Alloy steel, preparation method of alloy steel, rotating shaft assembly and electronic equipment

Abstract

The invention provides alloy steel, a preparation method of the alloy steel, a rotating shaft assembly and electronic equipment, and the alloy steel comprises the following components in percentage by mass: 8.0%-14.0% of Ni, 1.5%-5.0% of Mo, 12.0%-16.0% of Co, 1.5%-4.5% of Cr, 0.10%-1.0% of V, 0.20%-0.60% of C and more than 57.9% of Fe. A metal piece made of the alloy steel has high wear resistance and can be applied to a rotating shaft assembly, and the wear resistance of the rotating shaft assembly is improved.

Description

Technical Field

[0001] This application relates to the field of alloy technology, and in particular to an alloy steel, a method for preparing the alloy steel, a shaft assembly, and an electronic device. Background Technology

[0002] In recent years, electronic devices have become an important part of people's lives. With the increasing demand for electronic devices, various forms of electronic products have emerged. Among them, the demand for foldable electronic devices is also growing. For example, foldable phones, a new form of mobile phone, have gained popularity and developed rapidly since their introduction. Foldable electronic devices use a hinge assembly to open and close the device. This hinge assembly experiences wear during the opening and closing process, making improving its wear resistance a pressing issue. Summary of the Invention

[0003] The purpose of this application is to provide an alloy steel, a method for preparing the alloy steel, a shaft assembly, and an electronic device. Metal parts made using this alloy steel have high wear resistance and can be applied to shaft assemblies, thereby improving the wear resistance of the shaft assembly.

[0004] This application provides an alloy steel, wherein, based on the mass of the alloy steel, the composition of the alloy steel includes 8.0% to 14.0% Ni, 1.5% to 5.0% Mo, 12.0% to 16.0% Co, 1.5% to 4.5% Cr, 0.10% to 1.0% V, 0.20% to 0.60% C and more than 57.9% Fe.

[0005] The alloy steel provided in this application embodiment contains 0.20% to 0.60% carbon, making it a medium-carbon martensitic aging steel that can precipitate (Mo, Cr). x C y Phase strengthening is employed to enhance the strength of alloy steel. Furthermore, by simultaneously adding v (V) and carbon (C) elements to the alloy steel, these elements exhibit a high affinity. V readily reacts with the C element added to the alloy steel matrix through secondary hardening, generating micro-diffuse vanadium carbide (VC), a strong carbide compound. On one hand, vanadium carbide can be dispersed within the martensitic matrix of the alloy steel and can form coherent or semi-coherent phase interfaces with the martensitic matrix, exhibiting good bonding with it. On the other hand, vanadium carbide is a ceramic phase with a particle hardness reaching 2400 Hv–2600 Hv (Vickers hardness), exhibiting high hardness and excellent wear resistance, thus significantly improving the wear resistance of the alloy steel.

[0006] By controlling the C element content between 0.20% and 0.60%, the proportion of C element in the alloy steel is not too low. This avoids the problem that the alloy steel has poor wear resistance because the C element content is too low and cannot fully react to form a large number of dispersed hard vanadium carbide particles. At the same time, it also avoids the problem that the sintering temperature range is unstable during the preparation of alloy steel due to the C element content being too high.

[0007] Furthermore, Ni (nickel) in alloy steel can expand the austenite phase region, ensuring the volume of lath martensite after rapid cooling following solution treatment, and improving the plasticity and toughness of the alloy steel. However, Ni lowers the Ms point (Martensite Start, the temperature at which austenite transforms into martensite) of the alloy steel. Excessive Ni content can lead to excessive retained austenite during solution cooling in the alloy steel manufacturing process, preventing the formation of a fully austenitic structure and thus reducing the strength of the alloy steel. In this application, the Ni content is controlled between 10.0% and 13.0% to ensure that the proportion of Ni in the alloy steel is not too high, thus maintaining both the toughness and strength of the alloy steel.

[0008] Furthermore, by adding Mo to alloy steel, a strengthening alloying element, Mo can react with Ni and Fe to disperse and precipitate Mo-Fe and Mo-Ni reinforcing phases, thereby improving the material strength of the alloy steel. Co can, on the one hand, reduce the solid solubility of Mo in the lath martensite matrix of the alloy steel, thus promoting the precipitation of Mo-Fe and Mo-Ni reinforcing phases; on the other hand, it can inhibit the recovery of the martensitic substructure during the aging treatment in the alloy steel preparation process, providing more nucleation sites for the precipitated phases, thereby indirectly improving the strengthening effect of the alloy steel and thus contributing to the improvement of its material strength. In addition, by adding Cr to alloy steel, Cr can be used to generate solid solution strengthening, thereby improving the corrosion resistance of the alloy steel. The alloy steel provided in this application embodiment, by setting the composition and content of each component, enables the alloy steel to possess high material strength, toughness, and wear resistance. As a result, the metal parts made from this alloy steel possess high material strength, toughness, and wear resistance, which is beneficial for improving the wear performance of metal parts and achieving the effect of thinning. When the metal parts made from this alloy steel are used in the hinge assembly of electronic devices, the wear resistance of the hinge assembly can be improved.

[0009] In one possible embodiment, the alloy steel comprises 10.0% to 13.0% Ni, 2.0% to 4.5% Mo, 12.0% to 15.0% Co, 2.0% to 4.0% Cr, 0.20% to 0.8% V, 0.20% to 0.40% C, and more than 57.9% Fe.

[0010] In one possible implementation, the mass ratio of V to C in the alloy steel satisfies: 0.5 ≤ V / C ≤ 4.0. This allows V and C to react fully, precipitating vanadium carbide (VC), a high-hardness, strong carbon compound. This ensures that the alloy steel has high wear resistance and high strength.

[0011] In one possible implementation, the alloy steel composition further includes grain-refining strengthening elements, wherein the mass fraction of the grain-refining strengthening elements is ≤1.0% based on the mass of the alloy steel. These grain-refining strengthening elements are used to refine the grains of the alloy steel, thereby improving its strength and toughness.

[0012] In one possible implementation, the grain refiner is Nb. Nb can react with C to form the NbC phase, which can refine the grain structure of the alloy steel, thereby producing a grain refiner effect and improving the material strength and toughness of the alloy steel.

[0013] In one possible implementation, the alloy steel composition also includes unavoidable impurities, including at least one of Mn and Si.

[0014] In one possible implementation, the mass fraction of Mn is ≤1.0%, and the mass fraction of Si is ≤1.0%.

