Ultra-high strength steel, method for manufacturing the same, structural member for electronic device, and electronic device

Abstract

The application provides an ultrahigh-strength steel, a preparation method thereof, a structural member of an electronic device, and an electronic device. The ultrahigh-strength steel comprises iron, nickel, cobalt, molybdenum, and vanadium. In the ultrahigh-strength steel, the mass fraction of the iron is greater than or equal to 50 wt%, the mass fraction of the nickel is 16 wt% to 20 wt%, and the mass fraction of the cobalt is 15.1 wt% to 19 wt%. The mass fraction of the nickel is greater than that of the cobalt, the mass fraction of the cobalt is greater than that of the molybdenum, and the mass fraction of the molybdenum is greater than that of the vanadium. The ultrahigh-strength steel has high tensile strength, yield strength, and Vickers hardness, and has high toughness and elongation.

Description

TECHNICAL FIELD

[0001] The present application relates to the electronic field, and in particular to a super high strength steel and a preparation method thereof, a structural member of an electronic device and the electronic device. BACKGROUND

[0002] With the continuous development of electronic devices, the materials used for the structural members of electronic devices are also increasingly rich. Steel is one of the most widely used materials in the world due to its low price and reliable performance. Super high strength steel refers to steel material with a yield strength greater than 1180MPa and a tensile strength greater than 1380MPa, which is widely used due to its excellent strength. However, super high strength steel is hard and difficult to process, which limits the use of super high strength steel, and the performance of super high strength steel also needs to be further improved. SUMMARY

[0003] Embodiments of the present application provide a super high strength steel, which has a high tensile strength, yield strength and Vickers hardness, and has a high toughness and elongation.

[0004] In a first aspect, the present application provides a super high strength steel, the super high strength steel comprising iron, nickel, cobalt, molybdenum and vanadium, wherein the mass fraction of the iron is greater than or equal to 50wt%, the mass fraction of the nickel is 16wt% to 20wt%, and the mass fraction of the cobalt is 15.1wt% to 19wt%; the mass fraction of the nickel is greater than the mass fraction of the cobalt, the mass fraction of the cobalt is greater than the mass fraction of the molybdenum, and the mass fraction of the molybdenum is greater than the mass fraction of the vanadium.

[0005] In a second aspect, the present application provides a preparation method of a super high strength steel, comprising:

[0006] providing a metal powder and a binder, and performing injection molding to obtain a blank;

[0007] debinding and sintering the blank to obtain an intermediate state blank; and

[0008] performing heat treatment on the intermediate state blank to obtain the super high strength steel, the super high strength steel comprising iron, nickel, cobalt, molybdenum and vanadium, wherein the mass fraction of the iron is greater than or equal to 50wt%, the mass fraction of the nickel is 16wt% to 20wt%, and the mass fraction of the cobalt is 15.1wt% to 19wt%; the mass fraction of the nickel is greater than the mass fraction of the cobalt; the mass fraction of the cobalt is greater than the mass fraction of the molybdenum, and the mass fraction of the molybdenum is greater than the mass fraction of the vanadium.

[0009] In a third aspect, the present application provides a structural member of an electronic device, wherein the structural member of the electronic device comprises the ultrahigh-strength steel according to the first aspect of the present application, or the structural member of the electronic device is prepared by the method for preparing the ultrahigh-strength steel according to the second aspect of the present application.

[0010] In a fourth aspect, the present application provides an electronic device comprising the structural member of the electronic device according to the third aspect of the present application.

[0011] The ultrahigh-strength steel according to the embodiments of the present application comprises iron, nickel, cobalt, molybdenum and vanadium, and the ultrahigh-strength steel has high tensile strength, yield strength and Vickers hardness, and has high toughness and elongation by means of the complexing of the alloying elements in the ultrahigh-strength steel and the control of the contents of the iron element, the nickel element and the cobalt element. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0013] Figure 1 is a flowchart of the method for preparing the ultrahigh-strength steel according to an embodiment of the present application.

[0014] Figure 2 is a scanning electron microscope image of the metal powder according to an embodiment of the present application.

[0015] Figure 3 is a flowchart of the method for preparing the blank according to an embodiment of the present application.

[0016] Figure 4 is a flowchart of the method for preparing the intermediate blank according to an embodiment of the present application.

[0017] Figure 5 is a flowchart of the first sintering according to an embodiment of the present application.

[0018] Figure 6 is a flowchart of the third sintering according to an embodiment of the present application.

[0019] Figure 7 is a flowchart of the method for preparing the intermediate blank according to another embodiment of the present application.

[0020] Figure 8 is a flowchart of the heat treatment according to an embodiment of the present application.

[0021] Figure 9 is a flowchart of the solid solution treatment according to an embodiment of the present application.

[0022] Figure 10 is a flowchart of the aging treatment of an embodiment of the present application.

[0023] Figure 11 is a flowchart of the method for preparing the ultra-high strength steel of another embodiment of the present application.

[0024] Figure 12 is a scanning electron microscope metallographic image of the intermediate-state blank of embodiment 1 of the present application.

[0025] Figure 13 is a scanning electron microscope metallographic image of the intermediate-state blank of embodiment 2 of the present application.

[0026] Figure 14 is a scanning electron microscope metallographic image of the intermediate-state blank of embodiment 3 of the present application.

[0027] Figure 15 is a scanning electron microscope metallographic image of the intermediate-state blank of embodiment 4 of the present application.

[0028] Figure 16 is a scanning electron microscope metallographic image of the intermediate-state blank of embodiment 5 of the present application.

[0029] Figure 17 is a structural schematic diagram of an electronic device structural member of an embodiment of the present application.

[0030] Figure 18 is a flowchart of the method for preparing the electronic device structural member of an embodiment of the present application.

[0031] Figure 19 is a structural schematic diagram of an electronic device of an embodiment of the present application.

[0032] Figure 20 is Figure 19 is an enlarged view of the dashed box I. DETAILED DESCRIPTION

[0033] In order to enable persons skilled in the art to better understand the schemes of the present application, the technical schemes in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by persons skilled in the art without making creative efforts fall within the scope of protection of the present application.

[0034] The terms "first", "second", and the like in the description and in the claims of the present application and above drawings are used for distinguishing between similar objects talking about the application and are not necessarily describing a specific sequential or chronological order. Moreover, the terms "comprises", "comprising", "includes", "including" and the like are meant to be interpreted open-ended. For example, a process, method, system, product, or apparatus that comprises a list of steps or elements is not necessarily limited to only those steps or elements but can include other steps or elements not expressly listed or inherent to such process, method, system, product, or apparatus. Similarly, a step or an element preceded by "comprises... a" does not, without further constraints, foreclose the existence of additional steps or elements of that step or element.

[0035] The technical solutions in the embodiments of the present application will be described below with reference to the drawings.

[0036] It should be noted that, for the convenience of description, in the embodiments of the present application, the same reference signs represent the same parts, and for the sake of brevity, the detailed description of the same parts is omitted in different embodiments.

[0037] Ultra-high strength steel is a kind of alloy steel used to manufacture structural parts of electronic devices that bear high stress. The general yield strength is greater than 1180 MPa, and the tensile strength is greater than 1380 MPa. Such steel generally has sufficient toughness, high specific strength and yield strength ratio, and good weldability and formability. According to the degree of alloying and microstructure, it can be divided into three categories of low-alloy, medium-alloy and high-alloy ultra-high strength steel.

[0038] The embodiments of the present application provide an ultra-high strength steel, which comprises iron (Fe), nickel (Ni), cobalt (Co), molybdenum (Mo) and vanadium (V).

[0039] Optionally, in the ultra-high strength steel, the mass fraction of the iron is greater than or equal to 50wt%, the mass fraction of the nickel is 16wt% to 20wt%; the mass fraction of the nickel is greater than the mass fraction of the cobalt, the mass fraction of the cobalt is greater than the mass fraction of the molybdenum, and the mass fraction of the molybdenum is greater than the mass fraction of the vanadium.

[0040] In the embodiments of the present application, when a numerical range a to b is involved, if not specifically indicated, it means that the number can be any value between a and b, including the end point value a and the end point value b.

[0041] Further, in the ultra-high strength steel, the mass fraction of the iron is 50wt% to 63wt%. Still further, in the ultra-high strength steel, the mass fraction of the iron is 55wt% to 60wt%. Specifically, in the ultra-high strength steel, the mass fraction of the iron can be, but is not limited to, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, 56wt%, 57wt%, 58wt%, 59wt%, 60wt%, 61wt%, 62wt%, 63wt%, etc.

[0042] Further, in the ultra-high strength steel, the mass fraction of the nickel is 17wt% to 19wt%. Still further, in the ultra-high strength steel, the mass fraction of the nickel is 17wt% to 18wt%. Specifically, in the ultra-high strength steel, the mass fraction of the nickel can be, but is not limited to, 16wt%, 16.5wt%, 17wt%, 17.5wt%, 18wt%, 18.5wt%, 19wt%, 19.5wt%, 20wt%, etc. Nickel is an austenite forming element, which can lower the starting temperature of martensite transformation, promote the transformation and formation of martensite. Nickel can strengthen ferrite and refine and increase pearlite, improve the strength of the steel, and has little effect on the plasticity of the steel. When the mass fraction of nickel is too low, it is difficult to form single austenite, which reduces the content of residual austenite in the ultra-high strength steel, and is not conducive to the improvement of the ductility of the ultra-high strength steel; when the mass fraction of nickel is too high, it is not conducive to the formation of martensite, which increases the content of residual austenite in the ultra-high strength steel, and is not conducive to the improvement of the strength and Vickers hardness of the ultra-high strength steel.

[0043] Martensite is a kind of organization name of ferrous metal material, which is a supersaturated solid solution of carbon in α-Fe. Martensite has high strength and Vickers hardness. Austenite is a kind of lamellar microstructure of steel and iron, which is a non-magnetic solid solution of a small amount of carbon in γ-Fe. Austenite has good plasticity, low strength, and certain toughness.

[0044] Cobalt is an austenite forming element, which can promote the formation of intermetallic compounds, thereby improving the tensile strength and yield strength of the ultra-high strength steel. In addition, cobalt can also promote the improvement of the tensile strength and yield strength of the ultra-high strength steel by molybdenum. However, too high content of cobalt will reduce the plasticity and elongation of the ultra-high strength steel.

[0045] In some embodiments, the mass fraction of cobalt in the ultra-high strength steel is 15.1wt% to 19wt%. Specifically, the mass fraction of cobalt in the ultra-high strength steel can be, but is not limited to, 15.1wt%, 15.5wt%, 16wt%, 16.5wt%, 17wt%, 17.5wt%, 18wt%, 18.5wt%, 19wt%, etc. Cobalt is an austenite forming element and can promote the formation of intermetallic compounds. Within a certain range, increasing the content of cobalt can increase the tensile strength and yield strength of the ultra-high strength steel and make the ultra-high strength steel have better plasticity. In addition, cobalt can also promote molybdenum to form more strengthening phases, thereby improving the tensile strength and yield strength of the ultra-high strength steel. Therefore, if the content of cobalt is too low, it is not conducive to the improvement of the tensile strength and yield strength of the ultra-high strength steel, but can make the ultra-high strength steel have better plasticity and elongation. However, if the content of cobalt is too high (i.e., exceeds a certain value), although the ultra-high strength steel still has high tensile strength and yield strength, the plasticity and elongation of the ultra-high strength steel decrease. When the mass fraction of cobalt is 15.1wt% to 19wt%, the ultra-high strength steel can have high tensile strength and yield strength, and also have good plasticity and elongation.

[0046] Further, the mass fraction of cobalt in the ultra-high strength steel is 15.1wt% to 17.5wt%. In this way, the ultra-high strength steel can have high tensile strength and yield strength, and also have good plasticity and elongation.

[0047] Further, the mass fraction of cobalt in the ultra-high strength steel is 15.1wt% to 16wt%. In this way, the ultra-high strength steel can have high tensile strength and yield strength, and also have good plasticity and elongation.

[0048] Molybdenum is an alloying element and a strengthening element of the ultra-high strength steel. Molybdenum has solid solution strengthening effect on the iron base and can also improve the stability of carbides. Molybdenum can increase the tensile strength, yield strength, Vickers hardness and wear resistance of the ultra-high strength steel. Mo element can form various alloying compounds with carbon, chromium, nickel and other elements in the ultra-high strength steel, which can enhance the grain boundary strength and stability of the ultra-high strength steel, thereby improving the strength and Vickers hardness of the ultra-high strength steel. In addition, Mo element can also improve the grain refinement degree of the ultra-high strength steel, making the structure of the ultra-high strength steel more uniform, thereby improving the toughness and tensile properties of the ultra-high strength steel. However, when the content of molybdenum exceeds a certain amount, the content of carbon in the ultra-high strength steel increases, thereby increasing the brittleness of the ultra-high strength steel and reducing the elongation of the ultra-high strength steel.

[0049] Vanadium is a strengthening element of the ultra-high strength steel, which can refine the grain, and can improve the tensile strength and yield strength of the ultra-high strength steel. However, too high content of vanadium will reduce the plasticity and elongation of the ultra-high strength steel. In addition, vanadium is easy to combine with oxygen, and the oxygen combined with vanadium can promote decarburization, thereby further reducing the carbon content in the ultra-high strength steel, so that the ultra-high strength steel has higher tensile strength and yield strength.

