Purification device for efficiently removing impurities in cast aluminum melt outside furnace

Abstract

The invention discloses a purification device for efficiently removing impurities in cast aluminum melt outside a furnace, which comprises a vacuum pump, a pressure gauge, a high-purity nitrogen cylinder, a bottom box body, an aluminum ingot groove, a rectangular sealing gasket, a box cover, an annular sealing gasket, an isolating ring, a pouring cylinder, a porous ceramic filter sheet, a thermal insulation layer and a top cover, according to the device, the molten aluminum quickly flows through the porous ceramic filter sheet by utilizing negative pressure, so that inclusions and hydrogen can be effectively removed. The device is particularly suitable for aluminum product casting, secondary air suction of molten aluminum is effectively prevented through purification treatment of the molten aluminum, impurities are efficiently removed, the hydrogen content is reduced, and therefore the casting quality is improved.

Description

Technical Field

[0001] The present invention relates to the application field of high-quality aluminum products for new energy vehicles, and particularly designs a purification device for efficiently removing impurities in cast aluminum melt outside the furnace for low-cost engineering preparation of high-quality aluminum products.

Background Art

[0002] With the wide application of aluminum products in new energy vehicles, the main engine factories have put forward more stringent requirements for the quality and performance of aluminum alloys. Currently, industrial aluminum is processed in an atmospheric atmosphere, making it inevitable for aluminum alloys to undergo oxidation and hydrogen absorption during the melting process. After the aluminum alloy melts, its melt contains a large amount of gas and oxide inclusions. The presence of inclusions and hydrogen seriously affects the purity of the aluminum liquid, resulting in defects such as inclusions, porosity, and gas holes in aluminum castings. In order to obtain high-quality aluminum automotive parts, it is necessary to remove inclusions and hydrogen from the aluminum liquid. Aluminum liquid purification is divided into in-furnace treatment and out-of-furnace treatment.

[0003] (1) In-furnace treatment: Currently, domestic aluminum industries generally use a refining pipe to blow gas or a gas + refining agent for in-furnace refining. The hydrogen content in the aluminum liquid is roughly controlled at the level of 0.15 - 0.20 mL / 100g·Al, and the hydrogen content is relatively high. The reason is that there are a large number of suspended fine oxide inclusions in the aluminum liquid, and these inclusions are difficult to remove by skimming. Moreover, the oxide inclusions have a strong symbiotic relationship with hydrogen, creating adsorption conditions for hydrogen in the melt.

[0004] (2) Out-of-furnace treatment: At present, the out-of-furnace treatment of aluminum liquid mainly uses ceramic filter plates for purification, that is, the three-dimensional network structure of the ceramic filter plate is used as the flow channel of the aluminum liquid. By blocking oxide inclusions larger than the pore diameter of the mesh, the purity level of the aluminum liquid is further improved. The hydrogen content in the aluminum liquid can reach the level of 0.10 - 0.12 mL / 100g·Al. Since the aluminum liquid is still filtered by the ceramic filter plate in an atmospheric atmosphere, and due to the special tortuous three-dimensional network structure of the ceramic filter plate, there is a risk of re-hydrogen absorption during out-of-furnace purification, and the filtration time is relatively long, resulting in a relatively high cost.

Summary of the Invention

[0005] The invention object of the present invention is, in view of the above problems, to provide a purification device for efficiently removing impurities in cast aluminum melt outside the furnace, so as to achieve low-cost engineering mass production of high-quality aluminum melt.

[0006] To solve the above problems, the technical solution adopted by the present invention is:

[0007] A purification device for efficiently removing impurities in cast aluminum melt outside the furnace includes a vacuum pump, a pressure gauge, a high-purity nitrogen gas cylinder, a bottom box body, an aluminum ingot tank, a box cover, a spacer ring, a pouring cylinder, a porous ceramic filter plate, and a top cover;

[0008] The pressure gauge is connected to a vacuum pump through a hose 1, and is connected to a high-purity nitrogen cylinder through a hose 2. The pressure gauge is connected to the bottom box through a hose 3.

[0009] The bottom box is an enclosed box with an upper opening formed by four side plates surrounding the four sides of a bottom plate. A rectangular flange is provided around the upper port of the box, and the rectangular flange is reinforced by a number of first reinforcing ribs provided on the outer sides of the side plates. A pressure gauge connector is also provided on one side plate for inserting the hose 3.

[0010] The box cover covers the upper opening of the bottom box; a circular flange is provided at the center position of the box cover.

[0011] A through hole is provided at the center of the circular flange, and threaded blind holes are provided around the upper surface with it as the center.

[0012] The pouring cylinder is provided on the circular flange, and the top cover covers the top end of the pouring cylinder.

[0013] The pouring cylinder has a lower flange and an upper flange fixedly connected to the upper and lower ends of a hollow tube respectively; reinforcing ribs are also provided on the outer surface of the hollow tube for reinforcing the lower flange and the upper flange; third connection holes and fourth connection holes are respectively provided on the lower flange and the upper flange; the positions of the third connection holes correspond to those of the threaded blind holes one by one and bolts can be passed through for relative fixation; an isolation ring and a porous ceramic filter plate are respectively sleeved in the inner hole of the hollow tube from top to bottom; the outer peripheral walls of the isolation ring and the porous ceramic filter plate are attached to the inner peripheral wall of the hollow tube.

