Powder for metal injection molding, electronic equipment, steel structural member and preparation method of steel structural member

Abstract

The invention belongs to the technical field of steel materials, and particularly relates to powder for metal injection molding, electronic equipment, a steel structural part and a preparation method of the powder for metal injection molding, and the powder for metal injection molding comprises the following elements of, by weight, 16.01%-16.99% of Co, 7.31%-8.40% of Cr, 5.65%-6.65% of Mo, 7.01%-7.99% of Ni and 0.20%-0.40% of Nb. And the weight percentage of Fe is greater than or equal to 59.57%. By the adoption of the powder for metal injection molding, preparation of a high-strength and high-toughness steel structural part with the yield strength not lower than 2000 MPa and the elongation not lower than 5% can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel materials, and particularly relates to a powder for metal injection molding, an electronic device, a steel structure and a preparation method thereof. Background Art

[0002] Metal injection molding (MIM) involves mixing metal powder with a binder, granulating the mixture, and then injecting it into a mold to form the desired shape. MIM is a near-net-shape machining technology. Compared to traditional CNC machining, MIM boasts faster processing speeds, higher material utilization, less waste, and lower costs. It is widely used in consumer electronics, medical devices, and other fields, such as mobile phone frames and card slots, ultrasonic scalpel blades, and quadcopter body parts and shafts.

[0003] Compared with traditional steel, the materials currently suitable for MIM molding generally have problems of lower strength or greater brittleness. Faced with the miniaturization trend of products such as consumer electronics, it is urgent to develop high-strength and high-toughness raw materials for MIM molding. Summary of the Invention

[0004] The object of the present invention is to provide a powder for metal injection molding, an electronic device, a steel structure and a preparation method thereof. The metal injection molding powder of the present invention can be used to prepare high-strength and high-toughness steel structures with a yield strength of not less than 2000 MPa and an elongation of not less than 5%.

[0005] A first aspect of the present invention provides a powder for metal injection molding, which comprises the following elements in weight percentage: Co 16.01% to 16.99%, Cr 7.31% to 8.40%, Mo 5.65% to 6.65%, Ni 7.01% to 7.99%, Nb 0.20% to 0.40%; Fe, weight percentage ≥59.57%.

[0006] In some embodiments of the present invention, the weight percentage of Co in the powder is 16.40% to 16.87%; and / or the weight percentage of Ni in the powder raw material is 7.10% to 7.57%.

[0007] In some embodiments of the present invention, the weight percentage of Cr in the powder is 7.60% to 8.10%; and / or the weight percentage of Mo is 5.90% to 6.30%; and / or the weight percentage of Nb is 0.21% to 0.39%.

[0008] In some embodiments of the present invention, the powder further contains at least one of Si, Mn, and B, and the weight percentages of Si, Mn, and B are independently ≤0.5% and not 0.

[0009] In some embodiments of the present invention, the powder further contains at least one of O and C, the weight percentage of O is ≤0.38% and is not 0, and the weight percentage of C is ≤0.1% and is not 0.

[0010] The second aspect of the present invention further provides a steel structure, wherein the raw material used in the steel structure includes the metal injection molding powder described in the first aspect, and the tap density of the metal injection molding powder is 3.8g / cm 3 ~4.8g / cm 3 , the bulk density is 1.7g / cm 3 ~2.7g / cm 3 , with a specific surface area of 400m 2 / Kg~440m 2 / Kg.

[0011] The third aspect of the present invention further provides a method for preparing a steel structure, the method comprising: mixing the metal injection molding powder described in the first aspect with a binder to form a green body; degreasing, sintering and heat treating the green body to obtain the steel structure; wherein the sintered body obtained after sintering has a sintering density of not less than 7.85 g / cm 3 .

[0012] In some embodiments of the present invention, the metal injection molding powder is obtained by compounding a first powder and a second powder, the particle size D50 of the first powder is 5μm to 7μm; and / or the particle size D50 of the second powder is 8μm to 10μm.

[0013] In some embodiments of the present invention, the mass ratio of the first powder to the second powder is (40:60) to (60:40).

[0014] The fourth aspect of the present invention further provides an electronic device, which includes the steel structure member described in the second aspect or the steel structure member manufactured by the manufacturing method described in the third aspect.

[0015] The present invention designs the content of each component of the powder and controls the Co and Ni content within a specific weight percentage range to achieve the preparation of high-strength and high-toughness steel structural parts with a yield strength of not less than 2000 MPa and an elongation of not less than 5%.

[0016] The present invention can effectively obtain three-dimensional complex and precise steel structures in one go by designing the content of each component of the powder and compounding metal injection molding powders of different particle sizes in combination with the MIM method, with high efficiency and low cost, and can achieve the preparation of high-strength and high-toughness steel structures.

[0017] The steel structure of this invention is applicable to various electronic devices. By increasing the yield strength and elongation, the toughness of the steel is enhanced, reducing the risk of steel components breaking from drops or deforming during use, thereby improving the quality of the equipment. Furthermore, due to the high strength of the steel structure, reliability does not need to be increased by increasing the size, which facilitates miniaturization of the equipment.

[0018] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is a metallographic image of the steel structure obtained after heat treatment in Example 1 of the present invention.

[0021] Figure 2 This is a mechanical property curve diagram of the steel structure obtained in Example 1 of the present invention.

