Preparation method of steel-bonded cemented carbide with low oxygen content

Abstract

The present invention discloses a preparation method of steel-bonded cemented carbide with low oxygen content, belonging to the field of materials technology. In this method, a polymer compound solution M1 is mixed uniformly with the steel-bonded cemented carbide composite powder to form a paste, and after drying treatment, cold pressing or cold isostatic pressing is carried out to obtain a cold-pressed green body of steel-bonded cemented carbide; after vacuum sintering or low-pressure sintering, a vacuum-sintered or low-pressure-sintered ingot of steel-bonded cemented carbide is obtained. The present invention utilizes a carbon reduction reaction to eliminate the oxide film on the surface of the raw material powder, reduce the oxygen content of the steel-bonded cemented carbide, and at the same time can also improve its sinterability and hot workability, ultimately realizing the preparation of steel-bonded cemented carbide with high density, low micro-defects and high mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of materials, and particularly relates to a method for preparing steel-bonded cemented carbide with low oxygen content. Background Art

[0002] With the rapid development of fields such as petrochemical industry, mining, smelting, machining, and transportation, the demand for materials with high modulus, high strength, high hardness, wear resistance, and corrosion resistance is becoming increasingly urgent.

[0003] Steel-bonded cemented carbide is a steel-based composite material with steel as the binder and hard compounds as the reinforcing phase. Its tissue characteristic is that fine reinforcing phase particles are evenly distributed in the steel matrix. Therefore, it combines the advantages of the reinforcing phase and steel, has high hardness, wear resistance, relatively high elastic modulus and flexural strength, better plasticity and toughness than ordinary cemented carbide, and good physical and mechanical properties. At the same time, it has process characteristics such as the machinability, heat treatability, and forging property of steel, filling the gap between traditional cemented carbides (such as WC-Co, etc.) and steel. Moreover, there are many types of steel as the binder phase material, providing a good platform for its diverse performance characteristics. In the early 1960s, after TiC steel-bonded cemented carbide was first put on the market in the United States under the trademark Ferro-TiC, many countries in the world, such as Germany, the Netherlands, the Soviet Union, the United Kingdom, France, etc., successively promoted and used it, mainly applied in the fields of cutting tools, non-cutting metal processing tools, and wear-resistant components. In addition, due to the good damping characteristics of TiC steel-bonded cemented carbide, it is widely used in the manufacture of various shock-absorbing tools, such as the landing gear of the Boeing 737 aircraft in the United States, the drive screw in the coal gasification industry, etc.

[0004] Currently, the methods for preparing steel-bonded cemented carbide include melt infiltration, CVD, PVD, flame spraying, magnetron sputtering, laser cladding, in-situ synthesis, and powder metallurgy method, etc. Generally, the hard phases of steel-bonded cemented carbide (such as TiC, 4.9 g / cm 3 ; B4C, 2.5 g / cm 3 ; WC, 15.5 g / cm 3 ), and the alloy steel binder phase (7.8 g / cm 3There is a large density difference between the two (left and right). Using the traditional casting method will lead to the segregation of hard phases, making it difficult to prepare materials with a uniform distribution of hard phases. Therefore, it is necessary to first prepare the hard phase into a preform, and then infiltrate the molten alloy steel binder phase into the pores of the hard phase preform. However, the preform is composed of stacked hard phase particles, and it is difficult to adjust the volume fraction of the hard phase, which greatly limits the designability of steel-bonded cemented carbides. In addition, the high temperature of the liquid-phase method not only easily causes serious interfacial reactions, but also places higher requirements on molds, infiltration equipment, etc. Therefore, the powder metallurgy method still dominates at present. The powder metallurgy method for preparing steel-bonded alloys is mainly a process of preparing steel-bonded cemented carbide products by mixing, shaping, and sintering hard phase particles with elemental powders or alloy powders such as iron powder. The fact that this method can become the most widely used method in both the research field and the production field is mainly determined by a series of technical characteristics:

[0005] (1) The sintering temperature is relatively low, and the ratio of solid-liquid phases during sintering can be controlled according to the solid-liquidus temperature of the binder phase;

[0006] (2) The combined effects of different compositions of the hard phase and the steel matrix can be fully utilized to achieve various performance design requirements;

[0007] (3) Conditions are provided for adjusting the content and size range of the hard phase;

[0008] (4) It ensures the uniformity of the hard phase in the steel matrix and avoids serious segregation of components;

[0009] (5) It better inhibits grain growth, and at the same time, the higher dislocation density provides the possibility for steel-bonded cemented carbides to obtain superior mechanical properties.

[0010] However, the powder metallurgy method also has the following disadvantages:

[0011] (1) Raw material metal powders inevitably come into contact with air during production, storage, and mixing processes, and oxide films are formed on the surface of the metal powders. This will not only reduce the wettability between the binder phase and the hard phase and the interfacial bonding strength, but may even lead to the formation of defects such as pores in severe cases;

[0012] (2) The formation of oxide films on the surface of metal powders may also cause grain boundary embrittlement of the steel binder phase, reducing the flexural strength and impact toughness of steel-bonded cemented carbides;

[0013] (3) Although fine grain strengthening can improve the strength of materials, the finer the metal powder, the larger its specific surface area. A large amount of introduced oxide films can even reduce the sinterability of the composite powder of steel-bonded cemented carbides, ultimately resulting in loose structure and sharp decline in mechanical properties of steel-bonded cemented carbides.

