A gradient tool material for machining compacted graphite cast iron

Abstract

The present invention discloses a gradient tool material for machining vermicular graphite cast iron, which is made of the following raw materials: surface layer: WC87-94 parts, Al2O33-7 parts, Co2-6 parts, Y2O30-1 parts; sub-surface layer: WC87-94 parts, Al2O31-5 parts, Co4-8 parts, Y2O30-1 parts; middle layer: WC87-94 parts, Al2O30-3 parts, Co6-10 parts, Y2O30-1 parts; according to the proportion of each layer component, they are respectively loaded into a ball mill, ball milled, dried, and sieved; they are layered in a graphite sleeve and sintered in a vacuum sintering furnace. The present invention makes the metal phase and the ceramic phase symmetrically distributed in a gradient, the surface layer of the tool has high hardness and wear resistance, the middle layer has strong toughness and plasticity, and can withstand high impact loads; the thermal expansion coefficient and thermal conductivity coefficient between each layer of material gradually increase from the surface to the inside, effectively relieving thermal stress concentration, reducing thermal crack initiation, and improving tool life.

Description

Technical Field

[0001] The invention relates to a new type of gradient tool material specially used for machining vermicular graphite cast iron and a preparation method thereof, belonging to the technical field of new materials. Background Art

[0002] Vermicular graphite iron (CGI) has the high strength and wear resistance of ductile iron, and has good casting processability, thermal conductivity, and vibration damping similar to gray cast iron. It has much higher fatigue strength and heat fatigue resistance than gray cast iron. Its tensile strength is about twice that of gray cast iron, and its material strength at high temperature is higher than that of gray cast iron. It can obtain high strength at a higher carbon equivalent, making the casting thin-walled and lightweight. At present, vermicular graphite iron is mainly used in heavy trucks and internal combustion engine industries, such as cylinder blocks, cylinder heads, supercharger shells, cylinder liners, piston rings, brake hubs (brake hubs), brake discs (including those for railway locomotives), etc. Vermicular graphite iron is widely used, but in the process of cutting vermicular graphite iron, there are generally difficulties such as easy wear of tools, poor processing results, low efficiency, difficulty in ensuring precision, and high processing costs, which seriously hinder the promotion and application of vermicular graphite iron.

[0003] At present, the main tools for processing vermicular graphite cast iron are coated carbide tools, CBN tools, ceramic tools, etc. Researchers generally believe that coated carbide tools are the most suitable tool materials for processing CGI. However, due to the different thermal expansion coefficients of the coating and the substrate, there is a stress concentration phenomenon at the interface between the coating and the substrate. Thermal cracks are easily generated during the intermittent cutting (milling) of CGI. Thermal cracks cause micro-chipping of the tool, and chipping causes the tool substrate to be exposed, which in turn causes the tool to break and fail. At the same time, thermal cracks will increase the diffusion wear and oxidation wear of the tool. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a new gradient tool material specially used for machining vermicular graphite cast iron in view of the defects of the prior art, which can effectively alleviate the phenomenon of thermal stress concentration, reduce the initiation of thermal cracks, and thus improve the life of the tool.

[0005] In order to solve this technical problem, the present invention provides a gradient tool material for machining vermicular graphite cast iron, which is made of the following raw materials in parts by mass:

[0006] Surface layer: WC: 87-94 parts, Al 2 O 3 : 3 to 7 parts, Co: 2 to 6 parts, Y 2 O 3 : 0 to 1 portion;

[0007] Subsurface: WC: 87-94 parts, Al 2 O 3 :1~5 parts, Co:4~8 parts, Y 2 O 3: 0-1 portion;

[0008] Intermediate layer: WC: 87-94 parts, Al 2 O 3 :0~3 parts, Co:6~10 parts, Y 2 O 3 : 0~1 portion.

[0009] Preferably, it is made from the following raw materials in parts by weight:

[0010] Surface layer: WC: 90 parts, Al 2 O 3 : 7 parts, Co: 2 parts, Y 2 O 3 :1 copy;

[0011] Subsurface: WC: 90%, Al 2 O 3 : 5 parts, Co: 4 parts, Y 2 O 3 :1 copy;

[0012] Intermediate layer: WC: 90 parts, Al 2 O 3 : 3 parts, Co: 6 parts, Y 2 O 3 : 1 copy.

