A method for improving the production efficiency of thin slab continuous casting and rolling

Abstract

The application discloses a method for improving the production efficiency of thin slab continuous casting and rolling, and comprises the following steps: smelting molten steel according to the component requirements of pickling steel and auxiliary steel grade; cross-casting production of the pickling steel and the auxiliary steel grade; according to the offset detection data of the casted slab out of the soaking furnace, adjusting the slab centering to ensure that the slab is conveyed to the finishing mill along the rolling center line; in the finishing mill stage, after the finishing rolling work roll is replaced, thick-specification auxiliary steel grade is used for roll burning transition rolling, and then thin-specification pickling steel is directly rolled; the method can solve the problem that there is no thick-specification contract for the pickling steel, a large amount of roll burning transition material has no corresponding order matching, and the spot rate is high. The application can ensure the stability of production and quality, significantly improve the process production organization flexibility and the production efficiency of thin slab continuous casting and rolling, and reduce the production cost.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a method for improving the production efficiency of thin slab continuous casting and rolling. Background Technology

[0002] In the context of green manufacturing in the steel industry, the production of thin-gauge pickled steel using the CSP (Continuous Casting and Rolling) process, represented by the CSP process, has become an industry trend. However, its production potential has not been fully realized, with the limiting factor being the lack of efficient production in thin-gauge continuous casting. CSP continuous casting cannot achieve rapid ladle changeover; it typically batches steel of the same grade, sets the width of the billet for each casting cycle, and lacks large vertical rolls and a width-fixing press before the finishing mill, resulting in limited room for adjusting the finished product width. Furthermore, the integrated casting and rolling process makes the production organization of the thin-gauge continuous casting and rolling process less flexible than conventional processes. For certain specific varieties and specifications with low contract volumes, there are problems of high production costs and low production efficiency. For specific varieties and specifications in the CSP process, it is necessary to systematically optimize the process and equipment based on the characteristics of the production line to achieve efficient continuous casting of thin slabs.

[0003] Furthermore, pickled steel only has contracts for thin-gauge specifications, with no transition material available for hot rolling. After each roll change, the finishing mill needs to roll a certain amount of thicker transition material to meet the hot rolling requirements. Moreover, due to the difference in slab alignment between the two-strand casting machines in the CSP process, a separate transition is required, generating a large amount of transition material without matching orders for the corresponding thickness. This results in a spot rate of up to 16% for pickled steel, severely dragging down its profitability. Similar problems exist in other production lines in the industry, and no mature solution exists. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the production efficiency of thin slab continuous casting and rolling, which can significantly improve the flexibility of process production organization and the production efficiency of thin slab continuous casting and rolling, and reduce production costs while ensuring stable production and quality.

[0005] The technical solution adopted in this invention is:

[0006] A method for improving the production efficiency of thin slab continuous casting and rolling includes the following steps:

[0007] S1, steel is smelted according to the two composition requirements of pickled steel and auxiliary steel;

[0008] S2 is produced by cross-casting pickled steel and auxiliary steel grades to form their respective slabs.

[0009] S3. Based on the detection data of the offset of the cast slab exiting the homogenizing furnace, the slab is centered and adjusted to ensure that the slab is transported to the seven-stand finishing mill along the rolling centerline.

[0010] S4, in the seven-stand finishing mill stage, after the finishing mill changes the work rolls, thick-specification auxiliary steel is used for hot roll transition rolling, and then thin-specification pickled steel is directly rolled; this can solve the problem of no thick-specification contracts for pickled steel, resulting in a large number of hot roll transition materials without corresponding orders, leading to a high spot rate.

[0011] S5, during the winding stage, the pressure of the pinch rollers is controlled in segments.

[0012] Preferably, the casting machine speed is set according to the principle that the thinner the slab thickness, the narrower the slab width, and the lower the superheat of the molten steel, the faster the casting machine speed should be when casting pickled steel and auxiliary steel.

[0013] Preferably, the slab thickness is controlled at 60~85mm, the slab width at 1050~1550mm, and the casting machine speed at 4.1~5.5m / min.

