CN111673072A - Wheel forming device and method based on center pressurization of multiple lift pipes - Google Patents
Wheel forming device and method based on center pressurization of multiple lift pipes Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 27
- 239000007788 liquid Substances 0.000 claims abstract description 105
- 229910052751 metal Inorganic materials 0.000 claims abstract description 48
- 239000002184 metal Substances 0.000 claims abstract description 48
- 238000004321 preservation Methods 0.000 claims abstract description 25
- 230000007246 mechanism Effects 0.000 claims abstract description 22
- 239000000155 melt Substances 0.000 claims abstract description 9
- 238000003825 pressing Methods 0.000 claims abstract 2
- 229910052782 aluminium Inorganic materials 0.000 claims description 40
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 39
- 238000005266 casting Methods 0.000 claims description 30
- 229910000838 Al alloy Inorganic materials 0.000 claims description 17
- 238000002425 crystallisation Methods 0.000 claims description 6
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- 238000006243 chemical reaction Methods 0.000 claims description 3
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- 238000007711 solidification Methods 0.000 abstract description 18
- 230000008023 solidification Effects 0.000 abstract description 18
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- 238000004519 manufacturing process Methods 0.000 description 9
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 230000002146 bilateral effect Effects 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
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- 239000013078 crystal Substances 0.000 description 2
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- 238000004364 calculation method Methods 0.000 description 1
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- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D18/00—Pressure casting; Vacuum casting
- B22D18/04—Low pressure casting, i.e. making use of pressures up to a few bars to fill the mould
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/08—Shaking, vibrating, or turning of moulds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/09—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure
- B22D27/13—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure making use of gas pressure
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/02—Alloys based on aluminium with silicon as the next major constituent
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Abstract
The invention discloses a wheel forming device and a method based on center pressurization of multiple liquid lifting pipes.A plurality of liquid lifting pipes are arranged in a melt heat preservation furnace, the upper parts of the liquid lifting pipes are connected with a pouring gate of a mold through a heat preservation cup and a pouring gate component, the lower parts of the liquid lifting pipes are immersed in a metal melt, the melt rises along the multiple liquid lifting pipes under the action of air pressure and enters a mold cavity through the pouring gate, and the pouring gate of the mold is arranged on a circular ring surface right below a wheel rim; the local supercharging mechanism is arranged below the position, corresponding to the wheel center, on the mold; and applying pressure to the metal melt after the filling is finished. In the solidification and pressure maintaining stage after the mold filling is finished, high-pressure gas is adopted to pressurize and feed the melt at the gate, and a local pressurizing mechanism is adopted to apply high pressure to the melt at the wheel center, so that the possibility of shrinkage cavity and shrinkage porosity is eliminated.
Description
Technical Field
The invention relates to the technical field of casting, in particular to a wheel forming device and method based on central pressurization of multiple lift pipes.
Background
The light weight is one of the most important ways for saving energy and reducing emission of fuel automobiles and reducing consumption and increasing range of new energy automobiles, and light weight materials such as aluminum alloy and the like are used for replacing traditional steel materials, so that the light weight materials become necessary choices for the updating of automobile design. Aluminum alloys used in automobiles can be classified into cast aluminum alloys and wrought aluminum alloys, and cast aluminum alloys dominate the production of parts such as engines, clutch housings, wheels, chassis parts, and the like. With the demand for improving the quality of the wheel and the development of casting technology, more parts are produced by adopting low-pressure casting, counter-pressure casting and pressure-regulating casting, and all belong to anti-gravity casting methods. The basic principle of the casting is that low-pressure gas is used for driving metal melt in a crucible or a heat preservation furnace to rise through a riser tube and enter a mold cavity, and after mold filling is finished, the metal melt in the mold is solidified and fed under the action of pressure.