[0050] The ultra-high strength steel according to the embodiments of the present application comprises iron (Fe), nickel (Ni), cobalt (Co), molybdenum (Mo) and vanadium (V). By compounding the alloying elements in the ultra-high strength steel and controlling the contents of iron, nickel and cobalt, the ultra-high strength steel has higher tensile strength, yield strength and Vickers hardness, and has higher toughness and elongation.

[0051] In some embodiments, the ratio of the mass fraction of molybdenum to the mass fraction of cobalt in the ultra-high strength steel ranges from 0.3 to 0.5. Further, the ratio of the mass fraction of molybdenum to the mass fraction of cobalt in the ultra-high strength steel ranges from 0.35 to 0.45. Specifically, the ratio of the mass fraction of molybdenum to the mass fraction of cobalt in the ultra-high strength steel can be, but is not limited to, 0.3, 0.32, 0.35, 0.38, 0.4, 0.42, 0.45, etc. If the ratio of the mass fraction of molybdenum to the mass fraction of cobalt in the ultra-high strength steel is too large, the content of molybdenum in the ultra-high strength steel is too high, and the content of cobalt is too low, so the strengthening effect of cobalt on molybdenum and the ultra-high strength steel is not obvious, which is not conducive to the improvement of the tensile strength and yield strength of the ultra-high strength steel. If the ratio of the mass fraction of molybdenum to the mass fraction of cobalt in the ultra-high strength steel is too small, the content of molybdenum in the ultra-high strength steel is too small, and the content of cobalt is too high, although the ultra-high strength steel has higher tensile strength and yield strength, but the plasticity and elongation of the ultra-high strength steel are reduced. Cobalt can promote the improvement of the tensile strength and yield strength of the ultra-high strength steel by molybdenum, and when the ratio of the mass fraction of molybdenum to the mass fraction of cobalt is 0.3 to 0.5, the ultra-high strength steel has higher tensile strength and yield strength, and has better plasticity and elongation.

[0052] In some embodiments, the mass fraction of Mo in the ultra-high strength steel is 5.5wt% to 8.5wt%. Specifically, the mass fraction of Mo in the ultra-high strength steel can be, but is not limited to, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, etc. Mo is a strengthening element of the ultra-high strength steel, and Mo can increase the tensile strength, yield strength, Vickers hardness and wear resistance of the ultra-high strength steel. Mo element can form various alloying compounds with carbon, chromium, nickel and other elements in the ultra-high strength steel, which can enhance the grain boundary strength and grain boundary stability of the ultra-high strength steel, thereby improving the strength and Vickers hardness of the ultra-high strength steel. In addition, Mo element can also improve the grain refinement degree of the ultra-high strength steel, making the structure of the ultra-high strength steel more uniform, thereby improving the toughness and tensile properties of the ultra-high strength steel. However, a high content of Mo is not conducive to decarburization, so it will make the carbon content in the ultra-high strength steel too high, thereby reducing the plasticity and elongation of the ultra-high strength steel. When the mass fraction of Mo in the ultra-high strength steel is 5.5wt% to 8.5wt%, the ultra-high strength steel can have both high tensile strength and yield strength, and good plasticity and elongation.

[0053] Further, the mass fraction of Mo in the ultra-high strength steel is 6wt% to 8wt%. This can make the ultra-high strength steel have both high tensile strength and yield strength, and good plasticity and elongation.

[0054] Further, the mass fraction of Mo in the ultra-high strength steel is 6.1wt% to 7.5wt%. This can make the ultra-high strength steel have both high tensile strength and yield strength, and good plasticity and elongation.

[0055] Further, the mass fraction of Mo in the ultra-high strength steel is 6.1wt% to 7wt%. This can make the ultra-high strength steel have both high tensile strength and yield strength, and good plasticity and elongation.

[0056] In some embodiments, the ratio of the mass fraction of vanadium to the mass fraction of cobalt in the ultra-high strength steel ranges from 0.02 to 0.04. Further, the ratio of the mass fraction of vanadium to the mass fraction of cobalt in the ultra-high strength steel ranges from 0.025 to 0.35. Specifically, the ratio of the mass fraction of vanadium to the mass fraction of cobalt in the ultra-high strength steel can be, but is not limited to, 0.02, 0.023, 0.025, 0.028, 0.03, 0.033, 0.035, 0.038, 0.04, etc. Both vanadium and cobalt can increase the tensile strength and yield strength of the ultra-high strength steel. Vanadium is an oxygen forming element, and vanadium is prone to react with oxygen. Introducing oxygen into the ultra-high strength steel, the oxygen introduced by vanadium can promote decarburization at high temperature (e.g., 1300°C), thereby reducing the carbon content in the ultra-high strength steel, thereby improving the plasticity of the ultra-high strength steel. After the carbon content is reduced, it can also promote the formation of lath martensite, thereby improving the tensile strength, yield strength and plasticity of the ultra-high strength steel. When the ratio of the mass fraction of vanadium to the mass fraction of cobalt is too high, the plasticity of the ultra-high strength steel will decrease rapidly. When the ratio of the mass fraction of vanadium to the mass fraction of cobalt is too low, the strengthening phase is not enough, and the tensile strength and yield strength of the ultra-high strength steel decrease.

[0057] In some embodiments, the mass fraction of vanadium in the ultra-high strength steel is 0.2wt% to 0.8wt%. Specifically, the mass fraction of vanadium in the ultra-high strength steel can be, but is not limited to, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, etc. Vanadium is a strengthening element of the ultra-high strength steel, which can refine the grain and increase the tensile strength and yield strength of the ultra-high strength steel. In addition, vanadium is prone to combine with oxygen, and the oxygen combined with vanadium can promote decarburization, thereby further reducing the carbon content in the ultra-high strength steel, so that the ultra-high strength steel has higher tensile strength and yield strength. If the mass fraction of vanadium is too low, the strengthening phase formed in the ultra-high strength steel is not enough, and the improvement of the ultra-high strength steel is limited. If the mass fraction of vanadium is too high, the plasticity and elongation of the ultra-high strength steel will also decrease.

[0058] Further, the mass fraction of vanadium in the ultra-high strength steel is 0.3wt% to 0.7wt%. In this way, the ultra-high strength steel can have higher tensile strength and yield strength, and better plasticity and elongation.

[0059] Further, the mass fraction of vanadium in the ultra-high strength steel is 0.4wt% to 0.6wt%. In this way, the ultra-high strength steel can have higher tensile strength and yield strength, and better plasticity and elongation.

[0060] In some embodiments, the raw material of the ultra-high strength steel comprises a metal powder. Alternatively, the ultra-high strength steel is prepared by injection molding, debinding, sintering, solid solution, deep cooling and aging treatment of the metal powder.

[0061] Alternatively, the metal powder comprises at least one metal, and the D50 particle size of the metal powder ranges from 7 μm to 10 μm. Further, the raw material of the ultra-high strength steel comprises a metal powder, and the metal powder comprises at least one metal, and the D50 particle size of the metal powder ranges from 7.5 μm to 9.5 μm. Still further, the raw material of the ultra-high strength steel comprises a metal powder, and the metal powder comprises at least one metal, and the D50 particle size of the metal powder ranges from 8 μm to 9 μm. Specifically, the D50 particle size of the metal powder can be, but is not limited to, 7 μm, 7.3 μm, 7.5 μm, 7.8 μm, 8 μm, 8.3 μm, 8.5 μm, 8.8 μm, 9 μm, 9.3 μm, 9.5 μm, 9.8 μm, 10 μm, etc. The smaller the particle size of the metal powder, the denser the product obtained by sintering the metal powder, the larger the volume shrinkage, the more difficult to decarburize, the higher the carbon content in the ultra-high strength steel, thereby reducing the plasticity of the ultra-high strength steel, and the tensile strength and yield strength are also slightly reduced. The larger volume shrinkage results in larger size fluctuation of the product, affecting the yield of the product. In addition, the smaller the particle size of the metal powder, the larger the specific surface area, the larger the energy required for sintering, the larger the grain size, and the grains are prone to slip, further reducing the plasticity of the ultra-high strength steel. The larger the particle size of the metal powder, the larger the porosity of the product obtained after sintering, which increases the brittleness of the product and is prone to brittle segments, and the tensile strength and yield strength are reduced. When the D50 particle size of the metal powder ranges from 7 μm to 10 μm, the product after sintering has suitable density, can be better decarburized, and the grain size is small, which is less prone to slip and brittle segments, thereby having high tensile strength, yield strength and elongation. In addition, the product also has a small volume shrinkage, which can improve the yield of the product.

[0062] "D50" refers to the particle size corresponding to the cumulative particle size distribution percentage of 50% of a sample. Its physical meaning is that the particles with a particle size greater than it account for 50%, and the particles with a particle size less than it also account for 50%, and D50 is also called median diameter or median particle size.

[0063] Optionally, the D10 particle size of the metal powder is in the range of D10≤5 μm. Further, the D10 particle size of the metal powder is in the range of 1 μm≤D10≤5 μm. Yet further, the D10 particle size of the metal powder is in the range of 2 μm≤D10≤4 μm. Yet further, the D10 particle size of the metal powder is in the range of 2.5 μm≤D10≤3.5 μm. Specifically, the D10 particle size of the metal powder can be, but is not limited to, 1 μm, 1.3 μm, 1.5 μm, 1.8 μm, 2 μm, 2.3 μm, 2.5 μm, 2.8 μm, 3 μm, 3.3 μm, 3.5 μm, 3.8 μm, 4 μm, 4.3 μm, 4.5 μm, 4.8 μm, 5 μm, etc. When the D10 particle size of the metal powder is in this range, the sintered product can have suitable density, can be better decarburized, and have smaller grain size, and is less likely to produce slip and brittle section, thereby having higher tensile strength, yield strength and elongation. In addition, the product can have smaller volume shrinkage, and the yield of the product can be improved.

[0064] "D10" refers to the particle size at which the cumulative distribution of particles is 10%, i.e., the volume content of particles less than this particle size accounts for 10% of the total particles.

[0065] Optionally, the D90 particle size of the metal powder is in the range of 17 μm≤D90≤24 μm. Further, the D90 particle size of the metal powder is in the range of 18 μm≤D90≤22 μm. Specifically, the D90 particle size of the metal powder can be, but is not limited to, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, 20 μm, 20.5 μm, 21 μm, 21.5 μm, 22 μm, 22.5 μm, 23 μm, 23.5 μm, 24 μm, etc. When the D90 particle size of the metal powder is in this range, the sintered product can have suitable density, can be better decarburized, and have smaller grain size, and is less likely to produce slip and brittle section, thereby having higher tensile strength, yield strength and elongation. In addition, the product can have smaller volume shrinkage, and the yield of the product can be improved.

[0066] "D90" refers to the particle size at which the cumulative distribution of particles is 90%. That is, the volume content of particles less than this particle size accounts for 90% of the total particles.

[0067] Optionally, the tap density of the metal powder is greater than or equal to 4.4 g / cm3. 3 Further, the tap density of the metal powder can be 4.4 g / cm3 3 to 4.8 g / cm3 3Yet further, the tap density of the metal powder can be 4.4 g / cm3 3 to 4.7 g / cm3 3 Specifically, the tap density of the metal powder can be, but not limited to, 4.4 g / cm3 3 , 4.45 g / cm3 3 , 4.5 g / cm3 3 , 4.55 g / cm3 3 , 4.6 g / cm3 3 , 4.65 g / cm3 3 , 4.7 g / cm3 3 , 4.75 g / cm3 3 , 4.8 g / cm3 3 , etc. If the tap density of the metal powder is too high, it means that the particle size of the metal powder is too small, the product obtained after sintering with the metal powder is more compact, the volume shrinkage is larger, it is more difficult to decarburize, the carbon content in the ultra-high strength steel is too high, thereby reducing the plasticity of the ultra-high strength steel, and the tensile strength and yield strength are also slightly reduced; the volume shrinkage is larger, the size fluctuation of the product is larger, affecting the yield of the product; in addition, the smaller the particle size of the metal powder, the larger the specific surface area, the larger the energy required for sintering, the larger the grain size growth, and the grains are prone to slip, further reducing the plasticity of the ultra-high strength steel. If the tap density of the metal powder is too low, it means that the particle size of the metal powder is too large, the porosity of the product obtained after sintering is also large, the brittleness of the product is increased, brittle segments are prone to occur, and the tensile strength and yield strength are reduced.

[0068] In some embodiments, the ultra-high strength steel further comprises chromium (Cr), and the mass fraction of the chromium in the ultra-high strength steel is 0.1 wt% to 1 wt%. Specifically, the mass fraction of the chromium in the ultra-high strength steel can be, but not limited to, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%. Chromium can play a role in solid solution strengthening and alloy carbide strengthening, in addition, it can also control the carbon content in the ultra-high strength steel, thereby reducing the carbon content in the ultra-high strength steel, improving the mechanical properties such as the tensile strength, yield strength and wear resistance of the ultra-high strength steel. If the content of chromium is too low, the improvement of the tensile strength and yield strength of the ultra-high strength steel is limited; if the content of chromium is too high, the plasticity of the ultra-high strength steel is easily affected, reducing the elongation of the ultra-high strength steel.

