Roll gap control method for double-roll cast rolling

Abstract

The invention relates to the technical field of double-roller cast rolling, and provides a roller gap control method. According to the method, in the casting and rolling process, controlled floating of a roll gap is achieved under the condition of constant opening degree by controlling the overall movement of a driving device and a roll system and the relative movement between the driving device and the roll system, and therefore the material updating process in a molten pool is stabilized. Different from a traditional technical scheme, the method can keep the two roller bodies and the side sealing device static relative to the ground in the roller gap floating period, the thickness fluctuation of the green body is effectively avoided, the abrasion rate of the side sealing plate is reduced, and therefore the stability of the cast-rolling process and the quality of the green body are improved.

Description

Technical Field

[0001] This invention relates to the field of twin-roll casting technology, and more particularly to a method for controlling the roll gap in twin-roll casting. Background Technology

[0002] Twin-roll casting is a short-process metal forming process characterized by a moving crystallizer, which can directly produce billets from liquid metal. The concept of this process was first proposed in the mid-19th century and has since evolved into various equipment forms. Twin-roll strip casting machines are also known as twin-roll casting machines or twin-roll continuous casting machines. It should be noted that the industry term "strip" is a common name for this type of process and is not limited to producing strip materials; the billets produced can include strips, plates, bars, tubes, and other metal billets with specific cross-sectional shapes.

[0003] In twin-roll casting, the main components constituting the molten pool include two relatively parallel crystallizing rolls (hereinafter referred to as "rolls"), referred to as the first roll and the second roll, respectively. The two rolls together form the molten pool used to prepare the billet. During the preparation process, a drive device controls the two rolls to rotate in opposite directions. The drive device typically includes a driver and a gearbox. The driver can be an electric motor, an internal combustion engine, or a steam engine, and the electric motor can be a servo motor, an asynchronous motor, or a stepper motor. The gearbox is generally a reducer. The driver and the gearbox can be directly or indirectly connected, and the gearbox is connected to the rolls via a coupling. The axis of rotation of the roll is defined as the roll shaft. The roll shaft of the first roll is called the first roll shaft, and the roll shaft of the second roll is called the second roll shaft; both are collectively referred to as the two roll shafts. The roll shaft is a virtual straight line used to position the roll in space; the displacement of the roll relative to the ground will cause a change in the position of the roll shaft. The surface of the roll that directly contacts the molten pool material is called the roll working surface (or simply roll surface); the planes at both ends of the roll that are perpendicular to the roll shaft are called end faces. When using a contact-type side-sealing device, a portion of the end face periodically or non-periodically contacts the side-sealing plate. A gap exists between the two rollers; the minimum distance between them is called the roller gap, and this minimum distance is defined as the roller gap opening. For thin steel strips, the roller gap opening is generally in the range of 0.5–3 mm, but can be less than 1 mm or greater than 10 mm depending on process requirements. The midpoint of the roller gap is called the Nip point. When the molten pool depth is large, a side-sealing device is required to maintain the shape of the molten pool. The contact-type side-sealing plate is usually made of refractory material and is in close contact with the roller ends under external pressure. Cooling water channels can be installed inside the rollers to control the surface temperature. During the casting and rolling process, the two rollers rotate in opposite directions. Liquid or semi-solid material enters the molten pool through the distribution device and, under the shear driving force generated by the rollers, is discharged through the roller gap to form a billet. The viscosity of the material in the molten pool and the rotation of the rollers together generate a continuous shear driving force field, thereby realizing the transformation from liquid metal to solid billet. The material can be liquid metal, semi-solid or solid-liquid composite; solid components can be added simultaneously during the preparation of the multilayer material.

[0004] In twin-roll casting, the casting force acting between the two rolls is also called the roll clamping force. To stabilize the process and improve the quality of the billet, a roll gap floating method has been proposed in this field. Roll gap floating refers to a method in which at least one of the two rolls is driven by a drive device to act as a moving roll, thereby creating relative motion between the two rolls.

[0005] Due to the relative motion, the Nip point will change position accordingly; therefore, roll gap floating is often referred to as Nip point floating or roll gap motion. Considering factors such as the fit of the side sealing plate, the edge quality of the billet, thickness uniformity, and initial solidification consistency, when implementing roll gap floating, the velocity component of the Nip point in the roll axis direction is usually controlled to be close to zero. In other words, during the relative motion of the two rolls, the two roll axes remain parallel or nearly parallel, which is a technical requirement recognized by those skilled in the art.

[0006] Chinese patent application No. 2007101853779 discloses a vibrating twin-roll thin strip casting mill, the technical solution of which is single-sided roll vibration. Chinese patent application No. 2017800317704 discloses a method for operating a twin-roll thin strip continuous casting mill to reduce vibration. In patent application No. 2022101047141, the inventors disclose a method for yielding movement of the crystallizing rolls to enhance the stability of the twin-roll casting process. This method controls the relative movement of the two rolls to make the roll gap float bidirectionally. This design also leads to bidirectional fluctuations in the roll clamping force and changes in billet thickness. In patent application No. 2022110378783, the inventors disclose a method for angular displacement movement of the crystallizing rolls in twin-roll casting extrusion. This method controls one roll to rotate bidirectionally around the other roll to improve billet thickness uniformity, but it still causes bidirectional fluctuations in the roll clamping force. In patent application number 2023109424003, the inventors disclosed a method and apparatus for roll gap floating in a twin-roll thin strip process. This method allows the roll gap to float preferentially, meaning the roll gap changes in both directions but the floating amplitude in one direction is reduced, thus achieving a balance between real-time control and process stability. In patent application number 2023109424018, the inventors disclosed a roll gap floating method for a twin-roll casting and rolling process. This method partially or completely cancels out the effect of "roll gap floating changing the placement plane" and "roll system movement changing the placement plane," thereby achieving a control effect that only increases or only decreases the molten pool pressure.

[0007] In summary, while existing technologies have introduced roll gap floating to varying degrees to improve the stability of the casting and rolling process, none have considered or explicitly pointed out the impact of the relative motion between the casting roll and the side sealing plate on the wear of the side sealing plate, nor have they established a process window constrained by the stability of the side sealing plate. Since the stability of the side sealing plate and the molten pool side sealing is crucial for the continuous operation of the twin-roll casting and rolling process, existing solutions still have room for improvement in terms of process window width, side sealing plate life, and long-term operational stability. Therefore, this invention proposes an improved roll gap control method. By establishing a synergistic relationship between the external overall motion and the internal relative motion, controlled roll gap floating is achieved while keeping the side sealing plate stationary relative to the ground, thereby obtaining a larger process window, higher side sealing stability, better billet quality, and a more stable casting and rolling process. Summary of the Invention

[0008] This invention stems from a systematic study of the relationship between the lifespan of the side sealing plate and the stability of the molten pool material renewal during twin-roll casting. Research shows that the wear rate of the side sealing plate has a decisive influence on its lifespan, which in turn directly affects the continuous stability of the process and production costs. By changing the relative motion between the roll and the side sealing plate, the wear rate of the side sealing plate can be effectively adjusted, thereby significantly extending its service life. In processes using refractory materials for the side sealing plate, if the side sealing plate and the roll are kept relatively stationary, i.e., only the rotation of the roll around its own axis causes wear on the side sealing plate, the friction mode can be changed and the lifespan of the side sealing plate can be significantly extended. Theoretical analysis and experimental results show that the lifespan can be increased by more than 30%. Here, "the rotation of the roll around its own axis" includes the circumferential motion caused by the rotation of the roll itself or the rotation of the roll system.

[0009] Further research indicates that process stability issues and product defects in twin-roll casting are essentially closely related to the instability of the material renewal process within the molten pool. Molten pool shrinkage, the characteristics of the moving crystallizer, and the shear-thinning behavior of the semi-solid metal collectively lead to the discontinuity of the renewal process. Therefore, this invention proposes a shear-thinning-induced driving force interruption (ST-DFI) mechanism to explain the instability of material renewal in the molten pool.

[0010] like Figure 1 As shown, taking horizontal equal-diameter twin-roll casting as an example, the ST-DFI phenomenon mainly occurs in the semi-solid material region between the two billet shells at the bottom of the molten pool. This region is... Figure 2 The image shows the unstable region at the bottom of the molten pool. Due to the presence of ST-DFI, the semi-solid material renewal process within this unstable region is unstable, leading to stability problems such as cracks, macroscopic segregation, band jamming, band breakage, and leakage from the side sealing plate. Figure 3The image shows a typical "eye-like pore" defect in the core of the billet. In addition to being caused by uneven solidification, ST-DFI is also an important cause of this type of defect.

[0011] For most alloy systems, stable material renewal in the molten pool is crucial for achieving high-quality continuous forming. When preparing alloys with a wide two-phase region, the disturbances in the unstable region at the bottom of the molten pool are more significant, having a greater impact on the overall process stability.

[0012] like Figure 4 As shown, during a single roll gap floating process, if the first roll body is controlled to rotate clockwise around the second roll body, causing the Nip point to move from position N1 to position N2, the semi-solid material in the unstable zone at the bottom of the molten pool can be partially or completely removed from the molten pool, achieving material renewal. This renewal process can promote the renewal of the molten pool liquid phase, inhibit the enrichment of inclusions in the swirling zone, thereby reducing the requirements for the cleanliness of the molten metal; at the same time, it reduces the accumulation of inclusions at the side sealing plate, further extending the service life of the side sealing plate.

[0013] Based on the above understanding, this invention proposes a novel method for controlling the roll gap in twin-roll casting. This method employs a layered control mechanism of external overall motion and internal relative motion, and introduces a spatial position definition system of reference point, reference plane, and reference distance, enabling the effects of roll system control and drive control on the reference distance to partially or completely cancel each other out. This achieves the following: (1) Achieve controlled roll gap floating while keeping the side sealing plate stationary relative to the ground; (2) Significantly broaden the operable process window; (3) Improve the stability of molten pool material renewal; (4) Improve the structure and surface quality of the billet; (5) Extend the life of the side sealing plate and reduce production costs.

