Molten metal purification method for sand casting

Abstract

The invention belongs to the field of part manufacturing, and particularly relates to a molten metal purification method for sand mold casting, which comprises the following steps: S1, arranging a steel barrel piece between a pouring ladle and a casting mold for soft sealing, mounting a pressure-bearing pipeline on the steel barrel piece, and forming an angle of 45 degrees between an outlet of the pipeline and a vertical axis; s2, argon is introduced into the pressure-bearing pipeline 5 seconds before pouring, the pressure of the argon is 0.1-0.3 MPa, and argon introduction is stopped immediately when pouring is stopped; and S3, in the cooling process of the molten metal in the casting mold cavity, argon bubbles float upwards to bring inclusions to a top slag collecting groove, and a slag collecting groove is removed during sand cleaning and cutting. According to the steel barrel piece, contact between the atmosphere and molten metal is isolated, and oxide inclusion is effectively prevented; and meanwhile, argon is blown in in the pouring process to form bubbles and enter a casting mold cavity, and casting defects can be effectively reduced according to the principle that the bubbles float upwards to take away inclusions.

Description

Technical Field

[0001] The invention belongs to the field of parts manufacturing, and in particular relates to a method for purifying molten metal used in sand casting. Background Art

[0002] The existing method for purifying molten metal during the smelting process of sand casting is as follows: after the molten metal is poured into a pouring ladle, argon gas is introduced through the argon gas pipe at the bottom of the pouring ladle. The argon gas floats from the bottom to the top, and during the floating process, the impurities in the molten metal are carried out of the molten metal to the slag on the top surface, thereby achieving the effect of purifying the molten metal.

[0003] However, in the process of pouring molten metal into the mold cavity of sand casting, the molten metal leaks from the pouring ladle and comes into contact with the atmosphere during the journey into the casting cup, where it is oxidized to form oxide inclusions. Then, after entering the mold cavity, there is no purification measure. At the same time, the molten metal is subjected to high-temperature erosion of the sand mold during the process of entering the mold cavity, resulting in sand falling, and the formed sand inclusions are not purified. Their appearance affects the quality of the casting, causes unnecessary rework and scrapping, and affects the manufacturing cost and production cycle of the product.

[0004] In addition, the existing process relies on the top slag trough to passively collect slag inclusions, but lacks an active adsorption and disturbance mechanism for the slag. The fine slag particles are easy to sink back into the molten metal, resulting in 10%-15% slag inclusions remaining after sand cleaning, which increases the difficulty of subsequent machining. Summary of the Invention

[0005] The purpose of the present invention is to address the problems raised in the above background technology and provide a method for purifying molten metal for sand casting by isolating the contact between the atmosphere and the molten metal through a steel barrel and effectively preventing the appearance of oxidation inclusions.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for purifying molten metal for sand casting comprises the following steps:

[0008] S1. A steel barrel is provided between the pouring ladle and the casting mold for soft sealing. A pressure-bearing pipe is installed on the steel barrel, and the outlet of the pipe is at a 45° angle to the vertical axis;

[0009] S2. 5 seconds before pouring, argon gas is introduced from the pressure pipe at a pressure of 0.1-0.3 MPa. When pouring stops, the argon gas is immediately stopped;

[0010] S3. During the cooling process of the molten metal in the casting cavity, argon bubbles float up and carry the inclusions to the top slag groove, which is removed during sand cleaning and cutting.

[0011] Preferably, the pressure-bearing pipe is curved inside the steel barrel to ensure that bubbles are formed when the argon gas rushes into the molten metal.

[0012] Preferably, a resin self-hardening sand protection device is provided on the periphery of the casting cavity to fix the runner system and prevent the sand from being washed away by the sand mold.

