High-toughness thin-wall aluminum alloy electric power fitting and casting mold thereof

Abstract

The invention discloses a high-toughness thin-wall aluminum alloy electric power fitting and a casting mold thereof, and relates to the technical field of aluminum alloy preparation. The wall thickness of the aluminum alloy electric power fitting is 2.5-4 mm. The vacuum thin-wall die casting preparation method comprises the steps that a die is closed; raw materials are weighed according to the mass percent of elements in an aluminum alloy material and smelted, aluminum alloy liquid is obtained, and the aluminum alloy material comprises, by weight percent, 4%-6% of Si, 0.4%-0.65% of Mn, 0.05%-0.2% of Er, 0.1%-0.25% of Mg, 0.05%-0.2% of Zr, 0.02% of Sr, 0.15%-0.3% of Fe, 0.3%-0.55% of TiB2, no more than 0.2% of other impurity elements and the balance Al; aluminum alloy liquid is fed, and the pouring temperature is kept at 680-750 DEG C; starting a vacuum pump to exhaust the cavity of the mold, and pouring and filling the aluminum alloy liquid by adopting injection; and after pressure maintaining and cooling, opening the mold, discharging, and removing a casting head. Through material-process-structure collaborative innovation, the prepared aluminum alloy electric power fitting has high strength and toughness, and the requirements of power transmission and transformation lines for high mechanical performance and light weight of the electric power fitting are met.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy preparation, and in particular to a high-strength and toughness thin-walled aluminum alloy electric power fitting and a casting mold thereof. Background Art

[0002] Power fittings refer to metal accessories used for mechanical connection, fixation and protection of overhead transmission and transformation lines. Power fittings mainly include connection accessories, tension wire clamps, suspension wire clamps and protective accessories. Power fittings are the key to power transmission and transformation projects, and their reliability and stability directly affect the safety of the power grid system. In recent years, the construction of my country's ultra-high voltage transmission network has continued to expand, and transmission lines crossing areas with different terrains are easily affected by complex and changeable meteorological conditions. Therefore, power fittings require higher mechanical properties, reliability, durability, energy efficiency and cost-effectiveness, and the material, structure and forming process of power fittings are the key factors that determine their comprehensive performance.

[0003] Existing power fittings are typically made of metal materials using low-pressure casting or conventional high-pressure casting processes. Among various metal materials, aluminum alloys have broad application prospects in the field of power fittings due to their high performance and lightweight advantages. However, existing standard aluminum alloy fittings have many problems. For example, the commonly used ZL102 and ZL104 aluminum alloys have a tensile strength of only around 140-160 MPa, which is difficult to meet the needs of the power industry. A few research projects have improved the mechanical properties of aluminum alloys by adding nanofiber materials to them, but their complex forming process still cannot meet the large-scale needs of rapidly developing power transmission and transformation line projects. Summary of the Invention

[0004] The present invention aims to provide a high-strength and tough thin-walled aluminum alloy power fitting suitable for the needs of power transmission and transformation lines through collaborative innovation of materials, processes and structures.

[0005] The high-strength and tough thin-walled aluminum alloy electric power fitting provided by the present invention has a wall thickness of 2-4 mm.

[0006] The aluminum alloy electrical fittings are prepared by a vacuum thin-wall die-casting method, comprising the following steps:

[0007] S1, mold closing;

[0008] S2, weighing raw materials according to the mass percentage of elements in the aluminum alloy material and smelting them to obtain aluminum alloy liquid; the aluminum alloy material includes the following raw materials in the following weight percentages:

[0009] Si 4-6%, Mn 0.4-0.65%, Er 0.05-0.2%, Mg 0.1-0.25%, Zr 0.05-0.2%, Sr 0.02%, Fe 0.15-0.3%, TiB2 0.3-0.55%, the total amount of other impurity elements does not exceed 0.2%, the balance is Al;

[0010] S3, adding the aluminum alloy liquid and maintaining the pouring temperature at 680-750°C;

[0011] S4, starting a vacuum pump to evacuate the mold cavity, and pouring the aluminum alloy liquid into the mold by injection molding;

[0012] S5, after pressure holding and cooling, the mold is opened to discharge the material and the pouring head is removed; wherein, the pressure holding pressure is not less than 40 kPa, and the cooling and solidification rate of the aluminum alloy liquid is greater than 80°C / second.

[0013] Optionally, the wall thickness of the aluminum alloy electrical fitting is 3-4 mm.

