A method for making a textured ceramic cutting tool

Abstract

The application discloses a preparation method of a textured ceramic cutter and belongs to the technical field of ceramic cutting tools. The method comprises the following steps: preferentially preparing a ceramic core rod; placing the ceramic core rod into a circular table cavity; adding long strip beta-silicon nitride whiskers into ceramic slurry of the ceramic core rod; and slowly flowing the ceramic slurry into the circular table cavity through gravity, slowly rotating and moving away from the ceramic core rod, and moving the circular table cavity relative to the ceramic core rod in a slanting manner. The ceramic core rod slowly covers the surface slurry and thickens under the action of the slanting speed of the circular table cavity, and the long strip beta-silicon nitride whiskers are mostly distributed in the same movement direction under the movement, so that the effect of texturing the outer structure of the ceramic cutter is achieved.

Description

Technical Field

[0001] This invention relates to the field of ceramic cutting tools, and more particularly to a method for preparing textured ceramic cutting tools. Background Technology

[0002] In the field of modern machining, especially in high-end manufacturing industries such as aerospace, automobile manufacturing, and energy equipment, precision cutting operations on metals and composite materials place extremely high demands on tool performance. However, cutting tools made of traditional cemented carbide, ceramics, or superhard materials, which are currently widely used, generally suffer from technical bottlenecks such as short service life and rapid wear rate.

[0003] Silicon nitride ceramic cutting tools combine near-diamond hardness, significantly better impact toughness than alumina, and thermal conductivity far exceeding that of most ceramic materials. This allows for rapid heat dissipation during cutting, and the low coefficient of thermal expansion greatly reduces the risk of plastic deformation caused by thermal stress concentration at the tool tip. Therefore, it is one of the most suitable materials for use as cutting tools.

[0004] During the processing of ceramic knives, due to their rotational working characteristics, the overall force direction is oblique. The β-whisker structure of silicon nitride is stable and elongated. If the β-whiskers can be arranged along the force direction of the ceramic knife, exhibiting a textured structure, it will greatly improve the working life and stability of the ceramic knife. However, the ceramic knife itself has a cylindrical structure, and it is difficult to control its whiskers to exhibit a spiral arrangement during the sintering process. Summary of the Invention

[0005] The innovation of this invention lies in the priority of preparing a ceramic core rod, placing the ceramic core rod into a frustum cavity, and adding long strips of β-silicon nitride whiskers to the ceramic slurry of the ceramic core rod. The ceramic slurry slowly flows into the frustum cavity under the action of gravity, and the frustum cavity slowly rotates and slowly moves away from the ceramic core rod. The movement of the frustum cavity relative to the ceramic core rod is an oblique movement. Under the action of the oblique velocity of the frustum cavity, the ceramic core rod slowly covers the surface slurry, thickening and thickening it. Under this movement, most of the long strips of β-silicon nitride whiskers are distributed in the same direction of movement, achieving the effect of texturing the external structure of the ceramic cutting tool.

[0006] A method for preparing a textured ceramic cutting tool, characterized by the following steps: S1, preparing a mixed slurry; mixing Si3N4 powder with an α phase content higher than 85%, rare earth element compounds, β-silicon nitride whisker powder, and a dispersant and ball milling them until all particles have a particle size of 0.05-1.5μm, thus completing the preparation of the mixed slurry.

[0007] S2. Preparation of mandrel and frustum cavity: The mandrel is a cylinder or a frustum; the frustum cavity is divided into a cavity front end and a cavity rear end, the cavity part at the cavity front end is shaped like a frustum, and the cavity part at the cavity rear end is shaped like a cylinder.

[0008] S3. Fix the mandrel vertically. The fixed end of the mandrel has a mixing slurry spray outlet. The mixing slurry is sprayed out by a pressure device.

[0009] S4. Keep the frustum cavity and the mandrel on the same center line. The frustum cavity covers the mandrel and remains vertical. The front end of the cavity is below and the rear end of the cavity is above. The frustum cavity is connected to the horizontal power device and the vertical power device. The frustum cavity can rotate around the center line and can move vertically up and down.

[0010] S5. Start the pressure device, the horizontal power device, and the vertical power device. The pressure device sprays the mixed slurry into the inner wall below the nozzle of the truncated cone cavity, covering it with mixed slurry. Start the horizontal power device and the vertical power device. The truncated cone cavity rotates in one direction and moves downward to coat the mandrel surface with mixed slurry. After the mandrel is completely placed at the rear end of the cavity, stop the pressure device and all power devices to complete the preparation of the tool blank.

