CN110016621B - Powder metallurgy high-manganese austenite non-magnetic steel and preparation method thereof - Google Patents
Powder metallurgy high-manganese austenite non-magnetic steel and preparation method thereof Download PDFInfo
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- B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
- B22F3/225—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip by injection molding
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- C22C33/00—Making ferrous alloys
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- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
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Abstract
The powder metallurgy high manganese austenite non-magnetic steel comprises the following components in percentage by mass: 13-30% of Mn, 0.6-1.3% of graphite and 1.0-4.0% of Cu3P, 1.0-3.0% of nitrogen, and the balance of iron powder and inevitable impurities. The preparation method comprises the following steps: preparing manganese powder, carbon powder, phosphor-copper alloy powder, nitrogen source powder and iron powder according to the designed component content, placing the manganese powder, the carbon powder, the phosphor-copper alloy powder, the nitrogen source powder and the iron powder in a closed ball milling tank protected by nitrogen for ball milling and activation until the granularity of the mixed powder is less than or equal to 13 mu m, adding a binder, continuously ball milling and mixing, and then mixing and injection molding; and (3) carrying out solvent degreasing on the injection molding blank, and then carrying out thermal degreasing and sintering under the protection of nitrogen. The invention has the advantages that: the prepared material has the characteristics of high manganese content, high nitrogen content, no nickel content, no magnetism, higher density and low oxygen content, and is suitable for preparing high-performance small parts with complex shapes and no magnetism through one-step forming.
Description
Technical Field
The invention relates to the technical field of powder metallurgy, in particular to powder metallurgy high-manganese austenite non-magnetic steel and a preparation method thereof.
Background
Non-magnetic steel refers to non-magnetic steel which can not be magnetized or low-magnetic (magnetic permeability mu is less than or equal to 1.319 multiplied by 10)-6H/m), is commonly used in environments with low magnetism and certain mechanical property requirements, such as balance blocks of precision instruments, motors, hardware fittings and compressors, drill collars in the field of energy sources, and the like. The nonmagnetic mechanism of nonmagnetic steel is that the iron alloy is an austenitic structure. In order to maintain the structure of the iron alloy as austenite, Ni, Cr, Cu, and,Mn and other elements which are beneficial to austenite formation, such as those which are usually added when non-magnetic steel is prepared by a smelting and casting method. However, the nickel resource is insufficient in China, and the price of the nickel metal is high; the price of copper is also gradually rising; therefore, the development of the low-nickel and nickel-free grade steel is of great significance. If Mn is the main alloy element in the non-magnetic steel, the addition amount is generally required to be more than 13%. On the other hand, nitrogen is also an element which strongly promotes the formation of austenite, the content of N in steel is increased, and the non-magnetization of steel is facilitated, and the addition of N has positive effects on reducing the material cost, improving the mechanical property and corrosion resistance of the steel, so that the development of nickel-free steel and nickel-free stainless steel by N-generation Ni is always a hot spot of novel steel research in the last three decades.
When the nitriding austenitic steel is prepared by adopting a casting method, because the solubility of nitrogen in high-temperature ferrite is very low, nitrogen is enriched at the front end of a solidification phase in the solidification process, even if high-pressure nitrogen is filled into molten steel, the nitrogen can still escape during cooling, and the content of nitrogen in the cast steel is not high and is generally less than 1.3 percent. The high manganese non-magnetic steel prepared by the casting method has the defects of high casting temperature, easy manganese burning loss, unstable manganese content in the steel and the like.
