A semi-solid dual-alloy integrated die-casting forming method and system

Abstract

The application 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 following steps: preparing two kinds of semi-solid alloy slurries respectively: mixing at least two kinds of metals and then heating and melting; filling inert gas to clean residual oxygen in a resistance furnace, and then refining and degassing, so that the molten alloy liquid is subjected to eccentric rotation and indirect ultrasonic treatment with the same length at the same time in the inert gas closed environment to generate eddy current and grow solid phase particles, and at the same time, the high-pressure inert gas closed environment is subjected to vacuum treatment to obtain corresponding semi-solid alloy slurries; after cooling, the two kinds of semi-solid alloy slurries are respectively transferred to corresponding injection chambers in an inert atmosphere; the two kinds of semi-solid alloy slurries are sequentially or simultaneously injected into corresponding regions in a die casting mold, and the two kinds of semi-solid alloy slurries converge and form a metallurgical-mechanical composite bonding interface at the joint. Through the application, the effect of uniform material organization and high injection efficiency of integrated injection castings can be achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of integrated die casting, and more particularly, relates to a semi-solid double-alloy integrated die casting method and system. BACKGROUND

[0002] The current automobile rear-end body integrated die casting technology generally adopts a full-liquid metal and single injection system injection method. This method has the following defects: during the die casting process, the liquid aluminum alloy needs to be maintained at a high temperature of 680 DEG C to 720 DEG C, and the liquid magnesium alloy needs to be maintained at a high temperature of 640 DEG C to 680 DEG C, which causes the mold to bear a large thermal stress, the forming cycle is long, and the product has a high porosity. The semi-solid integrated die casting method can avoid the above problems because the semi-solid metal slurry has a lower temperature, usually 10 DEG C to 20 DEG C below the liquidus, and its cooling speed is 30% to 40% faster than that of the traditional full-liquid metal, thereby significantly reducing the shrinkage and shrinkage rate of the die casting parts. However, the traditional semi-solid alloy integrated die casting method has the following problems: 1) the semi-solid alloy slurry is prone to segregation during the injection forming process, resulting in uneven microstructure and performance; 2) stress concentration problems easily occur in the die casting parts, especially at the corners of complex structures, the stress concentration coefficient can reach 2 to 3 times, significantly reducing the fatigue life of the die casting parts; 3) single metal slurry die casting results in difficult improvement of the performance of the die casting parts, and cannot meet the performance requirements of different parts on the same structure in application scenarios such as automobile body structures. SUMMARY

[0003] In view of the defects of the prior art, the purpose of the present application is to provide a semi-solid double-alloy integrated die casting method and system, which aims to solve the problems of uneven microstructure of the die casting material caused by the segregation of the semi-solid alloy slurry during the injection die casting process and low die casting efficiency.

[0004] To achieve the above-mentioned purpose, in a first aspect, the present application provides a semi-solid double-alloy integrated die casting method, comprising:

[0005] S1, two kinds of semi-solid alloy slurries are prepared by the same method, and the preparation method is as follows: at least two metals are mixed and heated to melt to obtain a molten alloy liquid; the molten alloy liquid is subjected to eccentric rotation and indirect ultrasonic treatment at the same time for the same length in a high-pressure inert gas sealed environment, so that the molten alloy liquid generates eddy current to grow solid particles, and during the eccentric rotation and indirect ultrasonic treatment, the high-pressure inert gas sealed environment is subjected to vacuum treatment to obtain the corresponding semi-solid alloy slurry;

[0006] S2, after cooling, the two kinds of semi-solid alloy slurries are transferred to the corresponding injection chambers respectively, and the transfer process is carried out in an inert gas environment;

[0007] S3 injects the two semi-solid alloy slurries into the corresponding regions in the die casting mold in sequence or simultaneously until the two semi-solid alloy slurries meet and form a metallurgical-mechanical composite bonding interface at the joint, thereby obtaining an integrated die casting.

[0008] Further, in step S1, the time of eccentric rotation and ultrasonic treatment is 3-5 min, the speed of eccentric rotation is 500-600 r / min, and the solid phase rate of the two semi-solid alloy slurries is 35-45%.

[0009] Further, in step S1, the gas pressure in the high-pressure inert gas sealed environment is 60-80 kPa, and the temperature is 550-750℃.

[0010] Further, in step S1, the ultrasonic frequency of the ultrasonic treatment is not more than 30 kHz, and the ultrasonic power is not more than 2000 w.

[0011] Further, in step S3, when injecting in sequence, one semi-solid alloy slurry is first injected and filled into the corresponding region in the die casting mold, and when the flow front of the first semi-solid alloy slurry is filled to a distance of at least 8 mm from the region to be filled with the other semi-solid alloy slurry, the other semi-solid alloy slurry is then injected and filled into the remaining region.