[0011] S6. Silicon nitride ceramic cutting tools are prepared by cutting, degreasing, shaping, and sintering the tool blank.

[0012] Optionally, the mass fractions of Si3N4 powder, rare earth element compound, and β-silicon nitride whisker powder in step S1 are 70-90 parts, 2-11 parts, and 3-20 parts, respectively.

[0013] Optionally, the outer surface of the mandrel in step S2 is roughened.

[0014] Optionally, the inner wall of the frustum cavity described in step S2 is roughened.

[0015] Optionally, the core rod in step S2 is a silicon nitride material core rod.

[0016] Optionally, the lateral power unit and the longitudinal power unit mentioned in step S5 are started simultaneously.

[0017] Optionally, in step S5, the transverse power device provides a linear velocity v1 to the inner wall of the frustum cavity, and v1 always maintains a single direction of motion; the longitudinal power device provides a velocity v2 to the inner wall of the frustum cavity, and the angle formed by the β whisker arrangement trend and the horizontal plane is α, and the whisker arrangement trend angle satisfies the formula tan α=v2 / v1.

[0018] Optionally, the cutting in step S6 involves cutting the tool blank into a cylindrical shape, with the cutting surface flush with both ends of the mandrel.

[0019] Optionally, the molding method described in step S6 is dry pressing or cold isostatic pressing.

[0020] Optionally, the silicon nitride ceramic cutting tool prepared in step S6 can be cut into n segments to make n cutting tools, where n is a positive integer. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0022] Figure 1 Structural diagram of the device for preparing textured ceramic cutting tools;

[0023] Figure 2 A partial view of the working starting position of the frustum cavity and the mandrel;

[0024] Figure 3 This is a schematic diagram of a finished ceramic knife.

[0025] Figure 4 This is a conceptual diagram of the distribution of β whiskers in ceramic cutting tools. Detailed Implementation

[0026] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0027] The cutting tool used in this embodiment is model RCEM 120H4R150S, and its structural diagram is shown below. Figure 3 As shown, Figure 3 The left side is the cutting part, i.e., the cutter head, which is the part that needs to be protected by this invention. The right side is the cutter body, which can be replaced with tungsten carbide. If the cutter body is made of tungsten carbide, the cutter body and the cutter head are connected by brazing. The outer diameter of this model of silicon nitride cutter head is 12.0 mm.

[0028] 1. Preparation of mixed slurry: Si3N4 powder with α phase content higher than 85% (content is 75%), rare earth element compound (content is 5%), and β-silicon nitride whisker powder (content is 20%) are mixed into 20 kg of mixed powder. 5 kg of dispersant is added and the mixture is ball-milled for 3 hours to complete the preparation of mixed slurry.

[0029] 2. Preparation of mandrel: The mandrel is a cylinder with a groove on one side for connection with the fixing device. The mandrel is made of conventionally sintered silicon nitride material with conventional composition. It has a diameter of 6mm and a height of 4cm and a rough surface.

[0030] 3. Fabrication of the frustum-shaped cavity: The lower part of the inner cavity of the frustum-shaped cavity is a frustum structure, while the upper part is a cylinder. The inner cavity is tapered at the bottom and thickened at the top, with the lower end less than 6mm. The diameter of the frustum-shaped cavity is the same as the tool model being fabricated, at 12mm. The diameter of the cylinder in the upper part of the inner cavity is also 12mm. The outer surface shape of the inner cavity is proportional to that of the inner cavity. The frustum-shaped cavity is connected to two motors. One motor controls the rotation of the cavity around its vertical centerline, while the other motor controls the dimensional rotation, driving the cavity downwards. The inner wall of the frustum-shaped cavity has a rough structure.

[0031] 4. Fix the mandrel vertically. The fixed end of the mandrel has 8 small mixing slurry spray nozzles. The mixing slurry is sprayed out by a pressure device.

[0032] 5. Keep the frustum cavity and the mandrel on the same center line. The frustum cavity covers the mandrel, and the mandrel is kept vertical. Enter the working preparation state. In the working preparation state, the mandrel and the inner cavity of the frustum cavity are in a state of almost contact but not in contact.