Powder metallurgy is a process technology for preparing a required product by preparing powder and uniformly mixing, molding, sintering and the like, wherein the molding method is generally compression molding. The high-manganese non-magnetic steel prepared by the powder metallurgy method has the advantage of low cost, manganese is an element for strongly promoting the formation of austenite, the reserves are rich, the price is low, and the effect of reducing the cost of raw materials can be achieved by increasing the content of manganese. However, Mn powder is easily oxidized and has a high vapor pressure, and is easily oxidized during molding and sintering to hinder sintering and reduce the performance of the sintered material. The evaporation of manganese can be reduced by adopting Fe-Mn prealloyed powder to replace simple substance manganese powder, but a large amount of Fe-Mn powder is required to be added when the high-manganese non-magnetic steel is prepared, and the negative effects of the problems of high oxidation and strength and the like of the Fe-Mn powder on the molding and sintering of powder materials are still large. In order to improve the compactness of green bodies and products, the patent application with the publication number of CN 106270494A discloses a non-magnetic steel product and a powder metallurgy manufacturing method thereof, wherein the alloy powder comprises the following components in percentage by mass: 60-90% of Fe-Mn prealloying powder, 10-25% of Cu powder, 0-5% of Cr powder, 0-5% of Ni powder, 0-2% of P powder and 0-30% of Fe powder, wherein Mn in the Fe-Mn prealloying powder accounts for 20-50%. The increase of the pressed sintered density is promoted by adding 10-25 wt.% of copper which has good compressibility and forms a liquid phase during sintering. In order to solve the problems that the shape of a structural part is difficult to maintain before and after sintering due to high copper addition, the price of copper is high and the like in liquid phase sintering, the invention patent application with the publication number of CN 107034420A discloses a non-magnetic steel product and a manufacturing method thereof, and the mass percentage of alloy powder is as follows: 16-18.56% of Mn, 1.1-1.4% of C, 0.7-0.98% of Si, 0.1-0.5% of B, less than or equal to 0.08% of S, less than or equal to 0.09% of P, less than or equal to 0.02% of Pb, less than or equal to 0.2% of Sn, and the balance of Fe, wherein FeB intermediate alloy powder is used for replacing Cu to promote sintering densification. On the other hand, nitrogen source introduction in the preparation of iron-based composite materials by powder metallurgy is generally to add nitrogen-containing metal compounds or to introduce nitrogen gas during sintering, and for example, patent application with publication number CN 105772704a discloses a tungsten-containing iron-based powder metallurgy material and a preparation method thereof, and decomposed ammonia or nitrogen gas atmosphere is introduced during sintering for sintering. However, the nitride has poor deformation capability during pressing, so that the green density is reduced, and the nitrogen content of the product is not high when the nitrogen is introduced for sintering, and the increase is generally less than 1.3%.
As described above, the casting method easily causes a large loss of manganese, and the powder metallurgy method is advantageous for producing high manganese steel, but the addition of manganese alloy is not favorable for pressing when the conventional pressing/sintering method is used for production; passing only N2The nitrogen increase in atmosphere sintering cannot meet the requirement of high nitrogen content of the product; conventional powder metallurgy compaction/sintering methods have difficulty achieving both good compaction performance and higher nitrogen content in the article.
Disclosure of Invention
In order to solve the problems, the invention provides powder metallurgy high-manganese austenite non-magnetic steel with high manganese and nitrogen contents, easy forming and low cost and a preparation method thereof.
The invention relates to powder metallurgy high-manganese austenite non-magnetic steel which comprises the following components in percentage by mass:
the invention relates to powder metallurgy high-manganese austenite non-magnetic steel which comprises the following components in percentage by mass:
the invention relates to powder metallurgy high-manganese austenite non-magnetic steel which comprises the following components in percentage by mass:
the invention relates to a powder metallurgy high manganese austenite non-magnetic steel, wherein C is selected from graphite.
The invention relates to powder metallurgy high manganese austenite non-magnetic steel, and the Cu3P is commercial phosphorus copper alloy powder with the granularity of 8-11 mu m.
According to the powder metallurgy high-manganese austenite nonmagnetic steel, melamine is selected as a nitrogen source and added into the alloy.
The invention relates to a preparation method of powder metallurgy high-manganese austenite non-magnetic steel, which comprises the following steps:
the first step is as follows: preparing manganese powder, carbon powder, phosphor-copper alloy powder, nitrogen source powder and iron powder according to the designed component content, placing the manganese powder, the carbon powder, the phosphor-copper alloy powder, the nitrogen source powder and the iron powder in a closed ball milling tank protected by nitrogen for ball milling activation until the granularity of the mixed powder is less than or equal to 13 mu m, adding a binder, and continuing ball milling and mixing for at least 0.5 hour;
the second step is that: mixing the ball-milled powder obtained in the first step, and then performing injection molding;
the third step: and (3) carrying out solvent degreasing on the injection molding blank obtained in the second step, then carrying out thermal degreasing under the protection of nitrogen, and then carrying out high-temperature sintering.
The invention relates to a preparation method of powder metallurgy high-manganese austenite non-magnetic steel, wherein the average particle size of manganese powder, carbon powder, phosphor-copper alloy powder, nitrogen source powder and iron powder is less than or equal to 180 mu m, preferably less than or equal to 75 mu m.
