Aluminum alloy anti-gravity filling casting method and equipment

Abstract

The present invention relates to the field of casting technology, and in particular, to a method and equipment for counter-gravity mold-filling casting of aluminum alloys. The method comprises: heating a crucible in a smelting chamber device in an inert gas environment; connecting the smelting chamber device and the casting chamber device so that the molten metal in the crucible is connected to the bottom of the filling shell through a riser; evacuating the smelting chamber and the casting chamber at the same time; introducing an inert gas into the smelting chamber, and the pressure value is P1; introducing a mixed gas of oxygen and inert gas into the casting chamber, and the pressure value is P2, P2<P1; as the volume of the molten metal in the filling shell increases, gradually increasing the pressure in the casting chamber to reduce the pressure difference between the smelting chamber and the casting chamber, when the filling shell is filled with the molten metal, P2=P1; after the molten metal in the shell to be filled is cooled and solidified, the product is taken out. This solves the problem that the products produced by the counter-gravity mold-filling casting of aluminum alloys have defects and a low pass rate.

Description

Technical Field

[0001] The present invention relates to the field of casting technology, and in particular to an aluminum alloy counter-gravity filling casting method and equipment. Background Art

[0002] Counter-gravity casting is to provide filling pressure for alloy liquid in the opposite direction to gravity, so that the alloy liquid "reversely fills" the mold shell from bottom to top. According to the different ways of introducing filling pressure, counter-gravity casting can be divided into low-pressure casting, vacuum suction casting and differential pressure (positive or negative pressure) casting. The counter-gravity casting device is generally composed of an upper tank body, a lower tank body, a middle partition, a heat preservation furnace and a liquid riser. The mold is placed in the upper tank and the metal heat preservation furnace is placed in the lower tank. During low-pressure casting, the tank body is not covered, so that the mold is exposed to the atmosphere, and the filling pressure is established by the positive pressure control cabinet; vacuum suction casting is to evacuate only the upper tank body through the negative pressure control cabinet, while keeping the lower tank body at atmospheric pressure to form the casting. Compared with gravity casting, counter-gravity casting can achieve accurate control of the filling pressure, ensure the smooth filling of the casting, and prevent air from rolling during the alloy liquid filling process.

[0003] At present, aluminum alloy investment anti-gravity casting technology has been widely used in the production and development of high-end aluminum alloy castings such as aerospace. The traditional method is low-pressure casting or vacuum suction casting. The castings obtained by these two methods generally have many internal defects, especially the castings have serious pinhole defects, and the castings have coarse grains and low mechanical properties. In addition, the castings obtained by vacuum suction casting have serious sticky surface defects on the surface of the castings due to the penetration of molten metal into the tiny holes on the surface of the shell. For castings with complex inner cavity structures, the sticky surface defects in the dead corners of the inner cavity of the castings are difficult to remove, which seriously affects the delivery progress and qualified rate of the castings. The castings obtained by hot shell low-pressure casting have a slow cooling speed, which is easy to produce serious pinholes, and the pinholes are spread all over the castings, which can easily lead to the scrapping of the castings. In addition, the mold shells used in various types of domestic anti-gravity casting equipment are all closed cavities. Although the closed mold shell can prevent the alloy liquid from overflowing, it will cause the mold shell's exhaust capacity to be severely limited, which will reduce the alloy liquid filling capacity. The thin-walled and complex structural areas of the casting are prone to cold shut defects, and some gases break through the alloy surface and enter the casting to form pore defects. In addition, due to the impact of high-temperature molten metal and the increase in air pressure in the mold shell, the closed mold shell is easily damaged during the filling process.

[0004] Therefore, there is a need for an aluminum alloy investment precision casting device with anti-gravity filling and suspended solidification under pressure to meet the complete forming and quality requirements of complex structure precision castings. Summary of the invention

[0005] In order to solve the problem that products produced by counter-gravity filling casting have defects and low qualified rate, the present invention provides an aluminum alloy counter-gravity filling casting method and equipment.

[0006] The first aspect of the present invention provides an aluminum alloy anti-gravity mold-filling casting method, comprising: step S1, heating a crucible arranged in a smelting chamber device in an inert gas environment to melt the metal contained in the crucible into a molten metal; step S2, connecting the smelting chamber device and the casting chamber device so that the molten metal in the crucible is connected to the bottom of the filling mold shell through a riser pipe; step S3, simultaneously evacuating the smelting chamber and the casting chamber to a preset vacuum degree; step S4, introducing an inert gas into the smelting chamber and increasing the internal pressure thereof, wherein the pressure value in the smelting chamber is P1, so that the molten metal enters the smelting chamber through the riser pipe. into the filling shell; step S5, introducing a mixed gas of oxygen and inert gas into the casting cavity and increasing its internal pressure, the oxygen content in the mixed gas is 3%-20%, and the pressure value in the casting cavity is P2, at this time, P2<P1; step S6, as the volume of the molten metal in the filling shell increases, gradually increase the pressure in the casting cavity to reduce the pressure difference between the smelting cavity and the casting cavity, when the filling shell is filled with the molten metal, P2=P1; step S7, after the pressure value in the casting cavity is increased to the same as the pressure value in the smelting cavity, take out the product after the product in the filling shell is cooled and solidified.

[0007] In some embodiments, step S6 further includes: firstly, based on the first pressure difference value, allowing the molten metal to flow into the filling shell and reach a first volume value, and then gradually reducing the pressure difference between the smelting chamber and the casting chamber.

