Preparation method of high red hardness hard alloy tool material for high railway turnout machining

Abstract

The embodiment of the application provides a preparation method of a high red hardness hard alloy tool material for high railway turnout machining, wherein liquid phase dissolution, evaporation glue preparation, baking, ball milling and reduction carbonization are used on the material to obtain a nano WC-WB-Co composite powder; the nano composite powder is uniformly mixed with a grain inhibitor, and then is baked and formed through a two-step sintering method to obtain a nano-crystalline hard alloy tool blank; the nano-crystalline hard alloy tool blank is subjected to stress relief treatment, and finally the high red hardness hard alloy tool material for high railway turnout machining is obtained. The hard alloy tool material prepared by the application has a nano-crystalline structure, the fracture toughness of the material is greater than or equal to 13.5 MPa.m 1 / 2 , the microhardness is greater than or equal to 21.3 GPa, the bending strength is greater than or equal to 3460 MPa, and the high temperature (1000 DEG C) hardness is greater than or equal to 17.6 GPa.

Description

Technical Field

[0001] This invention belongs to the field of cemented carbide tool preparation technology, specifically relating to a method for preparing a high-red-hardness cemented carbide tool material for machining high-speed railway turnouts. Background Technology

[0002] Turnouts are an important component of high-speed railway tracks. However, since the main component of turnouts is high-manganese steel, which is a difficult-to-machine material, high requirements are placed on the hardness, strength, toughness, and high-temperature resistance of cutting tools. The strength (or hardness) and toughness of commonly used cemented carbide cutting tools have an inverse relationship, as well as weak resistance to high-temperature softening and oxidation, which limits their application in the field of high-speed railway turnout machining. Therefore, finding a new method to balance the relationship between strength and toughness and optimize high-temperature performance is crucial to improving the machining performance of high-speed railway turnouts.

[0003] Improving the red hardness and toughness of cemented carbide cutting tools through hard phase hardening, adding grain inhibitors, two-step sintering, and stress-relief heat treatment is a key approach to solving the aforementioned engineering problems. Summary of the Invention

[0004] In view of this, the main objective of the present invention is to provide a method for preparing high red hardness cemented carbide cutting tool material for machining high-speed railway turnouts.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing high-red-hardness cemented carbide cutting tool material for high-speed railway turnout machining, comprising:

[0007] Nano-WC-WB-Co composite powder was obtained by liquid-phase dissolution, evaporation to form a binder, calcination, ball milling, and reduction carbonization of the material.

[0008] The nanocomposite powder is mixed evenly with the grain inhibitor, and then sintered in a two-step sintering method to obtain a nanocrystalline cemented carbide tool blank.

[0009] The nanocrystalline cemented carbide tool blank is subjected to stress relief treatment to finally obtain a high red hardness cemented carbide tool material for high-speed railway turnout machining.

[0010] In the above scheme, the materials are ammonium metatungstate or ammonium paratungstate, boric acid, cobalt nitrate or cobalt sulfate, sucrose or caramel, and are composed of W:C:B:Co elements in a molar ratio of 1:29-36:0.4-0.7:2-3;

[0011] In the above scheme, the process of obtaining nano-WC-WB-Co composite powder by liquid-phase dissolution, evaporation to form a gel, calcination, ball milling, and reduction carbonization of the material is as follows: the material is uniformly dissolved in deionized water at a temperature of 46℃~59℃, and then the solution is evaporated by a stirring heater at a temperature of 130℃~145℃ and a speed of 180~230 rpm to form a gel. The gel is then calcined in a vacuum furnace at 560℃~620℃ for 35~45 minutes, followed by ball milling in a planetary ball mill at 400 rpm and a ball-to-material ratio of 5:1 for 4~6 hours. Finally, the material is reduced and carbonized in a vacuum furnace at 1350℃~1400℃ for 25~30 minutes to obtain nano-WC-WB-Co composite powder.

[0012] In the above scheme, the grain inhibitor is TaC or VC, with a mass percentage of 0.5% to 1%.

[0013] In the above scheme, the grain inhibitor is TaC or VC, with a mass percentage of 0.5% to 1%.

