Wheel anti-gravity casting equipment with molten pool insulation furnace

Abstract

The present invention discloses a wheel anti-gravity casting device with a molten pool insulation furnace, comprising a mold, a molten pool insulation furnace and a liquid riser; a central liquid riser is connected to the center of the molten pool insulation furnace cover, a liquid riser is connected above the central liquid riser, a plurality of shunt channels communicating with the liquid riser are arranged in the liquid riser box, and each shunt channel is connected to a shunt gate, the shunt gate corresponds to the position directly below the wheel mold rim, and is connected to the cavity inlet for pouring into the mold cavity, and the cross section of the shunt gate is roughly in line with the shape of the cavity inlet at the filling position of the casting mold. The present invention is suitable for a multi-gate side injection method in which the gate is arranged directly below the wheel rim, solves the problem that the traditional large-size wheel single liquid riser technology has poor long-distance shrinkage compensation effect and is difficult to control the solidification temperature field after enhanced cooling, improves the performance and production stability of the wheel, shortens the production cycle, and improves the production efficiency and the qualified rate of the wheel.

Description

Technical Field

[0001] The invention relates to the technical field of casting, in particular to a wheel anti-gravity casting device with a molten pool insulation furnace. 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 are mainly used to manufacture components such as engines, clutch housings, wheels, and chassis parts. With the demand for improved casting 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 pressure.

[0003] Traditional aluminum alloy low-pressure, differential pressure and pressure-regulated wheel casting technology usually adopts 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 easy to form. 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, strengthening the cooling greatly shortens the solidification time of the wheel. For example, the solidification time of a large-size wheel after strengthening cooling can be shortened to less than 100s, but at the same time, it 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 defects. For the method of combining the central gate and the gate on both sides, since the aluminum liquid enters from two inlets, it will form a convergence in the middle position, which is easy to cause cold shut due to reasons such as poor gas discharge.

[0006] The applicant has designed a rapid sequential solidification wheel molding device and method based on multiple riser tubes, in which the gate of the mold is set just below the wheel rim or outside the R angle above the lower rim. By filling the mold with liquid in multiple riser tubes, the problem of long-distance shrinkage compensation after filling is solved. However, due to the change in the position and shape of the gate, it is no longer possible to use the traditional circular casting assembly for filling. How to achieve stable filling in this way has become a problem to be solved urgently. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a wheel anti-gravity casting equipment with a molten pool insulation furnace.

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

[0009] A wheel anti-gravity casting device with a molten pool insulation furnace comprises at least a mold, a molten pool insulation furnace and a liquid riser;

[0010] The molten pool insulation furnace comprises a furnace body, an insulation layer formed of refractory material is provided on the inner wall of the furnace body, the insulation layer surrounds the molten pool, a furnace cover is provided on the upper part of the furnace body, and a central liquid riser is connected to the central position of the furnace cover. The molten pool insulation furnace is provided with a first electric heating device and a first temperature measuring thermocouple;

[0011] A central riser pipe is connected to the furnace cover, and a riser tank is connected above the central riser pipe. A plurality of diversion channels connected to the riser pipe are arranged in the riser tank body, and each diversion channel is connected to a diversion gate, which corresponds to the position directly below the rim of the wheel mold, is connected to the cavity inlet for pouring into the mold cavity, and pours the diverted molten metal into the cavity. A second electric heating device and a second temperature measuring thermocouple are arranged on the riser tank.

[0012] The cross-section of the diverter gate connected to the cavity inlet roughly follows the shape of the cavity inlet at the filling point of the casting.

[0013] The cross-sectional shape of the split gate section is: including a first arc segment and a second arc segment, the first arc segment and the second arc segment are concentric, and the radius and size of the first arc segment are smaller than the second arc segment, and the first arc segment and the second arc segment are connected on both sides by a connecting segment.

[0014] The length of the first arc segment is 72-76 mm, the length of the second arc segment is 76-80 mm, and the length of the connecting segments on both sides is 8-12 mm.

[0015] The inner surface of the diversion gate is provided with a mesh placement groove for placing a filter mesh.

[0016] There are two diversion gates, which are symmetrically arranged on both sides relative to the wheel axis.

[0017] The number of the diversion gates is greater than two and they are arranged around the wheel axis.

[0018] A roller is provided at the bottom of the furnace body, and the roller is located on a track and can move along the track.