[0008] In some embodiments, step S6 further includes: after the molten metal in the filling shell reaches a first volume value, dividing the remaining portion to be filled into a plurality of sub-filling portions from bottom to top, the volume value of the nth sub-filling portion is:

[0009] V n =0.5 n V 0 ;

[0010] Among them, V n is the volume value of the nth sub-filling part from bottom to top, V 0 The difference between the volume value of the filled shell and the first volume value;

[0011] Corresponding to each sub-filling portion, the pressure value in the casting cavity is:

[0012] P n = (1-0.5 n+1 )P1;

[0013] Among them, P n is the pressure value in the casting cavity corresponding to the nth sub-filling part, P1 is the pressure value in the smelting cavity; the pressure value P1 in the smelting cavity is 0.05MPa-0.1MPa.

[0014] In some embodiments, the first volume value is 40%-60% of the total volume of the filled mold shell.

[0015] In some embodiments, step S1 further includes: refining the metal in the crucible at 720°C-735°C for 5-20 minutes, cooling the metal melt to 715°C-730°C and keeping it warm; and preheating the riser tube to 350°C-500°C.

[0016] In some embodiments, step S3 further includes first heating the filling shell disposed in the casting chamber to 300° C.-700° C.; and the vacuum degree of the smelting chamber and the casting chamber is ≤20Pa.

[0017] In some embodiments, step S7 also includes synchronously increasing the pressure in the smelting chamber and the casting chamber to a pressurized cooling pressure of 0.3-0.8 MPa; while introducing cooling gas into the smelting chamber and the casting chamber respectively, exhausting the smelting chamber and the casting chamber to keep the pressure in the smelting chamber and the casting chamber at the cooling pressure.

[0018] The second aspect of the present invention further provides an aluminum alloy counter-gravity filling casting device, which is used for the aluminum alloy counter-gravity filling casting method in the above technical solution; the aluminum alloy counter-gravity filling casting device comprises a casting chamber device, a smelting chamber device, a partition device and a pressure control device; the smelting chamber device comprises a smelting chamber shell and a crucible, a smelting cavity is arranged inside the smelting chamber shell, the smelting cavity is provided with a first opening opened upward, a crucible for carrying molten metal is arranged in the smelting cavity, and a first connecting port is arranged on the upper side of the crucible and is connected to the smelting cavity; the casting chamber device comprises a casting chamber shell and a filling mold shell, a casting cavity is arranged in the casting chamber shell, and the casting cavity A second opening is provided facing downward, a filling shell is provided at the lower part of the casting cavity, and a second connecting port connected to the casting cavity is provided at the top of the filling shell; the partition device includes a partition plate and a riser, the lower side of the partition plate is sealed and connected to the first opening, and the upper side of the partition plate is sealed and connected to the second opening; the first end of the riser can extend into the molten metal in the crucible, and the second end of the riser can seal through the partition plate and be connected to the bottom of the filling shell; the pressure control device includes a first pressure component and a second pressure component, the first pressure component is connected to the smelting chamber and can control the pressure in the smelting chamber, and the second pressure component is connected to the casting chamber and can control the pressure in the casting chamber.

[0019] In some embodiments, the filling shell is divided into a plurality of sub-filling portions in sequence along the vertical direction, and a detection contact is provided at the bottom end of each sub-filling portion.

[0020] In some embodiments, the filling shell further includes a fast filling portion disposed below the plurality of sub-filling portions, and the volume of the sub-filling portion is: V n =0.5 n V 0 ;

[0021] Among them, V n is the volume value of the nth sub-filling part from bottom to top, V 0 It is the difference between the volume of the filling shell and the volume of the fast filling part.

[0022] In some embodiments, the aluminum alloy counter-gravity filling casting equipment also includes a sealing device, which includes a connecting flange fixed at the opening of the casting chamber and a sealing disk arranged at the opening of the smelting chamber. The sealing disk is in a circular ring shape, and a connecting portion is provided on the side facing the casting chamber. The connecting portion includes a plurality of grooves arranged along the circumferential direction of the sealing disk. The connecting flange includes a protruding structure corresponding to the groove, and the protruding structure can pass through the groove to extend into the interior of the sealing disk; the sealing disk can rotate relative to the smelting chamber, and a wedge block is provided on the lower side of the connecting portion, and the thickness of the wedge block gradually increases along the rotation direction of the sealing disk.

[0023] In some embodiments, the crucible includes a pot body and an induction coil disposed outside the pot body, and the induction coil is used to heat the pot body.

[0024] In some embodiments, the melting chamber device also includes a mold shell heating assembly, the mold shell heating assembly includes a heating hood and a lifting assembly, the heating hood includes a first state and a second state; in the first state, the heating hood is arranged on the outside of the filling mold shell and can heat the filling mold shell; in the second state, the heating hood is away from the filling mold shell and is arranged on the upper part of the casting cavity; the lifting assembly can drive the heating hood to switch between the first state and the second state.

[0025] In some embodiments, a through hole is provided in the middle of the partition plate for the riser pipe to pass through, and a flow-blocking ring is provided around the through hole on the upper side of the partition plate, and the flow-blocking ring is provided to protrude from the upper surface of the partition plate in the vertical direction; the filling shell includes a shell body and a pouring cup, the pouring cup is provided on the lower side of the shell body, the pouring cup is used to communicate with the riser pipe, the pouring cup is provided with a flow-blocking groove, the shape of the flow-blocking groove matches the flow-blocking ring, and the pouring cup can be pressed tightly onto the flow-blocking ring.