[0014] Optionally, the cross-section of the aluminum alloy electrical fitting includes at least one of an L-shaped structure, a T-shaped structure, and a cross-shaped structure;

[0015] The wall thickness of the L-shaped structure is 3-4 mm, the wall thickness of the T-shaped structure is 3-4 mm, and the wall thickness of the cross-shaped structure is 3-3.5 mm.

[0016] Optionally, the cross-section of the aluminum alloy electrical fitting includes a double T-shaped structure, the double T-shaped structure includes an upper T-shaped structure and a lower T-shaped structure connected laterally, the spacing distance between the upper T-shaped structure and the lower T-shaped structure is 1.25~1.35 times the wall thickness of the T-shaped structure, and the wall thickness of the T-shaped structure is 3~4mm.

[0017] Optionally, in step S4, the injection pressure is 95-105 MPa, the injection speed in the high-speed injection section is 3.5 m / s, and the injection speed in the low-speed injection section is 15-25% of the speed in the high-speed injection section.

[0018] Optionally, in step S4, the vacuum pump is started to exhaust the mold cavity to achieve a vacuum degree of ≤50~80kPa; according to the actual process optimization results, the vacuum degree can be selected to be ≤80kPa, or ≤50kPa, or a specific value within the range of ≤50~80kPa.

[0019] Optionally, if the porosity of the aluminum alloy electrical fitting is less than 3%, the tensile strength is ≥285 MPa, and the elongation is ≥11%, the aluminum alloy casting is judged to be qualified.

[0020] Optionally, the aluminum alloy electrical fitting is an aluminum alloy spacer bar frame.

[0021] Optionally, when the aluminum alloy spacer bar frame is prepared by the vacuum thin-wall die-casting method described above, the pouring temperature of the aluminum alloy liquid is 680° C., and the holding pressure during pressure-holding cooling is 40 kPa.

[0022] The present invention also provides a mold for preparing the above-mentioned high-strength and thin-walled aluminum alloy electrical hardware by vacuum thin-wall die casting. The wall thickness of the aluminum alloy electrical hardware is 2.5~4mm, preferably 3~4mm. The size of the cavity formed after the mold is closed matches the wall thickness of the aluminum alloy electrical hardware.

[0023] Optionally, the cross-section of the aluminum alloy electrical fitting includes a double T-shaped structure, the double T-shaped structure includes an upper T-shaped structure and a lower T-shaped structure connected laterally, the spacing distance between the upper T-shaped structure and the lower T-shaped structure is 1.25~1.35 times the wall thickness of the T-shaped structure, and the wall thickness of the T-shaped structure is 3~4mm; the cavity formed after the mold is closed includes a double T-shaped cavity corresponding to the double T-shaped structure, and the size of the double T-shaped cavity matches the wall thickness and spacing distance of the double T-shaped structure.

[0024] The present invention has the following beneficial effects:

[0025] The present invention achieves high strength and toughness in the thin-walled aluminum alloy electrical fittings prepared through the collaborative innovation of materials, processes and structures. Firstly, the present invention utilizes the extremely rapid cooling process of vacuum thin-wall die casting (cooling and solidification rate greater than 80°C / second) to achieve self-quenching, dissolving the alloying elements in the aluminum alloy into the aluminum matrix to form a supersaturated solid solution and fine grain strengthening. Secondly, the present invention enables the aluminum alloy material to effectively precipitate strengthening phases under die casting cooling conditions through the synergistic effect of multiple elements, and realizes self-aging heat treatment of the aluminum alloy by forming a stable and dispersed strengthening phase or a composite strengthening mechanism under vacuum die casting cooling conditions, that is, the partial or complete precipitation of the strengthening phase is completed directly in the cooling process after die casting, eliminating the need for traditional heat treatment. The solid solution, quenching and artificial aging steps in the process are greatly shortened, and high efficiency and low energy consumption are achieved; thirdly, the present invention addresses the problem that the cooling rates of different wall thickness areas in the vacuum thin-wall die-casting process are very different, resulting in uneven internal structure and performance of the same casting. By optimizing the wall thickness, the problems of uneven cooling rate, filling difficulty, increased defects, and process instability in the thin-wall die-casting process are effectively improved, providing strong support for the self-quenching and self-aging heat treatment of aluminum alloys; the porosity of the aluminum alloy electric hardware prepared by the present invention is less than 3%, the tensile strength is ≥285MPa, the elongation is ≥11%, and the thickness is only 2.5~4mm, which meets the high mechanical performance and lightweight requirements of power hardware for transmission and transformation lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 A flow chart of a vacuum thin-wall die-casting process according to some embodiments of the present invention;

