Semi-solid double-alloy integrated die-casting forming method and system

Abstract

The invention belongs to the technical field of integrated die-casting forming, and relates to a semi-solid double-alloy integrated die-casting forming method and system.The method comprises the steps that two kinds of semi-solid alloy slurry are prepared, specifically, at least two kinds of metal are mixed and then heated to be melted; after inert gas is filled to clean residual oxygen in the resistance furnace, refining and degassing are carried out, so that the molten alloy liquid is synchronously subjected to eccentric rotation and indirect ultrasonic treatment for the same time in the inert gas closed environment to generate vortexes and grow solid-phase particles, and meanwhile, the high-pressure inert gas closed environment is vacuumized; corresponding semi-solid alloy slurry is obtained; cooling the two kinds of semi-solid alloy slurry, and then respectively transferring the two kinds of semi-solid alloy slurry into corresponding injection chambers in an inert atmosphere; and the two kinds of semi-solid alloy slurry are sequentially or simultaneously injected into the corresponding areas in the die-casting die, the two kinds of semi-solid alloy slurry are converged, and a metallurgical-mechanical composite bonding interface is formed at the joint of the two kinds of semi-solid alloy slurry. According to the invention, the effects of uniform material structure and high injection efficiency of the integrated injection casting can be realized.

Description

Technical Field

[0001] The present application belongs to the field of one-piece die-casting technology, and more specifically, relates to a semi-solid dual-alloy one-piece die-casting method and system. Background Art

[0002] The current die-casting technology for integrated rear-end automotive bodies generally uses a full liquid metal and single-shot system injection method. This method has the following drawbacks: During the die-casting process, liquid aluminum alloys must be maintained at temperatures between 680°C and 720°C, and liquid magnesium alloys must be maintained at temperatures between 640°C and 680°C. This results in significant thermal stress on the mold, long molding cycles, and high product porosity. Semi-solid integrated die-casting can avoid these issues because the semi-solid metal slurry has a lower temperature, typically 10°C to 20°C below the liquidus, and its cooling rate is 30% to 40% faster than traditional full liquid metal, significantly reducing shrinkage cavities and porosity in die-cast parts. However, the traditional semi-solid alloy one-piece die-casting method has the following problems: 1) Semi-solid alloy slurry is prone to segregation during the injection molding process, resulting in uneven microstructure and performance; 2) Die-cast parts are prone to stress concentration problems, especially at the corners of complex structures, where the stress concentration coefficient can reach 2 to 3 times, significantly reducing the fatigue life of die-cast parts; 3) Die-casting with a single metal slurry makes it difficult to improve the performance of die-cast products, and it is impossible to take into account the performance requirements of different parts of the same structure in application scenarios such as automobile body structures. Summary of the Invention

[0003] In response to the defects of the existing technology, the purpose of this application is to provide a semi-solid dual-alloy integrated die-casting molding method and system, aiming to solve the problems of uneven casting material structure caused by the easy segregation of semi-solid alloy slurry during the injection die-casting process, as well as low die-casting efficiency.

[0004] To achieve the above objectives, in a first aspect, the present application provides a semi-solid dual alloy integral die-casting method, comprising: S1: preparing two semi-solid alloy slurries using the same method, respectively. The preparation method is: mixing at least two metals and then heating and melting them to obtain a molten alloy liquid; synchronously performing eccentric rotation and indirect ultrasonic treatment on the molten alloy liquid in a high-pressure inert gas sealed environment for the same length of time, so that the molten alloy liquid generates eddy currents to grow solid phase particles, and during the eccentric rotation and indirect ultrasonic treatment, the high-pressure inert gas sealed environment is vacuumed to obtain the corresponding semi-solid alloy slurry; S2 transfers the two semi-solid alloy slurries to corresponding injection chambers after cooling, and the transfer process is carried out in an inert gas environment; S3: sequentially or simultaneously injecting the two semi-solid alloy slurries into corresponding areas of the die casting mold until the two semi-solid alloy slurries merge and form a metallurgical-mechanical composite bonding interface at the joint, thereby obtaining an integrated die casting.

[0005] Furthermore, in step S1, the time for eccentric rotation and ultrasonic treatment is 3 min to 5 min, the speed of eccentric rotation is 500 r / min to 600 r / min, and the solid phase ratios of the two semi-solid alloy slurries are both 35% to 45%.

[0006] Furthermore, in step S1, the pressure of the high-pressure inert gas sealed environment is 60 kPa-80 kPa, and the temperature is 550° C.-750° C.

[0007] Furthermore, in step S1, the ultrasonic frequency of the ultrasonic treatment does not exceed 30kHz, and the ultrasonic power does not exceed 2000w.

[0008] Furthermore, in step S3, when the injection is performed sequentially, one semi-solid alloy slurry is first injection-filled into the corresponding area in the die-casting mold, and when the flow front of the first semi-solid alloy slurry is filled to a minimum distance of at least 8 mm from the area to be injected and filled with another semi-solid alloy slurry, injection-filling of another semi-solid alloy slurry into the remaining filling area is started.

