Preparation method of mixed grain cold heading die material and mixed grain cold heading die material

Abstract

This invention provides a method for preparing a mixed-grain cold heading die material and the mixed-grain cold heading die material itself. The method involves mixing two types of powders with different grain sizes—WC powder, Co powder, and Cr2C3 powder—with paraffin wax. The mixture is then subjected to wet milling in a ball mill, drying and sieving, pressing, dewaxing and pressure sintering, and rapid cooling to obtain a high-performance mixed-grain cold heading die material. This preparation method is simple, requires no special equipment, has low production costs, and has broad application prospects.

Description

Technical Field

[0001] This invention relates to a method for preparing cemented carbide, specifically to a method for preparing a mixed-grain cold heading die material and the mixed-grain cold heading die material. Background Technology

[0002] Carbide cold heading dies are tools used for cold heading of metals. Cold heading is a very common metalworking process that involves plastically deforming metal materials at room temperature to create the desired shape and size. Carbide cold heading dies must possess characteristics such as high precision, high hardness, and high stability to ensure the dimensional accuracy and surface quality of metal products.

[0003] WC-Co cemented carbide is composed of high-strength tungsten carbide (WC) and high-toughness Co binder. It has excellent properties such as high hardness, wear resistance, heat resistance, and corrosion resistance. Cold heading dies are usually made of the above-mentioned WC-Co cemented carbide.

[0004] When using mainstream WC-Co cemented carbide grades for cold heading dies under continuous, high-speed stamping conditions, these dies are prone to chipping and wear. The main reasons for this problem include the selection and formulation of raw materials for cemented carbide production, and the cemented carbide manufacturing process. In existing technologies, the raw material system of traditional cemented carbide is optimized by replacing the WC powder in the aforementioned WC-Co cemented carbide with a mixture of coarse and fine WC grains of specific particle sizes. However, this method requires specially prepared coarse and fine WC powders, resulting in demanding production conditions and high production costs. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides a method for preparing a mixed grain cold heading die material and the mixed grain cold heading die material. The preparation method is simple and efficient, with low production cost, and the prepared mixed grain cold heading die has high hardness, bending strength and impact strength.

[0006] The technical solution of this invention is:

[0007] A method for preparing a mixed-grain cold heading die material, wherein the raw materials of the cold heading die material are the following components by weight percentage: 18-20% Co powder, 78-80% WC powder, and 1-2% Cr2C3 powder, wherein the WC powder includes two different particle sizes, coarse and fine WC powder, the average particle size of the coarse WC powder is 4.5-5.0µm, the average particle size of the fine WC powder is 1.8-2.2µm, and the weight ratio of coarse WC powder to fine WC powder is 1:1 to 3:1;

[0008] The preparation method of the mixed grain cold heading die material includes the following steps:

[0009] S1, Ingredients: Weigh and mix WC powder, Co powder, and Cr2C3 powder in proportion, then mix with paraffin wax to form a wet-milled mixture;

[0010] S2, Wet milling: The above wet milling mixture is put into a wet ball mill for ball milling to form a solid-liquid mixture slurry of cold heading die material after ball milling;

[0011] S3, Drying and sieving: The solid-liquid mixture slurry of the cold heading mold material obtained in S2 is dried in a water bath at a temperature of 80℃~85℃ for 2~3 hours, and then sieved through vibration to obtain the mixed powder of the cold heading mold material.

[0012] S4, Pressing: The cold heading die material mixture powder obtained in S3 is placed in the die and pressed by a hydraulic press to obtain a cold heading die material pressed sample.

[0013] S5, Dewaxing and Pressure Sintering: Place the sample pressed in S4 into a dewaxing and pressure sintering furnace, heat it to 1350℃~1400℃ and then fill it with high-pressure argon gas. Hold it in the argon atmosphere for 60~70 minutes.

[0014] S6, rapid cooling and warming: The cold heading die material after pressure sintering in S5 is rapidly cooled to room temperature in the furnace within 2 hours.

[0015] Furthermore, the fine WC powder is obtained by ball milling a portion of the coarse WC powder for 32-36 hours; or, the fine WC powder is commercially available fine WC powder with an average particle size of 1.8~2.2µm.

[0016] Furthermore, the coarse WC powder and fine WC powder in S1 are first subjected to a semi-calcination process, and then weighed and batched with the Co powder and the Cr2C3 powder in proportion. The semi-calcination process includes calcining the coarse WC powder and fine WC powder at a temperature of 600~800℃ for 1.5~2 hours.

