Preparation method and application of hard alloy for wire-drawing die
By introducing rare earth tantalate powder and Cu powder into cemented carbide and adopting low-pressure sintering process, the problems of insufficient hardness, fracture toughness and wear resistance of cemented carbide are solved, and the performance of the alloy is significantly improved.
Patent Information
- Application Number
- CN202411432961.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-15
- Publication Date
- 2025-02-25
AI Technical Summary
When faced with the demand for high-strength and high-precision drawing, existing cemented carbide drawing dies have insufficient hardness, fracture toughness and wear resistance, resulting in poor product accuracy and surface quality.
By introducing rare earth tantalate powder and Cu powder as additives, it is ball milled with WC powder and Co powder, and densified by low-pressure sintering process to prepare a new cemented carbide.
This method effectively suppresses the growth of WC grains, reduces the average grain size, significantly enhances the hardness and fracture toughness of the alloy, and improves the overall performance of the drawing die.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of hard alloy for wire drawing dies, in particular to a preparation method and application of hard alloy for wire drawing dies. Background Art
[0002] In the metal processing industry, wire drawing dies are the core tools for producing wire, rod, pipe and profile products. Their performance and quality are directly related to the quality and production efficiency of the final product. With the continuous advancement of industrial technology, the materials and manufacturing processes of wire drawing dies have also undergone many innovations from cast iron molds to modern carbide molds. Each change has greatly promoted the development of the metal processing industry.
[0003] Traditionally, wire drawing dies are mostly made of cast iron or steel. Although these materials have certain hardness and wear resistance, they are often unable to cope with the high-strength and high-precision drawing requirements and are prone to wear, affecting the precision and surface quality of the products. With the advancement of materials science, new materials such as diamond dies and cemented carbide dies have emerged. Among them, cemented carbide dies have quickly become the leader in the field of wire drawing dies with their excellent wear resistance, high hardness, low friction coefficient and excellent processing adaptability.
[0004] Cemented carbide is a high-performance composite material made of refractory metal carbides (such as WC, TiC, etc.) and bonding metals (such as Co, Ni, etc.) through powder metallurgy. Among them, WC-Co cemented carbide has been widely used in wire drawing die manufacturing due to its good comprehensive performance. However, with the continuous improvement of modern industry's requirements for wire drawing die performance, how to further improve the hardness, fracture toughness and wear resistance of cemented carbide has become an urgent problem to be solved.
[0005] In response to this challenge, researchers continue to explore new alloying elements and preparation processes. This application proposes an innovative method for preparing cemented carbide wire drawing dies, which introduces an appropriate amount of rare earth tantalate powder and Cu powder as additives, mixes them with WC powder and Co powder by ball milling, and then densifies them using a low-pressure sintering process. This composite addition strategy not only effectively inhibits the growth trend of WC grains during the precipitation process, reduces the average grain size, but also significantly enhances the hardness and fracture toughness of the alloy. Summary of the invention
[0006] The purpose of the present invention is to provide a method for preparing a hard alloy for a wire drawing die and its application, so as to solve the problems existing in the prior art.
[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:
[0008] A hard alloy for a wire drawing die comprises, by weight percentage, 88-89% of WC powder, 10-11% of Co powder, 0.4-0.6% of rare earth tantalate powder, 1-1.2% of Cu powder and 0.25-0.3% of carbon black.
[0009] As an optimization, the purity of the WC powder is greater than 99.6%, and the total carbon content thereof is 5.9-6.1%.
[0010] As an optimization, the purity of the Cu powder is greater than 99.5%.
[0011] As an optimization, the carbon black has a purity greater than 99.7%.
[0012] As an optimization, the purity of the Co powder is greater than 99.6%, and the particle size is 2-4 μm.
