Self-tapping fusing screw with high torsional strength and efficient chip removal capacity

Abstract

The invention belongs to the technical field of fasteners, and discloses a self-tapping fusing screw with high torsional strength and efficient chip removal capacity, which comprises a screw cap and a screw rod, the screw rod comprises a threaded part, a drill tail part and a self-chip-removal part located between the threaded part and the drill tail part. The driving head of the screw cap is of a multi-tooth quincunx structure, the side wall of a driving tooth groove of the screw cap is designed to be an approximately vertical force transmission face, and the torsional strength and the anti-biting capacity are improved. A wedge-shaped self-chip-removal groove is spirally formed in the periphery of the self-chip-removal part, the groove depth and the groove width of the self-chip-removal groove are gradually narrowed and shallower from bottom to top, the self-chip-removal groove is in smooth transition with a thread groove, metal chips generated in the tapping process can be guided out of a connecting area, blocking is effectively prevented, it is ensured that a screw is screwed in smoothly, and the thread forming quality is protected. The technical problems that the head of an existing FDS screw is prone to slipping and chip removal is not smooth are solved, and the connection reliability, the production efficiency and the process stability are remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fasteners, and relates to a self-tapping screw for connecting dissimilar materials, in particular to a self-tapping melting screw with high torsional strength and efficient chip removal capacity. BACKGROUND

[0002] The self-tapping melting screw (Flow Drill Screw, FDS) is an advanced fastening technology for connecting dissimilar materials (especially metal and metal, or metal and composite materials). Its working principle is to generate heat through the friction of a high-speed rotating screw, which softens or even melts the base material at the contact point, and the screw is then driven into the base material and forms a high-strength connection after cooling. This technology does not require pre-drilled holes, greatly improving production efficiency and connection strength.

[0003] Currently, there are various FDS screw designs in the industry, such as the FDS screws widely used by Tesla and other new energy vehicle manufacturers in their vehicle body connections. However, through in-depth analysis and actual application testing of existing technologies (especially the FDS screws used by Tesla), we found that they have the following main defects:

[0004] (1) Insufficient torsional resistance of screw head: The driving head of the existing FDS screw (usually a standard torx head or similar form) has limited contact area when cooperating with the gun sleeve. Under extremely high tightening torque, it is easy to slip and "bite the head", causing damage to the screw head and failing to transmit enough torque to complete the tightening process, which seriously reduces the production yield and efficiency.

[0005] (2) Unreasonable design of chip removal groove: A large amount of metal chips is generated during the tapping process. The existing design of the chip removal groove has limited capacity and poor chip removal path, which easily causes the chips to be blocked in the thread groove or around the screw. This not only increases the tightening torque and affects the smoothness of the screw tightening, but also may damage the formed thread due to the extrusion of the chips, weaken the connection strength, and even cause appearance quality problems.

[0006] (3) Poor stability during tightening process: The above two problems together cause instability during the tightening process, with large fluctuations in the torque-angle curve, making it difficult to form consistent and reliable connection quality. This is a significant technical pain point for modern production lines that emphasize automation and high consistency, such as automobile body-in-white production lines.

[0007] Therefore, it is urgent to innovatively design the structure of the existing FDS screw to simultaneously solve the problems of low torsional strength and difficult chip removal, and to improve the reliability and efficiency of the fastening process. SUMMARY

[0008] The self-tapping fuse screw has high torsional strength and high efficient chip removal capacity, can effectively transmit high torque without slipping, and actively and smoothly removes metal chips generated in the tapping process, thereby ensuring stable and reliable connection quality.

[0009] To achieve the above object, the present application adopts the following technical scheme:

[0010] The first aspect of the present application provides a self-tapping fuse screw with high torsional strength and high efficient chip removal capacity, comprising a screw cap and a screw rod arranged coaxially, the screw rod comprising a threaded portion at the upper end, a drill tail portion at the lower end, and a self-chip removal portion coaxially arranged between the threaded portion and the drill tail portion, wherein:

[0011] The self-chip removal portion is helically provided with a self-chip removal groove on the circumference, the self-chip removal groove is a wedge-shaped groove, the groove depth and the groove width gradually narrow and become shallow from bottom to top, and smoothly transition with the thread groove on the threaded portion.

