A high-strength anti-brittle fracture bolt pair and its production process

Abstract

The present application discloses a high-strength anti-brittle-break bolt pair and its production process, which processes a processed substrate into a preformed bolt through a front-end preforming process, wherein the preformed bolt includes a bolt head and a light rod connected to one end of the bolt head, and then the bolt head of the preformed bolt is subjected to a head metal flow line detection; the preformed bolt is then surface treated through a back-end forming process, and threads are processed on the light rod of the preformed bolt to obtain a formed bolt, and finally the formed bolt is heat treated, wherein the front-end preforming process includes a bolt head preforming process, a surface treatment process, and a drawing process, etc., and the back-end forming process includes degreasing, dephosphorization, water washing, drying, etc. Compared with the traditional process, the production process provided by the present application realizes the improvement of bolt characteristics and enhances bolt strength. The production process of the high-strength anti-brittle-break bolt pair provided by the present application can produce high-strength anti-brittle-break bolts, which solves the problem of easy brittle breakage after installation.

Description

Technical Field

[0001] The present application relates to the technical field of bolt pair processing, and in particular to a high-strength anti-brittle fracture bolt pair and a production process thereof. Background Art

[0002] High-strength bolt connection is one of the main connection methods for various steel structures. Its reliability will directly determine the safety of the structure. The bolt pairs in facilities with higher safety requirements are high-strength bolt connection pairs. Each bolt pair includes a bolt, a nut, and two washers, which are all produced in the same batch and processed in the same heat treatment process.

[0003] In the market application, high-strength bolts, especially those of grade 10.9 and above, often break easily after installation due to improper production process, thus causing heavy losses. After research, the inventor found that the main reasons for the easy breakage of high-strength bolts after installation are as follows:

[0004] 1. Inappropriate material selection: High-strength bolts need to be made of materials with sufficient strength and toughness; if the selected material does not meet the standards or is inappropriate, it is easy to cause crisp fracture problems.

[0005] 2. Improper heat treatment: High-strength bolts usually need to undergo heat treatment to improve the strength of the material. If parameters such as temperature, time or cooling method are not properly controlled during the heat treatment process, it will lead to uneven material structure or internal stress, thereby increasing the risk of fracture.

[0006] 3. Incorrect cold heading process: When manufacturing high-strength bolts, the cold heading process is inevitable. If the cold heading parameters are not set correctly, such as excessive deformation, inappropriate process parameters, etc., it will lead to material embrittlement and stress accumulation, and then cause fracture.

[0007] 4. Lack of proper annealing treatment: High-strength bolts after cold heading usually need spheroidizing annealing or tempering treatment to improve their plasticity and toughness; if the annealing treatment is insufficient or defective, the material will still have stress concentration and brittleness, thus causing fracture.

[0008] 5. Poor processing surface quality: The surface quality of high-strength bolts is crucial to their performance and service life. If there are scratches, corrosion or other defects during the processing process, the fatigue life of the bolts will be reduced and the risk of breakage will be increased.

[0009] These reasons may affect the post-installation performance of high-strength bolts individually or simultaneously. Therefore, each link needs to be strictly controlled during the manufacturing and processing process to ensure reasonable material selection, correct heat treatment, appropriate cold heading and annealing treatment, and ensure the quality of the processed surface to reduce the occurrence of brittle fracture.

[0010] Therefore, the bolts obtained by traditional processing have the problem of insufficient strength and easy to break after installation. Therefore, it is urgent to propose a new technical solution to solve the problems existing in the prior art. Summary of the invention

[0011] The present application provides a high-strength anti-brittle fracture bolt pair and a production process thereof, which are used to solve the problem that bolts manufactured by traditional processing technology have insufficient strength and are easy to break brittlely after installation.

[0012] In order to achieve the above objectives, this application provides the following technical solutions:

[0013] On the one hand, the present application provides a production process for a high-strength anti-brittle fracture bolt pair, comprising the following steps:

[0014] S1: selecting a processing substrate, and processing the processing substrate into a preformed bolt through a front-end preforming process, wherein the preformed bolt includes a bolt head and a polished rod connected to one end of the bolt head;

[0015] S2: performing a head metal flow line test on the bolt head of the preformed bolt;

[0016] S3: After the head metal flow line inspection is qualified, the preformed bolt is surface treated through a post-forming process, and threads are processed on the polished rod of the preformed bolt to obtain a formed bolt;

[0017] S4: heat treating the formed bolts obtained by step S3, and the bolt processing is completed;

[0018] Among them, the front-end preforming process described in step S1 includes a bolt head preforming process, a surface treatment process and a drawing process; the back-end forming process described in step S3 performs surface treatment on the preformed bolt including degreasing, dephosphorization, water washing and drying.

[0019] Furthermore, in the above technical scheme, the bolt head preforming process in the front-end preforming process includes disc forming and cold heading forming; the surface treatment process in the front-end preforming process includes pickling, water washing, phosphating, water washing, and saponification; the drawing process in the front-end preforming process includes drawing and precision drawing; the front-end preforming process also includes spheroidizing annealing of the processed substrate.

