A local high pressure boost and refinement device and anti-gravity casting equipment using the device

Abstract

The present invention discloses a local high-pressurization and refinement device for wheel anti-gravity casting, the local high-pressurization and refinement device comprises a local pressurization mechanism and a refinement mechanism; the local pressurization mechanism is arranged below the position corresponding to the wheel center on the anti-gravity casting wheel mold, comprising a pressure driving unit, a pressure transmission unit and a pressure applying unit, the pressure applying mechanism contacts the metal melt, and applies pressure to the metal melt after the filling is completed; the refinement mechanism is arranged on the anti-gravity casting wheel mold, above the position corresponding to the wheel center, and refines the metal melt during its solidification process. The present invention can be applied to the anti-gravity casting molding device of aluminum alloy castings with multi-liter liquid tube filling, and locally pressurizes the metal melt at the center of the casting, eliminates shrinkage cavities and shrinkage, and realizes the refinement of grains, which significantly improves the mechanical properties of the casting.

Description

Technical Field

[0001] The invention relates to the technical field of casting, in particular to a local pressurization and refinement device for anti-gravity casting of wheels, and anti-gravity casting equipment using the device. Background Art

[0002] Lightweighting is one of the most important ways to save energy and reduce emissions for fuel vehicles and to reduce consumption and increase range for new energy vehicles. Replacing traditional steel materials with lightweight materials such as aluminum alloys has become an inevitable choice for the renewal of automobile design. Aluminum alloys used in automobiles can be divided into cast aluminum alloys and deformed aluminum alloys. Cast aluminum alloys dominate and are mainly used to manufacture engines, clutch housings, wheels, chassis parts and other components. With the demand for improved wheel quality and the development of casting technology, more parts are produced by low-pressure casting, differential pressure casting and pressure-regulated casting, all of which belong to anti-gravity casting methods. The basic principle of this type of casting is to use low-pressure gas to drive the molten metal in the crucible or holding furnace, so that it rises through the riser and enters the mold cavity. After the filling is completed, the molten metal in the mold completes solidification and shrinkage compensation under the action of pressure.

[0003] Traditional aluminum alloy low-pressure, differential pressure and pressure-regulated wheel casting technologies usually use a single-gate single-riser tube filling technology. Taking aluminum alloy wheels as an example, a riser tube is set at the center of the wheel, that is, the wheel center position of the wheel, so that the metal melt enters the mold cavity and completes the filling and solidification. This method is simple in design and easy to implement, but the disadvantages are that the filling distance is long and the molding is difficult. In order to avoid cold shut, the temperature of the wheel metal mold is generally as high as 400°C or above, resulting in a low cooling rate of the wheel, coarse structure, and easy formation of shrinkage cavities and shrinkage in the hot joints. Casting defects such as shrinkage cavities and shrinkage are easily formed. In order to refine the structure and eliminate casting defects such as shrinkage cavities and shrinkage, water cooling, water mist cooling and other methods are generally used in the prior art to strengthen the cooling of the wheel mold. However, while strengthening the cooling greatly shortens the solidification time of the wheel, such as the solidification time of a large-size wheel after strengthening cooling can be shortened to less than 100s, it also causes the problem of difficulty in controlling the temperature field of the wheel cooling and solidification process during the production process, resulting in difficulty in achieving sequential solidification, unstable product performance, and low pass rate.

[0004] There have been attempts at other filling methods in the prior art of wheels. Patent CN201010107026.8 discloses a low-pressure casting double-sided pouring process and device for aluminum alloy wheels. Gates are set on both sides of the wheel to allow molten aluminum to enter from the rim. By controlling the cooling, the molten aluminum crystallizes from the wheel center to the rim at the rapidly cooled mold temperature, shortening the distance the molten aluminum flows. Combined with cooling, shrinkage defects at the R angle or rim area are reduced. Patents CN201310557627.2, CN201410825962.0 and other documents disclose the use of a combination of a central gate and a gate on both sides in the hope of reducing the weight of the hub and improving the mechanical strength. CN201610390494.8 uses a one-machine dual-mold hub mold, and the gate is also set at the rim position to achieve one-time casting of two hubs.

