Hot-rolled acid-pickled carbon structural steel for automobile structure and production method of hot-rolled acid-pickled carbon structural steel

Abstract

The invention relates to the technical field of strip steel production and processing, in particular to hot-rolled acid-pickled carbon structural steel for an automobile structure and a production method of the hot-rolled acid-pickled carbon structural steel. A hot-rolled coil meeting the standard is selected as a raw material, cutting operation is carried out, the utilization rate and the processing efficiency of the raw material are improved, and a multi-pass rolling process can reduce the production cost on the premise that the steel quality is guaranteed. Energy consumption in the rolling process is reduced, environment-friendly mixed acid liquor is adopted for acid pickling, pollution to the environment in the acid pickling process can be effectively reduced, an improved YOLOv5-based steel surface defect detection model is adopted for efficiently and accurately detecting steel, a machine vision technology is adopted for size precision detection, and the detection precision is improved. The mechanical property detection adopts a mechanical property prediction model for prediction, so that the intelligent level of a detection link and the accuracy of a detection result are improved, and the technical problems of low production efficiency, relatively high energy consumption, environmental pollution risk and insufficient intelligence of the detection link in the production method of the structural steel for the automobile in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of strip steel production and processing, and particularly to a hot-rolled pickled carbon structural steel for automobile structures and a production method thereof. Background Art

[0002] In the booming development of the automobile manufacturing industry, structural steel, as the basic material for constructing the automobile skeleton and various components, its quality and performance are directly related to the safety, durability, and riding comfort of the whole vehicle. With the rapid development of the automobile industry and the increasing improvement of consumers' requirements for automobile quality, the demand for structural steel for automobiles also shows a trend of diversification and high quality. Hot-rolled pickled carbon structural steel, as a type of steel widely used in the automobile manufacturing field, has become one of the preferred materials for automobile manufacturers due to its good mechanical properties, processing performance, and cost-effectiveness.

[0003] However, the production methods of structural steel for automobiles in the prior art have problems such as low production efficiency, high energy consumption, environmental pollution risks, and insufficient intelligence in the inspection link. Summary of the Invention

[0004] The purpose of the present invention is to provide a hot-rolled pickled carbon structural steel for automobile structures and a production method thereof, aiming to solve the technical problems of low production efficiency, high energy consumption, environmental pollution risks, and insufficient intelligence in the inspection link existing in the production methods of structural steel for automobiles in the prior art.

[0005] To achieve the above purpose, a production method of a hot-rolled pickled carbon structural steel for automobile structures adopted by the present invention includes the following steps:

[0006] Select a hot-rolled coil that meets the standards as the raw material, ensure that the parameters of the raw material meet the requirements, and then perform a slitting operation on the hot-rolled coil to cut it into a size specification that meets the requirements of subsequent processing;

[0007] Feed the cut raw material into a continuous pickling line, and use an environmentally friendly mixed acid solution and an efficient spraying system to continuously pickle the raw material;

[0008] Feed the pickled raw material into an intelligent softening annealing device for softening annealing treatment;

[0009] Feed the steel after softening annealing into a rolling mill for multi-pass rolling, and obtain the steel with the required thickness and width by precisely controlling the rolling force and reduction;

[0010] Perform spheroidizing annealing treatment on the rolled steel and then perform finishing treatment;

[0011] Inspect the steel after finishing treatment, and after passing the inspection, perform slitting processing according to the requirements to make products of different specifications and lengths;

[0012] The cut steel is subjected to rust prevention treatment and then packaged with packaging materials.

[0013] Among them, when ensuring that the parameters of the raw materials meet the requirements, the parameters include chemical composition, dimensional accuracy, and surface quality;

[0014] When performing the shearing operation on the hot-rolled coil, it should be ensured that the sheared edge is neat, without obvious burrs and defects.

[0015] Among them, during the continuous pickling of the raw materials using an environmentally friendly mixed acid solution and an efficient spraying system, the environmentally friendly mixed acid solution is an acid solution prepared by mixing hydrochloric acid and sulfuric acid in a ratio of 3:1;

[0016] The pickling temperature is 50 - 70 °C, the acid concentration is 15 - 20%, the pickling time is 4 - 8 minutes, and after pickling, cleaning and passivation treatments are required.

