Preparation method for reducing defects of metal casting

Abstract

The invention relates to the technical field of metal material casting, and particularly discloses a preparation method capable of reducing defects of a metal casting, the method comprises the steps of smelting, refining, transferring and heat preservation, composite treatment before pouring, controllable pressure pouring and post-treatment, and a melt composite treatment device is adopted for conducting pre-pouring treatment on molten metal in a heat preservation furnace; a processing head of the device can synchronously execute rotary stirring and periodic vertical pulsation, and three-dimensional strong convection is established in a melt; the device realizes composite motion through a driving motor, a connecting rod type stirring assembly and a gear-rack type vertical pulsation assembly driven by a servo motor, and is provided with a sealed bin body protected by inert gas. Through the composite flow field, deep homogenization and efficient purification of the melt and active refinement of the solidification structure are achieved, casting defects are remarkably reduced, and meanwhile the process controllability and the operation reliability of equipment in the high-temperature environment are improved.

Description

Technical Field

[0001] This invention relates to the field of metal casting technology, specifically to a method for reducing defects in metal castings. Background Technology

[0002] Metal castings are prone to various defects during solidification, such as shrinkage cavities, porosity, gas pores, inclusions, coarse grains, and compositional segregation. These defects seriously impair the mechanical properties, sealing performance, and fatigue life of the castings. Traditional methods to reduce defects mainly include smelting optimization, pouring temperature control, adding grain refiners, and using special processes such as pressure casting or centrifugal casting.

[0003] Currently, Chinese patent application number CN202322799352.5 discloses a casting device for a metal CT scanner tube sleeve body, including a tube sleeve body casting. The tube sleeve body casting is a tubular structure, including a lower tube sleeve body coarse tube section and an upper tube sleeve body fine tube section. A transverse tube is connected to one side of the upper part of the tube sleeve body casting, and a riser is vertically connected to one side of the transverse tube. A riser-side sprue is connected to the side of the tube sleeve body casting with the transverse tube, and a non-riser-side sprue is connected to the side away from the transverse tube. The pouring ports of the riser-side sprue and the non-riser-side sprue are at the lower end. The tube sleeve body prepared by this device has no defects exceeding the grade.

[0004] However, while existing technologies have improved the quality of specific castings by optimizing the design of the gating system, their methods are inherently passive and localized. They are not easy to actively improve the uniformity, purity, and solidification characteristics of the melt itself before pouring, and the solutions lack versatility, making it difficult to systematically solve various defect problems caused by the melt state from the root. Summary of the Invention

[0005] The purpose of this invention is to provide a method for reducing defects in metal castings, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for reducing defects in metal castings, comprising the following steps: S1. Heat the metal raw material to a molten state in a smelting furnace to obtain molten metal liquid; S2. The molten metal liquid is refined and degassed. S3. Transfer the molten metal processed in step S2 to the casting and holding furnace, and adjust it to the preset casting temperature; S4. Before casting, a melt composite treatment device is used to treat the molten metal in the casting holding furnace; the melt composite treatment device includes a treatment head that can extend into the molten metal, and the treatment head can simultaneously perform rotary stirring and periodic vertical pulsation. S5. Pour the molten metal processed in step S4 into the preheated mold under controlled pressure. S6. After the casting has completely solidified and cooled, it is cleaned of sand and post-processed to obtain the metal casting.

[0007] Preferably, in step S4, the processing head of the melt composite processing device extends vertically below the surface of the molten metal from the top opening of the casting and holding furnace. The starting condition is that the temperature of the molten metal is stable within ±10°C of the preset casting temperature, and the processing time is 3-15 minutes.

[0008] Preferably, in step S4, the preset casting temperature is 150-250°C above the liquidus temperature of the metal.

[0009] Preferably, in step S4, the rotational speed of the processing head and the vertical pulsation frequency follow a preset coupling relationship, specifically: the rotational speed of the processing head is increased during the downward movement phase and decreased during the upward movement phase; this coupling relationship can be achieved through programming of the control system connected to the device, aiming to enhance the shearing and pumping effect on the bottom melt during downward movement and promote the mixing of the middle and upper melts during upward movement.