[0014] Traditional metal reduction methods include hydrogen reduction, carbon reduction, etc. Given the chemical properties of Fe element and phenomena such as hydrogen embrittlement, carbon reduction method is usually adopted in steel smelting. However, powder metallurgy method belongs to solid-phase method. It is difficult to achieve uniform distribution of carbon element by volume diffusion with traditional methods such as adding carbon powder, resulting in too high carbon content in some areas and the oxide film in some areas cannot be reduced by carbon. In addition, research shows that the carbon content of the binder phase is an important factor affecting the brittleness of steel-bonded cemented carbide. Too high local carbon content will lead to sharp deterioration of properties such as hot forging property and toughness of the material.

[0015] Therefore, how to reduce the oxygen content of steel-bonded cemented carbide, remove the oxide film at the grain boundaries of the metal binder phase and the phase interface between the hard phase and the binder phase, while not forming excessive carbon, is one of the key technologies for preparing high-performance steel-bonded cemented carbide. Summary of the Invention

[0016] The purpose of the present invention is to provide a preparation method of steel-bonded cemented carbide with low oxygen content. The prepared steel-bonded cemented carbide has characteristics such as good hot forging property, high toughness and strength, and has little influence on the current conventional powder metallurgy preparation process and its production cost.

[0017] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0018] A preparation method of steel-bonded cemented carbide with low oxygen content, comprising the following steps:

[0019] (1) Prepare a polymer compound solution M1 with a concentration of 0.2 - 10 wt.%.

[0020] (2) Weigh the hard phase particles and binder phase metal powder of steel-bonded cemented carbide in proportion, and mix them evenly by mechanical mixing and / or ball milling and other methods to obtain a steel-bonded cemented carbide composite powder.

[0021] (3) Mix the solution M1 and the steel-bonded cemented carbide composite powder obtained in step (2) evenly in proportion and form a paste to obtain a steel-bonded cemented carbide composite powder coated with a polymer compound film.

[0022] (4) Perform drying treatment on the steel-bonded cemented carbide composite powder coated with a polymer compound film obtained in step (3).

[0023] (5) Perform cold pressing or cold isostatic pressing treatment on the steel-bonded cemented carbide composite powder coated with a polymer compound film after drying treatment in step (4) to obtain a cold-pressed green body of steel-bonded cemented carbide.

[0024] (6) Perform sintering treatment on the cold-pressed green body of steel-bonded cemented carbide obtained in step (5). The sintering method is vacuum sintering or low-pressure sintering, etc. After sintering, a vacuum sintered or low-pressure sintered ingot of steel-bonded cemented carbide is obtained.

[0025] The vacuum sintered or low-pressure sintered ingot of steel-bonded cemented carbide obtained in step (6) can be further subjected to hot isostatic pressing sintering to obtain a hot isostatic pressing sintered ingot of steel-bonded cemented carbide.

[0026] In the above step (1), the polymer compound is one or more of sucrose, tar resin, phenolic resin, alkyd resin, vinyl tar, and dopamine hydrochloride; the polymer compound solution M1 is formed by dissolving the polymer compound in a solvent, and the solvent is a liquid such as water, gasoline, toluene, alcohols, esters, ether alcohols, or chlorinated hydrocarbons.

[0027] In the above step (1), the viscosity of the polymer compound solution M1 is adjusted by adding a binder, and the binder is one or more of rosin, natural rubber, cellulose, polyvinyl alcohol, and synthetic resin; the viscosity of the polymer compound solution M1 is adjusted to 1-100 Pa•s.

[0028] In the above step (2), the hard phase particles of the steel-bonded cemented carbide are one or more of WC, TiC, TiB2, B4C, and Ti(C,N) particles; the binder phase powder of the steel-bonded cemented carbide is alloy steel powder, such as 15-5PH, 17-4PH, 316L, and Fe-Cr-Ni-Co-Mo-Ti series stainless steel powder, etc.; or, the binder phase powder of the steel-bonded cemented carbide is alloy steel component element powder (i.e., the raw material powders for preparing alloy steel, including elemental powders and intermediate alloy powders of each element, also called alloy steel element powder), such as Fe powder, Al powder, Cr powder, Ni powder, Co powder, Mo powder, Cu powder, Ti powder, etc. mixed according to the chemical composition ratio of alloy steel.

[0029] In the above step (2), the volume fraction of the hard phase in the steel-bonded cemented carbide composite powder is 5-50%, and the particle sizes of the hard phase particles and the binder phase powder are both 0.2-100 μm.

[0030] In the above step (3), the ratio in the step of mixing the solution M1 and the steel-bonded cemented carbide composite powder evenly according to the ratio refers to the ratio between the number of moles of oxygen content in the steel-bonded cemented carbide composite powder and the number of moles of residual carbon of the polymer compound in the solution M1, and the ratio range is 1:(0.1-1.0).

[0031] In the above step (4), the drying treatment is natural drying treatment and / or heating drying, and the temperature of the drying treatment is 20-500°C.

[0032] In the above step (6), the temperature range of the vacuum sintering and low-pressure sintering is 1150-1450°C, and the pressure range of the low-pressure sintering is 0.1-10 MPa.

[0033] The temperature range of the hot isostatic pressing sintering is 1250-1450° C., and the pressure range of the hot isostatic pressing sintering is 10-200 MPa.

