification method, comprising a furnace body, a heating and heat preservation assembly, a smelting and pouring mechanism and a rotating lifting device. The heating and heat preservation assembly and the rotating lifting device are located in the furnace body, and the heating and heat preservation assembly is located below the smelting and pouring mechanism and above the rotating lifting device. The heat preservation temperature of the mold shell during alloy pouring is set above the liquidus temperature, and the flow of alloy liquid is strengthened by the motion of centrifugal rotation, realizing complete filling of thin-walled parts. Under the action of centrifugal rotation, the alloy receives strong melt convection during solidification, which refines the grains. The mold shell is gradually pulled out of the heating zone to form a sequential solidification process from bottom to top in the mold shell, thereby inhibiting the formation of shrinkage defects, and a high-temperature alloy complex thin-walled casting with complete filling, fine grains and no shrinkage and porosity defects can be obtained. The process is simple, has wide adaptability, low cost, and the minimum wall thickness of the produced casting is 0.5 mm.

Description

Technical Field

[0001] This invention relates to the field of precision casting technology, specifically a thermally controlled centrifugal solidification device and solidification method. Background Technology

[0002] With the rapid development of my country's aviation industry, the service environment of aero-engines is becoming increasingly complex, placing higher demands on the performance of complex thin-walled castings made of high-temperature alloys, such as casings, integral bladed disks, and turbine housings. Under ordinary investment casting conditions, these castings typically exhibit coarse equiaxed or columnar crystals, which easily lead to the initiation and development of fatigue cracks during use. Therefore, fine-grained structures are often adopted. Furthermore, these complex thin-walled castings with intricate structures and significant differences in wall thickness frequently suffer from defects such as incomplete filling, shrinkage porosity, and shrinkage cavities during the forming process, affecting both production quality and efficiency.

[0003] Therefore, the complete filling of complex thin-walled high-temperature alloy castings, along with the coordinated control of microstructure and defects, has become a major challenge. With ongoing research in this area, an improved thermal control solidification process has been proposed based on traditional thermal control methods. This improved process effectively controls filling and reduces defect formation. By increasing the preheating temperature of the mold shell, the improved thermal control solidification process enhances the fluidity of the melt, thereby effectively improving filling capacity and significantly suppressing the formation of defects such as incomplete filling, shrinkage porosity, and other defects in complex thin-walled castings.

[0004] However, in actual production, the cooling rate of the thermal solidification process decreases as the mold shell temperature increases, which often results in coarse grains in the casting structure. Therefore, solving the problem of coarse grains in the thermal solidification process has become an important issue in achieving complete filling, grain refinement, and the absence of shrinkage cavities in the forming process of complex thin-walled high-temperature alloy castings.

[0005] CN109396400 B discloses an integrated molding method and apparatus for large, complex, thin-walled, fine-grained castings. This method utilizes strong electromagnetic disturbances generated at the solid / liquid interface front to hinder crystal growth and refine grains, thereby refining the solidification structure of the casting. However, this method suffers from complex equipment structure, high cost, and stringent environmental requirements. Furthermore, the magnetic field may impose limitations on the casting dimensions, making it difficult to implement in actual production. Additionally, in existing methods, the mold shell's holding temperature is lower than the alloy's liquidus temperature, leading to solidification during the filling process and preventing the complete filling of components with small wall thicknesses. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies in achieving coordinated control of forming, microstructure, and defects of thin-walled high-temperature alloy parts, this invention proposes a thermally controlled centrifugal solidification device and solidification method.

[0007] The thermally controlled centrifugal solidification device proposed in this invention includes a furnace body, a heating and insulation component, a melting and casting mechanism, and a rotary lifting device, and is also equipped with a vacuum system.

[0008] The heating and heat preservation components are located below the melting and casting mechanism and above the rotary lifting device, both within the furnace body. The furnace shell is equipped with an extraction valve and a venting valve, connected to external air pumps and vacuum equipment to create or disrupt a vacuum environment.

[0009] Preferably, the furnace body has a sandwich structure; there is a cooling water channel in the sandwich; and the inner surface of the furnace body is covered with heat insulation cotton.

[0010] Preferably, the vacuum environment achieved by the furnace body has an ultimate vacuum degree of 6.67 × 10⁻⁶. -4 Pa.

[0011] The heating and insulation assembly includes a heating element and an insulation element, located in the middle of the furnace body. The insulation element consists of an upper insulation plate, an insulation sleeve, and a lower insulation plate. The heating element and insulation sleeve are annular, while the upper and lower insulation plates are circular. The upper insulation plate has a conical hole at its center, and the lower insulation plate has a cylindrical hole at its center. The insulation element, composed of the upper insulation plate, insulation sleeve, and lower insulation plate, forms a cylindrical structure that surrounds the heating element, collectively forming a heating zone for the casting mold shell. The axis of the heating element coincides with the axis of the insulation element.

