Hot-melting self-tapping screw with stable connecting threads and hot twisting process of hot-melting self-tapping screw

Abstract

The invention discloses a hot melting self-tapping screw with stable connection threads and a hot twisting technology of the hot melting self-tapping screw, and belongs to the field of thread product machining. The self-tapping screw comprises a tightening part, a thread part and a tip part which are sequentially arranged from left to right; wherein the tightening part is matched with a tightening tool; the threaded part comprises three threaded sections which are arranged in sequence, the thread size of the first threaded section is larger than that of the second threaded section, threads of the first threaded section are matched with the threaded hole, and the third threaded section is close to the sharp head part, is arranged in a gradual transition mode and transits from the connection section of the sharp head part to the second threaded section; the tip part comprises a connecting section, an arc section and a tip section, the connecting section is cylindrical, the arc section is an arc with constant curvature, and the tip section is conical. The special thread design realizes the single-sided connection effects of drilling, tapping and tightening on the metal plate by heat generated by high-speed rotation of the product. Therefore, stable connection of the screw in subsequent use is ensured, and the service life is ensured.

Description

Technical Field

[0001] The present invention relates to the field of processing equipment for threaded products, and particularly to a hot-melt self-tapping screw with a stable connecting thread and its hot rolling process. Background Art

[0002] Threaded products are common products, such as bolts or studs or screws, which can achieve the combination of different components.

[0003] The threaded area of a hot-melt self-tapping screw is divided into three parts: the tail arc and tip area, the self-tapping thread area, and the tightening area. The main function of the tail arc and tip area is to drill and ream holes. Improper design of the arc shape and tip size and length has a great impact on the drilling effect and rework. The function of the self-tapping thread area is to form threads after the product is reamed. The design of the thread size plays a key role in the tapping effect. The function of the tightening area is to generate a clamping force between the product and the connected plate to ensure the connection strength and tighten the threaded area. However, the existing hot-melt self-tapping screws have structural problems, resulting in unstable subsequent connections. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a hot-melt self-tapping screw with a stable connecting thread and its hot rolling process.

[0005] The technical solution of the present invention is: A hot-melt self-tapping screw with a stable connecting thread, comprising:

[0006] A tightening part, a threaded part, and a tip part arranged in sequence from left to right; wherein:

[0007] The tightening part is arranged in cooperation with a tightening tool;

[0008] The threaded part includes a first thread segment, a second thread segment, and a third thread segment arranged in sequence. The first thread segment is close to the tightening part. The thread pitch size of the first thread segment is larger than that of the second thread segment, and the thread teeth of the first thread segment are arranged in cooperation with the threaded hole. The third thread segment is close to the tip part. The third thread segment is arranged in a progressive transition manner and transitions from the connection segment of the tip part to the second thread segment; and

[0009] The tip part includes a connection segment, an arc segment, and a tip segment. The connection segment is arranged in a cylindrical shape. The arc segment is an arc with a constant curvature. The tip segment is arranged in a conical shape.

[0010] Further, the second thread segment is a standard metric thread.

[0011] Further, the length of the second threaded section is greater than that of the third threaded section. Generally, about 5 threads are provided for the second threaded section, and about 3 threads are provided for the third threaded section. 3-5 threads are also provided for the first threaded section. It can achieve a progressive transition dimension to a fully threaded self-tapping tooth. Compared with the non-progressive fixed threaded outer diameter dimension, the advantage of the progressive transition thread is that there is a progressive process from the reaming size to the thread forming, and it is not easy to cause cutting of the connecting plate during the tapping process. The entire self-tapping thread area has a triangular cross-section to facilitate reducing the self-tapping thread resistance. The thread size of the first threaded section is slightly larger than the standard metric thread outer diameter size, so as to ensure better connection tightening strength.

[0012] Further, the tightening tool that mates with the tightening portion is any one of a screwdriver and a wrench. Generally, it is a cross screwdriver or a hexagon wrench.

