High-temperature stretching process for fastener

Abstract

The invention provides a high-temperature stretching technology for a fastener. The high-temperature stretching technology comprises the following steps that S1, workpiece machining is conducted, specifically, a raw material is machined into a stretching blank with the needed size; s2, heating treatment: feeding the stretched blank into a heat treatment furnace for heating treatment, and keeping the temperature for a period of time after heating to a set temperature; s3, rapid cooling is conducted, specifically, oil cooling or an oil cooling and water cooling mode is used for rapidly cooling the stretched blank subjected to heating treatment; s4, tempering treatment: carrying out tempering treatment on the stretched blank for a period of time; and S5, normal-temperature cooling is conducted, specifically, the stretched blank obtained after tempering treatment is placed in a normal-temperature environment, and air cooling is conducted. The performance of the fastener can be improved, so that the fastener can be applied to a high-temperature environment.

Description

Technical Field

[0001] The present application relates to the technical field of fastener processing, and in particular to a fastener high-temperature stretching process. Background Art

[0002] Fasteners used in high-temperature environments, such as screws, will have their material properties changed under high temperature conditions, and higher requirements will be placed on their strength. For example, in nuclear power, fasteners will be in a high-temperature environment for a long time.

[0003] In order to ensure that the performance of fasteners in high temperature environments meets the requirements and is reliable, and to ensure that the molecular structure of fasteners does not change in high temperature environments, the fasteners need to be heat treated, and then subjected to room temperature tensile testing, high temperature endurance strength performance testing, and hardness testing to detect their performance. However, fasteners prepared by conventional heat treatment processes are difficult to meet performance requirements. Summary of the invention

[0004] In order to improve the performance of fasteners so that the fasteners can be used in high temperature environments, the present application provides a fastener high temperature stretching process.

[0005] The present application provides a fastener high temperature stretching process, which adopts the following technical solutions: A fastener high temperature stretching process, comprising the following steps: S1. Workpiece processing: Process the raw materials into the required size of the drawn raw materials; S2, heating treatment: sending the stretched wool into a heat treatment furnace for heating treatment, heating to a set temperature and then keeping the temperature for a period of time; S3. Rapid cooling: Use oil cooling or oil cooling plus water cooling to quickly cool the stretched wool after heating; S4, tempering treatment: tempering the stretched wool for a period of time; S5. Cooling at room temperature: Place the tempered stretched material in a room temperature environment for air cooling.

[0006] By adopting the above technical solution, the stretched wool is subjected to heat treatment, and the microstructure of the material is changed by high-temperature heating, thereby improving the hardness and strength of the material. The temperature of the stretched wool is quickly reduced by oil cooling or oil cooling plus water cooling. This step can further fix the microstructural changes produced during the heat treatment process and reduce the undesirable phase changes of the stretched wool during the cooling process, thereby obtaining better hardness and wear resistance. The material is then heated to a lower temperature and maintained for a period of time. This step can reduce the internal stress generated during the quenching process, improve the toughness and plasticity of the material, and reduce the brittle fracture of the material during use. The last step is to place the tempered stretched wool in a room temperature environment and let it cool naturally. This process helps to evenly distribute the temperature inside the stretched wool, reduce internal stress, and ensure the stable performance of the stretched wool.

[0007] Optionally, in step S2, the insulation time for the stretched wool material is T1 minutes, the diameter of the stretched wool material is D1 mm, and the relationship between the insulation time and the diameter of the stretched wool material is: T1=D1×6.

[0008] By adopting the above technical solution, the holding time is set according to the diameter of the stretched wool material, ensuring that the stretched wool material is evenly heated during the heat treatment process, thereby further improving the material performance.

[0009] Optionally, in step S4, the time for tempering the stretched wool is T2 minutes, and the relationship between the tempering time of the stretched wool and the diameter of the stretched wool is: T2=D1×8.

