Heat-treatable die-casting alloy, preparation method thereof, and die-casting part

Abstract

The present invention provides a heat - treat - free die - casting alloy, its preparation method and die - castings. The heat - treat - free die - casting alloy comprises the following components by mass percentage: Si 6 - 9.5%, Mn 0.35 - 0.65%, Fe 0.06 - 0.15%, Mg 0.09 - 0.25%, Sr 0.01 - 0.028%, high - temperature stable phase elements 0.05 - 0.25%, and the balance is Al and inevitable impurity elements, and the total amount of inevitable impurity elements ≤0.3%. The high - temperature stable phase elements are at least one of Cr, V, Co and Mo. The heat - treat - free die - casting alloy provided by this application, through alloy composition design, has a smaller pre - crystallization structure and a smaller volume fraction, so that the die - castings prepared from this alloy have excellent mechanical properties and uniform properties in different parts, and can effectively meet the service performance of integrated die - castings.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and in particular, to a heat-treatment-free die-casting alloy, a preparation method thereof, and a die-casting part. Background Art

[0002] In recent years, with the rapid development of die-casting equipment and process technologies, automotive load-bearing structural parts prepared by high-vacuum die-casting have become an important way for new energy vehicles to achieve lightweighting. At present, AlSiMnMg-based alloys are generally used in aluminum alloy die-casting structural parts in combination with heat treatment to achieve the strengthening and toughening of parts. Heat treatment usually causes deformation of thin-wall structural parts and an increase in cost. In order to improve the yield rate of thin-wall structural parts and reduce costs, using heat-treatment-free high-strength and tough aluminum alloys to prepare thin-wall structural parts is an important development direction. This requires that heat-treatment-free aluminum alloys not only have comprehensive mechanical properties such as high yield strength, high toughness, and high fatigue strength, but also have excellent casting fluidity, dimensional stability, and specific stiffness. According to their material characteristics, heat-treatment-free aluminum alloy die-casting structural parts are easily connected to other parts through bonding and self-piercing, significantly reducing the part weight compared to steel parts, and improving the mileage and handling performance of new energy vehicles. As the integration level of new energy vehicle structural parts is getting higher and higher, heat-treatment-free die-casting aluminum alloy materials have become the only choice.

[0003] In recent years, the development and breakthrough of large-tonnage (clamping force) die-casting machines and high-vacuum die-casting technologies have come at the right time, bringing a rare historical opportunity for the development of large-scale, integrated, and integrated structural die-castings. For the new energy vehicle manufacturing industry, the application of large-scale integrated die-casting structural parts will greatly promote its lightweight development, improve the overall strength of the vehicle body at the same time, and can more conveniently achieve weight reduction design and shape design, reduce the design difficulty, and significantly shorten the design cycle and production cycle of the whole vehicle, making the benefits brought by the lightweight of the new energy vehicle industry reach a higher level. Against the background of automotive lightweighting, the integrated design and integrated aluminum alloy die-casting forming of load-bearing body structural parts have become the focus of the lightweight technology layout of each automobile manufacturer, and the development of heat-treatment-free aluminum alloy materials suitable for large-scale and thin-wall die-castings has become the research focus of integrated aluminum alloy die-casting materials.

[0004] However, during the high-pressure die-casting process, after the melt enters the shot sleeve through the gating system, there is heat exchange between the alloy liquid and the shot sleeve wall during the residence process of the alloy liquid in the shot sleeve and the slow injection process. The α-Al phase in the melt near the inner wall of the shot sleeve nucleates and even grows in advance. During the subsequent fast injection filling process, some of the pre-crystallized structures are broken and redissolved by the shear force of the melt during the high-speed jet. Under the action of the rheological force, the undissolved pre-crystallized structures will segregate towards the center of the test bar and grow during the subsequent rapid solidification process, forming relatively thick dendritic α-Al phases. There are more pre-crystallized structures in the near-gate and wall-thickness center parts of the die-cast parts formed. The existence of this kind of structure is not conducive to the uniformity of the die-cast part structure, thereby reducing the overall mechanical properties of the die-cast part, especially more obvious in the heat-treatment-free aluminum alloy die-cast parts whose alloy mechanical properties cannot be improved by heat treatment.

[0005] With the increasing size, complexity, and lightweight requirements of integrated die-cast load-bearing parts, there is an urgent need to develop a die-cast part with small pre-crystallized structure size, good uniformity, and excellent mechanical properties. Summary of the Invention

[0006] The main object of the present invention is to provide a heat-treatment-free die-casting alloy, its preparation method and die-cast part, so as to solve the problems in the prior art that there are more pre-crystallized structures in the die-cast part, there are relatively thick dendritic α-Al phases, resulting in poor uniformity of the die-cast part structure and poor mechanical properties, and the service performance of the integrated die-cast part cannot be satisfied.

[0007] To achieve the above object, according to one aspect of the present invention, there is provided a heat-treatment-free die-casting alloy, which comprises the following components by mass percentage: Si 6-9.5%, Mn 0.35-0.65%, Fe 0.06-0.15%, Mg 0.09-0.25%, Sr 0.01-0.028%, high-temperature stable phase elements 0.05-0.25%, and the rest are Al and inevitable impurity elements; the content of a single element in the inevitable impurity elements ≤0.05%, the total amount of the inevitable impurity elements ≤0.3%, and the high-temperature stable phase elements are at least one of Cr, V, Co, and Mo.

[0008] Furthermore, the average value of the pre-crystallized structure size of the die-casting alloy is 25-45 μm, the maximum size is 40-64 μm, and the volume fraction is 1-4%.

[0009] Furthermore, the volume fraction of the high-temperature stable phase elements is 0.05-0.18%.

