Efficient bimetal self drilling screw high-strength welding production method

Abstract

The invention belongs to the field of composite screw manufacturing methods, and particularly relates to an efficient bimetal self-drilling screw high-strength welding production method, which comprises the following steps of: simultaneously heating two close ends of two base materials through an induction heating coil at a high-frequency electromagnetic frequency of 500kHz-2MkHz until hot areas on the end surfaces of the two base materials reach the temperature 10-50 DEG C of respective melting point temperature; the heating speed is high, the efficiency is high, it is guaranteed that the hot area of the base metal is located on the shallow layer of the end face by 1-2 mm, so that turnup deformation at the hot area during butt joint is reduced, the material utilization rate is increased, after heating is completed, ultrasonic pressure is applied to the two kinds of base metal, and the heated ends of the two kinds of base metal are in butt joint, spliced and welded into a whole to form a screw blank. Ultrasonic vibration with the oscillation frequency of 20 thousand times per second is applied to the two kinds of base metal, the welding firmness of the two kinds of base metal can be improved, and the residual internal stress in the base metal is eliminated.

Description

Technical Field

[0001] The invention belongs to the field of composite screw manufacturing methods, and in particular relates to an efficient high-strength welding production method for bimetallic self-drilling screws. Background Art

[0002] Screws are very common hardware products with a wide range of uses, low prices and many styles. Among them, self-drilling screws can be used to drill, tap and lock directly on materials or structures without pre-drilling, and are suitable for use in many scenarios. In some special scenarios, such as outdoor public places, corrosive scenes, solar bracket fixing scenes, coastal steel structure factories, etc., the exposed part of the screw is required to have good corrosion resistance. At the same time, it is necessary to ensure that the mechanical properties of the screw can meet high torsional strength and penetration, so as to ensure that the screw can be easy to use and can maintain its locking ability for a long time. Therefore, bimetallic self-drilling screws made of two different materials welded together have been born on the market.

[0003] Bimetallic self-drilling screws usually use corrosion-resistant stainless steel as the screw head and high-hardness alloy as the screw tail. The processing process is usually cutting, welding, turning, tail clamping and thread rolling, and heat treatment, and finally a bimetallic self-drilling screw with good corrosion resistance and mechanical properties is made.

[0004] The processing method commonly used in the industry at present is usually to weld two metal materials into one by friction welding or resistance butt welding. For example, Chinese patent No. CN101362277A discloses a manufacturing method of a composite material screw, which includes the steps of material preparation, welding, cutting, and forming in sequence. The main step is to divide the base materials of different materials into a rod body and a drill tail. The rod body is formed with a flat welding surface. The drill tail is provided with a pointed cone. The pointed cone has a pointed cone surface. During the welding process of the rod body and the drill tail, the welding surface and the pointed cone are friction welded with each other, so that the pointed cone is fed progressively, and finally the two base materials are welded into a whole.

[0005] For another example, a Taiwan patent with publication number TW201434561A discloses a method for manufacturing a high-strength composite screw, the steps of which are as follows: preparing a first base material made of stainless steel and having a welding surface, and a second base material made of a high-strength material and having a joint surface formed at the end edge and corresponding to the welding surface; joining the first base material and the second base material into a composite screw blank by welding, and during welding, a shielding gas is provided at the junction of the welding surface and the joint surface, wherein the shielding gas contains hydrogen; The composite screw blank is formed into a composite screw. During welding, the first parent material and the second parent material are placed in a welding device, and at least one electrode is arranged on each of the first parent material and the second parent material. Then, the first parent material and the second parent material are moved so that the welding surface of the first parent material and the joint surface of the second parent material are opposite to and in contact with each other, and then the electrodes are energized. Since contact resistance is generated on the contact surface, the contact resistance generates high heat after power is applied, and the metal at the contact position is melted to form a molten pool, so that the first parent material and the second parent material are joined together to form a composite screw blank.

[0006] However, in actual production, the above-mentioned friction welding and resistance butt welding methods have the following disadvantages:

[0007] 1. Friction welding requires the base material to rotate at high speed, causing the two base materials to rub violently until the end faces reach a hot-melt state, and then the machine is stopped for crimping, so that the two base materials fuse together to form a screw blank. However, this method has a slow processing efficiency and can only produce 10-12 screws per minute. Although resistance butt welding can reach 20-25 screws per minute, it is still inefficient and is affected by the conductivity of the material, making it difficult to control and stabilize production.

[0008] 2. During friction welding, the end faces of the two base materials that are welded to each other are subjected to intense friction and progressive feeding, resulting in curled and protruding burrs in the hot zone of the base materials. The degree of curling and protrusion of the burrs is large, which affects the turning efficiency in subsequent turning processing, and generates a large amount of metal waste, resulting in material waste.