[0014] Therefore, by establishing a coordinated relationship between the external overall motion and the internal relative motion, this invention achieves the unification of roll gap dynamic control and side seal stability, providing a new process control approach for twin-roll casting and rolling forming.

[0015] To address the current technical problems and further improve process stability and / or billet quality control, this patent application provides a roll gap control method for twin-roll casting, applied to a twin-roll thin strip casting machine including a roll system and a drive device. The roll system includes a first roll and a second roll arranged opposite each other for billet preparation. The drive device controls the first roll and the second roll to rotate in opposite directions. The roll shaft of the first roll is defined as the first roll shaft, and the roll shaft of the second roll is defined as the second roll shaft. The plane containing the first roll shaft and the second roll shaft is defined as the placement plane of the roll system. In its natural state, the placement plane is defined as a reference plane. A point on a fixed component of the drive device that does not pass through the first roll shaft or the second roll shaft is selected as a reference point. A plane parallel to or coincident with the reference plane and passing through the reference point is defined as the drive plane. The distance between the drive plane and the reference plane is defined as a reference distance. The method includes the following steps: Roller system control steps: Control the roller system and the drive device to move simultaneously relative to the ground, so as to change the reference distance; Drive control steps: Control the drive device to move relative to the roller system, so as to change the reference distance; The changes to the reference distance caused by the roller system control step and the changes to the reference distance caused by the drive control step are partially or completely canceled out.

[0016] It should be understood that the term "fixed" in the present invention refers to the component remaining stationary in the system coordinate system, rather than being absolutely stationary relative to the ground or external reference objects.

[0017] It should be understood that "selecting a point on a fixed component of the drive device that does not pass through the first roller or the second roller as a reference point" can also be expressed as: "selecting a reference point located on a fixed component of the drive device and not located on the first roller or the second roller."

[0018] It should be understood that "not located on the first or second roller" means that the first and second rollers are straight lines defined by an infinite number of points, and the reference point does not belong to any point on the straight line.

[0019] It should be understood that "selecting a point on a fixed component of the drive device that does not pass through the first roller or the second roller as a reference point" refers to a component of the drive device that does not move relative to the ground when the drive device is in normal operation and its entirety is stationary relative to the ground. Such components can be considered fixed components. For example, the base of the drive device is a fixed component; furthermore, when the drive device includes a motor, the stator, housing, and base of the motor can all be considered fixed components.

[0020] It should be understood that the reference point can be a fixed point in space that remains relatively stationary with respect to the entire drive unit. For example, a spatial point that remains relatively stationary with respect to the base of the drive unit can be selected as the reference point.

[0021] It should be understood that reference points are used to determine the driving plane. During a single fabrication process, reference points can be selected or changed as needed; after a change, appropriate conversions should be performed to maintain consistency in the reference coordinate relationship before and after the change. Those skilled in the art should be able to directly understand and perform these conversions, thereby ensuring consistency in the description of the motion relationships.

[0022] It should be understood that when the center of gravity or geometric center of the drive unit is not located on the first or second roller shaft, and its position remains stable during operation, the center of gravity or geometric center can be used as a reference point.

[0023] It should be understood that a drive unit includes a device for providing power and a device for transmitting power. The device for providing power can be an electric motor or a combustion engine; the device for transmitting power can be a universal joint or a gearbox.

[0024] It should be understood that "center of gravity of the drive unit" can refer to any of the following situations: (1) refers only to the center of gravity or geometric center of the power supply device; (2) refers only to the center of gravity or geometric center of the power transmission device; (3) refers to the combined center of gravity of the power supply device and the power transmission device as a whole.

[0025] It should be understood that when there are two or more drive devices in the system, a reference point can be selected on any one of the movable drive devices.

[0026] It should be understood that the movement of the drive device on the twin-roll thin strip casting machine can be controlled by the first kinematic pair; and the movement of the roller system on the twin-roll thin strip casting machine can be controlled by the second kinematic pair.

[0027] To avoid ambiguity, it should be understood that the movement of the drive device and the movement of the roller system are independent of each other, and neither directly causes a change in the relative position between the two rollers. Specifically: (1) The movement of the drive device alone will not cause a change in the relative position between the two rollers, nor will it cause or affect the roll gap floating; (2) The movement of the drive device alone will not cause the movement of the roller system; (3) The movement of the roller system alone will not cause a change in the relative position between the two rollers, nor will it cause or affect the roll gap floating; (4) The movement of the roller system alone will not cause the movement of the drive device.

[0028] It should be understood that in actual processes, due to the load generated during preparation and / or the intentionally designed roll shape, the first and second roll shafts are usually approximately straight lines. In this field, when studying molten pool transport behavior and / or roll gap floating, the roll shafts are generally considered to be absolutely straight, i.e., both rolls are assumed to be ideal rigid bodies of revolution. For example, for a constant-diameter twin-roll thin strip casting machine, the rolls can be considered as cylinders. A cylinder consists of two bases and one side: the two bases are identical circular surfaces, and the side is a curved surface. The two end faces of the roll correspond to the two bases of the cylinder, and the roll surface corresponds to the side of the cylinder.

[0029] It should be understood that during the relative motion between the two rollers, which causes the roller gap to float, a person skilled in the art can directly and without doubt determine that the two roller shafts always remain parallel.

[0030] It should be understood that "the two rollers always remain parallel" also includes "the two rollers are always nearly parallel". "Nearly parallel" refers to a measurable but difficult-to-complete deviation between the parallelism achievable under current technological conditions and the ideal geometric parallelism. Therefore, in this patent application, the term "parallel" should be broadly understood as "parallel or nearly parallel", that is, "basically parallel" or "approximately parallel".

[0031] It should be understood that since the two roller shafts are parallel, the placement plane can be determined by the plane on which the two roller shafts are located. In the actual manufacturing process, since it is impossible to achieve absolute parallelism, the placement plane can also be determined by points on the two roller shafts that are less affected by process changes. For example: (1) use the four intersection points of the two roller shafts with the end faces of the two roller bodies, or any three intersection points, to determine the placement plane; (2) take two points on the first roller shaft that intersect with the end face of the roller body, and take the point on the second roller shaft that is closest to the center of gravity of the second roller to determine the placement plane; (3) randomly select two points on the first roller shaft and randomly select one point on the second roller shaft to determine the placement plane.

[0032] Furthermore, it should be understood that a plane perpendicular to any one of the roller shafts can be selected, and the placement plane can be represented by the line connecting the intersection of this plane and the two roller shafts.

[0033] It should be noted that, under natural conditions, the plane on which the first and second rollers are placed is also called the reference plane.

[0034] It should be understood that "natural state" means that during the manufacturing process, the relative positions of the two rollers and the drive device remain unchanged from beginning to end, and only a pure shearing drive process occurs in the molten pool. In other words, in the natural state, the roller gap floating process, roller system movement process, or drive device movement process described in the present invention patent application do not occur.

[0035] It should be understood that the reference plane is the plane uniquely determined by the structural form of the twin-roll thin strip casting machine. For example: (1) For a horizontal equal-diameter twin-roll thin strip casting machine, the reference plane is parallel to or coincides with the horizontal plane; (2) For an inclined twin-roll thin strip casting machine, the reference plane forms a fixed angle with the horizontal plane; (3) For a horizontal equal-diameter twin-roll thin strip casting machine, the spatial position of the reference plane relative to the ground remains unchanged regardless of the type of roll gap floating, roll system movement or drive device movement that occurs during the preparation process; (4) Other types of twin-roll thin strip casting machines can be deduced in the same way.

[0036] It should be understood that, unlike the placement plane, the reference plane is a fixed plane, meaning that the position of the reference plane will not be changed by the floating of the roll gap, the movement of the roll system, or the movement of the drive device. This is because the range of such movements is constrained by the structural form of the twin-roll thin strip casting machine.

[0037] It should be noted that during the time intervals from t1 to t2 (t2>t1), if the drive device rotates by any angle ω around the reference point, the position of the drive plane will not change during this time interval. Therefore, when selecting the reference point, situations where the drive device rotates around the reference point should be avoided.

[0038] It should be understood that the "change of reference distance by the roller system control steps" and the "change of reference distance by the drive control steps" can be partially or completely offset.

[0039] The definition of "partial or complete cancellation" is as follows: (1) Let there be a point M on the driving plane, and let the normal vector of the driving plane be DN (vector); (2) During a preparation process, from time t1 to t2, the roller control step causes point M to be displaced by SR (vector), and the driving control step causes point M to be displaced by SD (vector); (3) Let the angle between SR and DN be α, and the angle between SD and DN be β; (4) When (|SR|×|DN|×cosα)≠(|SD|×|DN|×cosβ), it is considered as partial cancellation; (5) When (|SR|×|DN|×cosα)=(|SD|×|DN|×cosβ), it is considered as complete cancellation. Wherein, |SR|, |SD|, and |DN| are the magnitudes of vectors DN, SR, and SD, respectively, and are scalars.

[0040] By partially or completely offsetting variations in the reference distance through drive control steps, an unrestricted range of motion for the roll system can theoretically be provided. This unrestricted roll system motion expands the adjustment space for roll gap control, thereby significantly broadening the range of process parameters in the fabrication process.

[0041] It should be understood that the above-mentioned "change of reference distance by the roller system control steps" and "change of reference distance by the drive control steps" can refer to one or more changes, that is, both "one or more changes of reference distance by the roller system control steps" and "one or more changes of reference distance by the drive control steps" are included within the protection scope of this invention.

[0042] Furthermore, a method for controlling the roll gap in twin-roll casting and rolling, the method further includes the step of: a floating control step: controlling relative movement between the first roll and the second roll to change the placement plane; wherein the change to the placement plane by the floating control step and the change to the placement plane by the roll system control step are partially or completely canceled out.