[0012] Further, in step S3, when injecting in sequence, the injection speed of the first injected semi-solid alloy slurry is 3-5 m / s, the injection pressure of the first injected semi-solid alloy slurry is 40-60 MPa, the injection pressure of the second injected semi-solid alloy slurry is 50-80 MPa, and the injection speed of the second injected semi-solid alloy slurry is 2-4 m / s; when injecting simultaneously, the injection speed of the corresponding semi-solid alloy slurry in the region with corrosion resistance requirement is 3-3.5 m / s, and the injection pressure is 50-60 MPa, and the injection speed of the corresponding semi-solid alloy slurry in the region without corrosion resistance requirement is 3.5-4 m / s, and the injection pressure is 60-70 MPa.

[0013] Further, in step S2, when injecting in sequence, the first injected semi-solid alloy slurry is cooled to 610-630℃, and the second injected semi-solid alloy slurry is cooled to 560-570℃; when injecting simultaneously, the temperature of the corresponding semi-solid alloy slurry in the region with corrosion resistance requirement is cooled to 565-570℃, and the temperature of the corresponding semi-solid alloy slurry in the region without corrosion resistance requirement is cooled to 610-620℃.

[0014] Further, in step S3, during the injection process, the temperature difference between the two semi-solid alloy slurries at the meeting point is controlled to be not more than 10℃.

[0015] 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 .

[0016] 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:

[0017] 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;

[0018] The semi-solid alloy slurry transfer unit is used to transfer the two semi-solid alloy slurries to the corresponding injection chambers after cooling;

[0019] 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.

[0020] 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.

[0021] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the existing technologies:

[0022] (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.

[0023] (2) The application sequentially injects different semi-solid alloy slurries into the corresponding regions of the target mold according to a preset order, and 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 castings smaller; the injection order of the application is to first inject one kind of semi-solid alloy slurry to fill the corresponding region, and stop injecting when the distance to the remaining filling region is a preset width, and then start filling another kind of semi-solid alloy slurry into its corresponding filling region until the two kinds of semi-solid alloy slurries converge and form a metallurgical-mechanical composite bonding interface at the junction; the synergistic effect of metallurgical bonding (atomic diffusion) and mechanical interlocking (physical occlusion) between the two slurries significantly improves the interface shear strength, disperses local stress concentration, avoids the problem of easy cracking due to stress concentration after single alloy injection, and at the same time enables the two kinds of semi-solid alloy slurries in the integrated die casting to be accurately formed in the same die casting process, with higher processing efficiency and quality.

[0024] (3) The application controls the relevant process parameters of the semi-solid alloy slurry during the injection process, such as controlling the injection speed and pressure of the corresponding semi-solid alloy slurry within a specific injection speed range and a specific injection pressure range, to eliminate the shrinkage defects at the interface of the two semi-solid alloy slurries through temperature and pressure control, further reduce the occurrence of segregation, and effectively improve the performance strength and durability of the die casting.

[0025] (4) The slurry preparation and transfer process of the application is carried out in a high-pressure inert gas sealed environment, and hydrogen is removed by heating during the melting process of the molten alloy, and vacuum treatment is simultaneously performed during the eccentric rotation and ultrasonic indirect treatment process, thereby avoiding subsequent shrinkage porosity of the die casting; by respectively controlling the rotation rate of eccentric rotation, the relevant parameters of ultrasonic treatment (such as ultrasonic frequency, ultrasonic power), and the time of eccentric rotation and ultrasonic treatment, the solid phase rate of the obtained semi-solid alloy slurry is within the preset range, and the semi-solid alloy slurry with the best flowability is quickly and efficiently obtained; if the solid phase rate exceeds the preset range, the slurry flowability is poor, the subsequent die casting time is longer, and the die casting effect is worse.

[0026] (5) The application uses two kinds of semi-solid alloy slurries and adopts the method of sequentially injecting or simultaneously injecting in two injection chambers to obtain die castings, forming a metallurgical-mechanical composite bonding interface in the mold while retaining the advantages of integrated molding; and controlling the temperature difference between the two semi-solid alloy slurries on both sides of the interface during the injection process to be less than 10℃, so that the mechanical properties of the metallurgical-mechanical composite bonding interface are better, and the shear strength of the interface is improved by 3-5 times compared with traditional connection methods (such as welding connection) through optimization of the slurry preparation process and the injection die casting process; it can also eliminate more than 90% of the welds on automobile body structures and other die castings, making it easier to achieve seamless connection of dissimilar materials.

