Intelligent temperature control method for cutting line of new national standard common bar and rebar steel based on image recognition

Abstract

The present invention discloses an intelligent temperature control method for a new national standard common bar and threaded steel slitting line based on image recognition. The method comprises: obtaining temperature images of the edges of the parallel rolled pieces after slitting and the edges of each line after tearing according to an industrial camera; comparing the images with a preset standard temperature color card database to obtain the temperature and gradient distribution from the edge to the core of the parallel rolled pieces; calculating the temperature difference between the edge and the core of each line rolled piece; if the temperature difference exceeds a predetermined temperature, obtaining the water flow rate, water pressure parameter value and optimal temperature after cooling of the water tank between the slitting and the last two rolling mills according to the process database; transmitting the calculated optimal temperature value after cooling to the preset last two rolling mills, and if the processed temperature range exceeds the preset range, providing the corresponding reduction amount of the last two rolling mills at the new temperature after calculation. The present invention can significantly improve the quality consistency and stability requirements of DIFT slitting rolled pieces by using only a few image detection devices.

Description

Technical Field

[0001] The present invention relates to the field of intelligent temperature control of new national standard common bar and threaded steel cutting lines based on image recognition. Background Art

[0002] Rebar, used in infrastructure construction, is the most widely used steel product. In 2017, China implemented the "Notice on Resolutely Curbing Illegal New Capacity in Steel and Coal Industries, Combating 'Substandard Steel,' and Standardizing Construction, Production, and Operation Order," which resulted in the closure of over 600 "substandard steel" enterprises, eliminating approximately 140 million tons of production capacity. To standardize rebar production, the "GB / T1499.2-2018 Steel for Reinforced Concrete - Part 2: Hot-rolled Ribbed Bars" standard was implemented in November 2018. These requirements include: no formation of tempered martensite closed rings in rebar products (strictly prohibited through metallographic and hardness testing), a hardness difference between the surface and core areas below 40 Hv, a lower weight tolerance of ±6% for small sizes, and no re-inspection permitted. These requirements significantly impact the traditional process of producing standard rebar bars using slitting and forced water penetration.

[0003] The combination of high-intensity (low-temperature) rolling and deformation-induced ferrite transformation (DIFT) technology achieves refined ferrite and pearlite grain sizes, eliminating (or reducing the addition of) microalloying elements. This is the key to achieving high-quality, low-cost production of hot-rolled ribbed steel bars for construction. The full process involves: purification smelting—fully equiaxed crystallization and solidification—high-intensity and low-temperature rough rolling—deformation-induced ferrite transformation (DIFT) finishing rolling—and controlled cooling. In the rolling production line, the main requirements are (1) strong and low temperature rolling to refine the grains and reduce the cooling requirements for the rolled piece before subsequent finishing rolling; (2) the temperature of the rolled piece to be finished rolled should be cooled to near the zero point of the transformation from austenite to ferrite; (3) in the finishing rolling stage, the rolled piece should be subjected to an appropriate deformation reduction so that the matrix volume Gibbs free energy is increased from the deformation energy during the deformation process, the dynamic transformation temperature of austenite to ferrite is reduced, the austenite deformation-induced phase transformation to ferrite occurs, and the formation of fine proeutectoid equiaxed ferrite grains is promoted; (4) after finishing rolling, the rolled piece should be cooled rapidly in the form of rapid cooling to increase the supercooling degree of the microstructure transformation to increase the nucleation rate of the transformation from austenite to ferrite, and to inhibit the growth of ferrite grains after the phase transformation, so as to obtain a fine ferrite + pearlite microstructure. During the rapid cooling of the rolled piece leaving the finishing mill, the cooling rate must be controlled within a certain range to avoid the formation of other structures (such as tempered martensite, tempered bainite, bainite, etc.) due to excessive surface cooling rate and the accompanying core reheating and tempering. Ensure that the equilibrium transformation temperature of 20MnSi austenite to ferrite at the end of the finishing rolling is around 800℃. After a 30% to 50% reduction at 825℃, slightly higher than this temperature, 20MnSi can complete 60% to 100% of the deformation-induced ferrite phase transformation, and the ferrite grain size is 5 to 15μm. Since the rolling is carried out at the critical austenite-ferrite transformation point, the cross-section temperature uniformity when the rolled piece enters the finishing mill is the key to ensure the smooth execution of DIFT, and to avoid the occurrence of mixed crystals in the two-phase region rolling, or the inability to exert the DIFT mechanism and play a role when rolling only in the austenite single-phase region.

