A straight rolling continuous casting billet fixed-length dynamic adjustment method

Abstract

This invention relates to a method for dynamic adjustment of the length of continuously cast billets in direct rolling, belonging to the technical field of metallurgical continuous casting and direct rolling methods. The technical solution of this invention is as follows: Real-time acquisition of the average casting speed of each billet in each flow and the superheat of the molten steel in the tundish; calculation of the difference in average casting speed and superheat between the billet to be sheared and the previous sheared billet; employing feedforward compensation to predict the change in the unit weight of the continuously cast billet according to a formula; and performing length adjustment before shearing; and performing feedback automatic compensation to adjust the length of the next billet based on the real-time length of the last billet, setting a control target range for the last billet length, and calculating the adjustment length based on the difference between the actual length of the last billet and the expected value. The beneficial effects of this invention are: effectively reducing the length of the bar stock, increasing the billet temperature and direct rolling rate, having no adverse environmental impact, saving resources and reducing costs, and having promotional application value in the field of metallurgical continuous casting and direct rolling technology.

Description

Technical Field

[0001] This invention relates to a method for dynamic adjustment of the fixed length of a direct-rolled continuous casting billet, belonging to the technical field of continuous casting and direct rolling methods in metallurgy. Background Technology

[0002] Constant weight billet feeding is currently the main method for controlling the length of bar production lines in China. Most continuous casting machines on domestic bar production lines are equipped with billet weighing equipment, and the billet length is fine-tuned based on the billet weighing results to achieve constant weight billet feeding. This method has high applicability to ordinary bar production lines. However, with the rapid development of high-speed direct rolling technology, direct rolling lines have eliminated the traditional billet heating furnace. The billets produced by the continuous casting machine enter the rolling mill directly without heating. This requires rapid and high-temperature billet transportation. Traditional billet weighing equipment has a long weighing time and a large temperature loss of the billet during the weighing process. If the billet temperature does not meet the standard, direct rolling cannot be carried out. Especially in winter when the ambient temperature is low and heat dissipation is rapid, the applicability of constant weight billet feeding is greatly reduced.

[0003] During the direct rolling process in continuous casting, the weight of the billet is constantly changing due to factors such as tundish superheat, casting speed, and crystallizer throughput. Similarly, during the rolling mill process, the weight of the bar stock is also constantly changing due to factors such as roll wear and tolerance adjustments. On production lines where billet weighing is not applicable, these factors can lead to inaccurate control of the bar tail length, frequently resulting in insufficient or excessive length of the last bar, producing a large amount of uncut bars and causing significant cost waste. Therefore, effectively controlling the bar tail length during direct rolling while maintaining the high temperature of the billet has become a goal pursued by steel companies. Summary of the Invention

[0004] The purpose of this invention is to provide a method for dynamic adjustment of the length of continuously cast billets in direct rolling. Based on the last multiple length of the bar stock, it employs feedforward and automatic feedback compensation methods to achieve dynamic adjustment of the weight of the continuously cast billets, accurately control the last multiple length of the bar stock, and reduce tail-cut scrap. It eliminates the need for billet weighing equipment, avoids the weighing process, eliminates billet dwell time, prevents billet temperature loss, and does not affect direct rolling. It effectively reduces the overall length of the bar stock, increases billet temperature and direct rolling rate, has no adverse environmental impact, saves resources, and reduces costs. It has significant application value in the field of metallurgical continuous casting and direct rolling technology and effectively solves the aforementioned problems existing in the background technology.

[0005] The technical solution of this invention is: a method for dynamic adjustment of the fixed length of a direct-rolled continuous casting billet, comprising the following steps:

[0006] (1) Real-time acquisition of the average casting speed of each billet and the superheat of the molten steel in the tundish, and calculation of the difference in average casting speed and superheat between the billet to be sheared and the previous billet that has been sheared.

[0007] (2) Using feedforward advance compensation, predict the change in the single weight of the continuously cast billet according to the formula, and make length adjustment before shearing;

[0008] (3) Perform automatic feedback compensation and set the control target range of the last root multiple scale;

[0009] (4) No adjustment is needed within the control target range of the last length multiple; adjustment is required when it exceeds the control target range of the last length multiple. The feedback automatic compensation value is calculated based on the difference between the actual length value of the last length multiple and the expected value of the last length multiple.

[0010] (5) Determine the dynamic adjustment compensation value for the continuous casting billet length, which is the sum of the feedforward advance compensation value and the feedback automatic compensation value.

