Rotating shaft assembly, manufacturing method thereof, and foldable electronic device

Abstract

The application relates to the technical field of electronic equipment, in particular to a rotating shaft assembly, a preparation method thereof and a foldable electronic equipment. The rotating shaft assembly comprises a decoration piece and a structural piece, the structural piece is embedded on the decoration piece, the tensile strength of the structural piece is 1800 MPa-2300 MPa, and the yield strength is 1700 MPa-2200 MPa. In the rotating shaft assembly, the mechanical property of the structural piece is good, the structural piece is embedded on the decoration piece, the internal stress and the appearance requirement of the rotating shaft assembly can be met, the combination of the two is good, the internal space is saved, and the thinning and weight reduction of the rotating shaft assembly are facilitated.

Description

Technical Field

[0001] This application relates to the field of electronic device technology, and in particular to a hinge assembly, its manufacturing method, and a foldable electronic device. Background Technology

[0002] Foldable electronic devices generally consist of a flexible screen, a hinge, and a housing. The unfolding and folding motion of the electronic device is achieved by rotating the hinge. At this time, the hinge not only needs to bear the internal force to meet the folding requirements, but also needs to meet some of the appearance requirements. These requirements are difficult to meet with parts made of a single material, and using parts made of multiple materials will easily lead to increased thickness or weight, which is inconsistent with the current concept of thin and light electronic devices. Summary of the Invention

[0003] Based on this, this application provides a hinge assembly, a method for manufacturing the same, and a foldable electronic device.

[0004] The first aspect of this application provides a rotating shaft assembly, the technical solution of which is as follows:

[0005] A pivot assembly includes a decorative element and a structural element, the structural element being embedded in the decorative element, and the tensile strength of the structural element being 1800MPa~2300MPa and the yield strength being 1700MPa~2200MPa.

[0006] The second aspect of this application provides a method for manufacturing a rotating shaft assembly, the technical solution of which is as follows:

[0007] A method for manufacturing a rotating shaft assembly includes the following steps:

[0008] A 3D printing scheme is set according to the target structure of the pivot assembly. The target structure includes a target decorative part and a target structural part, and the target structural part is embedded on the target decorative part.

[0009] Decorative powder and structural powder are 3D printed separately according to the printing scheme to integrally form the target decorative part and the target structural part with tensile strength of 1800MPa~2300MPa and yield strength of 1700MPa~2200MPa.

[0010] A third aspect of this application provides a foldable electronic device, the technical solution of which is as follows:

[0011] A foldable electronic device includes a first housing, a second housing, a hinge assembly, and a flexible display assembly;

[0012] The rotating shaft assembly is manufactured as described above or by the manufacturing method described above, and is disposed between the first housing and the second housing. The first housing and the second housing are rotatably connected by the rotating shaft assembly to unfold or fold.

[0013] The flexible display assembly is disposed on the first housing and the second housing, and is located on the same side of the first housing and the second housing when the first housing and the second housing are unfolded.

[0014] This application has the following beneficial effects:

[0015] In the pivot assembly of this application, the tensile strength of the structural component is 1800MPa~2300MPa, and the yield strength is 1700MPa~2200MPa. The tensile strength and yield strength are relatively high, and the mechanical properties are relatively good. At the same time, the structural component is embedded on the decorative component. With the above arrangement, the internal stress and appearance requirements of the pivot assembly can be met by the structural component and the decorative component respectively. The two also have good bonding force and save internal space, which is conducive to the thinning and weight reduction of the pivot assembly. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application and to more completely understand this application and its beneficial effects, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a front view of the rotating shaft assembly according to one embodiment;

[0018] Figure 2 This is a top view of the rotating shaft assembly according to one embodiment;

[0019] Figure 3 This is a side view of the rotating shaft assembly according to one embodiment;

[0020] Figure 4 This is a schematic diagram of a method for manufacturing a rotating shaft assembly according to one embodiment;

[0021] Figure 5 A schematic diagram of the structure of an electronic device according to one embodiment;

[0022] Figure 6 Here is a SEM image of the powder structure from Example 1;

[0023] Figure 7 A figure showing the metallographic structure of the densified target decorative profile of Example 1;

[0024] Figure 8 Two figures showing the metallographic structure of the densified target decorative profile in Example 1;

[0025] Figure 9 A figure showing the metallographic structure of the densified target structural profile of Example 1;

[0026] Figure 10 Two images showing the metallographic structure of the densified target structural profile in Example 1;

