A method for preparing internally cooled cutting tools based on additive manufacturing and sintering optimization

Abstract

The present invention relates to the field of additive manufacturing, and more particularly to a method for producing internally coolant cutting tools based on additive manufacturing combined with sintering optimization. The method comprises: obtaining a target metal powder and a target adhesive; wherein the target metal powder comprises high-speed steel powder; alternatingly performing additive manufacturing on the target metal powder and the target adhesive to produce a pre-sintered body; and sintering the pre-sintered body using an optimized sintering process to produce an internally coolant cutting tool. This technical solution can meet the requirements of internally coolant cutting tools for complex internally coolant structures, such as those with irregular cross-sections.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a method for preparing an internally cooled tool based on additive manufacturing combined with sintering optimization. Background Art

[0002] The metal cutting process generates significant heat. Cutting tools with internal cooling (internal cooling tools, for short) can remove this heat through coolant. Compared to external cooling, internal cooling tools deliver coolant directly to the tool's machining area, dissipating heat efficiently and quickly there. This cooling method overcomes the physical limitations of traditional overflow coolant in transmitting and dissipating heat, significantly extending tool life and improving surface finish quality.

[0003] However, the current technology for preparing internally cooled tools is limited by machining processes or mold injection processes, and can only produce simple internal cooling channels through extrusion molding or later drilling methods, which cannot meet the requirements of internally cooled tools for complex internal cooling structures such as special-shaped sections.

[0004] Based on this, there is an urgent need for a method for optimizing the preparation of internally cooled tools based on additive manufacturing and sintering to solve the above technical problems. Summary of the Invention

[0005] The present invention provides a method for preparing internally cooled cutting tools based on additive manufacturing and sintering optimization, which can meet the requirements of internally cooled cutting tools for complex internally cooled structures such as special-shaped cross-sections.

[0006] An embodiment of the present invention provides a method for preparing an internally cooled tool based on additive manufacturing combined with sintering optimization, comprising:

[0007] Obtaining target metal powder and target adhesive; wherein the target metal powder includes high-speed steel powder;

[0008] Alternately performing additive manufacturing on the target metal powder and the target adhesive to obtain a calcined body;

[0009] The pre-burned body is sintered by adopting an optimized sintering process to obtain an internally cooled tool.

[0010] As can be seen from the above scheme, the method for preparing internally coolant tools based on additive manufacturing combined with sintering optimization provided by the present invention alternates between additive manufacturing of target metal powders and target adhesives. Based on the additive manufacturing layer-by-layer forming principle, it offers a high degree of forming freedom, enabling the integrated manufacture of complex internally coolant structures such as those with irregular cross-sections. Furthermore, sintering the pre-calcined body using an optimized sintering process increases the relative density of the internally coolant tool, eliminates porosity, and ultimately improves the mechanical properties of the tool. Therefore, the above technical solution can meet the requirements of internally coolant tools for complex internally coolant structures such as those with irregular cross-sections. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0012] Figure 1 A schematic flow chart of a method for preparing internally cooled cutting tools based on additive manufacturing combined with sintering optimization provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0014] See also Figure 1 The embodiment of the present invention provides a method for preparing an internally cooled tool based on additive manufacturing combined with sintering optimization, the method comprising:

[0015] Step S1, obtaining target metal powder and target adhesive; wherein the target metal powder includes high-speed steel powder;

[0016] Step S2, alternately performing additive manufacturing on the target metal powder and the target adhesive to obtain a calcined body;

[0017] Step S3: sintering the pre-burned body using the optimized sintering process to obtain an internally cooled tool.

[0018] In this embodiment, additive manufacturing alternates between the target metal powder and the target adhesive. Based on the additive manufacturing principle of layer-by-layer stacking, this method offers a high degree of freedom in forming, enabling the integrated manufacture of complex internally cooled structures, such as those with irregular cross-sections. Furthermore, sintering the pre-calcined body using an optimized sintering process increases the relative density of the internally cooled tool, eliminates porosity, and ultimately improves the mechanical properties of the tool. Therefore, this technical solution can meet the requirements of internally cooled tools for complex internally cooled structures, such as those with irregular cross-sections.

[0019] High-speed steel (HSS) is an important high-end tool material, characterized by high hardness, high red hardness, and high wear resistance. It plays a crucial role in tool manufacturing and metalworking, and is widely used in the manufacture of tools such as cutting tools, drills, planers, and milling cutters. In metal cutting, HSS tools efficiently cut a variety of metals, such as steel, aluminum alloys, and stainless steel, providing high precision and surface quality for workpieces. In mold manufacturing, HSS can be used to manufacture components such as mold cores and cavities, enduring high-strength and wear-resistant working environments. In machining, the high-speed cutting performance of HSS tools improves production efficiency, reduces processing costs, and meets the demand for efficient machining in industrial production.

