Steel billet surface defect detection method

Abstract

The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a steel billet surface defect detection method which comprises the following steps: controlling the moving speed of a roller way to be synchronous with the reaction rate of flame cleaning, and performing continuous scanning type cleaning and removal on an oxide layer on the surface of a steel billet through a flame cleaning device; the flame cleaning device comprises a flame nozzle and an air source; and then the surface of the steel billet is detected after flame cleaning, surface defects are recognized, and the defects comprise cracks and air holes. The flame cleaning device is adopted to remove the oxide layer on the surface of the steel billet, so that the surface of the steel billet can be quickly and effectively cleaned, tedious pretreatment processes such as acid pickling and shot blasting are avoided, expensive chemicals and shot blasting equipment are avoided, the chemical treatment and equipment maintenance cost is saved, and the production cost is remarkably reduced. The speed and efficiency of billet surface defect detection are greatly improved, and the dead time and manual intervention of a production line are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a method for detecting surface defects of a steel billet. Background Art

[0002] During the steel production process, steel reacts with oxygen in the air under high temperature to produce oxides. This layer of oxide covers the surface of the steel billet, forming a barrier that hides potential internal defects such as cracks, pores, pits, etc. Due to the presence of the oxide layer, the actual quality and internal defects of the steel billet are difficult to observe directly, and in some cases, the oxide layer itself may affect the detection accuracy of defects. Therefore, additional measures must be taken to remove this oxide layer in order to reveal and inspect potential surface defects.

[0003] The traditional method of surface defect inspection of steel billets mainly relies on pre-treatment processes such as pickling and shot blasting to remove the oxide layer, and then conducts defect detection through technical means such as magnetic particle inspection and ultrasonic testing. These methods have their own advantages and disadvantages, but there are some common problems.

[0004] Pickling usually involves soaking the steel billet in an acid solution to remove the oxide layer. This process not only requires a large amount of chemicals and equipment, but also requires manual monitoring and disposal of waste acid. Although it can effectively remove the oxide layer, the waste liquid generated during the pickling process and its disposal cost put a certain pressure on the environment and also lead to high resource consumption.

[0005] Shot blasting is the process of removing the oxide layer by spraying high-speed steel balls, steel shots and other substances on the surface of the steel billet. This process requires the use of expensive shot blasting equipment, and the consumption of steel shots also increases operating costs. In addition, the shot blasting process takes a long time, especially for large-scale steel billet production, which may lead to low cleaning efficiency and reduce the overall production capacity of the production line.

[0006] The above methods not only require a large amount of equipment, materials and manpower, but also consume a lot of time and resources. Especially when the batch size of steel billets is large and the processing volume is large, it is easy to cause the production cycle to be extended and the overall production efficiency to decrease, which in turn leads to an increase in production costs. For large-scale steel production lines, this not only increases operating costs, but also affects the delivery cycle of products. In order to solve these problems, there is an urgent need for a new, efficient and low-cost method for detecting surface defects of steel billets to improve production efficiency, reduce production costs, and reduce environmental pollution and waste of resources while ensuring the quality of steel billets.

[0007] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art known to those skilled in the art. Summary of the invention

[0008] The purpose of the present invention is to provide a method for detecting surface defects of steel billets, thereby reducing detection costs and improving production efficiency.

[0009] The above technical objectives of the present invention are achieved through the following technical solutions:

[0010] A method for detecting surface defects of a steel billet, comprising:

[0011] S01: Control the moving speed of the roller table to be synchronized with the reaction rate of the flame cleaning, and perform continuous scanning cleaning and removal of the oxide layer on the surface of the steel billet through the flame cleaning device; the flame cleaning device includes a flame nozzle and a gas source;

[0012] S02: Inspect the surface of the steel billet after flame cleaning to identify surface defects, including cracks and pores.

[0013] Preferably, step S01 includes:

[0014] A reaction rate model based on flame cleaning is established. The input of the model includes the thickness of the oxide layer, the spray intensity of the flame nozzle, and the moving speed of the flame nozzle. The output of the model includes the area of ​​the oxide layer removed and the cleaning time.

