Analysis and treatment process for fracture caused by surface defects and internal structure abnormity of spring steel

Abstract

The invention relates to the technical field of spring steel processing, and discloses a method for analyzing fracture caused by surface defects and internal structure abnormity of spring steel, which comprises the following steps: S1, sample information collection, S2, macroscopic morphology observation, S3, metallographic analysis, S4, component analysis, and S5, macrostructure rating and hardness detection. According to the analysis and treatment process for the fracture caused by the abnormal surface defects and internal structures of the spring steel, the analysis and treatment process improves the product quality, the surface defects of the spring steel are effectively reduced, the surface quality is improved, and the fracture risk caused by the surface problems is reduced through the measures of enhancing raw material inspection, optimizing the machining process, performing surface protection treatment and the like; according to the analysis and treatment process, the internal structure performance is optimized, composition segregation is reduced by optimizing the continuous casting process, abnormal structures are eliminated by improving the heat treatment process, the decarburization phenomenon is controlled, the internal structure of the spring steel is homogenized, and the toughness and strength of the spring steel are improved.

Description

Technical Field

[0001] The invention relates to the technical field of spring steel processing, in particular to an analysis and treatment process of fractures caused by surface defects and internal structural abnormalities of spring steel. Background Art

[0002] In the modern industrial field, spring steel, as a key basic material, is widely used in many industries such as automobile manufacturing, mechanical engineering, aerospace, etc. In the automotive suspension system, engine valve springs, and mechanical elastic elements, spring steel plays an important functional role due to its good elasticity, high strength and fatigue resistance. However, as industrial production develops towards high precision and high reliability, the requirements for spring steel quality are becoming more and more stringent.

[0003] In the actual production and use process, spring steel faces complex processing technology and service environment. Drawing, spring winding and other operations in the processing link are prone to cause surface damage to spring steel due to improper process, resulting in mechanical scratches, scrapes and other defects. In the continuous casting process, component segregation, the appearance of abnormal structure, and decarburization during heat treatment have become potential factors affecting the internal quality of spring steel. These surface defects and internal structural abnormalities greatly reduce the fatigue strength and comprehensive performance of spring steel, resulting in frequent fracture failures in subsequent use, seriously affecting the quality, reliability and service life of related products, and even causing safety hazards, increasing the production cost and after-sales risk of enterprises. Therefore, in-depth research on the causes of spring steel fracture and proposing effective treatment processes have become key issues that need to be urgently solved in the industry. Summary of the invention

[0004] 1. Technical issues to be resolved In view of the deficiencies in the prior art, the present invention provides an analysis and treatment process for fracture caused by surface defects and internal structural abnormalities of spring steel, which has the advantages of improving product quality, etc. It solves the problem that surface defects and internal structural abnormalities greatly reduce the fatigue strength and comprehensive performance of spring steel, leading to frequent fracture and failure in subsequent use, seriously affecting the quality of related products.

[0005] (II) Technical solution In order to achieve the above-mentioned purpose of improving product quality, the present invention provides the following technical solution: Analysis of the surface defects and internal structural abnormalities of spring steel leading to fracture, comprising the following steps: S1 collects sample information: After receiving the broken spring steel sample, record the sample's specifications, source, usage and working condition information when it broke in detail; S2 macroscopic morphology observation: Observe the macroscopic morphology of the fracture surface with the naked eye or a stereo microscope to determine the fracture origin and crack propagation direction; S3 Metallographic Analysis: Sampling: Samples are taken from the cross-section and longitudinal section near the fracture surface to ensure that the samples can represent the tissue characteristics of the fracture area; Sample Preparation and Observation: The samples are prepared and ground, and the metallographic structure is observed at different magnifications. Common metallographic structures include tempered troostite, sorbite, pearlite, and ferrite. For example, the metallographic structure of some samples is tempered troostite, but there are abnormal structures, such as undeformed bright bands and segregation bands, and there are also voids and microcrack defects in some areas; S4 Composition Analysis: Use appropriate analysis methods to analyze the composition near the fracture surface or at specific positions, compare with the standard composition requirements, and judge whether the composition is qualified and uniform; S5 Macrostructure Rating and Hardness Testing: The samples are rated for macrostructure, and whether there are defects such as porosity, shrinkage cavity, and cracks is observed, and the hardness is measured to judge whether it meets the process standards. The macrostructure rating of some samples is general porosity level 1.0. Although there are no shrinkage cavity and crack defects, abnormal hardness may also affect the performance of spring steel.