[0012] Preferably, the heating element is made of graphite or metal Ta, and the upper insulation board, insulation sleeve and lower insulation board are made of multi-layer graphite felt, with each part assembled together using graphite felt splicing methods.

[0013] Preferably, the heating element has the following dimensions: inner diameter D of 150–800 mm, ring width d of 10–80 mm, and ring height H of 200–500 mm.

[0014] Preferably, the preheating and temperature control range of the heating and heat preservation device is 20 to 1600°C.

[0015] The melting and casting mechanism includes a melting mechanism and a casting mechanism. The main function of the melting mechanism is to melt the master alloy. It is fixed on the casting mechanism and can realize the tilting of the melting mechanism.

[0016] Preferably, the melting mechanism is an induction melting temperature measuring mechanism, which consists of a melting crucible, an induction heating coil, and a melting temperature measuring instrument.

[0017] Preferably, the casting mechanism is a clamping and tilting mechanical structure, with a pair of semi-circular ring clamps at the front end and a tilting mechanical structure at the rear end, and the surface of the mechanism is covered with heat insulation cotton.

[0018] The rotary lifting device includes a rotating body and a pull-out body. The rotating body is located at the upper end of the pull-out body, and the two are connected by a detachable connector. The mold shell is mounted on the rotating body; the rotary lifting device, together with the mold shell, performs centrifugal rotation and lifting actions.

[0019] Preferably, the detachable connector is a flange.

[0020] Preferably, the rotating body is a motor rotating platform, which consists of a rotating platform housing, a rotating platform, a rotating shaft, and a motor; the rotating platform is located at the upper end of the rotating platform housing, and the outer diameter of the rotating platform is smaller than the outer diameter of the rotating platform housing; water cooling channels and heat insulation cotton are arranged inside the rotating body, and heat insulation cotton is laid on the surface of the rotating platform.

[0021] Preferably, the pull-out body is a ball screw lifting assembly.

[0022] Preferably, the centrifugal speed of the rotating body of the rotary lifting device is 0 to 1500 r / min, and the lifting control accuracy of the pull-out body is 0.1 μm.

[0023] The solidification method using the aforementioned thermally controlled centrifugal solidification device proposed in this invention is for casting complex thin-walled high-temperature alloy castings.

[0024] The specific process is as follows:

[0025] Step 1, Tooling preparation:

[0026] Install the mold shell onto the rotating platform, and run the pull-out body to make the lower edge of the mold shell flush with the lower insulation plate; place the master alloy ingot into the melting crucible; place the pouring cup into the central cone hole of the upper insulation plate, and insert the lower end of the pouring cup into the gate of the mold shell.

[0027] Step 2, Vacuuming:

[0028] Operate the vacuum system, open the evacuation valve, and evacuate the furnace of the thermally controlled centrifugal solidification device to a vacuum level of 10. -3 Pa ~ 10 Pa.

[0029] Step 3: Heat and maintain the temperature of the mold shell.

[0030] The heating element is powered on to heat the mold shell at a preset heat preservation temperature. The preset heat preservation temperature is 1340-1550℃, and the heating rate is 5-20℃ / min. After the temperature of the heating zone of the mold shell rises to the preheating heat preservation temperature, the heating zone is kept at the temperature for 1-2 minutes before the cooling in step 7.

[0031] Step 4, Melting the master alloy ingot:

[0032] The induction heating coil is energized to melt the master alloy ingot in the melting crucible. Once the master alloy ingot has been melted into a liquid alloy, the temperature is measured, and the heating power is adjusted to heat the liquid alloy to 1450–1600°C and maintain it for 1–2 minutes. Then, the temperature is lowered to 1400–1500°C and held until the pouring is completed.

[0033] Step 5, centrifugation:

[0034] Turn on the motor of the rotating body in the rotary lifting device, and the rotating platform will drive the mold shell to rotate centrifugally. The centrifugal speed is 0-1500 r / min.

[0035] Step 6, Pouring:

[0036] The molten alloy is poured from the melting crucible into the pouring cup through the pouring mechanism, and then enters the mold shell in a centrifugal rotating state through the pouring cup.

[0037] After the casting is completed, the melting mechanism is powered off; the rotary lifting device continues to drive the mold shell to rotate centrifugally until the mold shell is completely pulled out of the heating zone in step 7 for 0-5 minutes.

[0038] Step 7, Solidification and Pulling:

[0039] Lower the temperature of the heating zone to the temperature range of the solid-liquid phase line of the alloy, with a cooling rate of 5 to 15 °C / min; activate the pull-out program of the rotary lifting device, and pull the mold shell downwards at a pull-out rate of 50 to 500 μm / s until the mold shell is completely pulled out of the heating zone.

