A wheel casting forming apparatus and method based on three sprue filling of an outer rim

Abstract

The present application relates to the technical field of counter gravity casting, and particularly discloses a wheel casting forming equipment and method based on three-gating filling of outer rim, which comprises a holding furnace, a liquid lifting pipe, a mold and a pressure system; the metal liquid is made to rise through the liquid lifting pipe and enter the mold through the pressure system. The liquid lifting pipe is connected with a gating cup at the top, the gating cup is connected with the mold cavity through a gating structure, the gating on the mold is arranged at the position of the outer rim of the wheel, and the metal liquid is horizontally poured. The gating structure comprises a first gating channel responsible for pouring one spoke, and second and third gating channels responsible for pouring two spokes and having the same structure. The included angle between the gating channels is 120°. The present application has the advantages of stable filling, elimination of the risk of insufficient pouring, improvement of the feeding effect, shortening of the production rhythm, significant improvement of the casting forming quality of large-size aluminum alloy wheels larger than 18 inches, and especially the mechanical properties of the spoke core and the rim position.

Description

Technical Field

[0001] This invention relates to the field of anti-gravity casting technology, and in particular to a wheel casting molding equipment and method based on a three-gate filling system for the outer rim. Background Technology

[0002] Aluminum alloy wheels are of great significance for reducing fuel consumption, increasing mileage, mitigating environmental pollution, and improving handling performance in automobiles. Replacing steel with aluminum in automobile wheels can reduce wheel weight by 30-50%, reduce overall vehicle fuel consumption by 7-13%, and reduce emissions by 4-6%. Current aluminum alloy wheel casting production typically employs a single-gating low-pressure casting process with a single riser pipe filling the mold. This involves placing the gating and riser pipe at the wheel's central core, where molten metal enters the mold cavity through the core gating and completes filling and solidification. This casting method is simple to design and easy to implement, successfully solving the problems of safety, reliability, large-scale production, and low cost for small-to-medium-sized (e.g., 14-17 inches) aluminum alloy wheels for passenger vehicles. However, for large-sized (18 inches and above) aluminum alloy wheels for passenger vehicles, due to the single-gating method and solidification sequence, the cooling rate decreases from the rim to the spokes and core, resulting in a coarser microstructure, more shrinkage cavities and porosity, and lower mechanical properties, leading to a low yield rate. Large-sized wheels have complex shapes and varying wall thicknesses, making it difficult to simultaneously meet casting process requirements in terms of lightweight and low-noise structural designs. This further exacerbates the difficulty of microstructure control, and resolving the contradiction between large-size and high-performance casting has become a bottleneck restricting the industry's development. Currently, the industry uses forging or forging plus casting and spinning techniques, which are costly and difficult to promote. With the rapid increase in demand for large-sized wheels, the contradiction between high-performance requirements and low-cost casting production methods is becoming increasingly prominent.

[0003] Other filling methods have been attempted in the prior art. CN101837443A discloses a double-sided casting process and device for low-pressure casting of aluminum alloy wheels. Gates are set on both sides of the wheel, allowing molten aluminum to enter from the rim. Cooling control ensures the molten aluminum crystallizes from the wheel core to the rim at a rapidly cooled mold temperature. CN105855514A uses a single-machine, dual-mold wheel hub mold, with the gate also located on the rim, enabling the casting of two wheel hubs at once. CN212761058U discloses a multi-gate wheel casting molding equipment. A melt holding furnace connected to a gas source has multiple riser pipes. The riser pipes are connected to the mold gate via a heat-insulating cup and a gate sleeve. The lower part of the riser pipes is immersed in the molten metal. When the molten metal in the furnace is pressurized by gas pressure, the melt can rise along the multiple riser pipes and enter the mold cavity through the gate. The mold gate is located on the annular surface directly below the wheel rim.