[0011] In step (2), the prediction formula is:

[0012] ΔL1=K1Δx 2 +K2Δx+K3ΔT 2 +K4ΔT

[0013] In the formula: ΔL1 is the feedforward advance compensation value, in mm; K1 is the casting speed correlation coefficient 1; K2 is the casting speed correlation coefficient 2; K3 is the superheat correlation coefficient 3; K4 is the superheat correlation coefficient 4; Δx is the difference in average casting speed between the billet to be sheared and the previous sheared billet; ΔT is the difference in average superheat between the billet to be sheared and the previous sheared billet.

[0014] The coefficients K1, K2, and K in the formula 3和 K4 is related to the production section of the continuous casting machine, the cooling intensity of the crystallizer, and the cooling intensity of the secondary cooling system. The values ​​of each coefficient can be calculated through the prior data collection.

[0015] In step (4), the formula for calculating the billet adjustment length, i.e., the automatic feedback compensation value, is as follows:

[0016]

[0017] In the formula: ΔL2 is the feedback automatic compensation value; X is the actual length of the last multiple of the bar stock; X0 is the expected length of the last multiple of the bar stock; G1 is the weight per meter of the bar stock; G2 is the weight per meter of the cast billet; K5 is the conservative coefficient 2; K6 is the conservative coefficient 1; a is the lower limit of the control target for the difference between the actual length of the last multiple of the bar stock and the expected length of the last multiple of the bar stock; b is the upper limit of the control target for the difference between the actual length of the last multiple of the bar stock and the expected length of the last multiple of the bar stock.

[0018] The automatic feedback compensation takes into account the lag and sets a waiting time.

[0019] The automatic feedback compensation determines whether there is a gap between the rolled billet and the billet to be sheared based on the number of shearing operations of the hydraulic shear during the period from the completion of shearing to the completion of rolling.

[0020] In step (5), the calculation formula for the dynamic adjustment compensation value of the continuous casting billet length is as follows:

[0021] ΔL=ΔL1+ΔL2

[0022] In the formula: ΔL is the dynamic adjustment compensation value for the fixed length of the continuously cast billet; ΔL1 is the feedforward compensation value for the next fixed length of the billet; ΔL2 is the automatic feedforward compensation value for the next fixed length of the billet.

[0023] The beneficial effects of this invention are as follows: Based on the last multiple length of the bar stock, a feedforward and feedback automatic compensation method is adopted to achieve dynamic adjustment of the weight of the continuously cast billet, accurately control the last multiple length of the bar stock, and reduce tail-cut scrap; no billet weighing equipment is required, there is no weighing process, the billet does not need to stop, there is no billet temperature loss, and it does not affect the direct rolling of the billet; it effectively reduces the length of the bar stock, increases the billet temperature and the direct rolling rate, has no adverse environmental impact, saves resources and reduces costs, and has promotion and application value in the field of metallurgical continuous casting and direct rolling technology. Attached Figure Description

[0024] Figure 1 This is a time flow diagram of the billet conveying of the present invention;

[0025] Figure 2 This is a flowchart of the automatic feedback compensation adjustment process of the present invention. Detailed Implementation

[0026] To make the purpose, technical solutions, and advantages of the invention's embodiments clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only a small part of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0027] A method for dynamic adjustment of the fixed length of a direct-rolled continuous casting billet includes the following steps:

[0028] (1) Real-time acquisition of the average casting speed of each billet and the superheat of the molten steel in the tundish, and calculation of the difference in average casting speed and superheat between the billet to be sheared and the previous billet that has been sheared.

[0029] (2) Using feedforward advance compensation, predict the change in the single weight of the continuously cast billet according to the formula, and make length adjustment before shearing;

[0030] (3) Perform automatic feedback compensation and set the control target range of the last root multiple scale;

[0031] (4) No adjustment is needed within the control target range of the last length multiple; adjustment is required when it exceeds the control target range of the last length multiple. The feedback automatic compensation value is calculated based on the difference between the actual length value of the last length multiple and the expected value of the last length multiple.

[0032] (5) Determine the dynamic adjustment compensation value for the continuous casting billet length, which is the sum of the feedforward advance compensation value and the feedback automatic compensation value.

[0033] In step (2), the prediction formula is:

[0034] ΔL1=K1Δx 2 +K2Δx+K3ΔT 2 +K4ΔT

[0035] In the formula: ΔL1 is the feedforward advance compensation value, in mm; K1 is the casting speed correlation coefficient 1; K2 is the casting speed correlation coefficient 2; K3 is the superheat correlation coefficient 3; K4 is the superheat correlation coefficient 4; Δx is the difference in average casting speed between the billet to be sheared and the previous sheared billet; ΔT is the difference in average superheat between the billet to be sheared and the previous sheared billet.

