A method for preparing a continuous fiber reinforced ceramic matrix composite U-shaped beam

Abstract

The present invention relates to a method for preparing a U-shaped beam of continuous fiber reinforced ceramic matrix composite material, in order to solve the technical problem that the bottom surface of the U-shaped beam of carbon fiber reinforced ceramic matrix composite material with a large inner cavity depth is narrow, and when it is formed by means of a mold, it cannot be punctured and sewn according to the conventional process, thereby causing the bottom of the preform to be easily delaminated. The method includes 1. preparing a mold; 2. calculating the size and number of layers of carbon fiber cloth; 3. cutting and laying carbon fiber cloth, and puncturing and sewing the bottom surface corresponding to the position of the bottom surface of the inner mold; 4. wrapping the carbon fiber cloth in step 3 outside the inner mold and puncturing and sewing; 5. locking the end surface of the sewn preform; 6. closing the outer mold and fixing it with a reinforcement frame; 7. preparing a pyrolytic carbon interface layer and a silicon carbide matrix to obtain a U-shaped beam blank; 7. machining to obtain a U-shaped beam finished product. The method is simple to operate, enhances the bonding force between the carbon fiber cloth layers on the bottom surface of the U-shaped beam, and reduces the cost at the same time.

Description

Technical Field

[0001] The invention relates to a method for preparing a continuous fiber reinforced ceramic matrix composite material workpiece, in particular to a method for preparing a continuous fiber reinforced ceramic matrix composite material U-shaped beam. Background Art

[0002] Continuous fiber reinforced ceramic matrix composites have become ideal high-temperature structural materials in the aerospace field due to their excellent properties such as high temperature resistance, corrosion resistance, oxidation resistance, high strength, high toughness, etc. The two-dimensional laminated fiber preform has a simple weaving process and low cost, and is widely used in ceramic matrix composites.

[0003] In order to obtain carbon fiber reinforced ceramic matrix composite materials with good interlayer bonding strength, when the fiber preform is finalized, the carbon fiber cloth is first overlapped layer by layer to a certain thickness, and then punctured according to a specific needle method with the help of a molding mold, so as to obtain carbon fiber preforms with different structures and certain bonding strengths, and then SiC is deposited to obtain carbon fiber reinforced ceramic matrix composite materials with good interlayer bonding strength. However, for U-shaped beams with small opening sizes and deep inner cavity depths, their bottom surfaces are narrow, and when formed with the help of molds, they cannot be punctured and sewn according to conventional processes. Therefore, the interlayer bonding strength of the U-shaped beam, especially its bottom, is weak, and stratification is prone to occur, which in turn affects its mechanical properties. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problem that the bottom surface of a U-shaped beam of a carbon fiber reinforced ceramic matrix composite material with a large inner cavity depth is narrow, and when it is formed by a mold, it cannot be punctured and sewn according to the conventional process, which leads to easy stratification at the bottom of the preform. A preparation method of a U-shaped beam of a continuous fiber reinforced ceramic matrix composite material is proposed.

[0005] The technical solution provided by the present invention is:

[0006] A method for preparing a continuous fiber reinforced ceramic matrix composite U-shaped beam, which is special in that it comprises the following steps:

[0007] S1. Prepare a U-shaped beam mold: The U-shaped beam mold includes an inner mold, an outer mold and a reinforcement frame;

[0008] S2. Calculate the size and number of layers of the carbon fiber cloth according to the structural size of the U-shaped beam to be prepared: the length of the carbon fiber cloth L = 2h 1 +d 1 +2×(20~30)mm, width of carbon fiber cloth D=L 1 +2×(20~30)mm, number of carbon fiber cloth layers N=d 2 / d 3 , where h 1 is the height of the U-shaped beam to be prepared, d1 is the width of the U-shaped beam to be prepared, L 1 is the length of the U-shaped beam to be prepared, d 2 is the thickness of the U-beam to be prepared, d 3 is the thickness of a single carbon fiber cloth;

[0009] S3, cutting the carbon fiber cloth according to the result calculated in step S2, and overlapping the carbon fiber cloth layer by layer to a preset thickness, marking the position corresponding to the bottom surface of the inner mold on the laid carbon fiber cloth, and performing bottom surface puncture sewing at the marked position using a bottom surface puncture sewing line;