[0009] 3. During resistance butt welding, due to the residual oxides and impurities on the end faces of the two base materials, it is easy to produce undesirable inclusion spaces during welding, resulting in poor fusion of the two base materials and unstable strength of the formed screw blank.

[0010] 4. During resistance welding, there are differences in the melting points and electrical conductivity of the two base materials. In order to reach the temperature at which the two base materials can fuse, one side will have an excessively high temperature, causing the grains to become coarser, resulting in reduced strength and toughness of the final finished screw.

[0011] 5. Resistance butt welding requires electrodes to be clamped on the two butted base materials. When the base materials reach the melting point, especially in large-scale continuous production, the temperature on the electrodes is difficult to dissipate quickly. The electrodes are easily deformed by heat, and the electrodes frequently contact and rub against the base materials, causing wear of the electrodes. The machine must be shut down regularly for maintenance and replacement of electrodes, which affects production efficiency and increases production costs. Summary of the invention

[0012] In order to overcome the deficiencies of the prior art, the present invention provides an efficient high-strength welding production method for bimetallic self-drilling screws.

[0013] In order to achieve the above object, the present invention provides the following technical solution, comprising the following steps:

[0014] S1. Clamping and loading, respectively take the stainless steel base material with corrosion resistance and the alloy base material with high hardness, and clamp and fix the two base materials on the conveying equipment respectively, the stainless steel base material is used as the head of the screw, and the alloy base material is used as the tail of the screw;

[0015] S2. Synchronous feeding. The conveying equipment adopts a continuous conveying line type conveying equipment to continuously and synchronously convey the stainless steel base material and the alloy base material, thereby improving production efficiency, making the two base materials always correspond to each other and keep coaxial, and move together to carry out subsequent processing steps in sequence;

[0016] S3, induction heating, the two base materials are synchronously moved to the induction heating area, and the two ends of the two base materials close to each other are heated at the same time by the induction heating coil at a high frequency electromagnetic frequency of 500kHz-2MkHz, until the hot zones of the end surfaces of the two base materials reach 10-50℃ before their respective melting points. The heating speed is fast and the efficiency is high, and the hot zone of the base material is ensured to be located 1-2mm shallow from the end surface, so as to reduce the curling deformation at the hot zone during docking and improve the material utilization rate;

[0017] S4, pressurized docking, when the heating in step S3 is completed, pressure is applied to the two base materials so that the heated ends of the two base materials are docked and spliced, and welded into one to form a screw blank. At the same time, ultrasonic vibration with an oscillation frequency of 20,000 times per second is applied to the two base materials to increase the welding firmness of the two base materials and eliminate the residual internal stress in the base materials;

[0018] S5, turning burrs. When the two base materials are butt-jointed to form a screw blank in step S4 and cooled and shaped, the screw blank is conveyed to a turning device by a conveying device. The burrs that are curled and protruded at the butt joint position when the two base materials are butt-jointed are turned to make the surface of the screw blank smooth and tidy.

[0019] S6, tail clamping and thread rolling processing, when the turning in step S5 is completed, the screw blank is sequentially conveyed to the tail clamping machine and the thread rolling machine by the conveying equipment, and the tail of the screw blank is clamped and the surface of the screw blank is threaded in turn to form a drill tail and a thread, so that the screw blank is formed into a finished screw;

[0020] S7, heat treatment processing, finally, the conveying equipment sends the finished screws into the heat treatment equipment, heat treats the finished screws, and obtains the final product

[0021] In summary, compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. The present invention adopts electromagnetic induction heating to heat two parent materials simultaneously, with fast heating speed and high efficiency, thereby improving production processing efficiency. In addition, the heating effect of electromagnetic induction heating on the two parent materials is more uniform and controllable, which facilitates the control of the processing process.

[0023] 2. The present invention adopts electromagnetic induction heating, which does not contact the heating area of ​​the base material at all during heating. Therefore, the problem of deformation of the electrode due to high temperature when heating the base material will not occur, the processing is optimized to improve the quality of the finished product, and the problem of electrode wear requiring regular shutdown for replacement will not occur, thereby reducing production and maintenance costs while ensuring production efficiency.

[0024] 3. Since the hot zone of the two base materials is located in the shallow layer of the end surface of the base materials, the area where the deformation occurs during the butt joint of the two base materials is limited, which effectively reduces the degree of outward curling of the material at the butt joint position, thereby improving the material utilization rate. Compared with the conventional friction welding and resistance butt welding, the material utilization rate is increased by 3-5%.