[0040] Turn off the heating and insulation device and the rotating lifting device to allow the casting temperature to drop below 300℃. Turn off the vacuum valve and air pump, open the vent valve, break the vacuum, and remove the casting to complete the casting process.

[0041] Preferably, in step 6, the centrifugal speed is either uniformly accelerated, uniformly decelerated, or undergoes a speed transition. When the centrifugal speed is uniformly accelerated, the speed range is 400–1000 r / min, and the mold shell is pulled out for 400 s. When the centrifugal speed undergoes a speed transition acceleration, the speed range is 800–200 r / min, and the mold shell is pulled out for 2000 s. When the centrifugal speed is uniformly decelerated, the speed range is 1500–400 r / min, and the mold shell is pulled out for 1000 s.

[0042] The solid-liquid phase temperature range of the high-temperature alloy is 1260-1430℃, the minimum wall thickness of the casting is 0.5mm, the maximum proportion of thin-walled area is more than 70%, and the ratio of maximum wall thickness to minimum wall thickness reaches a maximum of 22:1.

[0043] The present invention aims to address the shortcomings of existing technologies in achieving coordinated control of the forming, microstructure, and defects of thin-walled high-temperature alloy parts, and provides a thermally controlled centrifugal solidification device and solidification method to obtain thin-walled castings with complete filling, fine grains, and no shrinkage cavities.

[0044] Using the thermally controlled centrifugal solidification apparatus provided by this invention, the holding temperature of the mold shell during alloy casting is set above the liquidus temperature. Simultaneously, the centrifugal rotation enhances the flow of the molten alloy, achieving complete filling of the thin-walled part. Furthermore, the centrifugal rotation induces strong melt convection during solidification, refining the grain size. Gradually pulling the mold shell out of the heating zone creates a bottom-up solidification process within the mold shell, thus suppressing the formation of shrinkage defects. Therefore, using the thermally controlled centrifugal apparatus provided by this invention for thin-walled part forming can yield high-temperature alloy complex thin-walled castings with complete filling, fine grains, and no shrinkage defects. It offers advantages such as simple process, wide applicability, and low cost, with a minimum wall thickness of 0.5 mm. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the thermally controlled centrifugal coagulation device of the present invention.

[0046] Figure 2 This is a flowchart illustrating the usage method of the thermally controlled centrifugal coagulation apparatus of the present invention.

[0047] Figure 3 This is a schematic diagram of the structure of the present invention.

[0048] Figure 4 This is a schematic diagram of the rotating lifting device 4 in Embodiment 1 of the present invention.

[0049] Figure 5 This is a schematic diagram of the structure of the heat insulation body 15 in Embodiment 1 of the present invention.

[0050] Figure 6 This is a schematic diagram of the structure of the heating element 16 in Embodiment 1 of the present invention.

[0051] Figure 7 This is a partial schematic diagram of the heating and insulation component fixing cylindrical sleeve bracket of the furnace body 1 in Embodiment 1 of the present invention.

[0052] Figure 8 This is a partial cross-sectional schematic diagram of the rotating body 18 in Embodiment 1 of the present invention.

[0053] In the diagram: 1. Furnace body; 2. Melting and casting mechanism; 3. Heating and insulation components; 4. Rotary lifting device; 5. Mold shell; 6. Pour cup; 7. Evacuation valve; 8. Vent valve; 9. Insulation cotton; 10. Melting thermometer; 11. Induction heating coil; 12. Insulation jacket; 13. Casting mechanism; 14. Melting crucible; 15. Insulation body; 16. Heating element; 17. Thermometer; 18. Rotating element; 19. Lifting device. 161. Lowering body; 162. Conductive column; 151. Heating body body; 152. Upper insulation plate; 153. Insulation sleeve; 154. Lower insulation plate; 181. Rotating platform shell; 182. Rotating platform; 183. Rotating shaft; 184. Transmission belt; 185. Motor; 191. Flange; 192. Pull rod; 193. Fixed seat; 194. Lifting seat; 195. Lifting screw; 196. Lifting motor. Specific implementation methods

[0054] Example 1:

[0055] This embodiment is a thermally controlled centrifugal solidification device, which includes a furnace body 1, a heating and heat preservation component 3, a melting and casting mechanism 2, and a rotary lifting device 4.

[0056] The heating and heat preservation component 3 is located below the melting and casting mechanism 2 and above the rotary lifting device 4, both within the furnace body 1. The furnace body is constructed of welded water-cooled stainless steel plates with internal water channels; the inner side of the furnace body is lined with heat insulation cotton, and there are welded supports inside for fixing the heating and heat preservation component.

