A preparation process of high-strength 30MnSi hot-rolled wire

Abstract

The present application relates to the field of hot rolling production technology, and specifically to a preparation process of a high-strength 30MnSi hot-rolled wire, which process includes: putting scrap steel and molten iron into an electric furnace, and after tapping, first adding lime and fluorite, and then adding silicon-manganese alloy and silicon-iron alloy to obtain smelted steel; adding the smelted steel into a refining furnace, feeding pure calcium wire for soft blowing, and obtaining molten steel; injecting the molten steel into the tundish of a continuous casting machine, and continuously casting into ingots of fixed shape and size; controlling the temperature in the heating furnace during the heating stage and the rolling stage; adjusting the speed of each section of the air-cooled roller based on the stacking density of the hot-rolled coils on each section of the air-cooled roller to obtain the air-cooled wire; coiling, finishing, bundling, weighing, and unwinding the air-cooled wire to obtain a high-strength 30MnSi hot-rolled wire. The present application aims to dynamically adjust the roller speed of each section of the air-cooled roller to improve the cooling uniformity of the hot-rolled wire during the air-cooling treatment.

Description

Technical Field

[0001] The present application relates to the technical field of hot rolling production, and in particular to a preparation process of high-strength 30MnSi hot-rolled wire. Background Art

[0002] 30MnSi hot-rolled wire, also known as hot-rolled wire rod, is the main raw material for prestressed steel bars. It is usually processed by straightening, drawing and grooving, and then tempered to obtain prestressed steel bars. This material is widely used in construction projects and has excellent mechanical properties, including high strength, high toughness and low relaxation characteristics, which can provide good bonding with concrete. In addition, 30MnSi hot-rolled wire has excellent weldability and forgeability, and has a good material utilization rate. Its comprehensive properties make it an important material in structural engineering such as buildings and bridges. In China, 30MnSi hot-rolled wire has been widely used in the production of prestressed components such as high-strength prestressed concrete centrifugal pipe piles, power poles, viaduct piers, and railway sleepers. With its excellent performance and reliability, the market prospects are very broad.

[0003] Prestressed steel bars have strict requirements on the microstructure distribution of 30MnSi hot-rolled wire rods. At present, the roller speed of the Stelmor air-cooled line is usually controlled to achieve the purpose of stable cooling to ensure the microstructure and mechanical properties of the final wire rod product. However, after the hot-rolled wire rods are spun, they are stacked on the air-cooled roller. There are overlapping points and non-overlapping points on the air-cooled roller. The cooling conditions at different positions are different. Using a fixed value of the segmented roller speed, the stacking density of the hot-rolled wire rod cannot be accurately controlled, resulting in uneven cooling at each position of the hot-rolled wire rod, which easily causes large performance fluctuations between the hot-rolled wire rods at different positions. Summary of the invention

[0004] In view of the above, it is necessary to provide a preparation process for high-strength 30MnSi hot-rolled wire to solve the problem that when using a fixed value of the segmented roller speed, the stacking density of the hot-rolled wire cannot be accurately controlled, resulting in uneven cooling of the hot-rolled wire at various positions, which easily causes large performance fluctuations between the hot-rolled wires at different positions.

[0005] One embodiment of the present application provides a process for preparing a high-strength 30MnSi hot-rolled wire, the process comprising:

[0006] S1: Put scrap steel and molten iron into an electric furnace. After tapping, add lime and fluorite, then add silicon-manganese alloy and ferrosilicon alloy to obtain molten steel;

[0007] S2: adding molten steel into a refining furnace, feeding pure calcium wire for soft blowing, and obtaining molten steel;

[0008] S3: injecting molten steel into the tundish of the continuous casting machine and continuously casting into ingots of fixed shape and size;

[0009] S4: Control the temperature in the heating furnace during the heating stage and the rolling stage;

[0010] S5: adjusting the speed of each section of the air-cooling roller according to the stacking density of the hot-rolled coils on each section of the air-cooling roller to obtain the air-cooled wire rod;

[0011] The specific process of adjusting the speed of each section of the air-cooled roller is as follows:

[0012] S501: collecting grayscale images of each wire material on each section of the air-cooling roller on the Stelmor air-cooling line;

[0013] S502: using a threshold segmentation algorithm to extract the wire area of ​​each wire grayscale image of each section of the air-cooled roller, and obtaining the central non-overlapping point probability of each edge point according to the gradient distribution characteristics of the pixel points of the wire area within the neighborhood of each edge point of the wire area and the direction characteristics of the edge where each edge point is located;

[0014] S503: classifying edge points in the wire area according to the number of edge points in the neighborhood range and the distribution of the probability of the central non-overlapping point to obtain accumulation evaluation points; obtaining the accumulation density evaluation value of each wire grayscale image according to the distribution and number of all accumulation evaluation points of each wire grayscale image;

[0015] S504: comparing the stacking density evaluation value of each wire grayscale image on each section of the air-cooled roller with that on the previous section, obtaining the roller speed adjustment factor of each section of the air-cooled roller, and adjusting the speed of each section of the air-cooled roller;

[0016] S6: The air-cooled wire is coiled, sized, bundled, weighed, and unloaded to obtain a high-strength 30MnSi hot-rolled wire.

[0017] Among them, the lime in S1 is lime containing 12-15kg / t steel, the fluorite is fluorite containing 3-4kg / t steel, the silicon-manganese alloy is a silicon-manganese alloy containing 12-15kg / t steel, and the ferrosilicon alloy is a ferrosilicon alloy containing 6-8kg / t steel.

[0018] The specific operation of feeding the pure calcium wire for soft blowing in S2 is as follows: the speed of feeding the pure calcium wire into the molten steel is controlled at 140-160 m / furnace, the soft blowing time is controlled at 10-16 min, and the molten steel shall not be exposed during soft blowing.

[0019] The specific operation of injecting the molten steel into the tundish of the continuous casting machine in S3 is as follows: the molten steel level in the tundish is controlled at 800-1000 mm, and the thickness of the slag layer in the tundish is controlled at 75 mm.