[0019] A heat-insulating layer is also arranged under the furnace cover, a feeding port is arranged on one side of the furnace cover, a high-pressure gas source is connected to the furnace cover, and the upper part of the liquid riser is connected to the lower template on the frame.

[0020] The method for performing anti-gravity casting of wheels according to the device comprises the following steps:

[0021] (1) Lifting the liquid: The aluminum liquid in the holding furnace is pressurized by a high-pressure gas source, so that the aluminum liquid rises along the central lift pipe to the lift tank under pressure, and reaches the split gate position through the split channel in the lift tank. The pressure increase rate in this stage is 2.8-4.0 KPa / s, and the pressure is increased to 20 KPa;

[0022] (2) Filling: Continue to increase the pressure so that the aluminum liquid enters the cavity through the diversion 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 cavity is filled. At this time, the pressure reaches 35 KPa.

[0023] The pressure increase speed P' of the second stage is determined as follows:

[0024]

[0025] Where:

[0026] 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 6; 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.

[0027] (3) Crystallization pressurization and pressure holding: After filling is completed, the pressure is rapidly increased to 150 KPa at a pressure increase rate of 8 to 10 KPa / , and the pressure is maintained for 60 to 150 seconds. At this time, the wheel solidification is completed.

[0028] (4) Depressurization and venting: After the aluminum alloy wheel has solidified, the gas pressure in the molten pool holding furnace is released, allowing the unsolidified aluminum liquid in the riser tank and the central riser pipe to flow back into the holding furnace.

[0029] Before the liquid is raised, the mold temperature is not higher than 400°C, preferably, the mold temperature is not higher than 350°C, and more preferably, the mold temperature is not higher than 300°C.

[0030] The advantages of the present invention over the prior art are:

[0031] The applicant has proposed a rapid sequential solidification wheel forming device and method based on multi-gate side injection, in which the gate of the mold is set just below the rim of the wheel. By filling the mold with liquid rising at the multi-gate side injection, the filling distance of the molten metal is shortened by more than half compared with the existing single riser tube mode, which naturally speeds up the cooling speed and cooling effect of the wheel and achieves rapid sequential solidification. Since the position and shape of the gate have changed, the traditional circular casting assembly can no longer be used for filling the mold. The molten pool furnace and riser box device designed by the present invention are suitable for the multi-gate side injection method in which the gate is set just below the rim of the wheel, and a stable casting and filling method is achieved at the edge of the wheel. The designed mesh placement trough can place a conforming filter mesh, and the liquid inlet channel on the inner surface is larger than the gate, so that the filter mesh can be compacted under the gate. When used in conjunction with the multi-gate side injection method, the filling distance of the molten metal can be shortened by more than half compared with the existing single-lift liquid tube mode, and the metal mold temperature can be reduced from the existing 420°C to below 320°C, which naturally accelerates the cooling speed and cooling effect of the wheel, achieves rapid sequential solidification, eliminates shrinkage holes and shrinkage defects at hot nodes, and solves the problems of poor long-distance shrinkage compensation effect of traditional single-lift liquid tube technology for large-size wheels and difficulty in controlling the solidification temperature field after enhanced cooling. It not only significantly improves the performance and production stability of the wheel, but also shortens the production cycle, improves production efficiency and the qualified rate of the wheel. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic structural diagram of the wheel counter-gravity casting equipment with a molten pool insulation furnace according to the present invention.

[0033] Figure 2 for Figure 1 sectional view of .

[0034] Figure 3 It is a schematic diagram of the distribution of the diversion gate of the present invention on the annular surface directly below the rim.

[0035] Figure 4 It is a schematic diagram of a wheel structure in the prior art.

[0036] Figure 5 a is Figure 1 The parts of the device that are prone to air entrainment during the filling process.

[0037] Figure 5 b is Figure 5 A partial enlarged view of a.