[0027] (6) The same semi-solid alloy slurry can be used in the application, or two different semi-solid alloy slurries can be used. When two different semi-solid alloy slurries are used, pressure casting parts with different properties in different parts can be obtained. For example, when a pressure casting mold requires an anti-corrosion area and a non-anti-corrosion area, two semi-solid alloy slurries can be simultaneously injected into the corresponding areas. Specifically, an anti-corrosion semi-solid alloy slurry and a lightweight semi-solid alloy slurry can be used to pressure cast a lightweight vehicle body structure with anti-corrosion properties.

[0028] (7) The inner wall of the mold used in the injection process of the application is coated with a nano ceramic coating, and the temperature of the two semi-solid alloy slurries filled into the pressure casting mold is reduced to a preset temperature range, which comprehensively improves the service life of the pressure casting mold compared to the case without coating and using liquid metal, further reducing the pressure casting cost. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a flowchart of a semi-solid dual-alloy integrated pressure casting forming method provided by an embodiment of the application;

[0030] Figure 2 is a schematic diagram of a semi-solid alloy slurry preparation device provided by an embodiment of the application;

[0031] Figure 3 is a schematic diagram of a vehicle body structure pressure casting mold structure provided by an embodiment of the application;

[0032] Figure 4 is a schematic diagram of a side view structure of a vehicle body structure pressure casting mold connected to a second injection chamber provided by an embodiment of the application;

[0033] Figure 5 is a schematic diagram of a side view structure of a vehicle body structure pressure casting mold connected to a first injection chamber provided by an embodiment of the application;

[0034] Figure 6 is a schematic diagram of a semi-solid dual-alloy integrated pressure casting forming process of a vehicle body structure provided by an embodiment of the application.

[0035] In all the drawings, the same reference signs are used to represent the same elements or structures, wherein:

[0036] 1 - material preparation machine; 2 - feeding hopper; 3 - high-purity argon bottle; 4 - vacuum pump; 5 - air pipe; 6 - vacuum extraction pipeline; 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 - pressure casting mold; 15 - first injection chamber; 16 - first push rod; 17 - second injection chamber; 18 - second push rod; 19 - integrated pressure casting rear vehicle body. DETAILED DESCRIPTION

[0037] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in details below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0038] The term "and / or" used herein is a description of an association relationship between associated objects, which means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. The symbol " / " used herein means that the associated objects are or relationships, for example, A / B means A or B.

[0039] The terms "first" and "second" and the like in the description and claims herein are used to distinguish different objects, rather than to describe a specific order of the objects. For example, the first response message and the second response message are used to distinguish different response messages, rather than to describe a specific order of the response messages.

[0040] In the embodiments of the present application, the words such as "exemplary" or "for example" are used to mean serving as an example, illustration, or description. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or having more advantages than other embodiments or design schemes. Rather, the words such as "exemplary" or "for example" are intended to present the relevant concept in a specific manner.

[0041] In the description of the embodiments of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more, for example, a plurality of processing units means two or more processing units, and the like; a plurality of elements means two or more elements, and the like.

[0042] The technical problem to be solved by the present application is to improve the mechanical properties of cast products produced by integrated die casting technology, especially the mechanical and lightweight properties of die castings related to the rear-end vehicle body structure.

[0043] The embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application.

[0044] The present embodiment provides an industrialized die casting vehicle body structure, which uses semi-solid magnesium alloy and semi-solid aluminum alloy to perform integrated die casting forming on the rear-end vehicle structure by a double compression injection method. The method has faster production efficiency and can make the castings have stronger performance.

[0045] Due to the difference in solid-liquid phase flowability of semi-solid alloy, the liquid phase is easy to flow to the edge area away from the pressure center, and a large amount of solid phase is left in the loading center area. The larger the semi-solid alloy, the more likely it is to appear solid-liquid phase segregation.

[0046] Therefore, in the embodiment, first, in the pulping step, the smelting crucible containing the molten alloy is placed in a high-pressure inert gas closed environment for a short time eccentric rotation, so that vortex is generated in the molten alloy, and then the heat of the melt is uniformly distributed and transferred, and the formation and growth of solid phase particles in the melt are promoted, and a semi-solid alloy slurry with a low solid phase rate is obtained; while eccentric rotation, the low solid phase rate alloy slurry is subjected to indirect ultrasonic treatment at the same time as the eccentric rotation, which can prevent the occurrence of the chilling layer, further increase the solid phase rate, and make the structure uniform and refined, and increase the spheroidization degree of the structure.

[0047] Secondly, the semi-solid alloy slurry is pressed from different pressure chambers to the corresponding area in the preset order in the double compression method, which can shorten the alloy flow path, reduce the pressure loss, reduce the solid phase accumulation in the center area, reduce the segregation phenomenon, make the semi-solid alloy slurry fill the corresponding cavity more uniformly, and improve the compression quality compared with the single compression chamber.