[0034] The advantages and beneficial effects of the present invention are as follows:

[0035] The method for preparing low-oxygen content steel-bonded cemented carbide of the present invention utilizes a carbon reduction reaction to eliminate the oxide film on the surface of the raw material powder, thereby reducing the oxygen content of the steel-bonded cemented carbide. At the same time, it can also improve its sintering properties and hot workability, ultimately achieving the preparation of steel-bonded cemented carbide with high density, low microscopic defects and high mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a microstructure photograph of 5 vol.% TiC / 316L steel-bonded cemented carbide prepared by the low-pressure sintering process in Example 1;

[0037] Figure 2 This is a microstructure photograph of the 10 vol.% TiC / 15-5PH steel-bonded cemented carbide prepared by the vacuum sintering process in Example 2;

[0038] Figure 3 Microstructure photographs of 5 vol.% B4C + 25 vol.% TiC / Fe-Cr-Ni-Co-Mo-Ti steel-bonded cemented carbide prepared by the low-pressure sintering process in Example 3; wherein: (a) low-magnification metallographic photograph; (b) high-magnification metallographic photograph;

[0039] Figure 4 This is a microstructure photograph of the 40 vol.% Ti(C,N) / 17-4PH steel-bonded cemented carbide prepared by vacuum sintering combined with hot isostatic pressing in Example 4;

[0040] Figure 5 Microstructure photographs of the 50 vol.% TiC / Fe-Cr-Ni-Co-Mo-Cu steel-bonded cemented carbide prepared by the hot isostatic pressing and sintering process in Example 5; including: (a) cold-pressed green body; (b) low-magnification metallographic photograph; (c) high-magnification metallographic photograph. DETAILED DESCRIPTION

[0041] See also Figures 1-5As shown, the present invention provides a method for preparing steel-bonded cemented carbide with low oxygen content. A high-residual-carbon-rate polymer compound is used as a precursor. The polymer compound is uniformly coated on the surface of hard-phase and binder-phase powders / particles by the solution coating method. After powder mixing, drying, cold pressing, vacuum / low-pressure / hot isostatic pressing sintering and other powder metallurgy processes, steel-bonded cemented carbide with low oxygen content is prepared. This method uses the carbon generated by the high-temperature decomposition / cracking of the polymer compound as a reducing agent, and combines the solution coating method to achieve the molecular-level uniform distribution of the polymer compound on the surface of hard-phase and binder-phase powders / particles. Furthermore, a carbon film is formed on the surface of metal powders by using the decomposition / cracking phenomenon of the polymer compound during the high-temperature sintering process. This carbon film then undergoes an oxidation-reduction reaction with the metal powder surface oxides, ultimately achieving the reduction of the oxygen content in the steel-bonded cemented carbide. In addition, the clean metal surface formed during the reduction of the metal powder surface oxides is also beneficial to improving the sinterability of the steel-bonded cemented carbide and enhancing the bonding strength of the interface between the hard phase and the binder phase, which plays an important role in improving the density, corrosion resistance and mechanical properties of the steel-bonded cemented carbide. In this application, by moderately adding a binder to the polymer compound solution, the coating property of the polymer compound on the surface of hard-phase / binder-phase powders is enhanced, and then the molecular-level distribution of the polymer compound participating in carbon elements is achieved. By strictly controlling the molar ratio between the oxygen element and the introduced carbon element in the steel-bonded cemented carbide, while effectively reducing the oxygen content in the steel-bonded cemented carbide, the formation of defects such as excessive carbon elements or carbon particles in the steel-bonded cemented carbide is avoided, which is of great significance for improving the impact toughness and flexural strength and other indicators of the steel-bonded cemented carbide.

[0042] The polymer compounds required in the present invention include sucrose, tar resin, phenolic resin, alkyd resin, vinyl tar, dopamine hydrochloride, etc.; the solvents of the polymer compound solution are liquids such as water, gasoline, toluene, alcohols, esters, ether alcohols, chlorinated hydrocarbons, etc.; to improve the film-forming property of the polymer organic solution on the surface of the hard phase / metal powder, a binder can be added to adjust the solution viscosity, and the binder includes rosin, natural rubber, cellulose, polyvinyl alcohol, synthetic resin, etc.

[0043] In the present invention, the oxygen content of the steel-bonded cemented carbide composite powder (i.e., the composite powder in which the hard-phase and binder-phase powders are uniformly mixed) and the residual carbon rate of the polymer compound are measured values. Under the condition that the preparation process remains unchanged (parameters such as the composition and addition ratio of the coated polymer solution and the sintering process are stable), the oxygen content of different batches of the steel-bonded cemented carbide composite powder should be detected. Then, according to the molar ratio value range of the oxygen content to the residual carbon of the polymer compound (1:0.1 - 1), the composition ratio of the polymer compound solution is calculated and determined.

[0044] Example 1

[0045] In this embodiment, 5 vol.% TiC / 316L steel-bonded cemented carbide was prepared, with a tensile strength above 1500 MPa and a hardness of HRC 45 or above at room temperature. Meanwhile, it has good hot deformation processing performance, wear resistance and corrosion resistance.

[0046] The specific steps of this embodiment are as follows:

[0047] (1) Using deionized water as the solvent, dopamine hydrochloride as the high molecular compound solute, and polyvinyl alcohol as the binder, a high molecular compound solution M1 with a viscosity of about 30 Pa•s was prepared according to the ratio of dopamine hydrochloride: polyvinyl alcohol: deionized water = 4 g: 3 g: 500 g for standby.