[0027] Figure 11 This is a SEM image of the surface of the densified target decorative profile in Example 1;

[0028] Figure 12 This is a cross-sectional SEM image of the decorative part during the static tensile test in Example 1;

[0029] Figure 13 This is a cross-sectional SEM image of the structural component during the static tensile test of Example 1. Detailed Implementation

[0030] The present application will be further described in detail below with reference to specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0032] the term

[0033] Unless otherwise stated or in case of conflict, the terms or phrases used in this application shall have the following meanings:

[0034] In this application, "multiple" means at least two, such as two, three, etc., unless otherwise expressly and specifically defined. In this application, "several" means at least one, such as one, two, etc., unless otherwise expressly and specifically defined.

[0035] In this application, the terms "optionally," "optionally," and "optional" refer to options that are optional, meaning they can be selected from either "with" or "without." If multiple "optional" options appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" option is independent.

[0036] In this application, the terms "first aspect," "second aspect," "third aspect," and "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," and "fourth," etc., serve only a non-exhaustive enumeration purpose and should be understood not to constitute a closed limitation on quantity.

[0037] In this application, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0038] In this application, when an element is referred to as "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. It should also be understood that, in interpreting the connection or positional relationship of elements, although not explicitly described, connection and positional relationships are interpreted to include a range of error, which should be within the acceptable deviation range of a specific value as determined by a person skilled in the art.

[0039] In this application, room temperature refers to a temperature between 10°C and 40°C.

[0040] The first aspect of this application provides a rotating shaft assembly. In one embodiment, please refer to [link to relevant documentation]. Figures 1 to 3 The figures show a front view, a top view, and a side view of the pivot assembly 100. The pivot assembly 100 includes a decorative component 11 and a structural component 12, with the structural component 12 embedded in the decorative component 11. The tensile strength of the structural component 12 is 1800 MPa to 2300 MPa, and the yield strength is 1700 MPa to 2200 MPa.

[0041] In the aforementioned pivot assembly, the structural component 12 has better mechanical properties. The structural component is embedded on the decorative component 11, which can not only meet the internal force and appearance requirements of the pivot assembly, but also has a good bonding force and saves internal space, which is conducive to the thinning and weight reduction of the pivot assembly.

[0042] The tensile strength of structural component 12 includes, but is not limited to, 1800 MPa, 1900 MPa, 2000 MPa, 2100 MPa, 2200 MPa, and 2300 MPa, and the yield strength includes, but is not limited to, 1700 MPa, 1800 MPa, 1900 MPa, 2000 MPa, 2100 MPa, and 2200 MPa. Structural component 12 has high mechanical properties and can meet the internal stress requirements of the rotating shaft assembly. Optionally, the mechanical properties of structural component 12 also satisfy at least one of the following conditions: 1) The core hardness of structural component 12 is 580HV~640HV; for example, the core hardness is 580HV, 600HV, 620HV, or 640HV; 2) The elastic modulus of structural component 12 is 160GPa~210GPa; for example, the elastic modulus is 160GPa, 170GPa, 180GPa, 190GPa, 200GPa, or 210GPa; 3) The elongation of structural component 12 is 4%~8%. For example, the elongation is 4%, 5%, 6%, 7%, or 8%. Optionally, the material of structural component 12 includes alloy steel, wherein the alloying elements in the alloy steel include one or more of B, O, S, P, N, W, Cr, Cu, Ni, Mo, Co, Si, Mn, V, and Nb. Alloy steel refers to steel containing alloying elements other than iron (Fe) and carbon (C). Understandably, alloy steel can be ultra-high strength structural steel. Ultra-high strength structural steel is a type of alloy steel used to manufacture structural components that withstand high stress. Generally, the tensile strength of ultra-high strength structural steel exceeds 1470 MPa, and the yield strength exceeds 1380 MPa. Ultra-high strength structural steel is divided into three types: low-alloy ultra-high strength steel, maraging steel, and precipitation-hardening stainless steel. As the strength increases, the ductility of the material decreases. The strength and toughness of the aforementioned ultra-high strength structural steel can ensure the internal stress requirements of the shaft assembly. However, due to the poor wear resistance of ultra-high strength structural steel, it can be used in conjunction with decorative parts 11 that have better wear resistance.

