A roll gap floating method for twin roll strip

Abstract

The application provides a roll gap floating method for double-roller thin strips, namely, roll gap fixed opening-synchronous floating, and belongs to the technical field of double-roller thin strips. In the preparation process, the change of the roll gap floating process to the laying plane and the change of the roll system movement process to the laying plane are real-time and fully offset, so that the two roller bodies are always kept stationary on the ground. Compared with the prior art, in the roll gap floating process, the two roller bodies and the side sealing device are always kept stationary on the ground, the influence of the roll gap floating process on the side sealing device can be completely eliminated in theory, and an unlimited process parameter interval is theoretically provided.

Description

Technical Field

[0001] This invention relates to the field of twin-roll thin strip technology, and more specifically to a method for floating the roll gap in twin-roll thin strip. Background Technology

[0002] The twin-roll strip casting process was proposed by the British metallurgist Sir Bessemer around 1850. Twin-roll strip casting machines are also known as twin-roll casting machines, twin-roll continuous casting machines, twin-roll casting and rolling mills, twin-roll strip mills, twin-roll casting extrusion mills, etc. The billets produced by twin-roll strip casting machines are not necessarily thin strips. "Thin strip" is merely a long-standing, customary term in the technical field to which this patent application pertains (hereinafter referred to as "the field"). "Thin strip" includes thin strips, pipes, bars, plates, and other billets with special cross-sectional shapes.

[0003] In the twin-roll thin-strip manufacturing process, the components constituting the molten pool include two crystallizing rolls arranged opposite and parallel to each other; the "crystallizing roll" is also referred to as the "roll body"; the two crystallizing rolls are respectively referred to as the first roll body and the second roll body, and "first roll body and second roll body" can be simply referred to as the "two roll bodies"; the axis of rotation of the roll body is simply referred to as the roller shaft; by reading the patent application documents of this invention, those skilled in the art can directly and unambiguously understand the term "roll shaft"; in the patent application documents of this invention, the use of the term "roll shaft" is appropriate, clear, and unambiguous; the first roll body's roller... The shaft is called the first roller shaft, and the roller shaft of the second roller body is called the second roller shaft. The roller shaft is a virtual straight line, and "first roller shaft and second roller shaft" can be simply referred to as "two roller shafts". The surface of the roller body that directly contacts the material in the molten pool is called the roller body working surface, which is simply referred to as "roller surface". Those skilled in the art can directly and unambiguously recognize "roller surface". The two ends of the roller body that are perpendicular to the roller shaft are called "end faces". When using contact side sealing plates, a portion of the "end faces" of the roller body interacts with the contact side sealing plates periodically or non-periodically. The two rolls are in contact; a gap is left between them, and the minimum distance between the two rolls is called the roll gap; the minimum distance between the two rolls is called the roll gap opening; the roll gap opening can be less than 1 mm or more than 10 mm; under normal circumstances, for thin steel strips, the roll gap opening is in the range of 0.5 to 3 mm; the midpoint of the roll gap is called the Nip point; side sealing devices are often required in twin-roll casting and rolling processes; contact side sealing devices are a relatively mature side sealing method; under normal circumstances, contact side sealing devices are generally made of refractory materials and require... Under certain pressure, the rollers come into close contact with the end face of the rolls, which causes wear on the side sealing device. Cooling water channels can be installed inside the rolls. During the preparation process, the two rolls rotate in opposite directions, and material needs to be added to the molten pool. Under the shearing driving force provided by the rolls, the material moves out of the molten pool through the roll gap, becoming a billet with specific dimensions. The rotation of the crystallizing rolls and the viscosity of the material being cast in the molten pool together generate a shearing driving force field in the molten pool that promotes continuous billet formation, thus giving twin-roll casting the characteristics of "moving crystallizer technology." The material entering the molten pool includes liquid metal, which can enter the molten pool via a distribution device. The material may also include solid substances; for example, when using the twin-roll method to prepare multilayer materials using a solid-liquid composite method, solid substances need to be added to the molten pool.

