Low-cost high-strength low-copper high-manganese non-magnetic steel and preparation method thereof

Abstract

The present application relates to a kind of low-cost high-strength low-copper high-manganese non-magnetic steel and its preparation method, adopt raw material powder composition: with high-manganese high-carbon pre-alloy powder as matrix, with 0.5-1% graphite powder, 0.3-0.5% copper powder, 2-2.5% Fe3P powder, 1-2% iron powder as composite activator, again with 1-1.5% SiC powder and Y2O3 powder mixed into the enhancement phase composition of matrix weight;Raw material powder is obtained by powder metallurgy method the high-strength low-copper high-manganese non-magnetic steel described above. Through once sintering, sintering density can be realized in 6.3-7.0 g / cm 3 , tensile strength is above 630 MPa, elongation after break is above 10.1%, excellent mechanical properties, by using lower content Cu element, cost is greatly reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of powder metallurgy, and particularly relates to a low-cost high-strength low-copper high-manganese non-magnetic steel and a preparation method thereof. BACKGROUND

[0002] The high-manganese non-magnetic steel has stable austenite at room temperature, and the relative magnetic permeability is less than 1. The non-magnetic steel is widely used in automatic control systems, precision instruments, telecommunications and motors, and many military fields. With the development of the refrigeration industry, the demand for compressors is increasing, and the balance block plays an important role in maintaining the stable state of the crankshaft during high-speed rotation. The material used for the balance block is gradually changed from high-cost copper-based to low-cost high-manganese steel iron-based, and the material is required to be non-magnetic or not magnetized.

[0003] The high-manganese non-magnetic steel is currently prepared by the powder metallurgy technology. This method has the advantages of energy saving, material saving, high product precision and good stability, and can be used to prepare materials and complex parts that cannot be prepared by traditional casting methods and mechanical processing methods. In addition, the powder metallurgy processing process can avoid the formation of a large amount of carbides, thereby maintaining the original physical properties of the non-magnetic steel.

[0004] The traditional method uses high-manganese pre-alloyed powder to solve the uneven distribution of manganese elements and evaporation, but this leads to poor compressibility of the powder and difficulty in obtaining high-strength green bodies. The existing technology usually uses copper or copper phosphide and boride as an activator to prepare high-manganese non-magnetic steel materials, but copper increases the production cost, and boron combines with the components in the alloy powder to form harmful phases, thereby reducing the mechanical properties of the material. In addition, the use of such activators leads to unstable sintering density and poor performance under low sintering temperature conditions, and in addition, due to the poor compressibility and flowability of the high-manganese pre-alloyed powder, a large pressure is required for the compaction.

[0005] Therefore, the traditional non-magnetic steel manufacturing method still cannot meet the requirements of low cost and high performance. It is urgent to develop a low-cost high-strength high-manganese non-magnetic steel powder metallurgy product to meet market requirements and promote industry development. SUMMARY

[0006] The application provides a low-cost high-strength low-copper high-manganese non-magnetic steel and a preparation method thereof, which solves the problems of high cost, insufficient strength and toughness of the current high-manganese non-magnetic steel. The high-manganese non-magnetic steel is a low-cost low-copper high-performance non-magnetic steel product, and the sintering density is 6.3-7.0 g / cm 3 , the tensile strength is greater than 630 MPa, and the elongation after fracture is greater than 10.1%, so that the mechanical properties are excellent, and the cost is greatly reduced by using a lower content of Cu element.

[0007] In a first aspect, the present application relates to a low-cost high-strength low-copper high-manganese non-magnetic steel, which is composed of raw material powder, wherein the raw material powder is composed of high-manganese high-carbon pre-alloy powder as a base, graphite powder accounting for 0.5-1% of the weight of the base, copper powder accounting for 0.3-0.5% of the weight of the base, Fe3P powder accounting for 2-2.5% of the weight of the base, iron powder accounting for 1-2% of the weight of the base as a composite activator, and SiC powder and Y2O3 powder accounting for 1-1.5% of the weight of the base as a reinforcing phase; and the high-strength low-copper high-manganese non-magnetic steel is obtained by powder metallurgy.

[0008] The high-manganese high-carbon pre-alloy powder comprises the following components by weight percentage: Mn 14-15%, C 0.4-0.7%, Si 0.5-0.8%, Ti 0.5-1.5%, rare earth Ce 0.05-0.15%, S≤0.05%, P≤0.1%, O≤0.15%, and the balance of Fe.

[0009] Preferably, the total amount of the composite activator accounts for 4.3-5% of the weight of the high-manganese high-carbon pre-alloy powder.