[0014] Fifth connection holes are provided on the top cover, corresponding to the fourth connection holes one by one and bolts can be passed through for relative fixation.

[0015] The aluminum ingot groove is sleeved inside the bottom box and is below the through hole.

[0016] Further, a first weight-reducing groove is provided on the outer surface of the bottom plate; first weight-reducing grooves are provided on both the upper and lower surfaces of the box cover.

[0017] Further, a number of connection holes are provided on the rectangular flange.

[0018] A first weight-reducing groove is provided on the outer surface of the bottom plate; first weight-reducing grooves are provided on both the upper and lower surfaces of the box cover.

[0019] A number of second connection holes are provided around the box cover, and the diameter of the second connection holes is the same as that of the connection holes. The box cover is fixedly covered on the bottom box by passing nuts through the corresponding second connection holes and connection holes.

[0020] A rectangular sealing gasket is also provided between the box cover and the bottom box, and sixth connection holes are provided on the rectangular sealing gasket. The positions of the sixth connection holes, the connection holes, and the second connection holes correspond to each other one by one and bolts can be passed through for relative fixation.

[0021] A first annular gasket is further provided between the lower flange and the circular flange. A seventh connection hole is also provided on the first annular gasket. The positions of the seventh connection holes correspond to those of the threaded blind holes one by one, and bolts can be inserted through them for relative fixation.

[0022] A second annular gasket is further provided between the top cover and the pouring cylinder. An eighth connection hole is also provided on the second annular gasket. The positions of the eighth connection holes correspond to those of the fourth connection holes one by one, and bolts can be inserted through them for relative fixation.

[0023] Furthermore, it includes a heat insulation layer wrapped around the outer wall of the pouring cylinder; the material of the heat insulation layer is asbestos, and the thickness ≥ 20mm. It realizes heat insulation and achieves the purpose of heat preservation of the molten aluminum in the pouring cylinder, thereby delaying the heat loss of the molten aluminum in the pouring cylinder and ensuring that the molten aluminum flows smoothly through the porous ceramic filter before solidification.

[0024] Furthermore, the isolation ring is a thin sheet annular structure, and the material is selected as titanium alloy TC4, with a first through hole opened in the middle. The purpose of selecting titanium alloy TC4 is to utilize the corrosion resistance of titanium alloy TC4 to molten aluminum to isolate the direct contact between the molten aluminum and the box cover, thereby reducing the thermal corrosion of the molten aluminum on the box cover. Among them, the function of the first through hole is the flow channel of the molten aluminum.

[0025] Furthermore, the pressure gauge includes a low-pressure gauge, a high-pressure gauge, a low-pressure valve, a high-pressure valve, hose 1, hose 2, and hose 3.

[0026] Furthermore, the following relationship exists between the pumping rate parameter S1 (L / s) of the vacuum pump and the volume V (L) of the bottom box body:

[0027] S1 ≥ 4V / [t×Log(P0 / P1)] (i)

[0028] In formula (i), t is the time required to reach the required vacuum degree. Considering that the molten aluminum is easy to solidify in the atmospheric atmosphere, the present invention requires t ≤ 30s; P0 is the atmospheric pressure of 101325 (Pa); P1 is the vacuum degree that the device of the present invention can reach within 30 seconds, and P1 ≤ -10Pa. In order to make the negative pressure formed between the pouring cylinder (10) and the bottom box body within 30 seconds much greater than the osmotic pressure P of the porous ceramic filter inf resistance, the present invention requires that the pressure difference △P (△P = P0 - P1) formed by the device of the present invention within 30 seconds and the osmotic pressure P inf The ratio between them ≥ 20.

[0029] Further explanation: To ensure that the molten aluminum in the hollow tube does not solidify within 30 seconds and flows through the porous ceramic filter quickly, it is required that under the action of the pressure difference △P, when the molten aluminum in the hollow tube flows out through the porous ceramic filter and the isolation ring from the through-hole of the box cover, its flow rate S2 is greater than the pumping rate S1 of the vacuum pump. The height H of the hollow tube and the diameter φD of the first through-hole of the isolation ring need to satisfy the following relationship:

[0030]

[0031] In formula (ii), ρ is the density of aluminum alloy, ρ = 2.7 * 10 3 kg / m 3 . g is the gravity, g = 9.8 N / kg.

[0032] Further explanation: The first weight reduction grooves are symmetrically arranged and form ribs to improve the overall stiffness of the bottom plate, and its depth is 4 - 5 mm.

[0033] Compared with the prior art, the advantages of this application are:

[0034] This device uses negative pressure to make the molten aluminum flow through the (Pyrotek) porous ceramic filter quickly, so as to effectively remove inclusions and hydrogen. This device is especially suitable for the casting of aluminum products. By purifying the molten aluminum, it effectively prevents the molten aluminum from sucking air again, efficiently removes inclusions and reduces the hydrogen content, thereby improving the quality of castings.

