Lightweight steel and its preparation methods, steel structural components and electronic equipment

Abstract

This application provides a lightweight steel comprising: Fe, with a weight percentage ≥ 48.18 wt%; Mn, with a weight percentage of 30.01 wt% to 35.01 wt%; Al, with a weight percentage of 12.01 wt% to 15.01 wt%; C, with a weight percentage of 1.0 wt% to 1.5 wt%; and O, with a weight percentage of 0.03 wt% to 0.3 wt%. This application also provides steel structural components and electronic devices using this lightweight steel, as well as a method for preparing the lightweight steel. The lightweight steel of this application has low density, high strength, and high ductility.

Description

Technical Field

[0001] This application relates to a lightweight steel and a method for preparing the same, as well as steel structural components and electronic devices using the lightweight steel. Background Technology

[0002] The hinge mechanism of existing foldable screen phones is basically composed of two materials. One is precipitation-hardening steel, which has good comprehensive mechanical properties, high strength, good toughness, yield strength of about 1000MPa, elongation of about 6%, but high density, about 7.8g / cm³. 3 Another type is made of aluminum alloy, which has a lower density of approximately 2.7 g / cm³. 3 However, its strength is relatively low. For the 7-series aluminum alloys, which are currently widely used and have the highest strength, such as 7075, the yield strength is about 500MPa, and it is prone to deformation during use. Summary of the Invention

[0003] The first aspect of this application provides a lightweight steel, comprising:

[0004] Fe, weight percentage ≥ 48.18 wt%;

[0005] Mn, with a weight percentage of 30.01 wt% to 35.01 wt%;

[0006] Al, with a weight percentage of 12.01 wt% to 15.01 wt%;

[0007] C, with a weight percentage of 1.0 wt% to 1.5 wt%;

[0008] O, with a weight percentage of 0.03wt% to 0.3wt%.

[0009] The composition of the lightweight steel in this application is innovatively designed with a high content of aluminum (12.01wt% to 15.01wt%) and a high content of oxygen (0.03wt% to 0.3wt%). The oxygen reacts with the aluminum to form aluminum oxide, thereby generating an aluminum oxide reinforcing phase in the lightweight steel and improving its strength and ductility.

[0010] Adding Al to steel can improve its density, making it lightweight. This application achieves this by incorporating a high Al content (12.01 wt% to 15.01 wt%) into the lightweight steel, resulting in a low density of 5.9 to 6.3 g / cm³. 3 This significantly reduces the weight of consumer electronics products using the lightweight steel, improving the user experience. The lightweight steel in this application is a material with high strength, high ductility, and low density.

[0011] In this embodiment of the application, the lightweight steel contains alumina particles, which are basically composed of alumina particles with a length and width of ≤5μm.

[0012] The alumina phase particles are small in size and dispersed in the lightweight steel, mainly at the phase interface, where they play a role in dispersion strengthening, thereby improving the strength of the lightweight steel.

[0013] In this embodiment of the application, the lightweight steel further includes V, and the weight percentage of V is ≤0.6wt%.

[0014] V plays two main roles. As a strong carbide-forming element, V can improve the stability of carbon during sintering. After carbon forms the κ phase, the excess carbon combines with V, which on the one hand reduces the combination of carbon and oxygen, forming CO2 that escapes and thus reduces the oxygen content in the steel. On the other hand, the formed VC also improves the strength of the steel.

[0015] In this embodiment of the application, the weight percentage of V in the lightweight steel is 0.2wt% to 0.55wt%.

[0016] In this embodiment of the application, the weight percentage of Mn in the lightweight steel is 30.01wt% to 32.01wt%.

[0017] In this embodiment of the application, the weight percentage of Al in the lightweight steel is 12.5wt% to 13.5wt%.

[0018] In this embodiment of the application, the weight percentage of C in the lightweight steel is 1.1wt% to 1.45wt%.

[0019] In this embodiment of the application, the weight percentage of oxygen in the lightweight steel is 0.05wt% to 0.2wt%.

[0020] In this embodiment of the application, the lightweight steel also includes other elements, including one or more of nitrogen, copper, chromium, nickel, titanium, sulfur, phosphorus, boron, hydrogen, zirconium, silicon, tantalum, calcium, zinc and rare earth metals, and the weight percentage of the other elements is ≤1%.

[0021] In this embodiment of the application, the lightweight steel is formed using powder raw materials through a metal injection molding process.