[0057] The heating and insulation assembly includes a heating element 16, an insulation element 15, and a thermometer 17. The heating element is a rotating circular ring made of graphite, arranged axially and fixed inside the insulation element. The maximum heating temperature of the heating element is 1700℃, and conductive posts 161 are provided on both sides of the heating element. Multiple thermometers are mounted on the heating element. The inner diameter D of the heating element is 300mm, the ring width d is 15mm, and the ring height H is 250mm.

[0058] The insulation body 15 is cylindrical and is used to insulate the heating zone to reduce heat loss. This insulation body is fixed to a cylindrical sleeve support in the middle of the furnace body. The axis of the heating element 16 coincides with the axis of the insulation body.

[0059] The insulation body is composed of three parts: an upper insulation board 151, an insulation sleeve 152, and a lower insulation board 153, all made of multiple layers of graphite felt, joined together using conventional mortise and tenon joints. The upper insulation board has a conical hole in its center for installing the pouring cup 6; the lower insulation board has a cylindrical hole in its center, with a clearance between the inner surface of the central hole and the circumferential surface of the rotating platform shell 181; the rotating platform 182 does not have direct contact with the insulation body 15.

[0060] The melting and casting mechanism 2 includes a melting mechanism and a casting mechanism. The main function of the melting mechanism is to melt the master alloy. It is fixed on the casting mechanism and can realize the tilting of the melting mechanism.

[0061] The melting mechanism includes a melting crucible 14, an induction heating coil 11, a melting thermometer 10, and a heat-insulating jacket 12. The melting crucible 14 is made of graphite and is used to melt the master alloy ingot; the melting crucible is surrounded by a heat-insulating jacket. The induction heating coil is located on the outside of the melting crucible and is used to heat the master alloy ingot. The melting thermometer is installed within the melting zone, located at the opening of the melting crucible. The heat-insulating jacket 12 is made of corundum and is used to house the induction heating coil and the melting crucible, providing heat insulation.

[0062] The casting mechanism 13 is a clamping and tilting mechanical structure. The front end of the casting mechanism is a pair of semi-circular annular clamps, which are fitted with the heat insulation jacket 12 of the melting mechanism. The rear end has a tilting mechanical structure connected to a motor, thereby realizing the tilting action of the melting crucible 1. When pouring the molten alloy, the outlet position of the melting crucible 14 corresponds to the opening position of the pouring cup 6. The surface of the casting mechanism is covered with heat insulation cotton.

[0063] The rotary lifting device 4 includes a rotating body 18 and a pull-out body 19. The rotating body is located at the upper end of the pull-out body, and the two are fixedly connected by a connecting flange 191. The mold shell 5 is installed on the rotating body 18, and the rotary lifting device 4 performs centrifugal rotation and lifting actions together with the mold shell.

[0064] The rotating body 18 is a motor rotating platform, including a rotating platform housing 181, a rotating platform 182, a rotating shaft 183, and a motor 185. The rotating platform is located at the upper end of the rotating platform housing; the rotating shaft is located at the center of the bottom plate of the rotating platform housing and is fixed by a bearing seat. The motor is mounted on the bottom plate inside the rotating platform housing. The output shaft of the motor is connected to the rotating shaft via a transmission belt. The centrifugal speed of the rotating body is controlled within the range of 0–1500 r / min.

[0065] The rotating platform 182 is used to install the mold shell 5. The rotating platform is provided with heat insulation cotton 9 as heat insulation material. The rotating platform shell is made of water-cooled metal plate with built-in water channels, which plays the role of cooling and protecting the internal motor 185.

[0066] The pull-out body 19 is a ball screw lifting assembly, including a pull-out rod 192, a fixed seat 193, a lifting seat 194, a lifting screw 195, and a lifting motor 196. The connecting flange 191 is located at the upper end of the pull-out rod and is connected to the rotating platform housing 181 by screws. The pull-out rod is welded to the fixed seat. The lifting seat, lifting screw, and lifting motor are ball screw assemblies installed on the furnace wall at the lower part of the furnace body. The motor drives the lifting screw to rotate, thereby realizing the up and down lifting of the lifting seat. The fixed seat is connected to the lifting seat by screws, driving the pull-out rod to realize the up and down lifting movement. The lifting movement control accuracy of the pull-out body is 0.1μm.

[0067] The mold shell 5 is an investment casting mold shell, which is fixed on the rotating platform of the rotary lifting device 4.

[0068] The pouring cup 6 is made of high-purity corundum and is used to connect the mold shell 5 and the pouring channel of the melting and pouring mechanism 2. The upper end of the pouring cup is funnel-shaped and is fitted into the conical hole in the center of the upper insulation plate 151, while the lower end is inserted into the pouring gate of the mold shell.

