Aluminum alloy anti-gravity casting online semi-solid pulping process and mold

Abstract

The invention belongs to the field of aluminum alloy casting, and particularly relates to an aluminum alloy anti-gravity casting online semi-solid pulping process and a mold. An aluminum alloy anti-gravity casting online semi-solid pulping process comprises the following steps that firstly, compressed air is injected through a compressed air injection opening, and molten aluminum in a heat preservation furnace rises through a liquid rising pipe and passes through a semi-solid pulping structure; secondly, the liquid level passes through a semi-solid pulping structure, and molten aluminum is crystallized, solidified and attached to the inner wall; and thirdly, through a semi-solid pulping structure, crystals fall off from the inner wall and are evenly mixed with molten aluminum. According to traditional low-pressure casting, a mold can be filled with semi-solid metal, a casting of a semi-solid structure is obtained, due to the fact that semi-solid slurry is good in fluidity under a certain pressure and has primary crystal nucleuses before filling, the solidification form of the semi-solid slurry is changed after metal filling is completed, a nearly-spherical crystal structure is obtained, segregation is reduced, feeding is easier, and the casting quality is improved. The mechanical property isotropic difference of the product is reduced, and the shrinkage cavities are few.

Description

Technical Field

[0001] The present invention belongs to the field of aluminum alloy casting, and particularly relates to an on-line semi-solid slurry preparation process and a mold for counter-gravity casting of aluminum alloy. Background Art

[0002] Counter-gravity casting of aluminum alloy is an advanced casting process. It uses pressure to push molten aluminum alloy from bottom to top into the mold. Compared with traditional gravity casting, this method can better control the quality and performance of the castings.

[0003] The existing counter-gravity casting (low-pressure, differential-pressure casting) process is to apply air pressure in a sealed holding furnace, press the molten aluminum in the holding furnace into the mold through a riser pipe, and finally solidify in the mold to obtain the casting. In this way of liquid lifting, the temperature of the molten aluminum in the holding furnace is generally 40-50 °C above the liquidus. The temperature of the molten aluminum entering the mold is also above the liquidus and solidifies after filling the mold. During the solidification process, the crystallization is dendritic crystallization, and feeding is carried out through the sprue and riser.

[0004] The disadvantages of the existing casting process are that the temperature of the molten aluminum is high when filling the mold, so the solidification time is long and the production cycle is long; at the same time, the material temperature is high, the feeding amount is large, and the hot spot is obvious; after solidification, it is dendritic structure, segregation is serious, and the product performance has obvious anisotropy; during the solidification process, due to the high material temperature, the mold deforms greatly, it is easy to cause problems such as leakage of the parting surface, and at the same time, due to the high material temperature, shrinkage cavities are easily formed in the casting, resulting in product quality problems.

[0005] Therefore, it is urgent to develop an on-line semi-solid slurry preparation process and a mold for counter-gravity casting of aluminum alloy to solve the above technical problems. Summary of the Invention

[0006] In order to overcome the above disadvantages of the prior art, the present invention provides an on-line semi-solid slurry preparation process and a mold for counter-gravity casting of aluminum alloy.

[0007] Technical Solution: The on-line semi-solid slurry preparation process for counter-gravity casting of aluminum alloy includes the following steps: Step 1: Inject compressed air through the compressed air injection port to make the molten aluminum in the holding furnace rise through the riser pipe and pass through the semi-solid slurry preparation structure; Step 2: The liquid level passes through the semi-solid slurry preparation structure, and the molten aluminum crystallizes and solidifies and adheres to the inner wall; Step 3: Through the semi-solid slurry preparation structure, the crystals are detached from the inner wall and mixed with the molten aluminum; Step 4: The mixed molten aluminum enters the mold for casting; Step 5: After the product is formed, the mold is opened and taken out, and the semi-solid slurry preparation structure is cooled.