[0022] Metal injection molding can produce small, precise, and complex curved lightweight steel parts, which can then be widely used in various electronic products.

[0023] In this embodiment of the application, the density of the lightweight steel is 5.9–6.3 g / cm³. 3 .

[0024] In this embodiment of the application, the yield strength of the lightweight steel is 700-1200 MPa, and the elongation is 1.5%-20%.

[0025] The lightweight steel has low density, high strength, and high ductility. The steel has high strength, and steel structural components made of this lightweight steel do not need to increase thickness to ensure the reliability of the steel structural components, which is conducive to the miniaturization of steel structural components, and thus conducive to the miniaturization of electronic equipment.

[0026] The second aspect of this application provides a steel structural component, wherein the material used in the steel structural component includes the lightweight steel described in the first aspect of this application.

[0027] A third aspect of this application provides a method for preparing lightweight steel, comprising:

[0028] Provide a powder raw material, the powder raw material comprising:

[0029] Fe, weight percentage ≥ 47.39 wt%,

[0030] Mn, with a weight percentage of 30.01 wt% to 36 wt%,

[0031] Al, with a weight percentage of 12.01 wt% to 15.01 wt%,

[0032] C, with a weight percentage of 0.8wt% to 1.5wt%,

[0033] O, with a weight percentage of 0.003wt% to 0.1wt%;

[0034] The powder raw material and binder are mixed and molded into a green body;

[0035] Sintering the green blank to form a sintered blank; and

[0036] The sintered blank is heat-treated.

[0037] The lightweight steel formed by the metal injection molding process provided in this application can effectively obtain three-dimensional complex and precise steel structural parts in one step. Compared with traditional machining, such as forming complex and precise steel structural parts by computer numerical control machine tools, no additional processing is required, which improves the production efficiency of preparing complex and precise steel materials, reduces the cost of preparing steel materials, and is conducive to the large-scale production of steel materials.

[0038] In this embodiment of the application, mixing the powder raw material and the binder to form a green body includes:

[0039] The powdered raw materials are mixed with a binder to form a paste-like feed;

[0040] The paste-like feed is granulated to form feed pellets; and

[0041] The feed pellets are molded into green blanks by injection molding.

[0042] Injection molding is a highly efficient and cost-effective method for producing lightweight steel green blanks. It allows for the efficient generation of three-dimensionally complex and precise lightweight steel green blanks in a single process, thus improving production efficiency. The powdered raw material is mixed with a binder; the powder's fluidity reduces or eliminates defects such as cracks or chipped corners in the green blank. Simultaneously, the mixture provides the green blank with sufficient strength to maintain its shape after extraction from the mold cavity, minimizing or eliminating deformation and improving yield.

[0043] In this embodiment of the application, before sintering the green blank, the method further includes: degreasing to remove the binder from the green blank.

[0044] In some embodiments, binders in green billets are removed by catalytic degreasing. Catalytic degreasing removes binders by utilizing the property that polymers can rapidly degrade under specific atmospheres. The green billet is degreased in the appropriate atmosphere, decomposing and removing the binders. In the embodiments of this application, removing binders from green billets by catalytic degreasing not only achieves rapid and defect-free degreasing but also increases degreasing efficiency, thereby improving the efficiency of steel production.

[0045] In this embodiment of the application, the heat treatment of the sintered blank includes: solution treatment of the sintered blank; and aging treatment of the sintered blank after solution treatment.

[0046] Heat treatment can further enhance the properties of the lightweight steel.

[0047] In this embodiment of the application, the powder raw material further includes V with a weight percentage of ≤0.6wt%.

[0048] The fourth aspect of this application provides a steel structural component, which is prepared using the lightweight steel preparation method described in the third aspect of this application.

[0049] The fifth aspect of this application provides an electronic device, including the steel structural member described in the second or fourth aspect of this application.

[0050] The lightweight steel has low density, high strength, and high ductility. When applied to electronic devices, it reduces the risk of breakage and deformation of structural components, improves the quality of electronic devices, and its low density facilitates the lightweight design of electronic devices.

[0051] In this embodiment of the application, the electronic device further includes a flexible display screen and a folding device for supporting the flexible display screen. The folding device is used to cause the flexible display screen to deform. The folding device includes the steel structural member.

[0052] In this embodiment of the application, the folding device includes a pivot, which is the steel structural component. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the structure of an electronic device according to an embodiment of this application.