[0020] Furthermore, the processing flow of the front-end preforming process specifically includes the following steps:

[0021] A disc element machine is used to press the processed substrate into a circular flat disc element blank, and the pressed flat disc element blank is subjected to spheroidizing annealing. The flat disc element blank that has completed spheroidizing annealing is pickled, washed with two steps of clean water, sprayed with clean water, phosphated, washed with water, and saponified. The flat disc element blank that has completed surface treatment is then drawn and fine-drawn, and the flat disc element blank is gradually thinned to obtain a drawn blank with the required diameter and length. The drawn blank is then cold-headed to obtain the preformed bolt.

[0022] Furthermore, the cold heading forming of the drawn blank includes: cutting the drawn blank according to the target length to obtain a plurality of sections of cylindrical cold heading blanks, and sequentially performing one-die, two-die, three-die and four-die forming on each cylindrical cold heading blank; wherein the one-die is used to make the cross-section of the cylindrical cold heading blank flat; the two-die is used to perform initial forging on the blank with a flat cross-section after passing through the one-die, forming a bolt head forging rough portion at one end of the cylindrical cold heading blank, and forming a light rod connected to the bolt head forging rough portion at the other end; the three-die is used to pre-form the bolt head after forging the bolt head forging rough portion, and the three-die is used to reduce the diameter and chamfer the light rod; the four-die is used to cut a hexagonal outer contour on the bolt head preformed by the three-die, and form the bolt head into a hexagonal head.

[0023] Furthermore, a metal streamline is formed in the center of the longitudinal section of the bolt head that passes the head metal streamline test, and the thickness of the metal streamline is greater than or equal to one third of the thickness of the bolt head.

[0024] Furthermore, the post-forming process in step S3 includes degreasing, two-step water washing, dephosphorization, water washing, and drying the preformed bolts formed by cold heading; in step S3, threads are processed on the polished rod of the preformed bolt by grinding or rolling, and the polished rod is formed into a bolt rod.

[0025] Based on the above-mentioned production process of a high-strength anti-brittle fracture bolt pair, the present application provides a high-strength anti-brittle fracture bolt pair, including a bolt, which is processed and manufactured according to the above-mentioned production process of the high-strength anti-brittle fracture bolt pair.

[0026] On the other hand, the present application also provides another production process for high-strength anti-brittle fracture bolt pairs, wherein the bolt head preforming process in the front-end preforming process in the above step S1 includes cutting, plane chamfering and head forming; the surface treatment process in the front-end preforming process includes lime lubrication; and the drawing process in the front-end preforming process includes drawing fine wire.

[0027] Furthermore, the processing flow of the front-end preforming process specifically includes the following steps:

[0028] The processed substrate is lubricated with lime, and then the processed substrate is drawn to gradually reduce the diameter of the processed substrate to the target diameter. The drawn processed substrate is cut according to the target length to obtain a number of cylindrical blanks. The end of each cylindrical blank is plane chamfered, and the blank after plane chamfering is head-formed. When the head is formed, the heating length and heating time of the bolt are controlled, and the preformed bolt is obtained through the hot bolting process.

[0029] Furthermore, a broken flow line is formed in the center of the longitudinal section of the bolt head that has passed the head metal streamline test, and the broken flow line is a wavy streamline; the formation position of the broken flow line is between one third and one half of the thickness of the bolt head.

[0030] Furthermore, the post-forming process in step S3 includes shot blasting to remove oxide scale, chamfering the bolt head, saponifying phosphorus, reducing the diameter of the polished rod, degreasing, dephosphorizing, washing, and drying the preformed bolt after head forming; in step S3, threads are processed on the polished rod after diameter reduction by grinding or rolling, and the polished rod is formed into a bolt rod.

[0031] Based on the above-mentioned production process of a high-strength anti-brittle fracture bolt pair, the present application provides a high-strength anti-brittle fracture bolt pair, including a bolt, which is processed and manufactured according to the above-mentioned production process of the high-strength anti-brittle fracture bolt pair.

[0032] Compared with the prior art, this application has the following beneficial effects:

[0033] The present application provides a production process for a high-strength anti-brittle-break bolt pair, which processes a processed substrate into a preformed bolt through a front-end preforming process, wherein the preformed bolt includes a bolt head and a light rod connected to one end of the bolt head, and then the bolt head of the preformed bolt is subjected to a head metal streamline detection; after the detection is qualified, the preformed bolt is surface treated through a back-end forming process, and threads are processed on the light rod of the preformed bolt to obtain a formed bolt, and finally the formed bolt is heat treated, wherein the front-end preforming process includes a bolt head preforming process, a surface treatment process and a drawing process, and the back-end forming process performs surface treatment on the preformed bolt. Compared with the traditional bolt processing technology, the production process provided by the present application achieves an improvement in bolt characteristics and enhances bolt strength through process flow improvements. The production process of the high-strength anti-brittle-break bolt pair provided by the present application can produce high-strength anti-brittle-break bolts, which solves the problem of easy brittle breakage after installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. It should be understood that the specific shapes and structures shown in the drawings should not usually be regarded as limiting conditions for implementing the present application; for example, based on the technical concepts and exemplary drawings disclosed in the present application, those skilled in the art are able to easily make routine adjustments or further optimizations to the increase / decrease / attribution division, specific shapes, positional relationships, connection methods, and dimensional ratios of certain units (components).