[0033] 6. Activate the pressure device. The mixed slurry is sprayed from eight nozzles onto the inner wall of the frustum-shaped cavity, ensuring a continuous and slow spray. Simultaneously, activate the two motors connected to the frustum-shaped cavity, which control the linear velocity of the inner wall of the cavity at 0.8 m / h and the downward movement speed of the cavity at 0.8 m / h. Under these dynamic conditions, the inner wall of the cavity moves at a 45° angle relative to the mandrel. This movement of the inner wall and the mixed slurry on it can be understood as two hands constantly applying the slurry at a 45° angle around the mandrel. The slurry contains irregularly distributed β-silicon nitride whiskers. Under this application, approximately 80% of the β-silicon nitride whiskers will fall towards the 45° angle. Figure 4 As shown in the conceptual diagram, the textured effect of the silicon nitride tool is achieved. After the motor runs for about 15 minutes, the mandrel moves to the position of the cylinder inside the frustum cavity and stops. After standing for half an hour, the frustum cavity is opened and the automatically formed tool blank is taken out.

[0034] 7. After the tool blank is removed, excess powder is removed to form a cylindrical shape. The cylindrical blank formed under this process has a textured structure but lacks density, requiring a molding process after degreasing. During the molding process, the groove at the mandrel fixing end is filled. Then, it is sintered using conventional processes. After sintering, it is machined according to the tool shape to achieve the desired result. Figure 3The structural diagram is shown. In this embodiment, the RCEM 120H4R150S model cutting tool has only a silicon nitride tip; the body is made of tungsten steel. The tungsten steel tip will not be damaged during operation and can be recycled. The tip is a consumable item, and its length can range from 10mm to 40mm. Therefore, this invention can also use a longer mandrel to prepare long silicon nitride cylinders. By cutting these cylinders, multiple silicon nitride cutting tips can be produced at once.

Claims

1. A method for preparing a textured ceramic cutting tool, characterized in that the steps are as follows: S1. Preparing a mixed slurry; Si3N4 powder with an alpha phase content higher than 85%, a rare earth compound, and β-silicon nitride whisker powder are mixed and ball milled until all particles have a particle size of 0.05-1.5 μm to complete the preparation of the mixed slurry; S2. Preparing a mandrel and a circular cone cavity; the mandrel is a cylinder or a circular cone; the circular cone cavity has a front cavity end and a rear cavity end, the cavity part of the front cavity end is in the shape of a circular cone, and the cavity part of the rear cavity end is in the shape of a cylinder; S3. Vertically fixing the mandrel, and the fixed end of the mandrel has a mixed slurry outlet, and the mixed slurry is sprayed by a pressure device; S4. Keeping the circular cone cavity and the mandrel in the same center line, and the circular cone cavity surrounds the mandrel and keeps a vertical state, the front cavity end is below, and the rear cavity end is above; the circular cone cavity is connected with a horizontal power device and a vertical power device, and the circular cone cavity can rotate around the center line and vertically move up and down; S5. Starting the pressure device, the horizontal power device, and the vertical power device, the pressure device sprays the mixed slurry to the inner wall of the circular cone cavity below the mixed slurry outlet, and the horizontal power device and the vertical power device are started to rotate and move downward to smear the mixed slurry on the surface of the mandrel; the linear velocity of the inner wall of the circular cone cavity provided by the horizontal power device is v1, which always keeps moving in one direction; the velocity of the inner wall of the circular cone cavity provided by the vertical power device is v2, the angle between the arrangement trend of the β whisker and the horizontal plane is α, and the angle of the arrangement trend of the whisker satisfies the formula tan α=v2 / v1; after the mandrel completely enters the rear cavity end, the pressure device and all power devices are stopped to complete the preparation of the cutting tool roughcast; S6. Preparing a silicon nitride ceramic cutting tool by cutting, degreasing, forming, and sintering the cutting tool roughcast.

2. The method of claim 1, wherein: The mass fraction of the Si3N4 powder, the rare earth compound, and the β-silicon nitride whisker powder in step S1 is 70-90 parts, 2-11 parts, and 3-20 parts, respectively.

3. The method of claim 1, wherein: The outer surface of the mandrel in step S2 is rough.

4. The method of claim 1, wherein: The inner wall of the circular cone cavity in step S2 is rough.

5. The method of claim 1, wherein: The mandrel in step S2 is a silicon nitride material mandrel.

6. The method of claim 1 wherein: The horizontal power device and the vertical power device in step S5 are started simultaneously.

7. The method of claim 1 wherein: the ceramic cutting tool is formed by the steps of: providing a ceramic cutting tool; and forming a plurality of grooves in the ceramic cutting tool. The cutting in step S6 is to cut the cutting tool roughcast into a cylinder, and the cutting surface is flush with the two ends of the mandrel.

8. The method of claim 1, wherein: The forming method in step S6 is dry pressing or cold isostatic pressing.

9. The method of claim 1 wherein: the ceramic cutting tool is textured. The silicon nitride ceramic cutting tool prepared in step S6 is cut into n segments to prepare n cutting tools, and n is a positive integer.

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