[0043] Furthermore, a method for controlling the roll gap in twin-roll casting and rolling, wherein the floating control step includes the following two sub-steps: First floating: control the second roller to remain stationary relative to the ground, while controlling the first roller to complete a continuous rotation within a predetermined angle range around the second roller shaft, and causing the roller system to rotate synchronously around the second roller shaft; Second floating: control the first roller to remain stationary relative to the ground, while controlling the second roller to complete continuous rotation around the first roller shaft within a predetermined angle range, and causing the roller system to rotate synchronously around the first roller shaft; In a single preparation process, the first float and the second float are performed at least once.

[0044] It should be understood that minimizing the relative displacement between the roller and the side sealing plate during the roll gap floating process is of great significance for enhancing the service life of the side sealing plate, reducing production costs, improving process stability, and improving the quality of the billet.

[0045] like Figure 5 The image shows the side sealing plate before use; as shown. Figure 6 The image shows the side sealing plate after use. Due to wear during contact with the roller end face, the side sealing plate will form... Figure 6 The slope shown may have gaps between it and the roller surface.

[0046] During the preparation of the green body, when using methods such as Figure 5When installing the side sealing plate as shown, the relative movement displacement between the roller and the side sealing device should be limited to a certain range to prevent the melt from entering the gap between the slope and the roller surface, thereby preventing process instability, production interruption, or deterioration of the quality of the blank edge.

[0047] Research has found that the following methods can effectively reduce relative displacement: (1) Keep the second roller stationary relative to the ground, control the first roller to rotate continuously around the second roller shaft, and simultaneously control the roller system to rotate around the second roller shaft (this method can reduce the relative displacement between the first roller and the side sealing plate, thereby reducing the risk of...). Figure 6 The gap between the slope and the roller surface shown expands the range of process parameters. (2) Keep the first roller stationary relative to the ground, and control the second roller to rotate continuously around the first roller shaft once, while simultaneously controlling the roller system to rotate around the first roller shaft (this method can reduce the relative displacement between the second roller and the side sealing plate, thereby reducing the risk of...). Figure 6 The gap between the slope and the roller surface shown can also expand the range of process parameters.

[0048] It should be understood that during the first and second floating processes described above, the roll gap opening remains unchanged.

[0049] Roll gap floating is generated by the alternating motion of the two rollers, which is of great significance to the uniformity of the billet structure. Specifically, it enhances the uniformity of the macroscopic and microscopic structure of the billet and maintains the stability of the billet shape.

[0050] If only one roller moves relative to the ground while the other roller remains stationary during the preparation process, the shape of the billet may become unstable, such as bending, when the roller gap shifts and causes changes in the placement plane.

[0051] It should be understood that “the roll gap floating is generated by the alternating motion of the two rolls” can be expressed as equivalent to: (1) without considering the influence of the roll system motion, the two rolls move alternately relative to the ground; (2) without considering the influence of the roll system motion: the first roll is stationary relative to the ground, the second roll moves relative to the ground; then the first roll moves relative to the ground, the second roll is stationary relative to the ground; (3) or, without considering the influence of the roll system motion: the first roll moves relative to the ground, the second roll is stationary relative to the ground; then the first roll is stationary relative to the ground, the second roll moves relative to the ground.

[0052] It should be noted that even without further explanation of "roll gap floating is generated by the alternating motion of the two rollers", those skilled in the art can directly and without doubt understand the specific implementation of "alternating motion of the two rollers".

[0053] Furthermore, in a method for controlling the roll gap in twin-roll casting, the occurrence frequencies of the first and second floats are both within the range of 1 Hz to 5 Hz.

[0054] Furthermore, in a method for controlling the roll gap in twin-roll casting, during one first or second floating process, the displacement amplitude of the first roll relative to the second roll is in the range of 10 to 200 micrometers.

[0055] Furthermore, in a twin-roll casting and rolling mill roll gap control method, the placement plane remains stationary relative to the ground during a first floating process; and / or, the placement plane remains stationary relative to the ground during a second floating process.

[0056] Through research, the inventors have discovered that, during the roll gap floating process, keeping the roll body and the side sealing plate relatively stationary is of greater significance for enhancing the service life of the side sealing plate, improving process stability, and improving the quality of the blank compared to "only minimizing the relative displacement between the roll body and the side sealing plate".

[0057] It should be understood that "keeping the roller body and the side sealing plate relatively stationary" can also be expressed as "keeping the position of the roller body and the side sealing plate relative to the ground unchanged".

[0058] It should be understood that a person skilled in the art can directly and without doubt understand that "keeping the roller's position relative to the ground unchanged" does not include the roller's own rotation around the roller axis.

[0059] Research has shown that during the first or second floating process, if the roll gap floating and the roll system movement are controlled to occur simultaneously and synchronously, and the changes to the placement plane caused by the roll gap floating process and the changes to the placement plane caused by the roll system movement are completely and instantly canceled out, the two rolls can remain stationary relative to the ground. Therefore, the parameter settings for roll gap floating are only limited by equipment conditions, and theoretically optimal process stability and / or optimal billet quality can be achieved.

[0060] When the above-mentioned "real-time, complete cancellation" state is achieved, the working surface of the roller body and... Figure 6 The "slopes" shown will not produce gaps, or only tiny gaps due to systematic errors, thus effectively avoiding process instability, process interruption and quality problems at the edges of the billet.

[0061] It should be noted that "during one of the first floating processes, the placement plane remains stationary relative to the ground" and "during one of the second floating processes, the placement plane remains stationary relative to the ground" both indicate that the positions of the two rollers and the side sealing plate relative to the ground remain unchanged. In this case, only the rotation of the rollers causes wear on the side sealing plate, thus significantly improving the service life of the side sealing plate and thereby enhancing process stability.

[0062] It should be noted that those skilled in the art can directly and without doubt understand that "the placement plane remains stationary relative to the ground" also includes "the placement plane is always nearly stationary relative to the ground"; where "nearly stationary" means that there is a definite but unavoidable slight deviation between "stationary" and "absolute stationary" achievable under current technical conditions.

[0063] It should be understood that in the present invention patent application documents, the term "still" includes "nearly still"; that is, "still" should be understood as "still or nearly still", "substantially still" or "approximately still".

[0064] Furthermore, a roll gap control method for twin-roll casting and rolling, wherein the midpoint of the roll gap is defined as the Nip point; the moving speed of the billet at the Nip point is defined as the preparation speed; the moving speed of the Nip point caused by the relative motion between the first roll and the second roll is defined as the floating speed of the Nip point; in the first floating process, the inner product of the floating speed and the preparation speed is a first inner product; in the second floating process, the inner product of the floating speed and the preparation speed is a second inner product; wherein, in one first floating process, the first inner product is less than zero; and in one second floating process, the second inner product is less than zero.

[0065] It should be noted that the moving speed of the billet at point Nip is called the preparation speed. The preparation speed is used to characterize the rate of billet preparation caused by the rotation of the roller. The direction of the preparation speed is called the preparation direction, which is always perpendicular to the plane of placement.

[0066] It should be noted that roll gap floating may affect the moving speed of the billet at the Nip point. However, for the sake of simplicity, unless otherwise explicitly stated, the preparation speed in this patent application does not include the effect of roll gap floating on the moving speed of the billet at the Nip point.

[0067] It should be noted that, under natural conditions, the preparation rate is also called the reference rate, and the preparation direction is also called the reference direction.

[0068] It should be noted that, under natural conditions, a straight line passing through point Nip and perpendicular to the reference plane is called a reference line.

[0069] It should be understood that during the preparation process under natural conditions, there is no relative motion between the two rollers, nor is there any roller system motion; therefore, the floating speed is zero, and the position of the placement plane remains unchanged.

[0070] It should be noted that the normal to the placement plane is called the placement normal; since any point on the placement plane can determine a normal, the number of placement normals is infinite.

[0071] It should be understood that the preparation speed is used to characterize the rate of billet preparation caused by the rotation of the rollers. In this patent application, the magnitude of the preparation speed is only related to the opposing rotation of the two rollers and is independent of the movement of the roller system and the floating of the roller gap. The preparation direction is always along the normal direction of placement and points to the side where the billet moves out of the molten pool.

[0072] It should be noted that the velocity of the Nip point caused by the roll gap floating is called the floating velocity. The component of the floating velocity in the manufacturing direction is called the effective velocity.

[0073] It should be understood that the floating velocity can be decomposed into two orthogonal components: one is the component in the fabrication direction; the other is the component in the placement plane. The component in the fabrication direction can be zero; the component in the placement plane can also be zero; but both cannot be zero simultaneously.

[0074] It should be understood that both the floating speed and the preparation speed are vectors. A "vector" can also be called a "vector vector".

[0075] It should be understood that in three-dimensional space, the actual shape of the roll gap is a surface. A line composed of countless Nip points is called a Nip line, and a line composed of countless Kiss points is called a Kiss line. However, in reality, the terms "Nip line" and "Kiss line" are rarely used in this field. For many years, the industry has generally used "Nip point" and "Kiss point" to describe the molten pool transport behavior or roll gap floating phenomenon in twin-roll casting. When using "Nip point" and "Kiss point" for description, it is usually not necessary to specifically state that the description is based on a plane perpendicular to the roll axis. In other words, using "Nip point" and "Kiss point" instead of "Nip line" and "Kiss line" is the common practice in this field. Therefore, in this patent application, in order to clearly express the geometric and kinematic relationships of the proposed technical solution, following the common practice in this field, a plane perpendicular to the roll axis is selected, and the relevant technical features are expressed on this plane. This descriptive method is the most intuitive and clear, and can be directly and unambiguously understood by those skilled in the art.

[0076] It should be noted that those skilled in the art, upon reading this invention patent application, can directly and without doubt understand that the midpoint of the roll gap is called the Nip point.