[0015] This application also provides a pivot assembly, which includes a metal component made of the aforementioned alloy steel. Alloy steel has high material strength, toughness, and wear resistance, which is beneficial for improving the strength, toughness, and wear resistance of the metal component made of alloy steel, thereby improving the strength, toughness, and wear resistance of the pivot assembly.

[0016] In one possible implementation, the pivot assembly includes a base, a first damping shaft, a damping bracket, a fixed bracket, a first elastic element, and a first damping swing arm. The first damping shaft is mounted on the base. The damping bracket and the fixed bracket are both sleeved on the first damping shaft and spaced apart from each other. The first elastic element is sleeved on the first damping shaft and abuts between the damping bracket and the fixed bracket. The first damping swing arm is sleeved on the first damping shaft and is located on the side of the damping bracket away from the first elastic element, and abuts against the damping bracket. The metal part is the fixed bracket, and / or the metal part is the first damping swing arm.

[0017] In one possible implementation, the rotating shaft assembly includes a first fixing member, a second fixing member, a casing, and a shaft core. The casing is fixedly connected to the first fixing member, and the shaft core is fixedly connected to the second fixing member. The shaft core is located inside the casing and can rotate relative to the casing. The metal part is the casing and / or the metal part is the shaft core.

[0018] This application also provides an electronic device, which includes a first housing, a second housing, and a rotating shaft assembly as described above, the rotating shaft assembly being connected between the first housing and the second housing.

[0019] This application also provides a method for preparing alloy steel, comprising:

[0020] Provide or prepare alloy steel powder;

[0021] A mixture is prepared by mixing materials including binder and alloy steel powder;

[0022] The mixture is shaped to obtain a green body;

[0023] Remove the binder from the green blank to prepare the blank to be sintered;

[0024] The sintered billet is sintered to obtain alloy steel, wherein, by mass, the alloy steel comprises 8.0%–14.0% Ni, 1.5%–5.0% Mo, 12.0%–16.0% Co, 1.5%–4.5% Cr, 0.10%–1.0% V, 0.20%–0.60% C, and greater than 57.9% Fe.

[0025] The alloy steel preparation method provided in this application embodiment uses a material comprising alloy steel powder and a binder for mixing. The binder serves as a flow carrier for the alloy steel powder, forming a green blank. The binder is then removed from the green blank, and the mixture is sintered and densified to form alloy steel. This process improves the strength, toughness, and wear resistance of the prepared alloy steel. This application embodiment, through the design of the alloy steel composition and the combination of the alloy steel preparation method, obtains an alloy steel with high strength, high toughness, and high wear resistance. When metal parts made from this alloy steel are used in the hinge assemblies of electronic devices, the wear resistance of the hinge assembly can be improved. Compared to existing hinge assembly materials, the alloy steel prepared using this application embodiment achieves significantly improved wear resistance while reaching near-high strength and toughness levels, thus improving the wear performance of metal parts made of alloy steel and achieving a thinning effect.

[0026] In one possible implementation, the step of sintering the blank to be sintered further includes: heat treatment of the alloy steel, the heat treatment including solution treatment and aging treatment performed sequentially, or the heat treatment including solution treatment, cryogenic treatment and aging treatment performed sequentially. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0028] Figure 1 This is a schematic diagram of the structure of the electronic device in the first embodiment of this application, where the alloy steel is used;

[0029] Figure 2 for Figure 1 A schematic diagram of the electronic device in its deployed state;

[0030] Figure 3 for Figure 1 A partial structural diagram of the hinge assembly in the electronic device shown;

[0031] Figure 4 This is a schematic diagram of the structure of an electronic device in the second embodiment of this application, where the alloy steel is used according to an embodiment of the present application.

[0032] Figure 5 for Figure 4 A schematic diagram of the structure of the rotating shaft component in the rotating shaft assembly of the electronic device shown;

[0033] Figure 6 for Figure 5 An exploded view of the rotating shaft component shown.

[0034] Figure 7 The metallographic structure of the alloy steel in Comparative Example 2 is shown.

[0035] Figure 8 The image shows the metallographic structure of the alloy steel in Example 10. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0037] This application provides an alloy steel that can be applied to equipment containing metal parts, such as machinery, automobiles, and electronic devices. The electronic devices include, but are not limited to, mobile phones, tablets, laptops, and wearable devices. For example, wearable devices can be watches, wristbands, etc. It should be understood that the electronic device can be a foldable electronic device, i.e., an electronic device that can switch between a folded state and an unfolded state; the electronic device can also be a non-foldable electronic device, and this application does not impose any limitations on this. The foldable electronic device is one that can be folded once or multiple times (two or more times).

[0038] See Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the structure of the electronic device 1 in the first embodiment of this application, which uses alloy steel. Figure 2 for Figure 1 The diagram shows the structure of electronic device 1 in its unfolded state. In this embodiment, alloy steel is used in the application of alloy steel to a mobile phone that can be folded once, as an example for explanation.

[0039] Electronic device 1 includes a first housing 110, a second housing 120, a hinge assembly 130, and a display screen 300. The hinge assembly 130 is rotatably connected between the first housing 110 and the second housing 120 to achieve a rotatable connection between the first housing 110 and the second housing 120. The hinge assembly 130 includes a metal component, which is made of alloy steel.

[0040] The display screen 300 is mounted on the first housing 110 and the second housing 120. The display screen 300 includes a first display portion 310, a second display portion 330, and a bendable portion 350. The first display portion 310 is mounted on the first housing 110, the second display portion 330 is mounted on the second housing 120, and the bendable portion 350 connects the first display portion 310 and the second display portion 330 and is disposed opposite to the pivot assembly 130.

[0041] Electronic device 1 has a folded state and an unfolded state. The first housing 110 and the second housing 120 can rotate relative to each other via a pivot assembly 130. The display screen 300 can move with the first housing 110, the second housing 120, and the pivot assembly 130 to switch between the folded and unfolded states. Specifically, the first housing 110 can rotate around the pivot assembly 130 and rotate relative to the second housing 120 to a relative position, so that the electronic device 1 is in the folded state. At this time, the first display portion 310 and the second display portion 330 of the display screen 300 are positioned opposite each other, the bendable portion 350 is bent, and the first housing 110 and the second housing 120 are positioned opposite each other. The electronic device 1 has a small size, making it convenient for users to carry and store. The first housing 110 can also rotate around the pivot assembly 130 and rotate relative to the second housing 120 to a relatively unfolded state, so that the electronic device 1 is in the unfolded state. At this time, the first display portion 310, the second display portion 330, and the bendable portion 350 in the display screen 300 are approximately on the same plane, and the included angle α between the first display portion 310, the second display portion 330, and the bendable portion 350 is 180 degrees, so the electronic device 1 has a large display area.