[0022] Figure 3 This is a mechanical property curve diagram of the steel structure obtained in Comparative Example 1 of the present invention.

[0023] Figure 4 This is a scanning electron microscope image of the powder for metal injection molding in the present invention.

[0024] Figure 5 This is a particle size distribution diagram of the powder raw material for metal injection molding after compounding in Example 1 of the present invention.

[0025] Figure 6 This is a particle size distribution diagram of the uncompounded powder raw material for metal injection molding in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0026] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0027] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "comprise", "include", "contain" and "have" are inclusive and therefore specify the presence of stated features, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the specific order described or illustrated, unless the order of execution is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0028] In the description of the embodiments of the present invention, technical terms such as "first" and "second" are used solely to distinguish between different objects and should not be understood to indicate or imply relative importance or to implicitly specify the quantity, specific order, or primary and secondary relationship of the technical features indicated. In the description of the embodiments of the present invention, "plurality" means more than two, unless otherwise specifically defined.

[0029] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute a separate or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0030] In the description of the embodiments of the present invention, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exists simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0031] In the description of the embodiments of the present invention, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0032] In the description of the embodiments of the present invention, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connect," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present invention based on specific circumstances.

[0033] Structural components of consumer electronic products are generally small precision parts with complex three-dimensional structures. They bear the requirements of smooth operation of the mechanism and structural reliability. Therefore, the requirements for materials are multi-dimensional. The preparation process is required to facilitate the formation of precise and complex structures to provide greater freedom in structural design. There are also high requirements for the strength (such as yield strength and tensile strength) and toughness (such as elongation) of the material.

[0034] Yield strength is the yield limit of a metal material when it yields, essentially the stress required to resist minimal plastic deformation. As you can imagine, the greater the yield strength of a steel structure, the greater its mechanical strength. Elongation (δ) is an indicator of a material's plastic properties. Elongation is the percentage of the total deformed length of a specimen after tensile fracture compared to its original length.

[0035] Currently, the yield strength of structural components in consumer electronic products has been disclosed to be as high as 1910MPa to 1989MPa, and the elongation can reach 4.6% to 6.52%. However, in order to meet the further miniaturization of consumer electronics such as wearable devices, the yield strength of existing structural components needs to be further improved, otherwise they will easily deform under high stress. At the same time, the elongation must be no less than 5%, otherwise it will easily cause brittle fracture and render the device unusable.

[0036] Based on the risk of deformation and fracture associated with complex steel structures in existing technologies, the present invention provides a steel structure with high strength and high elongation to reduce the risk of deformation, fracture, and failure of electronic equipment during drops. Furthermore, the high strength of the steel structure eliminates the need for increased thickness to ensure reliability, facilitating the miniaturization of the steel structure and, consequently, the miniaturization of electronic equipment. For example, the steel structure provided by the present invention has a yield strength of 2100 MPa and an elongation of 6%.

[0037] In the present invention, steel structural parts can be formed using powder raw materials through a metal injection molding process. In order to further obtain steel structural parts with greater strength and higher elongation, and to reduce the risk of deformation, fracture and failure of steel structural parts during the falling of electronic equipment, the present invention provides a powder for metal injection molding and a metal injection molding process based on the powder.

[0038] In an embodiment of the present invention, the powder for metal injection molding includes the following chemical components in weight percentage: Co16.01% to 16.99%, Cr 7.31% to 8.40%, Mo 5.65% to 6.65%, Ni 7.01% to 7.99%, Nb 0.20% to 0.40%; Fe, weight percentage ≥ 59.57%.

[0039] In the present invention, Co element, as a very important strengthening element, will promote the formation of precipitation phases. Co can reduce the size of the precipitate phase R in maraging stainless steel and increase the number density of the precipitate phase. That is, within a certain range, as the Co content increases, the precipitate phase in the maraging stainless steel in the aged state will be more dispersed (more evenly distributed), which can effectively enhance the precipitation strengthening effect of the precipitate phase. Smaller and more dispersed precipitates will give the material higher toughness and strength. On the other hand, Co is an austenite stabilizing element. When the Co content reaches a certain range, the γ phase region will be significantly expanded, resulting in a high proportion of retained austenite in the material at room temperature, and the strength will be significantly reduced. In the embodiment of the present invention, Co is controlled within a specific content range of 16.01% to 16.99%, ensuring that the comprehensiveness of the steel is high while having high strength and high toughness.

[0040] In some embodiments of the present invention, the mass percentage content of the Co element in the metal injection molding powder provided by the present invention can be a value in the interval consisting of any two values within the above range, for example, it can be 16.01% to 16.40%, or 16.40% to 16.87%, or 16.87% to 16.99%, and so on. For example, the mass percentage content of the Co element in the embodiment of the present invention can be 16.01%, 16.03%, 16.05%, 16.07%, 16.09%, 16.10%, 16.15%, 16.18%, 16.20%, 16.25%, 16.28%, 16.30%, 16.35%, 16.38%, 16.40%, 16.42%, 16.45%, 16.48%, 16.50%, 16.61%, 16.70%, 16.71%, 16.82%, 16.90%, 16.91%, 16.92%, 16.93%, 16.94%, 16.95%, 16.96%, 16.97%, 16.98%, 16.99%, 16.10%, 16.11%, 16.12%, 16.13%, 16.14%, 16.15%, 16.16%, 16.17%, 16.18%, 16.19%, 16.20%, 16.25%, 16.28%, 16.30%, 16.35%, 16.38%, 16.40%, 16.42%, 16.45%, 16.48%, 16. One of 50%, 16.52%, 16.55%, 16.58%, 16.60%, 16.62%, 16.65%, 16.68%, 16.70%, 16.72%, 16.75%, 16.78%, 16.80%, 16.82%, 16.85%, 16.88%, 16.90%, 16.92%, 16.95%, 16.99% or any value that meets the above range.