[0005] However, the above-mentioned device and method also have obvious defects. For the method in which the aluminum liquid enters only from the rim, the inlet is set in the middle of the rim, which will cause diversion after entering, that is, filling the wheel center and the wheel rim at the same time, resulting in uncontrollable filling time at each location, and then uncontrollable solidification sequence, which is easy to form shrinkage holes and shrinkage defects. For the method of combining the central gate and the two side gates, since the aluminum liquid enters from two inlets, it will form a convergence in the middle position, which is easy to cause breakpoints due to reasons such as poor gas discharge.

[0006] The applicant has designed a rapid sequential solidification wheel forming device and method based on multiple riser pipes, in which the gate of the mold is set just below the wheel rim. By filling the mold with liquid in multiple riser pipes, the filling distance can be significantly reduced and the problem of long-distance shrinkage compensation for large-sized wheels can be solved. However, since the gate is set just below the wheel rim, the filling and solidification time at the wheel center is relatively late, which may cause shrinkage cavities and shrinkage problems at this location. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a local high-pressure and refinement device for anti-gravity casting of wheels, and anti-gravity casting equipment using the device.

[0008] The complete technical solution of the present invention includes:

[0009] A local high pressure boost and refinement device for wheel anti-gravity casting, characterized in that the local high pressure boost and refinement device comprises a local pressure boost mechanism and a refinement mechanism;

[0010] The local pressurizing mechanism is arranged below the position corresponding to the wheel center of the anti-gravity casting wheel mold, and the local pressurizing mechanism contacts the metal melt and applies pressure to the metal melt after the filling is completed;

[0011] The refinement mechanism is arranged on the anti-gravity casting wheel mold, corresponding to the position above the wheel center, and refines the metal melt during its solidification process.

[0012] The local pressurization mechanism includes a pressure driving unit, a pressure transmission unit and a pressure applying unit. The pressure driving unit provides the pressure required for local pressurization, and the pressure transmission unit transmits the pressure to the pressure applying unit. The pressure applying unit contacts the metal melt and applies pressure to the metal melt after filling is completed.

[0013] The local pressurizing mechanism comprises a main frame with hydraulic cylinders on both sides, the piston rods of the hydraulic cylinders are connected to thrust joints, the thrust joints can slide on guide rails, the thrust joints are connected to connecting rods, the connecting rods are provided with two center holes, and the center holes are provided with sliding shafts; the connecting rods are connected to push rods, a pressure head is connected to the top of the push rods, and the pressure head is aligned with the wheel center position; when local pressurizing is performed, the piston rods of the hydraulic cylinders on both sides push the thrust joints to slide on the guide rails, and push the sliding shaft in the center hole below the connecting rod to slide, and the sliding shaft in the center hole above the connecting rod slides at the same time, driving the connecting rod to slide in the groove, and pushing the push rod to move upward, driving the pressure head to locally pressurize the melt at the wheel center position.

[0014] The thinning mechanism is an ultrasonic thinning mechanism or a vibration thinning mechanism.

[0015] Anti-gravity casting equipment with the device.

[0016] The counter-gravity casting equipment comprises a mold, and a gate on the mold is opened on a circular surface just below the wheel rim.

[0017] The anti-gravity casting equipment is one of low-pressure casting equipment, pressure-regulated casting equipment or differential pressure casting equipment.

[0018] The advantages of the present invention over the prior art are:

[0019] The applicant proposed a rapid sequential solidification wheel forming device and method based on multiple riser tubes, in which the gate of the mold is set just below the rim of the wheel. By filling the mold with liquid in multiple riser tubes, the filling distance can be significantly reduced and the problem of long-distance shrinkage compensation for large-sized wheels can be solved. However, since the gate is set just below the rim of the wheel, the filling and solidification time at the wheel center position is relatively late, and shrinkage cavities and shrinkage problems may occur here. In response to this problem, the present invention adds a local boosting device at the center of the wheel, and the pressure applying mechanism contacts the molten metal and applies pressure to the molten metal after the filling is completed. The aluminum liquid here is solidified under extremely high pressure, eliminating the possibility of shrinkage cavities and shrinkage defects. At the same time, a refinement device is set to vibrate the aluminum liquid during the solidification process, so that the dendrites formed by the crystallization of the aluminum liquid are broken, the nucleation is enhanced, the grains are refined, and the mechanical properties of the wheel are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a schematic diagram of the anti-gravity casting structure of a wheel with the local pressurization and refinement device of the present invention.