[0010] Furthermore, the liquidus temperature of the die-casting alloy is T1 and the solidus temperature is T2, wherein, T1 ≤ 625°C, T2 ≥ 565°C, and T1 - T2 ≤ 50°C.

[0011] To achieve the above object, according to another aspect of the present invention, a method for preparing a die-casting alloy is provided. The preparation method includes the following steps: Step S1, melting alloy raw materials into a to-be-treated alloy liquid, subjecting the to-be-treated alloy liquid to modification, degassing and slag removal to obtain a pre-die-casting alloy liquid, wherein the operating temperatures of modification, degassing and slag removal are not lower than the melting temperature, and the temperature of the pre-die-casting alloy liquid is 685 - 750 °C, preferably 710 - 720 °C; Step S2, transporting the pre-die-casting alloy to a die-casting machine for die-casting to obtain a die-casting alloy, and the temperature of the die-casting alloy is T3, T3 - T1 = 74 - 110 °C; wherein, the low speed of the die-casting punch is 0.15 - 0.2 m / s, and the high speed is 2 - 5 m / s.

[0012] Further, degassing includes: introducing an inert gas with a pressure of 0.18 - 0.25 MPa into the raw material alloy liquid; wherein, the inert gas is preferably high-purity nitrogen with a pressure of 5 N or more.

[0013] Further, slag removal includes: adding a slag removal agent to the raw material alloy liquid, and the mass of the slag removal agent is 0.1 - 0.3% of the total mass of the raw material alloy liquid. Preferably, the slag removal agent is a sodium-free refining agent.

[0014] Further, in Step S2, the temperature of the pre-die-casting alloy liquid entering the die-casting machine is T4, T4 - T1 = 5 - 10 °C; and / or, during the transportation of the pre-die-casting alloy liquid to the die-casting machine, the temperature reduction of the pre-die-casting alloy liquid does not exceed 20 °C.

[0015] Further, in Step S2, the pressure casting is vacuum die-casting, and the cavity vacuum degree of the vacuum die-casting is 90 - 95 Pa; and / or, during the vacuum die-casting process, the temperature of the mold is 150 - 250 °C.

[0016] Further, in Step S2, the low speed of the die-casting punch is 0.18 - 0.25 m / s, and the high speed is 2 - 4 m / s.

[0017] According to another aspect of the present invention, a die-casting part is provided, and the material of the die-casting part is any one of the die-casting alloys provided in the above first aspect or the die-casting alloy obtained by any one of the preparation methods provided in the above second aspect.

[0018] The heat-treatment-free die-casting alloy provided in this application has a smaller pre-crystalline structure and a smaller volume fraction through alloy composition design. Furthermore, the die-casting parts prepared from this alloy have excellent mechanical properties, and the properties of different parts are uniform, which can effectively meet the service performance of integrated die-casting parts, having significant technical significance and broad application prospects. Description of the Drawings

[0019] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0020] Figure 1 It is the micrograph of the metallographic structure of the aluminum alloy die-casting part in Embodiment 1 of this application;

[0021] Figure 2 It is the micrograph of the metallographic structure of the aluminum alloy die-casting part in Embodiment 2 of this application;

[0022] Figure 3 It is the micrograph of the metallographic structure of the aluminum alloy die-casting part in Embodiment 3 of this application;

[0023] Figure 4 It is the micrograph of the metallographic structure of the aluminum alloy die-casting part in Embodiment 4 of this application;

[0024] Figure 5 It is the micrograph of the metallographic structure of the aluminum alloy die-casting part in Embodiment 5 of this application;

[0025] Figure 6 It is the micrograph of the metallographic structure of the aluminum alloy die-casting part in Embodiment 6 of this application;

[0026] Figure 7 It is the micrograph of the metallographic structure of the aluminum alloy die-casting part in Embodiment 7 of this application;

[0027] Figure 8 It is the micrograph of the metallographic structure of the aluminum alloy die-casting part in Comparative Example 1 of this application;

[0028] Figure 9 It is the micrograph of the metallographic structure of the aluminum alloy die-casting part in Comparative Example 2 of this application;

[0029] Figure 10 It is the micrograph of the metallographic structure of the aluminum alloy die-casting part in Comparative Example 3 of this application;

[0030] Figure 11 It is the micrograph of the metallographic structure of the aluminum alloy die-casting part in Comparative Example 4 of this application;

[0031] Figure 12 It is the micrograph of the metallographic structure of the aluminum alloy die-casting part in Comparative Example 5 of this application. Detailed implementation manners

[0032] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0033] As analyzed in the background art of this application, in the prior art, there are many pre-crystallized structures in die-castings, with relatively thick dendritic α-Al phases, which is not conducive to the uniformity of the die-casting structure, resulting in poor overall mechanical properties of the die-casting. With the increase in the size, complexity, and lightweight requirements of integrated die-cast load-bearing parts, due to die-casting characteristics, the forming qualification rate of the load-bearing parts decreases, and the non-uniformity of service performance increases.

[0034] Currently, the control of pre-crystallization mainly focuses on die design. For example, CN 110216263 B designs a runner for crushing and collecting pre-crystallized structures in the shot chamber, reducing the thick pre-crystallized structures in the casting, but does not mention the die-casting alloy itself and die-casting process. Since die-casting aluminum alloys have significant differences in the precipitation sequence, types, and sizes of primary phases in the structure as the temperature decreases based on different chemical compositions, and the formation and growth rates of pre-crystallized structures are closely related to the actual temperature of the alloy liquid, how to control the pre-crystallized size and volume fraction in Al-Si-Mn heat-treatable die-casting alloys has become an urgent problem to be solved in this field. To solve this problem, this application provides a heat-treatable die-casting alloy, its preparation method, and die-castings.