[0041] In the present invention, Ni is an important austenite stabilizing element in steel and an important toughening element in steel. Ni can improve the resistance of martensitic structure to cleavage fracture and ensure that the steel has sufficient toughness. At the same time, the presence of too much Ni will inhibit the austenite-martensite transformation. Among them, austenite is a solid solution formed by solid dissolving one or several other elements (such as carbon) in γFe, also known as austenite or γFe; austenite is a face-centered cubic structure, the most closely packed lattice structure, and has high density; austenite has good plasticity, low strength, certain toughness, and is not ferromagnetic.

[0042] In some embodiments of the present invention, the mass percentage of Ni element in the metal injection molding powder provided by the present invention can be a value in the interval consisting of any two values within the above range, for example, it can be 7.01% to 7.10%, or 7.10% to 7.57%, or 7.57% to 7.99%, and so on. For example, the mass percentage of Ni element in the embodiment of the present invention can be 7.01%, 7.03%, 7.05%, 7.07%, 7.09%, 7.10%, 7.12%, 7.15%, 7.18%, 7.20%, 7.22%, 7.25%, 7.28%, 7.30%, 7.32%, 7.35%, 7.38%, 7.40%, 7.42%, 7.45%. , 7.48%, 7.50%, 7.52%, 7.55%, 7.58%, 7.60%, 7.62%, 7.65%, 7.68%, 7.70%, 7.72%, 7.75%, 7.78%, 7.80%, 7.82%, 7.85%, 7.88%, 7.90%, 7.92%, 7.95%, 7.99% or any value that meets the above range.

[0043] In the present invention, Cr plays a decisive role in the corrosion resistance of steel. However, Cr is a strong ferrite-stabilizing element. When the Cr content is too high, ferrite forms in the steel matrix, which reduces the strength of the steel. Taking all factors into consideration, the weight percentage of Cr in the embodiments of the present invention is within the range of 7.31% to 8.40%.

[0044] In some embodiments of the present invention, the mass percentage of the Cr element in the metal injection molding powder provided by the present invention can be a value in the interval consisting of any two values within the above range, for example, it can be 7.31% to 7.60%, or 7.60% to 8.10%, or 8.10% to 8.40%, and so on. Illustratively, in the embodiment of the present invention, the mass percentage of the Cr element can be 7.31%, 7.33%, 7.35%, 7.37%, 7.39%, 7.40%, 7.42%, 7.45%, 7.48%, 7.50%, 7.52%, 7.55%, 7.58%, 7.60%, 7.62%, 7.65%, 7.68%, 7.70%, 7.72%, 7.75%, 7.78%, 7.80%, 7.82%, 7.85%, 7.88%, 7.90%, 7.92%, 7.95%, 7.98%, 8.0%, 8.1%, 8.15%, 8.20%, 8.25%, 8.30%, 8.35%, 8.40%, or any value that meets the above range.

[0045] In the present invention, Mo promotes the formation of precipitated phases and increases matrix strength. Mo is also a ferrite-stabilizing element. Excessive Mo content can lead to excessive austenite formation in the alloy, which then transforms into stable ferrite, reducing matrix strength. Considering these combined effects, the content of Mo in the present embodiment is controlled within the range of 5.65% to 6.65%.

[0046] In some embodiments of the present invention, the mass percentage of the Mo element in the metal injection molding powder provided by the present invention can be a value in the interval consisting of any two values within the above range, for example, it can be 5.65% to 5.90%, or 5.90% to 6.30%, or 6.30% to 6.65%, and so on. Illustratively, the mass percentage of the Mo element in the embodiment of the present invention can be 5.65%, 5.68%, 5.70%, 5.72%, 5.75%, 5.78%, 5.80%, 5.82%, 5.85%, 5.90%, 5.92%, 5.95%, 6.0%, 6.05%, 6.10%, 6.15%, 6.18%, 6.20%, 6.25%, 6.28%, 6.30%, 6.35%, 6.38%, 6.40%, 6.45%, 6.48%, 6.50%, 6.55%, 6.58%, 6.60%, 6.65% or any value that meets the above range.

[0047] The Nb element can be dissolved in steel, causing lattice distortion, thereby playing a role in solid solution strengthening. It is also a carbide-forming element, which can refine grains and provide precipitation strengthening. In the present invention, Nb can also form a small amount of intermetallic compounds with Ni, thereby increasing the strength and toughness of the steel material. However, if the Nb content is too high, more carbides will be formed, forming a galvanic cell with the matrix and thus destroying the corrosion resistance of the material. Therefore, in the embodiments of the present invention, it is controlled within the range of 0.20% to 0.40%.

[0048] In some embodiments of the present invention, the mass percentage of the Nb element in the metal injection molding powder provided by the present invention can be a value within the interval consisting of any two values within the above range, for example, it can be 0.20% to 0.30%, or 0.21% to 0.39%, or 0.30% to 0.40%, and so on. For example, the mass percentage of the Nb element in the embodiment of the present invention can be one of 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.40%, or any value that meets the above range.