[0013] The preparation method steps are as follows:

[0014] (1) According to the composition ratio of each layer, three groups of powders with different composition ratios were prepared and loaded into polyurethane ball mills respectively. 2 O 3 Alumina balls are used as ball milling balls for powders, tungsten carbide balls are used as ball milling balls for other powders, alcohol is used as ball milling medium, and the powders are sealed and wet-milled on a drum-type ball mill for 48 hours; the milled raw material powders are placed in a vacuum drying oven for drying at a drying temperature of 100 to 150° C., preferably 120° C.; after drying, the powders are sieved with 80 to 120 meshes, preferably 100 meshes, and the sieved powders are packaged for standby use;

[0015] (2) Weighing the components of each layer according to their proportions and loading them into a polyurethane ball mill, using tungsten carbide balls as the ball milling balls, a ball-to-material ratio of 10:1, and alcohol as the ball milling medium, and then sealing and wet-milling them on a drum ball mill for 48 hours; placing the milled raw material powder in a vacuum drying oven for drying, and packaging for later use;

[0016] (3) Weigh the mass of each layer of powder according to the amount required for tool preparation, lay it layer by layer in a graphite sleeve by a manual laying method, and then put it into a vacuum sintering furnace; under vacuum conditions, raise the temperature to 750-850°C for 15-25 minutes, raise the temperature to 950-1050°C for 5-15 minutes, raise the temperature to 1350-1650°C for 25-35 minutes, and uniformly pressurize from 950-1050°C to 1350-1650°C, and increase the pressure to 28-36MPa; preferably, raise the temperature to 800°C for 20 minutes, raise the temperature to 1000°C for 10 minutes, raise the temperature to 1450°C for 30 minutes, and uniformly pressurize from 1000°C to 32MPa at 1450°C;

[0017] (4) hot pressing and sintering at a temperature of 1350-1650°C with a pressure of 28-36 MPa and keeping the temperature for 20-40 min; preferably, hot pressing and sintering at a temperature of 1450°C with a pressure of 32 MPa and keeping the temperature for 30 min.

[0018] Furthermore, the particle size of the WC is 0.3-0.5 μm, and the Al 2 O 3 The particle size of the Co is 0.4-0.6 μm, the particle size of the Y 2 O 3 The particle size is 0.8-1.2μm.

[0019] Preferably, the particle size of the WC is 0.4 μm, and the Al 2 O 3 The particle size of the Co is 0.5 μm, the particle size of the Y 2 O 3 The particle size is 1 μm.

[0020] Furthermore, the layer thickness ratios of the surface layer to the sub-surface layer and the sub-surface layer to the middle layer are both 0.2; the layer thickness ratio

[0021] Furthermore, the manual laying method is: first, the surface layer material is loaded into a high-strength graphite mold, and is flattened by rotating a graphite rod; then, the second layer, i.e., the sub-surface layer material, is laid, and is flattened by the same method; and then, the third layer, i.e., the middle layer material, the fourth layer, i.e., the sub-surface layer material, and the fifth layer, i.e., the surface layer material, are laid in the same manner.

[0022] Beneficial effects: The present invention adopts lamination technology to make the metal phase and the ceramic phase present a symmetrical bidirectional gradient distribution and a symmetrical bidirectional distribution law. Both sides of the blade manufactured in this way can be used as the front cutting surface, so that the two surface layers of the tool have high hardness and wear resistance, and the middle layer has good toughness and plasticity, so that the tool can withstand higher impact loads; by adjusting the material components, the thermal expansion coefficient and thermal conductivity coefficient between each layer of the tool material gradually increase from the surface to the inside, which can effectively alleviate the thermal stress concentration phenomenon, reduce the initiation of thermal cracks, and thereby increase the life of the tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the gradient tool structure of the present invention;

[0024] Figure 2 This is a scanning electron microscope image of the polished surface of the tool material prepared in Example 1 of the present invention.