[0054] Figure 2A and Figure 2B This is a scanning electron microscope image of the lightweight steel according to an embodiment of this application.

[0055] Figure 3 This is a schematic flowchart of the method for preparing lightweight steel according to an embodiment of this application.

[0056] Explanation of main component symbols

[0057] Electronic devices 100

[0058] Flexible display screen 20

[0059] Folding device 30 Detailed Implementation

[0060] The embodiments of this application are described below with reference to the accompanying drawings. Unless otherwise specified, the parameter ranges involved in this application include endpoint values.

[0061] Structural components in consumer electronics are generally small, precision parts with complex three-dimensional structures. They bear the requirements of smooth operation and structural reliability, so the requirements for materials are multi-dimensional. In addition to the requirements of being lightweight and low-density, they include at least strength (such as yield strength and tensile strength), ductility and toughness (such as elongation), and forming process (casting, forging, stamping, CNC, etc.). These dimensions are mutually restrictive. For lightweight steel, whether it is current metal matrix composites, work-hardened cold-rolled sheets, or melt-cast materials, there are problems such as insufficient strength, brittleness and poor ductility and toughness, insufficient ability to form complex parts, or high forming costs.

[0062] The electronic device of this application embodiment includes lightweight steel. The lightweight steel has the advantages of low density / lightweight, high strength, and can be manufactured using metal injection molding (MIM) technology. Metal injection molding is suitable for manufacturing small, precision, and complex curved surface parts due to its molding characteristics. The electronic device is a consumer electronics product, such as a mobile phone, tablet computer, e-reader, laptop computer, in-vehicle equipment, wearable device, or rollable / foldable electronic newspaper. The electronic device includes structural components, at least one of which is constructed of the lightweight steel.

[0063] See Figure 1 The following description uses a foldable screen phone as an example of electronic device 100. Figure 1 The foldable phone shown is in a semi-open state. For example... Figure 1 As shown, the electronic device 100 includes a flexible display screen 20 and a folding device 30. The flexible display screen 20 is used to display images. The folding device 30 is used to deform the flexible display screen 20. For example, the folding device 30 is connected to the flexible display screen 20 and is used to fold or unfold the flexible display screen 20. The folding device 30 includes a pivot that can rotate under a driving force to bend or unfold the flexible display screen 20. When the electronic device 100 is in the unfolded state, the flexible display screen 20 is located on the same plane. Figure 1 As shown, in another state, the electronic device 100 is not fully unfolded, and in this state, one part of the flexible display screen 20 and another part of the flexible display screen 20 are located on different planes. The electronic device 100 provided in this application can be folded or unfolded according to different usage scenarios, and the electronic device 100 presents different forms to meet different user needs.

[0064] In this embodiment, the lightweight steel structural component is described as the hinge of the electronic device 100 (foldable screen phone), but this is not a limitation. In other embodiments, the steel structural component can also be other types of structural parts in the electronic device 100, such as camera trim, gears, bracket parts that need to be bent, etc., and this application is not limited thereto. It is understood that the lightweight steel can also be used in vehicles as an on-board structural component.

[0065] In traditional technologies, the steel structural components in folding devices are prone to deformation and even breakage under significant stress. This can not only cause the folding device to jam, preventing the electronic device from switching between folding and unfolding, but also allow broken steel components to press against the flexible display screen, affecting the displayed image and thus impacting the overall quality of the electronic device. For example, the stainless steel used in traditional folding devices often lacks sufficient strength and toughness. When the electronic device is dropped from a height, the steel structural components in the folding device are prone to breakage, affecting the lifespan of the electronic device.

[0066] This application provides a lightweight steel with low density, high strength and high elongation. On the one hand, its light weight is conducive to the miniaturization of electronic devices. On the other hand, it can effectively reduce the risk of steel structural component fracture failure of electronic device 100 during drop. At the same time, the steel structural component has high strength, and the steel structural component does not need to increase its thickness to ensure its reliability, which is conducive to the miniaturization of the steel structural component, thereby facilitating the miniaturization of electronic device 100.

[0067] The lightweight steel described in this application embodiment has the following chemical composition:

[0068] Fe, weight percentage ≥ 48.18 wt%;

[0069] Mn, with a weight percentage of 30.01 wt% to 35.01 wt%;

[0070] Al, with a weight percentage of 12.01 wt% to 15.01 wt%;

[0071] C, with a weight percentage of 1.0 wt% to 1.5 wt%;

[0072] O, with a weight percentage of 0.03wt% to 0.3wt%.