[0025] 4. When the two base materials are pressurized and butt-jointed, ultrasonic vibration can be used to make the metallographic structures in the hot zone of the two base materials more tightly and firmly fused, thereby improving the overall structural strength of the screw. Ultrasonic vibration can also be used to release the internal stress of the lattice and improve the mechanical properties of the screw.

[0026] 5. The present invention adopts electromagnetic induction heating and ultrasonic vibration with fast heating speed, and efficiently cooperates with assembly line continuous conveying equipment. In addition, since the curling and protrusion degree of the burr is small, the speed of turning processing can be improved, thereby making the production speed of the entire production process compared with the conventional friction welding of 10-12 pieces per minute and the resistance butt welding of 20-25 pieces per minute. The production efficiency is greatly improved and can reach more than 40 pieces per minute. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the forming of bimetallic self-drilling screws.

[0028] Figure 2The figure is a flow chart of the method of the present invention.

[0029] Description of the accompanying drawings: stainless steel base material 10; alloy base material 11; hot zone 12; screw blank 13; drill tail 14; thread 15; finished screw 16. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0031] Embodiment 1:

[0032] An efficient high-strength welding production method for bimetallic self-drilling screws comprises the following steps:

[0033] S1. Clamping and feeding, taking a stainless steel base material 10 with corrosion resistance as the head of the screw, preferably 304 stainless steel in this embodiment, and taking an alloy base material 11 with high hardness as the tail of the screw, preferably SCM435 in this embodiment, so that the head of the finished screw 16 has corrosion resistance, and the tail of the finished screw 16 has high strength and high penetration, and the two base materials are clamped and fixed on the conveying equipment respectively, leaving a gap between the ends of the two base materials;

[0034] S2, synchronous feeding, the conveying equipment in step S1, in this embodiment, is preferably an assembly line conveying equipment capable of continuous conveying, which can continuously convey multiple groups of stainless steel base materials 10 and alloy base materials 11 to achieve efficient processing and production, and the stainless steel base materials 10 and the alloy base materials 11 are synchronously conveyed by the conveying equipment, and the positions of the two base materials correspond to each other and are always in a coaxial position, and move together to perform subsequent processing steps in sequence;

[0035] S3, induction heating, the two base materials are synchronously moved to the induction heating area, the induction heating coil adopts a high-frequency electromagnetic frequency of 500kHz-2MkHz, and heats the two ends of the two base materials close to each other at the same time, until the hot zone 12 of the end surface of the two base materials reaches 10-50°C before the melting point temperature of the two, and the production speed is compared with the conventional friction welding of 10-12 pieces per minute and the resistance butt welding of 20-25 pieces per minute. The induction heating speed is fast and uniform, thereby increasing the production speed to more than 40 pieces per minute;

[0036] In addition, compared with resistance butt welding, the induction heating coil has no contact with the base material, so there will be no problem of deformation of the electrode due to high temperature when heating the base material, which optimizes processing and improves the quality of finished products. There will be no problem of electrode wear requiring regular shutdown and replacement, thereby reducing production and maintenance costs while ensuring production efficiency.

[0037] S4, pressurized docking. When induction heating is performed in step S3, the hot zones 12 of the two base materials are controlled to be located at the shallow layer 1-2 mm of their respective end surfaces. After heating, ultrasonic vibration pressure is applied to the two base materials so that the hot zones 12 at the ends of the two base materials are docked and fused with each other. Since the hot zones 12 of the two base materials are located at the shallow layer of the end surfaces of the base materials, the area where the two base materials are deformed during the docking process is limited, which effectively reduces the degree of outward curling of the material at the docking position, thereby improving the material utilization rate. Compared with the conventional friction welding and resistance butt welding, the material utilization rate is increased by 3-5%;

[0038] In addition, during the pressurized butt-jointing process, ultrasonic vibration is applied to the base material to generate lattice oscillations of 20,000 times per second, so that the crystal phase structures of the hot zone 12 of the end faces of the two base materials are more tightly and firmly fused into one to form a screw blank 13, thereby improving the overall strength of the screw. At the same time, the application of high-frequency ultrasonic vibration can eliminate the residual internal stress in the base material, thereby optimizing the mechanical properties of the screw. In addition, during the butt-jointing and fusing process of the two base materials, the application of ultrasonic vibration can effectively remove the residual air between the two end faces, thereby avoiding the generation of pores in the fusion area after the two base materials are fused to affect the structural strength.