[0009] Furthermore, in step S3, when the semi-solid alloy slurry is injected sequentially, the injection speed of the semi-solid alloy slurry injected first is 3m / s~5m / s, the injection pressure of the semi-solid alloy slurry injected first is 40MPa~60MPa, the injection pressure of the semi-solid alloy slurry injected later is 50MPa~80MPa, and the injection speed of the semi-solid alloy slurry injected later is 2m / s~4m / s; when injected simultaneously, the injection speed of the semi-solid alloy slurry corresponding to the area with anti-corrosion requirements is 3m / s-3.5m / s, and the injection pressure is 50MPa~60MPa, and the injection speed of the semi-solid alloy slurry corresponding to the area without anti-corrosion requirements is 3.5m / s~4m / s, and the injection pressure is 60MPa~70MPa.

[0010] Furthermore, in step S2, when the semi-solid alloy slurry is injected first, the temperature is reduced to 610°C~630°C, and the semi-solid alloy slurry is injected later, and the temperature is reduced to 560°C~570°C; when the semi-solid alloy slurry is injected simultaneously, the temperature of the semi-solid alloy slurry corresponding to the area with anti-corrosion requirements is reduced to 565°C~570°C, and the temperature of the semi-solid alloy slurry corresponding to the area without anti-corrosion requirements is reduced to 610°C~620°C.

[0011] Furthermore, in step S3, during the injection process, the temperature difference between the two semi-solid alloy slurries at their confluence is controlled to be no greater than 10°C.

[0012] Furthermore, in step S3, the inner wall of the die-casting mold is coated with a nano-ceramic coating; and / or the thickness of the nano-ceramic coating is at least 80 μm .

[0013] According to a second aspect of the present application, a system for implementing the aforementioned semi-solid dual alloy integral die-casting method is provided, comprising: The semi-solid alloy slurry preparation module includes: a mixing and melting unit for mixing at least two metals and then heating and melting them to obtain a molten alloy liquid; a solid phase particle growth unit for simultaneously performing eccentric rotation and indirect ultrasonic treatment on the molten alloy liquid in a high-pressure inert gas sealed environment for the same length of time, so as to generate eddy currents in the molten alloy liquid and grow solid phase particles; a vacuum unit for vacuuming the high-pressure inert gas sealed environment during the eccentric rotation and indirect ultrasonic treatment process; The semi-solid alloy slurry transfer unit is used to transfer the two semi-solid alloy slurries to the corresponding injection chambers after cooling; The double-shot die-casting module includes a first shot die-casting unit for injection-filling a semi-solid alloy slurry into a corresponding area of ​​the die-casting mold; and also includes a second shot die-casting unit for injection-filling another semi-solid alloy slurry into the corresponding filling area.

[0014] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0015] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the existing technologies: (1) The present application optimizes the semi-solid alloy slurry forming process, that is, after the alloy metal is heated and melted, it is eccentrically rotated in a closed environment of high-pressure inert gas to generate eddy currents in the molten alloy, thereby evenly distributing and transferring the heat of the molten metal, thereby promoting the formation and growth of solid phase particles; while the eccentric rotation is performed, the molten alloy is also subjected to synchronous indirect ultrasonic treatment, and the eccentric rotation and synchronous indirect ultrasonic treatment start and end at the same time. Under the dual action, the occurrence of the chill layer can be prevented, the solid phase ratio can be increased, the slurry structure can be homogenized and refined, the degree of tissue spheroidization can be increased, and the mechanical strength and high-temperature service life of the subsequent die-casting parts can be improved; in addition, the indirect ultrasonic treatment can also avoid direct contact between the ultrasonic vibrator and the molten alloy, thereby preventing the molten alloy from corroding the ultrasonic vibrator and then contaminating the molten alloy.

[0016] (2) The present application sequentially injects different semi-solid alloy slurries into the corresponding areas of the target mold in a preset order. The solid phase particles in the optimized semi-solid alloy slurry can effectively suppress turbulent air entrainment and avoid segregation problems during the injection process, thereby making the porosity of the casting smaller. The injection sequence of the present application is to first inject one semi-solid alloy slurry to fill the corresponding area, and stop the injection when it is within a preset width of the remaining filling area, and then start to fill another semi-solid alloy slurry into its corresponding filling area until the two semi-solid alloy slurries merge and form a metallurgical-mechanical composite bonding interface at the junction. The two slurries significantly improve the interface shear strength through the synergistic effect of metallurgical bonding (atomic diffusion) and mechanical interlocking (physical bite), and disperse local stress concentration, avoiding the problem of easy cracking due to stress concentration after injection of a single alloy. At the same time, the two semi-solid alloy slurries in the integral die casting are accurately formed in the same die-casting process, and the processing efficiency and processing quality are better.

[0017] (3) This application controls the relevant process parameters of the semi-solid alloy slurry during the injection process, such as controlling the injection speed and injection pressure of the corresponding semi-solid alloy slurry within a specific injection speed range and a specific injection pressure range. By controlling the temperature and pressure, the shrinkage defects at the interface between the two semi-solid alloy slurries are eliminated, the occurrence of segregation is further reduced, and the performance strength and durability of the die-cast parts are effectively improved.