[0008] In addition, particularly preferably, when the molten aluminum passes through the semi-solid slurry preparation structure, it is mixed by means of inert gas agitation or electromagnetic stirring.

[0009] In addition, it is particularly preferred that when the molten aluminum in the holding furnace passes through the semi-solid slurry-making structure via the riser pipe, it can hover in the semi-solid slurry-making structure to ensure that the crystallization of the molten aluminum can be fully mixed with the molten aluminum.

[0010] In addition, it is particularly preferred that the semi-solid slurry-making structure can be replaced to control the contact area between the semi-solid slurry-making structure and the molten aluminum, so as to obtain semi-solid slurries of different weights. At the same time, the internal volume of the semi-solid slurry-making structure is consistent with the volume of materials required for product forming to ensure that one-time feeding is completed.

[0011] In addition, it is particularly preferred that a temperature monitoring unit is arranged inside the semi-solid slurry-making structure to monitor the temperature inside the semi-solid slurry-making structure to ensure that there is a temperature difference between the temperature of the semi-solid slurry-making structure and the molten aluminum.

[0012] In addition, it is particularly preferred that the semi-solid slurry-making structure is cooled by injecting flowing gas.

[0013] The on-line semi-solid slurry-making die for aluminum alloy counter-gravity casting includes a liquid injection seat, a semi-solid slurry-making structure and a die. The liquid injection seat, the semi-solid slurry-making structure and the die are installed in sequence from bottom to top. The semi-solid slurry-making structure includes a fixed plate, a spacer block, a semi-solid slurry-making unit, a first joint, a second joint and a sprue bush. The fixed plate is fixedly connected to the top of the liquid injection seat. Removable symmetric connections are provided between the fixed plate and the die with spacer blocks. The semi-solid slurry-making unit is removably installed on the top of the fixed plate between the spacer blocks. The first joint and the second joint are installed on the outer side wall of the semi-solid slurry-making unit. A sprue bush is arranged on the die above the semi-solid slurry-making unit.

[0014] In addition, it is particularly preferred that the semi-solid slurry-making unit is an annular ceramic sleeve. Micropores are provided on the inner wall of the annular ceramic sleeve. The first joint and the second joint are installed on the left side wall of the annular ceramic sleeve.

[0015] In addition, it is particularly preferred that the micropores allow gas phase to pass through but do not allow liquid phase to pass through.

[0016] In addition, it is particularly preferred that the semi-solid slurry-making unit is a coil and a slurry-making sleeve. The slurry-making sleeve is removably installed between the riser pipe and the sprue bush. The coil is sleeved on the outer side of the slurry-making sleeve. The first joint and the second joint are installed on the coil.

[0017] Compared with the prior art, the present invention has the following advantages: The present invention enables traditional low-pressure casting to fill the mold with semi-solid metal and obtain castings with semi-solid structures. Since the semi-solid slurry has good fluidity under a certain pressure and has primary crystal nuclei before filling, after the metal filling is completed, its solidification morphology is changed to obtain a near-spherical crystal structure, reducing segregation and making feeding easier. This is manifested in the product as reduced anisotropy in mechanical properties, fewer shrinkage cavities, faster filling speed during production, reduced filling time, and accelerated solidification time due to the existing primary crystal nuclei, thereby improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a flow chart of the present invention.

[0020] Figure 2 It is a three-dimensional structural schematic diagram of the casting mold of the present invention.

[0021] Figure 3 It is a cross-sectional view of the casting mold of the present invention.

[0022] Figure 4 It is a cross-sectional view of the liquid injection base of the present invention.

[0023] Figure 5 It is a cross-sectional view of the ceramic sleeve with a ring shape for the semi-solid slurry preparation unit of the present invention.

[0024] Figure 6 It is a cross-sectional view of the semi-solid slurry preparation unit with a coil and a slurry preparation sleeve of the present invention.

[0025] Figure 7 It is a cross-sectional view of the mold of the present invention.