[0004] The molten pool geometry and technical basis of the twin-roll thin-strip casting process are drastically different from those of conventional continuous casting. In the absence of experimental methods, the field generally believes that the growth pattern of the solidified billet shell within the molten pool is as follows: Figure 1 As shown, the two solidified shells begin at the meniscus and gradually increase in thickness until they are welded together to form the Kiss point.

[0005] The inventors disclosed a method for characterizing the transport behavior within the molten pool during twin-roll casting in Chinese patent application number 2021101226378. Following further experimental research, the inventors improved the tracer method in Chinese patent application number 2021112909655, specifically by using the Kiss angle method. The tracer method and the Kiss angle measurement method make it possible to study the actual transport process within the molten pool of twin-roll thin strip.

[0006] By implementing the aforementioned tracer method and Kiss angle measurement method in a laboratory using a twin-roll thin strip casting machine, the inventors discovered that the actual development process of the "solidified shell" in the molten pool is as follows: Figure 2 As shown.

[0007] like Figure 2 The "solidified shell" shown is different from the traditional solidified shell; for example... Figure 2 The "solidified shell" shown does not have a clear solid fraction characteristic as traditionally understood.

[0008] Through comparison, the inventors discovered that, as Figure 1 As shown and as Figure 2 The difference in the development patterns of the solidified shell shown is as follows: Figure 1 As shown, the two curves converge at the Kiss point; Figure 2 As shown, the two straight lines converge at the Kiss point. Figure 2 The experimental results shown indicate that, Figure 1 The understanding presented is fundamentally flawed, such as... Figure 2 The theoretical schematic diagram of the actual transmission process is shown below. Figure 3 As shown.

[0009] In the past, the field held that, under ideal conditions, the transport process within the molten pool of the twin-roll strip mill was stable; unsteady transport behavior within the molten pool was attributed to external factors, or in other words, process stability issues and / or billet quality problems were caused by external factors. These external factors included known process parameters such as molten pool depth, the geometry of the distribution device, the depth to which the distribution device was immersed in the molten pool, roll speed, roll diameter, roll cooling intensity, superheat, and roll gap opening. In short, the traditional view held that instability and / or billet quality problems in the twin-roll strip mill were caused by external factors; that process instability and / or billet quality problems were due to a lack of proper matching of existing process parameters; and that process instability and / or billet quality problems were simply due to the difficulty in matching process parameters—that is, the narrow process window of the twin-roll strip mill.

[0010] For a century and a half, the field has firmly believed in certain unproven ideas, including such as Figure 1The solidified shell development process is shown; in fact, the relevant field is unaware that their belief in the transport behavior occurring in the molten pool is one-sided; the relevant field firmly believes in the "basic fact" that changes in the roll gap can affect the solidification process in the molten pool; based on this firmly believed "basic fact", some technicians in the relevant field have proposed a technical solution to adjust the solidified shell development process by using the roll gap.

[0011] The implementation method of the "technical solution for adjusting the development process of solidified billet shell by utilizing the roll gap opening" is as follows: A driving device drives at least one of the two rollers to become a moving roller, causing relative motion between the two rollers, resulting in periodic and / or aperiodic changes in the distance between them; during this relative motion, the moving roller reciprocates near its equilibrium position. For example... Figure 4 The zero-angle roll gap floating method shown is detailed in Chinese patent document application number 2017800317704, which discloses a method for operating a twin-roll thin strip continuous casting machine to reduce vibration. The main technical solution is that relative movement occurs between the two rolls, causing the roll gap opening to change. The main technical effect is to reduce the vibration of the casting machine by sacrificing the uniformity of the billet thickness.

[0012] The casting and rolling force is also called the roll clamping force.