[0020] In some embodiments, the high speed steel powder is M2 high speed steel powder.

[0021] M2 high-speed steel (HSS) exhibits excellent hardness, wear resistance, and thermal stability. Its superior properties are based on a rational compositional design and elemental ratio. Its main components include carbon, molybdenum, vanadium, and chromium. Carbon is a key element for improving the steel's hardness and wear resistance; the addition of molybdenum improves hardness and thermal stability; vanadium enhances rigidity and wear resistance; and chromium improves corrosion resistance. As a key alloying element in HSS, tungsten (W) significantly improves its hardness, thermal stability, and wear resistance. During its production, M2 HSS undergoes rigorous heat treatment, which involves heating, holding, and cooling steps to adjust the material's microstructure and properties. Appropriate heat treatment can achieve the ideal hardness, toughness, and wear resistance of M2 HSS, meeting the requirements of various operating conditions. Due to its high carbon content and alloying elements (W, Mo, Cr, and V), traditional preparation processes are prone to elemental segregation, resulting in the formation of coarse primary carbides (such as M2C and M6C) and large inclusions, leading to premature failure of products such as cutting tools.

[0022] To address this technical issue, one approach could be to add the rare earth element La to high-speed steel powder. This element forms compounds with relatively high melting points in the steel, precipitating before the molten steel solidifies. These tiny particles are distributed throughout the molten steel, acting as heterogeneous nucleation centers and reducing the undercooling of the molten steel during crystallization. This refines the solidification structure and reduces segregation. Furthermore, as surface-active elements, rare earths can lower the surface tension of the molten steel, thereby reducing the work required to form nuclei of a critical size and increasing the number of crystal nuclei. Furthermore, rare earths also purify the steel. When added to the steel, they react with oxygen and sulfur in the molten steel to form rare earth oxides, oxysulfides, and sulfides, reducing their content while simultaneously inhibiting the segregation of these residual elements at grain boundaries.

[0023] Furthermore, considering the improvement of the mechanical properties of internally cooled tools, their relative density can be increased. The boron element, when reacting with the sintered material to form a eutectic, distorts the crystal lattice and activates it. This lowers the sintering temperature, accelerating diffusion and sintering. The presence of a suitable liquid during sintering often significantly promotes particle rearrangement and mass transfer. Another mechanism of action of boron is its ability to generate a liquid fluid at relatively low temperatures, promoting sintering.

[0024] Therefore, taking all factors into consideration, LaB6 powder can be added to the high-speed steel powder (ie, the target metal powder also includes LaB6 powder) to enhance the mechanical properties of the subsequent internally cooled tool.

[0025] In one embodiment of the present invention, the target metal powder comprises two M2 high-speed steel powders of different particle sizes. This arrangement allows the smaller powder to fill the gaps between the larger powders. Furthermore, the different particle sizes create different interfaces, which, due to the interface effect, accelerates the subsequent sintering process, facilitating subsequent sintering.

[0026] In one embodiment of the present invention, the parameters of the first particle size M2 high speed steel powder include: particle size range of 15 to 53 μm, D 50 The diameter of the steel bar is 36.43 μm. The chemical composition is calculated by mass percentage: C content is 0.86%, Mn content is 0.35%, Cr content is 4.15%, Si content is 0.36%, V content is 4.10%, W content is 6.20%, Mo content is 5.00%, and the balance is Fe. The apparent density is 4.18 g / cm 3 , the tap density is 4.8g / cm 3 ;

[0027] The parameters of the second particle size M2 high speed steel powder include: particle size range of 1 to 15 μm, D 50The thickness of the steel is 6.42 μm. The chemical composition is calculated by mass percentage, including C content of 0.87%, Mn content of 0.34%, Cr content of 4.23%, Si content of 0.45%, V content of 1.90%, W content of 6.21%, Mo content of 5.17%, and the balance of Fe. The apparent density is 4.12 g / cm 3 , the tap density is 4.99g / cm 3 ;

[0028] The mass fraction of the M2 high-speed steel powder with the first particle size is 63.17%, and the mass fraction of the M2 high-speed steel powder with the second particle size is 36.83%.

[0029] In this embodiment, by defining the specific parameters of two M2 high-speed steel powders with different particle sizes, the optimal mixing ratio (i.e., mass fraction) of the two can be calculated, so that the maximum relative theoretical packing density of the powder bed can be obtained, thereby maximizing the relative density of the internally cooled tool.