The invention relates to a preparation method of powder metallurgy high manganese austenite non-magnetic steel, wherein nitrogen source powder is selected from melamine; the nitrogen source powder accounts for 3-6% of the total mass of the alloy powder.
The invention relates to a preparation method of powder metallurgy high manganese austenite nonmagnetic steel, which fills 0.1-1MPa of nitrogen into a closed ball milling tank.
The invention relates to a preparation method of powder metallurgy high manganese austenite non-magnetic steel, which comprises the following steps of:
the rotation speed of the ball mill is 250-450rpm, the ball-material ratio is 12-15:1, the total volume of the ball-materials accounts for 1/3-2/3 of the capacity of the ball milling tank, the grinding balls are stainless steel balls,
grinding ball and
the number ratio of the grinding balls is 2:3-5, the ball milling is carried out in a clearance way, the ball milling is carried out for 25-35min, and the cycle is stopped for 10-15 min;
after the binder is added, the ball milling mixing technological parameters are as follows: the rotation speed of the ball mill is 100-.
The invention relates to a preparation method of powder metallurgy high manganese austenite non-magnetic steel, wherein in the first step, the addition amount of a binder accounts for 8-10% of the total mass of mixed materials during ball milling.
The invention relates to a preparation method of powder metallurgy high manganese austenite non-magnetic steel, in the second step, the mixing technological parameters are as follows:
when the binder is prepared from paraffin, peanut oil, polyethylene and stearic acid according to the mass ratio of paraffin: peanut oil: polyethylene: when stearic acid is 40-50:15-25:25-35:3-7, the mixing technological parameters are as follows:
heating the mixture after ball milling and mixing to 150 ℃ and 170 ℃ and mixing for 0.5-2 h;
when the binder is prepared from polyethylene glycol, organic glass and stearic acid according to the mass ratio of polyethylene glycol: organic glass: when the stearic acid is 60-70:25-35:3-7,
the mixing technological parameters are as follows:
adding the mixture after ball milling and mixing into a mixed solution of alcohol and trichloroethane for mixing at the mixing temperature of 55-65 ℃ for 1-2h, then drying at the temperature of 75-85 ℃ for 8-12h, and crushing until the particle size is less than or equal to 5 mm;
in the mixed solution, the mass ratio of the alcohol to the trichloroethane is 2-3: 1; the solid-liquid mass ratio of the mixture after ball milling to the mixed liquid is 1: 4-10.
The invention relates to a preparation method of powder metallurgy high manganese austenite non-magnetic steel, in the second step, the injection molding technological parameters are as follows: the feeding temperature is 150-.
The invention relates to a preparation method of powder metallurgy high manganese austenite nonmagnetic steel, in the third step, the solvent degreasing process of injection molding blank is as follows: heating the blank in trichloroethane to 50-60 deg.C for solvent degreasing for 1-2 hr per mm thickness, and drying at 60-75 deg.C.
The invention relates to a preparation method of powder metallurgy high manganese austenite non-magnetic steel, which comprises the following process parameters in the third step of thermal degreasing under the protection of nitrogen: the nitrogen pressure in the furnace is 0.02-0.10MPa, the degreasing temperature is 350-380 ℃, and the degreasing time of the blank with the thickness of each millimeter is 1.5-2 hours.
The invention relates to a preparation method of powder metallurgy high manganese austenite non-magnetic steel, which comprises the following sintering process parameters:
the nitrogen pressure in the furnace is 0.02-0.10MPa, the sintering temperature is 1120-1150 ℃, and the sintering time is 1-1.5 hours.