[0006] Preferably, the reasons obtained from S1 - S5 are as follows: Reason 1, fracture caused by surface defects: Surface mechanical damage, scratches, scabs, or foreign object indentation defects become stress concentration sources when the spring steel is stressed, reducing the fatigue strength and causing fracture. For example, during drawing or coiling, the damaged area on the surface is prone to crack first; Reason 2, fracture caused by abnormal internal structure; Segregation: During continuous casting of spring steel, due to composition segregation, the structure is uneven. In subsequent processing and use, the segregation area becomes a weak point, causing fracture. For example, there are obvious segregation bands in the core of some samples, and there are microcracks near the segregation bands; Abnormal structure: Such as the appearance of bright band structure, which is generated after heat treatment, has poor toughness and is prone to cracking; Decarburization: Decarburization on the surface of spring steel reduces the surface hardness and fatigue strength. When the decarburized layer depth reaches a certain level, an unstrengthened layer is formed on the surface, making it easy for the fracture source to generate on the surface; Reason 3, fracture caused by abnormal composition; The content of alloying elements in spring steel does not meet the standards or there are harmful elements, which affects its strength, toughness, and fatigue performance. For example, in some cases, the content of harmful element P is too high, reducing the plasticity and toughness of the steel.

[0007] Preferably, the treatment process for Reason 1 includes the following steps: Strengthen raw material inspection: During the procurement and production processes, strictly inspect the surface quality of spring steel. Use non-destructive testing techniques (such as magnetic particle inspection and ultrasonic testing) to detect surface defects, and promptly handle unqualified raw materials; Optimize the processing technology: In the processes of wire drawing and spring coiling, control the processing parameters to avoid surface damage caused by over-processing. Adopt advanced processing equipment and technology to reduce the generation of surface defects. For example, optimize the die design to reduce surface friction; Surface protection treatment: Conduct surface protection treatment on spring steel, such as coating with anti-rust paint and phosphating, to prevent surface damage during processing and use.

[0008] Preferably, the treatment process for reason two includes the following procedures: Optimize the continuous casting process: Control the cooling rate and casting speed parameters during continuous casting. Adopt electromagnetic stirring technology to reduce component segregation and homogenize the structure; Improve the heat treatment process: For spring steel with abnormal structures, adjust the heat treatment temperature, time, and cooling method. For example, appropriately extend the tempering time to eliminate the white bright band structure and improve the tissue performance; Control decarburization: During the heat treatment process, control the heating atmosphere, use protective gas heating to reduce surface decarburization. For spring steel that has already undergone decarburization, surface carburizing treatment can be carried out to restore the surface carbon content and improve surface hardness and fatigue strength.

[0009] Preferably, the treatment process for reason three includes the following procedures; Strictly control the quality of raw materials: Select reliable raw material suppliers, strengthen the inspection of incoming raw materials, and ensure that the alloy element content meets the standard requirements; Optimize the composition design: According to the usage requirements and performance characteristics of spring steel, optimize the composition design, reasonably adjust the alloy element content, and improve the comprehensive performance of spring steel; Refining treatment: During the steelmaking process, adopt a refining process to remove harmful impurity elements and improve the purity of the steel.

[0010] (III) Beneficial effects Compared with the prior art, the present invention provides an analysis and treatment process for spring steel surface defects and internal tissue abnormalities leading to fracture, having the following beneficial effects: 1. The analysis and treatment process for spring steel surface defects and internal tissue abnormalities leading to fracture can improve product quality: By strengthening raw material inspection, optimizing the processing technology, and surface protection treatment and other measures, effectively reduce the surface defects of spring steel, improve the surface quality, and reduce the fracture risk caused by surface problems, thereby enhancing the overall quality and stability of the final product.

