High-performance cemented carbide rod for woodworking knives and method for producing the same

Abstract

The application belongs to the technical field of hard alloy and particularly relates to high-performance hard alloy rod for woodworking knives and a preparation method thereof. x Complex carbide powder, spherical Co powder and carbonyl Ni powder; S2, mixing (W, Cr)C x carbide powder, spherical Co powder and carbonyl Ni powder are mixed, ball-milled and spray-dried to obtain mixed granules; S3, the mixed granules are loaded into a porous mold for vertical compression molding to obtain a hard alloy rod blank, and the hard alloy rod blank is sintered to obtain the hard alloy rod, and the sintering atmosphere is methane. The application improves the uniformity of the green compact density through the porous mold vertical compression molding process and the gradient carburizing sintering process, avoids the muscle edge cracks and abrasion loss caused by horizontal compression molding, and forms the binder phase distribution with a specific gradient structure through high-temperature carburizing sintering, thereby significantly improving the impact resistance, wear resistance and corrosion resistance of the material, and the material is suitable for high-speed, high-load and strong-vibration working conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hard alloy, in particular, the present application relates to a high-performance hard alloy rod for woodworking knives and a preparation method thereof. BACKGROUND

[0002] Hard alloy is widely used in the manufacture of woodworking tools due to its high hardness, high strength and excellent wear resistance. However, with the development of woodworking machinery towards high speed and high load, and the increasing demand for processing precision and surface quality, the existing hard alloy rods for woodworking tools gradually expose the problem of insufficient comprehensive performance.

[0003] At present, the mainstream woodworking tools mainly use subcrystalline tungsten carbide-based hard alloy with cobalt as the binder phase. Such materials mainly have the following defects in microstructure, mechanical properties and corrosion resistance:

[0004] Firstly, in terms of material composition and microstructure, the phase composition design of existing alloys is single, and it is difficult to balance high hardness and high toughness. Although high tungsten carbide content can ensure the hardness of the matrix, it usually leads to the decrease of toughness, resulting in the collapse of the blade when processing wood materials with obvious anisotropy due to uneven impact load. In addition, the binder phase of conventional alloys is mainly pure cobalt, which is easily chemically corroded by water and organic acid in wood during wood processing. After the corrosion and wear of the binder phase, the hard phase particles lose support and fall off, significantly accelerating the wear and failure of the tool.

[0005] Secondly, in terms of macroscopic performance, the existing homogeneous structure hard alloy rod has consistent composition, hardness and toughness on the surface and core, and cannot realize functional gradient. This leads to the fact that the blade part of the tool needs to have extremely high hardness to maintain sharpness and resistance to wear, and also needs sufficient toughness to resist impact. The single homogeneous material structure is difficult to meet the two contradictory performance requirements at the same time. As a result, the toughness is sacrificed for the pursuit of hardness, leading to brittle fracture, or the hardness is lost for the sake of toughness, resulting in rapid dulling of the blade.

[0006] Thirdly, in terms of preparation process, traditional powder metallurgy methods such as conventional die compaction and cross-pressing forming are prone to uneven density of the compact, especially for rod blanks with complex rib edge structure, which are prone to cracks from the rib edge with lower density during subsequent processing or use.

[0007] Therefore, there is an urgent need in the art for a new type of high-performance hard alloy rod which can solve the above technical bottlenecks. SUMMARY

[0008] To solve the above technical problems, the present application provides a preparation method of a high-performance hard alloy rod for woodworking knives, comprising the following steps: S1, obtaining (W, Cr)Cx The total carbon content of the raw materials is 5.93-5.97%, the mass ratio of the mixed carbide powder, the spherical Co powder and the carbonyl Ni powder is (98.2-97.6):(1.4-1.7):(0.4-0.7), the (W,Cr)C x The total carbon content of the raw materials is 5.93-5.97%, the mass ratio of the mixed carbide powder, the spherical Co powder and the carbonyl Ni powder is (98.2-97.6):(1.4-1.7):(0.4-0.7), the (W,Cr)C x The total carbon content of the raw materials is 5.93-5.97%, the mass ratio of the mixed carbide powder, the spherical Co powder and the carbonyl Ni powder is (98.2-97.6):(1.4-1.7):(0.4-0.7), the (W,Cr)C

[0009] As a preferred scheme of the preparation method of the high-performance cemented carbide rod for woodworking knives, in the step S1, the (W,Cr)C x The Feret particle size of the mixed carbide powder is 0.4-0.6 μm, the Feret particle size of the spherical Co powder is 0.6-0.8 μm, the (W,Cr)C x The mass ratio of the Cr element in the mixed carbide powder to the Ni element in the carbonyl Ni powder is (0.65-0.85):1.

[0010] As a preferred scheme of the preparation method of the high-performance cemented carbide rod for woodworking knives, in the step S1, the (W,Cr)C x The preparation method of the mixed carbide powder comprises: reducing blue tungsten under a hydrogen atmosphere to obtain nano W powder; obtaining carbon black through a cracking reaction of natural gas; mixing the nano W powder, the carbon black and Cr3C2 powder, and then carbonizing under an argon protective atmosphere to obtain carbide, and then crushing the carbide by using a high-performance airflow mill to obtain the (W,Cr)C x The mixed carbide powder, the (W,Cr)C x The mixed carbide powder has a porous branched structure, the (W,Cr)C x The branched length of the mixed carbide powder is 1-3 μm, the (W,Cr)C x The porosity of the mixed carbide powder is 40-60%.

[0011] As a preferred scheme of the preparation method of the high-performance cemented carbide rod for woodworking knives, the step S2 further comprises: adding paraffin and alcohol in the process of the ball milling, the mass of the paraffin is 2.0-2.3 wt% of the mass of the raw materials, the rotation speed of the ball milling is 600-800 rpm, and the ball milling time is 36-40 h.