[0028] Figure 2 Schematic diagram of the cross-sectional structure of the vacuum die-casting of the aluminum alloy spacer bar frame;

[0029] Figure 3 Schematic diagrams of the L-shaped structure, T-shaped structure, and cross-shaped structure of thin-walled aluminum alloy electrical fittings in some embodiments of the present invention;

[0030] Figure 4 This is a graph showing the relationship between the cooling rate and the wall thickness-structure shape during the vacuum thin-wall die-casting process of thin-walled aluminum alloy electrical fittings in some embodiments of the present invention;

[0031] Figure 5 Schematic diagram of the cross-shaped structure of thin-walled aluminum alloy electrical fittings optimized into a double T-shaped structure in some embodiments of the present invention;

[0032] Figure 6 These are cross-sectional metallographic micrographs of thin-walled aluminum alloy electrical fittings prepared according to some embodiments of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] Aiming at the high mechanical performance and lightweight requirements of power fittings for power transmission and transformation lines, the present invention prepares an aluminum alloy power fitting with high strength and toughness through the collaborative innovation of materials, processes and structures.

[0035] Aluminum alloy power fittings include but are not limited to connection accessories, tension clamps, suspension clamps and protective accessories used for mechanical connection, fixation and protection of overhead transmission and transformation lines.

[0036] The strength of metal materials mainly depends on their ability to resist plastic deformation, which is closely related to the movement of dislocations in the microstructure, the hindering effect of grain boundaries and the interaction of strengthening phases.

[0037] The strength of metallic materials generally increases with decreasing grain size, which is called the Hall-Petch effect and satisfies the following formula:

[0038]

[0039] Where, Indicates the yield strength of the material; Indicates the yield strength of single crystal or coarse grain material; is a material constant related to the ability of grain boundaries to hinder dislocation motion; represents the average grain diameter.

[0040] In the thin-wall die casting process, the cooling rate is very high (up to 10 2 ~10 3 K / s or even higher); rapid cooling is a non-equilibrium solidification process. When a high-temperature liquid transforms into a solid, the nucleation rate is much greater than the growth rate. A large number of nuclei are formed simultaneously and grow rapidly, but they stop growing due to mutual contact, eventually forming very fine equiaxed grains. Smaller grains mean more grain boundaries per unit volume. Grain boundaries are effective obstacles to dislocation movement. Dislocations have difficulty crossing grain boundaries and need to be controlled at the grain boundaries to accumulate or change direction, thereby increasing the yield strength of the material.

[0041] Rapid cooling also inhibits the growth of dendrites in aluminum alloy materials, resulting in a significant reduction in SDAS (secondary dendrite arm spacing); the size of SDAS reflects the distance and time of solute diffusion during solidification. The faster the cooling rate, the more solute atoms are captured by the solid phase front before they can diffuse over a long distance, and the dendrite arms do not have enough time to "grow fatter", resulting in a smaller spacing; a smaller SDAS means that the solute segregation area is smaller and more dispersed, and it may also make the subsequently precipitated strengthening phase finer and more dispersed, which is beneficial to improving strength and toughness.

[0042] The extremely fast cooling rate prevents the alloying elements from fully diffusing and precipitating from the aluminum matrix, and they are "frozen" in the matrix, forming a supersaturated solid solution. Solid solution strengthening comes from the lattice distortion caused by solute atoms (whose size and elastic modulus are different from those of matrix atoms) in the matrix lattice. These distortion fields interact with the stress field of dislocations, hindering dislocation movement and thus increasing strength. Rapid cooling maximizes the retention of alloying elements in the solid solution, making the strengthening effect more significant.

[0043] In the vacuum die-casting process, high pressure acts on the surface of the solidified aluminum alloy melt. The high pressure in the die-casting process helps the molten metal fill the details of the thin-walled cavity, and can effectively "compact" the solidified structure, reducing volume defects such as pores and shrinkage; porosity and void defects (especially holes) are sources of stress concentration, which will significantly reduce the material's bearing capacity and toughness; high-pressure die-casting improves the density of the molten metal, reduces these internal weaknesses that can initiate cracks, and thus improves the overall strength and reliability.

[0044] Vacuum thin-wall die casting combines the advantages of thin-wall die casting and vacuum die casting, and is suitable for the preparation of high-strength and tough thin-wall aluminum alloy electrical hardware; the process flow of vacuum thin-wall die casting can be found in Figure 1 It usually includes the steps of mold closing - aluminum alloy melting - loading (sodium feeding) - vacuum valve opening - mold venting - injection - pressure maintaining and cooling - mold opening and discharging - removal of pouring and riser - mold cleaning. After the part is taken out and self-inspected, the target casting can be obtained.