[0038] Figure 5 c is Figure 5 a Schematic diagram of the filling sequence during slow filling. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0040] like Figure 1-2 As shown, taking low-pressure casting as an example, the wheel anti-gravity casting equipment with a molten pool insulation furnace of the present invention comprises a molten pool insulation furnace 1, a mold 2 and a liquid riser 3;

[0041] The molten pool insulation furnace 1 comprises a furnace body 4, the inner wall of the furnace body is provided with an insulation layer 5 formed of refractory material, the insulation layer surrounds a molten metal pool 6, a furnace cover 7 is provided on the upper part of the furnace body, and an insulation layer is also provided under the furnace cover, a charging port is provided on one side of the furnace cover, a central liquid riser 8 is connected to the center of the furnace cover, a high-pressure gas source is connected to the furnace cover, a first electric heating device is provided in the furnace wall, and a first thermocouple is provided above the furnace cover; wherein the charging port, high-pressure gas source, first electric heating device and thermocouple provided on the furnace cover are prior art, and are not shown in the figure for the sake of simplifying the view. The first electric heating device and the thermocouple measure the temperature of the molten metal in the molten pool insulation furnace and control it to maintain the filling temperature, the charging port is used to add aluminum liquid, and the high-pressure gas source is used to make the molten metal rise to the mold cavity.

[0042] A riser tank 3 is connected above the central riser pipe, and the upper part of the riser tank is connected to the lower mold plate on the frame. A plurality of shunt channels communicating with the riser pipe are arranged in the riser tank, and each shunt channel is connected to a shunt gate 9. The riser tank is provided with multiple shunt gates, which correspond to the position directly below the wheel mold rim, are connected to the cavity inlet for pouring into the mold cavity, and the shunt molten metal is pressed and poured into the cavity. The riser tank is provided with a second electric heating device and a temperature measuring thermocouple. The shunt channel, the second electric heating device and the thermocouple are prior art, and are not shown in the figure for the sake of simplifying the view. The second electric heating device and the temperature measuring thermocouple measure the temperature and heat the molten metal in the riser tank to prevent it from freezing.

[0043] The mold cavity inlet corresponding to each diversion gate is set on the annular surface 10 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 3-4 Correspondingly, the position where the diversion gate is connected to the mold is also set at this location.

[0044] It is particularly preferred that the diverter gate and the cavity inlet 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.

[0045] In particular, the cross-section of the diverter gate, which is in communication with the cavity inlet, generally follows the shape of the cavity inlet at the filling point of the casting.

[0046] Specifically, Figure 3 As shown, the cross-sectional shape of the cross-section of the diversion gate 9 is: including a first arc segment 11 and a second arc segment 12, the first arc segment and the second arc segment are concentric, and the radius and size of the first arc segment are smaller than the second arc segment, and the first arc segment and the second arc segment are connected on both sides by a connecting segment 13.

[0047] The length of the first arc segment is 72-76 mm, the length of the second arc segment is 76-80 mm, and the length of the connecting segments on both sides is 8-12 mm.

[0048] The inner surface of the diversion gate is provided with a mesh placement groove for placing a filter mesh, and the shape of the filter mesh also follows the shape of the cavity entrance of the casting at this filling position.

[0049] The number of the diversion gates is two, which are symmetrically arranged on both sides relative to the wheel axis. The number of the diversion gates can also be greater than two, which are arranged around the wheel axis.

[0050] The furnace body bottom is provided with rollers, which are located on tracks and can be moved along the tracks. This is prior art and is not shown in the figure for the sake of simplifying the view.

[0051] The following is an explanation of the process method for low-pressure wheel casting that is compatible with the low-pressure wheel casting equipment of the present invention.

[0052] Figure 4 This 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.

[0053] 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 position of the wheel, and allow the melt to pass through the insulation cup and pouring assembly 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.

[0054] In the prior art, bilateral pouring is performed at the middle of the rim side. However, the filling and solidification sequence is uncontrollable due to the filling diversion, which also easily leads to shrinkage defects.

[0055] Based on this problem, the present invention proposes a wheel forming device based on a multi-liter liquid channel suitable for matching with the above-mentioned special-shaped casting component, such as Figure 1-2 As shown, it includes a molten pool insulation furnace containing aluminum liquid, a high-pressure gas source connected to the insulation furnace, and a central liquid riser pipe in the insulation furnace, the lower part of which is immersed in the aluminum liquid. When the aluminum liquid in the furnace is pressurized by the high-pressure gas source, the aluminum liquid can rise along the central liquid riser pipe into the liquid riser box, and be divided into 2, 4, or other ways in the liquid riser box. And through the diversion gate above the liquid riser box that conforms to the shape of the cavity entrance, it enters the mold cavity through the cavity entrance.

