Superfine pre-alloyed powder, preparation method thereof and diamond sintered body

Abstract

The invention discloses superfine pre-alloyed powder, a preparation method of the superfine pre-alloyed powder and a diamond sintered body. The superfine pre-alloyed powder at least comprises, by weight, 30%-50% of iron, 20%-30% of cobalt, 25%-40% of copper and 0.5%-1% of phosphorus. The preparation method comprises the following steps: dissolving soluble acidic salt of iron, soluble acidic salt of cobalt and soluble acidic salt of copper in water to prepare a metal ion solution; mixing phosphate and the metal ion solution to prepare a mixed system; heating the mixed system to 40-60 DEG C, adding weak base, and stirring to react to generate precipitate; washing the precipitate with water, and then drying to obtain a precursor; reducing the precursor to obtain superfine pre-alloyed powder; the phosphate is at least one of iron phosphate, cobalt phosphate and copper phosphate. By introducing a proper amount of phosphorus element, the sintering temperature is reduced, the compactness of 98% or above can be achieved through pressureless sintering at the temperature lower than 1000 DEG C, and the strength and hardness of the product are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy powders, and particularly relates to an ultrafine pre-alloy powder, a preparation method thereof, and a diamond sintered body. Background Art

[0002] The matrix material of diamond tools traditionally uses a hot pressing sintering process, where metal powders are subjected to high temperature and high pressure treatment in a graphite mold to obtain high density. However, this process has the following disadvantages: it requires the use of expensive graphite molds, increasing the manufacturing cost; limited by the mold, the tool shape design is not flexible enough; the process is complex, the equipment requirements are high, and the energy consumption is large.

[0003] Free sintering (also known as pressureless sintering) is an advanced forming technology that does not require a mold and external pressure. It relies on heat to induce atomic diffusion and bonding between particles. Without external pressure or a mold, it can produce components with complex shapes. Compared with the traditional hot pressing sintering process, it has low equipment cost, high production efficiency, and high operation flexibility. However, the free sintering process has extremely high requirements for the sintering activity and densification of powders, and there are still great challenges in the current free sintering process.

[0004] The information disclosed in this background art section is only intended to enhance the overall understanding of the present invention and should not be regarded as an admission or any form of implication that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide an ultrafine pre-alloy powder, a preparation method thereof, and a diamond sintered body, and the ultrafine pre-alloy powder can obtain a sintered body with a density of more than 98% under pressureless sintering.

[0006] To achieve the above purpose, the technical solution provided by a specific embodiment of the present invention is as follows:

[0007] An ultrafine pre-alloy powder, comprising at least the following components by weight percentage: 30% - 50% of iron, 20% - 30% of cobalt, 25% - 40% of copper, and 0.5% - 1% of phosphorus.

[0008] In one or more embodiments of the present invention, the Fisher particle size is less than or equal to 2 μm.

[0009] The technical solution provided by another specific embodiment of the present invention is as follows:

[0010] A preparation method of an ultrafine pre-alloy powder, comprising the following steps:

[0011] Dissolve the soluble acidic salts of iron, the soluble acidic salts of cobalt, and the soluble acidic salts of copper in water to form a metal ion solution;

[0012] Mix a phosphate and a metal ion solution to form a mixed system;

[0013] Heat the mixed system to 40°C - 60°C, add a weak base, and stir to react to form a precipitate;

[0014] Wash the precipitate with water and then dry it to obtain a precursor;

[0015] Reduce the precursor to obtain ultrafine pre-alloyed powder;

[0016] Wherein, the phosphate is at least one of iron phosphate, cobalt phosphate, and copper phosphate.

[0017] In one or more embodiments of the present invention, the particle size of the phosphate is 0.5 μm - 2 μm.

[0018] In one or more embodiments of the present invention, the weak base is at least one of sodium carbonate, ammonium bicarbonate, ammonium oxalate, ammonium carbonate, and ammonia water.

[0019] In one or more embodiments of the present invention, based on the amount of the weak base required in the stoichiometric ratio in the precipitate, when adding the weak base to the mixed system, the addition amount of the weak base is 5% - 10% in excess.

[0020] In one or more embodiments of the present invention, in the metal ion solution, the total metal ion concentration is 60 g / L - 180 g / L.

[0021] In one or more embodiments of the present invention, the drying temperature is 120°C - 160°C and the time is 6 h - 8 h.