[0035] In the present invention, each component cooperates with each other. Through research, it is found that after setting some specific parameters for the device of this application, the process flow can proceed smoothly. It is ensured that when the molten aluminum is poured into the pouring cylinder, the bottom box body is evacuated, which can help the molten aluminum overcome the osmotic pressure Pinf resistance of the porous ceramic filter. During the process of flowing into the aluminum ingot groove, it effectively filters inclusions and reduces the hydrogen content. Therefore, the device of the present invention can greatly improve the quality of aluminum ingots.

[0036] This device has the advantages of simple operation, low cost, high reliability, and can achieve the engineering mass production of high-quality aluminum melt in the atmospheric atmosphere.

Description of the Drawings

[0037] Figure 1 It is a schematic structural diagram of the pure purification device of the present invention.

[0038] Figure 2 It is a schematic diagram of the outer surface structure of the bottom plate of the bottom box body of the present invention.

[0039] Figure 3 It is a schematic structural diagram of the bottom box body of the present invention.

[0040] Figure 4 It is a schematic structural diagram of the box cover of the present invention.

[0041] Figure 5 This is a schematic structural diagram of the pouring cylinder of the present invention.

[0042] Figure 6 This is a schematic structural diagram of the top cover of the present invention.

[0043] Figure 7 This is a schematic structural diagram of the rectangular sealing gasket of the present invention.

[0044] Figure 8 This is a schematic structural diagram of the first circular sealing gasket or the second circular sealing gasket of the present invention.

[0045] Figure 9 This is a schematic structural diagram of the isolation ring of the present invention.

[0046] Figure 10 This is a schematic structural diagram of the pressure gauge of the present invention.

[0047] Figure 11 、 12 This is the on-site assembly drawing of the actual application of the present invention.

[0048] Figure 13 This is the metallographic inspection drawing of the product prepared by the device of the present invention.

[0049] Figure 14 This is the hydrogen content detection result drawing of the product prepared by the device of the present invention.

[0050] In the drawings: 1 vacuum pump, 2 pressure gauge, 3 high-purity nitrogen cylinder, 4 bottom box body, 5 aluminum ingot tank, 6 rectangular sealing gasket, 7 box cover, 8 circular sealing gasket, 9 isolation ring, 10 pouring cylinder, 11 porous ceramic filter plate, 12 heat preservation layer, 13 circular sealing gasket, 14 top cover, 15 rectangular flange, 16 bottom plate, 17 side plate, 18 first reinforcing rib, 19 pressure gauge joint, 20 first weight-reducing groove, 21 connecting hole, 22 weight-reducing groove, 23 circular flange, 24 through hole, 25 threaded blind hole, 26 second connecting hole, 27 hollow pipe, 28 lower flange, 29 upper flange, 30 reinforcing rib, 31 third connecting hole, 32 fourth connecting hole, 33 second weight-reducing groove, 34 fifth connecting hole, 35 sixth connecting hole, 36 seventh connecting hole, 37 eighth connecting hole, 38 first through hole, 39 low-pressure gauge, 40 high-pressure gauge, 41 low-pressure valve, 42 high-pressure valve, 43 hose 1, 44 hose 2, 45 hose 3.

Specific Embodiments

[0051] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further details the present invention in conjunction with 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.

[0052] Embodiment:

[0053] Please refer to Figure 1 , a purification device for efficiently removing impurities in molten cast aluminum outside the furnace, including a vacuum pump 1, a pressure gauge 2, a high-purity nitrogen gas cylinder 3, a bottom box body 4, an aluminum ingot tank 5, a box cover 7, a spacer ring 9, a pouring cylinder 10, a porous ceramic filter disc 11, and a top cover 14;

[0054] Please refer to Figure 1 , 10 , the pressure gauge 2 is connected to the vacuum pump 1 through a hose 1, the pressure gauge 2 is connected to the high-purity nitrogen gas cylinder through a hose 2, and the pressure gauge 2 is connected to the bottom box body 4 through a hose 3;

[0055] Please refer to Figure 1 , 2 , 3, the bottom box body 4 is a box body with a closed upper opening surrounded by four side plates 17 around the bottom plate 16. A rectangular flange 15 is provided around the upper port of the box body, and the rectangular flange 15 is reinforced by a number of first reinforcing ribs 18 provided on the outer side of the side plate 17; A pressure gauge connector 19 is also provided on one side plate 17 for inserting the hose 3;

[0056] Please refer to Figure 4 , the box cover 7 covers the upper opening of the bottom box body 4; A circular flange 23 is provided at the center of the box cover 7; A through hole 24 is provided at the center of the circular flange 23, and threaded blind holes 25 are provided around the upper surface with it as the center;

[0057] Please refer to Figure 1 , the pouring cylinder 10 is provided on the circular flange 23, and the top cover 14 covers the top end of the pouring cylinder 10;