[0069] In some embodiments, in the ultra-high strength steel, the mass fraction of the chromium is 0.1wt% to 0.8wt%. In this way, the content of carbon in the ultra-high strength steel can be better controlled, and the ultra-high strength steel has higher tensile strength and yield strength while having better plasticity and elongation.

[0070] Further, in the ultra-high strength steel, the mass fraction of the chromium is 0.1wt% to 0.5wt%. In this way, the content of carbon in the ultra-high strength steel can be better controlled, and the ultra-high strength steel has higher tensile strength and yield strength while having better plasticity and elongation.

[0071] Still further, in the ultra-high strength steel, the mass fraction of the chromium is 0.1wt% to 0.3wt%. In this way, the content of carbon in the ultra-high strength steel can be better controlled, and the ultra-high strength steel has higher tensile strength and yield strength while having better plasticity and elongation.

[0072] In some embodiments, the ultra-high strength steel further comprises impurity elements, and the mass fraction of the impurity elements is less than or equal to 0.5wt%. Specifically, in the ultra-high strength steel, the mass fraction of the impurity elements can be, but is not limited to, less than or equal to 0.45wt%, less than or equal to 0.4wt%, less than or equal to 0.35wt%, less than or equal to 0.3wt%, less than or equal to 0.25wt%, etc. In the ultra-high strength steel, the introduction of impurity elements will increase the defects in the ultra-high strength steel, reduce the tensile strength and yield strength of the ultra-high strength steel, so that the tensile strength and yield strength of the ultra-high strength steel cannot be improved. In addition, the impurity elements will also increase the brittleness of the ultra-high strength steel, reduce the plasticity of the ultra-high strength steel, so that the ultra-high strength steel is more likely to be brittle, and the elongation of the ultra-high strength steel is reduced. Although some impurities will inevitably be introduced into the ultra-high strength steel, by controlling the content of various impurities in the ultra-high strength steel, the ultra-high strength steel can have higher tensile strength, yield strength and wear resistance while having higher elongation.

[0073] In some embodiments, the impurity elements include carbon (C) and oxygen (O).

[0074] Optionally, in the ultra-high strength steel, the mass fraction of carbon is less than or equal to 0.03wt%. Further, in the ultra-high strength steel, the mass fraction of carbon is less than or equal to 0.025wt%. Still further, in the ultra-high strength steel, the mass fraction of carbon is less than or equal to 0.015wt%. Specifically, in the ultra-high strength steel, the mass fraction of carbon can be, but is not limited to, 0.004wt%, 0.005wt%, 0.006wt%, 0.007wt%, 0.008wt%, 0.009wt%, 0.01wt%, 0.012wt%, 0.013wt%, 0.014wt%, 0.015wt%, 0.02wt%, 0.025wt%, 0.03wt%, etc. The higher the content of carbon in the ultra-high strength steel, the higher the Vickers hardness and wear resistance of the ultra-high strength steel can be, but the plasticity and elongation of the ultra-high strength steel will be reduced.

[0075] Optionally, in the ultra-high strength steel, the mass fraction of oxygen is less than or equal to 0.5wt%. Further, in the ultra-high strength steel, the mass fraction of oxygen is less than or equal to 0.12wt%. Still further, in the ultra-high strength steel, the mass fraction of oxygen is less than or equal to 0.01wt%. Still further, in the ultra-high strength steel, the mass fraction of oxygen is less than or equal to 0.08wt%. Specifically, in the ultra-high strength steel, the mass fraction of oxygen can be, but is not limited to, 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.1wt%, 0.11wt%, 0.12wt%, 0.13wt%, 0.14wt%, 0.15wt%, etc. Oxygen mainly exists in the form of inclusions such as FeO, MnO and SiO2 in the ultra-high strength steel, which reduces the tensile strength, yield strength and plasticity of the ultra-high strength steel. In addition, too high a content of oxygen will also cause too large a size change of the ultra-high strength steel after sintering, reducing the precision of the product.

[0076] In some embodiments, in the ultra-high strength steel, the mass fraction of oxygen is 0.02wt% to 0.5wt%. In this way, the ultra-high strength steel can have better tensile strength, yield strength and plasticity.

[0077] In some embodiments, in the ultra-high strength steel, the mass fraction of oxygen is 0.02wt% to 0.2wt%. In this way, the ultra-high strength steel can have better tensile strength, yield strength and plasticity.

[0078] In some embodiments, in the ultra-high strength steel, the mass fraction of oxygen is 0.02wt% to 0.15wt%. In this way, the ultra-high strength steel can have better tensile strength, yield strength and plasticity.

[0079] In some embodiments, the mass fraction of oxygen in the ultra-high strength steel is 0.02wt% to 0.08wt%. In this way, the ultra-high strength steel has better tensile strength, yield strength and plasticity.

[0080] In some embodiments, the mass fraction of oxygen in the ultra-high strength steel is 0.02wt% to 0.08wt%. In this way, the ultra-high strength steel has better tensile strength, yield strength and plasticity.

[0081] The impurity elements also include at least one of sulfur (S), manganese (Mn) and silicon (Si).

[0082] Optionally, the mass fraction of sulfur in the ultra-high strength steel is less than or equal to 0.02wt%. Further, the mass fraction of sulfur in the ultra-high strength steel is less than or equal to 0.016wt%. Still further, the mass fraction of sulfur in the ultra-high strength steel is less than or equal to 0.013wt%. Still further, the mass fraction of sulfur in the ultra-high strength steel is less than or equal to 0.01wt%. Specifically, the mass fraction of sulfur in the ultra-high strength steel is 0.003wt%, 0.004wt%, 0.005wt%, 0.006wt%, 0.007wt%, 0.008wt%, 0.009wt%, 0.01wt%, 0.012wt%, 0.014wt%, 0.016wt%, 0.018wt%, 0.02wt% and the like. Sulfur is a harmful element in the ultra-high strength steel, and excessive content of sulfur makes the ultra-high strength steel prone to brittle fracture during high-temperature and pressure processing, reducing the ductility and toughness of the ultra-high strength steel.

[0083] In some embodiments, the mass fraction of sulfur in the ultra-high strength steel is 0.001wt% to 0.02wt%. In this way, the ultra-high strength steel has better toughness and elongation.

[0084] In some embodiments, the mass fraction of sulfur in the ultra-high strength steel is 0.001wt% to 0.02wt%. In this way, the ultra-high strength steel has better toughness and elongation.

[0085] In some embodiments, the mass fraction of sulfur in the ultra-high strength steel is 0.001wt% to 0.02wt%. In this way, the ultra-high strength steel has better toughness and elongation.

[0086] Optionally, in the ultra-high strength steel, the mass fraction of the manganese is less than or equal to 0.1 wt%. Further, in the ultra-high strength steel, the mass fraction of the manganese is less than or equal to 0.08 wt%. Still further, in the ultra-high strength steel, the mass fraction of the manganese is less than or equal to 0.06 wt%. Yet further, in the ultra-high strength steel, the mass fraction of the manganese is less than or equal to 0.04 wt%. Specifically, in the ultra-high strength steel, the mass fraction of the manganese can be, but is not limited to, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.1 wt%, etc. The manganese can improve the strength of the ultra-high strength steel, weaken or eliminate the adverse effects of sulfur, and improve the hardenability of the ultra-high strength steel. However, the manganese is easy to adsorb carbon, thereby reducing the plasticity and elongation of the ultra-high strength steel.

[0087] In some embodiments, in the ultra-high strength steel, the mass fraction of the manganese is 0.02 wt% to 0.08 wt%. In this way, the ultra-high strength steel can have good tensile strength and yield strength, and also have good plasticity and elongation.

[0088] In other embodiments, in the ultra-high strength steel, the mass fraction of the manganese is 0.02 wt% to 0.05 wt%. In this way, the ultra-high strength steel can have good tensile strength and yield strength, and also have good plasticity and elongation.

[0089] Optionally, the mass fraction of silicon in the ultra-high strength steel is less than or equal to 0.5 wt%. Further, the mass fraction of silicon in the ultra-high strength steel is less than or equal to 0.45 wt%. Still further, the mass fraction of silicon in the ultra-high strength steel is less than or equal to 0.44 wt%. Yet further, the mass fraction of silicon in the ultra-high strength steel is less than or equal to 0.35 wt%. Specifically, the mass fraction of silicon in the ultra-high strength steel can be, but is not limited to, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.28 wt%, 0.3 wt%, 0.32 wt%, 0.35 wt%, 0.38 wt%, 0.4 wt%, 0.42 wt%, 0.45 wt%, 0.48 wt%, 0.5 wt%, etc. Silicon can increase the Vickers hardness of the ultra-high strength steel, but silicon is prone to react with oxygen to form ceramic phase particles, which can form defects and reduce the plasticity and elongation of the ultra-high strength steel. When the mass fraction of silicon in the ultra-high strength steel is controlled within a certain range, the ultra-high strength steel can have both high Vickers hardness and high plasticity and elongation. In some embodiments, the mass fraction of silicon in the ultra-high strength steel is 0.24 wt% to 0.42 wt%. In this way, the ultra-high strength steel can have both high Vickers hardness and high plasticity and elongation.

[0090] Optionally, the ultra-high strength steel is a lath martensite, and the mass fraction of lath martensite in the ultra-high strength steel is greater than or equal to 99 wt%. Further, the mass fraction of lath martensite in the ultra-high strength steel is greater than or equal to 99.5 wt%. Specifically, the mass fraction of lath martensite in the ultra-high strength steel can be, but is not limited to, 99 wt%, 99.1 wt%, 99.2 wt%, 99.3 wt%, 99.4 wt%, 99.5 wt%, 99.6 wt%, 99.7 wt%, 99.8 wt%. In this way, the ultra-high strength steel can have higher strength and Vickers hardness, and in addition, can have better toughness and elongation. If the mass fraction of lath martensite in the ultra-high strength steel is too low, the strength and Vickers hardness of the ultra-high strength steel will be reduced.

[0091] The tensile strength Rm of the ultra-high strength steel according to the present application ranges from 1900Mpa to 2350Mpa. Further, the tensile strength Rm of the ultra-high strength steel ranges from 2000Mpa to 2350Mpa. Still further, the tensile strength Rm of the ultra-high strength steel ranges from 2100Mpa to 2350Mpa. Yet further, the tensile strength Rm of the ultra-high strength steel ranges from 2150Mpa to 2350Mpa. Yet further, the tensile strength Rm of the ultra-high strength steel ranges from 2200Mpa to 2350Mpa. Specifically, the tensile strength Rm of the ultra-high strength steel can be, but is not limited to, 1900Mpa, 1950Mpa, 2000Mpa, 2050Mpa, 2100Mpa, 2150Mpa, 2200Mpa, 2250Mpa, 2300Mpa, 2350Mpa, etc. The ultra-high strength steel according to the present application has a good tensile strength, and thus can be better applied to structural members of electronic devices with high requirements on tensile strength, impact resistance, etc.

[0092] The yield strength σs of the ultra-high strength steel according to the present application ranges from 1800Mpa to 2250Mpa. Further, the yield strength σs of the ultra-high strength steel ranges from 1900Mpa to 2250Mpa. Still further, the yield strength σs of the ultra-high strength steel ranges from 1950Mpa to 2250Mpa. Yet further, the yield strength σs of the ultra-high strength steel ranges from 2000Mpa to 2250Mpa. Yet further, the yield strength σs of the ultra-high strength steel ranges from 2050Mpa to 2250Mpa. Yet further, the yield strength σs of the ultra-high strength steel ranges from 2100Mpa to 2250Mpa. Specifically, the yield strength σs of the ultra-high strength steel can be, but is not limited to, 1800Mpa, 1850Mpa, 1900Mpa, 1950Mpa, 2000Mpa, 2050Mpa, 2100Mpa, 2150Mpa, 2200Mpa, 2250Mpa, etc. The ultra-high strength steel according to the present application has a good yield strength, and thus can be better applied to structural members of electronic devices with high requirements on yield strength, impact resistance, etc.

[0093] The elongation δ of the ultra-high strength steel according to the present application ranges from 1.8% to 7.5%. Further, the elongation δ of the ultra-high strength steel according to the present application ranges from 3% to 7.5%. Still further, the elongation δ of the ultra-high strength steel according to the present application ranges from 4% to 7.5%. Still further, the elongation δ of the ultra-high strength steel according to the present application ranges from 4% to 7.1%. Still further, the elongation δ of the ultra-high strength steel according to the present application ranges from 4.5% to 7.1%. Specifically, the elongation δ of the ultra-high strength steel according to the present application can be, but is not limited to, 1.8%, 2.1%, 2.5%, 3%, 3.5%, 4%, 4.3%, 4.5%, 4.8%, 5%, 5.3%, 5.5%, 5.8%, 6%, 6.3%, 6.5%, 6.8%, 7%, 7.1%, 7.3%, 7.5%, and the like. The elongation of the ultra-high strength steel according to the present application can be as high as 7.5%, which has a relatively high plasticity and elongation, and is beneficial to the application of the ultra-high strength steel.

[0094] The modulus E of the ultra-high strength steel according to the present application ranges from 180 GPa to 190 GPa. Further, the modulus E of the ultra-high strength steel according to the present application ranges from 185 GPa to 190 GPa. Specifically, the modulus E of the ultra-high strength steel according to the present application can be, but is not limited to, 180 GPa, 181 GPa, 182 GPa, 183 GPa, 184 GPa, 185 GPa, 186 GPa, 187 GPa, 188 GPa, 189 GPa, 190 GPa, and the like.