[0013] Based on the traditional understanding of the "technical solution for adjusting the development process of solidified billet shell by utilizing roll gap opening," some technicians in this field believe that unilateral roll vibration can refine grains, and that unilateral roll vibration causes relative movement between the two rolls; during this relative movement, the moving roll reciprocates around its equilibrium position. For example... Figure 5 The single-sided roller shown vibrates in a direction perpendicular to the reference plane. For details, see Chinese Patent Document No. 2007101853779, which discloses a vibrating twin-roll thin strip casting mill. The main technical solution is single-sided roller vibration. This technical solution will cause fluctuations in the roller clamping force and changes in the billet thickness. According to the published reports, this technology can reduce the probability of scratches on the billet surface. Of course, if the parameters of the roller gap floating (parameters include: frequency; amplitude) are not set properly, it will promote the generation of scratches. In fact, in the twin-roll casting process driven by a single shear force, when the shear force is insufficient to overcome the resistance encountered in the billet formation process, it will cause the roller surface to slip with the cast metal, thereby generating "scratches". Therefore, the root cause of scratches is that the driving force cannot overcome the resistance.

[0014] In this patent application, the inventors believe that the relative motion between the two rollers will cause changes in the roller gap, and the inventors refer to the changes in the roller gap caused by the relative motion between the two rollers as roller gap floating.

[0015] The relative motion between the two rollers causes the Nip point to move. Therefore, in this patent application, the roller gap floating can also be referred to as roller gap movement, roller gap shifting, Nip point floating, Nip point movement, or Nip point shifting, etc.

[0016] Due to considerations such as the side sealing plate and / or the quality of the billet edge and / or the uniformity of the billet thickness and / or the uniformity of initial solidification, during the relative movement between the two rolls, the field aims to control the component of the floating velocity of the Nip point in the direction of the roll axis to be as close to zero as possible; that is to say, when it comes to roll gap floating, those skilled in the art can directly and without doubt determine that during the relative movement of the two rolls, the roll axes of the two rolls are always parallel or nearly parallel.

[0017] In traditional technology, there is a method to generate molten pool oscillation by utilizing the overall motion of the twin-roll system. Chinese patent document with application number 2022108771736 discloses a method for molten pool oscillation in twin-roll casting and rolling. The "overall motion of the twin-roll system" can be simply referred to as "roll system motion". That is to say, "roll system motion" refers to the movement of the two rolls as a whole. "Roll system motion" does not cause the roll gap to float.

[0018] After the inventors studied the transport behavior within the molten pool using tracer and Kiss angle measurement methods, the inventors concluded that the growth pattern of the solidified shell within the molten pool is as follows: Figure 2 In the developmental state shown, the inventors proposed, in Chinese patent application number 2022101047141, the following... Figure 6 The tilted roll gap floating method shown is proposed in Chinese patent document application number 2022110378783. Figure 7 The method of floating roll gap at a fixed opening is shown.

[0019] In Chinese patent application number 2022101047141, the inventors disclosed a method for improving the stability of a crystallizing roll yielding motion in a twin-roll casting process, such as... Figure 6 As shown, the main technical solution is to control the relative movement between the two rollers, causing the roller gap to float. This technical solution will lead to fluctuations in the roller clamping force and changes in the thickness of the billet.

[0020] In Chinese patent application number 2022110378783, the inventors disclosed a method for the angled movement of the crystallizing roll in twin-roll casting and extrusion, such as... Figure 7As shown, the main technical solution is that one roller rotates around another roller. This technical solution is intended to enhance the uniformity of the blank thickness. However, this technical solution still causes fluctuations in the roller clamping force. Furthermore, when using a contact-type side sealing device, the presence of the side sealing plate limits the range of process parameters (e.g., the magnitude of the relative displacement caused by the relative movement between the roller and the side sealing plate).

[0021] like Figures 4 to 7 The traditional roll gap floating shown is based on the above "basic facts" and aims to control the solidification process.

[0022] In current industrial practices in the non-ferrous metals sector, enterprises urgently need to increase output, optimize quality, and enrich product variety. Among these, higher output is the most urgent and common pursuit. Many enterprises often use a dozen or even dozens of twin-roll casting machines to work simultaneously to meet their output needs. If the output of a single twin-roll casting machine could be increased tenfold, it would mean a dramatic reduction in key costs such as labor and equipment.