[0049] In some embodiments of the present invention, the metal injection molding powder further contains Si element, which may exist in the form of oxide inclusions to improve structural strength. In the embodiments of the present invention, the weight percentage of Si is controlled to be ≤ 0.5% and not 0.

[0050] In some embodiments of the present invention, the weight percentage of Si in the metal injection molding powder is ≤0.2% and is not 0.

[0051] Illustratively, the weight percentage of Si may be ≤0.5%, 0.4%, 0.3%, 0.2%, 0.1% or any value satisfying the above range.

[0052] In an embodiment of the present invention, the powder for metal injection molding includes the following chemical components in weight percentage: Co16.01% to 16.99%, Cr 7.31% to 8.40%, Mo 5.65% to 6.65%, Ni 7.01% to 7.99%, Nb0.20% to 0.40%; Si, weight percentage ≤0.5% and not 0; Fe, weight percentage ≥59.57%.

[0053] In some embodiments of the present invention, the powder for metal injection molding further contains Mn element. Mn element has the effect of deoxidation and desulfurization in steel. When the Mn content is too high, it will significantly reduce the toughness of the steel. Therefore, in the embodiments of the present invention, the weight percentage of Mn is controlled to be ≤0.5% and not 0.

[0054] In some embodiments of the present invention, the weight percentage of Mn in the metal injection molding powder is ≤0.2% and is not 0.

[0055] For example, the weight percentage of Mn may be one of 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, or any value within the above range.

[0056] In an embodiment of the present invention, the powder for metal injection molding includes the following chemical components in weight percentage: Co16.01% to 16.99%, Cr 7.31% to 8.40%, Mo 5.65% to 6.65%, Ni 7.01% to 7.99%, Nb0.20% to 0.40%; Mn, weight percentage ≤0.5% and not 0; Fe, weight percentage ≥59.57%.

[0057] In an embodiment of the present invention, the powder for metal injection molding includes the following chemical components in weight percentage: Co16.01% to 16.99%, Cr 7.31% to 8.40%, Mo 5.65% to 6.65%, Ni 7.01% to 7.99%, Nb 0.20% to 0.40%; Si, weight percentage ≤0.5% and not 0; Mn, weight percentage ≤0.5% and not 0; Fe, weight percentage ≥59.57%.

[0058] In some embodiments of the present invention, the metal injection molding powder further contains element B, which can exist in steel as a deoxidizer and has the effect of refining grains. In the present invention, the weight percentage of B is controlled to be ≤0.5% and not 0.

[0059] In some embodiments of the present invention, the weight percentage of B in the metal injection molding powder is ≤0.2% and is not 0.

[0060] For example, the weight percentage of B may be one of 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, or any value within the above range.

[0061] In an embodiment of the present invention, the powder for metal injection molding includes the following chemical components in weight percentage: Co16.01% to 16.99%, Cr 7.31% to 8.40%, Mo 5.65% to 6.65%, Ni 7.01% to 7.99%, Nb0.20% to 0.40%; Si, weight percentage ≤0.5% and not 0; Mn, weight percentage ≤0.5% and not 0; B, weight percentage ≤0.5% and not 0; Fe, weight percentage ≥59.57%.

[0062] In some embodiments of the present invention, the metal injection molding powder further contains O element, and the weight percentage of O is ≤0.38% and is not 0.

[0063] In some embodiments of the present invention, the weight percentage of O in the metal injection molding powder is 0.2% to 0.38%.

[0064] O element generally forms some oxide inclusions in steel and is usually regarded as a harmful element. However, in the present invention, a specific content of oxygen element is controlled to be combined with a small amount of Si and distributed in the steel matrix to improve the strength.

[0065] Illustratively, the weight percentage of O in the metal injection molding powder can be one of 0.01%, 0.05%, 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3%, 0.32%, 0.35%, 0.38%, or any value that meets the above range.

[0066] In some embodiments of the present invention, the metal injection molding powder further contains the element C, and the weight percentage of C is ≤0.1% and not 0.

[0067] In some embodiments of the present invention, the weight percentage of C in the metal injection molding powder is 0.009% to 0.03%.

[0068] Carbon is one of the most common elements in steel and an austenite-stabilizing element. It also improves the hardenability of steel. A small amount of carbon dissolved in the steel matrix can improve strength and toughness. Therefore, in the embodiments of the present invention, the carbon content is controlled to be ≤ 0.1% by weight and not 0.

[0069] Illustratively, the weight percentage of C in the metal injection molding powder can be one of 0.001%, 0.005%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, or any value that meets the above range.

[0070] In an embodiment of the present invention, the powder for metal injection molding includes the following chemical components in weight percentage: Co16.01% to 16.99%, Cr 7.31% to 8.40%, Mo 5.65% to 6.65%, Ni 7.01% to 7.99%, Nb0.20% to 0.40%; Si, weight percentage ≤0.5% and not 0; Mn, weight percentage ≤0.5% and not 0; B, weight percentage ≤0.5% and not 0; O, weight percentage ≤0.38% and not 0; C, weight percentage ≤0.1% and not 0; Fe, weight percentage ≥59.57%.