[0004] However, the aforementioned devices and methods also have significant drawbacks. For the method where the molten aluminum enters only from the rim, with the inlet located in the middle of the rim, the molten aluminum will cause splitting after entering, meaning it will simultaneously fill the mold at both the core and the rim. This results in uncontrollable filling times at each location, leading to uncontrollable solidification sequence and a tendency to form shrinkage cavities and porosity defects. For the method using a combination of a center gate and two side gates, since the molten aluminum enters from two inlets, a confluence will form in the middle, making it prone to breakage due to factors such as poor gas drainage. For the technical solution of setting the gate on the annular surface directly below the wheel rim, i.e., the bottom surface of the outer rim, there are several drawbacks. First, the area that the gate can correspond to is limited due to the width of the bottom surface of the outer rim, which affects the solidification and feeding effect. Second, the gate cross-section cannot be expanded, limiting the gate feeding area and making it unsuitable for large-sized wheels or situations where the spokes and the outer rim intersect at intervals on the circumference. Finally, because the wheel product design has high strength requirements for the annular surface directly below the rim, and the microstructure requirements such as the spacing of secondary dendrite arms are strict at this location, if the mold is filled at this location, it is difficult to meet the required specifications after solidification because a cooling system cannot be arranged there. As a result, the mechanical properties at this location cannot meet the design requirements after alloy heat treatment, which seriously affects the performance of the wheel. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides a wheel casting molding equipment and method based on the three-gate filling of the outer rim.

[0006] The complete technical solution of this invention includes:

[0007] A wheel casting molding device based on a three-gate filling system for the outer rim includes: a holding furnace, a riser pipe, a mold, and a pressure control system. The holding furnace stores molten metal and keeps it at a constant temperature. The mold forms a cavity for the molten metal to solidify and form the shape. The lower part of the riser pipe is located inside the holding furnace, and the upper part of the riser pipe is connected to a pouring cup. The pouring cup is connected to the gate on the mold via a gating assembly.

[0008] The pressure control system allows the molten metal to enter the mold cavity through the riser pipe, pouring cup, and pouring gate.

[0009] The gate on the mold is located on the outer rim of the wheel at the bottom, dividing the outer rim into a pouring position and a non-pouring position. The molten metal rises vertically through the riser pipe, is converted to a horizontal flow by the gating assembly, and is poured into the gate on the outer rim in a horizontal flow manner.

[0010] The casting assembly includes a first casting channel, a second casting channel, and a third casting channel, wherein the second casting channel and the third casting channel have the same structure;

[0011] The first pouring channel includes a first initial pouring area in the center and first outer rim pouring areas on both sides. The second pouring channel and the third pouring channel both include a second initial pouring area in the center, a transition area, and second outer rim pouring areas on both sides. The cross-sectional area of ​​the second pouring channel is larger than that of the first pouring channel.

[0012] Furthermore, the wheel diameter is greater than 18 inches.

[0013] Furthermore, the effective flow area and profile characteristics of the first, second, and third pouring channels are determined based on the molten metal filling flow conditions.

[0014] Furthermore, the included angles between the first pouring channel, the second pouring channel, and the third pouring channel are all 120°.

[0015] Furthermore, the wheel casting equipment also includes a cooling system, which enables four sequential solidification directions during the wheel forming process: from the uppermost inner rim to the gate, from the middle of the spokes to the gate, from the middle of the spokes to the central riser, and from the pouring position on the outer rim to the non-pouring position.

[0016] Furthermore, the second and third pouring channels are responsible for filling and pouring two spokes respectively, while the first pouring channel is responsible for filling and pouring one spoke.

[0017] Furthermore, the method for wheel casting using the aforementioned wheel casting molding equipment based on the outer rim three-gate filling is characterized by including a liquid rising stage, a filling stage, a shell formation stage, a pressure increasing and holding stage, and a pressure release and venting stage.

[0018] Furthermore, during the filling stage, the filling speed of the molten metal should not exceed 0.5 m / s.

[0019] Furthermore, during the filling stage, the filling pressure is adjusted when the molten metal enters the first, second, and third pouring channels.

[0020] Furthermore, during the filling process, the temperature of the molten metal at the very front end is not lower than the melting point of the aluminum alloy.

[0021] The advantages of this invention over the prior art are:

[0022] 1. Traditional wheel core casting methods involve top-down filling during the spoke filling stage. After the molten metal reaches the outer rim, its direction abruptly changes upwards, leading to significant air entrapment due to the abrupt change in cross-section. In contrast, the three-gate short-flow casting method for the outer rim of this invention feeds from the lowest point of the entire casting, maintaining a bottom-up filling process throughout. It also increases the total area of ​​the gates (feed inlets), reducing filling resistance and improving wheel formability.