[0026] In the figure: 1. Liquid injection seat, 101. Heat preservation furnace, 102. Aluminum liquid cavity, 103. Compressed air injection port, 104. Feeding port, 105. Rising pipe, 2. Semi-solid slurry preparation structure, 201. Fixed plate, 202. Spacer block, 203. Semi-solid slurry preparation unit, 204. Micropores, 205. First joint, 206. Second joint, 207. Sprue bushing, 208. Coil, 209. Slurry preparation sleeve, 3. Mold, 301. Bottom mold, 302. Optical axis, 303. Movable plate, 304. Top mold. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] Thus, a feature pointed out in this specification will be used to illustrate one feature of one embodiment of the present invention, rather than implying that each embodiment of the present invention must have the illustrated feature. In addition, it should be noted that this specification describes many features. Although some features may be combined to show possible system designs, these features can also be used in other combinations not explicitly described. Thus, unless otherwise stated, the illustrated combinations are not intended to be limiting.

[0029] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0030] Example 1: As Figures 1-7 shown, the present invention relates to an on-line semi-solid slurry preparation process for aluminum alloy counter-gravity casting, including the following steps: ① Inject compressed air through the compressed air injection port 103, so that the molten aluminum in the holding furnace 101 rises through the riser pipe 105 and passes through the semi-solid slurry preparation structure 2; ② When the liquid level passes through the semi-solid slurry preparation structure 2, the molten aluminum crystallizes and solidifies and adheres to the inner wall. When the molten aluminum in the holding furnace 101 passes through the semi-solid slurry preparation structure 2 through the riser pipe 105, it can hover in the semi-solid slurry preparation structure 2 to ensure that the aluminum liquid crystals can be fully mixed with the molten aluminum; ③ When the molten aluminum passes through the semi-solid slurry preparation structure 2, the crystals are detached from the inner wall and mixed with the molten aluminum by means of inert gas agitation or electromagnetic stirring; ④ The mixed molten aluminum enters the mold 3 for casting and forming; ⑤ After the product is formed, the mold is opened and taken out, and the semi-solid slurry preparation structure 2 is cooled.

[0031] As Figure 5 and Figure 6 shown, the semi-solid slurry preparation structure 2 can be replaced to control the contact area between the semi-solid slurry preparation structure 2 and the molten aluminum, obtain semi-solid slurries of different weights, and at the same time, the internal volume of the semi-solid slurry preparation structure 2 is consistent with the volume of materials required for product forming to ensure that one injection is completed.

[0032] As Figure 5 and Figure 6As shown, a temperature monitoring unit is provided inside the semi-solid slurry making structure 2 to monitor the temperature inside the semi-solid slurry making structure 2, so as to ensure that there is a temperature difference between the temperature of the semi-solid slurry making structure 2 and the molten aluminum.

[0033] An on-line semi-solid slurry making die for counter-gravity casting of aluminum alloy, as Figures 1-7 shown, includes a liquid injection seat 1, a semi-solid slurry making structure 2 and a die 3. The liquid injection seat 1, the semi-solid slurry making structure 2 and the die 3 are installed in sequence from bottom to top. The semi-solid slurry making structure 2 can be replaced to control the contact area between the semi-solid slurry making structure 2 and the molten aluminum, so as to obtain semi-solid slurries of different weights. At the same time, the internal volume of the semi-solid slurry making structure 2 is consistent with the volume of materials required for product forming to ensure that one-time feeding is completed. A temperature monitoring unit is provided inside the semi-solid slurry making structure 2 to monitor the temperature inside the semi-solid slurry making structure 2, so as to ensure that there is a temperature difference between the temperature of the semi-solid slurry making structure 2 and the molten aluminum. The semi-solid slurry making structure 2 includes a fixed plate 201, a spacer block 202, a semi-solid slurry making unit 203, a first joint 205, a second joint 206 and a sprue bushing 207. The fixed plate 201 is fixedly connected to the top of the liquid injection seat 1 by bolts to support the entire casting die 3. Between the fixed plate 201 and the die 3, spacer blocks 202 are detachably and symmetrically connected by bolts. The spacer blocks 202 make the fixed plate 201 and the die 3 in a suspended state. The semi-solid slurry making unit 203 is installed on the top of the fixed plate 201 between the spacer blocks 202. The first joint 205 and the second joint 206 are installed on the side wall of the semi-solid slurry making unit 203. A sprue bushing 207 is provided on the die 3 above the semi-solid slurry making unit 203. The vertical cross-section of the sprue bushing 207 is a frustum of a cone that tapers upward from bottom to top to facilitate the entry of molten aluminum into the die 3.