[0048] (2) The TiC particles (particle size 3 - 50 μm) selected in this embodiment are used as the hard phase, and 316L stainless steel alloy powder (particle size 5 - 100 μm) is selected as the raw material for the binder phase.

[0049] Furthermore, the TiC particles and 316L stainless steel alloy powder were weighed respectively according to the ratio of 3.2 wt.% and 96.8 wt.%.

[0050] Furthermore, the weighed TiC and 316L powders were put into a mixing tank, 5 mm diameter steel balls were weighed according to the ball-to-material weight ratio of 5:1 and put into the aforementioned mixing tank, and ball milling was carried out at a speed of 200 rpm for 6 hours, and then the steel balls were removed using a sieve to obtain a composite powder with uniformly mixed hard phase particles and binder phase metal powder.

[0051] (3) 800 g of the M1 solution prepared in step (1) was weighed, and 5 kg of the composite powder prepared in step (2) was weighed. The two were stirred evenly to form a paste to obtain a steel-bonded cemented carbide composite powder coated with a high molecular compound film.

[0052] (4) The steel-bonded cemented carbide composite powder coated with the high molecular compound film obtained in step (3) was put into a stainless steel tray, and then the stainless steel tray was put into an explosion-proof drying oven at 75 °C for drying treatment for 4 hours, and then put into a nitrogen atmosphere resistance furnace and kept at 500 °C for 2 hours to obtain a dried steel-bonded cemented carbide composite powder coated with a high molecular compound film.

[0053] (5) The steel-bonded cemented carbide composite powder coated with the high molecular compound film obtained in step (4) was put into a mold, and cold pressing was carried out at 150 MPa and kept the pressure for 1 minute to obtain a cold-pressed green body of steel-bonded cemented carbide.

[0054] (6) The cold-pressed green compact of steel-bonded cemented carbide described in step (5) is put into a low-pressure sintering furnace and evacuated first. When the pressure in the furnace is less than 5 Pa, it starts to heat up at a rate of 10 °C / min to 1250 °C and is kept warm for 1.5 hours, then heats up at a rate of 5 °C / min to 1450 °C and is kept warm for 1 hour. Then, under the condition of keeping the sintering temperature of 1450 °C unchanged, Ar gas is filled to 10 MPa and kept warm for 1 hour. After the low-pressure sintering treatment is completed, the furnace is cooled, and a low-pressure sintered ingot of TiC steel-bonded cemented carbide is obtained after being taken out of the furnace.

[0055] Note: In Example 1, the oxygen content of 5 kg of composite powder is about 32 grams (2 mol), and the residual carbon content of 800 grams of compound solution M1 during subsequent drying and vacuum sintering treatment is about 2.4 grams (i.e., 0.2 mol). The molar ratio of oxygen content to residual carbon content is about 1:0.1; under the preparation process of Example 2, a small amount of high-molecular compound undergoes a carbon reduction reaction with the oxide film on the surface of 316L alloy powder. Therefore, no carbonaceous particles are found in the TiC cemented carbide (as Figure 1 shown); Chemical analysis shows that the oxygen concentration of 5 vol.% TiC / 316L steel-bonded cemented carbide is 0.60 wt.%, and the oxygen content of 5 kg of steel-bonded cemented carbide is 30 grams, which is 2 grams lower than the oxygen content of the composite powder (32 g); In addition, high-speed ball milling can also effectively refine the particle sizes of the hard phase and the binder phase; after solid solution treatment (1050 °C, 60 min) and aging treatment (480 °C, 360 min), the room-temperature density of 5 vol.% TiC / 316L steel-bonded cemented carbide reaches 7.79 g / cm 3 (more than 99.5% of the theoretical density), the tensile strength reaches more than 1500 MPa, the hardness HRC reaches more than 45, and it also has good hot deformation processing performance, wear resistance and corrosion resistance.

[0056] Example 2

[0057] For 10 vol.% TiC / 15-5PH steel-bonded cemented carbide, its room-temperature flexural strength reaches more than 1400 MPa, the hardness HRC reaches more than 50, and it also has good hot deformation processing performance, wear resistance and corrosion resistance.

[0058] The specific steps of this example are as follows:

[0059] (1) Using anhydrous alcohol as the solvent, phenolic resin as the high-molecular compound solute, and rosin as the binder, prepare a high-molecular compound solution M1 with a viscosity of about 40 Pa•s for use according to the ratio of phenolic resin: rosin: alcohol = 10 g: 50 g: 500 g;

[0060] (2) The TiC particles (particle size: 0.2 - 50 μm) selected in this embodiment are used as the hard phase, and 15-5PH stainless steel alloy powder (20 - 30 μm) is selected as the raw material for the bonding phase;

[0061] Further, TiC and 15-5PH stainless steel alloy powder are weighed respectively according to a weight ratio of 6.45% and 93.55%;

[0062] Further, the weighed TiC and 15-5PH stainless steel alloy powder are put into a mixing tank. Steel balls with a diameter of 5 mm are weighed according to a ball-to-material weight ratio of 10:1 and put into the aforementioned mixing tank. Ball milling is carried out at a rotational speed of 200 rpm for 6 hours, and then the steel balls are removed using a sieve to obtain a composite powder with uniformly mixed hard phase particles and bonding phase metal powder;