[0014] Preferably, when the widths of the pickled steel and the auxiliary steel slabs are inconsistent, the crystallizer is rapidly widened and smoothly transitioned during cross casting. During rapid widening, the casting machine speed is controlled according to the auxiliary steel speed. The rapid widening rate is 40~50mm / s, the single width adjustment amount is ≤100mm, the interval between each adjustment is t1, and the total width adjustment amount in one casting is ≤500mm. The taper is adjusted simultaneously during rapid widening.

[0015] Preferably, the interval t1 is 2 minutes.

[0016] Preferably, pickled steel and auxiliary steel are produced by cross-casting on the same casting machine. Each casting machine is equipped with a soaking furnace for heating. In step S2, the two casting machines produce synchronously and are heated in two soaking furnaces respectively.

[0017] Preferably, in step S3, during the slab centering adjustment process, the deviation between the center line of the two-strand casting machine slab and the rolling center line is controlled to be ≤8mm, and the deviation between the center lines of the two-strand casting machine slab is ≤5mm.

[0018] Preferably, in step S3, the control timing is such that the automatic correction function is started at the same time as the vertical roll bites the steel, and ends before the work roll of the finishing mill stand F1 bites the steel, the vertical roll pressure is controlled at 300~500KN, and the slab running speed in front of the finishing mill stand F1 is 0.2~0.5m / s.

[0019] Preferably, the chemical composition of the pickled steel, by mass percentage, includes: C: 0.04-0.07%, Si: 0.02-0.10%, Mn: 0.35-0.85%, P≤0.015%, S≤0.008%, Cr: 0.20-0.40%, Ti: 0.02-0.08%, Nb: 0.02-0.04%, Als: 0.02-0.05%, N≤0.007%, with the balance being Fe and unavoidable impurities.

[0020] Preferably, the auxiliary steel is ordinary C-Mn steel.

[0021] Preferably, in S5, the pressure of the pinch roll at the head of the strip is controlled to be 50~120KN; when the head of the strip enters the coiler, the coil load is turned on and there is a delay of t2, the pinch roll light pressure mode is started, and the pinch roll pressure is reduced to 10~20KN; when the F3 steel throwing signal of the finishing mill is turned on, the pinch roll light pressure mode is deactivated, and the pinch roll pressure is controlled at 60~144KN.

[0022] t2 is 10 seconds.

[0023] The seven-stand finishing mill consists of seven stands, which are labeled F1, F2, F3, F4, F5, F6 and F7 respectively.

[0024] The beneficial effects of this invention are:

[0025] This invention utilizes a rapid width adjustment technology for thin slab continuous casting. The thin slab continuous casting employs a cross-casting production mode, while the finishing mill simultaneously uses thicker auxiliary steel grades for hot-roll transition rolling. This significantly improves the flexibility of process organization and the efficiency of thin slab continuous casting and rolling while ensuring stable production and quality. Automatic correction eliminates the difference in slab alignment between the two-strand casting machines, facilitating a rapid and smooth transition rolling after changing work rolls in the finishing mill. Furthermore, the use of thicker auxiliary steel grades for hot-roll transition rolling, followed by direct rolling of thin-gauge pickled steel, solves the problem of a lack of thick-gauge contracts for pickled steel, resulting in a large quantity of hot-roll transition material without corresponding orders and a high spot rate. Process costs are reduced by more than 50 yuan / ton, and the spot rate of pickled steel is reduced from 16% to less than 5%. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the operation of the crystallizer in an embodiment of the present invention.

[0027] Figure 2 This is a cross-sectional view of the crystallizer locking device according to an embodiment of the present invention.

[0028] In the diagram: 1-Measuring instrument; 2-Crystallizer; 3-Casting billet; 4-Adjusting shim; 5-Disc spring; 6-Hydraulic cylinder. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] In the description of this invention, it should be understood that if terms such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, they are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. They can refer to a mechanical connection or an electrical connection. They can refer to a direct connection or an indirect connection through an intermediate medium, and they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0032] Example 1

[0033] A method for improving the production efficiency of thin slab continuous casting and rolling includes the following steps:

[0034] S1, steel is smelted according to the two composition requirements of pickled steel and auxiliary steel;

[0035] S2 is produced by cross-casting pickled steel and auxiliary steel grades to form their respective slabs.