[0010] S4, folding the carbon fiber cloth after the bottom surface is punctured and sewn and wrapping it on the outside of the inner mold, and the position marked in step S3 corresponds to the bottom surface of the inner mold, and using the side puncture sewing line, the side surface of the carbon fiber cloth wrapped on the inner mold is punctured and sewn with the inner mold to obtain a U-shaped beam preform; cutting and flattening the end surface of the U-shaped beam preform after the side puncture sewing is completed, and then locking the edge;

[0011] S5, sleeve the outer mold on the outer side of the U-shaped beam preform, and use a reinforcement frame to fix the inner membrane (2) and the outer mold (3);

[0012] S6, sequentially preparing a pyrolytic carbon interface layer and a silicon carbide matrix to obtain a U-beam blank;

[0013] S7. Processing the U-shaped beam blank to a preset size through mechanical processing to obtain a U-shaped beam finished product.

[0014] Further, in step S1, the bottom surface and the side outer wall of the inner mold are adapted to the inner side surface of the U-shaped beam to be prepared; a plurality of inner mold air holes are provided on the inner mold, the aperture of the inner mold air holes is 3-5 mm, and the hole center distance between adjacent inner mold air holes is 6-10 mm; the inner mold is used to be wrapped by the U-shaped beam preform made of carbon fiber cloth;

[0015] The inner side wall of the outer mold is matched with the inner mold wrapping the U-shaped beam preform; a plurality of outer mold air holes are arranged on the outer mold, the aperture of the outer mold air holes is 3-5 mm, and the hole center distance between adjacent outer mold air holes is 6-10 mm;

[0016] The reinforcement frame is arranged on the outside of the outer mold and is used to fix the outer mold and the inner mold.

[0017] Further, in step S1, a boss is provided at the upper end of the inner mold, and the upper end surface of the boss has a draft angle of 0.5-2° with the bottom surface of the inner mold;

[0018] The contact surface between the reinforcement frame and the boss has a draft angle of 0.5-2°;

[0019] The position where the reinforcement frame is installed and fixed is the position where the inner side surface of the reinforcement frame is completely in contact with the upper end surface of the boss.

[0020] Furthermore, both ends of the inner mold have limiting surfaces;

[0021] When the outer mold and the inner mold are in a mold-clamping state, the upper end surface of the outer mold is flush with the upper end surface of the limiting surface.

[0022] Furthermore, in step S1, the U-beam mold is a graphite mold, and the graphite mold is made of high-strength fine graphite;

[0023] The density of the high-strength fine graphite is 1.75 g / cm 3 , flexural strength ≥20MPa, compressive strength ≥40MPa.

[0024] Furthermore, in step S2, the carbon fiber cloth is woven using 1K fiber bundles;

[0025] In steps S3 and S4, the bottom puncture sewing line, the side puncture sewing line and the hemming line are made of 3K fiber bundles.

[0026] Further, in step S4, the spacing between adjacent puncture holes formed by the side puncture sewing in the length direction of the U-shaped beam preform is 3-5 mm;

[0027] The side puncture sewing is performed by evenly sewing multiple rows along the length direction of the U-shaped beam preform, and the spacing between two adjacent rows is 6-10 mm.

[0028] Furthermore, in step S4, the edge locking is performed in a circular winding manner, the edge locking line width formed by the edge locking is 5-10 mm, and the distance between adjacent edge locking lines is 1-2 mm.

[0029] Further, in step S6, the preparation of the pyrolytic carbon interface layer adopts a pyrolytic carbon interface layer chemical vapor infiltration process, and the preparation process is: firstly, the U-shaped beam preform with the inner mold, the outer mold and the reinforcement frame is subjected to the pyrolytic carbon interface layer chemical vapor infiltration process at least once, then the reinforcement frame and the outer mold are removed, and the pyrolytic carbon interface layer chemical vapor infiltration process is repeated at least once. After the preparation of the pyrolytic carbon interface layer is completed, the outer mold and the reinforcement frame are assembled again on the outside of the preform with the pyrolytic carbon interface layer;

[0030] In step S6, the silicon carbide substrate is prepared by using a silicon carbide substrate chemical vapor infiltration process, and the preparation process is as follows:

[0031] A1. A U-shaped beam preform having an inner mold, an outer mold and a reinforcement frame and prepared with a pyrolytic carbon interface layer is subjected to a silicon carbide matrix chemical vapor infiltration process at least once, and the reinforcement frame and the outer mold are removed;

[0032] A2, repeating the chemical vapor infiltration process of the silicon carbide substrate in step A1 at least once, and removing the inner mold;

[0033] A3, repeat the chemical vapor infiltration process of the silicon carbide substrate in step A1 1-3 times, and cut off the lock edge;

[0034] A4. Repeat the chemical vapor infiltration process of the silicon carbide substrate in step A1 for multiple times until the deposition of the silicon carbide substrate is completed.

