High-manganese non-magnetic steel and method for manufacturing same

Abstract

The application relates to a high-manganese non-magnetic steel and a preparation method thereof. Raw material powder is used, which comprises: taking low-manganese low-carbon pre-alloy powder as a matrix, adding 5-10% of medium-manganese medium-carbon pre-alloy powder and 4-8% of high-manganese high-carbon pre-alloy powder to form an activator, and the sum of the medium-manganese medium-carbon pre-alloy powder and the high-manganese high-carbon pre-alloy powder accounts for 11-16% of the weight of the low-manganese low-carbon pre-alloy powder; the raw material powder is used to obtain the high-manganese non-magnetic steel through a powder metallurgy method. The organic mixing and mutual cooperation of the matrix pre-alloy powder, the medium-manganese medium-carbon pre-alloy powder and the high-manganese high-carbon pre-alloy powder can ensure that the required austenite structure is obtained, the cost is reduced by more than 500 yuan / ton, the density range is 6.5-7.2 g / cm 3 , the tensile strength is above 640 MPa, and the elongation after fracture is above 10.3%.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, specifically relating to a method for preparing low-cost, low-density, high-performance high-manganese non-magnetic steel using pre-alloyed powder compounding technology. Background Technology

[0002] High-manganese non-magnetic steel is a material with a stable austenitic structure at room temperature and a relative magnetic permeability of less than 1. Non-magnetic steel has a wide range of applications, including automatic control systems, precision instruments, telecommunications and motors, and many military fields. With the development of the refrigeration industry, the demand for compressors has increased. The balance weight in compressors plays a crucial role in maintaining the stability of the crankshaft during high-speed rotation. The materials used for balance weights have gradually shifted from high-cost copper-based materials to lower-cost high-manganese steel-based materials, and all materials are required to be non-magnetic or unmagnetized.

[0003] High-manganese non-magnetic steel is currently produced using powder metallurgy technology. This method has the advantages of energy saving, material saving, high product precision and good stability. It can be used for mass production of materials and complex parts that cannot be prepared by traditional casting and machining. In addition, the powder metallurgy process can avoid the formation of a large number of carbides and maintain the original physical properties of non-magnetic steel.

[0004] Manganese (Mn) is an active element with a strong affinity for oxygen. Direct mechanical alloying can lead to evaporation during sintering, resulting in uneven manganese distribution and the formation of numerous manganese oxides, negatively impacting material properties. Traditional methods use high-manganese pre-alloyed powders to address this uneven distribution and evaporation, but this results in poor powder compressibility, making it difficult to obtain high-strength green bodies. Furthermore, some manufacturers use copper or copper phosphides and borides as activators to prepare high-manganese non-magnetic steel materials. Copper increases production costs, while boron can combine with components in the alloy powder to form harmful phases, leading to a decline in the material's mechanical properties. Additionally, the use of such activators results in unstable sintering density at lower sintering temperatures (typically 1120℃~1140℃), leading to poor performance. Higher sintering temperatures result in higher densities, meaning the sintering density of the corresponding finished products cannot be precisely controlled.

[0005] Therefore, traditional non-magnetic steel manufacturing methods struggle to meet the demands for low density and precise control, while also avoiding the introduction of impurities and minimizing the formation of harmful phases in the material, and are costly. There is an urgent need to develop a low-cost, high-precision, low-density powder metallurgy product that can improve sintering density while maintaining control precision, thereby meeting market requirements and driving industry development. Summary of the Invention

[0006] This invention provides a high-manganese non-magnetic steel and its preparation method, solving the problems of high cost, low precision, and excessively high density in current high-manganese non-magnetic steel products. The obtained high-manganese non-magnetic steel is a low-cost, high-performance non-magnetic steel product, reducing costs by more than 500 yuan / ton. It exhibits good material stability and yields low-density high-manganese non-magnetic steel with a density range of 6.5–7.2 g / cm³. 3 (The density of the existing product is 7.2–7.6 g / cm³) 3 It is precisely adjustable, with a tensile strength of over 640 MPa and an elongation after fracture of over 10.3%.