[0010] Secondly, the present invention provides a melt composite processing apparatus for the above-described method. The apparatus includes a drive motor, which is locked and fixed to the top middle side of a bin cover. The bin cover is locked and fixed to the top side of a bin body. An inert gas interface is embedded and fixed inside the bin cover, and the top side of the inert gas interface is connected to an external inert gas source through a connecting pipe. A composite motion structure is connected to the bottom output end of the drive motor, and the composite motion structure is disposed inside the bin body. A processing head is connected to the bottom end of the composite motion structure, and the processing head is disposed through the bottom middle side of the bin body.

[0011] Preferably, a sealing sleeve is provided through the center of the bottom of the chamber, and the processing head passes through the inside of the sealing sleeve and extends downward.

[0012] Preferably, the composite motion structure includes a support block locked and fixed inside the chamber, a bearing block locked and fixed on the upper front side of the support block, an agitator rotating through the bearing block, the top of the agitator being connected to a drive motor, the rear side of the agitator being fastened to a vertical pulsation component, and the top side of the vertical pulsation component being fastened to the support block.

[0013] Preferably, the processing head includes a vertical rod connected to the agitation assembly at its top end, and a columnar head integrally formed at the bottom end of the vertical rod. The columnar head has at least four radially protruding turbulence blades evenly distributed on its sidewalls, and the turbulence blades are triangular.

[0014] Preferably, the agitation assembly includes a shaft connected to a drive motor at its top end, the shaft rotating through a bearing block, and an upper turntable integrally formed at the bottom end of the shaft. Two first connecting rods are rotatably connected to the bottom of the upper turntable, and a second connecting rod is rotatably connected to the bottom end of each of the two first connecting rods. The bottom ends of the two second connecting rods are rotatably connected to a lower turntable. The two first connecting rods and the two second connecting rods are symmetrically distributed on the central axis of the shaft. A rotating shaft is integrally formed at the bottom end of the lower turntable, the rotating shaft rotating through a displacement support, and the bottom end of the rotating shaft is connected to a processing head. The rear side of the displacement support is connected to a vertical pulsation assembly.

[0015] Preferably, the vertical pulsation assembly includes a frame whose top is fastened to a support block. A servo motor is locked and fixed to the top left side of the frame. A rotating rod is connected to the bottom output end of the servo motor. The bottom of the other end of the rotating rod is rotatably connected to a push rod. The end of the push rod away from the rotating rod is inserted into and rotates inside the left side of the spiral rod. The left side of the spiral rod is rotatably connected to the inside of the slide, and the rear side of the slide is laterally slidably connected to the frame. An inner spiral sleeve is wrapped around the side of the spiral rod away from the slide. The inner spiral sleeve passes through and rotates through the front part of the frame away from the servo motor. A gear is fixedly connected to the right side of the outer surface of the inner spiral sleeve. The front side of the gear meshes with a rack. The rack is locked and fixed to the right side of the rear part of the carrier plate, and the middle side of the rear part of the carrier plate slides longitudinally to the front side of the slot seat. The slot seat is fixedly connected to the right side of the front part of the carrier plate. The front part of the carrier plate is fastened to the displacement support.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention utilizes a melt composite processing device to simultaneously apply precise periodic vertical pulsations on top of the rotating stirring of the processing head. This creates a unique three-dimensional strong convection field within the molten metal. This composite motion breaks down the temperature and composition stratification within the molten pool, achieving high uniformity across the entire area. Furthermore, the resulting intense turbulence and periodic pressure changes effectively promote the precipitation of dissolved gases and the collision, aggregation, and flotation of non-metallic inclusions. Before casting, a melt with significantly improved purity and excellent uniformity can be obtained, fundamentally reducing casting defects caused by compositional segregation, inclusions, and porosity.