[0035] Furthermore, in step S3, overlapping the carbon fiber cloth layer by layer to a preset thickness specifically includes: overlapping and laying the carbon fiber cloth layer by layer, and the extension directions of the carbon fiber bundles of two adjacent layers of carbon fiber cloth are orthogonal.

[0036] Beneficial effects of the present invention:

[0037] 1. The present invention provides a method for preparing a U-shaped beam of continuous fiber reinforced ceramic matrix composite material. In particular, for a U-shaped beam with a narrow width and a deep depth, carbon fiber cloths overlapped layer by layer to a preset thickness are pierced and sewn at positions corresponding to the bottom surface of the U-shaped beam, so that there are also pierced fiber bundles on the bottom surface of the U-shaped beam, thereby enhancing the bonding force between the carbon fiber cloth layers on the bottom surface of the U-shaped beam.

[0038] 2. The method provided by the present invention is simple to operate and does not require the inner mold to be provided with sewing holes penetrating the upper end surface and the lower end surface, which reduces the requirements for mold strength and reduces the cost of preparing mold materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the U-shaped beam structure to be prepared in an embodiment of the present invention;

[0040] Figure 2 Schematic diagram of the carbon fiber cloth after the bottom surface is punctured and sewn in an embodiment of the present invention;

[0041] Figure 3 This is a schematic diagram of the inner mold structure for wrapping a U-beam preform in an embodiment of the present invention (the locking line is not shown in the figure);

[0042] Figure 4 Schematic diagram of the mold closing structure of the outer mold and the inner mold in an embodiment of the present invention (the outer mold vent hole is not shown in the figure);

[0043] Figure 5 Schematic diagram of the mold-closing structure of the reinforcement frame, outer mold and inner mold in an embodiment of the present invention (the outer mold air holes are not shown in the figure).

[0044] The reference numerals are as follows:

[0045] 1-U-beam prefabricated body, 11-bottom puncture sewing line, 12-side puncture sewing line, 13-locking line, 2-inner mold, 21-boss, 22-limiting surface, 3-outer mold, 31-reinforcement rib, 4-reinforcement frame. DETAILED DESCRIPTION

[0046] This embodiment provides a method for preparing a continuous fiber reinforced ceramic matrix composite U-shaped beam, the method comprising the following steps:

[0047] S1. Prepare a U-shaped beam mold: The U-shaped beam mold includes an inner mold 2, an outer mold 3 and a reinforcement frame 4. The U-shaped beam mold is made of graphite material;

[0048] The bottom surface and the side outer wall of the inner mold 2 are adapted to the inner surface of the U-shaped beam to be prepared; a boss 21 is provided at the upper end of the inner mold 2, and the angle between the upper end surface of the boss 21 and the bottom surface of the inner mold is a draft angle of 0.5-2°, which is convenient for demolding; both ends of the inner mold 2 have limit surfaces 22; a plurality of inner mold air holes are provided on the inner mold 2, the aperture of the inner mold air holes is 3-5mm, and the hole center distance between adjacent inner mold air holes is 6-10mm; the inner mold 2 is used to be wrapped by the U-shaped beam preform 1 made of carbon fiber cloth;

[0049] The inner wall of the outer mold 3 cooperates with the inner mold 2 that wraps the U-shaped beam preform 1; the outer mold 3 is provided with a plurality of outer mold air holes, the aperture of the outer mold air holes is 3-5mm, and the hole center distance between adjacent outer mold air holes is 6-10mm; the bottom and side surfaces of the outer mold 3 are provided with reinforcing ribs 31;

[0050] The reinforcement frame 4 is arranged outside the outer mold 3 and is used to fix the outer mold 3 and the inner mold 2; the contact surface between the reinforcement frame 4 and the boss 21 has a draft angle of 0.5-2°.