[0012] Preferably, the screw cap comprises a driving base and a driving head portion coaxially arranged on the top of the driving base, the outer sidewall of the driving head portion is spaced apart and provided with a plurality of driving tooth grooves along the circumference, forming a multi-tooth quincunx structure.

[0013] More preferably, the number of driving tooth grooves is 8 teeth, 10 teeth or 12 teeth structure, and the depth of the driving tooth groove is recessed around the center line in the tapping direction, so as to increase the contact area with the electric gun sleeve head.

[0014] More preferably, the end sidewall of the driving tooth groove away from the tapping direction is a straight surface perpendicular to the driving base, and the end close to the tapping direction is an inclined surface or a micro-arc surface approximately perpendicular to the driving base.

[0015] More preferably, the inclined surface or micro-arc surface has an inclination angle of 92-95° relative to the bottom surface of the driving base, and the vertical depth is 1.8-2.5mm.

[0016] Preferably, a recess cavity arranged in a ring is provided on the bottom of the driving base close to the position of the screw rod, and the recess cavity has an opening structure with a narrow top and a wide bottom.

[0017] More preferably, the central column surrounded by the inner periphery of the recess cavity is coaxial and equal-diameter connected with the top end of the threaded portion, forming a non-threaded optical axis portion.

[0018] Preferably, the self-chip removal groove has a straight angle triangle cross section, the groove bottom is a smooth arc, and the included angle between the upper and lower groove surfaces is 60-90°.

[0019] Preferably, the helix angle of the self-draining chip groove is 40-50°, the groove depth at the lower inlet is 0.5-1mm, and the groove width is 1.0-1.5mm.

[0020] Preferably, the screw cap and screw shank are integrally formed, and are made of 10B33 alloy steel with a surface hardness of HRC45-50.

[0021] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0022] (1) Extremely high torsional strength and reliability: Through the synergistic design of deep meshing multi-tooth Phillips head and deep concave cavity, the effective contact area and torque arm of the sleeve and screw head are greatly increased, which can withstand extremely high tightening torque without slipping or biting, ensuring that each tightening action can be completed smoothly, significantly improving the reliability of the connection point and the production yield.

[0023] (2) Excellent active chip removal capability: It adopts a unique wedge-shaped spiral self-removing chip groove design, which acts like a built-in screw conveyor to actively collect, guide and remove chips. This effectively solves the chip clogging problem, reduces screwing resistance, makes screw feed smoother, protects the quality of the formed thread, and thus obtains higher and more consistent connection strength.

[0024] (3) Improved production efficiency and economic benefits: Reduced downtime, rework and scrap caused by screw slippage, head damage and poor chip removal, thus improving the operating efficiency and cycle time of the automated production line. At the same time, it reduced abnormal wear and tear on tools such as electric gun sleeves, thereby reducing overall production costs.

[0025] (4) Wide material adaptability: This self-tapping fuse screw is especially suitable for application scenarios where chip removal is difficult, such as multi-layer board stacking, boards with coatings or adhesive layers, and the connection of various composite materials, thus expanding the application scope of FDS technology. Attached Figure Description

[0026] Figure 1 This is a three-dimensional structural diagram of the self-tapping fuse screw of the present invention. Figure 1 ;

[0027] Figure 2 This is a three-dimensional structural diagram of the self-tapping fuse screw of the present invention. Figure 2 ;

[0028] Figure 3 This is a schematic diagram of the main structure of the self-tapping fuse screw of the present invention;

[0029] Figure 4 For the present invention Figure 3 The diagram shows the AA section structure of the self-tapping fuse screw.

[0030] Figure 5 For the invention Figure 4 A partial enlarged structural schematic view of part A in the self-tapping fusing screw shown in the invention;

[0031] Figure 6 A top view structural schematic view of the self-tapping fusing screw of the invention;

[0032] In the drawings, the reference signs are as follows:

[0033] 100 - screw cap, 110 - driving base, 111 - concave cavity, 120 - driving head, 121 - driving tooth groove, 122 - straight surface, 123 - inclined surface or micro-arc surface;

[0034] 200 - screw rod, 210 - threaded part, 211 - threaded groove, 220 - drill tail part, 230 - self-removing part, 231 - self-removing groove, 240 - optical axis part. DETAILED DESCRIPTION

[0035] The invention provides a self-tapping fusing screw with high torsional strength and high-efficiency chip removal capability, comprising a screw cap and a screw rod arranged coaxially. The screw rod comprises a threaded part at the upper end, a drill tail part at the lower end, and a self-removing part coaxially arranged between the threaded part and the drill tail part. The key lies in that the screw cap is designed in combination of a deep-engagement multi-tooth torx head and a deep concave cavity; and the self-removing part is helically provided with a unique wedge-shaped self-removing groove on the peripheral body.