[0058] Please refer to Figure 1 , 5 , the pouring cylinder 10 has a lower flange 28 and an upper flange 29 fixedly connected to the upper and lower ends of a hollow tube 27 respectively; Reinforcing ribs 30 are also provided on the outer surface of the hollow tube 27 for strengthening the lower flange 28 and the upper flange 29; Third connection holes 31 and fourth connection holes 32 are respectively provided on the lower flange 28 and the upper flange 29; The positions of the third connection holes 31 correspond to those of the threaded blind holes 25 one by one and bolts can be passed through for relative fixation; A spacer ring 9 and a porous ceramic filter disc 11 are respectively sleeved in the inner hole of the hollow tube 27 from top to bottom; The outer peripheral walls of the spacer ring 9 and the porous ceramic filter disc 11 are attached to the inner peripheral wall of the hollow tube 27;

[0059] Please refer to Figure 6 , the top cover 14 is provided with fifth connection holes 34, which correspond to the positions of the fourth connection holes 32 one by one and bolts can be passed through for relative fixation;

[0060] Please refer to Figure 1 , the aluminum ingot tank 5 is sleeved inside the bottom box body 4 and is below the through hole 24.

[0061] Please refer to Figure 2 , a first weight-reducing groove 20 is formed on the outer surface of the bottom plate 16; weight-reducing grooves 22 are formed on both the upper and lower surfaces of the box cover 7.

[0062] Please refer to Figure 3 , a plurality of connecting holes 21 are formed on the rectangular flange 15; a first weight-reducing groove 20 is formed on the outer surface of the bottom plate 16; weight-reducing grooves 22 are formed on both the upper and lower surfaces of the box cover 7;

[0063] Please refer to Figure 1 , 4 , a plurality of second connecting holes 26 are formed around the box cover 7, and the diameter of the second connecting holes 26 is the same as that of the connecting holes 21. The box cover 7 is fixedly covered on the bottom box body 4 by a nut passing through the corresponding second connecting holes 26 and connecting holes 21; Please refer to Figure 7 , a rectangular sealing gasket 6 is further arranged between the box cover 7 and the bottom box body 4, and a sixth connecting hole 35 is also formed on the rectangular sealing gasket 6. The positions of the sixth connecting hole 35, the connecting hole 21, and the second connecting hole 26 correspond to each other and bolts can be passed through to be relatively fixed;

[0064] Please refer to Figure 1 , 8 , a first circular ring sealing gasket 8 is further arranged between the lower flange 28 and the circular flange 23, and a seventh connecting hole 36 is also formed on the first circular ring sealing gasket 8. The positions of the seventh connecting hole 36 and the threaded blind hole 25 correspond to each other and bolts can be passed through to be relatively fixed;

[0065] Please refer to Figure 1 , 9 , a second circular ring sealing gasket 13 is further arranged between the top cover 14 and the pouring cylinder 10, and an eighth connecting hole 37 is also formed on the second circular ring sealing gasket 13. The positions of the eighth connecting hole 37 and the fourth connecting hole 32 correspond to each other and bolts can be passed through to be relatively fixed.

[0066] Please refer to Figure 1 , it further includes a heat insulation layer 12 wrapped on the outer wall of the pouring cylinder 10; the material of the heat insulation layer 12 is asbestos, and the thickness ≥ 20 mm. Heat insulation is achieved to achieve the purpose of heat preservation of the molten aluminum in the pouring cylinder 10, thereby delaying the heat loss of the molten aluminum in the pouring cylinder 10 and ensuring that the molten aluminum smoothly flows through the porous ceramic filter plate 11 before solidification.

[0067] The isolation ring 9 is a thin circular ring structure, and the material is selected as titanium alloy TC4, and a first through hole 38 is formed in the middle. The purpose of selecting titanium alloy TC4 is to utilize the corrosion resistance of titanium alloy TC4 to molten aluminum to isolate the direct contact between the molten aluminum and the box cover 7, thereby reducing the thermal corrosion of the molten aluminum on the box cover 7. Among them, the function of the first through hole 38 is the flow channel of the molten aluminum.

[0068] Please refer to Figure 10, the pressure gauge 2 includes a low-pressure gauge 39, a high-pressure gauge 40, a low-pressure valve 41, a high-pressure valve 42, a hose 143, a hose 244, and a hose 345. The low-pressure valve 41 is arranged at the connecting end of the hose 143. The high-pressure gauge 40 is arranged at the connecting end of the hose 244. The hose 345 extends from the middle position of the pressure gauge and is connected to the pressure gauge joint 19 arranged on the side plate 17.

[0069] There is the following relationship between the pumping rate parameter S1 (L / s) of the vacuum pump 1 and the volume V (L) of the bottom box 4:

[0070] S1≥4V / [t×Log(P0 / P1)] (i)

[0071] In formula (i), t is the time required to reach the required vacuum degree. Considering that the aluminum liquid is easy to solidify in the atmospheric atmosphere, the present invention requires that t≤30s; P0 is the atmospheric pressure 101325 (Pa); P1 is the vacuum degree that the device of the present invention can reach within 30 seconds, and P1≤ -10Pa. In order to make the negative pressure formed between the pouring cylinder 10 and the bottom box 4 within 30 seconds much greater than the osmotic pressure P inf resistance of the porous ceramic filter 11, the present invention requires that the pressure difference △P (△P = P0 - P1) formed by the device of the present invention within 30 seconds and the osmotic pressure P inf The ratio between them ≥20.