[0015] Specifically, the cleaning efficiency is tested under different oxide layer thicknesses, nozzle pressures and flame temperatures. A database is established based on the oxide layer thickness and the spray intensity of the flame nozzle, the movement speed of the flame nozzle, the area of ​​the oxide layer removed and the cleaning time. The prediction accuracy of the model is verified using data fitting tools to ensure its applicability to a variety of working conditions.

[0016] After each batch of steel billets is cast, the thickness range of the oxide layer on the surface of the billets is measured, and the data is fed back to the control system after denoising, and the time required for flame cleaning is calculated through the model;

[0017] The control system receives feedback data and adjusts the roller speed through the control algorithm based on the area of ​​the oxide layer removed and the cleaning time. The feedback data includes: oxide layer thickness (measured by laser or ultrasonic sensor), flame temperature (monitored by temperature sensor), cleaning area and time (calculated by flame nozzle movement and roller speed); the control system adjusts the roller speed and flame parameters based on PID control algorithm or model predictive control (MPC).

[0018] Among them, the PID controller calculates the difference between the target value and the actual value of the cleaning time, and calculates the optimized roller speed through PID adjustment. The MPC controller predicts the system state in multiple steps in the future, selects a set of control inputs (such as roller speed, nozzle strength) to minimize the cleaning time and avoid overburning, and uses the optimization algorithm to dynamically adjust the nozzle parameters and roller speed.

[0019] Preferably, the flame nozzle is height-adjustable, and the spray intensity of the flame nozzle is determined by the pressure of the gas source and the height from the surface of the steel billet.

[0020] Preferably, the moving speed of the flame nozzle matches the thickness of the oxide layer on the surface of the steel billet and the spraying intensity of the flame nozzle.

[0021] Preferably, the gas source is a mixed gas of oxygen and acetylene, the oxygen pressure is 1.2 MPa, the acetylene pressure is 0.5 MPa, and the gas ratio is 1.5:1 to 2.0:1.

[0022] Preferably, the control system receives the feedback data and adjusts the roller speed through a control algorithm based on the area of ​​the oxide layer removed and the cleaning time, including:

[0023] The control system calculates the appropriate roller speed based on the thickness of the oxide layer on the surface of the steel billet and the required cleaning time. By adjusting the roller speed, it controls the residence time of the steel billet in the flame area. During the process, a temperature sensor is used to monitor the temperature of the steel billet surface in real time to prevent the flame temperature from being too high and causing the steel billet to overheat.

[0024] Preferably, the roller is made of high-chromium alloy that is resistant to high temperatures and corrosion, which can adapt to environments up to 1200°C during the flame cleaning process, ensure that the roller does not deform, and extend its service life.

[0025] Preferably, in step S2, the surface defects are identified by any one of manual inspection, visual detection or sensor detection.

[0026] Preferably, the visual inspection step includes taking images of the surface of the steel billet using a high-resolution camera or an industrial camera, and identifying surface defects using an image processing algorithm. Specifically, the image is preprocessed through steps such as grayscale, denoising, and edge enhancement, and then crack detection is performed based on Canny edge detection or convolutional neural network (CNN), pore detection is performed using morphological operations or Blob detection algorithms, and pit detection is achieved through gradient mapping or a deep learning network (such as U-Net).

[0027] Preferably, the sensor includes an infrared sensor and a temperature sensor, which are used to monitor the temperature change of the surface of the steel billet in real time, evaluate the cleaning effect and further determine whether the defects are exposed.

[0028] By means of the above technical solution, the present invention has at least the following beneficial effects:

[0029] (1) The present invention uses a flame cleaning device to remove the oxide layer on the surface of the steel billet, which can quickly and effectively clean the surface of the steel billet, avoid cumbersome pre-treatment processes such as pickling and shot blasting, avoid the use of expensive chemicals and shot blasting equipment, save chemical treatment and equipment maintenance costs, and significantly reduce production costs. The speed and efficiency of steel billet surface defect detection are greatly improved, and the downtime and manual intervention of the production line are reduced.