[0020] During the continuous casting process of S3, crystallization electromagnetic stirring was turned on throughout the whole process, the current intensity was controlled at 300-350A, the frequency was 3-3.5Hz, the secondary cooling water control mode adopted the weak cooling mode, and the pulling speed was controlled at 2.9-3.4m / min.

[0021] Wherein, the step of controlling the temperature in the heating furnace during the heating stage and the rolling stage in S4 includes:

[0022] In the heating stage, the air-fuel ratio of each section in the heating furnace is set to 0.7~1; when the furnace is charged in cold mode, the total time in the furnace is 70~80min, the temperature of the preheating section is 1040~1090℃, the temperature of the heating section is 1100~1200℃, and the temperature of the soaking section is 1090~1170℃; when the furnace is charged in hot mode, the total time in the furnace is 60~75min, the temperature of the preheating section is 1050~1080℃, the temperature of the heating section is 1110~1170℃, and the temperature of the soaking section is 1090~1150℃;

[0023] During the rolling stage, the starting rolling temperature is 1090~1120℃, the finishing rolling temperature is 980~1020℃, the wire drawing temperature is 850~890℃, and the rolling speed is 54~72m / s.

[0024] The probability of obtaining the central non-overlapping point of each edge point is specifically:

[0025] Calculate the degree of discreteness of the gradient direction of all pixel points belonging to the wire area in the neighborhood of each edge point; obtain the tangent direction of each edge point on the edge line, and obtain the tangent direction with the smallest angle between the tangent direction and the horizontal direction, which is recorded as the minimum tangent direction; calculate the cosine value of the angle between the minimum tangent direction of the edge line where each edge point is located and the roller moving direction; based on the cosine value of the angle of each edge point and combined with the degree of discreteness, obtain the probability of the central non-overlap point of each edge point.

[0026] The stacking evaluation point is obtained as follows:

[0027] The total number of edge points in the neighborhood of each edge point is counted; in the wire area of ​​each wire grayscale image, the leftmost pixel point of the roller middle line is taken as the origin, the roller middle line is taken as the x-axis, and the perpendicular line of the roller middle line at the origin is taken as the y-axis to obtain the characteristic coordinate system;

[0028] Calculate the mean of the difference between the probability of the central non-overlapping point of each edge point and all other edge points in its neighborhood, and combine the ordinate of each edge point in the characteristic coordinate system to obtain the characteristic value of the packing density of each edge point;

[0029] The edge points are clustered based on the stacking density eigenvalues, and all edge points in a class with the largest mean stacking density eigenvalue are recorded as stacking evaluation points.

[0030] The obtained stacking density evaluation value of each wire grayscale image is specifically:

[0031] In the characteristic coordinate system, the horizontal coordinate values ​​of all the stacking evaluation points are obtained and arranged in ascending order to obtain a density evaluation sequence; the negative correlation mapping of the differences between all adjacent elements in the density evaluation sequence is fused with the number of stacking evaluation points to obtain the stacking density evaluation value of each wire grayscale image.

[0032] The roller speed adjustment factor of each section of the air-cooled roller is obtained, and the speed of each section of the air-cooled roller is adjusted, specifically:

[0033] Obtain infrared thermal images corresponding to all wire grayscale images on each section of the air-cooled roller, calculate the temperature extreme difference value of the infrared thermal imaging image corresponding to each wire grayscale image, use the image with a temperature extreme difference value less than a preset value as the standard wire image of each section of the air-cooled roller, and use the average wire packing density assessment value of all standard wire images of each section of the air-cooled roller as the standard value of wire packing density of each section of the air-cooled roller;

[0034] The roller speed adjustment factor of the j-th air-cooled roller is recorded as , where j>1, its formula form is: ; In the formula, is the standard value of wire packing density of the j-th air-cooled roller table, , are the mean values ​​of wire rod stacking density assessment values ​​of the j-th section and the j-1-th section of the air-cooled roller conveyor, is the symbol function, Norm() is the normalization function; is the preset value;

[0035] The roller speed correction value of the j-th air-cooled roller is recorded as , its formula form is: ; In the formula, is the roller speed correction value output by the last roller speed control of the j-th section of air-cooled roller, and r represents the preset roller speed adjustment amount.

[0036] This application has at least the following beneficial effects:

[0037] 1. The present application extracts the wire area, analyzes the difference in the probability of non-overlapping points in the center of edge points in the local range, and the overlapping structural characteristics between the hot-rolled wire coils in the wire area, and obtains a stacking evaluation value, which is used to evaluate the characteristic significant intensity of the stacking density of the hot-rolled wire coil. The beneficial effect is that it solves the problem that the stacking density is difficult to evaluate due to the presence of multiple edge points in the local range that can evaluate the stacking density of the hot-rolled wire coil, and improves the accuracy of the subsequent coil stacking density evaluation on the air-cooled pipeline.

[0038] 2. This application deeply analyzes the relationship between wire packing density and roller speed, and obtains the roller speed adjustment factor of each section of air-cooled roller, and dynamically adjusts the roller speed of each section of air-cooled roller, so as to make the hot-rolled wire packing density appropriate and the coil overlap point change, improve the cooling uniformity of the hot-rolled wire during the air-cooling treatment, and enhance the uniformity of the organizational performance of the hot-rolled wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A flow chart of a preparation process of a high-strength 30MnSi hot-rolled wire provided in this application;

[0040] Figure 2 A schematic diagram of the movement of the hot-rolled wire rod on the air-cooled roller provided in this application;

[0041] Figure 3 A specific flow chart for adjusting the speed of each section of the air-cooled roller conveyor provided for this application. DETAILED DESCRIPTION

[0042] In the description of the embodiments of the present application, words such as "exemplary", "or", "for example" and the like are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "or", "for example" and the like is intended to present related concepts in a concrete manner.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0044] It should also be noted that the terms "first" and "second" in this application and its drawings are used to distinguish similar objects, rather than to describe a specific order or sequence. The method disclosed in the embodiments of the present application or the method shown in the flow chart includes one or more steps for implementing the method. Without departing from the scope of protection of this application, the execution order of multiple steps can be interchanged with each other, and some steps can also be deleted.