The invention idea is as follows: the Fe-Mn-C system is adopted to prepare the non-magnetic steel, the manganese content is required to be more than 13%, N is an element for strongly promoting the formation of austenite, the content of the manganese and the content of the N in the steel are improved, and the steel is beneficial to the non-magnetism of the steel. Mn is easily oxidized into MnO due to high activity, and MnO with high hardness can cause poor formability of a powder system, hinder sintering and reduce the mechanical properties of a product. In order to improve the formability and prevent Mn powder from being oxidized in the mixing and subsequent processes, the invention fills nitrogen in the high-energy ball mill to realize the nitriding and refining of Mn powder, improve the oxidation resistance and meet the requirement of the subsequent powder injection forming. MnN is hard and has poor pressing performance; gold (Au)Belongs to powder injection molding, is a novel powder metallurgy near-net forming technology which is derived from modern plastic injection molding, and is suitable for preparing small metal parts with complex shapes at low cost. The powder after ball milling is molded by adopting an injection molding technology, and the binder used in the injection molding technology is added during ball milling, so that the powder can be prevented from being oxidized by further utilizing the binding action of the binder. In order to further increase the nitrogen content of the product, in addition to filling nitrogen during ball milling and sintering in the nitrogen atmosphere, the invention also adds melamine as a nitrogen source, and utilizes nitrogen generated by decomposition of the melamine in the degreasing process at 350 ℃ to increase nitrogen from the inside of the product, thereby realizing nitrogen increase inside and outside the product and improving the nitrogen content in the material. Cu3P can activate and sinter, together with graphite, promote the shrinkage of products during sintering, counteract the problem of product size expansion in the sintering process caused by manganese, and achieve the purpose of near net shape.
The high-manganese high-nitrogen non-magnetic steel is prepared by the ball milling and metal powder injection molding method. The powder is ball milled to reduce the granularity and meet the requirement of metal powder injection molding. Considering that the nitride ceramic particles generated by the in-situ reaction have smaller size, clean surface, better compatibility with a metal matrix, higher interface bonding strength, dispersion strengthening, particle strengthening, dislocation strengthening and other advantages, the self-generated nitride ceramic particles are generated and uniformly distributed in the matrix, and the ceramic particle ceramic/metal matrix composite material with excellent comprehensive mechanical properties can be obtained.
Firstly, adding the powder into a ball milling tank filled with nitrogen for high-energy ball milling, wherein the surface of part of the powder is nitrided while the powder is uniformly mixed and the particle size is reduced, so that the oxidation resistance is improved; then adding a binder for ball milling, so that the binder is uniformly distributed, the surfaces of Mn powder and the like are coated by the binder, and the antioxidation of the Mn powder is further improved; the sintering temperature is far lower than the temperature required by a smelting-casting method, so that the manganese burning loss is reduced; the invention adopts the metal powder injection molding technology to prepare the non-magnetic steel, can make up the defect that the powder is hardened due to the powder ball milling treatment to reduce the pressing performance, thereby greatly improving the Mn content which can be more than 13 percent, and realizing the purpose of preparing the non-magnetic high manganese steel by adopting a powder metallurgy method. The nitrogen is increased because nitrogen with certain pressure is filled in the high-energy ball milling process. And because the nitrogen source powder is uniformly distributed in the product, nitrogen generated by decomposition in sintering and elements such as Mn and the like have a nitriding effect, and the sintering atmosphere is nitrogen, the surface and the interior of the product are simultaneously nitrided, and the nitrogen increasing effect is improved, so that the nitrogen content in the product is higher than that of a conventional single method.
The invention has the advantages that:
(1) the Mn content is higher than 13-30%, and after the powder is subjected to oxidation resistance treatment by high-energy ball milling under the protection of nitrogen, the low oxygen can be kept in the subsequent forming and sintering processes, so that the high sintering density and the high performance can be obtained. Nitride is generated on the nitrided surface in the ball milling process, so that manganese is protected from being oxidized easily. The powder after ball milling is formed by adopting an injection molding technology, and the requirements on the hardness and the pressing property of the powder are not high.
(2) In the high-energy ball milling process, nitrogen serves as protective gas and also serves as a nitrogen source for generating nitride through reaction with element powder, and part of element manganese and alloy powder are protected by nitridation, so that the interior of Mn powder is not easy to oxidize; the adhesive is added in advance, and paraffin and oil (or polyethylene glycol or organic glass) in the components can be coated on the surface of the powder, so that the anti-oxidation effect of the powder is further improved; the raw materials are uniformly dispersed, and the stainless steel balls and the raw materials are collided and crushed to reduce the particle size of the raw materials, so that the technical requirements of metal injection molding are met, the activity is good, and sintering densification is easy to realize;
(3) in the sintering process, the melamine uniformly distributed in the product is heated and decomposed to generate nitrogen, the sintering atmosphere is nitrogen, and Mn and other powder in the blank can be in full contact reaction with the nitrogen, so that the nitrogen content in the product is increased.
Detailed Description
The present invention is described in further detail below with reference to examples, which are intended to be illustrative of the present invention and are not to be construed as limiting the present invention.