[0035] In the first typical embodiment of this application, a heat-treatable die-casting alloy is provided. The die-casting alloy includes the following components by mass percentage: Si 6 - 9.5%, Mn 0.35 - 0.65%, Fe 0.06 - 0.15%, Mg 0.09 - 0.25%, Sr 0.01 - 0.028%, high-temperature stable phase elements 0.05 - 0.25%, and the balance is Al and inevitable impurity elements; the content of each individual element in the inevitable impurity elements ≤ 0.05%, and the total amount of inevitable impurity elements ≤ 0.3%; the high-temperature stable phase elements are at least one of Cr, V, Co, and Mo.

[0036] In the above die-casting alloy, the mass content of Si is, for example, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or a range value composed of any two numerical values; the mass content of Mn is, for example, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65% or a range value composed of any two numerical values; the mass content of Fe is, for example, 0.06%, 0.08%, 0.10%, 0.12%, 0.14%, 0.15% or a range value composed of any two numerical values; the mass content of Mg is, for example, 0.09%, 0.10%, 0.12%, 0.14%, 0.16%, 0.20%, 0.22%, 0.24%, 0.25% or a range value composed of any two numerical values; the mass content of Sr is, for example, 0.01%, 0.015%, 0.018%, 0.020%, 0.024%, 0.026%, 0.028% or a range value composed of any two numerical values; the mass content of the high-temperature stable phase element is, for example, 0.05%, 0.08%, 0.10%, 0.15%, 0.20%, 0.25% or a range value composed of any two numerical values.

[0037] The heat-treatment-free die-casting alloy provided by this application has a relatively small pre-crystallization structure and a relatively small volume fraction through alloy composition design, so that the mechanical properties of the die-castings prepared from this alloy are excellent, and the properties of different parts are uniform, which can effectively meet the service performance of integral die-castings, and has significant technical significance and broad application prospects.

[0038] In some embodiments, the average value of the pre-crystallization structure size of the above die-casting alloy is 25 - 45 μm (such as 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm or 45 μm, etc.), the maximum size is 40 - 64 μm (such as 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, 52 μm, 55 μm, 58 μm, 60 μm, 62 μm or 64 μm, etc.), and the volume fraction is 1 - 4% (such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5% or 4%, etc.). It has excellent mechanical properties and uniform properties in each part, and the die-castings prepared from it have more excellent service performance.

[0039] In order to further improve the mechanical properties of the die-casting alloy, it is preferably that the content of a single element in the inevitable impurity elements ≤ 0.03 wt%, and the total amount of the inevitable impurity elements ≤ 0.2%.

[0040] In some other embodiments, it is preferably to control the volume fraction of the high-temperature stable phase element to be 0.05 - 0.18% (such as 0.05%, 0.08%, 0.10%, 0.12%, 0.15%, 0.18%, etc.), so that the size of the pre-crystallization structure in the die-casting alloy is smaller and more uniform.

[0041] In some other embodiments, the liquidus temperature of the above die-casting alloy is T1, and the solidus temperature is T2, where T1 ≤ 625 °C, T2 ≥ 565 °C, and T1 - T2 ≤ 50 °C, which is conducive to forming die-castings with uniform properties and excellent mechanical properties in each part.

[0042] In the second typical embodiment of the present application, a method for preparing the above die-casting alloy is further provided, which includes the following steps: Step S1, melting alloy raw materials into a to-be-treated alloy liquid, subjecting the to-be-treated alloy liquid to modification, degassing, and slag removal to obtain a pre-die-casting alloy liquid; Step S2, conveying the pre-die-casting alloy liquid to a die-casting machine for die-casting, the die-casting temperature is T3, T3 - T1 (the liquidus temperature of the die-casting alloy) = 74 - 100 °C, and the low speed of the die-casting punch is 0.15 - 0.25 m / s, and the high speed is 2 - 5 m / s.

[0043] The method for preparing the die-casting alloy provided by the present application combines the raw material alloy liquid formed by specific components with an optimized die-casting process, and obtains a heat-treatment-free die-casting alloy with a small volume fraction and small size of the pre-crystalline structure. The die-castings formed by this die-casting alloy have more excellent mechanical properties and more uniform properties in different parts.

[0044] Specifically, in terms of alloy composition design, through specific alloy composition design, fine and uniformly distributed high-temperature stable phases are preferentially precipitated below the liquidus temperature of the alloy, providing nucleation cores for the subsequently precipitated primary α-Al phase or hindering its rapid growth. The types and volume fractions of the primary high-temperature stable phases are the key to alloy composition design; secondly, when designing the alloy, the liquidus and solidus temperatures and intervals of the alloy are fully considered, and the liquidus-solidus interval of the alloy is minimized as much as possible, so as to ensure that the alloy has excellent flow filling performance. In terms of die-casting process, it is determined that the die-casting temperature is 74 - 100 °C above the liquidus temperature, ensuring that the temperature of the alloy liquid entering the pressure chamber is relatively high, reducing the number of primary α-Al phases in the alloy liquid, and appropriately increasing the superheat degree during alloy solidification to reduce the nucleation rate of the alloy; secondly, a higher punch speed is designed, so that there is a higher rheological shear stress during the filling process of the alloy liquid, breaking the formed primary α-Al phase into small-size and high-density nucleation cores, thereby obtaining a pre-crystalline structure with a smaller size. When the filling speed increases, more turbulence will occur in the alloy liquid and high-density gas entrapment will be formed, so a higher cavity vacuum degree is required to reduce the pore size.