[0018] (4) The entire slurry preparation and transfer process of the present application is carried out in a closed environment of high-pressure inert gas, and hydrogen is removed by heating the molten alloy during the melting process, and vacuum treatment is simultaneously performed during the eccentric rotation and ultrasonic indirect treatment process, thereby avoiding shrinkage and porosity of subsequent die-cast parts; and by separately regulating the rotation rate of the eccentric rotation, the relevant parameters of the ultrasonic treatment (such as ultrasonic frequency, ultrasonic power), and the time of the eccentric rotation and ultrasonic treatment, the solid phase ratio of the obtained semi-solid alloy slurry is within a preset range, and the semi-solid alloy slurry with the best fluidity is obtained quickly and efficiently. If the solid phase ratio exceeds the preset range, the slurry has poor fluidity, the subsequent die-casting time is longer, and the die-casting effect is worse.

[0019] (5) This application uses two semi-solid alloy slurries and adopts the method of sequential injection die casting or simultaneous injection die casting in two injection chambers to obtain die castings, and forms a metallurgical-mechanical composite bonding interface in the mold while retaining the advantages of integrated molding; and controls the temperature difference between the two semi-solid alloy slurries on both sides of the interface to be less than 10°C during the injection process, so that the mechanical properties of the metallurgical-mechanical composite bonding interface are better, and by optimizing the slurry preparation process and the injection die casting process, the shear strength of the interface is increased by 3-5 times compared with traditional connection methods (such as welding connection); it can also omit more than 90% of the welds on die castings such as automobile body structures, making it easier to achieve seamless connection of dissimilar materials.

[0020] (6) This application may use the same semi-solid alloy slurry or two different semi-solid alloy slurries. When two different semi-solid alloy slurries are used, die-cast parts with different properties in different parts can be die-cast. For example, when the die-casting mold requires an anti-corrosion area and a non-anti-corrosion area, two semi-solid alloy slurries can be injected into the corresponding areas at the same time. Specifically, the anti-corrosion semi-solid alloy slurry and the lightweight semi-solid alloy slurry can be used to die-cast a lightweight body structure with both anti-corrosion properties.

[0021] (7) The inner wall of the die used in the injection molding process of this application is coated with a nano-ceramic coating, and the temperature of the two semi-solid alloy slurries filled into the die-casting die is reduced to within the preset temperature range. As a result, the service life of the die-casting die is greatly improved compared to when there is no coating and liquid metal is used, further reducing the die-casting cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic flow chart of a semi-solid dual alloy integral die-casting method provided in an embodiment of the present application; Figure 2 Schematic diagram of a semi-solid alloy slurry preparation device provided in an embodiment of the present application; Figure 3 This is a schematic diagram of the die-casting mold structure of the vehicle body structure provided in an embodiment of the present application; Figure 4 This is a side structural schematic diagram of the second injection chamber connected to the vehicle body structure die-casting mold provided by an embodiment of the present application; Figure 5 This is a schematic side view of the structure of the first injection chamber connected to the die-casting mold of the vehicle body structure provided in an embodiment of the present application; Figure 6 This is a schematic diagram of the semi-solid dual-alloy one-piece die-casting process of the vehicle body structure provided in an embodiment of the present application.

[0023] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-Material preparation machine; 2-Feeding hopper; 3-High-purity argon cylinder; 4-Vacuum pump; 5-Trachea; 6-Evacuation pipe; 7-Furnace cover; 8-Sealing ring; 9-Resistance heating furnace; 10-Eccentric rotating device; 11-Graphite clay crucible; 12-Indirect ultrasonic transducer; 13-Ultrasonic controller; 14-Die-casting mold; 15-First shot chamber; 16-First push rod; 17-Second shot chamber; 18-Second push rod; 19-Integrated die-cast rear end body. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0025] The term "and / or" as used herein describes an association between related objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. The symbol " / " as used herein indicates that the related objects are in an "or" relationship, for example, A / B means either A or B.

[0026] The terms "first" and "second" in this specification and claims are used to distinguish different objects rather than to describe a specific order of objects. For example, "first response message" and "second response message" are used to distinguish different response messages rather than to describe a specific order of response messages.

[0027] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0028] In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more, for example, multiple processing units means two or more processing units, etc.; multiple elements means two or more elements, etc.

[0029] The technical problem to be solved by this application is to improve the mechanical properties of casting products produced by one-piece die-casting technology, especially the mechanical and lightweight properties of die-cast parts related to the rear-end body structure of automobiles.

[0030] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0031] This embodiment provides a method for industrial die-casting of automobile rear-end structures using a double-shot die-casting process using semi-solid magnesium alloy and semi-solid aluminum alloy. This method offers faster production efficiency and produces castings with enhanced performance.