[0072] To ensure that the aluminum liquid in the hollow tube 27 does not solidify and flows through the porous ceramic filter 11 quickly within 30 seconds, it is required that under the action of the pressure difference △P, when the aluminum liquid in the hollow tube 27 flows out from the through hole 24 of the box cover 7 through the porous ceramic filter 11 and the isolation ring 9, its flow rate S2 is greater than the pumping rate S1 of the vacuum pump 1. The height H of the hollow tube 27 and the diameter φD of the first through hole 38 of the isolation ring 9 need to satisfy the following relationship:

[0073]

[0074] In formula (ii), ρ is the density of aluminum alloy, ρ = 2.7*10 3 kg / m 3 . g is the gravity, g = 9.8N / kg.

[0075] The first weight-reducing grooves 20 are symmetrically arranged and form ribs to improve the overall stiffness of the bottom plate 16, and its depth is 4 - 5mm.

[0076] Among them, the rectangular flange 15, the bottom plate 16, the side plate 17, and the first reinforcing rib 18 are all made of A3 steel plates. The pressure gauge connector 19 is also made of steel material. To improve the overall stiffness of the bottom box body 4 and minimize the elastic deformation generated during subsequent machining (such as milling and grinding), the thickness of the rectangular flange 15 steel plate is ≥16 mm, and the thickness of the bottom plate 16, the side plate 17, and the first reinforcing rib 18 steel plates is ≥10 mm. The first weight reduction groove 20 can also reduce the area of subsequent precision grinding, effectively ensuring that the outer surface of the bottom plate 16 can meet the requirements as a reference surface. Moreover, to effectively eliminate the stress concentration during subsequent machining (such as milling and grinding), the spacing between the first reinforcing ribs 18 is ≤100 mm. In addition, connection holes 21 are machined on the rectangular flange 15, and the spacing between the connection holes 21 is ≤100 mm.

[0077] The material of the box cover 7 is A3 steel plate. To improve the overall stiffness of the box cover 7 and minimize the elastic deformation generated during subsequent machining (such as milling and grinding), the thickness of the box cover 7 steel plate is ≥16 mm.

[0078] The depth of the weight reduction groove 22 is 5 mm, and it is symmetrically arranged to form ribs, taking into account both weight reduction and rigidity requirements.

[0079] The spacing between the second connection holes 26 is ≤100 mm.

[0080] The material of the hollow tube 27 is Q235 steel, and its height is H. The wall thickness of the hollow tube 27 is ≥5 mm, and the thickness of the lower flange 28, the upper flange 29, and the reinforcing rib 30 is ≥10 mm.

[0081] The material of the top cover 14 is A3 steel, and the thickness is ≥10 mm.

[0082] The material of the rectangular gasket 6 is asbestos fiber paper, and the thickness is 5 - 10 mm. The material of the first circular gasket 8 is asbestos fiber paper, and the thickness is 5 - 10 mm. The material of the second circular gasket 13 is asbestos fiber paper, and the thickness is 5 - 10 mm. The selection of asbestos fiber paper for the materials of the rectangular gasket 6, the first circular gasket 8, and the second circular gasket 13 mainly considers its high-temperature resistance characteristics and certain elasticity, that is: not only can it maintain the sealing performance under the impact of molten aluminum at 750 - 820 °C, but also it can rebound after disassembly, and thus still has sealing performance during the next installation, so as to facilitate repeated use.

[0083] A local negative pressure is formed inside the pure purification device, and the negative pressure is greater than the osmotic pressure of the porous ceramic filter plate, so that the molten aluminum liquid quickly flows through the porous ceramic filter plate and is filtered and purified. The specific implementation method is as follows:

[0084] Step 1: Prepare components

[0085] First, rough milling is performed on the outer surface of 16 to machine the first weight-reducing groove 20. Then, chamfers are respectively made on the edges of the rectangular flange 15, the bottom plate 16, and the side plate 17 to machine the welding grooves.

[0086] Step Two: Prepare the bottom box body

[0087] Weld the rectangular flange 15, the bottom plate 16, the side plate 17, the first reinforcing rib 18, and the pressure gauge joint 19 into one body to obtain the bottom box body 4. After eliminating the welding thermal stress, taking the rectangular flange 15 of the bottom box body 4 as the rough reference surface, mill the outer surface of the bottom plate 16 of the bottom box body 4 to obtain a plane. Then, taking the outer surface of the bottom plate 16 of the bottom box body 4 as the reference plane, mill the outer surface of the rectangular flange 15 of the bottom box body 4 to obtain a plane. Subsequently, taking the outer surface of the rectangular flange 15 of the bottom box body 4 as the reference plane, perform precision grinding on the outer surface of the bottom plate 16 of the bottom box body 4 to meet the requirements of flatness ≤ 0.05 mm and surface roughness Ra ≤ 1.6 μm. Finally, taking the outer surface of the bottom plate 16 of the bottom box body 4 as the reference plane, perform precision grinding on the outer surface of the rectangular flange 15 of the bottom box body 4 to meet the requirements of flatness ≤ 0.05 mm and surface roughness Ra ≤ 1.6 μm.