[0036] The coefficients K1, K2, and K in the formula 3和 K4 is related to the production section of the continuous casting machine, the cooling intensity of the crystallizer, and the cooling intensity of the secondary cooling system. The values ​​of each coefficient can be calculated through the prior data collection.

[0037] In step (4), the formula for calculating the billet adjustment length, i.e., the automatic feedback compensation value, is as follows:

[0038]

[0039] In the formula: ΔL2 is the feedback automatic compensation value; X is the actual length of the last multiple of the bar stock; X0 is the expected length of the last multiple of the bar stock; G1 is the weight per meter of the bar stock; G2 is the weight per meter of the cast billet; K5 is the conservative coefficient 2; K6 is the conservative coefficient 1; a is the lower limit of the control target for the difference between the actual length of the last multiple of the bar stock and the expected length of the last multiple of the bar stock; b is the upper limit of the control target for the difference between the actual length of the last multiple of the bar stock and the expected length of the last multiple of the bar stock.

[0040] The automatic feedback compensation takes into account the lag and sets a waiting time.

[0041] The automatic feedback compensation determines whether there is a gap between the rolled billet and the billet to be sheared based on the number of shearing operations of the hydraulic shear during the period from the completion of shearing to the completion of rolling.

[0042] In step (5), the calculation formula for the dynamic adjustment compensation value of the continuous casting billet length is as follows:

[0043] ΔL=ΔL1+ΔL2

[0044] In the formula: ΔL is the dynamic adjustment compensation value for the fixed length of the continuously cast billet; ΔL1 is the feedforward compensation value for the next fixed length of the billet; ΔL2 is the automatic feedforward compensation value for the next fixed length of the billet.

[0045] In practical applications, this invention calculates the dynamic adjustment length of the direct-rolling continuous casting billet by collecting and calculating data on the real-time multiple length of the last bar, the average casting speed of the continuous casting billet, and the superheat of the molten steel in the tundish. This data is then input into the continuous casting billet cutting system to adjust the billet length, thereby achieving precise control over the bar tail length of the next casting billet. This invention eliminates the need for billet weighing equipment, and the billet does not need to stop for weighing, ensuring the high temperature of the billet and allowing for normal conveyance to the direct rolling mill. The dynamic adjustment method consists of two parts: feedforward advance compensation and feedback automatic compensation.

[0046] Feedforward compensation is a feedforward control method that uses real-time data acquisition of each casting billet in each flow to calculate the difference in average casting speed and superheat between the billet to be sheared and the previous sheared billet, and predicts the change in the unit weight of the continuously cast billet according to the following formula, and performs length adjustment before shearing.

[0047] ΔL1=K1Δx 2 +K2Δx+K3ΔT 2 +K4ΔT

[0048] In the formula:

[0049] ΔL1—Pre-cutting compensation value for the billet to the next specified length, in mm

[0050] K1—Relevance coefficient of pulling speed 1.

[0051] K2 – Coefficient of correlation between pulling speed and speed.

[0052] K3 – Correlation coefficient of superheat 3.

[0053] K4 – Correlation coefficient of superheat: 4.

[0054] Δx — the difference in average casting speed between the billet to be sheared and the previous sheared billet.

[0055] ΔT — The difference in average superheat between the billet to be sheared and the previous sheared billet.

[0056] The coefficients K1, K2, K3, and K4 mentioned in the formula are related to the production cross-section of the continuous casting machine, the cooling intensity of the crystallizer, and the cooling intensity of the secondary cooling system. The values ​​of each coefficient can be calculated through the prior data collection.

[0057] The feedback automatic compensation is based on the material balance of the two zones of steel rolling. After the billet is directly rolled, the length of the last multiple length of the rolled bar is collected. The weight gain or loss is calculated based on the length of the last multiple length. The adjustment length of the billet is then deduced based on the weight gain or loss. The material balance is as follows:

[0058] Bar weight × (actual length of the last bar length - expected length of the last bar length) = - billet weight × billet adjustment length

[0059] The adjusted length can be directly added to the corresponding flow's automatic feedback compensation value to complete one automatic feedback adjustment function. Through the system's high-frequency adjustment, the actual length of the last multiple length of the bar can be controlled around the expected value of the last multiple length of the bar, thereby achieving precise control of the bar tail length, reducing the bar length pass rate, and improving the continuous casting yield and bar production rate.