[0014] In the above scheme, the process of uniformly mixing the nanocomposite powder with the grain inhibitor and then forming it through a two-step sintering method to obtain a nanocrystalline cemented carbide tool blank specifically involves: uniformly mixing the nanocomposite powder with the grain inhibitor and then obtaining the nanocrystalline cemented carbide tool blank through spark plasma sintering and vacuum pressureless sintering; wherein the spark plasma sintering temperature is 1050℃~1120℃, and the holding time is 1~2.5 minutes, and the vacuum pressureless sintering temperature is 1070℃~1140℃, and the holding time is 2.1~2.6 hours.

[0015] In the above scheme, the stress relief treatment of the nanocrystalline cemented carbide tool blank is specifically carried out by: using micro-plastic deformation technology, repeatedly loading the blank 5 to 8 times under a compressive stress load greater than the compressive elastic limit of the cemented carbide blank but not exceeding the yield strength of 3130 to 3180 MPa, with a pressure increase and decompression rate of 170 to 230 MPa / min.

[0016] In the above scheme, the cemented carbide tool material obtained has a nanocrystalline structure, and the fracture toughness of the material is greater than or equal to 13.5 MPa·m. 1 / 2 Microhardness greater than or equal to 21.3 GPa, flexural strength greater than or equal to 3460 MPa, and high temperature hardness at 1000℃ greater than or equal to 17.6 GPa.

[0017] Compared with existing technologies, the cemented carbide tool material prepared by this invention has a nanocrystalline structure and a fracture toughness greater than or equal to 13.5 MPa·m. 1 / 2 Microhardness greater than or equal to 21.3 GPa, flexural strength greater than or equal to 3460 MPa, and high temperature (1000℃) hardness greater than or equal to 17.6 GPa. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes that element.

[0020] This invention provides a method for preparing high-red-hardness cemented carbide cutting tool material for high-speed railway turnout machining, comprising:

[0021] S101, nano WC-WB-Co composite powder was obtained by liquid phase dissolution, evaporation gelation, calcination, ball milling and reduction carbonization of the material;

[0022] Specifically, the material is ammonium metatungstate or ammonium paratungstate, boric acid, cobalt nitrate or cobalt sulfate, sucrose or caramel, and is composed of W:C:B:Co elements in a molar ratio of 1:29-36:0.4-0.7:2-3;

[0023] The material is uniformly dissolved in deionized water at a temperature of 46℃~59℃, and then the solution is evaporated by a stirring heater at a temperature of 130℃~145℃ and a speed of 180~230 rpm to form a gel. The gel is then calcined in a vacuum furnace at 560℃~620℃ for 35~45 minutes, followed by ball milling in a planetary ball mill at 400 rpm and a ball-to-material ratio of 5:1 for 4~6 hours. Finally, it is reduced and carbonized in a vacuum furnace at 1350℃~1400℃ for 25~30 minutes to obtain nano WC-WB-Co composite powder.

[0024] S102, the nanocomposite powder is mixed evenly with the grain inhibitor, and then sintered by a two-step sintering method to obtain a nanocrystalline cemented carbide tool blank.

[0025] Specifically, the grain inhibitor is TaC or VC, with a mass percentage of 0.5% to 1%;

[0026] Nanocomposite powder and grain inhibitor are mixed evenly and then subjected to spark plasma sintering and vacuum pressureless sintering to obtain nanocrystalline cemented carbide tool blanks; wherein the spark plasma sintering temperature is 1050℃~1120℃ and the holding time is 1~2.5 minutes, and the vacuum pressureless sintering temperature is 1070℃~1140℃ and the holding time is 2.1~2.6 hours.

[0027] S103, the nanocrystalline cemented carbide tool blank is subjected to stress relief treatment to finally obtain high red hardness cemented carbide tool material for high-speed railway turnout machining.

[0028] Specifically, micro-plastic deformation technology is used to repeatedly load the material 5 to 8 times under a compressive stress load greater than the compressive elastic limit of the cemented carbide blank but not exceeding the yield strength of 3130 to 3180 MPa, with a pressurization and depressurization rate of 170 to 230 MPa / min.

[0029] The cemented carbide cutting tool material obtained by this invention has a nanocrystalline structure and a fracture toughness greater than or equal to 13.5 MPa·m. 1 / 2 Microhardness greater than or equal to 21.3 GPa, flexural strength greater than or equal to 3460 MPa, and high temperature hardness at 1000℃ greater than or equal to 17.6 GPa.