[0022] In one or more embodiments of the present invention, the reduction is carried out in a hydrogen atmosphere, the temperature is 500°C - 700°C, the time is 4 h - 6 h, and the hydrogen volume flux is 0.03 m / s - 0.05 m / s.

[0023] The technical solution provided by another specific embodiment of the present invention is as follows:

[0024] A diamond sintered body is made of at least the above ultrafine pre-alloyed powder or the ultrafine pre-alloyed powder obtained by the preparation method of the above ultrafine pre-alloyed powder.

[0025] Compared with the prior art, by introducing a specific content of phosphorus element, the present invention reduces the melting point of the alloy powder and thus reduces the sintering temperature, can adopt a pressureless sintering process, prepares a diamond sintered body with a density reaching more than 98%, and can also improve the hardness and strength of the diamond sintered body. Description of the Drawings

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a flowchart for the preparation of ultra-fine pre-alloyed powder in an embodiment of the present invention;

[0028] Figure 2 It is the first scanning electron microscope photograph of the ultra-fine pre-alloyed powder in Embodiment 1 of the present invention;

[0029] Figure 3 It is the second scanning electron microscope photograph of the ultra-fine pre-alloyed powder in Embodiment 1 of the present invention. Detailed implementation manners

[0030] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] Diamond tools are mainly prepared by mixing metal powder with diamond particles and then using a hot press sintering process (heating and pressurizing simultaneously). Since diamond particles are composed of carbon elements themselves and cannot withstand temperatures exceeding 1000°C, high temperatures will cause diamond to graphitize. Therefore, the traditional process is to use a hot press sintering process to load the mixed powder of metal powder and diamond into a graphite mold and heat and pressurize it in a hot press sintering machine to form a product with a density exceeding 98%. However, the hot press process has high energy consumption, low production efficiency, and consumes a large amount of graphite molds. Therefore, pressureless sintering has become the development direction.

[0032] For pressureless sintering, only cold pressing and forming with a steel mold are required, and a density exceeding 98% can be achieved in a sintering furnace without applying pressure. However, due to reasons such as high melting points of the original iron-cobalt-copper powder, the sintering temperature is high, and it is impossible to reach a density above 98% under the conditions of no pressure and below 1000°C, so it cannot be directly used in the pressureless sintering process.

[0033] The present invention reduces the melting point of the powder and thus reduces the sintering temperature by introducing an appropriate amount of phosphorus element. In pressureless sintering, a density above 98% can be achieved when the sintering temperature is below 1000°C, effectively reducing energy consumption and ensuring product quality at the same time.

[0034] A specific embodiment of the present invention provides a superfine pre-alloyed powder, which comprises at least the following components in percentage by weight: 30% - 50% of iron, 20% - 30% of cobalt, 25% - 40% of copper, and 0.5% - 1% of phosphorus.

[0035] Specifically, in terms of composition design, iron and copper, as the main elements, can provide good basic properties and relatively low prices, which can reduce costs. In addition, a part of cobalt element is used for solution strengthening of iron and copper. However, it is difficult for the iron-cobalt-copper ternary alloy to achieve a relative density of more than 98% below 1000°C during pressureless sintering. In the existing methods, low-melting-point metals such as tin are added to reduce the sintering temperature, but the addition of tin will reduce the strength of the product. By adding an appropriate amount of phosphorus element, the present invention can not only reduce the melting point of the powder and thus lower the sintering temperature, but also the phosphide can play the role of liquid-phase sintering, enabling better fusion of powder particles and at the same time playing the role of dispersion strengthening, thereby further improving the hardness and strength of the sintered product.

[0036] Regarding the content of phosphorus element, if the content is too small, the reduction of the sintering temperature is not obvious and the sintering density of the final product cannot be sufficiently improved. If the content is too high, the toughness of the sintered product is relatively low, thus reducing the product quality.

[0037] Furthermore, the Fisher particle size is less than or equal to 2 μm.

[0038] Specifically, diamond will be graphitized under high-temperature sintering, which will reduce the tool performance of diamond. Therefore, it is necessary to sinter densely at a lower temperature to prevent graphitization. The finer the powder, the higher the sintering activity and the lower the sintering temperature. By controlling the Fisher particle size of the pre-alloyed powder, the present invention can ensure the sintering effect.