[0036] S3. Based on the slab offset detection data from the soaking furnace, the slab is centered and adjusted to ensure that the slab is transported to the seven-stand finishing mill along the rolling centerline.

[0037] S4, in the seven-stand finishing mill stage, after the finishing mill changes the work rolls, thick-specification auxiliary steel is used for hot roll transition rolling, and then thin-specification pickled steel is directly rolled; this can solve the problem of no thick-specification contracts for pickled steel, resulting in a large number of hot roll transition materials without corresponding orders, leading to a high spot rate.

[0038] S5, during the winding stage, the pressure of the pinch rollers is controlled in segments.

[0039] Furthermore, the casting machine speed is set according to the principle that the thinner the slab thickness, the narrower the slab width, and the lower the superheat of the molten steel, the faster the casting machine speed should be.

[0040] Furthermore, the slab thickness is controlled at 60~85mm, the slab width at 1050~1550mm, and the casting machine speed at 4.1~5.5m / min.

[0041] Furthermore, when the widths of the pickled steel and auxiliary steel slabs are inconsistent, the crystallizer is rapidly widened and smoothly transitioned during cross-casting. During rapid widening, the casting machine speed is controlled according to the auxiliary steel speed. The rapid widening rate is 40~50mm / s, the single width adjustment amount is ≤100mm, the interval between each adjustment is t1, and the total width adjustment amount in one casting cycle is ≤500mm. The taper is adjusted simultaneously during rapid widening.

[0042] Furthermore, the interval t1 is 2 minutes.

[0043] Furthermore, pickled steel and auxiliary steel are produced by cross-casting on the same casting machine. Each casting machine is equipped with a soaking furnace for heating. In step S2, the two casting machines produce synchronously and are heated in two soaking furnaces respectively.

[0044] Furthermore, in step S3, during the slab centering adjustment process, the deviation between the center line of the two-strand casting machine slab and the rolling center line is controlled to be ≤8mm, and the deviation between the center lines of the two-strand casting machine slab is ≤5mm.

[0045] Furthermore, in step S3, during the slab centering adjustment process, the control timing is such that the automatic correction function is activated simultaneously with the vertical roll biting the steel, and ends before the work roll of the finishing mill stand F1 bites the steel. The vertical roll pressure is controlled at 300~500KN, and the slab running speed in front of the finishing mill stand F1 is 0.2~0.5m / s.

[0046] Example 2

[0047] Based on Example 1, the parameters of the pickled steel and auxiliary steel were further limited, resulting in Example 2 having even better performance.

[0048] The chemical composition of the pickled steel, by mass percentage, includes: C: 0.04-0.07%, Si: 0.02-0.10%, Mn: 0.35-0.85%, P≤0.015%, S≤0.008%, Cr: 0.20-0.40%, Ti: 0.02-0.08%, Nb: 0.02-0.04%, Als: 0.02-0.05%, N≤0.007%, with the balance being Fe and unavoidable impurities.

[0049] Furthermore, the auxiliary steel is ordinary C-Mn steel.

[0050] Furthermore, in S5, the pressure of the pinch roll at the head of the strip is controlled to be 50~120KN; when the head of the strip enters the coiler, the coil load is turned on and there is a delay of t2, the pinch roll light pressure mode is started, and the pinch roll pressure is reduced to 10~20KN; when the F3 steel throwing signal of the finishing mill is turned on, the pinch roll light pressure mode is deactivated, and the pinch roll pressure is controlled at 60~144KN.

[0051] t2 is 10 seconds.

[0052] The seven-stand finishing mill consists of seven stands, which are labeled F1, F2, F3, F4, F5, F6 and F7 respectively.