[0071] In embodiments of the present invention, the metal injection molding powder can be prepared by atomization, reduction, mechanical grinding, etc. In embodiments of the present invention, oxygen (O) can exist in the form of silicon oxide, chromium oxide, etc., or oxygen atoms can exist microscopically in the gaps between metal atoms (such as Fe).

[0072] The present invention provides a steel structure part. The raw materials used in the steel structure part include the above-mentioned powder for metal injection molding.

[0073] In an embodiment of the present invention, the particle size D50 of the metal injection molding powder is 5 μm to 10 μm (50% of the particles have a particle size within the range of 5 μm to 10 μm), and can be adjusted accordingly as needed.

[0074] For example, the particle size D50 of the metal injection molding powder may be one of 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm, or any value within the above range.

[0075] In an embodiment of the present invention, the particle size D90 of the metal injection molding powder is less than 25 μm (90% of the particles have a particle size less than 25 μm), and can be adjusted accordingly as needed.

[0076] Exemplarily, the particle size D90 of the powder for metal injection molding can be one of 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, or any value that meets the above range.

[0077] The particle size D10 of the powder for metal injection molding is less than 3 μm (10% of the particles have a particle size less than 3 μm), and can be adjusted accordingly as needed.

[0078] For example, the particle size D10 of the metal injection molding powder may be 1 μm, 2 μm, or any value within the above range.

[0079] In the embodiment of the present invention, the tap density of the powder for metal injection molding is 3.8 g / cm 3 ~4.8g / cm 3 For example, the tap density of the metal injection molding powder can be 3.8 g / cm 3 、3.9g / cm 3 , 4.0g / cm 3 , 4.1g / cm 3 , 4.2g / cm 3 , 4.3g / cm 3 , 4.4g / cm 3 , 4.5g / cm 3 , 4.6g / cm 3 , 4.7g / cm 3 , 4.8g / cm 3 or any value that satisfies the above range.

[0080] In the embodiment of the present invention, the bulk density of the powder for metal injection molding is 1.7 g / cm 3 ~2.7g / cm 3 For example, the bulk density of the metal injection molding powder can be 1.7 g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 , 2.0g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3 , 2.3g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 , 2.6g / cm 3 , 2.7g / cm 3 or any value that satisfies the above range.

[0081] In the embodiment of the present invention, the specific surface area of the powder for metal injection molding is 400m 2 / Kg~440m 2 / Kg. For example, the specific surface area of the powder for metal injection molding can be 400m 2 / Kg、410m 2 / Kg、420m 2 / Kg、430m 2 / Kg、440m 2 / Kg or any value that meets the above range.

[0082] Figure 1 The scanning electron microscope image of the metal injection molding powder of the present invention is shown. It can be seen from the image that the metal injection molding powder of the present invention is spherical or quasi-spherical in shape, has good powder fluidity, and reduces defects such as cracks.

[0083] In the embodiment of the present invention, the method for preparing the steel structure is specifically carried out according to the following steps.

[0084] Raw material preparation

[0085] In an embodiment of the present invention, the powder raw material used to prepare the steel structural parts is obtained by compounding powders for metal injection molding with different particle sizes, specifically including a first powder and a second powder, the particle size D50 of the first powder is 5μm~7μm, and the particle size D50 of the second powder is 8μm~10μm.

[0086] For example, the particle size D50 of the first powder may be 5 μm, 6 μm, 7 μm, or any value within the above range. The particle size D50 of the second powder may be 8 μm, 9 μm, 10 μm, or any value within the above range.

[0087] In an embodiment of the present invention, the mass ratio of the first powder to the second powder is (40:60) to (60:40). For example, the mass ratio of the first powder to the second powder can be one of 40:60, 50:50, 60:40, or any value within the above range.

[0088] In the embodiments of the present invention, the binder is a binder specifically designed for metal injection molding, typically an organic binder, which is used to bind the powdered raw materials together to facilitate subsequent injection molding. For example, the binder is prepared by mixing polyoxymethylene (POM): polyethylene (PE): stearic acid (SA) in a weight ratio of 90:8:2.

[0089] Feedstock preparation for metal injection molding

[0090] In an embodiment of the present invention, a powder for metal injection molding is mixed with a binder to form a paste feed, and the paste feed is granulated to form feed particles, thereby obtaining the feed for metal injection molding.

[0091] In some embodiments of the present invention, the volume ratio of the metal injection molding powder to the binder is (60-65):(35-40). For example, the volume ratio of the metal injection molding powder to the binder can be one of 65:35, 64:36, 63:37, 61:39, 60:40, or any value within the above range.

[0092] In some embodiments of the present invention, a method for preparing a feedstock for metal injection molding comprises uniformly mixing a powder for metal injection molding and a binder, and then extruding and granulating the mixture to obtain the feedstock for metal injection molding.

[0093] In some embodiments of the present invention, powder for metal injection molding and a binder are mixed in a preset volume ratio, and then added to a mixer for kneading into a uniformly mixed paste feed; the paste feed is moved into a granulator, and the screw of the granulator extrude the gradually cooled feed through a die head, and a rotating blade cuts the strip feed into cylindrical particles with a length of 2 mm to 3 mm to obtain feed particles that can be directly used for molding.

[0094] Injection molding green body

[0095] In an embodiment of the present invention, the metal injection molding feedstock is molded into a green body by injection molding. The green body molded by injection molding has a certain strength and can maintain its shape after demolding, thereby reducing the probability of green body deformation and improving the yield rate.