[0048] In addition, the semi-solid alloy slurry of the double compression chamber can use the same semi-solid alloy slurry, or two different semi-solid alloy slurries. For the integrated pressure casting forming of the rear-end body structure, different semi-solid alloy slurries can make different parts of the body structure have different properties. For example, a semi-solid aluminum alloy with corrosion resistance can be used to form the wheel cover part which is often in contact with water and sand, and a lightweight magnesium alloy can be used to form the rear floor part which has low load bearing requirements and does not contact water and sand, so that the solid-liquid phase segregation phenomenon of the semi-solid alloy in the pressure casting process can be avoided, and the corrosion resistance and lightweight performance of the pressure casting part can be improved.

[0049] The embodiment provides a semi-solid double-alloy integrated pressure casting forming method, which adopts different kinds of semi-solid alloy slurries to pressure cast a body structure, such as Figure 1 As shown in the figure, the specific steps include:

[0050] S1, respectively preparing a corrosion-resistant semi-solid alloy slurry and a lightweight semi-solid alloy slurry, the preparation method being: mixing at least two metals, heating and melting to obtain a molten alloy liquid; simultaneously performing eccentric rotation and indirect ultrasonic treatment on the molten alloy liquid in a high-pressure inert gas closed environment for the same length of time, so that vortex is generated in the molten alloy liquid to grow solid phase particles, and during the eccentric rotation and indirect ultrasonic treatment, the high-pressure inert gas closed environment is simultaneously subjected to vacuumizing treatment, thereby obtaining the corresponding semi-solid alloy slurry;

[0051] S2, after cooling, the corrosion-resistant semi-solid alloy slurry and the lightweight semi-solid alloy slurry are respectively transferred to the corresponding compression chamber, and the transfer process is carried out in an inert gas environment;

[0052] S3 injects the two semi-solid alloy slurries into the corresponding regions in the die casting mold 14 in sequence or simultaneously until the two semi-solid alloy slurries meet and form a metallurgical-mechanical composite bonding interface at the joint, thereby obtaining an integrated die casting; specifically, the metallurgical-mechanical composite bonding interface refers to the joint interface of the two semi-solid alloy slurries under the combined action of mechanical bonding and metallurgical bonding, the two slurries realize metallurgical bonding through atomic diffusion, and mechanical interlocking through physical engagement of the two slurries, the synergistic effect of metallurgical bonding and mechanical interlocking significantly improves the interface shear strength, and disperses local stress concentration, avoiding the problem of easy cracking due to stress concentration after single alloy injection.

[0053] First, according to the shape, size and technical requirements of the rear-end body product, the reinforcing rib at the rear wheel cover of the body is used as a runner, which is more convenient for die casting of the rear wheel cover at the rear-end body. The rear floor surface is selected as the mold parting surface to facilitate product demolding. The surface of the cavity is sprayed with 80 μm A thick nano-ceramic coating prevents the semi-solid alloy slurry from adhering to the die casting mold.

[0054] The present embodiment does not have special restrictions on the corrosion-resistant semi-solid alloy slurry and the lightweight semi-solid alloy slurry composition. The lightweight semi-solid alloy slurry is selected from magnesium alloy, specifically AZ91D, and the alloy composition is 9% Al, 1% Zn, 0.15% Mn, and the balance is Mg.

[0055] In step S1, the eccentric rotation and ultrasonic treatment start and end at the same time, and the treatment time is 3-5 minutes, the eccentric rotation speed is 500-600 r / min, and the solid phase rate of the corrosion-resistant semi-solid alloy slurry and the lightweight semi-solid alloy slurry is 35-45%.

[0056] Specifically, first prepare the magnesium alloy AZ91D semi-solid slurry, and the preparation steps are:

[0057] S101 as Figure 2 shown, high-purity aluminum (9wt%), zinc (1wt%), and magnesium (the balance) metals are mixed uniformly in the material preparation machine 1 and then sent to the graphite clay crucible 11 in the feeding hopper 2;

[0058] S102 open the furnace cover 7, and send the graphite clay crucible 11 into the electric resistance furnace 9, which is provided with an eccentric rotating device 10 that can be connected to the graphite clay crucible 11 inside, so that the graphite clay crucible 11 rotates eccentrically, and a sealing ring 8 is provided between the furnace cover 7 and the furnace body for sealing;

[0059] S103 open the vacuum pump 4 through the extraction of air in the furnace cavity, until the vacuum degree reaches 30 mbar. Then from the high purity argon cylinder 3 extraction of high purity argon through the gas pipe 5 into the furnace, to clean the residual oxygen and nitrogen in the furnace, the final furnace argon pressure control in 60 kPa~80 kPa, such as 60 kPa, 65 kPa, 70 kPa, 75 kPa, 80 kPa, or any one of the two pressure values between the above, to inhibit magnesium liquid oxidation combustion;