[0045] Based on the above-mentioned principle of vacuum thin-wall die-casting and the achievable beneficial effects, the technical solution of the present invention adopts vacuum thin-wall die-casting to prepare a high-strength and toughness thin-walled aluminum alloy electrical hardware.

[0046] In some embodiments, the preparation of aluminum alloy electrical fittings includes the following steps S1 to S5:

[0047] S1, mold closing.

[0048] After the mold is closed, a rectangular integral sealing box + foam plastic sealing plug can be used to ensure good air tightness of the cavity.

[0049] S2, weighing raw materials according to the mass percentage of elements in the aluminum alloy material and smelting them to obtain aluminum alloy liquid; the aluminum alloy material contains the following raw materials in the following weight percentages:

[0050] Si 4-6%, Mn 0.4-0.65%, Er 0.05-0.2%, Mg 0.1-0.25%, Zr 0.05-0.2%, Sr 0.02%, Fe 0.15-0.3%, TiB2 0.3-0.55%, the total amount of other impurity elements does not exceed 0.2%, and the balance is Al.

[0051] S3, add aluminum alloy liquid and maintain the pouring temperature at 680~750℃.

[0052] S4, start the vacuum pump to exhaust the mold cavity, and the vacuum degree meets ≤50~80kPa. According to the actual process optimization results, the vacuum degree can be selected to be ≤80kPa, or ≤50kPa, or a specific value within the range of ≤50~80kPa.

[0053] The aluminum alloy liquid is poured and filled by injection molding; the injection pressure is 95~105MPa, the injection speed in the high-speed injection section is 3.5m / s, and the injection speed in the low-speed injection section is 15~25% of the speed of the high-speed injection section.

[0054] S5, after pressure-maintaining and cooling, the mold is opened to discharge the material, the pouring head is removed, and the aluminum alloy power fittings are obtained after passing the inspection or after subsequent mechanical processing steps;

[0055] Among them, the holding pressure during pressure holding cooling is not less than 40kPa, and the cooling and solidification rate of the aluminum alloy liquid is greater than 80℃ / second; preferably, the cooling and solidification rate of the aluminum alloy liquid is greater than 100℃ / second; the cooling and solidification rate of the aluminum alloy liquid can be obtained through the coordinated design of wall thickness, mold temperature, pouring temperature, injection speed and mold material.

[0056] In the embodiment of the present invention, the extremely rapid cooling process of die casting is equivalent to "self-quenching", which can dissolve a large amount of alloying elements in the aluminum matrix to form a supersaturated solid solution, which is the basis for the subsequent precipitation strengthening phase; the relationship between the cooling rate and the crystal microstructure size satisfies the following formula:

[0057] d=A×R (-n) ;

[0058] λ2=B×R (-m) Or SDAS = B × (dT / dt) (-m) ;

[0059] Where d represents the grain size, λ2 and SDAS represent the secondary dendrite arm spacing, A, B, n, and m are constants related to materials and processes. Usually, n is in the range of 0.3–0.5, and m is in the range of 0.3–0.5.

[0060] As can be seen from the above formula, the cooling rate has a nonlinear relationship with the size of the crystal microstructure. As the wall thickness decreases, the cooling rate accelerates, the strengthening mechanism of vacuum thin-wall die casting becomes more significant, and the material strength increases. However, if the wall thickness is too small, the material strength will decrease. The reasons include at least: (1) saturation of the strengthening effect. When the wall thickness decreases to a certain extent, the cooling rate may reach a limit. (2) There is a "surface effect" in the die casting. The metal liquid closest to the mold wall cools the fastest, forming a very fine "chilled layer". The "chilled layer" has the highest strength, and the cooling rate inside is relatively slow, and the structure is slightly coarse. When the wall thickness is very thin, the entire cross section is almost composed of a fine chilled layer, and the strength reaches its peak. value; (3) Too thin wall thickness leads to increased defect sensitivity; (4) When the wall thickness is too thin, the flow resistance of the molten metal increases sharply, and filling becomes difficult. Even under high pressure, defects such as incomplete filling, cold shut, and flow marks may occur. These macro defects will seriously weaken the strength of the component; (5) During the thin wall filling process, the molten metal flow rate is high and turbulence may occur, which is more likely to involve gas or surface oxide film, forming internal defects and reducing strength and toughness; (6) The molten metal may solidify prematurely at the front end during the filling process, hindering subsequent molten metal filling and forming defects; (7) The die casting of extremely thin walls requires extremely high stability of process parameters (temperature, pressure, speed), and even slight fluctuations may cause defects.