[0077] It should be understood that when studying the roll gap floating process, the two rolls are usually considered as ideal rigid rotating bodies with their roller axes parallel. On any plane perpendicular to the roller axes, the floating velocity of point Nip is consistent. Therefore, the method that a person skilled in the art can directly and unambiguously understand for studying the roll gap floating process is as follows: (1) Take any plane perpendicular to the roller shaft, and denote it as plane Ω.i ; (2) Nip line and plane Ω i The intersection point is called the Nip point N. i ; (3) Studying the Nip point N i The motion pattern can represent the characteristics of the entire roll gap floating process.

[0078] It should be understood that, from a plurality of normal planes perpendicular to the reference plane, a normal plane passing through the Nip line in its natural state is selected and denoted as the reference plane Π. i Reference plane Π i With plane Ω i The line of intersection is called the reference line π. i .

[0079] It should be understood that, without considering the influence of the roller system's motion, when relative motion occurs between the two rollers, the Nip line and Nip point N... i Both the surface on which they are placed can move relative to the ground.

[0080] It should be understood that "not considering the influence of the roller system movement" can also be expressed as "no roller system movement occurs, or the influence caused by the roller system movement is eliminated"; among them, "eliminate" can also be expressed as "remove", "remove" or "exclude".

[0081] It should be understood that during the relative motion between the two rollers, the reference plane and the analysis plane Ω... i Reference plane Π i and the reference line π i Their positions relative to the ground remain fixed.

[0082] It should be understood that a reference plane has an infinite number of normals in space; in this patent application, the normal of the reference plane that passes through the Nip point in its natural state is selected as the reference line. In other words, the reference line has two characteristics: first, the reference line is the normal of the reference plane; second, the reference line passes through the Nip point in its natural state.

[0083] It should be understood that a reference line is defined as the normal to the reference plane passing through a Nip point in its natural state. In three-dimensional space, there are infinitely many Nip points, and therefore infinitely many reference lines; these reference lines together constitute a reference plane.

[0084] It should be noted that whether the reference line passes through the Nip point in its natural state does not affect the concept and scope of protection of the technical solution described in this invention.

[0085] It should be understood that Figure 1The diagram shows a horizontal constant-diameter twin-roll casting process, where the symbol "ξ" represents the molten pool depth angle. Horizontal constant-diameter twin-roll casting is a commercially available method for producing thin steel strips.

[0086] It should be noted that, as Figure 7 As shown, a horizontal equal-diameter twin-roll casting machine is used as an example for illustration. A plane perpendicular to the roll shafts is selected, and a schematic diagram is shown on this plane illustrating the relationship between the two rolls, the two roll shafts, the placement plane, the reference plane, the roll gap, the Nip point, the reference line, the speed at which the roll surface passes through the roll gap, the production speed, the production direction, and the reference direction under different conditions.

[0087] It should be understood that "in different states" can also be expressed as "in a natural state or in an unnatural state".

[0088] It should be noted that, as Figure 7 As shown, the "speed of the roller surface passing through the roller gap" is always in the same direction as the "processing speed" because the roller body is considered an ideal rigid rotating body; in other words, the "direction of the speed of the roller surface passing through the roller gap" is always the same as the "processing direction".

[0089] It should be noted that, as Figure 7 As shown, in its natural state, the plane containing the two rollers is called the reference plane; the direction of the billet's moving speed at point Nip is called the "reference direction," which is always perpendicular to the reference plane. In its natural state, the placement plane coincides with the reference plane, and the preparation direction is the same as the reference direction. Therefore, the reference plane can be considered a special case of the placement plane, the reference direction can be considered a special case of the preparation direction, and the reference line can be considered a special case of the placement normal.

[0090] It should be noted that, "in the first floating process, the inner product of the floating speed and the preparation speed is the first inner product; in the second floating process, the inner product of the floating speed and the preparation speed is the second inner product." The meaning of "inner product" is readily and unambiguously understood by those skilled in the art.

[0091] It should be noted that in a three-dimensional rectangular coordinate system (X, Y, Z), let vector U = [x1, y1, z1] and vector V = [x2, y2, z2]. Then, the inner product of vectors U and V is: U·V = x1x2 + y1y2 + z1z2.

[0092] It should be noted that the "inner product" can also be called the "scalar product" or the "dot product".

[0093] It should be understood that "change in the placement plane" means: under the condition that no roller system movement occurs (or the influence caused by roller system movement is eliminated), and no relative movement occurs between the two rollers (i.e., in the natural state), let the plane where the two roller shafts are located be the placement plane Θ. 1s When relative motion occurs between the two rollers, let the plane where the two roller shafts are located be the placement plane Θ. 2s If plane Θ 1s With plane Θ 2s If they do not overlap but intersect, it is said that "the placement plane has changed".

[0094] It should be understood that the roller system can move on a twin-roll strip casting machine. However, when there is no relative movement between the two rollers, the floating speed is zero, and the effective speed is also zero.

[0095] It should be understood that, as mentioned above, "effective speed" is the component of "floating speed" in the fabrication direction. "Effective speed" and its variation can be used to characterize the extent to which the roll gap floating process affects the molten pool transport behavior.

[0096] It should be understood that at some point when the first or second float occurs, the velocity of point Nip relative to the ground (expressed as vector V) T The expression can be decomposed into two parts: first, the ground-relative velocity caused by the movement of the roller system, expressed as a vector V. W Secondly, the velocity relative to the ground caused by the relative motion between the two rollers is expressed as a vector V. F Therefore, we have: V F =V T -V W .

[0097] Because V in the above process T =0, then we can obtain: V F =-V W .

[0098] It should be understood that in this invention patent application, "floating velocity" (i.e., vector V) F This is unrelated to the movement of the roller system. This is because: simple roller system movement causes a change in the position of the Nip point relative to the ground; similarly, simple roll gap floating also causes a change in the position of the Nip point relative to the ground; however, their mechanisms of action on the molten pool transport behavior are completely different. If only roller system movement occurs without roll gap floating, there is no need to discuss the change in the state of the Nip point, because discussing the change in the state of the Nip point in this case has no practical significance for the technical solution described in this invention.

[0099] It should be understood that, based on the above explanation of "floating speed", it is clear that "floating speed" is generated solely by the relative motion between the two rollers.

[0100] It should be noted that even without the above detailed explanation, those skilled in the art can directly and without doubt understand that "floating speed" must be generated solely by the relative motion between the two rollers.

[0101] It should be noted that those skilled in the art can directly and unambiguously understand that both "floating speed equals zero" and "effective speed equals zero" include the case of "approaching zero." "Approaching zero" means that, under current technological conditions, there may be a definite but unavoidable deviation between the speed value and zero. For example, during the manufacturing process, the elastic deformation and vibration of the two rollers under load that cannot be completely eliminated, or the deviation between the actual and set movements of the rollers due to the non-ideal nature of the molten pool transfer process, can all cause such differences.

[0102] It should be understood that, unless otherwise specified, in this patent application, "equal to zero" includes the case of "approaching zero". In other words, "equal to zero" should be understood as "equal to zero or approaching zero", or it can be expressed as "substantially equal to zero" or "approximately equal to zero". For example, "angular velocity equal to zero" should be understood as "angular velocity equal to zero or approaching zero", or "angular velocity substantially equal to zero", or "angular velocity approximately equal to zero".

[0103] It should be noted that those skilled in the art will directly and unambiguously understand that during the movement of the roller system, the two rollers move as a whole on the twin-roll thin strip casting machine. Components in the twin-roll thin strip casting machine that are directly or indirectly connected to the first and / or second rollers—such as side sealing devices, distribution devices, drive mechanisms, etc.—can be configured to move with the roller system or remain stationary, as needed. The key is to ensure that the relative movement between the two rollers and the overall movement of the roller system do not interfere with each other spatially and temporally, thereby ensuring the normal operation of the system. In other words, it is sufficient to ensure that the movement of the roller system and the internal movement of the roller system can proceed independently and without mutual influence.

[0104] It should be understood that "in one of the first floating processes" refers to the time period between the start and end of one of the first movements.

[0105] It should be understood that the time period is an open interval, that is, it does not include the start time and the end time.

[0106] Through research, the inventors discovered that when the conditions of "the first inner product is less than zero" and "the second inner product is less than zero" are met, the relative motion between the two rollers will generate a component force in the molten pool. This component force acts independently of viscosity and does not depend on the shear driving force generated by the rotation of the rollers. In other words, this component force can be regarded as a shear-independent driving force that can affect the transport behavior of the material in the molten pool without changing the roller gap opening.

[0107] It should be noted that in the present invention patent application: the driving force generated by the rotation of the first roller and the second roller is referred to as the first driving force; and the shear-independent driving force induced by the relative motion between the two rollers is referred to as the second driving force.

[0108] The inventors discovered through research that, as Figure 8 As shown, after the second driving force acts on the molten pool, it will guide the material in different regions to be renewed along specific paths: firstly, it will cause the first vortex in the molten pool to flow and be renewed along the first vortex renewal path; secondly, it will cause the second vortex in the molten pool to flow and be renewed along the second vortex renewal path; and thirdly, it will cause the semi-solid material in the unstable region between the first and second billets to be renewed along the semi-solid material renewal path.

[0109] Therefore, the second driving force can directly regulate the circulating flow structure and material renewal process inside the molten pool without changing the roll gap, thereby improving the uniformity and stability of material renewal in the molten pool.

[0110] It should be understood that the presence of the second driving force can stabilize the material renewal process in the molten pool, thereby improving the uniformity and continuity of material flow and renewal in the molten pool.

[0111] It should be understood that, as mentioned above, the condition for the generation of the second driving force is: V NF ˙U C <0. When V is satisfied. NF ˙U C When V < 0, it can be determined that the second driving force is generated and plays a role in the material renewal process within the molten pool. Wherein, V NF U represents the floating velocity vector of point Nip. C This indicates the preparation velocity vector.