[0069] The temperature measuring instrument 17 is a corundum high-temperature thermocouple, which is symmetrically distributed in two groups, upper and lower. It passes through the holes opened on the insulation body 15, through the installation gap of the heating body 16, and is evenly distributed along the circumference of the heating body in the heating area of ​​the mold shell to accurately measure the overall temperature of the heating area.

[0070] The vacuum valve 7 and vent valve 8 are channels used for evacuating and breaking the vacuum inside the furnace body 1. One end of the vacuum valve and vent valve is connected to the furnace body, the other end of the vacuum valve is connected to the air pump, and the other end of the vent valve is connected to the external environment.

[0071] Example 2

[0072] This embodiment describes a method for casting a high-temperature alloy fine-grained rotary casting using the aforementioned thermally controlled centrifugal solidification apparatus. The minimum wall thickness of the high-temperature alloy fine-grained rotary casting is 0.5 mm, and the solid-liquid phase range of the master alloy is 1430℃~1380℃. The casting height is 200 mm.

[0073] The specific process of this embodiment is as follows:

[0074] Step 1: Lower the rotary lifting device 4 to the bottom of the furnace body 1. Install the prepared mold shell 5 on the rotating platform 182 of the rotating body 18, and install heat insulation cotton 9 in the installation gap of the mold shell on the rotating platform. Place the master alloy ingot into the melting crucible 14. Raise the rotary lifting device 4 so that the entire mold shell enters the heating zone, and the lower edge of the mold shell is flush with the lower insulation body 153. Install the pouring cup 6, place the pouring cup into the central conical hole of the upper insulation plate 151, and insert the lower end of the pouring cup into the pouring gate of the mold shell. Close the furnace door.

[0075] Step 2: Turn on the air pump and open the vacuum valve 7 to evacuate the furnace to a vacuum level of 10. -2 Pa.

[0076] Step 3: The heating element 16 is powered on to heat the mold shell at the preset insulation temperature.

[0077] The predetermined holding temperature is 1450℃, and the heating rate is 5℃ / min. After the temperature of the heating zone rises to the preheating holding temperature of 1450℃, the heating zone is held at this temperature until 2 minutes before the cooling begins in step 7.

[0078] Step 4: The induction heating coil 11 is energized to melt the master alloy ingot in the melting crucible 14.

[0079] The melting temperature is 1550℃. After the master alloy ingot is melted into a liquid alloy, the temperature is measured with a melting thermometer 10. The temperature of the liquid alloy is maintained at 1550℃ for 2 minutes, and then cooled to 1500℃ and held until the casting is completed.

[0080] Step 5: Turn on the motor of the rotating body 18 in the rotary lifting device, and drive the mold shell to rotate centrifugally through the rotating platform; the centrifugal speed is 400 r / min.

[0081] Step 6: The molten alloy is poured from the melting crucible 14 into the pouring cup 6 through the pouring mechanism 13, so that the molten alloy enters the mold shell in a centrifugal rotating state through the pouring cup.

[0082] After casting is completed, the induction heating coil 11 is de-energized; the rotating body 18 continues to drive the mold shell in centrifugal rotation at a uniformly accelerated speed, ranging from 400 to 1000 r / min, with an initial speed of 400 r / min and a final speed of 1000 r / min. The mold shell is pulled out for 400 seconds. After the mold shell is completely pulled out of the heating zone, the rotating body continues to rotate at a final speed of 1000 r / min until the mold shell is completely pulled out of the heating zone for 3 minutes in step 7.

[0083] Step 7: Lower the temperature of the heating zone to the alloy solid-liquid phase temperature range of 1400℃; the cooling rate is 10℃ / min; activate the pulling program of the lifting body 19, and pull the mold shell downwards at a pulling rate of 500μm / s until the entire mold shell is completely pulled out of the heating zone. During this period, the rotating body continues the centrifugal rotation of Step 6 until the mold shell is completely pulled out of the heating zone for 3 minutes, after which the centrifugal rotation ends.

[0084] Step 8: Turn off the heating element 16 and the rotating lifting device to cool the casting to below 300°C. Then, turn off the air extraction valve 7 and the air pump, open the venting valve 8, and remove the casting after breaking the vacuum to complete the casting process.

[0085] Example 3

[0086] This embodiment describes a method for casting complex thin-walled high-temperature alloy castings using the aforementioned thermally controlled centrifugal solidification apparatus. The ratio of the maximum wall thickness to the minimum wall thickness of the high-temperature alloy casting is 22:1, and the solid-liquid phase range of the master alloy is 1380℃~1320℃. The casting height is 100mm.