[0045] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0046] The chemical composition of the high-strength 30MnSi hot-rolled wire in the present application includes: C: 0.29~0.32wt%, Si: 1.10~1.40wt%, Mn: 0.92~1.00wt%, P: ≤0.015wt%, S: ≤0.015wt%, Cu: ≤0.100wt%, Cr: ≤0.100wt%, Ni: ≤0.050wt%, O: ≤25ppm, N: ≤55ppm, H: ≤2ppm, as shown in Table 1.

[0047] Table 1: Chemical composition of high strength 30MnSi hot rolled wire

[0048]

[0049] The following is a further explanation of the role of various chemical components in high-strength 30MnSi hot-rolled wire:

[0050] C is the main source of improving the strength of steel. With the increase of C content, the yield strength and tensile strength of steel will increase, but the plasticity and impact toughness will decrease.

[0051] As an alloying element in steel, Si exists in ferrite or austenite in the form of solid solution, which can reduce the austenite phase area. Si can improve the elastic limit, yield strength and yield ratio of steel, as well as fatigue strength and fatigue ratio. Too high Si content, that is, more than 2.0%, will reduce toughness.

[0052] Mn can effectively improve the strength of hot-rolled wire, and is also a good deoxidizer and desulfurizer, which can reduce the hot brittleness of steel and improve the corrosion resistance of steel. Mn can expand the austenite region, increase the critical temperature of steel, improve the hardenability of steel, and make the quenched and tempered structure of steel uniform and refined.

[0053] P is a harmful impurity in steel. P is unevenly distributed in steel and easily segregates at grain boundaries, thereby reducing the adhesion of grain boundaries. When the P content exceeds the standard, this will lead to reduced adhesion between grains, making it impossible for the grain boundaries to withstand external forces in low-temperature environments, resulting in the disintegration of grain boundaries and a phenomenon similar to sand, which in turn causes cold brittle failure.

[0054] Sulfur usually exists in the form of FeS in steel and is distributed in a network at the grain boundaries. Sulfur and iron can form a eutectic with a lower melting point and are distributed on the grain boundaries of austenite.

[0055] N can be used as a solid solution strengthening element to improve the strength of steel. As an interstitial atom, N can significantly reduce the plasticity of steel, so it has a solid solution strengthening effect and can improve the mechanical properties of steel. H can play a reducing and deoxidizing role in steel.

[0056] Example 1

[0057] Example 1 of the present application proposes a preparation process for a high-strength 30MnSi hot-rolled wire, which is applied to the technical field of hot rolling production. Figure 1 , the process comprises:

[0058] S1: Put the scrap steel into the electric furnace as raw material. The scrap steel entering the furnace should be kept clean and dry, and must not be mixed with steel slag, sediment, explosives, lead, tin and other harmful elements. The amount of molten iron added is controlled to be 40t. The tapping temperature is 1635℃. After 30 seconds of tapping, add lime containing 12kg / t steel, fluorite containing 3kg / t steel, and then add silicon manganese alloy containing 12kg / t steel and ferrosilicon alloy containing 6kg / t steel. The whole tapping process adopts argon blowing operation, and the argon flow rate is 15NL / min to obtain smelting molten steel.

[0059] S2: Add the molten steel into the LF (Ladle Furnace) refining furnace and control the inlet temperature to 1550℃. It should be noted that the LF refining furnace needs to strictly check the working condition of the furnace cover before production and use to ensure that there is no water leakage. Heat the molten steel to 1580℃ in the LF refining furnace, feed the pure calcium wire into the molten steel at a speed of 140 meters / furnace, control the soft blowing time to 10min, and the molten steel must not be exposed during soft blowing. The total refining time of the molten steel in the LF refining furnace is controlled to be 35min.

[0060] S3: The cover of the large continuous casting ladle is covered throughout the whole process, with asbestos pads on the long water nozzle, aluminum carbon material, and an insertion depth of 100mm. Argon protection is used for the whole continuous casting process. The molten steel is injected into the tundish of the continuous casting machine. The molten steel level in the tundish is controlled at 800mm, and the thickness of the slag layer in the tundish is controlled at 75mm. The submerged water nozzle is made of aluminum zirconium carbon, the baking temperature is 850℃, and the insertion depth is controlled at 80mm. During the continuous casting process, the crystallization electromagnetic stirring is turned on throughout the whole process, the current intensity is controlled at 300A, the frequency is 3Hz, the secondary cooling water control mode adopts weak cooling mode, the pulling speed is controlled at 2.9m / min, and the molten steel is continuously cast through the billet casting machine to obtain a 150mm×150mm billet.

[0061] S4: In the heating stage, the total heating time of the billet is minimized while the temperature is normal in the walking beam heating furnace. At the same time, the atmosphere in each section of the heating furnace is strictly controlled, and the air-fuel ratio of each section is set to 0.7 to maintain the reducing atmosphere in the furnace. When the furnace is charged in cold mode, the total time in the furnace is 70 minutes, the temperature of the preheating section is 1040°C, the temperature of the heating section is 1100°C, and the temperature of the soaking section is 1090°C; when the furnace is charged in hot mode, the total time in the furnace is 60 minutes, the temperature of the preheating section is 1050°C, the temperature of the heating section is 1110°C, and the temperature of the soaking section is 1090°C.

[0062] During the rolling stage, the starting rolling temperature is 1090°C, the finishing rolling temperature is 980°C, the wire drawing temperature is 850°C, and the rolling speed is 54m / s.

[0063] S5: The wire rod after spinning is air-cooled by Stelmor air-cooling line. The Stelmor air-cooling line has 4 sections of air-cooling rollers. The initial roller speeds of each section of the air-cooling rollers are 1.1m / s, 1.2m / s, 1.3m / s, and 1.4m / s, respectively. The speed of each section of the air-cooling rollers is adjusted based on the stacking density of the hot-rolled coils on each section of the air-cooling rollers to obtain the air-cooled wire rod.

[0064] The specific process of adjusting the speed of each section of the air-cooled roller is as follows:

[0065] S501: Collect grayscale images of each wire material on each section of the air-cooling roller on the Stelmor air-cooling line.