[0051] S2. Calculate the size and number of layers of carbon fiber cloth according to the structural size of the U-shaped beam to be prepared: Figure 1 The carbon fiber cloth in this embodiment is woven from 1K fiber bundles; the length of the carbon fiber cloth is L = 2h 1 +d 1 +2×(20~30)mm, width of carbon fiber cloth D=L 1 +2×(20~30)mm, number of carbon fiber cloth layers N=d 2 / d 3 , where h 1 is the height of the U-shaped beam to be prepared, d 1 is the width of the U-shaped beam to be prepared, L 1 is the length of the U-shaped beam to be prepared, d 2 is the thickness of the U-beam to be prepared, d 3 is the thickness of a single carbon fiber cloth.

[0052] S3, see Figure 2 , cut the carbon fiber cloth according to the result calculated in step S2, and lay the carbon fiber cloth layer by layer in an overlapping manner, and satisfy the requirement that the extension directions of the carbon fiber bundles of two adjacent layers of carbon fiber cloth are orthogonal. After laying to the preset thickness, mark the corresponding position of the bottom surface of the inner mold 2 on the laid carbon fiber cloth, and use the bottom surface puncture stitching line 11 to perform bottom surface puncture stitching on the marked position. The bottom surface puncture stitching line 11 uses a 3K fiber bundle. Since the position on the laid carbon fiber cloth corresponding to the bottom surface of the inner mold 2 is punctured and sewn in advance, there is no need to set a sewing hole that runs through the inner mold 2 from top to bottom, which reduces the requirements for the preparation material of the inner mold 2. Only high-strength fine graphite needs to be selected to meet the use requirements, and expensive high-purity graphite is not required, which greatly reduces the preparation cost of the mold; specifically, the density of the high-strength fine graphite is 1.75g / cm 3 , flexural strength ≥20MPa, compressive strength ≥40MPa.

[0053] S4. See Figure 3 , fold the carbon fiber cloth after the bottom surface is punctured and sewn and wrap it on the outside of the inner mold 2, and the position marked in step S3 corresponds to the bottom surface of the inner mold 2, and use the side puncture sewing line 12 to puncture and sew the side of the carbon fiber cloth wrapped on the inner mold 2 with the inner mold 2, the side puncture sewing line 12 uses a 3K fiber bundle, and the spacing between adjacent puncture holes in the length direction of the U-shaped beam preform 1 is 3-5mm, and the side puncture sewing is uniformly sewn in multiple rows along the length direction of the U-shaped beam preform 1, and the spacing between two adjacent rows is 6-10mm, so as to obtain a U-shaped beam preform 1;

[0054] The end surface of the sewn U-shaped beam preform 1 is cut flat and then locked. The locking is performed by annularly winding 3K fiber bundles. The locking line 13 formed by the locking has a width of 5-10 mm, and the distance between adjacent locking lines 13 is 1-2 mm.

[0055] The carbon fiber cloth adopts 1K fiber bundles, and the bottom puncture sewing, side puncture sewing and locking edge adopt 3K fiber bundles. The sewing and locking edge of the fiber bundles of 3K fiber bundles can not only make the size of the sewing hole suitable for the subsequent chemical vapor infiltration process, but also avoid the stress concentration caused by the use of too thick fiber bundles, which in turn causes the U-shaped beam to easily break along the sewing hole.

[0056] S5. See Figure 4 and Figure 5 The outer mold 3 is sleeved on the outside of the U-shaped beam preform 1, the upper end surface of the outer mold 3 is flush with the upper end surface of the limiting surface 22, and is fixed with a reinforcing frame 4. The position where the reinforcing frame 4 is installed and fixed is the position where the inner side surface of the reinforcing frame 4 is completely in contact with the upper end surface of the boss 21 at the upper end of the inner mold 2.