[0036] Specifically, the screw cap comprises a driving base and a driving head coaxially arranged at the top of the driving base. The outer lateral wall of the driving head is provided with a plurality of driving tooth grooves at intervals in the circumferential direction, forming a multi-tooth torx structure with 8 teeth, 10 teeth or 12 teeth, so as to increase the contact line with the sleeve. The side wall of the driving tooth groove is designed as a nearly vertical force transmission surface to optimize the stress angle. The inner recess depth of the driving tooth groove is much larger than that of the conventional design, so that the matching electric gun sleeve can be embedded deeper, forming strong torsional resistance and radial shear resistance.

[0037] The self-removing groove on the self-removing part is a wedge-shaped groove, the groove depth and groove width gradually narrow and become shallower from the lower end (close to the drill tail part) to the upper end (close to the threaded part), and the end of the self-removing groove smoothly transitions with the threaded groove on the threaded part. This structure makes the self-removing groove entrance volume maximum, facilitating the collection of chips generated from the drill tail; as the screw is screwed in, the chips are guided and compressed in the groove, and with the help of centrifugal force and interaction with the hole wall, they are efficiently and continuously discharged along the open side of the groove to the rear and outside of the screw, avoiding accumulation in the threaded area.

[0038] Preferably, the screw cap and the screw rod are integrally formed, made of materials such as 10B33 alloy steel, and the surface hardness is treated to reach HRC45-50 to ensure its wear resistance and strength.

[0039] The working principle of this invention is as follows: When the electric gun is driven, its specially designed sleeve is deeply embedded in the deep cavity and multi-tooth drive groove of the screw head, achieving a large-area, deep rigid engagement, thereby transmitting high torque to the screw without loss. Under high-speed rotation and axial pressure, the screw's tail end softens the base material through friction and begins to penetrate. The generated metal chips are pushed backward by the rotating thread and enter the wide wedge-shaped groove entrance of the chip removal section. As the screw continues to penetrate deeper, the chips are squeezed and guided in the gradually narrowing and shallowing groove. Under the action of the axial thrust and centrifugal force generated by the helix angle, they are forced to be discharged from the side of the groove (i.e., the gap between the screw and the hole wall) to the outside of the connection area without blocking the thread path. The entire process results in smooth torque transmission and smooth chip removal, ultimately forming a clean, high-strength threaded connection.

[0040] The present invention will now be described in detail and specifically through specific embodiments to enable a better understanding of the invention. However, the following embodiments do not limit the scope of the invention.

[0041] Example 1

[0042] like Figures 1 to 4 As shown, this embodiment provides a basic structure for a self-tapping fusing screw with high torsional strength and efficient chip removal capability. The screw is a one-piece molded structure, comprising a screw head 100 and a screw shank 200 from top to bottom along the axis.

[0043] The screw shank 200 is further divided into three functional sections: the uppermost section is a threaded portion 210 with continuous threads, used to form a final mechanical locking connection in the base material; the lowermost section is a drill tail 220 with a sharp tip, used for initial positioning, frictional heat generation and guiding screw insertion; and a key self-chip removal section 230 is coaxially arranged between the threaded portion 210 and the drill tail 220.

[0044] One of the core features of this invention is the self-dumping chip removal section 230. For example... Figure 4 and Figure 5 As shown, one or more self-removing chip grooves 231 are spirally formed on the cylindrical periphery of the self-removing chip section 230. Typically, there are 2-4 self-removing chip grooves 231, preferably 3. These self-removing chip grooves 231 are not uniform cross-section grooves, but rather wedge-shaped grooves. Specifically, the self-removing chip groove 231 has the maximum groove depth H1 and groove width W1 at its lower end (near the entrance of the drill tail section 220); along the spiral upwards (towards the threaded section 210), its groove depth and width gradually and continuously narrow and become shallower; finally, at the upper end of the self-removing chip groove 231, its groove depth and width decrease to zero or a minimum value, and smoothly transition to the first threaded groove 211 at the lowermost end of the threaded section 210, forming a streamlined channel without steps or abrupt changes.