[0042] See also Figure 1 and Figure 3 , Figure 3 for Figure 1 A partial structural schematic diagram of the rotating shaft assembly 130 in the electronic device 1 shown.

[0043] The pivot assembly 130 includes a base ( Figure 3 (Not shown in the image) Damping mechanism 133, first fixed frame 135, and second fixed frame 137. Damping mechanism 133 is mounted on the base and connected between the first fixed frame 135 and the second fixed frame 137. The first fixed frame 135 is fixedly connected to the first housing 110, and the second fixed frame 137 is fixedly connected to the second housing 120.

[0044] Specifically, the damping mechanism 133 includes a first damping shaft 21, a second damping shaft 22, a first elastic element 31, a second elastic element 32, a damping bracket 41, a fixed bracket 42, a first damping swing arm 51, and a second damping swing arm 52. The first damping shaft 21 and the second damping shaft 22 are both mounted on the base and are spaced apart from each other.

[0045] The damping bracket 41 and the fixed bracket 42 are both sleeved on the first damping shaft 21 and the second damping shaft 22, and are spaced apart from each other. The damping bracket 41 has a first cam 411 and a third cam 413. The first cam and the third cam are both located on the surface of the damping bracket 41 opposite to the fixed bracket 42, and are spaced apart from each other. The first elastic member 31 is sleeved on the first damping shaft 21 and abuts against the damping bracket 41 and the fixed bracket 42. The second elastic member 32 is sleeved on the second damping shaft 22 and abuts against the damping bracket 41 and the fixed bracket 42, and is spaced apart from the first elastic member 31. For example, both the first elastic member 31 and the second elastic member 32 are springs.

[0046] The first damping swing arm 51 is sleeved on the first damping shaft 21 and located on the side of the damping bracket 41 facing away from the first elastic member 31, and abuts against the damping bracket 41. The first damping swing arm 51 is provided with a second cam 511, which is located on the surface of the first damping swing arm 51 facing the damping bracket 41 and abuts against the first cam 411. The second damping swing arm 52 is sleeved on the second damping shaft 22 and located on the side of the damping bracket 41 facing away from the second elastic member 32, and abuts against the damping bracket 41. The second damping swing arm 52 is provided with a fourth cam 521, which is located on the surface of the second damping swing arm 52 facing the damping bracket 41 and abuts against the third cam 413.

[0047] The first fixed frame 135 is slidably connected to the first damping swing arm 51 and fixedly connected to the first housing 110. The second fixed frame 137 is slidably connected to the second damping swing arm 52 and fixedly connected to the second housing 120.

[0048] During the switching between the unfolded and folded states of electronic device 1, when the first housing 110 is flipped, the first housing 110 drives the first fixing frame 135 to rotate. The rotation of the first fixing frame 135 drives the first damping swing arm 51 to rotate. Since the second cam 511 of the first damping swing arm 51 is in contact with the first cam 411 of the damping bracket 41, the damping bracket 41 moves along the first damping axis 21 under the action of the first damping swing arm 51. The movement of the damping bracket 41 compresses the first elastic member 31. After being subjected to pressure, the first elastic member 31 undergoes compression deformation and generates elastic force on the damping bracket 41, thereby generating a damping force to prevent the flipping of the first housing 110. Similarly, when the second housing 120 is flipped, the second housing 120 drives the second fixed frame 137 to rotate. The rotation of the second fixed frame 137 also drives the second damping swing arm 52 to rotate. Since the fourth cam 521 of the second damping swing arm 52 is in contact with the third cam 413 of the damping bracket 41, the damping bracket 41 will move along the second damping axis 22 under the action of the second damping swing arm 52. The movement of the damping bracket 41 compresses the second elastic member 32. After being subjected to pressure, the second elastic member 32 undergoes compression deformation and generates elastic force on the damping bracket 41, thereby generating a damping force against the flipping of the second housing 120.

[0049] The damping bracket 41 is subjected to a compressive force by the first damping swing arm 51 in the opposite direction to the elastic force of the first elastic member 31, and the damping bracket 41 is subjected to a compressive force by the second damping swing arm 52 in the opposite direction to the elastic force of the second elastic member 32, so that the damping mechanism 133 achieves the damping effect.

[0050] The electronic device 1 mainly achieves the damping feel when switching between the unfolded and folded states through the damping mechanism 133. The damping bracket 41, the first damping swing arm 51, and the second damping swing arm 52 are important components that provide the damping feel. During the switching process between the unfolded and folded states, the pressure applied by the first elastic element 31 to the damping bracket 41 along the extension direction of the first damping axis 21 causes the first cam 411 of the damping bracket 41 to contact the second cam 511 of the first damping swing arm 51. The damping bracket 41 and the first damping swing arm 51 move relative to each other along the contact surface of the first cam 411 and the second cam 511, thereby generating friction and wear. Similarly, the pressure applied by the second elastic element 32 to the damping bracket 41 along the extension direction of the second damping shaft 22 causes the third cam 413 of the damping bracket 41 to contact the fourth cam 521 of the second damping swing arm 52. The damping bracket 41 and the second damping swing arm 52 move relative to each other along the contact surface of the third cam 413 and the fourth cam 521, thereby generating friction and wear.

[0051] Currently, in order to achieve a thinner and lighter shaft assembly 130, the thickness of the damping bracket 41 is gradually decreasing. This leads to an increase in the contact stress between the damping bracket 41 and the first damping swing arm 51 and the second damping swing arm 52, resulting in increased wear between them. Furthermore, the first damping swing arm 51 and the second damping swing arm 52 are subjected to fatigue stress during the opening and closing of the electronic device 1, placing higher demands on their strength and toughness.

[0052] The alloy steel provided in this application embodiment can be applied to at least one of the damping bracket 41, the first damping swing arm 51, and the second damping swing arm 52 in the rotating shaft assembly 130 of the electronic device 1 in the first embodiment. That is, the metal parts made of alloy steel in the rotating shaft assembly 130 are at least one of the damping bracket 41, the first damping swing arm 51, and the second damping swing arm 52, so as to improve the wear resistance and toughness of the damping bracket 41, the first damping swing arm 51, or the second damping swing arm 52.