[0007] In a first aspect, the present invention relates to a high-manganese non-magnetic steel, which uses raw material powder comprising: a low-manganese low-carbon pre-alloyed powder as a matrix, 5-10% by weight of low-manganese low-carbon pre-alloyed powder of medium-manganese medium-carbon pre-alloyed powder, and 4-8% by weight of high-manganese high-carbon pre-alloyed powder as an activator, wherein the sum of the medium-manganese medium-carbon pre-alloyed powder and the high-manganese high-carbon pre-alloyed powder activator accounts for 11-16% by weight of low-manganese low-carbon pre-alloyed powder, and the raw material powder is used to obtain the high-manganese non-magnetic steel by powder metallurgy.

[0008] The low-manganese, low-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 5-9%, C 0.2-0.4%, Si 0.3-0.6%, Ni 0.5-1.5%, S≤0.05%, P≤0.1%, O≤0.15%, with the balance being Fe;

[0009] The medium-manganese, medium-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 10-13%, C 0.4-0.6%, Si 0.4-0.6%, S≤0.05%, P≤0.1%, O≤0.15%, with the balance being Fe; the high-manganese, high-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 20-30%, C 1.9-2.9%, Si 0.5-0.9%, S≤0.05%, P≤0.1%, O≤0.15%, with the balance being Fe.

[0010] Preferably, the low-manganese, low-carbon pre-alloyed powder has a particle size of 100–200 μm;

[0011] The particle size of the medium-manganese and medium-carbon pre-alloyed powder is 50–80 μm.

[0012] The high-manganese, high-carbon pre-alloyed powder has a particle size of 30–50 μm.

[0013] Preferably, the low-manganese, low-carbon pre-alloyed powder has a particle size of 130–160 μm;

[0014] The particle size of the medium-manganese and medium-carbon pre-alloyed powder is 60–70 μm.

[0015] The high-manganese, high-carbon pre-alloyed powder has a particle size of 35–45 μm.

[0016] Secondly, the present invention relates to a method for preparing a high-manganese non-magnetic steel, wherein the alloy powder green blank is prepared by pressing the raw material powder at 500-800 MPa to obtain an alloy powder green blank.

[0017] Sintering: The alloy powder green billet is sintered in a high-temperature sintering pusher furnace at 1060 ℃~1160 ℃ for 1~2 h to obtain the high manganese non-magnetic steel.

[0018] Preferably, the green body is pressed into shape at 600-700 MPa.

[0019] Preferably, the sintering is carried out at a temperature of 1100 ℃~1150 ℃ for 1~1.5 h to obtain the high manganese non-magnetic steel.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention provides a low-cost matrix using a low-manganese, low-carbon pre-alloyed powder composition, significantly reducing costs compared to traditional processes that use large amounts of alloying elements such as Cu. The medium-manganese, medium-carbon pre-alloyed powder, acting as a transition activator, has a slightly higher manganese and carbon content than the matrix, locally enhancing austenite stability, increasing material toughness, and reducing interface defects caused by abrupt compositional changes during sintering. The high-manganese, high-carbon pre-alloyed powder activator, through its high carbon content, forms a transient liquid phase, lowering the sintering temperature by 50–100 °C, promoting densification. The high manganese content further enhances austenite stability, ensuring the product's non-magnetic properties. The high-manganese, high-carbon pre-alloyed powder, through its strong activating effect, reduces overall dependence on high-cost alloying elements (such as Mn and Ni). By organically mixing and interacting with the matrix pre-alloyed powder, the medium-manganese, medium-carbon, and high-manganese, high-carbon pre-alloyed powders, and by precisely controlling their addition amounts, the desired austenitic structure and stable non-magnetic properties can be ensured.