[0013] Further, the R angle of the arc is 14 ± 1.5 mm. The R angle size of the arc has studied and compared the influence of the design of different-shaped R angles and taper angles on the drilling effect of the product, and found that the smooth arc design with a constant curvature (R14 ± 1.5 mm) has the best drilling effect on the product. This arc design size balances the advantages and disadvantages brought by too small taper angles or R angles of the arc. During the drilling process of too large, too sharp taper angles, arc angles and triangular cross-section arcs, the resistance is small and the drilling time can be saved, but it has disadvantages for the cast aluminum connection with slightly poor ductility. Too fast drilling is easy to cause the cast aluminum to crack. At the same time, a small arc of the arc R angle is obviously easy to cause too large drilling resistance, affecting the drilling efficiency and even unable to penetrate.

[0014] Further, the diameter of the connecting portion is smaller than the bottom diameter size of the threaded portion. It is convenient to form a fixed cylindrical diameter after drilling, making full preparations for tapping. This ensures that if the installation is improper during the installation process, it is easy to be unscrewed backwards, which is beneficial for repair.

[0015] Further, the difference between the diameter of the connecting portion and the bottom diameter inside the thread does not exceed 0.3 mm. If the diameter size is too small, the drilling and reaming hole diameters will be small, which will affect the tapping effect.

[0016] The hot rolling process of a hot-melt self-tapping screw with a stable connecting thread includes:

[0017] Phosphorus removal treatment of the raw material;

[0018] Heating treatment of the raw material, and the heating temperature is 300 - 800 degrees;

[0019] Thread rolling treatment, and the heated raw material is treated at a thread rolling device;

[0020] Finished product cooling and inspection. After the finished product is cooled to room temperature, the finished product is inspected and divided into qualified products and defective products.

[0021] Furthermore, the raw material is a cold-heading formed screw blank.

[0022] Furthermore, the heating treatment equipment is a high-frequency induction heating device. Of course, other heating equipment can also be used, but the high-frequency induction heating has higher efficiency.

[0023] Furthermore, after the dephosphorization treatment of the raw material, a phosphorus content test is carried out, and the value per liter does not exceed 0.1 mg.

[0024] Furthermore, the heating temperature of the raw material is 350 - 450 degrees. Temperature range setting for the hot-melt self-tapping screw: 400℃ ± 50℃. During the research process, the appearance and cross-section of products at different temperatures were compared. At low temperatures, defects such as hollow, insufficient surface finish with peeling, incomplete tip forming, and material breakage occurred in the products. If the temperature is too high, the metallographic structure of the products will change, affecting the performance of the products.

[0025] Furthermore, the threading die plate of the threading equipment includes a blanking area, an arc forming area, and a thread forming area. The thread forming area is arranged horizontally; the blanking area is located below the thread forming area and at the front side in the moving direction, and the arc forming area is located at the rear side of the blanking area. The screw moves horizontally, for example, from left to right. The left side is the front side, and the right side is the rear side, that is, the front side and the rear side in the moving direction of the screw.

[0026] Furthermore, the lubricant used during the threading process is a mixture of TM-9605 semi-synthetic cutting fluid and 80% water.

[0027] Furthermore, a temperature sensor is also set on the threading equipment. Heating-related operation processes during heated thread rolling: Before heating, check whether the connection control line between the main heater and the auxiliary heater is normal, and whether the installation position of the heating induction coil and the equipment is reasonable. Adjust the infrared laser temperature probe to align with the position of the screw on the track that needs to be heated, and observe whether the laser red dot correctly irradiates the position point where the temperature needs to be sampled. After adjustment, fix the laser temperature probe. The parameters of the heater are input on the screen interface, including operations such as the output power of the heater, displaying the real-time temperature curve, setting the upper and lower temperature limits, and controlling the switch of the heater. Heating output adjustment: Click the +1.5% button to increase the heater power by 1.5%. The functions of other buttons are the same. Curve display window: Displays the real-time value of the temperature detected by the infrared probe, visually shown in a curve manner. Temperature range setting: Set the minimum and maximum temperatures. In the automatic mode and with the heater turned on, when the temperature is lower than the minimum value, the blanking device does not feed material until the temperature exceeds the minimum value and then the feeding is opened. When the temperature exceeds the maximum value, the reject device is opened, and after all the screws that are over-temperature in the heating coil are removed, the reject device automatically closes. When producing screws that do not require heating, the heater can be removed. In the manual state of the heater, click the heating equipment on button and the heater works, release the button and the heater stops.