[0013] Preferably, in step S1, the lower end of the pouring ladle is fixedly connected to a nozzle brick, a steel barrel cover is provided on the periphery of the nozzle brick and is movably connected to the lower end of the pouring ladle, the lower end of the steel barrel is sealingly and rotatably connected to asbestos, the lower end of the asbestos is provided with a pouring cup, the resin self-hardening sand protection device is sealed and fixedly connected to the periphery of the pouring cup, the lower end of the pouring cup is sealed and fixedly connected to a casting pipe, the casting pipe extends to the inside of the mold cavity, a vibration mechanism is provided on the periphery of the steel barrel for accelerating the floating of bubbles, and an adsorption mechanism is provided between the asbestos and the pouring cup for adsorbing and collecting slag by electromagnetic force.

[0014] Preferably, the vibration mechanism includes a fixed ring plate fixedly connected to the lower end of the casting ladle, a plurality of first springs distributed in a circumferential array are provided between the fixed ring plate and the steel barrel part, two symmetrically arranged push rods are fixedly connected to the outer wall of the steel barrel part, the two push rods extend through the fixed ring plate and are fixedly connected to a hinge seat, each of the hinge seats is hingedly connected to a first guide wheel, the upper end of the casting mold is fixedly connected to the first motor, the output end of the first motor is coaxially fixedly connected to the driving gear through a connecting rod, the upper end of the casting mold is provided with an annular groove, two arc plates are slidably connected in the annular groove along a circumferential trajectory, the upper ends of the two arc plates are jointly fixedly connected with a gear ring, the gear ring and the driving gear mesh with each other, a plurality of trapezoidal blocks distributed in a circumferential array are fixedly connected to the inner wall of the gear ring, and the first guide wheel periodically contacts and rolls with the inclined surfaces of the plurality of trapezoidal blocks.

[0015] Preferably, the adsorption mechanism includes a collecting frame fixedly connected between the asbestos and the pouring cup, and a collecting groove is opened inside the collecting frame. The collecting groove is composed of a plurality of receiving grooves distributed in a circumferential array, and a buffer groove connecting two adjacent receiving grooves. The side wall of the buffer groove is corrugated, and the collecting groove is connected to the bottom of the collecting frame. A disturbance rod is sealed and slidably connected to the inner wall of the collecting frame. The part of the disturbance rod extending into the collecting groove is rotatably connected to a second guide wheel, and the second guide wheel rolls in contact with the side walls of the receiving groove and the buffer groove. The part of the disturbance rod extending into the collecting groove is fixedly connected to a stopper, and a second spring is provided between the stopper and the inner wall of the collecting groove.

[0016] Preferably, a mounting block is fixedly connected to the outer wall of the steel barrel, a second motor is fixedly connected to the lower end of the mounting block, a transmission gear is fixedly connected to the output end of the second motor, and an annular tooth groove is fixedly connected to the peripheral side wall of the asbestos, and the annular tooth groove is meshed with the transmission gear.

[0017] Preferably, in step S2, an air pressure control mechanism is provided above the pressure pipe, and the air pressure control mechanism includes a shunt pipe connected to the pressure pipe, the upper end of the shunt pipe is fixedly connected to a horizontal control box, and a piston block is sealingly and slidingly connected inside the horizontal control box, and the lower end of the horizontal control box on the side away from the pressure pipe is fixedly connected to a vertical control box, and the interiors of the horizontal control box and the vertical control box are respectively fixedly connected with a horizontal conductive block and a vertical conductive block, and a conductive sheet is fixedly connected to a side wall of the piston block close to the horizontal conductive block and the vertical conductive block. A low-pressure valve and a high-pressure valve are provided on the part of the pressure pipe extending into the steel barrel, and the high-pressure valve is opened when the horizontal conductive block contacts the conductive sheet, and the low-pressure valve is opened when the vertical conductive block contacts the conductive sheet.

[0018] Compared with the existing technology, the advantages of this method for purifying molten metal in sand casting are:

[0019] 1. The present invention uses a steel barrel to isolate the contact between the atmosphere and the molten metal, effectively preventing the occurrence of oxidation inclusions. At the same time, argon is blown into the casting process to form bubbles that enter the casting cavity. The bubbles float up and carry away inclusions, effectively reducing the occurrence of casting defects.

[0020] 2. The present invention is provided with a vibration mechanism, which can destroy the interfacial tension between bubbles and molten metal through low-frequency axial vibration, so that the bubble floating speed is increased to 0.5-0.8m / s, ensuring that the slag inclusions are completely floated to the slag accumulation tank before the thick-walled parts solidify.