[0035] Figure 1 This is a production process flow chart of a high-strength anti-brittle fracture bolt pair provided by the present application;

[0036] Figure 2 is a production process flow chart of a high-strength anti-brittle-break bolt pair provided in Example 1, which shows a production process flow of a cold-heading bolt in more detail;

[0037] Figure 3 The time-temperature variation line graph of a wire material XG835NH undergoing spheroidizing annealing in a spheroidizing furnace is shown. The graph mainly shows the time-temperature variation of a spheroidizing annealing process during a processing process, which can guide the spheroidizing annealing process;

[0038] Figure 4 The shape change process of the blank formed by cold heading in Example 1 is shown, wherein Figure (a) is a cylindrical cold heading blank obtained after cutting; Figure (b) is a cylindrical cold heading blank after the cross section of the first die is flattened; Figure (c) is a blank after the second die is pre-formed; Figure (d) is a blank after the bolt head is pre-formed by the third die and the polished rod is reduced in diameter and chamfered; Figure (e) is a pre-formed bolt after the hexagonal outer contour of the bolt head is cut out by the fourth die;

[0039] Figure 5 This is a physical longitudinal section diagram obtained by extracting a bolt from a production batch in Example 2 and performing a metal flow line test on the head of the extracted bolt, showing the shape and position of the metal flow line. The metal flow line in the diagram is centered, and the metal flow line test on the head is qualified;

[0040] Figure 6 This is a physical longitudinal section diagram obtained by extracting a bolt from another production batch in Example 2 and performing a head metal flow line test on the extracted bolt, showing the shape and position of the metal flow line. The metal flow line in the diagram is centered, and the head metal flow line test is qualified;

[0041] Figure 7is a production process flow chart of a high-strength anti-brittle-break bolt pair provided in Example 3, which shows a production process flow of a hot-punched bolt in more detail;

[0042] Figure 8 A bolt was extracted from a production batch, and the head metal flow line test was performed on the extracted bolt to obtain the actual longitudinal section diagram, which shows the shape and position of the broken flow line (or metal flow line). The broken flow line in the figure forms a wavy flow line in the middle of the bolt head, and the head metal flow line test is qualified.

[0043] Description of reference numerals:

[0044] 1. Thick part of bolt head; 2. Polished rod; 3. Bolt head formed by three-die cold heading; 4. Bolt head formed by four-die cold heading. DETAILED DESCRIPTION

[0045] The present application is further described below in detail through specific embodiments in conjunction with the accompanying drawings.

[0046] In the description of this application: unless otherwise specified, the meaning of "plurality" is two or more. The terms "first", "second", "third", etc. in this application are intended to distinguish the objects referred to, and do not have special meanings in terms of technical connotations (for example, they should not be understood as emphasizing the importance or order, etc.). Expressions such as "including", "comprising", "having", etc. also mean "not limited to" (certain units, components, materials, steps, etc.).

[0047] The terms such as "upper", "lower", "left", "right", "middle", etc. used in this application are usually used to facilitate intuitive understanding by comparing with the accompanying drawings, and are not absolute limitations on the positional relationship in the actual product. Without departing from the technical concept disclosed in this application, changes in these relative positional relationships should also be regarded as the scope of this application.

[0048] In order to solve the problem that bolts manufactured by traditional processing technology are insufficient in strength and are easy to break brittlely after installation, the present application provides a production process for high-strength anti-brittle fracture bolt pairs. The bolts are obtained by processing through an innovative production process. After testing, it can effectively prevent the bolts from breaking brittlely during production and storage and transportation.

[0049] See also Figure 1 The production process of a high-strength anti-brittle fracture bolt pair provided in this application can be roughly divided into the following steps:

[0050] S1: selecting a processing substrate, and processing the processing substrate into a preformed bolt through a front-end preforming process, wherein the preformed bolt includes a bolt head and a polished rod connected to one end of the bolt head;

[0051] S2: Conduct metal flow line inspection on the bolt head of the preformed bolt;

[0052] S3: After the head metal flow line inspection is qualified, the preformed bolt is surface treated through the post-forming process, and threads are processed on the polished rod of the preformed bolt to obtain a formed bolt;

[0053] S4: heat treating the formed bolts obtained by the process in step S3, and the bolt processing is completed.

[0054] The front-end preforming process mentioned in step S1 at least includes: a bolt head preforming process, a surface treatment process and a drawing process.

[0055] The post-forming process mentioned in step S3 at least includes surface treatment of the preformed bolts, such as degreasing, dephosphorization, water washing, and drying processes.

[0056] The above-mentioned head metal streamline detection is a test method for evaluating and inspecting the internal streamline of the head metal parts. Specifically, the bolt head is longitudinally sectioned from the middle part, and the metal streamlines on the longitudinal section are observed. The shape and thickness of the metal streamlines are used to judge whether the head metal parts are processed properly.

[0057] In the production process of high-strength anti-brittle fracture bolt pairs, many bolts are produced in the same batch. Therefore, in specific production practice, the head metal flow line detection can be carried out on the randomly inspected products.