[0017] Furthermore, the amount of paraffin added in the S1 ingredient is 2% of the total weight of the Co powder, WC powder and Cr2C3 powder mentioned above.

[0018] Furthermore, the wet milling medium is alcohol with a purity of ≥99%, the solid-liquid ratio of the ball mill is 220~260ml / kg, the ball-to-material ratio of the ball mill is 4:1~5:1, the rotation speed of the ball mill is 50r / min~55r / min, and the milling time is 10~12h.

[0019] Furthermore, the pressing pressure in the S4 pressing is 10~15T, and the holding time is 25~30s.

[0020] Furthermore, the pressure during the S5 dewaxing and pressurized sintering is 5~5.5MPa; the dewaxing includes first heating to 320~370℃ and holding for 120~150min; then heating to 1390~1430℃ and holding for 60~70min.

[0021] Furthermore, in the S6 rapid cooling and warming process, after the cold heading die material pressed part reaches the preset holding time in the S5 dewaxing and pressurizing sintering step, the power supply of the dewaxing and pressurizing sintering integrated furnace is cut off under a high-pressure argon atmosphere. After the furnace temperature drops to 700-750°C within 70-80 minutes, the power supply and heat preservation door of the dewaxing and pressurizing sintering integrated furnace is opened, and the dewaxing and pressurizing sintering integrated furnace and the sample placed in the dewaxing and pressurizing sintering integrated furnace are cooled to room temperature by a fan within 20-30 minutes.

[0022] Furthermore, the present invention provides a mixed-grain cold heading die material, which is prepared by the preparation method described in the present invention.

[0023] The beneficial technical effects of the present invention are as follows: The present invention provides a method for preparing a mixed grain cold heading die material and a mixed grain cold heading die material. The present invention uses two WC mixed crystals with different grain sizes as the hard phase of the cold heading die material. By relying on the impediment of dislocation movement at the mixed crystal interface, the hardness, bending strength and impact strength of the cold heading die are comprehensively improved.

[0024] This invention ensures the stability of the mechanical properties between the hard phase and the binder phase system in the cold heading die material through a rapid cooling and stabilization process.

[0025] This invention prepares fine-grained WC required for mixed crystals from coarse-grained WC, so that the performance indicators of the fine-grained WC are the same as those of coarse WC, such as particle morphology, particle size distribution range, and types and contents of impurities. This further optimizes the performance of the mixed combination of fine-grained WC and coarse WC, thereby further optimizing the physical and mechanical properties of the cold heading die material.

[0026] This invention performs a semi-burning process on the two WC crystals with different grain sizes before mixing them, so that the edges and corners of the two WC crystals with different grain sizes are relatively smooth after ball milling, thereby further optimizing the degree of mixing of the two WC crystals with different grain sizes.

[0027] In addition, the present invention also provides a mixed grain cold heading die material prepared by the above preparation method, which has a long service life. Attached Figure Description

[0028] Figure 1 Metallographic image of the mixed-grain cold heading die material of Embodiment 1 of the present invention:

[0029] Figure 2Metallographic image of the mixed-grain cold heading die material of Embodiment 2 of the present invention:

[0030] Figure 3 Metallographic image of the mixed-grain cold heading die material of Embodiment 3 of the present invention:

[0031] Figure 4 Metallographic image of the mixed-grain cold heading die material of Embodiment 4 of the present invention:

[0032] Figure 5 Metallographic image of the mixed-grain cold heading die material of Embodiment 5 of the present invention:

[0033] Figure 6 Metallographic image of the mixed-grain cold heading die material of Comparative Example 1 of this invention:

[0034] Figure 7 Metallographic image of the homogeneous cold heading die material of Comparative Example 2 of this invention: Detailed Implementation

[0035] In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0036] This invention provides a method for preparing a mixed-grain cold heading die material, including processes such as S1 batching, S2 wet grinding, S3 drying and sieving, S4 pressing, S5 dewaxing and pressure sintering, and S6 rapid cooling and warming.

[0037] Example 1

[0038] S1, Ingredients: The raw materials for the mixed grain cold heading die material are the following components by weight percentage: 20% Co powder with an average particle size of 2.0µm, 79% WC powder, and 1% Cr2C3 powder with an average particle size of 1.0µm. The above raw materials are weighed and mixed with paraffin wax according to the specified proportions, wherein the amount of paraffin wax added is 2% of the total weight of the Co powder, WC powder, and Cr2C3 powder. The WC includes two different particle sizes: coarse WC (Jinlu-GWC050) with a particle size of 4.5~5.0µm and fine WC (Jinlu-GWC020) with a particle size of 1.8~2.2µm, with a weight ratio of coarse WC to fine WC of 1:1.