[0066] The present application installs an industrial camera at the center position of each section of the air-cooling roller on the Stelmore air-cooling line. Since the hot-rolled wire moves on the roller of the Stelmore air-cooling line, the industrial camera is adjusted so that a boundary of the image captured by the industrial camera is parallel to the moving direction of the roller; and the center line of the roller is located at the median line of the image; wherein the center line of the roller is specifically a line connected by the center of the roller and parallel to the moving direction of the roller; the camera is fixed at this position to capture images of the hot-rolled wire on the air-cooling roller, and RGB images of the wire on each section of the air-cooling roller during the air-cooling treatment are obtained. The collection time interval of the industrial camera is 5s; the implementer can adjust it according to the actual situation, and the present application does not impose any restrictions on this.

[0067] The wire RGB images of each section of the air-cooled roller are enhanced by using the adaptive histogram equalization (AHE) method, and then the enhanced wire RGB images are subjected to the bilateral filtering algorithm to remove noise while keeping the edges of the wire RGB images clear. Finally, the wire RGB images after bilateral filtering are converted into grayscale images, which are recorded as wire grayscale images. It should be noted that the implementer can select a suitable image processing algorithm to process the image, and this application does not limit this.

[0068] S502: A threshold segmentation algorithm is used to extract the wire area of ​​each wire grayscale image of each section of the air-cooled roller, and the probability of a central non-overlapping point of each edge point is obtained based on the gradient distribution characteristics of the pixel points of the wire area within the neighborhood of each edge point of the wire area and the direction characteristics of the edge where each edge point is located.

[0069] The Stelmor air-cooling line is the most widely used and efficient wire cooling method at this stage. The hot-rolled wire is stacked on the air-cooling roller after spinning. The stacking density of the hot-rolled wire coil is uneven, which easily causes uneven cooling of the hot-rolled wire coil at different positions, making it difficult to ensure the stability of the internal structure change of the hot-rolled wire, and easily causing large performance fluctuations.

[0070] Since each wire grayscale image contains not only a wire area but also a background area, and since the grayscale difference of pixels between the hot-rolled wire coil area and the background area is obvious, the Otsu threshold segmentation method is used to obtain the grayscale threshold for each wire grayscale image, and the pixels with grayscale values ​​greater than the grayscale threshold in each wire grayscale image are taken as the pixels of the wire area.

[0071] There are overlapping points and non-overlapping points on the air-cooled rollers for hot-rolled wires. The schematic diagram of the movement of hot-rolled wires on the air-cooled rollers is shown in the figure. Figure 2 As shown, 301 is the overlap point of the hot-rolled wire coil, 302 is the non-overlap point of the hot-rolled wire coil, and the arrow below is the moving direction of the air-cooled roller. For the non-overlap point position, most of them are distributed in the middle of the air-cooled roller, with good heat exchange conditions and good air cooling effect. For the overlap point position, the hot-rolled wire coils overlap each other, the coils affect each other, the heat exchange conditions are poor, and the air cooling effect is poor. The hot-rolled wire coils overlap each other, it is difficult to identify each coil and calculate the stacking density, and the coils in the middle part of the air-cooled roller are sparsely arranged.

[0072] This application takes the wire area of ​​any air-cooled roller as an example and performs the following operations:

[0073] The Sobel operator is used to calculate the gradient direction of any pixel point in the wire area, and the Canny edge detection algorithm is used to obtain all edge lines in the wire area. The size of the neighborhood can be adjusted by the implementer according to the actual situation. In each wire grayscale image, the coils in the overlapped point neighborhood are closely arranged, the number of pixels in the wire area in the neighborhood is large, and the degree of gradient direction dispersion is high; the coils in the non-overlapped point neighborhood are sparsely arranged, the number of pixels in the wire area in the neighborhood is small, and the degree of gradient direction dispersion is low.

[0074] Based on this, according to the gradient distribution characteristics of the pixel points in the wire area within the neighborhood of each edge point in the wire area, and the direction characteristics of the edge where each edge point is located, the probability of the central non-overlapping point of each edge point is obtained: the discrete degree of the gradient direction of all pixel points belonging to the wire area in the neighborhood of each edge point is calculated; the tangent direction of each edge point on the edge line is obtained, and the tangent direction with the smallest angle between the tangent direction and the horizontal direction is obtained, which is recorded as the minimum tangent direction; the cosine value of the angle between the minimum tangent direction of the edge line where each edge point is located and the moving direction of the roller is calculated; based on the cosine value of the angle of each edge point and combined with the discrete degree, the probability of the central non-overlapping point of each edge point is obtained.

[0075] In this embodiment, the variance is used to measure the degree of discreteness of the gradient direction of the pixel point; the probability of the central non-overlap point is specifically calculated by calculating the difference between 1 and the absolute value of the cosine value of the angle; the ratio of the difference to the variance is normalized to obtain the probability of the non-overlap point of each edge point, and the normalization of this application uses the sigmoid function, which can be adjusted by the implementer according to the actual situation. It should be noted that in order to avoid the situation where the denominator is zero, a preset value needs to be added to the denominator, and the value of the preset value is 0.01.

[0076] The lower the dispersion of the gradient direction of the pixel points belonging to the wire area within the neighborhood of the edge point, that is, the smaller the variance, the more sparse the coil arrangement within the neighborhood of the edge point may be. At the same time, when the tangent direction corresponding to the edge line where the edge point is located is more perpendicular to the moving direction of the roller, the greater the difference between 1 and the absolute value of the cosine value of the angle, the more likely the edge point is to be on the middle line of the roller, and the greater the probability that the edge point is a central non-overlapping point.

[0077] S503: Classify the edge points in the wire area according to the number of edge points in the neighborhood and the distribution of the probability of the central non-overlapping point to obtain the accumulation evaluation points; obtain the accumulation density evaluation value of each wire grayscale image according to the distribution and number of all accumulation evaluation points of each wire grayscale image.