[0063] (3) Weigh 750 g of the M1 solution prepared in step (1) and 5 kg of the composite powder prepared in step (2), stir the two evenly to form a paste, and obtain a steel-bonded cemented carbide composite powder coated with a polymer compound film;

[0064] (4) The steel-bonded cemented carbide composite powder coated with the polymer compound film obtained in step (3) is put into a stainless steel tray, and then the stainless steel tray is put into an explosion-proof drying oven at 75 °C for drying treatment for 4 hours to obtain a dried steel-bonded cemented carbide composite powder coated with a polymer compound film;

[0065] (5) The steel-bonded cemented carbide composite powder coated with the polymer compound film obtained in step (4) is put into a mold, and cold pressing is carried out at 200 MPa and holding the pressure for 1 minute to obtain a steel-bonded cemented carbide cold-pressed green compact;

[0066] (6) The steel-bonded cemented carbide cold-pressed green compact described in step (5) is put into a vacuum sintering furnace to evacuate first. When the pressure in the furnace is less than 5 Pa, it starts to heat up at a rate of 10 °C / min to 1200 °C and hold for 1.5 hours, then heats up at a rate of 5 °C / min to 1430 °C and holds for 2 hours to complete the vacuum sintering treatment, and then cools in the furnace. After taking out of the furnace, a 10 vol.% Ti(C,N) / 15-5PH steel-bonded cemented carbide vacuum sintered ingot is obtained.

[0067] Note: In Example 2, the oxygen content of 5 kg of the composite powder is about 15 grams (2 mol), and the residual carbon content of 750 grams of the compound solution M1 during the subsequent drying and vacuum sintering treatment is about 2.4 grams (i.e., 0.2 mol). The molar ratio of the oxygen content to the residual carbon content is about 1:0.2; Under the preparation process of Example 2, high-energy ball milling can effectively reduce the particle size of the hard phase (such as Figure 2(as shown), and high-energy ball milling can also improve the dispersion of the hard phase; chemical analysis shows that the oxygen concentration of 10 vol.% TiC / 15-5PH steel-bonded carbide is 0.23 wt.%, and the oxygen content of 5 kg of steel-bonded carbide is 11.5 grams, which is 3.5 g lower than the oxygen content of the composite powder (15 g); after solution treatment (1050 °C, 12 min) and aging treatment (500 °C, 360 min), the room-temperature density of this steel-bonded carbide reaches 7.62 g / cm 3 (more than 99% of the theoretical density), the tensile strength reaches more than 1400 MPa, the hardness HRC reaches more than 50, and it also has good hot deformation processing performance, wear resistance and corrosion resistance.

[0068] Example 3

[0069] 5 vol.% B4C + 25 vol.% TiC / Fe-Cr-Ni-Co-Mo-Ti steel-bonded carbide, its room-temperature flexural strength reaches more than 1350 MPa, the hardness HRC reaches more than 60, and it also has good hot deformation processing performance, wear resistance and corrosion resistance.

[0070] The specific steps of this example are as follows:

[0071] (1) Using anhydrous alcohol as the solvent, phenolic resin as the macromolecular compound solute, and rosin as the binder, prepare a macromolecular compound solution M1 with a viscosity of 1 Pa•s according to the ratio of phenolic resin: rosin: methanol = 10 g: 5 g: 500 g for later use;

[0072] (2) The B4C particles (particle size of 7 μm) and TiC particles (particle size of 5 μm) selected in this example are used as the hard phase, and the Fe-12Cr-5Ni-5Co-5Mo-1.5Ti maraging stainless steel alloy powder (particle size of 5 - 100 μm) is selected as the binder phase raw material;

[0073] Further, weigh B4C, TiC, and 15-5PH stainless steel powder according to the ratio of 1.89%, 18.0%, and 80.1% respectively;

[0074] Further, put the weighed B4C, TiC, and Fe-Cr-Ni-Co-Mo-Ti stainless steel powder into the mixing tank, weigh steel balls with a diameter of 5 - 10 mm according to the ball-to-material weight ratio of 3:1 and put them into the aforementioned mixing tank, and perform mechanical mixing treatment at a speed of 20 rpm for 6 hours, then use a sieve to remove the steel balls to obtain a composite powder with uniformly mixed hard phase particles and binder phase metal powder;

[0075] (3) Weigh 750 g of the M1 solution prepared in step (1) and 5 kg of the composite powder prepared in step (2), stir the two evenly to form a paste, and obtain a steel-bonded cemented carbide composite powder coated with a polymer compound film;

[0076] (4) Place the steel-bonded cemented carbide composite powder coated with the polymer compound film obtained in step (3) into a stainless steel tray, and then place the stainless steel tray into an explosion-proof drying oven at 45 °C for drying treatment for 4 hours to obtain a dried steel-bonded cemented carbide composite powder coated with a polymer compound film;

[0077] (5) Place the steel-bonded cemented carbide composite powder coated with the polymer compound film obtained in step (4) into a mold, and perform cold pressing treatment at 150 MPa and hold the pressure for 1 minute to obtain a steel-bonded cemented carbide cold-pressed green compact;

[0078] (6) Place the steel-bonded cemented carbide cold-pressed green compact described in step (5) into a vacuum sintering furnace to evacuate first. When the pressure in the furnace is less than 5 Pa, start to heat up at a rate of 10 °C / min to 1250 °C and hold for 1 hour, then heat up at a rate of 5 °C / min to 1420 °C and hold for 2 hours. Then, under the condition of keeping the sintering temperature of 1420 °C unchanged, fill Ar gas to 0.1 MPa and hold for 1 hour. After completing the low-pressure sintering treatment, cool the furnace. After taking out of the furnace, obtain a 5vol.% B4C + 25vol.%TiC / Fe-Cr-Ni-Co-Mo-Ti steel-bonded cemented carbide low-pressure sintered ingot.