[0061] In an embodiment of the present invention, the wall thickness of the high-strength and tough thin-walled aluminum alloy electric hardware is 2.5-4 mm; in some preferred embodiments, the wall thickness of the high-strength and tough thin-walled aluminum alloy electric hardware is selected to be 3-4 mm.

[0062] The embodiment of the present invention achieves high strength and toughness by means of collaborative innovation of materials, processes and structures.

[0063] Firstly, the embodiment of the present invention utilizes the extremely rapid cooling process of vacuum thin-wall die casting (the cooling and solidification rate of the aluminum alloy liquid is greater than 80°C / second) to achieve self-quenching, dissolving the alloying elements in the aluminum alloy into the aluminum matrix to form a supersaturated solid solution and fine grain strengthening.

[0064] Secondly, the aluminum alloy material used in the embodiment of the present invention can effectively precipitate strengthening phases under die-casting cooling conditions; wherein, the Si content balances the casting fluidity of the aluminum alloy and the toughness of the casting, and the appropriate Mg / Si ratio controls the type, nucleation rate and growth rate of the precipitated phase to form a suitable Mg2Si phase; Zr and Er elements can form thermally stable dispersed particles Al3M phase, which can be formed during the die-casting cooling process, providing a certain degree of dispersion strengthening and can serve as heterogeneous nucleation points for subsequent precipitation phases; Sr elements can refine the eutectic silicon in the aluminum alloy, improve the alloy strength and inhibit shrinkage cavities and porosity; controlling the appropriate Fe and Mn contents can improve the toughness of the casting and Improve the fluidity of aluminum alloy liquid; TiB2 is formed by the combination of B element and Ti element in the refiner used in casting, and the appropriate TiB2 phase content can significantly refine the cast grains of the aluminum alloy and improve the thermal stability of the aluminum alloy during the casting process; the present invention uses the synergistic effect of multiple elements to enable the aluminum alloy material to effectively precipitate a strengthening phase under the die-casting cooling conditions, and realizes the self-aging heat treatment of the aluminum alloy by forming a stable and dispersed strengthening phase or a composite strengthening mechanism under the vacuum die-casting cooling conditions, that is, the partial or complete precipitation of the strengthening phase is completed directly in the cooling process after the die-casting, eliminating the solid solution, quenching, and artificial aging steps in the traditional heat treatment, greatly shortening the process flow, and achieving high efficiency and low energy consumption.

[0065] Thirdly, the embodiments of the present invention address the problem of huge differences in cooling rates in different wall thickness areas in the vacuum thin-wall die-casting process, which leads to uneven internal structure and performance of the same casting. By optimizing the wall thickness (wall thickness is 2.5~4mm, preferably 3~4mm), the problems of uneven cooling rate, filling difficulty, increased defects, and process instability in the vacuum thin-wall die-casting process are effectively improved, providing strong support for self-quenching and self-aging heat treatment of aluminum alloys.

[0066] The aluminum alloy power fittings prepared in the embodiment of the present invention have a porosity of less than 3%, a tensile strength of ≥285 MPa, and an elongation of ≥11%, meeting the high mechanical performance and lightweight requirements of power fittings for power transmission and transformation lines.

[0067] Based on the above embodiments, further, in order to better achieve self-quenching and self-aging in the vacuum thin-wall die-casting process of aluminum alloy and improve the mechanical strength and casting performance of aluminum alloy, in some embodiments, the present invention also performs wall thickness design and structural optimization for the structure of aluminum alloy electrical hardware.

[0068] See Figure 2 、 3 , Figure 2 It is a vacuum die-casting structure of an aluminum alloy spacer bar frame. The cross section of the aluminum alloy spacer bar frame can be divided into three types: L-type structure, T-type structure and cross-type structure. The wall thickness of the structure is represented by t0.

[0069] See Figure 3 , even if different types of structures, the maximum wall thickness T m Also greater than the wall thickness t0, (t1, t2, t3 represent other dimensions in the structure); see Figure 4 , Figure 4 The relationship diagram between the cooling rate of the aluminum alloy liquid and the wall thickness-structure shape during the vacuum thin-wall die-casting process is obtained by finite element analysis of these three structures. Due to the difference in structural characteristics, the cooling and solidification rate of the cross-shaped structure is lower than that of the T-shaped structure and the L-shaped structure, and the cooling and solidification rate of the L-shaped structure is the fastest; the wall thickness affects the cooling and solidification rates. Therefore, in the design of the aluminum alloy power fitting structure, it is necessary not only to control the uniform wall thickness, but also to correctly utilize the reinforced nonlinear relationship of the wall thickness to fully improve the mechanical properties of the thin-walled aluminum alloy power fittings.