[0095] The Vickers hardness of the ultra-high strength steel according to the present application ranges from 580 HV to 680 HV. Specifically, the Vickers hardness of the ultra-high strength steel according to the present application can be, but is not limited to, 580 HV, 600 HV, 620 HV, 640 HV, 660 HV, 680 HV, and the like. The ultra-high strength steel according to the present application has a relatively high Vickers hardness, and thus has a good wear resistance.

[0096] In summary, the ultra-high strength steel according to the present application has a relatively high tensile strength and yield strength, a relatively high Vickers hardness, and a relatively high elongation.

[0097] The ultra-high strength steel according to the present application can be prepared by the method described in the following embodiments of the present application, and can also be prepared by other methods. The preparation method of the present application is only one or more preparation methods of the ultra-high strength steel according to the present application, and should not be understood as a limitation on the ultra-high strength steel provided in the embodiments of the present application.

[0098] Please refer to Figure 1 The present application provides a preparation method of an ultra-high strength steel, which comprises the following steps:

[0099] S101, providing metal powder and binder, and performing injection molding to obtain a blank;

[0100] S102, defatting and sintering the blank to obtain an intermediate blank; and

[0101] S103, heat treating the intermediate blank to obtain the ultra-high strength steel, the ultra-high strength steel comprising iron, nickel, cobalt, molybdenum and vanadium, the mass fraction of the iron being greater than or equal to 50wt%, the mass fraction of the nickel being 16wt% to 20wt%, the mass fraction of the cobalt being 15.1wt% to 19wt%, the mass fraction of the nickel being greater than the mass fraction of the cobalt, the mass fraction of the cobalt being greater than the mass fraction of the molybdenum, and the mass fraction of the molybdenum being greater than the mass fraction of the vanadium.

[0102] The ultra-high strength steel prepared by the method of the embodiment of the present application comprises iron (Fe), nickel (Ni), cobalt (Co), molybdenum (Mo) and vanadium (V). By compounding alloy elements in the ultra-high strength steel, controlling the contents of iron and nickel elements, and adjusting the process, the ultra-high strength steel has high tensile strength, yield strength and Vickers hardness, and has high toughness and elongation.

[0103] Optionally, in S101, the metal powder can be prepared by water-vapor integrated atomization of high-purity metal or alloy blank.

[0104] Optionally, the high-purity metal or alloy blank is melted at a temperature of 1500°C to 1700°C in a vacuum environment according to the ratio, and the metal powder is prepared by water-vapor integrated atomization. The temperature for preparing the metal powder can be, but is not limited to, 1500°C, 1550°C, 1600°C, 1650°C, 1700°C, etc.

[0105] The scanning electron microscope (SEM) image of the metal powder prepared by the embodiment of the present application is shown in Figure 2 .

[0106] The composition of each element in the prepared metal powder is shown in Table 1 below, and the particle size and tap density of the metal powder are shown in Table 2 below.

[0107] Table 1 Composition of each element in the metal powder and parameters of the metal powder

[0108]

[0109] Table 2 Particle size and tap density of the metal powder

[0110]

[0111] Optionally, the tap density can be 4.4 g / cm3 3 to 4.8 g / cm3 3 For example, it can be, but is not limited to, 4.4 g / cm3 3 , 4.5 g / cm3 3 , 4.6 g / cm3 3 , 4.7 g / cm3 3 , 4.8 g / cm3 3 , etc.

[0112] The particle size of the metal powder has a significant influence on the density and performance of the sintered material. For detailed description of D10, D50 and D90 of the metal powder, please refer to the description in the corresponding part of the above examples.

[0113] Optionally, the particle size of the metal powder can be controlled by sieving.

[0114] Optionally, the binder can include polyformaldehyde, an antioxidant (such as BASF antioxidant 1010), polyethylene and vinyl acetate polymer. Optionally, the preparation of the binder includes (by mass fraction): placing 80wt% to 90wt% polyformaldehyde, 1wt% to 3wt% antioxidant, 3wt% to 5wt% polyethylene and 2wt% to 6wt% vinyl acetate polymer in a kneader, mixing at a temperature of 150°C to 170°C for 60min to 120min to obtain the binder.

[0115] Please refer to Figure 3 , in the S101, the metal powder and the binder are provided and injection molding is performed to obtain a blank, which includes:

[0116] S1011, the binder and the metal powder are mixed in a volume ratio and are subjected to banburying to obtain a feedstock; and

[0117] Specifically, the binder and the metal powder are mixed in a volume ratio of 38:62 to 42:58 and are placed in a banburying machine, and are mixed and banburyed at a temperature of 150°C to 160°C for 90min to 120min to obtain the feedstock.

[0118] Optionally, the volume ratio of the binder and the metal powder can be, but is not limited to, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.68, 0.7, 0.72, etc. If the volume ratio of the binder and the metal powder is too large, the fluctuation of the size of the blank obtained by injection molding and the final product is too large, which affects the precision and yield of the product. If the volume ratio of the binder and the metal powder is too small, the flowability of the melt is not enough during injection molding, and the blank obtained is prone to defects, and in severe cases, the injection cannot be performed.

[0119] Optionally, the feeding material has a melt index in the range of 1200 g / 10 min to 1700 g / 10 min. Specifically, the melt index of the feeding material can be, but is not limited to, 1200 g / 10 min, 1300 g / 10 min, 1400 g / 10 min, 1500 g / 10 min, 1600 g / 10 min, 1700 g / 10 min, etc. Controlling the stable melt index is the core of controlling the dimensional accuracy of the final product. The key control point of the internal mixing is to control the melt index of the feeding material after the internal mixing. When the melt index is too high, the material shrinkage is too high, the material flowability is good, and the injection molding defects and unevenness are prone to occur; when the melt index is too low, the injection obtained blank is prone to have pores, defects, flow lines, etc. When the melt index is 1200 g / 10 min to 1700 g / 10 min, the shrinkage can be more appropriate, and the product has a higher yield.

[0120] Optionally, the feeding material has a theoretical shrinkage of 1.135 to 1.195.

[0121] S1012, placing the feeding material in an injection molding machine to perform injection molding to obtain a blank.

[0122] Optionally, the feeding material is placed in an injection molding machine, and the injection molding is performed under the conditions that the temperature parameter is 150°C to 250°C, the injection pressure is 80 MPa to 150 MPa, and the mold cavity surface temperature is 100°C to 140°C to obtain a blank.

[0123] It can be understood that the blank of the present application is prepared by metal injection molding (MIM).

[0124] Please refer to Figure 4 In some embodiments, the sintering includes first sintering, second sintering and third sintering; and the debinding and sintering of the blank to obtain an intermediate blank includes:

[0125] S1021, debinding the blank to remove part of the binder;

[0126] Optionally, the green body is placed in a nitric acid degreasing furnace for degreasing, the degreasing temperature is 105-125℃, the flow rate of nitric acid gas in the degreasing furnace is 0.5-3L / min, the flow rate of nitrogen is 60-120L / min, and the degreasing time is 4-10h. The polyformaldehyde in the binder in the green body is removed, and the degreasing rate is controlled to be greater than 7.7wt% (for example, the degreasing rate is 7.75wt%, 7.8wt%, 7.85wt%, 7.9wt%, etc.). The nitric acid can react with the polyformaldehyde, and the generated product zone is carried out by nitrogen, so as to achieve the purpose of removing the polyformaldehyde in the green body.

[0127] S1022, the green body is subjected to first sintering, and the temperature T1 of the first sintering is 370-610℃;

[0128] Optionally, the first sintering is carried out in a negative pressure and nitrogen atmosphere, and the vacuum degree of the first sintering is less than 5KPa, which is beneficial to the removal of organic matter.

[0129] S1023, the green body is subjected to second sintering, and the temperature T2 of the second sintering is 610-920℃, and

[0130] Optionally, the second sintering is carried out under negative pressure, and the vacuum degree of the second sintering is less than 5KPa, which is beneficial to deoxidation and decarburization.

[0131] S1024, the green body is subjected to third sintering, and the temperature T3 of the third sintering is 920-1380℃, so as to obtain an intermediate state green body; wherein the grain size (also referred to as the metallographic size) d of the intermediate state green body is ≤250μm, the mass fraction of carbon in the intermediate state green body is ≤0.025wt%, and the mass fraction of oxygen in the intermediate state green body is ≤0.5wt%.

[0132] Optionally, the third sintering is carried out in a nitrogen atmosphere, and the vacuum degree of the third sintering is 10-30KPa, which is beneficial to the densification of the intermediate state green body.

[0133] It should be noted that the first sintering is a thermal degreasing stage, the second sintering is a negative pressure degreasing stage, and the third sintering is a high temperature sintering stage.

[0134] Further, the mass fraction of carbon in the intermediate state green body is less than or equal to 0.02wt%. Still further, the mass fraction of carbon in the intermediate state green body is less than or equal to 0.015wt%.

[0135] Specifically, the mass fraction of carbon in the intermediate blank can be, but is not limited to, 0.025wt%, 0.024wt%, 0.023wt%, 0.022wt%, 0.021wt%, 0.02wt%, 0.018wt%, 0.016wt%, 0.014wt%, 0.012wt%, 0.01wt%, 0.008wt%, etc. After sintering, the intermediate blank is mainly austenite and a small amount of martensite and impurity phase. When the mass fraction of carbon in the intermediate blank is less than or equal to 0.02wt%, it can promote the formation of lath-shaped martensite in the product obtained after heat treatment. If the carbon content is too high, the Vickers hardness after sintering is too high, which can easily make the product obtained after final heat treatment change into granular martensite, greatly increasing the brittleness of the material.

[0136] Further, the mass fraction of oxygen in the intermediate blank is less than or equal to 0.5wt%. Still further, the mass fraction of oxygen in the intermediate blank is less than or equal to 0.3wt%. Still further, the mass fraction of oxygen in the intermediate blank is less than or equal to 0.15wt%. Still further, the mass fraction of oxygen in the intermediate blank is less than 0.1wt%.

[0137] Specifically, the mass fraction of oxygen in the intermediate blank can be, but is not limited to, 0.5wt%, 0.45wt%, 0.4wt%, 0.35wt%, 0.3wt%, 0.25wt%, 0.2wt%, 0.15wt%, 0.14wt%, 0.13wt%, 0.12wt%, 0.11wt%, 0.1wt%, 0.08wt%, 0.07wt%, 0.06wt%, etc. If the mass fraction of oxygen in the intermediate blank is too high, it can cause the strength of the material after heat treatment to decrease, and at the same time, the shrinkage rate becomes small, the size of the part becomes large, and the yield of the product is reduced.

[0138] Optionally, the grain size d of the intermediate blank can be, but is not limited to, 250μm, 230μm, 210μm, 200μm, 180μm, 160μm, 140μm, 120μm, 100μm, 80μm, etc. If the grain size is too large, the plasticity of the product obtained after final heat treatment is reduced, and for thin-walled parts, brittle fracture can easily occur under stress.

[0139] The grain size can be measured by metallographic graph, and the average value is calculated by randomly selecting a maximum of 7 grain sizes and removing the maximum and minimum grain sizes.

[0140] Optionally, the density of the intermediate blank is greater than or equal to 7.9g / cm 3 If the density of the intermediate blank is too small, the compactness is not enough, which affects the tensile strength and yield strength of the ultra-high strength steel finally prepared.

[0141] In some embodiments, the mass fraction of the sulfur in the intermediate-state blank obtained by sintering is less than or equal to 0.02wt%; the mass fraction of the manganese is less than or equal to 0.1wt%; and the mass fraction of the silicon is less than or equal to 0.5wt%.

[0142] In the present embodiment, the binder and other organic matters in the blank can be removed by heat debinding the blank at 370-610°C; vacuum deoxidization and decarburization can be performed while further removing the organic matters by negative pressure debinding at 610-920°C; and the intermediate-state blank can be gradually shaped and the compactness gradually improved by the third sintering at 920-1380°C.

[0143] See Figure 5 Optionally, the first sintering includes a first sub-sintering, a second sub-sintering and a third sub-sintering, and the first sintering of the blank includes:

[0144] S1022a, warming up to a first temperature T11 of 370°C≤T11≤390°C at a first warming-up rate V11 and performing heat preservation to perform the first sub-sintering;

[0145] Optionally, the first warming-up rate V11 is in the range of 3.8°C / min≤V11≤4.5°C / min; and specifically, but not limitedly, can be 3.8°C / min, 4.0°C / min, 4.1°C / min, 4.2°C / min, 4.3°C / min, 4.5°C / min, etc.

[0146] Optionally, the first temperature T11 can be, but is not limited to, 370°C, 375°C, 380°C, 385°C, 390°C, etc.

[0147] Optionally, the heat preservation time of the first sub-sintering can be, but is not limited to, 25-35min. Specifically, the heat preservation time of the first sub-sintering can be, but is not limited to, 25min, 28min, 30min, 33min, 35min, etc.

[0148] In a specific embodiment, the blank is warmed up to 380°C within 90min and heat preserved for 30min.