[0023] 2. Existing wheel designs employ multiple gates on the outer side, with molten metal entering the mold cavity vertically or obliquely. Due to the abrupt change in area, this results in abrupt changes in flow pattern, easily causing splashing, turbulence, air entrapment, and oxide inclusions. Furthermore, excessively high local flow velocities and uneven temperature fields can lead to localized structural abnormalities and cold shuts. To address these issues, this invention creatively transforms the vertical flow of molten metal into a horizontal flow along the outer rim through a pouring channel. This channel connects the gate and the outer rim cavity. The molten metal rises vertically within the gate, and upon entering the horizontal pouring channel, its flow direction changes from vertical to horizontal, entering the mold cavity along the outer rim in a laminar flow state. This achieves smooth, uniform, and synchronous molten metal flow along the circumference of the outer rim, increasing the inlet area while reducing the molten metal velocity, resulting in more stable filling. It effectively avoids direct flow, turbulence, air entrapment, and oxide inclusions, significantly improving filling stability and solving the problem of secondary oxide inclusions caused by air entrapment during the filling process.

[0024] 3. For the structural characteristics of large-sized wheels with asymmetrical spoke structures (such as five-spoke wheels), the gating assembly was specifically designed. Two types of gating channels were employed, one for pouring a single spoke and the other for pouring two spokes. The relevant dimensional parameters of the two types of gating channels were designed. Furthermore, to address the issue of varying heat transfer due to the different heat dissipation areas of the different gating channels, the double-spoke gating channel was insulated. To address the issue of different flow rates of the molten metal during the filling process due to the significant difference in the actual flow area between the single and double-spoke channels, a safe flow rate was designed, and a targeted local pressure acceleration adjustment method was implemented to ensure smooth and rapid filling, avoiding air entrapment, turbulence, and casting defects.

[0025] 4. Traditional processes aim to achieve a theoretically unidirectional solidification sequence from the inner rim to the gate to ensure feeding. However, due to the thin wall thickness of the wheel rim and the long filling distance, the temperature at the leading edge of the molten metal drops extremely rapidly when filling the thin-walled rim. To prevent premature solidification at the thin-walled area, leading to cold shuts or insufficient filling, the filling temperature of the molten metal must be significantly increased. However, the long-distance flow of high-temperature molten metal results in coarse grains in the casting, significantly reducing its mechanical properties. Furthermore, the traditional single-gate process has only one main feeding channel (from the wheel core to the rim), which easily leads to isolated hot spots in areas far from the gate. Once the thin-walled part in the middle (such as the rim) solidifies first, closing the channel, the distant hot spots lose their feeding source, easily resulting in concentrated shrinkage cavities and porosity defects. This invention innovatively combines mold cooling processes (spot cooling, water-cooled blocks, circular water cooling, cooling pipes, etc.) to redesign the traditional single solidification path into four directions, reducing the effective solidification and feeding distance of all areas by more than half. Previously distant areas are now covered by the short shrinkage channel, fundamentally eliminating remote hot spots and preventing the formation of concentrated shrinkage cavities and porosity defects.

[0026] 5. In the present invention, the metal liquid enters each area of ​​the mold cavity with a shorter pouring distance than the traditional wheel center. The multi-gate design is beneficial for the metal liquid to be fed back during the solidification process at the junction of the wheel rim and spokes. Some of the front oxide can be collected at the wheel core, and casting defects can be eliminated by extrusion. This significantly improves the mechanical properties of the wheel, especially the mechanical properties of the spokes, wheel core and rim, achieving the mechanical properties of large-size aluminum alloy wheels produced by "casting + spinning" or forging technology.

[0027] 6. By adopting the three-gate short-process casting scheme for the outer rim of the present invention, the air at the spoke position can enter the central riser from bottom to top and be discharged. Compared with the traditional single-gate casting method in the center, the air venting requirement of the spoke is reduced, and there is no need to vent through the parting surface vent plug, which reduces the risk of air hole formation.

[0028] 7. The filling process of this invention is short, and the areas with long contact time with air are mainly located in the inner rim and the center riser. After pouring, the temperature of the wheel top is higher than 616°C, and there is no problem of under-pouring. The solidification process solidifies in the designed sequence, without obvious isolated liquid phase regions, which can eliminate shrinkage defects and improve the mechanical properties of the product. Attached Figure Description

[0029] Figure 1 This is a cross-sectional structural diagram of the wheel formed according to the present invention.