[0053] Working principle of the invention:

[0054] A method for manufacturing pickled steel using a thin slab continuous casting and rolling process mainly includes the following steps: molten steel smelting → two-strand thin slab continuous casting → heating in two soaking furnaces → automatic thin slab correction → vertical roll rolling → seven-stand precision rolling → laminar flow cooling → coiling, thereby obtaining hot-rolled raw material coils of pickled steel, which are then pickled to obtain the final pickled steel coils.

[0055] (1) During the smelting stage, steel is smelted according to the composition requirements of pickled steel and auxiliary steel respectively.

[0056] (2) In the two-strand thin slab continuous casting stage, a cross-casting production mode of pickled steel and auxiliary steel is adopted, namely, 1 heat of auxiliary steel → 3 heats of pickled steel → 1 heat of auxiliary steel → 3 heats of pickled steel, and so on. The slab thickness is controlled at 60~85mm, the slab width at 1050~1550mm, and the casting machine speed at 4.1~5.5m / min. The slab thickness, width, and casting machine speed are adjusted simultaneously during cross-casting. The casting machine speed is set according to the principle that the thinner the slab thickness, the narrower the slab width, and the lower the superheat of the molten steel, the faster the casting machine speed should be, as shown in the table below:

[0057]

[0058] When the widths of pickled steel and auxiliary steel slabs are inconsistent, a rapid width adjustment technique is used to ensure a smooth width transition during cross-casting. During rapid width adjustment, the casting machine speed is controlled according to the auxiliary steel casting speed. The rapid width adjustment rate is 40~50mm / s, the single width adjustment amount is ≤100mm, the interval between each adjustment is 2min, and the total width adjustment amount in one casting cycle is ≤500mm. The taper is adjusted simultaneously during rapid width adjustment.

[0059] The locking force requirements for the crystallizer locking device are as follows: when adjusting the width rapidly, the locking pressure should be 45-75 bar at the top and 88-138 bar at the bottom.

[0060] To meet the above requirements for rapid width adjustment, the crystallizer locking device needs to provide sufficient locking force, otherwise it will cause polarization of the continuous casting machine.

[0061] The crystallizer locking principle is as follows: When the hydraulic cylinder presses up, the piston rod moves upward, compressing the disc springs. This causes the locking rod to move upward, releasing the crystallizer. After the hydraulic cylinder releases pressure, the spring force of the disc springs causes the locking rod to move downward, thus locking the crystallizer. The crystallizer is locked by the spring force generated by the compression of six disc springs. The compression of the disc springs can be adjusted by adjusting shims, thus changing the locking force.

[0062] The crystallizer vibrates according to a sinusoidal curve. At the zero position, the velocity and kinetic energy are at their maximum; at the highest position, the crystallizer velocity is zero. According to the law of conservation of energy:

[0063] 1 / 2mVc=Fh

[0064] m -- crystallizer mass (kg), Vc -- pulling speed (m / min), h -- amplitude (m), F -- crystallizer locking force (N)

[0065] Where the crystallizer mass m = 21 tons = 21 * 10³ kg, the pulling speed Vc = 5 m / min, and the amplitude h = 3 * 10⁻³ m, substituting into the above formula, we get:

[0066] F=1 / 2*21*103*(5 / 60)2 / 3*10-3=22400N=22.4KN

[0067] The crystallizer has four locking devices, so the total required locking force is 22.4 * 4 = 89.6 kN. The original design of the crystallizer's locking force F was 70 kN < 89.6 kN, which was insufficient. According to the performance curve of the decanter spring: when F is 70 kN, the spring compression is 12.78 mm. Based on the linear relationship, the spring compression when F is 89.6 kN is calculated to be: 89.6 * 12.78 / 70 = 16.358 mm. Therefore, the required increase in spring compression is 16.358 - 12.78 = 3.578 ≈ 3.6 mm. Therefore, we increased the thickness of the adjusting shim by 3.6 mm, achieving the required locking force and solving the problem.