[0021] 3. The present invention is provided with an adsorption mechanism, which can utilize the cooperation of the electromagnet and the disturbance rod to actively adsorb fine slag particles with a diameter of ≤0.1mm. The slag collection efficiency reaches more than 90%, and the residual slag after sand cleaning is reduced to less than 3%, which greatly reduces the workload of the subsequent cutting process. At the same time, the asbestos is driven to rotate by the second motor, and the residual slag layer on the surface is melted by friction heat, which automatically maintains the sealing effect and avoids the failure of the traditional sealing structure due to thermal expansion.

[0022] 4. The present invention can adjust the pressure gradient of argon through the air pressure control mechanism, and realize the gradient control of "high pressure at the beginning of pouring and low pressure at the end". At the beginning of pouring, argon is quickly rushed into the molten metal to form a large number of tiny bubbles, which effectively stirs the molten metal and promotes the rapid dispersion of inclusions. After pouring for a period of time, the argon pressure is reduced to 0.1MPa. The lower pressure can slow down the speed of bubble generation, avoid mutual interference caused by excessive bubbles, and enable bubbles to float more orderly in the molten metal, reducing the risk of bubbles being retained and forming pores in thin-walled parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a partial structural schematic diagram of the present invention;

[0024] Figure 2 It is a partial structural diagram of the vibration mechanism in the present invention;

[0025] Figure 3 It is a partial structural schematic diagram of the adsorption mechanism in the present invention;

[0026] Figure 4 This is a schematic diagram of the top view of the interior of the collection frame of the present invention;

[0027] Figure 5 It is a partial structural diagram of the air pressure control mechanism in the present invention.

[0028] In the picture:

[0029] 1. Steel barrels; 11. Pressure pipes; 12. Resin self-hardening sand protection device; 13. Sprue bricks; 14. Asbestos; 15. Sprue cups; 16. Cast pipes;

[0030] 2. Vibration mechanism; 21. Fixed ring plate; 22. First spring; 23. Push rod; 24. Articulated seat; 25. First guide wheel; 26. First motor; 27. Drive gear; 28. Annular groove; 29. ​​Arc plate; 210. Gear ring; 211. Trapezoidal block;

[0031] 3. Adsorption mechanism; 31. Collection frame; 32. Storage tank; 33. Buffer tank; 34. Disturbance rod; 35. Second guide wheel; 36. Stop block; 37. Second spring; 38. Mounting block; 39. Second motor; 310. Transmission gear; 311. Annular tooth groove; 312. Collection tank;

[0032] 4. Air pressure control mechanism; 41. Diversion pipe; 42. Horizontal control box; 43. Piston block; 44. Vertical control box; 45. Horizontal conductive block; 46. Vertical conductive block. DETAILED DESCRIPTION

[0033] The following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0034] Example: Refer to Figures 1 to 5 A method for purifying molten metal for sand casting comprises the following steps:

[0035] S1. A steel barrel 1 is provided between the pouring ladle and the mold for soft sealing. A pressure pipe 11 is installed on the steel barrel, with the pipe outlet at a 45° angle to the vertical axis.

[0036] Specifically, a resin self-hardening sand protection device 12 is provided on the periphery of the mold cavity to fix the runner system and prevent the sand from being washed away from the sand mold.

[0037] In step S1, the lower end of the pouring ladle is fixedly connected to the nozzle brick 13, the steel barrel 1 is covered on the side of the nozzle brick 13 and is movably connected to the lower end of the pouring ladle, the lower end of the steel barrel 1 is sealed and rotatably connected to the asbestos 14, the lower end of the asbestos 14 is provided with a pouring cup 15, the resin self-hardening sand protection device 12 is sealed and fixedly connected to the side of the pouring cup 15, the lower end of the pouring cup 15 is sealed and fixedly connected to the casting pipe 16, the casting pipe 16 extends into the inside of the casting cavity, the peripheral side of the steel barrel 1 is provided with a vibration mechanism 2 for accelerating the floating of bubbles, and an adsorption mechanism 3 is provided between the asbestos 14 and the pouring cup 15 for adsorbing and collecting slag by electromagnetic force.