[0010] By adopting the above technical solution, the tempering treatment time is set according to the diameter of the stretched raw material, which helps to eliminate the internal stress generated during the heat treatment process and improve the stability and durability of the fastener.

[0011] Optionally, the following steps are also included: S6, take the sample; S7, mechanical properties test; S8, acid leaching low magnification test; S9, metallographic examination.

[0012] By adopting the above technical solution, a comprehensive quality inspection is carried out at the final stage of the process, including taking samples for mechanical property inspection, acid immersion low-magnification inspection and metallographic inspection, to ensure that the quality and performance of the fasteners meet the predetermined standards.

[0013] Optionally, step S7 specifically includes the following steps: S71, room temperature mechanical test: extract samples from each batch of stretched wool, fine-process the extracted samples to obtain stretched samples, and conduct mechanical tests on the stretched samples at room temperature. The mechanical properties of qualified products must meet the following requirements: tensile strength greater than or equal to 1275Mpa, yield strength greater than or equal to 1034Mpa, shrinkage greater than or equal to 15%, elongation greater than or equal to 12%, and hardness greater than or equal to 331HB.

[0014] By adopting the above technical solution, the stretched raw material is sampled at room temperature, and the mechanical properties of the stretched samples are tested, so as to judge the qualified products and ensure that the quality and performance of the fasteners meet the predetermined standards.

[0015] Optionally, step S7 further includes the following steps: S72, high temperature environment mechanical test: extract samples from each batch of stretched wool, and finely process the extracted samples to obtain stretched samples. Perform mechanical tests on the stretched samples in a high temperature environment of 649°C. The test time is at least 23 hours, and the stress is 690Mpa. The mechanical properties of qualified products must meet the following requirements: elongation after break (gauge length 4D) is greater than or equal to 5%.

[0016] By adopting the above technical solution, the stretched wool is sampled and the mechanical properties of the stretched samples are tested in a high temperature environment of 649°C, so as to judge the qualified products and ensure that the quality and performance of the fasteners meet the predetermined standards.

[0017] Optionally, in step S8, the specific steps of acid leaching low magnification inspection are: S81. Sample preparation: First, samples need to be taken from the stretched wool, and the drawn samples are finely processed to obtain stretched samples. Then, one side of the stretched samples is polished to facilitate subsequent acid leaching treatment; S82, acid leaching: immerse the sample in an acid solution and observe the chemical reaction between the acid and the metal surface; S83, cleaning and drying: After acid leaching, the sample needs to be removed from the acid solution, cleaned to remove the residual acid solution, and then dried; S84. Microscope observation: Use a microscope to observe the acid-etched samples to identify the microstructure of the material, such as grain size, grain boundaries and inclusions; S85. Analysis and evaluation: Evaluate the quality and performance of materials based on observed microstructural features and select qualified products.

[0018] By adopting the above technical solution, acid immersion low-magnification inspection can be used to detect the uniformity, microscopic defects and consistency of microstructure of materials, ensuring that the processing quality of materials and the performance of the final product meet the predetermined standards.

[0019] Optionally, in step S3, the cooling time is greater than or equal to 30 minutes. After cooling, the stretched wool is taken out from the cooling oil or cooling water, and the oil or water is drained for greater than or equal to 20 minutes; if the stretched wool is taken out from the cooling oil, the surface of the stretched wool is cleaned after the oil is drained.

[0020] By adopting the above technical solution, the drawn wool material needs to be drained of oil or water after being taken out from the cooling medium. If the drawn wool material is taken out from the cooling oil, the surface of the drawn wool material needs to be additionally cleaned to reduce the impact on subsequent steps.

[0021] Optionally, after step S9, step S10 is further included: rust prevention treatment, which specifically includes the following steps: S101, cleaning: cleaning the batches of stretched wool materials that have passed the inspection; S102, soaking in anti-rust liquid: soaking the drawn wool material in the anti-rust liquid; S103, rinsing: rinsing the stretched wool material in running clean water for several times; S104, drying: air-drying the washed stretched wool; S105, oiling: applying anti-rust oil on the surface of the stretched wool; S106. Packaging: Packaging and storing the stretched wool.