[0021] Figure 2 a is the structural diagram of the local boosting mechanism.

[0022] Figure 2 b is Figure 2 Top view of a.

[0023] Figure 3 It is a schematic diagram of a wheel structure in the prior art.

[0024] Figure 4 a is Figure 1 The part of the equipment that is prone to air entrainment when filling.

[0025] Figure 4 b is Figure 4 A partial enlarged view of a.

[0026] Figure 4 c is Figure 4 a Schematic diagram of the filling sequence during slow filling.

[0027] In the figure: 1-heat holding furnace, 2-liquid riser, 3-aluminum liquid, 4-special-shaped gate assembly, 5-cavity, 6-pressure drive unit, 7-pressure transmission unit, 8-pressure application unit, 9-vibration generator, 10-vibration rod, 11-guide rail mounting seat, 12-guide rail, 13-hydraulic cylinder, 14-hydraulic cylinder mounting seat, 15-connecting plate, 16-guide sleeve, 17-thrust connector, 18-first sliding shaft, 19-sliding bushing, 20-spacer, 21-connecting rod, 22-top rod, 23-retaining ring, 24-second sliding shaft, 25-mounting table, 26-lower mold. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0029] like Figure 1 As shown, a local high-pressure and refinement device for wheel anti-gravity casting, the local high-pressure and refinement device includes a local pressure mechanism and a refinement mechanism; the local pressure mechanism is arranged below the mold, below the position of the wheel center on the mold, and includes a pressure driving unit 6, a pressure transmission unit 7 and a pressure applying unit 8, the pressure applying unit 8 contacts the metal melt and applies pressure to the metal melt after the filling is completed; the refinement mechanism is arranged above the wheel mold, above the position corresponding to the wheel center, and refines the metal melt during its solidification process. The refinement mechanism is an ultrasonic refinement mechanism or a vibration refinement mechanism. In this specific embodiment, it includes a vibration generator 9 and a vibration rod 10, which penetrates into the aluminum liquid and vibrates the aluminum liquid during the solidification process, so that the dendrites formed by the aluminum liquid crystallization are broken, the nucleation is enhanced, the grains are refined, and the mechanical properties of the wheel are improved. In order to more clearly indicate the structure of the device, the figure also shows the matching mounting plate 25 and the lower mold 26.

[0030] The local boost mechanism is arranged below the mold, below the position of the wheel center on the mold. The detailed structure of one specific implementation is as follows: Figure 2 As shown, it includes a main frame, and hydraulic cylinders 13 are provided on the left and right sides. The hydraulic cylinders are installed on the hydraulic cylinder mounting seat 14. A connecting plate 15 is provided on the main frame in front of the hydraulic cylinder, and a guide sleeve 16 is provided on the connecting plate to guide the movement of the piston rod. The piston rod of the hydraulic cylinder is connected to the thrust joint 17, and the guide rail 12 is installed on the guide rail mounting seat 11. The thrust joint can slide on the guide rail 12. The thrust joint is connected to the connecting rod 21 through the first sliding shaft 18, and the first sliding shaft is covered with a sliding bushing 19 and a spacer 20. The connecting rod 21 is connected to the push rod 22. Through the action of the first sliding shaft 18 located in the lower center hole of the connecting rod and the second sliding shaft 24 located in the upper center hole of the connecting rod, the thrust transmitted by the thrust joint is transmitted to the push rod 22, forming an upward pressure. A pressure head is connected to the top of the push rod, and the pressure head is aligned with the wheel center position. A retaining ring 23 is provided on the push rod.

[0031] When local pressurization is performed, the piston rods of the hydraulic cylinders on both sides push the thrust joints, slide on the guide rails, and push the first sliding shaft in the center hole below the connecting rod to slide. The second sliding shaft in the center hole above the connecting rod slides at the same time, driving the connecting rod to slide in the groove, and pushing the ejector rod upward, driving the pressure head to extrude the melt.