[0039] During the processing of cemented carbide materials, WC grain growth can occur. Excessively large WC grains weaken the matrix interface and impair the strength of the tooling. Cr2C3 powder, acting as an inhibitor, effectively controls WC grain growth during production. This is a common technique in this field and will not be elaborated upon further. Paraffin wax, as a forming agent, facilitates subsequent pressing and molding.

[0040] S2, Wet milling: The weighed and batched coarse WC powder, fine WC powder, Co powder, Cr2C3 powder, and paraffin wax are put into a wet ball mill for ball milling. The wet milling medium is alcohol with a purity of ≥99%. The solid-liquid ratio of the ball mill is 220ml of alcohol added to 1kg of the batched powder in S1. The ball-to-material ratio of the ball mill is 4:1. The speed of the ball mill is 50r / min. The ball milling time is 12h to form a solid-liquid mixture slurry of cold heading mold material after ball milling.

[0041] S3, Drying and sieving: The solid-liquid mixture of cold heading mold material obtained in S2 is dried in a water bath at a temperature of 80℃~85℃ for 2~3 hours, and then sieved to obtain the mixed powder of cold heading mold material.

[0042] S4, Pressing: The cold heading die material mixture powder obtained in S3 is placed in a 10×10×55mm die and pressed by a hydraulic press to obtain a cold heading die material pressed part, wherein the pressing pressure is 10-15T and the holding time is 25-30s.

[0043] S5, Dewaxing and Pressure Sintering: The cold heading die material pressed by S4 is placed in a dewaxing and pressure sintering furnace. Under an argon atmosphere and a pressure of 5.5 MPa, the temperature is first raised to 370℃ and held for 120 minutes, which is the dewaxing stage; then the temperature is raised to 1430℃ and held for 70 minutes, which is the sintering stage.

[0044] S6, rapid cooling and warming: After the cold heading mold material pressing part in S5 reaches the preset heat preservation time, the power supply of the above-mentioned dewaxing and pressurizing sintering integrated furnace is cut off under high pressure argon atmosphere. After the furnace temperature drops to 700~750℃ within 70min~80min, the power supply heat preservation door of the dewaxing and pressurizing sintering integrated furnace is opened, and the dewaxing and pressurizing sintering integrated furnace and the cold heading mold material pressing part placed in the dewaxing and pressurizing sintering integrated furnace are cooled to room temperature by a fan within 20min~30min.

[0045] Example 2

[0046] Compared with Example 1, Example 2 differs only in the weight ratio of coarse WC to fine WC. The weight ratio of coarse WC to fine WC in the S1 batch of Example 2 is set to 3:1. Then, it is mixed with 20% Co powder, 79% coarse and fine WC powder, 1% Cr2C3 powder and paraffin wax. The amount of paraffin wax added is 2% of the total weight of the Co powder, WC powder and Cr2C3 powder. All other process conditions are the same.

[0047] Example 3

[0048] Compared to Example 1, Example 3 differs only in the S1 ingredient preparation step; all other process conditions remain the same. Specifically, the fine WC in the S1 ingredient is obtained by ball milling the coarse WC (Jinlu-GWC050) from Example 1. Specifically, a predetermined amount of 4.5~5.0µm coarse WC (Jinlu-GWC050) is ball-milled at 50 r / min, a ball-to-material ratio of 4:1, with 99% pure alcohol as the milling medium and a solid-liquid ratio of 1 kg / ml in 220 ml of alcohol. After 36 hours of ball milling, fine WC-2 with an average particle size of 1.6µm is obtained. Since the fine WC-2 in Example 3 is prepared from coarse WC, the performance indicators of the fine WC-2, such as particle morphology, particle size distribution range, and the types and amounts of impurities, are the same as those of the coarse WC, thereby further optimizing the performance of the mixture of fine WC-2 and coarse WC.

[0049] In Example 3, the weight ratio of coarse WC to fine WC-2 in the S1 batch was set to 1:1. Then, it was mixed with 20% Co powder, 79% coarse WC and fine WC-2 powder, 1% Cr2C3 powder and paraffin wax. The amount of paraffin wax added was 2% of the total weight of the Co powder, WC powder and Cr2C3 powder. The remaining process conditions were the same as those in Example 1.

