A method for controlling the linear speed and torque balance of a continuous-casting light-press-down straightening roller

Abstract

This invention relates to a method for balancing the linear speed and torque of the straightening rolls during light-pressure continuous casting, belonging to the field of metallurgical engineering. By establishing a functional relationship between the cumulative reduction of each roll, the change in billet width, and the change in the linear speed of the straightening rolls, the method corrects the error of the original system's calculated value with actual test values, optimizes the linear speed of the straightening rolls during light-pressure, and classifies and manages the straightening rolls before, during, and after light-pressure. This achieves stable control of torque balance, effectively solving the problems of drastic changes in the linear speed and unstable torque of the straightening rolls during the light-pressure process in continuous casting. It also improves the billet shape and surface transverse cracks, thus enhancing the surface quality of the continuous casting billet.

Description

Technical Field

[0001] This invention relates to a method for controlling the linear speed and torque balance of the straightening rolls in continuous casting under light pressure, belonging to the technical field of metallurgical engineering. Background Technology

[0002] Light reduction technology at the end of solidification is an effective means to improve the center quality of cast billets, and the continuous casting straightener is a key piece of equipment for performing the light reduction process, mainly performing the functions of billet pulling, straightening, and reduction. The stable operation of the continuous casting straightener directly affects the surface and core quality of the cast billet. When performing the light reduction process, the continuous casting straightener needs to set a pressure to cause a certain deformation of the cast billet, and this deformation will cause changes in the pulling speed, and the linear speed of each roller of the straightener will also change accordingly. Once the change in the linear speed of the straightener rollers does not match the deformation of the cast billet, it will cause sliding friction between the roller surface and the surface of the cast billet, and each roller will bear a large surface stress along the square of the cast billet. Specifically, the roller surface of the straightener rollers will wear more easily, and transverse cracks will easily appear in the cast billet.

[0003] An unreasonable linear speed usually leads to an unbalanced load. When the linear speed setting of the straightening rollers in the continuous casting straightening machine is unreasonable and the torque of the straightening rollers is abnormal, the linear speed of the straightening rollers changes drastically when the light pressing process is executed, and the torque of the straightening rollers that are not pressed is negative, resulting in unstable billet shape and surface cracks.

[0004] Patent application CN 118976876 A discloses a dynamic load balance control method for a continuous casting machine drive roller transmission system. It mainly solves problems such as load imbalance and frequency converter failure in the continuous casting machine drive roller transmission system, but does not address the load and torque of the straightening rollers when the billet is deformed under light pressure.

[0005] Patent application CN 106111929 A discloses a dynamic load distribution control system and control method for a straightening motor in continuous casting of round billets, which solves the problem of frequency converter failure in continuous casting machine of round billets.

[0006] There is currently no existing technology that specifically addresses the issues of linear velocity variation and torque balance of the straightening rollers during light pressure operation, and a solution is urgently needed. Summary of the Invention

[0007] To address the aforementioned problems, this invention discloses a method for controlling the linear speed and torque balance of the continuous casting light-pressure pull-down straightening rolls, the specific technical solution of which is as follows: A method for controlling the linear speed and torque balance of the straightening rolls in continuous casting under light pressure includes the following steps: Step 1: Before production, inspect the wear of the leveling rollers and correct the roller gap, pressure parameters, and levelness. Step 2: Adjust the linear speed V of the leveling roller according to the following formula. , V set Set the pulling speed for the process, in m / min. 'a' represents the thickness of the hot-state cross-section of the billet, in mm. b is the width of the hot cross-section of the billet, in mm. μ is the coefficient of thermal expansion of the billet from cold to hot state. ∆a is the cumulative pressing amount from the first pressing roller to the current adjusting roller, in mm. ∆b ​​is the cumulative increase in billet width (in mm) corresponding to the cumulative reduction value ∆a from the first pressing roller to the current adjusting roller; Step 3: Establish the relationship between the linear velocity and reduction of each straightening roll in the continuous casting control system according to the formula in Step 2.

[0008] Furthermore, the specific requirements for step 1 are as follows: the diameter error of the straightening roller is ≤0.5mm, the roller gap accuracy error of each straightening roller under the hot blank is ≤0.5mm, the output pressure error of each straightening roller is ≤10kN, and the roller surface levelness of the straightening roller is ≤0.2mm / m.