The nitrogen and oxygen content in the embodiment of the invention is measured by a TCH-600 oxygen nitrogen hydrogen analyzer and the magnetism by a JDZ-2 type magnetic permeability measuring instrument.
Example 1
A powder metallurgy high manganese austenite non-magnetic steel comprises the following chemical components in percentage by mass: 13% Mn, 1.0% Cu3P, 1.3% of graphite, 3.0% of melamine, and the balance of iron powder and inevitable impurities.
Adding the above raw materials and stainless steel ball into a stainless steel ball-milling tank, sealing, vacuumizing the ball-milling tank, charging 0.5MPa nitrogen, and performing high-energy ball milling for 45h (the diameter of the stainless steel ball is equal to that of the stainless steel ball)
The number ratio is 2:3, the ball material ratio is 12:1, and the rotating speed is 350 rpm); then adding a binder for ball milling for 10h, naturally cooling the composite powder to room temperature in a ball milling tank, collecting the ball milled mixture, mixing for 1h at 160 ℃, and then performing injection molding (injection process parameters: injection pressure 13MPa, pressure maintaining pressure 10MPa, pressure maintaining time 3s, initial mold temperature 100 ℃, melting temperature 190 ℃, demolding temperature 120 ℃); and putting the blank obtained by injection molding into trichloroethane, heating to 50 ℃ for solvent degreasing, drying at 65 ℃, then putting into a tubular furnace filled with nitrogen for thermal degreasing, sintering at a high temperature region, wherein the degreasing temperature is 360 ℃, the time is 2.0h, the sintering temperature is 1140 ℃, the time is 1h, and cooling along with the furnace is carried out to obtain the required high-manganese austenite nonmagnetic steel. Permeability of the product is 1.051X 10-6H/m, density 7.25g cm-3Nitrogen content 1.54%, [ O ]]＝0.17％。
Comparative example 1
The components, sintering process and parameters were the same as in example 1, except that mechanical mixing was performed with a V-blender at 45 rpm for 6 hours, the powder was prepared by the conventional powder metallurgy pressing/sintering method, unidirectional pressing was performed at 600 MPa. Permeability of the obtained product is 1.086 × 10-6H/m, density 6.54g cm-3Nitrogen content 0.32%, [ O ]]＝1.09％。
Therefore, on the premise of no magnetism, the high manganese austenite non-magnetic steel sintered body prepared by the invention has higher density and nitrogen content and lower oxygen content.
Example 2
A powder metallurgy high manganese austenite non-magnetic steel comprises chemical components in mass fractionComprises the following steps: 18% Mn, 2.0% Cu3P, 1.0% of graphite, 4.0% of melamine, and the balance of iron and inevitable impurities.
The preparation process and parameters are the same as example 1, and the magnetic permeability of the product is 1.043 multiplied by 10-6H/m, density 7.17g cm-3Nitrogen content 1.78%, [ O ]]＝0.23％。
Comparative example 2
The components, sintering process and parameters were the same as in experimental example 1, except that mechanical mixing was performed with a V-blender at a speed of 45 rpm for 4 hours, the powder was prepared by a conventional powder metallurgy pressing/sintering method, unidirectional pressing was performed, and the pressure was 600 MPa. Permeability of the obtained product is 1.069 × 10-6H/m, density 6.39g cm-3Nitrogen content 0.38%, [ O ]]＝1.21％。
Therefore, on the premise of no magnetism, the high manganese austenite non-magnetic steel sintered body prepared by the invention has higher density and nitrogen content and lower oxygen content.
Example 3
A powder metallurgy high manganese austenite non-magnetic steel comprises the following chemical components in percentage by mass: 22% Mn, 2.0% Cu3P, 0.8% of graphite, 4.5% of melamine, and the balance of iron and inevitable impurities.