[0045] This application suppresses the quantity and size of primary α-Al phase in the shot sleeve by preferentially forming a high-temperature stable phase and increasing the die-casting temperature. By increasing the rheological shear force of the alloy liquid, the nucleation rate of α-Al phase grains is increased, the size and volume fraction of the final pre-crystallized structure are reduced. Finally, the average value of the pre-crystallized size in the die-cast part is 25-45 μm, the maximum size is 40-64 μm, and the volume fraction is 1-4%.

[0046] In addition, the tensile strength, yield strength, and elongation of the die-casting alloy obtained by the preparation method provided in this application are generally better than those of the alloy prepared by the conventional method. The alloy design and die-casting method of the heat-treatment-free die-casting alloy provided in this application are widely applicable and have good operability under industrial conditions. The required cost is comparable to that of the traditional method, fully considering the industrial applicability of Al-Si-Mn heat-treatment-free die-casting alloy, and can significantly improve the qualified rate of thin-wall die-cast structural parts products.

[0047] In the above step S1, the operating temperatures of modification, degassing, and slag removal are not lower than the melting temperature, and the temperature of the pre-die-casting alloy liquid is 685-750 °C (such as 685 °C, 690 °C, 700 °C, 710 °C, 712 °C, 715 °C, 718 °C, 720 °C, 730 °C, 740 °C, 750 °C, etc.). Especially when the temperature of the pre-die-casting alloy liquid is 710-720 °C, it is more conducive to saving energy while maintaining excellent fluidity, and further conducive to preparing die-cast parts with excellent mechanical properties and uniform properties in each part through the die-casting process.

[0048] In the above step S2, the die-casting temperature is 74-100 °C above the liquidus temperature of the die-casting alloy (such as 74 °C, 75 °C, 80 °C, 82 °C, 85 °C, 88 °C, 90 °C, 92 °C, 95 °C, 98 °C, 100 °C). The low speed of the die-casting punch is, for example, 0.15 m / s, 0.18 m / s, 0.20 m / s, 0.22 m / s, 0.25 m / s, or a range value composed of any two values; the low speed of the die-casting punch is, for example, 2 m / s, 2.5 m / s, 3 m / s, 3.5 m / s, 4 m / s, 4.5 m / s, 5 m / s, or a range value composed of any two values. Especially when the low speed of the die-casting punch is 0.18-0.25 m / s and the high speed is 2-4 m / s, it is more conducive to reducing the size and quantity of the pre-crystallized structure formed during die-casting.

[0049] In some embodiments, in the above step S1, degassing includes: introducing an inert gas with a pressure of 0.18-0.25 MPa (such as 0.18 MPa, 0.20 MPa, 0.22 MPa, 0.24 MPa, 0.25 MPa) into the raw material alloy liquid, where the inert gas includes but is not limited to argon or high-purity nitrogen above 5N.

[0050] In some other embodiments, slag removal includes: adding a slag-removing agent to the raw material alloy liquid, and the dosage of the slag-removing agent is 0.1-0.3 wt% of the total amount of the raw material alloy liquid (such as 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, etc.); the slag-removing agent is a commonly used slag-removing agent in the art, including but not limited to a sodium-free refining agent.

[0051] To facilitate controlling the temperature of the pre-pressed casting alloy liquid after it enters the die-casting machine, preferably in step S2, the temperature of the pre-pressed casting alloy liquid entering the die-casting machine is T4, and T4 is 5-10 °C higher than T1 (the liquidus temperature of the die-casting alloy) (such as 5 °C, 6 °C, 7 °C, 8 °C, 9 °C, 10 °C, etc.).

[0052] To further reduce energy consumption, preferably during the process of transporting the pre-pressed casting alloy liquid to the die-casting machine, the temperature reduction of the pre-pressed casting alloy liquid does not exceed 20 °C.

[0053] To further improve the performance uniformity of each part in the die-casting alloy, preferably in step S2, die-casting is vacuum die-casting, and the cavity vacuum degree of the vacuum die-casting is 90-95 Pa (such as 90 Pa, 91 Pa, 92 Pa, 93 Pa, 94 Pa, 95 Pa, etc.). To further maintain the temperature stability during the vacuum die-casting process, preferably the temperature of the mold is 150-250 °C (such as 150 °C, 180 °C, 200 °C, 220 °C, 250 °C, etc.).

[0054] In the third typical embodiment of the present application, a die-casting part is further provided, and the material of the die-casting part is the die-casting alloy provided by the first typical embodiment or the die-casting alloy obtained by the preparation method provided by the second typical embodiment.

[0055] Through alloy composition design, the pre-crystalline structure of the die-casting part provided by the present application is smaller and the volume fraction is less, so that the die-casting part prepared from this alloy has excellent mechanical properties, uniform properties in different parts, can effectively meet the service performance of the integrated die-casting part, and has significant technical significance and broad application prospects.

[0056] The beneficial effects provided by the present application will be further described below in combination with examples and comparative examples.

[0057] Example 1

[0058] This embodiment provides a die-cast part made of an Al-Si-Mn heat-treatment-free die-casting alloy, which contains the following components by mass percentage: Si 9.5%, Mn 0.43%, Fe 0.12%, Mg 0.23%, Sr 0.028%, Cr 0.09%, and the rest is Al and inevitable impurity elements. The content of a single element in the inevitable impurity elements is ≤0.03%, and the total amount of the inevitable impurity elements is ≤0.2%. And the liquidus temperature of this die-casting alloy is 605°C, and the solidus temperature is 570°C.