[0112] Furthermore, a roll gap control method for twin-roll casting and rolling, wherein the midpoint of the roll gap is defined as the Nip point; the moving speed of the billet at the Nip point is defined as the preparation speed; the moving speed of the Nip point caused by the relative motion between the first roll and the second roll is defined as the floating speed of the Nip point; during the first floating process, the inner product of the floating speed and the preparation speed is the first inner product; during the second floating process, the inner product of the floating speed and the preparation speed is the second inner product. In one of the first floating processes, the first inner product is greater than zero; and in one of the second floating processes, the second inner product is greater than zero.

[0113] It should be noted that when V NF ˙U C When V > 0, this state also has engineering application significance. For alloy compositions with extremely narrow two-phase regions, satisfying V NF ˙U C The >0 control mode can be used to reduce the pressure of the molten pool, thereby preventing the static pressure of the molten pool from connecting with the core of the billet that has not yet fully solidified, thus reducing the resulting fluctuations in process stability and / or defects in billet quality.

[0114] It should be noted that, with V NF ˙U C Compared to the case where V > 0, satisfying V NF ˙U C The condition of <0 has a wider range of applicability, and therefore has higher universality in practical applications.

[0115] Furthermore, in a method for controlling the roll gap in twin-roll casting, the drive control step is triggered when the reference distance is greater than or equal to a preset distance threshold to initiate the drive control process.

[0116] Furthermore, in a method for controlling the roll gap in twin-roll casting, the position of the driving device is defined as the initial position in its natural state; the driving plane is controlled to move to a preset position so that the change in the reference distance caused by the roll system control step and the change in the reference distance caused by the driving control step cancel each other out by at least a portion. The preset position includes at least one of the following: (1) The initial position of the driving device; (2) The preset position range of the driving device along its direction of motion.

[0117] Furthermore, in a method for controlling the roll gap in twin-roll casting, the temporal relationship between the roll system control step and the drive control step includes at least one of the following: (1) The roller system control step and the drive control step are performed sequentially; (2) The roller system control step and the drive control step are started sequentially and partially overlapped; (3) The roller system control step and the drive control step are performed simultaneously, but the changes to the reference distance are not synchronized; (4) The roller system control step and the drive control step are performed simultaneously, and the changes to the reference distance are synchronized.

[0118] It should be understood that "the roller system control steps and the drive control steps are performed simultaneously" means that the roller system and its drive device, as a whole, move relative to a fixed reference (such as the ground or frame base), i.e., "external motion"; while the time relationship specified above, "the temporal relationship between the roller system control steps and the drive control steps includes at least one of the following...", refers to the relative motion of the drive device within the overall system relative to the roller system (i.e., "internal motion"). "External motion" and "internal motion" have different levels of action and are logically independent, therefore they can coexist without conflict.

[0119] It should be understood that "simultaneous execution" in this application means that the two steps are executed in parallel in macroscopic time, that is, their time periods overlap; "synchronous execution" means that the two steps correspond to each other moment by moment in the time domain, and their changes to the reference distance cancel each other out or cancel each other out by the same magnitude in real time, so that the placement plane remains constant. Therefore, "synchronous execution" necessarily includes "simultaneous execution", but "simultaneous execution" does not necessarily mean "synchronous execution". Therefore, there can be a situation of "simultaneous execution but not synchronous", that is, the two steps are parallel in macroscopic time, but their changes to the reference distance do not correspond to each other moment by moment.

[0120] Furthermore, a method for controlling the roll gap in twin-roll casting and rolling, wherein the movement of the roll system includes at least one of the following: (1) Rotate about the second roller shaft; (2) Rotate about the first roller shaft; (3) Move in a straight line relative to the ground in a direction perpendicular to the reference plane; (4) Move in a straight line relative to the ground in a direction at an oblique angle to the reference plane; (5) Rotate about any axis parallel to the first roller shaft or the second roller shaft that is allowed by the structure of the device.

[0121] Furthermore, in a method for controlling the roll gap in twin-roll casting, during one of the drive control steps, the inner product of the speed of the drive device and the preparation speed is less than zero.

[0122] Furthermore, in a method for controlling the roll gap in twin-roll casting, the roll gap opening remains constant during one of the drive control steps.

[0123] It should be understood that "keeping the roll gap opening constant" is of great significance for the uniformity of the billet thickness.

[0124] Furthermore, in a method for controlling the roll gap in twin-roll casting, the angular velocity of the driving device remains zero during the execution of the drive control step.

[0125] Through research, the inventors discovered that when relative motion occurs between the drive device and the roller system, the drive device itself maintains an angular velocity of zero, which can prevent the drive shaft system from moving, thereby simplifying the system structure and reducing equipment complexity.

[0126] Furthermore, a roll gap control method for twin-roll casting and rolling is provided, wherein the roll system and the drive device are movably mounted on a twin-roll thin strip casting machine via a first kinematic pair, enabling them to move as a whole relative to a fixed reference (e.g., the ground or a machine frame base); the drive device is also movably mounted on the twin-roll thin strip casting machine via a second kinematic pair, enabling it to move relative to the roll system; the first kinematic pair is used to control the overall movement of the roll system and the drive device to adjust the reference distance; the second kinematic pair is used to control the relative movement of the drive device relative to the roll system to adjust the reference distance.

[0127] It should be noted that, compared with the existing technology, this invention proposes a completely new paradigm for roll gap control, which has significant technological progress and originality, as detailed below: First, this invention introduces a hierarchical mechanism of external overall motion and internal relative motion in its control logic. By defining a geometric system of "reference point—reference plane—reference distance," the motion of the roller system and the drive control can be quantified and coordinated within a unified framework, thus overcoming the limitations of traditional methods. Second, this invention establishes a cancellation mechanism, enabling the effects of roller system control and drive control on the reference distance to partially or completely cancel each other out, thereby theoretically achieving an infinite range of roller gap floating, significantly expanding the process parameter window, and providing a new means of controlling process stability. Third, this invention proposes a semi-solid metal... The invention employs a shear-thinning induced driving force interruption (ST-DFI) mechanism and designs an alternating first and second floating mechanism to ensure sufficient material renewal in unstable regions of the molten pool, avoiding defects such as "core eye pores" and resulting in a more uniform microstructure of the prepared billet. Finally, through innovative control methods, the side sealing plate and roller remain stationary relative to the ground during the floating process, avoiding additional relative wear. Theoretical analysis shows that the lifespan of the side sealing plate can be significantly extended, while reducing the stringent requirements for the cleanliness of the molten metal, further improving process stability and economy.

[0128] In summary, this invention not only proposes a novel technical solution that effectively addresses long-standing issues in existing technologies such as limited process window, unstable melt pool renewal, and insufficient side seal life, but also possesses outstanding substantive features and significant progress.

[0129] The advantages of the method proposed in this patent application include: (1) using independent kinematic pairs to control the drive device separately, so that the ground motion of the drive device and the ground motion of the roller system do not interfere with each other, thus offsetting the relative position change between the drive system and the roller system in the traditional roll gap floating method; (2) the process parameters of roll gap floating (including amplitude and floating speed) can be flexibly set according to actual needs, and their values ​​are only limited by equipment conditions; (3) during one roll gap floating process, the casting and rolling force changes unidirectionally, applying a normal driving force unrelated to viscosity to the semi-solid material in the molten pool, thereby enhancing process stability and / or improving billet quality; (4) the roll gap opening remains constant, which can theoretically ensure the uniformity of billet thickness. (5) Effectively suppresses the shear-thinning behavior and / or thixotropic behavior of semi-solid metals; (6) For materials with a narrow two-phase region, it can promote the formation of Kiss corners, and use Kiss corners to block the connection between the molten pool pressure and the core of the unsolidified billet, avoiding billet defects such as "ridge", "snake egg" and "egg pancake"; (7) For materials with a wide two-phase region, by applying a normal driving force independent of viscosity to maintain the stability of the total driving force, it promotes the renewal of Kiss corner material and inhibits its rapid development, reduces the pressure peak when the long-range shear-thinning interface collapses, and prevents various stability problems such as leakage, damage, jamming, breakage and cracking of the side sealing plate caused by excessive pressure peaks and shortens the life of key components. (8) By alternating the movement of the two rollers, the roll gap can be floated, thereby further improving the uniformity and performance of the billet structure, such as refining the grains and suppressing segregation; (9) By stabilizing the total driving force, the roller diameter can be further increased, thereby significantly improving production efficiency; (10) When the roll gap is used to increase the pressure of the molten pool, the formation of an air gap between the billet shell and the roller surface can be avoided, improving heat transfer performance and increasing output; at the same time, the casting and rolling force can be reduced, extending the service life of the rollers and bearings; it can also break through the shear thinning interface to suppress macrosegregation and reduce the peak shear stress, thereby reducing or avoiding crack generation; (11) The contact pressure between the roller surface and the material being cast and rolled is increased, the heat transfer resistance is reduced, and the heat transfer efficiency is improved. (12) During the roll gap floating process, due to the coordinated action of the roll system movement, the two rolls remain stationary relative to the ground, thereby completely eliminating the disturbance of the melt in the molten pool caused by the roll gap floating or the roll system movement; (13) The rolls and the side sealing device remain relatively stationary, significantly extending the service life of the side sealing plate and reducing production costs; (14) The alternating movement of the two rolls is conducive to the symmetrical distribution and uniform performance of the billet structure; (15) Controlling the stable renewal of the molten pool material enables the continuous and stable preparation of large batches of high-quality billets; (16) The cause of "eye-shaped pores" is revealed, indicating that when the roll gap floating is always used to increase the pressure of the molten pool, the probability of the occurrence of core eye-shaped pore defects can be effectively avoided or significantly reduced. Attached Figure Description

[0130] Figure 1 The diagram shown is a schematic of a horizontal equal-diameter twin-roll casting and rolling mill.