[0009] Furthermore, the method for obtaining each parameter in the formula of step 2 is as follows: The hot cross-sectional thickness 'a' of the billet is the average value of the gap between each straightening roll when light pressure is not applied. The width b of the hot cross-section of the billet is calculated according to the following formula. , a1 is the thickness of the inner cavity at the lower opening of the copper tube in the crystallizer, in mm. b1 is the width of the inner cavity at the lower opening of the copper tube of the crystallizer, in mm; The coefficient of thermal expansion μ of the billet from cold to hot state is calculated according to the following formula: , a3 is the thickness of the billet in the cold state, which is the average value of the low-magnification measurement of the billet without light pressure. The increase in billet width ∆b corresponding to the reduction amount ∆a is calculated using the following formula: , The coefficient K is estimated using the width increase value of each light pressing process. 平 When performing a light reduction process, three different reduction amounts are taken. At each reduction amount, several ingots are taken from each flow and their width is measured at low magnification. mean If we obtain b2, b3, and b4, then , ∆a1, the total reduction of all flows under the first reduction, in mm. ∆a2, the total reduction of each flow under the second reduction, in mm. ∆a3, the total reduction of all flows under the third reduction, in mm. b5 represents the width of the billet in the cold state, taken as the average of the low-magnification measurements of the billet under no light pressure.

[0010] Furthermore, step 3 specifically involves: assuming that the nth roller of a certain flow is the first roller to perform the light pressing process, and the mth roller is the last roller to perform the light pressing process, then the rotational speed of the straightening rollers before the nth roller is Vset, the rotational speed of the straightening rollers between the nth and nth rollers is V, and the rotational speed of the straightening rollers after the mth roller is equal to the rotational speed of the mth roller.

[0011] Furthermore, step 4 is also included: although the tensioning rolls after the m-th roll do not perform the light pressing process, they still adopt the pressing displacement mode, and their pressing amount is set to 0, instead of the hot billet pressure mode; the tensioning rolls before the n-th roll adopt the hot billet pressure mode, and their hot billet pressure is set to 30kN-50kN.

[0012] The beneficial effects of this invention are: This invention solves the problem of surface cracks in cast billets caused by the mismatch between the linear speed change of the straightening roller and the deformation of the cast billet, without requiring additional equipment and manpower. Attached Figure Description

[0013] Figure 1 This is a photograph of the cast billet obtained in Example 1, showing no transverse cracks detected during magnetic particle testing. Figure 2 The image shows a photograph of a corner transverse crack obtained from magnetic particle inspection of a cast billet, as shown in Comparative Example 1. Detailed Implementation

[0014] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0015] This invention is applicable to high-carbon steels such as spring steel, ball steel, and bearing steel with a carbon content of 0.50~1.00%. It is suitable for use on a 210 cubic meter continuous casting machine with the following process parameters: casting speed 1.10~1.30 m / min, secondary cooling water 0.30~0.50 kg / L, total reduction of 5~15 mm in the light reduction process, and single-roll reduction of 1-5 mm. The steps are as follows: First, before production, the wear of the leveling rolls is inspected, and the roll gap, pressure parameters, and levelness of the leveling rolls are corrected. The requirements are: roll diameter error ≤ 0.5mm, roll gap accuracy error ≤ 0.5mm under hot billet, output pressure error of each roll ≤ 10kN, and roll surface levelness ≤ 0.2mm / m. Then, the linear speed V of the leveling rolls is adjusted according to the following formula. , V setSet the pulling speed for the process, in m / min. 'a' represents the thickness of the hot-state cross-section of the billet, in mm. b is the width of the hot cross-section of the billet, in mm. μ is the coefficient of thermal expansion of the billet from cold to hot state. ∆a is the cumulative pressing amount from the first pressing roller to the current adjusting roller, in mm. ∆b ​​is the cumulative increase in billet width (in mm) corresponding to the cumulative reduction value ∆a from the first pressing roller to the current adjusting roller.

[0016] The parameters involved in the formula are obtained through the following methods: a. Hot cross-sectional thickness of the billet: The straightening roller with light pressing function has a displacement sensor. The hot cross-sectional thickness of the billet can be directly used as the average value of the roll gap when light pressing is not performed. Here, we take 216mm.