[0026] In some embodiments, the first pressure assembly includes an inert gas inlet valve, a cooling gas inlet valve and an exhaust valve connected to the smelting chamber, the inert gas inlet valve is connected to the inert gas supply device, and the cooling gas inlet valve is connected to the cooling gas supply device.

[0027] In order to solve the problem that products produced by aluminum alloy counter-gravity filling casting have defects and low qualified rate, the present invention has the following advantages:

[0028] In the above technical solution, the equipment is first installed and assembled in place, and the smelting chamber and the casting chamber are simultaneously evacuated and filled with inert gas, and the metal is smelted in an inert gas environment to form a relatively pure metal melt with low hydrogen content and less impurities, and then the smelting chamber and the casting chamber are simultaneously evacuated to achieve the same vacuum degree and make the pressure in the two cavities consistent. At this time, no metal melt will enter the mold shell, and the above steps S4 to S6 are used to form a pressure difference between the smelting chamber and the casting chamber, so that the metal melt enters the filling mold shell under the action of the pressure difference, wherein, in the process of filling the filling mold shell, the gradually reduced pressure is used. The pressure difference between the small smelting cavity and the casting cavity is reduced, so that the speed of filling the filling shell is gradually slowed down. Since the liquid level of the molten metal in the filling shell is gradually rising, the gradually slowed filling speed can avoid the occurrence of air entrainment, slag inclusion and cold shut defects in the product. At the same time, the steady filling speed can also prevent the metal solution from overflowing from the top of the filling shell. Further, the above technical solution adopts a filling shell with an opening at the upper end. Compared with the closed filling shell used in the conventional technical solution, it can significantly improve the exhaust capacity, eliminate the back pressure of the cavity, further ensure the complete molding of the casting, and prevent the formation of pore defects due to rolling up of the molten metal. Further, in the above technical solution, the molten metal fills the shell in a high-purity oxygen and high-purity inert gas atmosphere, so that the aluminum alloy solution can react with the oxygen therein and form a dense oxide shell, so that a smooth casting surface can be obtained, avoiding the defect of the casting surface sticking to the shell surface layer, and greatly improving the production efficiency of the product. Furthermore, after the aluminum liquid fills the mold shell, it is cooled under cooling gas and high pressure conditions, so that a casting with dense structure, high bulk mechanical properties and excellent internal quality can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A flowchart of an aluminum alloy counter-gravity filling casting method according to an embodiment is shown;

[0030] Figure 2 A schematic structural diagram of an aluminum alloy counter-gravity filling casting device according to an embodiment is shown;

[0031] Figure 3 A schematic cross-sectional structure diagram of an aluminum alloy counter-gravity filling casting device according to an embodiment is shown;

[0032] Figure 4 Shows Figure 3 A partial enlarged structural diagram of the middle A part;

[0033] Figure 5 Shows Figure 3 A schematic diagram of the partial enlarged structure of the middle B part;

[0034] Figure 6A schematic structural diagram of a smelting chamber shell according to an embodiment is shown;

[0035] Figure 7 A schematic structural diagram of a sealing disk according to an embodiment is shown;

[0036] Figure 8 A schematic cross-sectional structure diagram of a sealing disk according to an embodiment is shown.

[0037] Figure numerals: 10-casting chamber device; 11-casting chamber shell; 12-filling shell; 121-pouring cup; 122-shell body; 13-detection contact; 14-casting cavity; 15-heating assembly; 151-heating hood; 152-lifting assembly; 20-smelting chamber device; 21-smelting chamber shell; 211-crucible fixing frame; 2111-connecting hole; 22-smelting cavity; 23-crucible; 24-induction coil; 30-partitioning device; 31-partitioning plate; 311-blocking ring; 32-liquid rising pipe; 41-first pressure assembly; 411-mixed gas inlet valve; 412-cooling gas inlet valve; 413-exhaust valve; 42-second pressure assembly; 50-sealing device; 51-connecting flange; 52-sealing disk; 521-connecting part; 5211-groove; 5212-wedge block; 53-hydraulic rod. DETAILED DESCRIPTION

[0038] The present disclosure will now be discussed with reference to several exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and thus implement the present disclosure, rather than implying any limitation on the scope of the present disclosure.