[0030] Figure 2 This is a top view of the wheel.

[0031] Figure 3 A front view of the cast wheel structure.

[0032] Figure 4 A top view of the cast wheel structure.

[0033] Figure 5 This is a structural diagram of the pouring channel.

[0034] In the diagram: 1-Wheel core, 2-Center hole, 3-Helical hole, 4-Wheel spoke, 5-Inner rim, 6-Inner bead seat, 7-Wheel rim, 8-Wheel neck, 9-Outer bead seat, 10-Outer rim, 11-Lift pipe, 12-Pour cup, 13-Pouring assembly, 14-First pouring channel, 15-Second pouring channel, 16-Third pouring channel, 17-First initial pouring area, 18-First outer rim pouring area, 19-Second initial pouring area, 20-Transition area, 21-Second outer rim pouring area. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0036] like Figures 1-2 The cross-sectional structure and top view of the wheel formed by the present invention are shown. It includes a wheel core 1 located at the center of the wheel, a central hole 2 in the center of the wheel core, and a spiral hole 3 for installation on the outer side of the wheel core. On the outer side of the wheel, there is a part that mates with the tire. The wheel part that is installed and connected with the axle wheel core and supports the rim is the spoke 4. In the specific embodiment of the present invention, the wheel has five spokes, and the gap between the five spokes is called a window.

[0037] In the rim section, among which Figure 1 The highest, first protruding part is called the inner rim 5, which is closer to the inside of the vehicle body when the wheel is installed; the first stepped slope below the inner rim 5 is the inner tube bead seat 6, which is the mounting surface closer to the inside of the vehicle body when the tire is installed; below the inner tube bead seat 6 is the rim 7, the portion with increased cross-sectional area below the rim 7 is the wheel collar 8, and the stepped slope below the wheel collar 8 is the outer tube bead seat 9, which is the mounting surface closer to the outside of the vehicle body when the tire is installed; below the outer tube bead seat 9... Figure 1 The second protrusion at the lowest point is the outer rim 10, which is located near the outer side of the vehicle body when the wheel is installed.

[0038] Based on the above wheel structure, this invention discloses a wheel casting and molding equipment with a three-gating system for the outer rim, such as... Figure 3As shown, the equipment includes a heat-preserving furnace, a riser pipe, a mold, and a pressure control system. The heat-preserving furnace stores and keeps the molten metal at a constant temperature. The mold has a cavity for the molten metal to solidify and form. The riser pipe is located below the heat-preserving furnace, and the molten metal is propelled upward through the riser pipe 11 and into the mold cavity by the gas pressure of the pressure control system. The riser pipe 11 is connected to a sprue cup 12 at the top, and the sprue cup is connected to the mold cavity via a gating assembly 13. The gate on the mold is located on the outer rim of the wheel. The molten metal rises vertically through the riser pipe, then flows horizontally through the gating assembly, and is poured into the gate on the outer rim in a horizontal flow manner.

[0039] The aforementioned filling method aims to overcome the problems in existing technologies, such as flow diversion due to filling only from the rim, uncontrollable solidification sequence, breakage due to poor gas venting caused by using a combination of center and side gates, and insufficient strength due to filling the annular surface directly below the wheel rim. Firstly, the filling position was optimized by selecting the outer rim 10 of the wheel as the filling inlet, dividing the entire outer rim into two parts: the pouring position and the non-pouring position.

[0040] Furthermore, existing wheel designs employ multiple gates on the outer side, where molten metal enters the mold cavity vertically or obliquely. Due to the abrupt change in area, this results in abrupt changes in flow pattern, easily leading to turbulent flow, air entrapment, and oxidation inclusions. To address these issues, this invention utilizes a casting assembly with multiple casting channels, transforming the molten metal flow from vertical to horizontal into the outer rim, allowing it to enter the mold cavity in a horizontal laminar flow state along the circumference of the outer rim. This achieves the smoothest possible synchronous molten metal entry along the circumference of the outer rim, increasing the entry area while simultaneously reducing the molten metal velocity, resulting in smoother filling, reduced turbulent flow, and less secondary oxidation inclusions caused by air entrapment during the filling process.