[0017] Among them, the preparation method of the environmentally friendly mixed acid solution is as follows:

[0018] Weigh hydrochloric acid and sulfuric acid according to a mass ratio of 3:1. Slowly pour the hydrochloric acid into an acid-resistant corrosion container, and slowly add sulfuric acid while stirring. Stir for 10 - 15 minutes to make them fully mixed evenly, and prepare an environmentally friendly mixed acid solution with hydrochloric acid and sulfuric acid mixed in a ratio of 3:1.

[0019] Among them, when performing softening annealing treatment on the pickled raw materials, it should be under the protection atmosphere of a nitrogen-hydrogen mixed gas. The annealing temperature is 680 - 720 °C, the holding time is 2.5 hours, and the cooling rate is 6 - 8 °C / min.

[0020] Among them, the inspection methods for the finished steel after finishing include appearance quality inspection, dimensional accuracy inspection, mechanical property inspection, and chemical composition inspection;

[0021] For appearance quality inspection, a steel surface defect detection model based on improved YOLOv5 is used to efficiently and accurately detect defects such as cracks, pitting, inclusions, and scratches on the steel surface;

[0022] For dimensional accuracy inspection, machine vision technology is used. Images of the steel are collected through an industrial camera, and image processing algorithms are used to accurately measure and analyze the dimensions of the steel to ensure that the dimensional accuracy of the steel meets the requirements;

[0023] For mechanical property inspection, a mechanical property prediction model is used for prediction;

[0024] For chemical composition inspection, a spectral analyzer device is used to detect the chemical composition of the steel to ensure that the chemical composition of the steel meets the standard requirements.

[0025] Among them, the steel surface defect detection model is based on the YOLOv5 algorithm, and the YOLOv5s-ADW algorithm is proposed. The self-attention and convolutional hybrid module (ACmix) is incorporated into the backbone network layer to enhance the feature sensitivity of the model. The deformable large kernel attention mechanism (D-LKA) is added to the feature fusion layer to enhance the model's ability to capture irregular defects in the image. The original loss function is replaced with the Wise-IoU loss function to reduce the impact of low-quality examples in the dataset on the model's detection effect and improve the detection ability of small target defects.

[0026] Among them, the specific method for dimensional accuracy detection is as follows:

[0027] Use a high-resolution industrial camera to take pictures of the steel to obtain its image;

[0028] Subsequently, preprocess the collected image to remove noise, enhance the contrast and clarity of the image;

[0029] After that, adopt edge detection algorithms (such as Sobel, Canny, etc.) to identify the contour and boundary of the steel in the image;

[0030] According to the edge information of the steel, determine the size of the steel by calculating parameters such as the distance and angle between the edges;

[0031] The mechanical property prediction model uses machine learning algorithms such as support vector machine (SVM), random forest (RF), etc. to establish the mapping relationship between the mechanical properties of steel and chemical composition, microstructure characteristics;

[0032] Through the training and learning of a large amount of experimental data, build an accurate mechanical property prediction model;

[0033] Subsequently, conduct mechanical property detection on the finished steel through the mechanical property prediction model.

[0034] Among them, when the cut steel is subjected to rust prevention treatment and packaged with packaging materials:

[0035] First, adopt an oil-free rust prevention treatment process, which forms a dense rust prevention layer on the surface of the steel through special chemical treatment;

[0036] After that, use polyolefin shrink film as the packaging material, which has good flexibility and anti-aging performance, and can effectively protect the steel from the influence of the external environment during transportation and storage.

[0037] A hot-rolled pickled carbon structural steel for automotive structures is produced by using the production method of the hot-rolled pickled carbon structural steel for automotive structures as described above.

[0038] A hot-rolled pickled carbon structural steel for automotive structures and its production method according to the present invention, in specific use, first, a hot-rolled coil meeting the standards is selected as the raw material to ensure that all parameters of the raw material meet the requirements. Then, the hot-rolled coil is subjected to a shearing operation to cut it into size specifications meeting the requirements of subsequent processing; the cut raw material is fed into a continuous pickling line, and an environment-friendly mixed acid solution and an efficient spraying system are used to continuously pickle the raw material; the pickled raw material is fed into an intelligent softening annealing device for softening annealing treatment; the softened annealed steel is fed into a rolling mill for multi-pass rolling, and by precisely controlling the rolling force and reduction, steel with the required thickness and width is obtained; the rolled steel is subjected to spheroidizing annealing treatment and then finishing treatment; the finished steel is inspected, and after passing the inspection, it is cut and processed according to requirements to produce products of different specifications and lengths; the cut steel is subjected to rust prevention treatment and then packaged with packaging materials, thereby solving the technical problems of low production efficiency, high energy consumption, environmental pollution risk, and insufficient intelligence in the inspection link in the existing production methods of structural steel for automobiles.