[0038] Specifically, asbestos 14 is filled between the steel barrel, the pouring ladle and the casting mold to achieve soft sealing.

[0039] Specifically, the steel barrel 1 is made of Q235 steel plate with a thickness of 5-8mm and is cylindrical. Its inner diameter is loosely matched to the outer diameter of the nozzle brick 13 (clearance ≤ 2mm). Its lower end forms a soft seal with the top surface of the pouring cup 15 via an annular asbestos ring 14 (50mm thick, with inner and outer diameters of 180mm / 280mm, respectively). The elastic deformation of the asbestos ring 14 compensates for thermal expansion during the pouring process, preventing molten metal leakage. The pressure-bearing pipe 11 is a 20mm diameter hollow steel pipe. The section extending inside the steel barrel 1 is curved, with the outlet end at a 45° angle to the vertical axis. This angle allows argon gas to be injected obliquely into the molten metal flow, breaking up the argon column using fluid shear force, forming tiny bubbles with a diameter of 1-3mm, ensuring uniform distribution of the bubbles in the molten metal.

[0040] Furthermore, the lower end of the pouring ladle is fixedly connected to the nozzle brick 13 (made of refractory material, with an inner diameter consistent with the outlet of the pouring ladle), and the steel barrel 1 is movably sleeved on the outside of the nozzle brick 13 through an annular groove. The second motor 39 is fixed on the mounting block 38 welded on its peripheral side. The transmission gear 310 at the output end of the motor is engaged with the annular tooth groove 311 on the peripheral side of the asbestos 14, which can drive the asbestos 14 to rotate slowly (speed 5-10r / min), and the residual slag layer on the surface is melted by friction heat to maintain the sealing effect.

[0041] Furthermore, the resin self-hardening sand protection device 12 (thickness 100-150mm) is wrapped around the outside of the pouring cup 15, and a steel mesh (diameter 8mm, spacing 100mm) is embedded inside it, which can withstand the erosion of molten metal and prevent sand from falling off the sand mold. At the same time, it forms a rigid support to ensure the stability of the runner system during vibration.

[0042] S2. 5 seconds before pouring, argon gas is introduced from the pressure pipe 11 at a pressure of 0.1-0.3 MPa. When pouring stops, the argon gas is immediately stopped.

[0043] Specifically, the pressure-bearing pipe 11 is curved inside the steel barrel 1 to ensure that bubbles are formed when the argon gas rushes into the molten metal.

[0044] In step S2, an air pressure control mechanism 4 is provided above the pressure pipe 11. The air pressure control mechanism 4 includes a diversion pipe 41 connected to the pressure pipe 11. The upper end of the diversion pipe 41 is fixedly connected to a horizontal control box 42. A piston block 43 is sealed and slidably connected inside the horizontal control box 42. The lower end of the horizontal control box 42 on the side away from the pressure pipe 11 is fixedly connected to a vertical control box 44. A horizontal conductive block 45 and a vertical conductive block 46 are fixedly connected to the interior of the horizontal control box 42 and the vertical control box 44 respectively. A conductive sheet is fixedly connected to the side wall of the piston block 43 close to the horizontal conductive block 45 and the vertical conductive block 46. A low-pressure valve and a high-pressure valve are provided on the part of the pressure pipe 11 extending into the steel barrel 1. The high-pressure valve is opened when the horizontal conductive block 45 contacts the conductive sheet, and the low-pressure valve is opened when the vertical conductive block 46 contacts the conductive sheet.

[0045] Specifically, the upper end of the pressure pipe 11 is fixedly connected to a hydraulic pump, which is used to move the piston block 43 back to the initial position in the horizontal control box 42 and the vertical control box 44 to facilitate the next pouring and purification of the molten metal.