[0022] This invention utilizes low-manganese, low-carbon pre-alloyed powder to provide skeletal support for large particles, ensuring green density and formability. Medium-manganese, medium-carbon pre-alloyed powder fills the gaps between large particles, improving green uniformity. High-manganese, high-carbon pre-alloyed powder, with its fine particles, further fills these gaps and accelerates sintering diffusion. The small particle size provides a high specific surface area, promoting rapid carbon diffusion and austenite homogenization, while reducing the amount of high-manganese powder used to control costs. By effectively combining the large-particle matrix of low-manganese, low-carbon pre-alloyed powder with two small-sized activator pre-alloyed powders of different particle sizes, the gaps between particles can be fully filled, increasing the compact density. Furthermore, the effective combination of the large-particle matrix of low-manganese, low-carbon pre-alloyed powder with the two small-sized activator pre-alloyed powders in different proportions helps to obtain a precise sintering relative density, making the sintering density controllable, resulting in better material stability and low-density, high-manganese, non-magnetic steel.

[0023] This invention enables continuous liquid-phase activation sintering at relatively low sintering temperatures, promoting liquid-phase penetration. Utilizing the activation effect of an activator, austenite stability is controlled through carbon diffusion. A tensile strength exceeding 640 MPa can be achieved in a single sintering process. The resulting non-magnetic steel material exhibits good stability, producing low-density, high-manganese non-magnetic steel with a density range of 6.5–7.2 g / cm³. 3 (The density of the existing product is 7.2–7.6 g / cm³) 3 It is also precisely adjustable, with an elongation at break of over 10.3%. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the preparation process of a high-manganese non-magnetic steel disclosed in an embodiment of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0027] Existing traditional non-magnetic steel manufacturing methods struggle to meet the demands for low density and precise control, while also avoiding the introduction of impurities and minimizing the formation of harmful phases in the material, and are at a high cost. There is an urgent need to develop a low-cost, high-precision, low-density powder metallurgy product that improves the accuracy of sintering density control, meets market requirements, and drives industry development.

[0028] To address the aforementioned technical problems, this invention provides a high-manganese non-magnetic steel, which uses raw material powder comprising: a low-manganese low-carbon pre-alloyed powder as a matrix, 5-10% by weight of medium-manganese medium-carbon pre-alloyed powder, and 4-8% by weight of high-manganese high-carbon pre-alloyed powder as an activator. The sum of the medium-manganese medium-carbon pre-alloyed powder and the high-manganese high-carbon pre-alloyed powder activator accounts for 11-16% by weight of the low-manganese low-carbon pre-alloyed powder. The high-manganese non-magnetic steel is obtained by powder metallurgy.

[0029] The low-manganese, low-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 5-9%, C 0.2-0.4%, Si 0.3-0.6%, Ni 0.5-1.5%, S≤0.05%, P≤0.1%, O≤0.15%, with the balance being Fe;

[0030] The medium-manganese and medium-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 10-13%, C 0.4-0.6%, Si 0.4-0.6%, S≤0.05%, P≤0.1%, O≤0.15%, with the balance being Fe;

[0031] The high-manganese, high-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 20-30%, C 1.9-2.9%, Si 0.5-0.9%, S≤0.05%, P≤0.1%, O≤0.15%, with the balance being Fe.

[0032] Carbon is an alloying element that expands the γ-Fe phase region. It is a common alloying element in steel materials and also frequently used in powder metallurgy materials. It enhances the matrix strength through interstitial solid solution and, in conjunction with manganese, expands the austenite region. As carbon content increases, the self-diffusion rate of iron increases, which promotes the formation and growth of interparticle bonding necks, accelerates material densification, and facilitates material shrinkage. Manganese (Mn) expands the austenite phase region and inhibits the formation of ferromagnetic phases (α-Fe), ensuring the steel's non-magnetic properties. Adding 0.5–1.5% Ni to low-manganese, low-carbon pre-alloyed powder compensates for the austenite instability caused by insufficient manganese content. Nickel also has a solid solution strengthening effect, while simultaneously improving the material's strength, hardness, and toughness. Gradient design confines Ni to the low-manganese, low-carbon pre-alloyed powder, avoiding repeated addition in high-manganese powder. Si, dissolved in austenite, provides solid solution strengthening, enhancing the material's tensile strength.