[0131] Figure 2 The diagram shown is a schematic of the unstable region of the molten pool.

[0132] Figure 3 The diagram illustrates the formation mechanism of "core eye-like pores" under the traditional opposing roll gap floating method, where "Dynamic roll" refers to the moving roll and "Stationary roll" refers to the stationary roll.

[0133] Figure 4 The diagram shows the material renewal process in the unstable region of the molten pool discovered by the inventors, where points N1 and N2 represent Nip points in different states.

[0134] Figure 5 The diagram shows the side sealing plate before use, before any wear and tear.

[0135] Figure 6 The diagram shows a side sealing plate after use, with a slope caused by wear.

[0136] Figure 7 The diagram shown illustrates the placement plane, reference plane, first roll body, second roll body, Nip point, first roll shaft, second roll shaft, preparation direction, reference speed, reference direction, and reference line for horizontal equal-diameter twin-roll casting under different conditions.

[0137] Figure 8 The diagram shows the material renewal path in the molten pool.

[0138] Figure 9 The diagram shown is a schematic diagram of Embodiment 1 of the present invention at time t0, where both the first roller shaft O1 and the second roller shaft O2 are located on the reference plane.

[0139] Figure 10 The diagram shown is a schematic diagram of the first roller rotating clockwise around the second roller shaft O2 in Embodiment 1 of the present invention.

[0140] Figure 11 The diagram shows the overall rotation of the roller system and drive device of Embodiment 1 of the present invention around the second roller shaft O2 in a counterclockwise direction.

[0141] Figure 12 The diagram shown is a schematic of the second roller rotating counterclockwise around the first roller shaft O1 in Embodiment 1 of the present invention.

[0142] Figure 13 The diagram shows the overall rotation of the roller system and drive device of Embodiment 1 of the present invention around the first roller shaft O1 clockwise.

[0143] Figure 14The diagram shown is a schematic diagram of the first roller shaft O1 and the second roller shaft O2 returning to the reference plane in Embodiment 1 of the present invention.

[0144] Figure 15 The diagram shown is a schematic diagram of Embodiment 2 of the present invention, in which both the first roller shaft O1 and the second roller shaft O2 are located on a reference plane.

[0145] Figure 16 The diagram shows the overall rotation of the roller system and drive device of Embodiment 2 of the present invention around the second roller shaft O2 in a counterclockwise direction.

[0146] Figure 17 The diagram shows the overall rotation of the roller system and drive device of Embodiment 2 of the present invention around the first roller shaft O1 clockwise.

[0147] Figure 18 The diagram shown is a schematic diagram of the first roller shaft O1 and the second roller shaft O2 returning to the reference plane in Embodiment 2 of the present invention.

[0148] Figure 19 The diagram shown is a schematic diagram of Embodiment 3 of the present invention, in which both the first roller shaft O1 and the second roller shaft O2 are located on a reference plane.

[0149] Figure 20 The diagram shown is a schematic diagram of the first roller body rotating clockwise around the second roller body in Embodiment 3 of the present invention, and the entire assembly consisting of the first roller body, the second roller body, the first driving device, and the second driving device rotating counterclockwise around the second roller shaft O2 after the rotation is completed.

[0150] Figure 21 The diagram shown is a schematic diagram of the second roller body rotating counterclockwise around the first roller shaft O1 in Embodiment 3 of the present invention, and the entire assembly consisting of the first roller body, the second roller body, the first driving device, and the second driving device rotating clockwise around the first roller shaft O1 after the rotation is completed.

[0151] Figure 22 The diagram shown is a schematic diagram of the first roller shaft O1 and the second roller shaft O2 returning to the reference plane in Embodiment 3 of the present invention.

[0152] The correspondence between the figure numbers in the following figures is as follows: 1. First roller, 2. Second roller, 3. Roll gap, 4. Distribution device, 5. Molten pool, 6. Free liquid surface, 7. Billet, 8. Reference plane, 9. Gravity direction, 10. Unstable region, 11. First billet shell, 12. Second billet shell, 13. Material from unstable region 10, 14. First vortex (caused by the rotation of first roller 1), 15. Second vortex (caused by the rotation of second roller 2), 16. Update path of first vortex 14, 17. Update path of second vortex 15, 18. Update path of semi-solid material, 19. Driving device (can be a driver, a reducer, or a combination of a driver and a reducer), 20. Driving plane; 21. First driving device; 22. Second driving device. Detailed Implementation

[0153] The present invention will now be described in further detail with reference to the accompanying drawings.

[0154] For clarity, please refer to the following: Figure 1 Let Ω be any plane perpendicular to the first roller axis; the roller axes of the first roller body 1 and the second roller body 2 are defined as the first roller axis and the second roller axis, respectively; the minimum distance between the first roller body 1 and the second roller body 2 is called the roller gap 3. During the preparation process, molten metal enters between the two rollers through the distribution device 4, forming a molten pool 5, which has a free liquid surface 6; the billet 7 is removed from the molten pool 5 through the roller gap 3. The midpoint of the roller gap 3 is called the Nip point; in the natural state, the plane containing the first roller axis and the second roller axis is defined as the reference plane 8; in the static state, the normal line passing through the Nip point in the reference plane 8 is defined as the reference line. The first roller axis and the second roller axis intersect the plane Ω at points O1 and O2, respectively.

[0155] All embodiments of the present invention employ a horizontal equal-diameter twin-roll thin strip casting machine. Therefore, in the following embodiments, the reference direction is consistent with the gravity direction 9. Example 1:

[0156] Embodiment 1 of the present invention discloses a method for controlling the roll gap in twin-roll casting and rolling, such as... Figures 9 to 14 As shown. For ease of explanation of "rotation of the rollers", the first roller 1 and the second roller 2 are shown as cubes, that is, their projections on the plane Ω are squares. The terms "first motion" and "reference speed" used herein are consistent with the definitions above in the specification.

[0157] Figures 9 to 14Point A is a fixed point on the first roller 1, and point B is a fixed point on the second roller 2. To highlight the contribution of the roller system rotation to the "rotation of the rollers," the influence of the rotation of the two rollers on the positions of points A and B is not considered below; that is, the "rotation of the rollers" is caused only by the rotation of the roller system. In other words, it can be equivalently stated as ignoring or eliminating the influence of the rotation of the two rollers on the positions of points A and B. Points A and B are set to assist those skilled in the art in understanding the roller system control steps, drive control steps, floating control steps, and the relationship between the first floating and the second floating. Note: If the angular velocity of the first roller's rotation is Ω1, and the angular velocity of the roller system around the first roller axis is Ω2 (Ω1 and Ω2 are both vectors), then the actual angular velocity of the first roller is the sum of the two; for ease of analysis in this embodiment, only the component Ω2 generated by the rotation of the roller system is taken.

[0158] like Figure 9 As shown, at time t0 (t0≥0), the first roller 1, the second roller 2, and the drive device 19 are all in their initial positions. The first and second roller shafts are located on the reference plane 8, and the placement plane coincides with the reference plane 8. Points A and B are symmetrical about the reference line. The center of gravity of the drive device 19 is located at point E1 on the reference plane 8 (see...). Figure 9 The driving plane 20 coincides with the reference plane 8.

[0159] like Figures 9 to 10 The diagram illustrates one floating control step. Starting at time t1 (t1 ≥ t0), the first roller 1 rotates continuously clockwise around the second roller 2, while the roller gap 3 remains constant; at time t2 (t2 > t1), the first roller 1 reaches... Figure 10 The roller is positioned as shown and rotation stops. This step lasts for 0.05 to 0.5 seconds, and the displacement of the first roller 1 is within the range of 10 to 100 micrometers. This step applies a pressure wave to the molten pool 5 to increase the instantaneous pressure of the molten pool 5. This pressure wave can exert penetrating pressure on the shear-thinning interface to destroy or break it down, thereby suppressing macroscopic segregation; it can also be used to enhance heat transfer, accelerate the solidification of the interfacial liquid phase to eliminate the shear-thinning interface; and it can also suppress interface formation by reducing the shear rate and reduce local shear stress to avoid cracking.

[0160] like Figures 10 to 11 The diagram illustrates the control steps of a single roller system. Starting at time t3 (t3 ≥ t2), the entire assembly of the roller system and drive unit 19 rotates counterclockwise around the second roller shaft; during this process, no relative motion occurs between the roller system and drive unit 19. At time t4 (t4 > t3), the first roller 1 reaches... Figure 11 Stop rotating at the indicated position. At this point, the placement plane coincides with the reference plane 8, and the center of gravity of the drive device 19 is located at point E2 (see...). Figure 11 The driving plane 20 (or plane Φ1) is located below the reference plane 8.

[0161] like Figures 11 to 12 The diagram illustrates the second floating control step. Starting at time t5 (t5≥t4), the second roller 2 rotates continuously counterclockwise around the first roller 1, while the opening of the roller gap 3 remains constant; at time t6 (t6>t5), the second roller 2 reaches... Figure 12 Move to the indicated position and stop rotating.

[0162] like Figures 12 to 13 The diagram illustrates the second roller system control step. Starting at time t7 (t7 ≥ t6), the entire assembly of the roller system and drive device 19 rotates clockwise around the first roller shaft; during this process, no relative motion occurs between the roller system and drive device 19. At time t8 (t8 > t7), the second roller 2 reaches... Figure 13 The device moves to the indicated position and stops rotating. At this point, the placement plane coincides with the reference plane 8, and the center of gravity of the drive device 19 is located at point E3 (see...). Figure 13 The driving plane 20 (or plane Φ2) is located below the reference plane 8.

[0163] like Figures 13 to 14 The diagram illustrates one drive control step. Starting at time t9 (t9 ≥ t8), the drive unit 19 performs a first motion, its center of gravity moving from point E3 along the straight line E3E1 to point E1 (see...). Figure 14 ); at t 10 (t) 10 At time >t9), the center of gravity of the drive device 19 returns to the reference plane 8 and stops moving relative to the ground, and the step ends. During this first movement, the inner product of the velocity of the drive device 19 relative to the ground and the reference velocity is always less than zero.