[0041] Furthermore, the wheel to be formed in this invention is a large-size aluminum alloy wheel with a diameter greater than 18 inches. The wheel has a spoke structure, featuring a five-spoke or more-spoke design. In recent years, multi-spoke wheels have been widely used in the automotive industry due to their longer and simpler spokes, better overall appearance, more even force distribution during driving, and lower wind resistance. Taking a 20-inch large-size wheel with five spokes as an example, the spokes have an asymmetrical structure, with an angle of 72° between each spoke. This is a naturally asymmetrical structure. For wheel casting, symmetrical casting methods (2, 3, 4 pouring channels, etc.) are usually used because these methods are more convenient for equipment and mold design, have better versatility, and can be more easily applied to the production of other types of wheels. Therefore, when using symmetrical multi-channel filling for asymmetrical five-spoke wheels, it is impossible to ensure that the distances between multiple riser pipes and the wheel spoke gates are the same. Consequently, the pouring times at different spokes will inevitably differ, which can easily lead to inconsistent filling times for each spoke. This can cause problems such as air entrapment and uncontrollable solidification sequence, resulting in casting defects. Therefore, when casting five-spoke wheels, it is necessary to design the wheel structure and gating system structure to avoid the above problems.

[0042] Based on the above considerations, this invention has made targeted designs for the wheel structure and casting components, such as... Figure 4 As shown, the casting assembly 13 includes two types of casting channels: a first casting channel 14, a second casting channel 15, and a third casting channel 16. The second casting channel 15 and the third casting channel 16 have the same structure and are responsible for the filling and casting of two wheel spokes, respectively. The first casting channel 14 is responsible for the filling and casting of one wheel spoke. The angle between the three casting channels and the center of the wheel is 120°.

[0043] Furthermore, because this invention employs a different method from existing technologies—utilizing a casting channel for horizontal pouring—the two casting channels have different numbers of spokes, significantly different flow areas, and different arc lengths, resulting in noticeable differences in flow behavior. Secondly, the molten metal flow field is highly sensitive to channel cross-sectional characteristics and process parameters. Cross-sections with abrupt area changes or high irregularity can lead to turbulent flow and air entrapment, and mismatches between filling speed and pressure can cause uneven filling.

[0044] Based on the above issues, it is necessary to design the relevant dimensional parameters of the pouring channels for both structures to ensure smooth and rapid mold filling, avoid air entrapment, turbulence, and casting defects, and minimize the amount of molten metal used. Specifically:

[0045] First, define the design parameters for the gating system, including:

[0046] 1) Effective flow area : refers to the cross-sectional area of ​​the upper surface of the pouring channel;

[0047] 2) Profile feature value W: is the ratio of the perimeter of the profile of the upper surface of the pouring channel to the perimeter of a circle with the same area as the pouring channel.

[0048] The following constraints are adopted:

[0049]

[0050] In the formula, The effective flow area of ​​the second pouring channel (the second pouring channel and the third pouring channel are the same). This represents the effective flow area of ​​the first pouring channel.

[0051]

[0052] In the formula, The contour feature value of the second pouring channel (similarly, the second pouring channel and the third pouring channel are the same). The contour feature value of the first pouring channel.

[0053] and:

[0054]

[0055] In determining the above indicators, the five-spoke wheel casting system of this invention adopts a distribution method of 1 single-spoke channel + 2 double-spoke channels. The effective flow area directly determines the flow capacity and is the core of flow matching; the profile feature value determines the regularity of the cross section and is the core of controlling flow resistance and eddies. The two indicators work together. The limitation of the effective flow area ratio reduces the time difference of the molten metal reaching the spokes, avoiding the problem of some spokes being filled too quickly and others too slowly. Through the constraint of the profile feature value, the liquid flow separation and eddies caused by rapidly expanding cross sections and highly irregular cross sections are avoided, allowing the molten metal to maintain a laminar / weakly turbulent state in the channel, greatly reducing the probability of gas being trapped in the cavity, and achieving a balance between quality, efficiency and cost.

[0056] Based on the above principles and after practical verification, the cross-sectional structures of the first pouring channel 14 and the second pouring channel 15 are as follows: Figure 5 As shown, the first pouring channel 14 includes a first initial pouring area 17 located in the center and first outer rim pouring areas 18 on both sides. The second pouring channel 15 and the third pouring channel 16 both include a second initial pouring area 19 located in the center, a transition area 20, and second outer rim pouring areas 21 on both sides.