[0013] A method for preparing a hard alloy for a wire drawing die comprises the following steps:
[0014] S1. Weigh 88-89% of WC powder, 10-11% of Co powder, 0.4-0.6% of rare earth tantalate powder, 1-1.2% of Cu powder and 0.25-0.3% of carbon black according to the above weight percentages; add the weighed materials into a ball mill for 46-48 hours. After the ball milling is completed, take out the liquid slurry for standby use;
[0015] S2, take out the liquid slurry after ball milling in S1 and place it in a tray, vacuum it for 2-3 hours, extract the upper layer of anhydrous ethanol, and then place it in a vacuum drying oven at a temperature of 75-80°C for 3-4 hours. After drying, sieve it and vacuum package it for later use;
[0016] S3, placing the vacuum-encapsulated dry powder in S2 in a vacuum degreasing furnace for pre-sintering after compression molding, and then sending it to a low-pressure sintering furnace for sintering to prepare a cemented carbide.
[0017] As an optimization, the ball milling medium in the ball milling process is anhydrous ethanol, the liquid-solid ratio is 280-300 mL / kg, the ball-to-material ratio is 4.5-5:1, and the ball milling speed is 80-90 r / min.
[0018] As an optimization, during the compression molding process, the compression pressure is 3 to 3.5 MPa, and the pressure is maintained for 10 to 20 seconds.
[0019] As an optimization, nitrogen is introduced during the pre-sintering process, and the temperature is increased to 380-420°C at 5°C / min, and then kept warm for 1-1.2 hours. After the insulation is completed, the temperature is lowered to room temperature and then placed in a low-pressure sintering furnace for sintering, and the temperature is increased to 800-850°C at 10°C / min, and then increased to 1050-1100°C at 5°C / min, and kept warm for 30-40 minutes. After the insulation is completed, the temperature is increased to 1400-1450°C at 5°C / min, and kept warm for 30-40 minutes. After the insulation is completed, the material is taken out and cooled to room temperature to prepare a cemented carbide.
[0020] An application of the cemented carbide as described above in a wire drawing die.
[0021] Compared with the prior art, the beneficial effects achieved by the present invention are:
[0022] This application uses a series of powder raw materials, including WC powder, Co powder, rare earth tantalate powder, Cu powder and carbon black, which are mixed by ball milling and then manufactured by low-pressure sintering process. In particular, an appropriate amount of rare earth tantalate powder and Cu powder are introduced into the formula. The synergistic effect of these two additives effectively inhibits the growth trend of WC grains during the precipitation process, thereby improving the overall performance of cemented carbide. Compared with the addition of rare earth tantalate powder or Cu powder alone, this composite addition strategy significantly reduces the average grain size of WC and simultaneously enhances the hardness and fracture toughness of the alloy;
[0023] As an additive, rare earth tantalate powder exhibits excellent grain refinement effect, which is crucial to improving the comprehensive performance of the alloy and optimizing the microstructure. It tends to gather at the WC grain boundaries and material defect areas, stabilizing the grain boundaries and preventing the WC particles from dissolving and then precipitating and growing during sintering. In addition, the dispersed particles formed by rare earth elements at the grain boundaries further limit the migration of the solid solution grain boundaries, making the alloy grains finer and more evenly distributed;
[0024] On the other hand, the addition of Cu powder also has a positive effect on grain refinement. Given that the radius of Cu atoms is similar to that of Co atoms, Cu can be smoothly dissolved in the cobalt-based binder phase. This characteristic reduces the solubility of WC in cobalt and slows down the growth rate of WC grains during sintering, thereby achieving grain size refinement. The melting point of Cu is much lower than that of Co. After being dissolved in cobalt, it can reduce the sintering temperature of the alloy and promote the activation sintering process. This low-temperature sintering condition helps to reduce the coarsening of WC grains and further optimizes the microstructure of the alloy. DETAILED DESCRIPTION
[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0026] Example 1
[0027] S1. Add the weighed materials into the ball mill for 46 hours. After the ball milling is completed, take out the liquid slurry for use. During the ball milling process, the ball milling medium is anhydrous ethanol, the liquid-solid ratio is 280 mL / kg, the ball-to-material ratio is 4.5:1, and the ball milling speed is 80 r / min.