[0078] In the wire area, the coils in the middle part of the air-cooled roller are sparsely arranged. Since there is a high probability of central non-overlapping points of multiple edge points in the local range of a coil, it is difficult to evaluate the packing density of the hot-rolled wire coils. Therefore, based on the number of edge points in the neighborhood range of each edge point in the wire area and the distribution of the probability of central non-overlapping points, the packing density characteristic value of each edge point is obtained: the total number of edge points in the neighborhood of each edge point is counted; in the wire area of ​​each wire grayscale image, the leftmost pixel point of the middle line of the roller is taken as the origin, the middle line of the roller is taken as the x-axis, and the perpendicular line of the middle line of the roller at the origin is taken as the y-axis. The x value of the pixel point in the wire area increases with the direction of roller movement, and the y value of the pixel point in the wire area increases with the upward direction, so as to obtain the characteristic coordinate system. The packing density characteristic value of the i-th edge point is recorded as , which is used to evaluate the characteristics of the bulk density of hot rolled wire coils, and its formula form is: ;in, is the distance from the ith edge point to the x-axis in the feature coordinate system, that is, the absolute value of the y-coordinate value of the ith edge point in the edge feature coordinate system. is the probability of the central non-overlapping point of the nth edge point in the neighborhood of the i-th edge point, represents the probability of the central non-overlapping point of the i-th edge point, is the number of edge points in the neighborhood of the i-th edge point, and e represents a natural constant.

[0079] when The larger the value is, the higher the possibility that the edge point belongs to the non-overlapping point of the coil in the middle of the cold roller. Its beneficial effect is that according to the difference in the suspected probability of the edge points in the local range of the coil, it prevents the existence of multiple edge points in the neighborhood range that can evaluate the stacking density of the hot-rolled wire coil, thereby improving the accuracy of the subsequent coil stacking density evaluation on the air-cooling pipeline. The larger the value is, the closer the edge point is to the center line of the roller, and the greater the weight should be given to avoid the problem that there are multiple edge points on the coil that can evaluate the bulk density of the hot-rolled wire coil and the bulk density is difficult to evaluate.

[0080] The stacking density eigenvalues ​​of all edge points in the wire area are used as the input of the K-means clustering algorithm, and all edge points in the wire area are divided into two categories. The edge points in the category with the largest mean stacking density eigenvalue are taken as significant points for evaluating the stacking density of hot-rolled wire coils and are recorded as stacking evaluation points.

[0081] According to the difference between the horizontal coordinate values ​​of all the stacking evaluation points of each wire grayscale image in the characteristic coordinate system and the number of the stacking evaluation points, the stacking density evaluation value of each wire grayscale image is obtained: in the characteristic coordinate system, the horizontal coordinate values ​​of all the stacking evaluation points are obtained, and they are arranged in ascending order to obtain a density evaluation sequence; the negative correlation mapping of the difference between all adjacent elements in the density evaluation sequence is merged with the number of the stacking evaluation points to obtain the stacking density evaluation value of each wire grayscale image.

[0082] In this embodiment, the negative correlation mapping of the differences between variables is measured by the reciprocal of the difference. It should be noted that in order to prevent the denominator from being equal to zero, a preset value needs to be added to the denominator, and the preset value is 0.01. Multiple variables are fused in a mixed addition and multiplication manner. The specific method for obtaining the stacking density evaluation value described in this embodiment is: the reciprocal of the difference of all adjacent elements in the density evaluation sequence is added, and then multiplied by the number of stacking evaluation points to obtain the stacking density evaluation value of each wire grayscale image.

[0083] The more the number of stacking evaluation points in each wire grayscale image, the more likely it is that the air-cooled roller has multiple hot-rolled wire coils within a fixed range. At the same time, the larger the result of the cumulative reciprocal of the difference of all adjacent elements in the density evaluation sequence, the closer the hot-rolled wire coils on the air-cooled roller are, the higher the stacking density may be, and the larger the wire stacking density evaluation value.

[0084] S504: Compare the stacking density evaluation values ​​of the grayscale images of each wire on each section of the air-cooled roller with those of the previous section, obtain the roller speed adjustment factor of each section of the air-cooled roller, and adjust the speed of each section of the air-cooled roller.

[0085] The hot-rolled wire moves on the Stelmor air-cooling line, and there is a natural drop between each section of the air-cooling roller. By changing the roller speed of the adjacent air-cooling rollers and increasing the roller speed of the next air-cooling roller, the stacking density of the hot-rolled wire coils can be reduced, and the overlap point of the hot-rolled wire coils can be changed, which promotes the cooling effect of the same circle of wire during the air-cooling phase change process and improves the uniformity of the organizational performance of the hot-rolled wire. Therefore, the present application controls the roller speed of the second section and the subsequent air-cooling rollers.

[0086] The more uniform and appropriate the overlap density between the non-overlap points and overlap points in the coil in the air-cooled roller, the more uniform the cooling of the wire can be ensured, and the uniformity of the microstructure and performance of the hot-rolled wire can be improved. Therefore, the infrared thermal images corresponding to the grayscale images of all wires on each section of the air-cooled roller are obtained through infrared imaging equipment, and the temperature extreme difference value of the infrared thermal imaging image corresponding to each wire grayscale image is calculated. The image with a temperature extreme difference value less than the preset temperature threshold is used as the standard wire image of each section of the air-cooled roller, and the average wire stacking density evaluation value of all standard wire images of each section of the air-cooled roller is used as the standard wire stacking density value of each section of the air-cooled roller. In this implementation, the temperature threshold value is 20°C. The smaller the temperature extreme difference value, the more uniform the temperature distribution of the coil in the air-cooled roller, and the more uniform the overlap density. The roller speed adjustment factor of the j-th section of the air-cooled roller is recorded as follows: , where j>1: ; In the formula, is the standard value of wire packing density of the j-th air-cooled roller table, , are the mean values ​​of wire rod stacking density assessment values ​​of the j-th section and the j-1-th section of the air-cooled roller conveyor, is a symbolic function, Norm() is a normalization function, and this application uses the sigmoid function; It is a preset value, which is used to avoid the denominator being 0. In this embodiment, the value is 0.01.