[0068] When adjusting the width and taper of the crystallizer, the basic automation system first automatically reduces the setpoint of the proportional valve on the wide side of the casting face from 15.5 MPa to 13.0 MPa at the top and from 17.5 MPa to 15.0 MPa at the bottom. These are empirical values ​​derived from multiple tests, ensuring that the adjustment of the narrow face during casting will not cause steel leakage. Simultaneously, the servo motor overcomes the relatively small friction between the copper plates, quickly and smoothly adjusting the position of the narrow-face copper plate. Then, based on the new crystallizer width and taper setpoints, the basic automation system continuously calculates the actual width and taper values ​​from the servo motor resolver signals and compares them with the setpoints, continuously calculating the rotation direction and speed setpoints for each servo motor, and transmitting them to the corresponding inverter units via fieldbus. Each inverter unit, based on the rotation direction and speed setpoints, simultaneously monitors the actual speed calculated from the resolver signals, optimizing the speed adjustment process to quickly and smoothly follow the speed setpoints, ensuring precise positioning of the actual narrow-face copper plate. The entire control system is a double closed-loop structure with servo motor speed control as the inner loop and narrow-face copper plate position control as the outer loop. The top width and left and right taper of the narrow copper plate are manually set on the HMI monitoring screen in the main control room.

[0069] Adjustment speed optimization: The adjustment speed is directly proportional to the casting machine's pulling speed. For casting safety considerations, the adjustment speed coefficient in the width-increasing direction is less than that in the width-decreasing direction. To prevent over-adjustment, when within 2mm of the set position, the adjustment speed is reduced by a ratio of 2mm to the relative distance difference. Based on an average pulling speed of 4m / min, the adjustment speed in the width-increasing direction is 6mm / min, and the adjustment speed in the width-decreasing direction is 10mm / min. A lower limit of 2.5mm / min is also set to prevent excessively slow adjustment near the end point. When only the upper side is adjusted after the lower width is reached, the adjustment speed is a constant 5mm / min. Optimizing the adjustment speed minimizes the slab length in the width transition zone.

[0070] (3) During the automatic correction stage of the thin slab, the slab centering is adjusted according to the slab offset detection data after exiting the soaking furnace to ensure that the slab is transported to the seven-stand finishing mill along the rolling centerline. The deviation between the slab centerline and the rolling centerline of the two-strand casting machine is controlled to be ≤8mm, and the deviation of the slab centerline of the two-strand casting machine is ≤5mm. The control sequence is to start the automatic correction function at the same time as the vertical roll bites the steel, and end before F1 bites the steel. The vertical roll pressure is controlled to be 300~500KN, and the slab running speed before F1 is 0.2~0.5m / s.

[0071] Table 2 Main process parameters for automatic slab alignment in Examples 1-6

[0072]

[0073] Automatic correction can eliminate the difference in slab alignment between two-strand casting machines, which is beneficial for a rapid and smooth transition rolling after changing work rolls in the finishing mill, and can effectively reduce the amount of transition material.

[0074] (4) In the seven-stand finishing rolling stage, after changing the work rolls, thick-gauge auxiliary steel is used for hot roll transition rolling, and then thin-gauge pickled steel is directly rolled. This can solve the problem of no thick-gauge contracts for pickled steel, resulting in a large number of hot roll transition materials without corresponding orders, leading to a high spot rate.

[0075] Example 5: When the width of the auxiliary steel slab is 1250mm, the width of the pickled steel slab is 1150mm, and the contract thickness is 1.2mm, the rolling scheme within one roll change unit is as follows:

[0076]

[0077] Example 6: When the width of the auxiliary steel slab is 1500mm, the width of the pickled steel slab is 1500mm, and the contract thickness is 1.4mm, the rolling scheme within one roll change unit is as follows:

[0078]

[0079] The work rolls of the finishing mill F1~4 stand are made of high-speed steel rolls with pre-formed oxide film. A uniform and dense Fe3O4 oxide film is pre-formed on the surface of the rolls offline. During the rolling process, under the action of high temperature, Fe3O4 is further continuously generated. The oxide film has good retention and regeneration properties.