[0025] In the figure: 1, surface layer; 2, sub-surface layer; 3, middle layer. DETAILED DESCRIPTION

[0026] like Figure 1 and Figure 2 As shown, the present invention provides a gradient tool material for machining vermicular graphite cast iron, which is made of the following raw materials by weight: surface layer: WC 86-90 parts, Al 2 O 3 3 to 7 parts, Co 2 to 6 parts, Y 2 O 3 0~2 parts; Subsurface: WC 86~90 parts, Al 2 O 3 1-5 parts, Co 4-8 parts, Y 2 O 3 0-1 parts; middle layer: WC 86-90 parts, Al 2 O 3 0~3 parts, Co 6~10 parts, Y 2 O 3 0-1 part; its preparation method is as follows:

[0027] (1) According to the composition ratio of each layer, three groups of powders were prepared and loaded into polyurethane ball mills respectively. 2 O 3 Alumina balls are used as ball milling balls for powders, and tungsten carbide balls are used as ball milling balls for other powders. Alcohol is used as the ball milling medium. After sealing, the raw material powder is wet-milled on a drum ball mill for 48 hours. The milled raw material powder is placed in a vacuum drying oven for drying at a drying temperature of 100-150°C. After drying, it is sieved through a 80-120 mesh sieve, and the sieved powder is packaged for standby use.

[0028] (2) Weighing the components of each layer according to their proportions and loading them into a polyurethane ball mill, using tungsten carbide balls as the ball milling balls, a ball-to-material ratio of 10:1, and alcohol as the ball milling medium, and then sealing and wet-milling them on a drum ball mill for 48 hours; placing the milled raw material powder in a vacuum drying oven for drying, and packaging for later use;

[0029] (3) Weigh the mass of each layer of powder according to the amount required for tool preparation, lay it layer by layer in a graphite sleeve by manual laying method, and then put it into a vacuum sintering furnace; under vacuum conditions, increase the temperature to 750-850°C for 15-25 minutes, increase it to 950-1050°C for 5-15 minutes, and increase it to 1350-1650°C for 25-35 minutes. Start to pressurize at a uniform speed from 950-1050°C, and increase the pressure to 28-36MPa at 1350-1650°C;

[0030] (4) Hot pressing and sintering at a temperature of 1350-1650°C with a pressure of 28-36 MPa and heat preservation for 20-40 minutes.

[0031] In order to suppress the generation of thermal cracks in the tool, the present invention is based on the three-dimensional transient temperature field and thermal stress field of the high-speed milling vermicular cast iron tool established in the early stage, and is based on the principle of reducing the temperature gradient and thermal stress inside the tool, and designs a tool with gradient characteristics in component content distribution and microstructure. By adjusting the content of each layer of the gradient tool component to adjust the physical parameters of the overall material, the temperature gradient inside the tool is reduced, and the thermal stress inside the tool is reduced. Based on this principle, the present invention designs a variety of gradient tool material component optimization schemes. For the gradient tool, each layer of the component should not only be conducive to improving its mechanical properties, but also the thermal expansion coefficient and thermal conductivity between the layers should meet the requirements of gradual change from the surface to the inside, which can relieve the thermal stress of the tool. Through a large number of experiments, the present invention has optimized multiple groups of components, and finally optimized a gradient tool with excellent comprehensive mechanical properties, and satisfied the physical parameters such as thermal expansion coefficient and thermal conductivity coefficient that gradually change from the surface to the inside, relieve the thermal stress inside the tool, and suppress the generation of thermal cracks inside the tool.

[0032] According to the three-dimensional transient temperature field model of high-speed milling vermicular cast iron tools based on periodic heat transfer established in the early stage, it can be concluded that when the carbide tool is milling vermicular cast iron at high speed, the highest temperature is mainly distributed on the front face of the tool, and there is a large temperature gradient between the front face, back face and each point on the tool edge at different times and at different points at the same time. The maximum temperature gradient of a certain point on the tool edge at the moment when the tool cuts out the workpiece and the moment when the air cutting ends reaches 500°C. The maximum temperature gradient between different points on the tool edge at the moment when the tool cuts out the workpiece reaches 580°C. The generation of temperature gradient eventually leads to the generation of thermal cracks in the tool. In order to suppress the generation of thermal cracks in the tool, the present invention designs a tool with gradient characteristics in component content distribution and microstructure. According to the temperature field model, the highest temperature of high-speed milling of vermicular graphite cast iron is about 900°C, while the working temperature of cemented carbide tools is much lower than this temperature. Therefore, according to the tool temperature of high-speed milling of vermicular graphite cast iron, the present invention selects to add Al with higher hardness, better chemical stability, wear resistance, heat resistance, oxidation resistance and high temperature mechanical properties to the WC matrix. 2 O 3 , add a higher content of Al to the front face of the tool with the highest temperature 2 O 3 , so that the tool can be used at higher cutting temperatures.