[0046] In addition, the initial pressure is set to 0.3 MPa, and the pressure gradient is adjusted by the air pressure control mechanism 4:

[0047] The diversion pipe 41 of the air pressure control mechanism 4 is connected to the pressure pipe 11. A piston block 43 is provided in a transverse control box 42 at the upper end thereof. During the initial stage of argon gas delivery, the piston block 43 is in the transverse control box 42. The conductive sheet on the piston block 43 contacts the transverse conductive block 45, triggering the high-pressure valve to open. The delivery pressure of argon gas reaches 0.3 MPa, and the argon gas is injected into the molten metal at high pressure.

[0048] After the unit time of conveying, the piston block 43 is pushed from the horizontal control box 42 to the vertical control box 44, and the conductive sheet on the piston block 43 contacts the vertical conductive block 46, switching to a low-pressure valve (0.1MPa), realizing the gradient control of "high pressure at the beginning of pouring and low pressure in the later stage". At the beginning of pouring, argon gas is quickly rushed into the molten metal to form a large number of tiny bubbles, which effectively stirs the molten metal and promotes the rapid dispersion of inclusions. After pouring for a period of time, the argon pressure is reduced to 0.1MPa. The lower pressure can slow down the speed of bubble generation, avoid mutual interference caused by excessive bubbles, and enable bubbles to float up more orderly in the molten metal, reducing the risk of bubbles being retained in thin-walled parts to form pores.

[0049] Furthermore, the end of the pressure pipe 11 extending into the steel barrel 1 is provided with a multi-porous nozzle (aperture 0.5 mm, number of holes 12), which, combined with a 45° inclined outlet, allows the argon bubbles to form a spiral upward trajectory in the molten metal, thereby extending the residence time of the bubbles in the molten metal and improving the slag adsorption efficiency.

[0050] S3. During the cooling process of the molten metal in the casting cavity, argon bubbles float up and carry the inclusions to the top slag groove, which is removed during sand cleaning and cutting.

[0051] The vibration mechanism 2 includes a fixed ring plate 21 fixedly connected to the lower end of the casting ladle, a plurality of first springs 22 distributed in a circumferential array are provided between the fixed ring plate 21 and the steel barrel 1, two symmetrically arranged push rods 23 are fixedly connected to the outer wall of the steel barrel 1, the two push rods 23 extend through the fixed ring plate 21 and are fixedly connected to an articulated seat 24, each articulated seat 24 is hinged with a first guide wheel 25, the upper end of the casting mold is fixedly connected to a first motor 26, the first motor 26 is fixedly connected to the upper end of the casting mold, and the first motor 26 is fixedly connected to the upper end of the casting mold. The output end is coaxially fixedly connected to a driving gear 27 through a connecting rod. An annular groove 28 is provided at the upper end of the casting. Two arc-shaped plates 29 are slidably connected in the annular groove 28 along a circumferential trajectory. The upper ends of the two arc-shaped plates 29 are fixedly connected to a gear ring 210. The gear ring 210 and the driving gear 27 are meshed with each other. A plurality of trapezoidal blocks 211 distributed in a circumferential array are fixedly connected to the inner wall of the gear ring 210. The first guide wheel 25 periodically contacts and rolls with the inclined surfaces of the plurality of trapezoidal blocks 211.

[0052] Specifically, the two first springs 22 are respectively disposed around the circumferences of the two push rods 23 .

[0053] During actual use, the first motor 26 (power 1.5kW) drives the driving gear 27 to rotate, and the meshing gear ring 210 makes a circular motion along the annular groove 28. The trapezoidal block 211 on its inner wall periodically squeezes the first guide wheel 25, and drives the steel barrel 1 to vibrate axially through the push rod 23. The mechanical vibration destroys the interfacial tension between the bubbles and the molten metal, prompting the bubbles to quickly float to the top slag groove.