[0088] Step Three: Prepare the box cover

[0089] Taking the upper surface of the box cover 7 as the rough reference, mill the lower surface of the box cover 7 and machine the weight-reducing groove 22, the circular flange 23, etc. Then, taking the lower surface of the box cover 7 as the reference, mill the upper surface of the box cover 7 and machine the weight-reducing groove 22, the circular flange 23, etc. Subsequently, taking the upper surface of the box cover 7 as the reference, perform precision grinding on the lower surface of the box cover 7. Finally, taking the lower surface of the box cover 7 as the reference, perform precision grinding on the upper surface of the box cover 7 until the flatness of the upper surface and the lower surface of the box cover 7 is ≤ 0.05 mm and the surface roughness Ra is ≤ 1.6 μm.

[0090] Step Four: Prepare the pouring cylinder

[0091] Turn welding grooves at both ends of the hollow tube 27, then respectively sleeve on the lower flange 28 and the upper flange 29, and then weld the hollow tube 27, the lower flange 28, the upper flange 29, and the reinforcing rib 30 into one body to obtain the pouring cylinder 10. After the pouring cylinder cools down, taking the central axis of the hollow tube 27 as the reference, turn the outer surfaces of the lower flange 28 and the upper flange 29 respectively to make the perpendicularity between the lower flange 28, the upper flange 29 and the hollow tube 27 ≤ 0.05 mm. Subsequently, taking the lower flange 28 of the pouring cylinder 10 as the reference, perform precision grinding on the upper flange 29. Finally, taking the upper flange 29 of the pouring cylinder 10 as the reference, perform precision grinding on the lower flange 28 to make the lower flange 28 and the upper flange 29 meet the requirements of flatness ≤ 0.05 mm and surface roughness Ra ≤ 1.6 μm.

[0092] Step Five: Prepare the top cover

[0093] Machine the 14 and its second weight reduction groove 33 by turning. Then, precisely grind the upper and lower surfaces of the top cover 14 by grinding to meet the requirements of flatness ≤ 0.05 mm and surface finish Ra ≤ 1.6 μm.

[0094] Step Six: Installation

[0095] After placing the aluminum ingot groove 5 in the middle of the bottom box body 4, place the rectangular gasket 6 correctly above the rectangular flange 15 of the bottom box body 4. Subsequently, place the box cover 7 correctly above the rectangular gasket 6, and align the connecting holes 21, the second connecting holes 26, and the sixth connecting holes 35. Then, connect the bottom box body 4, the rectangular gasket 6, and the box cover 7 into one body with bolts. Among them, the bolt connection adopts the principle of tightening diagonally to achieve pressure balance, and by following the principle of alternating counterclockwise tightening and clockwise tightening, to ensure that the bolts are tightened evenly;

[0096] Next, place the first circular gasket 8 correctly above the circular flange 23 of the box cover 7. Subsequently, place the pouring cylinder 10 correctly above the first circular gasket 8, and align the third connecting holes 31 of the lower flange 28, the seventh connecting holes 36 of the circular gasket, and the threaded blind holes 25 of the circular flange 23. Then, connect the box cover 7, the first circular gasket 8, and the pouring cylinder 10 into one body with bolts. Among them, the bolt connection adopts the principle of tightening diagonally to achieve pressure balance, and by following the principle of alternating counterclockwise tightening and clockwise tightening, to ensure that the bolts are tightened evenly;

[0097] Secondly, after putting the isolation ring 9 into the pouring cylinder 10, place the second circular gasket 13 correctly above the upper flange 29 of the pouring cylinder 10. Then, place the top cover 14, and align the fifth connecting holes 34 of the top cover 14, the eighth connecting holes 37 of the second circular gasket 13, and the fourth connecting holes 32 of the upper flange 29 of the pouring cylinder 10. Then, connect the top cover 14, the second circular gasket 13, and the pouring cylinder 10 into one body with bolts. Then, put the heat insulation layer 12 outside the pouring cylinder 10. Among them, the bolt connection adopts the principle of tightening diagonally to achieve pressure balance, and by following the principle of alternating counterclockwise tightening and clockwise tightening, to ensure that the bolts are tightened evenly;

[0098] Finally, connect the hose 3 of the pressure gauge 2 to the pressure gauge joint 19 of the bottom box body 4, the hose 1 to the vacuum pump 1, and the hose 2 to the high-purity nitrogen cylinder 3.

[0099] Step Seven: Debugging

[0100] Close the high-pressure valve 42 of the pressure gauge 2 and open the low-pressure valve 41. Start the vacuum pump 1, observe the change value P1 of the low-pressure gauge 39 within 30 seconds, and calculate the difference △P between the atmospheric pressure P0 and P1. Calculate the ratio of △P / Pinf and determine whether it is ≥20. If it is less than 20, check the leakage point and perform sealing treatment. At the same time, adjust the sealing performance of the device by tightening the bolts until △P / Pinf≥20.