The traditional aluminum alloy low-pressure, differential-pressure and pressure-regulating wheel casting technology generally adopts a single-sprue single-riser tube mold filling technology. Taking an aluminum alloy wheel as an example, a riser tube is arranged at the center of the wheel, namely the wheel center of the wheel, so that metal melt enters a cavity and is filled and solidified. In order to refine the structure and eliminate the casting defects of shrinkage cavity, shrinkage porosity and the like, the cooling of a wheel mold is generally enhanced in the prior art by adopting water cooling, water mist cooling and the like, however, the enhanced cooling greatly shortens the solidification time of the wheel, for example, the solidification time of the large-size wheel after the enhanced cooling can be shortened to be within 100s, and the problem that the temperature field in the processes of cooling and solidifying the wheel in the production process is difficult to control is caused, so that the sequential solidification is difficult to realize, the product performance is unstable, and the qualification rate is low.
Other filling approaches have been attempted in the prior art for wheels. Patent CN201010107026.8 discloses a bilateral casting technology and device of aluminum alloy wheel low pressure casting sets up the runner in wheel both sides, makes aluminium liquid get into from rim, makes aluminium liquid crystallize to the rim by the wheel center under the mould temperature of quench through to cooling control, has shortened the distance that aluminium liquid flows, and the shrinkage porosity defect at R angle or rim position has been reduced in the cooperation cooling. Documents CN201310557627.2 and CN201410825962.0 disclose that a center gate and two side gates are combined to reduce the weight of the hub and improve the mechanical strength. CN201610390494.8 adopts a quick-witted bimodulus wheel hub mould, and the runner sets up on the rim position equally, realizes once pouring two wheel hubs.
However, the device and the method also have obvious defects, and for the mode that the aluminum liquid only enters from the rim, the inlet is arranged in the middle of the rim, and the aluminum liquid can be shunted after entering, namely the aluminum liquid is filled to the wheel center and the wheel edge at the same time, so that the filling time at each position is uncontrollable, the solidification sequence is uncontrollable, and the defects of shrinkage cavity and shrinkage porosity are easily formed. And for the mode that adopts central runner and both sides runner to combine, because aluminium liquid gets into from two entrances, can form at the intermediate position and converge, cause the breakpoint because of reasons such as gas outgoing irregularity easily.
Based on the above, the applicant designs a rapid sequential solidification wheel forming device and method based on multiple lift pipes, wherein a pouring gate of a mold is arranged right below a rim of a wheel. By lifting liquid and filling in a plurality of lift pipes, the filling distance can be obviously reduced, and the problem of long-distance feeding of large-size wheels is solved, but as the pouring gate is arranged right below the wheel rim of the wheel, the filling and solidification time at the wheel center position is later, and the problems of shrinkage cavity and shrinkage porosity can be generated at the position.
Disclosure of Invention
In order to solve the technical problems, the invention provides a wheel forming device and a wheel forming method based on multiple lift pipes and central pressurization.
The complete technical scheme of the invention comprises the following steps:
a wheel forming device based on pressurization of center of a plurality of liquid lifting channels is characterized by comprising: the device comprises a heat-insulating container, a liquid lifting channel, a mould, a gas pressurizing mechanism and a local pressurizing mechanism;
the heat preservation container is used for storing metal melt, at least two liquid lifting channels are arranged in the heat preservation container, at least one part of each liquid lifting channel is positioned in the metal melt, and each liquid lifting channel is used for conveying the metal melt;
the heat-insulating container is connected with a gas pressurizing mechanism which can provide pressure so that the melt in the heat-insulating container rises along the liquid-lifting channel under the pressure and enters the die cavity;
the mould is provided with a cavity for solidifying and forming the metal melt, and the liquid lifting channel is communicated with the cavity through a pouring gate on the mould at the upper part;
the pouring gate on the mold is arranged on the circular ring surface right below the wheel rim;
the positions of the local supercharging mechanism are as follows: the position of the counter-gravity casting wheel mold corresponding to the wheel center of the wheel is arranged below the counter-gravity casting wheel mold; and transferring pressure to the metal melt after the filling is finished.
The number of the gates is two, and the gates are symmetrically arranged on two sides of the wheel axis.
The number of the liquid lifting channels corresponding to the gates is two, and the liquid lifting channels are symmetrically arranged on two sides of the wheel axis.
The number of the gates is more than two and the gates are arranged around the axis of the wheel.