[0030] (2) Traditional pickling and shot blasting processes often produce a large amount of waste liquid, waste gas or waste material, and the waste treatment cost is high and the pollution is serious. Flame cleaning does not involve chemicals, does not produce waste acid, waste liquid and other pollutants, and reduces the risk of environmental pollution. The energy consumption of the flame cleaning device is low, and it has better environmental protection effect and energy efficiency than traditional methods. The surface removed iron oxide can also be recycled and the cost is low.

[0031] (3) During the flame cleaning process, the oxide layer on the surface of the steel billet can be accurately removed by controlling the flame intensity and cleaning time, so that the defects on the surface of the steel billet can be exposed. In this process, by adjusting the flame nozzle, overheating can be avoided to ensure that the surface matrix of the steel billet is not damaged, thereby improving the accuracy of defect detection and ensuring product quality. The present invention can also dynamically adjust the spray intensity, moving speed and cleaning time of the flame nozzle according to the thickness of the oxide layer on the surface of the steel billet and the actual cleaning requirements, so as to meet the surface treatment requirements of steel billets of different specifications and thicknesses. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 The present invention is a flowchart of a method for detecting surface defects of a steel billet according to an embodiment of the present invention.

[0034] Figure 2 This is a diagram of the defect structure exposed after flame cleaning in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] like Figure 1 and Figure 2 A method for detecting surface defects of a steel billet is shown, comprising:

[0037] S01: Control the moving speed of the roller table to be synchronized with the reaction rate of the flame cleaning, and perform continuous scanning cleaning and removal of the oxide layer on the surface of the steel billet through the flame cleaning device; the flame cleaning device includes a flame nozzle and a gas source;

[0038] During the billet generation process, the oxide layer thickness of the billets smelted and cast in the same batch presents the same fluctuation range. The present invention can ensure that the billet surface is treated evenly and continuously during the flame cleaning by synchronously controlling the moving speed of the roller and the reaction rate of the flame cleaning, ensuring that each part of the billet can be flame cleaned within an appropriate time, thereby avoiding the phenomenon of local overburning or incomplete cleaning during the cleaning process. The continuous scanning cleaning method can also maximize the removal of the oxide layer, exposing surface defects more thoroughly, thereby improving the accuracy of defect detection.

[0039] Preferably, step S01 includes:

[0040] A model based on the reaction rate of flame cleaning is established. The input of the model includes the thickness of the oxide layer, the spray intensity of the flame nozzle, and the movement speed of the flame nozzle. The output of the model includes the area of ​​the oxide layer removed and the cleaning time. The purpose is to achieve precise control of the flame cleaning process, optimize the exposure of surface defects of the steel billet, and ensure the optimal balance between cleaning effect and production efficiency.

[0041] Among them, the thickness of the oxide layer will directly affect the intensity and cleaning efficiency of the flame cleaning; the thicker the oxide layer, the more time and energy are required to remove it; the nozzle's spray intensity affects the flame temperature and cleaning efficiency. Too high an intensity may lead to overburning, while too low an intensity may not clean thoroughly; the nozzle's moving speed directly affects the time the flame acts on the billet surface. Too fast a speed will lead to incomplete cleaning, while too slow a speed may lead to overburning; the ratio of oxygen to acetylene determines the nature of the flame, and a suitable gas source ratio can ensure that the intensity of the flame achieves the best cleaning effect while avoiding overheating; the area of ​​the oxide layer removed reflects the effect of the flame cleaning, indicating the area where the oxide layer has been successfully removed; the cleaning time indicates the total time required to complete the flame cleaning, and optimizing the cleaning time can improve production efficiency.

[0042] The model can be expressed using the following mathematical formula:

[0043] A=f(T OX ,S,V,P)

[0044] Where: A represents the area of ​​the oxide layer removed; T ox It indicates the thickness of the oxide layer; S indicates the spray intensity of the nozzle; V indicates the moving speed of the nozzle; P indicates the gas source ratio (the ratio of oxygen to acetylene).