[0057] The length of the arc between the starting and ending points of the first gating channel and concentric with the outer rim is defined as the arc length of the first gating channel. The length of the arc between the starting and ending points of the second gating channel and concentric with the outer rim is defined as the arc length of the second gating channel, such that the arc length of the first gating channel : the arc length of the second gating channel = 0.45~0.5. The effective flow area of ​​the first gating channel is approximately 323.9 cm². 2 The effective flow area of ​​the second pouring channel is approximately 588.7 cm². 2 .

[0058] Subsequently, the angles between each pouring channel and each spoke pouring inlet were designed, such as... Figure 4 As shown, taking the outer rim surface below the wheel as the reference surface, the lines connecting the center of each casting channel to the wheel core ( Figure 4 Using the dotted line in the diagram as a reference, the line connecting the center of each spoke's casting inlet to the wheel core ( Figure 4 The included angles between the double-dotted lines in the figure are A1, A2, A3, A4, and A5, respectively. The angle (A1) between the line connecting the center of the first pouring channel 14 to the wheel core and the line connecting the center of the pouring port of the adjacent spoke in the counterclockwise direction to the wheel core is 8°; the angle (A2) between the line connecting the center of the second pouring channel 15 to the wheel core and the line connecting the center of the pouring port of the adjacent spoke in the counterclockwise direction to the wheel core is 55.56°; the angle (A3) between the line connecting the center of the second pouring channel 15 to the wheel core and the line connecting the center of the pouring port of the adjacent spoke in the clockwise direction to the wheel core is 16.44°; the angle (A4) between the line connecting the center of the third pouring channel 16 to the wheel core and the line connecting the center of the pouring port of the adjacent spoke in the counterclockwise direction to the wheel core is 31.56°; and the angle (A5) between the line connecting the center 6 of the first pouring channel 1 to the wheel core and the line connecting the center of the pouring port of the adjacent spoke in the clockwise direction to the wheel core is 40.44°.

[0059] Verification has shown that the above design allows for a larger feed area at each spoke and a closer filling distance at the set filling speed. The overall filling speed is also lower, not exceeding 0.5 m / s, with no turbulence or air entrapment, resulting in smoother bottom-up filling. Furthermore, the short filling process, with areas of prolonged air contact primarily located at the inner rim and center riser, effectively alleviates or even eliminates heat spots at the spoke-rim junction. Metal utilization is increased by 15%–25%.

[0060] In the above process, since the first pouring channel 14 and the second pouring channel 15 adopt different structures, their volumes and flow areas are significantly different. Therefore, this invention further considers the heat dissipation and the temperature drop of the molten metal in the pouring channels during the filling process and conducts an analysis. The temperature drop of the molten metal in the pouring channels follows the basic law of casting heat conduction. The temperature drop rate is related to parameters such as the heat dissipation area per unit volume, the thermal conductivity of the mold, the heat preservation capacity of the channel, the volume of the molten metal, and its specific heat. Based on thermodynamic formulas, the temperature drop difference of the molten metal in single / double spoke channels is calculated, and combined with actual process verification, it is found that the temperature drop of the molten metal in the double spoke channel during the filling process is significantly higher than that in the single spoke channel. Therefore, it may lead to an increase in the viscosity of the molten metal handled by the double spoke pouring channel during the subsequent spoke filling process, resulting in slower spoke filling and causing air blockage or cold shut. Based on this, the present invention employs heat insulation for the double-spoke casting channel. The double-spoke channel adopts an inner + outer composite insulation structure, selecting insulation cotton-like materials with low thermal conductivity and high temperature resistance, balancing insulation effect, fit of irregular cross-section, and durability. This ensures that the temperatures of the first casting channel 14 and the second casting channel 15 are basically the same during the casting process. Furthermore, the temperature of the molten metal at the front end during the filling process is not lower than 616℃, eliminating the risk of incomplete casting.