[0056] As mentioned above, the cavity inlet is arranged on the annular surface directly below the rim of the wheel, and the definition of "the annular surface directly below the rim" in the present invention is as mentioned above.

[0057] In addition, a refinement device may be provided above the position of the wheel mold corresponding to the wheel center, that is, at the diversion cone corresponding to the traditional center bottom injection molding method. The refinement mechanism may be an ultrasonic refinement mechanism or a vibration refinement mechanism. For example, the refinement mechanism may include a vibration generator and a vibration rod. The vibration rod is inserted into the aluminum liquid to vibrate 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.

[0058] The present invention also discloses a low-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.

[0059] The specific steps include:

[0060] (1) Lifting the liquid: The aluminum liquid in the holding furnace is pressurized by a high-pressure gas source, so that the aluminum liquid rises along the central lift pipe to the lift tank under pressure, and reaches the split gate position through the split channel in the lift tank. The pressure increase rate in this stage is 2.8-4.0 KPa / s, and the pressure is increased to 20 KPa;

[0061] (2) Filling: Continue to increase the pressure so that the aluminum liquid enters the cavity through the diversion 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 cavity is filled. At this time, the pressure reaches 35 KPa.

[0062] The pressure increase speed P' of the second stage is determined as follows:

[0063]

[0064] Where:

[0065] 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 6; 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.

[0066] (3) Crystallization pressurization and pressure holding: After filling is completed, the pressure is rapidly increased to 150 KPa at a pressure increase rate of 8 to 10 KPa / , and the pressure is maintained for 60 to 150 seconds. At this time, the wheel solidification is completed.

[0067] (4) Depressurization and venting: After the aluminum alloy wheel has solidified, the gas pressure in the molten pool holding furnace is released, allowing the unsolidified aluminum liquid in the riser tank and the central riser pipe to flow back into the holding furnace.

[0068] As for the selection of the pressure increase speed in the liquid raising stage and the mold filling stage, since the inner diameter of the liquid raising pipe and the diverter runner in the liquid raising box is fixed during the liquid raising, basically no turbulence will be generated, so a fast pressure increase speed is adopted to enable the metal melt to quickly rise to the diverter gate position, shortening the liquid raising time. In the mold filling stage, the complex shapes of the cavity inlet 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 cavity inlet and the gate is not much different, and the cavity cross-sectional area at the wheel center is large, and turbulence is not easy to generate. Therefore, the filling pressure increase 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 cavity inlet. The shape area of ​​the diverter channel 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 ideal conditions, combined with the resistance coefficient, etc. for correction. The flow state change caused by the change of the cross-sectional area of ​​the runner and the gate is not taken into account. Therefore, it is impossible to obtain the ideal filling and pressure increasing speed by using the empirical formula in the prior art.

[0069] Therefore, the present invention has studied the above problems, combined with the riser box runner, the diverter gate, the cavity shape and cross-sectional area above the cavity inlet, and the flow characteristics of the metal melt. It is found that for the wheel rim position, if Figure 5 In the circle indicated by the arrow in a, there are two parts where the area changes significantly in the initial stage of filling, such as Figure 5 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 5 c (the arrow here indicates the melt filling direction), 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 diversion gates, because the traditional method of pouring from the wheel center position has only one liquid riser 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 diversion 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 cavity entrance will change significantly, resulting in uncontrollable filling flow mode. Therefore, the present invention obtains the second stage of the boosting method through research. It can be seen from formula (1) that within the same preset filling time, as the number of diversion gates increases, the liquid rise rate 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.

[0070] Embodiment 1:

[0071] Two split flow gates are used, and the mass percentage of the metal melt used is as follows: Si: 7-9%, Mg: 0.6-0.9%, Zr: 0.01-0.02%, B: 0.005-0.007%, RE: 0.002-0.005%, Nd: 0.002-0.005%, Fe: 0-0.15%, Mn: 0.05-0.1%, Ti: 0.12-0.14%, and the rest is Al and unavoidable impurities.

[0072] (1) Lifting the liquid: The aluminum liquid in the holding furnace is pressurized by a high-pressure gas source, so that the aluminum liquid rises along the central lift pipe to the lift tank under pressure, and reaches the split gate position through the split channel in the lift tank. The pressure increase rate in this stage is 3.5 KPa / s, and the pressure is increased to 20 KPa;

[0073] (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 5 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.

