Low-pressure casting forming method for electromagnetic pump

Abstract

The invention belongs to the technical field of low-pressure casting, and particularly relates to an electromagnetic pump low-pressure casting forming method which is characterized by comprising the steps of equipment preparation, molten metal preheating, electromagnetic pump casting, sealing pressurization and forming demolding, an extrusion head moves downwards, a mold sprue bush can be closed, meanwhile, extrusion force of 50-100 MPa is applied to molten aluminum in a mold cavity, and the molten aluminum in the mold cavity is extruded to form an electromagnetic pump. And the molten aluminum is cooled and solidified under the pressure. The method has the beneficial effects that the gas content in the casting is greatly reduced through the low-pressure mold filling operation mode of the electromagnetic pump, so that the number of air holes mixed in the casting is obviously reduced; the capacity of the magnetic current pressurizing furnace is large, continuous filling of molten aluminum can be achieved, generation of impurities in the molten aluminum is reduced, the effect of precipitating and purifying the molten aluminum is achieved, and the impurity content in a casting is low; the casting efficiency is obviously improved; and the design of the extrusion head with sealing and pressurizing improves the density of the casting and is beneficial to ensuring the strength and quality of the product.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of low-pressure casting, and particularly relates to a low-pressure casting forming method of an electromagnetic pump. BACKGROUND

[0002] Traditional low-pressure casting equipment mostly adopts a direct filling mode of a gas pressure furnace, and has low filling pressure, stable and controllable filling speed, and sufficient exhaust of a mold cavity. However, the low-pressure casting equipment has the following disadvantages: 1) low specific pressure of a casting, resulting in insufficient density of the casting: in the traditional low-pressure casting process, because the filling pressure is relatively low (usually not more than 0.1 MPa), the pressure gradient of the molten metal in the mold is limited when the molten metal flows in the mold, so that the molten metal is difficult to be fully compacted in the filling process. 2) rough appearance profile and wall thickness of the casting, and large processing amount in the later stage: the main reason for this phenomenon is poor cooling conditions and other factors. It is necessary to introduce surface treatment technologies such as electrochemical polishing and other means, and the manufacturing cost is high. 3) gas immersion in the aluminum liquid during the pressurization process of the gas pressure furnace, resulting in an increase in the gas content of the aluminum liquid: because in the pressurization forming process, oxygen in the air and impurities in the aluminum liquid are easily mixed into the casting to form bubbles, affecting the product quality. 4) a large amount of oxidation slag is generated on the surface of the aluminum liquid due to repeated pressurization of the gas pressure furnace: frequent opening and closing of the air valve can cause the aluminum liquid to be exposed to air for a long time, accelerating the surface oxidation reaction rate and generating a large amount of dross. 5) pressure fluctuation caused by temperature change and volume change of compressible air: due to the physical properties of the gas itself, it is difficult to maintain a constant pressure value like a liquid, making the density of the casting product unstable.

[0003] An electromagnetic pump is a pump that makes an electrically conductive fluid in a magnetic field flow in a certain direction under the action of electromagnetic force. By utilizing the interaction between the magnetic field and the current in the conductive fluid, the fluid is subjected to electromagnetic force to generate a pressure gradient, thereby driving the fluid to move. In practice, it is mostly used for pumping liquid metal, so it is also called liquid metal electromagnetic pump. The electromagnetic pump has no mechanical moving parts, simple structure, good sealing, reliable operation, and does not need shaft sealing, so it is used to transport some toxic heavy metals such as mercury and lead in the chemical and printing industries, to transport liquid metals (sodium or potassium, sodium-potassium alloy) as heat carriers in nuclear power devices, and to transport molten non-ferrous metals in casting production. The flow can reach 13000 m / h, the pressure can reach 1.7 MPa, and the temperature can reach 1200℃.