[0039] As used herein, the term "including" and its variants are to be interpreted as open-ended terms meaning "including but not limited to". The term "based on" is to be interpreted as "based at least in part on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment". The term "another embodiment" is to be interpreted as "at least one other embodiment". The orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like is based on the orientation or position relationship shown in the accompanying drawings. These terms are mainly for better describing the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation. In addition, in addition to being used to indicate an orientation or position relationship, some of the above terms may also be used to indicate other meanings, such as the term "upper" may also be used to indicate a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to the specific circumstances. In addition, the terms "install", "set", "provided with", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be an internal connection between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0040] This embodiment discloses a method for counter-gravity mold filling casting of aluminum alloy. Figure 1As shown, it may include: step S1, heating the crucible 23 provided in the smelting chamber device 20 in an inert gas environment to melt the metal contained in the crucible 23 into a molten metal; step S2, connecting the smelting chamber device 20 and the casting chamber device 10, so that the molten metal in the crucible 23 is connected to the bottom of the filling shell 12 through the riser 32; step S3, evacuating the smelting chamber 22 and the casting chamber 14 at the same time to reach a preset vacuum degree; step S4, introducing an inert gas into the smelting chamber 22 and increasing its internal pressure, the pressure value in the smelting chamber 22 is P1, so that the molten metal enters the filling shell 12 through the riser 32; Step S5, introducing a mixed gas of oxygen and inert gas into the casting cavity 14 and increasing its internal pressure, the pressure value in the casting cavity 14 is P2, at this time, P2<P1; the oxygen content in the mixed gas is 3%-20%; Step S6, as the volume of the molten metal in the filling shell 12 increases, gradually increase the pressure in the casting cavity 14 to reduce the pressure difference between the smelting cavity 22 and the casting cavity 14, when the filling shell 12 is filled with the molten metal, P2=P1; Step S7, after the pressure value in the casting cavity 14 is increased to the same as the pressure value in the smelting cavity 22, the product in the filling shell 12 is cooled and solidified, and then the product is taken out.

[0041] In the above technical solution, the metal is first smelted in an inert gas environment to form a relatively pure molten metal with less impurities to improve product quality. Then, after the equipment is installed and assembled in place, the smelting chamber 22 and the casting chamber 14 are simultaneously evacuated to achieve the same vacuum degree and make the pressures in the two chambers consistent. At this time, no molten metal enters the mold shell. The above steps S4 to S6 are used to form a pressure difference between the smelting chamber 22 and the casting chamber 14, so that the molten metal enters the filling mold shell 12 under the action of the pressure difference. In the process of filling the filling mold shell 12, the pressure difference between the smelting chamber 22 and the casting chamber 14 is gradually reduced, so that the speed of filling the filling mold shell 12 is gradually slowed down. The liquid level of the body in the filling shell 12 rises gradually, and the gradually slowed filling speed can avoid the appearance of internal cavities, pore defects and cold shut defects in thin-walled complex structure areas in the product. At the same time, the steady filling speed can also prevent the metal solution from overflowing from the top of the filling shell 12 due to improper control; further, the above-mentioned technical scheme adopts a filling shell 12 with an opening at the upper end. Compared with the closed filling shell 12 used in the conventional technical scheme, it can significantly improve the exhaust capacity and eliminate the back pressure of the cavity, further ensure the complete molding of the casting, and prevent the formation of pore defects due to rolling up inside the metal melt. Due to the use of an open shell and a gradually slowed filling speed, the filling capacity of thin-walled castings can be greatly improved and the pore defects of castings can be reduced.

[0042] Furthermore, in the above technical solution, the molten metal fills the mold shell in the atmosphere of high-purity oxygen and high-purity inert gas. At the moment when the high-temperature aluminum liquid contacts the mold shell, the aluminum alloy solution can react with the oxygen therein and form a dense oxide film, so that a smooth casting surface can be obtained, avoiding the defect of the casting surface sticking to the mold shell surface layer, and greatly improving the production efficiency of the product. Furthermore, after the aluminum liquid fills the mold shell, it is cooled under cooling gas and high pressure conditions to prevent further contact between the aluminum liquid and the mold shell, which can greatly improve the mold shell cleaning efficiency, and can obtain castings with dense organization, high mechanical properties of the body and excellent internal quality, especially for castings with complex inner cavity structures. According to experimental data, the shell cleaning efficiency can be improved by 70%; it can also greatly avoid the deformation of thin-walled castings during the shell cleaning process, and the dimensional accuracy of the casting can be improved from HB6103CT8 to HB6103CT6. Specifically, the oxygen content in the mixed gas is 3%-20%, preferably, 20% oxygen content is adopted. Before mixing, the oxygen is high-purity oxygen with a concentration ≥ 99.995%, and the inert gas is also high-purity gas with a concentration ≥ 99.99%.

[0043] The above technical solution of the present application is mainly used for the manufacture of aluminum alloy casting products. Therefore, the metal melted in the crucible 23 may include multiple metals to form an alloy material with an appropriate ratio. The inert gas environment can be formed by filling the inert gas into the smelting chamber 22, wherein the inert gas can be high-purity argon or high-purity nitrogen. During the smelting process, the metal is in a high-temperature environment. In this state, the metal is more likely to react with oxygen in the air to form oxides, which will become impurities in the product. Therefore, by melting in an inert gas environment, the metal can be effectively prevented from oxidizing to form oxides, thereby improving the product quality.

[0044] During the smelting process, the smelting chamber and the casting chamber can be in a connected state, thereby reducing the installation process. However, due to the presence of the riser 32, inert gas needs to be introduced into both the smelting chamber and the casting chamber, which will cause a waste of inert gas. Therefore, it is also possible to choose to connect the smelting chamber and the casting chamber after the smelting is completed, that is, after the metal becomes a metal melt. When the smelting chamber 22 and the casting chamber 14 are vacuumed, they need to be performed at the same time, and the pressures in the two cavities should be kept consistent as much as possible to prevent the metal melt from entering the filling shell 12 uncontrolled due to the pressure difference. For the same reason as during metal smelting, when the metal melt is pressed into the filling shell 12, an inert gas is also used as a regulating gas to regulate the air pressure of the smelting chamber 22 and the casting chamber 14. Specifically, the gradually increasing pressure in the casting cavity 14 can be a linear increase or a step-by-step increase. Since the air pressure regulation has the characteristics of high efficiency and high speed, the pressure regulation method can be set to quickly adjust the pressure in the casting cavity 14 when the metal in the filling shell 12 reaches a set volume or liquid level. Since the molten metal does not solidify immediately after entering the filling shell 12, especially for products with larger volumes, a certain solidification time is required, so the molten metal needs to be able to stay stably in the filling shell 12. Therefore, after the molten metal is filled, the above technical solution controls the pressure of the smelting cavity 22 to be consistent with that of the casting cavity 14, so that the molten metal can stay stably in the filling shell 12 to wait for cooling.