[0043] Understandably, decorative component 11 has a good aesthetic effect. Furthermore, decorative component 11 with suitable performance can be selected according to actual needs. For example, when structural component 12 needs to be paired with a decorative component with good wear resistance, the surface hardness of decorative component 11 is greater than that of structural component 12. Meanwhile, since structural component 12 can distribute most of the stress, the requirements for the mechanical properties of decorative component 11 are relatively relaxed. Optionally, the mechanical properties of decorative component 11 meet at least one of the following conditions: 1) The core hardness of decorative component 11 is 460HV~520HV; for example, core hardness is 460HV, 480HV, 500HV, 520HV; 2) The tensile strength of decorative component 11 is 900MPa~1200MPa; for example, tensile strength is 900MPa, 1000MPa, 1100MPa, 1200MPa; 3) Decorative component... The yield strength of decorative part 11 is 800MPa~1100MPa; for example, yield strengths of 800MPa, 900MPa, 1000MPa, and 1100MPa; 4) The elastic modulus of decorative part 11 is 100GPa~150GPa; for example, elastic modulus of 100GPa, 110GPa, 120GPa, 130GPa, 140GPa, and 150GPa; 5) The elongation of decorative part 11 is 10%~15%. For example, elongation of 10%, 11%, 12%, 13%, 14%, and 15%. Optionally, the material of decorative part 11 includes one or more of titanium, titanium alloy, and stainless steel. The titanium alloy may be titanium alloy TC4 or titanium alloy TA2.

[0044] Optionally, the hinge assembly also includes a coating layer located on the side of the decorative element away from the structural element. The coating layer can be a color layer. Furthermore, the coating layer can also provide a higher surface hardness than the decorative layer, improving the wear resistance of the hinge assembly. Optionally, the surface hardness of the coating layer is 250HV to 2000HV, including but not limited to 250HV, 265HV, 325HV, 365HV, 435HV, 450HV, 600HV, 800HV, 1000HV, 1500HV, and 2000HV.

[0045] In the above embodiments, decorative parts 11 and structural parts 12 of different materials and properties are combined to form a pivot assembly 100 by embedding. Compared with the traditional welding method of assembling two parts of different materials and properties with solder, the embedding method can not only save the space and weight occupied by solder, but also save more space than direct splicing assembly, which is conducive to the miniaturization and thinning of the pivot assembly.

[0046] Optionally, the decorative part 11 and the structural part 12 are integrally formed by 3D printing. By setting the 3D printing scheme, the structural part 12 can be embedded in the decorative part 11. At the same time, by integrally forming the decorative part 11 and the structural part 12 by 3D printing, the bonding strength between the two is better. In addition, compared with making two parts in two steps and then assembling them, one-step molding can also save costs.

[0047] To further improve the bonding strength between decorative component 11 and structural component 12, please continue reading. Figure 1 and Figure 3 The structural component 12 includes a main segment 121 and several embedded segments 122 connected to the main segment 121. Each embedded segment 122 embeds a decorative component 11, and each embedded segment 122 independently satisfies the following: the end face area of ​​the end connected to the main segment 121 is not greater than the end face area of ​​the end away from the main segment 121. Further optionally, some embedded segments 122 satisfy the following: the end face area of ​​the end connected to the main segment 121 is smaller than the end face area of ​​the end away from the main segment 121. When the end face area of ​​the embedded segment 122 connected to the main segment 122 is smaller than the end face area of ​​the embedded segment 122 away from the main segment 122, the bonding force between the decorative component 11 and the structural component 12 is higher. Further optionally, some embedded segments 122 satisfy the following: as the embedding depth of the embedded segment 122 increases, the cross-sectional area of ​​the embedded segment 122 increases, where the cross-section refers to the surface perpendicular to the direction of the embedding depth z. At this point, as seen from the front and side views, these embedded segments 122 are dovetail-shaped, narrower at the top and wider at the bottom. This also results in a stronger bond between the decorative element 11 and the structural element 12.

[0048] In other embodiments, all embedded segments may also satisfy the following condition: the end face area of ​​the end connected to the main body segment 121 is smaller than the end face area of ​​the end away from the main body segment 121. Further optionally, all embedded segments may also satisfy the following condition: as the embedding depth of the embedded segment 122 increases, the cross-sectional area of ​​the embedded segment 122 increases.

[0049] The embedded structure of the above-mentioned structural component 12 can all be realized by setting a 3D printing scheme.