[0039] By selecting a hot-rolled coil meeting the standards as the raw material and performing a shearing operation to cut it into size specifications meeting the requirements of subsequent processing, the present invention can improve the utilization rate and processing efficiency of the raw material. At the same time, using a continuous pickling line and an efficient spraying system for pickling can quickly remove the scale and impurities on the surface of the raw material, shorten the pickling time, and improve the production efficiency.

[0040] The intelligent softening annealing device used can precisely control parameters such as temperature and time during annealing, avoiding energy waste in the traditional annealing process. In addition, the multi-pass rolling process can reduce energy consumption during rolling on the premise of ensuring the quality of the steel by precisely controlling the rolling force and reduction.

[0041] Using an environment-friendly mixed acid solution for pickling can effectively reduce environmental pollution during pickling. At the same time, the efficient spraying system can reduce the consumption and emission of the acid solution, further reducing the environmental pollution risk.

[0042] An improved YOLOv5-based steel surface defect detection model is used to efficiently and accurately detect defects such as cracks, pitting, inclusions, and scratches on the steel surface. Machine vision technology is used for dimensional accuracy detection, and a mechanical property prediction model is used for mechanical property detection. It can achieve efficient and accurate detection of the appearance quality, dimensional accuracy, mechanical properties, and chemical composition of the steel, improve the intelligence level of the inspection link and the accuracy of the detection results. A strict inspection link can ensure that only qualified steel can enter the subsequent cutting processing and packaging links, thereby improving the quality of the final product.

[0043] Slitting and processing are carried out according to customer requirements to produce products of different specifications and lengths, which can meet the processing requirements of different parts in the automobile manufacturing process. Brief Description of the Drawings

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0045] Figure 1 It is a flowchart of the production method of hot-rolled pickled carbon structural steel for automobile structures of the present invention. Detailed Embodiments

[0046] The following will describe in detail the embodiments of the present invention. The examples of the embodiments are shown in the drawings. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, but should not be construed as a limitation to the present invention.

[0047] Please refer to Figure 1 , Figure 1 It is a flowchart of the production method of hot-rolled pickled carbon structural steel for automobile structures of the present invention.

[0048] The present invention provides a production method of hot-rolled pickled carbon structural steel for automobile structures, including the following steps:

[0049] S1. Select a hot-rolled coil that meets the standards as the raw material, ensure that all parameters of the raw material meet the requirements, and then perform a slitting operation on the hot-rolled coil to cut it into a size specification that meets the requirements of subsequent processing;

[0050] For this specific embodiment, when ensuring that all parameters of the raw material meet the requirements, the parameters include chemical composition, dimensional accuracy, and surface quality;

[0051] When performing a slitting operation on the hot-rolled coil, it should be ensured that the shearing edge is neat, without obvious burrs and defects.

[0052] S2. Feed the cut raw material into a continuous pickling line, and use an environmentally friendly mixed acid solution and an efficient spraying system to continuously pickle the raw material;

[0053] For this specific embodiment, during the process of continuously pickling the raw material with an environmentally friendly mixed acid solution and an efficient spraying system, the environmentally friendly mixed acid solution is an acid solution obtained by mixing hydrochloric acid and sulfuric acid in a ratio of 3:1;

[0054] The pickling temperature is 50 - 70 °C, the acid concentration is 15 - 20%, the pickling time is 4 - 8 minutes, and after pickling, cleaning and passivation treatments are required.

[0055] The preparation method of the environment-friendly mixed acid solution is as follows:

[0056] Weigh hydrochloric acid and sulfuric acid according to a mass ratio of 3:1. Slowly pour the hydrochloric acid into an acid-resistant corrosion container, and slowly add sulfuric acid while stirring. Stir for 10 - 15 minutes to make them fully mixed evenly, and prepare an environment-friendly mixed acid solution with hydrochloric acid and sulfuric acid mixed in a ratio of 3:1.