[0054] The adsorption mechanism 3 includes a collecting frame 31 fixedly connected between the asbestos 14 and the pouring cup 15. A collecting groove 312 is opened inside the collecting frame 31. The collecting groove 312 is composed of a plurality of receiving grooves 32 distributed in a circular array and a buffer groove 33 connecting two adjacent receiving grooves 32. The side wall of the buffer groove 33 is corrugated. The collecting groove 312 is connected to the bottom of the collecting frame 31. A disturbance rod 34 is sealed and slidably connected on the inner wall of the collecting frame 31. The part of the disturbance rod 34 extending into the collecting groove 312 is rotatably connected to the second guide wheel 35. The second guide wheel 35 contacts and rolls with the side walls of the receiving groove 32 and the buffer groove 33. The part of the disturbance rod 34 extending into the collecting groove 312 is fixedly connected to a stopper 36. A second spring 37 is provided between the stopper 36 and the inner wall of the collecting groove 312.

[0055] Specifically, a mounting block 38 is fixedly connected to the outer wall of the steel barrel 1, a second motor 39 is fixedly connected to the lower end of the mounting block 38, a transmission gear 310 is fixedly connected to the output end of the second motor 39, and an annular tooth groove 311 is fixedly connected to the peripheral side wall of the asbestos 14, and the annular tooth groove 311 is engaged with the transmission gear 310.

[0056] While the vibration mechanism 2 is working, the adsorption mechanism 3 collects the scum in real time:

[0057] After being energized, the electromagnet (rated voltage 24V, suction force ≥50N) in the collection frame 31 absorbs scum on the surface of the molten metal. The second guide wheel 35 on the disturbance rod 34 rotates with the asbestos 14, rolling on the side walls of the receiving groove 32 and the corrugated buffer groove 33, driving the block 36 to reciprocate (stroke 5-10mm), thereby driving the disturbance rod 34 to move back and forth inside the steel barrel 1, increasing the amount of bubbles generated during the introduction of argon gas, destroying the surface tension of the scum layer, and improving the electromagnet's adsorption efficiency of fine slag particles.

[0058] The present invention can be explained through the following operation mode:

[0059] (1) Sealing and pretreatment before pouring

[0060] 1. Sealing Mechanism of the Steel Barrel: The steel barrel 1 forms a soft seal with the pouring ladle's pouring brick 13 and pouring cup 15 through an annular asbestos ring 14. The elastic deformation of the asbestos 14 compensates for thermal expansion during the pouring process (expansion ≤ 2mm), isolating the molten metal from the atmosphere and fundamentally preventing the formation of oxidized inclusions. A resin self-hardening sand protection device 12 encases the pouring cup 15. Its internal steel mesh structure withstands molten metal erosion, preventing sand loss and sand inclusion defects.

[0061] 2. Preparation for bubble generation in the argon pipeline: The pressure pipeline 11 is curved inside the steel barrel 1, and the outlet is at 45 degrees to the vertical axis. This design allows the argon gas to be injected obliquely into the molten metal flow, and the shear force of the fluid is used to break the argon gas column into tiny bubbles with a diameter of 1-3 mm, ensuring that the bubbles are evenly distributed in the molten metal, laying the foundation for subsequent slag adsorption.

[0062] (2) Dynamic purification control during pouring process

[0063] 1. Principle of gradient air pressure control: 5 seconds before pouring, the air pressure control mechanism 4 is started: In the initial stage, the piston block 43 is located in the horizontal control box 42, the conductive sheet contacts the horizontal conductive block 45, and the high-pressure valve (0.3 MPa) is opened. High-pressure argon rushes into the molten metal, quickly forming bubbles and carrying slag upward; 10-15 seconds after pouring (adjusted according to the wall thickness of the casting), the argon pressure pushes the piston block 43 to move to the vertical control box 44, the conductive sheet contacts the vertical conductive block 46, and the low-pressure valve (0.1 MPa) is switched to reduce the bubble floating speed to meet the needs of rapid solidification of thin-walled parts and avoid bubble retention.

[0064] 2. Vibration-Assisted Bubble Migration: First motor 26 rotates drive gear 27, driving gear ring 210 along annular groove 28. Trapezoidal blocks 211 on the inner wall of the gear ring periodically squeeze first guide wheel 25, causing axial vibration of steel barrel 1. This vibration breaks the interfacial tension between the bubbles and the molten metal, causing them to rise to the slag trough at a speed of 0.5-0.8 m / s, improving efficiency by approximately 40% compared to traditional methods.