[0059] The preparation method of this die-cast part includes the following steps:

[0060] (1) Add and melt the alloy raw materials in sequence to obtain the raw alloy liquid. During the melting process, perform modification, degassing, and slag removal operations on the raw alloy liquid, and the operation temperatures of modification, degassing, and slag removal are not lower than the melting temperature. Among them, slag removal includes: adding a slag remover to the raw material mixture, and the dosage of the slag remover accounts for 0.11 wt.% of the total amount of the raw alloy liquid; degassing includes: introducing 5N high-purity nitrogen with a pressure of 0.24 MPa to obtain a pre-die-casting alloy liquid, and the temperature of this pre-die-casting alloy liquid is 695°C.

[0061] (2) Transport the pre-die-casting alloy liquid to a die-casting machine for die-casting operations. During die-casting, the die-casting temperature is 712°C, the low speed of the die-casting punch is 0.15 m / s, the high speed of the die-casting punch is 2.1 m / s, and a die-cast part is obtained through vacuum die-casting. The cavity vacuum degree is maintained at 90 - 92 Pa, and the mold temperature is 180°C.

[0062] Example 2

[0063] This embodiment provides a die-cast part made of an Al-Si-Mn heat-treatment-free die-casting alloy. This die-casting alloy includes the following components by mass percentage: Si 8.1%, Mn 0.38%, Fe 0.11%, Mg 0.09%, Sr 0.027%, Mo 0.25%, and the rest is Al and inevitable impurity elements. The content of a single element in the inevitable impurity elements is ≤0.03%, and the total amount of the inevitable impurity elements is ≤0.2%. The liquidus temperature of this die-casting alloy is 604°C, and the solidus temperature is 574°C.

[0064] The preparation method of this die-cast part includes the following steps:

[0065] (1) Add and melt the alloy raw materials in sequence to obtain the raw material alloy liquid. During the melting process, modification, degassing, and slag removal are carried out, and the melting temperature does not exceed the temperature for carrying out the modification, degassing, and slag removal operations on the raw material alloy liquid. Among them, slag removal includes: adding a slag remover to the raw material mixture, and the dosage of the slag remover accounts for 0.12 wt.% of the total amount of the raw material alloy liquid; degassing includes: introducing 5N high-purity nitrogen with a pressure of 0.24 MPa to obtain the pre-die-casting alloy liquid, and the temperature of the pre-die-casting alloy liquid is 718 °C;

[0066] (2) Transport the pre-die-casting alloy liquid to a die-casting machine for die-casting operations. During the die-casting process, the die-casting temperature is 687 °C, the low speed of the die-casting punch is 0.21 m / s, the high speed of the die-casting punch is 2.5 m / s, and a die-cast part is obtained through vacuum die-casting. The cavity vacuum degree is maintained at 90 - 93 Pa, and the mold temperature is 200 °C.

[0067] Example 3

[0068] This example provides a die-cast part made of an Al-Si-Mn heat-treatment-free die-casting alloy. Its die-casting alloy includes the following components by mass percentage: Si 7.7%, Mn 0.55%, Fe 0.12%, Mg 0.13%, Sr 0.02%, V 0.18%, and the rest are Al and inevitable impurity elements. The content of each single element in the inevitable impurity elements is ≤ 0.03%, and the total amount of the inevitable impurity elements is ≤ 0.2%. The liquidus temperature of this die-casting alloy is 611 °C, and the solidus temperature is 567 °C.

[0069] The preparation method of this die-cast part includes the following steps:

[0070] (1) Add and melt the alloy raw materials in sequence to obtain the raw material alloy liquid. Add and melt the alloy raw materials in sequence to obtain the raw material alloy liquid. During the melting process, modification, degassing, and slag removal are carried out, and the melting temperature does not exceed the temperature for carrying out the modification, degassing, and slag removal operations on the raw material alloy liquid. Among them, slag removal includes: adding a slag remover to the raw material mixture, and the dosage of the slag remover accounts for 0.15 wt.% of the total amount of the raw material alloy liquid; degassing includes: introducing 5N high-purity nitrogen with a pressure of 0.24 MPa to obtain the pre-die-casting alloy liquid, and the temperature of the pre-die-casting alloy liquid is 716 °C;

[0071] (2) Transport the pre-die-casting alloy liquid to a die-casting machine for die-casting operations. During the die-casting process, the die-casting temperature is 685 °C, the low speed of the die-casting punch is 0.19 m / s, the high speed of the die-casting punch is 3.5 m / s, and a die-cast part is obtained through vacuum die-casting. The cavity vacuum degree is maintained at 91 - 94 Pa, and the mold temperature is 220 °C.

[0072] Example 4

[0073] This embodiment provides a die-cast part made of an Al-Si-Mn heat-treatment-free die-casting alloy. The die-casting alloy comprises the following components by mass percentage: Si 7.8%, Mn 0.53%, Fe 0.10%, Mg 0.017%, Sr 0.018%, Co 0.16%, and the balance is Al and inevitable impurity elements. The content of each single impurity element is ≤0.03%, and the total content of impurity elements is ≤0.23%. The liquidus temperature of the die-casting alloy is 617°C, and the solidus temperature is 573°C.

[0074] The preparation method of the die-cast part comprises the following steps:

[0075] (1) Add and melt the aluminum alloy raw materials in sequence to obtain a raw material alloy liquid. During the melting process, perform modification, degassing, and slag removal operations on the raw material alloy liquid, and the operation temperatures of modification, degassing, and slag removal are not lower than the melting temperature. Among them, slag removal includes: adding a slag remover to the raw material mixture, and the dosage of the slag remover accounts for 0.15 wt.% of the total amount of the raw material alloy liquid; degassing includes: introducing 5N high-purity nitrogen with a pressure of 0.24 MPa to obtain a pre-die-casting alloy liquid, and the temperature of the pre-die-casting alloy liquid is 718°C;

[0076] (2) Transport the pre-die-casting alloy liquid to a die-casting machine for die-casting operations. During die-casting, the die-casting temperature is 713°C, the low speed of the die-casting punch is 0.24 m / s, the high speed of the die-casting punch is 4.7 m / s, and a die-cast part is obtained by vacuum die-casting. The cavity vacuum degree is maintained at 90 - 92 Pa, and the mold temperature is 170°C.