[0012] As a preferred scheme of the preparation method of the high-performance cemented carbide rod for woodworking knives, in the step S2, the process parameters of the spray drying are as follows: the feed pressure is 10-11 bar, the spray hole diameter is 1.0-1.3 mm, the cyclone dust collection pressure difference is 8-11 mbar, the spray temperature is 110-120 DEG C, and the outlet cooling temperature is 80-90 DEG C; the flow rate of the mixed granules is < 30 s / 50 g, and the loose bulk density of the mixed granules is 3.25-3.75 g / cm 3 .

[0013] As a preferred scheme of the preparation method of the high-performance cemented carbide rod for woodworking knives, in the step S3, the mold for the vertical pressure forming is a multi-hole mold, and the process parameters of the vertical pressure forming are as follows: the unit pressing force is 1.5-1.8 T / cm 2 , the pressing speed is 25-30 seconds per mold, the shrinkage coefficient is 18-19%, and the single weight tolerance is ± 0.08 g.

[0014] As a preferred scheme of the preparation method of the high-performance cemented carbide rod for woodworking knives, in the step S3, the sintering temperature is 1400-1430 DEG C, the sintering time is 30-60 min, and the flow rate of the methane is 0.4-0.8 mL / s.

[0015] The application further provides a high-performance cemented carbide rod for woodworking knives, which is prepared by the above preparation method of the high-performance cemented carbide rod for woodworking knives.

[0016] As a preferred scheme of the high-performance cemented carbide rod for woodworking knives, the cemented carbide rod has a gradient structure, which comprises, from outside to inside, a surface layer, a subsurface layer, and a core portion, the volume fraction of the binder phase in the surface layer accounts for 0.5-1.2%, the volume fraction of the binder phase in the subsurface layer accounts for 3-5%, the volume fraction of the binder phase in the core portion accounts for 2-2.8%, the thickness of the surface layer is 0.2-0.4 mm, the residual compressive stress of the surface layer is ≥ 450 MPa, the Rockwell hardness HRA of the surface layer is 94-95, the fracture toughness KIC of the surface layer is ≥ 7.5 MPa·m 1 / 2 , the thickness of the subsurface layer is 0.6-0.8 mm, the residual tensile stress of the subsurface layer is ≥ 360 MPa, the Rockwell hardness HRA of the subsurface layer is 91-92, and the fracture toughness KIC of the subsurface layer is ≥ 9.8 MPa·m 1 / 2 , the residual compressive stress of the core portion is ≥ 120 MPa, the Rockwell hardness HRA of the core portion is 92-93, and the fracture toughness KIC of the core portion is ≥ 8 MPa·m 1 / 2The bending strength TRS of the hard alloy rod is greater than or equal to 3000 MPa.

[0017] As a preferred scheme of the high-performance hard alloy rod for woodworking knives, the hard alloy rod comprises a Cr3Ni2 nickel-chromium alloy phase, the content of the Cr3Ni2 nickel-chromium alloy phase of the hard alloy rod is 0.7-1.1 wt%, the self-corrosion potential of the hard alloy rod in a hydrochloric acid solution with pH=1 is-0.26 to-0.22 V, and the self-corrosion potential of the hard alloy rod in a sodium hydroxide solution with pH=13 is-0.18 to-0.15 V.

[0018] The beneficial effects of the present application are as follows:

[0019] Compared with the prior art, the high-performance hard alloy rod for woodworking knives and the preparation method thereof provided by the present application, by combining a unique material formula with an innovative preparation process, the following remarkable beneficial effects are achieved:

[0020] 1. The synergistic improvement of high hardness and high toughness is realized: by accurately controlling the content of tungsten carbide (WC) hard phase to 97.6-98.2 wt%, the surface hardness of the alloy matrix is improved to a high level of HRA94-95, which ensures the sharpness of the knife edge and excellent wear resistance. At the same time, through the synergistic design of cobalt (Co, 1.4-1.7 wt%) and nickel (Ni, 0.4-0.7 wt%) in the binder phase, and the control of (W, Cr)C x The mass ratio of Cr element in the complex carbide powder to Ni element in the carbonyl Ni powder is (0.65-0.85):1, and the total carbon content is 5.93-5.97%; in-situ generation of a Cr3Ni2 nickel-chromium alloy phase with a content of 0.7-1.1 wt% in the system. This strengthening phase effectively enhances the strength and toughness of the binder phase, so that the material obtains high hardness while the impact toughness and plasticity are guaranteed, fundamentally solving the contradiction between high hardness and high toughness, and effectively preventing the collapse and fracture of the knife.

[0021] 2. The performance-optimized gradient structure is constructed, and the functional zoning is realized: through a special high-temperature gradient carburizing sintering process, a gradient structure including a surface layer, a subsurface layer and a core from the surface to the inside of the alloy rod is successfully constructed. The essential feature of this structure is that the volume fraction of the binder phase is regularly gradient distributed:

[0022] Surface layer: with the lowest volume fraction of the binder phase, a hard phase-rich zone with high tungsten carbide and low binder phase is formed, thereby giving the alloy surface layer extremely high hardness (HRA94-95) and excellent wear resistance, directly dealing with the most severe wear in the cutting process.

[0023] Subsurface: with the highest volume fraction of binder phase, forming a high binder phase toughness-rich zone, which is high in toughness and plasticity, can effectively absorb and disperse impact energy during processing, prevent micro-cracks on the surface from expanding to the interior, and enable the alloy to withstand high working loads.

[0024] Core: with a volume fraction of binder phase between the surface layer and the subsurface, maintaining good rigidity to provide solid support for the entire tool, ensuring dimensional stability under high-speed operation.

[0025] This "hard outer surface-tough middle- rigid core" gradient structure design enables different regions of a single sample to optimize the functions of wear resistance, impact resistance, and rigidity retention, respectively.

[0026] 3. Significantly enhanced chemical corrosion and wear resistance: Traditional pure cobalt binder phase is easily corroded in wood processing environments. The introduction of Ni element and the formation of Cr3Ni2 strengthening phase with Cr element significantly improve the corrosion resistance of the binder phase itself, effectively slowing down the chemical corrosion caused by moisture and organic acid in wood, thereby prolonging the service life of the tool in harsh working conditions.