[0039] S5, turning burrs. When the two base materials are butt-jointed to form a screw blank 13 in step S4 and cooled and shaped, the screw blank 13 is conveyed to the turning equipment by the conveying equipment. The burrs 17 that are curled and protruded at the butt joint position when the two base materials are butt-jointed are turned and formed, so that the surface of the screw blank 13 is smooth and tidy. Since there are fewer curled and protruded burrs 17, the turning speed is fast and the efficiency is high, and less metal waste is generated during turning, thereby achieving the effect of improving production efficiency and saving materials.

[0040] S6, tail clamping and thread rolling processing, when the burr turning in step S5 is completed, the conveying equipment conveys the screw blank 13 to the tail clamping machine, and the tail of the screw blank 13 is subjected to tail clamping processing to form a drill tail 14, and then the conveying equipment conveys the screw blank 13 to the thread rolling machine, and the surface of the screw blank 13 is subjected to thread rolling processing to form a thread 15, so that the screw blank 13 is finally formed into a finished screw 16;

[0041] S7, heat treatment processing, finally, the conveying equipment sends the formed finished screw 16 into the heat treatment equipment, and the finished screw 16 is heat treated to obtain the final product.

[0042] Embodiment 2:

[0043] In this embodiment, the parent material targeted by this patent is not limited to 304 stainless steel and SCM435 alloy materials. As long as it is stainless steel and alloy carbon steel that can be heated by electromagnetic induction, it can be fused and welded.

[0044] When induction heating is performed on two base materials of different materials, two sets of separately controlled induction coils can be set up to heat the two base materials separately. Different electromagnetic frequencies are used for base materials of different materials, so that the two base materials of different materials can reach the appropriate welding temperature at the same time, ensuring the synchronization of the two base materials during high-speed continuous processing, thereby further improving production continuity and production efficiency.

[0045] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. For example, "including" mentioned throughout the specification and claims is an open term, so it should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect.

[0046] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0047] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

Claims

1. An efficient bimetallic self-drilling screw high-strength welding production method, comprising the following steps: S1, clamping and loading materials, respectively taking a stainless steel base material (10) with corrosion resistance and an alloy base material (11) with high hardness, and clamping and fixing the two base materials on the conveying equipment, respectively, with the stainless steel base material (10) serving as the head of the screw and the alloy base material (11) serving as the tail of the screw; S2, synchronous feeding, using the conveying equipment in step S1, the stainless steel base material (10) and the alloy base material (11) are synchronously conveyed, so that the two base materials always correspond to each other, move together and perform subsequent processing steps in sequence; S3, induction heating, the two base materials are synchronously moved to the induction heating area, and the two ends of the two base materials close to each other are heated at the same time until the hot zones (12) at the ends of the two base materials reach the specified temperature; S4, pressurized docking, when the heating in step S3 is completed, applying pressure and ultrasonic vibration to the two base materials so that the heated ends of the two base materials are docked and welded together to form a screw blank (13); S5, turning burrs. When the two base materials are butt-jointed to form a screw blank (13) in step S4 and cooled and shaped, the screw blank (13) is conveyed to a turning device by a conveying device, and the burrs (17) that are curled and protruded at the butt joint position when the two base materials are butt-jointed are turned and formed, so that the surface of the screw blank (13) is smooth and neat. S6, tail clamping and thread rolling processing, after the turning in step S5 is completed, the screw blank (13) is transported to the tail clamping machine and the thread rolling machine in sequence by the conveying equipment, and the tail of the screw blank (13) is clamped and the surface of the screw blank (13) is thread rolled in sequence to form a drill tail (14) and a thread (15), so that the screw blank (13) is formed into a finished screw (16); S7, heat treatment processing, finally, the conveying device sends the formed finished screw (16) to the heat treatment equipment, and the finished screw (16) is heat treated to obtain the final product.

2. The efficient high-strength welding production method for bimetallic self-drilling screws according to claim 1 is characterized in that: The conveying equipment in step S2 is an assembly line feeding equipment capable of continuous feeding.

3. The efficient high-strength welding production method for bimetallic self-drilling screws according to claim 1 is characterized in that: The electromagnetic frequency of the induction heating in step S3 is 500kHz-2MkHz.

4. The efficient high-strength welding production method for bimetallic self-drilling screws according to claim 1 is characterized in that: In step S3, the hot zone (12) of the two base materials is located at the shallow layer 1-2 mm of the end surface of the base materials.

5. The efficient high-strength welding production method for bimetallic self-drilling screws according to claim 1 is characterized in that: In step S3, the two base materials are heated by induction heating to a temperature 10-50°C below their respective melting points.

6. The efficient high-strength welding production method for bimetallic self-drilling screws according to claim 1 is characterized in that: The frequency of ultrasonic vibration is 20,000 times per second.

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