[0053] See Figure 4 , Figure 5 and Figure 6 , Figure 4 This is a schematic diagram of the structure of the electronic device 1 in the second embodiment of this application, which uses alloy steel according to an embodiment of this application. Figure 5 for Figure 4 A schematic diagram of the structure of the rotating shaft component 136 in the rotating shaft assembly 130 of the electronic device 1 shown. Figure 6 for Figure 5 The diagram shows an exploded view of the hinge component 136. In this embodiment, alloy steel is used as an example for illustration in a laptop computer (PC).

[0054] Electronic device 1 includes a first housing 110, a second housing 120, a hinge assembly 130, a display screen 300, and a keyboard 500. The hinge assembly 130 is rotatably connected between the first housing 110 and the second housing 120 to achieve a rotatable connection between them. The hinge assembly 130 includes a metal component made of alloy steel. The display screen 300 is mounted on the first housing 110, and the keyboard 500 is mounted on the second housing 120.

[0055] Specifically, the pivot assembly 130 includes a first fixing member ( Figure 4 (not shown in the image), second fastener ( Figure 4(Not shown) and a rotating shaft 136, the first fixing member is fixedly connected to the first housing 110, the second fixing member is fixedly connected to the second housing 120, and the rotating shaft 136 is connected between the first fixing member and the second fixing member. In this embodiment, the rotating shaft 136 includes a concentric circle 60 and a shaft core 70. The concentric circle 60 is fixedly connected to the first fixing member, and the shaft core 70 is fixedly connected to the second fixing member. The shaft core 70 is located inside the concentric circle 60 and can rotate within the concentric circle 60.

[0056] The electronic device 1 has a closed state and an open state. The first housing 110 and the second housing 120 can rotate relative to each other via a rotating shaft assembly 130 to switch between the closed and open states. Specifically, when the first housing 110 is opened, it drives the first fixing member to rotate, and the shaft core 70 rotates within the enclosure 60. Due to the interference between the enclosure 60 and the shaft core 70, friction is generated between them, thus producing a damped feel in the electronic device 1. During the switching between the closed and open states, wear is prone to occur at the mating points of the shaft core 70 and the enclosure 60. Therefore, high requirements are placed on the wear resistance and toughness of both the shaft core 70 and the enclosure 60.

[0057] The alloy steel provided in this application embodiment can be applied to the outer circle 60 and / or the shaft core 70 of the rotating shaft assembly 130 of the electronic device 1 in the second embodiment. That is, the metal parts made of alloy steel in the rotating shaft assembly 130 are the outer circle 60 and / or the shaft core 70 to improve the wear resistance and toughness of the outer circle 60 and / or the shaft core 70.

[0058] The following description, in conjunction with the specific composition of the alloy steel, illustrates the alloy steel provided in the embodiments of this application.

[0059] Specifically, based on the mass of the alloy steel, the alloy steel provided in this application embodiment comprises 8.0% to 14.0% Ni (nickel), 1.5% to 5.0% Mo (molybdenum), 12.0% to 16.0% Co (cobalt), 1.5% to 4.5% Cr (chromium), 0.10% to 1.0% V (vanadium), 0.20% to 0.60% C (carbon), and more than 57.9% Fe (iron).

[0060] In some embodiments, the alloy steel comprises, by weight, 10.0% to 13.0% Ni, 2.0% to 4.5% Mo, 12.0% to 15.0% Co, 2.0% to 4.0% Cr, 0.20% to 0.8% V, 0.20% to 0.40% C and greater than 57.9% Fe.

[0061] For example, based on the mass of alloy steel, the weight percentage of Ni (nickel) in the alloy steel can be 8.0%, 10.0%, 12.0%, 14.0%, or any value between these values. For example, based on the mass of alloy steel, the weight percentage of Mo (molybdenum) in the alloy steel can be 1.5%, 3.0%, 4.5%, 5.0%, or any value between these values. For example, based on the mass of alloy steel, the weight percentage of Co (cobalt) in the alloy steel can be 12.0%, 13.0%, 14.0%, 15.0%, 16.0%, or any value between these values. For example, based on the mass of alloy steel, the weight percentage of Cr (chromium) can be 1.5%, 3.0%, 4.5%, or any value between these values. For example, based on the mass of alloy steel, the weight percentage of vanadium (V) can be 0.10%, 0.30%, 0.50%, 0.70%, 0.90%, 1.0%, or any value between these values. Similarly, based on the mass of alloy steel, the weight percentage of carbon (C) can be 0.20%, 0.4%, 0.60%, or any value between these values.

[0062] Existing martensitic aging alloy steels typically employ carbon-free (containing no C) or low-carbon (low C content) schemes, improving the material strength of the alloy steel through aging strengthening. The strengthening phases are usually FeMo, FeNi, or MoNi phases. Martensitic aging alloy steels exhibit good strength and toughness but poor wear resistance. Conversely, high-carbon (high C content) die steels offer good wear resistance but have lower material strength.

[0063] The alloy steel provided in this application embodiment contains 0.20% to 0.60% carbon, making it a medium-carbon martensitic aging steel that can precipitate (Mo, Cr). x C y Phase strengthening is used to improve the material strength of alloy steel. Furthermore, by adding v (vitamin V) and carbon (carbon) elements to the alloy steel, the high affinity between V and C elements allows V to readily react with the carbon elements added to the alloy steel matrix through secondary hardening, generating micro-diffuse vanadium carbide (VC). On one hand, VC can be dispersed within the martensitic matrix of the alloy steel and can form coherent or semi-coherent phase interfaces with the martensitic matrix, exhibiting good bonding with it. On the other hand, VC is a ceramic phase with a particle hardness reaching 2400 Hv to 2600 Hv (Vickers hardness), exhibiting high hardness and excellent wear resistance, thus significantly improving the wear resistance of the alloy steel.

[0064] By controlling the C element content between 0.20% and 0.60%, the proportion of C element in the alloy steel is not too low. This avoids the problem that the alloy steel has poor wear resistance because the C element content is too low and cannot fully react to form a large number of dispersed hard vanadium carbide particles. At the same time, it also avoids the problem that the sintering temperature range is unstable during the preparation of alloy steel due to the C element content being too high.