[0017] The vertical pulsation mechanism of this invention plays a highly efficient mechanical pumping role, which can force the early crystal nucleus fragments broken by the rotational shear force to be transported to all parts of the melt, thereby significantly increasing the effective nucleation points in the entire molten pool and realizing active and uniform global nucleation. At the same time, the strong three-dimensional convection continuously destroys the solute enrichment layer at the solidification front, inhibiting the growth tendency of columnar crystals, so that the casting finally obtains a fine and uniform equiaxed crystal structure, which greatly improves the conventional mechanical properties of the casting and effectively enhances its resistance to thermal cracking and fatigue.

[0018] This invention integrates rotary stirring and vertical pulsation functions into a single device, reliably achieved through linkages and transmission mechanisms. This simplifies the process flow, and all motion parameters (rotation speed, pulsation frequency, and amplitude, etc.) can be precisely programmed and independently adjusted by the control system, ensuring a high degree of controllability and repeatability of the process and reducing reliance on operator experience. Furthermore, the positive pressure protection system formed by the sealed chamber and inert gas provides reliable protection for moving parts, significantly improving the durability and long-term operational stability of the equipment under harsh high-temperature conditions. Attached Figure Description

[0019] Figure 1 This is a flowchart of the preparation method of the present invention; Figure 2 This is a schematic diagram of the melt composite processing device of the present invention; Figure 3 This is a schematic diagram of the composite motion structure of the present invention; Figure 4 This is a schematic diagram of the vertical pulsation component of the present invention; Figure 5 For the present invention Figure 4 Front view after removing the servo motor; Figure 6 For the present invention Figure 5 A schematic diagram of the right-side structure.

[0020] In the diagram: Drive motor-1, Compartment cover-2, Compartment body-3, Inert gas interface-4, Composite motion structure-5, Processing head-6, Support block-51, Bearing block-52, Agitator assembly-53, Vertical pulsation assembly-54, Vertical rod-61, Column head-62, Turbulent blade-63, Shaft-531, Upper turntable-532, First connecting rod-533, Second connecting rod-534, Lower turntable-535, Rotating shaft-536, Displacement support-537, Carrier frame-541, Servo motor-542, Rotating rod-543, Push rod-544, Helical rod-545, Slide-546, Inner helical sleeve-547, Gear-548, Rack-549, Carrier plate-5410, Slot seat-5411. Detailed Implementation

[0021] To further explain the technical solution of the present invention, a detailed description is provided below through specific embodiments.

[0022] Please see Figure 1 This invention provides a method for reducing defects in metal castings, comprising the following steps: S1. Heat the metal raw material to a molten state in a smelting furnace to obtain molten metal liquid; S2. Refining and degassing the molten metal; S3. Transfer the molten metal processed in step S2 to the casting and holding furnace, and adjust it to the preset casting temperature; S4. Before casting, a melt composite treatment device is used to treat the molten metal in the casting holding furnace; the melt composite treatment device includes a treatment head 6 that can extend into the molten metal, which can simultaneously perform rotary stirring and periodic vertical pulsation. S5. Pour the molten metal processed in step S4 into the preheated mold under controlled pressure. S6. After the casting has completely solidified and cooled, it is cleaned of sand and post-processed to obtain the metal casting.

[0023] In step S4, the processing head of the melt composite processing device extends vertically below the surface of the molten metal from the top opening of the casting and holding furnace. The starting condition is that the temperature of the molten metal is stable within ±10℃ of the preset casting temperature, and the processing time is 3-15 minutes. The preset casting temperature is 150-250℃ above the liquidus temperature of the molten metal.

[0024] In step S4, the rotational speed of the processing head 6 and the vertical pulsation frequency follow a preset coupling relationship. Specifically, the rotational speed of the processing head 6 is increased during the downward movement phase and decreased during the upward movement phase. This coupling relationship can be achieved through programming of the control system connected to the device, which aims to enhance the shearing and pumping effect on the bottom melt during downward movement and promote the mixing of the middle and upper melts during upward movement.