[0032] Due to the difference in fluidity between the solid and liquid phases of semi-solid alloys, the liquid phase tends to flow to the edge area away from the pressure center, and a large amount of solid phase will remain in the loaded center area. The larger the volume of the semi-solid alloy, the more likely it is to have solid-liquid phase segregation.

[0033] Therefore, in this embodiment, first, in the slurry making step, the melting crucible containing the molten alloy is placed in a closed environment of high-pressure inert gas and eccentrically rotated for a short time to generate eddy currents in the molten alloy, thereby evenly distributing and transferring the heat of the melt, promoting the formation and growth of solid phase particles in the melt, and obtaining a semi-solid alloy slurry with a low solid phase ratio; while the eccentric rotation is being performed, the alloy slurry with a low solid phase ratio is subjected to indirect ultrasonic treatment with the same duration and synchronous start and stop as the eccentric rotation, which can prevent the occurrence of a chilled layer, further increase the solid phase ratio, make the structure homogenized and refined, and increase the degree of structure spheroidization.

[0034] Secondly, this embodiment uses a double injection method to inject the corresponding semi-solid alloy slurry from different injection chambers to the corresponding areas in a preset order. Compared with injecting from a single injection chamber, it can shorten the alloy flow path and reduce pressure loss, thereby reducing solid phase accumulation in the central area and the occurrence of segregation, so that the semi-solid alloy slurry can fill the corresponding cavity more evenly and improve the injection quality. In addition, the semi-solid alloy slurry for the dual-shot chamber can use the same semi-solid alloy slurry or two different semi-solid alloy slurries. For the integrated die-casting of the rear-end body structure, different semi-solid alloy slurries can give different parts of the body structure different properties. For example, the wheel arch, which is frequently in contact with water and mud, can be formed using a corrosion-resistant semi-solid aluminum alloy, while parts such as the rear floor, which have lower load-bearing requirements and are not in contact with water and mud, can be formed using a lightweight magnesium alloy. This can avoid the solid-liquid phase segregation of the semi-solid alloy during the die-casting process while improving the corrosion resistance and lightweight performance of the die-casting.

[0035] This embodiment provides a semi-solid dual alloy integral die-casting method, which uses different types of semi-solid alloy slurries to die-cast the vehicle body structure, such as Figure 1 As shown, the specific steps include: S1 prepares a corrosion-resistant semi-solid alloy slurry and a lightweight semi-solid alloy slurry respectively, and the preparation method is as follows: mixing at least two metals and then heating and melting them to obtain a molten alloy liquid; the molten alloy liquid is simultaneously subjected to eccentric rotation and indirect ultrasonic treatment for the same length of time in a high-pressure inert gas closed environment to generate eddy currents in the molten alloy liquid to grow solid phase particles, and during the eccentric rotation and indirect ultrasonic treatment process, the high-pressure inert gas closed environment is simultaneously vacuumed to obtain the corresponding semi-solid alloy slurry; S2 transfers the anti-corrosion semi-solid alloy slurry and the lightweight semi-solid alloy slurry to the corresponding injection chambers after cooling, and the transfer process is carried out in an inert gas environment; S3 sequentially or simultaneously presses the two semi-solid alloy slurries into the corresponding areas in the die-casting mold 14 until the two semi-solid alloy slurries merge and form a metallurgical-mechanical composite bonding interface at the joint, thereby obtaining an integrated die-casting part; specifically, the metallurgical-mechanical composite bonding interface refers to the interface where the joint interface of the two semi-solid alloy slurries is an interface under the combined action of mechanical bonding and metallurgical bonding. The two slurries are metallurgically bonded through atomic diffusion, and mechanical interlocking is achieved through the physical bite of the two slurries. The synergistic effect of metallurgical bonding and mechanical interlocking significantly improves the interface shear strength and disperses local stress concentration, thereby avoiding the problem of easy cracking due to stress concentration after single alloy injection.

[0036] First, according to the shape, size and technical requirements of the rear body product, the reinforcement ribs at the rear wheel cover of the body are used as runners, which makes it easier to die-cast the rear wheel cover of the rear body. The rear floor surface is selected as the mold parting surface to facilitate product demoulding, and the cavity surface is sprayed with 80 μm Thick nano-ceramic coating prevents semi-solid alloy slurry from sticking to the die-casting mold.

[0037] In this embodiment, there is no particular restriction on the composition of the anti-corrosion semi-solid alloy slurry and the lightweight semi-solid alloy slurry. The lightweight semi-solid alloy slurry is made of a magnesium alloy, specifically AZ91D, with the following alloy composition by mass percentage: 9% Al, 1% Zn, 0.15% Mn, and the balance Mg. The anti-corrosion semi-solid alloy slurry is made of an aluminum alloy, specifically AlSi10Mg, with the following alloy composition by mass percentage: 10% Si, 0.3% Mg, and the balance Al.

[0038] In step S1, the eccentric rotation and ultrasonic treatment start and end at the same time, and the treatment time is 3 min to 5 min, the eccentric rotation speed is 500 r / min to 600 r / min, and the solid phase ratio of the anti-corrosion semi-solid alloy slurry and the lightweight semi-solid alloy slurry is 35% to 45%.