[0032] A design idea of ​​the local increase mechanism of the present invention is described below:

[0033] The ram of the local increase mechanism of the present invention is extruded in the metal melt and is designed to transmit a pressure of 0 to 120 MPa. The design idea is explained below using the commonly used 20 MPa pressure as an example, and the ram design method for other pressures is similar.

[0034] 1. Parameter calculation

[0035] (1) Pressure calculation:

[0036] According to the calculation of 20MPa pressure in the melt and 60mm diameter of the extrusion rod, we get:

[0037] F=3.14*0.06*0.06*0.25*20*10 6

[0038] Calculate F = 5.7 tons.

[0039] (2) Displacement calculation:

[0040] The distance between the two center holes of the connecting rod is 150mm, then:

[0041] tan 3°=0.052, unilateral magnification is 19.2 times, 10 / 19*2=0.263 tons (unilateral thrust), considering other resistances and long-term fatigue impact, the safety factor is set to 2.5, and the thrust is considered to be 0.68 tons.

[0042] 150*cos 10°=149.79;

[0043] 150*cos 3°=147.72;

[0044] The difference is 2 mm, and the lateral thrust stroke of the cylinder on one side is 19 mm.

[0045] Considering the push rod stability requirements, a hydraulic cylinder with a cylinder diameter of 50, a piston rod diameter of 28, and a working pressure of 1Mpa is selected.

[0046] Taking load reduction and space compactness into consideration, the connecting rods are designed to be two on the left and right.

[0047] After verification calculation, the strength and stiffness verification meet the requirements.

[0048] The wheel forming device used in conjunction with the present invention and the supporting process are described below.

[0049] Figure 3This is a typical wheel structure diagram, in which in the prior art, the center of the wheel is usually called the wheel center, the part on the outside of the wheel that is assembled with the tire and supports the tire is called the rim, the wheel part that is installed and connected to the axle wheel center and supports the rim is called the spoke, and there is a window in the middle of the multiple spokes. The rim part that maintains and supports the direction of the tire is called the flange.

[0050] In the existing production of low-pressure or differential-pressure cast aluminum alloy wheels, almost all of them use a riser pipe set at the central wheel center of the wheel, and allow the melt to pass through the insulation cup and gate sleeve connected to the riser pipe, enter the mold cavity from the gate at the wheel center, and be diverted under the action of the diverter cone, and fill the mold in the order of wheel center-spoke-rim-rim, and solidify after filling the mold cavity. This is because in actual production, it is easiest to set the gate and riser pipe here, and the cross-sectional shape of the gate is a regular circle, which is simple to process. At the same time, the area of ​​the gate is large, which can make the filling speed fast. However, some problems caused by the above-mentioned pouring and filling method have never been well solved, such as the long gate distance, the long filling distance, and it is very difficult to compensate for shrinkage at the hot joints such as the connection between the rim and the spoke, which is easy to form shrinkage cavities and shrinkage, becoming a major problem that plagues the production of the wheel industry. Although water cooling, water mist cooling and other methods are used to enhance cooling in order to achieve sequential solidification, the short filling and solidification time of the wheel makes it difficult to accurately control the temperature field, and a considerable proportion of scrap is still inevitable.

[0051] In the prior art, however, double-sided pouring is performed in the middle of the rim side. However, due to the uncontrollable filling and solidification sequence caused by the filling diversion, shrinkage cavities and shrinkage defects are easily formed. Currently, the wheel industry does not widely adopt the double-sided pouring. The center pouring is still the main method, which also shows that the value of this method in industrial application is not great.

[0052] Based on this problem, the present invention proposes a wheel forming device based on a multi-liter liquid channel that is suitable for matching with the previous invention, such as Figure 1 As shown, it includes a heat preservation furnace 1 containing aluminum liquid, a high-pressure gas source connected to the heat preservation furnace, and multiple riser pipes 2 are arranged in the heat preservation furnace, and the lower parts of the multiple riser pipes are immersed in the aluminum liquid 3. When the aluminum liquid in the furnace is pressurized by the high-pressure gas source, the aluminum liquid can rise along the multiple riser pipes. The riser pipe is connected to the gate of the mold through a thermos cup and a special-shaped gate assembly 4 disclosed in the present invention, and enters the mold cavity 5 of the mold. The gate assembly includes a gate cup and a special-shaped gate sleeve above it, and the gate sleeve is connected to the gate.