[0033] Low-manganese and low-carbon pre-alloyed powder provides a low-cost matrix. The lower manganese and carbon content can significantly reduce costs while ensuring good pressing and flow properties. When the manganese content of low-manganese and low-carbon pre-alloyed powder is less than 5%, it is difficult to guarantee the austenite stability of the product. At the same time, the low carbon content inhibits the precipitation of grain boundary carbides and ensures the strength of the green blank.

[0034] Medium manganese and medium carbon pre-alloyed powder (Mn 10-13%, C 0.4-0.6%), as a transition activator (5-10%), has a slightly higher manganese and carbon content than the matrix. The addition of medium manganese and medium carbon powder can locally improve the stability of austenite, enhance the toughness of the material, and reduce interface defects caused by abrupt changes in composition during sintering.

[0035] High-manganese, high-carbon pre-alloyed powder (Mn 20-30%, C 1.9-2.9%) is used as an activator (4-8%). The high carbon content forms a transient liquid phase, lowering the sintering temperature by 50-100 °C and promoting densification. The high manganese content further enhances austenite stability, ensuring the product's non-magnetic properties. The high-manganese, high-carbon pre-alloyed powder reduces dependence on high-cost alloying elements (such as Mn and Ni) through its strong activating effect. An activator composed of 5-10% by weight of low-manganese, low-carbon pre-alloyed powder, 4-8% by weight of high-manganese, high-carbon pre-alloyed powder, and organically mixes and interacts with the matrix pre-alloyed powder, ensuring the desired austenitic structure and stable non-magnetic properties.

[0036] The study also found that the sum of manganese medium-carbon pre-alloyed powder and high-manganese high-carbon pre-alloyed powder in the activator accounts for 11-16% of the weight of low-manganese low-carbon pre-alloyed powder. If the total content is too high, it will not only increase the cost, but also lead to a decrease in sintering strength. If the total content is too low, it will lead to insufficient liquid phase formation, affecting the activation effect and failing to guarantee that the steel is non-magnetic.

[0037] In one embodiment, the low-manganese, low-carbon pre-alloyed powder has a particle size of 100–200 μm;

[0038] The particle size of the medium-manganese and medium-carbon pre-alloyed powder is 50–80 μm.

[0039] The high-manganese, high-carbon pre-alloyed powder has a particle size of 30–50 μm.

[0040] In one embodiment, the low-manganese, low-carbon pre-alloyed powder has a particle size of 130–160 μm;

[0041] The particle size of the medium-manganese and medium-carbon pre-alloyed powder is 60-70 μm.

[0042] The high-manganese, high-carbon pre-alloyed powder has a particle size of 35–45 μm.

[0043] Low-manganese, low-carbon pre-alloyed powder provides skeletal support for large particles, ensuring green density and formability. The compact density of powder compacts with a particle size of 100–200 μm can reach 80–85% of the theoretical density, while reducing the risk of demolding cracking.

[0044] Medium-manganese, medium-carbon pre-alloyed powder (60–70 μm) fills the gaps between large particles, improving the uniformity of the green body. This particle size range balances flowability and pressing pressure, preventing fine powder agglomeration that could lead to uneven pressing.

[0045] The fine particles of high-manganese, high-carbon pre-alloyed powder (35–45 μm) further fill the gaps between large particles and accelerate sintering diffusion. The small particle size provides a high specific surface area, promoting rapid carbon diffusion and austenite homogenization, while reducing the amount of high-manganese powder used to control costs.

[0046] By effectively combining a large-particle matrix of low-manganese, low-carbon pre-alloyed powder with two small-sized activator pre-alloyed powders of different particle sizes, the interparticle gaps can be fully filled, facilitating compaction and increasing compact density. Furthermore, the effective combination of the large-particle matrix of low-manganese, low-carbon pre-alloyed powder with the two small-sized activator pre-alloyed powders in different addition ratios helps to obtain precise sintering relative density, making the sintering density controllable, resulting in good material stability and producing low-density, high-manganese, non-magnetic steel with a density range of 6.5–7.2 g / cm³. 3 (The density of the existing product is 7.2–7.6 g / cm³) 3 Furthermore, it is precisely adjustable. When the pre-alloyed powder ratio and particle size selection exceed the selected range, the relative density will gradually decrease, the porosity will increase, the relative density will become uncontrollable, and the performance will be unstable.