[0039] Specifically, a semi-solid slurry of magnesium alloy AZ91D is first prepared, and the preparation steps are as follows: S101 Figure 2 As shown, high-purity aluminum (9wt%), zinc (1wt%), and magnesium (the rest) are placed in a material preparation machine 1 and mixed evenly, and then fed into a graphite clay crucible 11 through a feeding hopper 2; S102: Open the furnace cover 7 and place the graphite clay crucible 11 into the resistance heating furnace 9. The resistance heating furnace 9 is provided with an eccentric rotating device 10, which can be connected to the graphite clay crucible 11 inside the resistance heating furnace 9 to make the graphite clay crucible 11 rotate eccentrically. A sealing ring 8 is provided between the furnace cover 7 and the furnace body for sealing. S103: Turn on the vacuum pump 4 to extract air from the furnace chamber through the vacuum pipe 6 until the vacuum reaches 30 mbar. Then, high-purity argon gas is drawn from the high-purity argon bottle 3 and introduced into the furnace through the air pipe 5 to purge the residual oxygen and nitrogen in the furnace. Ultimately, the argon pressure in the furnace is controlled to be between 60 kPa and 80 kPa, such as 60 kPa, 65 kPa, 70 kPa, 75 kPa, 80 kPa, or any other pressure value in between, to inhibit oxidation and combustion of the magnesium liquid. S104 starts the resistance heating furnace 9, heats the mixed metal to 700±5°C for refining and removing hydrogen, and when the mixed metal is completely melted to obtain a molten alloy liquid, cools it to 610°C to 630°C, such as 610°C, 615°C, 620°C, 625°C or 630°C, or any temperature between any two of the above temperature values; S105 starts the eccentric rotating device 10 to make the graphite clay crucible 11 rotate eccentrically at a rotation speed of 600 r / min. At the same time, the ultrasonic controller 13 is used to turn on the indirect ultrasonic transducer 12 on the wall of the graphite clay crucible to start ultrasonic treatment, applying ultrasound with a frequency of 20 kHz and an ultrasonic power of 2000 W to the molten alloy liquid. The eccentric rotation and ultrasonic treatment are carried out for a total of 3 minutes to avoid the formation of a chilled layer and make the alloy composition uniform. During the eccentric rotation and indirect ultrasonic treatment process, the high-pressure inert gas closed environment in the furnace is vacuumed to reduce bubbles in the slurry, and finally the preparation of AZ91D semi-solid slurry is completed, thereby reducing the porosity defects of subsequent die-casting parts.

[0040] Then prepare AlSi10Mg aluminum alloy slurry, the preparation steps are as follows: S111: High-purity Si (10 wt%), Mg (0.3 wt%), and Al (the rest) are placed in a material preparation machine, mixed, and fed into a graphite clay crucible 11; S112: Place the graphite clay crucible 11 into the resistance heating furnace 9, turn on the vacuum pump 4, and extract air from the furnace chamber through the vacuum pipe 6 until the vacuum degree reaches 30 mbar. S113 introduces high-purity argon gas into the furnace to purge residual oxygen and nitrogen in the furnace, and ultimately controls the argon pressure in the furnace to be between 60 kPa and 80 kPa, such as 62 kPa, 68 kPa, 72 kPa, 78 kPa, 80 kPa, or any pressure value between the above two pressure values, so as to inhibit oxidation of the molten aluminum and prevent inclusion defects in subsequent die castings; S114 starts the resistance heating furnace 9, heats the mixed metal until it is completely melted into an alloy solution, then continues heating to 720° C. to refine and remove hydrogen, then cools it to 630° C. to 640° C., such as 630° C., 635° C., or 640° C., or any temperature between any two of the above values, and then proceeds to the next step; S115 starts the eccentric rotating device 10 to make the graphite clay crucible 11 rotate eccentrically at a rotation speed of 500r / min. At the same time, the indirect ultrasonic transducer 12 on the wall of the graphite clay crucible is started to start ultrasonic treatment, and ultrasound with a frequency of 18kHz and an ultrasonic power of 1800W is applied to the molten alloy liquid. The eccentric rotation and ultrasonic oscillation start and end at the same time, and the treatment time is 5 minutes. Finally, a spherical primary α-Al phase with a diameter of ≤30um is obtained, and the Si phase is evenly dispersed. During the eccentric rotation and indirect ultrasonic treatment process, the high-pressure inert gas closed environment in the furnace is vacuumed to reduce bubbles in the slurry, complete the preparation of the AlSi10Mg aluminum alloy slurry, and thereby reduce the porosity defects of subsequent die-casting parts.

[0041] In step S2, the prepared AZ91D semi-solid slurry cooled to 560°C to 570°C (such as 560°C, 565°C or 570°C) and the AlSi10Mg semi-solid slurry cooled to 610°C to 630°C (such as 610°C, 620°C or 630°C) are respectively transferred into the inert gas pressurized feeding hopper. Figure 3 and 4 The slurry transfer is realized in the second shot chamber 17 and the first shot chamber 15 shown, and the argon gas is protected during the whole transfer process to ensure the stability of the solid phase ratio of the two semi-solid alloy slurries.