[0096] In some embodiments of the present invention, feed particles for metal injection molding are added to the hopper of an injection molding machine, and injection molding is performed under set temperature and pressure conditions to obtain a green body.

[0097] In some embodiments of the present invention, the molding temperature may be 240°C.

[0098] In some embodiments of the present invention, the molding pressure may be 240 MPa.

[0099] Degreasing

[0100] In the embodiment of the present invention, the green body is degreased.

[0101] In some embodiments of the present invention, catalytic degreasing is used to remove the binder from the green body. Catalytic degreasing utilizes the rapid degradation of polymers in specific atmospheres to degrease the green body in the appropriate atmosphere, decomposing and removing the binder. Removing the binder from the green body through catalytic degreasing can increase degreasing efficiency.

[0102] In some embodiments of the present invention, the green body is placed flat on an alumina ceramic plate and placed in a catalytic degreasing furnace, and catalytic degreasing is performed under set conditions to remove part of the binder in the green body.

[0103] In some embodiments of the present invention, the degreasing temperature may be 120±10°C.

[0104] In some embodiments of the present invention, the amount of fuming nitric acid introduced during the degreasing process is 60 mL / h to 65 mL / h. For example, the amount of fuming nitric acid introduced can be one of 60 mL / h, 61 mL / h, 62 mL / h, 63 mL / h, 64 mL / h, and 65 mL / h, or any value within the above range.

[0105] In some embodiments of the present invention, the degreasing time may be 3 hours.

[0106] sintering

[0107] In the embodiment of the present invention, the green compact is sintered to form a sintered compact. During the sintering process, the binder is removed.

[0108] In some embodiments of the present invention, the green body obtained after degreasing is placed in a sintering furnace together with the alumina ceramic plate, and sintered under set temperature and atmosphere conditions.

[0109] In some embodiments of the present invention, the sintering temperature may be 1270°C to 1350°C, and the holding time may be 2 hours to 5 hours. For example, the sintering temperature may be one of 1270°C, 1275°C, 1280°C, 1285°C, 1290°C, 1295°C, 1300°C, 1310°C, 1320°C, 1330°C, 1340°C, 1350°C, or any value within the above range. The holding time may be one of 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, or any value within the above range.

[0110] In some embodiments of the present invention, the sintering atmosphere may be an Ar atmosphere, a H2 atmosphere, or a vacuum condition.

[0111] In some embodiments of the present invention, the sintered compact obtained after sintering has a sintered density of not less than 7.85 g / cm 3 .

[0112] Heat treatment

[0113] In an embodiment of the present invention, the sintered compact is subjected to heat treatment.

[0114] In some embodiments of the present invention, the obtained sintered blank is placed in a heat treatment furnace for solution treatment and aging treatment, and finally a steel structure with good comprehensive mechanical properties is obtained.

[0115] In some embodiments of the present invention, the solution temperature is 1000°C to 1100°C, and the solution time is 1 hour to 1.5 hours. For example, the solution temperature can be 1000°C, 1050°C, 1100°C, or any value within the aforementioned range. The solution time can be 1 hour, 1.5 hours, or any value within the aforementioned range.

[0116] In some embodiments of the present invention, the aging temperature is 520°C to 580°C, and the holding time is 2 hours to 3 hours. For example, the aging temperature can be 520°C, 550°C, 580°C, or any value within the aforementioned range. The aging time can be 2 hours, 2.5 hours, 3 hours, or any value within the aforementioned range.

[0117] In the embodiment of the present invention, the steel structure is manufactured by the above-mentioned manufacturing method, so that the steel structure has high strength and high ductility, is not prone to fracture and deformation, and has a long service life.

[0118] In the embodiment of the present invention, the yield strength of the steel structure is ≥2000 MPa and the elongation is greater than 5%, thereby ensuring the toughness of the steel structure.

[0119] In an embodiment of the present invention, the steel structural member includes the following chemical composition in weight percentage: Co 16.01% to 16.99%, Cr 7.31% to 8.40%, Mo 5.65% to 6.65%, Ni 7.01% to 7.99%, Nb 0.20% to 0.40%; O, the weight percentage content is ≤0.38% and not 0; C, the weight percentage content is ≤0.1% and not 0; the balance is Fe.

[0120] In some embodiments of the present invention, the weight percentage of Fe in the steel structure is ≤64.68%.

[0121] In the present invention, Co, as a very important strengthening element, promotes the formation of precipitation phases. Co can reduce the size of the precipitate phase R in maraging stainless steel and increase the number density of the precipitate phase. That is, within a certain range, as the Co content increases, the precipitate phase in the maraging stainless steel in the aged state will be more dispersed (more evenly distributed), which can effectively enhance the precipitation strengthening effect of the precipitate phase. Smaller and more dispersed precipitates will give the material higher toughness and strength. On the other hand, Co is an austenite stabilizing element. When the Co content reaches a certain range, the γ phase region will be significantly expanded, resulting in a high proportion of retained austenite in the material at room temperature, and the strength will be significantly reduced. In the embodiment of the present invention, Co is controlled within the weight percentage range of 16.01% to 16.99%, ensuring that the comprehensiveness of the steel is high while having high strength and high toughness.