[0077] Example 5

[0078] This embodiment provides a die-cast part made of an Al-Si-Mn heat-treatment-free die-casting alloy. The die-casting alloy comprises the following components by mass percentage: Si 7.1%, Mn 0.52%, Fe 0.14%, Mg 0.13%, Sr 0.011%, Cr 0.05%, Mo 0.17%, and the balance is Al and inevitable impurity elements. The content of each single impurity element is ≤0.03%, and the total content of inevitable impurity elements is ≤0.2%. The liquidus temperature of the die-casting alloy is 606°C, and the solidus temperature is 573°C. The preparation method of the alloy die-cast part comprises the following steps:

[0079] (1) Add and melt the alloy raw materials in sequence to obtain alloy liquid, and smelt to obtain the raw material alloy liquid. During the smelting process, perform modification, degassing, and slag removal operations on the raw material alloy liquid, and the operation temperatures of modification, degassing, and slag removal are not lower than the smelting temperature. Among them, slag removal includes: adding a slag remover to the raw material mixture, and the dosage of the slag remover accounts for 0.15 wt.% of the total amount of the raw material alloy liquid. Degassing includes: introducing 5N high-purity nitrogen with a pressure of 0.24 MPa to obtain a pre-cast alloy liquid, and the temperature of this pre-cast alloy liquid is 715 °C;

[0080] (2) Transport the pre-cast alloy liquid to a die-casting machine for die-casting operations. During die-casting, the die-casting temperature is 690 °C, the low speed of the die-casting punch is 0.15 m / s, the high speed of the die-casting punch is 2.2 m / s, and obtain a die-cast part through vacuum die-casting. The cavity vacuum degree is maintained at 90 - 93 Pa, and the mold temperature is 230 °C.

[0081] Example 6

[0082] This example provides a die-cast part made of an Al-Si-Mn heat-treatment-free die-casting alloy. This die-casting alloy includes the following components by mass percentage: Si 9.5%, Mn 0.35%, Fe 0.15%, Mg 0.25%, Sr 0.01%, Cr 0.05%, and the rest are Al and inevitable impurity elements, and the content of a single element in these inevitable impurity elements ≤ 0.05%, and the total amount of inevitable impurity elements ≤ 0.3%. The liquidus temperature of this die-casting alloy is 600 °C, and the solidus temperature is 568 °C. The preparation method of the alloy die-cast part includes the following steps:

[0083] (1) Add and melt the alloy raw materials in sequence to obtain alloy liquid, and smelt to obtain the raw material alloy liquid. During the smelting process, perform modification, degassing, and slag removal operations on the raw material alloy liquid, and the operation temperatures of modification, degassing, and slag removal are not lower than the smelting temperature. Among them, slag removal includes: adding a slag remover to the raw material mixture, and the dosage of the slag remover accounts for 0.15 wt.% of the total amount of the raw material alloy liquid. Degassing includes: introducing 5N high-purity nitrogen with a pressure of 0.24 MPa to obtain a pre-cast alloy liquid, and the temperature of this pre-cast alloy liquid is 712 °C;

[0084] (2) Transport the pre-cast alloy liquid to a die-casting machine for die-casting operations. During die-casting, the die-casting temperature is 690 °C, the low speed of the die-casting punch is 0.15 m / s, the high speed of the die-casting punch is 2.3 m / s, and obtain a die-cast part through vacuum die-casting. The cavity vacuum degree is maintained at 90 - 93 Pa, and the mold temperature is 170 °C.

[0085] Example 7

[0086] This embodiment provides a die-cast part made of an Al-Si-Mn heat-treatable die-casting alloy. The die-casting alloy includes the following components by mass percentage: Si 6.0%, Mn 0.65%, Fe 0.06%, Mg 0.23%, Sr 0.01%, Cr 0.05%, Mo 0.17%, and the balance is Al and inevitable impurity elements. The content of each single element in the inevitable impurity elements is ≤0.05%, and the total content of the inevitable impurity elements is ≤0.3%. The liquidus temperature of the die-casting alloy is 617°C, and the solidus temperature is 568°C. The preparation method of the alloy die-cast part includes the following steps:

[0087] (1) Add and melt the alloy raw materials in sequence to obtain alloy liquid, and smelt to obtain the raw material alloy liquid. During the smelting process, perform modification, degassing, and slag removal operations on the raw material alloy liquid, and the operation temperatures of modification, degassing, and slag removal are not lower than the smelting temperature. Among them, slag removal includes: adding a slag remover to the raw material mixture, and the dosage of the slag remover accounts for 0.15 wt.% of the total amount of the raw material alloy liquid. Degassing includes: introducing 5N high-purity nitrogen with a pressure of 0.25 MPa to obtain a pre-die-casting alloy liquid, and the temperature of the pre-die-casting alloy liquid is 714°C;

[0088] (2) Transport the pre-die-casting alloy liquid to a die-casting machine for die-casting operation. During the die-casting process, the die-casting temperature is 690°C, the low speed of the die-casting punch is 0.15 m / s, the high speed of the die-casting punch is 3.0 m / s, and a die-cast part is obtained by vacuum die-casting. The cavity vacuum degree is maintained at 90 - 93 Pa, and the mold temperature is 250°C.