[0087] When the wire packing density between adjacent air-cooled rollers is closer, The smaller the roller speed, the more the roller speed of the air-cooled roller should be adjusted in order to promote the change of the hot-rolled wire coil overlap point. and The larger the value is, the greater the packing density of the hot-rolled wire coils on the air-cooled roller table is, and the roller speed of the air-cooled roller table should be increased, that is, the roller speed adjustment factor is a positive number and the larger it is; on the contrary, when and The smaller the value, the smaller the packing density of hot rolled wire coils on the air-cooled roller, and the roller speed of the air-cooled roller should be reduced, that is, the roller speed adjustment factor The smaller the negative number is.

[0088] In the embodiment of the present application, the maximum roller speed adjustment amount of 0.1m / s means that the maximum roller speed adjustment amount of the air-cooled roller each time does not exceed 0.1m / s. The reason for this setting is that if the roller speed is adjusted too fast or too slow, it will easily lead to insufficient cooling of the hot-rolled wire and affect the mechanical properties of the hot-rolled wire product.

[0089] The roller speed adjustment value r in this embodiment is 0.1 m / s. The roller speed correction value of the j-th air-cooled roller is obtained by the following formula: , where j>1: ; In the formula, is the roller speed correction value output by the last roller speed control of the j-th section of air-cooled roller, is the roller speed adjustment factor of the j-th section of air-cooled roller; it should be noted that the roller speed correction value output by the first roller speed control of the j-th section of air-cooled roller is obtained based on the initial roller speed.

[0090] when and The smaller it is, the smaller the packing density of the hot-rolled wire coils on the air-cooled roller is, and the roller speed should be reduced to increase the packing density of the hot-rolled wire coils. The smaller the roller speed correction value is. and The larger the value, the greater the packing density of the hot-rolled wire coils on the air-cooled roller, and the more the roller speed should be increased to reduce the packing density of the hot-rolled wire coils. The smaller the roller speed correction value is.

[0091] At this point, the roller speed of the air-cooled roller is adjusted to obtain the air-cooled wire.

[0092] Among them, the specific flow chart for adjusting the speed of each section of the air-cooled roller is as follows: Figure 3 shown.

[0093] S6: The air-cooled wire is coiled, sized, bundled, weighed, and unloaded to obtain a high-strength 30MnSi hot-rolled wire.

[0094] Example 2

[0095] Example 2 of the present application proposes a preparation process for a high-strength 30MnSi hot-rolled wire, which is applied to the technical field of hot rolling production. Figure 1 , the process comprises:

[0096] S1: Put scrap steel into the electric furnace as raw material. The scrap steel entering the furnace should be kept clean and dry, and must not be mixed with steel slag, sediment, explosives, lead, tin and other harmful elements. The amount of molten iron added is controlled to be 48t. The tapping temperature is 1610℃. After 30 seconds of tapping, lime containing 12kg / t steel, fluorite containing 4kg / t steel, silicon manganese alloy containing 14kg / t steel, and silicon iron alloy containing 8kg / t steel are added. The whole tapping process adopts argon blowing operation, and the argon flow rate is 20NL / min to obtain smelting molten steel.

[0097] S2: Add the molten steel into the LF refining furnace and control the inlet temperature to 1550℃; it should be noted that the LF refining furnace needs to strictly check the working condition of the furnace cover before production and use to ensure that there is no water leakage. Heat the molten steel to 1600℃ in the LF refining furnace, feed the pure calcium wire into the molten steel at a speed of 150 meters / furnace, control the soft blowing time to 12 minutes, the molten steel must not be exposed during soft blowing, and control the total refining time of the molten steel in the LF refining furnace to 40 minutes.

[0098] S3: The cover of the large continuous casting ladle is covered throughout the whole process, and the long water nozzle is equipped with an asbestos pad. The long water nozzle is made of aluminum carbon material, with an insertion depth of 100mm, and the continuous casting process is argon protected. The molten steel is injected into the tundish of the continuous casting machine. The molten steel level of the tundish is controlled at 850mm, and the thickness of the slag layer of the tundish is controlled at 75mm. The submerged nozzle is made of aluminum zirconium carbon, the baking temperature is 850℃, and the insertion depth is controlled at 120mm. During the continuous casting process, the crystallization electromagnetic stirring is turned on throughout the process, the current intensity is controlled at 320A, the frequency is 3Hz, the secondary cooling water control mode adopts the weak cooling mode, the pulling speed is controlled at 3m / min, and the molten steel is continuously cast through the billet casting machine to obtain a 150mm×150mm billet.

[0099] S4: In the heating stage, the casting is kept in the walking beam heating furnace to ensure that the temperature is normal and the total heating time is shortened as much as possible. At the same time, the atmosphere in each section of the heating furnace is strictly controlled, and the air-fuel ratio of each section is set to 0.9 to maintain the reducing atmosphere in the furnace. When the furnace is charged in cold mode, the total time in the furnace is 75 minutes, the temperature of the preheating section is 1050°C, the temperature of the heating section is 1150°C, and the temperature of the soaking section is 1130°C; when the furnace is charged in hot mode, the total time in the furnace is 60 minutes, the temperature of the preheating section is 1050°C, the temperature of the heating section is 1140°C, and the temperature of the soaking section is 1120°C.

[0100] During the rolling stage, the starting rolling temperature is 1100°C, the finishing rolling temperature is 1000°C, the wire drawing temperature is 870°C, and the rolling speed is 67m / s.

[0101] S5: After spinning, the wire is air-cooled using a Stelmore air-cooling line. The Stelmore air-cooling line has a total of 4 sections of air-cooling rollers. The initial roller speeds of each section of the air-cooling rollers are 1.1 m / s, 1.2 m / s, 1.3 m / s, and 1.4 m / s, respectively. The speed of each section of the air-cooling rollers is adjusted based on the stacking density of the hot-rolled coils on each section of the air-cooling rollers, using the same method as in Example 1 to obtain the air-cooled wire.

[0102] S6: The air-cooled wire is coiled, sized, bundled, weighed, and unloaded to obtain a high-strength 30MnSi hot-rolled wire.