[0004] In actual industrial production, the production line must adopt a slitting process to increase production line capacity and reduce the cost per ton of steel. However, before K4 pre-cutting, the cross-sectional morphology of the rolled piece is rectangular and the heat dissipation conditions at the edge are good, resulting in a temperature gradient from the edge to the center. This temperature gradient is further expanded in the pre-cutting of K4 and K3, and then expanded during cooling before the slitting wheel and K2. Finally, when entering K2, the temperature gradient of a single rolled piece and between rolled pieces is significant, affecting the structure and performance of the finished product. Currently, thermometers are mainly used to directly detect the temperature distribution and values ​​of parallel rolled pieces before and after slitting. However, since the parallel rolled pieces are too large before slitting, the edge-center temperature on the contour cannot be obtained by line scanning. After slitting, the temperature of the rolled piece drops sharply in the water cooling of the water tank, resulting in a large amount of water vapor leaking out, blocking and affecting the thermometer detection. At the same time, the rolling vibration also makes it difficult to align the thermometer detection point, which makes the detection value of the secondary system inaccurate and unable to form effective regulation.

[0005] In summary, in order to carry out the new national standard common bar and threaded steel cutting process based on the DIFT method, ensure the mechanical properties and dimensional accuracy of the finished product, increase the stability of the production process, and improve the quality consistency of each line after the cutting method, the water flow should be adjusted according to the temperature requirements of the DIFT mechanism, but the premise is to ensure that the detected temperature value is true, effective and reliable. The present invention proposes an intelligent temperature control method for the new national standard common bar and threaded steel cutting line based on image recognition, which obtains the image from the edge to the center of the rolled piece before and after cutting in the form of image processing, and optimizes the water cooling process parameter settings of the water tanks of each line before K2, so that the temperature gradient between the single section and each other is as small as possible when the cut rolled piece enters K2, thereby improving the quality consistency of the finished product. Summary of the Invention

[0006] In order to overcome the above-mentioned defects, the purpose of the present invention is to provide a low-cost, effective method for improving the stability of new national standard common bar and threaded steel products after slitting by improving temperature uniformity.

[0007] To achieve the above object, the present invention provides a method for improving the stability of new national standard common bar and threaded steel products after slitting based on improving temperature uniformity, the method comprising the following steps:

[0008] The temperature images of the edges of the parallel rolled pieces and the edges of each line after tearing are obtained by industrial cameras set before and after the bar splitting and rolling;

[0009] The temperature image is compared with the preset standard temperature color card database to obtain the temperature and gradient distribution from the edge to the center of the parallel rolled piece;

[0010] Calculate the temperature difference between the edge and center of each line rolling piece. If the temperature difference does not exceed the preset temperature, execute the original process parameters. If the temperature difference exceeds the preset temperature, obtain the water flow and water pressure parameters of the water tank between the cutting and the last two rolling mills and the optimal temperature after cooling according to the process database.

[0011] The calculated optimal temperature value after cooling is passed to the preset last two rolling mills. If the processed temperature range meets the acceptable range of the original reduction, the preset value is taken out from the online reduction process database of the last two rolling mills. Otherwise, if it exceeds the preset range, the corresponding reduction of the last two rolling mills at the new temperature is given after calculation, and adjusted in the online reduction adjustment system of the last two rolling mills.

[0012] The present invention uses image recognition that takes into account the temperature distribution from the edge to the center of the parallel rolled piece before and after pre-slitting, and extracts characteristic temperature values ​​through RGB conversion and standard color card comparison, thereby eliminating (or weakening) the temperature gradient from the edge to the center of the parallel rolled piece, ensuring that the parallel rolled piece is pre-slit and cut by 2 to 5 lines of K4 and K3, and is further torn by the cutting wheel before entering the K3 water tank. The temperature inside each line of the rolled piece is less than 50°C, and the temperature difference between the edge rolled piece and the core rolled piece is less than 35°C. When entering the last two stands K2 and K1 for rolling based on the DIFT mechanism, the temperature uniformity inside each line and between each other is less than 40°C, thereby solving the problems of uneven organization and unstable performance caused by the temperature difference between each line and between each other caused by the traditional slitting method, and meeting the quality requirements of the finished product of the new national standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1-a Layout of hot-rolled threaded steel bar cutting production line based on DIFT+ cutting

[0014] Figure 1-b Temperature distribution of parallel rolled pieces obtained by finite element simulation

[0015] Figure 1-c Actual rolled product image detection results, image processing, and color chart corresponding temperature values

[0016] Figure 2-a A production line layout diagram based on improving temperature uniformity to enhance product stability after slitting of new national standard ordinary bar and threaded steel.