[0042] In step S3, if the two semi-solid alloy slurries are injected sequentially, the corrosion-resistant semi-solid alloy slurry is first injected into the corrosion-resistant area of ​​the die-casting mold 14. When the corrosion-resistant semi-solid alloy slurry has completely filled the corrosion-resistant area and is spaced apart from the area filled with the other semi-solid alloy slurry by a predetermined distance, the lightweight semi-solid alloy slurry is injected into the remaining area until the lightweight semi-solid alloy slurry and the corrosion-resistant semi-solid alloy slurry are completely bonded to form a metallurgical-mechanical composite interface, thereby obtaining an integral die-casting. The predetermined distance is at least 8 mm.

[0043] The inner wall of the die casting mold is also coated with a nano ceramic coating, the thickness of the nano ceramic coating is at least 80 μ m , which can prevent the semi-solid alloy slurry from adhering to the inner wall of the mold.

[0044] In this embodiment, the injection speed of the anti-corrosion semi-solid alloy slurry is set to 3m / s~5m / s, such as 3m / s, 3.5m / s, 4m / s, 4.5m / s or 5m / s, or any one of the two injection speeds mentioned above; the injection pressure of the anti-corrosion alloy slurry is set to 40MPa~60MPa, such as 40MPa, 50MPa or 60MPa, or any one of the two injection pressures mentioned above. The injection pressure of the lightweight alloy slurry is set to 50MPa~80MPa, such as 50MPa, 60MPa, 70MPa or 80MPa, or any one of the two injection pressures mentioned above, and the injection speed of the lightweight semi-solid alloy slurry is set to 2m / s~4m / s, such as 2m / s, 3m / s or 4m / s, or any one of the two injection speeds mentioned above, to ensure that the joint surfaces of the two slurries can form a metallurgical-mechanical composite bonding interface under the action of temperature and pressure, thereby eliminating shrinkage defects at the bonding interface.

[0045] like Figure 5 As shown, pouring gate a is a semi-solid aluminum alloy die-casting gate, and pouring gate b is a semi-solid magnesium alloy die-casting gate.

[0046] like Figure 6 As shown in FIG, (a) to (c) are schematic diagrams of the process from the start of injection molding to the end of injection molding. The blank area in the figure is the unfilled area. The semi-solid aluminum alloy is the AlSi10Mg semi-solid slurry, and the semi-solid magnesium alloy is the AZ91D semi-solid slurry.

[0047] Specifically, the injection speed at the pouring gate b on the die-casting mold is set to 4m / s, and the injection pressure is set to 60MPa. The second push rod 18 is used to inject the AZ91D semi-solid slurry in the second injection chamber 17 into the mold cavity, thereby achieving the filling of the rear floor area of ​​the one-piece die-cast rear end body 19, which has low load-bearing requirements and will not come into contact with corrosive liquids.

[0048] Monitor the flow front of the AZ91D semi-solid slurry in real time, such as using a laser ranging method or setting a temperature and pressure sensor to monitor the temperature and pressure changes of the flow front to monitor the flow front of the AZ91D semi-solid slurry. Ensure that the injection switching signal is triggered when the flow front is about 10 mm away from the rear wheel cover boundary A, and switch the pouring end to the pouring gate a for injection of the AlSi10Mg semi-solid slurry.

[0049] The injection speed at gate a was set to 3 m / s, and the injection pressure was set to 80 MPa. The rear wheel arch was rapidly filled through the rib runner. Specifically, the AlSi10Mg semi-solid slurry in the first injection chamber 15 was injected into the rear wheel arch using the first push rod 16 until a mechanical-metallurgical composite interface was formed at interface A between the rear wheel arch (the area requiring corrosion protection) and the rear floor panel (the lightweight area). Because the injection of the AZ91D semi-solid slurry was initiated 10 mm from interface A, the AZ91D semi-solid slurry was prevented from flowing into the rear wheel arch cavity, preventing the AlSi10Mg semi-solid slurry from filling the corrosion-resistant cavity and, in turn, affecting the corrosion resistance of the vehicle body structure.

[0050] During the latter slurry injection process, a laser scanning method is also used to synchronously monitor the temperature of the semi-solid alloy slurries on both sides of the joint interface of the two semi-solid alloy slurries. The temperature difference at the connection between the rear floor and the rear wheel cover is controlled to be less than 10°C through an external temperature control device. The smaller the temperature difference, the more it can promote the diffusion and bonding of dissimilar alloys.