[0070] In the embodiment of the present invention, the aluminum alloy power fittings include one or more of an L-shaped structure, a T-shaped structure and a cross-shaped structure. Figure 4 The relationship between the cooling rate and the wall thickness-structure shape is shown. The wall thickness of the L-type structure is preferably 3~4mm, the wall thickness of the T-type structure is preferably 3~4mm, and the wall thickness of the cross-type structure is preferably 3~3.5mm, so as to meet the requirement that the cooling and solidification rate of the aluminum alloy liquid is greater than 80℃ / second.

[0071] Furthermore, in some preferred embodiments, the present invention optimizes the cross-shaped structure with the slowest cooling and solidification rate during the casting process into a double T-shaped structure, see Figure 5 , that is, splitting the cross-shaped structure and translating it into upper T-shaped and lower T-shaped structures connected laterally.

[0072] The distance between the upper T-shaped structure and the lower T-shaped structure of the double T-shaped structure is expressed as t x The wall thickness of the T-type structure is expressed as t0. The incompatibility between the upper T-type structure and the lower T-type structure ensures that the cooling rate and casting strength of this structure are the same as those of the single T-type structure.

[0073] Taking into account the needs of structural design, as well as the needs of mold demoulding angle, manufacturing error, and manufacturing convenience, in the embodiment of the present invention, the spacing distance between the two T-shaped structures is selected to be 1.25 to 1.35 times the wall thickness of the T-shaped structure (the wall thickness of the T-shaped structure is the wall thickness of the upper T-shaped structure or the wall thickness of the lower T-shaped structure, or the average of the two), that is, the distance between the two T-shaped structures t x =(1.25~1.35)t0, where the wall thickness t0 of the T-type structure is 3~4mm.

[0074] The present invention also provides a casting mold for vacuum die-casting to prepare the aluminum alloy electrical hardware proposed in the above embodiment. The size of the cavity formed after the mold is closed is designed to match the wall thickness of the aluminum alloy electrical hardware. Since the aluminum alloy shrinks during the casting process, the size of the mold cavity is the target size of the casting × (1 + shrinkage rate). Tolerances and demolding angles usually need to be considered, and the size of the mold cavity needs to be further optimized.

[0075] In some embodiments, the cross-section of the aluminum alloy electrical hardware includes a double T-shaped structure, and the cavity formed after the casting mold is closed includes a double T-shaped cavity corresponding to the double T-shaped structure. The size of the double T-shaped cavity is designed to match the wall thickness and spacing distance of the double T-shaped structure in the aforementioned aluminum alloy electrical hardware structure embodiment, which will not be repeated here.

[0076] Based on the above embodiments, the present invention takes the spacer rod frame commonly used in electrical hardware as an example and proposes the following specific embodiments. It should be noted that the following specific embodiments are only illustrative and do not limit the scope of protection of the present invention in any form.

[0077] Example 1

[0078] An aluminum alloy spacer bar frame with a wall thickness of 3 mm, comprising the following raw materials in the following weight percentages:

[0079] Si 4.5%, Mn 0.6%, Er 0.05%, Mg 0.15%, Zr 0.15%, Sr 0.02%, Fe 0.25%, TiB2 0.5%, the total amount of other impurity elements does not exceed 0.2%, and the balance is Al.

[0080] The preparation is carried out by vacuum thin-wall die casting, which includes the following steps:

[0081] S1, mold closing; the mold is selected to be an aluminum alloy spacer bar frame mold with a wall thickness of 3mm. After the mold is closed, a rectangular integral sealing box + foam plastic sealing plug is used to ensure good airtightness of the cavity.

[0082] S2, weighing raw materials according to the mass percentage of elements in the aluminum alloy material and smelting them to obtain aluminum alloy liquid.

[0083] S3, aluminum alloy liquid is added, and the pouring temperature is maintained at 680℃.

[0084] S4, start the vacuum pump to exhaust the mold cavity, monitor the vacuum pressure value at the vacuum end of the mold to ensure sufficient negative pressure.

[0085] The aluminum alloy liquid is poured and filled by injection molding; the injection pressure is 95~105MPa, the injection speed in the high-speed injection section is 3.5m / s, and the injection speed in the low-speed injection section is 15~25% of the speed of the high-speed injection section to prevent air entrainment.

[0086] S5, after cooling under 40kPa pressure, open the mold and discharge the material (using a water-based release agent), remove the pouring head, and complete the sample preparation after passing the test.