[0030] This invention first uses a series of techniques including liquid phase, binder preparation, reduction carbonization, and ball milling to obtain nano-WC-WB-Co composite powder. Then, the nano-composite powder is uniformly mixed with a grain inhibitor, and subsequently sintered using a two-step sintering method to obtain a nanocrystalline cemented carbide tool blank. Finally, the tool blank undergoes stress relief treatment. The liquid phase, binder preparation, reduction carbonization, and ball milling series of techniques can be used to synthesize WC-Co composite powder and to dope the WB phase. This series of techniques can achieve component uniformity and higher hardness and high-temperature resistance in the nano-WC-WB-Co composite powder. The two-step sintering method uses spark plasma sintering technology to rapidly densify and solidify the mixed powder, followed by vacuum pressureless sintering to complete the final densification and microstructure homogenization, facilitating the utilization of the performance advantages of the nano-WC-WB-Co composite powder and the grain inhibitor. The stress relief treatment is used to reduce or eliminate residual thermal stress in the cemented carbide tool, further improving its toughness.

[0031] Furthermore, in the process of preparing cemented carbide materials, this invention addresses the engineering problems of the inverse relationship between strength (or hardness) and toughness in commonly used cemented carbide cutting tools, as well as their weak resistance to high-temperature softening and oxidation. It employs a method involving hard phase hardening, the addition of grain inhibitors, two-step sintering, and stress-relief heat treatment. The invention investigates the relationship between composite powder composition, composite powder preparation process, type and amount of grain inhibitors, two-step sintering process, stress-relief treatment process, and the strength, toughness, and high-temperature mechanical properties of cemented carbide. Specifically, it identifies the optimal composite powder composition ratio, composite powder preparation process parameters, type and amount of grain inhibitors, two-step sintering process parameters, and stress-relief treatment process parameters for high-red-hardness cemented carbide cutting tool materials used in high-speed railway turnout machining, maintaining high strength, toughness, and high-temperature mechanical properties. This method features high precision in composition control, strong process stability and repeatability, and can achieve both high strength and high red hardness in cemented carbide materials.

[0032] The toughness and high-temperature properties of the high-red-hardness cemented carbide cutting tool materials for machining high-speed railway turnouts prepared in the following examples are shown in Table 1.

[0033] Example 1

[0034] (1) Nano WC-WB-Co composite powder was obtained by liquid phase + gel making + reduction carbonization + ball milling series technology. First, ammonium metatungstate (or ammonium paratungstate), boric acid, cobalt nitrate (or cobalt sulfate) and sucrose (or caramel) were uniformly dissolved in deionized water at 46℃ according to the molar ratio of W:C:B:Co of 1:29:0.4:2. Then, the solution was evaporated at 130℃ and 180 rpm using a stirring heater to form a gel. The gel was then calcined in a vacuum furnace at 560℃ for 35 minutes. Subsequently, it was ball milled in a planetary ball mill at 400 rpm and a ball-to-material ratio of 5:1 for 4 hours. Finally, it was reduced carbonized in a vacuum furnace at 1350℃ for 25 minutes.

[0035] (2) The nanocomposite powder is mixed evenly with grain inhibitor (TaC or VC, mass percentage of 0.5%), and then the mixture is subjected to discharge plasma sintering at 1050℃ for 1 minute. The second sintering is then completed at 1070℃ for 2.1 hours using vacuum pressureless sintering technology to obtain nanocrystalline cemented carbide tool blank.

[0036] (3) The nanocrystalline cemented carbide tool blank was subjected to stress relief treatment using microplastic deformation technology. It was repeatedly loaded 5 times under a compressive stress load greater than the compressive elastic limit of the cemented carbide blank but not exceeding the yield strength (3130MPa). The pressure increase and decompression rate was 170MPa / min. Finally, high red hardness cemented carbide tool material for high-speed railway turnout processing was obtained.