[0058] According to the different process selections of the front-end preforming process and the back-end forming process in the above steps S1 to S4, the production process of a high-strength anti-brittle fracture bolt pair provided by the present application can be divided into two parallel processes: 1. Cold heading bolt production process; 2. Hot striking bolt production process. The following describes these two production processes in detail using different embodiments.

[0059] Embodiment 1

[0060] This embodiment provides a production process for a high-strength anti-brittle fracture bolt pair. Specifically, it is a cold heading bolt production process. For details, see Figure 2 , the process flow is as follows:

[0061] S1. Select a processing base material, and process the processing base material into a preformed bolt through a front-end preforming process. The preformed bolt includes a bolt head and a polished rod connected to one end of the bolt head.

[0062] S2: Conduct metal flow line inspection on the bolt head of the preformed bolt;

[0063] S3: After the head metal flow line inspection is qualified, the preformed bolt is surface treated through the post-forming process, and threads are processed on the polished rod of the preformed bolt to obtain a formed bolt;

[0064] S4: heat treating the formed bolts obtained by the process in step S3, and the bolt processing is completed.

[0065] The processing substrate in step S1 is usually made of carbon steel, alloy steel and other materials. The material can be subjected to pre-treatment processes such as cutting and forging as needed to ensure that the size and quality of the material meet the requirements.

[0066] According to the process processing function, the front-end preforming process in step S1 can be divided into: bolt head preforming process, surface treatment process, drawing process and spheroidizing annealing. Among them: the bolt head preforming process includes plate element and cold heading; the surface treatment process includes pickling, water washing, phosphating, water washing, saponification; the drawing process includes drawing and fine drawing.

[0067] See also Figure 2 , the processing flow of the front-end preforming process is:

[0068] 1) Use a coil forming machine to press the processed substrate into a round flat coil forming blank, that is, press the initial metal blank into a flat coil forming blank with a certain shape. This step is usually performed using a cold press or a coil forming machine to press the metal blank into the desired shape by applying pressure.

[0069] 2) Spheroidizing annealing is performed on the pressed flat disc blank, that is, the disc blank is heated to an appropriate temperature and maintained for a period of time to allow the grains inside the material to grow again and become spherical. Spheroidizing annealing can improve the plasticity and toughness of the material, reduce stress concentration, and improve the quality of the thread. Figure 3 , showing a time-temperature change line graph of a wire material XG835NH undergoing spheroidizing annealing in a spheroidizing furnace. The graph mainly shows the time-temperature change of a spheroidizing annealing process during a processing process, which can guide the spheroidizing annealing process.

[0070] 3) The flat disk blank that has completed spheroidizing annealing is pickled, washed with two steps of clean water, sprayed with clean water, phosphated, washed with water, and saponified.

[0071] 4) The surface treated flat disc blank is then subjected to fine drawing to gradually thin the flat disc blank to obtain a drawn blank of the required diameter and length, that is, the material is gradually thinned through a continuous stretching and compression process until the requirements are met.

[0072] 5) The drawn blank is cold headed to obtain a preformed bolt.

[0073] In the above step 3), the flat disk element blank is pickled, washed with two steps of clean water, sprayed with clean water, phosphated, washed with water, and saponified. This is a surface treatment process, which can be summarized as a material pickling and phosphating saponification process. The specific treatment process is: pickling (weak pickling, medium pickling, strong pickling), high-pressure water washing, water washing, water washing, phosphating, water washing, water washing, and saponification.

[0074] The aforementioned weak pickling refers to using 6-10% hydrochloric acid to soak the product at room temperature to 40°C for 10-30 minutes; the aforementioned medium pickling refers to using 10-20% hydrochloric acid to soak the product at room temperature to 40°C for 10-20 minutes; the aforementioned strong pickling refers to using 20-25% hydrochloric acid to soak the product at room temperature to 40°C for 5-10 minutes. Pickling can remove impurities such as grease, dirt and oxides on the surface, ensuring that the phosphating solution can fully contact the metal surface.

[0075] The high pressure water washing and water washing mentioned above are to use tap water to wash the product at room temperature for 1-2 minutes. The purpose of water washing is to avoid carrying residual acid and debris into the next process.

[0076] The aforementioned phosphating is to immerse the metal parts in a solution containing a phosphating agent, and form a phosphating layer on the metal surface through a chemical reaction. Phosphating can provide good corrosion resistance and wear resistance for the metal, and can improve lubricity and reduce friction coefficient. The phosphating agent used can be an acidic phosphate solution, an alkaline phosphate solution or an organic solution containing phosphate.

[0077] Usually after phosphating, metal parts need to be cleaned and neutralized to remove excess phosphating agent and other residues.

[0078] Saponification is the process of immersing the phosphating metal parts into a saponification tank. The solution in the saponification tank reacts with the phosphating layer to form a saponification layer. The purpose is to form a saponification layer with excellent adsorption and lubricity on the surface of the material, so as to facilitate the smooth progress of subsequent processing technology.

[0079] See also Figure 4 The above step 5) cold heading the drawn blank includes: cutting the drawn blank according to the target length to obtain a plurality of cylindrical cold heading blanks, such as Figure 4 (a) in the figure, and then each cylindrical cold heading blank is subjected to one die, two die, three die and four die in sequence.