[0028] S2, take out the liquid slurry after ball milling in S1 and place it in a tray, vacuum stand for 2 hours, and then place it in a vacuum drying oven after extracting the upper layer of anhydrous ethanol, vacuum dry it at a temperature of 75°C for 3 hours, sieve it after drying and vacuum package it for standby use; during the compression molding process, the compression pressure is 3MPa, and the pressure is maintained for 10;
[0029] S3. Place the vacuum-encapsulated dry powder in S2 in a vacuum degreasing furnace for pre-sintering after molding, and then send it to a low-pressure sintering furnace for sintering to prepare a cemented carbide; during the pre-sintering process, nitrogen is introduced, and the temperature is increased to 380°C at 5°C / min, and then kept warm for 1h. After the insulation is completed, it is cooled to room temperature and then placed in a low-pressure sintering furnace for sintering, and the temperature is increased to 800°C at 10°C / min, and then increased to 1050°C at 5°C / min, and kept warm for 30min. After the insulation is completed, the temperature is increased to 1400°C at 5°C / min, and kept warm for 30min. After the insulation is completed, it is taken out and cooled to room temperature to prepare a cemented carbide.
[0030] Example 2
[0031] S1. Add the weighed materials into the ball mill for 47 hours. After the ball milling is completed, take out the liquid slurry for use. During the ball milling process, the ball milling medium is anhydrous ethanol, the liquid-solid ratio is 290 mL / kg, the ball-to-material ratio is 4.5:1, and the ball milling speed is 85 r / min.
[0032] S2, take out the liquid slurry after ball milling in S1 and place it in a tray, vacuum stand for 2.5 hours, and then place it in a vacuum drying oven after extracting the upper layer of anhydrous ethanol, vacuum dry it at a temperature of 75°C for 3.5 hours, sieve it after drying and vacuum package it for standby use; during the compression molding process, the compression pressure is 3.2MPa, and the pressure is maintained for 15s;
[0033] S3. Place the vacuum-encapsulated dry powder in S2 in a vacuum degreasing furnace for pre-sintering after molding, and then send it to a low-pressure sintering furnace for sintering to prepare a cemented carbide; during the pre-sintering process, nitrogen is introduced, and the temperature is raised to 400°C at 5°C / min, and then kept warm for 1.1 hours. After the insulation is completed, it is cooled to room temperature and then placed in a low-pressure sintering furnace for sintering, and the temperature is raised to 825°C at 10°C / min, and then raised to 1080°C at 5°C / min, and kept warm for 30-40 minutes. After the insulation is completed, the temperature is raised to 1425°C at 5°C / min, and kept warm for 35 minutes. After the insulation is completed, it is taken out and cooled to room temperature to prepare a cemented carbide.
[0034] Example 3
[0035] S1. Add the weighed materials into the ball mill for 48 hours. After the ball milling is completed, take out the liquid slurry for use. During the ball milling process, the ball milling medium is anhydrous ethanol, the liquid-solid ratio is 300 mL / kg, the ball-to-material ratio is 5:1, and the ball milling speed is 90 r / min.
[0036] S2, take out the liquid slurry after ball milling in S1 and place it in a tray, vacuum stand for 3 hours, and then place it in a vacuum drying oven after extracting the upper layer of anhydrous ethanol, vacuum dry it at a temperature of 80°C for 4 hours, sieve it after drying and vacuum package it for standby use; during the compression molding process, the compression pressure is 3.5MPa, and the pressure is maintained for 20s;
[0037] S3. The vacuum-encapsulated dry powder in S2 is placed in a vacuum degreasing furnace for pre-sintering after being molded, and then sent to a low-pressure sintering furnace for sintering to prepare a cemented carbide; nitrogen is introduced during the pre-sintering process, and the temperature is increased to 420°C at 5°C / min, and then kept warm for 1.2 hours. After the insulation is completed, it is cooled to room temperature and then placed in a low-pressure sintering furnace for sintering, and the temperature is increased to 850°C at 10°C / min, and then increased to 1100°C at 5°C / min, and kept warm for 40 minutes. After the insulation is completed, the temperature is increased to 1450°C at 5°C / min, and kept warm for 40 minutes. After the insulation is completed, it is taken out and cooled to room temperature to prepare a cemented carbide.
[0038] Test Example 1
[0039] Cemented carbide was prepared according to the steps in Example 2. The relevant ingredients are shown in Table 1 below. In terms of weight percentage, 10% Co powder and 0.28% carbon black were fixed and remained unchanged. Except for the following additives, the remaining materials were WC powder.