[0039] More specifically, the higher the Fisher particle size of the pre-alloyed powder, the higher the sintering temperature required, and the high sintering temperature will cause diamond to be graphitized and lose its function. Controlling the Fisher particle size within 2 μm can sinter densely at a lower temperature, which can not only ensure sufficient relative density of the sintered matrix but also ensure that diamond will not be graphitized.

[0040] Another specific embodiment of the present invention provides a preparation method of a superfine pre-alloyed powder, which comprises steps 1 - 4.

[0041] Step 1, dissolve soluble acidic salts of iron, soluble acidic salts of cobalt, and soluble acidic salts of copper in water to prepare a metal ion solution.

[0042] Specifically, the soluble acidic salt of iron is at least one of iron sulfate, nitrate, and chloride; the soluble acidic salt of cobalt is at least one of iron sulfate, nitrate, and chloride; the soluble acidic salt of copper is at least one of iron sulfate, nitrate, and chloride. In the metal ion solution, the total metal ion concentration is 60 g / L to 180 g / L.

[0043] Step 2: Mix the phosphate and the first solution to form a mixed system.

[0044] Specifically, the phosphate is at least one of iron phosphate, cobalt phosphate, and copper phosphate. The above types of phosphates are insoluble in water and are dispersed in the mixed system.

[0045] Furthermore, the particle size of the phosphate is 0.5 μm to 2 μm. By controlling the particle size of the phosphate, on the one hand, it is beneficial to obtain pre-alloyed powder with a Fisher particle size less than or equal to 2 μm; on the other hand, during the subsequent precipitation process, the generated precipitate and the phosphate can be better mixed, enabling the phosphate to be evenly distributed among other metal elements, so that a more uniform phosphorus-containing alloy phase can be formed during the subsequent reduction and sintering processes.

[0046] Step 3: Heat the mixed system to 40°C to 60°C, add a weak base, and stir to react to form a precipitate.

[0047] Specifically, the stirring speed is 60 r / min to 120 r / min, and the weak base is at least one of sodium carbonate, ammonium bicarbonate, ammonium oxalate, ammonium carbonate, and ammonia water. When used, the weak base (such as sodium carbonate, ammonium bicarbonate, ammonium oxalate, ammonium carbonate) is made into an aqueous solution, and the mass concentration is controlled to be 40 g / L to 120 g / L. After the weak base is added to the mixed system, through acid-base neutralization, the corresponding coprecipitate is generated. According to the amount of the weak base required by the stoichiometric ratio in the precipitate, when actually adding the weak base, an additional 5% to 10% of the weak base is actually added, that is, 5% to 10% more weak base is added, to promote the precipitation of all metal ions.

[0048] The phosphate used in the present invention is insoluble in water and does not react with the above types of weak bases under normal pressure. After adding the weak base, the weak base reacts with the metal ions to form a precipitate. Since the precipitate is generated from the system, the precipitate and the phosphate will be evenly distributed in the system. Furthermore, in the finally prepared pre-alloyed powder, the phosphorus element can be evenly distributed among other metal elements, thereby effectively reducing the sintering temperature of the pre-alloyed powder and effectively ensuring the performance of the pre-alloyed powder. In addition, even if the phosphate reacts with the above types of weak bases, the reaction is only non-violent and extremely minor. Considering this factor, when adding the phosphate to the second solution, the feeding amount of the phosphate can be appropriately increased to make up for the loss caused by the reaction with the weak base, so that the finally prepared pre-alloyed powder contains the required phosphorus element content.

[0049] Step 4: Wash the precipitate with water and then dry it to obtain the precursor.

[0050] Specifically, wash the precipitate obtained in Step 3 with water until the chloride ion concentration in the filtrate is less than 50 ppm, and then dry it at 120°C to 160°C for 6 h to 8 h. After drying, the coprecipitate forms the corresponding metal oxide, and the metal oxide and phosphate together form the precursor.

[0051] Step 5: Reduce the precursor to obtain the ultrafine pre-alloyed powder.

[0052] Specifically, the reduction is carried out in a hydrogen atmosphere at a temperature of 500°C to 700°C for 4 h to 6 h, and the hydrogen volume flux is 0.03 to 0.05 m / s. During this process, the metal oxide in the precursor is reduced, and at the same time, the phosphate is reduced, and the phosphorus element diffuses among other metal elements to achieve alloying.

[0053] Another specific embodiment of the present invention provides a diamond sintered body prepared at least using the above ultrafine pre-alloyed powder.