[0050] A second aspect of this application provides a method for manufacturing a rotating shaft assembly. In one embodiment, please refer to [link to relevant documentation]. Figure 4 The manufacturing method of the rotating shaft assembly includes the following steps:

[0051] S10. Set a 3D printing scheme according to the target structure of the rotating shaft assembly. The target structure includes a target decorative part and a target structural part, and the target structural part is embedded on the target decorative part.

[0052] The target structure can be found in the structure of the pivot assembly described above, and will not be repeated here.

[0053] S20. The decorative powder and structural powder are 3D printed according to the printing scheme to form the target decorative part and the target structural part with tensile strength of 1800MPa~2300MPa and yield strength of 1700MPa~2200MPa in one piece.

[0054] Optionally, the decorative powder and structural powder are 3D printed separately according to the printing scheme to integrally form the target decorative part and the target structural part, including the following steps:

[0055] S21. Print the decorative powder and structural powder separately to form the target decorative intermediate and the target structural intermediate in one piece.

[0056] Understandably, most particles in decorative powders and structural powders are spherical. Better sphericity results in better flowability, making it suitable for powder-feed laser cladding.

[0057] By controlling the particle size of the powder, the porosity of the 3D printed product can be reduced. Optionally, the particle size of the decorative powder satisfies the following: 1) D10 is 3μm~8μm; for example, D10 is 3μm, 5μm, 8μm; 2) D50 is 9μm~17μm; for example, D50 is 9μm, 11μm, 13μm, 15μm, 17μm; 3) D90 is 19μm~35μm; for example, D90 is 19μm, 25μm, 29μm, 35μm. Optionally, the particle size of the structured powder satisfies the following: 1) D10 is 4μm~8μm; for example, D10 is 4μm, 5μm, 6μm, 7μm, 8μm; 2) D50 is 15μm~20μm; for example, D50 is 15μm, 16μm, 17μm, 18μm, 19μm, 20μm; 3) D90 is 25μm~38μm. For example, D90 is 25μm, 30μm, 35μm, 38μm.

[0058] The appropriate decorative powder can be selected based on the performance of the decorative component. Optionally, the decorative powder includes one or more of titanium powder, titanium alloy powder, and stainless steel powder. The titanium alloy can be titanium alloy TC4 powder or titanium alloy TA2 powder.

[0059] In some examples, the decorative powder is titanium alloy TA2 powder, with a D10 of 4μm~8μm, a D50 of 10μm~17μm, and a D90 of 21μm~35μm. The fine particle size of the powder helps to reduce the formation of pores.

[0060] In other examples, the decorative powder is titanium alloy TC4 powder, with a D10 of 3μm~7μm, a D50 of 9μm~13μm, and a D90 of 19μm~23μm. The finer particle size of these powders helps to reduce the formation of pores.

[0061] Similarly, a suitable structural powder can be selected based on the performance of the structural component. Optionally, the structural powder includes alloy steel powder, wherein the alloying elements in the alloy steel powder include one or more of B, O, S, P, N, W, Cr, Cu, Ni, Mo, Co, Si, Mn, V, and Nb. Optionally, the alloy steel powder has a tensile strength of 1200 MPa to 2200 MPa, a yield strength of 1000 MPa to 2000 MPa, and an elongation of 4% to 10%.

[0062] Optionally, the alloy steel powder can be 316L, high-strength steel, high-strength steel II (Thor), 17-4PH, or 420W. The composition and mechanical properties of high-strength steel I, high-strength steel II (Thor), 17-4PH, and 420W are shown in Table 1.

[0063] Table 1

[0064]

[0065] Note: "-" indicates that it does not contain.

[0066] Optionally, the process parameters for printing decorative powder include at least one of the following: 1) coaxial powder feeding method; 2) laser power P of 1800W~2400W; 3) scanning speed V of 400mm / min~800mm / min; 4) spot diameter of 2mm~4mm; 5) powder feeding rate Vf of 12g / min~16g / min; 6) powder carrier gas flow rate Lf of 5L / min~8L / min; 7) protective gas flow rate Lb of 8L / min~12L / min. Understandably, the protective gas is an inert gas, such as argon, which prevents metal oxidation and protects the molten pool. Before formally printing the decorative powder, the substrate can be polished with 400# or 200# silicon carbide sandpaper, and then the substrate surface can be cleaned with anhydrous ethanol.