The number of the liquid lifting channels corresponding to the pouring gates is more than two, and the liquid lifting channels are arranged around the axis of the wheel.
And a pouring gate assembly is arranged above the liquid lifting channel, and a pouring gate on the pouring gate assembly mold is communicated with the pouring gate.
The pressure transmitted by the local pressurization mechanism to the metal melt is 1-120 MPa.
The method for forming the wheel by using the device is characterized by comprising the following steps:
(1) liquid lifting: pressurizing the aluminum liquid in the heat preservation furnace through a high-pressure air source, so that the aluminum liquid rises to the position of the pouring gate along the liquid lifting pipe under the pressure, wherein the pressure rising speed at the stage is 2.8-4.0 kPa/s, and the pressure is increased to 20 kPa;
(2) filling a mold: continuously boosting to enable the aluminum liquid to enter the cavity through the pouring gate, wherein the filling stage is two-stage pressurization, the boosting speed of the first stage is 0.1-0.2 kPa/s, the time is 2-4 s, and then the second stage is performed to rapidly boost until the cavity is filled, and the pressure reaches 35kPa at the moment;
the boosting speed P' in the second stage is determined as follows:
in the formula: p' is the pressure increasing speed with the unit of kPa/s; h is the total height of the cavity and the unit is mm; rho is the density of the metal melt and has the unit of g/cm3(ii) a K is a resistance coefficient, and the value range of K is 1-1.5; t is preset mold filling time with the unit of s; 102 is a unit conversion coefficient; n is the number of the liquid lifting pipes, and the value range of N is 2-6; x is the liquid raising index of the compound, and the value range is 0.2-0.8;
(3) and (3) crystallization, pressurization and pressure maintaining: after the mold filling is finished, rapidly increasing the pressure to 150kPa at a pressure increasing speed of 8-10 kPa/and maintaining the pressure, wherein a local increasing mechanism applies pressure to the metal melt at the wheel center until the wheel is solidified;
(4) pressure relief and air release: and (4) after the aluminum alloy wheel is solidified, relieving the gas pressure in the heat preservation furnace, and enabling the aluminum liquid which is not solidified at the riser tube and the pouring gate to flow back to the heat preservation furnace.
The preset filling time t is preferably 10 s.
N is preferably 2 to 4.
x is 0.5.
The mold temperature prior to ramping is no greater than 400 c, preferably no greater than 350 c, and more preferably no greater than 300 c.
Compared with the prior art, the invention has the advantages that:
compared with the prior art that the mold filling is carried out at the wheel center position and the middle part of the side surface of the rim, the rapid mold filling mode with multiple liquid lifting pipes is adopted, the mold filling position of the wheel is changed, the multiple liquid lifting pipes are arranged right below the rim part of the wheel, the mold filling distance of the metal melt is shortened by more than half compared with the prior single liquid lifting pipe mode, the temperature of a metal mold can be reduced to be lower than 320 ℃ from the prior 420 ℃, the cooling speed and the cooling effect of the wheel are naturally accelerated, and the rapid sequential solidification is realized. Meanwhile, a local pressurizing device is arranged at the center of the wheel, the pressure applying mechanism is in contact with the metal melt, and directly applies pressure to the metal melt after the filling is finished, so that the molten aluminum at the position is solidified under extremely high pressure, the thick part can be directly fed, and the defects of shrinkage cavity and shrinkage porosity at the position are eliminated. The device and the method for quickly forming the aluminum alloy casting based on the multiple lift pipes and the central pressurization solve the problem that the existing large-size aluminum alloy casting is difficult to perform long-distance feeding, not only remarkably improve the performance and the production stability of the aluminum alloy casting, but also shorten the production beat and improve the production efficiency and the qualification rate of wheels. Through the optimized two-section type filling and pressurizing process design, the metal melt in the initial filling stage flows stably, then the cavity is filled quickly, the advantage of quick filling of the multiple lift tubes is played, and the production efficiency is improved. Meanwhile, the antigravity casting method of low pressure, differential pressure or pressure regulation of a multi-lift system is adopted, so that the material utilization rate of the wheel is improved.