[0087] The specific process of this embodiment is as follows:

[0088] Step 1: Lower the rotary lifting device 4 to the bottom of the furnace body 4. Install the prepared mold shell 5 on the rotating platform 182 of the rotating body 18, and install heat insulation cotton 9 in the installation gap of the mold shell on the rotating platform. Place the master alloy ingot into the melting crucible 14. Raise the rotary lifting device 4 so that the entire mold shell enters the heating zone, and the lower edge of the mold shell is flush with the lower insulation body 153. Install the pouring cup 6, place the pouring cup into the central conical hole of the upper insulation plate 151, and insert the lower end of the pouring cup into the pouring gate of the mold shell. Close the furnace door.

[0089] Step 2: Turn on the air pump and open the vacuum valve 7 to evacuate the furnace to a vacuum level of 10. -2 Pa.

[0090] Step 3: The heating element 16 is powered on to heat the mold shell at the preset insulation temperature.

[0091] The predetermined holding temperature is 1400℃, and the heating rate is 10℃ / min. After the temperature of the heating zone rises to the preheating holding temperature of 1450℃, the heating zone is held at this temperature until 2 minutes before the cooling begins in step 7.

[0092] Step 4: The induction heating coil 11 is energized to melt the master alloy ingot in the melting crucible 1.

[0093] The melting temperature is 1500℃. After the master alloy ingot is melted into a liquid alloy, the temperature is measured with a melting thermometer 10. The temperature of the liquid alloy is maintained at 1500℃ for 2 minutes, and then cooled to 1450℃ and held until the casting is completed.

[0094] Step 5: Turn on the motor of the rotating body 18 in the rotary lifting device, and drive the mold shell to rotate centrifugally through the rotating platform; the centrifugal speed is 800 r / min.

[0095] Step 6: The molten alloy is poured from the melting crucible 14 into the pouring cup 6 through the pouring mechanism 13, so that the molten alloy enters the mold shell in a centrifugal rotating state through the pouring cup.

[0096] After the casting is completed, the induction heating coil 11 is de-energized; the rotating body 18 continues to drive the mold shell to rotate centrifugally, and the centrifugal speed changes by speed jumps; the centrifugal speed range of this speed jump change is 800~200r / min, that is, 800r / min and 200r / min cycle periodically, the period is 5min, and the total centrifugal time is the mold shell pulling time of 2000s; until the mold shell is completely pulled out of the heating zone in step 7 for 0min.

[0097] Step 7: Lower the temperature of the heating zone to the alloy solid-liquid phase temperature range of 1350℃, with a cooling rate of 5℃ / min; activate the pulling program of the lifting body 19, and pull the mold shell downwards at a pulling rate of 50μm / s until the entire mold shell is completely pulled out of the heating zone. During this period, the rotating body continues the centrifugal rotation as in Step 6 until the mold shell is completely pulled out of the heating zone, at which point the centrifugal rotation ends.

[0098] Step 8: Turn off the heating element 16 and the rotating lifting device to cool the casting to below 300°C. Then, turn off the air extraction valve 7 and the air pump, open the venting valve 8, and remove the casting after breaking the vacuum to complete the casting process.

[0099] Example 4

[0100] This embodiment describes a method for casting large, complex, thin-walled high-temperature alloy castings using the aforementioned thermally controlled centrifugal solidification apparatus. The large, complex, thin-walled high-temperature alloy casting is a casing, with a minimum wall thickness of 2 mm, a maximum wall thickness of 16 mm, and a thin-walled area accounting for more than 70%. The solid-liquid phase range of the master alloy is 1340℃~1260℃. The casting height is 200 mm.

[0101] The specific process of this embodiment is as follows:

[0102] Step 1: Lower the rotary lifting device 4 to the bottom of the furnace body 4. Install the prepared mold shell 5 on the rotating platform 182 of the rotating body 18, and install heat insulation cotton 9 in the installation gap of the mold shell on the rotating platform. Place the master alloy ingot into the melting crucible 14. Raise the rotary lifting device 4 so that the entire mold shell enters the heating zone, and the lower edge of the mold shell is flush with the lower insulation body 153. Install the pouring cup 6, place the pouring cup into the central conical hole of the upper insulation plate 151, and insert the lower end of the pouring cup into the pouring gate of the mold shell. Close the furnace door.

[0103] Step 2: Turn on the air pump and open the vacuum valve 7 to evacuate the furnace to a vacuum level of 10. -2 Pa.

[0104] Step 3: The heating element 16 is powered on to heat the mold shell at the preset insulation temperature.

[0105] The predetermined holding temperature is 1350℃, and the heating rate is 20℃ / min. After the temperature of the heating zone rises to the preheating holding temperature of 1350℃, the heating zone is held at this temperature until 2 minutes before the cooling begins in step 7.

[0106] Step 4: The induction heating coil 11 is energized to melt the master alloy ingot in the melting crucible 14.