[0030] In one embodiment of the present invention, the mass fractions of two M2 high speed steel powders with different particle sizes are obtained by mixing the D 50 The tap density is input into a preset mathematical calculation model. The mathematical calculation model is not limited here, wherein the mathematical calculation model is obtained by Python programming.

[0031] In some embodiments, the target metal powder is obtained by high-energy ball milling (the ball milling method is dry mixing, and the ball milling time is 48 hours) of M2 high-speed steel powder with a first particle size of 63.17% by mass and M2 high-speed steel powder with a second particle size of 36.83% by mass, and then drying and sieving.

[0032] In one embodiment of the present invention, the chemical composition of the target adhesive includes 17.54% by mass of 4-pentyn-2-ol, 1.13% by mass of isopropyl alcohol, 3.42% by mass of ethylene glycol, 76.79% by mass of ethylene glycol monobutyl ether, 1% by mass of pentaethylenehexamine, and 0.12% by mass of tris(2-aminoethyl)amine.

[0033] In this embodiment, the above-mentioned chemical components do not contain harmful substances, and the target adhesive will not volatilize (therefore, it needs to be removed through subsequent drying), so it will not cause harm to the environment and human body; and the target adhesive has good bonding properties and can firmly bond two M2 high-speed steel powders of different particle sizes together.

[0034] In one embodiment of the present invention, the parameters of additive manufacturing include: the thickness of each layer of target metal powder is 80 μm, the D 50 The diameter is 24.81 μm and the tap density is 5.36 g / cm3 , the saturation of the target adhesive is 10.95%.

[0035] It is understandable that some parameters of additive manufacturing are obtained by using modeling software to construct a three-dimensional model of the workpiece to be processed and slicing the three-dimensional model of the workpiece to be processed in computer slicing software, while other parameters are set manually.

[0036] In one embodiment of the present invention, after obtaining the calcined body and before sintering the calcined body, the method further comprises:

[0037] The pre-calcined body is heated and cured and dried to remove glue in sequence; wherein, the heating temperature is 200°C, the heating time is 4 to 5 hours, the drying temperature is 600°C, and the drying time is 1 to 2 hours.

[0038] In this embodiment, the pre-burned body is heated and solidified to give it a certain strength and solid shape; and the target adhesive is removed by drying the heat-cured pre-burned body to ensure the mechanical properties of the subsequently obtained internally cooled tool.

[0039] In one embodiment of the present invention, after sintering the pre-calcined body, the method further comprises:

[0040] The sintered finished product is cleaned and polished in sequence; wherein, the cleaning time is 0.5 to 1 hour, and the cleaning medium is anhydrous ethanol.

[0041] In some embodiments, cleaning can be ultrasonic cleaning; polishing can be grinding the sintered finished product on sandpaper of #240, #400, #600, #800, #1000, #1200, #1500, #2000, and 3000 in sequence, and then polishing it with a diamond polishing agent, so as to obtain an internally cooled tool with good mechanical properties.

[0042] In one embodiment of the present invention, the optimized sintering process is: sintering at a first preset temperature range for a first preset time under an inert gas atmosphere, increasing the sintering temperature to a second preset temperature range within a second preset time, and continuing to sinter for a third preset time under a vacuum atmosphere.

[0043] In some embodiments, the inert gas can be argon, helium and nitrogen, preferably argon, because nitrogen may form nitrides on the metal surface during sintering, thereby affecting the mechanical properties of the internally cooled tool, while helium is relatively expensive.

[0044] In this embodiment, after the first sintering process is completed, argon is introduced during the cooling process to effectively prevent oxidation reactions between oxygen and the metal powder, reducing the degree of oxidation in the sintered part, maintaining stable material composition and properties, and improving the quality and surface finish of the sintered part. Furthermore, due to its excellent thermal conductivity, the introduction of argon accelerates the cooling of the sintered part, shortening the sintering time, improving sintering efficiency, and reducing production costs. Furthermore, continuing sintering in a vacuum atmosphere effectively increases the relative density of the internally cooled tool and eliminates porosity.

[0045] In one embodiment of the present invention, the first preset temperature range is 1200-1280°C, the second preset temperature range is 1300-1380°C, the first preset time is 50-45 minutes, the second preset time is 3-6 minutes, and the third preset time is 10-15 minutes.

[0046] In this embodiment, the sintered part is first sintered within a first preset temperature range to form a matrix. During the sintering process, localized liquefaction occurs at the junctions between the powder particles, meaning that atoms or molecules on the surface of the powder particles diffuse (i.e., form a fluid), increasing the contact area between the particles. When the atoms or molecules between the particles diffuse to a certain extent, they form a strong bond between the particles, thereby achieving inter-particle fixation. However, due to the relatively small amount of fluid generated by liquefaction during the sintering process, the bond strength between the powder particles is weak, resulting in a low relative density of the pre-sintered part. Subsequently, the sintering temperature is rapidly increased to the second preset temperature range within a very short period of time (i.e., the second preset duration) and maintained for a relatively short period of time (i.e., the third preset duration). The large amount of fluid generated in the matrix fills the pores between the particles, resulting in a sintered product with a higher relative density, thereby improving the mechanical properties, tensile strength, and hardness of the internally cooled tool.