[0004] The scroll plate of an air compressor is a core component of the scroll air compressor, and the manufacturing process thereof directly affects the performance and reliability of the air compressor. The traditional manufacturing process of the scroll plate of an air compressor, such as conventional casting and mechanical processing, has many problems. For example, the scroll plate produced by the conventional casting process is prone to defects such as pores and shrinkage in the interior, resulting in unstable product quality; the mechanical processing process has problems such as low material utilization rate, long processing cycle and high cost. Although some existing low-pressure casting equipment can improve the forming quality to some extent, it still cannot fully meet the production needs of high-precision and high-performance scroll plates of air compressors. In particular, in the design of the gating system, it is difficult for the traditional method to effectively avoid the defects of gas entrapment and cold shut, and innovation and improvement are urgently needed. SUMMARY

[0005] The purpose of the present application is to provide an electromagnetic pump low-pressure casting forming method, which overcomes the shortcomings of the prior art, facilitates the completion of the casting of the scroll plate of an air compressor by the electromagnetic pump low-pressure casting machine, improves the density of the casting, reduces the quality problems such as pores and porosity of the casting due to the incorporation of gas and oxidized slag, improves the filling pressure, reduces the roughness of the appearance profile of the casting product, reduces the processing amount and cost in the later stage, and improves the competitiveness of the product.

[0006] To achieve the above-mentioned purpose, the present application realizes the following technical scheme: An electromagnetic pump low-pressure casting forming method, comprising equipment preparation, metal liquid preheating, electromagnetic pump casting, sealing and pressurizing, and forming demolding, and the specific operation of each step is as follows: 1) Equipment preparation: the upper mold and the lower mold used for forming the scroll plate of an air compressor are respectively installed on the moving mold plate and the static mold plate of the squeeze casting machine, the upper mold and the lower mold form a cavity for forming after being closed, and at the same time, the exhaust passage at the joint of the upper mold and the lower mold is ensured to be unobstructed; 2) Metal liquid preheating: aluminum alloy raw materials are added to the hearth of a magnetic flow pressure furnace, and the aluminum liquid is allowed to stand for more than 10 minutes after melting; 3) Electromagnetic pump casting: the electromagnetic pump is started, the aluminum liquid slowly rises along the liquid riser under the action of the electromagnetic pump, enters the cavity from the bottom of the mold through the mold sprue bushing, and the electromagnetic pump controls the aluminum liquid to uniformly fill the mold cavity at a speed of 5-10 cm / s; 4) Sealing and pressurizing: after the aluminum liquid fills the mold cavity, the electromagnetic pump is turned off and the filling is stopped; the squeeze piston on the squeeze casting machine is started, and the squeeze piston drives the squeeze head to move downward, closes the mold sprue bushing, and isolates the aluminum liquid in the liquid riser from the mold cavity; the squeeze head continues to move downward, and the surface of the squeeze head applies an extrusion pressure of 50-100 MPa to the aluminum liquid in the mold cavity, so that the aluminum liquid cools and solidifies under this pressure; 5) Forming demolding: after the mold cools to 80-100 DEG C, the mold is opened by a mold moving device, and the rough blank of the scroll plate of an air compressor is taken out, the flash and burrs on the surface of the rough blank are removed, and the finished product of the scroll plate of an air compressor is obtained.

[0007] Further, the downward movement distance of the squeeze head is 60-200 mm, which is proportional to the pressure applied to the aluminum liquid in the mold cavity.

[0008] Further, the molten aluminum is heated to 720 DEG C in the hearth, and the mold is preheated at the same time, and the preheating temperature is 220 DEG C.

[0009] Further, the filling speed is controlled by adjusting the current and frequency of the electromagnetic pump, and the filling speed is preferably 7 cm / s.

[0010] Further, the scroll plate of the air compressor is a disc-shaped structure made of 319s aluminum alloy material, and the sprue bush is located at the middle of the lower mold bottom.

[0011] Further, the top of the extrusion head is connected with a pneumatic cylinder, a hydraulic cylinder or an electric push rod.

[0012] Further, the mold moving device is at least two devices arranged on the left and right, and the structure is a vertically arranged pneumatic cylinder, and the piston end of the pneumatic cylinder is connected with the movable mold plate.

[0013] Further, the slag ring is arranged between the upper mold and the lower mold, the slag ring is connected with the lower mold, the slag ring and the lower mold surround the slag collecting bag, and the exhaust passage is arranged on the cooperation surface between the slag ring and the upper mold, and the exhaust passage is opened on the outer circle of the upper mold.

[0014] Further, the top of the magnetic flow pressure furnace is provided with a furnace cover, the furnace cover is provided with a thermocouple and a flange hole, one side of the magnetic flow pressure furnace is provided with a heating distribution box and a soup discharging port.