[0089] Example 8

[0090] The difference between this embodiment and Example 1 is that in step (2), the low speed of the die-casting punch is 0.25 m / s, and the high speed of the die-casting punch is 5.0 m / s.

[0091] Example 9

[0092] The difference between this embodiment and Example 1 is that in step (2), the low speed of the die-casting punch is 0.18 m / s, and the high speed of the die-casting punch is 2.0 m / s.

[0093] Example 10

[0094] The difference between this embodiment and Example 1 is that in step (2), the die-casting temperature is 704°C.

[0095] Comparative Example 1

[0096] This embodiment provides a die-cast part made of an Al-Si-Mn heat-treatment-free die-casting alloy. The die-casting alloy includes the following components by mass percentage: Si 7.4%, Mn 0.58%, Fe 0.12%, Mg 0.25%, Sr 0.018%, Cr 0.2%, and the balance is Al and inevitable impurity elements. The content of each single element in the inevitable impurity elements is ≤0.03%, and the total amount of impurity elements is ≤0.2%.

[0097] The preparation method of the die-cast part includes the following steps:

[0098] (1) Add and melt the alloy raw materials in sequence to obtain a raw alloy liquid. During the melting process, perform modification, degassing, and slag removal operations on the raw alloy liquid, and the operation temperatures of modification, degassing, and slag removal are not lower than the melting temperature. Among them, slag removal includes: adding a slag remover to the raw material mixture, and the dosage of the slag remover accounts for 0.11 wt.% of the total amount of the raw alloy liquid; degassing includes: introducing 5N high-purity nitrogen with a pressure of 0.24 MPa to obtain a pre-die-casting alloy liquid, and the temperature of the pre-die-casting alloy liquid is 711°C;

[0099] (2) Transport the pre-die-casting alloy liquid to a die-casting machine for die-casting operation. During the die-casting process, the die-casting temperature is 692°C, the low speed of the die-casting punch is 0.12 m / s, the high speed of the die-casting punch is 2.2 m / s, and a die-cast part is obtained by vacuum die-casting. The cavity vacuum degree is maintained at 90 - 91 Pa, and the mold temperature is 180°C.

[0100] Comparative Example 2

[0101] This embodiment provides a die-cast part made of an Al-Si-Mn heat-treatment-free die-casting alloy. The die-casting alloy includes the following components by mass percentage: Si 7.6%, Mn 0.4%, Fe 0.12%, Mg 0.15%, Sr 0.018%, and the balance is Al and inevitable impurity elements. The content of each single element in the inevitable impurity elements is ≤0.03%, and the total amount of impurity elements is ≤0.2%.

[0102] The preparation method of the die-cast part includes the following steps:

[0103] (1) Add and melt the alloy raw materials in sequence to obtain a raw alloy liquid. During the melting process, perform modification, degassing, and slag removal operations on the raw alloy liquid, and the operation temperatures of modification, degassing, and slag removal are not lower than the melting temperature. Among them, slag removal includes: adding a slag remover to the raw material mixture, and the dosage of the slag remover accounts for 0.11 wt.% of the total amount of the raw alloy liquid; degassing includes: introducing 5N high-purity nitrogen with a pressure of 0.24 MPa to obtain a pre-die-casting alloy liquid, and the temperature of the pre-die-casting alloy liquid is 709°C;

[0104] (2) Transfer the pre-cast alloy liquid to a die-casting machine for die-casting operations. During the die-casting process, the die-casting temperature is 685 °C, the low speed of the die-casting punch is 0.14 m / s, the high speed of the die-casting punch is 1.85 m / s. Obtain die-cast parts through vacuum die-casting. The cavity vacuum degree is maintained at 90 - 93 Pa, and the mold temperature is 200 °C.

[0105] Comparative Example 3

[0106] This example provides a die-cast part made of an Al-Si-Mn heat-treatment-free die-casting alloy. The die-casting alloy includes the following components by mass percentage: Si 8.7%, Mn 0.64%, Fe 0.12%, Mg 0.11%, Sr 0.021%, and the rest is Al and inevitable impurity elements. The content of a single element in the inevitable impurity elements is ≤ 0.03%, and the total amount of impurity elements is ≤ 0.2%. The preparation method of the alloy die-cast part includes the following steps:

[0107] The preparation method of this die-cast part includes the following steps:

[0108] (1) Add and melt the alloy raw materials in sequence to obtain the raw material alloy liquid. During the melting process, perform modification, degassing, and slag removal operations on the raw material alloy liquid, and the operation temperatures of modification, degassing, and slag removal are not lower than the melting temperature. Among them, slag removal includes: adding a slag remover to the raw material mixture, and the dosage of the slag remover accounts for 0.11 wt.% of the total amount of the raw material alloy liquid; degassing includes: introducing 5N high-purity nitrogen with a pressure of 0.24 MPa to obtain the pre-cast alloy liquid, and the temperature of this pre-cast alloy liquid is 717 °C;

[0109] (2) Transfer the pre-cast alloy liquid to a die-casting machine for die-casting operations. During the die-casting process, the die-casting temperature is 700 °C, the low speed of the die-casting punch is 0.10 m / s, the high speed of the die-casting punch is 1.75 m / s. Obtain die-cast parts through vacuum die-casting. The cavity vacuum degree is maintained at 90 - 92 Pa, and the mold temperature is 170 °C.

[0110] Comparative Example 4

[0111] The difference between this comparative example and Example 1 is that in step (2), the die-casting temperature is 664 °C.