[0047] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing high-manganese non-magnetic steel, wherein the alloy powder green blank is prepared by pressing the raw material powder under 500-800 MPa to obtain the alloy powder green blank.

[0048] Sintering: The alloy powder green billet is sintered in a high-temperature sintering pusher furnace at a temperature of 1060 ℃~1160 ℃ for 1~2 h to obtain the high manganese non-magnetic steel.

[0049] In one embodiment, the green body is pressed into shape at 600–700 MPa.

[0050] In one embodiment, the sintering is carried out at a temperature of 1100 ℃ to 1150 ℃ for 1 to 1.5 h to obtain the high manganese non-magnetic steel.

[0051] Powder metallurgy can manufacture complex parts structures that are difficult to achieve using traditional methods. Compared with smelting, powder metallurgy can effectively reduce component segregation and uneven casting structure.

[0052] The pressing pressure is selected as 500-800 MPa. On the one hand, the low-manganese and low-carbon pre-alloyed powder, as the skeleton powder, requires higher pressure to overcome the mechanical interlocking resistance between large particles. On the other hand, the medium-manganese and medium-carbon pre-alloyed powder / high-manganese and high-carbon pre-alloyed powder, as the filler phase, requires moderate pressure to avoid uneven pressing caused by fine powder agglomeration, improve the green body density, enhance the green body strength, and ensure that high density and high material stability can be achieved in one sintering process. However, excessive pressure (above 800 MPa) will increase mold wear.

[0053] The sintering temperature is selected between 1060 ℃ and 1160 ℃. At this relatively low sintering temperature, continuous liquid-phase activation sintering can be achieved, promoting liquid-phase penetration. Utilizing the activation effect of the activator, the stability of austenite is controlled through carbon diffusion. A tensile strength exceeding 640 MPa can be achieved in a single sintering process. The resulting non-magnetic steel material exhibits good stability, and the sintering density is controllable, yielding low-density, high-manganese non-magnetic steel with a density range of 6.5–7.2 g / cm³. 3 The elongation after fracture is above 10.3%.

[0054] Example 1:

[0055] A method for preparing high-manganese non-magnetic steel uses raw material powder comprising: a matrix of low-manganese low-carbon pre-alloyed powder, an activator consisting of 5% by weight of medium-manganese medium-carbon pre-alloyed powder and 6% by weight of high-manganese high-carbon pre-alloyed powder, and the raw material powder is processed by powder metallurgy to obtain the high-manganese non-magnetic steel.

[0056] The low-manganese, low-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 5%, C 0.4%, Si 0.4%, Ni 1.5%, S 0.03%, P 0.08%, O 0.10%, with the balance being Fe;

[0057] The medium-manganese, medium-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 10%, C 0.6%, Si 0.5%, S 0.03%, P 0.08%, O 0.10%, with the balance being Fe;

[0058] The high-manganese, high-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 20%, C 2.9%, Si 0.6%, S 0.03%, P 0.08%, O 0.10%, with the balance being Fe.

[0059] The low-manganese, low-carbon pre-alloy powder has a particle size of 100 μm; the medium-manganese, medium-carbon pre-alloy powder has a particle size of 70 μm; and the high-manganese, high-carbon pre-alloy powder has a particle size of 30 μm.

[0060] Alloy powder green preparation: The raw material powder is pressed into an alloy powder green under 800 MPa to obtain an alloy powder green;

[0061] Sintering: The alloy powder green billet is sintered in a high-temperature sintering pusher furnace at a temperature of 1060 °C for 2 h to obtain the high-manganese non-magnetic steel.

[0062] Example 2:

[0063] A method for preparing high-manganese non-magnetic steel, the raw material powder used includes: a matrix of low-manganese low-carbon pre-alloyed powder, an activator consisting of 8% by weight of medium-manganese medium-carbon pre-alloyed powder and 4% by weight of high-manganese high-carbon pre-alloyed powder, and the raw material powder is used to obtain the high-manganese non-magnetic steel by powder metallurgy.