[0037] Example 2

[0038] (1) Nano WC-WB-Co composite powder was obtained by liquid phase + gel making + reduction carbonization + ball milling series technology. First, ammonium metatungstate (or ammonium paratungstate), boric acid, cobalt nitrate (or cobalt sulfate) and sucrose (or caramel) were uniformly dissolved in deionized water at 59℃ according to the molar ratio of W:C:B:Co of 1:36:0.7:3. Then, the solution was evaporated at 145℃ and 230 rpm using a stirring heater to form a gel. The gel was then calcined at 620℃ in a vacuum furnace for 45 minutes, and then ball milled at 400 rpm and ball-to-material ratio of 5:1 for 6 hours in a planetary ball mill. Finally, it was reduced carbonized at 1400℃ in a vacuum furnace for 30 minutes.

[0039] (2) The nanocomposite powder is mixed evenly with grain inhibitor (TaC or VC, mass percentage of 1%), and then subjected to discharge plasma sintering at 1120℃ for 2.5 minutes. The second sintering is then completed at 1140℃ for 2.6 hours using vacuum pressureless sintering technology to obtain nanocrystalline cemented carbide tool blank.

[0040] (3) The nanocrystalline cemented carbide tool blank was subjected to stress relief treatment using microplastic deformation technology. It was repeatedly loaded 8 times under a compressive stress load greater than the compressive elastic limit of the cemented carbide blank but not exceeding the yield strength (3180MPa). The pressure increase and decompression rate was 230MPa / min. Finally, high red hardness cemented carbide tool material for high-speed railway turnout processing was obtained.

[0041] Example 3

[0042] (1) Nano WC-WB-Co composite powder was obtained by liquid phase + gel making + reduction carbonization + ball milling series technology. First, ammonium metatungstate (or ammonium paratungstate), boric acid, cobalt nitrate (or cobalt sulfate) and sucrose (or caramel) were uniformly dissolved in deionized water at 51℃ according to the molar ratio of W:C:B:Co of 1:32:0.5:2.4. Then, the solution was evaporated at 135℃ and 190 rpm using a stirring heater to form a gel. The gel was then calcined in a vacuum furnace at 580℃ for 42 minutes, and then ball milled in a planetary ball mill at 400 rpm and a ball-to-material ratio of 5:1 for 5 hours. Finally, it was reduced carbonized in a vacuum furnace at 1370℃ for 27 minutes.

[0043] (2) The nanocomposite powder is mixed evenly with grain inhibitor (TaC or VC, mass percentage of 0.7%), and then the mixture is subjected to discharge plasma sintering at 1090℃ for 1.5 minutes. The second sintering is then completed by vacuum pressureless sintering technology at 1090℃ for 2.3 hours to obtain nanocrystalline cemented carbide tool blank.

[0044] (3) The nanocrystalline cemented carbide tool blank was subjected to stress relief treatment using microplastic deformation technology. It was repeatedly loaded 6 times under a compressive stress load greater than the compressive elastic limit of the cemented carbide blank but not exceeding the yield strength (3150MPa). The pressure increase and decompression rate was 190MPa / min. Finally, high red hardness cemented carbide tool material for high-speed railway turnout processing was obtained.

[0045] Example 4

[0046] (1) Nano WC-WB-Co composite powder was obtained by liquid phase + gel making + reduction carbonization + ball milling series technology. First, ammonium metatungstate (or ammonium paratungstate), boric acid, cobalt nitrate (or cobalt sulfate) and sucrose (or caramel) were uniformly dissolved in deionized water at 56℃ according to the molar ratio of W:C:B:Co of 1:34:0.6:3. Then, the solution was evaporated at 140℃ and 220 rpm using a stirring heater to form a gel. The gel was then calcined in a vacuum furnace at 620℃ for 45 minutes, and then ball milled in a planetary ball mill at 400 rpm and a ball-to-material ratio of 5:1 for 6 hours. Finally, it was reduced carbonized in a vacuum furnace at 1380℃ for 29 minutes.

[0047] (2) The nanocomposite powder is mixed evenly with grain inhibitor (TaC or VC, mass percentage of 0.7%), and then the mixture is subjected to discharge plasma sintering at 1120℃ for 2.4 minutes. The second sintering is then completed by vacuum pressureless sintering technology at 1120℃ for 2.5 hours to obtain nanocrystalline cemented carbide tool blank.