[0057] S3. Send the pickled raw materials into an intelligent softening annealing equipment for softening annealing treatment;

[0058] For this specific embodiment, when performing softening annealing treatment on the pickled raw materials, it should be under the protection atmosphere of nitrogen-hydrogen mixed gas, the annealing temperature is 680 - 720 °C, the holding time is 2.5 hours, and the cooling rate is 6 - 8 °C / min.

[0059] S4. Send the softened and annealed steel into a rolling mill for multi-pass rolling, and obtain steel with the required thickness and width by precisely controlling the rolling force and reduction;

[0060] S5. Perform spheroidizing annealing treatment on the rolled steel and then carry out finishing treatment;

[0061] S6. Inspect the steel after finishing treatment. After passing the inspection, cut and process it according to requirements to make products of different specifications and lengths;

[0062] For this specific embodiment, the inspection methods for the steel after finishing treatment include appearance quality inspection, dimensional accuracy inspection, mechanical property inspection, and chemical composition inspection;

[0063] For appearance quality inspection, use a steel surface defect detection model based on improved YOLOv5 to efficiently and accurately detect defects such as cracks, pitting, inclusions, and scratches on the steel surface;

[0064] For dimensional accuracy inspection, use machine vision technology. Collect images of the steel through an industrial camera, and use image processing algorithms to precisely measure and analyze the dimensions of the steel to ensure that the dimensional accuracy of the steel meets the requirements;

[0065] For mechanical property inspection, use a mechanical property prediction model for prediction;

[0066] For chemical composition inspection, use a spectral analyzer device to detect the chemical composition of the steel to ensure that the chemical composition of the steel meets the standard requirements.

[0067] Among them, the steel surface defect detection model is based on the YOLOv5 algorithm, and the YOLOv5s-ADW algorithm is proposed. The self-attention and convolution hybrid module (ACmix) is incorporated into the backbone network layer to enhance the feature sensitivity of the model. The deformable large kernel attention mechanism (D-LKA) is added to the feature fusion layer to enhance the model's ability to capture irregular defects in the image. The original loss function is replaced with the Wise-IoU loss function to reduce the impact of low-quality examples in the dataset on the model's detection effect and improve the detection ability of small target defects.

[0068] Among them, the specific method for dimensional accuracy detection is as follows:

[0069] Use a high-resolution industrial camera to take pictures of the steel to obtain its image;

[0070] Subsequently, preprocess the collected image to remove noise, enhance the contrast and clarity of the image;

[0071] After that, adopt edge detection algorithms (such as Sobel, Canny, etc.) to identify the contour and boundary of the steel in the image;

[0072] According to the edge information of the steel, determine the size of the steel by calculating parameters such as the distance and angle between the edges;

[0073] The mechanical property prediction model adopts machine learning algorithms such as support vector machine (SVM), random forest (RF), etc. to establish the mapping relationship between the mechanical properties of steel and chemical composition, microstructure characteristics;

[0074] Through training and learning of a large amount of experimental data, construct an accurate mechanical property prediction model;

[0075] Subsequently, use the mechanical property prediction model to detect the mechanical properties of the finished steel.

[0076] S7. Perform rust prevention treatment on the cut steel and use packaging materials for packaging.

[0077] For this specific implementation, an oil-free rust prevention treatment process is adopted. This process forms a dense rust prevention layer on the steel surface through special chemical treatment;

[0078] After that, use polyolefin shrink film as the packaging material. It has good flexibility and anti-aging performance, and can effectively protect the steel from the influence of the external environment during transportation and storage.