Adding the above raw materials and stainless steel balls into a stainless steel ball-milling tank, sealing, vacuumizing the ball-milling tank, charging 0.5MPa nitrogen, and ball-milling for 45 hr (the diameters of the stainless steel balls are respectively
The number ratio is 2:3, the ball material ratio is 12:1, and the rotating speed is 350 rpm); then adding an adhesive for ball milling for 10h, naturally cooling the composite powder to room temperature in a ball milling tank, collecting the ball milled mixture, adding the ball milled mixture into a mixed solution of alcohol and trichloroethane for mixing, drying at the temperature of 60 ℃ for 2h, crushing after drying at the temperature of 75 ℃ for 12h, and then performing injection molding (injection process parameters: injection pressure 13MPa, pressure maintaining pressure 10MPa, pressure maintaining time 3s, initial mold temperature 100 ℃, melting temperature 190 ℃ and demolding temperature 120 ℃); placing the blank obtained by injection molding into trichloroethane, heating to 50 deg.C for solvent degreasing, and drying at 65 deg.CDrying, putting the steel into a tubular furnace filled with nitrogen for hot degreasing, sintering the steel in a high-temperature area at the degreasing temperature of 360 ℃ for 2.0h and the sintering temperature of 1140 ℃ for 1h, and cooling the steel along with the furnace to obtain the required high-manganese austenite nonmagnetic steel. Permeability of the obtained product is 1.034 × 10-6H/m, density 7.08g cm-3Nitrogen content 1.87%, [ O ]]＝0.25％。
Comparative example 3
The components, sintering process and parameters were the same as in experimental example 3, except that mechanical mixing was performed using a V-blender at a speed of 45 rpm for 4 hours, the powder was prepared by a conventional powder metallurgy pressing/sintering method, unidirectional pressing was performed, and the pressure was 600 MPa. Permeability of the obtained product is 1.058 × 10-6H/m, density 6.27g cm-3Nitrogen content 0.45%, [ O ]]＝1.47％。
Therefore, on the premise of no magnetism, the high manganese austenite non-magnetic steel sintered body prepared by the invention has higher density and nitrogen content and lower oxygen content.
Example 4
A powder metallurgy high manganese austenite non-magnetic steel comprises the following chemical components in percentage by mass: 25% Mn, 3.0% Cu3P, 0.7% of graphite, 5.0% of melamine, and the balance of iron and inevitable impurities.
The preparation process and parameters are the same as those in example 3, and the magnetic permeability of the product is 1.026 multiplied by 10-6H/m, density 6.98g cm-3Nitrogen content 2.09%, [ O ]]＝0.35％。
Comparative example 4
The components, sintering process and parameters were the same as in experimental example 3, except that mechanical mixing was performed using a V-blender at a speed of 45 rpm for 4 hours, the powder was prepared by conventional powder metallurgy pressing/sintering method, unidirectional pressing was performed at a pressure of 600MPa, and the permeability μ of the obtained product was 1.047 × 10-6H/m, density 6.16g cm-3Nitrogen content 0.47%, [ O ]]＝1.53％。)
Therefore, on the premise of no magnetism, the high manganese austenite non-magnetic steel sintered body prepared by the invention has higher density and nitrogen content and lower oxygen content.
Example 5
A powder metallurgy high manganese austenite non-magnetic steel comprises the following chemical components in percentage by mass: 30% Mn, 3.0% Cu3P, 0.6% of graphite, 6.0% of melamine, and the balance of iron and inevitable impurities.
The preparation process and parameters were the same as in example 3, and the permeability μ of the product was 1.014 × 10-6H/m, density 6.85g cm-3Nitrogen content 2.37%, [ O ]]＝0.35％。
Comparative example 5
The components, sintering process and parameters were the same as in experimental example 3, except that mechanical mixing was performed using a V-blender at a speed of 45 rpm for 4 hours, the powder was prepared by the conventional powder metallurgy pressing/sintering method, unidirectional pressing was performed, and the pressure was 600 MPa. Permeability of the obtained product is 1.038 × 10-6H/m, density 5.94g cm-3Nitrogen content 0.52%, [ O ]]＝1.75％。
Therefore, on the premise of no magnetism, the high manganese austenite non-magnetic steel sintered body prepared by the invention has higher density and nitrogen content and lower oxygen content.
The performance parameters of the alloys prepared in examples 1-5 and comparative examples 1-5 are shown in Table 1.
TABLE 1
Claims (9)
1. A preparation method of powder metallurgy high manganese austenite nonmagnetic steel comprises the following steps:
the first step is as follows: manganese powder, carbon powder, phosphor-copper alloy powder, nitrogen source powder and iron powder are prepared according to the designed component content of the powder metallurgy high manganese austenite nonmagnetic steel, and are placed in a closed ball milling tank under the protection of nitrogen for ball milling and activation until the granularity of the mixed powder is less than or equal to 13 mu m, and then a binder is added for continuous ball milling and mixing for at least 0.5 hour;
the powder metallurgy high manganese austenite non-magnetic steel comprises the following components in percentage by mass:
Mn 13-30 %，
C 0.6-1.3 %，
Cu3P 1.0-4.0 %，
1.0-3.0% of nitrogen and the balance of iron;
the second step is that: mixing the ball-milled powder obtained in the first step, and then performing injection molding;
the third step: and (3) carrying out solvent degreasing on the injection molding blank obtained in the second step, and then carrying out thermal degreasing and high-temperature sintering under the protection of nitrogen.