[0051] After injection molding is complete, the rear floor area of ​​the one-piece die-casting (i.e., the area filled with the AZ91D semi-solid slurry) is water-cooled at a rate of approximately 30°C / s. The rear wheel arch (the area filled with the AlSi10Mg semi-solid slurry) is water-cooled to a rate of 10°C / s to reduce thermal stress. Modifying the diameter, flow rate, spacing, and other parameters of the cooling water channels in the mold is well known to those skilled in the art. Once the one-piece die-casting has solidified and the cavity pressure in the die-casting mold has dropped below 5 MPa, the mold is opened and demolded using a servo motor-driven ejector mechanism with a demolding force of ≤200 kN. After demolding, the one-piece die-casting is immediately transferred to an argon-protected chamber to prevent surface oxidation of the magnesium alloy.

[0052] In the above-mentioned step S2, if the method of simultaneously die-casting two semi-solid alloy slurries is adopted, the temperature of the corresponding semi-solid alloy slurry in the area with anti-corrosion requirements is cooled to 565℃~570℃ before die-casting, and the temperature of the corresponding semi-solid alloy slurry in the area without anti-corrosion requirements is cooled to 610℃~620℃ before die-casting. By regulating the solid phase ratio and flow characteristics, the microstructure density (low temperature) is prioritized in the anti-corrosion area, and the forming efficiency (high temperature) is prioritized in the non-anti-corrosion area. At the same time, by zoned temperature control, insufficient filling or uneven structure due to temperature deviation can be avoided.

[0053] In step S3, if the method of simultaneously injecting and die-casting two kinds of semi-solid alloy slurries is adopted, the injection speed of the corresponding semi-solid alloy slurry in the area with anti-corrosion requirements is set to 3m / s~3.5m / s, and the injection pressure is adjusted to 50MPa~60MPa, and the injection speed of the corresponding semi-solid alloy slurry in the area without anti-corrosion requirements is 3.5m / s~4m / s, and the injection pressure is adjusted to 60MPa~70MPa. For areas with anti-corrosion requirements, lower injection speed and pressure help to reduce turbulence and gas entrapment during slurry filling, thereby reducing the risk of pores and shrinkage defects. Higher speed and pressure injection is adopted in areas without anti-corrosion requirements, which can give priority to ensuring filling efficiency and filling integrity of complex structures. If the anti-corrosion area of ​​the die casting is larger, the numerical values ​​of its corresponding injection speed, injection pressure and pouring temperature also increase accordingly.

[0054] Compared to conventional single-metal single-shot single-shot die-casting methods, the semi-solid dual-alloy integrated die-casting method for vehicle body structures provided in this application reduces the molding cycle of the entire die-casting to as little as 95 seconds through the differentiated design of the preparation of different semi-solid alloy slurries and injection process parameters. Conventional single-metal injection molding methods require at least 126 seconds to die-cast the same die-casting. In comparison, the die-casting efficiency provided by this application is improved by 25%. Furthermore, the production process is simplified, multiple assembly and processing steps are reduced, production efficiency and product quality are improved, scrap and defective rates are reduced, and manufacturing costs are lowered.

[0055] The semi-solid dual-alloy integrated die-casting molding system provided by the present application is described below. The semi-solid dual-alloy integrated die-casting molding system described below and the semi-solid dual-alloy integrated die-casting molding method described above can be referred to each other.

[0056] This embodiment provides a system for implementing the aforementioned semi-solid dual alloy integral die-casting method, comprising: The semi-solid alloy slurry preparation module includes: a mixing and melting unit for mixing at least two metals and then heating and melting them to obtain a molten alloy liquid; a solid phase particle growth unit for simultaneously performing eccentric rotation and indirect ultrasonic treatment on the molten alloy liquid in a closed environment of high-pressure inert gas to grow solid phase particles in the molten alloy liquid; and a vacuum unit for vacuuming the closed environment of high-pressure inert gas during the eccentric rotation and indirect ultrasonic treatment process. The semi-solid alloy slurry transfer unit is used to transfer the corrosion-resistant semi-solid alloy slurry and the lightweight semi-solid alloy slurry to the corresponding injection chambers after cooling; The double-shot die-casting module includes a first shot die-casting unit for injection-filling a semi-solid alloy slurry into a corresponding area of ​​the die-casting mold; and a second shot die-casting unit for injection-filling another semi-solid alloy slurry into the remaining filling area.

[0057] It should be understood that expressions such as "include" and "may include" used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "include" and / or "have" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0058] In addition, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0059] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Among them, "fixed connection" means that the two are connected to each other and the relative position relationship after the connection remains unchanged. "Rotational connection" means that the two are connected to each other and can rotate relative to each other after the connection. "Sliding connection" means that the two are connected to each other and can slide relative to each other after the connection. The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only reference to the directions of the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0060] In addition, in the embodiments of the present application, the mathematical concepts mentioned include symmetry, equality, parallelism, and perpendicularity. These limitations are all for the current state of the art, rather than being absolutely strict definitions in a mathematical sense. A small amount of deviation is allowed, and it is possible to be approximately symmetric, approximately equal, approximately parallel, or approximately perpendicular. For example, A and B are parallel, which means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. A and B are perpendicular, which means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0061] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A semi-solid dual alloy integral die casting method, characterized in that: include: S1 prepares two semi-solid alloy slurries using the same method, wherein the preparation method is: mixing at least two metals and then heating and melting them to obtain molten alloy liquid; The molten alloy liquid is subjected to eccentric rotation and indirect ultrasonic treatment for the same duration in a high-pressure inert gas sealed environment, so that the molten alloy liquid generates a vortex to grow solid phase particles, and during the eccentric rotation and indirect ultrasonic treatment, the high-pressure inert gas sealed environment is vacuumed to obtain a corresponding semi-solid alloy slurry; S2 transfers the two semi-solid alloy slurries to corresponding injection chambers after cooling, and the transfer process is carried out in an inert gas environment; S3: sequentially or simultaneously injecting the two semi-solid alloy slurries into corresponding areas of the die casting mold until the two semi-solid alloy slurries merge and form a metallurgical-mechanical composite bonding interface at the joint, thereby obtaining an integrated die casting.