[0080] Traditional hot-rolling methods produce a three-layer oxide film on the roll surface: a bottom layer of FeO, a middle layer of Fe3O4, and a top layer of Fe2O3. The bottom FeO layer is porous and easily detaches, making it difficult to maintain and regenerate the oxide film produced by conventional hot-rolling methods. Among the three iron oxides, Fe3O4 has high hardness, exhibits certain toughness at high temperatures, and has high thermal stability, allowing it to withstand high temperatures and pressures, and is less prone to cracking and detachment during rolling. This invention pre-forms a uniform and dense Fe3O4 oxide film on the surface of high-speed steel rolls. During the high-temperature rolling process, Fe3O4 is further continuously generated, resulting in an oxide film with excellent retention and regenerability.

[0081] (5) During the coiling stage, the pinch roll pressure is controlled in segments. The pinch roll pressure at the head of the strip is controlled at 50~120KN; when the head of the strip enters the coiler, the drum load is turned on and delayed for 10 seconds, the pinch roll light pressure mode is started, and the pinch roll pressure is reduced to 10~20KN; when the finishing F3 steel throwing signal is turned on, the pinch roll light pressure mode is deactivated, and the pinch roll pressure is controlled at 60~144KN.

[0082] Table 3. Process parameters for segmented pressure control of take-up and pinch rolls in Examples 1-6.

[0083]

[0084] After the strip head enters the coiler, tension is established between the coil and the finishing mill, and the coiling pinch rolls reach a steady state. At this point, the function of the pinch rolls is essentially eliminated. If the original pinch roll pressure is maintained, it will cause uneven wear on the pinch rolls, resulting not only in defects such as bright strips in the strip, but also affecting the service life of the pinch rolls. This invention implements segmented control of the coiling pinch roll pressure, which can avoid the generation of bright strip defects in thin-gauge pickled steel, reduce pinch roll wear by more than 60%, and increase service life by 2 to 3 times.

[0085] (6) The chemical composition of the pickled steel, by mass percentage, includes: C: 0.04-0.07%, Si: 0.02-0.10%, Mn: 0.35-0.85%, P≤0.015%, S≤0.008%, Cr: 0.20-0.40%, Ti: 0.02-0.08%, Nb: 0.02-0.04%, Als: 0.02-0.05%, N≤0.007%, with the balance being Fe and unavoidable impurities.

[0086] (7) The auxiliary steel is ordinary C-Mn steel.

[0087] Table 1. Main process parameters for thin slab continuous casting in Examples 1-6

[0088]

[0089] In summary, 1. This invention develops a rapid width adjustment technology for thin slab continuous casting, achieving a single slab adjustment of 100mm and a total width adjustment of 500mm within a single casting cycle. Thin slab continuous casting adopts a cross-casting production mode, with the finishing mill simultaneously using thicker auxiliary steel grades for hot-roll transition rolling. While ensuring stable production and quality, this significantly improves the flexibility of CSP process organization and the production efficiency of thin slab continuous casting and rolling. 2. This invention eliminates the difference in slab alignment between the two-strand casting machine through automatic correction, facilitating rapid and smooth transition rolling after changing work rolls in the finishing mill. Furthermore, using thicker auxiliary steel grades for hot-roll transition rolling, followed by direct rolling of thin-gauge pickled steel, solves the problem of a lack of thick-gauge contracts for pickled steel, resulting in a large amount of hot-roll transition material without corresponding orders, leading to a high spot rate. Process costs are reduced by more than 50 yuan / ton, and the spot rate of pickled steel is reduced from 16% to less than 5%. 3. This invention applies pre-formed oxide film high-speed steel rolls to the F1-4 stands in the finishing mill section. This effectively prevents oxide scale defects in the roll system caused by the peeling of the oxide film, thereby improving the surface quality of pickled steel, extending the roll change cycle, reducing the amount of heat-treated roll material, and thus reducing the spot rate of pickled steel. Furthermore, the pre-formed oxide film high-speed steel rolls can be reused repeatedly, significantly reducing roll consumption and alleviating the pressure of spare roll shortages.