[0101] Step Eight: Filling with Nitrogen

[0102] Shut down the vacuum pump 1, close the low-pressure valve 41, open the high-pressure valve 42, and open the handwheel of the high-purity nitrogen cylinder 3 to allow high-purity nitrogen to flow into the pure purification device of the present invention. When the reading of the high-pressure gauge 40 reaches 1 atmospheric pressure, close the handwheel of the high-purity nitrogen cylinder 3 and close the high-pressure valve 42. After loosening the bolts at the top cover 14, remove the second ring gasket 13 and the top cover 14;

[0103] Step Nine: Placing the Porous Ceramic Filter

[0104] During this period, place the porous ceramic filter 11 in a muffle furnace and heat it to 750 - 800 °C, and keep it warm for 2 - 3 hours. Then, use a forging tong to clamp the porous ceramic filter 11 out of the muffle furnace and place it in the pouring cylinder 10. The purpose of preheating the porous ceramic filter 11 is to improve the wettability of the porous ceramic filter 11 with the molten aluminum, reduce the heat loss of the molten aluminum, and facilitate the rapid flow of the molten aluminum;

[0105] Step Ten: Purification of Molten Aluminum

[0106] Pour the molten aluminum into the pouring cylinder 10, open the low-pressure valve 41, and open the low-pressure valve 41 to allow the molten aluminum to rapidly flow through: porous ceramic filter 11 → isolation ring 9 → through hole 24 under the action of negative pressure, and then reach the aluminum ingot trough 5 and solidify into ingot blocks;

[0107] The working principle of the device of the present invention is as follows:

[0108] Through precision grinding, the bottom box body 4, the box cover 7, and the pouring cylinder 10 have very high flatness and surface finish, thereby improving the fit between the bottom box body 4 and the box cover 7, between the box cover 7 and the pouring cylinder 10, and between the pouring cylinder 10 and the top cover 14. On this basis, by using the large elastic deformation of the rectangular gasket 6, the first ring gasket 8, and the second ring gasket 13 to adapt to and fully fill the microscopic uneven topography on the surfaces of the bottom box body 4, the box cover 7, and the pouring cylinder 10, the purpose of sealing can be achieved. In the operation steps of the device of the present invention, the purpose of filling with nitrogen is to form a nitrogen protection to reduce the contact between oxygen and water vapor in the isolated air and the molten aluminum. In addition, when the molten aluminum is poured into the pouring cylinder 10, performing a vacuum treatment on the bottom box body 4 can help the molten aluminum overcome the osmotic pressure P of the porous ceramic filter 11 infThe resistance effectively filters inclusions and reduces the hydrogen content during the process of flowing into the aluminum ingot groove 5. Therefore, the device of the present invention can greatly improve the quality of aluminum ingots.

[0109] The aluminum products prepared by this device are subjected to metallographic inspection and hydrogen content inspection. It is found through the inspection that there are non-metallic inclusions in the aluminum products, the grain size is 4.3 μm, and the hydrogen content is 0.098 (μg / g).

[0110] The above description is a detailed description of the preferred feasible embodiment of the present invention. However, the embodiment is not intended to limit the patent application scope of the present invention. Any equivalent changes or modified changes made under the technical spirit disclosed by the present invention shall fall within the patent scope covered by the present invention.

Claims

1. An external furnace high-efficiency purification device for removing impurities in molten casting aluminum, characterized in that It includes a vacuum pump (1), a pressure gauge (2), a high-purity nitrogen cylinder (3), a bottom box body (4), an aluminum ingot groove (5), a box cover (7), a spacer ring (9), a pouring cylinder (10), a porous ceramic filter disc (11), and a top cover (14); The pressure gauge (2) is connected to the vacuum pump (1) through a hose 1 (43), the pressure gauge (2) is connected to the high-purity nitrogen cylinder through a hose 2 (44), and the pressure gauge (2) is connected to the bottom box body (4) through a hose 3 (45); The bottom box body (4) is an enclosed box with an upper opening formed by four side plates (17) surrounding a bottom plate (16) on four sides. A rectangular flange (15) is provided around the upper port of the box body, and the rectangular flange (15) is reinforced by a number of first reinforcing ribs (18) provided on the outer sides of the side plates (17); A pressure gauge joint (19) is also provided on one side plate (17) for inserting the hose 3 (45); The box cover (7) covers the upper opening of the bottom box body (4); A circular flange (23) is provided at the center position of the box cover (7); A through hole (24) is opened at the center of the circular flange (23), and threaded blind holes (25) are opened around the upper surface with it as the center; The pouring cylinder (10) is provided on the circular flange (23), and the top cover (14) covers the top end of the pouring cylinder (10); The pouring cylinder (10) has a lower flange (28) and an upper flange (29) fixedly connected to the upper and lower ends of a hollow tube (27) respectively; Reinforcing ribs (30) are also provided on the outer surface of the hollow tube (27) for reinforcing the lower flange (28) and the upper flange (29); Third connection holes (31) and fourth connection holes (32) are opened on the lower flange (28) and the upper flange (29) respectively; The positions of the third connection holes (31) correspond one by one to the threaded blind holes (25) and bolts can be passed through for relative fixation; An isolation ring (9) and a porous ceramic filter disc (11) are sleeved in the inner hole of the hollow tube (27) from top to bottom respectively; The outer peripheral walls of the isolation ring (9) and the porous ceramic filter disc (11) are attached to the inner peripheral wall of the hollow tube (27); Fifth connection holes (34) are opened on the top cover (14), and the positions correspond one by one to the fourth connection holes (32) and bolts can be passed through for relative fixation; The aluminum ingot groove (5) is sleeved inside the bottom box body (4) and is below the through hole (24).