[0045] Furthermore, in order to speed up the speed of the metal melt entering the filling shell 12, step S6 also includes: first, based on the first pressure difference, the metal melt flows into the filling shell 12 and reaches the first volume value, and then gradually reduces the pressure difference between the smelting chamber 22 and the casting chamber 14. Due to the effect of pressure, the speed of the metal melt entering the filling shell 12 in the above scheme of the present invention is gradually slowed down. Therefore, the metal melt can be firstly made to flow into the filling shell 12 quickly and in large quantities based on the first pressure difference. Specifically, the first pressure difference is the pressure difference between the smelting chamber 22 and the casting chamber 14, wherein the casting chamber 14 can be in a vacuum state, at which time the pressure difference is the largest, and only then the metal melt flows in at the fastest speed. The first volume value can be determined according to the shape, structural characteristics and total volume of the cast product, for example, a structural part with a large volume and a simple structure can be quickly filled.

[0046] As a specific implementation, step S6 further includes: after the molten metal in the filling shell 12 reaches a first volume value, the remaining portion to be filled is divided into a plurality of sub-filling portions from bottom to top, and the volume value of the nth sub-filling portion is:

[0047] V n =0.5 n V 0 ;

[0048] Among them, V n is the volume value of the nth sub-filling part from bottom to top, V 0 The difference between the volume value of the filling shell 12 and the first volume value;

[0049] Corresponding to each sub-filling portion, the pressure value in the casting cavity 14 is:

[0050] P n = (1-0.5 n+1 )P1;

[0051] Among them, P n is the pressure value corresponding to the nth sub-filling portion casting cavity 14, P1 is the pressure value in the smelting cavity 22; the pressure value P1 in the smelting cavity 22 is 0.05MPa-0.1MPa.

[0052] In the above embodiment, the portion that needs to gradually slow down the filling is divided into multiple sub-filling portions in a step-by-step manner, and the pressure value in the casting cavity 14 is controlled accordingly, so as to control the filling speed of the metal melt in a step-by-step manner. In this filling method, the closer to filling the filling shell 12, the slower the filling speed, leaving more ample exhaust time for the internal metal melt, and the pressure difference can be accurately controlled to prevent the metal melt from overflowing from the top of the shell. It should be noted that the above division is based on the volume value. Since the products produced are usually not uniform structures, the volume value is not the liquid level height in the filling shell 12. Specifically, the volume value needs to be calculated according to the products produced, but in order to simplify the control and design process, it can also be divided according to the liquid level height.

[0053] As a specific implementation, the first volume value is 40%-60% of the total volume of the filling shell 12. The setting of the first volume value can quickly fill most of the volume in the filling shell 12, thereby speeding up the production process.

[0054] In some embodiments, step S1 also includes: refining the metal in the crucible 23 at 720℃-735℃ for 5-20 minutes, cooling the metal melt to 715℃-730℃ and keeping it warm; preheating the riser tube 32 to 350℃-500℃; and preheating the filling shell 12 to 300℃-700℃.

[0055] Although the production equipment includes components for heating, the temperature of the molten metal is relatively high. Accordingly, in order to prevent the molten metal from solidifying prematurely, it is necessary to preheat the riser pipe 32, the filling shell 12, etc. that the molten metal can contact. On the one hand, it can reduce the time required for subsequent heating. On the other hand, it can heat and evaporate the residual liquid on these structures, such as water, to prevent it from evaporating after contacting the high-temperature molten metal to form water vapor hollowing, resulting in defective products.

[0056] To further improve product quality and prevent the metal melt from cooling prematurely, specifically, step S3 also includes first heating the filling shell 12 arranged in the casting chamber to 300°C-700°C; the vacuum degree of the smelting chamber 22 and the casting chamber 14 is less than or equal to 20Pa.

[0057] In order to further improve the product quality, step S7 also includes: synchronously increasing the pressure in the smelting chamber 22 and the casting chamber 14 to the pressurized cooling pressure, and the pressurized cooling pressure is 0.3-0.8MPa; while introducing cooling gas into the smelting chamber and the casting chamber respectively, the smelting chamber and the casting chamber are exhausted to keep the pressure in the smelting chamber and the casting chamber at the cooling pressure. In order to reduce costs, compressed air can also be introduced into the smelting chamber at this stage.