[0149] S1022b, warming up to a second temperature T12 of 470°C≤T12≤490°C at a second warming-up rate V12 and performing heat preservation to perform the second sub-sintering, wherein V11>V12 and V12≤2°C / min; and

[0150] Optionally, the second warming-up rate V12 is in the range of V12≤2°C / min.

[0151] Further, the second temperature-increasing rate V12 is in the range of 1℃ / min≤V12≤2℃ / min; specifically, it can be but is not limited to 1℃ / min, 1.2℃ / min, 1.4℃ / min, 1.5℃ / min, 1.6℃ / min, 1.7℃ / min, 1.8℃ / min, 2.0℃ / min, etc.

[0152] Optionally, the second temperature T12 can be but is not limited to 470℃, 475℃, 480℃, 485℃, 490℃, etc.

[0153] Optionally, the holding time of the second sub-sintering can be but is not limited to 100min to 140min. Specifically, the holding time of the second sub-sintering can be but is not limited to 100min, 110min, 120min, 130min, 140min, etc.

[0154] In a specific embodiment, the blank is heated from 380℃ to 480℃ within 60min, and is held for 120min.

[0155] S1022c, the blank is heated to a third temperature T13 in the range of 590℃≤T12≤610℃ at a third temperature-increasing rate V13, and is held for a third sub-sintering, wherein V11>V13, and V13≤2℃ / min.

[0156] Optionally, the third temperature-increasing rate V13 is in the range of V13≤2℃ / min.

[0157] Further, the third temperature-increasing rate V13 is in the range of 1℃ / min≤V13≤2℃ / min; specifically, it can be but is not limited to 1℃ / min, 1.2℃ / min, 1.4℃ / min, 1.5℃ / min, 1.6℃ / min, 1.7℃ / min, 1.8℃ / min, 2.0℃ / min, etc.

[0158] Optionally, the third temperature T13 can be but is not limited to 590℃, 595℃, 600℃, 605℃, 610℃, etc.

[0159] Optionally, the holding time of the third sub-sintering can be but is not limited to 100min to 140min. Specifically, the holding time of the third sub-sintering can be but is not limited to 100min, 110min, 120min, 130min, 140min, etc.

[0160] In a specific embodiment, the blank is heated from 480℃ to 600℃ within 90min, and is held for 120min.

[0161] Optionally, V11>V12, and V11>V13.

[0162] In the embodiment, the first temperature is reached by a first higher heating rate, which can improve the efficiency of sintering. The first temperature is kept for a certain time, which can make the temperature in the sintering furnace more uniform and increase the debinding time. The second and third heating rates are lower than the first heating rate, which can improve the uniformity of the temperature in the sintering furnace, increase the debinding time and improve the debinding efficiency. By debinding in stages, the uniformity of the sintering furnace temperature can be better controlled, and the organic matter can be better removed, and the carbon and oxygen contents can be better controlled. When the carbon and oxygen contents in the blank are too high, the first sintering holding stage (also referred to as the platform stage) and the holding time can be increased.

[0163] In some embodiments, the second sintering of the blank comprises: heating to a fourth temperature T21 of 880℃≤T21≤920℃ at a fourth heating rate V2 and keeping for a certain time to perform the second sintering.

[0164] Optionally, the fourth heating rate V2 is in the range of 2℃ / min≤V2≤3℃ / min; specifically, it can be, but is not limited to, 2℃ / min, 2.1℃ / min, 2.2℃ / min, 2.4℃ / min, 2.5℃ / min, 2.6℃ / min, 2.7℃ / min, 2.8℃ / min, 3.0℃ / min, etc.

[0165] Optionally, the fourth temperature T21 can be, but is not limited to, 880℃, 885℃, 890℃, 895℃, 900℃, 905℃, 915℃, 920℃, etc.

[0166] Optionally, the holding time of the second sintering can be, but is not limited to, 50min to 70min. Specifically, the holding time of the second sintering can be, but is not limited to, 50min, 55min, 60min, 65min, 70min, etc.

[0167] In a specific embodiment, the blank is heated from 600℃ to 900℃ in 120min and kept for 60min.

[0168] The second sintering is a negative pressure debinding stage, therefore, the fourth heating rate is slightly increased compared with the second and third heating rates, but is still relatively slow, which is beneficial to better remove the organic matter in the blank and perform deoxidization and decarburization.

[0169] Please refer to Figure 6 In some embodiments, the third sintering comprises a first sub-stage and a second sub-stage; the third sintering of the blank comprises:

[0170] S1024a, warming up to a fifth temperature T31 of 1200℃≤T31≤1300℃ at a fifth warming rate V31, and performing heat preservation to perform first sub-stage sintering, wherein V31>V2, V31≥5℃ / min; and

[0171] Optionally, the fifth warming rate V31 is in the range of 5℃ / min≤V31≤7℃ / min; specifically, it can be but is not limited to 5℃ / min, 5.2℃ / min, 5.4℃ / min, 5.6℃ / min, 5.8℃ / min, 6℃ / min, 6.2℃ / min, 6.4℃ / min, 6.6℃ / min, 6.8℃ / min, 7℃ / min, etc.

[0172] Optionally, the fifth temperature T31 can be but is not limited to 1200℃, 1220℃, 1240℃, 1260℃, 1280℃, 1300℃, etc.

[0173] Optionally, the heat preservation time of the first sub-stage sintering can be but is not limited to 100min to 140min. Specifically, the heat preservation time of the fifth sub-sintering can be but is not limited to 100min, 110min, 120min, 130min, 140min, etc.

[0174] Understandably, the fifth warming rate V31 is greater than the fourth warming rate V2. When the temperature is warmed up to above 900℃, the de-organics, deoxygenation, and decarburization of the blank are basically completed. Continuing to warm up, the blank starts to densify. Increasing the warming rate can increase the powder forming driving force, which is conducive to the densification of the intermediate blank.

[0175] In a specific embodiment, the blank is warmed up from 900℃ to 1250℃ within 120min, and is heat preserved for 120min.

[0176] S1024b, warming up to a sixth temperature T32 of 1340℃≤T32≤1380℃ at a sixth warming rate V32, and performing heat preservation to perform second sub-stage sintering, wherein V32<V31, V32≤2.3℃ / min.

[0177] Optionally, the sixth warming rate V32 is in the range of 1.5℃ / min≤V31≤2.3℃ / min; specifically, it can be but is not limited to 1.5℃ / min, 1.6℃ / min, 1.7℃ / min, 1.8℃ / min, 1.9℃ / min, 2.0℃ / min, 2.1℃ / min, 2.2℃ / min, 2.3℃ / min, etc.

[0178] Optionally, the sixth temperature T32 can be, but is not limited to, 1340℃, 1345℃, 1350℃, 1355℃, 1360℃, 1365℃, 1370℃, 1375℃, 1380℃, etc.

[0179] Optionally, the holding time of the second sub-stage sintering can be, but is not limited to, 210min to 270min. Specifically, the holding time of the fifth sub-sintering can be, but is not limited to, 210min, 220min, 230min, 240min, 250min, 260min, 270min, etc.

[0180] It can be understood that the fifth heating rate V31 is greater than the sixth heating rate V32. After the first sub-stage sintering is performed, the product has basically grown, and the heating rate is reduced, so that the sixth heating rate is less than the fifth heating rate. In this way, the densification time can be increased, thereby increasing the densification degree of the product.

[0181] In a specific embodiment, the blank is heated from 1250℃ to 1360℃ within 60min, and is held for 240min.

[0182] Optionally, the Vickers hardness of the intermediate blank obtained after sintering ranges from 240HV to 340HV. Specifically, after sintering, the Vickers hardness of the intermediate blank can be, but is not limited to, 240HV, 250HV, 260HV, 270HV, 280HV, 290HV, 300HV, 310HV, 320HV, 330HV, 340HV, etc. If the Vickers hardness of the intermediate blank is too high, the content of impurity elements such as carbon in the material is too high, which causes carbon strengthening and makes the material brittle. Although the Vickers hardness or tensile properties are good at this time, the performance of the product obtained after heat treatment of the intermediate blank is often poor. If the Vickers hardness of the intermediate blank is too low, the performance of the material is too low, which may be caused by the low content of strengthening elements or the high content of oxygen elements after sintering, etc.

[0183] See Figure 7 In some embodiments, the sintering includes a first sintering, a second sintering, and a third sintering; and the sintering and debinding of the blank to obtain an intermediate blank further includes:

[0184] S1025, cooling the blank after the third sintering.

[0185] Optionally, the cooling includes a first-stage cooling and a second-stage cooling. The cooling rate of the first-stage cooling is less than the cooling rate of the second-stage cooling. Optionally, the first-stage cooling is slow cooling, and the second-stage cooling is rapid cooling.

[0186] Specifically, the blank after the third sintering is slowly cooled from the sixth temperature T32 to 950°C to 1050°C (first stage cooling), and then rapidly cooled to room temperature (second stage cooling). The first stage cooling is equivalent to the tempering process. Segmented cooling can make full use of the temperature above 950°C from the sixth temperature, which is beneficial to the densification of the intermediate blank.

[0187] Please see Figure 8 In some embodiments, the heat treatment of the intermediate blank to obtain the ultra-high strength steel includes:

[0188] S1031, the intermediate blank is subjected to solution treatment to make the Vickers hardness of the intermediate blank 250HV to 350HV.

[0189] Optionally, the solution treatment is carried out under negative pressure, with the gas pressure of the solution treatment ≤0.1 kPa.

[0190] Optionally, the Vickers hardness of the intermediate state blank after solution treatment is greater than that of the sintered blank.

[0191] Optionally, the Vickers hardness of the solution-treated intermediate preform ranges from 250 HV to 350 HV. Specifically, the Vickers hardness of the solution-treated intermediate preform can be, but is not limited to, 250 HV, 260 HV, 270 HV, 280 HV, 290 HV, 300 HV, 310 HV, 320 HV, 330 HV, 340 HV, and 350 HV. The Vickers hardness of the solution-treated intermediate preform is slightly higher than that of the sintered preform. If the Vickers hardness of the solution-treated intermediate preform is too low, it indicates that the martensite content in the solution-treated intermediate preform is insufficient, the solution treatment is incomplete, and this affects the performance of the final product.

[0192] In this embodiment, the intermediate-state blank obtained after sintering contains metallic carbides (such as iron carbide, nickel carbide, etc.), and its microstructure includes martensite, austenite, and pearlite. If these impurities or impurity phases cannot be completely dissolved in the iron matrix, they will remain as impurity phases after heat treatment, forming grain boundary defects and affecting the material properties. Therefore, after sintering, a solution treatment is performed first to dissolve the sintered impurity elements and impurity phases into the iron matrix, so that the material is completely transformed into austenite during the high-temperature holding stage of solution treatment.

[0193] Please see Figure 9 In some embodiments, the solution treatment of the intermediate blank includes:

[0194] S1031a undergoes a first-stage solution treatment at a temperature of 180℃ to 220℃;

[0195] Optionally, the temperature is raised at a temperature raising rate of 5-8 ℃ / min, and the temperature is raised to 180-220 ℃ for 25-35 min to perform the first-stage solid solution treatment.

[0196] Specifically, the temperature of the first-stage solid solution treatment can be, but is not limited to, 180, 185, 190, 195, 200, 205, 210, 215, 220 ℃, etc.

[0197] Specifically, the temperature raising rate of the first-stage solid solution treatment can be, but is not limited to, 5, 5.5, 6, 6.5, 7, 7.5, 8 ℃ / min, etc.

[0198] In an embodiment, the temperature is raised to 200 ℃ for 30 min, and then is kept at 200 ℃ for 30 min to perform the first-stage solid solution treatment.

[0199] In this embodiment, the first-stage solid solution treatment is performed at 180-220 ℃, which can avoid rapid temperature rising to the target value, avoid temperature non-uniformity in the furnace chamber, and make the overall temperature consistency of the furnace chamber better, so that the finally prepared ultra-high strength steel has better comprehensive performance.

[0200] S1031b, performing a second-stage solid solution treatment at a temperature of 580-620 ℃; and

[0201] Optionally, the temperature is raised at a temperature raising rate of 11-16 ℃ / min, and the temperature is raised to 580-620 ℃ for 15-25 min to perform the second-stage solid solution treatment.

[0202] Specifically, the temperature of the second-stage solid solution treatment can be, but is not limited to, 580, 585, 590, 595, 600, 605, 610, 615, 620 ℃, etc.

[0203] Specifically, the temperature raising rate of the second-stage solid solution treatment can be, but is not limited to, 11, 12, 13, 14, 15, 16 ℃ / min, etc.

[0204] In an embodiment, the temperature is raised to 600 ℃ from 200 ℃ for 30 min, and then is kept at 600 ℃ for 20 min to perform the second-stage solid solution treatment.

[0205] Because the austenite transformation starting temperature of the material is 600℃, and the austenite transformation ending temperature is about 750℃, in the present embodiment, the second stage solid solution treatment is performed at 580℃ to 620℃, so that the austenite transformation is more sufficient. In addition, by controlling the heating rate of the second stage solid solution treatment to be 11℃ / min to 16℃ / min, the speed of the transformation can be better promoted by controlling the internal driving force of the material, while preventing the grain growth from affecting the tensile strength, yield strength and toughness of the finally obtained ultra-high strength steel. Too slow heating rate or too long holding time can easily cause the grain size to become large.