[0028] Based on the functional change of the heater host, the output function of the matching circulating chiller is excessive, resulting in the heating equipment having to bear a high water pressure, causing the circulating water pipeline to burst. To avoid such a failure, the outlet pipeline is modified to add a bypass pressure-regulating valve. Remember: This valve must not be closed. In the future, when the water output function of the chiller decreases, this valve can be appropriately closed to increase the circulating water volume and pressure required by the heating equipment. For the water outlet connection interface of the chiller, when disassembling the pipeline and moving the equipment, it must not be connected wrongly with other return water pipelines. When replacing the pipeline, pay attention to protecting the interface so that no external garbage enters, otherwise it will cause the heating equipment to be blocked and the service life to decrease.

[0029] This machine adopts external signal linkage control, so the start and stop operations on the machine panel are invalid operations, and the power adjustment button on this panel must be set to the minimum position.

[0030] The beneficial technical effects of the present invention are:

[0031] Through the special thread design of the hot melt self-tapping screw, the present invention realizes the single-sided connection function of drilling, tapping, and tightening on the metal plate by generating heat during the high-speed rotation of the product. It ensures the stable connection of the screw during subsequent use and guarantees the service life.

[0032] By means of the hot rubbing process, the present invention increases the fluidity of the material, reduces the deformation resistance of the material, thereby realizing the formation of the threads of the hot melt self-tapping screw and achieving the mass production of special screws. Description of the Drawings

[0033] Figure 1 It is a schematic diagram of a hot melt self-tapping screw with stable connecting threads.

[0034] Figure 2 It is a schematic diagram of a thread rolling die.

[0035] Wherein:

[0036] 1. Tightening part, 2. Thread part, 21. First thread section, 22. Second thread section, 23. Third thread section, 3. Tip part, 31. Connecting section, 32. Arc section, 33. Tip section,

[0037] 4. Cutting area, 5. Thread forming area, 6. Arc forming area. Detailed Embodiments

[0038] In order to be able to more clearly understand the technical means of the present invention and implement it in accordance with the content of the specification, the following combines the drawings and embodiments to further describe in detail the specific embodiments of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0039] The particularity of the threaded part of the hot-melt self-tapping screw determines that the conventional thread rolling process cannot achieve the processing of the product. Due to the relatively long arc at the tail, there is a relatively large amount of material to be removed, and the force during the thread rolling process is large. In addition, the surface fluidity of the material is inconsistent with the internal fluidity. The normal-temperature thread rolling process will cause the product to be hollow, and the size and shape of the tip are unstable, so the product cannot meet the performance and installation requirements.

[0040] See the appendix Figure 1-2 The hot-melt self-tapping screw with a stable connecting thread shown in the appendix includes:

[0041] Set in sequence from left to right: a tightening part 1, a threaded part 2, and a tip part 3; where:

[0042] The tightening part 1 is arranged in cooperation with a tightening tool;

[0043] The threaded part 2 includes, arranged in sequence: a first threaded section 21, a second threaded section 22, and a third threaded section 23. The first threaded section 21 is close to the tightening part 1. The thread size of the first threaded section 21 is larger than that of the second threaded section 22, and the thread of the first threaded section 21 is arranged in cooperation with the threaded hole. The third threaded section 23 is close to the tip part 3, and the third threaded section 23 is arranged in a progressive transition, and transitions from the connection section 31 of the tip part 3 to the second threaded section 22; and

[0044] The tip part 3 includes a connection section 31, an arc section 32, and a tip section 33. The connection section 31 is arranged in a cylindrical shape, the arc section 32 is an arc with a constant curvature, and the tip section 33 is arranged in a conical shape. The tip section can be set to a rounded corner or a sharp corner.

[0045] Furthermore, the second threaded section 22 is a standard metric thread.