[0073] In some embodiments, the lightweight steel further includes V, with a V weight percentage ≤ 0.6 wt%. In some embodiments, the V weight percentage in the lightweight steel is 0.2 wt% to 0.55 wt%.

[0074] In some embodiments, the weight percentage of Fe in the lightweight steel is ≤56.95 wt%. In some embodiments, the weight percentage of Mn in the lightweight steel is 30.01 wt% to 32.01 wt%. In some embodiments, the weight percentage of Al in the lightweight steel is 12.5 wt% to 13.5 wt%. In some embodiments, the weight percentage of C in the lightweight steel is 1.1 wt% to 1.45 wt%. In some embodiments, the weight percentage of O in the lightweight steel is 0.05 wt% to 0.2 wt%.

[0075] The lightweight steel also includes other elements, including one or more of nitrogen, copper, chromium, nickel, titanium, sulfur, phosphorus, boron, hydrogen, zirconium, silicon, tantalum, calcium, zinc, and rare earth metals, with the weight percentage of the other elements being ≤1%.

[0076] It is understandable that the lightweight steel may contain other unavoidable impurity elements, but their content is extremely low and negligible.

[0077] The lightweight steel mainly comprises austenite, ferrite, and the κ phase. These three microstructures are common in low-density steel. Austenite serves as the main phase of the steel matrix, ferrite is distributed at the austenite grain boundaries, and the κ phase is a conventional strengthening phase in low-density steel, primarily existing within or at the grain boundaries of austenite crystals. Austenite is a lamellar microstructure of steel, typically a solid solution of one or more other elements (e.g., carbon) dissolved in γ-Fe, also known as wostenite or γ-Fe. Austenite has a face-centered cubic structure, a close-packed lattice structure, and high density. It exhibits good plasticity, low strength, some toughness, and is non-ferromagnetic. Ferrite is a body-centered cubic solid solution of iron or iron dissolved in one or more other elements (e.g., carbon). It possesses good plasticity and toughness, but lower strength and hardness. The κ phase is a precipitate formed by covalent bonds of at least three elements: Fe, Al, and C, and may also selectively contain Mn.

[0078] In this application, Al is one of the core elements of lightweight steel. A higher aluminum content results in a lower density. If lattice distortion is disregarded and only a simple mixing rule is used for estimation, after the aluminum content exceeds 10 wt%, for every 1 wt% increase in aluminum, the density decreases by approximately 0.1 g / cm³. 3 While ensuring the performance of steel materials (such as the yield strength and elongation described in this application), how to broaden the upper limit of aluminum content has always been a major challenge. This application extends the aluminum content to 12.01wt% to 15.01wt%, while still maintaining good strength and ductility.

[0079] When the content of other elements meets the requirements of this application, the content of Al is in the range of 12.01wt% to 15.01wt%. In particular, when it is in the range of 12.5wt% to 13.5wt%, in addition to obtaining a lower density as mentioned above, higher strength and / or higher elongation can also be obtained through appropriate processing technology, as shown in Table 1 below. Under the condition that the content of other elements is the same, the performance law obtained by a large number of experiments is as follows: This application improves the upper limit of yield strength by increasing the aluminum content, while the elongation remains basically the same. It was found that the combination of aluminum content (12.5wt% to 13.5wt%) and oxygen content (0.05 to 0.2wt%) has the best comprehensive performance.

[0080] Table 1

[0081]

[0082] The lightweight steel has a high Al content (12.01 wt% to 15.01 wt%), resulting in a low density of 5.9 to 6.3 g / cm³. 3 Compared to the density of conventional steel (7.98 g / cm³), 3 This reduces weight by 21% to 26%, thus significantly reducing the weight of consumer electronics products using this lightweight steel and improving the user experience.

[0083] In conventional steelmaking (including low-density steel), oxygen is usually controlled as an impurity element. The lower the oxygen content, the higher the quality grade of the steel. It is controlled in the same way as phosphorus and sulfur. The oxygen content in steel is generally required to be <0.005wt%. If the oxygen content exceeds this requirement, it will become inferior steel that cannot be formed or used.

[0084] The lightweight steel described in this application innovatively incorporates a high content of aluminum (12.01wt% to 15.01wt%) and a high content of oxygen (0.03wt% to 0.3wt%), with oxygen reacting with aluminum to form alumina, thereby introducing an alumina-reinforcing phase into the lightweight steel.