[0027] 4. Preparation process ensures the uniformity and integrity of the material structure: The use of porous mold vertical compression molding process effectively improves the uniformity of the green density, avoiding the muscle edge cracks and wear loss caused by traditional horizontal compression molding, laying a structural foundation for subsequent high-performance sintered body. This preparation method closely combines material design and is the key to achieving the above excellent microstructure and macroscopic properties.

[0028] In summary, through the synergistic innovation of composition, structure and process, the hard alloy rod prepared by the present application has excellent comprehensive performance, especially suitable for woodworking tool applications under high-speed, high-load and strong vibration conditions, effectively solving the problems of early edge collapse, fracture and excessive wear caused by the lack of hardness, strength, toughness and corrosion resistance of existing tools. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] The present application provides a preparation method of a high-performance hard alloy rod for woodworking tools, comprising the following steps: S1, obtaining (W, Cr)C x The total carbon content in the raw materials is 5.93-5.97%, and the (W, Cr)Cx The mass ratio of the complex carbide powder, the spherical Co powder, and the carbonyl Ni powder is (98.2-97.6):(1.4-1.7):(0.4-0.7);

[0031] The (W,Cr)C x The Fisher particle size of the complex carbide powder is 0.4-0.6 μm, the Fisher particle size of the spherical Co powder is 0.6-0.8 μm, and the (W,Cr)C x The mass ratio of the Cr element in the complex carbide powder to the Ni element in the carbonyl Ni powder is (0.65-0.85):1;

[0032] Specifically, the total carbon content in the raw material is any one of 5.93%, 5.94%, 5.95%, 5.96%, 5.97% and a range between any two of them; the (W,Cr)C x The mass ratio of the Cr element in the complex carbide powder to the Ni element in the carbonyl Ni powder is any one of 0.65:1, 0.70:1, 0.75:1, 0.80:1, 0.85:1 and a range between any two of them;

[0033] The (W,Cr)C x The preparation method of the complex carbide powder comprises the following steps:

[0034] (1) reducing blue tungsten with a specific surface area of 12-15 m 2 / g in a hydrogen atmosphere to obtain nano-W powder with a particle size of 50-80 nm;

[0035] (2) generating carbon black with a particle size of 80-120 nm by cracking natural gas;

[0036] (3) mixing the nano-W powder, the carbon black, and Cr3C2 powder, wherein the addition amount of Cr3C2 accounts for 0.5-0.8 wt% of the total mass of the final complex carbide powder, and the particle size of Cr3C2 is 0.6-1.0 μm;

[0037] (4) performing carbonization treatment in a rotary tube furnace under an argon protective atmosphere, with an argon flow rate of 0.8-1.2 m 3 / h, at 1400-1480 °C to obtain carbide, and the carbonization degree is ≥99.5%;

[0038] (5) performing crushing treatment on the carbide by using a high-performance airflow mill to obtain the (W,Cr)C x The complex carbide powder is crushed to a Fisher particle size of 0.4-0.6 μm under a working pressure of 0.8-1.0 MPa;

[0039] The (W,Cr)Cx The complex carbide powder has a porous branch structure, and the (W, Cr)C x The branch length of the complex carbide powder is 1-3 μm, and the (W, Cr)C x The porosity of the complex carbide powder is 40-60%.

[0040] S2, the (W, Cr)C x The complex carbide powder, the spherical Co powder and the carbonyl Ni powder are mixed, and then ball milling and spray drying are performed to obtain mixed particles;

[0041] In the process of the ball milling, paraffin and alcohol are further added, the mass of the paraffin is 2.0-2.3 wt% of the mass of the raw material, the rotation speed of the ball milling is 600-800 rpm, and the ball milling time is 36-40 h; the process parameters of the spray drying are as follows: the feeding pressure is 10-11 bar, the nozzle aperture is 1.0-1.3 mm, the cyclone dust collection pressure difference is 8-11 mbar, the spray material temperature is 110-120℃, and the outlet cooling temperature is 80-90℃; the flow rate of the mixed particles is <30 s / 50 g, and the loose bulk density of the mixed particles is 3.25-3.75 g / cm 3 .

[0042] S3, the mixed particles are loaded into a porous mold to perform vertical compression molding to obtain a cemented carbide rod blank, and the cemented carbide rod blank is sintered to obtain a cemented carbide rod material, and the sintering atmosphere is methane;

[0043] The mold for the vertical compression molding is a porous mold, and the process parameters of the vertical compression molding are as follows: the unit pressing force is 1.5-1.8 T / cm 2 , the pressing speed is 25-30 seconds per mold, the shrinkage coefficient is 18-19%, and the single weight tolerance is ±0.08 g; the sintering temperature is 1400-1430℃, the sintering time is 30-60 min, and the flow rate of the methane is 0.4-0.8 mL / s;

[0044] Specifically, the unit pressing force is 1.5 T / cm 2 , 1.6 T / cm 2 , 1.7 T / cm 2 , 1.8 T / cm 2any one of and a range between any two of 25 s / mold, 26 s / mold, 27 s / mold, 28 s / mold, 29 s / mold, 30 s / mold; the sintering temperature is any one of and a range between any two of 1400℃, 1405℃, 1410℃, 1415℃, 1420℃, 1425℃, 1430℃; the sintering time is any one of and a range between any two of 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min; the flow rate of the methane is any one of and a range between any two of 0.4 mL / s, 0.5 mL / s, 0.6 mL / s, 0.7 mL / s, 0.8 mL / s.

[0045] The technical scheme of the present application is further described below in conjunction with specific embodiments.

[0046] Embodiment 1

[0047] The present application provides a preparation method of high-performance hard alloy rod for woodworking knives, comprising the following steps:

[0048] S1, obtaining (W, Cr)C x The total carbon content in the raw materials is 5.95%, (W, Cr)C x The mass ratio of the complex carbide powder, the spherical Co powder, and the carbonyl Ni powder is 98.0:1.5:0.5; (W, Cr)C x The Fisher particle size of the complex carbide powder is 0.5 μm, the Fisher particle size of the spherical Co powder is 0.7 μm, and (W, Cr)C x The mass ratio of the Cr element in the complex carbide powder to the Ni element in the carbonyl Ni powder is 0.75:1; (W, Cr)C x The complex carbide powder has a porous branched structure, the branch length is 2.2 μm, and the porosity is 48%.