[0010] Preferably, the ratio of SiC powder to Y2O3 powder in the reinforcing phase is 2-4:1.

[0011] Preferably, the particle size of the high-manganese high-carbon pre-alloy powder is 60-100 μm.

[0012] The particle size of the graphite powder is less than 20 μm; the particle size of the copper powder is 30-40 μm; the particle size of the Fe3P powder and the iron powder is 20-30 μm; and the particle size of the SiC powder and the Y2O3 powder is 5-15 μm.

[0013] In a second aspect, the present application relates to a preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel, which comprises the following steps:

[0014] Alloy powder green body preparation: the raw material powder is mixed with a lubricant and uniformly mixed in a mixer, and then is pressed and formed at 350-400 MPa to obtain an alloy powder green body.

[0015] Sintering: the alloy powder green body is sintered in a mesh belt sintering furnace in a nitrogen-hydrogen mixed atmosphere at a temperature of 1050-1130 ℃ for 1-2 h to obtain the low-cost high-strength low-copper high-manganese non-magnetic steel.

[0016] Preferably, the green body is pressed and formed at 350-380 MPa.

[0017] Preferably, the lubricant is micro-paraffin powder, and the amount of the lubricant added accounts for 2-2.5% of the mass of the raw material powder.

[0018] Preferably, the lubricant is a combination of micro-paraffin powder and stearic acid with a mass ratio of 1:1, and the lubricant is added in an amount of 2-2.5% of the mass of the raw material powder.

[0019] Preferably, the lubricant is a combination of micro-paraffin powder and stearic acid with a mass ratio of 1:1, and the lubricant is added in an amount of 2.2% of the mass of the raw material powder.

[0020] Preferably, the sintering atmosphere is a mixture of 50% nitrogen and 50% hydrogen.

[0021] Preferably, the sintering is carried out at a temperature of 1080 DEG C for 1.5 h to obtain the low-cost high-strength low-copper high-manganese non-magnetic steel.

[0022] The beneficial effects of the present application are:

[0023] The present application uses high-manganese high-carbon pre-alloy powder as a matrix, and graphite powder, copper powder, Fe3P powder and iron powder are added as activators, and the coordination of multiple activators ensures good sintering and composite activation effect, ensures the non-magnetic property of the steel, and obtains high strength and elongation. Compared with adding copper powder alone as an activator, the amount of copper powder is greatly reduced, and the cost is greatly reduced.

[0024] SiC powder and Y2O3 powder are reinforcing phases, and the gap distribution of the mixed activators enhances the compressibility of the whole powder, which is beneficial to improve the density and mechanical properties of the material.

[0025] The high-manganese high-carbon pre-alloy powder large particle matrix is effectively matched with activator powders of different particle sizes, which can fully fill the gap between particles, facilitate the compaction of the green body, and improve the density of the green body.

[0026] The combination of micro-paraffin powder and stearic acid lubricant shows a synergistic effect in lubrication, further improving the flowability of the powder, and high density can be achieved at a lower green body pressure. Compared with the traditional green body pressure of more than 500 MPa, the alloy powder green body can be formed at a lower pressure of 350-400 MPa, and high density and excellent mechanical properties after sintering can be achieved. Through one sintering, the sintering density is 6.3-7.0 g / cm 3 , the tensile strength is more than 630 MPa, and the elongation after fracture is more than 10.1%. The non-magnetic steel material prepared by sintering has good stability, high strength and excellent mechanical properties, and the use of lower Cu element greatly reduces the cost. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0028] Figure 1 A preparation process flow diagram of a low-cost high-strength low-copper high-manganese non-magnetic steel disclosed in the embodiments of the present application is shown. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be described clearly and completely in combination with the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0030] The existing traditional non-magnetic steel manufacturing method uses copper as the main activator, which has high cost and poor performance. In addition, due to the poor compressibility and low flowability of high-manganese pre-alloy powder, a larger pressure is required for the compact. Therefore, the traditional non-magnetic steel manufacturing method cannot meet the requirements of low cost and high performance. It is urgent to develop a low-cost high-strength high-manganese non-magnetic steel powder metallurgy product to meet the market requirements and promote the development of the industry.

[0031] In view of the above technical problems, the embodiments of the present application provide a low-cost high-strength low-copper high-manganese non-magnetic steel. The raw material powder composition comprises: high-manganese high-carbon pre-alloy powder as the base body, 0.5-1% graphite powder, 0.3-0.5% copper powder, 2-2.5% Fe3P powder, and 1-2% iron powder as the composite activator, and 1-1.5% SiC powder and Y2O3 powder as the reinforcing phase, which are mixed to form the high-strength low-copper high-manganese non-magnetic steel by powder metallurgy method.