[0080] Specifically, a die is used to flatten the cross section of a cylindrical cold-forged blank to obtain Figure 4 (b)

[0081] The second die is used to perform initial forging on the blank with a flat cross section after the first die, forming a bolt head forging rough portion 1 at one end of the cylindrical cold forged blank, and forming a polished rod 2 connected to the bolt head forging rough portion at the other end, Figure 4 (c)

[0082] The three-die is used to preform the bolt head after roughening the bolt head roughening part 1, and the three-die is used to reduce the diameter and chamfer the polished rod to obtain Figure 4 (d)

[0083] The fourth die is used to cut out a hexagonal outer contour on the bolt head preformed by the third die, forming the bolt head into a hexagonal head to obtain a preformed bolt. Figure 4 In (e), the preformed bolt has a bolt head and a polished rod connected to one end of the bolt head.

[0084] In the production process of high-strength anti-brittle fracture bolt pairs, many bolts are produced in the same batch, so in specific production practice, the head metal flow line detection can be carried out on the sampled products. In step S2, the head metal flow line detection of the bolt head of the preformed bolt is carried out by longitudinally sectioning the bolt head from the middle part, observing the metal flow line on the longitudinal section, and judging whether the head metal parts processing is qualified by the shape and thickness of the metal flow line. In this application, a metal flow line is formed in the center of the longitudinal section of the bolt head that passes the head metal flow line detection, and the thickness of the metal flow line is greater than or equal to one third of the thickness of the bolt head.

[0085] Of course, in specific production practice, head metal flow line detection can also include the following inspection methods:

[0086] Visual inspection: The staff visually observes the surface of the metal parts of the head and checks whether there are obvious defects such as dents, scratches, deformation, etc.; this is the simplest and most commonly used inspection method, but it requires a high level of experience and judgment from the operator.

[0087] Tactile testing: Use touch or feel to check the surface smoothness and bumps of the head metal parts. Gently touch the surface with your fingers to feel any uneven or rough areas.

[0088] Optical inspection: Use optical instruments such as microscopes, magnifiers or projectors to check for subtle defects and unevenness on the surface of head metal parts; these devices can provide more precise observation and measurement and can detect smaller defects.

[0089] Surface scanning: Use a 3D scanner or laser scanner to perform a comprehensive surface scan of the head metal parts to obtain its 3D data; by analyzing the scan results, the surface streamline can be evaluated and any anomalies or defects can be detected.

[0090] The above methods can be used alone or in combination. Through the head metal flow line detection, it can be ensured that the head metal parts have good appearance and quality during the manufacturing process to meet the design requirements of the product.

[0091] The post-forming process in step S3 includes degreasing, two-pass water washing, dephosphorization, water washing, and drying the preformed bolts formed by cold heading.

[0092] Specifically, degreasing is to degrease the cold-forged bolts to remove grease, lubricants and other organic impurities on the surface. Common degreasing methods include solvent cleaning, alkaline cleaning or ultrasonic cleaning.

[0093] The double water washing is to wash the degreased bolts with water in two steps to thoroughly remove the degreaser residue and other impurities. Between each water washing, sufficient sedimentation or other appropriate separation methods should be used to ensure that the water quality of the bolts is improved from one water washing to the next.

[0094] Dephosphorization is the process of removing phosphorus from preformed bolts after washing. Preformed bolts are immersed in an acid solution for dephosphorization. For example, dilute sulfuric acid is used to immerse the bolts, which can reduce or dissolve the oxides on the surface of the bolts. Dephosphorization is mainly to remove oxides, dirt and other impurities on the surface of the bolts to improve the effect of subsequent treatment steps.

[0095] After the preformed bolt has been processed by the post-forming process, threads can be processed on the polished rod of the preformed bolt by grinding or rolling, and the polished rod is formed into a bolt rod. At this point, the bolt head and the bolt rod have been formed to obtain a formed bolt.

[0096] Thread rolling is a plastic deformation processing method that places the bolt between two or more rollers of a thread rolling machine. Under the extrusion of the rollers, the metal material of the workpiece undergoes plastic flow to form threads. Thread rolling can produce high-precision, high-quality threads with good strength and fatigue life.

[0097] Thread rolling is a cold working method similar to pressure working. The bolt is clamped between two thread rolling rollers. The rotation of the rollers squeezes and cuts the thread along the axial direction of the workpiece. Compared with traditional cutting methods, thread rolling has higher efficiency and better surface quality, and can provide higher strength and fatigue life.

[0098] In actual production, the choice of thread rolling or thread rolling depends on the specific application requirements, workpiece materials, production batch and other factors. Generally speaking, thread rolling is suitable for large-scale thread processing, which can achieve high efficiency and high precision production. Thread rolling is more suitable for small batch or single piece thread processing, which can obtain very high thread quality.

[0099] In step S4, heat treatment is performed on the formed bolt to achieve hardness and strength control. Appropriate heating and cooling processes can change the structure and performance of the bolt. The following are general heat treatment methods for formed bolts:

[0100] 1. Solution Treatment: Solution treatment is to heat the bolts to a suitable temperature to make the solid solution reach a uniform state; this process helps to reduce grain size, improve uniformity, and eliminate internal stress; high temperature is usually used for solution treatment.