[0023] Current industrial practices in the steel industry show that steel grades with too wide or too narrow a two-phase region are undesirable. Furthermore, while a very few steel grades can be commercially produced, the production process is highly sensitive to process parameters, requires extremely high manufacturing precision for core equipment, and suffers from diverse process stability issues and / or billet quality problems, resulting in high production costs. Summary of the Invention

[0024] Through research, the inventors have discovered that, since the process is based on moving crystallizer technology, viscosity (or, stickiness) becomes the foundation for the implementation of the twin-roll thin-sheet process; viscosity is the ability of a substance to resist shear deformation in motion; according to the principle that "viscosity is the foundation for the implementation of the twin-roll thin-sheet process," factors affecting viscosity will all affect process stability and / or billet quality; over the past century and a half, the field has conducted sustained, extensive, and in-depth research on the solidification process and its control; the solidification process is an important factor affecting viscosity; however, the solidification process is not the only factor affecting viscosity.

[0025] It should be noted that for twin-roll thin strip milling, due to the special geometry of the molten pool, the space for the material to move forward in the shear force field gradually narrows. Therefore, the resistance experienced by the material in the molten pool along the normal direction (or, the reference direction; the explanation of "reference direction" is detailed below) is not zero. The geometry of the molten pool forces the semi-solid metal to undergo shear deformation before it leaves the molten pool. During the shear deformation process of the semi-solid metal, rheological behavior and / or thixotropic behavior may occur. Thixotropic behavior is not significantly related to the casting and rolling speed. Both rheological and thixotropic behaviors can lead to macroscopic segregation. Therefore, segregation caused by shear motion may occur at any casting and rolling speed.

[0026] The inventors have discovered that when semi-solid metals exhibit shear rheological and / or thixotropic behavior, their viscosity decreases significantly (by more than two orders of magnitude). This results in the shear force generated by the rotation of the crystallizing rollers being unable to be effectively transmitted in the molten pool, or even being interrupted. The twin-roll thin-strip process, as a typical "moving crystallizer technology," relies on the movement of the cooling substrate (or the rotation of the crystallizing rollers) to provide a single shear driving force for the formation of the billet. Since viscosity is the basis for the transmission of shear driving force, when viscosity undergoes a sudden and significant decrease, the shear driving force transmission process becomes unstable, making the "moving crystallizer technology" practically impossible. This (the practical impossibility of the "moving crystallizer technology") will adversely affect process stability and / or billet quality.

[0027] It should be noted that, based on the current level of equipment, the casting and rolling speed can be precisely controlled; and when viscosity is independent of shear motion, the shear force field can also be accurately predicted and controlled (for example, the preparation of glass sheets / strips using the twin-roll method, which was achieved a century ago); however, when viscosity is related to shear motion, the actual motion is quite complex due to the geometry of the molten pool and / or the coupling effect of multiphase fields, making it difficult to predict and control the changes in viscosity and / or viscosity.

[0028] Through research, the inventors discovered that, due to the shear rheological and / or thixotropic behavior of semi-solid metals, maintaining the stable transmission of shear driving force in semi-solid metals is not easy. Therefore, a wide two-phase region is not sufficient. For alloy compositions with a narrow two-phase region, the semi-solid material at the bottom of the molten pool is difficult to aggregate to form a sufficient two-phase region, and the shear force still cannot be effectively transmitted. The static pressure of the molten pool and the unsolidified core of the billet exiting the molten pool are prone to communication (or connection), resulting in defects such as ridges, snake eggs, and egg pancakes.

[0029] It is understandable that for semi-solid metals with a relatively wide two-phase region, the shear driving force provided by the roller rotation is mainly used to promote the movement of the core metal; however, for semi-solid metals with an extremely narrow two-phase region, the shear driving force provided by the roller rotation is mainly used to hinder the movement of the core metal.

[0030] Through research, the inventors discovered that shear motion is another important factor affecting viscosity, and the "moving crystallizer technology" relies on shear motion to achieve continuous green body formation. Both the solidification process and shear motion significantly affect viscosity, but the effect of shear motion on viscosity is unknown in the field. The effect of shear motion on viscosity leads to diverse and common technical challenges.