[0206] S1031c, performing a third stage solid solution treatment at a temperature of 920℃ to 1040℃.

[0207] Optionally, the temperature is heated to 920℃ to 1040℃ at a heating rate of 10℃ / min to 15℃ / min, and the temperature is held for 50min to 70min.

[0208] Specifically, the temperature of the third stage solid solution treatment can be, but is not limited to, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃, 1010℃, 1020℃, 1030℃, 1040℃, etc.

[0209] Specifically, the heating rate of the third stage solid solution treatment can be, but is not limited to, 10℃ / min, 10.6℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 14.67℃ / min, 15℃ / min, etc.

[0210] In a specific embodiment, the temperature is heated from 600℃ to 1000℃ at a rate of 60min, and held for 60min to perform the third stage solid solution treatment.

[0211] In the present embodiment, the third stage solid solution treatment is performed at 920℃ to 1040℃, so that the material is completely transformed into austenite, and the impurity elements and impurity phases after sintering are better dissolved in the iron matrix, so that the finally obtained ultra-high strength steel has better tensile strength, yield strength and plasticity. In addition, by controlling the heating rate of the third stage solid solution treatment to be 10℃ / min to 15℃ / min, the speed of the transformation can be better promoted by controlling the internal driving force of the material, while preventing the grain growth from affecting the tensile strength, yield strength and toughness of the finally obtained ultra-high strength steel. Too slow heating rate or too long holding time can easily cause the grain size to become large.

[0212] Optionally, the solid solution treatment of the intermediate state blank further comprises:

[0213] S1031d, rapidly cooling to room temperature.

[0214] Optionally, liquid nitrogen is used for rapid cooling to cool the intermediate blank to room temperature. In this embodiment, rapid cooling is performed to convert most of the austenite in the material into lath-shaped martensite, so that the final ultra-high strength steel has better tensile strength, yield strength and toughness.

[0215] Please refer again to Figure 8 In some embodiments, the heat treatment of the intermediate blank to obtain the ultra-high strength steel further comprises:

[0216] S1032, deep cooling treatment is performed on the intermediate blank after solid solution treatment, and the temperature of the deep cooling treatment is -196 to -180.

[0217] Optionally, liquid nitrogen is used for deep cooling treatment of the intermediate blank after solid solution treatment, and the temperature of the deep cooling treatment is -196 to -180.

[0218] Specifically, the temperature of the deep cooling treatment can be, but is not limited to, -180, -183, -185, -188, -190, -193, -196.

[0219] Optionally, the holding time of the deep cooling treatment can be 20 to 90 minutes. Specifically, the holding time of the deep cooling treatment can be, but is not limited to, 20, 30, 40, 50, 60, 70, 80, 90 minutes, etc.

[0220] Since the martensite transformation end point temperature of the material system of this embodiment is below zero, it cannot be completely transformed into full martensite at room temperature, so the deep cooling treatment of the intermediate blank after solid solution treatment can increase the content of lath-shaped martensite in the product, so that the content of lath-shaped martensite in the product can be increased to more than 99.5wt%, so that the final ultra-high strength steel has better tensile strength, yield strength and toughness.

[0221] Optionally, the Vickers hardness of the intermediate-state blank after the deep cooling ranges from 250HV to 350HV. Specifically, the Vickers hardness of the intermediate-state blank after the deep cooling can be, but is not limited to, 250HV, 260HV, 270HV, 280HV, 290HV, 300HV, 310HV, 320HV, 330HV, 340HV, 350HV, or the like. The Vickers hardness of the intermediate-state blank after the deep cooling is slightly improved compared to the Vickers hardness of the blank after the sintering. If the Vickers hardness of the intermediate-state blank after the deep cooling is too low, it indicates that the content of the martensite in the intermediate-state blank after the deep cooling is insufficient, which affects the performance of the final product.

[0222] Please refer again to Figure 8 In some embodiments, the heat treatment of the intermediate-state blank to obtain the ultra-high strength steel further includes:

[0223] S1033, aging treatment of the intermediate-state blank after the deep cooling treatment to obtain the ultra-high strength steel, wherein the Vickers hardness of the ultra-high strength steel ranges from 580HV to 680HV.

[0224] Optionally, the Vickers hardness of the ultra-high strength steel can be, but is not limited to, 580HV, 590HV, 600HV, 610HV, 620HV, 630HV, 640HV, 650HV, 660HV, 670HV, 680HV, or the like. When the Vickers hardness of the ultra-high strength steel is too low, the plasticity is improved, but the tensile strength and yield strength of the ultra-high strength steel are greatly reduced. When the Vickers hardness of the ultra-high strength steel is too high, the ultra-high strength steel is brittle and is prone to brittle fracture, and the plasticity and elongation are reduced.

[0225] Optionally, the aging treatment is performed in a negative pressure state, and the air pressure of the aging treatment is less than or equal to 0.1 KPa.

[0226] In the present embodiment, the aging treatment is performed after the deep cooling treatment, so that the precipitation phase between the grain boundaries of the material can be precipitated, the resistance to sliding between the grain boundaries is increased by forming dislocations at the grain boundaries, and the strength of the material is increased. In addition, in the process of aging strengthening, part of the lath-shaped martensite is reversely transformed into austenite, and the tensile strength, yield strength and plasticity of the material are adjusted by adjusting the reversely transformed austenite.

[0227] Please refer to Figure 10 In some embodiments, the aging treatment of the intermediate-state blank includes:

[0228] S1033a, first-stage aging treatment at a temperature ranging from 180°C to 220°C; and

[0229] Optionally, the temperature is raised at a temperature raising rate of 5-8℃ / min, and the temperature is raised to 180-220℃ for 25-35min to perform the first aging treatment.

[0230] Specifically, the temperature of the first aging treatment can be, but is not limited to, 180℃, 185℃, 190℃, 195℃, 200℃, 205℃, 210℃, 215℃, 220℃, etc.

[0231] Specifically, the temperature raising rate of the first aging treatment can be, but is not limited to, 5℃ / min, 5.5℃ / min, 6℃ / min, 6.5℃ / min, 7℃ / min, 7.5℃ / min, 8℃ / min, etc.

[0232] In a specific embodiment, the temperature is raised to 200℃ for 30min, and the temperature is kept for 30min to perform the first aging treatment.

[0233] S1033b, the second aging treatment is performed at a temperature of 460-540℃.

[0234] Optionally, the temperature is raised at a temperature raising rate of 8-12℃ / min, and the temperature is raised to 460-540℃ for 3-5h to perform the second aging treatment.

[0235] Specifically, the temperature of the second aging treatment can be, but is not limited to, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, etc.

[0236] Specifically, the temperature raising rate of the second aging treatment can be, but is not limited to, 8℃ / min, 8.5℃ / min, 9℃ / min, 9.5℃ / min, 10℃ / min, 10.5℃ / min, 11℃ / min, 11.5℃ / min, 12℃ / min, etc.

[0237] In a specific embodiment, the temperature is raised to 500℃ from 200℃ for 30min, and the temperature is kept for 4h to perform the second aging treatment.

[0238] In the present embodiment, the temperature is first raised to 180-220℃ to perform the first aging treatment, and then the temperature is raised to 460-540℃ to perform the second aging treatment, so that the temperature in the furnace chamber is more uniform, which is conducive to improving the tensile strength, yield strength and toughness of the ultra-high strength steel prepared.

[0239] Please refer to Figure 11 In some embodiments, the method for preparing the ultra-high strength steel of the present application further comprises:

[0240] S104, undergoes surface anti-corrosion treatment;

[0241] Alternatively, manganese-based phosphate is applied to the surface of ultra-high strength steel, followed by passivation (oil-based sealing) for corrosion protection to form an anti-corrosion layer, which allows the salt spray time to reach 48 hours. However, the surface contains oily substances, making it unsuitable for use as an appearance part.

[0242] Optionally, nickel plating can be applied to the surface of ultra-high strength steel to form an anti-corrosion layer, allowing the salt spray time to reach 24 hours.

[0243] The following specific embodiments further describe the ultra-high strength steel of this application.

[0244] Examples 1 to 3

[0245] The intermediate blanks (i.e., sintered parts) of Examples 1 to 3 were prepared by the following steps:

[0246] 1) Provide metal powder and binder, with a volume ratio of binder to metal powder of 40:60, and obtain feed by intensive mixing;

[0247] 2) The material is fed into an injection molding machine for injection molding to obtain a blank;

[0248] 3) Degreasing was carried out at 120℃ with a nitric acid flow rate of 1.5 L / min and a nitrogen flow rate of 100 L / min for 10 h, and the degreasing rate was 7.81 wt%.

[0249] 4) Sintering is performed to obtain an intermediate blank. The sintering includes:

[0250] (i) Using nitrogen as a protective gas at a pressure < 5 kPa, the temperature is increased to 380°C in 90 min, held for 30 min, then increased to 480°C in 60 min, held for 120 min, followed by increasing to 600°C in 90 min, and held for 120 min, to proceed with...

[0251] First sintering;

[0252] (ii) The temperature is increased to 900°C in 120 min and held for 60 min to carry out the second sintering; and

[0253] (iii) Increase the temperature to 1250℃ in 60 minutes, hold for 120 minutes, then increase the temperature to 1370℃ in 60 minutes and hold for 240 minutes.

[0254] To carry out the third sintering.

[0255] The D50 and tap density of the metal powders in Examples 1 to 3 are shown in Table 3 below.

[0256] The metallographic pictures of Examples 1 to 3 were measured by SEM, the metallographic picture of the intermediate blank of Example 1 is shown in Figure 1, the metallographic picture of the intermediate blank of Example 2 is shown in Figure 2, and the metallographic picture of the intermediate blank of Example 3 is shown in Figure 3. Figure 12 Figure 13 Figure 14

[0257] Table 3 Parameter information of Examples 1 to 3

[0258]

[0259]

[0260] From the test results of Examples 1 to 3, it can be seen that the larger the D50 particle size of the metal powder, the greater the density of the intermediate blank prepared, the smaller the carbon content of the intermediate blank, and the smaller the metallographic size (grain size) of the intermediate blank.

[0261] Example 4

[0262] The ultra-high strength steel of the present example is prepared by the following steps:

[0263] 1) Provide an alloy blank, melt at a high temperature of 1600°C in a vacuum environment, and prepare a metal powder by water vapor integrated atomization, and the element composition of the prepared metal powder is shown in Table 4.

[0264] Table 4 Composition of each element in the metal powder and parameters of the metal powder

[0265]

[0266] 2) Binder preparation: Put 92wt% of polyformaldehyde, 2.5wt% of antioxidant, 4.5wt% of polyethylene, and 1wt% of vinyl acetate polymer into a kneader, mix at a temperature of 168°C for 120 minutes;

[0267] 3) Mix the binder and the metal powder in a volume ratio of 45:55 in a Banbury mixer at 160°C for 120 minutes to obtain a feedstock, and control the melt index of the feedstock at 1300;

[0268] 4) Inject the feedstock in an injection molding machine to obtain a blank, the injection temperature is 200°C, the injection pressure is 120MPa, the temperature of the mold wall is 120°C, and the density of the blank is 5.42g / cm 3 ;

[0269] 5) Degreasing: Put the blank in a nitric acid and nitrogen atmosphere, heat to 120°C, the flow rate of nitric acid is 1.5L / min, the flow rate of nitrogen is 100L / min, and the degreasing rate is 7.81wt% after degreasing for 10h; ​​​

[0270] 6) sintering to obtain an intermediate blank. The sintering comprises:

[0271] (i) first sintering by using nitrogen as protective gas, at a pressure < 5 KPa, heating up to 380°C in 90 min, holding for 30 min, then heating up to 480°C in 60 min, holding for 120 min, and then heating up to 600°C in 90 min, holding for 120 min;

[0272] (ii) second sintering by using nitrogen as protective gas, at a pressure < 5 KPa, heating up to 900°C in 120 min, holding for 60 min at a pressure of 15 KPa; and

[0273] (iii) third sintering by using nitrogen as protective gas, at a pressure of 15 KPa, heating up to 1250°C in 60 min, holding for 120 min, and then heating up to 1360°C in 60 min, holding for 240 min; and

[0274] (iv) slow cooling to 1000°C, and then rapid cooling to 60°C by using nitrogen;

[0275] After sintering, the intermediate blank obtained has a rod density > 8.04 g / cm 3 , a metallographic size < 250 μm, a carbon content of 0.012 wt%, an oxygen content of 0.034 wt%, and a metallographic image as shown in Figure 15 ;

[0276] 7) solution treatment: placing the intermediate blank in a vacuum heat treatment furnace, heating up to 200°C in 30 min at a pressure < 0.1 KPa, holding for 30 min, then heating up to 600°C in 30 min, holding for 20 min, and then heating up to 960°C in 30 min, holding for 60 min, and then cooling to room temperature by using liquid nitrogen;

[0277] 8) cryogenic treatment: cooling the intermediate blank after solution treatment to -196°C by using liquid nitrogen, holding for 1 h;

[0278] 9) aging treatment: heating up to 200°C in 30 min at a pressure < 0.1 KPa, holding for 30 min, then heating up to 500°C in 30 min at a pressure < 0.1 KPa, holding for 240 min, and then cooling for 30 min by using nitrogen at a pressure < 0.1 KPa.