[0090] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0091] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for improving the production efficiency of thin slab continuous casting and rolling, characterized in that: Includes the following steps: Steel is smelted according to the composition requirements of both pickled steel and auxiliary steel. Pickled steel and auxiliary steel grades are produced by cross-casting. Based on the offset detection data of the cast slab exiting the soaking furnace, the slab is centered and adjusted to ensure that the slab is transported to the finishing mill along the rolling centerline. In the finishing mill stage, after the finishing mill changes the work rolls, thick-specification auxiliary steel is used for hot roll transition rolling, and then thin-specification pickled steel is directly rolled. When the widths of pickled steel and auxiliary steel slabs are inconsistent, the crystallizer is rapidly widened and smoothly transitioned during cross-casting. During rapid widening, the casting machine speed is controlled according to the casting speed of the auxiliary steel. The rapid widening rate is 40~50mm / s, the single width adjustment amount is ≤100mm, the interval between each adjustment is t1, and the total width adjustment amount in one casting is ≤500mm. The taper is adjusted simultaneously during rapid widening.

2. The method for improving the production efficiency of thin slab continuous casting and rolling as described in claim 1, characterized in that: When casting pickled steel and auxiliary steel grades, the casting machine speed is set according to the principle that the thinner the slab thickness, the narrower the slab width, and the lower the superheat of the molten steel, the faster the casting machine speed.

3. The method for improving the production efficiency of thin slab continuous casting and rolling as described in claim 2, characterized in that: The slab thickness is controlled at 60~85mm, the slab width at 1050~1550mm, and the casting machine speed at 4.1~5.5m / min.

4. The method for improving the production efficiency of thin slab continuous casting and rolling as described in claim 1, characterized in that: Pickled steel and auxiliary steel grades are produced by cross-casting on the same casting machine. Each casting machine is equipped with a soaking furnace for heating. The two casting machines operate synchronously, and each is heated in a separate soaking furnace.

5. The method for improving the production efficiency of thin slab continuous casting and rolling as described in claim 1, characterized in that: During the slab centering adjustment process, the deviation between the slab centerline and the rolling centerline of the two-strand casting machine is controlled to be ≤8mm, and the deviation of the slab centerline of the two-strand casting machine is ≤5mm.

6. The method for improving the production efficiency of thin slab continuous casting and rolling as described in claim 1, characterized in that: During the slab centering adjustment process, the control sequence is to start the automatic correction function at the same time as the vertical roll bites the steel, and end before the work roll of stand F1 of the finishing mill bites the steel. The vertical roll pressure is controlled at 300~500KN, and the slab running speed in front of stand F1 of the finishing mill is 0.2~0.5m / s.

7. The method for improving the production efficiency of thin slab continuous casting and rolling as described in claim 1, characterized in that: The chemical composition of the pickled steel, by mass percentage, includes: C: 0.04-0.07%, Si: 0.02-0.10%, Mn: 0.35-0.85%, P≤0.015%, S≤0.008%, Cr: 0.20-0.40%, Ti: 0.02-0.08%, Nb: 0.02-0.04%, Als: 0.02-0.05%, N≤0.007%, with the balance being Fe and unavoidable impurities.

8. The method for improving the production efficiency of thin slab continuous casting and rolling as described in claim 1, characterized in that: The auxiliary steel is ordinary C-Mn steel.

9. The method for improving the production efficiency of thin slab continuous casting and rolling as described in claim 1, characterized in that: After the slab passes through the finishing mill, the pressure of the pinch rolls is controlled in segments during the coiling stage. Control the pressure of the pinch rolls at the head of the strip to 50~120KN; when the strip head enters the coiler, the drum load is turned on and there is a delay of t2, start the pinch roll light pressure mode and reduce the pinch roll pressure to 10~20KN; when the F3 steel throwing signal of the finishing mill is turned on, the pinch roll light pressure mode is deactivated and the pinch roll pressure is controlled at 60~144KN.

Images