[0031] Through research, the inventors have discovered that, as a twin-roller thin-strip process based on "moving crystallizer technology," the effective transmission of driving force is of direct and undeniable importance to both process stability and billet quality. Currently, the driving force for billet formation is entirely provided by the shear force generated by the rotation of the crystallizing rolls. This results in an insurmountable defect in the twin-roller thin-strip process for preparing metal billets, caused by a sudden change in viscosity. To overcome this defect, a second driving force is urgently needed. Furthermore, under a given phase, the second driving force should be unaffected by viscosity. Based on this, pressure (or, to distinguish it from shear force, described as normal force; or, shear-independent driving force) is the ideal second driving force. The transmission mode of normal driving force (or shear-independent driving force) is fundamentally different from that of shear driving force (or shear-dependent driving force). Changes in viscosity caused by the motion do not affect the transmission of normal driving force.

[0032] Through research, the inventors have discovered that, based on the current equipment level, a normal driving force capable of driving the formation of a billet can be generated by controlling the relative motion between two crystallizing rollers; furthermore, the relative motion between the two crystallizing rollers can be controlled quickly and precisely, and the inventors believe that the resulting cost is low and should be acceptable for actual production.

[0033] It should be noted that the movement of the cooling matrix provides the shear driving force for the continuous formation of the billet; therefore, during twin-roll casting, the velocity direction of the billet moving out of the molten pool (or, the velocity direction of the material at the Nip point) can be at any angle to the direction of gravity. This allows for flexible arrangement of the crystallizing rolls according to actual needs. Although gravity has been shown to have some influence on billet quality, it cannot be used to modify the shear driving force. Gravity is generally several orders of magnitude smaller than shear force; it is a negligible force relative to shear force, and its adjustability is extremely low.

[0034] It should be noted that the magnitudes of the normal driving force (or, shear-independent driving force) and the shear driving force (or, shear-dependent driving force) should be on the same order of magnitude.

[0035] It should be noted that for over a century and a half, the field was unaware of the inherent limitations of "moving crystallizer technology" in preparing metals where shear motion strongly influences viscosity. Traditional fixed crystallizer technology is driven by gravity, and the driving force generated by gravity is independent of the solidification process and motion; that is, for traditional fixed crystallizer technology, the driving force provided by a single gravity field is absolutely stable, thus leading to widespread success and significant social impact. However, the limitation of twin-roller thin-strip process, as a typical "moving crystallizer technology," lies in the transmission process of the single shear driving force generated by cooling the matrix. For twin-roller thin-strip process based on "moving crystallizer technology," the transmission process of the shear driving force is affected by viscosity. Viscosity is closely related to both the solidification process and motion. The sub-rapid solidification process of twin-roller thin-strip process is difficult to control, and the special geometry of the twin-roller casting pool inevitably leads to strong shear motion within the pool.

[0036] Through research, the inventors have discovered that when preparing a billet with a wide two-phase region, the viscosity change caused by the shearing motion of the semi-solid metal in the molten pool is the key reason why the process is difficult to achieve. Therefore, for alloy compositions with a wide two-phase region, it is beneficial to apply a normal driving force (or an independent shear driving force) to the molten pool.

[0037] Through research, the inventors have discovered that, logically speaking, those skilled in the art can directly and unequivocally understand that reducing the molten pool pressure is beneficial for alloy compositions with a narrow two-phase region. Reducing the molten pool pressure can inhibit the rapid flow of the core melt, thereby promoting the accumulation of semi-solid material at the bottom of the molten pool. This prevents the static pressure in the molten pool from connecting with the unsolidified core of the billet exiting the molten pool, thus avoiding defects such as ridges, snake eggs, and egg pancakes.

[0038] It should be noted that when using twin-roll casting to produce steel strip, the side sealing plate thickness is generally around 40mm; during production, it must be guaranteed to be above 6mm, otherwise breakage may occur; in actual production, 8mm is generally used to avoid accidents caused by accidental breakage of the side sealing plate as much as possible.