[0060] Automatic feedback compensation needs to consider adjustment lag. After a certain flow of billets has produced multiple lengths, the adjustment should specify which billet after that particular billet in that flow is being rolled. Taking our company as an example, the billet delivery time flow is tracked as follows: Figure 1 The total conveying time is 170 seconds plus the waiting time. The time to complete the cutting of the next billet is 12 meters ÷ 4.0 meters / min = 180 seconds. The length of the next billet can be adjusted, and at most one billet will be skipped.

[0061] The automatic feedback compensation system automatically determines whether there is a gap between the rolled billet and the billet to be sheared. This is based on the number of hydraulic shear cuts performed on the current billet from shearing completion to rolling completion. If the number of cuts is 1, then one billet is spaced, using a conservative coefficient of 1. If the number of cuts is 0, then no gap is performed, using a conservative coefficient of 2. The conservative coefficient 1 setting range is 0-0.5; the conservative coefficient 2 setting range is 0-1. This adjustment method prevents over-adjustment and eliminates the phenomenon of the last multiple-length billet oscillating back and forth between the desired value, thereby eliminating the influence of billet gaps.

[0062] The feedback automatic compensation is set with a clearly defined control target range for the last multiple of the scale. No adjustment is needed within this range; adjustments are required outside the range. Specific adjustments are determined based on the difference between the length of the last multiple of the scale and the desired value. The adjustment flowchart is as follows: Figure 2 The formula is adjusted as follows:

[0063]

[0064] in:

[0065] ΔL2 — Automatic feedback compensation value, mm;

[0066] X — Actual length of the last multiple of the bar, in mm;

[0067] X0 — Expected value of the last multiple length of the bar stock, in mm;

[0068] G1 – Weight per meter of bar stock, kg;

[0069] G2 — Weight per meter of cast billet, kg;

[0070] K5 – Conservative coefficient of 2;

[0071] K6 – Conservative coefficient 1;

[0072] a——Lower limit of the control target for the difference between the actual length of the last multiple of the bar and the expected length of the last multiple of the bar, mm;

[0073] b—The upper limit of the control target for the difference between the actual length of the last multiple of the bar and the expected length of the last multiple of the bar, in mm. The dynamic adjustment compensation value for the continuous casting billet length is the sum of the feedforward advance compensation and the feedback automatic compensation, and the specific formula is as follows:

[0074] ΔL=ΔL1+ΔL2

[0075] ΔL——Compensation value for the next cut length of the billet, in mm;

[0076] ΔL1——Pre-feedback compensation value for the next cut length of the billet, mm;

[0077] ΔL2——Automatic compensation value after the billet is cut to length for the next time, in mm;

[0078] The accuracy of the last multiple length of the bar in the dynamic adjustment of the billet length is higher than that of the fixed weight weighing. The accuracy of the two bars multiple length shearing is related to the finished product rolling speed. The total length error of ordinary bars is ±200mm, and the total length error of high bars is ±500mm. The overall equipment length accuracy is controlled within 0.03%-0.08% (see Table 1). Compared with the fixed weight weighing accuracy of 0.3%, the accuracy of the basic data of this method is improved by an order of magnitude.

[0079] Table 1: Length Accuracy of Different Thread Specifications

[0080]

[0081] The dynamic adjustment of the fixed length of the continuously cast billet described in this invention is suitable for short-process direct rolling production lines. It eliminates the need for additional weighing equipment on the production infrastructure, significantly reducing equipment modification investment. Data collection and automatic adjustment can be achieved through the existing production infrastructure. The billet can be transported normally without stopping, reducing sensible heat loss and ensuring the billet temperature meets direct rolling standards. The tail length of the bar can be precisely controlled within 2-4m, reducing the average tail length of each billet by 3m. With a scrap steel price difference of approximately 1000 yuan, an average bar weight of 6kg / m, and each billet weighing 2.5t, the profit per ton of steel can reach: 3*6 / 1000 / 2.5*1000 = 7.2 yuan / ton. This invention achieves dynamic adjustment of the fixed weight of the continuously cast billet, offering advantages such as high equipment precision, no additional investment, and no additional temperature drop in the billet. It enables precise control of the last multiple length of the bar, reducing tail scrap. It has no adverse environmental impact, saves resources, and reduces costs, making it valuable for widespread application in the field of metallurgical continuous casting and direct rolling technology.

[0082] Example:

[0083] I. Data Collection

[0084] Continuous casting machine integral length measurement system or camera length measurement system: collects the actual cutting length of the continuously cast billet;

[0085] Flow classification system: determines the flow classification of direct-rolled billets;

[0086] Bar length acquisition system: acquisition;

[0087] II. Establishing an automated computation model

[0088] An automated computational model is established, which includes feedforward advance compensation and feedback automatic compensation. The input parameter is the actual production length of the bar stock, and the output parameter is the compensation value for the cutting length of the continuously cast billet.