[0017] b. Width of the hot cross-section of the billet: The width is calculated based on the shrinkage of the thickness, specifically calculated as 216mm using the following formula. , a1, the inner thickness of the lower opening of the copper tube in the crystallizer, is 218.5 mm for this casting machine. b1, the inner width of the lower opening of the copper tube in the crystallizer, which is 218.5mm on this casting machine. μ is the coefficient of thermal expansion of the billet from cold to hot state, and a is the thickness a of the hot cross-section of the billet. , a3, the thickness of the cold-state billet, can be taken as the average of the thickness measured at low magnification under no light pressure.

[0018] ∆b, the increase in billet width corresponding to the reduction ∆a, is calculated using the following formula: , coefficient K 平 The width increase value of each light reduction process is used for estimation. The light reduction process can be taken as a conventional process; here, reduction amounts of 8mm, 10mm, and 17mm are used. The different reduction roller distribution amounts affect K. 平 The impact is minor and will not be considered. Under a set reduction of 8mm, take one billet per flow at low magnification, measure the width, and take the average value to obtain b2; subsequently set reductions of 10mm and 17mm to obtain b3 and b4, respectively. , ∆a1, 8mm total reduction ∆a2, 10mm total reduction ∆a3, 17mm total reduction.

[0019] b5 represents the width of the billet in the cold state, taken as the average of the low-magnification measurements of the billet under no light pressure.

[0020] Then, based on the above formula, the relationship between the linear velocity of each roll and the reduction amount is established in the continuous casting control system. Specifically: Let the nth roll of a certain flow be the first roll to perform the light reduction process, and let the mth roll be the last roll to perform the light reduction process. Then the rotational speed of the straightening rolls before the nth roll is V. set The rotational speed of the straightening rollers between rollers n and n (including rollers m and n) is V, and the rotational speed of the straightening rollers after roller m is equal to the rotational speed of roller m.

[0021] Finally, to reduce the influence of elastic deformation, the straightening rolls after the m-th roll do not perform a light pressing process, but still adopt the pressing displacement mode, with the pressing amount set to 0, instead of the hot billet pressure mode; the straightening rolls before the n-th roll adopt the hot billet pressure mode, with the hot billet pressure set to 30kN-50kN.

[0022] The above method can solve the problem of surface cracks in the billet caused by the mismatch between the linear speed change of the straightening roller and the deformation of the billet, without increasing the consumption of equipment, manpower and material resources.

[0023] Comparative Example 1 For the production of 60Si2Cr, the original control method of a certain manufacturer's continuous casting machine was adopted: continuous casting speed 1.15m / min, tundish steel superheat 35℃, secondary cooling water 0.36L / kg, light reduction process 3-6 rolls 2mm-3mm-3mm-2mm, the linear velocity parameters of each flow 1-3 rolls are shown in Table 1 below. After implementing light reduction, the casting speed increased by 0.05~0.08m / min, which is significantly too large.

[0024] Table 1 Roller #1 1.15 Roller #1 1.15 Roller #1 1.15 Roller #1 1.15 Roller #1 1.15 Roller #2 1.15 Roller #2 1.15 Roller #2 1.15 Roller #2 1.15 Roller #2 1.15 Roller #3 1.20 Roller #3 1.20 Roller #3 1.20 Roller #3 1.20 Roller #3 1.20 Roller #4 1.21 Roller #4 1.20 Roller #4 1.21 Roller #4 1.21 Roller #4 1.21 5# roller 1.22 5# roller 1.22 5# roller 1.22 5# roller 1.21 5# roller 1.22 Roller #6 1.23 Roller #6 1.23 Roller #6 1.24 Roller #6 1.23 Roller #6 1.23 7# roller 1.15 7# roller 1.15 7# roller 1.15 7# roller 1.15 7# roller 1.15 The torque parameters of rollers 1-7 for each flow are shown in Table 2 below. The torque opening of the straightening rollers under light pressure is negative.