[0061] Subsequently, the safe flow rate during the filling process was analyzed. During the filling process, when the liquid flows to this pouring channel, under the premise of a fixed gate area, the actual flow area of ​​the single / double spoke channels differs significantly, resulting in a noticeable difference in the flow velocity of the molten metal. According to the fluid continuity equation and Bernoulli effect, for smaller cavity areas, the flow velocity will increase significantly, impacting the cavity end or opposite sidewall. The high-speed flow of the liquid easily entrains air from the cavity into the molten metal, forming pores. Furthermore, the intense turbulence will damage the oxide film on the liquid surface, causing it to break and be drawn into the casting.

[0062] Therefore, the following pressure rise correction method was set:

[0063]

[0064]

[0065] In the formula, To correct the pressure rise rate, For initial pressure ramp-up, The upper limit of the safe flow rate can be obtained through actual experiments (e.g., 0.57 m / s). The initial flow velocity (can be 0.5 m / s). Let be the cross-sectional area of ​​the pouring cup. For contour feature correction coefficients, The contour feature value of the first pouring channel. It is the absolute value of the difference between the contour feature values ​​of the first pouring channel and the second pouring channel.

[0066] Furthermore, the wheel casting molding equipment disclosed in this invention also includes a cooling system, which includes at least an upper mold cooling unit and a lower mold cooling unit. The upper mold cooling unit includes at least a first upper mold water-cooling block (corresponding to the gate position) located on the inner side of the intersection of the outer wheel rim and the spoke, a second upper mold water-cooling block (not at the gate position) located on the inner side of the intersection of the outer wheel rim and the spoke, an upper mold annular water-cooling channel corresponding to the middle position of the spoke, and an upper mold annular water-cooling channel corresponding to the intersection position of the spoke and the wheel core.

[0067] The lower die cooling mechanism includes at least: a lower die annular air cooling channel located at the intersection of the spokes and the outer rim, a lower die annular water cooling channel located in the middle of the spokes, and a lower die annular water cooling channel located at the intersection of the spokes and the wheel core.

[0068] By controlling the aforementioned cooling components, four sequential solidification directions are established during the wheel forming process: from the uppermost inner rim to the gate, from the center of the spokes to the gate, from the center of the spokes to the center riser, and from the pouring position on the outer rim to the non-pouring position. This shortens the filling and solidification feeding distances of all areas of the wheel by more than half, significantly reducing the risk of excessively low molten metal temperature at the filling front, ensuring sufficient molten metal feeding in all areas of the wheel during solidification, thereby avoiding related casting defects.

[0069] For the direction from the center of the spoke to the gate, the upper mold annular water cooling channel and the lower mold annular water cooling channel at the center of the spoke are opened simultaneously first. Then, the second upper mold water cooling block, the lower mold annular air cooling channel at the intersection of the spoke and the outer rim, and the first upper mold water cooling block are opened in sequence.

[0070] For the direction from the center of the wheel spoke to the center riser, after the upper and lower die annular water cooling channels at the center of the wheel spoke are opened simultaneously, the upper die annular water cooling channel at the intersection of the wheel spoke and the wheel core and the lower die annular water cooling channel at the intersection of the wheel spoke and the wheel core are opened simultaneously.

[0071] The method for wheel forming using the above-mentioned device includes stages of liquid raising, mold filling, crystallization pressurization and holding, and pressure release. The molten metal used is aluminum alloy liquid, and the specific steps are as follows:

[0072] (1) Liquid rising stage: The aluminum alloy liquid in the heat preservation furnace is pressurized by a high-pressure gas source, so that the aluminum alloy liquid rises along the liquid rising pipe to a position about 100mm below the gate under pressure. The pressurization rate in this stage is 13mbar / s to 18mbar / s, and the pressure is increased to 115mbar to 125mbar.

[0073] (2) Filling stage: Continue to increase the pressure. The liquid rising speed in this stage is 4mbar / s to 6mbar / s. When flowing through the casting assembly, the liquid rising speed is adjusted by the above method, and then the aluminum alloy liquid fills the cavity. After filling, the pressure is increased to 220mbar to 240mbar.

[0074] (3) Shell formation stage: After the filling is completed, the pressure is increased to 230mbar to 250mbar at a pressurization rate of 2mbar / s to 4mbar / s.