[0053] The gate of the mold is set on the annular surface directly below the wheel rim. It is particularly noted that the "annular surface directly below the wheel rim" in the present invention refers to the annular surface formed on the side of the rim opposite to the wheel flange, surrounding the center axis of the wheel. The outer circle of the annular surface is the circle formed by the outermost contour line of the wheel on the surface, and the inner circle is the circle formed by the outer contour line of the window area of ​​the wheel around the center axis of the wheel. Figure 3 Correspondingly, the position where the gate assembly is connected to the mold is also set at this location.

[0054] Particularly preferably, the gate and the gate assembly can be arranged at a position on the annular surface corresponding to the outer side of the window area, or can be arranged at a position on the annular surface corresponding to the connection between the rim and the spoke.

[0055] In a preferred embodiment, the gate can be provided with two, which can be symmetrically arranged on both sides of the wheel, or multiple gates can be arranged around the wheel axis. Corresponding to the gate, the riser can be provided with two, which can be symmetrically arranged on both sides of the wheel, or multiple riser can be arranged around the wheel axis.

[0056] The present invention also discloses a low-pressure / differential pressure casting process suitable for the filling mode. Since the pouring and filling method of the present invention has undergone tremendous changes compared with the prior art, the original filling method and solidification process cannot be applied to the present invention. Based on this, the present invention also designs a process suitable for the filling position.

[0057] The specific steps include:

[0058] (1) Liquor lifting: The aluminum liquid in the holding furnace is pressurized by a high-pressure gas source, so that the aluminum liquid rises to the pouring gate position along the liquid riser under pressure. The pressure raising speed in this stage is 2.8-4.0 kPa / s, and the pressure is increased to 20 kPa;

[0059] (2) Filling: Continue to increase the pressure to allow the aluminum liquid to enter the mold cavity through the gate. This filling stage is a two-stage pressurization. The pressure increase rate in the first stage is 0.1-0.2 kPa / s for 2-4 seconds. Then enter the second stage to increase the pressure rapidly until the mold cavity is filled. At this time, the pressure reaches 35 kPa.

[0060] The pressure increase speed P' of the second stage is determined as follows:

[0061]

[0062] Where:

[0063] P′ is the pressure increase rate, in kPa / s; H is the total height of the cavity, in mm; ρ is the density of the metal melt, in g / cm 3; K is the resistance coefficient, and its value range is 1 to 1.5; t is the preset filling time, in seconds, preferably 10 seconds; 102 is the unit conversion coefficient; N is the number of liquid riser tubes, and its value range is 2 to 6, which can be selected according to the number of windows of different types of wheels, preferably 2 to 4; x is its liquid rise index, and its value range is 0.2 to 0.8. In the wheel type scheme adopted in this embodiment, the value is 0.5.

[0064] (3) Crystallization pressurization and pressure holding: After filling is completed, the pressure is rapidly increased to 150KPa at a pressure increase rate of 8-10KPa / and the pressure is maintained. At the same time, a local pressure increase mechanism applies a pressure of 1-120MPa to the metal melt at the wheel center until the wheel solidifies.

[0065] (4) Depressurization and venting: After the aluminum alloy wheel has solidified, the gas pressure in the holding furnace is released, allowing the unsolidified aluminum liquid in the riser and pouring nozzle to flow back into the holding furnace.

[0066] As for the selection of the pressure increasing speed in the liquid raising stage and the mold filling stage, since the inner diameter of the liquid raising pipe is fixed during the liquid raising, turbulence will basically not be generated, so a fast pressure increasing speed is adopted so that the metal melt can be quickly raised to the gate position and the liquid raising time is shortened. In the mold filling stage, the complex shapes of the mold cavity and the gate must be taken into consideration. In the traditional mold filling method, since the method of pouring from the wheel center position is adopted, the cross-sectional area of ​​the liquid raising pipe and the gate is not much different, and the cross-sectional area of ​​the mold cavity at the wheel center is large, and turbulence is not easy to be generated. Therefore, the filling pressure increasing speed can be obtained by experience or experiment. For the mold filling method of the present invention, the mold filling is carried out on the annular surface of the rim, which is an irregular conformal gate. The shape area of ​​the liquid raising pipe and the gate is very different. At the same time, the space at the rim is small. If the filling pressure is unreasonable, turbulent air is easily generated, resulting in pore defects. The filling pressure design in the prior art adopts the calculation method under the ideal state, combined with the resistance coefficient, etc. for correction. The flow state change caused by the change of the cross-sectional area of ​​the liquid raising pipe and the gate is not considered. Therefore, it is impossible to obtain the ideal filling and pressurizing speed by using the empirical formula in the prior art.