[0074] (3) Crystallization pressure boost and pressure holding: After the filling is completed, the pressure is quickly increased to 150KPa at a pressure boost rate of 8KPa / s and the pressure is maintained until the wheel solidifies. During the pressure holding process, the high pressure shrinkage of the rim hot section is maintained at the diversion gate. Under the high pressure aluminum liquid shrinkage, the possibility of shrinkage cavities and shrinkage at this location is eliminated. At the same time, the metal liquid at the wheel center is vibrated and refined.

[0075] (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 central riser pipe and the riser tank to flow back into the holding furnace.

[0076] 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 method for wheel counter-gravity casting using a wheel counter-gravity casting device with a molten pool insulation furnace, characterized in that: The wheel anti-gravity casting equipment with a molten pool holding furnace comprises at least a mold, a molten pool holding furnace and a liquid riser; The molten pool insulation furnace comprises a furnace body, an insulation layer formed of refractory material is provided on the inner wall of the furnace body, the insulation layer surrounds the molten pool, a furnace cover is provided on the upper part of the furnace body, and a central liquid riser is connected to the central position of the furnace cover. The molten pool insulation furnace is provided with a first electric heating device and a first temperature measuring thermocouple; The furnace cover is connected to a central liquid riser, and a liquid riser is connected above the central liquid riser. A plurality of shunt channels communicating with the liquid riser are arranged in the liquid riser, and each shunt channel is connected to a shunt gate. The shunt gate corresponds to a position directly below the wheel mold rim, is connected to a cavity inlet for pouring into the mold cavity, and pours the shunt molten metal into the cavity. A second electric heating device and a second temperature measuring thermocouple are arranged on the liquid riser; The cross section of the diverter gate connected to the cavity inlet follows the shape of the cavity inlet at the filling point of the casting; The steps include: (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 lifting tank along the central lifting pipe under pressure, and reaches the split gate position through the split channel in the lifting tank. 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 diversion gate. The 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 of the second stage Determined by: （1） 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 is completed, the pressure is rapidly increased to 150 KPa at a pressure increase rate of 8~10 kPa / , and the pressure is maintained for 60~150s. At this time, the wheel solidification is completed; (4) Depressurization and venting: After the aluminum alloy wheel has solidified, the gas pressure in the molten pool holding furnace is released, allowing the unsolidified aluminum liquid in the riser tank and the central riser pipe to flow back into the holding furnace.

2. The method for wheel anti-gravity casting according to claim 1, characterized in that: The cross-sectional shape of the split gate section is: including a first arc segment and a second arc segment, the first arc segment and the second arc segment are concentric, and the radius and size of the first arc segment are smaller than the second arc segment, and the first arc segment and the second arc segment are connected on both sides by a connecting segment.

3. The method for wheel anti-gravity casting according to claim 1, characterized in that: The length of the first arc segment is 72-76 mm, the length of the second arc segment is 76-80 mm, and the length of the connecting segments on both sides is 8-12 mm.

4. The method for wheel counter-gravity casting according to claim 1, characterized in that: The inner surface of the diversion gate is provided with a mesh placement groove for placing a filter mesh.

5. The method for wheel anti-gravity casting according to claim 1, characterized in that: There are two diversion gates, which are symmetrically arranged on both sides relative to the wheel axis.

6. The method for wheel counter-gravity casting according to claim 1, characterized in that: The number of the diversion gates is greater than two and they are arranged around the wheel axis.

7. The method for wheel counter-gravity casting according to claim 1, characterized in that: A roller is provided at the bottom of the furnace body, and the roller is located on a track and can move along the track.

8. The method for wheel anti-gravity casting according to claim 1, characterized in that: A heat-insulating layer is also arranged under the furnace cover, a feeding port is arranged on one side of the furnace cover, a high-pressure gas source is connected to the furnace cover, and the upper part of the liquid riser is connected to the lower template on the frame.

9. The method for wheel counter-gravity casting according to claim 1, characterized in that: Before liquid heating, the mold temperature is not higher than 400℃.

10. The method for wheel counter-gravity casting according to claim 9, characterized in that: Before liquid heating, the mold temperature is not higher than 350℃.

11. The method for wheel counter-gravity casting according to claim 10, characterized in that: Before liquid heating, the mold temperature should not exceed 300℃.

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