[0060] S104 open the resistance heating furnace 9, the mixed metal is heated to 700±5℃ refining and remove hydrogen, when the mixed metal completely melted to obtain the molten alloy liquid, it is cooled to 610℃~630℃, such as 610℃, 615℃, 620℃, 625℃ or 630℃, or any one of the two temperature values between the above;

[0061] S105 start eccentric rotating device 10 makes graphite clay crucible 11 eccentric rotation, the rotation speed is 600 r / min, at the same time with ultrasonic controller 13 open graphite clay crucible wall on the indirect ultrasonic transducer 12 start ultrasonic treatment, to the molten alloy liquid is applied to 20 kHz frequency, ultrasonic power is 2000 W ultrasonic, eccentric rotation and ultrasonic treatment for a total of 3 min, avoid the emergence of the cold layer and make the alloy composition uniform; in the process of eccentric rotation and indirect ultrasonic treatment, the high pressure inert gas in the furnace is extracted to reduce the bubbles in the slurry, and finally the preparation of AZ91D semi solid slurry is completed, and the subsequent pressure casting gas hole defect is less.

[0062] Again, the preparation of AlSi10Mg aluminum alloy slurry, the preparation steps are:

[0063] S111 high purity Si (10wt%), Mg (0.3wt%), Al (the rest) metal is placed in the material machine mixing and sent into graphite clay crucible 11;

[0064] S112 graphite clay crucible 11 is sent into the resistance heating furnace 9, open the vacuum pump 4 through the extraction of air in the furnace cavity, until the vacuum degree reaches 30 mbar;

[0065] S113 to the furnace into the high purity argon cleaning furnace residual oxygen and nitrogen, the final furnace argon pressure control in 60 kPa~80 kPa, such as 62 kPa, 68 kPa, 72 kPa, 78 kPa, 80 kPa, or any one of the two pressure values between the above, to inhibit the aluminum liquid oxidation, prevent the subsequent pressure casting inclusions defects;

[0066] S114 starts the resistance heating furnace 9 to heat the mixed metal to melt into alloy solution, and then continues to heat to 720℃ to remove hydrogen, and then cools to 630℃-640℃, such as 630℃, 635℃ or 640℃, or any temperature between any two of the above temperatures, and then the next step is performed;

[0067] S115 starts the eccentric rotating device 10 to make the graphite clay crucible 11 rotate eccentrically at a speed of 500r / min, and starts the indirect ultrasonic transducer 12 on the wall of the graphite clay crucible to start ultrasonic treatment, and applies 18kHz frequency ultrasonic waves with a power of 1800W to the molten alloy liquid. The eccentric rotation and ultrasonic treatment start and end at the same time, and the treatment time is 5min. Finally, the spherical primary α-Al phase with a diameter of ≤30um is obtained, and the Si phase is uniformly dispersed. During the eccentric rotation and indirect ultrasonic treatment, the high-pressure inert gas in the furnace is vacuumized to reduce the bubbles in the slurry, and the preparation of the AlSi10Mg aluminum alloy slurry is completed, thereby reducing the porosity defects of the subsequent die casting.

[0068] In step S2, the prepared AZ91D semi-solid slurry cooled to 560℃-570℃ (such as 560℃, 565℃ or 570℃) and the AlSi10Mg semi-solid slurry cooled to 610℃-630℃ (such as 610℃, 620℃ or 630℃) are transferred into the second injection chamber 17 and the first injection chamber 15 as shown in Figure 3 and 4 to achieve slurry transfer, and the whole transfer process is protected by argon to ensure the stability of the solid phase rate of the two kinds of semi-solid alloy slurries.

[0069] In step S3, if the two kinds of semi-solid alloy slurries are injected in sequence, the corrosion-resistant semi-solid alloy slurry is first injected and filled into the corrosion-resistant area in the die casting mold 14, and when the corrosion-resistant semi-solid alloy slurry is filled in the corrosion-resistant area and the distance between the corrosion-resistant semi-solid alloy slurry and the filling area of the other semi-solid alloy slurry reaches the preset interval, the lightweight semi-solid alloy slurry is injected and filled into the remaining filling area, until the lightweight semi-solid alloy slurry and the corrosion-resistant semi-solid alloy slurry are completely joined to form a metallurgical-mechanical composite bonding interface, thereby obtaining an integrated die casting. The aforementioned preset interval is at least 8mm.

[0070] The inner wall of the aforementioned die casting mold is also coated with a nano ceramic coating, and the thickness of the nano ceramic coating is at least 80 μ m This can prevent the semi-solid alloy slurry from adhering to the inner wall of the mold.