[0054] The following further elaborates the present invention with specific embodiments.

[0055] Example 1

[0056] Weigh 22.5 kg of ferrous sulfate heptahydrate, 11.8 kg of copper sulfate pentahydrate, and 12.2 kg of cobalt sulfate heptahydrate, dissolve them in deionized water, and add water to make the total volume of the solution 100 L to obtain a metal ion solution. The iron ion concentration in the solution is 45 g / L, the cobalt ion concentration is 25 g / L, and the copper ion concentration is 30 g / L.

[0057] Weigh 245 g of iron phosphate and add it to the metal ion solution.

[0058] Weigh 20.1 kg of sodium carbonate, add it to deionized water, and add water to make the total volume of the solution 201 L to obtain a sodium carbonate solution with a sodium carbonate concentration of 100 g / L.

[0059] Heat both the metal ion solution and the sodium carbonate solution to 60°C, and slowly add the sodium carbonate solution to the metal ion solution at a stirring speed of 100 r / min. After the addition, continue stirring for 30 minutes until the precipitation reaction is completely completed.

[0060] Filter the reaction product and wash it repeatedly with water until the chloride ion concentration in the filtrate is less than 50 ppm to obtain a precipitate.

[0061] Put the precipitate into an oven and dry it at 150°C for 6 hours to obtain the precursor.

[0062] Put the precursor into a hydrogen reduction furnace and reduce it at 620 °C for 4 hours. Set the hydrogen volume flux to 0.03 m / s.

[0063] Crush and screen the reduced product to obtain ultrafine pre-alloyed powder.

[0064] In this example, the composition of the ultrafine pre-alloyed powder is: iron 44.9 wt%, cobalt 24.7 wt%, copper 29.5 wt%, phosphorus 0.5 wt%, oxygen 0.3 wt%, and the balance is inevitable impurities. Its Fisher particle size is 1.4 μm.

[0065] Load the pre-alloyed powder into a steel mold with dimensions of 50 * 10 * 5 mm, cold press it at a pressure of 2 tons per square centimeter, and place the formed blank in a hydrogen atmosphere sintering furnace. Sinter it at 900 °C for 60 min to obtain a diamond tool sintered body.

[0066] After testing, the density of the diamond sintered body reaches 98.6%, the Rockwell hardness HRB106, the flexural strength 1500 MPa, and the impact toughness is 32 J / cm 2 .

[0067] Example 2

[0068] Weigh 21.5 kg of ferrous sulfate heptahydrate, 12.5 kg of copper sulfate pentahydrate, and 12.2 kg of cobalt sulfate heptahydrate, dissolve them in deionized water, and add water to make the total volume of the solution 100 L to obtain a metal ion solution. The iron ion concentration in the solution is 43 g / L, the cobalt ion concentration is 25 g / L, and the copper ion concentration is 32 g / L.

[0069] Weigh 490 g of iron phosphate and add it to the metal ion solution.

[0070] Weigh 19.55 kg of sodium carbonate, add it to deionized water, and add water to make the total volume of the solution 195.5 L to obtain a sodium carbonate solution. The sodium carbonate concentration is 100 g / L.

[0071] Heat both the metal ion solution and the sodium carbonate solution to 50 °C. At a stirring speed of 120 r / min, slowly add the sodium carbonate solution to the metal ion solution. After adding, continue stirring for 30 minutes until the precipitation reaction is completely completed.

[0072] Filter the reaction product and wash it repeatedly with water until the chloride ion concentration in the filtrate is less than 50 ppm to obtain a precipitate.

[0073] Put the precipitate into an oven and dry it at 130 °C for 8 hours to obtain a precursor.

[0074] Put the precursor into a hydrogen reduction furnace and reduce it at 600 °C for 5 hours. Set the hydrogen volume flux to 0.03 m / s.

[0075] The reduced product is crushed and screened to obtain ultrafine pre-alloyed powder.

[0076] In this example, the composition of the ultrafine pre-alloyed powder is: iron 42.5 wt%, cobalt 24.5 wt%, copper 31.5 wt%, phosphorus 1 wt%, oxygen 0.4 wt%, and the balance is inevitable impurities. Its Fisher particle size is 1.2 μm.