[0017] Figure 2-b A schematic diagram showing a method for improving the stability of new national standard common bar and threaded steel products after slicing based on improving temperature uniformity. DETAILED DESCRIPTION

[0018] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0019] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0020] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0021] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0022] like Figure 1-a In the current DIFT-based hot-rolled threaded steel bar slitting production line layout, 1 to 2 water tanks are used for temperature control after intermediate rolling, and the average temperature of the rolled pieces is in the range of 900-950°C when entering the finishing mill. Then, by adding 1 to 2 water tanks after the K3 stand, the finishing mill group is divided into two groups. The main function of the finishing mill group before the K3 stand is to perform stable 2-line to 4-line slitting; then, each single-line rolled piece separated by the slitting wheel is cooled and heated in the 1 to 2 water tanks after the K3 stand and the recovery section to ensure that the rolled piece temperature when entering the K2 stand is 10-30°C above the actual austenite → ferrite transformation critical temperature; finally, to ensure that the rolled piece obtains fine proeutectoid ferrite after DIFT, a large degree of deformation must be performed in the K1 and K2 stands depending on the product specifications and rolled piece temperature. Figure 1-b The temperature distribution of the parallel rolled pieces when they leave the K5 stand, K3 stand, pass through the slitting wheel, and become finished products under this method is given. It can be seen that the temperature differences between individual rolled pieces (edges and centers) and between each other are significant. Since the DIFT process requires a narrow temperature deformation temperature range for the rolled pieces, it is ultimately not conducive to the consistency and stability of the product's microstructure and performance.

[0023] The present invention proposes a new national standard general bar thread steel tangent temperature intelligent control layout and principle diagram based on image recognition, as shown in Figure 2. Compared with the original process layout ( Figure 1-a), the present invention adds a preset rolling process database based on the rolling program table, an industrial camera, a standard steel billet color card, and the morphology and temperature of the parallel rolled piece after K5 obtained after processing by the information module, and gives the temperature difference range of the parallel rolled piece from the edge to the center after comparison, and further gives the reliability of the temperature difference between the cross section of the single rolled piece and each other for the verification of each line rolled piece after the slitting wheel. At a temperature greater than 30°C, the water cooling parameters (water flow, water pressure) of the water tank of each line before K2 are calculated for temperature adjustment, and the calculated optimal temperature value is passed to the preset DIFT process database of the last two rolling mills for processing. If the processed temperature range meets the acceptable range of the original reduction, the preset value is taken out from the online reduction process database of the last two rolling mills. Otherwise, if it exceeds the preset range, the reduction of the last two rolling mills corresponding to the new temperature is given after calculation, and the online reduction adjustment system of the last two rolling mills is adjusted to meet the rolling of the last two rolling mills with DIFT for each line rolled piece. The information processing and process parameters involved in the invention are all stored in the form of a database and standard color matrix, thus eliminating computational time and making it suitable for online use. This process, without adding complex online rolling process calculations or online mill adjustment algorithms, can significantly improve the quality consistency and stability requirements of DIFT-slit rolled products by reducing temperature differences between lines with minimal investment, using only a small amount of image detection equipment, electrical control systems, and a database.

[0024] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0025] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A new national standard bar and threaded steel cutting line intelligent temperature control method based on image recognition, characterized in that: The method comprises the following steps: The temperature images of the edges of the parallel rolled pieces and the edges of each line after tearing are obtained by industrial cameras set before and after the bar splitting and rolling; The temperature image is compared with the preset standard temperature color card database to obtain the temperature and gradient distribution from the edge to the center of the parallel rolled piece; Calculate the temperature difference between the edge and center of each line rolling piece. If the temperature difference does not exceed the preset temperature, execute the original process parameters. If the temperature difference exceeds the preset temperature, obtain the water flow and water pressure parameters of the water tank between the cutting and the last two rolling mills and the optimal temperature after cooling according to the process database. The calculated optimal temperature value after cooling is passed to the preset last two rolling mills. If the processed temperature range meets the acceptable range of the original reduction, the preset value is taken out from the online reduction process database of the last two rolling mills. Otherwise, if it exceeds the preset range, the corresponding reduction of the last two rolling mills at the new temperature is given after calculation, and adjusted in the online reduction adjustment system of the last two rolling mills.

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