[0045] Cleaning time t clean It can be expressed as:

[0046] t clean =g(T ox ,S,V,P)

[0047] Where: g is a function related to the input parameters, which represents the relationship between the cleaning time and various factors. In practical applications, the model will be further adjusted and optimized in combination with experimental data and engineering experience.

[0048] Specifically, the cleaning efficiency is tested under different oxide layer thicknesses, nozzle pressures, and flame temperatures. A database based on the oxide layer thickness and the jet intensity of the flame nozzle, the movement speed of the flame nozzle, the area of ​​the oxide layer removed, and the cleaning time is established. The prediction accuracy of the model is verified using data fitting tools to ensure its applicability to a variety of working conditions. The model can take into account the combined effects of multiple factors and automatically optimize the cleaning strategy under different billet and oxide layer conditions. It avoids the uncertainty and errors caused by manual intervention and ensures that each cleaning operation can maintain consistent quality and efficiency.

[0049] After each batch of steel billets is cast, the thickness range of the oxide layer on the surface of the billets is measured, and the data is fed back to the control system after denoising, and the time required for flame cleaning is calculated through the model;

[0050] By accurately calculating the required cleaning time and cleaning area, the model can help avoid overheating the billet and reduce the surface damage of the billet caused by overburning. By adjusting the spray intensity of the flame nozzle and the movement speed of the nozzle, the control system can maximize the removal of the oxide layer without affecting the quality of the billet.

[0051] The present invention uses a flame cleaning device to remove the oxide layer on the surface of the steel billet, which can quickly and effectively clean the surface of the steel billet, avoid cumbersome pre-treatment processes such as pickling and shot blasting, avoid the use of expensive chemicals and shot blasting equipment, save chemical treatment and equipment maintenance costs, and significantly reduce production costs. The speed and efficiency of surface defect detection of steel billets are greatly improved, and the downtime and manual intervention of the production line are reduced. In addition, flame cleaning does not involve chemicals, and does not produce pollutants such as waste acid and waste liquid, thereby reducing the risk of environmental pollution. The flame cleaning device has low energy consumption and has better environmental protection effects and energy efficiency than traditional methods. The surface-removed iron oxide scale can also be recycled and reused at a low cost.

[0052] The control system receives feedback data and adjusts the roller speed through the control algorithm based on the area of ​​the oxide layer removed and the cleaning time. The feedback data includes: oxide layer thickness (measured by laser or ultrasonic sensor), flame temperature (monitored by temperature sensor), cleaning area and time (calculated by flame nozzle movement and roller speed); the control system adjusts the roller speed and flame parameters based on PID control algorithm or model predictive control (MPC).

[0053] Among them, the PID controller calculates the difference between the target value and the actual value of the cleaning time, and calculates the optimized roller speed through PID adjustment. The MPC controller predicts the system state in multiple steps in the future, selects a set of control inputs (such as roller speed, nozzle strength) to minimize the cleaning time and avoid overburning, and uses the optimization algorithm to dynamically adjust the nozzle parameters and roller speed.

[0054] Preferably, the flame nozzle is height-adjustable, allowing the nozzle to maintain an optimal distance from the surface of the steel billet, and the spray intensity of the flame nozzle is determined by the pressure of the gas source and the height from the surface of the steel billet.

[0055] The pressure of the gas source directly determines the intensity of the flame, while the height of the nozzle and the surface of the billet determines the contact intensity between the flame and the surface of the billet. When the height of the nozzle changes, the distribution range and contact area of ​​the flame will change accordingly, which has a direct impact on the intensity of the flame and the efficiency of heat transfer. By reasonably adjusting the pressure of the gas source and the height of the nozzle, the flame intensity can be accurately controlled, the oxide layer removal effect can be optimized, and overburning can be avoided. Oxide layers of different thicknesses require flames of different intensities to remove. By adjusting the height of the nozzle, the area of ​​action of the flame can be adjusted to ensure that the flame can remove the oxide layer at the most appropriate intensity, thereby achieving precise cleaning.