[0058] In this embodiment, by further increasing the pressure in the smelting chamber 22 and the casting chamber 14 at the same time, the produced product can be cooled in a high-pressure environment. On the one hand, it can effectively prevent the molten metal from flowing back into the crucible 23 under the action of gravity. On the other hand, it can also solidify the product under pressure to improve the internal quality of the casting product, refine the grains, reduce vacuum defects, and improve the strength of the casting body. The flow of air into the smelting chamber 22 and the casting chamber 14 can use the effect of the airflow to quickly take away the heat in the filling shell 12 and the product, thereby quickly cooling down and improving production efficiency. The cooling gas can be compressed air or inert gas with a lower temperature. According to experimental data, under the preferred embodiment of the present application, the pinhole degree of the casting can be reduced from 3 to 6 levels to below 1 level, the mechanical tensile strength of the ZL114A material casting body can be increased from 310Mpa to more than 360Mpa, and the yield strength can be increased from 280Mpa to more than 310Mpa, and the elongation of the casting body can be stably maintained at more than 4%.

[0059] The second aspect of the present invention also provides an aluminum alloy counter-gravity filling casting device, such as Figures 2 to 8As shown, the aluminum alloy counter-gravity filling casting equipment is used for the aluminum alloy counter-gravity filling casting method in the above technical solution; the aluminum alloy counter-gravity filling casting equipment includes a casting chamber device 10, a smelting chamber device 20, a partition device 30 and a pressure control device; the smelting chamber device 20 includes a smelting chamber shell 21 and a crucible 23, a smelting chamber 22 is arranged inside the smelting chamber shell 21, the smelting chamber 22 is provided with a first opening opened upward, the smelting chamber 22 is provided with a crucible 23 for carrying molten metal, the upper side of the crucible 23 is provided with a first connecting port and is connected to the smelting chamber 22; the casting chamber device 10 includes a casting chamber shell 11 and a filling mold shell 12, the casting chamber shell 11 is provided with a casting cavity 14, the casting cavity 14 is provided with a second opening opened downward, A filling shell 12 is provided at the lower part of the making cavity 14, and a second connecting port connected to the casting cavity 14 is provided at the top of the filling shell 12; the partition device 30 includes a partition plate 31 and a riser pipe 32, the lower side of the partition plate 31 is sealed and connected to the first opening, and the upper side of the partition plate 31 is sealed and connected to the second opening; the first end of the riser pipe 32 can extend into the molten metal in the crucible 23, and the second end of the riser pipe 32 can be sealed through the partition plate 31 and connected to the bottom of the filling shell 12; the pressure control device includes a first pressure component 41 and a second pressure component 42, the first pressure component 41 is connected to the smelting cavity 22 and can control the pressure in the smelting cavity 22, and the second pressure component 42 is connected to the casting cavity 14 and can control the pressure in the casting cavity 14.

[0060] Specifically, the smelting chamber shell 21 and the casting chamber shell 11 can adopt a similar structure, specifically, they can be cylindrical, and at one closed end, they are set to be hemispherical or ellipsoidal, so that the shell is subjected to balanced forces at all places under the action of internal pressure, and prevents the shell from leaking due to weak stress. It can be made of metal materials, and it can be selected whether to provide a thermal insulation layer according to actual conditions. In order to fix the crucible 23, a crucible 23 fixing frame 211 can be provided in the smelting chamber. Specifically, the crucible 23 fixing frame 211 can be fixed on the inner side wall of the smelting chamber, and the crucible 23 is provided with a flange, so that it can be mounted on the crucible 23 fixing frame 211. A plurality of connecting ports can be provided on the crucible 23 fixing frame 211, so that the crucible 23 can be connected to the smelting chamber 22. In order to monitor the temperature in the crucible 23, a temperature sensor can also be provided. The heating of the crucible 23 preferably adopts an electric heating method such as an induction coil 24. The crucible 23 may be a graphite crucible 23 or an alumina ceramic crucible 23. The partition plate 31 may be a simple plate-like structure. To fix the partition plate 31, a placement groove for the partition plate 31 may be provided at the first opening of the smelting chamber shell 21, so that the partition plate 31 can be fixed by supporting the partition plate 31 on all sides. Similarly, the riser 32 may be fixed on the partition plate 31 using a similar structure, and such a setting method can facilitate the disassembly and installation of the structure. The pressure control device may include a control device and a pipeline connected to a gas source, and the pressure in the smelting chamber 22 and the casting chamber 14 is controlled by introducing or extracting gas.

[0061] Furthermore, in order to monitor the filled volume in the filling shell 12, a measuring device such as a liquid level meter may be provided in the filling shell 12. However, since the casting product is not a uniform structure, when it is divided equally according to the height, the volumes of its parts are not the same, and the liquid level measurement requires recalculating the corresponding volume value, which is troublesome and inefficient. The product produced in the filling shell 12 is already designed, so it can be adjusted according to predetermined rules, such as by using a 3D model. Figure 3 as well as Figure 4 As shown, the filling shell 12 is divided into a plurality of sub-filling portions in sequence along the vertical direction, and a detection contact 13 is provided at the bottom end of each sub-filling portion.

[0062] It is divided into multiple sub-filling parts according to its volume, and a detection contact 13 for monitoring whether the liquid level reaches this place is set at the bottom of the sub-filling part, that is, the intersection of two sub-filling parts. Specifically, the detection contact 13 can be wrapped with a high-strength heat-resistant insulating ceramic tube of BN or Al2O3, wherein the ceramic tube is flush with the mold shell wall, and the detection contact 13 extends 1~2mm from the end face of the ceramic tube. The detection contact 13 can pass through the side wall of the filling shell 12 and be connected to the control device through a wire to transmit the detection result to the control device. In addition, a runner for connecting with the casting cavity 14 can be set at the top of the filling shell 12. The runner is tubular and extends in the vertical direction. The setting of the runner can prevent the metal melt from overflowing from the filling shell 12 and completely fill the product cavity to be produced. In order to further prevent the overflow of the molten metal, a detection contact 13 may be provided in the runner. Specifically, the runner may be set 100-500 mm higher than the casting, and the detection contact 13 may be set 10-20 mm from the top of the runner, thereby leaving a control margin.