[0048] (3) The nanocrystalline cemented carbide tool blank was subjected to stress relief treatment using microplastic deformation technology. It was repeatedly loaded 8 times under a compressive stress load greater than the compressive elastic limit of the cemented carbide blank but not exceeding the yield strength (3170MPa). The pressure increase and decompression rate was 200MPa / min. Finally, high red hardness cemented carbide tool material for high-speed railway turnout processing was obtained.

[0049] The performance parameters of the cemented carbide materials prepared in Examples 1-4 are shown in Table 1:

[0050] Table 1

[0051]

[0052] As can be seen from the table above, the cemented carbide tool material prepared by this invention has a nanocrystalline structure, and the fracture toughness of the material is greater than or equal to 13.5 MPa·m. 1 / 2 Microhardness greater than or equal to 21.3 GPa, flexural strength greater than or equal to 3460 MPa, and high temperature (1000℃) hardness greater than or equal to 17.6 GPa.

[0053] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-red-hardness cemented carbide cutting tool material for machining high-speed railway turnouts, characterized in that, The preparation method includes: Nano-WC-WB-Co composite powder was obtained by liquid-phase dissolution, evaporation to form a binder, calcination, ball milling, and reduction carbonization of the material. The nanocomposite powder is mixed evenly with the grain inhibitor, and then sintered in a two-step sintering method to obtain a nanocrystalline cemented carbide tool blank. The nanocrystalline cemented carbide tool blank is subjected to stress relief treatment to finally obtain a high red hardness cemented carbide tool material for high-speed railway turnout machining. The process of uniformly mixing nanocomposite powder with grain inhibitor and then sintering it using a two-step sintering method to obtain a nanocrystalline cemented carbide tool blank specifically involves: uniformly mixing nanocomposite powder with grain inhibitor and then subjecting the mixture to spark plasma sintering and vacuum pressureless sintering to obtain the nanocrystalline cemented carbide tool blank; wherein the spark plasma sintering temperature is 1050℃~1120℃ and the holding time is 1~2.5 minutes, and the vacuum pressureless sintering temperature is 1070℃~1140℃ and the holding time is 2.1~2.6 hours; The stress relief treatment of the nanocrystalline cemented carbide tool blank is specifically carried out by: using micro-plastic deformation technology, repeatedly loading the blank 5 to 8 times under a compressive stress load greater than the elastic limit of the cemented carbide blank but not exceeding the yield strength, with a pressure increase and decompression rate of 170 to 230 MPa / min. The material is ammonium metatungstate or ammonium paratungstate, boric acid, cobalt nitrate or cobalt sulfate, sucrose or caramel, and is composed of W:C:B:Co elements in a molar ratio of 1:29~36:0.4~0.7:2~3.

2. The method for preparing high-red-hardness cemented carbide cutting tool material for high-speed railway turnout machining according to claim 1, characterized in that, The process of obtaining nano-WC-WB-Co composite powder by liquid-phase dissolution, evaporation to form a gel, calcination, ball milling, and reduction carbonization is as follows: The material is uniformly dissolved in deionized water at a temperature of 46℃~59℃, and then the solution is evaporated by a stirring heater at a temperature of 130℃~145℃ and a speed of 180~230 rpm to form a gel. The gel is then calcined in a vacuum furnace at 560℃~620℃ for 35~45 minutes, followed by ball milling in a planetary ball mill at 400 rpm and a ball-to-material ratio of 5:1 for 4~6 hours. Finally, it is reduced carbonized in a vacuum furnace at 1350℃~1400℃ for 25~30 minutes to obtain nano-WC-WB-Co composite powder.

3. The method for preparing high-red-hardness cemented carbide cutting tool material for high-speed railway turnout machining according to claim 1 or 2, characterized in that, The grain inhibitor is TaC or VC, with a mass percentage of 0.5-1%.

4. The method for preparing high-red-hardness cemented carbide cutting tool material for high-speed railway turnout machining according to claim 3, characterized in that, The prepared cemented carbide tool material has a nanocrystalline structure and a fracture toughness greater than or equal to 13.5 MPa·m. 1 / 2 Microhardness greater than or equal to 21.3 GPa, flexural strength greater than or equal to 3460 MPa, and high temperature hardness at 1000 ℃ greater than or equal to 17.6 GPa.

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