[0015] Further, the ratio of the inlet diameter to the outlet diameter of the mold sprue bush is 2-3:1.

[0016] Compared with the prior art, the beneficial effects of the present application are: 1) The low-pressure filling operation mode of the electromagnetic pump greatly reduces the gas content in the casting, and the pressurization process can make the gas fully escape, so that the number of gas inclusions in the casting is significantly reduced; 2) The structure of the magnetic flow pressure furnace can realize continuous charging of the molten aluminum, impurities are separated by sufficient deposition or floating, the generation of impurities in the molten aluminum is reduced, and the outlet of the furnace is also provided with an aluminum water filter plate, which has a purifying effect on the molten aluminum, so that the impurity content in the casting is low; 3) Continuous charging of the molten aluminum also significantly improves the heating efficiency of the casting, and reduces the time consumption caused by frequent heating; 4) The extrusion head of the extrusion casting machine performs pressurization operation in the later stage of casting forming, so that the density of the casting is improved, which is beneficial to ensure the strength and quality of the product. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a structure schematic view of the low-pressure casting forming system of the electromagnetic pump of the embodiment of the present application; Figure 2It is a structure schematic diagram of the magnetic flow pressurizing furnace in the embodiment of the present application. Figure 3 It is a structure schematic diagram of the squeeze casting machine in the embodiment of the present application. Figure 4 It is a schematic diagram of the liquid lifting filling state in the embodiment of the present application. In the figure: 1-squeeze casting machine, 2-moving die plate, 3-static die plate, 4-upper die, 5-lower die, 6-magnetic flow pressurizing furnace, 7-electromagnetic pump, 8-liquid lifting runner, 9-mold sprue bushing, 10-extrusion head, 11-slag ladle ring, 12-exhaust passage, 13-thermocouple, 14-flange hole, 15-heating distribution box, 16-soup discharging port, 17-furnace cover, 18-slag collecting ladle, 19-moving die device, 20-aluminum liquid filter plate, 21-cylinder. DETAILED DESCRIPTION

[0018] The technical solutions of the present application will be described clearly and completely in combination with specific embodiments. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments.

[0019] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the specific embodiments needed to be used in the description of the specific embodiments or the prior art will be briefly introduced. Obviously, the specific embodiments described below are some embodiments of the present application, and other specific embodiments can also be obtained by those skilled in the art without creative labor on the basis of these specific embodiments.

[0020] The components of the embodiments of the present application described and shown in the specific embodiments herein can be arranged and designed in countless different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the specific embodiments is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application.

[0021] See Figures 1-4 It is a schematic diagram of an embodiment of the electromagnetic pump low-pressure casting forming method of the present application, which comprises equipment preparation, metal liquid preheating, electromagnetic pump casting, sealing pressurizing and forming demolding. The scroll disc of the air compressor is a disc-shaped structure made of 319s aluminum alloy material. The specific operation of each step is as follows: 1) Equipment preparation, the upper die 4 and the lower die 5 used for forming the scroll disc of the air compressor are respectively installed on the moving die plate 2 and the static die plate 3 of the squeeze casting machine 1. After the upper die 4 and the lower die 5 are combined, a cavity for forming is formed, and at the same time, it is ensured that the exhaust passage at the joint of the upper die 4 and the lower die 5 is unobstructed, so as to ensure the smooth operation of the subsequent operation; 2) Preheating of the liquid metal, the aluminum alloy raw material is added to the furnace chamber of the magnetic pressure furnace 6, and the aluminum liquid is heated to 720°C in the furnace chamber. The mold is preheated at the same time, and the preheating temperature is 220°C. After the aluminum liquid is melted, it is left to stand for more than 10 minutes. An aluminum liquid filter plate 20 is arranged in the furnace chamber of the magnetic pressure furnace 6 to realize purification of the aluminum liquid. The magnetic pressure furnace 6 is an electromagnetic melting furnace, and the aluminum alloy special melting furnace of Shenzhen Yedamai Technology leads the industry upgrading with the advantages of high efficiency, energy saving, metal purity and the like. Its advantages are: fast melting: electromagnetic eddy current penetration heating, melting speed is 50% faster than traditional furnace, improve production capacity; intelligent operation and maintenance: equipped with Internet of Things remote monitoring system, real-time diagnosis of equipment state, early warning of fault risk; customized design: support flexible configuration from 500kg to 5T capacity, adapt to various production line scenes such as die casting and ingot casting.