[0047] Experiments show that the internally cooled tool produced by the method provided in the embodiment of the present invention has a relative density of up to 99.95%, a hardness of 52 to 54 HRC at room temperature, and a tensile strength of 800 to 1200 MPa, and has good mechanical properties.

[0048] In summary, the method provided in the embodiment of the present invention improves the mechanical properties of the internally cooled tool by the following means: 1) adding LaB6 powder to the high-speed steel powder; 2) the target metal powder includes two M2 high-speed steel powders of different particle sizes, and the optimal mixing ratio of the two is further determined; 3) the pre-sintered body is sintered using the optimized sintering process.

[0049] It should be noted that, in the present invention, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0050] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is intended only to illustrate the technical solution of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for preparing an internally cooled tool based on additive manufacturing combined with sintering optimization, characterized in that: include: Obtaining target metal powder and target adhesive; wherein the target metal powder includes high-speed steel powder and LaB6 powder; Alternately performing additive manufacturing on the target metal powder and the target adhesive to obtain a calcined body; The pre-sintered body is sintered by using an optimized sintering process to obtain an internally cooled tool; The target metal powder includes two M2 high-speed steel powders of different particle sizes; The optimized sintering process is as follows: sintering at a first preset temperature range for a first preset time in an inert gas atmosphere, increasing the sintering temperature to a second preset temperature range within a second preset time, and continuing sintering in a vacuum atmosphere for a third preset time; The parameters of the first particle size M2 high speed steel powder include: particle size range of 15 to 53 μm, D 50 The diameter of the steel bar is 36.43 μm. The chemical composition is calculated by mass percentage: C content is 0.86%, Mn content is 0.35%, Cr content is 4.15%, Si content is 0.36%, V content is 4.10%, W content is 6.20%, Mo content is 5.00%, and the balance is Fe. The apparent density is 4.18 g / cm 3 , the tap density is 4.8g / cm 3 ; The parameters of the second particle size M2 high speed steel powder include: particle size range of 1 to 15 μm, D 50 The thickness of the steel is 6.42 μm. The chemical composition is calculated by mass percentage, including C content of 0.87%, Mn content of 0.34%, Cr content of 4.23%, Si content of 0.45%, V content of 1.90%, W content of 6.21%, Mo content of 5.17%, and the balance of Fe. The apparent density is 4.12 g / cm 3 , the tap density is 4.99g / cm 3 ; The mass fraction of the M2 high-speed steel powder with the first particle size is 63.17%, and the mass fraction of the M2 high-speed steel powder with the second particle size is 36.83%.

2. The method according to claim 1, characterized in that The mass fractions of two M2 high-speed steel powders with different particle sizes were calculated by dividing the D 50 The tap density is input into the preset mathematical calculation model.

3. The method according to claim 1, characterized in that The chemical composition of the target adhesive includes 17.54% by mass of 4-pentyn-2-ol, 1.13% by mass of isopropyl alcohol, 3.42% by mass of ethylene glycol, 76.79% by mass of ethylene glycol monobutyl ether, 1% by mass of pentaethylenehexamine, and 0.12% by mass of tris(2-aminoethyl)amine.

4. The method according to claim 1, wherein The parameters of the additive manufacturing include: the thickness of each layer of the target metal powder is 80 μm, the D 50 The diameter is 24.81 μm and the tap density is 5.36 g / cm 3 , the saturation of the target adhesive is 10.95%.

5. The method according to claim 1, wherein After obtaining the calcined body and before sintering the calcined body, the method further comprises: The pre-calcined body is heated and cured and dried to remove glue in sequence; wherein the heating temperature is 200° C., the heating time is 4 to 5 hours, the drying temperature is 600° C., and the drying time is 1 to 2 hours.

6. The method according to claim 1, characterized in that After sintering the calcined body, the method further comprises: The sintered finished product is cleaned and polished in sequence; wherein, the cleaning time is 0.5 to 1 hour, and the cleaning medium is anhydrous ethanol.

7. The method according to any one of claims 1 to 6, characterized in that The first preset temperature range is 1200-1280°C, the second preset temperature range is 1300-1380°C, the first preset time is 50-45 minutes, the second preset time is 3-6 minutes, and the third preset time is 10-15 minutes.

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