[0075] (4) Extrusion, pressurization and holding stage: ① After the shelling process is completed, the pressure is rapidly increased to 800 mbar at a pressurization rate of 30 mbar to 60 mbar / s and held for 100 to 120 s. At this time, the wheel solidification is completed; ② When the timer reaches 50 to 70 s after the filling is completed, the extrusion cylinder is started, and the extrusion pin connected to it is driven to move downward from the initial position by 40 to 50 mm at a speed of 2 mm / s to 5 mm / s (the initial extrusion position and stroke vary depending on the center structure of the wheel) and held in this position for 50 to 70 s. After that, under the drive of the extrusion cylinder, the extrusion pin is withdrawn to the initial position, that is, separated from the extruded wheel to avoid affecting the normal demolding of the product.

[0076] (5) Pressure relief and exhaust stage: After the pressure holding stage is completed, that is, the aluminum alloy wheel is solidified, the gas pressure in the heat preservation furnace is released, so that the unsolidified aluminum alloy liquid in the riser pipe and the gate flows back into the heat preservation furnace. Then, the wheel is kept in the mold for 70s to 100s before the mold is opened and the part is removed.

[0077] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A wheel casting molding equipment based on a three-gate filling system for the outer rim, comprising: The system includes a holding furnace, a riser pipe, a mold, and a pressure control system. The holding furnace stores and maintains the temperature of the molten metal. The mold forms a cavity for the solidification and shaping of the molten metal. The lower part of the riser pipe is located inside the holding furnace, and the upper part of the riser pipe is connected to a pouring cup. The pouring cup is connected to the gate on the mold via a gating assembly. The pressure control system allows the molten metal to enter the mold cavity through the riser pipe, pouring cup, and pouring gate. Its features are, The gate on the mold is located on the outer rim of the wheel at the bottom, dividing the outer rim into a pouring position and a non-pouring position. The molten metal rises vertically through the riser pipe, is converted to a horizontal flow by the gating assembly, and is poured into the gate on the outer rim in a horizontal flow manner. The casting assembly includes a first casting channel, a second casting channel, and a third casting channel, wherein the second casting channel and the third casting channel have the same structure; The effective flow area and profile characteristics of the first, second, and third pouring channels are determined based on the molten metal filling flow conditions; The effective flow area is the cross-sectional area of ​​the upper surface of the pouring channel; the profile feature value is the ratio of the perimeter of the cross-sectional profile of the upper surface of the pouring channel to the perimeter of a circle with the same area as the pouring channel; the following constraint relationship is adopted: In the formula, The effective flow area of ​​the second pouring channel is the same as that of the third pouring channel. The effective flow area of ​​the first pouring channel; Let be the contour feature value of the second pouring channel, where the contour feature values ​​of the second and third pouring channels are the same. The contour feature value of the first pouring channel; The first pouring channel includes a first initial pouring area in the center and first outer rim pouring areas on both sides. The second pouring channel and the third pouring channel both include a second initial pouring area and a transition area in the center and second outer rim pouring areas on both sides. The cross-sectional area of ​​the second pouring channel is larger than that of the first pouring channel. The included angles between the first pouring channel, the second pouring channel, and the third pouring channel are all 120°; The second and third pouring channels are responsible for filling and pouring two spokes respectively, while the first pouring channel is responsible for filling and pouring one spoke. The wheel casting equipment also includes a cooling system, which creates four sequential solidification directions during the wheel forming process: from the uppermost inner rim to the gate, from the middle of the spokes to the gate, from the middle of the spokes to the center riser, and from the pouring position on the outer rim to the non-pouring position.

2. The wheel casting molding equipment based on the three-gate filling of the outer rim according to claim 1, characterized in that, The wheel diameter is greater than 18 inches.

3. A method for wheel casting using a wheel casting molding equipment based on a three-gate filling system for the outer rim, as described in any one of claims 1-2, characterized in that... It includes the liquid rising stage, the filling stage, the shell forming stage, the extrusion pressurization and holding stage, and the pressure relief and venting stage.

4. The method for casting wheels according to claim 3, characterized in that, During the filling stage, the filling speed of the molten metal should not exceed 0.5 m / s.

5. The method for casting wheels according to claim 4, characterized in that, During the filling stage, the filling pressure is adjusted when the molten metal enters the first pouring channel, the second pouring channel, and the third pouring channel.

6. The method for casting wheels according to claim 5, characterized in that, During the filling stage, the temperature of the molten metal at the very front end should not be lower than the melting point of the aluminum alloy.

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