[0049] S2, mixing (W, Cr)C x The complex carbide powder, the spherical Co powder, the carbonyl Ni powder, paraffin, and alcohol are mixed and then subjected to ball milling and spray drying to obtain mixed particles; wherein the mass of the paraffin is 2.1 wt% of the mass of the raw materials, the rotation speed of the ball milling is 700 rpm, and the ball milling time is 38 h; the process parameters of the spray drying are specifically as follows: the feeding pressure is 10.5 bar, the nozzle aperture is 1.2 mm, the cyclone dust collection pressure difference is 9.5 mbar, the spray material temperature is 115℃, and the outlet cooling temperature is 85℃; the flow rate of the mixed particles is <30 s / 50 g, and the loose bulk density of the mixed particles is 3.55 g / cm 3 .

[0050] S3, the mixed particles are loaded into a porous mold for vertical compression molding to obtain a hard alloy rod blank, and the hard alloy rod blank is sintered to obtain a hard alloy rod material, and the atmosphere of the sintering is methane; wherein the process parameters of the vertical compression molding are as follows: the unit pressing force is 1.65 T / cm 2 , the pressing speed is 28 seconds / mold, the shrinkage coefficient is 18.5%, and the single weight tolerance is ±0.08 g; the sintering temperature is 1415℃, the sintering time is 45 min, and the flow rate of methane is 0.6 mL / s.

[0051] The hard alloy rod material prepared in Example 1 is tested, and the results show that the hard alloy rod material has a gradient structure, and the gradient structure from outside to inside includes a surface layer, a subsurface layer and a core, the volume fraction of the binder phase in the surface layer accounts for 0.9%, the volume fraction of the binder phase in the subsurface layer accounts for 3.6%, the volume fraction of the binder phase in the core accounts for 2.2%, the thickness of the surface layer is 0.28 mm, the residual compressive stress is 480 MPa, the Rockwell hardness HRA is 94.6, and the fracture toughness KIC is 7.9 MPa·m 1 / 2 ; the thickness of the subsurface layer is 0.73 mm, the residual tensile stress is 390 MPa, the Rockwell hardness HRA is 91.3, and the fracture toughness KIC is 10.2 MPa·m 1 / 2 ; the residual compressive stress of the core is 135 MPa, the Rockwell hardness HRA is 92.5, and the fracture toughness KIC is 8.3 MPa·m 1 / 2 ; the bending strength TRS of the hard alloy rod material is 3250 MPa; the hard alloy rod material contains Cr3Ni2 nickel-chromium alloy phase, the content of the Cr3Ni2 nickel-chromium alloy phase in the hard alloy rod material is 0.88wt%, the self-corrosion potential of the hard alloy rod material in a hydrochloric acid solution with pH=1 is-0.23V, and the self-corrosion potential of the hard alloy rod material in a sodium hydroxide solution with pH=13 is-0.15V.

[0052] Example 2

[0053] The application provides a preparation method of a high-performance hard alloy rod material for woodworking knives, comprising the following steps:

[0054] S1, obtaining (W, Cr)C x complex carbide powder, spherical Co powder and carbonyl Ni powder as raw materials, wherein the total carbon content in the raw materials is 5.94%, (W, Cr)C x The mass ratio of the complex carbide powder, the spherical Co powder and the carbonyl Ni powder is 97.6:1.7:0.7; the total carbon content (W, Cr)C x The Fisher particle size of the complex carbide powder is 0.45μm, the Fisher particle size of the spherical Co powder is 0.65μm, and (W, Cr)C xThe mass ratio of Cr element in the complex carbide powder to Ni element in the carbonyl Ni powder is 0.7:1; (W, Cr)C x The complex carbide powder has a porous dendritic structure, the dendritic length is 2.5 μm, and the porosity is 52%.

[0055] S2, (W, Cr)C x The complex carbide powder, the spherical Co powder, the carbonyl Ni powder, paraffin and alcohol are mixed, ball-milled and spray-dried to obtain mixed granules; wherein the mass of paraffin is 2.0 wt% of the mass of raw materials, the rotation speed of ball-milling is 650 rpm, and the ball-milling time is 37 h; the process parameters of spray-drying are as follows: the feeding pressure is 10.8 bar, the nozzle diameter is 1.2 mm, the cyclone dust collection pressure difference is 9.2 mbar, the spraying temperature is 116℃, and the outlet cooling temperature is 86℃; the flow rate of the mixed granules is <30 s / 50 g, and the loose bulk density of the mixed granules is 3.62 g / cm 3 .

[0056] S3, the mixed granules are loaded into a porous mold to perform vertical compression molding to obtain a cemented carbide rod blank, and the cemented carbide rod blank is sintered to obtain a cemented carbide rod material, and the sintering atmosphere is methane; wherein the process parameters of vertical compression molding are as follows: the unit pressing force is 1.55 T / cm 2 , the pressing speed is 28 seconds / mold, the shrinkage coefficient is 18.5%, and the single weight tolerance is ±0.08 g; the sintering temperature is 1405℃, the sintering time is 35 min, and the methane flow is 0.5 mL / s.