[0071] In this embodiment, the injection speed of the corrosion-resistant semi-solid alloy slurry is set to 3 m / s to 5 m / s, such as 3 m / s, 3.5 m / s, 4 m / s, 4.5 m / s, or 5 m / s, or any one of the two injection speeds; the injection pressure of the corrosion-resistant alloy slurry is set to 40 MPa to 60 MPa, such as 40 MPa, 50 MPa, or 60 MPa, or any one of the two injection pressures. The injection pressure of the lightweight alloy slurry is set to 50 MPa to 80 MPa, such as 50 MPa, 60 MPa, 70 MPa, or 80 MPa, or any one of the two injection pressures, and the injection speed of the lightweight semi-solid alloy slurry is set to 2 m / s to 4 m / s, such as 2 m / s, 3 m / s, or 4 m / s, or any one of the two injection speeds, to ensure that the bonding surface of the two slurries can form a metallurgical-mechanical composite bonding interface under the action of temperature and pressure, and eliminate the shrinkage defects of the bonding interface.

[0072] As shown in Figure 5 The pouring gate a is a semi-solid aluminum alloy pressure casting gate, and the pouring gate b is a semi-solid magnesium alloy pressure casting gate.

[0073] As shown in Figure 6 From (a) to (c) are process diagrams from the start of injection to the end of injection, and the blank area is the unfilled area. The semi-solid aluminum alloy is AlSi10Mg semi-solid slurry, and the semi-solid magnesium alloy is AZ91D semi-solid slurry.

[0074] Specifically, the injection speed at the pouring gate b on the pressure casting mold is set to 4 m / s, and the injection pressure is set to 60 MPa. The second push rod 18 is used to inject and fill the AZ91D semi-solid slurry in the second injection chamber 17 from here into the mold cavity, realizing the filling of the rear floor area of the rear-end vehicle body 19 which has low load-bearing requirements and does not contact corrosive liquid.

[0075] The flow front of the AZ91D semi-solid slurry is monitored in real time, such as using a laser ranging method or a method of setting temperature and pressure sensors to monitor the temperature and pressure changes of the flow front to monitor the flow front of the AZ91D semi-solid slurry, to ensure that the flow front is triggered to switch the injection signal when it is about 10 mm away from the rear wheel cover boundary A, and the pouring end is switched to the pouring gate a for the injection of the AlSi10Mg semi-solid slurry.

[0076] The injection speed at the sprue a is set to 3 m / s, the injection pressure is set to 80 MPa, and the rear wheel cover is quickly filled through the reinforcing rib runner, that is, the AlSi10Mg semi-solid slurry in the first injection chamber 15 is injected and filled into the rear wheel cover by the first push rod 16 until a mechanical-metallurgical composite interface is formed at the interface A of the rear wheel cover (corrosion prevention area) and the rear floor of the vehicle body (lightweight area). Since the AlSi10Mg semi-solid slurry injection is started at a position 10 mm away from the interface A, the AZ91D semi-solid slurry is prevented from flowing into the rear wheel cover cavity, which affects the filling of the AlSi10Mg semi-solid slurry in the corrosion prevention cavity, and further affects the corrosion prevention performance of the vehicle body structure.

[0077] In the latter semi-solid slurry injection process, a laser scanning method is also used to synchronously monitor the temperature of the semi-solid alloy slurry on both sides of the interface between the two semi-solid alloy slurries. An external temperature control device is used to control the temperature difference at the connection between the rear floor and the rear wheel cover to be less than 10°C. The smaller the temperature difference, the better the diffusion bonding of the dissimilar alloys.

[0078] After the injection and filling are completed, the rear floor area of the integrated die casting (that is, the AZ91D semi-solid slurry filling area) is water-cooled at a rate of about 30°C / s; and the rear wheel cover (AlSi10Mg semi-solid slurry filling area) is water-cooled at a rate of 10°C / s by modifying the diameter, flow rate, spacing, and other related parameters of the cooling water path in the mold to reduce thermal stress. It should be understood that those skilled in the art know how to modify the diameter, flow rate, spacing, and other related parameters of the cooling water path in the mold. When the integrated die casting is solidified and the cavity pressure in the die casting mold is reduced to below 5 MPa, the mold is opened, and a servo motor driven ejection mechanism is used for demolding, and the demolding force of the ejection mechanism is ≤200 kN. After demolding, the integrated die casting is immediately transferred to an argon protection room to avoid oxidation of the magnesium alloy surface.