[0085] The oxygen element in this application is uniformly present in the lightweight steel. The method for determining the O content of the lightweight steel described in this application involves sampling at any location on the lightweight steel sample, including after the surface has been polished to remove the oxide layer and a fresh, clean surface has been obtained, and the oxygen content is then measured.

[0086] This application improves both the strength and ductility of the material by introducing oxygen and aluminum to form alumina. As shown in Table 2, under the same conditions, steel with higher oxygen content exhibits higher strength and elongation. According to Table 2, under the same conditions, steel with oxygen content within the range of 0.03wt% to 0.3wt% in this application exhibits significantly higher strength and ductility than steel with low oxygen content.

[0087] Table 2

[0088]

[0089] Oxygen plays two main roles. Firstly, it reacts with aluminum to form the alumina phase, which is small in size and dispersed throughout the lightweight steel of the composition described in this application, primarily at the phase interface, where it acts as dispersion strengthening, thereby increasing the strength of the lightweight steel. For example... Figure 2AIn the scanning electron microscope image of the lightweight steel shown, the particles indicated by the arrows are in-situ generated alumina reinforcing phases (not directly added alumina, but generated through a chemical reaction). These alumina reinforcing phases are granular and diffusely distributed (uniformly distributed) within the lightweight steel matrix, and their shapes can be equiaxed, ellipsoidal, or elongated. Generally, the length and width of the granular alumina are ≤5μm, for example, between 500nm and 5μm. However, a small number of alumina particles may grow abnormally large, exceeding 5μm in size, but the proportion of large-sized alumina particles generally does not exceed 20%.

[0090] On the other hand, the combination of oxygen and aluminum eliminates the brittleness caused by excess aluminum that cannot form the κ phase, thereby improving the material's plasticity. Aluminum is a ferrite-forming element; excess aluminum promotes the ferrite phase. Once the ferrite content is too high and forms a network, it will significantly reduce the material's strength and toughness.

[0091] right Figure 2B Two locations were selected for energy dispersive spectroscopy (EDS) analysis in the scanning electron microscope image of the light steel shown, where the spectrum... Figure 1 The first location is where alumina is located, and the second location is where there is no alumina. The two selected locations were analyzed to determine the types and contents of elements in the micro-regions of the material.

[0092] Table 3

[0093] project C / wt% O / wt% Al / wt% Mn / wt% Fe / wt% Spectrum Figure 1 0.17 21.68 22.5 21.26 34.39 Spectrum 2 0.19 0 11.97 33.13 54.71

[0094] As shown in Table 3, no O element was detected at position 2 in spectrum 2, while the spectrum Figure 1 O and Al elements were detected at the positions, and based on the mass percentages of O and Al elements, the ratio of Al atoms to O atoms was calculated to be approximately 2:3, which verifies the spectral... Figure 1 The presence of aluminum oxide.

[0095] Furthermore, the lightweight steel boasts high strength, with a yield strength of 800–1200 MPa; it also exhibits high plasticity and toughness, with an elongation of 2%–20%. The lightweight steel is manufactured using a MIM (Metal Injection Molding) process, enabling high-precision, low-cost molding of small, complex three-dimensional parts.

[0096] In this application, the addition of V element mainly serves two purposes. V is a strong carbide-forming element, which can improve the stability of carbon element during sintering. After carbon element forms the κ phase, the excess carbon combines with V element, which on the one hand reduces the combination of carbon and oxygen element, forming CO2 that escapes and thus reduces the oxygen content in the steel material. On the other hand, the formed VC also improves the strength of the steel.

[0097] As shown in Table 4 below, the mechanical properties (tensile strength, yield strength, elongation, etc.) of the steel samples were significantly improved after adding V.

[0098] Table 4

[0099]

[0100] In the lightweight steel of this application, several elements, except for Fe, Mn, Al, and C, exhibit direct or indirect interactions with O, O, and V.

[0101] The surface of the lightweight steel may be coated with a functional coating as needed, and the coating may be formed by processes such as passivation, electroplating, spraying, and physical vapor deposition (PVD).

[0102] The lightweight steel can be formed from powder raw materials using a metal injection molding process. For example... Figure 3 As shown, the method for preparing the lightweight steel specifically includes the following steps.