[0032] The high-manganese high-carbon pre-alloy powder comprises the following components by weight percentage: Mn 14-15%, C 0.4-0.7%, Si 0.5-0.8%, Ti 0.5-1.5%, rare earth Ce 0.05-0.15%, S≤0.05%, P≤0.1%, O≤0.15%, and the balance of Fe.

[0033] In one embodiment, the total amount of the composite activator accounts for 4.3-5% of the weight of the high-manganese high-carbon pre-alloy powder.

[0034] In one embodiment, the ratio of SiC powder to Y2O3 powder in the reinforcing phase is 2-4:1.

[0035] High manganese high carbon pre-alloy powder is the base, carbon in the pre-alloy powder is an alloying element to expand the γ-Fe phase area, which is a common alloying element in steel materials and a commonly used alloying element in powder metallurgy materials. The carbon content is increased, the iron self-diffusion rate is increased, the bonding neck between the particles is formed and grown, the material densification is accelerated, and the material shrinkage is promoted. The carbon content is preferably 0.4-0.7%.

[0036] Manganese (Mn) can expand the austenite phase area and inhibit the formation of ferromagnetic phase (α-Fe), ensuring that the steel structure is completely austenitic and ensuring that the steel is non-magnetic. The manganese content is preferably 14-15%.

[0037] Silicon (Si) is dissolved in austenite, which can play a solid solution strengthening role to improve the tensile strength of the material. The silicon content is preferably 0.5-0.8%.

[0038] Rare earth Ce can refine the grain and improve the purity of the pre-alloy powder. The addition of Ti also helps to refine the grain and improve the strength and fatigue resistance of the material. In addition, titanium can also improve the high temperature performance of the material, so that it can still maintain good stability at high temperature. The titanium content is preferably 0.5-1.5%, and the rare earth Ce content is preferably 0.05-0.15%.

[0039] Cu has a relatively low melting point (1083℃) and a relatively low microhardness. For the relatively hard pre-alloy powder of iron and manganese, the addition of Cu powder can improve the pressing performance of the pre-alloy powder. In addition, the sintering process will produce a liquid phase, which will enhance the material diffusion between the base particles and accelerate the material densification process, thereby improving the material density. The copper powder is preferably added in an amount of 0.3-0.5%.

[0040] Graphite powder can be used as a reducing agent to reduce the oxygen content in the raw material powder. It can also be used to lubricate and reduce friction during the pressing process. During the sintering process, it can react with iron to form Fe3C, thereby adjusting the overall carbon content of the non-magnetic steel and ensuring high strength of the non-magnetic steel. However, if the amount of graphite added is too high, the non-magnetic steel may exhibit magnetic properties. The graphite powder is preferably added in an amount of 0.5-1%.

[0041] Fe3P powder also has a relatively low melting point. As an activator, the addition of Fe3P powder can help to improve the uniformity of phosphorus in the mixed powder, prevent segregation, and enhance its flowability and bulk density. It can also reduce the sintering temperature and form a Fe-P eutectic liquid phase to accelerate densification. Iron powder is used as a carrier to prevent Fe3P segregation and ensure uniform distribution of phosphorus. The Fe3P powder is preferably added in an amount of 2-2.5% by weight, and the iron powder is preferably added in an amount of 1-2% by weight.

[0042] By combining graphite powder, copper powder, Fe3P powder, and iron powder as activators, a good sintering composite activation effect is ensured through the synergistic effect of multiple activators. This avoids the formation of a network structure at grain boundaries. The combined effect of graphite powder, copper powder, Fe3P powder, and iron powder ensures that the steel is non-magnetic and achieves high tensile strength. Compared to adding copper powder alone as an activator, this significantly reduces the amount of copper powder required, resulting in a substantial cost reduction. Excessive total content of the composite activator increases costs and leads to a decrease in sintering strength, while insufficient total content prevents the formation of a sufficient liquid phase, affecting the activation effect and failing to guarantee the non-magnetic nature of the steel. The preferred total amount of the composite activator is 4.3%–5%.