[0056] During the flame cleaning process, the oxide layer on the surface of the steel billet can be accurately removed by controlling the flame intensity and cleaning time, so that the defects on the surface of the steel billet can be exposed. In this process, by adjusting the flame nozzle, overheating can be avoided, ensuring that the surface matrix of the steel billet is not damaged, thereby improving the accuracy of defect detection and ensuring product quality. The present invention can also dynamically adjust the spray intensity, moving speed and cleaning time of the flame nozzle according to the thickness of the oxide layer on the surface of the steel billet and the actual cleaning requirements, so as to meet the surface treatment requirements of steel billets of different specifications and thicknesses.

[0057] Preferably, the moving speed of the flame nozzle matches the thickness of the oxide layer on the surface of the steel billet and the spraying intensity of the flame nozzle, which can significantly improve the accuracy and efficiency of the flame cleaning process.

[0058] The speed of the nozzle directly affects the contact time between the flame and the oxide layer on the surface of the billet. By adjusting the speed of the nozzle according to the thickness of the oxide layer and the spray intensity, the depth and range of the oxide layer removal can be precisely controlled, and uniform heating can be ensured to prevent excessive oxide layer removal due to excessive local flame intensity, which may cause damage to the billet surface or excessive temperature. For example, a thinner oxide layer can be removed quickly, exposing potential surface defects such as cracks or pores, while a thicker oxide layer can be thoroughly removed by slowing down the nozzle speed, making it easier to find deep-seated defects.

[0059] Preferably, the gas source is a mixed gas of oxygen and acetylene, with an oxygen pressure of 1.2 MPa, an acetylene pressure of 0.5 MPa, and a gas ratio of 1.5:1 to 2.0:1. By adjusting the ratio of oxygen and acetylene, the temperature of the flame and the oxidation reaction rate can be flexibly controlled. For example, a higher oxygen ratio (close to 2.0:1) can provide more oxygen, making the oxidation reaction more intense, which is suitable for cleaning thick oxide layers; while a lower oxygen ratio (close to 1.5:1) can provide a milder flame, which is more suitable for cleaning thin oxide layers, thereby avoiding overburning.

[0060] Preferably, the control system receives the feedback data and adjusts the roller speed through a control algorithm based on the area of ​​the oxide layer removed and the cleaning time, including:

[0061] Based on the thickness of the oxide layer on the surface of the billet and the required cleaning time, the control system calculates the appropriate roller speed so that the time the billet stays in the flame area matches the cleaning requirements of the oxide layer. Through this precise adjustment, it is possible to ensure that the flame action time is just right, thereby avoiding incomplete cleaning or excessive cleaning and improving the efficiency of surface cleaning. During the process, a temperature sensor is used to monitor the temperature changes on the surface of the billet in real time, and the temperature data is fed back to the control system in real time. The system can dynamically adjust the roller speed according to the temperature data, control the residence time of the billet in the flame area, avoid excessive heating of the billet surface due to excessive flame temperature, thereby preventing problems such as overburning, surface melting or deformation of the billet and ensuring the quality of the billet.

[0062] Preferably, the roller is made of a high-temperature-resistant and corrosion-resistant high-chromium alloy. The high-temperature-resistant property of the high-chromium alloy ensures that the roller will not expand or deform due to excessive temperature at high temperatures, and maintains a high structural stability. In the high-temperature environment of the flame cleaning process, the roller will not be damaged or deformed prematurely due to continuous high-temperature treatment, thereby improving the stability and service life of the equipment.

[0063] S02: Inspect the surface of the steel billet after flame cleaning to identify surface defects, including cracks and pores. Figure 2 shown.

[0064] Preferably, in step S2, surface defects are identified by any one of manual visual inspection, visual detection or sensor detection. The combined use of manual visual inspection, visual detection and sensor detection can give full play to their respective advantages in the detection of surface defects of steel billets. Manual visual inspection provides flexibility and intuitiveness, visual detection improves automation and accuracy, and sensor detection enhances the diversity and accuracy of detection. The combination of multiple detection methods effectively improves the coverage and reliability of defect detection.