[0057] The cemented carbide rod material prepared in Example 2 is tested, and the results show that the cemented carbide rod material has a gradient structure, and the gradient structure from outside to inside includes a surface layer, a subsurface layer and a core, the volume fraction of binder phase in the surface layer accounts for 1.0%, the volume fraction of binder phase in the subsurface layer accounts for 3.5%, the volume fraction of binder phase in the core accounts for 2.5%, the thickness of the surface layer is 0.32 mm, the residual compressive stress is 525 MPa, the Rockwell hardness HRA is 94.2, and the fracture toughness KIC is 8.2 MPa·m 1 / 2 ; the thickness of the subsurface layer is 0.76 mm, the residual tensile stress is 410 MPa, the Rockwell hardness HRA is 91.5, and the fracture toughness KIC is 10.4 MPa·m 1 / 2 ; the residual compressive stress of the core is 156 MPa, the Rockwell hardness HRA is 92.6, and the fracture toughness KIC is 8.2 MPa·m 1 / 2The bending strength TRS of the cemented carbide rod is 3150 MPa; the cemented carbide rod contains Cr3Ni2 nickel-chromium alloy phase, the content of the Cr3Ni2 nickel-chromium alloy phase of the cemented carbide rod is 0.91 wt%, the self-corrosion potential of the cemented carbide rod in a hydrochloric acid solution with pH=1 is -0.24 V, and the self-corrosion potential of the cemented carbide rod in a sodium hydroxide solution with pH=13 is -0.16 V.

[0058] Example 3

[0059] The application provides a preparation method of a high-performance cemented carbide rod for woodworking knives, comprising the following steps:

[0060] S1, obtaining (W, Cr)C x The total carbon content in the raw materials is 5.96%, (W, Cr)C x The mass ratio of the double carbide powder, the spherical Co powder and the carbonyl Ni powder is 98.2:1.4:0.4; the total carbon content (W, Cr)C x The Fisher particle size of the double carbide powder is 0.58 μm, and the Fisher particle size of the spherical Co powder is 0.75 μm, (W, Cr)C x The mass ratio of the Cr element in the double carbide powder to the Ni element in the carbonyl Ni powder is 0.8:1; (W, Cr)C x The double carbide powder has a porous branch structure, the branch length is 2.4 μm, and the porosity is 55%.

[0061] S2, mixing (W, Cr)C x The double carbide powder, the spherical Co powder, the carbonyl Ni powder, paraffin and alcohol are mixed and then subjected to ball milling and spray drying to obtain mixed particles; wherein the mass of the paraffin is 2.2 wt% of the mass of the raw materials, the rotation speed of the ball milling is 750 rpm, and the ball milling time is 39 h; the process parameters of the spray drying are as follows: the feeding pressure is 10.2 bar, the nozzle aperture is 1.2 mm, the cyclone dust collection pressure difference is 8.7 mbar, the spraying temperature is 112 DEG C, and the outlet cooling temperature is 82 DEG C; the flow rate of the mixed particles is <30 s / 50 g, and the loose bulk density of the mixed particles is 3.65 g / cm 3 .

[0062] S3, loading the mixed particles into a porous mold to perform vertical compression molding to obtain a cemented carbide rod blank, and sintering the cemented carbide rod blank to obtain a cemented carbide rod, wherein the sintering atmosphere is methane; wherein the process parameters of the vertical compression molding are as follows: the unit pressing force is 1.75 T / cm 2, the pressing speed is 28 seconds per mold, the shrinkage coefficient is 18.5%, the single weight tolerance is ±0.08g; the sintering temperature is 1425℃, the sintering time is 55min, and the methane flow is 0.7mL / s.

[0063] The hard alloy rod prepared in Example 3 is tested, and the results show that the hard alloy rod has a gradient structure, and the gradient structure includes a surface layer, a subsurface layer and a core from outside to inside, the volume fraction of the binder phase in the surface layer accounts for 0.93%, the volume fraction of the binder phase in the subsurface layer accounts for 3.7%, the volume fraction of the binder phase in the core accounts for 2.4%, the thickness of the surface layer is 0.36mm, the residual compressive stress is 517MPa, the Rockwell hardness HRA is 94.7, and the fracture toughness KIC is 7.7MPa·m 1 / 2 ; the thickness of the subsurface layer is 0.79mm, the residual tensile stress is 405MPa, the Rockwell hardness HRA is 91.2, and the fracture toughness KIC is 10.5MPa·m 1 / 2 ; the residual compressive stress of the core is 141MPa, the Rockwell hardness HRA is 92.5, and the fracture toughness KIC is 8.5MPa·m 1 / 2 ; the bending strength TRS of the hard alloy rod is 3200MPa; the hard alloy rod contains Cr3Ni2 nickel-chromium alloy phase, the content of the Cr3Ni2 nickel-chromium alloy phase in the hard alloy rod is 0.87wt%, the self-corrosion potential of the hard alloy rod in hydrochloric acid solution with pH=1 is-0.25V, and the self-corrosion potential of the hard alloy rod in sodium hydroxide solution with pH=13 is-0.17V.

[0064] Comparative Example 1

[0065] The difference between the present comparative example and Example 1 is that the total carbon content in the raw material in step S1 is 5.91%, and the other steps are consistent with Example 1.

[0066] The hard alloy rod prepared in Comparative Example 1 is tested, and the results show that the hard alloy rod has a gradient structure, and the gradient structure includes a surface layer, a subsurface layer and a core from outside to inside, the volume fraction of the binder phase in the surface layer accounts for 1.3%, the volume fraction of the binder phase in the subsurface layer accounts for 2.8%, the volume fraction of the binder phase in the core accounts for 2.6%, the thickness of the surface layer is 0.31mm, the residual compressive stress is 410MPa, the Rockwell hardness HRA is 93.5, and the fracture toughness KIC is 8.1MPa·m 1 / 2 ; the thickness of the subsurface layer is 0.52mm, the residual tensile stress is 280MPa, the Rockwell hardness HRA is 92.7, and the fracture toughness KIC is 8.9MPa·m 1 / 2 ; the residual compressive stress of the core is 80MPa, the Rockwell hardness HRA is 91.8, and the fracture toughness KIC is 8.5MPa·m1 / 2 ; the bending strength TRS of the cemented carbide rod is 2940 MPa; the cemented carbide rod contains Cr3Ni2 nickel-chromium alloy phase, the content of the Cr3Ni2 nickel-chromium alloy phase of the cemented carbide rod is 0.81 wt%, the self-corrosion potential of the cemented carbide rod in a hydrochloric acid solution with pH = 1 is -0.24 V, and the self-corrosion potential of the cemented carbide rod in a sodium hydroxide solution with pH = 13 is -0.16 V.