[0039] The inventors have discovered that maintaining the relative stillness of the roller body and the side sealing plate during the roller gap floating process is of great significance for enhancing the service life of the side sealing plate and / or process stability and / or billet quality. For example... Figure 8 The image shows the side sealing plate before use; as shown. Figure 9 The image shows the side sealing plate after use; due to wear during the contact process between the side sealing plate and the roller end face, the following will appear... Figure 9 The slope shown can contact the working surface of the roller, and a gap can be formed between the slope and the working surface of the roller. During the preparation of the billet, if it is necessary to use... Figure 8As shown in the side sealing plate, the relative displacement between the roller and the side sealing device needs to be limited to a certain range to prevent the melt from entering the gap between the slope and the working surface of the roller, causing process instability, process interruption, or quality problems at the edge of the billet.

[0040] It is understandable that "keeping the roller body and the side sealing plate relatively stationary" can also be expressed as: keeping the positions of the roller body and the side sealing plate relative to the ground unchanged.

[0041] It is understandable that a person skilled in the art would know directly and without question that "keeping the roller's position relative to the ground unchanged" does not take into account the roller's rotation.

[0042] Through research, the inventors discovered that controlling the roll gap floating and the roll system movement to occur simultaneously and synchronously, and controlling the changes in the placement plane caused by the roll gap floating process and the changes in the placement plane caused by the roll system movement process to cancel each other out in real time, so that the two rolls remain stationary relative to the ground at all times; in this way, the parameter settings of the roll gap floating are only limited by the equipment, and theoretically optimal process stability and / or optimal billet quality can be obtained.

[0043] The inventors discovered through research that controlling the roller gap floating and the roller system movement to occur simultaneously and synchronously, and controlling the changes in the placement plane caused by the roller gap floating process and the changes in the placement plane caused by the roller system movement process to cancel each other out in real time, so that the two rollers remain stationary relative to the ground at all times; in this way, the working surface of the rollers is in contact with... Figure 9 The slopes shown will not produce gaps or gaps will only be caused by errors, which can avoid process instability, process interruption or quality problems at the edge of the billet.

[0044] Through research, the inventors discovered that roll gap floating, generated by the alternating movement of two rolls, is of great significance to the uniformity of the billet's structure. This significance is mainly reflected in two aspects: first, the uniformity of the macro- and micro-structures of the billet; and second, the stability of the billet's morphology. If, during the preparation process, only one roll moves relative to the ground while the other roll remains stationary, then when roll gap floating causes a change in the placement plane, this roll gap floating usually leads to instability issues in the billet's morphology, such as the billet bending.

[0045] It is understandable that "roll gap floating is generated by the alternating motion of the two rollers", where "alternating motion of the two rollers" can also be expressed as: "ignoring the influence of the roller system motion, the two rollers alternately move relative to the ground"; or, "ignoring the influence of the roller system motion: the first roller is stationary relative to the ground, the second roller moves relative to the ground; then, the first roller moves relative to the ground, the second roller is stationary relative to the ground"; or, "ignoring the influence of the roller system motion: the first roller moves relative to the ground, the second roller is stationary relative to the ground; then, the first roller is stationary relative to the ground, the second roller moves relative to the ground".

[0046] It should be noted that even without explaining that "the roll gap is generated by the alternating motion of the two rolls", a person skilled in the art can directly and without doubt understand the specific way in which "the two rolls move alternately".

[0047] To address the current technical challenges and further improve process stability and / or billet quality control, this patent application provides a method for floating roll gaps in twin-roll thin strip casting. The roll system is movably mounted on a twin-roll thin strip casting machine. The roll system includes a first roll and a second roll arranged opposite each other for billet preparation. The roller shaft of the first roll is referred to as the first roller shaft, and the roller shaft of the second roll is referred to as the second roller shaft. The plane containing the first roller shaft and the second roller shaft is referred to as the placement plane of the roll system.

[0048] The method includes the following steps:

[0049] First floating: The second roller body is stationary relative to the ground, and the first roller body is controlled to rotate once without stopping around the second roller axis. At the same time, the roller system is controlled to rotate around the second roller axis, and the placement plane is always stationary relative to the ground.