[0064] The low-manganese, low-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 6%, C 0.3%, Si 0.4%, Ni 0.8%, S 0.02%, P 0.06%, O 0.10%, with the balance being Fe;

[0065] The medium-manganese, medium-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 12%, C 0.5%, Si 0.6%, S 0.02%, P 0.07%, O 0.10%, with the balance being Fe;

[0066] The high-manganese, high-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 21%, C 2.6%, Si 0.8%, S 0.02%, P 0.08%, O 0.10%, with the balance being Fe.

[0067] The low-manganese, low-carbon pre-alloy powder has a particle size of 130 μm; the medium-manganese, medium-carbon pre-alloy powder has a particle size of 60 μm; and the high-manganese, high-carbon pre-alloy powder has a particle size of 35 μm.

[0068] Alloy powder green preparation: The raw material powder is pressed into an alloy powder green under 600 MPa to obtain an alloy powder green;

[0069] Sintering: The alloy powder green billet is sintered in a high-temperature sintering pusher furnace at a temperature of 1150°C for 1.5 h to obtain the high-manganese non-magnetic steel.

[0070] Example 3:

[0071] A method for preparing high-manganese non-magnetic steel, the raw material powder used includes: a matrix of low-manganese low-carbon pre-alloyed powder, an activator consisting of 10% by weight of medium-manganese medium-carbon pre-alloyed powder and 6% by weight of high-manganese high-carbon pre-alloyed powder, and the raw material powder is used to obtain the high-manganese non-magnetic steel by powder metallurgy.

[0072] The low-manganese, low-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 8%, C 0.4%, Si 0.6%, Ni 1.0%, S 0.01%, P 0.08%, O 0.08%, with the balance being Fe;

[0073] The medium-manganese, medium-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 13%, C 0.4%, Si 0.6%, S 0.01%, P 0.08%, O 0.10%, with the balance being Fe;

[0074] The high-manganese, high-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 26%, C 2.8%, Si 0.8%, S 0.01%, P 0.08%, O 0.10%, with the balance being Fe.

[0075] The low-manganese, low-carbon pre-alloy powder has a particle size of 160 μm; the medium-manganese, medium-carbon pre-alloy powder has a particle size of 70 μm; and the high-manganese, high-carbon pre-alloy powder has a particle size of 45 μm.

[0076] Alloy powder green preparation: The raw material powder is pressed into an alloy powder green under 700 MPa to obtain an alloy powder green;

[0077] Sintering: The alloy powder green billet is sintered in a high-temperature sintering pusher furnace at a temperature of 1100℃ for 1.5 h to obtain the high-manganese non-magnetic steel.

[0078] Example 4:

[0079] A method for preparing high-manganese non-magnetic steel uses raw material powder comprising: a matrix of low-manganese low-carbon pre-alloyed powder, an activator consisting of 6% by weight of medium-manganese medium-carbon pre-alloyed powder and 8% by weight of high-manganese high-carbon pre-alloyed powder, and the raw material powder is processed by powder metallurgy to obtain the high-manganese non-magnetic steel.

[0080] The low-manganese, low-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 9%, C 0.2%, Si 0.3%, Ni 0.5%, S 0.03%, P 0.08%, O 0.10%, with the balance being Fe;

[0081] The medium-manganese, medium-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 13%, C 0.4%, Si 0.5%, S 0.03%, P 0.08%, O 0.10%, with the balance being Fe;

[0082] The high-manganese, high-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 30%, C 1.9%, Si 0.6%, S 0.03%, P 0.08%, O 0.10%, with the balance being Fe.

[0083] The low-manganese, low-carbon pre-alloy powder has a particle size of 200 μm; the medium-manganese, medium-carbon pre-alloy powder has a particle size of 70 μm; and the high-manganese, high-carbon pre-alloy powder has a particle size of 40 μm.

[0084] Alloy powder green preparation: The raw material powder is pressed into an alloy powder green under 500 MPa to obtain an alloy powder green;

[0085] Sintering: The alloy powder green billet is sintered in a high-temperature sintering pusher furnace at a temperature of 1160 °C for 1 h to obtain the high-manganese non-magnetic steel.