Drawings
Fig. 1 is a view showing a structure of a wheel in the prior art.
Fig. 2 is a schematic structural diagram of a wheel forming apparatus according to an embodiment of the present invention.
Fig. 3a shows a portion of the embodiment of fig. 2 where curling is likely to occur.
Fig. 3b is a partial enlarged view of fig. 3 a.
FIG. 3c is a schematic view of the slow charging sequence of FIG. 3 a.
In the figure: 1-a holding furnace, 2-a riser tube, 3-aluminum liquid, 4-a special-shaped pouring gate component, 5-a cavity, 6-a pressure driving unit, 7-a pressure transmission unit, 8-a pressure applying unit, 9-a vibration generator, 10-a vibration rod, 11-a mounting bedplate and 12-a lower die.
Detailed Description
The invention is further described with reference to the following figures and detailed description.
Fig. 1 is a view showing a typical wheel construction in which the central position of the wheel is generally referred to as the center of the wheel, the outer side of the wheel is fitted and fitted with a tire, the portion supporting the tire is referred to as the rim, the portion mounted and connected to the center of the wheel axle, and the portion of the wheel supporting the rim is referred to as the spoke, and a window is left between the spokes in the prior art. The portion of the rim that holds and supports the tire orientation is called the rim.
In the production of the existing low-pressure or differential-pressure cast aluminum alloy wheel, a single liquid lifting pipe is almost arranged at the center wheel center of the wheel, so that a melt enters a cavity from a sprue at the wheel center through a vacuum cup, a sprue bush and a sprue cup which are connected to the liquid lifting pipe, is divided under the action of a dividing cone, is sequentially filled along the sequence of the wheel center, a spoke, a rim and a wheel rim, and is solidified after being filled with the cavity. Meanwhile, the area of the sprue is large, so that the mold filling speed is high. However, the problems of difficult long-distance feeding and difficult solidification temperature field control after cooling control are applied caused by the pouring and filling mode can not be solved well all the time. The long sprue distance, the overlong mold filling distance and the slow mold filling speed cause the temperature of a metal mold of a casting to be as high as more than 400 ℃, the cooling speed of the casting is low, and the casting defects of shrinkage cavity, shrinkage porosity and the like formed at a hot spot part of the casting are caused, so that the problem which troubles the production of the wheel industry is solved. Although the cooling of the casting is enhanced by adopting the modes of water cooling, water mist cooling and the like so as to realize sequential solidification, the solidification time of the wheel is greatly shortened while the cooling is enhanced, the temperature fields of the casting in the processes of cooling and solidification are difficult to control in the production process, and waste products with a certain proportion are inevitably generated, so that the product performance is unstable and the qualified rate is low.
In the prior art, a mode of bilateral pouring is adopted in the middle of the side surface of the rim, and the defects of shrinkage cavity and shrinkage porosity are easily formed due to uncontrollable filling and solidification sequences caused by filling and shunting. The above-described double-sided casting is not widely used in the current wheel industry. The method still takes the center casting as the main part, and also shows that the method has little value in industrial application.