[0065] Furthermore, Ni (nickel) in alloy steel can expand the austenite phase region, ensuring the volume of lath martensite after rapid cooling following solution treatment, and improving the plasticity and toughness of the alloy steel. However, Ni lowers the Ms point (Martensite Start, the temperature at which austenite transforms into martensite) of the alloy steel. Excessive Ni content can lead to excessive retained austenite during solution cooling in the alloy steel manufacturing process, preventing the formation of a fully austenitic structure and thus reducing the strength of the alloy steel. In this application, the Ni content is controlled between 10.0% and 13.0% to ensure that the proportion of Ni in the alloy steel is not too high, thus maintaining both the toughness and strength of the alloy steel.

[0066] Furthermore, by adding Mo to alloy steel, a strengthening alloying element, Mo can react with Ni and Fe to disperse and precipitate Mo-Fe and Mo-Ni reinforcing phases, thereby improving the material strength of the alloy steel. Co can, on the one hand, reduce the solid solubility of Mo in the lath martensite matrix of the alloy steel, thus promoting the precipitation of Mo-Fe and Mo-Ni reinforcing phases; on the other hand, it can inhibit the recovery of the martensitic substructure during the aging treatment in the alloy steel preparation process, providing more nucleation sites for the precipitated phases, thereby indirectly improving the strengthening effect of the alloy steel and thus contributing to the improvement of its material strength. In addition, by adding Cr to alloy steel, Cr can be used to generate solid solution strengthening, thereby improving the corrosion resistance of the alloy steel.

[0067] The alloy steel provided in this application embodiment, by setting the composition and content of each component, enables the alloy steel to possess high material strength, toughness, and wear resistance. As a result, the metal parts made from this alloy steel possess high material strength, toughness, and wear resistance, which is beneficial for improving the wear performance of metal parts and achieving the effect of thinning. When the metal parts made from this alloy steel are used in the hinge assembly of electronic devices, the wear resistance of the hinge assembly can be improved.

[0068] In some possible implementations, the mass ratio of V to C in the alloy steel, V / C, can be further controlled to satisfy: 0.5 ≤ V / C ≤ 4.0. Within this range, V and C react sufficiently to precipitate vanadium carbide (VC), a high-hardness, strong carbon compound, thus ensuring the alloy steel has high wear resistance and high strength. When the V / C ratio is too low, the C content is too high relative to the V content, causing excess C to react with Cr to form chromium carbide, which precipitates along the grain boundaries. This results in the alloy steel being brittle. Furthermore, the hardness of chromium carbide is 1300 Hv to 1700 Hv, lower than that of vanadium carbide, thus relatively reducing the wear resistance of the alloy steel. When the V / C ratio is too high, the C content is relatively low relative to the V content, resulting in insufficient C to react with V in the alloy steel matrix. This reduces the content of vanadium carbide, further decreasing the wear resistance of the alloy steel. In addition, excessive V can lead to poor fluidity of molten steel during powder atomization in the preparation of alloy steel, resulting in uneven particle size distribution of the alloy steel powder. This increases the porosity of the sintering blank formed from the alloy steel powder, which can easily cause defects such as uneven sintering during the sintering process of the sintering blank to form alloy steel, thus leading to a relative decrease in the strength of the alloy steel.

[0069] In some embodiments, the alloy steel composition further includes grain-refining strengthening elements, wherein the mass fraction of the grain-refining strengthening elements is ≤1.0% based on the mass of the alloy steel. These grain-refining strengthening elements are used to refine the grain structure of the alloy steel, thereby improving its strength and toughness. For example, the grain-refining strengthening element is Nb (niobium). Nb can react with carbon to form the NbC phase, which refines the grain structure of the alloy steel, resulting in a grain-refining strengthening effect and thus improving the material strength and toughness of the alloy steel.

[0070] In some embodiments, the alloy steel further comprises at least one of rare earth elements, Al, and Ti. Specifically, based on the mass of the alloy steel, the mass fraction of rare earth elements is ≤0.5%, the mass fraction of Al is ≤0.5%, and the mass fraction of Ti is ≤0.5%.

[0071] It is understood that the composition of alloy steel also includes unavoidable impurities, including at least one of Mn (manganese) and Si (silicon). For example, the weight percentage of Mn (manganese) in the alloy steel is <1.0% by weight. For example, the weight percentage of Si (silicon) in the alloy steel is <1.0% by weight.

[0072] This application also provides a method for preparing the above-mentioned alloy steel, comprising:

[0073] S1. Provide or prepare alloy steel powder.

[0074] In some possible implementations, step S1 specifically involves: taking raw materials for alloy steel according to the composition of alloy steel, melting the raw materials of alloy steel to form molten alloy steel, and then using high-pressure water atomization or gas atomization to prepare alloy powder from the molten alloy steel.

[0075] The particle size characteristics of the alloy steel powder meet the following requirements: D10 is 1μm to 5μm, D50 is 6μm to 12μm, and D90 is 15μm to 25μm. Here, D10 represents the particle size corresponding to 10% of the cumulative particle size distribution in the alloy steel powder, meaning that 10% of the alloy steel powder particles have a diameter smaller than the value of D10. D50 represents the particle size corresponding to 50% of the cumulative particle size distribution in the alloy steel powder, meaning that 50% of the alloy steel powder particles have a diameter smaller than the value of D50. D90 represents the particle size corresponding to 90% of the cumulative particle size distribution in the alloy steel powder, meaning that 90% of the alloy steel powder particles have a diameter smaller than the value of D90. By controlling the particle size characteristics of the alloy steel powder to meet the above conditions, the alloy steel powder has better injection molding flowability and sintering activity in subsequent steps, thus ensuring a sintering density of 95% or higher, which in turn helps to guarantee the strength, toughness, and wear resistance of the prepared alloy steel. For example, the raw material for alloy steel with Ni element can be pure nickel, the raw material for alloy steel with Mo element can be pure molybdenum, the raw material for alloy steel with Co element can be pure cobalt, the raw material for alloy steel with Cr element can be pure chromium, the raw material for alloy steel with V element can be ferrovanadium alloy, and the raw material for alloy steel with C or Fe element can be carbon steel.

[0076] For example, in some embodiments, the particle size characteristics of the alloy steel powder can be further controlled to meet the following requirements: D10 is 2μm to 4μm, D50 is 7μm to 10μm, and D90 is 16μm to 21μm.

[0077] In this embodiment, the tap density of the alloy steel powder is ≥4.20 g / cm³. 3 This ensures that the alloy steel powder possesses good injection molding flowability and sintering activity, thereby guaranteeing a sintering density of 95% or higher, which in turn helps to ensure the strength, toughness, and wear resistance of the prepared alloy steel. For example, in some embodiments, the tap density of the alloy steel powder can be further controlled to ≥4.40 g / cm³. 3 .