[0164] Figures 9 to 14 The five steps shown can be repeated sequentially, causing the drive device 19 to undergo multiple first movements, which are performed continuously; during each first movement, the drive device 19 only undergoes translational motion. From t0 to t... 10 During this period, the changes to the reference distance caused by the roller control steps and the changes to the reference distance caused by the drive control steps completely cancel each other out. The cancellation relationship can be determined according to the aforementioned definition or actual settings. In another embodiment, the two can also partially cancel each other out, and the measurement method can refer to the aforementioned definition.

[0165] Figures 9 to 14 The steps shown constitute a complete process, which can occur only once in a single preparation process or be repeated multiple times. In this complete process, the changes in the reference distance caused by the roller control steps and the drive control steps completely cancel each other out. The drive unit 19 rotates twice in this process, but the centers of rotation are not aligned, and the overall effect is equivalent to the drive unit 19 completing one translational motion.

[0166] t0 to t 10The time period refers to a time interval during the preparation process, where t0 is any time and is not necessarily the start time of the preparation process; t 10 It is not necessarily the end point of the preparation process.

[0167] Alternatively, in another embodiment, during the preparation process, the drive device 19 and the roller system undergo only one relative motion, and during this relative motion, the inner product of the velocity vector of the drive device 19 and the reference velocity vector is always less than zero.

[0168] Alternatively, in another embodiment, the drive device 19 and the roller system undergo only one relative movement, and during this process, the inner product is first less than zero and then greater than zero. Example 2:

[0169] Embodiment 2 of the present invention discloses a method for controlling the roll gap in twin-roll casting and rolling, such as... Figures 15 to 18 As shown.

[0170] Similar to Embodiment 1, for ease of description, both the first roller 1 and the second roller 2 are shown as squares.

[0171] like Figures 15 to 18 As shown, point A is a fixed point on the first roller 1, and point B is a fixed point on the second roller 2. In this embodiment, the influence of the rotation of the first roller 1 and the second roller 2 on the positions of points A and B is not considered; that is, the "rotation of the rollers" is only caused by the movement of the roller system.

[0172] The difference between this embodiment and Embodiment 1 is that the floating control step and the roller system control step occur simultaneously and synchronously, and their changes to the placement plane cancel each other out in real time and space. Because the two steps occur simultaneously and cancel each other out, the placement plane remains stationary relative to the ground throughout the process, and there is no relative movement between the roller and the side sealing plate.

[0173] In industrial practice, when the floating control step and the roller system control step occur simultaneously, the rotation speed of the first roller 1 and the second roller 2 can be set to zero; even, in some embodiments, the velocity direction of the roller surface through the roller gap 3 can be opposite to the movement direction of the material at the Nip point.

[0174] It should be understood that in the phrase "the floating control step and the roller system control step occur simultaneously and synchronously," "occur simultaneously" means that the two are executed in parallel in macroscopic time, that is, the changes to the placement plane by the floating control step and the changes to the placement plane by the roller system control step overlap in time. "Occur synchronously" means that the two steps correspond to each other at every moment in the time domain, and their changes to the placement plane are completely canceled out in real time, so that the placement plane remains stationary or nearly stationary throughout the entire process.

[0175] It should be understood that the term "synchronization" in this application refers to the fact that the effective ranges of the two steps in the time domain highly overlap. They can start and end strictly at the same time, or they can be carried out almost simultaneously within a preset tolerance range. As long as the two steps work together on the placement plane within the main effective range, keeping its position constant or basically constant, they are considered to be synchronized.

[0176] It should be understood that the term "simultaneously" in this application only limits the overlap of the two steps in time, and does not require that their effects be completely consistent at every moment. In summary, "simultaneously" and "occurring synchronously" provide a dual limitation on the relationship between the two steps: "simultaneously" defines parallelism in macroscopic time, while "synchronously" defines real-time cancellation of the effects. By combining the two, both the time condition and the effect condition can be defined simultaneously, giving the technical features of this invention a clear criterion for judgment.

[0177] like Figure 15 As shown, at time t0 (t0≥0), the first roller 1, the second roller 2 and the driving device 19 are in the initial position, the first roller shaft and the second roller shaft are both located on the reference plane 8, the placement plane coincides with the reference plane 8, the center of gravity of the driving device 19 is located at point E1 on the reference plane 8, and the driving plane 20 coincides with the reference plane 8.

[0178] like Figures 15 to 16 The diagram illustrates the simultaneous and synchronous occurrence of a floating control step and a roller system control step. Starting at time t1 (t1 ≥ t0), the first roller 1 rotates continuously clockwise around the second roller 2 with an angular velocity of ω1, while the opening of the roller gap 3 remains constant. Simultaneously, the entire roller system and drive device 19 rotate counterclockwise around the second roller axis with an angular velocity of ω2, where ω1 and ω2 are vectors satisfying ω1 = −ω2. At time t2 (t2 > t1), the rotation of the first roller 1 around the second roller 2 stops. During the time interval from t1 to t2, the placement plane always coincides with the reference plane 8. The drive device 19... Figure 15 Move to the position shown Figure 16 The center of gravity at the position shown has shifted from E1 to E2 (see...). Figure 16 At this time, the driving plane 20 (or plane Φ1) is located below the reference plane 8.

[0179] like Figures 16 to 17 The diagram illustrates the simultaneous and synchronous occurrence of the second floating control step and the roller system control step. Starting at time t3 (t3≥t2), the second roller 2 rotates continuously counterclockwise around the first roller 1 with an angular velocity of ω′1, while the roller gap 3 remains unchanged. Simultaneously, the entire assembly of the roller system and drive device 19 rotates clockwise around the first roller axis with an angular velocity of ω′2, and ω′1 and ω′2 are vectors satisfying ω′1=−ω′2. At time t4 (t4>t3), the placement plane and the reference plane 8 remain coincident. The drive device 19 then... Figure 16 Move to the position shown Figure 17 The center of gravity at the position shown has shifted from E2 to E3 (see...). Figure 17 At this time, the driving plane 20 (or plane Φ2) is located below the reference plane 8.

[0180] like Figures 17 to 18 The diagram illustrates one drive control step. Starting at time t5 (t5≥t4), the drive device 19 undergoes a relative motion with respect to the ground, generating the first motion; its center of gravity shifts from... Figure 17 Point E3, as shown, moves along the straight line E3–E1 to... Figure 18 Point E1 is shown. At time t6 (t6 > t5), the center of gravity of the drive device 19 returns to the reference plane 8. Throughout the entire first motion, the inner product of the velocity of the drive device 19 relative to the ground and the reference velocity is always less than zero.

[0181] Repeat in sequence Figures 15 to 18 The steps shown cause the drive device 19 to undergo multiple first movements, which occur consecutively; during each first movement, the drive device 19 only undergoes translational motion. t0 to t6 is a time period in one preparation process, where t0 can be any time and is not necessarily the start time; t6 is also not necessarily the end time.

[0182] like Figures 15 to 16 The process shown corresponds to one first float, such as Figures 16 to 17 The process shown corresponds to a second float.

[0183] Alternatively, in another embodiment, the drive control step may occur prior to the floating control step and / or the roller system control step.

[0184] Alternatively, in another embodiment, the floating control step, the roller system control step, and the drive control step may occur simultaneously.

[0185] It should be noted that, compared with the traditional method of floating the opposing roll gap, the technical solution proposed in Embodiment 2 of this invention can effectively avoid, when the floating of the roll gap 3 is used to increase the pressure in the molten pool 5, the following: Figure 3 As shown, the "eye-shaped pore" defect generated in the core of the billet when using the traditional method. Example 3:

[0186] Embodiment 3 of the present invention discloses a method for controlling the roll gap in twin-roll casting and rolling, such as... Figures 19 to 22 As shown.

[0187] This embodiment is applicable to both twin-roll casting and rolling and conventional rolling processes (such as cold rolling or hot rolling). When used in twin-roll casting, the substance entering between the first roll 1 and the second roll 2 is liquid metal; when used in conventional cold rolling, the substance entering between the two rolls is room-temperature solid metal; when used in conventional hot rolling, the substance entering between the two rolls is generally solid metal at a certain high temperature.

[0188] Similar to Embodiments 1 and 2, for ease of explanation, both the first roller 1 and the second roller 2 are schematically represented as squares. Figures 19 to 22 As shown, point A is a fixed point on the first roller 1, and point B is a fixed point on the second roller 2. In this embodiment, the influence of the rotation of the first roller 1 and the second roller 2 on the positions of points A and B is not considered; that is, the "rotation of the rollers" is only caused by the movement of the roller system.

[0189] The main difference between this embodiment and embodiment 2 is that the first drive device 21 drives the first roller 1 and the second drive device 22 drives the second roller 2, thereby realizing a composite drive mode in which independent control and collaborative control coexist.

[0190] like Figure 19 As shown, at time t0 (t0≥0), the first roller 1, the second roller 2, the first drive device 21, and the second drive device 22 are all in their initial positions. The first roller shaft and the second roller shaft are both located on the reference plane 8, and the placement plane coincides with the reference plane 8. Point E1 of the first drive device 21 is selected as the reference point, and the drive plane 20 is kept parallel to the reference plane 8.

[0191] like Figures 19 to 20 The diagram illustrates the simultaneous and synchronous occurrence of a floating control step and a roller system control step. Starting at time t1 (t1 ≥ t0), the first roller 1 rotates continuously clockwise around the second roller 2 with an angular velocity of ω1, while the opening of the roller gap 3 remains constant. Simultaneously, the roller system, along with the first drive device 21 and the second drive device 22, rotates counterclockwise around the second roller axis with an angular velocity of ω2, where ω1 and ω2 are vectors satisfying ω1 = −ω2. At time t2 (t2 > t1), the rotation of the first roller 1 around the second roller 2 stops, and the rotation of the roller system and the two drive devices around the second roller axis also stops. During the period from t1 to t2, the placement plane always coincides with the reference plane 8. The first drive device 21... Figure 19 Move to the indicated position Figure 20 At the position shown, the driving plane transitions from Φ1 to Φ2; at time t2, the driving plane 20 (or plane Φ2) is located below the reference plane 8.