[0050] Example 4

[0051] Compared with Example 1, Example 4 differs only in the S1 ingredient preparation step. Specifically, both the coarse and fine WC required for S1 ingredient preparation undergo a semi-calcination process. Coarse WC is calcined at 600-800℃ for 2 hours to obtain coarse WC-2, and fine WC is calcined at 600-800℃ for 2 hours to obtain fine WC-3. Then, in Example 4, the weight ratio of coarse WC-2 to fine WC-3 in the S1 ingredient preparation is 1:1, mixed with 20% Co powder, totaling 79% coarse WC-2 and fine WC-3 powder, and 1% Cr2C3 powder and paraffin wax. The amount of paraffin wax added is 2% of the total weight of the Co powder, WC powder, and Cr2C3 powder. The remaining processes and required raw materials are the same as in Example 1.

[0052] Example 5

[0053] Compared with Example 3, Example 5 differs only in the processing technology of fine WC; all other process conditions and raw materials are the same as in Example 3.

[0054] Specifically, the fine WC-2 obtained in Example 3 is subjected to a semi-calcination process, that is, the fine WC-2 is calcined at a temperature of 600-800℃ for 2 hours to obtain fine WC-4. Then, the weight ratio of coarse WC-2 and fine WC-4 in the S1 batch of Example 5 is set to 1:1, and then mixed with 20% Co powder, 79% coarse WC-2 and fine WC-4 powder, 1% Cr2C3 powder and paraffin wax. The amount of paraffin wax added is 2% of the total weight of the Co powder, WC powder and Cr2C3 powder. The rest of the process and the required raw materials are the same as in Example 3.

[0055] Comparative Example 1

[0056] In this invention, Comparative Example 1 differs from Example 3 in that the S6 rapid cooling and warming process is omitted, while the remaining processes and required raw materials are the same as in Example 3.

[0057] Comparative Example 2

[0058] Compared with Example 1, Comparative Example 2 differs only in the WC raw material in the S1 batching step; all other process conditions and raw materials are the same as in Example 1.

[0059] Specifically, the average particle size of the homogeneous WC powder (Zhangyuan, ZWC30) required for ingredient S1 is 2.4µm. 79% homogeneous WC powder is mixed with 20% Co powder, 79% homogeneous WC powder, and 1% Cr2C3 powder. These raw materials are weighed and mixed with paraffin wax according to the specified proportions. The amount of paraffin wax added is 2% of the total weight of the Co powder, WC powder, and Cr2C3 powder. The remaining processes and required raw materials are the same as in Example 1.

[0060] The physical and mechanical properties test results of the cold heading dies of Examples 1-5 and Comparative Examples 1-2 are shown in Table 1 below.

[0061] Table 1. Physical and mechanical properties of cold heading dies in Examples 1-5 and Comparative Examples 1-2

[0062]

[0063] As can be seen from Table 1 above, the mixed grain cold heading die materials of Examples 1-5 of the present invention all have good comprehensive physical and mechanical properties, among which the improvement in hardness, bending strength and impact strength of Example 5 is more obvious.

[0064] Specifically, compared to Comparative Example 2, the hardness, bending strength, and impact strength of Example 1 are significantly improved. This is because, unlike Comparative Example 2 where the hard phase of the cold heading die is homogeneous WC, the hard phase of the cold heading die in Example 1 is a mixture of coarse and fine WC, with a weight ratio of 1 to 1. Mixed crystals refer to the phenomenon of different grains being mixed in a metal alloy. The degree of mixed crystals refers to the extent of this mixing, usually expressed by the proportion of mixed crystals or the grain size of the mixed crystals. The degree of mixed crystals affects the mechanical and physical properties of the alloy because the interfaces between the mixed crystal grains hinder dislocation movement, thus strengthening the material. However, an excessively high degree of mixed crystals can also reduce the alloy's toughness, thereby lowering its overall performance. The degree of mixed crystals is related to factors such as the alloy's manufacturing process, the content of alloying elements, and the cooling rate.