[0279] The properties of the ultra-high strength steel prepared in Example 4 are shown in Table 5, in which three measurements were taken and averaged.

[0280] Table 5 Properties of the ultra-high strength steel of Example 4

[0281] Sample Tensile strength (Mpa) Yield strength (Mpa) Modulus (Gpa) Elongation (%) Hardness (HV) Sample 1 Sample 2 2347.8 2202.7 187.47 4.12 643 Sample 3 2332 2185.06 188.33 4.24 637 Average 2321.1 2177.68 184.34 4.2 648 Figure 16 2333.6 2188.5 186.7 4.19 642.7

[0282] From the test results of Table 5, it can be seen that the ultrahigh-strength steel prepared by the embodiment has a higher tensile strength of 2333.6 MPa, a yield strength of 2188.5 MPa, a modulus of 186.7 GPa, an elongation of 4.19%, and a hardness of 642.7 HV.

[0283] The ultrahigh-strength steel prepared in the embodiment is subjected to phosphating of the manganese system, and is subjected to corrosion protection and blackening treatment, so that the product is directly made black, and the neutral salt spray can reach 48 h.

[0284] Example 5

[0285] The ultrahigh-strength steel of the embodiment is prepared by the following steps:

[0286] 1) An alloy blank is provided, and is melted at a high temperature of 1650 °C in a vacuum environment, and is made into a metal powder by a water-vapor integrated atomization method. The element composition of the prepared metal powder is shown in Table 6.

[0287] Table 6 Composition of each element in the metal powder and parameters of the metal powder

[0288]

[0289] 2) Binder preparation: polyformaldehyde 92 wt%, antioxidant 2.5 wt%, polyethylene 4.5 wt%, and vinyl acetate polymer 1 wt% are placed in a kneader, and are mixed at a temperature of 168 °C for 120 minutes;

[0290] 3) The volume ratio of the binder to the metal powder is 40:60, and is mixed in a banbury mixer at 160 °C for 120 min to obtain a feedstock. The melt index of the feedstock is controlled at 1500;

[0291] 4) The feedstock is injected into an injection molding machine to obtain a blank. The injection temperature is 200 °C, the injection pressure is 180 MPa, the die wall surface temperature is 110 °C, and the density of the blank is 5.47 g / cm 3 ;

[0292] 5) Degreasing: the blank is placed in a nitric acid and nitrogen atmosphere, heated to 120 °C, the nitric acid flow is 1.5 L / min, the nitrogen flow is 100 L / min, and the degreasing is performed for 10 h. The degreasing rate is 7.81 wt%;

[0293] 6) Sintering is performed to obtain an intermediate blank. The sintering includes:

[0294] (i) first sintering: temperature rising to 380°C in 90 min under nitrogen atmosphere with pressure <5 KPa, holding for 30 min, then rising to 480°C in 60 min, holding for 120 min, and then rising to 600°C in 90 min, holding for 120 min;

[0295] (ii) second sintering: temperature rising to 920°C in 120 min under nitrogen atmosphere with pressure <5 KPa, holding for 60 min under pressure 15 KPa; and

[0296] (iii) third sintering: temperature rising to 1200°C in 60 min under nitrogen atmosphere with pressure 15 KPa, holding for 120 min, and then rising to 1370°C in 60 min, holding for 240 min; and

[0297] (iv) slow cooling to 1000°C, and then rapid cooling to room temperature by liquid nitrogen;

[0298] After sintering, the intermediate blank has a tensile strength >8.05 g / cm 3 , a metallographic size <230 μm, a carbon content of 0.03 wt%, an oxygen content of 0.021 wt%, and a metallographic image as shown in Sample ;

[0299] 7) solution treatment: the intermediate blank is placed in a vacuum heat treatment furnace, and temperature rising to 200°C in 30 min under pressure <0.1 KPa, holding for 30 min, then rising to 600°C in 30 min, holding for 20 min, and then rising to 940°C in 30 min, holding for 60 min, and then cooling to room temperature by liquid nitrogen;

[0300] 8) cryogenic treatment: the intermediate blank after solution treatment is cooled to -196°C by liquid nitrogen, holding for 1 h;

[0301] 9) aging treatment: temperature rising to 200°C in 30 min under pressure <0.1 KPa, holding for 30 min, and then rising to 480°C in 30 min under pressure <0.1 KPa, holding for 240 min, and then cooling for 30 min by nitrogen.

[0302] The properties of the ultra-high strength steel prepared in Example 5 are shown in Table 7, in which the average of three measurements is taken.

[0303] Table 7 Properties of the ultra-high strength steel of Example 5

[0304] Tensile strength (Mpa) Yield strength (Mpa) Modulus (Gpa) Elongation (%) Hardness (HV) Sample 1 Sample 2 Sample 3 2226 2096.81 182.02 4.8 617 Average 2230.9 2099.24 185.58 4.76 623 Figure 17 2235.3 2113.72 181.52 4.8 627 Figure 17 2230.7 2103.3 183.0 4.79 622.3

[0305] The ultrahigh-strength steel prepared in this example is subjected to nickel-phosphorus alloy chemical plating (3-5 μm, for example 4 μm), and then subjected to color treatment by physical vapor deposition (PVD). The neutral salt spray test can reach 24 h, and the surface hardness after PVD can reach >800 HV.

[0306] Examples 6-13 and Comparative Examples 1-6

[0307] The ultrahigh-strength steel of each example and comparative example is prepared by the following steps:

[0308] 1) Provide an alloy blank, melt at a high temperature of 1650°C in a vacuum environment, and prepare a metal powder by water vapor integrated atomization. The composition of each element in the metal powder of each example and comparative example is shown in Table 8 below, and the parameters of the metal powder are shown in Table 9 below.

[0309] Table 8 Composition of each element in the metal powder of Examples 6-13 and Comparative Examples 1-6

[0310]

[0311] Table 9 Parameters of the metal powder of Examples 6-13 and Comparative Examples 1-6

[0312]

[0313] 2) Binder preparation: polyformaldehyde 92 wt%, antioxidant 2.5 wt%, polyethylene 4.5 wt%, and vinyl acetate 1 wt% are placed in a kneader and mixed at a temperature of 168°C for 120 minutes;

[0314] 3) The volume ratio of the binder to the metal powder is 40:60, and the mixture is mixed in a Banbury mixer at 160°C for 120 min to obtain a feedstock;

[0315] 4) The feedstock is injected into an injection molding machine to obtain a blank, with an injection temperature of 200°C, an injection pressure of 180 MPa, and a mold wall surface temperature of 110°C;

[0316] 5) Debinding: the blank is placed in a nitric acid and nitrogen atmosphere, heated to 120°C, with a nitric acid flow of 1.5 L / min and a nitrogen flow of 100 L / min, and debound for 10 h, with a debinding rate of greater than 7.7 wt%;

[0317] 6) Sintering is performed to obtain an intermediate blank. The sintering includes:

[0318] (i) first sintering by raising temperature to 380°C for 90 min, maintaining for 30 min, then raising temperature to 480°C for 60 min, maintaining for 120 min, and then raising temperature to 600°C for 90 min, maintaining for 120 min, under nitrogen atmosphere with pressure < 5 KPa;

[0319] (ii) second sintering by raising temperature to 900°C for 120 min, maintaining for 60 min under nitrogen atmosphere with pressure < 5 KPa, and then raising temperature to 15 KPa;

[0320] (iii) third sintering by raising temperature to 1250°C for 60 min, maintaining for 120 min, and then raising temperature to 1360°C for 60 min, maintaining for 240 min, under nitrogen atmosphere with pressure 15 KPa; and

[0321] (iv) slowly lowering temperature to 1000°C, and then rapidly cooling to room temperature using liquid nitrogen;

[0322] 7) solution treatment by raising temperature to 200°C for 30 min, maintaining for 30 min, and then raising temperature to 600°C for 30 min, maintaining for 20 min, and then raising temperature to 980°C for 30 min, maintaining for 60 min, under vacuum with pressure < 0.1 KPa, and then cooling to room temperature using liquid nitrogen;

[0323] 8) cryogenic treatment by lowering temperature to -196°C for 30 min using liquid nitrogen;

[0324] 9) aging treatment by raising temperature to 200°C for 30 min, maintaining for 30 min, and then raising temperature to 500°C for 30 min, maintaining for 240 min, under vacuum with pressure < 0.1 KPa, and then cooling for 30 min using nitrogen.

[0325] The elemental compositions of the ultra-high strength steels produced in Examples 6 to 13 and Comparative Examples 1 to 6 are shown in Table 10. The performance parameters of the ultra-high strength steels produced in Examples 6 to 13 and Comparative Examples 1 to 6 are shown in Table 11.

[0326] Table 10 Elemental compositions of the ultra-high strength steels of Examples 6 to 13 and Comparative Examples 1 to 6

[0327]

[0328] Table 11 Performance parameters of the ultra-high strength steels of Examples 6 to 13 and Comparative Examples 1 to 6

[0329]

[0330]

[0331] From the test results of Table 11, it can be seen that the tensile strength of the ultrahigh-strength steel prepared by each embodiment of the present application is greater than 1900 MPa, the yield strength is greater than 1800 MPa, and the elongation at break is high.

[0332] In Example 6, the mass fraction of vanadium is low, so the promoting effect of vanadium on decarburization is weakened, the content of carbon in the prepared ultrahigh-strength steel is increased, thereby increasing the brittleness of the ultrahigh-strength steel, and the tensile strength, yield strength and elongation of the ultrahigh-strength steel are slightly lower than those of other embodiments. In addition, the grain size after sintering is too large, thereby further reducing the plasticity of the prepared ultrahigh-strength steel.

[0333] In Example 7, the mass fraction of vanadium is high, so vanadium can promote decarburization, which is beneficial to improve the tensile strength, yield strength and elongation of the ultrahigh-strength steel. In addition, the mass fraction of nickel in Example 7 is also high, so the tensile strength and yield strength of the obtained ultrahigh-strength steel are slightly reduced, and the elongation is slightly increased. In summary, the comprehensive effect of each element makes the tensile strength, yield strength and elongation of the ultrahigh-strength steel all high.

[0334] In Example 8, the content of oxygen is too high, so the tensile strength and yield strength of the finally prepared ultrahigh-strength steel are slightly reduced, the plasticity is improved, and thereby the elongation is improved.

[0335] In Example 9, the decarburization is not sufficient, so the content of carbon in the prepared ultrahigh-strength steel is too high. Although this makes the ultrahigh-strength steel still have high tensile strength and yield strength, the brittleness is greatly increased, and the elongation is greatly reduced.

[0336] In Example 10, the content of chromium is too low, which reduces the strengthening effect of chromium, thereby reducing the tensile strength and yield strength of the ultrahigh-strength steel. However, the ultrahigh-strength steel still retains good plasticity and has high elongation.

[0337] In Example 11, the content of chromium is too high, which can increase the tensile strength and yield strength of the ultrahigh-strength steel, but reduces the elongation of the ultrahigh-strength steel.

[0338] In Example 12, although the content of carbon is slightly increased, the tensile strength, yield strength and elongation of the ultrahigh-strength steel are slightly reduced, but still remain at a high level.

[0339] In Example 13, the ratio of each element of the ultrahigh-strength steel is reasonable, and the interaction between each element makes the ultrahigh-strength steel have high tensile strength, yield strength and elongation.

[0340] In the comparative example 1, the mass fraction of nickel is too low, so it is difficult to form iron-nickel-molybdenum phase, which reduces the tensile strength and yield strength of the ultra-high strength steel.

[0341] In the comparative example 2, the mass fraction of nickel is too high, which is easy to form carbide impurities, so the tensile strength and yield strength of the ultra-high strength steel are also reduced.

[0342] In the comparative example 3, the mass fraction of cobalt is too low, which has limited strengthening effect on the ultra-high strength steel, and the formed strengthening phase is less, which reduces the improvement of the tensile strength and yield strength of the ultra-high strength steel, but makes the ultra-high strength steel have a higher elongation.

[0343] In the comparative example 4, the mass fraction of cobalt is too high, which can improve the tensile strength and yield strength of the ultra-high strength steel, but reduces the elongation of the ultra-high strength steel.

[0344] In the comparative example 5, the content of molybdenum element is too high, which is not conducive to decarburization, so the content of carbon in the ultra-high strength steel is too high, which reduces the plasticity and elongation of the ultra-high strength steel. However, the ultra-high strength steel has a higher tensile strength and yield strength.

[0345] In the comparative example 6, the content of molybdenum element is too low, which has limited strengthening effect on the ultra-high strength steel, and the tensile strength and yield strength are reduced, but the elongation is still high.

[0346] Please refer to Figure 18 , the electronic device structure 200 of the present application also provides an ultra-high strength steel, or the electronic device structure 200 of the present application is prepared by the preparation method of the ultra-high strength steel of the present application.

[0347] Optionally, the electronic device structure 200 can be, but is not limited to, a rotating shaft (such as a rotating shaft of a foldable device), a shell, a middle frame, a key, a hinge, a gear, and the like. In the present application Figure 19 , the electronic device structure 200 is taken as an example of a rotating shaft in the schematic diagram, which should not be understood as a limitation of the electronic device structure of the present application.