[0045] This wedge design allows the self-draining groove 231 to have the largest volume at the entrance, facilitating efficient capture and containment of the initial swarf generated from the shank 220. As the screw is screwed in, the swarf is pushed back into the groove by the thread and moves along the groove, being moderately compressed and guided under the constraint of the gradually narrowing channel, making it easier to be flung out of the connection area along the open side of the groove (i.e. the annular gap between the screw and the hole wall) by the axial component of the helical motion and the centrifugal force, achieving the function of active and continuous swarf removal.

[0046] Embodiment 2

[0047] As shown in Figure 1 , Figure 3 and Figure 6 , this embodiment is based on Embodiment 1 and elaborates on the screw cap 100, focusing on the design of its high torsional strength. The screw cap 100 includes a driving base 110 and a driving head 120 coaxially and integrally formed on the top of the driving base 110. The driving head 120 is used to cooperate with the sleeve head of the electric gun to transmit torque.

[0048] The outer side wall of the driving head 120 is uniformly and spacedly provided with a plurality of driving tooth grooves 121 along its circumference. These driving tooth grooves 121 collectively form a multi-tooth quincunx structure. Compared with the standard 6-tooth quincunx head (such as Torx®), the present application preferably adopts an 8-tooth, 10-tooth or 12-tooth structure. Increasing the number of teeth means that the contact line length (i.e. the meshing line) between the sleeve and the screw head is significantly increased under the same head diameter, thereby increasing the contact area for torque transmission and dispersing the contact stress.

[0049] The tooth shape of each driving tooth groove 121 is specially designed. In combination with Figure 1 and Figure 6 , from the tapping direction (i.e. the direction of the screw being screwed into the workpiece), the end side wall of the driving tooth groove 121 away from the tapping direction is a straight face 122 perpendicular to the bottom surface of the driving base 110, which serves as a limiting face for positioning and installing the sleeve. The end side wall close to the tapping direction is a slope or a micro-curved surface 123 approximately perpendicular to the driving base 110, which serves as the main bearing surface and can withstand the large reverse torque exerted by the sleeve (such as the torque during final tightening or subsequent disassembly).

[0050] The near vertical here means that the angle between the inclined plane or micro-arc surface 123 and the normal of the bottom surface of the driving base 110 is very small. Preferably, the angle a of the inclined plane or micro-arc surface 123 relative to the bottom surface of the driving base 110 is 92° to 95° (i.e. slightly greater than 90 degrees). This design of near vertical but slightly guiding angle not only ensures efficient transmission of positive tapping torque, but also facilitates the embedding and extraction of the sleeve. At the same time, the depth D of the driving tooth groove 121 in the vertical direction is designed to be larger, preferably 1.8mm to 2.5mm, which is much deeper than the depth of 1.2-1.6mm of the conventional FDS screw, allowing the corresponding protruding part of the electric gun sleeve to be embedded deeper inside the screw head.

[0051] In cooperation with the driving head 120, a coaxial recess cavity 111 is arranged on the bottom of the driving base 110 and adjacent to the upper end of the screw shaft 200. See Figure 2 The longitudinal section of the recess cavity 111 is in the shape of an open structure with a narrow top and a wide bottom, similar to an inverted truncated cone or a bowl. The central area surrounded by the inner periphery of the recess cavity 111 extends downward to form an optical axis 240 coaxial and equal-diameter connected with the top end of the threaded part 210. The design of this deep recess cavity 111 allows the threaded groove 121 at the top end of the threaded part 120 to extend into the recess cavity 111 or to be flush with the mouth surface of the recess cavity 111 during processing, so that the screw is not easy to rotate.

[0052] When the electric sleeve is used with the self-tapping fuse screw, the teeth on the inner wall of the sleeve can be deeply engaged into the driving tooth groove 121 (with a depth of 1.8-2.5mm), which makes the sleeve and the screw head form a three-dimensional deep engagement: both the circumferential contact area is increased by the multiple tooth grooves, and the axial support depth and the ability to resist radial shear are increased by the cooperation of the straight surface 122 and the inclined plane or micro-arc surface 123 of each driving tooth groove 121. This design fundamentally avoids radial slipping or axial biting between the sleeve and the screw head under high torque, ensuring smooth and reliable transmission of high torque.