[0077] The pre-alloyed powder is loaded into a steel mold with dimensions of 50 * 10 * 5 mm and cold-pressed into shape under a pressure of 2 tons per square centimeter. The formed blank is placed in a hydrogen atmosphere sintering furnace and sintered at 900 °C for 60 min to obtain a sintered body of diamond tools.

[0078] After testing, the density of the sintered body of diamond tools reaches 99.1%, the Rockwell hardness HRB110, the flexural strength 1350 MPa, and the impact toughness is 29 J / cm 2 。

[0079] Comparative Example 1

[0080] Weigh 22.96 kg of ferrous sulfate heptahydrate, 11.8 kg of copper sulfate pentahydrate, and 12.2 kg of cobalt sulfate heptahydrate, dissolve them in deionized water, and add water to make the total volume of the solution 100 L to obtain a metal ion solution. The concentration of iron ions in the solution is 45 g / L, the concentration of cobalt ions is 25 g / L, and the concentration of copper ions is 30 g / L.

[0081] Weigh 103.69 g of iron phosphate and add it to the metal ion solution.

[0082] Weigh 20 kg of sodium carbonate and add it to deionized water, and add water to make the total volume of the solution 200 L to obtain a sodium carbonate solution. The concentration of sodium carbonate is 100 g / L.

[0083] Heat both the metal ion solution and the sodium carbonate solution to 60 °C. Under a stirring speed of 100 r / min, slowly add the sodium carbonate solution to the metal ion solution. After the addition, continue stirring for 30 minutes until the precipitation reaction is completely completed.

[0084] Filter the reaction product and wash it repeatedly with water until the chloride ion concentration in the filtrate is less than 50 ppm to obtain a precipitate.

[0085] Put the precipitate into an oven and dry it at 150 °C for 6 hours to obtain a precursor.

[0086] Put the precursor into a hydrogen reduction furnace and reduce it at 620 °C for 4 hours. The hydrogen volume flux is set to 0.03 m / s.

[0087] The reduced product is crushed and screened to obtain ultrafine pre-alloyed powder.

[0088] In this embodiment, the composition of the ultra-fine pre-alloyed powder is: iron 45.3 wt%, cobalt 24.7 wt%, copper 29.5 wt%, phosphorus 0.2 wt%, oxygen 0.2 wt%, and the balance is inevitable impurities. Its Fisher particle size is 1.4 μm.

[0089] Load the pre-alloyed powder into a steel mold with dimensions of 50 * 10 * 5 mm, cold press it into shape under a pressure of 2 tons per square centimeter, place the formed blank in a hydrogen atmosphere sintering furnace, and sinter it at 900 °C for 60 min to obtain a sintered body of the diamond tool.

[0090] After testing, the density of the sintered body of the diamond tool reaches 92%, the Rockwell hardness HRB100, the flexural strength is 1235 MPa, and the impact toughness is 25 J / cm 2 .

[0091] Comparative Example 2

[0092] Weigh 21.89 kg of ferrous sulfate heptahydrate, 11.8 kg of copper sulfate pentahydrate, and 12.2 kg of cobalt sulfate heptahydrate, dissolve them in deionized water, and add water to make the total volume of the solution 100 L to obtain a metal ion solution. The concentration of iron ions in the solution is 45 g / L, the concentration of cobalt ions is 25 g / L, and the concentration of copper ions is 30 g / L.

[0093] Weigh 1037 g of iron phosphate and add it to the metal ion solution.

[0094] Weigh 19 kg of sodium carbonate and add it to deionized water, and add water to make the total volume of the solution 190 L to obtain a sodium carbonate solution with a concentration of 100 g / L.

[0095] Heat both the metal ion solution and the sodium carbonate solution to 60 °C, and slowly add the sodium carbonate solution to the metal ion solution at a stirring speed of 100 r / min. After the addition, continue stirring for 30 minutes until the precipitation reaction is completely completed.

[0096] Filter the reaction product and wash it repeatedly with water until the chloride ion concentration in the filtrate is less than 50 ppm to obtain a precipitate.

[0097] Put the precipitate into an oven and dry it at 150 °C for 6 hours to obtain a precursor.

[0098] Put the precursor into a hydrogen reduction furnace and reduce it at 620 °C for 4 hours, and set the hydrogen volume flux to 0.03 m / s.

[0099] Crush and screen the reduction product to obtain ultra-fine pre-alloyed powder.