[0067] Therefore, the present invention has studied the above problems, combined with the riser, the gate, the shape and cross-sectional area of ​​the cavity above the gate, and the flow characteristics of the metal melt. It is found that for the wheel rim position, if Figure 4 In the circle indicated by the arrow in a, there are two parts with obvious changes in area in the initial stage of filling, such as Figure 4 At the circular frame indicated by the arrow in b, if turbulence occurs, air entrainment is very likely to form at this position. After design and calculation, the present invention adopts a two-stage pressurization. The first stage significantly reduces the pressurization speed so that the metal melt can flow smoothly in the initial stage of filling and fill the above area to avoid air entrainment. Figure 4c (the arrow here indicates the direction of melt filling), and then enters the second stage of rapid pressure increase to shorten the filling time. In the second stage of the filling process of the present invention, it is found that the filling stability is significantly related to the number of riser tubes, because the traditional method of pouring from the wheel center position has only one riser tube and gate, so the law can be obtained through experiments and quantitative processing can be performed. In the filling method of the present invention, the number of riser tubes and gates can be 2 or more. Under the same boosting conditions, the flow rate at the gate and the flow rate in the cavity above the gate will change significantly, resulting in uncontrollable filling flow mode. Therefore, the present invention obtains the boosting method of the second stage through research. It can be seen from formula (1) that within the same preset filling time, as the number of riser tubes increases, the boosting speed that can be adopted can be gradually increased, and will not cause turbulent air entrainment and other problems. The value of the resistance coefficient is related to the viscosity of the molten metal, the complexity of the casting cavity, etc. When the resistance is small, the lower limit is taken, and when the resistance is large, the upper limit is taken.

[0068] Embodiment 1:

[0069] Two riser tubes and pouring gates are used, and the mass percentage composition of the metal melt used is as follows: Si: 5-9%, Mg: 0.3-0.5%, Zr: 0.01-0.02%, B: 0.005-0.007%, Re: 0.002-0.005%, Nd: 0.002-0.005%, Fe: 0.05-0.15%, Mn: 0.05-0.1%, Ti: 0.08-0.14%, and the rest is Al and unavoidable impurities.

[0070] (1) Liquor lifting: The aluminum liquid in the holding furnace is pressurized by a high-pressure gas source, so that the aluminum liquid rises to the pouring gate position along the liquid riser under pressure. The pressure raising speed in this stage is 3.5 kPa / s, and the pressure is increased to 20 kPa;

[0071] (2) Filling: Continue to increase the pressure to allow the aluminum liquid to enter the mold cavity through the gate. The pressure increase rate in the first stage is 0.2 kPa / s and the time is 1.8 s, so that the metal melt is filled smoothly. Figure 4 b The area indicated by the arrow enters the second stage and then quickly fills the mold at a pressure increase rate of 0.66 kPa / s until the cavity is filled.

[0072] (3) Crystallization pressurization and pressure holding: After the filling is completed, the pressure is quickly increased to 150kPa at a pressure increase rate of 8KPa / s, and the pressure is maintained. The hydraulic cylinder drives the hydraulic rod to drive the pressure head to apply 2000kPa mechanical pressure to the wheel center position, and the vibration generator drives the vibration rod to vibrate and refine the aluminum liquid until the wheel solidifies. During the pressure holding process, the high pressure shrinkage of the rim hot section is maintained at the gate. Under the high-pressure aluminum liquid shrinkage, the possibility of shrinkage cavities and shrinkage at this location is completely eliminated. At the same time, the pressure head locally pressurizes the metal liquid at the wheel center by 20MPa, eliminating the possibility of shrinkage cavities and shrinkage at this location.