[0022] 3) Electromagnetic pump casting, start the electromagnetic pump 7, the aluminum liquid slowly rises along the riser 8 under the action of the electromagnetic pump 7, enters the cavity from the bottom of the mold through the mold sprue bushing 9, the ratio of the inlet diameter to the outlet diameter of the mold sprue bushing 9 is 2-3:1, and the preferred value is 2.6. The sprue bushing 9 is located at the middle of the bottom of the lower mold 5. The electromagnetic pump 7 fills the aluminum liquid into the mold cavity at a speed of 5-10 cm / s; the filling speed is controlled by adjusting the current and frequency of the electromagnetic pump 7, and the preferred filling speed is 7 cm / s. The electromagnetic pump is a new type of fluid conveying equipment with shaftless design, and its working principle is based on the theory of deep integration of multiple physical fields, realizing the function of straight-line motion of fluid.

[0023] 4) Sealing and pressurizing, after the aluminum liquid fills the mold cavity, the electromagnetic pump 7 is turned off and the mold filling is stopped; the extrusion piston on the extrusion casting machine 1 is started, the extrusion piston drives the extrusion head 10 to move downward, closes the mold sprue bushing 9, and isolates the mold cavity from the aluminum liquid in the riser 8, and the top of the extrusion head 10 is connected with the cylinder 21, hydraulic cylinder or electric push rod. The extrusion head 10 continues to move downward, and the aluminum liquid in the mold cavity is subjected to an extrusion force of 50-100 MPa by the surface of the extrusion head 10, so that the aluminum liquid cools and solidifies under the pressure, further compacts the aluminum liquid, refines the grain structure, increases the density of the casting, and reduces defects such as shrinkage and porosity; the downward movement distance of the extrusion head 10 is 60-200 mm, and the downward movement distance is proportional to the pressure applied to the aluminum liquid in the mold cavity.

[0024] 5) Molding and demolding, after the mold is cooled to 80-100°C, the mold is opened with the mold moving device 19, and the rough blank of the air compressor scroll plate is taken out. The flash and burr on the surface of the rough blank are removed to obtain the finished product of the air compressor scroll plate. The mold moving device is at least two, which are arranged on the left and right, and the structure is a vertically arranged cylinder, and the piston end of the cylinder is connected with the movable mold plate 2.

[0025] In order to improve the surface quality of the casting, a slag pocket ring 11 is arranged between the upper die 4 and the lower die 5, the slag pocket ring 11 is connected with the lower die 5, a slag pocket 18 is surrounded between the slag pocket ring 11 and the lower die 5, and an exhaust passage 12 is arranged on the matching surface between the slag pocket ring 11 and the upper die 4, the exhaust passage 12 is opened on the outer circle of the upper die 4, so as to ensure smooth exhaust. The air in the cavity is moved to the outside of the cavity under the pushing of the aluminum liquid, and is exhausted to the atmosphere through the slag pocket 18 and the exhaust passage 12.

[0026] The top of the magnetic flow pressurizing furnace 6 is provided with a furnace cover 17, the furnace cover 17 is provided with a thermocouple 13 and a flange hole 14, one side of the magnetic flow pressurizing furnace 6 is provided with a heating distribution box 15 and a soup discharge port 16, the heating distribution box 15 is used for adjusting the heating and temperature rising speed, and the soup discharge port 16 is used for discharging the excess aluminum liquid after the casting is finished. The flange hole 14 is opened when the electromagnetic pump starts casting, so that the pressure in the magnetic flow pressurizing furnace 6 is kept balanced when the aluminum liquid flows out.

[0027] The deburred air compressor scroll disc is subjected to T6 heat treatment, including solid solution treatment (heating to 545 DEG C, holding for 4.5 hours) and aging treatment (heating to 185 DEG C, holding for 10 hours), so as to further improve the mechanical properties of the scroll disc, eliminate internal residual stress, and perform comprehensive size detection and performance test on the air compressor scroll disc after heat treatment, including shape precision, size tolerance, surface roughness, hardness, strength and other indexes of scroll teeth, through detection, the mechanical properties of the air compressor scroll disc product obtained by the embodiment of the application reach tensile strength ≥ 390 MPa, yield strength ≥ 310 MPa, elongation ≥ 6%, and meet the mechanical property requirements of the product and relevant standards.