[0065] (3) Slag collection and slag treatment during the cooling stage

[0066] 1. Bubble Slag and Slag Tank Design: During the cooling process of the molten metal, argon bubbles continuously rise, carrying defects such as oxide inclusions and sand inclusions to the top slag tank. The slag tank volume is designed to be 5%-8% of the casting volume to ensure sufficient slag inclusions to prevent defects from remaining.

[0067] 2. Real-time slag removal by the adsorption mechanism: A second motor 39 drives the transmission gear 310, which in turn slowly rotates the asbestos 14 and the collection frame 31 (5-10 rpm). An electromagnet (24V, suction force ≥ 50N) within the collection frame 31 absorbs slag from the surface of the molten metal. Simultaneously, the second guide wheel 35 on the disturbance rod 34 rotates with the collection frame, rolling along the sidewalls of the collection trough 32 and the corrugated buffer trough 33, driving a reciprocating motion of the stopper 36, pushing the slag into the collection trough 32. The corrugated structure of the buffer trough 33 prevents slag backflow, increasing slag collection efficiency to over 90%, and reducing slag inclusions during subsequent sand cleaning and cutting processes.

[0068] (IV) Optimization mechanism for thin-walled parts

[0069] For thin-walled parts (wall thickness ≤ 5mm), the bubble retention problem is solved through the following synergistic effects:

[0070] 1. Low-frequency vibration accelerates bubble floating: The vibration frequency of 80Hz increases the bubble migration speed to 0.6m / s, ensuring that the bubble floats before the metal liquid solidifies (solidification time ≤ 15s);

[0071] 2. Gradient gas pressure adapts to the solidification rate: 0.3MPa high-pressure argon gas quickly generates bubbles in the initial pouring stage, while 0.1MPa low pressure is used in the later stage to reduce bubble generation and avoid the risk of bubble retention caused by excessive bubbles;

[0072] 3. Pouring temperature compensation: Increase the pouring temperature by 20-30℃ and extend the solidification time by 5-10s to provide sufficient time for bubbles to float up.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for purifying molten metal for sand casting, characterized in that: The following steps are involved: S1. A steel barrel (1) is provided between the pouring ladle and the casting mold for soft sealing. A pressure-bearing pipe (11) is installed on the steel barrel, and the outlet of the pipe is at a 45° angle to the vertical axis; S2, 5 seconds before pouring, argon gas is introduced into the pressure pipe (11), the argon gas pressure is 0.1-0.3 MPa, and the argon gas flow is stopped immediately when pouring stops; S3. During the cooling process of the molten metal in the casting cavity, argon bubbles float up and carry the inclusions to the top slag groove, which is removed during sand cleaning and cutting.

2. The method for purifying molten metal for sand casting according to claim 1, wherein: The pressure-bearing pipe (11) is curved inside the steel barrel (1) to ensure that bubbles are formed when the argon gas rushes into the molten metal.

3. The method for purifying molten metal for sand casting according to claim 1, wherein: A resin self-hardening sand protection device (12) is provided on the periphery of the casting mold cavity for fixing the runner system and preventing the sand from being washed away by the sand mold.

4. The method for purifying molten metal for sand casting according to claim 3, wherein: In the S1, the lower end of the pouring ladle is fixedly connected to a nozzle brick (13), the steel barrel (1) cover is arranged on the periphery of the nozzle brick (13) and is movably connected to the lower end of the pouring ladle, the lower end of the steel barrel (1) is sealed and rotatably connected to asbestos (14), the lower end of the asbestos (14) is provided with a pouring cup (15), the resin self-hardening sand protection device (12) is sealed and fixedly connected to the periphery of the pouring cup (15), the lower end of the pouring cup (15) is sealed and fixedly connected to a casting pipe (16), the casting pipe (16) extends into the interior of the casting mold cavity, the periphery of the steel barrel (1) is provided with a vibration mechanism (2) for accelerating the floating of bubbles, and an adsorption mechanism (3) is provided between the asbestos (14) and the pouring cup (15) for adsorbing and collecting slag using electromagnetic force.