[0067] Optionally, the process parameters for printing the structural powder include at least one of the following: 1) coaxial powder feeding method; 2) laser power P of 1800W~2400W; 3) scanning speed V of 400mm / min~800mm / min; 4) spot diameter of 2mm~4mm; 5) powder feeding rate Vf of 12g / min~16g / min; 6) powder carrier gas flow rate Lf of 5L / min~8L / min; 7) protective gas flow rate Lb of 8L / min~12L / min. Understandably, the protective gas is an inert gas, such as argon, which serves to prevent metal oxidation and protect the molten pool.

[0068] Among them, coaxial powder-feed laser 3D printing technology involves simultaneously feeding powder and a laser beam during the manufacturing process, eliminating the need for a specific order. The key feature of this technology is that while the laser is incident on the substrate surface, a powder feeder continuously delivers metallic powder material, ensuring that the powder flow axis is coaxial with the laser axis. The laser simultaneously heats both the substrate and the metallic powder material, causing them to rapidly heat up and solidify at the same time. This coaxiality between the powder and laser axes guarantees the continuity of the manufacturing process, eliminating the need for pre-laying powder for each processing step, as required by selective laser melting (SLM) technology.

[0069] First, decorative powder can be printed to form an intermediate target decorative part. The intermediate target decorative part has reserved a position for embedding the intermediate target structural part. Then, structural powder can be printed at the embedding position to form the intermediate target structural part.

[0070] S22. Sintering to densify the intermediate products of the target decorative part and the target structural part, forming the target decorative part and the target structural part.

[0071] The intermediate decorative component and the intermediate structural component can be integrally sintered to densify them, resulting in a densified profile. Optionally, the density of the densified target decorative component profile is 4.2 g / cm³. 3 ~4.5g / cm 3 For example, the density of the densified target decorative profile is 4.2 g / cm³. 3 4.3g / cm 3 4.4 g / cm 3 The density of the target structural profile for densification is 7.85 g / cm³. 3 ~8.00g / cm 3 For example, the density of the target structural profile after densification is 7.85 g / cm³. 3 7.90g / cm 3 7.92g / cm 37.96 g / cm 3 8.00g / cm 3 .

[0072] The resulting densified profile has poor surface roughness, exhibiting rough cladding marks. Optionally, after sintering, the process further includes the following step: surface treatment of the resulting densified profile. Surface treatment includes polishing. Optionally, surface treatment also includes coloring, which can produce different color appearances. Coloring includes the following step: forming a color layer through PVD.

[0073] To meet the mechanical properties of the structural components, optionally, after sintering, the following step is further included: heat-treating the sintered densified profile for strengthening, wherein the maximum temperature for heat treatment strengthening satisfies the following condition: the variation range of grain size in the densified target decorative profile is ≤10%. Here, the variation range of grain size refers to the ratio of the change in grain size after heat treatment to the original grain size relative to the original grain size before heat treatment strengthening. Through heat treatment strengthening, the strength of the densified target structural profile can be improved. Considering that the performance of the densified target decorative profile is not affected, the maximum temperature for heat treatment strengthening is limited to ensure that the variation range of grain size in the densified target decorative profile is ≤10%. This avoids excessive growth in grain size in the densified target decorative profile, which would affect its performance. Optionally, the variation range is ≤8%. Optionally, the variation range is ≤5%.

[0074] Optionally, the heat treatment strengthening includes solution treatment, cryogenic treatment, and aging treatment.

[0075] The purpose of solution treatment is to fully dissolve various elements into the solid solution by heating, so that the crystal structure is austenite, and then to fix the supersaturated solid solution structure by cooling, thus transforming austenite into martensite.

[0076] Optionally, the solution treatment includes the following procedure: holding at 920℃~980℃ for 30min~90min, cooling under N2 conditions, and controlling the time from 920℃~980℃ to room temperature to be 20min~40min.

[0077] Optionally, the solution treatment further includes the following procedures: holding at 180℃~220℃ for 20min~40min, and holding at 580℃~620℃ for 10min~30min. The time for raising the temperature from room temperature to 180℃~220℃ can be 20min~40min, the time for raising the temperature from 180℃~220℃ to 580℃~620℃ can be 20min~40min, and the time for raising the temperature from 580℃~620℃ to 920℃~980℃ can be 20min~40min.

[0078] Optionally, the solution treatment is carried out in an environment with a pressure ≤0.1 kPa.

[0079] After solution treatment, cryogenic treatment is carried out to promote the transformation of residual austenite inside the material into martensite.

[0080] Optionally, cryogenic treatment includes the following procedure: holding at -210℃ to -180℃ for 30 min to 90 min.

[0081] After cryogenic treatment, aging treatment is carried out to rearrange the internal microstructure of the material and enhance phase precipitation.