[0022] By adopting the above technical solution, after the stretch wool is heat treated and sampled for testing, the qualified batch of stretch wool is subjected to rust-proof treatment, which can effectively protect the stretch wool, reduce rust and extend its service life.

[0023] In summary, the present application includes at least one of the following beneficial effects: 1. Through specific heat treatment and cooling steps, the high temperature stretching process of fasteners can improve the performance of fasteners in high temperature environments, so that they maintain good strength and stability, meeting the use requirements in high temperature environments; 2. Set the holding time according to the diameter of the stretched wool material to ensure that the stretched wool material is evenly heated during the heat treatment process, which is conducive to further improving the material performance; 3. By setting the tempering time related to the diameter of the stretched raw material, it helps to eliminate the internal stress generated during the heat treatment process and improve the stability and durability of the fastener; 4. Through comprehensive quality inspection steps, including taking samples for mechanical property inspection, acid immersion low-magnification inspection and metallographic inspection, it is ensured that the quality and performance of fasteners meet the predetermined standards, thereby improving the reliability and safety of the products. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1is a process flow chart of a high temperature stretching process of a fastener according to an embodiment of the present application; DETAILED DESCRIPTION The following is combined with Figure 1 This application is described in further detail.

[0025] The embodiment of the present application provides a fastener high temperature stretching process, comprising the following steps: S1. Workpiece processing: According to actual needs, the raw materials are processed into the required size of the drawn raw materials. This step is to provide the appropriate workpiece size and shape for the subsequent heat treatment and cooling process.

[0026] S2. Heating treatment: The stretched wool is sent to a heat treatment furnace for heating treatment. After heating to 830°C to 900°C, the holding time T1 is determined according to the diameter D1 of the stretched wool. The specific relationship is T1=D1×6, where T1 is in minutes and D1 is in mm. This step helps to ensure that the stretched wool is evenly heated during the heating process, improve the material properties, change the microstructure of the material through high-temperature heating, and improve the hardness and strength of the material.

[0027] S3. Rapid cooling: After the heating treatment is completed, the drawn wool is rapidly cooled by oil cooling or oil cooling plus water cooling. The cooling time is greater than or equal to 30 minutes to ensure that the material quickly passes through the martensitic transformation zone to obtain the ideal structure and performance. After the cooling is completed, the drawn wool is taken out of the cooling medium and drained for oil or water for a time greater than or equal to 20 minutes. If the drawn wool is taken out of the cooling oil, its surface needs to be cleaned after the oil is drained to remove the residual oil stains.

[0028] S4, tempering treatment: After rapid cooling, the stretched raw material is tempered. The tempering time T2 is determined according to the diameter D1 of the stretched raw material, and the specific relationship is T2=D1×8, where T2 is in minutes and D1 is in mm. Tempering treatment helps to eliminate the internal stress generated during the heat treatment process and improve the stability and durability of the fastener. At the same time, by adjusting the tempering temperature and time, the performance and organizational structure of the material can be further optimized, the toughness and plasticity of the material can be improved, and the brittle fracture of the material during use can be reduced.

[0029] S5. Cooling at room temperature: After tempering, the drawn material is placed in a room temperature environment for air cooling. This step is to slowly cool the drawn material to room temperature. This process helps to evenly distribute the temperature inside the material, reduce internal stress, and ensure stable material performance.

[0030] S6. Sample collection: Take a part of a batch of drawn wool for fine processing and use it as a sample for inspection; S7, mechanical property test. Step S7 specifically includes steps S71 and S72.

[0031] S71, Room temperature mechanical test: Take samples from each batch of stretched wool and perform mechanical tests at room temperature. Qualified products need to meet the following mechanical performance standards: tensile strength greater than or equal to 1275MPa, yield strength greater than or equal to 1034MPa, shrinkage greater than or equal to 15%, elongation greater than or equal to 12%, hardness greater than or equal to 331HB. These standards ensure that the fasteners have sufficient strength and toughness at room temperature.