[0079] In the foregoing step S2, if the method of simultaneously injecting and die casting two semi-solid alloy slurries is used, the temperature of the corresponding semi-solid alloy slurry in the corrosion prevention area is lowered to 565°C-570°C before injection, and the temperature of the corresponding semi-solid alloy slurry in the non-corrosion prevention area is lowered to 610°C-620°C before injection. By adjusting the solid phase rate and flow characteristics, the microstructure density is preferentially ensured in the corrosion prevention area (low temperature), and the forming efficiency is preferentially ensured in the non-corrosion prevention area (high temperature). At the same time, by controlling the temperature in different areas, the temperature deviation is avoided to cause underfilling or uneven organization.

[0080] In step S3, if the method of simultaneously injecting and pressure casting two kinds of semi-solid alloy slurries is adopted, the injection speed of the semi-solid alloy slurry in the region with anticorrosion requirement is set to 3 m / s-3.5 m / s, and the injection pressure is adjusted to 50 MPa-60 MPa; the injection speed of the semi-solid alloy slurry in the region without anticorrosion requirement is set to 3.5 m / s-4 m / s, and the injection pressure is adjusted to 60 MPa-70 MPa. For the region with anticorrosion requirement, the lower injection speed and pressure help to reduce the turbulence and gas entrainment when the slurry fills the mold, thereby reducing the risk of porosity and shrinkage defects. The region without anticorrosion requirement is injected at a higher speed and pressure, which can preferentially ensure the filling efficiency and the filling integrity of complex structures. If the anticorrosion region of the pressure casting part is larger, the corresponding injection speed, injection pressure and pouring temperature values also increase accordingly.

[0081] Compared with the conventional single metal single injection integrated pressure casting method, the semi-solid dual-alloy integrated pressure casting forming method for the vehicle body structure provided by the embodiment of the present application can shorten the forming cycle of the entire pressure casting part to 95 seconds through the differential design of the preparation and injection process parameters of different semi-solid alloy slurries. The conventional single metal injection forming method needs at least 126 seconds to pressure cast the same pressure casting part. In comparison, the pressure casting efficiency provided by the present application is improved by 25%. At the same time, the production process is simple, the multiple assembly and processing are reduced, the production efficiency and product quality are improved, the waste rate and substandard rate are reduced, and the manufacturing cost is reduced.

[0082] The semi-solid dual-alloy integrated pressure casting forming system provided by the present application is described below. The semi-solid dual-alloy integrated pressure casting forming system described below can be mutually corresponding to the semi-solid dual-alloy integrated pressure casting forming method described above.

[0083] The embodiment provides a system for implementing the semi-solid dual-alloy integrated pressure casting forming method as described above, comprising:

[0084] The semi-solid alloy slurry preparation module comprises a mixed melting unit for mixing and melting at least two metals 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 to grow solid phase particles in the molten alloy liquid; and a vacuum extraction unit for vacuum extraction treatment on the high-pressure inert gas sealed environment during the eccentric rotation and indirect ultrasonic treatment.

[0085] The semi-solid alloy slurry transfer unit is used for cooling the anticorrosion semi-solid alloy slurry and the lightweight semi-solid alloy slurry and then transferring them into corresponding injection chambers, respectively.

[0086] A dual shot die casting module includes a first shot die casting unit for shot filling a corresponding area of a die casting mold with one kind of semi-solid alloy slurry; and a second shot die casting unit for shot filling a remaining filling area with another kind of semi-solid alloy slurry.

[0087] It is to be understood that the terms such as "include", "may include", "including", and "may including" used in the present application indicate the presence of the disclosed functions, operations, or components, and do not limit one or more additional functions, operations, and components. In the present application, terms such as "include" and / or "have" can be interpreted as indicating the presence of a specific characteristic, number, operation, component, element, or combination thereof, but can not be interpreted as excluding the presence or addition of one or more other characteristics, numbers, operations, components, elements, or combinations thereof.

[0088] In addition, in the present application, the expression "and / or" includes any and all combinations of the associated listed terms. For example, the expression "A and / or B" can include A, can include B, or can include both A and B.

[0089] In the description of the embodiments of the present application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be understood broadly, for example, "connection" can be detachable connection, or can be non-detachable connection; can be direct connection, or can be indirect connection through an intermediate medium. Among them, "fixed connection" means that the relative positional relationship after connection is unchanged. "Rotational connection" means that the relative rotation after connection is connected. "Sliding connection" means that the relative sliding after connection is connected. The orientation language mentioned in the embodiments of the present application, such as "top", "bottom", "inner", "outer", "left", "right", etc., is only the direction of the drawing, therefore, the orientation language used is to better, more clearly illustrate and understand the embodiments of the present application, and is not to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the embodiments of the present application.