Based on the problem, the invention provides a wheel forming device based on multiple liquid lifting channels and with center pressurization, as shown in fig. 2, the wheel forming device comprises a heat preservation furnace 1 filled with aluminum liquid, a high-pressure air source is connected in the heat preservation furnace, a plurality of liquid lifting pipes 2 are arranged in the heat preservation furnace, and the lower parts of the liquid lifting pipes are immersed in the aluminum liquid 3. When a high-pressure air source is adopted to pressurize the aluminum liquid in the furnace, the aluminum liquid can rise along the plurality of liquid lifting pipes. The upper part of the riser tube is connected with a pouring gate of the mould through a vacuum cup and a pouring gate component 4 and enters a cavity 5 of the mould, and the pouring component comprises a pouring gate cup and a special-shaped pouring gate sleeve positioned above the pouring gate cup. The local supercharging mechanism is located: the position of the counter-gravity casting wheel mold corresponding to the wheel center of the wheel is arranged below the counter-gravity casting wheel mold; and transferring pressure to the metal melt after the filling is finished. The local pressurization mechanism comprises a pressure driving unit 6, a pressure transmission unit 7 and a pressure applying unit 8, wherein the pressure applying unit 8 is in contact with the metal melt and applies pressure to the metal melt after the mold filling is finished; the refining mechanism is arranged above the wheel die and above the position corresponding to the wheel center of the wheel and is used for refining the metal melt in the solidification process of the metal melt. The thinning mechanism is an ultrasonic thinning mechanism or a vibration thinning mechanism. The vibration generator 9 and the vibration rod 10 are included in the specific embodiment, the vibration rod 10 is inserted into the aluminum liquid, and the aluminum liquid is vibrated in the solidification process, so that dendritic crystals formed by crystallization of the aluminum liquid are broken, nucleation is enhanced, crystal grains are refined, and the mechanical performance of the wheel is improved. To more clearly illustrate the structure of the apparatus, the accompanying mounting platen 11 and lower die 12 are also shown.
In the present embodiment, the gate of the mold is provided on a torus directly below the rim of the wheel, and in particular, in the present invention, the "torus directly below the rim" means a torus formed around the central axis of the wheel on the side of the rim opposite to the rim. The excircle forming the ring is a circle formed by the outline of the outermost ring of the wheel on the surface, and the inner circle is a circle formed by the outline of the outer side of the window area of the wheel around the central axis of the wheel. As shown in fig. 1. Correspondingly, the position where the gate component is communicated with the mold is also arranged at the position.
It is particularly preferred that the gate and gate assembly be located on the torus outside the window area or on the torus corresponding to the rim to spoke connection.
In a preferred embodiment, the gates may be provided in two, may be symmetrically provided on both sides of the wheel, or may be provided in a plurality around the wheel axis. Corresponding with this runner, the stalk can set up to two, can set up in wheel bilateral symmetry, also can be for encircleing the wheel axis and set up a plurality of stalks.
The invention also discloses a low-pressure/counter-pressure casting process suitable for the mold filling mode, and because the pouring mold filling mode of the invention is greatly changed compared with the prior art, the original mold filling mode and the original solidification process can not be suitable for the invention.
The method specifically comprises the following steps:
(1) liquid lifting: pressurizing the aluminum liquid in the heat preservation furnace through a high-pressure air source, so that the aluminum liquid rises to the position of the pouring gate along the liquid lifting pipe under the pressure, wherein the pressure rising speed at the stage is 2.8-4.0 kPa/s, and the pressure is increased to 20 kPa;
(2) filling a mold: continuously boosting to enable the aluminum liquid to enter the cavity through the pouring gate, wherein the filling stage is two-stage pressurization, the boosting speed of the first stage is 0.1-0.2 kPa/s, the time is 2-4 s, and then the second stage is performed to rapidly boost until the cavity is filled, and the pressure reaches 35kPa at the moment;
the boosting speed P' in the second stage is determined as follows:
in the formula:
p' is the pressure increasing speed with the unit of kPa/s; h is the total height of the cavity and the unit is mm; rho is the density of the metal melt and has the unit of g/cm3(ii) a K is a resistance coefficient, and the value range of K is 1-1.5; t is preset mold filling time with the unit of s, preferably 10 s; 102 is a unit conversion coefficient;n is the number of the lift tubes, the value range of N is 2-6, the number can be selected according to the number of windows of wheels of different types, and 2-4 is preferred; and x is the liquid raising index of the steel plate, the value range is 0.2-0.8, and in the wheel type scheme adopted in the embodiment, the value is 0.5.
(3) And (3) crystallization, pressurization and pressure maintaining: after the mold filling is finished, the pressure is rapidly increased to 150kPa at the boosting speed of 8-10 kPa/for pressure maintaining, and meanwhile, the local increasing mechanism applies the pressure of 1-120 MPa to the metal melt at the wheel center until the wheel is solidified.
(4) Pressure relief and air release: and (4) after the aluminum alloy wheel is solidified, relieving the gas pressure in the heat preservation furnace, and enabling the aluminum liquid which is not solidified at the riser tube and the pouring gate to flow back to the heat preservation furnace.