[0103] Example 3

[0104] Example 3 of the present application proposes a preparation process for a high-strength 30MnSi hot-rolled wire, which is applied to the technical field of hot rolling production. Figure 1 , the process comprises:

[0105] S1: Put scrap steel into the electric furnace as raw material. The scrap steel entering the furnace should be kept clean and dry, and must not be mixed with steel slag, sediment, explosives, lead, tin and other harmful elements. The amount of molten iron added is controlled to be 60t. The tapping temperature is 1640℃. After 30 seconds of tapping, lime containing 15kg / t steel, fluorite containing 4kg / t steel, silicon manganese alloy containing 15kg / t steel, and silicon iron alloy containing 8kg / t steel are added. The whole tapping process adopts argon blowing operation, and the argon flow rate is 25NL / min to obtain smelting molten steel.

[0106] S2: Add the molten steel into the LF refining furnace and control the inlet temperature to 1550℃; it should be noted that the furnace cover of the LF refining furnace needs to be strictly checked before production and use to ensure that there is no water leakage. The molten steel temperature is heated to 1610℃ in the LF refining furnace, and the speed of feeding pure calcium wire into the molten steel is controlled at 160 meters / furnace, and the soft blowing time is controlled to 16 minutes. The molten steel must not be exposed during soft blowing, and the total refining time of the molten steel in the LF refining furnace is controlled to be 45 minutes.

[0107] S3: The cover of the large continuous casting ladle is covered throughout the whole process, with asbestos pads on the long water nozzle, aluminum carbon material, and an insertion depth of 100mm. The continuous casting process is argon protected. The molten steel is injected into the tundish of the continuous casting machine. The molten steel level in the tundish is controlled at 850mm, and the thickness of the slag layer in the tundish is controlled at 75mm. The submerged nozzle is made of aluminum zirconium carbon, the baking temperature is 1000℃, and the insertion depth is controlled at 120mm. During the continuous casting process, the crystallization electromagnetic stirring is turned on throughout the process, the current intensity is controlled at 350A, the frequency is 3.5Hz, the secondary cooling water control mode adopts weak cooling mode, the pulling speed is controlled at 3.4m / min, and the molten steel is continuously cast through the billet casting machine to obtain a 150mm×150mm billet.

[0108] S4: In the heating stage, the casting in the walking beam heating furnace is guaranteed to keep the temperature normal and the total heating time is shortened as much as possible. At the same time, the atmosphere in each section of the heating furnace is strictly controlled, and the air-fuel ratio of each section is set to 0.9 to maintain the reducing atmosphere in the furnace. When the furnace is charged in cold mode, the total time in the furnace is 80 minutes, the temperature of the preheating section is 1090°C, the temperature of the heating section is 1200°C, and the temperature of the soaking section is 1170°C; when the furnace is charged in hot mode, the total time in the furnace is 75 minutes, the temperature of the preheating section is 1080°C, the temperature of the heating section is 1170°C, and the temperature of the soaking section is 1150°C.

[0109] During the rolling stage, the starting rolling temperature is 1120°C, the finishing rolling temperature is 1020°C, the wire drawing temperature is 890°C, and the rolling speed is 72m / s.

[0110] S5: After spinning, the wire is air-cooled using a Stelmore air-cooling line. The Stelmore air-cooling line has a total of 4 sections of air-cooling rollers. The initial roller speeds of each section of the air-cooling rollers are 1.1 m / s, 1.2 m / s, 1.3 m / s, and 1.4 m / s, respectively. The speed of each section of the air-cooling rollers is adjusted based on the stacking density of the hot-rolled coils on each section of the air-cooling rollers, using the same method as in Example 1 to obtain the air-cooled wire.

[0111] S6: The air-cooled wire is coiled, sized, bundled, weighed, and unloaded to obtain a high-strength 30MnSi hot-rolled wire.

[0112] The tensile strength of the 30MnSi hot-rolled wire obtained in this embodiment is higher than that of the common 30MnSi hot-rolled wire on the market. The tensile strength and cross-sectional shrinkage of the hot-rolled wire produced by controlling the roller speed (embodiment) and not controlling the roller speed (comparative example) are compared. The statistical results are shown in Table 2:

[0113] Table 2: Test results of hot-rolled wire properties produced in Examples and Comparative Examples

[0114]

[0115] The flowchart and block diagram in the accompanying drawings show the possible architecture, function and operation of the system, method and computer program product according to the embodiment of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of the code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. In some alternative implementations, the function marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two continuous boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. In the description corresponding to the flowchart and the block diagram in the accompanying drawings, the operations or steps corresponding to different boxes can also occur in a different order from the order disclosed in the description, and sometimes there is no specific order between different operations or steps. For example, two continuous operations or steps can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. Each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by a dedicated hardware-based system that performs the specified functions or actions, or may be implemented by a combination of dedicated hardware and computer instructions.

[0116] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A process for preparing high-strength 30MnSi hot-rolled wire, characterized in that: The process includes: S1: Put scrap steel and molten iron into an electric furnace. After tapping, add lime and fluorite, then add silicon-manganese alloy and ferrosilicon alloy to obtain molten steel; S2: adding molten steel into a refining furnace, feeding pure calcium wire for soft blowing, and obtaining molten steel; S3: injecting molten steel into the tundish of the continuous casting machine and continuously casting into ingots of fixed shape and size; S4: Control the temperature in the heating furnace during the heating stage and the rolling stage; S5: adjusting the speed of each section of the air-cooling roller according to the stacking density of the hot-rolled coils on each section of the air-cooling roller to obtain the air-cooled wire rod; The specific process of adjusting the speed of each section of the air-cooled roller is as follows: S501: collecting grayscale images of each wire material on each section of the air-cooling roller on the Stelmor air-cooling line; S502: using a threshold segmentation algorithm to extract the wire area of ​​each wire grayscale image of each section of the air-cooled roller, and obtaining the central non-overlapping point probability of each edge point according to the gradient distribution characteristics of the pixel points of the wire area within the neighborhood of each edge point of the wire area and the direction characteristics of the edge where each edge point is located; S503: classifying edge points in the wire area according to the number of edge points in the neighborhood range and the distribution of the probability of the central non-overlapping point to obtain accumulation evaluation points; obtaining the accumulation density evaluation value of each wire grayscale image according to the distribution and number of all accumulation evaluation points of each wire grayscale image; S504: comparing the stacking density evaluation value of each wire grayscale image on each section of the air-cooled roller with that on the previous section, obtaining the roller speed adjustment factor of each section of the air-cooled roller, and adjusting the speed of each section of the air-cooled roller; S6: The air-cooled wire is coiled, sized, bundled, weighed, and unloaded to obtain a high-strength 30MnSi hot-rolled wire.