[0101] 2. Quenching: Quenching is to quickly cool the bolts after solution treatment to room temperature or low temperature to quickly form a hard structure; through rapid cooling, the structure of the bolts can be changed to produce higher hardness and strength; the choice of quenching medium depends on the material and specific requirements of the bolts.

[0102] 3. Tempering: Tempering is to heat the bolts to a lower temperature again after quenching and keep it for a certain period of time so that the hardness and brittleness of the bolts can be properly adjusted; tempering can reduce the hardness of the bolts, improve toughness and impact resistance, and reduce the possible risk of brittle fracture.

[0103] Through a reasonable combination of heat treatment processes such as solution treatment, quenching and tempering, the hardness, strength and toughness of the formed bolts can be controlled according to requirements. In production practice, the heat treatment process design and optimization can be carried out according to specific factors such as materials, dimensions and performance requirements. In addition, parameters such as temperature, time and cooling rate during the heat treatment process can also be controlled and adjusted according to actual processing requirements to ensure the quality and performance stability of the bolts.

[0104] Embodiment 2

[0105] Based on the production process of a high-strength anti-brittle-break bolt pair provided in the first embodiment, the present application provides a high-strength anti-brittle-break bolt pair, including bolts. The bolts constituting the bolt pair are processed according to the production process of the high-strength anti-brittle-break bolt pair provided in the first embodiment.

[0106] See also Figure 5 , 6 , is a physical longitudinal section diagram obtained by taking a bolt from each of the two production batches and inspecting the metal flow line of the head of the bolt, showing the shape and position of the metal flow line. The metal flow line in the figure is centered. The metal flow line position is generally controlled to be more than one-third of the head thickness for the best.

[0107] The inventors conducted hardness and tensile tests on the processed cold-headed bolts. The test data showed that the standard value of the 8.8 grade (A325) hardness is HRC25-34, the actual internal control value is within HRC25-30, the tensile strength is above the standard value, and the toughness is optimal.

[0108] Therefore, the bolts obtained by using the production process of the high-strength anti-brittle fracture bolt pair provided in the present application have been tested to have excellent hardness and tensile properties, and can effectively prevent brittle fracture during the production, storage and transportation of the bolts.

[0109] Embodiment 3

[0110] This embodiment provides another production process for high-strength anti-brittle fracture bolt pairs, specifically, it is a hot-punching bolt production process, specifically, see Figure 7 , the process flow is as follows:

[0111] S1. Select a processing base material, and process the processing base material into a preformed bolt through a front-end preforming process. The preformed bolt includes a bolt head and a polished rod connected to one end of the bolt head.

[0112] S2: Conduct metal flow line inspection on the bolt head of the preformed bolt;

[0113] S3: After the head metal flow line inspection is qualified, the preformed bolt is surface treated through the post-forming process, and threads are processed on the polished rod of the preformed bolt to obtain a formed bolt;

[0114] S4: heat treating the formed bolts obtained by the process in step S3, and the bolt processing is completed.

[0115] According to the process processing function, the front-end preforming process in step S1 can be divided into: bolt head preforming process, surface treatment process and drawing process. Among them: the bolt head preforming process includes cutting, plane chamfering and head forming; the surface treatment process includes lime lubrication; the drawing process includes drawing fine wire.

[0116] See also Figure 7 , the processing flow of the front-end preforming process is:

[0117] 1) Lime lubrication of the processing substrate; lime lubrication is to apply a layer of lime paste or lime powder on the surface of the substrate as a lubricant. Lime lubrication can reduce friction and heat accumulation, help reduce the friction coefficient of the material during processing, and improve processing efficiency and surface quality.

[0118] 2) The processed substrate lubricated with lime is then drawn to gradually reduce the diameter of the processed substrate to the target diameter; that is, the lubricated substrate is placed in a drawing machine for drawing. The drawing process is to gradually reduce the diameter of the material by passing it through a series of steel die apertures, thereby obtaining the desired wire diameter and size. This process can improve the strength and surface finish of the material.

[0119] 3) The drawn processed substrate is cut into pieces according to the target length to obtain a number of cylindrical blanks; the cutting can be performed using a cutting machine or a saw blade.

[0120] 4) The end of each cylindrical blank is plane chamfered; that is, the cut or edge of the material is plane chamfered. This step can be performed using a chamfering tool or a grinder to remove sharp edges, improve safety, and improve appearance quality.

[0121] 5) The blank after plane chamfering is then subjected to head forming. During the head forming, the heating length and heating time of the bolt are controlled, and a preformed bolt is obtained through a hot bolting process.

[0122] The hot bolting process can be used to produce bolts with high strength and high performance requirements. The hot bolting process includes the following processes: heating the blank to a specific temperature to make it more plastic and convenient for subsequent forming operations; after preheating, forging the blank, and applying pressure and impact force to make the raw material quickly form the shape of the bolt under the action of the die. During this period, the processing parameters such as the blank heating length, heating temperature and heating time can be controlled according to the processing requirements.