The design basis of the specific process is explained as follows: for the selection of the pressure increasing speed in the liquid lifting stage and the mold filling stage, the inner diameter of the liquid lifting pipe is fixed during liquid lifting, and turbulence is basically not generated, so that the metal melt can quickly lift to the position of a pouring gate by adopting the quick pressure increasing speed, and the liquid lifting time is shortened. In the mold filling stage, the complicated shapes of the cavity and the sprue are considered, in the traditional mold filling mode, because a mode of pouring from the position of the wheel center is adopted, the sectional areas of the liquid lifting pipe and the sprue are not greatly different, and the sectional area of the cavity at the wheel center is large, turbulence is not easy to generate, so that the mold filling and pressure boosting speed can be obtained by experience or experiment. The invention adopts the mould filling mode on the circular ring surface of the rim, the mould filling mode is an irregular conformal gate, the shape area difference between the liquid lifting pipe and the gate is large, and the space at the rim is small, so that turbulent air entrainment is easy to generate if the mould filling pressure is unreasonable, and the defect of air holes is caused. The mold filling pressure design in the prior art adopts a calculation mode in an ideal state, and is corrected by combining a resistance coefficient and the like, and the change of the flowing state caused by the change of the sectional areas of the liquid lifting pipe and the pouring gate is not considered. Therefore, the ideal mold-filling boosting speed cannot be obtained by adopting the empirical formula in the prior art.
The present inventors have therefore studied the above problems in combination with the riser, the gate, the shape and cross-sectional area of the cavity above the gate, and the flow characteristics of the molten metal. It has been found that for the wheel rim position, as shown by the circular frame indicated by the arrow in fig. 3a, there are two locations with significantly varying areas in the initial stage of the mold filling, as shown by the circular frame indicated by the arrow in fig. 3b, where the gas entrapment is very likely to form if turbulence is generated, and it has been designed and calculated that the present invention employs two-stage pressurization, the first stage significantly reduces the pressure increase rate, so that the molten metal flows smoothly in the initial stage of the mold filling, fills the above-mentioned areas to avoid the gas entrapment, as shown in fig. 3c (where the arrow is the direction of the melt mold filling), and then enters the second stage for rapid pressure increase to shorten the mold filling time. In the second stage of the mold filling process, researches show that the mold filling speed, the melt flowing state and the number of the liquid lifting pipes are obviously related, and because the traditional mode of pouring from the center of the wheel only has one liquid lifting pipe and one pouring gate, the rules can be obtained through tests and quantitative treatment can be carried out. In the mold filling mode of the invention, the number of the liquid lifting pipes and the gates can be 2 or more. Under the same pressure increasing condition, the flow rate at the pouring gate and the flow rate in the square cavity above the pouring gate can be obviously changed, so that the mold filling flow mode is uncontrollable. Therefore, the invention obtains the pressure boosting mode of the second stage through research, and as can be seen from the formula (1), the adopted pressure boosting speed can be gradually increased along with the increase of the number of the liquid lifting pipes in the same preset mold filling time, and the problems of turbulent air entrainment and the like are not caused, wherein the resistance coefficient value is related to the viscosity of molten metal, the complexity of a mold cavity and the like, the lower limit is taken when the resistance is small, and the upper limit is taken when the resistance is large.
Example 1:
2 liquid lifting pipes and pouring gates are adopted, and the metal melt comprises the following components in percentage by mass: si: 5-9%, Mg: 0.3-0.5%, Zr: 0.01-0.02%, B: 0.005-0.007%, REe: 0.002-0.005%, 0.05-0.15% of Fe, Mn: 0.05-0.1%, Ti: 0.08-0.14%, and the balance of Al and inevitable impurities.