[0082] Optionally, the aging treatment includes the following procedure: holding at 460℃~540℃ for 3h~5h, then cooling. Optionally, cooling can be carried out under N2 conditions, and the time to cool from 460℃~540℃ to room temperature can be 20min~40min.

[0083] Optionally, the aging treatment also includes the following procedure: holding at 180℃~220℃ for 20min~40min. The time for raising the temperature from room temperature to 180℃~220℃ can be 20min~40min, and the time for raising the temperature from 180℃~220℃ to 460℃~540℃ can be 20min~40min.

[0084] Optionally, the aging process is carried out in an environment with an air pressure ≤0.1 kPa.

[0085] Optionally, after heat treatment strengthening, the process further includes the following step: surface treatment of the strengthened profile obtained by heat treatment strengthening. Surface treatment includes polishing. Polishing controls the surface roughness within a desired range. Polishing can be magnetic abrasion, removing burrs through magnetic abrasion. Optionally, the surface treatment includes forming a coating layer on the side of the decorative part away from the structural part. Optionally, PVD coating is applied to the side of the decorative part away from the structural part to form a coating layer. Optionally, the surface hardness of the coating layer is higher than the surface hardness of the decorative part. Optionally, the surface hardness of the coating layer is 250HV~2000HV. Optionally, the coating layer is a color layer, which can present different color appearance effects.

[0086] The above method uses 3D printing to integrally form the target decorative part and the target structural part, integrating the decorative part that provides surface hardness and the structural part that provides mechanical properties together. As a pivot assembly, it can meet the usage requirements of foldable electronic devices and also has the advantage of being lightweight and thin.

[0087] The structural components can be made of ultra-high strength structural steel. To ensure the material properties of ultra-high strength structural steel, high metallurgical quality is required, with a yield strength reaching 2000 MPa and good ductility (elongation > 4%). Traditional methods employ vacuum induction furnaces or vacuum consumable arc furnaces for smelting. Furthermore, high requirements are placed on heat treatment equipment after smelting, as excessive impurities such as C / O / S / P significantly affect the material's stress-resistance. Therefore, a good vacuum effect and atmosphere protection are necessary during heat treatment. In contrast, the above implementation method uses 3D printing to obtain ultra-high strength structural steel with a tensile strength of 1800 MPa~2300 MPa, a yield strength of 1700 MPa~2200 MPa, and an elongation of 4%~8% as structural components. The processing steps are simplified, and the structural components can be integrally formed with decorative components or directly embedded into them, saving space and manufacturing costs for the rotating shaft assembly.

[0088] A third aspect of this application provides a foldable electronic device; please refer to [link / reference]. Figure 5 In one embodiment, the foldable electronic device 01 includes a first housing 10, a second housing 20, a hinge assembly 30, and a flexible display assembly 40;

[0089] The pivot assembly 30 is manufactured as described above or by the manufacturing method described above, and is disposed between the first housing 10 and the second housing 20. The first housing 10 and the second housing 20 are rotatably connected by the pivot assembly 30 so as to unfold or fold.

[0090] The flexible display assembly 40 is disposed on the first housing 10 and the second housing 20, and is located on the same side of the first housing 10 and the second housing 20 when the first housing 10 and the second housing 20 are unfolded.

[0091] The following description is further illustrated with specific embodiments and comparative examples. Unless otherwise specified, the raw materials involved in the following specific embodiments and comparative examples are all commercially available. Unless otherwise specified, the instruments used are all commercially available. Unless otherwise specified, the processes involved are conventionally selected by those skilled in the art.

[0092] Example 1

[0093] This embodiment provides a rotating shaft assembly and its manufacturing method, the steps of which are as follows:

[0094] Step 1, according to Figures 1 to 3 The target structure of the rotating shaft assembly shown is designed for 3D printing. The target structure includes a target decorative part and a target structural part, with the target structural part embedded on the target decorative part.

[0095] Step 2: Prepare decorative and structural powders. The decorative powder is titanium alloy TC4 powder with a D10 of 7.21 μm, a D50 of 16.31 μm, and a D90 of 34.51 μm. The composition and properties of the structural powder are shown in Table 2; its D10 is 4.31 μm, D50 is 15.55 μm, and D90 is 25.51 μm. SEM images of the structural powder are shown below. Figure 6 .