[0123] In the production process of high-strength anti-brittle fracture bolt pairs, many bolts are produced in the same batch, so in specific production practice, the head metal streamline detection can be carried out on the sampled products. In step S2, the head metal streamline detection of the bolt head of the preformed bolt is to longitudinally section the bolt head from the middle part, observe the metal streamlines on the longitudinal section, and judge whether the head metal parts processing is qualified by the shape and thickness of the metal streamlines. In this application, a broken streamline is formed in the center of the longitudinal section of the bolt head that has passed the head metal streamline detection, and the broken streamline is a wavy streamline; the formation position of the broken streamline is between one-third and one-half of the thickness of the bolt head.

[0124] Of course, in specific production practice, head metal flow line detection can also be assisted by visual inspection, tactile inspection, optical inspection and surface scanning.

[0125] See also Figure 7 In step S3, the post-forming process includes shot blasting to remove oxide scale, chamfering the bolt head, saponifying phosphorus, reducing the diameter of the polished rod, degreasing, dephosphorizing, washing, and drying the preformed bolt after head forming.

[0126] Shot blasting is a surface treatment method used to remove scale, rust, dirt and other impurities on the surface of metal materials. The removal principle is: using high-speed rotating shot blasting equipment, the shot blasting media (such as steel balls, sand, etc.) are projected onto the metal surface, and through impact and friction, the scale, rust or dirt is peeled off to achieve a clean and smooth effect.

[0127] The chamfer on the bolt head can further shape the bolt head to achieve a good appearance.

[0128] Phosphate saponification is to carry out phosphating and saponification treatments in sequence. After a phosphating layer is formed on the surface of the blank, further saponification treatment is performed to form a saponified layer, which can provide lubricity, reduce friction and wear of the bolts during assembly and use, and improve their corrosion resistance. It also helps to improve the quality of the thread surface and improve the assembly performance and reliability of the bolts.

[0129] Polished rod reduction is to reduce the diameter of the polished rod of the preformed bolt to achieve the target design size and diameter. For example, the reduction can be achieved by cold forging or rolling.

[0130] Degreasing is the process of degreasing cold-forged bolts to remove grease, lubricants and other organic impurities on the surface. Common degreasing methods include solvent cleaning, alkaline cleaning or ultrasonic cleaning.

[0131] Dephosphorization is the process of removing phosphorus from preformed bolts after degreasing. Preformed bolts are immersed in an acid solution for dephosphorization. For example, dilute sulfuric acid is used to immerse the bolts, which can reduce or dissolve the oxides on the surface of the bolts. The purpose of dephosphorization is to remove oxides, dirt and other impurities on the surface of the bolts to improve the effect of subsequent treatment steps.

[0132] After the preformed bolt has been processed by the post-forming process, threads can be processed on the polished rod of the preformed bolt by grinding or rolling, and the polished rod is formed into a bolt rod. At this point, the bolt head and the bolt rod have been formed to obtain a formed bolt.

[0133] In step S4, the formed bolt is heat treated to achieve hardness and strength control. Appropriate heating and cooling processes can change the organizational structure and performance of the bolt. For example, through a reasonable combination of heat treatment processes such as solution treatment, quenching and tempering, the hardness, strength and toughness of the formed bolt can be controlled according to demand. In production practice, the heat treatment process design and optimization can be carried out according to specific factors such as material, size and performance requirements. In addition, parameters such as temperature, time and cooling rate during the heat treatment process can also be controlled and adjusted according to actual processing requirements to ensure the quality and performance stability of the bolt.

[0134] Embodiment 4

[0135] Based on the production process of a high-strength anti-brittle-break bolt pair provided in the third embodiment, the present application provides a high-strength anti-brittle-break bolt pair, including bolts. The bolts constituting the bolt pair are processed according to the production process of the high-strength anti-brittle-break bolt pair provided in the third embodiment.

[0136] See also Figure 8, is a physical longitudinal section diagram obtained by extracting a bolt from a production batch and performing metal streamline detection on the head of the extracted bolt, showing the shape and position of the broken flow line (or metal streamline). The broken flow line shown in the figure forms a wavy streamline in the middle of the bolt head. The broken flow line is generally controlled at one-third to one-half of the total thickness of the head as the best position, which can effectively reduce the forming folding phenomenon and avoid hidden dangers caused by head deformation.

[0137] The inventors conducted hardness and tensile tests on the processed hot-punched bolts. The test data showed that the standard value of the 10.9 grade (A490) hardness is HRC32-39, the actual internal control value is within HRC35-38, the tensile strength is above the standard value, and the toughness is optimal.

[0138] Therefore, the bolts obtained by using the production process of the high-strength anti-brittle fracture bolt pair provided in the present application have been tested to have excellent hardness and tensile properties, and can effectively prevent brittle fracture during the production, storage and transportation of the bolts.

[0139] The technical features of the above embodiments may be arbitrarily combined (as long as there is no contradiction in the combination of these technical features). To make the description concise, not all possible combinations of the technical features in the above embodiments are described; these embodiments that are not explicitly written should also be considered to be within the scope of this specification.

[0140] The above is a relatively specific and detailed description of the present application through general description and specific embodiments. It should be understood that, based on the technical concept of the present application, several conventional adjustments or further innovations can be made to these specific embodiments; however, as long as they do not deviate from the technical concept of the present application, the technical solutions obtained by these conventional adjustments or further innovations also fall within the scope of protection of the claims of the present application.