[0033] Based on the three-dimensional transient temperature field model of high-speed milling compacted graphite cast iron tool, a design model with gradient characteristics of component content distribution and microstructure is proposed. The metal phase Co and ceramic phase Al are made by lamination technology. 2 O 3 The two sides of the blade made in this way can be used as the front cutting edge, so that the two surfaces of the tool have high hardness and wear resistance, and the middle layer has good toughness and plasticity. At the same time, the thermal expansion coefficient of the gradient tool is gradually increased from the surface to the inside to ensure that the residual compressive stress is formed on the surface during the cooling process of the tool material after sintering, which is beneficial to improve the hardness of the front cutting edge and the thermal shock resistance of the material; at the same time, the thermal conductivity of the gradient tool is increased from the surface to the inside, and the low thermal conductivity of the front cutting edge can play a role in heat insulation so that more cutting heat is taken away by the chips, thereby protecting the tool body and improving the residual strength of thermal shock resistance. In addition, the thermal conductivity of the tool gradually increases, which can reduce the temperature gradient inside the tool and thus reduce the thermal stress inside the tool.

[0034] Example 1

[0035] Table 1-1 shows the components of each layer of the tool material described in this embodiment.

[0036] Table 1-1 (wt%)

[0037]

[0038] The preparation method steps are as follows:

[0039] (1) According to the composition ratio of each layer, three groups of powders were prepared and loaded into polyurethane ball mills respectively. 2 O 3 Alumina balls are used as ball milling balls for powders, and tungsten carbide balls are used as ball milling balls for other powders. Alcohol is used as the ball milling medium. After sealing, the raw material powder is wet-milled on a drum ball mill for 48 hours. The milled raw material powder is placed in a vacuum drying oven for drying at a drying temperature of 120°C. After drying, it is sieved with a 100-mesh sieve, and the sieved powder is packaged for standby use.

[0040] (2) Weighing the components of each layer according to their proportions and loading them into a polyurethane ball mill, using tungsten carbide balls as the ball milling balls, a ball-to-material ratio of 10:1, and alcohol as the ball milling medium, and then sealing and wet-milling them on a drum ball mill for 48 hours; placing the milled raw material powder in a vacuum drying oven for drying, and packaging for later use;

[0041] (3) Weigh the mass of each layer of powder according to the amount required for tool preparation, and lay it layer by layer in the graphite sleeve by a manual laying method, that is: first, load the material of the surface layer 1 into a high-strength graphite mold and use a graphite rod to rotate and flatten it; then lay the material of the second layer, i.e., the sub-surface layer 2, and use the same method to flatten it; then, use the same method to lay the material of the third layer, i.e., the middle layer 3, the fourth layer, i.e., the sub-surface layer 2, and the fifth layer, i.e., the surface layer 1; the layer thickness ratio of the surface layer 1 to the sub-surface layer 2, and the sub-surface layer 2 to the middle layer 3 is 0.2; the layer thickness ratio Then put it into a vacuum sintering furnace; under vacuum conditions, raise the temperature to 800℃ for 20 minutes, 1000℃ for 10 minutes, and 1450℃ for 30 minutes. Pressurize at a uniform speed from 1000℃ to 32MPa at 1450℃.

[0042] (4) Hot pressing and sintering are performed at 1450°C under a pressure of 32 MPa and heat preservation for 30 minutes to obtain the obtained product.

[0043] Using stacking technology, the metal phase Co and the ceramic phase Al 2 O 3The two sides of the blade made in this way can be used as the front cutting edge, so that the two surfaces of the tool have high hardness and wear resistance, and the middle layer has good toughness and plasticity. At the same time, the thermal expansion coefficient of the gradient tool is gradually increased from the surface to the inside to ensure that the residual compressive stress is formed on the surface during the cooling process of the tool material after sintering, which is beneficial to improve the hardness of the front cutting edge and the thermal shock resistance of the material; at the same time, the thermal conductivity of the gradient tool is increased from the surface to the inside, and the low thermal conductivity of the front cutting edge can play a role in heat insulation so that more cutting heat is taken away by the chips, thereby protecting the tool body and improving the residual strength of thermal shock resistance. In addition, the thermal conductivity of the tool gradually increases, which can reduce the temperature gradient inside the tool and thus reduce the thermal stress inside the tool.

[0044] Table 1-2 shows the physical properties of each layer of the tool material prepared in this embodiment.

[0045] Table 1-2

[0046]

[0047] Table 1-3 shows the mechanical properties of the tool material prepared in this embodiment.