[0090] In addition, in the embodiments of the present application, the mathematical concepts mentioned, symmetry, equality, parallel, perpendicular, etc. These limitations are all for the current process level, and are not absolutely strict definitions in the mathematical sense, allowing a small amount of deviation, approximately symmetrical, approximately equal, approximately parallel, approximately perpendicular, etc. can be. For example, A is parallel to B, which means that A and B are parallel or approximately parallel, the included angle between A and B can be between 0 degrees and 10 degrees. A and B are perpendicular, which means that A and B are perpendicular or approximately perpendicular, the included angle between A and B can be between 80 degrees and 100 degrees.

[0091] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A semi-solid dual-alloy integrated die-casting molding method, characterized by, Comprising: S1 two kinds of semi-solid alloy slurries are prepared by the same method, the preparation method is: at least two metals are mixed and heated to melt, and a molten alloy liquid is obtained; The molten alloy liquid is subjected to eccentric rotation and indirect ultrasonic treatment for the same length of time in a high-pressure inert gas closed environment, so that the molten alloy liquid generates eddy current to grow solid phase particles, and the high-pressure inert gas closed environment is subjected to vacuum treatment during the eccentric rotation and indirect ultrasonic treatment, thereby obtaining the corresponding semi-solid alloy slurry; S2 the two kinds of semi-solid alloy slurries are transferred to the corresponding injection chambers after cooling, and the transfer process is carried out in an inert gas environment; wherein, when the semi-solid alloy slurries are injected in sequence, the semi-solid alloy slurry injected first is cooled to 610-630 DEG C, and the semi-solid alloy slurry injected later is cooled to 560-570 DEG C; when the semi-solid alloy slurries are injected simultaneously, the temperature of the corresponding semi-solid alloy slurry in the region with corrosion resistance requirement is cooled to 565-570 DEG C, and the temperature of the corresponding semi-solid alloy slurry in the region without corrosion resistance requirement is cooled to 610-620 DEG C; S3 the two kinds of semi-solid alloy slurries are injected into the corresponding regions in the die casting mold in sequence or simultaneously: When the semi-solid alloy slurries are injected in sequence, one kind of semi-solid alloy slurry is first injected and filled into the corresponding region in the die casting mold, and when the flow front of the first semi-solid alloy slurry is filled to a distance of at least 8 mm from the region to be filled with the other semi-solid alloy slurry, the other semi-solid alloy slurry is then injected and filled into the remaining region; the injection speed of the semi-solid alloy slurry injected first is 3-5 m / s, and the injection pressure is 40-60 MPa; the injection pressure of the semi-solid alloy slurry injected later is 50-80 MPa, and the injection speed is 2-4 m / s; When the semi-solid alloy slurries are injected simultaneously, the injection speed of the corresponding semi-solid alloy slurry in the region with corrosion resistance requirement is 3-3.5 m / s, and the injection pressure is 50-60 MPa; the injection speed of the corresponding semi-solid alloy slurry in the region without corrosion resistance requirement is 3.5-4 m / s, and the injection pressure is 60-70 MPa; until the two kinds of semi-solid alloy slurries converge and form a metallurgical-mechanical composite bonding interface at the joint, thereby obtaining an integrated die casting.

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

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

4. The semi-solid dual alloy integrated die-casting forming method according to claim 1, characterized in that, In step S1, the ultrasonic frequency of the ultrasonic treatment is not more than 30 kHz, and the ultrasonic power is not more than 2000 w.

5. The semi-solid dual alloy integrated die-casting forming method according to claim 1, wherein, In step S3, during the injection process, the temperature difference of the two kinds of semi-solid alloy slurries at the convergence point is not more than 10 DEG C.

6. The semi-solid dual alloy integrated die-casting forming method according to claim 1, wherein, 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 .

7. A system for implementing the semi-solid dual-alloy integrated die-casting molding method according to any one of claims 1 to 6, characterized in that, Comprising: The semi-solid alloy slurry preparation module comprises a mixed melting unit for mixing and heating at least two metals to obtain a molten alloy liquid; a solid phase particle growth unit for synchronously performing eccentric rotation and indirect ultrasonic treatment of the molten alloy liquid for the same length of time in a high-pressure inert gas closed environment, so that eddy current is generated in the molten alloy liquid and solid phase particles are grown; and a vacuum extraction unit for vacuum extraction treatment of the high-pressure inert gas closed environment during the eccentric rotation and indirect ultrasonic treatment. The semi-solid alloy slurry transfer unit is used for transferring two kinds of semi-solid alloy slurries after cooling to corresponding injection chambers. The double-injection die-casting module comprises a first injection die-casting unit for injecting and filling one kind of semi-solid alloy slurry into a corresponding area of a die-casting mold; and a second injection die-casting unit for injecting and filling another kind of semi-solid alloy slurry into a corresponding filling area.

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