[0034] As Figure 4 shown, the liquid injection seat 1 includes a holding furnace 101, a molten aluminum chamber 102, a compressed air injection port 103, a feeding port 104 and a riser pipe 105. A molten aluminum chamber 102 is provided inside the holding furnace 101 to store molten aluminum. The compressed air injection port 103 is connected and installed on the left side of the top of the molten aluminum chamber 102. The feeding port 104 is connected and provided on the right side of the top of the molten aluminum chamber 102. The riser pipe 105 is connected and provided on the top of the molten aluminum chamber 102. By adjusting the compressed air pressure, the molten aluminum rises through the riser pipe 105. The connection between the riser pipe 105 and the molten aluminum chamber 102 is a semi-circular shape that tapers upward from bottom to top. The semi-circular inlet allows the molten aluminum to enter the riser pipe 105 from all around.

[0035] As Figure 7As shown, the mold 3 includes a bottom mold 301, an optical axis 302, a movable plate 303 and a top mold 304. The bottom mold 301 is fixedly connected to the top of the cushion block 202 by bolts, the gate sleeve 207 is installed in the center of the bottom mold 301, and the gate sleeve 207 passes through the bottom mold 301, and the optical axis 302 is symmetrically arranged on the top of the fixed plate 201. The movable plate 303 is slidably connected to the optical axis 302 through a linear bearing, and the bottom of the movable plate 303 is fixedly connected to the top mold 304 by bolts. The top of the top mold 304 can be connected to a cylinder or a servo electric cylinder to drive the top mold 304 to move vertically for mold closing and opening.

[0036] When casting aluminum alloy, the top mold 304 is first moved downward to close the bottom mold 301 for mold closing, and then aluminum liquid is added into the aluminum liquid cavity 102 through the feeding port 104. The aluminum liquid is raised through the liquid riser 105 and passes through the semi-solid slurry making unit 203 by adjusting the compressed air pressure. The rising speed of the liquid level when passing through the semi-solid slurry making unit 203 is controlled to ensure that the semi-solid slurry with the required solid phase ratio is obtained. The insulation furnace 101 is used to heat the aluminum liquid in the aluminum liquid cavity 102. The high-temperature aluminum liquid passes through the low-temperature semi-solid slurry making unit 203. The aluminum liquid in contact with the inner wall of unit 203 will crystallize, solidify and adhere to the inner wall. At this time, the crystals will fall off the inner wall and mix with the aluminum liquid through inert gas disturbance stirring or electromagnetic stirring. In actual use, by controlling the contact area, time and blowing time of the aluminum liquid passing through the semi-solid slurry making unit 203, semi-solid slurries of different weights can be obtained, and then this part of the slurry is further filled into the mold 3 by pressure, and a casting product is obtained after solidification. At this time, the aluminum liquid returns to the aluminum liquid cavity 102, and the product molding is completed and the mold is opened to take out the product.