[0048] Table 1-3

[0049]

[0050] pass Figure 2 It can be seen that the microscopic morphology of the polished surface of the tool material prepared in Example 1 has the characteristics of relatively uniform component distribution, obvious growth of some grains, fewer pores, and better density.

[0051] Example 2

[0052] Table 2-1 shows the components of each layer of the tool material described in this embodiment.

[0053] Table 2-1 (wt%)

[0054]

[0055] The preparation method steps are the same as those in Example 1.

[0056] Table 2-2 shows the physical properties of each layer of the tool material prepared in this embodiment

[0057] Table 2-2

[0058]

[0059] Table 2-3 shows the mechanical properties of the tool material prepared in this embodiment.

[0060] Table 2-3

[0061]

[0062] Example 3

[0063] Table 3-1 shows the components of each layer of the tool material described in this embodiment.

[0064] Table 3-1 (wt%)

[0065]

[0066] The preparation method steps are the same as those in Example 1.

[0067] Table 3-2 shows the physical properties of each layer of the tool material prepared in this embodiment.

[0068] Table 3-2

[0069]

[0070] Table 3-3 shows the mechanical properties of the tool material prepared in this embodiment.

[0071] Table 3-3

[0072]

[0073] Example 4

[0074] Table 4-1 shows the components of each layer of the tool material described in this embodiment.

[0075] Table 4-1 (wt%)

[0076]

[0077] The preparation method steps are the same as those in Example 1.

[0078] Table 4-2 shows the physical properties of each layer of the tool material prepared in this embodiment.

[0079] Table 4-2

[0080]

[0081] Table 4-3 shows the mechanical properties of the tool material prepared in this embodiment.

[0082] Table 4-3

[0083]

[0084] Example 5

[0085] Table 5-1 shows the components of each layer of the tool material described in this embodiment.

[0086] Table 5-1 (wt%)

[0087]

[0088] The preparation method steps are the same as those of Example 1, but

[0089] In step (3), under vacuum conditions, the temperature is raised to 800°C for 20 minutes, to 1000°C for 10 minutes, and to 1450°C for 30 minutes. The pressure is increased uniformly from 1000°C to 1500°C, and the pressure is increased to 32 MPa.

[0090] (4) Hot pressing and sintering are performed at 1500°C with a pressure of 32 MPa and heat preservation for 30 minutes to obtain the obtained product.

[0091] Table 5-2 shows the physical properties of each layer of the tool material prepared in this embodiment.

[0092] Table 5-2

[0093]

[0094] Table 5-3 shows the mechanical properties of the tool material prepared in this embodiment.

[0095] Table 5-3

[0096]

[0097] Example 6

[0098] Table 6-1 shows the components of each layer of the tool material described in this embodiment.

[0099] Table 6-1 (wt%)

[0100]

[0101] The preparation method steps are the same as those of Example 1, but

[0102] In step (3), under vacuum conditions, the temperature is raised to 800°C for 20 minutes, to 1000°C for 10 minutes, and to 1450°C for 30 minutes. The pressure is then increased uniformly from 1000°C to 1550°C, and the pressure is increased to 32 MPa.

[0103] (4) Hot pressing and sintering are performed at 1550°C under a pressure of 32 MPa and heat preservation for 30 minutes to obtain the obtained product.

[0104] Table 6-2 shows the physical properties of each layer of the tool material prepared in this embodiment.

[0105] Table 6-2

[0106]

[0107] Table 6-3 shows the mechanical properties of the tool material prepared in this embodiment.

[0108] Table 6-3

[0109]

[0110] Comparison Example

[0111] Chinese invention patent ZL 202010112689.2 discloses "a high comprehensive performance cemented carbide tool material and its preparation method", the homogeneous WC-Al 2 O 3 The components and mechanical properties of composite tool materials are shown in Table 7-1.

[0112] Table 7-1 (wt%)

[0113]

[0114] The gradient tool material prepared in Example 1 of the present invention has a surface layer of 90 parts WC, Al 2 O 3 7 parts, Co 2 parts, Y 2 O 3 1 part; Subsurface: WC90 parts, Al 2 O 3 5 parts, Co 4 parts, Y 2 O 3 1 part; middle layer: WC 90 parts, Al 2 O 3 3 parts, Co 6 parts, Y 2 O 3 1 piece, after testing, its fracture toughness is 15.0±0.6MPa·m 1 / 2 , bending strength is 1211.2±64.1MPa, and Vickers hardness is 20.1±0.3GPa. Compared with No. 5 in Table 7-1 of the comparative example, its hardness and fracture toughness are increased by 6% and 37.7% respectively while its bending strength is slightly improved; compared with No. 6 in Table 7-1 of the comparative example, its fracture toughness and bending strength are increased by 21.6% and 20.8% respectively while maintaining high hardness.