[0043] SiC powder and Y2O3 powder serve as reinforcing phases. After being mixed with an activator, they are distributed in the interstices of the high-manganese, high-carbon pre-alloyed powder matrix. This interstic distribution of the SiC and Y2O3 reinforcing phases enhances the overall compressibility of the powder, which is beneficial for improving the material's density and mechanical properties. Furthermore, the formation of a liquid phase during sintering promotes the rearrangement and migration of SiC and Y2O3, thereby increasing the material's density and mechanical properties. The reinforcing phase is preferably a mixture of 1–1.5% SiC powder and Y2O3 powder, with the preferred SiC to Y2O3 ratio being 2–4:1.

[0044] In one embodiment, the high-manganese, high-carbon pre-alloyed powder has a particle size of 60–100 μm; the graphite powder has a particle size of less than 20 μm; the copper powder has a particle size of 30–40 μm; the Fe3P powder and iron powder have a particle size of 20–30 μm; and the SiC powder and Y2O3 powder have a particle size of 5–15 μm.

[0045] The effective combination of large-particle matrix of high-manganese, high-carbon pre-alloyed powder and activator powders of different particle sizes can fully fill the gaps between particles and improve the compact density. Small-particle-size powders have poor flowability and are prone to agglomeration during the pressing process, affecting the mold filling effect and leading to increased porosity. Large-particle-size powders have better flowability, which helps to improve the pressing density and uniformity. Small-particle-size activators have higher activity during sintering, which helps to improve the degree of sintering densification, but excessive fineness may lead to excessive shrinkage and even the formation of large pores, reducing material properties. Although coarse-particle powders have lower sintering activity, they help to reduce the difference in sintering shrinkage and improve density. The optimal combination of matrix powder and activator powder particle sizes was determined through research. The particle size of the high-manganese, high-carbon pre-alloyed powder is 60-100 μm, the particle size of the graphite powder is below 20 μm, the particle size of the copper powder is 30-40 μm, and the particle size of the Fe3P powder and iron powder is 20-30 μm. Fine reinforcing phases are more conducive to exerting the reinforcing effect, and the particle size of the SiC powder and Y2O3 powder is 5-15 μm.

[0046] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing low-cost, high-strength, low-copper, high-manganese non-magnetic steel, comprising the following steps:

[0047] Alloy powder green compact preparation: the raw material powder is mixed with a lubricant and mixed uniformly in a mixer, and the alloy powder green compact is obtained by compression molding at 350-400 MPa;

[0048] Sintering: the alloy powder green compact is sintered in a mesh belt sintering furnace, the sintering atmosphere is a mixture of nitrogen and hydrogen, and the low-cost high-strength low-copper high-manganese non-magnetic steel is obtained by sintering at a temperature of 1050-1130 ℃ for 1-2 h.

[0049] In one embodiment, the green compact is compression molded at 350-380 MPa.

[0050] In one embodiment, the lubricant is micro-paraffin powder, and the amount of lubricant added is 2-2.5% of the mass of the raw material powder.

[0051] In one embodiment, the lubricant is a combination of micro-paraffin powder and stearic acid in a mass ratio of 1:1, and the amount of lubricant added is 2-2.5% of the mass of the raw material powder.

[0052] In one embodiment, the lubricant is a combination of micro-paraffin powder and stearic acid in a mass ratio of 1:1, and the amount of lubricant added is 2.2% of the mass of the raw material powder.

[0053] In one embodiment, the sintering atmosphere is a mixture of 50% nitrogen and 50% hydrogen.

[0054] In one embodiment, the sintering is carried out at a temperature of 1080 ℃ for 1.5 h to obtain the low-cost high-strength low-copper high-manganese non-magnetic steel.

[0055] Micro-paraffin powder is a lubricant, and the combination of micro-paraffin powder and stearic acid lubricant shows a synergistic effect in lubrication. Micro-paraffin powder, as an external lubricant, can uniformly coat the surface of the powder to form a lubricating film, reduce friction resistance, and improve flowability. Stearic acid can enhance the stability of the lubricating film. After the combination of the two, the micro-paraffin powder lubricating film is further strengthened by stearic acid, which improves the lubrication effect compared to adding micro-paraffin powder alone. Thus, the powder flowability is further improved, and high density can be achieved at a lower compacting pressure. Preferably, the lubricant is a combination of micro-paraffin powder and stearic acid in a mass ratio of 1:1, and the amount of lubricant added is 2-2.5% of the mass of the raw material powder.

[0056] By selecting a specific lubricant and combining with the selection of the particle size of the raw material powder, the compacting pressure can be effectively reduced. Compared with the traditional compacting pressure of more than 500 MPa, the alloy powder green compact can be obtained by compression molding at a lower pressure of 350-400 MPa, which can achieve high density and excellent mechanical properties after sintering.