(1) Liquid lifting: pressurizing the aluminum liquid in the heat preservation furnace by a high-pressure air source, so that the aluminum liquid rises to the position of the pouring gate along the liquid lifting pipe under the pressure, wherein the pressure rising speed is 3.5kPa/s at the stage, and the pressure is increased to 20 kPa;
(2) filling a mold: and continuously boosting, so that the molten aluminum enters the cavity through the pouring gate, the boosting speed of the first stage is 0.2kPa/s, the time is 1.8s, the area indicated by an arrow in the figure 3b is stably filled with the molten metal, and then the molten metal enters the second stage and is rapidly filled with the molten metal at the boosting speed of 0.66kPa/s until the cavity is filled.
(3) And (3) crystallization, pressurization and pressure maintaining: after the mold filling is finished, the pressure is quickly increased to 150kPa at the pressure increasing speed of 8kPa/s, the pressure is maintained, the hydraulic oil cylinder drives the hydraulic rod driving pressure head to apply the mechanical pressure of 2000KPa to the wheel center position, and the vibration generator drives the vibrating rod to vibrate and refine the aluminum liquid until the wheel solidification is finished. In the pressure maintaining process, the high pressure of the rim hot spot is always kept at the sprue, and the possibility of shrinkage cavity and shrinkage porosity at the sprue is completely eliminated under the feeding of high-pressure aluminum liquid. Meanwhile, the pressure head carries out 20MPa local pressurization on the molten metal at the wheel center, and the possibility of generating shrinkage cavity and shrinkage porosity at the wheel center is eliminated.
(4) Pressure relief and air release: and (4) after the aluminum alloy wheel is solidified, relieving the gas pressure in the heat preservation furnace, and enabling the aluminum liquid which is not solidified at the riser tube and the pouring gate to flow back to the heat preservation furnace.
Example 2:
4 liquid lifting pipes and pouring gates are adopted, and the metal melt comprises the following components in percentage by mass: si: 5-9%, Mg: 0.3-0.5%, Zr: 0.01-0.02%, B: 0.005-0.007%, RE: 0.002-0.005%, 0.05-0.15% of Fe, Mn: 0.05-0.1%, Ti: 0.08-0.14%, and the balance of Al and inevitable impurities.
(1) Liquid lifting: pressurizing the aluminum liquid in the heat preservation furnace by a high-pressure air source, so that the aluminum liquid rises to the position of the pouring gate along the liquid lifting pipe under the pressure, wherein the pressure rising speed is 3.5kPa/s at the stage, and the pressure is increased to 20 kPa;
(2) filling a mold: and continuously boosting, so that the molten aluminum enters the cavity through the pouring gate, the boosting speed of the first stage is 0.15kPa/s, the time is 2.2s, the area indicated by an arrow in the figure 3b is stably filled with the molten metal, and then the molten metal enters the second stage and is rapidly filled with the molten metal at the boosting speed of 0.92kPa/s until the cavity is filled.
(3) And (3) crystallization, pressurization and pressure maintaining: after the mold filling is finished, the pressure is quickly increased to 150kPa at the pressure increasing speed of 8kPa/s, the pressure is maintained, the hydraulic oil cylinder drives the hydraulic rod driving pressure head to apply the mechanical pressure of 2000KPa to the wheel center position, and the vibration generator drives the vibrating rod to vibrate and refine the aluminum liquid until the wheel solidification is finished. In the pressure maintaining process, the high pressure of the rim hot spot is always kept at the sprue, and the possibility of shrinkage cavity and shrinkage porosity at the sprue is completely eliminated under the feeding of high-pressure aluminum liquid. Meanwhile, the pressure head carries out 20MPa local pressurization on the molten metal at the wheel center, and the possibility of generating shrinkage cavity and shrinkage porosity at the wheel center is eliminated.
(4) Pressure relief and air release: and (4) after the aluminum alloy wheel is solidified, relieving the gas pressure in the heat preservation furnace, and enabling the aluminum liquid which is not solidified at the riser tube and the pouring gate to flow back to the heat preservation furnace.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.