[0037] Embodiment 2: as Figure 5As shown in the figure, the semi-solid slurry-making unit 203 is a ring-shaped ceramic sleeve. Micropores 204 are provided on the inner wall of the ring-shaped ceramic sleeve. The first joint 205 and the second joint 206 are installed on the left side wall of the ring-shaped ceramic sleeve. The micropores 204 can only allow gas to enter and cannot allow liquid to flow out. When the first joint 205 is opened, the second joint 206 is closed, and when the second joint 206 is opened, the first joint 205 is closed; when the molten aluminum passes through the ring-shaped ceramic sleeve, because the temperature of the inner surface of the ring-shaped ceramic sleeve is lower than the temperature of the molten aluminum, when the molten aluminum passes through the ring-shaped ceramic sleeve, it solidifies and crystallizes on the inner surface of the ring-shaped ceramic sleeve. At this time, an inert gas is injected through the second joint 206. Due to the porous structure on the inner wall of the semi-solid slurry-making unit 203, the semi-solid slurry-making unit 203 blows out the inert gas outward through the porous structure. The inert gas drives the molten aluminum to convect, causing the crystallized and solidified metal to break away from the inner wall and diffuse towards the center, forming fine crystal nuclei. This continuously occurs when the molten aluminum surface passes through the entire inner wall. During the upward movement of the molten aluminum, it solidifies while diffusing into the internal liquid under the pressure of the inert gas, so that the primary crystal nuclei are evenly dispersed in the molten aluminum that has passed through the semi-solid slurry-making unit 203, forming a semi-solid state of solid-liquid mixture. After the product is molded and the mold is opened to take out the product, at this time, the control signal opens the first joint 205 in the semi-solid slurry-making unit 203, and the compressed air can take away the heat on the inner wall of the semi-solid slurry-making unit 203. By controlling the flow rate and time of the compressed air, the temperature of the inner wall of the ring-shaped ceramic sleeve can be reduced to the required value, which is more than 100°C lower than the temperature of the molten aluminum. Then, the control switch is switched, the first joint 205 on the semi-solid slurry-making unit 203 is closed, and at the same time the second joint 206 is opened. By controlling the ventilation pressure and time, after all the air in the semi-solid slurry-making unit 203 is exhausted, the next casting cycle can be started.

[0038] Embodiment 3: As Figure 6 shown in the figure, the semi-solid slurry-making unit 203 is a coil 208 and a slurry-making sleeve 209. The slurry-making sleeve 209 is detachably installed between the liquid-rising pipe 105 and the gate sleeve 207. The coil 208 is sleeved on the outer side of the slurry-making sleeve 209. The first joint 205 and the second joint 206 are installed on the coil 208; when the molten aluminum passes through the inner wall of the slurry-making sleeve 209, because the temperature of the inner surface of the slurry-making sleeve 209 is lower than the temperature of the molten aluminum, when the molten aluminum passes through the inner wall of the slurry-making sleeve 209, it solidifies and crystallizes on the inner wall of the slurry-making sleeve 209. At this time, the coil is energized, causing the molten aluminum inside the slurry-making sleeve 209 to rotate. During the rotation process, the crystals on the inner wall of the slurry-making sleeve 209 are mixed with the molten aluminum. After the molten aluminum is mixed evenly, it enters the mold 3 for molding. After the product is molded and the mold is opened to take out the product, the first joint 205 is connected to the compressed air inlet, and the second joint 206 is connected to the compressed air outlet. Then, compressed air is introduced to cool down the slurry-making sleeve 209 until the temperature of the inner wall of the slurry-making sleeve 209 is more than 100°C lower than the temperature of the molten aluminum.

[0039] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those skilled in the art.

Claims

1. Aluminum alloy counter-gravity casting online semi-solid pulping process, characterized in that: The following steps are involved: Step 1: Compressed air is injected through the compressed air injection port (103) to cause the aluminum liquid in the holding furnace (101) to rise through the riser (105) and pass through the semi-solid slurrying structure (2); Step 2: the liquid surface passes through the semi-solid slurrying structure (2), and the aluminum liquid crystallizes, solidifies and adheres to the inner wall; Step 3: Using the semi-solid slurrying structure (2), the crystals are removed from the inner wall and mixed with the aluminum liquid; Step 4: The mixed aluminum liquid enters the mold (3) for casting; Step 5: After the product is formed, the mold is opened and taken out, and the semi-solid pulping structure (2) is cooled.