[0086] Comparative Example 1

[0087] The difference between the preparation method of the high-manganese non-magnetic steel in Comparative Example 1 and Example 2 is only that: the raw material powder includes: an activator composed of low-manganese low-carbon pre-alloyed powder as the matrix, 5% by weight of medium-manganese medium-carbon pre-alloyed powder, and 4% by weight of high-manganese high-carbon pre-alloyed powder, and the raw material powder is obtained by powder metallurgy.

[0088] Comparative Example 2

[0089] The difference between the preparation method of the high-manganese non-magnetic steel in Comparative Example 2 and Example 2 is only that: the raw material powder includes: an activator composed of low-manganese low-carbon pre-alloyed powder as the matrix, 10% by weight of low-manganese low-carbon pre-alloyed powder of medium-manganese medium-carbon pre-alloyed powder, and 8% by weight of high-manganese high-carbon pre-alloyed powder, and the raw material powder is used to obtain the high-manganese non-magnetic steel by powder metallurgy.

[0090] Comparative Example 3

[0091] The difference between the preparation method of the high-manganese non-magnetic steel in Comparative Example 3 and Example 2 is that the low-manganese and low-carbon pre-alloyed powder includes the following components by weight percentage: Mn 4%, C 0.1%, Si 0.3%, Ni 0.8%, S 0.02%, P 0.06%, O 0.10%, with the balance being Fe.

[0092] Comparative Example 4

[0093] The difference between the preparation method of the high-manganese non-magnetic steel in Comparative Example 4 and Example 2 is that the medium-manganese and medium-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 9%, C 0.2%, Si 0.3%, S 0.02%, P 0.07%, O 0.10%, with the balance being Fe;

[0094] The high-manganese, high-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 18%, C 1.6%, Si 0.8%, S 0.02%, P 0.08%, O 0.10%, with the balance being Fe.

[0095] Comparative Example 5

[0096] The only difference between the preparation method of the high-manganese non-magnetic steel in Comparative Example 5 and Example 2 is that the low-manganese low-carbon pre-alloy powder has a particle size of 90 μm; the medium-manganese medium-carbon pre-alloy powder has a particle size of 90 μm; and the high-manganese high-carbon pre-alloy powder has a particle size of 60 μm.

[0097] Comparative Example 6

[0098] The difference between the preparation method of the high-manganese non-magnetic steel in Comparative Example 6 and Example 2 is only in the following: preparation of alloy powder green blank: the raw material powder is pressed into shape at 400MPa to obtain alloy powder green blank.

[0099] Comparative Example 7

[0100] The only difference between the preparation method of the high-manganese non-magnetic steel in Comparative Example 7 and Example 2 is that:

[0101] Sintering: The alloy powder green billet is sintered in a high-temperature sintering pusher furnace at a temperature of 1000℃ for 1.5 hours to obtain the high-manganese non-magnetic steel.

[0102] The high-manganese non-magnetic steel materials prepared in Examples 1-4 and Comparative Examples 1-7 were subjected to performance tests, and the results are shown in Table 1.

[0103] Table 1: Performance data of high-manganese nonmagnetic steel prepared in the examples and comparative examples

[0104] <![CDATA[Sintered density (g / cm 3 )]]> Tensile strength (MPa) Elongation after fracture (%) Example 1 6.5 645 10.3 Example 2 7.2 661 14.2 Example 3 6.8 657 12.5 Example 4 7.0 640 16.8 Comparative Example 1 6.0 445 8.1 Comparative Example 2 6.4 500 9.5 Comparative Example 3 5.8 410 9.2 Comparative Example 4 6.3 432 9.8 Comparative Example 5 5.9 389 7.9 Comparative Example 6 5.5 275 6.5 Comparative Example 7 5.7 300 6.7

[0105] Table 1 shows that the sintering density of the high-manganese non-magnetic steel prepared by this invention is 6.5–7.2 g / cm³. 3 The tensile strength is above 640 MPa, and the elongation after fracture is above 10.3%. The sintered non-magnetic steel material has good stability, and low-density high-manganese non-magnetic steel is obtained with a precise and adjustable density range. By using lower levels of alloying elements such as manganese and Ni, the cost is reduced by more than 500 yuan / ton.