[0046] Furthermore, the length of the second threaded section 22 is greater than that of the third threaded section 23. Generally, about 5 threads are arranged in the second threaded section 22, and about 3 threads are arranged in the third threaded section 23. 3 - 5 threads are also arranged in the first threaded section 21. It can achieve a progressive transition in size to a fully tapped full tooth. Compared with the non-progressive fixed thread outer diameter size, the advantage of the progressive transition thread is that there is a progressive process from the reaming size to the thread formation, and it is not easy to cause cutting of the connecting plate during the tapping process. The entire self-tapping thread area has a triangular cross-section, which is convenient for reducing the self-tapping thread resistance. The thread size of the first threaded section 21 is slightly larger than the standard metric thread outer diameter size, so as to ensure better connection and tightening strength.

[0047] Furthermore, the tightening tool cooperating with the tightening part 1 is any one of a screwdriver and a wrench. Generally, it is a cross screwdriver or a hex wrench.

[0048] Furthermore, the R angle of the arc is 14 ± 1.5 mm. The study of the R angle size of the arc compared the influence of the design of different-shaped R angles and taper angles on the drilling effect of the product, and found that the smooth arc design with a constant curvature (R14 ± 1.5 mm) has the best drilling effect on the product. This arc design size balances the advantages and disadvantages brought by too small taper angles or R angles of the arc. During the drilling process of too large and too sharp taper angles, arc angles, and triangular cross-section arcs, the resistance is small, and the drilling time can be saved, but it is disadvantageous for the cast aluminum connection with slightly poor ductility. Drilling too fast easily causes the cast aluminum to crack. At the same time, a small arc of the arc R angle obviously easily leads to too large drilling resistance, affecting the drilling efficiency and even unable to penetrate.

[0049] Furthermore, the diameter of the connecting part is smaller than the bottom diameter size of the thread part 2. It is convenient to form a fixed cylindrical diameter after drilling, making full preparations for tapping. This ensures that if the installation is improper during the installation process, it is easy to be unscrewed backwards, which is conducive to repair.

[0050] Furthermore, the difference between the diameter of the connecting part and the bottom diameter inside the thread does not exceed 0.3 mm. If the diameter size is too small, the small hole diameter of drilling and reaming will affect the tapping effect.

[0051] The hot rolling process of a hot-melt self-tapping screw with a stable connecting thread includes:

[0052] The dephosphorization treatment of the raw material;

[0053] The heat treatment of the raw material, and the heating temperature is between 300 - 800 degrees;

[0054] The thread rolling treatment, and the heated raw material is processed at the thread rolling equipment;

[0055] The finished product cooling and inspection. After the finished product is cooled to room temperature, the finished product is inspected and divided into qualified products and defective products.

[0056] Furthermore, the raw material is a cold-heading formed screw blank.

[0057] Furthermore, the equipment for heat treatment is a high-frequency induction heating device. Of course, other heating equipment can also be used, but the efficiency of high-frequency induction heating is higher.

[0058] Furthermore, after the dephosphorization treatment of the raw material, the phosphorus content test is carried out, and the value per liter does not exceed 0.1 mg.

[0059] Furthermore, the heating temperature of the raw material is 350 - 450 degrees. The temperature range setting of the hot-melt self-tapping screw: 400℃ ± 50℃. During the research process, the appearance and cross-section of products at different temperatures were compared. At low temperatures, defects such as hollow, insufficient surface finish, peeling, incomplete tip forming, and material breaking occurred in the products. Too high a temperature will cause changes in the metallographic structure of the products, affecting the performance of the products.

[0060] Furthermore, the threading die plate of the threading device includes a blanking area 4, an arc forming area 6, and a thread forming area 5. The thread forming area 5 is arranged horizontally. The blanking area 4 is located below the thread forming area 5 and at the front side in the moving direction, and the arc forming area 6 is located at the rear side of the blanking area 4. The screw moves horizontally, for example, from left to right. The left side is the front side, and the right side is the rear side, that is, the front side and the rear side in the moving direction of the screw.

[0061] Furthermore, the lubricant used in the threading process is a mixture of TM-9605 semi-synthetic cutting fluid and 80% water.