[0078] S2. Take materials including binder and alloy steel powder and mix them to prepare a mixture.

[0079] In this embodiment, the volume ratio of alloy steel powder to binder in step S2 is (1.2~2.3):1. Exemplarily, in some embodiments, the volume ratio of alloy steel powder to binder is (1.27~1.78):1.

[0080] In some possible implementations, step S2 specifically involves: taking materials comprising alloy steel powder and binder and mixing them in a mixer according to a volume ratio of alloy steel powder to binder of (1.2 to 2.3):1, to obtain a mixture. For example, the mixing temperature is 170°C to 210°C, and the mixing time is 1 hour to 4 hours.

[0081] In this embodiment, the adhesive is a polymeric adhesive. For example, the polymeric adhesive comprises polyoxymethylene, high-density polyethylene, polypropylene, paraffin wax, ethylene-vinyl acetate copolymer (EVA), polymethyl methacrylate (PMMA), stearic acid, and antioxidants.

[0082] S3. The mixture is shaped to obtain a green body.

[0083] In this embodiment, step S2 involves injection molding the mixture. In some possible implementations, step S2 specifically involves using an injection molding machine to inject the mixture. For example, the injection temperature is 170°C to 210°C.

[0084] S4. Remove the binder from the green blank to prepare the blank to be sintered.

[0085] In some possible implementations, step S2 specifically involves removing the binder from the green blank using acid-catalyzed degreasing or solvent degreasing to prepare a green blank to be sintered. For example, the degreasing temperature for acid-catalyzed degreasing or solvent degreasing is 120℃~130℃. For example, the degreasing time for acid-catalyzed degreasing is 1h~12h, and the catalytic medium for acid-catalyzed degreasing is nitric acid or oxalic acid.

[0086] S5. Sinter the billet to be sintered to obtain alloy steel, wherein, by mass, the alloy steel composition includes 8.0%–14.0% Ni, 1.5%–5.0% Mo, 12.0%–16.0% Co, 1.5%–4.5% Cr, 0.10%–1.0% V, 0.20%–0.60% C and greater than 57.9% Fe.

[0087] In this embodiment, the blank to be sintered is placed in a vacuum or a protective atmosphere for sintering to obtain alloy steel. For example, the protective atmosphere is argon, and the partial pressure of argon is 10 kPa to 80 kPa. For example, the sintering temperature in step S5 is 1200°C to 1400°C, and the holding time is 60 min to 360 min.

[0088] In some possible implementations, the sintering temperature in step S5 is 1260℃~1340℃, and the holding time is 120min~300min. In some possible implementations, in step S5, the blank to be sintered is placed in an argon atmosphere for sintering, and the partial pressure of the argon gas is 15Kpa~80Kpa.

[0089] The alloy steel preparation method provided in this application embodiment uses a material comprising alloy steel powder and a binder for mixing. The binder serves as a flow carrier for the alloy steel powder, forming a green blank. The binder is then removed from the green blank, and the mixture is sintered and densified to form alloy steel. This process improves the material strength, toughness, and wear resistance of the prepared alloy steel. This application embodiment, through the design of the alloy steel composition and the combination of the alloy steel preparation method, obtains an alloy steel with high material strength, toughness, and wear resistance. When metal parts made from this alloy steel are used in the hinge assemblies of electronic devices, the wear resistance of the hinge assembly can be improved. Compared to existing hinge assembly materials, the alloy steel prepared using this application embodiment achieves significantly improved wear resistance while reaching near-high toughness levels, thus improving the wear performance of metal parts made from alloy steel and achieving a thinning effect.

[0090] In this embodiment of the application, step S5 is followed by step S6: heat treatment of the alloy steel. By heat treating the sintered alloy steel, the material strength, toughness, and wear resistance of the prepared alloy steel can be further improved.

[0091] In some possible implementations, the heat treatment includes sequential solution treatment and aging treatment. For example, the solution treatment process involves holding at 850℃ to 1100℃ for 60 to 180 minutes, followed by rapid cooling of the furnace cavity to below 30℃ using high-pressure inert gas (pressure > 6 bar). For example, the cooling time is less than 30 minutes to achieve rapid cooling to below 30℃. For example, the aging treatment process involves holding at 400℃ to 600℃ for 60 to 360 minutes. During the solution treatment, rapid cooling is typically employed to ensure a uniform material microstructure, the formation of martensitic structure, and the formation of a supersaturated solid solution of alloying elements, thereby ensuring that the prepared alloy steel possesses high strength and high toughness.

[0092] In some possible implementations, the heat treatment includes sequential solution treatment, cryogenic treatment, and aging treatment. For example, the solution treatment process involves holding at 1000℃ to 1100℃ for 60 to 150 minutes, followed by rapid cooling of the furnace cavity to below 30℃ using high-pressure inert gas (pressure > 8 bar). For example, the cryogenic treatment temperature is -100℃ to -196℃, and the holding time is greater than 1 hour. For example, the aging treatment process involves holding at 460℃ to 550℃ for 240 to 300 minutes. In the preparation of alloy steel, the use of cryogenic treatment can reduce the formation of retained austenite and generate martensite, thereby improving the material strength of the alloy steel.

[0093] The properties of the alloy steel provided in this application will be described below with reference to specific embodiments.

[0094] Examples 1 to 12 and Comparative Examples 1 to 4 all provide an alloy steel prepared according to the following steps:

[0095] Step S1: Prepare alloy steel powder.

[0096] Alloy steel powder was prepared using a high-pressure water mist method, and raw materials with specific particle size characteristics were separated by airflow classification. The particle size characteristics of the alloy steel powder were: D10 of 1 μm to 5 μm, D50 of 6 μm to 12 μm, and D90 of 15 μm to 25 μm.

[0097] Step S2: Feeding and mixing.

[0098] A polymeric adhesive is provided, the composition of which is at least one of the following: polyoxymethylene, high-density polyethylene, polypropylene, paraffin wax, ethylene-vinyl acetate copolymer (EVA), polymethyl methacrylate (PMMA), stearic acid, and antioxidant.

[0099] The alloy steel powder and polymer binder from step S1 were mixed in a Σ-type kneader at a volume ratio of 1.27:1. The mixing temperature was 190℃, and the mixing time was 1 hour. After mixing, a mixture was obtained and then extruded into granules using a mixing extruder.