[0115] It can be seen from the above embodiments that the tool material prepared by the present invention not only has excellent comprehensive mechanical properties, but also its elastic modulus, thermal expansion coefficient and thermal conductivity gradually increase from the outside to the inside, which can effectively alleviate the thermal stress concentration phenomenon, reduce the initiation of thermal cracks, and further improve the service life of the tool.

[0116] The present invention adds a large amount of Al 2 O3 , so that the two surfaces of the tool have high hardness and wear resistance, and then adjust the Al 2 O 3 The content of Al and Co in the metal phase makes the middle layer of the tool have good toughness and plasticity, so that the tool can withstand higher impact loads. 2 O 3 The content of Co makes its thermal conductivity and thermal expansion coefficient gradually increase from the surface to the inside. It can effectively alleviate the phenomenon of thermal stress concentration, reduce the initiation of thermal cracks, and thus increase the life of the tool.

[0117] The above embodiments of the present invention are merely illustrative and not exclusive, and all modifications within the scope of the invention or equivalent to the scope of the present invention are encompassed by the present invention.

Claims

1. A gradient tool material for machining compacted graphite cast iron, characterized in that: Made from the following raw materials in parts by weight: Surface layer (1): WC: 90 parts, Al2O3: 7 parts, Co: 2 parts, Y2O3: 1 part; Subsurface layer (2): WC: 90 parts, Al2O3: 5 parts, Co: 4 parts, Y2O3: 1 part; Intermediate layer (3): WC: 90 parts, Al2O3: 3 parts, Co: 6 parts, Y2O3: 1 part; The particle size of WC is 0.4 μm, the particle size of Al2O3 is 0.5 μm, the particle size of Co is 0.5 μm, and the particle size of Y2O3 is 1 μm; The layer thickness ratio of the surface layer (1) to the sub-surface layer (2), and the sub-surface layer (2) to the middle layer (3) is 0.2; the layer thickness ratio The preparation method steps are as follows: (1) According to the ratio of each layer, three groups of powders were prepared and loaded into polyurethane ball mills respectively. Alumina balls were used as ball mills for Al2O3 powder, and tungsten carbide balls were used as ball mills for other powders. Alcohol was used as the ball milling medium. After sealing, the raw material powders were wet-milled on a drum ball mill for 48 hours. The milled raw material powders were placed in a vacuum drying oven for drying at a drying temperature of 120°C. After drying, the raw material powders were sieved with a 100-mesh sieve, and the sieved powders were packaged for standby use. (2) Weighing the components of each layer according to their proportions and loading them into a polyurethane ball mill, using tungsten carbide balls as the ball milling balls, a ball-to-material ratio of 10:1, and alcohol as the ball milling medium, and then sealing and wet-milling them on a drum ball mill for 48 hours; placing the milled raw material powder in a vacuum drying oven for drying, and packaging for later use; (3) Weigh the mass of each layer of powder according to the amount required for tool preparation, lay it layer by layer in a graphite sleeve by manual laying method, and then put it into a vacuum sintering furnace; under vacuum conditions, raise the temperature to 800°C for 20 minutes, raise it to 1000°C for 10 minutes, and raise it to 1450°C for 30 minutes. Start pressurizing at a uniform speed from 1000°C, and increase the pressure to 32MPa at 1450°C; (4) Hot pressing and sintering at 1450°C with a pressure of 32 MPa and keeping the temperature for 30 min.

2. The gradient tool material for machining compacted graphite cast iron according to claim 1, characterized in that: The manual layering method is as follows: first, the material of the surface layer (1) is loaded into a high-strength graphite mold and is flattened by rotating a graphite rod; then, the material of the second layer, i.e., the sub-surface layer (2), is laid and is flattened by the same method; and then, the material of the third layer, i.e., the middle layer (3), the material of the fourth layer, i.e., the sub-surface layer (2), and the material of the fifth layer, i.e., the surface layer (1), are laid in the same manner.

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