[0062] Furthermore, a temperature sensor is also provided on the threading device. Heating-related operation procedures during hot threading: Before heating, check whether the connection control line between the main heater and the auxiliary heater is normal, and whether the installation position of the heating induction coil and the equipment is reasonable. Adjust the infrared laser temperature probe to align with the position of the screw on the track that needs to be heated, and observe whether the laser red dot correctly irradiates the position point where the temperature needs to be sampled. After adjustment, fix the laser temperature probe. The parameters of the heater are input on the screen interface, including the output power of the heater, display the real-time temperature curve, set the upper and lower temperature limits, control the switch of the heater, and other operations. Heating output adjustment: Click the +1.5% button to increase the heater power by 1.5%. The functions of other buttons are the same. Curve display window: Display the real-time value of the temperature detected by the infrared probe and visually display it in a curve manner. Temperature range setting: Set the minimum and maximum temperatures. In the automatic mode and when the heater is turned on, when the temperature is lower than the minimum value, the blanking device does not discharge materials until the temperature exceeds the minimum value and then the blanking is turned on. When the temperature exceeds the maximum value, the reject device is turned on. After all the screws that are over-temperature in the heating coil are removed, the reject device is automatically turned off. When producing screws that do not require heating, the heater can be removed. In the manual state of the heater, click the heating device on button and the heater works, and release the button to stop the heater.

[0063] Due to the change in the function of the heater main unit, the output function of the matching circulating chiller is excessive, resulting in the heating equipment needing to bear a high water pressure, causing the circulating water pipeline to burst. To avoid this kind of failure, modify the outlet pipeline to add a bypass pressure regulating valve. Note: This valve is strictly prohibited from being closed. In the future, when the water output function of the chiller decreases, this valve can be appropriately closed to increase the circulating water volume and pressure required by the heating equipment. The water outlet connection interface of the chiller. When disassembling the pipeline and moving the equipment, it cannot be connected wrongly with other return water pipelines. When replacing the pipeline, pay attention to protecting the interface so that no external garbage enters, otherwise it will cause the heating equipment to be blocked and the service life to decrease.

[0064] This machine adopts external signal linkage control, so the start and stop operations on the machine panel are invalid. The power adjustment button on this panel must be set to the minimum position.

[0065] The present invention realizes the single-sided connection function of drilling, tapping, and tightening on a metal plate by generating heat through the high-speed rotation of the product with a special thread design of the hot-melt self-tapping screw. This ensures the stable connection of the screw during subsequent use and guarantees its service life.

[0066] The present invention increases the fluidity of the material through the hot rolling process, reduces the deformation resistance of the material, and thus realizes the formation of the threads of the hot-melt self-tapping screw, achieving the production of a large number of special screws.

[0067] An embodiment:

[0068] Taking the M5 hot-melt self-tapping screw as an example,

[0069] It is more reasonable to design the diameter to be 4.0 ± 0.1 mm. The tip is designed as a smooth arc and the diameter is ensured to be reasonable. If the diameter is too large, the drilling resistance will be large, affecting the installation pressure and efficiency. If the diameter is too small, it will affect the life of the tooth plate. The tip diameter size is preferably 0.3 - 1.0 mm. The designed size of the arc length should consider the application effect of the thickness of the connected plates. Currently, the total thickness of the connected plates generally does not exceed 6 mm. The arc section length is preferably designed to be 4 - 6 mm. The total length of the arc section plus the length at the connection between the arc and the self-tapping thread area and the tip area should exceed 6 mm.

[0070] The designed size of the outer diameter of the thread of the first thread section is 5.0 - 5.1 mm. The bottom diameter of the thread is also larger than the standard metric thread bottom diameter size of the second thread section. This is to make the formed hole as large as possible while not affecting rework in consideration of the previous drilling and forming process.

[0071] For high-strength products with a heat treatment hardness exceeding HRC32, a dephosphorization treatment is required before heat treatment. Since the hot-melt self-tapping screw needs to be heated during the thread rolling process, a pretreatment of the dephosphorization process needs to be done in advance before the thread rolling process. After the dephosphorization treatment, the residual phosphorus content is detected by a bluing test and does not exceed 0.1 mg. The content of phosphorus residues on the surface is detected by cleaning the phosphorus on the surface of the parts into a certain liquid chemical substance.