[0073] (4) Depressurization and venting: After the aluminum alloy wheel has solidified, the gas pressure in the holding furnace is released, allowing the unsolidified aluminum liquid in the riser and pouring nozzle to flow back into the holding furnace.

[0074] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A counter-gravity casting device with a local high-pressure and refinement device for wheel counter-gravity casting, characterized in that: The local high pressure boost and refinement device comprises a local pressure boost mechanism and a refinement mechanism; The local pressurizing mechanism is arranged below the position corresponding to the wheel center of the anti-gravity casting wheel mold, and the local pressurizing mechanism contacts the metal melt and applies pressure to the metal melt after the filling is completed; The local pressurizing mechanism comprises a main frame, with hydraulic cylinders on both sides, the piston rods of the hydraulic cylinders are connected to thrust joints, the thrust joints can slide on the guide rails, the thrust joints are connected to the connecting rods, the connecting rods are provided with two center holes, and the center holes are provided with sliding shafts; the connecting rods are connected to the push rods, the top of the push rods is connected with a pressure head, and the pressure head is aligned with the wheel center position; when performing local pressurization, the piston rods of the hydraulic cylinders on both sides push the thrust joints to slide on the guide rails, and push the sliding shaft in the center hole below the connecting rod to slide, and the sliding shaft in the center hole above the connecting rod slides at the same time, driving the connecting rod to slide in the groove, and pushing the push rod to move upward, driving the pressure head to locally pressurize the melt at the wheel center position; The pressure head is extruded in the metal melt and is designed to deliver a pressure of 0~120Mpa. The refinement mechanism is arranged on the anti-gravity casting wheel mold, corresponding to the position above the wheel center, and refines the molten metal during its solidification process; The process of the anti-gravity casting equipment is: (1) Liquor lifting: The aluminum liquid in the holding furnace is pressurized by a high-pressure gas source, so that the aluminum liquid rises to the pouring gate position along the liquid riser under pressure. The pressure increase rate in this stage is 2.8~4.0kPa / s, and the pressure is increased to 20kPa; (2) Filling: Continue to increase the pressure so that the aluminum liquid enters the cavity through the gate. This filling stage is a two-stage pressurization. The pressure increase rate in the first stage is 0.1~0.2kPa / s, and the time is 2~4s. Then enter the second stage of rapid pressure increase until the cavity is filled. At this time, the pressure reaches 35kPa; The boost speed 𝑃 of the second stage is determined as follows: Where: is the pressure increase rate, in kPa / s; H is the total height of the cavity, in mm; is the density of the metal melt, in g / cm 3 ; is the resistance coefficient, and its value range is 1~1.5; is the preset filling time, in seconds; 102 is the unit conversion factor; N is the number of riser tubes, and its value range is 2~6; is its liquid rise index, ranging from 0.2 to 0.8; (3) Crystallization pressurization and pressure holding: After filling, the pressure is rapidly increased to 150 KPa at a pressure increase rate of 8-10 KPa / and the pressure is maintained. At the same time, a local pressure increase mechanism applies a pressure of 1-120 MPa to the metal melt at the wheel center until the wheel solidifies. (4) Depressurization and venting: After the aluminum alloy wheel has solidified, the gas pressure in the holding furnace is released, allowing the unsolidified aluminum liquid in the riser and pouring gate to flow back into the holding furnace.

2. The anti-gravity casting equipment according to claim 1, characterized in that: The local pressurization mechanism includes a pressure driving unit, a pressure transmission unit and a pressure applying unit. The pressure driving unit provides the pressure required for local pressurization, and the pressure transmission unit transmits the pressure to the pressure applying unit. The pressure applying unit contacts the metal melt and applies pressure to the metal melt after filling is completed.

3. The anti-gravity casting equipment according to claim 1, characterized in that: The thinning mechanism is an ultrasonic thinning mechanism or a vibration thinning mechanism.

4. A counter-gravity casting device as claimed in claim 3, characterized in that: The counter-gravity casting equipment comprises a mold, and a gate on the mold is opened on a circular surface just below the wheel rim.

5. A counter-gravity casting device as claimed in claim 4, characterized in that: The anti-gravity casting equipment is one of low-pressure casting equipment, pressure-regulated casting equipment or differential pressure casting equipment.

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