[0032] S72, High temperature environment mechanical test: Take samples from each batch of stretched wool and conduct mechanical tests in a high temperature environment of 649℃. The test time is at least 23 hours, and the stress is 690Mpa. Qualified products need to meet the following mechanical performance standards: elongation after fracture (gauge length 4D) is greater than or equal to 5%. This test is designed to simulate the use of fasteners in high temperature environments to ensure that they can maintain good performance after long-term high temperature exposure.

[0033] S8, acid leaching low magnification inspection. Step S8 includes steps S81-S85.

[0034] S81. First, it is necessary to take samples from the stretched raw material, fine-process the extracted samples to obtain stretched samples, and then grind one side of the stretched sample to facilitate subsequent acid leaching treatment.

[0035] S82. Acid leaching: Immerse the sample in an acidic solution. The acid will react chemically with the metal surface, making the microstructural characteristics of the material more obvious.

[0036] S83. Cleaning and drying: After acid leaching, remove the sample from the acid solution, clean it to remove residual acid, and then dry it.

[0037] S84. Microscope observation: Use a microscope to observe the samples after pickling and identify the microstructure of the material, such as grain size, grain boundaries and inclusions.

[0038] S85, Analysis and evaluation: Based on the observed microstructural features, evaluate the quality and performance of the material and select qualified products. Through acid immersion low-magnification inspection, we can have a deeper understanding of the internal structure and quality of the fasteners, providing strong support for ensuring their high-temperature performance.

[0039] S9. Metallographic inspection. Metallographic inspection can observe the microstructure of the drawn material, such as grain size, morphology and distribution, which directly affect the mechanical properties of the drawn material, such as strength, toughness and hardness. Metallographic inspection can analyze the phase composition of the material, including the distribution of different phases and interface characteristics. Metallographic inspection can also identify defects inside the material, such as inclusions, cracks and holes, which may affect the integrity and durability of the material.

[0040] In steps S7-S9, if the mechanical properties test, acid immersion low-magnification test and metallographic test are found to be unqualified, it is allowed to take double the number of samples of the batch for re-testing the unqualified items. If the re-testing fails, all the drawn raw materials corresponding to the heat treatment batch should be scrapped.

[0041] S10, anti-rust treatment. After the stretch wool material is heat treated and sampled for testing, the stretch wool material of the qualified batch is subjected to anti-rust treatment, which can effectively protect the stretch wool material, reduce corrosion, and extend its service life. Step S10 includes S101-S106.

[0042] S101, cleaning: Clean the stretched wool that has passed the inspection to remove oil and impurities on the surface.

[0043] S102. Immersion in anti-rust liquid: Immerse the drawn wool in anti-rust liquid to form an anti-rust film to reduce rust on the fasteners during use.

[0044] S103, rinsing: rinse the drawn wool in running clean water for several times to remove excess anti-rust liquid and impurities.

[0045] S104, drying: air-dry the cleaned stretched wool to ensure that the surface is dry and free of moisture.

[0046] S105, oiling: Apply a layer of anti-rust oil on the surface of the stretched wool to further enhance the anti-rust effect.

[0047] S106. Packaging: Pack and store the stretched wool to reduce damage or contamination during storage and transportation.

[0048] The implementation principle of a high-temperature stretching process for fasteners in the embodiment of the present application is: through specific heat treatment and cooling steps and matching holding time and tempering treatment time settings, the fasteners can still maintain excellent performance in a high temperature environment. Through comprehensive quality inspection steps, including taking samples for mechanical property inspection, acid immersion low-magnification inspection and metallographic inspection, it is ensured that the quality and performance of the fasteners meet the predetermined standards.