[0100] In this example, the composition of the ultra-fine pre-alloyed powder is as follows: iron 43.2 wt%, cobalt 24.7 wt%, copper 29.5 wt%, phosphorus 2 wt%, oxygen 0.5 wt%, and the balance is inevitable impurities. Its Fisher particle size is 1.4 μm.

[0101] Load the pre-alloyed powder into a steel mold with dimensions of 50*10*5 mm, and cold press it into shape under a pressure of 2 tons per square centimeter. Place the formed blank in a hydrogen atmosphere sintering furnace and sinter it at 900 °C for 60 min to obtain a sintered body of the diamond tool.

[0102] After testing, the density of the sintered body of the diamond tool reaches 96.1%, the Rockwell hardness HRB98, the flexural strength 1074 MPa, and the impact toughness is 5 J / cm 2 .

[0103] Comparative Example 3

[0104] Weigh 22.5 kg of ferrous sulfate heptahydrate, 11.8 kg of copper sulfate pentahydrate, and 12.2 kg of cobalt sulfate heptahydrate, dissolve them in deionized water, and add water to make the total volume of the solution 100 L to obtain a metal ion solution. The iron ion concentration in the solution is 45 g / L, the cobalt ion concentration is 25 g / L, and the copper ion concentration is 30 g / L.

[0105] Weigh 20 kg of sodium carbonate and add it to deionized water, and add water to make the total volume of the solution 200 L to obtain a sodium carbonate solution. The sodium carbonate concentration is 100 g / L.

[0106] Heat both the metal ion solution and the sodium carbonate solution to 60 °C. Under a stirring speed of 100 r / min, slowly add the sodium carbonate solution to the metal ion solution. After the addition, continue stirring for 30 minutes until the precipitation reaction is completely completed.

[0107] Filter the reaction product and wash it repeatedly with water until the chloride ion concentration in the filtrate is less than 50 ppm to obtain a precipitate.

[0108] Put the precipitate into an oven and dry it at 150 °C for 6 hours. Mix the dried precipitate with 245 g of iron phosphate and stir it at 120 revolutions per minute for 30 minutes to obtain a precursor.

[0109] Put the precursor into a hydrogen reduction furnace and reduce it at 620 °C for 4 hours. Set the hydrogen volume flux to 0.03 m / s.

[0110] Crush and screen the reduction product to obtain ultra-fine pre-alloyed powder.

[0111] In this example, the composition of the ultra-fine pre-alloyed powder is as follows: iron 44.9 wt%, cobalt 24.7 wt%, copper 29.5 wt%, phosphorus 0.5 wt%, oxygen 0.3 wt%, and the balance is inevitable impurities. Its Fisher particle size is 1.4 μm.

[0112] The pre-alloyed powder was loaded into a steel mold with dimensions of 50*10*5 mm and cold-pressed into shape under a pressure of 2 tons per square centimeter. The formed green body was placed in a hydrogen atmosphere sintering furnace and sintered at 900 °C for 60 min to obtain a sintered body of the diamond tool.

[0113] After testing, the density of the sintered body of the diamond tool reached 95.6%, the Rockwell hardness HRB was 102, the flexural strength was 1257 MPa, and the impact toughness was 16 J / cm 2 It is considered that the precipitated powder after drying will agglomerate, the particles will become coarser, the uniformity of mechanical mixing is insufficient, and phosphorus segregation will occur, resulting in a decrease in both the density and toughness of the product.

[0114] Comparative Example 4

[0115] Weigh 22.5 kg of ferrous sulfate heptahydrate, 11.8 kg of copper sulfate pentahydrate, and 12.2 kg of cobalt sulfate heptahydrate, dissolve them in deionized water, and add water to make the total volume of the solution 100 L to obtain a metal ion solution. The iron ion concentration in the solution is 45 g / L, the cobalt ion concentration is 25 g / L, and the copper ion concentration is 30 g / L.

[0116] Weigh 20 kg of sodium carbonate and add it to deionized water, and add water to make the total volume of the solution 200 L to obtain a sodium carbonate solution. The sodium carbonate concentration is 100 g / L.

[0117] Heat both the metal ion solution and the sodium carbonate solution to 60 °C. Under a stirring speed of 100 r / min, slowly add the sodium carbonate solution to the metal ion solution. After the addition is completed, continue stirring for 30 minutes until the precipitation reaction is completely finished.

[0118] Filter the reaction product and wash it repeatedly with water until the chloride ion concentration in the filtrate is less than 50 ppm to obtain a precipitate.