[0057] The activator is added to effectively reduce the sintering temperature, the sintering temperature is selected as 1050-1130 ℃, and the sustained liquid phase activation sintering can be formed at the lower sintering temperature condition, the liquid phase penetration is promoted, the austenite stability is regulated through carbon diffusion by the activation of the activator, and the sintering density of 6.3-7.0 g / cm 3 , the tensile strength is above 630 MPa, the elongation after fracture is above 10.1%, the sintered non-magnetic steel material has good stability, high strength and excellent mechanical properties, and the lower Cu element is used as a whole, and the cost is greatly reduced.

[0058] Example 1

[0059] A preparation method of a low-cost high-strength low-copper high-manganese non-magnetic steel, the raw material powder composition comprises: taking high-manganese high-carbon pre-alloy powder as a matrix, adding 0.6% graphite powder, 0.3% copper powder, 2.1% Fe3P powder and 1.3% iron powder as a composite activator, the total amount of the composite activator is 4.3%, and then adding 0.8% SiC powder and 0.2% Y2O3 powder mixed into a reinforcing phase.

[0060] The high-manganese high-carbon pre-alloy powder comprises the following components by weight percentage: Mn 14%, C 0.5%, Si 0.5%, Ti 0.8%, rare earth Ce 0.06%, S 0.03%, P 0.06%, O 0.07%, and the balance is Fe.

[0061] The particle size of the high-manganese high-carbon pre-alloy powder is 65 μm; the particle size of the graphite powder is below 18 μm; the particle size of the copper powder is 32 μm; the particle size of the Fe3P powder is 21 μm, and the particle size of the iron powder is 22 μm; the particle size of the SiC powder and the Y2O3 powder is 5 μm.

[0062] Comprising the following steps:

[0063] Green body preparation of alloy powder: the raw material powder is mixed with a lubricant and uniformly mixed in a mixer, and an alloy powder green body is obtained by pressing at 350 MPa; the lubricant is a combination of micro-paraffin wax powder and stearic acid in a mass ratio of 1:1, and the lubricant is added in an amount of 2% of the mass of the raw material powder.

[0064] Sintering: the alloy powder green body is sintered in a mesh belt sintering furnace, the sintering atmosphere is a mixture of 50% nitrogen and 50% hydrogen, and the sintering temperature is 1050 ℃ for 2 h to obtain the low-cost high-strength low-copper high-manganese non-magnetic steel.

[0065] Example 2

[0066] The application discloses a preparation method of a low-cost high-strength low-copper high-manganese non-magnetic steel.

[0067] The high-manganese high-carbon pre-alloy powder comprises the following components in percentage by weight: Mn 14%, C 0.6%, Si 0.6%, Ti 1%, rare earth Ce 0.05%, S 0.03%, P 0.06%, O 0.07%, and the balance of Fe.

[0068] The high-manganese high-carbon pre-alloy powder has a particle size of 80 μm; the graphite powder has a particle size of 16 μm or below; the copper powder has a particle size of 30 μm; the Fe3P powder has a particle size of 20 μm; the iron powder has a particle size of 21 μm; and the SiC powder and the Y2O3 powder have a particle size of 6 μm.

[0069] The application further discloses a preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel.

[0070] The alloy powder green body is prepared by mixing the raw material powder with a lubricant and uniformly mixing in a mixer, and then being pressed into the alloy powder green body at 360 MPa; the lubricant is a combination of micro-paraffin wax powder and stearic acid at a mass ratio of 1:1, and the lubricant accounts for 2.2% of the mass of the raw material powder.

[0071] The alloy powder green body is sintered in a mesh belt sintering furnace in a sintering atmosphere of 50% nitrogen and 50% hydrogen mixed gas at a temperature of 1080 ℃ for 1.5 hours to obtain the low-cost high-strength low-copper high-manganese non-magnetic steel.

[0072] Example 3:

[0073] The application discloses a preparation method of a low-cost high-strength low-copper high-manganese non-magnetic steel.

[0074] The high-manganese high-carbon pre-alloy powder comprises the following components in percentage by weight: Mn 15%, C 0.4%, Si 0.7%, Ti 1.5%, rare earth Ce 0.1%, S 0.03%, P 0.06%, O 0.07%, and the balance of Fe.

[0075] The high-manganese high-carbon pre-alloy powder has a particle size of 60 μm; the graphite powder has a particle size of 10 μm or less; the copper powder has a particle size of 40 μm; the Fe3P powder has a particle size of 30 μm, and the iron powder has a particle size of 20 μm; and the SiC powder and the Y2O3 powder have a particle size of 8 μm.