[0103] S1: Prepare a powdered raw material, wherein the powdered raw material comprises the following chemical components:

[0104] Fe, weight percentage ≥ 47.39 wt%,

[0105] Mn, with a weight percentage of 30.01 wt% to 36 wt%,

[0106] Al, with a weight percentage of 12.01 wt% to 15.01 wt%,

[0107] C, with a weight percentage of 0.8wt% to 1.5wt%,

[0108] O, with a weight percentage of 0.003wt% to 0.1wt%.

[0109] In this embodiment, the powder raw material can be prepared by atomization, reduction, mechanical grinding, etc. The particle size D50 of the powder raw material is 5-15 μm (90% of the particles have a particle size ≤45 μm), and can be adjusted accordingly as needed. The powder raw material may also include V with a weight percentage ≤0.6 wt%.

[0110] Powdered raw materials can generally be divided into two types of preparation methods: one is to pre-alloy them into powder, in which each element exists in an alloy form; the other is to mix multiple elemental substances or multiple compounds in adjusted proportions, still exhibiting multiple elemental substances or multiple compounds. In the embodiments of this application, oxygen (O) may exist in the form of iron oxide, or microscopically, oxygen atoms may exist in the interstices of metal atoms (such as Fe).

[0111] S2: Preparation of feed pellets: The powder raw material from step S1 is mixed with the binder and then granulated to form feed pellets.

[0112] In step S1, the powder raw material and binder are mixed at a certain volume ratio (56:44) to form a paste-like feedstock. The paste-like feedstock is then granulated to form feedstock particles. Granulation can be performed using a granulator. The binder is a binder specifically for alloy powders, typically an organic binder, used to bind the powder raw materials together for easy subsequent injection molding.

[0113] S3: Inject the feed pellets from step S2 into a green blank.

[0114] The feed pellets from step S2 are added to the injection molding machine and injected into the mold cavity for injection molding to obtain a green blank.

[0115] Injection molding is a highly efficient and cost-effective method for producing lightweight steel green blanks. It allows for the efficient generation of three-dimensionally complex and precise lightweight steel green blanks in a single process, thus improving production efficiency. The powdered raw material is mixed with a binder; the powder's fluidity reduces or eliminates defects such as cracks or chipped corners in the green blank. Simultaneously, the mixture provides the green blank with sufficient strength to maintain its shape after extraction from the mold cavity, minimizing or eliminating deformation and improving yield.

[0116] S4: Degrease the green body.

[0117] In some embodiments, the green body is subjected to catalytic degreasing (temperature set to 110°C to 160°C, catalyst used is fuming nitric acid) to remove some of the binder from the green body.

[0118] Catalytic degreasing removes binders by utilizing the property that polymers can rapidly degrade under specific atmospheres. This process degreases the green billet in a suitable atmosphere, decomposing and removing the binder. In the embodiments of this application, catalytic degreasing removes binders from the green billet, achieving not only rapid and defect-free degreasing but also increased degreasing efficiency, thereby improving the efficiency of steel production.

[0119] S5: Sinter the green blank to form a sintered blank.

[0120] The catalytically degreased green body is placed in a sintering furnace and sintered at a certain temperature (e.g., 1150℃~1300℃) and under certain atmospheric conditions (e.g., Ar, H2 or vacuum).

[0121] The sintering process refers to the process of transforming powdered materials (the powder raw materials described in this application) into a dense body. This involves heating the powder to give molecules or atoms in the solid state sufficient energy to migrate, causing particle bonding, strength, densification, and recrystallization. For example, in the embodiments of this application, sintering may involve heating to 1150℃~1300℃ and holding for 2~3 hours. During the sintering process, the binder is removed.

[0122] S6: Heat-treat the sintered blank.

[0123] The sintered billet obtained in step S5 is subjected to solution treatment (e.g., temperature set at 1000℃~1180℃, time 1h) and aging treatment (e.g., temperature raised to 350℃~550℃, held for 2h) in a heat treatment furnace to finally obtain steel with good comprehensive mechanical properties.

[0124] The solid solution refers to the heat treatment process of heating the alloy (the sintered product of this application) to a high-temperature single-phase region and holding it at a constant temperature to allow the excess phase to fully dissolve into the solid solution, followed by rapid cooling to obtain a supersaturated solid solution. The purpose of the solid solution treatment is to dissolve the second phase, γ' phase, etc. in the matrix to obtain a uniform supersaturated solid solution, which facilitates the recrystallization of fine-grained and uniformly distributed precipitates and strengthening phases such as γ' during aging, while eliminating the stress generated by cold and hot working and allowing the alloy to recrystallize.