[0100] Step S3: Injection molding.

[0101] The granulated mixture from step S2 is injection molded using an injection molding machine and a product mold to obtain a green body. The injection temperature is 190°C.

[0102] Step S4: Remove the adhesive.

[0103] The injection-molded green body was subjected to acid-catalyzed debinding to remove the polymer binder, resulting in a green body to be sintered. The debinding temperature was 120°C, and the debinding time was 2 hours. Nitric acid was used as the catalytic medium, and nitrogen was used as the protective atmosphere.

[0104] Step S5: Sinter the billet to be sintered to obtain alloy steel.

[0105] The sintering equipment is a vacuum batch furnace. The sintering process is as follows: sintering is carried out under the conditions of vacuum atmosphere, argon protective atmosphere, and argon partial pressure of 15 kPa. The maximum sintering temperature is 1320℃, and the holding time is 180 minutes.

[0106] Step S51: Plastic surgery.

[0107] The alloy steel obtained by sintering in step S5 is cold-formed to ensure the dimensional and shape accuracy of the obtained parts.

[0108] Step S6: Heat treatment, which includes solution treatment, cryogenic treatment and aging treatment.

[0109] The alloy steel was subjected to solution treatment, cryogenic treatment, and aging treatment sequentially. The solution treatment was performed in a vacuum high-pressure gas quenching furnace. The process involved heating the alloy steel to 1070℃ and holding it for 120 minutes. After holding, the furnace temperature was rapidly cooled to below 30℃ using high-pressure inert gas (nitrogen or argon) at a pressure of 8 bar. The cryogenic treatment was conducted in a cryogenic bath at a temperature below -150℃ for a holding time greater than 1 hour. The aging treatment was performed in a vacuum heat treatment furnace. The process involved heating the steel to 480℃ under a vacuum atmosphere and holding it for 240 minutes.

[0110] The composition and content of the alloy steels in Examples 1-12 and Comparative Examples 1-4 are shown in Table 1.

[0111] Table 1. Composition and content of alloy steels in Examples 1-12 and Comparative Examples 1-4

[0112]

[0113]

[0114] The alloy steels from Comparative Example 2 and Example 10 were used to characterize the alloy steels, and the results are as follows: Figure 7 and Figure 8 As shown, Figure 7 The image shows the metallographic structure of the alloy steel in Comparative Example 2. Figure 8 The image shows the metallographic structure of the alloy steel from Example 10. Figure 8(a) shows a metallographic structure diagram with a magnification of 100, (b) shows a metallographic structure diagram with a magnification of 200, and (c) shows a metallographic structure diagram with a magnification of 500.

[0115] from Figure 7 It can be seen that the matrix of the alloy steel in Comparative Example 2 is lath martensite, with a certain proportion of retained austenite distributed at the grain boundaries, and the precipitated phases are rod-shaped M7C3 phases (MoFe and MoNi phases). The alloy steel exhibits poor wear resistance. Figure 8 As can be seen, the matrix of the alloy steel provided in Example 10 is lath martensite. The addition of Ni and C, both austenitizing elements, results in a certain proportion of retained austenite in the metallographic structure of the alloy steel. This small amount of austenite can improve the material's plasticity by absorbing strain. Example 10 controls the addition of alloying elements such as Ni / Mo and C to ensure the volume percentage of retained austenite, thus avoiding the problem of decreased material strength due to excessive retained austenite. Furthermore, the alloy steel of Example 10 also precipitates a spherical VC (vanadium carbide) hard phase in its matrix. This VC hard phase is tightly bonded to the matrix, and the spherical VC phase has a stronger crack-blocking effect than the rod-shaped M7C3 phase, thus giving the alloy steel higher strength and wear resistance.

[0116] Alloy steels from Examples 1-12 and Comparative Examples 1-4 were tested, and their room temperature mechanical properties are shown in Table 2. The wear resistance test method in Table 2 was as follows: An alloy steel sample was fixed on a testing machine. A spherical friction ball was used as a standard friction head, placed above the alloy steel sample. The pressure between the standard friction head and the alloy steel sample was kept constant by the force application device and force sensor of the testing machine. The standard friction head was used to rub the alloy steel sample, and its linear reciprocating motion relative to the sample was controlled. After the standard friction head had reciprocated a preset number of times, the rubbed alloy steel sample was removed, and the wear track depth was measured and analyzed. The average wear track depth characterized the wear resistance of the alloy steel material.

[0117] Table 2. Room temperature mechanical properties of alloy steels from Examples 1-12 and Comparative Examples 1-4

[0118]

[0119] As can be seen from Tables 1 and 2, by comparing Comparative Examples 1-2 and Examples 1-12, the alloy steels provided by Comparative Examples 1 and 2, by adjusting the added elements and their contents, exhibited relatively good yield strength, tensile strength, and elongation. However, the average wear depth of the alloy steels in Comparative Examples 1 and 2 was over 9.0 μm, indicating poor wear resistance, making them unsuitable for components requiring both high material strength and wear resistance. Specifically, the C (carbon) content in the alloy steels of Comparative Examples 1 and 2 was <0.1%, indicating a low C content. The Ni (nickel) content in the alloy steel of Comparative Example 1 was 18.5%, indicating a high Ni content, while the Ni (nickel) content in the alloy steel of Comparative Example 2 was 6.0%, indicating a low Ni content. Adjusting the Ni content by increasing or decreasing it did not improve the wear resistance of the alloy steels.

[0120] Examples 1-12 of this application, by adjusting the composition and content of the alloy steel, achieve a yield strength exceeding 1600 MPa, a tensile strength greater than 1800 MPa, an elongation greater than 3.5%, and an average wear track depth less than 6.0 μm. The alloy steels of Examples 1-12 simultaneously possess high material strength, high elongation, and high wear resistance. Experimental results show that, by adding various constituent elements and controlling the mass fraction of each component to meet the following conditions: 8.0% ≤ Ni ≤ 14.0%, 1.5% ≤ Mo ≤ 5.0%, 12.0% ≤ Co ≤ 16.0%, 1.5% ≤ Cr ≤ 4.5%, 0.10% ≤ V ≤ 1.0%, and 0.20% ≤ C ≤ 0.60%, the alloy steel can guarantee high material strength, high toughness, and high wear resistance. Furthermore, comparing Examples 3-12 and Examples 1-2, the alloy steel of Examples 3-12 exhibits higher yield strength, tensile strength, elongation, and wear resistance compared to the alloy steel of Examples 1-2. Extensive experimental research in this application has revealed that controlling the mass fraction of each component in the alloy steel to meet the following conditions—10.0% ≤ Ni ≤ 13.0%, 2.0% ≤ Mo ≤ 4.5%, 12.0% ≤ Co ≤ 15.0%, 2.0% ≤ Cr ≤ 4.0%, 0.20% ≤ V ≤ 0.8%, and 0.20% ≤ C ≤ 0.40%—results in alloy steel with relatively high strength, toughness, and wear resistance.