[0040] Table 1 Powder ingredients
[0041]
[0042] The materials were weighed according to the weight percentage in Table 1 above, and after preparing the cemented carbide according to the steps in Example 2, the hardness and bending strength of the cemented carbide were measured;
[0043] The hardness measurement uses a digital Vickers hardness tester to determine the hardness value of the alloy, and the load used is 10N;
[0044] The bending strength was measured using the three-point bending method, with the support point distance set at 25 mm and the correction factor set at 1. The measurement results are shown in Table 2 below.
[0045] Table 2 Measurement results
[0046]
[0047]
[0048] From the comparison of the experimental data in Table 2, it can be found that on the basis of adding 0.4wt% rare earth tantalate powder, the hardness and bending strength of the alloy will show a pattern of first increasing and then decreasing with the addition of rare earth tantalate powder. On the basis of adding 1wt% Cu powder, the performance is the same as the effect of rare earth tantalate powder on the alloy. Therefore, the present application adopts the use of the two in combination. After the use in combination, the hardness and bending strength are greatly increased, and the comprehensive performance of the alloy is better.
[0049] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.
Claims
1. A cemented carbide for a wire drawing die, characterized in that: Calculated by weight percentage, the invention comprises 88-89% of WC powder, 10-11% of Co powder, 0.4-0.6% of rare earth tantalate powder, 1-1.2% of Cu powder and 0.25-0.3% of carbon black.
2. The hard alloy for wire drawing die according to claim 1, characterized in that: The purity of the WC powder is greater than 99.6%, and the total carbon content thereof is 5.9-6.1%.
3. The hard alloy for wire drawing die according to claim 1, characterized in that: The purity of the Cu powder is greater than 99.5%.
4. The hard alloy for wire drawing die according to claim 1, characterized in that: The carbon black has a purity greater than 99.7%.
5. The hard alloy for wire drawing die according to claim 1, characterized in that: The purity of the Co powder is greater than 99.6%, and the particle size is 2-4 μm.
6. A method for preparing a hard alloy for a wire drawing die, characterized in that: The following steps are involved: S1. Weigh 88-89% of WC powder, 10-11% of Co powder, 0.4-0.6% of rare earth tantalate powder, 1-1.2% of Cu powder and 0.25-0.3% of carbon black according to the above weight percentages; add the weighed materials into a ball mill for 46-48 hours. After the ball milling is completed, take out the liquid slurry for standby use; S2, take out the liquid slurry after ball milling in S1 and place it in a tray, vacuum it for 2-3 hours, extract the upper layer of anhydrous ethanol, and then place it in a vacuum drying oven at a temperature of 75-80°C for 3-4 hours. After drying, sieve it and vacuum package it for later use; S3, placing the vacuum-encapsulated dry powder in S2 in a vacuum degreasing furnace for pre-sintering after compression molding, and then sending it to a low-pressure sintering furnace for sintering to prepare a cemented carbide.
7. The method for preparing a hard alloy for a wire drawing die according to claim 6, characterized in that: In the ball milling process, the ball milling medium is anhydrous ethanol, the liquid-solid ratio is 280-300 mL / kg, the ball-to-material ratio is 4.5-5:1, and the ball milling speed is 80-90 r / min.
8. The method for preparing cemented carbide for wire drawing dies according to claim 6, characterized in that: During the compression molding process, the compression pressure is 3-3.5 MPa and the pressure is maintained for 10-20 seconds.
9. The method for preparing a hard alloy for a wire drawing die according to claim 6, characterized in that: During the pre-sintering process, nitrogen is introduced, and the temperature is increased to 380-420°C at 5°C / min, and then kept warm for 1-1.2 hours. After the insulation is completed, the temperature is lowered to room temperature and then placed in a low-pressure sintering furnace for sintering, and the temperature is increased to 800-850°C at 10°C / min, and then increased to 1050-1100°C at 5°C / min, and kept warm for 30-40 minutes. After the insulation is completed, the temperature is increased to 1400-1450°C at 5°C / min, and kept warm for 30-40 minutes. After the insulation is completed, the material is taken out and cooled to room temperature to prepare a cemented carbide.
10. Use of the cemented carbide according to claims 6 to 9 in a wire drawing die.