[0112] Comparative Example 5

[0113] The difference between this comparative example and Example 1 is that in step (2), the die-casting temperature is 724 °C.

[0114] Test Example 1

[0115] Measure the primary crystal grain size, volume fraction, and mechanical properties of the die-cast parts provided in the above examples and comparative examples respectively. The results are shown in Table 1 below.

[0116] Among them, (1) the test method for the size of the pre-crystallized structure is as follows: Select 10 representative metallographic structure photos of the same embodiment. Grains with a size exceeding 50 μm are determined as the pre-crystallized structure. Measure the maximum caliper diameter of the pre-crystallized structure as the maximum size, and obtain the average size by dividing the sum of all the maximum sizes of the pre-crystallized structure by the total number;

[0117] (2) The test method for the volume fraction of the pre-crystallized structure is as follows: Select 10 representative metallographic structure photos of the same embodiment. Grains with a size exceeding 50 μm are determined as the pre-crystallized structure. Calculate the percentage of the area of the pre-crystallized structure in the total area through image processing software as the pre-crystallized volume fraction;

[0118] (3) The test method for the volume fraction of the high-temperature phase is to select 10 representative scanning electron microscope structure photos of the same embodiment. Determine the alloy phase containing elements such as Mo, Cr, V, Co, etc. as the high-temperature phase. Calculate the percentage of the area of the pre-crystallized structure in the total area through image processing software as the pre-crystallized volume fraction and the high-temperature phase volume fraction;

[0119] (4) The mechanical properties include tensile strength, yield strength, and elongation. The test standard is GB / T 228.1-2010, and a die-cast tensile test piece with a thickness of 3.0 mm is selected.

[0120] Table 1

[0121]

[0122]

[0123] Note: When performing the above mechanical property determination, take 10 samples and take the average value after testing.

[0124] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: The die-casting alloy provided in this application has a small pre-crystallized structure and a small volume fraction through alloy composition design. Furthermore, the die-castings prepared from this alloy have excellent mechanical properties, and the properties of different parts are uniform, which can effectively meet the service performance of integrated die-castings, having significant technical significance and broad application prospects.

[0125] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A die-casting alloy that does not require heat treatment, characterized in that, The die-casting alloy comprises the following components by mass percentage: Si 6-9.5%, Mn 0.35-0.65%, Fe 0.06-0.15%, Mg 0.09-0.25%, Sr 0.01-0.028%, high-temperature stable phase elements 0.05-0.25%, and the balance is Al and inevitable impurity elements; The content of each single element in the inevitable impurity elements is ≤0.05%, and the total amount of the inevitable impurity elements is ≤0.3%; the high-temperature stable phase elements are at least one of Cr, V, Co and Mo; The average value of the pre-crystallization structure size of the die-casting alloy is 25-45 μm, the maximum size is 40-64 μm, and the volume fraction is 1-4%.

2. The die-casting alloy according to claim 1, wherein The volume fraction of the high-temperature stable phase elements is 0.05-0.18%.

3. The die-casting alloy according to claim 1 or 2, characterized in that, The liquidus temperature of the die-casting alloy is T1, and the solidus temperature is T2, wherein, T1≤625°C, T2≥565°C, and T1 - T2≤50°C.

4. A method for preparing a die-casting alloy according to any one of claims 1 to 3, characterized in that, The preparation method comprises the following steps: Step S1, melting alloy raw materials into raw alloy liquid, subjecting the raw alloy liquid to modification, degassing and slag removal to obtain pre-die-casting alloy liquid, wherein the operating temperatures of the modification, the degassing and the slag removal are not lower than the melting temperature, and the temperature of the pre-die-casting alloy liquid is 685-750°C; Step S2, conveying the pre-die-casting alloy liquid to a die-casting machine for die-casting to obtain the die-casting alloy, the temperature of the die-casting is T3, and T3 - T1 = 74-110°C; wherein, the low speed of the die-casting punch is 0.15-0.25 m / s, and the high speed is 2-5 m / s; wherein, the liquidus temperature of the die-casting alloy is T1, and the solidus temperature is T2, wherein, T1≤625°C, T2≥565°C, and T1 - T2≤50°C.

5. The preparation method according to claim 4, characterized in that, The temperature of the pre-die-casting alloy liquid is 710-720°C.

6. The preparation method according to claim 4, characterized in that In step S1, the degassing includes: introducing an inert gas or nitrogen with a pressure of 0.18-0.25 MPa into the raw alloy liquid; And / or, the slag removal includes: adding a slag remover to the raw alloy liquid, and the mass of the slag remover is 0.1-0.3% of the total mass of the raw alloy liquid.

7. The preparation method according to claim 6, characterized in that, The inert gas is argon, and the nitrogen is high-purity nitrogen with a purity of more than 5N.

8. The preparation method according to claim 6, wherein The slag remover is a sodium-free refining agent.

9. The preparation method according to claim 4, characterized in that, During the process of conveying the pre-die-casting alloy liquid to the die-casting machine, the temperature reduction of the pre-die-casting alloy liquid does not exceed 20°C.

10. The preparation method according to claim 4, characterized in that, In step S2, the die-casting is vacuum die-casting, and the cavity vacuum degree of the vacuum die-casting is 90-95 Pa; And / or, during the vacuum die-casting process, the temperature of the mold is 150-250°C.

11. The preparation method according to any one of claims 4 to 10, characterized in that, In step S2, the low speed of the die-casting punch is 0.18-0.25 m / s, and the high speed is 2-4 m / s.

12. A die-cast part, characterized in that, The material of the die-casting part is the die-casting alloy according to any one of claims 1 to 3 or the die-casting alloy obtained by the preparation method according to any one of claims 4 to 11.

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