[0348] Optionally, the electronic device can be, but is not limited to, a mobile phone, a tablet computer, a notebook computer, a desktop computer, a smart bracelet, a smart watch, an e-book reader, a game console, and the like.

[0349] Please refer to Figure 20 , in some embodiments, the preparation method of the electronic device structure 200 of the present application includes:

[0350] S201 provides metal powder and binder, and performs injection molding to obtain a blank;

[0351] S202, the blank is degreased and sintered to obtain an intermediate blank; and

[0352] S203, the intermediate blank is heat-treated to obtain the structural component 200 of the electronic device. The structural component 200 of the electronic device includes iron, nickel, cobalt, molybdenum and vanadium. In the structural component 200 of the electronic device: the mass fraction of iron is greater than or equal to 50 wt%, the mass fraction of nickel is 16 wt% to 20 wt%, and the mass fraction of cobalt is 15.1 wt% to 19 wt%. The mass fraction of nickel is greater than the mass fraction of cobalt, the mass fraction of cobalt is greater than the mass fraction of molybdenum, and the mass fraction of molybdenum is greater than the mass fraction of vanadium.

[0353] For detailed descriptions of S201-S203, please refer to the descriptions of the corresponding parts (e.g., S101 to S103) in the above embodiments, which will not be repeated here. For detailed descriptions of the composition of the structural component 200 of the electronic device, please refer to the description of the corresponding part of ultra-high strength steel, which will not be repeated here.

[0354] Please see Figure 19 and ​ This application embodiment also provides an electronic device 300, which includes the structural component 200 of the electronic device described in this application embodiment, wherein the structural component 200 of the electronic device serves as the force-bearing component of the electronic device 300.

[0355] The electronic device 300 in this application embodiment can be, but is not limited to, a mobile phone, a foldable phone, a tablet computer, a foldable tablet computer, a laptop computer, a desktop computer, a smart bracelet, a smartwatch, smart glasses, an e-reader, a game console, and other portable electronic devices 300. The electronic device 300 described in this embodiment is merely one form of the electronic device 300 used in the structural component 200 of the electronic device. ​ The accompanying drawings are for illustrative purposes only. The electronic device 300 is illustrated using a foldable electronic device as an example, and the structural component 200 of the electronic device is illustrated using the hinge of the foldable electronic device as an example. They should not be construed as limiting the electronic device 300 provided in this application, nor should they be construed as limiting the structural component 200 of the electronic device provided in the various embodiments of this application.

[0356] For a detailed description of the structural component 200 of the electronic device, please refer to the description of the corresponding part of the above embodiment, which will not be repeated here.

[0357] The phrase "in one embodiment", "in an embodiment", "in some embodiments" or "in other embodiments" as used herein does not necessarily refer to the same embodiment, although it may. In other words, different embodiments can have different features. Similarly, the use of "in one embodiment" or "in an embodiment" to highlight or emphasize certain features is not meant to necessarily exclude or minimize other features of the same, different or additional embodiments, or to restrict the scope of the application to particular features. Rather, the use of "in one embodiment" or "in an embodiment" is generally used to provide an example of the subject matter. In other words, different embodiments can have different features, and the use of "in one embodiment" or "in an embodiment" to highlight or emphasize certain features is not meant to necessarily exclude or minimize other features of the same, different or additional embodiments, or to restrict the scope of the application to particular features.

[0358] Finally, it should be noted that the above-mentioned embodiments are merely used to illustrate the technical solutions of the present application, but not to limit the present application. Although the present application is described in detail with reference to the above preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the present application.

Claims

1. An ultra-high strength steel, characterized in that, The super-high-strength steel comprises iron, nickel, cobalt, molybdenum and vanadium, wherein the mass fraction of the iron is greater than or equal to 50 wt%, the mass fraction of the nickel is 16 wt% to 20 wt%, and the mass fraction of the cobalt is 15.1 wt% to 19 wt%; the mass fraction of the nickel is greater than the mass fraction of the cobalt, the mass fraction of the cobalt is greater than the mass fraction of the molybdenum, and the mass fraction of the molybdenum is greater than the mass fraction of the vanadium; the mass fraction of the molybdenum in the super-high-strength steel is 5.5 wt% to 8.5 wt%; the mass fraction of the vanadium in the super-high-strength steel is 0.2 wt% to 0.8 wt%; the super-high-strength steel further comprises chromium, and the mass fraction of the chromium is 0.1 wt% to 1 wt%; the super-high-strength steel further comprises impurity elements, and the mass fraction of the impurity elements is less than or equal to 0.5 wt%; the impurity elements comprise carbon, oxygen, manganese and silicon, wherein the mass fraction of the carbon is less than or equal to 0.025 wt%, the mass fraction of the oxygen is 0.02 wt% to 0.5 wt%, the mass fraction of the manganese is less than or equal to 0.1 wt%, and the mass fraction of the silicon is less than or equal to 0.5 wt%; and the sum of the mass fractions of the iron, the nickel, the cobalt, the molybdenum, the vanadium, the chromium and the impurity elements in the super-high-strength steel is 100%. The super-high-strength steel is prepared by the following steps: providing a metal powder and a binder, and performing injection molding to obtain a blank; performing debinding and sintering on the blank to obtain an intermediate blank; and performing heat treatment on the intermediate blank; wherein the sintering comprises first sintering, second sintering and third sintering. The debinding and sintering on the blank to obtain an intermediate blank comprises: performing debinding on the blank to remove part of the binder; performing first sintering on the blank, wherein the temperature T1 of the first sintering is 370℃≤T1≤610℃; performing second sintering on the blank, wherein the temperature T2 of the second sintering is 610℃<T2≤920℃; and performing third sintering on the blank, wherein the temperature T3 of the third sintering is 920℃<T3≤1380℃, to obtain an intermediate blank.

2. The ultra-high strength steel according to claim 1, characterized in that, The raw material of the ultra-high strength steel comprises a metal powder, the metal powder comprising at least one metal; the D50 particle size of the metal powder ranges from 7 μm to 10 μm; the D10 particle size of the metal powder ranges from 5 μm; the D90 particle size of the metal powder ranges from 17 μm to 24 μm; the tap density of the metal powder is greater than or equal to 4.4 g / cm 3 .

3. The ultra-high strength steel of claim 1, wherein, The mass fraction of the nickel in the super-high-strength steel is 17 wt% to 18 wt%.

4. The ultra-high strength steel of claim 1, wherein, The mass fraction of the cobalt in the super-high-strength steel is 15.1 wt% to 16 wt%.

5. The ultra-high strength steel of claim 1, wherein, The mass fraction of the molybdenum in the super-high-strength steel is 6.1 wt% to 7.0 wt%.

6. The ultra-high strength steel of claim 1, wherein, The mass fraction of the vanadium in the super-high-strength steel is 0.4 wt% to 0.6 wt%.

7. The ultra-high strength steel of claim 1, wherein, The mass fraction of the chromium is 0.1 wt% to 0.5 wt%.

8. The ultra-high strength steel according to any one of claims 1 to 7, characterized in that, The impurity elements further comprise sulfur, and the mass fraction of the sulfur is less than or equal to 0.02 wt%.

9. The ultra-high strength steel according to any one of claims 1-7, characterized in that, The ratio of the mass fraction of the molybdenum to the mass fraction of the cobalt ranges from 0.3≤Mo / Co≤0.5; and / or, the ratio of the mass fraction of the vanadium to the mass fraction of the cobalt ranges from 0.02≤V / Co≤0.

04.

10. A method of producing an ultra-high strength steel, characterized by, comprises: The metal powder and the binder are provided and injection molding is performed to obtain a green part; The green part is debound and sintered to obtain an intermediate state green part; and The intermediate state green part is heat treated to obtain the ultra-high strength steel; The sintering includes first sintering, second sintering and third sintering; The debinding and sintering of the green part to obtain the intermediate state green part includes: The green part is debound to remove part of the binder; The green part is first sintered, and the temperature T1 of the first sintering is: 370℃≤T1≤610℃; The green part is second sintered, and the temperature T2 of the second sintering is: 610℃<T2≤920℃, and The green part is third sintered, and the temperature T3 of the third sintering is: 920℃<T3≤1380℃, to obtain the intermediate state green part; The ultra-high strength steel includes iron, nickel, cobalt, molybdenum and vanadium, and the mass fraction of the iron in the ultra-high strength steel is greater than or equal to 50wt%, the mass fraction of the nickel is: 16wt% to 20wt%, and the mass fraction of the cobalt is: 15.1wt% to 19wt%; the mass fraction of the nickel is greater than the mass fraction of the cobalt; the mass fraction of the cobalt is greater than the mass fraction of the molybdenum, and the mass fraction of the molybdenum is greater than the mass fraction of the vanadium; the mass fraction of the molybdenum in the ultra-high strength steel is: 5.5wt% to 8.5wt%; the mass fraction of the vanadium in the ultra-high strength steel is: 0.2wt% to 0.8wt%; the ultra-high strength steel further includes chromium, and the mass fraction of the chromium is: 0.1wt% to 1wt%; the ultra-high strength steel further includes impurity elements, and the mass fraction of the impurity elements is less than or equal to 0.5wt%; the impurity elements include carbon, oxygen, manganese and silicon, and the mass fraction of the carbon in the ultra-high strength steel is less than or equal to 0.025wt%; the mass fraction of the oxygen is 0.02wt% to 0.5wt%; the mass fraction of the manganese is less than or equal to 0.1wt%; and the mass fraction of the silicon is less than or equal to 0.5wt%; and the sum of the mass fractions of the iron, nickel, cobalt, molybdenum, vanadium, chromium and impurity elements in the ultra-high strength steel is 100%.

11. The preparation method of the ultra-high strength steel according to claim 10, wherein wherein The grain size d of the intermediate state green part is ≤250μm, and the mass fraction of carbon in the intermediate state green part is ≤0.025wt%; and the mass fraction of oxygen in the intermediate state green part is ≤0.5wt%.

12. The method of producing ultra-high strength steel according to claim 11, characterized by, The first sintering includes first sub-sintering, second sub-sintering and third sub-sintering, and the first sintering of the green part includes: The temperature T11 is raised to 370℃≤T11≤390℃ at a first temperature rising rate V11 and is kept for a certain time to perform the first sub-sintering; The temperature T12 is raised to 470℃≤T12≤490℃ at a second temperature rising rate V12 and is kept for a certain time to perform the second sub-sintering, wherein V11>V12, and V12≤2℃ / min; and The temperature T13 is raised to 920℃<T13≤1380℃ at a third temperature rising rate V13 and is kept for a certain time to perform the third sub-sintering, wherein V12>V13, and V13≤2℃ / min. heating to a third temperature T13 of 590℃≤T12≤610℃ at a third heating rate V13 and holding, to perform a third sub-sintering, wherein V11>V13, V13≤2℃ / min.

13. The method of producing ultra-high strength steel according to claim 12, characterized in that, The second sintering of the blank comprises: heating to a fourth temperature T21 of 880℃≤T21≤920℃ at a fourth heating rate V2 and holding, to perform the second sintering.

14. The method of producing ultra-high strength steel according to claim 13, characterized by, The third sintering comprises a first sub-stage and a second sub-stage; the third sintering of the blank comprises: heating to a fifth temperature T31 of 1200℃≤T31≤1300℃ at a fifth heating rate V31 and holding, to perform the first sub-stage sintering, wherein V31>V2, V31≥5℃ / min; and heating to a sixth temperature T32 of 1340℃≤T32≤1380℃ at a sixth heating rate V32 and holding, to perform the second sub-stage sintering, wherein V32V31, V32≤2.3℃ / min.

15. The method of producing ultra-high strength steel according to claim 10, wherein The heat treatment of the intermediate blank to obtain the ultra-high strength steel comprises: solution treatment of the intermediate blank to make the Vickers hardness of the intermediate blank 250HV to 350HV.

16. The method of producing ultra-high strength steel according to claim 15, characterized in that, The solution treatment of the intermediate blank comprises: first-stage solution treatment at a temperature of 180℃ to 220℃; second-stage solution treatment at a temperature of 580℃ to 620℃; and third-stage solution treatment at a temperature of 920℃ to 1040℃.

17. The method of producing ultra-high strength steel according to claim 15, characterized in that, The heat treatment of the intermediate blank to obtain the ultra-high strength steel further comprises: deep cryogenic treatment of the solution-treated intermediate blank, the temperature of the deep cryogenic treatment being -196℃ to -180℃.

18. The method of producing ultra-high strength steel according to claim 17, characterized by, The heat treatment of the intermediate blank to obtain the ultra-high strength steel further comprises: aging treatment of the deep cryogenic-treated intermediate blank to obtain the ultra-high strength steel, wherein the Vickers hardness of the ultra-high strength steel is 580HV to 680HV.

19. The method of producing ultra-high strength steel according to claim 18, characterized in that, The aging treatment of the intermediate blank comprises: first-stage aging treatment at a temperature of 180℃ to 220℃; and second-stage aging treatment at a temperature of 460℃ to 540℃.

20. A structural member for an electronic device, characterized by The structural member of the electronic device comprises the ultra-high strength steel of any one of claims 1-9, or the structural member of the electronic device is prepared by the method of preparing the ultra-high strength steel of any one of claims 10-19.

21. An electronic device, comprising: The structural member of the electronic device of claim 20. The structural member of the electronic device of claim 20.

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