2. A semi-solid dual alloy integral die-casting method according to claim 1, characterized in that: In step S1, the time for eccentric rotation and ultrasonic treatment is 3 min to 5 min, the speed of eccentric rotation is 500 r / min to 600 r / min, and the solid phase ratio of the two semi-solid alloy slurries is 35% to 45%.

3. The semi-solid dual alloy integral die-casting method according to claim 1, characterized in that: In step S1, the pressure of the high-pressure inert gas sealed environment is 60 kPa-80 kPa, and the temperature is 550° C.-750° C.

4. The semi-solid dual alloy integral die-casting method according to claim 1, characterized in that: In step S1, the ultrasonic frequency of the ultrasonic treatment does not exceed 30 kHz, and the ultrasonic power does not exceed 2000w.

5. The semi-solid dual alloy integral die-casting method according to claim 1, characterized in that: In step S3, when injecting sequentially, one semi-solid alloy slurry is first injected into the corresponding area in the die-casting mold, and when the flow front of the first semi-solid alloy slurry is filled to a minimum distance of at least 8 mm from the area to be injected and filled with another semi-solid alloy slurry, injection filling of another semi-solid alloy slurry is started into the remaining filling area.

6. The semi-solid dual alloy integral die casting method according to claim 1, characterized in that: In step S3, when the semi-solid alloy slurry is injected sequentially, the injection speed of the semi-solid alloy slurry injected first is 3m / s~5m / s, the injection pressure of the semi-solid alloy slurry injected first is 40MPa~60MPa, the injection pressure of the semi-solid alloy slurry injected later is 50MPa~80MPa, and the injection speed of the semi-solid alloy slurry injected later is 2m / s~4m / s; when the semi-solid alloy slurry is injected simultaneously, the injection speed of the semi-solid alloy slurry corresponding to the area with anti-corrosion requirements is 3m / s-3.5m / s, and the injection pressure is 50MPa~60MPa, and the injection speed of the semi-solid alloy slurry corresponding to the area without anti-corrosion requirements is 3.5m / s~4m / s, and the injection pressure is 60MPa~70MPa.

7. The semi-solid dual alloy integral die casting method according to claim 1, characterized in that: In step S2, when the injection is performed sequentially, the temperature of the semi-solid alloy slurry injected first is cooled to 610°C~630°C, and the temperature of the semi-solid alloy slurry injected later is cooled to 560°C~570°C; when the injection is performed simultaneously, the temperature of the corresponding semi-solid alloy slurry in the area with anti-corrosion requirements is cooled to 565°C~570°C, and the temperature of the corresponding semi-solid alloy slurry in the area without anti-corrosion requirements is cooled to 610°C~620°C.

8. The semi-solid dual alloy integral die-casting method according to claim 1, characterized in that: In step S3, during the injection process, the temperature difference between the two semi-solid alloy slurries at their confluence is controlled to be no greater than 10°C.

9. The semi-solid dual alloy integral die-casting method according to claim 1, characterized in that: In step S3, the inner wall of the die-casting mold is coated with a nano-ceramic coating; the thickness of the nano-ceramic coating is at least 80 μm .

10. A system for implementing the semi-solid dual alloy integral die-casting method according to any one of claims 1 to 9, characterized in that: include: The semi-solid alloy slurry preparation module includes: a mixing and melting unit for mixing at least two metals and then heating and melting them to obtain a molten alloy liquid; a solid phase particle growth unit for simultaneously performing eccentric rotation and indirect ultrasonic treatment on the molten alloy liquid in a high-pressure inert gas sealed environment for the same length of time, so as to generate eddy currents in the molten alloy liquid and grow solid phase particles; a vacuum unit for vacuuming the high-pressure inert gas sealed environment during the eccentric rotation and indirect ultrasonic treatment process; The semi-solid alloy slurry transfer unit is used to transfer the two semi-solid alloy slurries to the corresponding injection chambers after cooling; The double-shot die-casting module includes a first shot die-casting unit for injection-filling a semi-solid alloy slurry into a corresponding area of ​​the die-casting mold; and also includes a second shot die-casting unit for injection-filling another semi-solid alloy slurry into the corresponding filling area.

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