[0125] The aging process refers to the heat treatment process by which the product after solution treatment in this application is placed at a higher temperature or room temperature to maintain its shape, size, and properties over time.

[0126] This application also provides a steel structural component (not shown) formed using the above-described preparation method. The steel structural component, manufactured using the above method, possesses low density, high strength, and high ductility; it is less prone to breakage and deformation, and has a long service life.

[0127] This application also provides a steel structural component (not shown in the figure), the material of which includes the aforementioned lightweight steel. The use of lightweight steel in the steel structural component increases its strength, eliminating the need to increase its thickness to further ensure reliability, thus facilitating miniaturization.

[0128] The embodiments of this application will be further described below through specific examples.

[0129] Examples 1-6

[0130] The specific method for preparing the lightweight steel in Example 1 is as follows.

[0131] (1) Alloy powder was prepared by atomization method, with powder particle size D50 = 5~15um and D90 ≤ 45um;

[0132] (2) The powder and the binder are thoroughly mixed at 180°C in a volume ratio of 56 / 44 to prepare the feed. The binder used is polyoxymethylene (POM): ethylene-vinyl acetate copolymer (EVA): polyethylene (PE): microcrystalline wax (CW): stearic acid (SA) in a weight ratio of 85:1:5.5:2:1.

[0133] (3) Place the feed material in the injection molding machine and inject it into the mold cavity to shape the blank; and use a catalytic degreasing process on the shaped blank at a temperature of 130°C and fuming nitric acid as the catalyst to remove part of the binder.

[0134] (4) Heat to 1200℃±5℃ and hold for 2~3h for sintering;

[0135] (5) Solid solution was prepared at 1100±5℃ for 1 hour;

[0136] (6) Aging at 500±5℃ for 2 hours.

[0137] The process parameters and corresponding test results for other examples 2-6 are shown in Table 6. Other parameters and steps are the same as in Example 1. A total of 6 steel products were obtained from Examples 1-6, and their specific compositions are shown in Table 5. Table 5 lists the weight percentage of Fe as a balance, representing the weight percentage of Fe obtained by subtracting the weight percentage of the other listed elements from 1.

[0138] Table 5

[0139] wt% Mn Al C O V Fe Example 1 32.2 12.31 1.192 0.1609 0.29 margin Example 2 33.4 12.53 1.2049 0.2339 0.4 margin Example 3 32.05 13.01 1.1784 0.1877 0.21 margin Example 4 33.8 13.43 1.1491 0.1554 0.22 margin Example 5 30.1 12.02 1.3319 0.0956 0.42 margin Example 6 31.6 12.11 1.4493 0.1617 0.51 margin

[0140] Table 6

[0141]

[0142] As can be seen from Table 6, this application can obtain a density of 5.9–6.3 g / cm³ by powder sintering followed by solution treatment and aging. 3The lightweight steel, with a yield strength of 700–1200 MPa and an elongation of 1.5%–15%, exhibits the aforementioned finely dispersed alumina particle phase in the microstructure of the steel products obtained in each embodiment. The current density and mechanical properties are attributed to the material composition and the in-situ alumina strengthening phase generated in the matrix by processes such as sintering in this application. It is understandable that the performance of a product depends on its composition and the manufacturing process. For MIM molding processes, there are many steps and parameter variables. For example, in MIM molding technology, the particle size distribution range of the powder raw material, the binder system and ratio, and the binder removal method can all be adjusted according to the equipment environment. Suitable processing techniques can obtain the composition and properties disclosed in this application, and suitable processing techniques in this application may further reduce density and improve strength and toughness.

[0143] It should be noted that the above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Where there is no conflict, the embodiments and features described in the embodiments of this application can be combined with each other. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A lightweight steel, characterized in that, include: Mn, with a weight percentage of 30.01wt%~35.01wt%; Al, with a weight percentage of 12.01 wt% to 15.01 wt%; C, with a weight percentage of 1.0wt%~1.5wt%; O, with a weight percentage of 0.03wt%~0.3wt%; V, with a weight percentage of 0~0.6wt%; Other elements, with a weight percentage of 0-1 wt%, include one or more of nitrogen, copper, chromium, nickel, titanium, sulfur, phosphorus, boron, hydrogen, zirconium, silicon, tantalum, calcium, zinc, and rare earth metals; The balance consists of Fe and unavoidable impurity elements, of which Fe contains ≥48.18 wt% by weight. Alumina particles are dispersed in the lightweight steel.