[0087] Example 2

[0088] An aluminum alloy spacer bar frame with a wall thickness of 2.5 mm, comprising the following raw materials in the following weight percentages:

[0089] Si 5.5%, Mn 0.45%, Er 0.15%, Mg 0.20%, Zr 0.10%, Sr 0.02%, Fe 0.20%, TiB2 0.35%, the total amount of other impurity elements does not exceed 0.2%, and the balance is Al.

[0090] The preparation is carried out by vacuum thin-wall die casting, which includes the following steps:

[0091] S1, mold closing; the mold is selected to be an aluminum alloy spacer bar frame mold with a wall thickness of 2.5mm. After the mold is closed, a rectangular integral sealing box + foam plastic sealing plug is used to ensure good airtightness of the cavity.

[0092] S2, weighing raw materials according to the mass percentage of elements in the aluminum alloy material and smelting them to obtain aluminum alloy liquid.

[0093] S3, aluminum alloy liquid is added, and the pouring temperature is maintained at 680℃.

[0094] S4, start the vacuum pump to exhaust the mold cavity, monitor the vacuum pressure value at the vacuum end of the mold to ensure sufficient negative pressure.

[0095] The aluminum alloy liquid is poured and filled by injection molding; the injection pressure is 95~105MPa, the injection speed in the high-speed injection section is 3.5m / s, and the injection speed in the low-speed injection section is 15~25% of the speed of the high-speed injection section to prevent air entrainment.

[0096] S5, after cooling under 40kPa pressure, open the mold and discharge the material (using a water-based release agent), remove the pouring head, and complete the sample preparation after passing the test.

[0097] Example 3

[0098] An aluminum alloy spacer bar frame is prepared by referring to the aluminum alloy raw material and vacuum thin-wall die-casting method of Example 2, except that the wall thickness is 3.0 mm.

[0099] Example 4

[0100] An aluminum alloy spacer bar frame is prepared by referring to the aluminum alloy raw material and vacuum thin-wall die-casting method of Example 2, except that the wall thickness is 4.0 mm.

[0101] Comparative Example 1

[0102] An aluminum alloy spacer bar frame is prepared by referring to the aluminum alloy raw material and vacuum thin-wall die-casting method of Example 2, except that the wall thickness is 2.0 mm.

[0103] The tensile strength test of the aluminum alloy spacer bar frame specimens prepared in Examples 2-4 and Comparative Example 1 was performed (according to GB / T 228.1-2021 standard), and the test results are shown in Table 1.

[0104] Table 1 Measured tensile strength values of aluminum alloy spacer frame specimens

[0105]

[0106] It can be seen from the test data in Table 1 that when the wall thickness of the aluminum alloy spacer bar frame increases from 2.0 mm to 3.0 mm, its tensile strength increases from 280 MPa to 316 MPa, with a strength increase of 12.5%; when the wall thickness continues to increase to 4 mm, the tensile strength decreases to 305 MPa, with a strength increase of less than 10%; this result verifies the nonlinear relationship between the cooling rate and the size of the crystal microstructure; the tensile strength of the aluminum alloy spacer bar frame specimens of Examples 2-4 are all greater than 285 MPa, meeting the tensile strength requirements of power fittings for transmission and transformation lines.

[0107] The aluminum alloy spacer bar frame specimens prepared in Examples 1 and 3 were subjected to experimental tests on tensile strength, yield strength, and elongation. The test results are shown in Table 2.

[0108] Table 2 Experimental test results of 3.0 mm thick specimens

[0109]

[0110] (In Tables 1 and 2, the tensile strength of the aluminum alloy spacer bar frame specimens prepared in Example 3 was obtained from different tests. The test values are essentially the same, and slight differences are normal measurement errors.)

[0111] From the test data in Table 2, it can be seen that the aluminum alloy spacer frame samples prepared in Example 1 and Example 3 have a tensile strength greater than 285 MPa, an elongation greater than 11%, and a relatively high yield strength. Figure 6It can be seen that the aluminum alloy grains are small and uniform; and by observing the metallographic structure of the casting cross section, it can be known that the porosity of the sample is significantly lower than 3% (no obvious pores).

[0112] It can be seen that the aluminum alloy spacer bar frame prepared in the above specific embodiments has excellent mechanical strength and toughness, and meets the requirements of power transmission and transformation lines for high mechanical performance and lightweight aluminum alloy spacer bar frames.