[0096] Table 2

[0097]

[0098] Step 3: According to the process parameters shown in Table 3, use coaxial powder feeding to print the above-mentioned decorative powder and structural powder respectively, and form the target decorative part intermediate product and the target structural part intermediate product in one piece.

[0099] Table 3

[0100]

[0101] Step 4: Sintering to densify the target decorative intermediate and the target structural intermediate, resulting in a density of 4.3 g / cm³. 3 The target decorative profile for densification has a density of 7.9 g / cm³. 3 The target structural profile for densification. Figure 7 and Figure 8 The metallographic structure of the target decorative profile is to achieve a denser structure. Figure 9 and Figure 10 The metallographic structure of the target structural profile for densification. (From...) Figure 7 and Figure 8 It can be seen that the densified target decorative profile exhibits obvious TC4 microstructure characteristics (TC4 titanium alloy has a mixed microstructure composed of α and β phases). From Figure 9 and Figure 10 It can be seen that the densified target structural profile has obvious lath martensite structure. Figure 11 The SEM image of the surface of the target decorative profile for densification shows that the surface exhibits rough cladding marks.

[0102] Step 5: The sintered densified profiles are subjected to solution treatment, cryogenic treatment, and aging treatment. The solution treatment procedure is as follows: Heating from room temperature to 200°C at a constant rate for 30 min, holding for 30 min; heating at a constant rate for 30 min to 600°C, holding for 20 min; heating at a constant rate for 30 min to 960°C, holding for 60 min; then cooling at a constant rate for 30 min under N2 conditions to room temperature. This solution treatment is performed at a pressure of 10 Pa. The cryogenic treatment procedure is as follows: Holding at -196°C for 60 min. The aging treatment procedure is as follows: Heating from room temperature to 200°C at a constant rate for 30 min, holding for 30 min; heating at a constant rate for 30 min to 500°C, holding for 4 h; then cooling at a constant rate for 30 min under N2 conditions to room temperature. This aging treatment is performed at a pressure of 10 Pa, resulting in a reinforced profile.

[0103] Step 5: Polish the reinforced profile obtained by heat treatment to obtain the target decorative part and target structural part in one piece.

[0104] The core hardness of the decorative part in Example 1 was tested by static tensile testing of its tensile strength, yield strength, elastic modulus, and elongation at break (i.e., elongation at break). Three parallel measurements were performed, and the results are shown in Table 4. The cross-section of the decorative part in Example 1 during the static tensile test is shown in Table 4. Figure 12 It can be seen that the fracture is a ductile fracture with good dimples. The core hardness of the structural component of Example 1 was tested by static tensile testing of its tensile strength, yield strength, elastic modulus, and elongation at break (i.e., elongation at break). Three parallel measurements were performed, and the results are shown in Table 5. The cross-section of the structural component of Example 1 during the static tensile test is shown in Table 5. Figure 13 It can be seen that its fracture is a ductile fracture with good dimples.

[0105] Table 4

[0106]

[0107] Table 5

[0108]

[0109] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0110] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A rotating shaft assembly, characterized in that, It includes decorative parts and structural parts, the structural parts being embedded on the decorative parts, and the tensile strength of the structural parts being 1800MPa~2300MPa and the yield strength being 1700MPa~2200MPa.

2. The rotating shaft assembly according to claim 1, characterized in that, The decorative part and the structural part are integrally formed by 3D printing.

3. The rotating shaft assembly according to claim 1, characterized in that, The structural component includes a main body segment and several embedded segments connected to the main body segment. Each embedded segment is embedded in the decorative component, and each embedded segment independently satisfies the following condition: the end face area connected to one end of the main body segment is not greater than the end face area away from the main body segment.

4. The rotating shaft assembly according to claim 2, characterized in that, Some or all of the embedded segments satisfy the following condition: as the embedding depth of the embedded segment increases, the cross-sectional area of ​​the embedded segment increases, and the cross-section is a surface perpendicular to the direction of the embedding depth.

5. The shaft assembly according to any one of claims 1 to 4, characterized in that, The decorative component is made of one or more of titanium, titanium alloy, and stainless steel; and / or the structural component is made of alloy steel, wherein the alloying elements in the alloy steel include one or more of B, O, S, P, N, W, Cr, Cu, Ni, Mo, Co, Si, Mn, V, and Nb.

6. The shaft assembly according to any one of claims 1 to 4, characterized in that, The pivot assembly also includes a coating layer located on the side of the decorative element away from the structural element.