[0067] Comparative Example 2

[0068] The difference between the present comparative example and Example 2 is that the sintering temperature in step S3 is 1450℃, and the other steps are consistent with Example 2.

[0069] The cemented carbide rod prepared in Comparative Example 2 is tested, and the results show that the cemented carbide rod has a gradient structure, and the gradient structure from outside to inside includes a surface layer, a subsurface layer and a core, the volume fraction of the binder phase in the surface layer is 1.5%, the volume fraction of the binder phase in the subsurface layer is 2.5%, the volume fraction of the binder phase in the core is 2.5%, the thickness of the surface layer is 0.45 mm, the residual compressive stress is 390 MPa, the Rockwell hardness HRA is 93.7, and the fracture toughness KIC is 8.2 MPa·m 1 / 2 ; the thickness of the subsurface layer is 0.52 mm, the residual tensile stress is 310 MPa, the Rockwell hardness HRA is 92.5, and the fracture toughness KIC is 8.5 MPa·m 1 / 2 ; the residual compressive stress of the core is 105 MPa, the Rockwell hardness HRA is 91.6, and the fracture toughness KIC is 8.2 MPa·m 1 / 2 ; the bending strength TRS of the cemented carbide rod is 2940 MPa; the cemented carbide rod contains Cr3Ni2 nickel-chromium alloy phase, the content of the Cr3Ni2 nickel-chromium alloy phase of the cemented carbide rod is 0.81 wt%, the self-corrosion potential of the cemented carbide rod in a hydrochloric acid solution with pH = 1 is -0.24 V, and the self-corrosion potential of the cemented carbide rod in a sodium hydroxide solution with pH = 13 is -0.16 V.

[0070] Comparative Example 3

[0071] The difference between the present comparative example and Example 3 is that the sintering time in step S3 is 80 min, and the other steps are consistent with Example 3.

[0072] The hard alloy rod prepared in Comparative Example 3 was tested, and the results showed that the hard alloy rod had a gradient structure, and the gradient structure included a surface layer, a subsurface layer and a core from outside to inside, the volume fraction of the binder phase in the surface layer accounted for 1.4%, the volume fraction of the binder phase in the subsurface layer accounted for 2.7%, the volume fraction of the binder phase in the core accounted for 2.6%, the thickness of the surface layer was 0.46mm, the residual compressive stress was 425MPa, the Rockwell hardness HRA was 93.2, and the fracture toughness KIC was 8.3MPa·m 1 / 2 ; the thickness of the subsurface layer was 0.51mm, the residual tensile stress was 295MPa, the Rockwell hardness HRA was 92.8, and the fracture toughness KIC was 8.7MPa·m 1 / 2 ; the residual compressive stress of the core was 98MPa, the Rockwell hardness HRA was 91.5, and the fracture toughness KIC was 8.4MPa·m 1 / 2 ; the bending strength TRS of the hard alloy rod was 2970MPa; the hard alloy rod contained Cr3Ni2 nickel-chromium alloy phase, the content of the Cr3Ni2 nickel-chromium alloy phase in the hard alloy rod was 0.82wt%, the self-corrosion potential of the hard alloy rod in hydrochloric acid solution with pH=1 was-0.24V, and the self-corrosion potential of the hard alloy rod in sodium hydroxide solution with pH=13 was-0.16V.

[0073] The same model 1 / 2 6 20 3T three-blade chip-breaking cutting knives, 5 knives were taken respectively, and the composite plates were milled on the Maishi / MKB25Z cutting machine, the average service life of the cutting knives prepared from the hard alloy rod of Example 1 was 285m, which was 1.44 times of the average service life of the cutting knives prepared from the hard alloy rod of Comparative Example 1 (198m). 6 20 3T three-blade chip-breaking cutting knives, 5 knives were taken respectively, and the composite plates were milled on the Maishi / MKB25Z cutting machine, the average service life of the cutting knives prepared from the hard alloy rod of Example 2 was 304m, which was 1.37 times of the average service life of the cutting knives prepared from the hard alloy rod of Comparative Example 2 (221m). 6 20 3T three-blade chip-breaking cutting knives, 5 knives were taken respectively, and the composite plates were milled on the Maishi / MKB25Z cutting machine, the average service life of the cutting knives prepared from the hard alloy rod of Example 3 was 298m, which was 1.45 times of the average service life of the cutting knives prepared from the hard alloy rod of Comparative Example 3 (205m).

[0074] Comparative Example 4

[0075] The difference between this comparative example and Example 1 is that the raw material in step S1 does not contain carbonyl nickel powder. To maintain the total mass of 100%, the mass of (W, Cr)C is made up by (W, Cr)C x The other steps are consistent with Example 1.

[0076] The cemented carbide rod prepared in Comparative Example 4 is tested, and the results show that no Cr3Ni2 phase is detected in the microstructure, and the corrosion resistance is significantly deteriorated, with a self-corrosion potential of -0.34 V in HCl with pH = 1. It is proved that the introduction of Ni element and the generation of Cr3Ni2 phase are the key to improving corrosion resistance.

[0077] Comparative Example 5

[0078] The difference between this comparative example and Example 1 is that the raw material in step S1 contains (W, Cr)C x The other steps are consistent with Example 1.

[0079] The cemented carbide rod prepared in Comparative Example 5 is tested, and the results show that no Cr3Ni2 phase is detected in the microstructure, and the corrosion resistance is significantly deteriorated, with a self-corrosion potential of -0.36 V in HCl with pH = 1. It is proved that the introduction of Cr element and the generation of Cr3Ni2 phase are the key to improving corrosion resistance.

[0080] Comparative Example 6

[0081] The difference between this comparative example and Example 1 is that step S3 is performed by horizontal pressing, and the other steps are consistent with Example 1.

[0082] The cemented carbide rod prepared in Comparative Example 6 is tested, and the results show that the green density is uneven, and some rods have visible cracks at the rib edges after sintering, resulting in a significant reduction in yield. It is proved that the vertical pressing process is irreplaceable for ensuring the integrity of the structure.