2. The method for preparing powder metallurgy high manganese austenite nonmagnetic steel according to claim 1, characterized in that: the average particle size of the manganese powder, the carbon powder, the phosphor-copper alloy powder, the nitrogen source powder and the iron powder is less than or equal to 180 mu m.
3. The method for preparing powder metallurgy high manganese austenite nonmagnetic steel according to claim 1, characterized in that: the nitrogen source powder is melamine; the nitrogen source powder accounts for 3-6% of the total mass of the alloy component powder.
4. The method for preparing powder metallurgy high manganese austenite nonmagnetic steel according to claim 1, characterized in that: in the first step, the ball milling activation process parameters are as follows:
filling 0.1-1MPa of nitrogen into a closed ball milling tank, enabling the rotation speed of the ball mill to be 250-450rpm, enabling the ball-material ratio to be 12-15:1, enabling the total volume of ball materials to account for 1/2-2/3 of the capacity of the ball milling tank, enabling grinding balls to be stainless steel balls, enabling the number ratio of the grinding balls with the diameter of 6 mm to the grinding balls with the diameter of 10 mm to be 2:3-5, performing gap ball milling, and performing periodic cycle of ball milling for 25-35min and stopping for 10-15 min;
after the binder is added, the ball milling mixing technological parameters are as follows: the rotation speed of the ball mill is 100-.
5. The method for preparing powder metallurgy high manganese austenite non-magnetic steel according to claim 4, wherein: in the first step, the addition of the binder accounts for 8-10% of the total mass of the ball-milled mixture.
6. The method for preparing powder metallurgy high manganese austenite non-magnetic steel according to claim 5, characterized in that: in the second step, the parameters of the binder and the mixing process are the following two types:
when the binder is prepared from paraffin, peanut oil, polyethylene and stearic acid according to the mass ratio of paraffin: peanut oil: polyethylene: when the stearic acid =40-50:15-25:25-35:3-7, the mixing technological parameters are as follows:
heating the mixture after ball milling and mixing to 150 ℃ and 170 ℃ and mixing for 0.5-2 h;
when the binder is prepared from polyethylene glycol, organic glass and stearic acid according to the mass ratio of polyethylene glycol: organic glass: when the stearic acid is composed of 60-70:25-35:3-7, the mixing technological parameters are as follows:
adding the mixture after ball milling and mixing into a mixed solution of alcohol and trichloroethane for mixing at the mixing temperature of 55-65 ℃ for 1-2h, then drying at the temperature of 75-85 ℃ for 8-12h, and crushing until the particle size is less than or equal to 5 mm;
in the mixed solution, the mass ratio of the alcohol to the trichloroethane is 2-3: 1; the solid-liquid mass ratio of the mixture after ball milling to the mixed liquid is 1: 4-10.
7. The method for preparing powder metallurgy high manganese austenite non-magnetic steel according to claim 6, characterized in that: in the second step, the injection molding process parameters are as follows: the feeding temperature is 150-.
8. The method of claim 7, wherein the powder metallurgy high manganese austenitic non-magnetic steel comprises: in the third step, the solvent degreasing process of the injection molding blank comprises the following steps: placing the blank in trichloroethane, heating to 50-60 ℃ for solvent degreasing, wherein the degreasing time of the blank with the thickness of each millimeter is 1-2h, and then drying at 60-75 ℃;
the parameters of the thermal degreasing process under the protection of nitrogen are as follows: the nitrogen pressure in the furnace is 0.02-0.10MPa, the degreasing temperature is 350-380 ℃, and the degreasing time of the blank with the thickness of each millimeter is 1.5-2 hours.
9. The method of claim 8, wherein the powder metallurgy high manganese austenitic non-magnetic steel comprises: the sintering process parameters are as follows:
the nitrogen pressure in the furnace is 0.02-0.10MPa, the sintering temperature is 1120-1150 ℃, and the sintering time is 1-1.5 hours.
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