[0057] S6, sequentially preparing a pyrolytic carbon interface layer and a silicon carbide matrix to obtain a U-beam blank;

[0058] The pyrolytic carbon interface layer is prepared by a pyrolytic carbon interface layer chemical vapor infiltration process; in the preparation process of this embodiment, the U-shaped beam preform 1 with the inner mold 2, the outer mold 3 and the reinforcement frame 4 is first subjected to a pyrolytic carbon interface layer chemical vapor infiltration process, and then the reinforcement frame 4 and the outer mold 3 are removed, and the pyrolytic carbon interface layer chemical vapor infiltration process is repeated once. After the pyrolytic carbon interface layer preparation is completed, the outer mold 3 and the reinforcement frame 4 are assembled again on the outside of the preform with the pyrolytic carbon interface layer.

[0059] The silicon carbide substrate is prepared by using a silicon carbide substrate chemical vapor infiltration process, and the preparation process is as follows:

[0060] A1, subjecting a U-shaped beam preform 1 having an inner mold 2, an outer mold 3 and a reinforcement frame 4 and prepared with a pyrolytic carbon interface layer to a silicon carbide matrix chemical vapor infiltration process once, and removing the reinforcement frame 4 and the outer mold 3;

[0061] A2, repeating the chemical vapor infiltration process of the silicon carbide substrate in step A1 once, and removing the inner mold 2;

[0062] A3, repeat the chemical vapor infiltration process of the silicon carbide substrate in step A1 1-2 times, and cut off the lock edge;

[0063] A4: Repeat the chemical vapor infiltration process of the silicon carbide substrate in step A1 for multiple times until the silicon carbide deposition density is 1.80-1.90 g / cm 3 , the silicon carbide substrate deposition is completed.

[0064] S7. Processing the U-shaped beam blank to a preset size through mechanical processing to obtain a U-shaped beam finished product.

Claims

1. A method for preparing a continuous fiber reinforced ceramic matrix composite U-shaped beam, wherein the U-shaped beam has a small opening size and a deep inner cavity depth, characterized in that: The following steps are involved: S1. Prepare a U-shaped beam mold: The U-shaped beam mold includes an inner mold (2), an outer mold (3) and a reinforcement frame (4); the U-shaped beam mold is a graphite mold, and the graphite mold is made of high-strength fine graphite; the density of the high-strength fine graphite is 1.75 g / cm 3 , flexural strength ≥ 20MPa, compressive strength ≥ 40MPa; S2. Calculate the size and number of layers of the carbon fiber cloth according to the structural size of the U-shaped beam to be prepared: the length of the carbon fiber cloth L = 2h1 + d1 + 2 × (20 ~ 30) mm, the width of the carbon fiber cloth D = L1 + 2 × (20 ~ 30) mm, the number of layers of carbon fiber cloth N = d2 / d3, wherein h1 is the height of the U-shaped beam to be prepared, d1 is the width of the U-shaped beam to be prepared, L1 is the length of the U-shaped beam to be prepared, d2 is the thickness of the U-shaped beam to be prepared, and d3 is the thickness of a single carbon fiber cloth; the carbon fiber cloth is woven from 1K fiber bundles; S3, cutting the carbon fiber cloth according to the result calculated in step S2, and overlapping the carbon fiber cloth layer by layer to a preset thickness, marking the corresponding position of the bottom surface of the inner mold (2) on the laid carbon fiber cloth, and performing bottom surface puncture sewing at the marked position using the bottom surface puncture sewing line (11); The carbon fiber cloth is overlapped layer by layer to a preset thickness, specifically: the carbon fiber cloth is overlapped layer by layer, and the extension directions of the carbon fiber bundles of two adjacent layers of carbon fiber cloth are orthogonal; the bottom surface puncture sewing line (11) uses 3K fiber bundles; S4, wrapping the carbon fiber cloth after the bottom surface is punctured and sewn on the outside of the inner mold (2), and the position of the mark in step S3 corresponds to the bottom surface of the inner mold (2), and using the side puncture sewing line (12), the side surface of the carbon fiber cloth wrapped on the inner mold (2) is punctured and sewn with the inner mold (2) to obtain a U-shaped beam preform (1); after the end surface of the U-shaped beam preform (1) after the side puncture sewing is completed is cut flat, and then the edge is locked using the locking line (13); the side puncture sewing line (12) and the locking line (13) use 3K fiber bundles; S5, sleeve the outer mold (3) on the outer side of the U-shaped beam preform (1), and use a reinforcing frame (4) to fix the inner mold (2) and the outer mold (3); S6, sequentially preparing a pyrolytic carbon interface layer and a silicon carbide matrix to obtain a U-shaped beam blank; the pyrolytic carbon interface layer is prepared by a pyrolytic carbon interface layer chemical vapor infiltration process, and the preparation process is as follows: firstly, a U-shaped beam preform (1) with an inner mold (2), an outer mold (3) and a reinforcement frame (4) is subjected to a pyrolytic carbon interface layer chemical vapor infiltration process at least once, then the reinforcement frame (4) and the outer mold (3) are removed, and the pyrolytic carbon interface layer chemical vapor infiltration process is repeated at least once. After the pyrolytic carbon interface layer is prepared, the outer mold (3) and the reinforcement frame (4) are assembled again on the outside of the preform with the pyrolytic carbon interface layer; The silicon carbide substrate is prepared by a silicon carbide substrate chemical vapor infiltration process, and the preparation process is as follows: A1. A U-shaped beam preform (1) having an inner mold (2), an outer mold (3) and a reinforcement frame (4) and prepared with a pyrolytic carbon interface layer is subjected to a silicon carbide matrix chemical vapor infiltration process at least once, and the reinforcement frame (4) and the outer mold (3) are removed; A2, repeating the chemical vapor infiltration process of the silicon carbide substrate in step A1 at least once, and removing the inner mold (2); A3, repeat the chemical vapor infiltration process of the silicon carbide substrate in step A1 1-3 times, and cut off the lock edge; A4, repeating the chemical vapor infiltration process of the silicon carbide substrate in step A1 for multiple times until the deposition of the silicon carbide substrate is completed; S7. Processing the U-shaped beam blank to a preset size through mechanical processing to obtain a U-shaped beam finished product.