[0079] Note: In Example 3, the oxygen content of 5 kg of the composite powder is about 15 g (0.9375 mol), and the residual carbon content of 750 g of the compound solution M1 during the subsequent drying and vacuum sintering treatment is about 7.2 g (i.e., 0.6 mol). The molar ratio of the oxygen content to the residual carbon content is about 1:0.64; under the preparation process of Example 3, a small amount of polymer compound reacts with the oxide film on the surface of the metal powder by carbon reduction reaction. Therefore, no carbonaceous particles are found in the 5vol.% B4C + 25vol.%TiC / Fe-Cr-Ni-Co-Mo-Ti steel-bonded cemented carbide (such as Figure 3As shown in the figure, during the sintering process, part of the B4C hard phase can decompose and react with Ti in the binder phase to form TiB2 + TiC. This in-situ reaction can effectively improve the bonding strength between the hard phase and the binder phase. Chemical analysis shows that the oxygen concentration of 5vol.% B4C + 25vol.%TiC / Fe-Cr-Ni-Co-Mo-Ti steel-bonded cemented carbide is 0.11wt.%. In terms of 5kg of steel-bonded cemented carbide, the oxygen content is 5.5 grams, which is 9.5 grams lower than the oxygen content of the composite powder (15g). After the 5vol.% B4C + 25vol.%TiC / Fe-Cr-Ni-Co-Mo-Ti steel-bonded cemented carbide is subjected to solid solution treatment (1050 °C, 60 min) and aging treatment (480 °C, 360 min), its room temperature density reaches 7.31g / cm 3 (more than 99.5% of the theoretical density), the flexural strength reaches 1350 MPa, the hardness HRC reaches above 60, and at the same time, it has good hot deformation processing performance, wear resistance and corrosion resistance.

[0080] Example 4

[0081] For the 40vol.% Ti(C,N) / 17-4PH steel-bonded cemented carbide, its room temperature flexural strength reaches above 1250 MPa, the hardness HRC reaches above 60, and at the same time, it has good hot deformation processing performance, wear resistance and corrosion resistance.

[0082] The specific steps of this example are as follows:

[0083] (1) Using anhydrous alcohol as the solvent, phenolic resin as the high molecular compound solute, and rosin as the binder, prepare a high molecular compound solution M1 with a viscosity of about 25 Pa•s according to the ratio of phenolic resin: rosin: alcohol = 10g: 20g: 500g for later use;

[0084] (2) The Ti(C,N) particles (particle size 0.2 - 5μm) selected in this example are used as the hard phase, and the metal element or alloy powder of Fe (43μm), Cr (38μm), Ni (2μm), Cu (38μm), Mn (38μm) and FeNb70 (38μm) are selected as the binder phase raw materials;

[0085] Further, weigh Ti(C,N), Fe, Cr, Ni, Cu, Mn and FeNb70 powders according to the ratios of 29.5%, 51.83%, 11.49%, 3.0%, 2.5%, 0.5% and 0.82% respectively;

[0086] Further, the weighed Ti(C,N) and metal powder are put into a mixing tank. Steel balls with a diameter of 5 mm are weighed according to a ball-to-material weight ratio of 10:1 and then put into the aforementioned mixing tank. Ball milling is carried out at a rotation speed of 200 rpm for 6 hours, and then the steel balls are removed using a sieve to obtain a composite powder in which the hard-phase particles and the binder-phase metal powder are evenly mixed;

[0087] (3) Weigh 1500 g of the M1 solution prepared in step (1) and 10 kg of the composite powder prepared in step (2), stir the two evenly to form a paste, and obtain a steel-bonded cemented carbide composite powder coated with a polymer compound film;

[0088] (4) Put the steel-bonded cemented carbide composite powder coated with the polymer compound film obtained in step (3) into a stainless-steel tray, and then put the stainless-steel tray into an explosion-proof drying oven at 75 °C for drying treatment for 4 hours to obtain a dried steel-bonded cemented carbide composite powder coated with a polymer compound film;

[0089] (5) Put the steel-bonded cemented carbide composite powder coated with the polymer compound film obtained in step (4) into a mold, and carry out cold pressing at 200 MPa and hold the pressure for 1 minute to obtain a cold-pressed green compact of steel-bonded cemented carbide;

[0090] (6) Put the cold-pressed green compact of steel-bonded cemented carbide in step (5) into a vacuum sintering furnace to evacuate first. When the pressure in the furnace is less than 5 Pa, start heating at a rate of 10 °C / min to 1200 °C and hold for 1.5 hours, then heat at a rate of 5 °C / min to 1420 °C and hold for 2 hours. After the vacuum sintering treatment is completed, cool the furnace. After taking out of the furnace, a 40 vol.% Ti(C,N) / 17-4PH steel-bonded cemented carbide vacuum sintered ingot is obtained;

[0091] (7) Put the 40 vol.% Ti(C,N) / 17-4PH steel-bonded cemented carbide vacuum sintered ingot in step (6) into a hot isostatic pressing furnace, evacuate to 5 Pa and then fill with Ar gas, and then heat at a rate of 10 °C / min to 1400 °C and hold, hold the pressure (100 MPa) for 2 hours and then cool the furnace to obtain a 40 vol.% Ti(C,N) / 17-4PH steel-bonded cemented carbide hot isostatic pressing sintered ingot.