[0053] Embodiment 3

[0054] As shown in Figure 4 and Figure 5 , this embodiment further optimizes the chip removal performance by specifying the geometric parameters of the self-chip removal groove 231 of the self-chip removal part 230 based on embodiment 1.

[0055] The cross section of the self-chip removal groove 231 is preferably a right triangle or a shape close to a triangle. The bottom of the groove (i.e. the hypotenuse of the triangle) is processed as a smooth arc to reduce stress concentration and facilitate chip flow. The included angle β between the two groove surfaces (i.e. the upper and lower groove surfaces) of the right triangle is preferably between 60° and 90°. A larger included angle makes the groove relatively open, facilitating the entry of chips.

[0056] The helix angle γ of the self-draining flute 231 (i.e. the included angle between the center line of the flute and the vertical plane of the screw axis) is a key parameter. The present application is designed in a relatively large angle range of 40° to 50°. The larger helix angle means that the helix of the self-draining flute 231 is steeper, which endows it with strong axial chip-removing thrust. When the screw rotates, the force acting on the chip inside the flute can be decomposed into a larger axial component, thus more actively pushing the chip to the rear of the screw (i.e. the reverse direction of the tapping direction).

[0057] Regarding the dimensions, the flute depth H1 of the self-draining flute 231 at its lower end entrance is preferably 0.5mm to 1.0mm, and the flute width W1 is preferably 1.0mm to 1.5mm. This initial size provides sufficient chip space. As mentioned before, the size gradually decreases along the helix until it smoothly connects with the thread groove 121 at the lower end of the threaded portion 120.

[0058] In the initial stage of tapping, the large pieces or long strips of chips generated are captured by the thread and sent into the wide entrance of the self-draining flute 231. Due to the large helix angle of 40-50° of the flute, the chip obtains a large amount of axial displacement in the flute per revolution of the screw. At the same time, the wedge-shaped flute channel produces a certain extrusion and guiding effect on the chip, making it move tightly against the outer side wall of the flute. Under the combined action of centrifugal force and flute wall guidance, the chip is effectively thrown out of the screw-hole gap and continuously drained to the external surface of the workpiece, ensuring the cleanliness of the tapping channel.

[0059] Example 4

[0060] This embodiment integrates the features of the above-mentioned embodiments, providing a specific implementation of a preferred FDS screw for connecting a 1.2mm thick 6016 aluminum alloy plate and a 2.0mm thick galvanized steel plate in an automobile body.

[0061] The overall structure of the self-tapping fuse screw is as follows: the total length of the screw is 40mm, the nominal diameter of the threaded portion 210 is 5.5mm, and the head diameter of the screw cap 100 is 10mm. The screw is made of 10B33 alloy steel and is integrally cold upset formed, and is heat treated to make the surface hardness reach HRC 48, and the core remains good toughness.

[0062] The driving head 120 adopts a special 10-tooth quill design. The side wall of the driving tooth groove 121 near the tapping direction side is a micro-arc surface 123 with an angle of 93°, and the vertical depth is 2.0mm. The concave cavity 111 at the bottom of the driving base 110 is a tapered cone with a narrow top and a wide bottom, with a depth sufficient to accommodate the boss of the matching sleeve.

[0063] Three self-draining grooves 231 are arranged on the self-draining part 230 and evenly distributed along the circumference. The starting end (lower end) of the groove has a depth of 0.8 mm and a width of 1.2 mm. The cross section of the groove is an approximate triangle with an included angle of 75°, and the bottom of the groove is a circular arc with a radius of 0.2 mm. The helix angle of the self-draining groove 231 is 45°. The size of the groove gradually and uniformly decreases upwards, and after about 1.5 turns of the helix, it smoothly transitions to the first turn of the thread groove 211 of the threaded part 210.

[0064] The working process of the self-tapping fuse screw of the embodiment is as follows:

[0065] (1) The electric gun sleeve (with a matching FDS-10 inner tooth shape) is axially sleeved into the screw head and deeply embedded into the driving tooth groove 121 and the recess 111, achieving rigid locking.

[0066] (2) Start the electric gun and control the electric gun to press the screw against the workpiece with high pressure (such as 2-3 kN) and start high-speed (such as 8000 rpm) rotation.