[0089] III. Correcting the billet length

[0090] The compensation value for the cutting length of the continuously cast billet is connected to the continuous casting billet cutting system. Based on the existing fixed length, the compensation value is accumulated to calculate the automatic fixed length, and the billet is cut to that length.

[0091] For producing 25mm rebar from bar stock, the rolling length of a 5-strand cast billet is X = 340m. The average drawing speed difference between the billet to be sheared and the previous sheared billet is Δx = 0.1m / min. The calculated automatic feedback compensation ΔL1 = 0.071m, the feedforward advance compensation ΔL2 = -0.012m, and the dynamic adjustment compensation value for the continuous casting billet length ΔL = ΔL1 + ΔL2 = 0.059m result in a 5-strand continuous casting billet length of 12.012m. The next billet length after accumulating the compensation values ​​is also 12.071m. This completes one automatic compensation cycle. Through continuous adjustment using the automated model, the billet rolling length X is controlled at 336m, reducing the overall bar length and achieving cost reduction.

Claims

1. A method for on-line length adjustment of a continuously cast billet by direct rolling, characterized in that Includes the following steps: (1) Real-time acquisition of the average casting speed of each billet and the superheat of the molten steel in the tundish, and calculation of the difference in average casting speed and superheat between the billet to be sheared and the previous billet that has been sheared; (2) Using feedforward advance compensation, predict the change in the single weight of the continuously cast billet according to the formula, and make length adjustment before shearing; (3) Perform feedback automatic compensation and set the control target range of the last root multiple scale; (4) No adjustment is required within the control target range of the last length multiple; adjustment is required if it exceeds the control target range of the last length multiple. The feedback automatic compensation value is calculated based on the difference between the actual length value of the last length multiple and the expected value of the last length multiple. (5) Determine the dynamic adjustment compensation value for the continuous casting billet length, which is the sum of the feedforward advance compensation value and the feedback automatic compensation value; In step (2), the prediction formula is: ΔL1 = K1 Δx 2 + K2 Δx + K3 ΔT 2 + K4 ΔT In the formula: ΔL1 is the feedforward advance compensation value, in mm; K1 is the casting speed correlation coefficient 1; K2 is the casting speed correlation coefficient 2; K3 is the superheat correlation coefficient 3; K4 is the superheat correlation coefficient 4; Δx is the difference in average casting speed between the billet to be sheared and the previous sheared billet; ΔT is the difference in average superheat between the billet to be sheared and the previous sheared billet. The coefficient K mentioned in the formula 1、 K 2、 K3 and K4 are related to the production section of the continuous casting machine, the cooling intensity of the crystallizer and the cooling intensity of the secondary cooling unit. The values ​​of each coefficient can be calculated through the data collection in the early stage. In step (4), the formula for calculating the billet adjustment length, i.e., the automatic feedback compensation value, is as follows: ， In the formula: ΔL2 is the feedback automatic compensation value; X is the actual length of the last multiple of the bar stock; X0 is the expected length of the last multiple of the bar stock; G1 is the weight per meter of the bar stock; G2 is the weight per meter of the cast billet; K5 is the conservative coefficient 2; K6 is the conservative coefficient 1; a is the lower limit of the control target for the difference between the actual length of the last multiple of the bar stock and the expected length of the last multiple of the bar stock; b is the upper limit of the control target for the difference between the actual length of the last multiple of the bar stock and the expected length of the last multiple of the bar stock. The conservative coefficient 1 is set in the range of 0-0.5; the conservative coefficient 2 is set in the range of 0-1.

2. A method for dynamic length adjustment of straight rolling continuous casting billets according to claim 1, characterized in that: The automatic feedback compensation takes into account the lag and sets a waiting time.

3. A method of straight rolling of a continuously cast billet with length adjustment according to claim 1, characterized in that: The automatic feedback compensation determines whether there is a gap between the rolled billet and the billet to be sheared based on the number of shearing operations of the hydraulic shear during the period from the completion of shearing to the completion of rolling.

4. A method of straight rolling of a continuously cast billet with length adjustment according to claim 1, characterized in that: In step (5), the calculation formula for the dynamic adjustment compensation value of the continuous casting billet length is as follows: ΔL=ΔL1 +ΔL2 In the formula: ΔL is the dynamic adjustment compensation value for the fixed length of the continuously cast billet; ΔL1 is the feedforward compensation value for the next fixed length of the billet; ΔL2 is the automatic feedforward compensation value for the next fixed length of the billet.

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