[0192] like Figures 20 to 21The diagram illustrates the simultaneous and synchronous occurrence of the second floating control step and the roller system control step. Starting at time t3 (t3≥t2), the second roller 2 rotates continuously counterclockwise around the first roller 1 with an angular velocity of ω′1, while the opening of the roller gap 3 remains constant. Simultaneously, the roller system, together with the first drive device 21 and the second drive device 22, rotates clockwise around the first roller axis with an angular velocity of ω′2, where ω′1 and ω′2 are vectors satisfying ω′1=−ω′2. At time t4 (t4>t3), the placement plane and the reference plane 8 remain aligned. During this period, the first drive device 21... Figure 20 Move to the indicated position Figure 21 At the position shown, the center of gravity of the second drive unit 22 synchronously moves from... Figure 20 Move to the indicated position Figure 21 The position shown. At time t4, the driving plane 20 (or plane Φ3) is located below the reference plane 8.

[0193] like Figures 21 to 22 The diagram illustrates one drive control step. Starting at time t5 (t5≥t4), the first drive device 21 and the second drive device 22 are controlled to undergo a relative motion with respect to the ground, generating a first motion. This first motion causes the centers of gravity of the first drive device 21 and the second drive device 22 to shift from... Figure 21 Return to the indicated position along the corresponding trajectory Figure 22 The position is shown. At time t6 (t6 > t5), the centers of gravity of both the first drive device 21 and the second drive device 22 return to the reference plane 8. During this first motion, the inner product of the velocities of the two drive devices relative to the ground and the reference velocity is always less than zero.

[0194] In sequence, repeat Figures 19 to 22 The steps shown cause the first driving device 21 and the second driving device 22 to undergo multiple first movements, which are performed continuously. During each first movement, the two driving devices only undergo translational motion, without rotation or additional angular motion. t0 to t6 is a time interval in one preparation process, where t0 is any time and does not necessarily have to be the start time of preparation, and t6 does not necessarily have to be the end time of preparation.

[0195] This embodiment achieves complete cancellation of linkage between the two rolls under "simultaneous and synchronous" conditions through independent control of dual drive devices. This generates normal pulse pressure while maintaining a constant roll gap, making it suitable for various process scenarios. When applied to twin-roll casting and rolling, it can stabilize the molten pool pressure field and promote the renewal of semi-solid materials. When applied to cold rolling or hot rolling, it can modulate the normal load distribution while maintaining a constant plate thickness, thereby reducing peak rolling force and suppressing crack formation.

[0196] This application discloses two common drive configurations for twin-roll thin strip casting machines: Embodiments 1 and 2 show a structure where a single drive device simultaneously drives two casting rolls; Embodiment 3 shows a structure where two drive devices drive two casting rolls separately. It should be understood that the roll gap control technology proposed in this invention is applicable to any of the above drive configurations and is not limited to a specific drive method. In practical applications, the number, layout, type, and connection method of the drive devices to the roll system can be adjusted according to process requirements without affecting the realization of the core principles of this invention.

[0197] In this application, the embodiments employ a horizontal equal-diameter twin-roll thin strip casting machine. It should be understood that the horizontal equal-diameter twin-roll thin strip casting machine is only one structural form of twin-roll thin strip casting machine. Twin-roll thin strip casting machines come in various forms and can be classified in many ways: (1) according to the relationship between the roller diameters, they can be divided into equal-diameter, unequal-diameter, and variable-diameter types; (2) according to the arrangement of the two rollers, they can be divided into horizontal, inclined, and vertical types; (3) according to the direction of billet drawing, they can be divided into drawing out along the direction of gravity, drawing out at an angle of less than 180° to the direction of gravity, and drawing out in the opposite direction of gravity. Among them, the variable-diameter twin-roll casting and rolling process also belongs to the field of twin-roll thin strip casting and rolling, characterized in that the diameter of at least one of the two rollers changes along the roller axis direction. This process can be used to prepare composite materials such as clad tubes, clad rods, and clad thin plates.

[0198] It should be understood that the roll gap control technology proposed in this invention is applicable to any form of twin-roll thin strip casting machine, and is not limited to a specific structure or arrangement.

[0199] The numbering of the embodiments in this invention is only used to distinguish different implementation methods and does not indicate superiority or inferiority. The above embodiments are only used to illustrate the technical solutions of this invention and are not intended to limit it. Although this invention has been described in detail with reference to the above embodiments, those skilled in the art can make various modifications, equivalent substitutions or improvements after reading this specification without departing from the essential spirit and scope of protection of this invention; all such modifications or equivalent substitutions should fall within the scope of protection claimed by this invention.

[0200] Finally, it should be noted that although the technical solution proposed in this invention originates from the research background of twin-roll casting and rolling processes, its principles and effects are not limited to this field. Those skilled in the art will understand that this solution is also applicable to related rolling processes, including but not limited to cold rolling and hot rolling. In rolling processes, the technical solution proposed in this invention can introduce pulsating pressure waves in the action area (deformation zone), thereby reducing rolling force, extending the service life of key components (including bearings and rolls), and reducing the formation of cracks in the billet. In other words, the application scope of this invention is not limited to the field of twin-roll thin strip continuous casting, but has broader process applicability and engineering promotion potential.

Claims

1. A method for controlling the roll gap of a twin roll casting machine, the twin roll casting machine comprising a roll set and a drive device, the roll set comprising a first roll body and a second roll body arranged opposite to each other for preparing a cast strip, the drive device being configured to control the counter-rotating of the first roll body and the second roll body, the roll shaft of the first roll body being defined as a first roll shaft, the roll shaft of the second roll body being defined as a second roll shaft, the plane on which the first roll shaft and the second roll shaft lie being defined as a laying plane of the roll set, the laying plane being defined as a reference plane in a natural state, a point on a fixed component of the drive device and not passing through the first roll shaft or the second roll shaft being selected as a reference point, a plane parallel to or coinciding with the reference plane and passing through the reference point being defined as a drive plane, the distance between the drive plane and the reference plane being defined as a reference distance; characterized in that the method comprising the following steps: a roll set control step of controlling the roll set and the drive device to move relative to the ground at the same time so as to change the reference distance; a drive control step of controlling the drive device to move relative to the roll set so as to change the reference distance; wherein the change of the reference distance by the roll set control step and the change of the reference distance by the drive control step are partially or completely offset. 2.The method according to claim 1, wherein the method further comprises a floating control step of controlling the first roll body and the second roll body to move relative to each other so as to change the laying plane; wherein the change of the laying plane by the floating control step and the change of the laying plane by the roll set control step are partially or completely offset. 3.The method according to claim 2, wherein the floating control step comprises the following two sub-steps: a first floating of controlling the second roll body to remain stationary relative to the ground while controlling the first roll body to continuously rotate within a predetermined rotation angle range around the second roll shaft and synchronously rotating the roll set around the second roll shaft; a second floating of controlling the first roll body to remain stationary relative to the ground while controlling the second roll body to continuously rotate within a predetermined rotation angle range around the first roll shaft and synchronously rotating the roll set around the first roll shaft; wherein at least one of the first floating and the second floating is performed at least once during a preparation process. 4.The method according to claim 3, wherein the laying plane remains stationary relative to the ground during one of the first floating and the second floating. 5.The method according to claim 3, wherein ​ ​ ​ ​ The midpoint of the roll gap is defined as a nip point; the moving speed of the blank at the nip point is defined as a production speed; the moving speed of the nip point caused by the relative motion between the first roll body and the second roll body is defined as a floating speed of the nip point; the inner product of the floating speed and the production speed in the first floating process is a first inner product; the inner product of the floating speed and the production speed in the second floating process is a second inner product; Wherein, in one of the first floating process, the first inner product is less than zero; and, in one of the second floating process, the second inner product is less than zero.

6. The roll gap control method of twin roll casting according to claim 1, characterized in that: The driving control step is triggered when the reference distance is greater than or equal to a preset distance threshold, to start the driving control process.

7. The roll gap control method of twin roll casting according to claim 1, characterized in that: In a natural state, the position of the driving device is defined as an initial position; the driving plane is controlled to move to a preset position, so that the change of the reference distance caused by the roll system control step and the change of the reference distance caused by the driving control step offset each other at least partially; The preset position at least includes one of the following: (1) the initial position of the driving device; (2) a preset position interval of the driving device along its moving direction.

8. The roll gap control method of twin roll casting according to claim 1, characterized in that: The time relationship between the roll system control step and the driving control step at least includes one of the following: (1) the roll system control step and the driving control step are performed in sequence; (2) the roll system control step and the driving control step are performed in a partially overlapped manner after being started; (3) the roll system control step and the driving control step are performed simultaneously, but the changes of the reference distance caused by the two steps are not synchronized; (4) the roll system control step and the driving control step are performed simultaneously, and the changes of the reference distance caused by the two steps are synchronized.

9. The roll gap control method of twin roll casting according to claim 1, characterized in that: The movement of the roll system at least includes one of the following: (1) rotating around the second roll shaft; (2) rotating around the first roll shaft; (3) moving linearly relative to the ground in a direction perpendicular to the reference plane; (4) moving linearly relative to the ground in a direction at an oblique angle to the reference plane; (5) rotating around any axis parallel to the first roll shaft or the second roll shaft allowed by the device structure.

10. The roll gap control method of twin roll casting according to claim 1, characterized in that: In the process of one of the driving control steps, the inner product of the speed of the driving device and the production speed is less than zero.

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