Claims

1. A production process for a high-strength anti-brittle fracture bolt pair, characterized in that: The steps include: S1: selecting a processing substrate, and processing the processing substrate into a preformed bolt through a front-end preforming process, wherein the preformed bolt includes a bolt head and a polished rod connected to one end of the bolt head; S2: performing a head metal flow line test on the bolt head of the preformed bolt; S3: After the head metal flow line inspection is qualified, the preformed bolt is surface treated through a post-forming process, and threads are processed on the polished rod of the preformed bolt to obtain a formed bolt; S4: heat treating the formed bolts obtained by step S3, and the bolt processing is completed; The front-end preforming process in step S1 includes a bolt head preforming process, a surface treatment process and a drawing process; the back-end forming process in step S3 performs surface treatment on the preformed bolts including degreasing, dephosphorization, water washing and drying; The bolt head preforming process in the front-end preforming process includes plate forming and cold heading forming; The surface treatment process in the front-end preforming process includes pickling, water washing, phosphating, water washing, and saponification; The drawing process in the front-end preforming process includes fine drawing; The front-end preforming process also includes spheroidizing annealing of the processed substrate; A bolt head that has passed the head metal flow line test has a metal flow line formed in the center of the longitudinal section, and the thickness of the metal flow line is greater than or equal to one third of the thickness of the bolt head; The post-forming process in step S3 includes degreasing, two-step water washing, dephosphorization, water washing, and drying the preformed bolts formed by cold heading; In step S3, threads are processed on the polished rod of the preformed bolt by means of thread milling or thread rolling, and the polished rod is formed into a bolt rod.

2. The production process of the high-strength anti-brittle fracture bolt pair according to claim 1 is characterized in that: The processing flow of the front-end preforming process specifically includes the following steps: A disc element machine is used to press the processed substrate into a circular flat disc element blank, and the pressed flat disc element blank is subjected to spheroidizing annealing. The flat disc element blank that has completed spheroidizing annealing is pickled, washed with two steps of clean water, sprayed with clean water, phosphated, washed with water, and saponified. The flat disc element blank that has completed surface treatment is then drawn and fine-drawn, and the flat disc element blank is gradually thinned to obtain a drawn blank with the required diameter and length. The drawn blank is then cold-headed to obtain the preformed bolt.

3. The production process of the high-strength anti-brittle fracture bolt pair according to claim 2 is characterized in that: The cold heading forming of the drawn blank includes: cutting the drawn blank according to the target length to obtain a plurality of sections of cylindrical cold heading blanks, and sequentially performing one-die, two-die, three-die and four-die forming on each cylindrical cold heading blank; wherein the one-die is used to make the cross section of the cylindrical cold heading blank flat; the two-die is used to perform initial forging on the blank with a flat cross section after passing through the one-die, forming a bolt head forging rough portion at one end of the cylindrical cold heading blank, and forming a polished rod connected to the bolt head forging rough portion at the other end; the three-die is used to pre-form the bolt head after forging the bolt head forging rough portion, and the three-die is used to reduce the diameter and chamfer the polished rod; the four-die is used to cut a hexagonal outer contour on the bolt head preformed by the three-die, and form the bolt head into a hexagonal head.

4. A production process for a high-strength anti-brittle fracture bolt pair, characterized in that: The steps include: S1: selecting a processing substrate, and processing the processing substrate into a preformed bolt through a front-end preforming process, wherein the preformed bolt includes a bolt head and a polished rod connected to one end of the bolt head; S2: performing a head metal flow line test on the bolt head of the preformed bolt; S3: After the head metal flow line inspection is qualified, the preformed bolt is surface treated through a post-forming process, and threads are processed on the polished rod of the preformed bolt to obtain a formed bolt; S4: heat treating the formed bolts obtained by step S3, and the bolt processing is completed; The front-end preforming process in step S1 includes a bolt head preforming process, a surface treatment process and a drawing process; the back-end forming process in step S3 performs surface treatment on the preformed bolts including degreasing, dephosphorization, water washing and drying; The bolt head preforming process in the front-end preforming process includes cutting, plane chamfering and head forming; The surface treatment process in the front-end preforming process includes lime lubrication; The drawing process in the front-end preforming process includes drawing a fine wire; The processing flow of the front-end preforming process specifically includes the following steps: The processed substrate is lubricated with lime, and then the processed substrate is drawn and fine-lined to gradually reduce the diameter of the processed substrate to a target diameter, and then the drawn processed substrate is cut according to the target length to obtain a plurality of cylindrical blanks, and the end of each cylindrical blank is plane-chamfered, and then the blank after plane-chamfering is head-formed, and the heating length and heating time of the bolt are controlled during the head-forming process, and the preformed bolt is obtained by the hot bolting process; A bolt head that has passed the head metal flow line test has a broken flow line formed in the center of the longitudinal section, and the broken flow line is a wave pattern flow line; the formation position of the broken flow line is between one third and one half of the thickness of the bolt head; The post-forming process in step S3 includes shot blasting to remove oxide scale, chamfering the bolt head, saponifying phosphorus, reducing the diameter of the polished rod, degreasing, dephosphorizing, washing, and drying the preformed bolt after head forming; In step S3, threads are processed on the polished rod after the diameter reduction by means of grinding or rolling, and the polished rod is formed into a bolt rod.

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