[0072] The temperature range and equipment accuracy of the hot rolling equipment have a decisive impact on the processing of the product. A high-frequency induction heating device is used, and the temperature range is 300 - 800 degrees. The temperature range must ensure that it covers the reasonable processing temperature range of the product.

[0073] The size and design of the tooth plate are also very important in the process of realizing the product threads. The processing specifications of the product are M5 - M8, and the length dimension is within 100 mm; the size specification of the tooth plate seat is 130 * 150 * 35. The tooth plate needs to realize the functions of forming an arc, cutting the material, and forming the threads during the thread rolling process. At the same time, the tooth plate supplier needs to cooperate with the design requirements of the product to trial-produce the product, and adjust the design of the tooth plate according to the trial-production results of the sample parts.

[0074] For threaded nails of other sizes, just set the die plate according to the actual length.

[0075] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A hot melt self-tapping screw with a stable connection thread, characterized in that: include: Arranged from left to right are: a tightening portion (1), a threaded portion (2) and a pointed portion (3); wherein: The tightening part (1) is arranged in cooperation with a tightening tool; The threaded portion (2) comprises: a first thread segment (21), a second thread segment (22) and a third thread segment (23) which are arranged in sequence, the first thread segment (21) being close to the tightening portion (1), the thread size of the first thread segment (21) being larger than the size of the second thread segment (22), and the thread of the first thread segment (21) being arranged in cooperation with the threaded hole, the third thread segment (23) being close to the pointed portion (3), the third thread segment (23) being arranged in a progressive transition manner, and transitioning from the connecting segment (31) of the pointed portion (3) to the second thread segment (22); and The pointed portion (3) comprises a connecting section (31), an arc section (32) and a pointed section (33); the connecting section (31) is arranged in a cylindrical shape, the arc section (32) is an arc with a constant curvature, and the pointed section (33) is arranged in a conical shape.

2. The hot-melt self-tapping screw with stable connection thread according to claim 1, characterized in that: The second thread section (22) is a standard metric thread.

3. The hot-melt self-tapping screw with stable connection thread according to claim 1, characterized in that: The length of the second thread segment (22) is greater than the length of the third thread segment (23).

4. The hot-melt self-tapping screw with stable connection thread according to claim 1, characterized in that: The R angle of the arc is 14±1.5 mm.

5. The hot-melt self-tapping screw with stable connection thread according to claim 1, characterized in that: The diameter of the connecting portion is smaller than the bottom diameter of the threaded portion (2).

6. The hot-melt self-tapping screw with stable connection thread according to claim 5, characterized in that: The difference between the diameter of the connecting portion and the bottom diameter of the inner part of the thread does not exceed 0.3 mm.

7. A hot-rubbing process for hot-melt self-tapping screws with stable connection threads, characterized in that: include: Dephosphorization of raw materials; Heating treatment of raw materials, and the heating temperature is 300-800 degrees; Thread rolling treatment, the heated raw materials are processed in the thread rolling equipment; Finished product cooling and testing: After the finished product has cooled to room temperature, it is tested and divided into qualified products and defective products.

8. The hot-rubbing process of hot-melt self-tapping screws with stable connection threads according to claim 7, characterized in that: The raw materials are tested for phosphorus content after dephosphorization, and the value shall not exceed 0.1 mg per liter.

9. The hot-rubbing process of hot-melt self-tapping screws with stable connection threads according to claim 7, characterized in that: The heating temperature of the raw materials is 350-450 degrees.

10. The hot-rubbing process of hot-melt self-tapping screws with stable connection threads according to claim 1, characterized in that: The thread rolling plate of the thread rolling device comprises a cutting area (4), an arc forming area (6) and a thread forming area (5), wherein the thread forming area (5) is arranged in a horizontal direction; the cutting area (4) is located below the thread forming area (5) and at the front side in the moving direction, and the arc forming area (6) is located at the rear side of the cutting area (4).

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