[0113] It can be understood that the technical solutions of the various embodiments of the present invention are not only applicable to the preparation of high-strength and tough aluminum alloy spacer rod frames, but are also applicable to the preparation of other high-strength and tough aluminum alloy electrical hardware, including but not limited to various connection accessories, tension wire clamps, suspension wire clamps and protective accessories used for mechanical connection, fixation and protection of overhead transmission and transformation lines.

[0114] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-strength and thin-walled aluminum alloy power fitting, characterized in that: The wall thickness of the aluminum alloy electrical fittings is 2.5-4 mm; The aluminum alloy electrical fittings are prepared by a vacuum thin-wall die-casting method, comprising the following steps: S1, mold closing; S2, weighing raw materials according to the mass percentage of elements in the aluminum alloy material and smelting them to obtain aluminum alloy liquid; the aluminum alloy material includes the following raw materials in the following weight percentages: Si 4-6%, Mn 0.4-0.65%, Er 0.05-0.2%, Mg 0.1-0.25%, Zr 0.05-0.2%, Sr 0.02%, Fe0.15-0.3%, TiB2 0.3-0.55%, the total amount of other impurity elements does not exceed 0.2%, the balance is Al; S3, adding the aluminum alloy liquid and maintaining the pouring temperature at 680-750°C; S4, starting a vacuum pump to evacuate the mold cavity, and pouring the aluminum alloy liquid into the mold by injection molding; S5, after pressure holding and cooling, the mold is opened to discharge the material and the pouring head is removed; wherein, the pressure holding pressure is not less than 40 kPa, and the cooling and solidification rate of the aluminum alloy liquid is greater than 80°C / second.

2. The high-strength and tough thin-walled aluminum alloy electrical fitting according to claim 1, characterized in that: The wall thickness of the aluminum alloy electrical fitting is 3-4 mm.

3. The high-strength and tough thin-walled aluminum alloy electrical fitting according to claim 2, characterized in that: The cross-section of the aluminum alloy electrical fitting includes at least one of an L-shaped structure, a T-shaped structure, and a cross-shaped structure; The wall thickness of the L-shaped structure is 3-4 mm, the wall thickness of the T-shaped structure is 3-4 mm, and the wall thickness of the cross-shaped structure is 3-3.5 mm.

4. The high-strength and tough thin-walled aluminum alloy electrical fitting according to claim 2, characterized in that: The cross-section of the aluminum alloy electrical fitting includes a double T-shaped structure, which includes an upper T-shaped structure and a lower T-shaped structure connected laterally. The spacing between the upper T-shaped structure and the lower T-shaped structure is 1.25 to 1.35 times the wall thickness of the T-shaped structure, and the wall thickness of the T-shaped structure is 3 to 4 mm.

5. The high-strength and tough thin-walled aluminum alloy electrical fitting according to claim 1, characterized in that: In step S4, the injection pressure is 95-105 MPa, the injection speed in the high-speed injection section is 3.5 m / s, and the injection speed in the low-speed injection section is 15-25% of the speed in the high-speed injection section.

6. The high-strength and tough thin-walled aluminum alloy electrical fitting according to claim 1, characterized in that: In step S4, a vacuum pump is started to exhaust the cavity of the mold to a vacuum degree of ≤50-80 kPa.

7. The high-strength and tough thin-walled aluminum alloy electrical fitting according to claim 1, characterized in that: The porosity of the aluminum alloy electrical fittings is less than 3%, the tensile strength is ≥285MPa, and the elongation is ≥11%.

8. The high-strength and tough thin-walled aluminum alloy electrical fitting according to any one of claims 1 to 7, characterized in that: The aluminum alloy electrical hardware is an aluminum alloy spacer bar frame.

9. A casting mold for preparing the high-strength and tough thin-walled aluminum alloy electrical fittings according to any one of claims 1 to 8 by vacuum thin-wall die casting, characterized in that: The wall thickness of the aluminum alloy electric hardware is 2.5-4 mm, and the size of the cavity formed after the mold is closed matches the wall thickness of the aluminum alloy electric hardware.

10. The casting mold according to claim 9, characterized in that The cross-section of the aluminum alloy electrical fitting includes a double T-shaped structure, and the double T-shaped structure includes an upper T-shaped structure and a lower T-shaped structure connected laterally. The spacing between the upper T-shaped structure and the lower T-shaped structure is 1.25 to 1.35 times the wall thickness of the T-shaped structure, and the wall thickness of the T-shaped structure is 3 to 4 mm. The cavity formed after the mold is closed includes a double T-shaped cavity corresponding to the double T-shaped structure, and the size of the double T-shaped cavity matches the wall thickness and spacing distance of the double T-shaped structure.

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