[0079] When using the production method of hot-rolled pickled carbon structural steel for automotive structures in this embodiment, in specific use, first, select hot-rolled coils that meet the standards as raw materials to ensure that all parameters of the raw materials meet the requirements. Then, perform a slitting operation on the hot-rolled coils to cut them into size specifications that meet the requirements of subsequent processing; feed the cut raw materials into a continuous pickling line, and use an environmentally friendly mixed acid solution and an efficient spraying system to continuously pickle the raw materials; feed the pickled raw materials into an intelligent softening annealing device for softening annealing treatment; feed the softened annealed steel into a rolling mill for multi-pass rolling, and obtain steel with the required thickness and width by precisely controlling the rolling force and reduction; perform spheroidizing annealing treatment on the rolled steel and then perform finishing treatment; inspect the finished steel, and after passing the inspection, perform slitting processing according to requirements to make products of different specifications and lengths; perform rust prevention treatment on the slit steel and package it with packaging materials. In this way, the technical problems in the existing production methods of structural steel for automobiles, such as low production efficiency, high energy consumption, environmental pollution risks, and lack of intelligence in the inspection link, are solved.

[0080] The present invention also provides a hot-rolled pickled carbon structural steel for automotive structures, which is produced by using the production method of the hot-rolled pickled carbon structural steel for automotive structures as described above.

[0081] For this specific embodiment, the weight percentage content of chemical components is: C 0.10%-0.14%, Mn 0.42%-0.52%, S≤0.011%, P≤0.021%, Si≤0.03%, Als 0.018%-0.062%, N≤0.0060%, Cu≤0.08%, Cr≤0.06%, Ni≤0.06%, Mo≤0.04%, and the rest are iron and inevitable impurities.

[0082] By selecting hot-rolled coils that meet the standards as raw materials and performing a slitting operation to cut them into size specifications that meet the requirements of subsequent processing, the present invention can improve the utilization rate and processing efficiency of raw materials. At the same time, using a continuous pickling line and an efficient spraying system for pickling can quickly remove the scale and impurities on the surface of the raw materials, shorten the pickling time, and improve production efficiency.

[0083] The intelligent softening annealing device used can precisely control parameters such as temperature and time during the annealing process, avoiding energy waste in the traditional annealing process. In addition, the multi-pass rolling process can reduce energy consumption during rolling while ensuring the quality of the steel by precisely controlling the rolling force and reduction.

[0084] Using an environmentally friendly mixed acid solution for pickling can effectively reduce environmental pollution during the pickling process. At the same time, the efficient spraying system can reduce the consumption and emission of acid solution, further reducing the risk of environmental pollution.

[0085] An improved YOLOv5-based steel surface defect detection model is used to efficiently and accurately detect defects such as cracks, pitting, inclusions, and scratches on the steel surface. Machine vision technology is used for dimensional accuracy detection, and a mechanical property prediction model is used for mechanical property detection. It can achieve efficient and accurate detection of the appearance quality, dimensional accuracy, mechanical properties, and chemical composition of steel, improve the intelligent level of the inspection process and the accuracy of the detection results. A strict inspection process can ensure that only qualified steel can enter the subsequent slitting processing and packaging links, thereby improving the quality of the final product.

[0086] Slitting processing is carried out according to customer requirements to produce products of different specifications and lengths, which can meet the processing requirements of different parts in the automotive manufacturing process.

[0087] The above-disclosed is only a preferred embodiment of the present invention. Of course, it cannot be used to limit the scope of the rights of the present invention. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A method for producing hot-rolled pickled carbon structural steel for automobile structure, characterized in that: The steps include: Select standard hot-rolled coils as raw materials, ensure that all parameters of the raw materials meet the requirements, and then perform shearing operations on the hot-rolled coils to cut them into size specifications that meet the requirements of subsequent processing; The cut raw materials are sent to the continuous pickling line, where environmentally friendly mixed acid and efficient spraying system are used to continuously pickle the raw materials; The pickled raw materials are sent to the intelligent soft annealing equipment for soft annealing treatment; The steel after softening and annealing is sent to the rolling mill for multiple rolling passes. The steel of the required thickness and width is obtained by accurately controlling the rolling force and the amount of reduction. The rolled steel is subjected to spheroidizing annealing and finishing treatment; Inspect the steel after finishing treatment, and cut and process it according to the needs after passing the inspection to make products of different specifications and lengths; The cut steel is subjected to rust-proof treatment and then packed with packaging materials.

2. The method for producing hot-rolled pickled carbon structural steel for automobile structure according to claim 1, characterized in that: Ensure that all parameters of raw materials meet the requirements, including chemical composition, dimensional accuracy and surface quality; When shearing hot-rolled coils, ensure that the sheared edges are neat and free of obvious burrs and defects.