[0063] As a specific implementation method, the sub-filling part can be set according to the following rules as in the aluminum alloy counter-gravity filling casting method described above. The filling shell 12 also includes a fast filling part arranged below the multiple sub-filling parts, and the volume of the sub-filling part is: V n =0.5 n V 0 ; Among them, V n is the volume value of the nth sub-filling part from bottom to top, V 0 It is the difference between the volume of the filling shell 12 and the volume of the rapid filling part.

[0064] Since the entire production process requires relatively strict pressure control, a relatively reliable sealing device 50 is required to seal the casting chamber 14 and the smelting chamber 22. Figure 2 , Figure 3 as well as Figure 7 , Figure 8 As shown, the aluminum alloy counter-gravity filling casting equipment also includes a sealing device 50, which includes a connecting flange 51 fixed at the opening of the casting chamber and a sealing disk 52 arranged at the opening of the smelting chamber. The sealing disk 52 is in a circular ring shape, and a connecting portion 521 is arranged on the side facing the casting chamber. The connecting portion 521 includes a plurality of grooves 5211 arranged along the circumferential direction of the sealing disk 52, and the connecting flange 51 includes a protruding structure corresponding to the groove 5211, and the protruding structure can pass through the groove 5211 to extend into the interior of the sealing disk 52; the sealing disk 52 can rotate relative to the smelting chamber, and a wedge block 5212 is arranged on the lower side of the connecting portion 521, and the thickness of the wedge block 5212 gradually increases along the rotation direction of the sealing disk 52.

[0065] By using the above structure, after the sealing disk 52 rotates, the protruding structure of the connecting flange 51 can be pressed against the lower side of the wedge block 5212, thereby generating a large axial pressing force and further achieving a reliable sealing effect. The force driving the sealing disk 52 to rotate can come from a driving device, which can include a hydraulic drive, a motor drive, etc. Since the hydraulic drive can generate a large thrust, preferably, a hydraulic drive method is adopted. Specifically, the hydraulic drive cylinder can be hinged on the sealing disk 52 at one end and hinged in the smelting chamber at the other end, thereby driving the sealing disk 52 to rotate.

[0066] As a specific implementation method, Figure 3 As shown, the crucible 23 includes a pot body and an induction coil 24 disposed outside the pot body, and the induction coil 24 is used to heat the pot body. The induction coil 24 can utilize the principle of electromagnetic induction to generate an alternating magnetic field through an AC power supply. The magnetic field generates an eddy current in the conductive material, and the heating purpose is achieved by relying on the energy of the eddy current. Compared with the fuel heating method, this heating method can avoid consuming oxygen and generating additional exhaust gas, and avoid affecting the pressure control in the production process.

[0067] In order to heat the filling shell 12 to the working temperature, as Figure 3 As shown, the melting chamber device 20 also includes a mold shell heating component 15, and the mold shell heating component 15 includes a heating hood 151 and a lifting component 152. The heating hood 151 includes a first state and a second state; in the first state, the heating hood 151 is arranged on the outside of the filling shell 12 and can heat the filling shell 12; in the second state, the heating hood 151 is away from the filling shell 12 and is arranged on the upper part of the casting cavity 14; the lifting component 152 can drive the heating hood 151 to switch between the first state and the second state.

[0068] The heating cover 151 may include a cover body and a heating resistor wire disposed in the cover body, and the filling shell 12 may be heated to the working temperature by electric heating. At the same time, since the filling shell 12 needs to be heated first, there is no need for heating after reaching the predetermined temperature, especially in the later stage when the product needs to be cooled, it is more necessary to remove the heating component 15. Therefore, the above technical solution also provides a lifting component 152 to drive the heating cover 151 to switch between the first state and the second state. The lifting component 152 may be a telescopic rod, a gear rack, a hydraulic rod 53, a slide slider and other components.

[0069] In order to further prevent the metal melt from leaking from the interface between the riser 32 and the filling shell 12, as shown in FIG. Figure 3 as well as Figure 5As shown, a through hole for the liquid riser 32 to pass through is provided in the middle of the partition plate 31, and a flow blocking ring 311 is provided around the through hole on the upper side of the partition plate 31, and the flow blocking ring 311 is provided to protrude from the upper surface of the partition plate 31 in the vertical direction;

[0070] The filling mold shell 12 includes a mold shell body 122 and a pouring cup 121. The pouring cup 121 is arranged on the lower side of the mold shell body 122. The pouring cup 121 is used to be connected with the riser pipe 32. The pouring cup 121 is provided with a flow blocking groove. The shape of the flow blocking groove matches the flow blocking ring 311. The pouring cup 121 can be pressed onto the flow blocking ring 311.