[0119] Put the precipitate into an oven and dry it at 150 °C for 6 hours to obtain a precursor.

[0120] Put the precursor into a hydrogen reduction furnace and reduce it at 620 °C for 4 hours. The hydrogen volume flux is set to 0.03 m / s.

[0121] Crush and screen the reduction product to obtain ultrafine pre-alloyed powder with a Fisher particle size of 1.4 μm.

[0122] The pre-alloyed powder was loaded into a steel mold with dimensions of 50*10*5 mm and cold-pressed into shape under a pressure of 2 tons per square centimeter. The formed green body was placed in a hydrogen atmosphere sintering furnace and sintered at 900 °C for 60 min to obtain a sintered body of the diamond tool.

[0123] Upon detection, the density of the diamond tool sintered body reaches 92%, the Rockwell hardness is HRB97, and the flexural strength is 1069 MPa.

[0124] Comparative Example 5

[0125] The difference between this comparative example and Comparative Example 4 is that the pre-alloyed powder is filled into a steel mold with dimensions of 50*10*5 mm and cold-pressed into shape under a pressure of 2 tons per square centimeter. The formed green body is placed in a hydrogen atmosphere sintering furnace and sintered at 1000 °C for 60 min to obtain a diamond tool sintered body.

[0126] Upon detection, the density of the diamond tool sintered body reaches 95%, the Rockwell hardness is HRB99, and the flexural strength is 1214 MPa.

[0127] Comparative Example 6

[0128] The difference between this comparative example and Example 1 is that the ultrafine pre-alloyed powder obtained by crushing and screening the reduction product has a Fisher particle size of 5 μm. The density of the prepared diamond tool sintered body reaches 95%, the Rockwell hardness is HRB98, and the flexural strength is 1176 MPa.

[0129] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present invention. Any reference signs in the claims should not be construed as limiting the claimed rights.

[0130] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An ultrafine pre-alloyed powder, characterized in that, Comprising at least the following components by weight percentage: iron 30% - 50%, cobalt 20% - 30%, copper 25% - 40%, phosphorus 0.5% - 1%.

2. The superfine pre-alloyed powder according to claim 1, characterized in that, The Fisher particle size is less than or equal to 2 μm.

3. A method for preparing an ultrafine pre-alloyed powder, characterized in that, Including the following steps: Dissolve the soluble acidic salts of iron, the soluble acidic salts of cobalt, and the soluble acidic salts of copper in water to prepare a metal ion solution; Mix the phosphate and the metal ion solution to prepare a mixed system; Heat the mixed system to 40°C - 60°C, add a weak base, and stir to react to form a precipitate; Wash the precipitate with water and then dry to obtain a precursor; Reduce the precursor to obtain an ultrafine pre-alloy powder; Wherein, the phosphate is at least one of iron phosphate, cobalt phosphate, and copper phosphate.

4. The method for preparing the ultrafine pre-alloyed powder according to claim 3, characterized in that, The particle size of the phosphate is 0.5 μm - 2 μm.

5. The method for preparing the ultrafine pre-alloyed powder according to claim 3, wherein The weak base is at least one of sodium carbonate, ammonium bicarbonate, ammonium oxalate, ammonium carbonate, and ammonia water.

6. The preparation method of the superfine pre-alloyed powder according to claim 3, characterized in that, Based on the amount of the weak base required in the stoichiometric ratio in the precipitate, when adding the weak base to the mixed system, the addition amount of the weak base is 5% - 10% in excess.

7. The method for preparing the superfine pre-alloyed powder according to claim 3, characterized in that, In the metal ion solution, the total metal ion concentration is 60 g / L - 180 g / L.

8. The method for preparing the ultrafine pre-alloyed powder according to claim 3, wherein, The drying temperature is 120°C - 160°C, and the time is 6 h - 8 h.

9. The preparation method of the superfine pre-alloyed powder according to claim 3, characterized in that, The reduction is carried out in a hydrogen atmosphere, the temperature is 500°C - 700°C, the time is 4 h - 6 h, and the hydrogen volume flux is 0.03 m / s - 0.05 m / s.

10. A diamond sintered body, characterized in that, Prepared at least using the ultrafine pre-alloy powder described in any one of claims 1 - 2 or the ultrafine pre-alloy powder obtained by the preparation method of the ultrafine pre-alloy powder described in any one of claims 3 - 9.

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