[0067] (3) The drill tail part 220 at the lower end of the screw rubs against the upper aluminum alloy plate, instantly generating high temperature to soften and melt it, and the lower end of the drill tail part 220 starts to tap in.

[0068] (4) The aluminum chips and a small amount of galvanized steel chips generated during the tapping process are scraped backward by the threads of the threaded part 210 and introduced into the wide wedge-shaped self-draining groove 231 entrance of the self-draining part 230.

[0069] (5) Under the guidance of the strong axial thrust generated by the 45° helix angle and the wedge-shaped groove, the chips are continuously discharged along the path of the self-draining groove 231 and accumulated on the surface of the steel plate outside the connection point.

[0070] By using the self-tapping fuse screw, during the entire tapping and final tightening stages, the large torque is smoothly and non-slip transferred to the screw rod through the deeply engaged screw cap, until the preset torque or angle value is reached, the electric gun stops and reverses, and the connection is completed. The entire process has a smooth torque curve, smooth chip removal, and no jamming or slipping phenomenon, thereby ensuring the stable and reliable connection quality of the aluminum alloy plate and the galvanized steel plate.

[0071] The specific embodiments of the present application are described in detail above, but they are only examples, and the present application is not limited to the specific embodiments described above. Any equivalent modifications and alternatives to the present application made by those skilled in the art are also within the scope of the present application. Therefore, any equivalent transformation and modification made without departing from the spirit and scope of the present application should be covered within the scope of the present application.

Claims

1. A self-tapping fusing screw with high torsional strength and efficient chip removal capability, comprising a screw cap (100) and a screw shank (200) arranged coaxially, characterized in that, The screw shank (200) includes a threaded portion (210) at the upper end, a drill tail portion (220) at the lower end, and a self-drilling chip removal portion (230) coaxially disposed between the threaded portion (210) and the drill tail portion (220), wherein: The self-chip removal part (230) has a self-chip removal groove (231) spirally opened on its periphery. The self-chip removal groove (231) is a wedge-shaped groove. Its groove depth and groove width gradually narrow and become shallower from bottom to top, and it smoothly transitions with the thread groove (211) on the threaded part (210).

2. The self-tapping fuse screw according to claim 1, characterized in that, The screw cap (100) includes a drive base (110) and a drive head (120) coaxially disposed on the top of the drive base (110). The outer side wall of the drive head (120) is provided with a plurality of drive tooth grooves (121) spaced apart along its circumference to form a multi-tooth plum blossom structure.

3. The self-tapping fuse screw according to claim 2, characterized in that, The number of drive tooth grooves (121) is 8, 10 or 12 teeth, and they are recessed inward along the tapping direction with the center line as the center to increase the contact area with the electric gun sleeve head.

4. The self-tapping fuse screw according to claim 2, characterized in that, The sidewall of the drive tooth groove (121) away from the tapping direction is a straight surface (122) perpendicular to the drive base (110), while the sidewall closer to the tapping direction is an inclined surface or a micro-arc surface (123) approximately perpendicular to the drive base (110).

5. The self-tapping fuse screw according to claim 4, characterized in that, The inclined angle of the inclined surface or micro-arc surface (123) relative to the bottom surface of the drive base (110) is 92-95°, and its vertical depth is 1.8-2.5mm.

6. The self-tapping fuse screw according to claim 1, characterized in that, The bottom of the drive base (110) near the screw rod (200) has an annular cavity (111), which is an open structure that is narrow at the top and wide at the bottom.

7. The self-tapping fuse screw according to claim 6, characterized in that, The central column formed by the periphery of the cavity (111) is coaxial with the top end of the threaded part (210) and connected with the same diameter to form an unthreaded optical shaft part (240).

8. The self-tapping fuse screw according to claim 1, characterized in that, The self-removing chip groove (231) has a right-angled triangle cross section, a smooth arc bottom, and an included angle of 60-90° between its upper and lower groove surfaces.

9. The self-tapping fuse screw according to claim 1, characterized in that, The self-draining chip groove (231) has a helix angle of 40-50°, a groove depth of 0.5-1mm at the lower inlet, and a groove width of 1.0-1.5mm.

10. The self-tapping fuse screw according to claim 1, characterized in that, The screw cap (100) and screw rod (200) are integrally formed structures, made of 10B33 alloy steel with a surface hardness of HRC45-50.

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