2. The lightweight steel according to claim 1, characterized in that, The alumina particles include alumina particles with both length and width dimensions ≤ 5 μm.

3. The lightweight steel according to claim 1, characterized in that, The weight percentage of V in the light steel is 0.2wt% to 0.55wt%.

4. The lightweight steel according to claim 1, characterized in that, The weight percentage of Mn in the light steel is 30.01wt%~32.01wt%.

5. The lightweight steel according to claim 1, characterized in that, The weight percentage of Al in the light steel is 12.5wt%~13.5wt%.

6. The lightweight steel according to claim 1, characterized in that, The weight percentage of carbon in the light steel is 1.1wt% to 1.45wt%.

7. The lightweight steel according to claim 1, characterized in that, The weight percentage of oxygen in the light steel is 0.05wt%~0.2wt%.

8. The lightweight steel according to claim 1, characterized in that, The lightweight steel is formed using powder raw materials through a metal injection molding process.

9. The lightweight steel according to claim 1, characterized in that, The density of the light steel is 5.9~6.3g / cm 3 .

10. The lightweight steel according to any one of claims 1 to 9, characterized in that, The light steel has a yield strength of 700~1200MPa and an elongation of 1.5%~20%.

11. A steel structural component, characterized in that, The steel structural components are made of lightweight steel as described in any one of claims 1 to 10.

12. A method for preparing lightweight steel as described in any one of claims 1 to 10, characterized in that, include: A powdered raw material is provided, the powdered raw material being composed of the following components: Fe, weight percentage ≥ 47.39 wt%, Mn, with a weight percentage of 30.01wt%~36wt%, Al, with a weight percentage of 12.01 wt% to 15.01 wt%. C, with a weight percentage of 0.8wt%~1.5wt%, O, with a weight percentage of 0.003wt%~0.1wt%; and V, with a weight percentage of 0~0.6wt%; The powder raw material and binder are mixed and molded into a green body; Sintering the green blank to form a sintered blank; and The sintered blank is heat-treated.

13. The method for preparing lightweight steel according to claim 12, characterized in that, Mixing the powder raw material and the binder to form a green body includes: The powdered raw materials are mixed with a binder to form a paste-like feed; The paste-like feed is granulated to form feed pellets; and The feed pellets are molded into green blanks by injection molding.

14. The method for preparing lightweight steel according to claim 12 or 13, characterized in that, The process further includes degreasing to remove the binder from the green body before sintering.

15. The method for preparing lightweight steel according to claim 12, characterized in that, The heat-treated sintered blank includes: the sintered blank after solution treatment; and the sintered blank after solution treatment by aging.

16. A steel structural component, characterized in that, It is prepared by the method of any one of claims 12 to 15.

17. An electronic device, characterized in that, Including the steel structural members as described in claim 11 or 16.

18. The electronic device according to claim 17, characterized in that, The electronic device further includes a flexible display screen and a folding device for supporting the flexible display screen, the folding device being used to cause the flexible display screen to deform; the folding device includes the steel structural component.

19. The electronic device according to claim 18, characterized in that, The folding device includes a pivot, which is the steel structural component.

20. A powder raw material for metal injection molding, characterized in that, The powder raw material consists of the following components composition: Fe, weight percentage ≥ 47.39 wt%, Mn, with a weight percentage of 30.01wt%~36wt%, Al, with a weight percentage of 12.01 wt% to 15.01 wt%. C, with a weight percentage of 0.8wt%~1.5wt%, O, with a weight percentage of 0.003wt%~0.1wt%; and V, with a weight percentage of 0~0.6wt%.

21. A feed pellet for metal injection molding, characterized in that, The feed pellets include: Adhesives; and The powder raw material mixed with the binder, the powder raw material being composed of the following components: Fe, weight percentage ≥ 47.39 wt%, Mn, with a weight percentage of 30.01wt%~36wt%, Al, with a weight percentage of 12.01 wt% to 15.01 wt%. C, with a weight percentage of 0.8wt%~1.5wt%, O, with a weight percentage of 0.003wt%~0.1wt%; and V, with a weight percentage of 0~0.6wt%.

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