[0122] In some embodiments of the present invention, the weight percentage of Co in the steel structure is 16.40% to 16.87%.

[0123] In some embodiments of the present invention, the weight percentage of Cr in the steel structure is 7.60% to 8.10%.

[0124] In some embodiments of the present invention, the weight percentage of Mo in the steel structure is 5.90% to 6.30%.

[0125] Ni can improve the cleavage fracture resistance of the martensite structure and ensure that the steel has sufficient toughness. In the embodiment of the present invention, the Ni content is controlled within the range of 7.01% to 7.99% by weight.

[0126] In some embodiments of the present invention, the weight percentage of Ni in the steel structure is 7.10% to 7.57%.

[0127] In some embodiments of the present invention, the weight percentage of Nb in the steel structure is 0.21% to 0.39%.

[0128] In some embodiments of the present invention, the weight percentage of O in the steel structure is 0.20% to 0.38%.

[0129] In some embodiments of the present invention, the weight percentage of C in the steel structure is 0.009% to 0.03%. A small amount of C solid-solved in the steel matrix can improve the strength and toughness.

[0130] In some embodiments of the present invention, the steel structure further contains Si, and the weight percentage of Si is ≤0.5% and not 0, so as to improve the strength of the steel matrix.

[0131] In some embodiments of the present invention, the weight percentage of Si in the steel structure is ≤0.2% and is not 0.

[0132] In the present invention, the O element, whose weight percentage is controlled to be ≤0.38%, can be combined with a small amount of Si and distributed in the steel matrix to improve strength. In general steel, even if Si is not actively added, a small amount of Si will still exist, and Si will preferentially combine with O.

[0133] In some embodiments of the present invention, the steel structure further contains Mn, and the weight percentage of Mn is ≤0.5% and not 0, which has the effect of deoxidation and desulfurization without significantly reducing the toughness of the steel.

[0134] In some embodiments of the present invention, the weight percentage of Mn in the steel structure is ≤0.2% and is not 0.

[0135] In some embodiments of the present invention, the steel structure also contains B, which can exist in the steel as a deoxidizer and can have the effect of refining grains. In the present invention, the weight percentage of B is controlled to be ≤0.05% and not 0.

[0136] In some embodiments of the present invention, the steel structure further includes other elements, including one or more of tungsten, nitrogen, rhenium, copper, aluminum, titanium, sulfur, phosphorus, hydrogen, zirconium, magnesium, tantalum, calcium, vanadium, zinc, and rare earth metals, with the mass percentage of such other elements being ≤1%. It is understood that the steel structure may contain other unavoidable impurity elements, but their content is extremely low and negligible.

[0137] In some embodiments of the present invention, the chemical composition of the steel structure includes, by weight percentage, Co 16.57%; Cr 7.89%; Mo 6.15%; Ni 7.37%; O 0.31%; C 0.016%; Nb 0.3%; Si 0.27%; Mn 0.15%; B 0.01%; and the balance is Fe.

[0138] An electronic device according to an embodiment of the present invention includes a steel structure having high strength and high toughness. The electronic device may be a consumer electronic product, such as a mobile phone, tablet computer, e-reader, laptop computer, vehicle-mounted device, wearable device, or a rollable electronic newspaper; or a medical device, such as an ultrasonic scalpel or surgical forceps; or a component for other industrial applications, such as a speed reducer gear.

[0139] For example, the steel structure can be a rotating shaft, which can be used in foldable mobile phones, laptops, etc. In other embodiments, the steel structure can also be other structural parts with more complex shapes in electronic devices, such as gears, wear-resistant parts with arc structures, bracket parts that need to be bent, etc., and the present invention is not limited thereto.

[0140] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the raw materials, instruments and equipment used in the following examples, etc., can all be purchased on the market or can be obtained by existing methods; the amounts of the experimental reagents used, unless otherwise specified, are the amounts of reagents used in conventional experimental operations; the experimental methods, unless otherwise specified, are all conventional methods. It should be further noted that the following description is merely exemplary and does not specifically limit the present invention.

[0141] Example 1

[0142] A steel structure is provided, and a preparation method thereof comprises:

[0143] (1) A first powder and a second powder of different particle sizes are compounded to obtain a powder raw material for metal injection molding. The particle size distribution diagram is shown in FIG. Figure 5 The first powder is a metal injection molding powder with a particle size D50 of 6 μm, and the second powder is a metal injection molding powder with a particle size D50 of 9 μm. The mass ratio of the first powder to the second powder is 50:50. The first powder and the second powder each contain the following elements, in weight percentage: Co 16.57%, Cr 7.89%, Mo 6.15%, Ni 7.37%, O 0.31%, C 0.016%, Nb 0.3%, Si 0.27%, Mn 0.15%, B 0.01%, and the balance is Fe. The tap density of the metal injection molding powder raw material is 4.3 g / cm 3 , bulk density is 2.2g / cm 3 , with a specific surface area of 420m 2 / Kg.

[0144] The binder is prepared by mixing polyoxymethylene (POM): polyethylene (PE): stearic acid (SA) in a weight ratio of 90:8:2.

[0145] (2) The powder raw material for metal injection molding and the binder are mixed in a volume ratio of 63:37, and then added to an internal mixer for mixing at a mixing temperature of 180°C, a mixing time of 5 hours, and a blade speed of 25 r / min; the evenly mixed paste feed is then transferred to a granulator, and the screw of the granulator extrude the gradually cooled feed through the die head, and the rotating blade cuts the strip feed into cylindrical particles of 2 mm to 3 mm in length, thereby obtaining feed particles that can be directly used for molding.