[0025] Please see Figures 2 to 6 The present invention provides a melt composite processing device for the above method. The melt composite processing device includes a drive motor 1, which is locked and fixed to the top middle side of the bin cover 2. The bin cover 2 is locked and fixed to the top side of the bin body 3. An inert gas interface 4 is embedded and fixed inside the bin cover 2. The top side of the inert gas interface 4 is connected to an external inert gas source through a pipe to continuously introduce inert gas into the sealed chamber formed by the bin body 3 and the bin cover 2, forming a positive pressure protection environment to prevent high temperature oxidizing gas from entering and damaging the internal mechanism. The bin body 3 can be installed on the top opening of the casting and holding furnace through a flange. The bottom output end of the drive motor 1 is connected to a compound motion structure 5, which is located inside the chamber 3. The bottom end of the compound motion structure 5 is connected to a processing head 6, which is located through the middle of the bottom of the chamber 3. A sealing sleeve is provided through the center of the bottom of the chamber 3, and the processing head 6 passes through the inside of the sealing sleeve and extends downward. The drive motor 1 provides a rotational power source for the compound motion structure 5 to drive the compound motion structure 5 to move the processing head 6.

[0026] The composite motion structure 5 includes a support block 51 locked and fixed inside the chamber 3. A bearing block 52 is locked and fixed on the upper front side of the support block 51. An agitator 53 rotates through the bearing block 52. The top of the agitator 53 is connected to the drive motor 1. The rear side of the agitator 53 is fastened to the vertical pulsation assembly 54. The top side of the vertical pulsation assembly 54 is fastened to the support block 51. The bottom end of the agitator 53 is connected to the processing head 6 to transmit the rotational power to the processing head 6. Under the action of the vertical pulsation assembly 54, the processing head 6 generates a longitudinal reciprocating driving force, thereby driving the processing head 6 to perform relative axial displacement while rotating, generating radial and axial turbulence.

[0027] The processing head 6 includes a vertical rod 61 connected to the agitation assembly 53 at its top end. A columnar head 62 is integrally formed at the bottom end of the vertical rod 61. At least four radially protruding turbulence blades 63 are evenly distributed on the side wall of the columnar head 62. The turbulence blades 63 are triangular in shape, so as to generate strong radial and axial turbulence when the entire processing head 6 moves, which can more effectively disperse and pump the molten metal.

[0028] The agitation component 53 includes a shaft 531 connected to the drive motor 1 at its top end. The shaft 531 rotates through the bearing block 52, and an upper turntable 532 is integrally formed at the bottom end of the shaft 531. Two first connecting rods 533 are rotatably connected to the bottom of the upper turntable 532. A second connecting rod 534 is rotatably connected to the bottom end of each of the two first connecting rods 533, and the bottom ends of both second connecting rods 534 are rotatably connected to a lower turntable 535. The two first connecting rods 533 and the second connecting rods 534 are symmetrically distributed on the central axis of the shaft 531. The bottom end of the disc 535 is integrally formed with a rotating shaft 536, which passes through and rotates inside the displacement support 537. The bottom end of the rotating shaft 536 is connected to the processing head 6. The rear side of the displacement support 537 is connected to the vertical pulsation assembly 54. It transmits the rotational motion to the lower disc 535 and the rotating shaft 536 through two sets of symmetrically arranged first connecting rods 533 and second connecting rods 534, thereby causing the processing head 6 to rotate. This linkage mechanism allows axial relative displacement between the lower disc 535 and the upper disc 532 while transmitting rotational power.