[0076] The method comprises the following steps:

[0077] The alloy powder green body is prepared by mixing the raw material powder with a lubricant and uniformly mixing in a mixer, and then being pressed into an alloy powder green body at 380 MPa; the lubricant is a combination of micro-paraffin powder and stearic acid at a mass ratio of 1:1, and the lubricant accounts for 2.4% of the mass of the raw material powder.

[0078] Sintering: the alloy powder green body is sintered in a mesh belt sintering furnace in a sintering atmosphere of a mixture of 50% nitrogen and 50% hydrogen at a temperature of 1130 ℃ for 1 h to obtain the low-cost high-strength low-copper high-manganese non-magnetic steel.

[0079] Example 4:

[0080] A method for preparing a low-cost high-strength low-copper high-manganese non-magnetic steel, which uses raw material powder composed of high-manganese high-carbon pre-alloy powder as a base, 0.5% graphite powder, 0.3% copper powder, 2% Fe3P powder, and 2% iron powder as a composite activator, which accounts for 4.8% of the weight of the base, and 1.2% SiC powder and 0.3% Y2O3 mixed as a reinforcing phase.

[0081] The high-manganese high-carbon pre-alloy powder comprises the following components by weight: Mn 15%, C 0.7%, Si 0.8%, Ti 0.5%, rare earth Ce 0.15%, S 0.03%, P 0.06%, O 0.07%, and the balance being Fe.

[0082] The high-manganese high-carbon pre-alloy powder has a particle size of 100 μm; the graphite powder has a particle size of 11 μm or less; the copper powder has a particle size of 35 μm; the Fe3P powder has a particle size of 26 μm, and the iron powder has a particle size of 30 μm; and the SiC powder and the Y2O3 powder have a particle size of 15 μm.

[0083] The method comprises the following steps:

[0084] The alloy powder green body is prepared by mixing the raw material powder with a lubricant and uniformly mixing in a mixer, and then being pressed into an alloy powder green body at 380 MPa; the lubricant is a combination of micro-paraffin powder and stearic acid at a mass ratio of 1:1, and the lubricant accounts for 2.4% of the mass of the raw material powder.

[0085] Sintering: the green body of the alloy powder is sintered in a mesh belt sintering furnace, a sintering atmosphere of 50% nitrogen and 50% hydrogen mixed gas, sintering at a temperature of 1100 ℃ for 1.2 h to obtain the low-cost high-strength low-copper high-manganese non-magnetic steel.

[0086] Example 5:

[0087] The preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel in Example 5 is different from that of Example 2 only in that the raw material powder composition is as follows: taking high-manganese high-carbon pre-alloy powder as the base, adding 0.8% graphite powder, 0.3% copper powder, 2% Fe3P powder and 1% iron powder as the composite activator, the total amount of the composite activator being 4.1%, and further adding 0.6% SiC powder and 0.6% Y2O3 mixed to form the reinforcing phase.

[0088] Example 6:

[0089] The preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel in Example 6 is different from that of Example 2 only in that the raw material powder composition is as follows: taking high-manganese high-carbon pre-alloy powder as the base, adding 1% graphite powder, 0.4% copper powder, 2.4% Fe3P powder and 1.8% iron powder as the composite activator, the total amount of the composite activator being 5.6%, and further adding 0.5% SiC powder and 0.7% Y2O3 mixed to form the reinforcing phase.

[0090] Example 7:

[0091] The preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel in Example 7 is different from that of Example 2 only in that the lubricant is micro-paraffin wax powder, and the amount of the lubricant added is 2.2% of the mass of the raw material powder.

[0092] Comparative Example 1

[0093] The preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel in Comparative Example 1 is different from that of Example 2 only in that the raw material powder composition is as follows: taking high-manganese high-carbon pre-alloy powder as the base, adding 0.3% graphite powder, 0.3% copper powder, 1% Fe3P powder and 1% iron powder as the composite activator, the total amount of the composite activator being 2.6%, and further adding 0.8% SiC powder and 0.4% Y2O3 mixed to form the reinforcing phase.

[0094] Comparative Example 2

[0095] The preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel in Comparative Example 2 is different from that of Example 2 only in that the raw material powder composition is as follows: taking high-manganese high-carbon pre-alloy powder as the base, adding 2% graphite powder, 0.5% copper powder, 3% Fe3P powder, and 3% iron powder as the composite activator, the total amount of the composite activator being 8.5%, and further adding 0.8% SiC powder and 0.4% Y2O3 mixed to form the reinforcing phase.