[0011] 2. Analysis and treatment process for spring steel surface defects and abnormal internal structure leading to fracture. This analysis and treatment process optimizes the internal structure performance: by optimizing the continuous casting process to reduce composition segregation, improving the heat treatment process to eliminate abnormal structures, controlling decarburization phenomena, homogenizing the internal structure of spring steel, improving its toughness and strength, and enhancing the reliability of the product under complex working conditions. Detailed implementation manners

[0012] The following will describe the technical solutions in the embodiments of the present invention clearly and completely in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0013] Analysis of spring steel surface defects and abnormal internal structure leading to fracture includes the following steps: S1 Collect sample information: After receiving the fractured spring steel sample, record in detail the sample specifications, source, usage, and working condition information at the time of fracture. For example, in a certain case, it was recorded that the sample fractured during the drawing or spring coiling process, as well as the original and processed specifications of the sample. S2 Macroscopic morphology observation: Observe the macroscopic morphology of the fracture surface through the naked eye or a stereomicroscope to determine the fracture origin location and crack propagation direction. For example, in some samples, the fracture origin is on the surface, and there are obvious mechanical damages, scratch bands, or pit defects on the surface; in some, the origin is inside, showing patterns that diverge from a point to the surroundings. S3 Metallographic analysis: Sampling: Take samples from the cross-section and longitudinal section near the fracture surface to ensure that the samples can represent the tissue characteristics of the fracture area. Sample preparation and observation: Process the samples for sample preparation and grinding, and observe the metallographic structure at different magnifications. Common metallographic structures include tempered troostite, sorbite, pearlite, and ferrite. For example, the metallographic structure of some samples is tempered troostite, but there are abnormal structures such as undeformed bright bands, segregation bands, and there are also voids and microcrack defects in some areas. S4 Composition analysis: Use appropriate analysis methods to analyze the composition near the fracture surface or at specific positions, compare with the standard composition requirements, and judge whether the composition is qualified and uniform. For example, in some cases, it is found that the content of harmful elements is too high or the content of some alloy elements is abnormal, affecting the performance of spring steel. S5 Low-power structure grading and hardness testing: The sample is subjected to macrostructure grading to observe whether there are porosity, shrinkage cavity, and crack defects, and the hardness is detected to determine whether it meets the process standards. The macrostructure grading of some samples is general porosity level 1.0. Although no shrinkage cavity and crack defects are found, abnormal hardness may also affect the properties of spring steel; Reason 1: Fracture caused by surface defects: Surface mechanical damage, scratches, scabs, or foreign object indentation defects become stress concentration sources when the spring steel is stressed, reducing the fatigue strength and causing fracture. For example, during wire drawing or spring winding, the damaged area on the surface is prone to crack first; Reason 2: Fracture caused by abnormal internal structure; Segregation: During continuous casting of spring steel, due to composition segregation, the structure is uneven. In subsequent processing and use, the segregated area becomes a weak point, causing fracture. For example, obvious segregation bands exist in the core of some samples, and there are microcracks near the segregation bands; Abnormal structure: Such as the appearance of white bright band structure, which is generated after heat treatment, has poor toughness, and is prone to cracking; Decarburization: Decarburization on the surface of spring steel reduces the surface hardness and fatigue strength. When the depth of the decarburized layer reaches a certain level, an unstrengthened layer is formed on the surface, making it easy for fracture sources to occur on the surface; Reason 3: Fracture caused by abnormal composition; The content of alloying elements in spring steel does not meet the standards or there are harmful elements, which affect its strength, toughness, and fatigue performance. For example, in some cases, the content of harmful element P is too high, reducing the plasticity and toughness of the steel; The treatment process for Reason 1 includes the following steps: Strengthen raw material inspection: During procurement and production, strictly inspect the surface quality of spring steel, use non-destructive testing techniques (such as magnetic particle inspection, ultrasonic inspection) to detect surface defects, and promptly process unqualified raw materials; Optimize the processing technology: In the wire drawing and spring winding processes, control the processing parameters to avoid surface damage caused by overprocessing. Adopt advanced processing equipment and technology to reduce the generation of surface defects. For example, optimize the die design to reduce surface friction; Surface protection treatment: Carry out surface protection treatment on spring steel, such as coating with anti-rust paint and phosphating treatment, to prevent surface damage during processing and use; The treatment process for Reason 2 includes the following steps: Optimize the continuous casting process: Control the cooling rate and billet withdrawal speed parameters during continuous casting, and use electromagnetic stirring technology to reduce composition segregation and make the structure uniform; Improve the heat treatment process: For spring steel with abnormal structure, adjust the heat treatment temperature, time, and cooling method. For example, appropriately extend the tempering time to eliminate the white bright band structure and improve the tissue performance; Controlling decarburization: During the heat treatment process, control the heating atmosphere, use protective gas for heating to reduce surface decarburization. For spring steel that has already undergone decarburization, surface carburization treatment can be carried out to restore the surface carbon content and improve the surface hardness and fatigue strength; The treatment process for reason three includes the following processes; Strictly control the quality of raw materials: Select reliable raw material suppliers, strengthen the inspection of incoming raw materials to ensure that the alloy element content meets the standard requirements; Optimize the composition design: According to the usage requirements and performance characteristics of spring steel, optimize the composition design, reasonably adjust the alloy element content, and improve the comprehensive performance of spring steel; Refining treatment: During the steelmaking process, adopt a refining process to remove harmful impurity elements and improve the purity of the steel.