[0146] (3) The feed pellets were added to the hopper of the injection molding machine and injection molded under the conditions of a molding temperature of 240° C. and a molding pressure of 240 MPa to obtain a green body.

[0147] (4) The green body was placed flat on an alumina ceramic plate and placed in a catalytic degreasing furnace for catalytic degreasing at 130°C with a fuming nitric acid flow rate of 63 mL / h for 3 h.

[0148] (5) The catalytically degreased green body was placed in a sintering furnace together with an alumina ceramic support plate and sintered at 1300 °C in an Ar atmosphere for 4 h to obtain a sintered density of 7.85 g / cm 3 sintered blank.

[0149] (6) The sintered blank is placed in a heat treatment furnace and solutionized at 1000 °C for 1.5 h. It is then quickly cooled in oil and then heated to 520 °C for aging treatment. The temperature is then kept at this temperature for 3 h, and finally a steel structure with good comprehensive mechanical properties is obtained.

[0150] The chemical composition of the steel structure prepared in Example 1 was determined. The components thereof were, by weight percentage, Co16.57%, Cr 7.89%, Mo 6.15%, Ni 7.37%, O 0.18%, C 0.1%, Nb 0.3%, Si 0.27%, Mn 0.15%, B 0.01%, and the balance being Fe and unavoidable impurity elements.

[0151] Comparative Example 1

[0152] A steel structure is provided, and its preparation method refers to Example 1. The difference between it and Example 1 is that the powder raw material for metal injection molding is not compounded. The particle size distribution diagram thereof is shown in FIG. Figure 6 The particle size D50 of the powder raw material for metal injection molding is 10 μm. The sintered density of the sintered blank in the comparative example is 7.78 g / cm 3 .

[0153] Performance Testing

[0154] The tensile strength, specified plastic extension strength and total elongation at break of the steel structure in the embodiments and comparative examples of the present invention were tested in accordance with GB / T228. Figure 2 and Figure 3 shown.

[0155] At the same time, the steel structure obtained after heat treatment in Example 1 was sampled, the sample was ground and polished, and then treated with aqua regia corrosion, and its metallographic structure was obtained using an optical microscope, see Figure 1 shown.

[0156] Table 1 Summary of mechanical properties of steel structures in the embodiments and comparative examples

[0157]

[0158] Combine Figures 1 to 6 As can be seen from the data in Table 1, the present invention uses MIM technology to achieve one-time molding of complex products, and uses the metal injection molding powder with a specific composition in the present invention and compounding powders of different particle sizes as the powder raw material of the MIM technology, so that the prepared steel structural parts have both strength and toughness. It can also be seen from the metallographic diagram that its structure is a martensite matrix, achieving high strength and good elongation.

[0159] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A powder for metal injection molding, characterized in that The powder comprises the following elements in weight percentage: Co 16.01%~16.99%, Cr 7.31%~8.40%, Mo 5.65%~6.65%, Ni 7.01%~7.99%, Nb0.20%~0.40%; Fe, weight percentage ≥59.57%.

2. The metal injection molding powder according to claim 1, wherein The weight percentage of Co in the powder is 16.40% to 16.87%; and / or, The weight percentage of Ni in the powder raw material is 7.10% to 7.57%.

3. The metal injection molding powder according to claim 1, wherein The weight percentage of Cr in the powder is 7.60% to 8.10%; and / or, The weight percentage of Mo is 5.90% to 6.30%; and / or, The weight percentage of Nb is 0.21% to 0.39%.

4. The metal injection molding powder according to claim 1, wherein The powder further contains at least one of Si, Mn, and B. The weight percentages of Si, Mn and B are independently ≤0.5% and not 0.

5. The metal injection molding powder according to claim 1, wherein The powder further contains at least one of O and C. The weight percentage of O is ≤0.38% and is not 0, and the weight percentage of C is ≤0.1% and is not 0.

6. A steel structure, characterized in that: The raw material used for the steel structure comprises the metal injection molding powder according to any one of claims 1 to 5, wherein the tap density of the metal injection molding powder is 3.8 g / cm 3 ~4.8g / cm 3 , the bulk density is 1.7g / cm 3 ~2.7g / cm 3 , with a specific surface area of 400m 2 / Kg~440m 2 / Kg.

7. A method for preparing a steel structure according to claim 6, characterized in that: The preparation method comprises: Mixing the metal injection molding powder according to any one of claims 1 to 5 with a binder to form a green body; The green body is degreased, sintered and heat-treated to obtain the steel structure; wherein the sintered green body obtained after sintering has a sintering density of not less than 7.85 g / cm 3 .

8. The method for preparing a steel structure according to claim 7, wherein: The metal injection molding powder is obtained by compounding a first powder and a second powder. The particle size D50 of the first powder is 5 μm to 7 μm; and / or the particle size D50 of the second powder is 8 μm to 10 μm.

9. The method for preparing a steel structure according to claim 8, wherein: The mass ratio of the first powder to the second powder is (40:60) to (60:40).

10. An electronic device, characterized in that: The invention comprises the steel structure member according to claim 6 or the steel structure member produced by the production method according to any one of claims 7 to 9.

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