[0071] The setting of the flow blocking ring 311 makes the fitting surface of the pouring cup 121 and the partition plate 31 form a more complex structure, so it is difficult for the metal melt to overflow from the fitting surface. Furthermore, an asbestos pad can be set at the fitting surface, and the self-weight of the filling shell 12 is used to press it on the asbestos pad and the partition plate 31, so as to achieve a better sealing effect. Specifically, the cross-sectional shape of the flow blocking ring 311 can be set to a stepped, trapezoidal, triangular or other shape that is narrow at the top and wide at the bottom. During the falling and installation process of the filling shell 12, it can play a certain guiding role, and can be stably installed even if a small range of deviation occurs. A filter screen for filtering impurities in the metal melt can also be set at the inlet or outlet end of the riser 32. The filter screen can be set to a 304 stainless steel gas-liquid filter screen with a mesh size of about 5 mm and a wire diameter of 0.23 mm.

[0072] As a specific implementation method, Figure 2 As shown, the first pressure assembly 41 includes an inert gas inlet valve 411, a cooling gas inlet valve 412 and an exhaust valve 413 connected to the smelting chamber 22, the inert gas inlet valve 411 is connected to the inert gas supply device, and the cooling gas inlet valve 412 is connected to the cooling gas supply device. Among them, in order to reduce costs, the cooling gas inlet valve 412 can also be passed through compressed air. In the second pressure assembly 42, the second pressure assembly 42 can adopt the same structure as the first pressure assembly 41, with a slight difference. In the second pressure assembly, an inert gas can be selected to be passed through the inert gas inlet valve, or a mixed gas of inert gas and oxygen can be selected to be passed through. Specifically, the above-mentioned inlet valve and exhaust valve can both be electrically controlled valves, which can be controlled to open or close by the control assembly, so that more precise control can be achieved. In addition, pressure detection sensors can also be set on the smelting chamber 22 and the casting chamber 14.

[0073] Those skilled in the art will appreciate that the above-mentioned embodiments are specific examples for implementing the present disclosure, and in actual applications, various changes may be made thereto in form and detail without departing from the scope of the present disclosure.

Claims

1. A method for casting an aluminum alloy by counter-gravity filling, characterized in that: The aluminum alloy anti-gravity filling casting method comprises: Step S1, heating a crucible provided in a smelting chamber device in an inert gas environment to melt the metal contained in the crucible into a metal melt; Step S2, connecting the smelting chamber device and the casting chamber device so that the molten metal in the crucible is connected to the bottom of the filling shell through the riser; Step S3, evacuating the smelting chamber and the casting chamber simultaneously to reach a preset vacuum degree; Step S4, introducing inert gas into the smelting chamber to increase the internal pressure thereof, wherein the pressure value in the smelting chamber is P1, so that the molten metal enters the filling shell through the riser pipe; Step S5, introducing a mixed gas of oxygen and inert gas into the casting cavity and increasing the internal pressure thereof, wherein the pressure value in the casting cavity is P2, at which point P2<P1; and the oxygen content in the mixed gas is 3%-20%; Step S6, as the volume of the molten metal in the filling shell increases, gradually increasing the pressure in the casting cavity to reduce the pressure difference between the smelting cavity and the casting cavity, when the filling shell is filled with the molten metal, P2=P1; The step S6 further comprises: After the molten metal in the filling shell reaches a first volume value, the remaining portion to be filled is divided into a plurality of sub-filling portions from bottom to top, and the volume value of the nth sub-filling portion is: V n =0.5 n V0; Among them, V n is the volume value of the nth sub-filling portion from bottom to top, and V0 is the difference between the volume value of the filling shell and the first volume value; Step S7, after the pressure value in the casting cavity is raised to the same as the pressure value in the smelting cavity, the product is taken out after the molten metal in the filling shell is cooled and solidified.

2. The aluminum alloy counter-gravity filling casting method according to claim 1, characterized in that: The step S6 further comprises: Firstly, based on the first pressure difference, the metal melt flows into the filling shell and reaches a first volume value, and then the pressure difference between the smelting chamber and the casting chamber is gradually reduced.

3. The aluminum alloy counter-gravity filling casting method according to claim 1, characterized in that: Corresponding to each of the sub-filling parts, the pressure value in the casting cavity is: P n =(1-0.5 n+1 )P1; Among them, P n is the pressure value in the casting cavity corresponding to the nth sub-filling portion, and P1 is the pressure value in the smelting cavity; The pressure value P1 in the smelting chamber is 0.05MPa-0.1MPa.

4. The aluminum alloy counter-gravity filling casting method according to claim 3, characterized in that: The first volume value is 40%-60% of the total volume of the filling shell.

5. The aluminum alloy counter-gravity filling casting method according to claim 1, characterized in that: The step S1 further comprises: After refining the metal in the crucible at 720° C.-735° C. for 5-20 min, the metal melt is cooled to 715° C.-730° C. and kept warm; The riser tube was preheated to above 350°C.

6. The aluminum alloy counter-gravity filling casting method according to claim 1, characterized in that: The step S3 further comprises: Firstly, the filling shell disposed in the casting chamber is heated to 300°C-700°C; The vacuum degree of the smelting chamber and the casting chamber is ≤20Pa.

7. The aluminum alloy counter-gravity filling casting method according to claim 1, characterized in that: The step S7 further includes synchronously increasing the pressure in the smelting chamber and the casting chamber to a pressurized cooling pressure, wherein the pressurized cooling pressure is 0.3-0.8 MPa; While cooling gas is introduced into the smelting chamber and the casting chamber respectively, the smelting chamber and the casting chamber are exhausted to keep the pressure in the smelting chamber and the casting chamber at the cooling pressure.

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