[0107] The melting temperature is 1450℃. After the master alloy ingot is melted into a liquid alloy, the temperature is measured with a melting thermometer 10. The temperature of the liquid alloy is maintained at 1450℃ for 2 minutes, and then cooled to 1390℃ and held until the casting is completed.

[0108] Step 5: Turn on the motor of the rotating body 18 in the rotary lifting device, and drive the mold shell to rotate centrifugally via the rotating platform. The centrifugal speed is 1500 r / min.

[0109] Step 6: The molten alloy is poured from the melting crucible 14 into the pouring cup 6 through the pouring mechanism 13, so that the molten alloy enters the mold shell in a centrifugal rotating state through the pouring cup.

[0110] After casting is completed, the induction heating coil 11 is de-energized; the rotating body 18 continues to drive the mold shell 5 to rotate centrifugally at a uniformly decelerated speed, with a speed range of 1500–400 r / min. The initial speed is 1500 r / min, and the final speed is 400 r / min. The mold shell is pulled out for 1000 seconds. After the mold shell is completely pulled out of the heating zone, the rotating body continues to rotate centrifugally at a final speed of 400 r / min until the mold shell is completely pulled out of the heating zone for 5 minutes in step 7.

[0111] Step 7: Lower the temperature of the heating zone to the alloy solid-liquid phase temperature range of 1300℃, at a cooling rate of 15℃ / min; activate the pulling program of the lifting body 19, and pull the mold shell downwards at a pulling rate of 200μm / s until the entire mold shell is completely pulled out of the heating zone. During this process, the rotating body continues the centrifugal rotation as in Step 6, and ends the centrifugal rotation 5 minutes after the mold shell is completely pulled out of the heating zone.

[0112] Step 8: Turn off the heating element 16 and the rotating lifting device to cool the casting to below 300°C. Then, turn off the air extraction valve 7 and the air pump, open the venting valve 8, and remove the casting after breaking the vacuum to complete the casting process.

[0113] Table 1 Process parameters for each embodiment

[0114]

[0115]

Claims

1. A method for solidification using a thermally controlled centrifugal solidification device, characterized in that, Used for casting large, complex, thin-walled high-temperature alloy castings; the thermal control centrifugal solidification device includes a furnace body (1), a heating and heat preservation component (3), a melting and pouring mechanism (2), and a rotary lifting device (4); the heating and heat preservation component (3) is located below the melting and pouring mechanism (2) and above the rotary lifting device (4), and they are all located inside the furnace body (1); The heating and insulation component (3) includes a heating element, an insulation element and a thermometer, which are installed in the middle of the furnace body; the heating element is a rotating ring, arranged along the central axis of the furnace body (1) and fixed in the insulation element; the insulation element is cylindrical, including an upper insulation plate, an insulation sleeve and a lower insulation plate, which are fixed on the cylindrical sleeve support in the middle of the furnace body. The melting and casting mechanism (2) includes a melting mechanism and a casting mechanism. The melting mechanism is fixed on the casting mechanism (13) and can realize the tilting of the melting mechanism. The melting mechanism is an induction melting and temperature measuring mechanism. The melting crucible is surrounded by a heat insulation jacket (12). The induction heating coil (11) is located on the outside of the melting crucible. The heat insulation jacket is used to fit the induction heating coil and the melting crucible. The casting mechanism (13) is a mechanical structure for clamping and tilting. It is fitted with the heat insulation jacket (12) of the melting mechanism. There is a tilting mechanical structure at the rear end, which is connected to a motor, thereby realizing the tilting action of the melting crucible. The rotary lifting device (4) includes a rotating body (18) and a lifting body; the rotating body is located at the upper end of the lifting body, and the two are fixedly connected by a connecting flange (191); the rotating platform of the rotating body is used to install the mold shell (5) and to perform centrifugal rotation and lifting actions together with the mold shell; The specific process is as follows: Step 1, Tooling preparation: Install the mold shell (5) onto the rotating platform and run the lifting body (19) to make the lower edge of the mold shell flush with the lower insulation plate; put the master alloy ingot into the melting crucible (14); put the pouring cup (6) into the central cone hole of the upper insulation plate and insert the lower end of the pouring cup into the pouring gate of the mold shell; Step 2, Vacuuming: Turn on the air pump and open the vacuum valve (7) to evacuate the furnace to 10°C. -3 Pa-10Pa; Step 3: Heat and maintain the temperature of the mold shell. When the heating element is powered on, it heats the mold shell to the preset insulation temperature. The predetermined heat preservation temperature is 1340~1550℃, and the heating rate is 5~20℃ / min. After the temperature of the heating area of ​​the mold shell rises to the preheating heat preservation temperature, the heating area is kept warm and maintained at this temperature until 1~2 minutes before the cooling begins in step 7. Step 4, Melting the master alloy ingot: The induction heating coil (11) is energized to melt the master alloy ingot in the melting crucible (14); wait for the master alloy ingot to melt into alloy liquid, measure the temperature, adjust the heating power to heat the alloy liquid to 1450~1600℃ and maintain it for 1~2 minutes, then cool it down to 1400~1500℃ and maintain it until the casting is completed. Step 5, centrifugation: Turn on the motor of the rotating body (18) in the rotary lifting device, and drive the mold shell to rotate centrifugally through the rotating platform; the centrifugal speed is 0~1500r / min; Step 6, Pouring: The molten alloy is poured from the melting crucible (14) into the pouring cup (6) through the pouring mechanism (13), so that the molten alloy enters the mold shell in a centrifugal rotating state through the pouring cup; After the casting is completed, the induction heating coil (11) is de-energized; the rotating body (18) continues to drive the mold shell to rotate centrifugally until the mold shell is completely pulled out of the heating zone in step 7 for 0~5 minutes; After casting, the centrifugal speed of the mold shell is either uniformly accelerated, uniformly decelerated, or undergoes a speed transition. When the centrifugal speed is uniformly accelerated, the speed range is 400~1000 r / min, and the mold shell is pulled out for 400 s. When the centrifugal speed undergoes a speed transition acceleration, the speed range is 800~200 r / min, and the mold shell is pulled out for 2000 s. When the centrifugal speed is uniformly decelerated, the centrifugal speed range is 1500~400 r / min, and the mold shell pulling time is 1000 s; Step 7, Solidification and Pulling: Lower the temperature of the heating zone to the temperature range of the solid-liquid phase line of the alloy, with a cooling rate of 5-15℃ / min; open the pulling program of the lifting body (19) and pull the mold shell downward at a pulling rate of 50-500μm / s until the mold shell is completely pulled out of the heating zone. Turn off the heating element and the rotating lifting device to cool the casting to below 300°C. Then, turn off the air extraction valve (7) and the air pump, open the vent valve (8), and remove the casting after breaking the vacuum to complete the casting process.