7. A method for manufacturing a rotating shaft assembly, characterized in that, Includes the following steps: A 3D printing scheme is set according to the target structure of the pivot assembly. The target structure includes a target decorative part and a target structural part, and the target structural part is embedded on the target decorative part. Decorative powder and structural powder are 3D printed separately according to the printing scheme to integrally form the target decorative part and the target structural part with tensile strength of 1800MPa~2300MPa and yield strength of 1700MPa~2200MPa.

8. The method for preparing the rotating shaft assembly according to claim 7, characterized in that, The decorative powder and the structural powder are 3D printed separately according to the printing scheme to integrally form the target decorative part and the target structural part, including the following steps: The decorative powder and the structural powder are printed separately to form an intermediate target decorative part and an intermediate target structural part. Sintering densifies the target decorative intermediate and the target structural intermediate, forming the target decorative part and the target structural part.

9. The method for preparing the rotating shaft assembly according to claim 8, characterized in that, The particle size of the decorative powder satisfies: 1) D10 is 3μm~8μm; 2) D50 is 9μm~17μm; 3) D90 is 19μm~35μm; and / or, the particle size of the structural powder satisfies: 1) D10 is 4μm~8μm; 2) D50 is 15μm~20μm; 3) D90 is 25μm~38μm.

10. The method for preparing the rotating shaft assembly according to claim 8, characterized in that, The decorative powder includes one or more of titanium powder, titanium alloy powder, and stainless steel powder; and / or, the structural powder includes alloy steel powder, wherein the alloying elements in the alloy steel powder include one or more of B, O, S, P, N, W, Cr, Cu, Ni, Mo, Co, Si, Mn, V, and Nb.

11. The method for preparing the rotating shaft assembly according to claim 8, characterized in that, The process parameters for printing the decorative powder include at least one of the following parameters: 1) coaxial powder feeding method; 2) laser power of 1800W~2400W; 3) scanning speed of 400mm / min~800mm / min; 4) spot diameter of 2mm~4mm; 5) powder feeding rate of 12g / min~16g / min; 6) powder carrier gas flow rate of 5L / min~8L / min; 7) protective gas flow rate of 8L / min~12L / min; and / or Alternatively, the process parameters for printing the structured powder may include at least one of the following parameters: 1) coaxial powder feeding method; 2) laser power of 1800W~2400W; 3) scanning speed of 400mm / min~800mm / min; 4) spot diameter of 2mm~4mm; 5) powder feeding rate of 12g / min~16g / min; 6) powder carrier gas flow rate of 5L / min~8L / min; 7) protective gas flow rate of 8L / min~12L / min.

12. The method for preparing the rotating shaft assembly according to claims 8 to 11, characterized in that, After sintering, the process further includes the following steps: heat treatment to strengthen the sintered densified profile, wherein the maximum temperature of the heat treatment strengthens the profile to ensure that the grain size variation in the densified target decorative part is ≤10%.

13. The method for preparing the rotating shaft assembly according to claim 12, characterized in that, The heat treatment strengthening includes solution treatment, cryogenic treatment, and aging treatment, and satisfies at least one of the following conditions: 1) The solution treatment includes the following procedure: holding at 920℃~980℃ for 30min~90min, cooling under N2 conditions, and controlling the time from 920℃~980℃ to room temperature to be 20min~40min; 2) The cryogenic treatment includes the following procedure: holding at -210℃ to -180℃ for 30 min to 90 min; 3) The aging treatment includes the following procedure: heat preservation at 460℃~540℃ for 3h~5h, followed by cooling.

14. The method for preparing a rotating shaft according to claim 12, characterized in that, After sintering or heat treatment strengthening, the following steps are also included: surface treatment of the densified profile obtained by sintering or the strengthened profile obtained by heat treatment strengthening.

15. The method for preparing a rotating shaft according to claim 14, characterized in that, The surface treatment includes at least one of the following steps: 1) Polishing treatment; 2) A coating layer is formed on the side of the decorative component away from the structural component.

16. A foldable electronic device, characterized in that, It includes a first housing, a second housing, a hinge assembly, and a flexible display assembly; The pivot assembly is manufactured as described in any one of claims 1 to 6 or by the manufacturing method of any one of claims 7 to 15, and is disposed between the first housing and the second housing, wherein the first housing and the second housing are rotatably connected by the pivot assembly to unfold or fold. The flexible display assembly is disposed on the first housing and the second housing, and is located on the same side of the first housing and the second housing when the first housing and the second housing are unfolded.

Images