[0029] The vertical pulsation assembly 54 includes a frame 541 whose top is fastened to the support block 51. A servo motor 542 is locked to the top left side of the frame 541. A rotating rod 543 is connected to the bottom output end of the servo motor 542. The bottom of the other end of the rotating rod 543 is rotatably connected to a push rod 544. The end of the push rod 544 away from the rotating rod 543 is inserted into and rotates inside the left side of the spiral rod 545. The left side of the spiral rod 545 is rotatably connected to the inside of the slide 546. The rear side of the slide 546 is laterally slidably connected to the frame 541. The side of the spiral rod 545 away from the slide 546 wraps around and cooperates with the frame 541. An inner spiral sleeve 547 is provided, which rotates through the front of the carrier 541 on the side away from the servo motor 542. The inner spiral sleeve 547 is restricted to only rotating. A gear 548 is fixedly connected to the right side of the outer surface of the inner spiral sleeve 547. The front side of the gear 548 meshes with the rack 549. The rack 549 is locked and fixed to the right side of the rear part of the carrier plate 5410. The middle side of the rear part of the carrier plate 5410 slides longitudinally to the front side of the slot seat 5411. The slot seat 5411 is fixedly connected to the right side of the front part of the carrier 541. The front part of the carrier plate 5410 is fastened to the displacement support 537. The servo motor 542 drives the rotating rod 543 and the push rod 544 to push the screw rod 545 to move axially. Since the inner spiral sleeve 547 and the screw rod 545 are threaded together, the axial movement of the screw rod 545 will force the inner spiral sleeve 547 to rotate. The gear 548 on the inner spiral sleeve 547 drives the rack 549 that meshes with it to move linearly. The rack 549 is fixed on the carrier plate 5410, thereby driving the carrier plate 5410 and the displacement support 537 fastened to it to make precise vertical reciprocating motion along the slot seat 5411. The up and down movement of the displacement support 537 causes the lower half of the entire stirring assembly 53 (lower turntable 535, rotating shaft 536 and processing head 6) to produce periodic vertical pulsations.

[0030] Combination Figure 1 The steps for preparing castings using this device are as follows: 1. Melt aluminum alloy (e.g., A356) raw material in a smelting furnace to obtain a molten liquid at approximately 720°C.

[0031] 2. Argon gas is introduced through a rotary degasser for refining and degassing.

[0032] 3. Transfer the molten liquid into a casting and holding furnace at 720℃ for heat preservation.

[0033] 4. When the temperature stabilizes at 710±5℃ (preset pouring temperature), start the melt composite treatment device. The treatment head is inserted into the melt pool to a depth of about 1 / 2 below the liquid surface and rotates at 300 rpm. At the same time, it pulsates vertically at a frequency of 1.5Hz for 8 minutes. During this period, the control system couples the rotation speed and direction of movement according to the preset program.

[0034] 5. After the process is completed, immediately pour the molten liquid into a metal mold that has been preheated to 300°C under a pressure of 0.3 MPa.

[0035] 6. After the casting solidifies and cools, it undergoes sand removal, heat treatment, and machining to obtain the aluminum alloy wheel hub casting.

[0036] Testing revealed that, compared to castings produced using traditional methods without the S4 step, castings prepared using this method exhibited improved porosity and shrinkage cavities upon X-ray inspection, as well as increased tensile strength and elongation.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for reducing defects in metal castings, characterized in that, Includes the following steps: S1. Heat the metal raw material to a molten state in a smelting furnace to obtain molten metal liquid; S2. The molten metal liquid is refined and degassed. S3. Transfer the molten metal processed in step S2 to the casting and holding furnace, and adjust it to the preset casting temperature; S4. Before casting, a melt composite treatment device is used to treat the molten metal in the casting holding furnace; the melt composite treatment device includes a treatment head (6) that can extend into the molten metal, and the treatment head (6) can simultaneously perform rotary stirring and periodic vertical pulsation. S5. Pour the molten metal processed in step S4 into the preheated mold under controlled pressure. S6. After the casting has completely solidified and cooled, it is cleaned of sand and post-processed to obtain the metal casting.

2. The preparation method for reducing defects in metal castings according to claim 1, characterized in that: In step S4, the processing head of the melt composite processing device extends vertically below the surface of the molten metal from the top opening of the casting and holding furnace. The starting condition is that the temperature of the molten metal is stable within ±10℃ of the preset casting temperature, and the processing time is 3-15 minutes.

3. The preparation method for reducing defects in metal castings according to claim 1, characterized in that: In step S4, the preset pouring temperature is 150-250°C above the liquidus temperature of the metal.