[0083] From the above examples and comparative examples, it can be seen that: Example 1 (total carbon content of initial alloy 5.95%) and Comparative Example 1 (total carbon content of initial alloy 5.91%), the difference in alloy performance after high-temperature carburizing is due to the equal content of cobalt-nickel binder phase in the formula composition of the alloy, that is, the carbon content transported by the liquid binder phase to the inside of the alloy per unit time and per unit volume is equal during high-temperature carburizing. The infiltrated carbon reacts with the decarburized phase to form WC+γ two-phase structure. The lower the initial total carbon content of the alloy, the higher the degree of decarburization, the less the decarburized phase in the alloy, and the more carbon required to eliminate the decarburized phase per unit volume during carburizing, the thinner the gradient layer thickness formed in the same carburizing time. The residual compressive stress of the surface layer is smaller, which reduces the bending strength of the alloy. The performance difference between Example 2 and Comparative Example 2 is due to the same formula composition of the alloy and the equal content of cobalt-nickel binder phase, that is, the carbon content transported by the liquid binder phase to the inside of the alloy per unit time and per unit volume is equal during high-temperature carburizing. By increasing the carburizing temperature to 1450°C, it is found that the WC grains in the surface layer of the alloy grow significantly, and the binder phase decreases due to evaporation, the carburizing diffusion channel decreases, the carburizing amount per unit time decreases, and the gradient layer thickness formed is thinner. The bending strength of the alloy is reduced, and the WC grains in the surface layer are coarsened, which reduces the surface hardness. The performance difference between Example 3 and Comparative Example 3 is due to the same formula composition of the alloy and the equal content of cobalt-nickel binder phase, that is, the carbon content transported by the liquid binder phase to the inside of the alloy per unit time and per unit volume is equal during high-temperature carburizing. By increasing the high-temperature carburizing time to 80 min, it is found that the WC grains in the surface layer of the alloy grow significantly, and the binder phase decreases due to evaporation, the carburizing diffusion channel decreases, the carburizing amount per unit time decreases, and the gradient layer thickness formed is thinner. The bending strength of the alloy is reduced, and the WC grains in the surface layer are coarsened and the binder phase is aggregated, which reduces the surface hardness and wear resistance. Example 1 combined with Comparative Examples 4 and 5 shows that, without Ni element or without Cr element, Cr3Ni2 phase cannot be formed, and the corrosion resistance is significantly deteriorated, which leads to the failure of the alloy tool to be used normally, proving that the introduction of Ni element and Cr element and the generation of Cr3Ni2 phase are the key to improving corrosion resistance. Example 1 combined with Comparative Example 6 shows that, horizontal pressure forming will lead to uneven density of the compact, and visible cracks will appear at the rib edge of part of the rods after sintering, and the yield rate is greatly reduced, proving the irreplaceability of vertical pressure forming process for guaranteeing the structural integrity.

[0084] Compared with the prior art, the high-performance hard alloy rod for woodworking knives and the preparation method thereof provided by the present application have the following remarkable beneficial effects:

[0085] 1. Achieved the synergistic promotion of high hardness and high toughness: By accurately controlling the content of hard phase tungsten carbide (WC) at 97.6-98.2wt%, the surface hardness of the alloy matrix reaches a high level of HRA94-95, ensuring the sharpness of the cutting edge and excellent wear resistance. At the same time, through the synergistic design of cobalt (Co, 1.4-1.7wt%) and nickel (Ni, 0.4-0.7wt%) in the binder phase, and controlling (W, Cr)C x The mass ratio of Cr element in complex carbide powder to Ni element in carbonyl Ni powder is (0.65-0.85):1, and the total carbon content is 5.93-5.97%; In-situ generation of 0.7-1.1wt% Cr3Ni2 nickel-chromium alloy phase in the system. This strengthening phase effectively enhances the strength and toughness of the binder phase, so that the material can obtain high hardness while ensuring impact toughness and plasticity, fundamentally solving the contradiction between high hardness and high toughness, effectively preventing the collapse of the cutting tool and fracture.

[0086] 2. Constructed a performance-optimized gradient structure and realized functional partitioning: Through a special high-temperature gradient carburizing sintering process, a gradient structure including surface layer, subsurface layer and core from surface to inside is successfully constructed in the alloy bar. The essential feature of this structure is that the volume fraction of the binder phase is regularly gradient distributed:

[0087] Surface layer: with the lowest volume fraction of binder phase, forming a hard phase-rich zone with high tungsten carbide and low binder phase, thus giving the alloy surface layer extremely high hardness (HRA94-95) and excellent wear resistance, directly dealing with the most severe wear in the cutting process.

[0088] Subsurface layer: with the highest volume fraction of binder phase, forming a toughness-rich zone with high binder phase, which has high toughness and good plasticity, can effectively absorb and disperse the impact energy in the processing process, preventing the micro-cracks generated on the surface from expanding to the inside, so that the alloy can withstand high working load.

[0089] Core: the volume fraction of the binder phase is between the surface layer and the subsurface layer, maintaining good rigidity to provide solid support for the entire cutting tool, ensuring its dimensional stability under high-speed operation.

[0090] This "hard outer surface-tough intermediate-rigid inner core" gradient structure design makes different regions of a single sample respectively optimize the functions of wear resistance, impact resistance and rigidity preservation.

[0091] 3. The chemical corrosion resistance is significantly improved: the traditional pure cobalt binder phase is easily corroded in the wood processing environment. The introduction of Ni element and the formation of Cr3Ni2 strengthening phase with Cr element significantly improve the corrosion resistance of the binder phase itself, effectively slow down the chemical corrosion caused by water and organic acid in wood, thereby prolonging the service life of the tool in harsh working conditions.

[0092] 4. The preparation process ensures the uniformity and integrity of the material structure: the porous mold vertical compression forming process effectively improves the uniformity of the green density, avoids the edge cracks and wear loss caused by the traditional horizontal compression forming, and lays a structural foundation for subsequent high-performance sintered body. The preparation method is closely combined with material design, which is the key to realize the above excellent microstructure and macroscopic performance.