[0121] Furthermore, comparing Examples 9 and 10, the alloy steel of Example 10, compared to the alloy steel of Example 9, also contained the fine-grained strengthening element Nb, resulting in improved yield strength, tensile strength, and elongation. Comparing Examples 10 and 11-12, the mass ratio of V to C in the alloy steel of Example 10 satisfies 0.5 ≤ V / C ≤ 4.0. In contrast, the alloy steel of Example 11 has a lower V / C ratio (V / C < 0.5), and the alloy steel of Example 12 has a higher V / C ratio (V / C > 4.0). The yield strength, tensile strength, elongation, and wear resistance of the alloy steels of Examples 11 and 12 are all lower than those of the alloy steel of Example 10. The experimental results indicate that both excessively low and excessively high V / C mass ratios negatively impact the performance of alloy steel. Through extensive experimental research, this application has found that controlling the mass ratio of V to C elements (V / C) at 0.5 ≤ V / C ≤ 4.0 ensures that V and C elements react fully, thereby guaranteeing that the resulting alloy steel possesses high material strength, high toughness, and high wear resistance.

[0122] Furthermore, comparing Comparative Examples 3-4 and Examples 1-12, the alloy steel in Comparative Example 3 had a C element mass fraction of <0.20%, indicating a low C element content. Insufficient C element was present to react with V element to form vanadium carbide particles, resulting in an excessively low vanadium carbide content. Consequently, the average wear track depth of the resulting alloy steel was as high as 9.8 μm, indicating poor wear resistance. Similarly, the alloy steel in Comparative Example 2 had a V element mass fraction of <0.10%, indicating a low V element content. The amount of vanadium carbide formed by the reaction of V and C element was too low, resulting in an average wear track depth of as high as 9.5 μm, indicating poor wear resistance. The experimental results show that simultaneously controlling the V element content to 0.10%–1.0% and the C element content to 0.20%–0.60% in the alloy steel is beneficial for ensuring the strength, elongation, and wear resistance of the alloy steel.

[0123] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art will understand that all or part of the processes for implementing the above embodiments and equivalent variations made in accordance with the claims of this application are still within the scope of this application.

Claims

1. An alloy steel, characterized in that, Based on the mass of the alloy steel, the alloy steel comprises 8.0% to 14.0% Ni, 1.5% to 5.0% Mo, 12.0% to 16.0% Co, 1.5% to 4.5% Cr, 0.10% to 1.0% V, 0.20% to 0.60% C and greater than 57.9% Fe.

2. The alloy steel according to claim 1, characterized in that, The alloy steel comprises 10.0%–13.0% Ni, 2.0%–4.5% Mo, 12.0%–15.0% Co, 2.0%–4.0% Cr, 0.20%–0.8% V, 0.20%–0.40% C, and more than 57.9% Fe.

3. The alloy steel according to claim 1, characterized in that, In the alloy steel, the mass ratio of V to C elements, V / C, satisfies: 0.5 ≤ V / C ≤ 4.

0.

4. The alloy steel according to any one of claims 1 to 3, characterized in that, The alloy steel also includes grain-refining strengthening elements, and the mass fraction of the grain-refining strengthening elements is ≤1.0% based on the mass of the alloy steel.

5. The alloy steel according to claim 4, characterized in that, The grain-refining strengthening element is Nb.

6. The alloy steel according to any one of claims 1 to 3, characterized in that, The alloy steel also contains unavoidable impurities, including at least one of Mn and Si.

7. The alloy steel according to claim 6, characterized in that, Based on the mass of the alloy steel, the mass fraction of Mn is ≤1.0%, and the mass fraction of Si is ≤1.0%.

8. A rotating shaft assembly, characterized in that, The shaft assembly includes a metal component made of alloy steel as described in any one of claims 1 to 7.

9. The rotating shaft assembly according to claim 8, characterized in that, The rotating shaft assembly includes a base, a first damping shaft, a damping bracket, a fixed bracket, a first elastic element, and a first damping swing arm. The first damping shaft is mounted on the base. The damping bracket and the fixed bracket are both sleeved on the first damping shaft and are spaced apart from each other. The first elastic element is sleeved on the first damping shaft and abuts between the damping bracket and the fixed bracket. The first damping swing arm is sleeved on the first damping shaft and is located on the side of the damping bracket away from the first elastic element, and abuts against the damping bracket. The metal component is the fixed bracket, and / or the metal component is the first damping swing arm.

10. The rotating shaft assembly according to claim 8, characterized in that, The rotating shaft assembly includes a first fixing member, a second fixing member, a circumferential ring, and a shaft core. The circumferential ring is fixedly connected to the first fixing member, and the shaft core is fixedly connected to the second fixing member. The shaft core is located inside the circumferential ring and can rotate relative to the circumferential ring. The metal part is the outer circle, and / or the metal part is the shaft core.

11. An electronic device, characterized in that, The electronic device includes a first housing, a second housing, and a pivot assembly as described in any one of claims 8 to 10, the pivot assembly being connected between the first housing and the second housing.

12. A method for preparing alloy steel, characterized in that, include: Provide or prepare alloy steel powder; A mixture is prepared by mixing a material including a binder and the alloy steel powder; The mixture is shaped to obtain a green body; The binder in the green blank is removed to prepare a green blank to be sintered; The blank to be sintered is sintered to obtain alloy steel, wherein, based on the mass of the alloy steel, the composition of the alloy steel includes 8.0% to 14.0% Ni, 1.5% to 5.0% Mo, 12.0% to 16.0% Co, 1.5% to 4.5% Cr, 0.10% to 1.0% V, 0.20% to 0.60% C and greater than 57.9% Fe.

13. The method for preparing alloy steel according to claim 12, characterized in that, The step of sintering the blank to be sintered further includes: heat treatment of the alloy steel, wherein the heat treatment includes solution treatment and aging treatment performed sequentially, or the heat treatment includes solution treatment, cryogenic treatment and aging treatment performed sequentially.

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