[0106] Comparative Examples 1-4 adjusted the ratio and composition of manganese medium-carbon pre-alloyed powder and high-manganese high-carbon pre-alloyed powder in the activator. Too high an activator content led to a decrease in sintering strength, while too low a content resulted in insufficient liquid phase formation, affecting the activation effect. The sintering density of the obtained high-manganese non-magnetic steel decreased sharply, the tensile strength decreased, and the elongation performance decreased.

[0107] In Comparative Examples 5-6, after adjusting the particle size of the pre-alloyed powder, the low-manganese, low-carbon pre-alloyed powder matrix and the activator pre-alloyed powder could not achieve effective matching, and the precise sintering relative density could not be obtained, which reduced the material stability and consequently led to a decrease in tensile strength and elongation performance.

[0108] In Comparative Examples 7-8, adjusting the pressing pressure of the green blank too low can lead to uneven pressing, reduced green blank density and strength, and adjusting the sintering temperature too low can not ensure the formation of a continuous liquid phase to achieve activated sintering. As a result, the sintering density of the high manganese non-magnetic steel decreases sharply, the tensile strength decreases, and the elongation performance decreases.

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

Claims

1. A high-manganese non-magnetic steel, characterized in that, The raw material powder used includes: low manganese low carbon pre-alloy powder as the matrix, with 5-10% by weight of medium manganese medium carbon pre-alloy powder and 4-8% by weight of high manganese high carbon pre-alloy powder as activator. The sum of medium manganese medium carbon pre-alloy powder and high manganese high carbon pre-alloy powder activator accounts for 11-16% by weight of low manganese low carbon pre-alloy powder. The raw material powder is used to obtain the high manganese non-magnetic steel by powder metallurgy. The low-manganese, low-carbon pre-alloy powder comprises the following components by weight percentage: Mn 5-9%, C 0.2-0.4%, Si 0.3-0.6%, Ni 0.5-1.5%, S≤0.05%, P≤0.1%, O≤0.15%, with the balance being Fe; the medium-manganese, medium-carbon pre-alloy powder comprises the following components by weight percentage: Mn 10-13%, C 0.4-0.6%, Si 0.4-0.6%, S≤0.05%, P≤0.1%, O≤0.15%, with the balance being Fe; the high-manganese, high-carbon pre-alloy powder comprises the following components by weight percentage: Mn 20-30%, C 1.9-2.9%, Si 0.5-0.9%, S≤0.05%, P≤0.1%, O≤0.15%, with the balance being Fe. The low-manganese, low-carbon pre-alloyed powder has a particle size of 100–200 μm; the medium-manganese, medium-carbon pre-alloyed powder has a particle size of 50–80 μm; and the high-manganese, high-carbon pre-alloyed powder has a particle size of 30–50 μm.

2. The high-manganese non-magnetic steel according to claim 1, characterized in that, The low-manganese, low-carbon pre-alloyed powder has a particle size of 130–160 μm. The particle size of the medium-manganese and medium-carbon pre-alloyed powder is 60-70 μm. The high-manganese, high-carbon pre-alloyed powder has a particle size of 35–45 μm.

3. The method for preparing a high-manganese non-magnetic steel according to any one of claims 1 to 2, characterized in that, Preparation of alloy powder green blank: The raw material powder is pressed into shape at 500-800 MPa to obtain alloy powder green blank; Sintering: The alloy powder green billet is sintered in a high-temperature sintering pusher furnace at a temperature of 1060℃~1160℃ for 1~2 hours to obtain the high manganese non-magnetic steel.

4. The method for preparing high-manganese non-magnetic steel according to claim 3, characterized in that, The green body is pressed and formed at 600-700 MPa.

5. The method for preparing high-manganese non-magnetic steel according to claim 3, characterized in that, The sintering is carried out at a temperature of 1100℃~1150℃ for 1~1.5h to obtain the high manganese non-magnetic steel.

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