3. The method for producing hot-rolled pickled carbon structural steel for automobile structure according to claim 2, characterized in that: Environmentally friendly mixed acid solution and efficient spraying system are used to continuously pickle the raw materials. The environmentally friendly mixed acid solution is a mixture of hydrochloric acid and sulfuric acid in a ratio of 3:

1. The pickling temperature is 50-70°C, the acid concentration is 15-20%, and the pickling time is 4-8 minutes. After the pickling is completed, cleaning and passivation treatment are required.

4. The method for producing hot-rolled pickled carbon structural steel for automobile structure according to claim 3, characterized in that: The preparation method of environmentally friendly mixed acid solution is as follows: Weigh hydrochloric acid and sulfuric acid in a mass ratio of 3:1, slowly pour the hydrochloric acid into an acid corrosion-resistant container, slowly add sulfuric acid while stirring, and stir for 10-15 minutes to fully mix them, so as to prepare an environmentally friendly mixed acid solution in which hydrochloric acid and sulfuric acid are mixed in a ratio of 3:

1.

5. The method for producing hot-rolled pickled carbon structural steel for automobile structure according to claim 4, characterized in that: When the pickled raw material is subjected to softening annealing treatment, the annealing temperature should be 680-720°C, the holding time should be 2.5 hours, and the cooling rate should be 6-8°C / min under the protective atmosphere of nitrogen-hydrogen mixed gas.

6. The method for producing hot-rolled pickled carbon structural steel for automobile structure according to claim 5, characterized in that: The inspection methods for steel after finishing include appearance quality inspection, dimensional accuracy inspection, mechanical property inspection and chemical composition inspection; Appearance quality inspection uses a steel surface defect detection model based on improved YOLOv5 to efficiently and accurately detect cracks, pitting, inclusions, and scratches on the steel surface; The dimensional accuracy detection uses machine vision technology to collect images of steel through industrial cameras and use image processing algorithms to accurately measure and analyze the dimensions of steel to ensure that the dimensional accuracy of the steel meets the requirements; Mechanical properties testing uses mechanical properties prediction models for prediction; Chemical composition testing uses spectrometer equipment to test the chemical composition of steel to ensure that the chemical composition of steel meets the standard requirements.

7. The method for producing hot-rolled pickled carbon structural steel for automobile structure according to claim 6, characterized in that: The steel surface defect detection model is based on the YOLOv5 algorithm. The YOLOv5s-ADW algorithm is proposed, which integrates self-attention and convolutional hybrid modules (ACmix) into the backbone network layer to enhance the feature sensitivity of the model. The deformable large kernel attention mechanism (D-LKA) is added to the feature fusion layer to enhance the model's ability to capture irregular defects in the image. The original loss function is replaced by the Wise-IoU loss function to reduce the impact of low-quality examples in the data set on the model detection effect and improve the small target defect detection capability.

8. The method for producing hot-rolled pickled carbon structural steel for automobile structure according to claim 7, characterized in that: The specific method of dimensional accuracy detection is: Use a high-resolution industrial camera to photograph the steel and obtain its image; The acquired images are then preprocessed to remove noise and enhance image contrast and clarity; Then, an edge detection algorithm is used to identify the outline and boundaries of the steel in the image; According to the edge information of the steel, the size of the steel is determined by calculating the distance and angle parameters between the edges; The mechanical properties prediction model uses a machine learning algorithm to establish a mapping relationship between the mechanical properties of steel and its chemical composition and microstructural characteristics; By training and learning from a large amount of experimental data, an accurate mechanical properties prediction model is constructed; Then, the mechanical properties of the steel after finishing treatment were tested using the mechanical properties prediction model.

9. The method for producing hot-rolled pickled carbon structural steel for automobile structure according to claim 8, characterized in that: When the cut steel is subjected to rust-proof treatment and packed with packaging materials: First, an oil-free anti-rust treatment process is used, which forms a dense anti-rust layer on the surface of the steel through special chemical treatment; After that, polyolefin shrink film is used as packaging material for packaging.

10. A hot-rolled pickled carbon structural steel for automobile structure, characterized in that: The steel is produced by the production method of hot-rolled pickled carbon structural steel for automobile structure as claimed in claim 9.

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