4. The preparation method for reducing defects in metal castings according to claim 1, characterized in that: The melt composite processing device includes a drive motor (1), which is locked and fixed to the top middle side of the bin cover (2). The bin cover (2) is locked and fixed to the top side of the bin body (3). An inert gas interface (4) is embedded and fixed inside the bin cover (2), and the top side of the inert gas interface (4) is connected to an external inert gas source through a pipe. A composite motion structure (5) is connected to the bottom output end of the drive motor (1), and the composite motion structure (5) is set inside the bin body (3). A processing head (6) is connected to the bottom end of the composite motion structure (5), and the processing head (6) is set through the bottom middle side of the bin body (3).

5. The preparation method for reducing defects in metal castings according to claim 4, characterized in that: A sealing sleeve is provided through the center of the bottom of the chamber (3), and the processing head (6) passes through the inside of the sealing sleeve and extends downward.

6. The preparation method for reducing defects in metal castings according to claim 4, characterized in that: The composite motion structure (5) includes a support block (51) locked and fixed inside the chamber (3). A bearing block (52) is locked and fixed on the upper front side of the support block (51). An agitator (53) is rotatably inserted inside the bearing block (52). The top of the agitator (53) is connected to the drive motor (1). The rear side of the agitator (53) is fastened to the vertical pulsation assembly (54). The top side of the vertical pulsation assembly (54) is fastened to the support block (51).

7. The preparation method for reducing defects in metal castings according to claim 6, characterized in that: The rotational speed of the agitation component (53) and the frequency of the vertical pulsation component (54) follow a preset coupling relationship, so that the rotational speed of the processing head (6) increases when it moves downward and decreases when it moves upward.

8. The preparation method for reducing defects in metal castings according to claim 6, characterized in that: The processing head (6) includes a vertical rod (61) connected to the agitation assembly (53) at the top end. The bottom end of the vertical rod (61) is integrally formed with a columnar head (62). The sidewall of the columnar head (62) is evenly distributed with no less than four radially protruding turbulence blades (63), and the turbulence blades (63) are triangular.

9. The preparation method for reducing defects in metal castings according to claim 6, characterized in that: The agitation assembly (53) includes a shaft (531) whose top end is connected to a drive motor (1). The shaft (531) rotates through the bearing block (52), and an upper turntable (532) is integrally formed at the bottom end of the shaft (531). Two first connecting rods (533) are rotatably connected to the bottom of the upper turntable (532). A second connecting rod (534) is rotatably connected to the bottom end of each of the two first connecting rods (533), and the bottom end of each of the two second connecting rods (534) is also connected to the bottom end of the second connecting rod (534). Rotatably connected to the lower turntable (535), the two first connecting rods (533) and the second connecting rod (534) are symmetrically distributed on the central axis of the shaft (531). The bottom end of the lower turntable (535) is integrally formed with a rotating shaft (536). The rotating shaft (536) passes through and rotates inside the displacement support (537). The bottom end of the rotating shaft (536) is connected to the processing head (6). The rear side of the displacement support (537) is connected to the vertical pulsation assembly (54).

10. The preparation method for reducing defects in metal castings according to claim 9, characterized in that: The vertical pulsating assembly (54) includes a frame (541) whose top is fastened to a support block (51). A servo motor (542) is locked to the top left side of the frame (541). A rotating rod (543) is connected to the bottom output end of the servo motor (542). The bottom of the other end of the rotating rod (543) is rotatably connected to a push rod (544). The end of the push rod (544) away from the rotating rod (543) is inserted into and rotated on the inner left side of a spiral rod (545). The left side of the spiral rod (545) is rotatably connected to the inner side of a slide (546), and the rear side of the slide (546) is laterally slidably connected to the frame (541). The spiral rod (545) away from the slide (541) 6) One side is wrapped with an inner spiral sleeve (547), which rotates through the front of the carrier (541) away from the servo motor (542). A gear (548) is fixedly connected to the right side of the outer surface of the inner spiral sleeve (547). The front side of the gear (548) meshes with the rack (549). The rack (549) is locked and fixed to the right side of the rear of the carrier plate (5410). The middle side of the rear of the carrier plate (5410) slides longitudinally to the front side of the slot seat (5411). The slot seat (5411) is fixedly connected to the right side of the front of the carrier (541). The front of the carrier plate (5410) is fastened to the displacement support (537).

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