2. The method for solidification using a thermally controlled centrifugal solidification device as described in claim 1, characterized in that, The preheating and temperature control range of the heating and heat preservation device is 20~1600℃; the material of the heating body is graphite or metal Ta; the dimensions of the heating body are: inner diameter D is 150~800mm, ring width d is 10~80mm, and ring height H is 200~500mm. The insulation body is made of multiple layers of graphite felt; the upper insulation board has a conical hole in the center for installing the pouring cup (6); the lower insulation board has a cylindrical hole in the center, and there is a fitting gap between the inner surface of the central hole of the lower insulation board and the circumferential surface of the rotating platform shell; the rotating platform (182) has no direct contact with the insulation body; The thermometers are arranged in two symmetrical groups, one above the other.

3. The method for solidification using a thermally controlled centrifugal solidification device as described in claim 1, characterized in that: The rotating platform (182) of the rotating body (18) is provided with heat insulation cotton (9) as heat insulation material; the rotating platform shell is made of water-cooled metal plate with built-in water channel; the rotating platform is located at the upper end of the rotating platform shell, and the outer diameter of the rotating platform is smaller than the outer diameter of the rotating platform shell; The flange (191) is located at the upper end of the pull rod in the lifting body and is connected to the rotating platform housing by screws; the pull rod is welded to the fixed seat, and the lifting seat, lifting screw and lifting motor are ball screw assemblies, which are installed on the furnace wall at the lower part of the furnace body. The motor drives the lifting screw to rotate, thereby realizing the up and down lifting of the lifting seat. The fixed seat is connected to the lifting seat by screws, which drives the pull rod to realize the up and down lifting movement.

4. The method for solidification using the thermally controlled centrifugal solidification apparatus as described in claim 1, characterized in that, The solid-liquid phase temperature range of the high-temperature alloy is 1260~1430℃, the minimum wall thickness of the casting is 0.5mm, the maximum proportion of thin-walled area is more than 70%, and the ratio of maximum wall thickness to minimum wall thickness reaches a maximum of 22:

1.

5. The method for solidification using the thermally controlled centrifugal solidification apparatus as described in claim 1, characterized in that, When melting the master alloy ingot, wait for the master alloy ingot to melt into a liquid alloy, use a melting thermometer (10) to measure the temperature, heat the liquid alloy to 1450~1600℃ and maintain it for 1~2 minutes, then cool it down to 1400~1500℃ and keep it at that temperature until the casting is completed.

6. The method for solidification using the thermally controlled centrifugal solidification apparatus as described in claim 1, characterized in that, When the casting is solidified and pulled out, the temperature of the heating zone is reduced to the temperature range of the solid-liquid phase line of the alloy; the pulling speed range is 50~500μm / s.

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