[0025] Table 2 Roller #1 -6.1 Roller #1 -0.8 Roller #1 -4.8 Roller #1 -0.3 Roller #1 -5.5 Roller #2 -2.9 Roller #2 -7.1 Roller #2 -2.8 Roller #2 -3.4 Roller #2 -9.1 Roller #3 24.8 Roller #3 26.2 Roller #3 21.2 Roller #3 15.5 Roller #3 27.4 Roller #4 26.2 Roller #4 24.9 Roller #4 29.1 Roller #4 24.9 Roller #4 33.0 5# roller 35.8 5# roller 42.4 5# roller 39.0 5# roller 38.8 5# roller 48.1 Roller #6 31.9 Roller #6 35.0 Roller #6 31.2 Roller #6 24.6 Roller #6 37.1 7# roller -4.6 7# roller -4.3 7# roller -4.6 7# roller -7.5 7# roller -3.0 The magnetic particle inspection of the corresponding cast billet revealed transverse cracks at the corners, such as... Figure 2 As shown.

[0026] Example 1 The production of 60Si2Cr adopts the same process as the comparative example: continuous casting speed 1.15m / min, tundish steel superheat 30℃, secondary cooling water 0.36L / kg, and light reduction process 3-6 rolls 2mm-3mm-3mm-2mm.

[0027] First, before production, the wear of the straightening rollers is checked, and the roller gap, pressure parameters and levelness of the straightening rollers are corrected. The requirements are that the diameter error of the straightening rollers is ≤0.5mm, the roller gap accuracy error of each roller under the hot blank is ≤0.5mm, the output pressure error of each roller is ≤10kN, and the roller surface levelness is ≤0.2mm / m.

[0028] Then adjust the linear speed of the straightening rollers according to the following formula. , V set The process setting is a pulling speed of 1.15 m / min. a. Thickness of the hot-state cross-section of the cast billet: 216 mm b, the width of the hot cross-section of the billet. b = b1 * a / a1 = 216 mm μ, the coefficient of thermal expansion of the billet from cold to hot state. μ=(216-210) / 210*100%=2.78% ∆a, the cumulative amount of pressure applied from the first pressing roller to this roller, can be taken as the actual value. coefficient K 平 The width increase value of each light reduction process is used for estimation. The light reduction process can be taken as a conventional process; here, reduction amounts of 8mm, 10mm, and 17mm are used. The different reduction roller distribution amounts affect K. 平 The impact is minor and will not be considered. With a set reduction of 8mm, take one billet from each flow at low magnification, measure the width, and take the average value to obtain a4 as 213.1mm; successively setting reductions of 10mm and 17mm, we obtain a5 as 214.2mm and a6 as 216.5mm. Therefore, K_flat = 0.397, and ∆b = 0.397∆a. Then V=V set *216*216 / [(216-∆a)*(216+102.78%*0.397∆a)] =46656V set / [(216-∆a)*(216+0.408∆a)] The linear velocity parameters of rollers 1-3 for each flow obtained from the above formula are shown in Table 3 below.

[0029] Table 3 Roller #1 1.15 Roller #1 1.15 Roller #1 1.15 Roller #1 1.15 Roller #1 1.15 Roller #2 1.15 Roller #2 1.15 Roller #2 1.15 Roller #2 1.15 Roller #2 1.15 Roller #3 1.15 Roller #3 1.15 Roller #3 1.15 Roller #3 1.15 Roller #3 1.15 Roller #4 1.16 Roller #4 1.16 Roller #4 1.16 Roller #4 1.16 Roller #4 1.16 5# roller 1.17 5# roller 1.17 5# roller 1.17 5# roller 1.17 5# roller 1.17 Roller #6 1.18 Roller #6 1.17 Roller #6 1.18 Roller #6 1.18 Roller #6 1.18 7# roller 1.18 7# roller 1.18 7# roller 1.19 7# roller 1.18 7# roller 1.18 The torque parameters of rollers 1-7 for each flow are shown in Table 4 below. All values ​​of the tension rollers are positive.

[0030] Table 4 Roller #1 3.5 Roller #1 2.5 Roller #1 5.0 Roller #1 1.5 Roller #1 5.6 Roller #2 6.1 Roller #2 9.0 Roller #2 6.8 Roller #2 4.5 Roller #2 10 Roller #3 20.7 Roller #3 20.8 Roller #3 17.7 Roller #3 15.5 Roller #3 21.0 Roller #4 39.2 Roller #4 38.8 Roller #4 32.2 Roller #4 27.9 Roller #4 21.8 5# roller 34.4 5# roller 33.5 5# roller 41.0 5# roller 38.8 5# roller 38.4 Roller #6 34.1 Roller #6 33.9 Roller #6 21.0 Roller #6 31.2 Roller #6 30.0 7# roller 1.0 7# roller 5.1 7# roller 4.6 7# roller 4.2 7# roller 3.0 No transverse cracks were found during magnetic particle testing of the obtained cast billet. Figure 1 As shown.