Claims (10)
1. A wheel forming device based on pressurization of center of a plurality of liquid lifting channels is characterized by comprising: the device comprises a heat-insulating container, a liquid lifting channel, a mould, a gas pressurizing mechanism and a local pressurizing mechanism;
the heat preservation container is used for storing metal melt, at least two liquid lifting channels are arranged in the heat preservation container, at least one part of each liquid lifting channel is positioned in the metal melt, and each liquid lifting channel is used for conveying the metal melt;
the heat-insulating container is connected with a gas pressurizing mechanism which can provide pressure so that the melt in the heat-insulating container rises along the liquid-lifting channel under the pressure and enters the die cavity;
the mould is provided with a cavity for solidifying and forming the metal melt, and the liquid lifting channel is communicated with the cavity through a pouring gate on the mould at the upper part;
the pouring gate on the mold is arranged on the circular ring surface right below the wheel rim;
the positions of the local supercharging mechanism are as follows: the position of the counter-gravity casting wheel mold corresponding to the wheel center of the wheel is arranged below the counter-gravity casting wheel mold; and applying pressure to the metal melt after the filling is finished.
2. The device for forming the wheel based on the central pressurization of the multi-lift liquid channel as claimed in claim 1, wherein the number of the gates is two, and the gates are symmetrically arranged relative to the axis of the wheel.
3. The wheel forming device based on multi-lift channel central pressurization as claimed in claim 2, wherein the number of the lift channels corresponding to the gates is two, and the lift channels are symmetrically arranged relative to the wheel axis.
4. The device for forming the wheel based on the central pressurization of the multi-lift liquid channel as claimed in claim 1, wherein the number of the gates is more than two and is arranged around the axis of the wheel.
5. The wheel forming device based on center pressurization of multiple liquid lifting channels according to claim 4, wherein the number of the liquid lifting channels corresponding to the pouring gates is more than two and is arranged around the wheel axis.
6. The wheel forming device based on central pressurization of multiple liquid lifting channels as claimed in claim 1, 2 or 4, wherein a gate component is arranged above the liquid lifting channels, and the gate component is communicated with a gate on the mold.
7. The wheel forming device based on multi-lift liquid channel center pressurization is characterized in that the pressure applied to the metal melt by the local pressurization mechanism is 1-120 MPa.
8. A method of wheel forming using the apparatus of any one of claims 1 to 7, comprising the steps of:
(1) liquid lifting: pressurizing the aluminum liquid in the heat preservation furnace through a high-pressure air source, so that the aluminum liquid rises to the position of the pouring gate along the liquid lifting pipe under the pressure;
(2) filling a mold: continuously boosting to enable the aluminum liquid to enter the cavity through the pouring gate, wherein the filling stage is two-stage pressurization, the boosting speed of the first stage is 0.1-0.2 kPa/s, the time is 2-4 s, and then the second stage is performed to rapidly boost the pressure until the cavity is full;
the boosting speed P' in the second stage is determined as follows:
in the formula: p' is the pressure increasing speed with the unit of kPa/s; h is the total height of the cavity and the unit is mm; rho is the density of the metal melt and has the unit of g/cm3(ii) a K is a resistance coefficient, and the value range of K is 1-1.5; t is theoretical mold filling time with the unit of s; 102 is a unit conversion coefficient; n is the number of the liquid lifting pipes, and the value range of N is 2-6; x is the liquid raising index of the compound, and the value range is 0.2-0.8;
(3) and (3) crystallization, pressurization and pressure maintaining: after the mold filling is finished, rapidly increasing the pressure in the liquid lifting pipe for pressure maintaining, and simultaneously applying 1-120 MPa of pressure to the metal melt at the wheel center position by the local increasing mechanism until the wheel is solidified;
(4) pressure relief and air release: and (4) after the aluminum alloy wheel is solidified, relieving the gas pressure in the heat preservation furnace, and enabling the aluminum liquid which is not solidified at the riser tube and the pouring gate to flow back to the heat preservation furnace.
9. The method for forming a wheel according to claim 8, wherein the theoretical mold filling time t is preferably 10s, and N is preferably 2-4 and 0.5.
10. A method of forming a wheel according to claim 9, wherein the wheel is formed by a method of molding a wheel according to claim 9. The mold temperature prior to ramping is no greater than 400 c, preferably no greater than 350 c, and more preferably no greater than 300 c.
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