2. A process for preparing a high-strength 30MnSi hot-rolled wire according to claim 1, characterized in that: The lime in S1 is lime containing 12-15 kg / t steel, the fluorite is fluorite containing 3-4 kg / t steel, the silicon-manganese alloy is a silicon-manganese alloy containing 12-15 kg / t steel, and the ferrosilicon alloy is a ferrosilicon alloy containing 6-8 kg / t steel.

3. A process for preparing a high-strength 30MnSi hot-rolled wire according to claim 1, characterized in that: The specific operation of feeding the pure calcium wire for soft blowing in S2 is: the speed of feeding the pure calcium wire into the molten steel is controlled at 140-160 m / furnace, the soft blowing time is controlled at 10-16 min, and the molten steel must not be exposed during soft blowing.

4. A process for preparing a high-strength 30MnSi hot-rolled wire according to claim 1, characterized in that: The specific operation of injecting the molten steel into the tundish of the continuous casting machine described in S3 is: the molten steel level in the tundish is controlled at 800~1000mm, and the thickness of the slag layer in the tundish is controlled at 75mm.

5. A process for preparing a high-strength 30MnSi hot-rolled wire according to claim 1, characterized in that: During the continuous casting process of S3, crystallization electromagnetic stirring was turned on throughout the whole process, the current intensity was controlled at 300-350A, the frequency was 3-3.5Hz, the secondary cooling water control mode adopted weak cooling mode, and the pulling speed was controlled at 2.9-3.4m / min.

6. A process for preparing a high-strength 30MnSi hot-rolled wire according to claim 1, characterized in that: Controlling the temperature in the heating furnace during the heating stage and the rolling stage as described in S4 includes: In the heating stage, the air-fuel ratio of each section in the heating furnace is set to 0.7~1; when the furnace is charged in cold mode, the total time in the furnace is 70~80min, the temperature of the preheating section is 1040~1090℃, the temperature of the heating section is 1100~1200℃, and the temperature of the soaking section is 1090~1170℃; when the furnace is charged in hot mode, the total time in the furnace is 60~75min, the temperature of the preheating section is 1050~1080℃, the temperature of the heating section is 1110~1170℃, and the temperature of the soaking section is 1090~1150℃; During the rolling stage, the starting rolling temperature is 1090~1120℃, the finishing rolling temperature is 980~1020℃, the wire drawing temperature is 850~890℃, and the rolling speed is 54~72m / s.

7. A process for preparing a high-strength 30MnSi hot-rolled wire according to claim 1, characterized in that: The probability of obtaining the central non-overlapping point of each edge point is specifically: Calculate the degree of discreteness of the gradient direction of all pixel points belonging to the wire area in the neighborhood of each edge point; obtain the tangent direction of each edge point on the edge line, and obtain the tangent direction with the smallest angle between the tangent direction and the horizontal direction, which is recorded as the minimum tangent direction; calculate the cosine value of the angle between the minimum tangent direction of the edge line where each edge point is located and the roller moving direction; based on the cosine value of the angle of each edge point and combined with the degree of discreteness, obtain the probability of the central non-overlap point of each edge point.

8. A process for preparing a high-strength 30MnSi hot-rolled wire according to claim 1, characterized in that: The obtained accumulation evaluation points are specifically: The total number of edge points in the neighborhood of each edge point is counted; in the wire area of ​​each wire grayscale image, the leftmost pixel point of the roller middle line is taken as the origin, the roller middle line is taken as the x-axis, and the perpendicular line of the roller middle line at the origin is taken as the y-axis to obtain the characteristic coordinate system; Calculate the mean of the difference between the probability of the central non-overlapping point of each edge point and all other edge points in its neighborhood, and combine the ordinate of each edge point in the characteristic coordinate system to obtain the characteristic value of the packing density of each edge point; The edge points are clustered based on the stacking density eigenvalues, and all edge points in a class with the largest mean stacking density eigenvalue are recorded as stacking evaluation points.

9. A process for preparing a high-strength 30MnSi hot-rolled wire according to claim 8, characterized in that: The stacking density evaluation value of each wire grayscale image is obtained as follows: In the characteristic coordinate system, the horizontal coordinate values ​​of all the stacking evaluation points are obtained and arranged in ascending order to obtain a density evaluation sequence; the negative correlation mapping of the differences between all adjacent elements in the density evaluation sequence is fused with the number of stacking evaluation points to obtain the stacking density evaluation value of each wire grayscale image.

10. A process for preparing high-strength 30MnSi hot-rolled wire according to claim 1, characterized in that: The roller speed adjustment factor of each section of the air-cooled roller is obtained, and the speed of each section of the air-cooled roller is adjusted, specifically: Obtain infrared thermal images corresponding to all wire grayscale images on each section of the air-cooled roller, calculate the temperature extreme difference value of the infrared thermal imaging image corresponding to each wire grayscale image, use the image with a temperature extreme difference value less than a preset value as the standard wire image of each section of the air-cooled roller, and use the average wire packing density assessment value of all standard wire images of each section of the air-cooled roller as the standard value of wire packing density of each section of the air-cooled roller; The roller speed adjustment factor of the j-th air-cooled roller is recorded as , where j>1, its formula form is: ; In the formula, is the standard value of wire packing density of the j-th air-cooled roller, , are the mean values ​​of wire rod bulk density assessment values ​​of the j-th section and the j-1-th section of the air-cooled roller conveyor, is the symbol function, Norm() is the normalization function; is the preset value; The roller speed correction value of the j-th air-cooled roller is recorded as , its formula form is: ; In the formula, is the roller speed correction value output by the last roller speed control of the j-th section of air-cooled roller, and r represents the preset roller speed adjustment amount.

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