[0031] Torque is positively correlated with linear velocity. Normally, if the linear velocity setting is correct, the force exerted by each roller on the casting billet will be relatively balanced; this force is reflected in the motor as torque. The problem this invention addresses is how to correct for negative torque caused by excessive linear velocity deviation due to improper design.

[0032] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0033] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for controlling the linear speed and torque balance of a light-pressure straightening roll in continuous casting, characterized in that, Includes the following steps: Step 1: Before production, inspect the wear of the leveling rollers and correct the roller gap, pressure parameters, and levelness. Step 2: Adjust the linear speed V of the leveling roller according to the following formula. ， V set Set the line speed, m / min, for the process, 'a' represents the thickness of the hot-state cross-section of the billet, in mm. b is the width of the hot cross-section of the billet, in mm. μ is the coefficient of thermal expansion of the billet from cold to hot state. ∆a is the cumulative pressing amount from the first pressing roller to the current adjusting roller, in mm. ∆b ​​is the cumulative increase in billet width (in mm) corresponding to the cumulative reduction value ∆a from the first pressing roller to the current adjusting roller; Step 3: Establish the relationship between the linear velocity and reduction of each straightening roll in the continuous casting control system according to the formula in Step 2.

2. The control method for balancing the linear speed and torque of the continuous casting light-pressure pull-down straightening rolls according to claim 1, characterized in that, The specific requirements for step 1 are as follows: the diameter error of the straightening roller is ≤0.5mm, the roller gap accuracy error of each straightening roller under the hot blank is ≤0.5mm, the output pressure error of each straightening roller is ≤10kN, and the roller surface levelness of the straightening roller is ≤0.2mm / m.

3. The method for controlling the linear speed and torque balance of the continuous casting light-pressure pull-down straightening rolls according to claim 1, characterized in that, The method for obtaining each parameter in the formula of step 2 is as follows: The hot cross-sectional thickness 'a' of the billet is the average value of the gap between each straightening roll when light pressure is not applied. The width b of the hot cross-section of the billet is calculated according to the following formula. ， a1 is the thickness of the inner cavity at the lower opening of the copper tube in the crystallizer, in mm. b1 is the width of the inner cavity at the lower opening of the copper tube of the crystallizer, in mm; The coefficient of thermal expansion μ of the billet from cold to hot state is calculated according to the following formula: ， a3 is the thickness of the billet in the cold state, which is the average value of the low-magnification measurement of the billet without light pressure. The increase in billet width ∆b corresponding to the reduction amount ∆a is calculated using the following formula: ， The coefficient K is estimated using the width increase value of each light pressing process. 平 When performing a light reduction process, three different reduction amounts are taken. At each reduction amount, several ingots are taken from each flow and their width is measured at low magnification. mean If we obtain b2, b3, and b4, then ， ∆a1, the total reduction of all flows under the first reduction, in mm. ∆a2, the total reduction of each flow under the second reduction, in mm. ∆a3, the total reduction of all flows under the third reduction, in mm. b5 represents the width of the billet in the cold state, taken as the average of the low-magnification measurements of the billet under no light pressure.

4. The control method for balancing the linear speed and torque of the continuous casting light-pressure pull-down straightening rollers according to claim 1, characterized in that, Step 3 specifically involves: Let the nth roller of a certain flow be the first roller performing the light pressing process, and let the mth roller be the last roller performing the light pressing process. Then the rotational speed of the straightening rollers before the nth roller is V. set The rotational speed of the straightening rollers between rollers numbered m is V, and the rotational speed of the straightening rollers after roller number m is equal to the rotational speed of roller number m.

5. The method for controlling the linear speed and torque balance of the continuous casting light-pressure pull-down straightening rolls according to claim 1, characterized in that, It also includes step 4: Although the tensioning rolls after the m-th roll do not perform the light pressing process, they still adopt the pressing displacement mode, and their pressing amount is set to 0, instead of the hot billet pressure mode; the tensioning rolls before the n-th roll adopt the hot billet pressure mode, and their hot billet pressure is set to 30kN-50kN.

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