2. The method for preparing a continuous fiber reinforced ceramic matrix composite U-shaped beam according to claim 1, characterized in that: In step S1, the bottom surface and the side outer wall of the inner mold (2) are adapted to the inner side surface of the U-shaped beam to be prepared; a plurality of inner mold air holes are provided on the inner mold (2), the hole diameter of the inner mold air holes is 3-5 mm, and the hole center distance between adjacent inner mold air holes is 6-10 mm; the inner mold (2) is used to be wrapped by the U-shaped beam preform (1); The inner side wall of the outer mold (3) is used to cooperate with the inner mold (2) that wraps the U-shaped beam preform (1); a plurality of outer mold air holes are provided on the outer mold (3), the aperture of the outer mold air holes is 3-5 mm, and the distance between the centers of adjacent outer mold air holes is 6-10 mm; The reinforcement frame (4) is arranged on the outside of the outer mold (3) and is used to fix the outer mold (3) and the inner mold (2).

3. The method for preparing a continuous fiber reinforced ceramic matrix composite U-shaped beam according to claim 2, characterized in that: In step S1, a boss (21) is provided at the upper end of the inner mold (2), and the upper end surface of the boss (21) has a draft angle of 0.5-2° with the bottom surface of the inner mold; The contact surface between the reinforcement frame (4) and the boss (21) has a draft angle of 0.5-2°; The position where the reinforcing frame (4) is installed and fixed is the position where the inner side surface of the reinforcing frame (4) is completely in contact with the upper end surface of the boss (21).

4. The method for preparing a continuous fiber reinforced ceramic matrix composite U-shaped beam according to claim 3, characterized in that: The inner mold (2) has limiting surfaces (22) at both ends; when the outer mold (3) and the inner mold (2) are in a mold-clamping state, the upper end surface of the outer mold (3) is flush with the limiting surface (22); The bottom surface and side surfaces of the outer mold (3) are both provided with reinforcing ribs (31).

5. The method for preparing a continuous fiber reinforced ceramic matrix composite U-shaped beam according to claim 4, characterized in that: In step S4, the spacing between adjacent puncture holes formed by the side puncture sewing in the length direction of the U-shaped beam preform (1) is 3-5 mm; The side puncture sewing is performed by evenly sewing multiple rows along the length direction of the U-shaped beam preform (1), and the spacing between two adjacent rows is 6-10 mm.

6. The method for preparing a continuous fiber reinforced ceramic matrix composite U-shaped beam according to claim 5, characterized in that: In step S4, the edge locking is performed in a circular winding manner, the edge locking line (13) formed by the edge locking has a width of 5-10 mm, and the distance between adjacent edge locking lines (13) is 1-2 mm.

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