[0014] Furthermore, this analysis and treatment process improves product quality: By strengthening raw material inspection, optimizing processing technology, and surface protection treatment and other measures, effectively reduce the surface defects of spring steel, improve the surface quality, and reduce the fracture risk caused by surface problems, thereby enhancing the overall quality and stability of the final product; Furthermore, this analysis and treatment process optimizes the internal tissue performance: By optimizing the continuous casting process to reduce composition segregation, improving the heat treatment process to eliminate abnormal tissues, and controlling the decarburization phenomenon, make the internal tissue of spring steel uniform, improve its toughness and strength, and enhance the reliability of the product under complex working conditions; Furthermore, this analysis and treatment process reduces production costs: Control the quality of raw materials from the source, reasonably optimize the composition design, and adopt a refining process to remove harmful impurities, which not only improves the purity of the steel, but also reduces the scrap rate and rework costs caused by abnormal composition. At the same time, it reduces the after-sales repair and replacement costs caused by spring steel fracture; Furthermore, this analysis and treatment process ensures production and use safety: Effectively reduce the occurrence of spring steel fracture accidents, reduce the safety hazards caused by product failure, provide reliable guarantee for the safety production and product use of related industries, and safeguard the reputation of enterprises and the rights and interests of consumers.

[0015] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made in these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Analysis of fracture caused by surface defects and abnormal internal structure of spring steel, characterized in that: It includes the following steps: S1 Collect sample information: After receiving the fractured spring steel sample, record in detail the specifications, source, usage conditions of the sample, and the working conditions at the time of fracture; S2 Macroscopic morphology observation: Observe the macroscopic morphology of the fracture surface through naked eyes or a stereomicroscope to determine the fracture origin location and crack propagation direction; S3 Metallographic analysis: Sampling: Take samples from the cross-section and longitudinal section near the fracture surface to ensure that the samples can represent the tissue characteristics of the fracture area; Sample preparation and observation: Carry out sample preparation and grinding treatment on the samples, observe the metallographic structure at different magnification levels. Common metallographic structures include tempered troostite, sorbite, pearlite, and ferrite. For example, the metallographic structure of some samples is tempered troostite, but there are abnormal structures such as non-deformable white bright bands and segregation bands, and there are also voids and microcrack defects in some areas; S4 Composition analysis: Use appropriate analysis methods to perform composition analysis on the area near the fracture surface or specific locations, compare with the standard composition requirements, and judge whether the composition is qualified and uniform; S5 Low-power structure rating and hardness testing: Carry out low-power structure rating on the samples, observe whether there are defects such as porosity, shrinkage cavity, and cracks, and detect the hardness to judge whether it meets the process standards. The low-power rating of some samples is general porosity level 1.