[0092] Note: In Example 4, the oxygen content of 10 kg of composite powder is approximately 64 grams (4 mol), and the residual carbon content of 1500 grams of compound solution M1 during subsequent drying and vacuum sintering processes is approximately 12 grams (i.e., 1 mol). The molar ratio of oxygen content to residual carbon content is approximately 1:0.25. Under the preparation process of Example 4, a small amount of polymer compound undergoes a carbon reduction reaction with the oxide film on the surface of metal powder. Therefore, no carbonaceous particles (such as Figure 4 as shown) are found in 40 vol.% Ti(C,N) / 17-4PH steel-bonded cemented carbide. Meanwhile, the carbon reduction reaction occurring on the oxide film on the surface of the binder-phase metal powder can effectively improve the sinterability of Ti(C,N) / 17-4PH steel-bonded cemented carbide. Chemical analysis shows that the oxygen concentration of 40 vol.% Ti(C,N) / 17-4PH steel-bonded cemented carbide is 0.49 wt.%. The oxygen content of 5 kg of steel-bonded cemented carbide is 49 grams, which is 15 grams lower than the oxygen content (64 g) of the composite powder. After the 40 vol.% Ti(C,N) / 17-4PH steel-bonded cemented carbide undergoes solution treatment (1050 °C, 60 min) and aging treatment (480 °C, 360 min), its room-temperature anti-density reaches 6.69 g / cm 3 (above 99.0% of the theoretical density), the bending strength reaches 1250 MPa, the hardness HRC reaches above 60, and it also has good hot deformation processing performance, wear resistance, and corrosion resistance.

[0093] Example 5

[0094] For 50 vol.% TiC / Fe-Cr-Ni-Co-Mo-Cu steel-bonded cemented carbide, its room-temperature bending strength reaches 1000 MPa, the hardness HRC reaches above 65, and it has good corrosion resistance.

[0095] The specific steps of this example are as follows:

[0096] (1) Using gasoline as the solvent, tar resin as the polymer compound solute, and natural rubber as the binder, prepare a polymer compound solution M1 with a viscosity of approximately 100 Pa•s according to the ratio of tar resin: natural rubber: gasoline = 50 g: 60 g: 500 g for later use;

[0097] (2) In this example, TiC particles with a particle size of 3 - 50 μm are selected as the hard phase, and metal element powders of Fe (10 - 13 μm), Cr (4 - 6 μm), Ni (4 - 5 μm), Co (0.2 - 2 μm), Mo (4 - 6 μm), and Cu (10 - 13 μm) are selected as the binder-phase raw materials;

[0098] Further, weigh TiC, Fe, Cr, Mo, Co, Ni, and Cu powders according to the ratios of 38.6%, 41.5%, 8.8%, 3.2%, 5.0%, 2.4%, and 0.5% respectively;

[0099] Further, put the weighed TiC, Fe, Cr, Mo, Co, Ni, and Cu powders into a mixing tank, weigh steel balls with a diameter of 5 mm according to the ball-to-material weight ratio of 1:1 and put them into the aforementioned mixing tank, and perform mechanical powder mixing at a rotation speed of 10 rpm for 96 hours, then remove the steel balls using a sieve to obtain a composite powder with uniformly mixed hard-phase particles and binder-phase metal powders;

[0100] (3) Weigh 780 g of the M1 solution prepared in step (1) and 5 kg of the composite powder prepared in step (2), stir the two evenly to form a paste to obtain a steel-bonded carbide composite powder coated with a polymer compound film;

[0101] (4) Put the steel-bonded carbide composite powder coated with the polymer compound film obtained in step (3) into a stainless-steel tray, and then place the stainless-steel tray in a cool and ventilated place to dry naturally for 3 days to obtain a dried steel-bonded carbide composite powder coated with a polymer compound film;

[0102] (5) Put the steel-bonded carbide composite powder coated with the polymer compound film obtained in step (4) into a mold, and perform cold pressing treatment under the condition of maintaining a pressure of 200 MPa for 2 minutes to obtain a TiC steel-bonded carbide cold-pressed green compact;

[0103] (6) Put the cold-pressed green compact of the steel-bonded carbide in step (5) into a hot isostatic pressing sintering furnace and evacuate it. When the pressure in the furnace is less than 5 Pa, start to heat up to 450 °C at a rate of 10 °C / min, hold for 1 hour for degumming treatment, and then heat up to 1450 °C at a rate of 8 °C / min and hold for 1 hour; then fill Ar gas to 10 MPa and hold for 1.5 hours under the conditions of 1420 °C and 10 MPa. After completing the hot isostatic pressing sintering treatment, cool the furnace, and after taking out of the furnace, obtain a 50 vol.% TiC / Fe-Cr-Ni-Co-Mo-Cu steel-bonded carbide hot isostatic pressing sintered ingot.