[0065] Preferably, the visual inspection step includes taking images of the surface of the steel billet using a high-resolution camera or an industrial camera, and identifying surface defects through an image processing algorithm. Specifically, the image is preprocessed through steps such as graying, denoising, and edge enhancement, and then crack detection is performed based on Canny edge detection or convolutional neural network (CNN), pore detection is performed using morphological operations or Blob detection algorithms, and pit detection is achieved through gradient mapping or deep learning networks (such as U-Net). The sensor includes an infrared sensor and a temperature sensor, which are used to monitor the temperature changes on the surface of the steel billet in real time, evaluate the cleaning effect, and further determine whether the defects are exposed. It should be understood by those skilled in the art that the present invention is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions are only used to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have various changes and improvements, and these changes and improvements all fall within the scope of the invention claimed for protection. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for detecting surface defects of a steel billet, characterized in that: include: S01: Controlling the moving speed of the roller table to be synchronized with the reaction rate of the flame cleaning, and performing continuous scanning cleaning and removal of the oxide layer on the surface of the steel billet by a flame cleaning device; the flame cleaning device includes a flame nozzle and a gas source; S02: Inspect the surface of the steel billet after flame cleaning to identify surface defects, including cracks and pores.

2. A method for detecting surface defects of a steel billet according to claim 1, characterized in that: Step S01 includes: A reaction rate model based on flame cleaning is established. The input of the model includes the thickness of the oxide layer, the spray intensity of the flame nozzle, and the moving speed of the flame nozzle. The output of the model includes the area of ​​the oxide layer removed and the cleaning time. After each batch of steel billets is cast, the thickness range of the oxide layer on the surface of the billets is measured, and the data is fed back to the control system after denoising, and the time required for flame cleaning is calculated through the model; The control system receives the feedback data and adjusts the roller speed through the control algorithm based on the area of ​​the oxide layer removed and the cleaning time.

3. A method for detecting surface defects of a steel billet according to claim 2, characterized in that: The flame nozzle can be adjusted in height, and the spray intensity of the flame nozzle is determined by the pressure of the gas source and the height from the surface of the steel billet.

4. A method for detecting surface defects of a steel billet according to claim 2, characterized in that: The moving speed of the flame nozzle matches the thickness of the oxide layer on the surface of the steel billet and the spraying intensity of the flame nozzle.

5. A method for detecting surface defects of a steel billet according to claim 3, characterized in that: The gas source is a mixed gas of oxygen and acetylene, the oxygen pressure is 1.2 MPa, the acetylene pressure is 0.5 MPa, and the gas ratio is 1.5:1~2.0:

1.

6. A method for detecting surface defects of a steel billet according to claim 2, characterized in that: The control system receives the feedback data and adjusts the roller speed based on the area of ​​​​the oxide layer removed and the cleaning time through the control algorithm, including: The control system calculates the appropriate roller speed based on the thickness of the oxide layer on the surface of the steel billet and the required cleaning time. By adjusting the roller speed, it controls the residence time of the steel billet in the flame area. During the process, a temperature sensor is used to monitor the temperature of the steel billet surface in real time to prevent the flame temperature from being too high and causing the steel billet to overheat.

7. A method for detecting surface defects of a steel billet according to claim 2, characterized in that: The roller is made of high-chromium alloy which is resistant to high temperature and corrosion.

8. A method for detecting surface defects of a steel billet according to claim 1, characterized in that: In step S2, the surface defects are identified by any one of manual inspection, visual detection or sensor detection.

9. A method for detecting surface defects of a steel billet according to claim 8, characterized in that: The visual inspection step includes taking images of the surface of the steel billet using a high-resolution camera or an industrial camera, and identifying surface defects using an image processing algorithm.

10. A method for detecting surface defects of a steel billet according to claim 8, characterized in that: The sensors include infrared sensors and temperature sensors, which are used to monitor the temperature changes on the surface of the steel billet in real time, evaluate the cleaning effect and further determine whether defects are exposed.

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