0. Although there are no shrinkage cavity and crack defects, abnormal hardness may also affect the performance of spring steel.

2. Analysis of spring steel fracture caused by surface defects and abnormal internal structure according to claim 1, characterized in that: The following reasons are obtained from S1 - S5: Reason 1: Fracture caused by surface defects: Surface mechanical damage, scratches, scabs, or foreign object pressing-in defects become stress concentration sources when the spring steel is stressed, reducing the fatigue strength and causing fracture. For example, during the drawing or spring winding process, the damaged area on the surface is prone to crack first; Reason 2: Fracture caused by abnormal internal structure; Segregation: During the continuous casting process of spring steel, due to composition segregation, the structure is uneven. In subsequent processing and use, the segregation area becomes a weak point, causing fracture. For example, there are obvious segregation bands in the core of some samples, and there are microcracks near the segregation bands; Abnormal structure: Such as the appearance of white bright band structure, which is generated after heat treatment, has poor toughness, and is prone to crack; Decarburization: Decarburization on the surface of spring steel will reduce the surface hardness and fatigue strength. When the decarburized layer depth reaches a certain level, an unstrengthened layer is formed on the surface, making the fracture origin prone to occur on the surface; Reason 3: Fracture caused by abnormal composition; The content of alloying elements in spring steel does not meet the standards or there are harmful elements, which affect its strength, toughness, and fatigue performance. For example, in some cases, the content of harmful element P is on the high side, reducing the plasticity and toughness of the steel.

3. The treatment process for fracture caused by surface defects and abnormal internal structure of spring steel according to claim 2, characterized in that: The treatment process for Reason 1 includes the following procedures: Strengthen raw material inspection: During procurement and production, strictly inspect the surface quality of spring steel, use non-destructive testing techniques (such as magnetic particle inspection, ultrasonic inspection) to detect surface defects, and promptly handle unqualified raw materials; Optimize the processing technology: In the drawing and spring winding processing procedures, control the processing parameters to avoid surface damage caused by overprocessing, adopt advanced processing equipment and technology to reduce the generation of surface defects. For example, optimize the die design to reduce surface friction; Surface protection treatment: Carry out surface protection treatment on spring steel, such as coating with anti-rust paint and phosphating treatment, to prevent surface damage during processing and use.

4. The treatment process for fracture caused by surface defects and abnormal internal structure of spring steel according to claim 2, characterized in that: The treatment process for Reason 2 includes the following steps: Optimize the continuous casting process: Control the cooling rate and billet withdrawal speed parameters during continuous casting, and adopt electromagnetic stirring technology to reduce composition segregation and homogenize the structure; Improve the heat treatment process: For spring steel with abnormal structure, adjust the heat treatment temperature, time, and cooling method. For example, appropriately extend the tempering time to eliminate the white bright band structure and improve the structure performance; Control decarburization: During the heat treatment process, control the heating atmosphere, use protective gas heating to reduce surface decarburization. For spring steel that has already undergone decarburization, surface carburizing treatment can be carried out to restore the surface carbon content, improve surface hardness and fatigue strength.

5. The treatment process for fracture caused by surface defects and abnormal internal structure of spring steel according to claim 2, characterized in that: The treatment process for Reason 3 includes the following steps; Strictly control the quality of raw materials: Select reliable raw material suppliers, strengthen the inspection of raw materials when they enter the factory, and ensure that the alloy element content meets the standard requirements; Optimize the composition design: According to the usage requirements and performance characteristics of spring steel, optimize the composition design, reasonably adjust the alloy element content, and improve the comprehensive performance of spring steel; Refining treatment: During the steelmaking process, adopt refining technology to remove harmful impurity elements and improve the purity of the steel.