[0096] Comparative Example 3

[0097] The preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel in Comparative Example 3 is different from that of Example 2 only in that the reinforcing phase is composed of 0.3% SiC powder and 0.2% Y2O3 mixed.

[0098] Comparative Example 4

[0099] The preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel in Comparative Example 4 is different from that of Example 2 only in that the reinforcing phase is composed of 2% SiC powder and 1% Y2O3 mixed.

[0100] Comparative Example 5

[0101] The preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel in Comparative Example 5 is different from that of Example 2 only in that the high-manganese high-carbon pre-alloy powder comprises the following components by weight percentage: Mn 10%, C 0.3%, Si 0.6%, Ti 1%, rare earth Ce 0.05%, S 0.03%, P 0.06%, O 0.07%, and the balance being Fe.

[0102] Comparative Example 6

[0103] The preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel in Comparative Example 6 is different from that of Example 2 only in that the particle size of the high-manganese high-carbon pre-alloy powder is 80 μm; the particle size of the graphite powder is 30 μm or less; the particle size of the copper powder is 50 μm; the particle size of the Fe3P powder is 40 μm, and the particle size of the iron powder is 40 μm; and the particle size of the SiC powder and Y2O3 powder is 30 μm.

[0104] Comparative Example 7

[0105] The preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel in Comparative Example 7 is different from that of Example 2 only in that the green body of the alloy powder is prepared by mixing the raw material powder with a lubricant and uniformly mixing in a mixer, and then being pressed into a green body of the alloy powder under 300 MPa; and the lubricant is a combination of micro-paraffin wax powder and stearic acid in a mass ratio of 1:1, and the amount of the lubricant added is 2.2% of the mass of the raw material powder.

[0106] Comparative Example 8

[0107] The preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel in Comparative Example 8 differs from that of Example 2 only in that: the alloy powder green body is prepared by mixing the raw material powder with a lubricant and mixing uniformly in a mixer, and the alloy powder green body is formed by pressing at 360 MPa; the lubricant is a combination of micro-paraffin powder and stearic acid in a mass ratio of 1:1, and the amount of the lubricant added accounts for 1.5% of the mass of the raw material powder.

[0108] Comparative Example 9

[0109] The preparation method of the low-cost high-strength low-copper high-manganese non-magnetic steel in Comparative Example 9 differs from that of Example 2 only in that: sintering is performed by sintering the alloy powder green body in a mesh belt sintering furnace in a sintering atmosphere of a mixture of 50% nitrogen and 50% hydrogen at a temperature of 1000 ℃ for 1.5 h to obtain the low-cost high-strength low-copper high-manganese non-magnetic steel.

[0110] The high-manganese non-magnetic steel materials prepared in Examples 1-7 are subjected to performance testing, and the results are shown in Table 1.

[0111] Table 1: Performance data of the high-manganese non-magnetic steel prepared in Examples 1-7

[0112] Sintered density (g / cm 3 ) Tensile strength (MPa) Elongation at break (%) Example 1 6.7 645 11.1 Example 2 7.0 651 13.2 Example 3 6.8 642 12.3 Example 4 6.5 640 14.1 Example 5 6.3 630 10.5 Example 6 6.3 630 10.2 Example 7 6.2 632 10.1

[0113] As can be seen from Table 1, the sintered density of the high-manganese non-magnetic steel prepared in the present application is 6.3-7.0 g / cm 3 , the tensile strength is above 630 MPa, and the elongation after fracture is above 10.1%, and the sintered non-magnetic steel material has good stability, and a low-cost high-strength low-copper high-manganese non-magnetic steel is obtained, which has high strength and excellent mechanical properties, and the use of lower Cu element greatly reduces the cost.

[0114] The total amount of the activator in Examples 1-4 is preferably in the range of 4.3%-5%, and the ratio of SiC powder to Y2O3 powder in the reinforcing phase is in the range of 2-4:1, which has better sintered density and mechanical properties than Examples 5-6. Example 7 uses a single lubricant, and the sintered density is lower and the mechanical properties are slightly decreased compared with the combination of micro-paraffin powder and stearic acid in a mass ratio of 1:1 used in Examples 1-4.

[0115] The high-manganese non-magnetic steel materials prepared in Example 2 and Comparative Examples 1-7 are subjected to performance testing, and the results are shown in Table 2.