[0049] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A fastener high temperature stretching process, characterized in that: The following steps are involved: S1. Workpiece processing: Processing the raw materials into the required size of the drawn raw materials; S2, heating treatment: sending the stretched wool into a heat treatment furnace for heating treatment, heating to a set temperature and then keeping the temperature for a period of time; S3. Rapid cooling: Use oil cooling or oil cooling plus water cooling to quickly cool the stretched wool after heating; S4, tempering treatment: tempering the stretched wool for a period of time; S5. Cooling at room temperature: Place the tempered stretched material in a room temperature environment for air cooling.

2. A fastener high temperature stretching process according to claim 1, characterized in that: In step S2, the holding time of the stretched wool material is T1 minutes, the diameter of the stretched wool material is D1 mm, and the relationship between the holding time and the diameter of the stretched wool material is: T1=D1×6.

3. A fastener high temperature stretching process according to claim 2, characterized in that: In step S4, the time for tempering the stretched wool is T2 minutes, and the relationship between the tempering time of the stretched wool and the diameter of the stretched wool is: T2=D1×8.

4. A fastener high temperature stretching process according to claim 1, characterized in that: The following steps are also included: S6, take the sample; S7, mechanical properties test; S8, acid leaching low magnification test; S9, metallographic examination.

5. A fastener high temperature stretching process according to claim 4, characterized in that: Step S7 specifically includes the following steps: S71, room temperature mechanical test: extract samples from each batch of stretched wool, fine-process the extracted samples to obtain stretched samples, and conduct mechanical tests on the stretched samples at room temperature. The mechanical properties of qualified products must meet the following requirements: tensile strength greater than or equal to 1275Mpa, yield strength greater than or equal to 1034Mpa, shrinkage greater than or equal to 15%, elongation greater than or equal to 12%, and hardness greater than or equal to 331HB.

6. A fastener high temperature stretching process according to claim 5, characterized in that: Step S7 also includes the following steps: S72, high temperature environment mechanical test: extract samples from each batch of stretched wool, and finely process the extracted samples to obtain stretched samples. Perform mechanical tests on the stretched samples in a high temperature environment of 649°C. The test time is at least 23 hours, and the stress is 690Mpa. The mechanical properties of qualified products must meet the following requirements: elongation after break (gauge length 4D) is greater than or equal to 5%.

7. A fastener high temperature stretching process according to claim 4, characterized in that: In step S8, the specific steps of acid leaching low-magnification inspection are: S81. Sample preparation: First, samples need to be taken from the stretched wool, and the drawn samples are finely processed to obtain stretched samples. Then, one side of the stretched samples is polished to facilitate subsequent acid leaching treatment; S82, acid leaching: immerse the sample in an acid solution and observe the chemical reaction between the acid and the metal surface; S83, cleaning and drying: After acid leaching, the sample needs to be removed from the acid solution, cleaned to remove the residual acid solution, and then dried; S84. Microscope observation: Use a microscope to observe the acid-etched samples to identify the microstructure of the material, such as grain size, grain boundaries and inclusions; S85. Analysis and evaluation: Evaluate the quality and performance of materials based on observed microstructural features and select qualified products.

8. A fastener high temperature stretching process according to claim 1, characterized in that: In step S3, the cooling time is greater than or equal to 30 minutes. After cooling, the drawn wool material is taken out from the cooling oil or cooling water, and the oil or water is drained for greater than or equal to 20 minutes. If the drawn wool material is taken out from the cooling oil, the surface of the drawn wool material is cleaned after the oil is drained.

9. A fastener high temperature stretching process according to claim 4, characterized in that: After step S9, step S10 is also included: rust prevention treatment, which specifically includes the following steps: S101, cleaning: cleaning the batches of stretched wool materials that have passed the inspection; S102, soaking in anti-rust liquid: soaking the drawn wool material in the anti-rust liquid; S103, rinsing: rinsing the stretched wool material in running clean water for several times; S104, drying: air-drying the washed stretched wool; S105, oiling: applying anti-rust oil on the surface of the stretched wool; S106. Packaging: Packaging and storing the stretched wool.

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