5. The method for purifying molten metal for sand casting according to claim 4, characterized in that: The vibration mechanism (2) includes a fixed ring plate (21) fixedly connected to the lower end of the casting ladle, a plurality of first springs (22) distributed in a circumferential array are provided between the fixed ring plate (21) and the steel barrel (1), two symmetrically arranged push rods (23) are fixedly connected to the outer wall of the steel barrel (1), the two push rods (23) extend through the fixed ring plate (21) and are fixedly connected to a hinge seat (24), each hinge seat (24) is hinged to a first guide wheel (25), the upper end of the casting mold is fixedly connected to a first motor (26), the first motor (2 6) is coaxially fixedly connected to the output end via a connecting rod, an annular groove (28) is provided at the upper end of the casting, two arc-shaped plates (29) are slidably connected in the annular groove (28) along a circumferential track, a gear ring (210) is fixedly connected to the upper ends of the two arc-shaped plates (29), the gear ring (210) and the driving gear (27) are meshed with each other, a plurality of trapezoidal blocks (211) distributed in a circumferential array are fixedly connected to the inner wall of the gear ring (210), and the first guide wheel (25) periodically contacts and rolls with the inclined surfaces of the plurality of trapezoidal blocks (211).

6. The method for purifying molten metal for sand casting according to claim 5, characterized in that: The adsorption mechanism (3) includes a collection frame (31) fixedly connected between the asbestos (14) and the pouring cup (15), a collection trough (312) is provided inside the collection frame (31), an electromagnet for adsorbing scum is fixedly connected to the inner side wall of the collection trough (312), the collection trough (312) is composed of a plurality of receiving troughs (32) distributed in a circumferential array, and a buffer trough (33) connecting two adjacent receiving troughs (32), the side wall of the buffer trough (33) is arranged in a corrugated shape, and the collection trough (312) and the collection trough (312) are connected to each other. The lower part of the frame (31) is connected, and a disturbance rod (34) is sealed and slidably connected to the inner wall of the collection frame (31). The part of the disturbance rod (34) extending into the collection groove (312) is rotatably connected to the second guide wheel (35). The second guide wheel (35) rolls in contact with the side walls of the receiving groove (32) and the buffer groove (33). The part of the disturbance rod (34) extending into the collection groove (312) is fixedly connected to a stopper (36). A second spring (37) is provided between the stopper (36) and the inner wall of the collection groove (312).

7. The method for purifying molten metal for sand casting according to claim 6, wherein: A mounting block (38) is fixedly connected to the outer wall of the steel barrel (1), a second motor (39) is fixedly connected to the lower end of the mounting block (38), a transmission gear (310) is fixedly connected to the output end of the second motor (39), and an annular tooth groove (311) is fixedly connected to the peripheral side wall of the asbestos (14), and the annular tooth groove (311) and the transmission gear (310) are meshed with each other.

8. The method for purifying molten metal for sand casting according to claim 1, wherein: In the S2, an air pressure control mechanism (4) is provided above the pressure pipe (11), the air pressure control mechanism (4) comprises a shunt pipe (41) in communication with the pressure pipe (11), the upper end of the shunt pipe (41) is fixedly connected to a transverse control box (42), a piston block (43) is sealed and slidably connected inside the transverse control box (42), the lower end of the transverse control box (42) away from the pressure pipe (11) is fixedly connected to a vertical control box (44), and the transverse control box (42) is fixedly connected to the lower end of the side away from the pressure pipe (11). 2) A horizontal conductive block (45) and a vertical conductive block (46) are fixedly connected to the interior of the vertical control box (44), and a conductive sheet is fixedly connected to a side wall of the piston block (43) close to the horizontal conductive block (45) and the vertical conductive block (46). A low-pressure valve and a high-pressure valve are provided on the portion of the pressure-bearing pipe (11) extending into the steel barrel (1). When the horizontal conductive block (45) contacts the conductive sheet, the high-pressure valve is opened, and when the vertical conductive block (46) contacts the conductive sheet, the low-pressure valve is opened.

Images