[0065] In Example 1, the coarse WC grains with intact grains and few defects provide good plasticity and toughness for its cold heading die; the fine WC, uniformly dispersed among the coarse WC, increases the hardness and wear resistance of the cold heading die by hindering dislocation movement at the mixed grain interface. This is reflected in the test data in Table 1, where Example 1 shows a significant improvement in hardness, flexural strength, and impact strength compared to Comparative Example 2. Furthermore, as... Figure 1 As shown, in Example 1, the coarse WC and fine WC are in a continuous and uniform distribution, which further illustrates that the fine WC is relatively uniformly dispersed among the coarse WC, creating a good barrier to dislocation movement between the coarse and fine WC grains, thereby strengthening the material; while as Figure 7 As shown, in Comparative Example 2, the microstructure of the cold heading die exhibits significant voids between the homogeneous WC grains. Therefore, the mechanical and physical properties of the hard phase of the cold heading die of this invention, which uses mixed WC, are superior to those of the hard phase using homogeneous WC.

[0066] In Example 2, the hard phase of the cold heading die is a mixture of coarse and fine WC, with a weight ratio of 3 to 1, meaning the amount of coarse WC is much greater than the amount of fine WC. Figure 2 As shown, the microstructure of Example 2 indicates that the fine WC in Example 2 is dispersed among the coarse WC, but... Figure 1 In comparison, the degree of continuous and uniform distribution of coarse and fine WC in Example 2 is significantly lower than that in Example 1, resulting in inferior mixed-crystal strengthening of coarse and fine WC compared to Example 1. This is reflected in the test data in Table 1, where the bending strength and impact strength of Example 2 are both lower than those of Example 1. Therefore, it is indicated that a 1:1 weight ratio of coarse to fine WC in the cemented carbide of the cold heading die in this invention provides the best mixed-crystal strengthening effect.

[0067] Regarding Examples 3 and 1, in Example 3, the fine WC-2 was prepared from coarse WC, ensuring that the fine WC-2 had the same performance indicators as the coarse WC in terms of particle morphology, particle size distribution range, and the types and contents of impurities. This further optimized the performance of the mixed combination of fine WC-2 and coarse WC. This is reflected in the test structures in Table 1, where the flexural strength and impact strength of Example 3 are both improved compared to Example 1.

[0068] As shown in Table 1, compared with Example 3, the flexural strength and impact strength of Comparative Example 1 are both lower than those of Example 3. Figure 3 and Figure 6 It can be seen that the microstructure of the cold heading dies corresponding to Example 3 and Comparative Example 2 is continuous and homogeneous. Compared with Example 3, Comparative Example 1 is identical in raw material composition and other process conditions except that it did not undergo a rapid cooling and reheating process. In this invention, the cold heading die is composed of hard WC and soft binder metal Co. WC provides the cold heading die with load-bearing capacity and wear resistance. Due to the good wettability and adhesion of Co to the hard phase of WC, WC has a high solubility in Co. Therefore, the binder metal Co imparts impact toughness to the cemented carbide through its ability to undergo plastic deformation at room temperature. After high-temperature sintering, the hard phase and binder phase Co of the cold heading die in Comparative Example 1 are in a solid solution state. During its slow cooling process, the binder phase Co precipitates from this solid solution state to varying degrees, thus affecting the solubility of WC in the binder phase Co. In Example 3, based on Comparative Example 1, a rapid cooling and warming process was performed after high-temperature sintering, thereby reducing the degree of Co precipitation and improving the various mechanical properties of the WC-Co cemented carbide system.

[0069] As shown in Table 1, the improvements in hardness, flexural strength, and impact strength are more significant in Examples 4-5. This is because, before mixing the two different grain sizes of WC in Examples 4-5 to prepare the cemented carbide, a semi-sintering process was performed. The semi-sintered process resulted in relatively smoother edges and corners for both the coarse and fine WC particles, further optimizing the degree of mixing between coarse and fine WC. Figures 4-5 It can be seen that the microstructure of the corresponding cold heading dies in Examples 4 and 5 exhibits a good continuous and uniform distribution. In Example 5, compared to Example 4, the fine WC-4 is obtained by ball milling coarse WC followed by a semi-sintering process. Therefore, the two different grain sizes of WC in the cold heading die of Example 5 are more compatible in mixed-grain formulation. The specific reasons have been discussed above and will not be repeated here. Thus, Example 5 exhibits the best overall mechanical properties compared to the other examples.

[0070] In addition, the cold heading die materials of Embodiments 1-5 and Comparative Examples 1-2 of the present invention were subjected to continuous stamping screw and nut tests. The product performance of the cold heading die materials was comprehensively judged based on the service life and internal surface condition failure mode of the cold heading die materials of the above embodiments and comparative examples. The test results are shown in Table 2.