[0116] Table 1: Performance data of the high-manganese non-magnetic steel prepared in Examples 2 and Comparative Examples 1-9

[0117] Tensile strength (MPa) Magnetic induction (mT) Example 2 651 0.04 Comparative Example 1 455 0.08 Comparative Example 2 533 0.04 Comparative Example 3 430 0.06 Comparative Example 4 532 0.05 Comparative Example 5 431 0.31 Comparative Example 6 440 0.06 Comparative Example 7 410 0.08 Comparative Example 8 442 0.10 Comparative Example 9 420 0.12

[0118] The addition amount of each component of the activator and the addition amount and ratio of the reinforcing phase are adjusted in Comparative Examples 1-4. Too high content of the activator leads to a decrease in sintering strength, and too low content leads to an insufficient liquid phase, affecting the activation effect, and a sharp decrease in the tensile strength of the high-manganese non-magnetic steel obtained.

[0119] After adjusting the content of manganese and other components of the pre-alloyed powder, a single austenite structure is not formed in Comparative Example 5, leading to a decrease in the tensile strength and an increase in the magnetic induction intensity.

[0120] After adjusting the particle size of the activator and the compaction pressure, the content of the lubricant and the sintering temperature, the activation effect is reduced in Comparative Examples 6-9, the compacts fail to form sufficient density, sintering cannot ensure the formation of a continuous liquid phase to achieve activation sintering, the precise sintering relative density cannot be obtained, the material stability is reduced, and the tensile strength is further reduced, and the magnetic induction intensity is increased.

[0121] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not contradict, they should be considered within the scope of the present disclosure.

Claims

1. A low cost high strength low copper high manganese non-magnetic steel, characterized in that, The raw material powder used is composed of: a high-manganese, high-carbon pre-alloyed powder as the matrix, combined with a composite activator consisting of 0.5-1% graphite powder, 0.3-0.5% copper powder, 2-2.5% Fe3P powder, and 1-2% iron powder, accounting for 1% of the matrix weight; and a reinforcing phase consisting of 1-1.5% SiC powder and Y2O3 powder, accounting for 1% of the matrix weight. The raw material powder is used to obtain the high-strength, low-copper, high-manganese non-magnetic steel by powder metallurgy. The high-manganese, high-carbon pre-alloyed powder comprises the following components by weight percentage: Mn 14-15%, C 0.4-0.7%, Si 0.5-0.8%, Ti 0.5-1.5%, rare earth Ce 0.05-0.15%, S≤0.05%, P≤0.1%, O≤0.15%, with the balance being Fe; The total amount of the composite activator accounts for 4.3% to 5% of the weight of the high-manganese high-carbon pre-alloyed powder; The ratio of SiC powder to Y2O3 powder in the reinforcing phase is 2 to 4:1; The high-manganese, high-carbon pre-alloyed powder has a particle size of 60–100 μm. The graphite powder has a particle size of less than 20 μm; the copper powder has a particle size of 30–40 μm; the Fe3P powder and iron powder have a particle size of 20–30 μm; and the SiC powder and Y2O3 powder have a particle size of 5–15 μm.

2. The method of producing a low cost high strength low copper high manganese non-magnetic steel as claimed in claim 1, characterized in that, Includes the following steps: Preparation of alloy powder green blank: The raw material powder is mixed with a lubricant and thoroughly mixed in a mixer, and then pressed into a green blank at 350-400 MPa to obtain the alloy powder green blank; Sintering: The alloy powder green billet is sintered in a mesh belt sintering furnace under a nitrogen and hydrogen mixture at a temperature of 1050 ℃~1130 ℃ for 1~2 h to obtain the low-cost, high-strength, low-copper, high-manganese non-magnetic steel. The lubricant is a combination of micro-paraffin powder and stearic acid in a mass ratio of 1:1, and the amount of lubricant added accounts for 2 to 2.5% of the mass of the raw material powder.

3. The method for preparing low-cost, high-strength, low-copper, high-manganese non-magnetic steel according to claim 2, characterized in that, The green body is pressed into shape at 350–380 MPa.

4. The method for preparing low-cost, high-strength, low-copper, high-manganese non-magnetic steel according to claim 2, characterized in that, The lubricant is a combination of micro-paraffin powder and stearic acid in a mass ratio of 1:1, and the amount of lubricant added accounts for 2.2% of the mass of the raw material powder.

5. The method for preparing low-cost, high-strength, low-copper, high-manganese non-magnetic steel according to claim 2, characterized in that, The sintering atmosphere is a mixture of 50% nitrogen and 50% hydrogen, and the sintering is carried out at a temperature of 1080 °C for 1.5 h to obtain the low-cost, high-strength, low-copper, high-manganese non-magnetic steel.

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