2. The purification device according to claim 1, wherein First weight-reducing grooves (20) are opened on the outer surface of the bottom plate (16); Weight-reducing grooves (22) are opened on both the upper and lower surfaces of the box cover (7).

3. The purification device according to claim 1, characterized in that, A number of connection holes (21) are opened on the rectangular flange (15); First weight-reducing grooves (20) are opened on the outer surface of the bottom plate (16); Weight-reducing grooves (22) are opened on both the upper and lower surfaces of the box cover (7); A number of second connection holes (26) are opened around the box cover (7), the diameters of the second connection holes (26) are the same as those of the connection holes (21), and the box cover (7) is fixedly covered on the bottom box body (4) by passing nuts through the corresponding second connection holes (26) and connection holes (21); A rectangular gasket (6) is also provided between the lid (7) and the bottom box body (4). A sixth connection hole (35) is also provided on the rectangular gasket (6). The positions of the sixth connection hole (35), the connection hole (21), and the second connection hole (26) correspond to each other and bolts can be inserted therethrough for relative fixation. A first annular gasket (8) is also provided between the lower flange (28) and the circular flange (23). A seventh connection hole (36) is also provided on the first annular gasket (8). The positions of the seventh connection hole (36) and the threaded blind hole (25) correspond to each other and bolts can be inserted therethrough for relative fixation. A second annular gasket (13) is also provided between the top cover (14) and the pouring cylinder (10). An eighth connection hole (37) is also provided on the second annular gasket (13). The positions of the eighth connection hole (37) and the fourth connection hole (32) correspond to each other and bolts can be inserted therethrough for relative fixation.

4. The purification device according to claim 1, characterized in that, It also includes a thermal insulation layer (12) wrapped on the outer wall of the pouring cylinder (10); the thermal insulation layer (12) is made of asbestos and its thickness ≥ 20 mm.

5. The purification device according to claim 1, characterized in that, The isolation ring (9) is a thin circular ring structure, made of titanium alloy TC4, and has a first through hole (38) in the middle.

6. The purification device according to claim 1, wherein The pressure gauge (2) includes a low-pressure gauge (39), a high-pressure gauge (40), a low-pressure valve (41), a high-pressure valve (42), a hose 1 (43), a hose 2 (44), and a hose 3 (45).

7. The purification device according to claim 1, characterized in that, The pumping rate parameter S1 (L / s) of the vacuum pump (1) and the volume V (L) of the bottom box body (4) have the following relationship: S1 ≥ 4V / [t×Log(P0 / P1)] (i) In formula (i), t is the time required to reach the required vacuum degree. Considering that the molten aluminum is easy to solidify in the atmospheric atmosphere, the present invention requires that t ≤ 30 s; P0 is the atmospheric pressure of 101325 (Pa); P1 is the vacuum degree that the device of the present invention can reach within 30 seconds, and P1 ≤ -10 Pa. In order to make the negative pressure formed between the pouring cylinder (10) and the bottom box body (4) within 30 seconds much greater than the osmotic pressure P inf resistance of the porous ceramic filter plate, the present invention requires that the pressure difference △P (△P = P0 - P1) formed by the device of the present invention within 30 seconds and the osmotic pressure P inf The ratio between them is ≥ 20.

8. The purification device according to claim 1, characterized in that, To ensure that the molten aluminum in the hollow tube (27) does not solidify within 30 seconds and flows quickly through the porous ceramic filter (11), it is required that under the action of the pressure difference △P, when the molten aluminum in the hollow tube (27) flows out through the porous ceramic filter (11) and the isolation ring (9) from the through hole (24) of the lid (7), its flow rate S2 is greater than the pumping rate S1 of the vacuum pump (1). The height H of the hollow tube (27) and the diameter φD of the first through hole (38) of the isolation ring (9) need to satisfy the following relationship: In formula (ii), ρ is the density of the aluminum alloy, ρ = 2.7 * 10 3 kg / m 3 . g is the gravity, g = 9.8 N / kg.

9. The purification device according to claim 1, characterized in that, The first weight-reducing grooves (20) are symmetrically arranged to form ribs, improving the overall stiffness of the bottom plate (16).

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