[0028] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. An electromagnetic pump low pressure casting molding method characterized by, The steps include equipment preparation, metal liquid preheating, electromagnetic pump casting, sealing and pressurizing, and forming and demolding. 1) Equipment preparation, the upper die and the lower die for forming the scroll disc of the air compressor are respectively installed on the moving die plate and the static die plate of the squeeze casting machine. After the upper die and the lower die are combined, a cavity for forming is formed, and meanwhile, the exhaust passage at the joint of the upper die and the lower die is ensured to be unobstructed. 2) Metal liquid preheating, the aluminum alloy raw material is added into the hearth of the magnetic flow pressurizing furnace, and the aluminum liquid is allowed to stand for more than 10 minutes after being melted. 3) Electromagnetic pump casting, the electromagnetic pump is started, the aluminum liquid slowly rises along the liquid riser under the action of the electromagnetic pump, enters the cavity from the bottom of the die through the die sprue bushing, and the electromagnetic pump controls the aluminum liquid to uniformly fill the die cavity at a speed of 5-10 cm / s. 4) Sealing and pressurizing, after the die cavity is filled with the aluminum liquid, the electromagnetic pump is turned off, and the filling is stopped. The squeeze piston on the squeeze casting machine is started, the squeeze piston drives the squeeze head to move downward, the die sprue bushing is closed, the die cavity is isolated from the aluminum liquid in the liquid riser, and the squeeze head continues to move downward to apply an extrusion force of 50-100 MPa to the aluminum liquid in the die cavity, so that the aluminum liquid is cooled and solidified under the pressure. 5) Forming and demolding, after the die is cooled to 80-100℃, the die is opened by the die moving device, and the rough blank of the air compressor scroll disc is taken out. The flash and burrs on the surface of the rough blank are removed, and the finished product of the air compressor scroll disc is obtained.

2. The electromagnetic pump low pressure casting molding method according to claim 1, wherein The downward moving distance of the squeeze head is 60-200 mm, which is proportional to the pressure applied to the aluminum liquid in the die cavity.

3. The electromagnetic pump low pressure casting molding method according to claim 1, wherein The aluminum liquid is heated to 720℃ in the hearth, and the die is preheated at the same time, and the preheating temperature is 220℃.

4. The electromagnetic pump low pressure casting molding method according to claim 1, wherein The filling speed is controlled by adjusting the current and frequency of the electromagnetic pump, and the preferred filling speed is 7 cm / s.

5. The electromagnetic pump low pressure casting molding method according to claim 1, wherein The air compressor scroll disc is a disc-shaped structure made of 319s aluminum alloy material, and the sprue bushing is located at the center of the bottom of the lower die.

6. The electromagnetic pump low pressure casting molding method according to claim 1, wherein The top of the squeeze head is connected with a pneumatic cylinder, a hydraulic cylinder or an electric push rod.

7. The electromagnetic pump low pressure casting molding method according to claim 1, wherein The die moving device is at least two devices arranged on the left and right, and the structure is a vertically arranged pneumatic cylinder, and the piston end of the pneumatic cylinder is connected with the moving die plate.

8. The electromagnetic pump low pressure casting molding method according to claim 1, wherein A slag pocket ring is arranged between the upper die and the lower die, the slag pocket ring is connected with the lower die, a slag pocket is surrounded between the slag pocket ring and the lower die, an exhaust passage is arranged on the matching surface between the slag pocket ring and the upper die, and the exhaust passage is opened on the outer circle of the upper die.

9. The electromagnetic pump low pressure casting molding method according to claim 1, wherein A furnace cover is arranged on the top of the magnetic flow pressurizing furnace, a thermocouple and a flange hole are arranged on the furnace cover, a heating distribution box and a soup outlet are arranged on one side of the magnetic flow pressurizing furnace.

10. The electromagnetic pump low pressure casting molding method according to claim 1, wherein The ratio of the inlet diameter to the outlet diameter of the die sprue bushing is 2-3:1.

Images