[0104] Note: In Example 5, the oxygen content of the 5 kg composite powder is about 30.7 grams (i.e., 1.92 mol), and the residual carbon content of the 780-gram compound solution M1 during subsequent drying and vacuum sintering treatment is about 23.0 grams (i.e., Also, the molar ratio of the oxygen content to the residual carbon content is 1:1; under the preparation process of Example 5, the polymer compound wrapped on the surface of the metal powder undergoes a carbon reduction reaction with the oxide film on the surface of the metal powder after carbonization, so no carbonaceous particles are found in the steel-bonded carbide (such asFigure 5 As shown), at the same time, the carbon reduction reaction occurring on the oxide film on the surface of the bonded-phase metal powder can effectively improve the sinterability of TiC cemented carbide; chemical analysis shows that the oxygen concentration of 50 vol.% TiC / Fe-Cr-Ni-Co-Mo-Cu steel-bonded cemented carbide is < 0.05 wt.%, and the oxygen content of 5 kg of steel-bonded cemented carbide is < 2.5 g, which is significantly lower than the oxygen content of the composite powder (30.7 g). After solution treatment (850 °C, 120 min) and aging treatment (480 °C, 480 min), its room-temperature density reaches 6.35 g / cm 3 (more than 98% of the theoretical density), the flexural strength reaches 1000 MPa, the hardness HRC reaches above 65, and it exhibits good wear resistance and corrosion resistance.

[0105] It is easy for those skilled in the art to understand that, on the premise of no conflict, the above advantageous ways can be freely combined and superimposed.

[0106] The above are only the preferred embodiments of this application, and are not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the protection scope of this application. The above is only the preferred implementation manner of this application. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the technical principle of this application, several improvements and modifications can still be made, and these improvements and modifications should also be regarded as within the protection scope of this application.

Claims

1. A method for preparing low-oxygen content steel-bonded cemented carbide, characterized by: The method comprises the following steps: (1) preparing a polymer compound solution M1 with a concentration of 0.2-10 wt.%; (2) Weighing hard phase particles and binder phase metal powder of steel-bonded cemented carbide in proportion, mixing them evenly by mechanical mixing to obtain steel-bonded cemented carbide composite powder; (3) mixing the solution M1 and the steel-bonded cemented carbide composite powder obtained in step (2) in proportion to form a paste, thereby obtaining a steel-bonded cemented carbide composite powder coated with a polymer compound film; The ratio in which the solution M1 and the steel-bonded cemented carbide composite powder are uniformly mixed in proportion refers to the ratio between the molar number of oxygen content in the steel-bonded cemented carbide composite powder and the molar number of residual carbon content of the polymer compound in the solution M1, and the ratio range is 1:(0.1-1.0); (4) drying the steel-bonded cemented carbide composite powder coated with the polymer compound film obtained in step (3); (5) cold pressing or cold isostatic pressing the steel-bonded cemented carbide composite powder coated with the polymer compound film after the drying treatment in step (4) to obtain a steel-bonded cemented carbide cold-pressed green body; (6) The cold-pressed steel-bonded cemented carbide green body obtained in step (5) is subjected to sintering treatment, wherein the sintering method is vacuum sintering or low-pressure sintering, and a vacuum-sintered or low-pressure-sintered steel-bonded cemented carbide ingot is obtained after sintering.

2. The method for preparing low-oxygen steel-bonded cemented carbide according to claim 1, wherein: The vacuum-sintered or low-pressure-sintered steel-bonded cemented carbide ingot obtained in step (6) is subjected to hot isostatic pressing to obtain a hot isostatically pressed steel-bonded cemented carbide ingot.

3. The method for preparing low-oxygen steel-bonded cemented carbide according to claim 1, wherein: In step (1), the polymer compound is one or more of sucrose, tar resin, phenolic resin, alkyd resin, ethylene tar and dopamine hydrochloride; the polymer compound solution M1 is formed by dissolving the polymer compound in a solvent, and the solvent is water, gasoline, toluene, alcohols, esters, ether alcohols or chlorinated hydrocarbons.

4. The method for preparing low-oxygen content steel-bonded cemented carbide according to claim 1 or 3, characterized in that: In step (1), the viscosity of the polymer compound solution M1 is adjusted by adding a viscous material, wherein the viscous material is one or more of rosin, natural rubber, cellulose, polyvinyl alcohol and synthetic resin; and the viscosity of the polymer compound solution M1 is adjusted to 1-100 Pa·s.

5. The method for preparing low-oxygen steel-bonded cemented carbide according to claim 1, wherein: In step (2), the hard phase particles of the steel-bonded cemented carbide are one or more of WC, TiC, TiB2, B4C and Ti (C, N); the bonding phase powder of the steel-bonded cemented carbide is alloy steel powder; or, the bonding phase powder of the steel-bonded cemented carbide is powder of alloy steel constituent elements.

6. The method for preparing low-oxygen-content steel-bonded cemented carbide according to claim 5, characterized in that: In step (2), the volume fraction of the hard phase in the steel-bonded cemented carbide composite powder is 5-50%, and the particle sizes of the hard phase particles and the binder phase powder are both 0.2-100 μm.

7. The method for preparing low-oxygen steel-bonded cemented carbide according to claim 1, wherein: In step (4), the drying treatment is natural drying and / or heating drying, and the drying temperature is 20 to 500°C.

8. The method for preparing low-oxygen steel-bonded cemented carbide according to claim 1, wherein: In step (6), the temperature range of the vacuum sintering and low-pressure sintering is 1150-1450°C.

9. The method for preparing low-oxygen steel-bonded cemented carbide according to claim 2, wherein: The temperature range of the hot isostatic pressing sintering is 1250-1450°C.

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