[0093] In summary, through the synergistic innovation of composition, structure and process, the hard alloy rod prepared by the present application has excellent comprehensive performance, especially suitable for woodworking tool applications under high speed, high load and strong vibration conditions, effectively solving the problems of early collapse, fracture and excessive wear caused by the lack of hardness, strength, toughness and corrosion resistance of existing tools.

[0094] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation or direct / indirect application in other related technical fields based on the inventive concept of the present application is included in the patent protection scope of the present application.

Claims

1. A method for preparing a high-performance cemented carbide rod for woodworking knives, characterized in that, Includes the following steps: S1, Obtain (W, Cr)C x The raw materials are complex carbide powder, spherical Co powder, and carbonyl Ni powder, wherein the total carbon content of the raw materials is 5.93-5.97%, and the (W,Cr)C... x The mass ratio of the compound carbide powder, the spherical Co powder, and the carbonyl Ni powder is (98.2-97.6):(1.4-1.7):(0.4-0.7). S2, the (W, Cr)C x The compound carbide powder, the spherical Co powder, and the carbonyl Ni powder are mixed and then ball-milled and spray-dried to obtain mixed granules; S3. The mixed material particles are loaded into a porous mold and vertically pressed to obtain a cemented carbide billet. The cemented carbide billet is then sintered to obtain a cemented carbide rod. The sintering atmosphere is methane. The (W, Cr)C x The mass ratio of Cr in the compound carbide powder to Ni in the carbonyl Ni powder is (0.65-0.85):1; The cemented carbide rod has a gradient structure, which includes, from the outside to the inside, a surface layer, a sub-surface layer, and a core. The volume fraction of the binder phase in the surface layer is 0.5-1.2%, the volume fraction of the binder phase in the sub-surface layer is 3-5%, and the volume fraction of the binder phase in the core is 2-2.8%. The thickness of the surface layer is 0.2-0.4 mm, the residual compressive stress of the surface layer is ≥450 MPa, the Rockwell hardness (HRA) of the surface layer is 94-95, and the fracture toughness (KIC) of the surface layer is ≥7.5 MPa·m. 1 / 2 The thickness of the subsurface layer is 0.6-0.8 mm, the residual tensile stress of the subsurface layer is ≥360 MPa, the Rockwell hardness (HRA) of the subsurface layer is 91-92, and the fracture toughness (KIC) of the subsurface layer is ≥9.8 MPa·m. 1 / 2 The residual compressive stress of the core is ≥120MPa, the Rockwell hardness (HRA) of the core is 92-93, and the fracture toughness (KIC) of the core is ≥8MPa·m. 1 / 2 The bending strength TRS of the cemented carbide rod is ≥3000MPa; The cemented carbide rod contains a Cr3Ni2 nickel-chromium alloy phase, the content of the Cr3Ni2 nickel-chromium alloy phase in the cemented carbide rod is 0.7-1.1 wt%, the self-corrosion potential of the cemented carbide rod in hydrochloric acid solution with pH=1 is -0.26 to -0.22 V, and the self-corrosion potential of the cemented carbide rod in sodium hydroxide solution with pH=13 is -0.18 to -0.15 V.

2. The method for preparing a high-performance cemented carbide rod for woodworking tools according to claim 1, characterized in that, In step S1, the (W, Cr)C x The composite carbide powder has a Fisher particle size of 0.4-0.6 μm, and the spherical Co powder has a Fisher particle size of 0.6-0.8 μm.

3. The method for preparing a high-performance cemented carbide rod for woodworking tools according to claim 1, characterized in that, In step S1, the (W, Cr)C x The preparation method of the complex carbide powder includes: reducing blue tungsten in a hydrogen atmosphere to obtain nano-W powder; obtaining carbon black by cracking natural gas; mixing the nano-W powder, the carbon black, and Cr3C2 powder, and then carbonizing them in an argon protective atmosphere to obtain carbides; and pulverizing the carbides using a high-performance air jet mill to obtain the (W,Cr)C powder. x Complex carbide powder, wherein (W, Cr)C x The complex carbide powder has a porous branched structure, wherein the (W,Cr)C x The branch length of the complex carbide powder is 1-3 μm, and the (W,Cr)C x The porosity of the complex carbide powder is 40-60%.

4. The method for preparing a high-performance cemented carbide rod for woodworking tools according to claim 1, characterized in that, Step S2 further includes adding paraffin wax and alcohol during the ball milling process, wherein the mass of the paraffin wax is 2.0-2.3 wt% of the mass of the raw material, the ball milling speed is 600-800 rpm, and the ball milling time is 36-40 h.

5. The method for preparing a high-performance cemented carbide rod for woodworking tools according to claim 1, characterized in that, In step S2, the specific process parameters for spray drying are as follows: feeding pressure of 10-11 bar, nozzle diameter of 1.0-1.3 mm, cyclone dust collection pressure difference of 8-11 mbar, spray temperature of 110-120℃, and outlet cooling temperature of 80-90℃; the flow rate of the mixed particles is <30 s / 50 g, and the loose packing density of the mixed particles is 3.25-3.75 g / cm³. 3 .

6. The method for preparing a high-performance cemented carbide rod for woodworking tools according to claim 1, characterized in that, In step S3, the mold for vertical pressing is a multi-hole mold, and the specific process parameters for vertical pressing are: unit pressing force of 1.5-1.8 T / cm. 2 The pressing speed is 25-30 seconds per mold, the shrinkage coefficient is 18-19%, and the weight tolerance is ±0.08g.

7. The method for preparing a high-performance cemented carbide rod for woodworking tools according to claim 1, characterized in that, In step S3, the sintering temperature is 1400-1430℃, the sintering time is 30-60 min, and the methane flow rate is 0.4-0.8 mL / s.

8. A high-performance cemented carbide rod for woodworking knives, characterized in that, It is prepared by the method for preparing a high-performance cemented carbide rod for woodworking tools according to any one of claims 1-7.