2. The online semi-solid slurry making process for aluminum alloy counter-gravity casting according to claim 1 is characterized in that: When the aluminum liquid passes through the semi-solid slurrying structure (2), it is mixed by inert gas disturbance stirring or electromagnetic stirring.

3. The online semi-solid slurry making process for aluminum alloy counter-gravity casting according to claim 2 is characterized in that: When the aluminum liquid in the insulation furnace (101) passes through the semi-solid slurrying structure (2) via the riser pipe (105), it can hover in the semi-solid slurrying structure (2) to ensure that the aluminum liquid crystals can be fully mixed with the aluminum liquid.

4. The online semi-solid slurry making process for aluminum alloy counter-gravity casting according to claim 3 is characterized in that: The semi-solid pulping structure (2) can be replaced to control the contact area between the semi-solid pulping structure (2) and the aluminum liquid to obtain semi-solid pulps of different weights. At the same time, the internal volume of the semi-solid pulping structure (2) is consistent with the material volume required for product molding to ensure that the injection is completed in one time.

5. The online semi-solid slurry making process for aluminum alloy counter-gravity casting according to claim 4 is characterized in that: A temperature monitoring unit is arranged inside the semi-solid pulping structure (2) for monitoring the temperature inside the semi-solid pulping structure (2) to ensure that there is a temperature difference between the temperature of the semi-solid pulping structure (2) and the aluminum liquid.

6. The online semi-solid slurry making process for aluminum alloy counter-gravity casting according to claim 1 is characterized in that: The semi-solid pulping structure (2) is cooled by injecting flowing gas.

7. Aluminum alloy anti-gravity casting online semi-solid pulping mold, characterized by: The invention comprises a liquid injection seat (1), a semi-solid pulping structure (2) and a mould (3), wherein the liquid injection seat (1), the semi-solid pulping structure (2) and the mould (3) are sequentially installed from bottom to bottom, wherein the semi-solid pulping structure (2) comprises a fixed plate (201), a cushion block (202), a semi-solid pulping unit (203), a first joint (205), a second joint (206) and a sprue sleeve (207), wherein the fixed plate (201) is fixedly connected to the top of the liquid injection seat (1), a cushion block (202) is detachably and symmetrically connected between the fixed plate (201) and the mould (3), a semi-solid pulping unit (203) is detachably installed on the top of the fixed plate (201) between the cushion blocks (202), a first joint (205) and a second joint (206) are installed on the outer side wall of the semi-solid pulping unit (203), and a sprue sleeve (207) is arranged on the mould (3) above the semi-solid pulping unit (203).

8. The online semi-solid pulping mold for aluminum alloy counter-gravity casting according to claim 7 is characterized in that: The semi-solid pulping unit (203) is an annular ceramic sleeve, the inner wall of which is provided with micropores (204), and the first joint (205) and the second joint (206) are mounted on the left side wall of the annular ceramic sleeve.

9. The online semi-solid pulping mold for aluminum alloy counter-gravity casting according to claim 8 is characterized in that: The micropores (204) allow the gas phase to pass therethrough but do not allow the liquid phase to pass therethrough.

10. The online semi-solid pulping mold for aluminum alloy counter-gravity casting according to claim 7, characterized in that: The semi-solid pulping unit (203) comprises a coil (208) and a pulping sleeve (209); the pulping sleeve (209) is detachably installed between the riser tube (105) and the gate sleeve (207); the coil (208) is sleeved on the outer side of the pulping sleeve (209); and the first joint (205) and the second joint (206) are installed on the coil (208).

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