[0071] Table 2. Statistical Comparison of Mold Lifespan between Examples 1-5 and Comparative Examples 1-2

[0072]

[0073] As can be seen from Table 2, Example 5 of the present invention has an average service life of 1 million cycles and no obvious failure mode. The average service life of Examples 1-4 is lower than that of Example 5, and all of them show wear. In addition to the shorter service life, Comparative Examples 1-2 also show slight chipping, which is related to their lower impact strength.

[0074] The present invention also provides a mixed grain cold heading die material, which is prepared by the above preparation method.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit 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 technical principles 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 of producing a mixed grain cold header die material, characterized by: The raw materials for this mixed-grain cold heading die material are the following components by weight percentage: 18-20% Co powder, 78-80% WC powder, and 1-2% Cr2C3 powder. The WC powder includes two different particle sizes: coarse and fine. The average particle size of the coarse WC powder is 4.5-5.0µm, and the average particle size of the fine WC powder is 1.8-2.2µm. The weight ratio of coarse WC powder to fine WC powder is 1:1 to 3:

1. The preparation method of the mixed grain cold heading die material includes the following steps: S1, Ingredients: Weigh and mix WC powder, Co powder, and Cr2C3 powder in proportion, then mix with paraffin wax to form a wet-milled mixture; S2, Wet milling: The above wet milling mixture is put into a wet ball mill for ball milling to form a solid-liquid mixture slurry of cold heading die material after ball milling; S3, Drying and sieving: The solid-liquid mixture slurry of the cold heading mold material obtained in S2 is dried in a water bath at a temperature of 80℃~85℃ for 2~3 hours, and then sieved through vibration to obtain the mixed powder of the cold heading mold material. S4, Pressing: The cold heading die material mixture powder obtained in S3 is placed in the die and pressed by a hydraulic press to obtain a cold heading die material pressed sample. S5, Dewaxing and Pressure Sintering: Place the sample pressed in S4 into a dewaxing and pressure sintering furnace, heat it to 1350℃~1400℃ and then fill it with high-pressure argon gas. Hold it in the argon atmosphere for 60~70 minutes. S6, rapid cooling and warming: The cold heading die material after pressure sintering in S5 is rapidly cooled to room temperature in the furnace within 2 hours; The coarse WC powder and fine WC powder are first subjected to a semi-calcination process, and then weighed and batched with the Co powder and the Cr2C3 powder in proportion. The semi-calcination process includes calcining the coarse WC powder and fine WC powder at a temperature of 600~800℃ for 1.5~2 hours.

2. The method of claim 1, wherein: The fine WC powder is obtained by ball milling a portion of the coarse WC powder for 32-36 hours; or, the fine WC powder is commercially available fine WC powder with an average particle size of 1.8~2.2µm.

3. The method of claim 1, wherein: The amount of paraffin added in the S1 ingredient is 2% of the total weight of the Co powder, WC powder and Cr2C3 powder mentioned above.

4. The method of claim 1, wherein: The wet grinding medium is alcohol with a purity of ≥99%, the solid-liquid ratio of the ball mill is 220~260ml / kg, the ball-to-material ratio of the ball mill is 4:1~5:1, the rotation speed of the ball mill is 50r / min~55r / min, and the ball milling time is 10~12h.

5. The method of claim 1, wherein: The pressing pressure in the S4 pressing is 10~15T, and the holding time is 25~30s.

6. The method for preparing the mixed-grain cold heading die material according to claim 1, characterized in that: The pressure during the S5 dewaxing and pressurized sintering process is 5~5.5MPa; the dewaxing process includes first heating to 320~370℃ and holding for 120~150min; then heating to 1390~1400℃ and holding for 60~70min.

7. The method for preparing the mixed-grain cold heading die material according to claim 1, characterized in that: In the S6 rapid cooling and warming process, after the cold heading die material pressed sample reaches the preset holding time in the S5 dewaxing and pressurizing sintering step, the power supply of the dewaxing and pressurizing sintering integrated furnace is cut off under a high-pressure argon atmosphere. After the furnace temperature drops to 700-750°C within 70-80 minutes, the power supply and heat preservation door of the dewaxing and pressurizing sintering integrated furnace is opened, and the dewaxing and pressurizing sintering integrated furnace and the sample placed in the dewaxing and pressurizing sintering integrated furnace are cooled to room temperature by a fan within 20-30 minutes.

8. A mixed-grain cold heading die material, characterized in that: Prepared by the method according to any one of claims 1 to 7.

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