[0050] Second floating: The first roller is stationary relative to the ground, and the second roller is controlled to rotate around the first roller shaft once without stopping. At the same time, the roller system is controlled to rotate around the first roller shaft, and the placement plane is always stationary relative to the ground.

[0051] In a single preparation process, the first float occurs at least once, and the second float occurs at least once.

[0052] Understandably, in actual manufacturing processes, due to the "load generated during the preparation process" and / or the "deliberately designed roll shape," the roller shafts of both rollers are approximately straight lines. In fact, in the field of study on molten pool transport behavior and / or roll gap floating, the roller shafts are generally considered to be absolutely straight lines, meaning that both rollers are considered ideal rigid bodies of rotation. For example, in a constant-diameter twin-roll thin strip casting machine, the rollers are cylinders; a cylinder consists of two bottom surfaces and one side surface; the two bottom surfaces of a cylinder are two identical circular surfaces; the side surface of a cylinder is a curved surface; the two end faces of the roller are the two bottom surfaces of the cylinder, and the roller surface is the side surface of the cylinder.

[0053] It should be noted that what a person skilled in the art can directly and without doubt determine is that during the process of relative movement between the two rollers causing the roller gap to float, the two roller shafts are always parallel.

[0054] It should be noted that those skilled in the art can directly and without doubt understand "first roller", "second roller", and "two rollers".

[0055] It should be noted that what a person skilled in the art can directly and unequivocally determine is that "the two rollers are always parallel" includes "the two rollers are always nearly parallel"; where "the two rollers are always nearly parallel" means that, under the current technological conditions, there may be a definite but unavoidable deviation between the "parallelism" achievable and "absolute, idealized parallelism".

[0056] It is understood that in the present invention patent application documents, "parallel" includes "nearly parallel"; that is, "parallel" should be understood as "parallel or nearly parallel", or "basically parallel", or "approximately parallel".

[0057] Understandably, since the two rollers are parallel, the placement plane can be determined using the plane containing the two rollers. However, since perfect parallelism is impossible, in actual manufacturing, the placement plane can also be determined using points on the two rollers that are less affected by changes in the manufacturing process. For example, the placement plane can be determined using the four intersection points of the two rollers with the end faces of the two roller bodies, or any three intersection points. Another example is taking two points on the first roller where the end faces of the roller bodies intersect, and taking the point on the second roller closest to the center of gravity of the second roller body, to determine the placement plane. Yet another example is taking any two points on the first roller and any one point on the second roller to determine the placement plane.

[0058] Understandably, a plane perpendicular to one roller axis can be selected; then, the line connecting the intersection of this plane and the two roller axes can be used to represent the placement plane.

[0059] It should be noted that those skilled in the art can directly and without doubt know the terms "first float" and "second float": "first" and "second" are not used to specify the order of generation.

[0060] It should be noted that those skilled in the art can directly and without doubt understand that for the phrase "first floating: the second roller is stationary relative to the ground, the first roller is controlled to rotate once without stopping around the second roller axis, and at the same time, the roller system is controlled to rotate around the second roller axis, and the placement plane remains stationary relative to the ground," it can be inferred that if the reference frame does not change, then: if the first roller rotates clockwise around the second roller axis, then the roller system rotates counterclockwise around the second roller axis; if the first roller rotates counterclockwise around the second roller axis, then the roller system rotates clockwise around the second roller axis.

[0061] It should be noted that those skilled in the art can directly and without doubt understand that for "first floating: the second roller is stationary relative to the ground, the first roller is controlled to rotate once around the second roller axis without stopping, and at the same time, the roller system is controlled to rotate around the second roller axis, and the placement plane is always stationary relative to the ground", the magnitudes of "angular velocity of the first roller rotating around the second roller axis" and "angular velocity of the roller system rotating around the second roller axis" are the same, but their directions are opposite.

[0062] It should be noted that those skilled in the art can directly and unequivocally understand that for the phrase "second floating: the first roller is stationary relative to the ground, the second roller is controlled to rotate once without stopping around the first roller axis, and simultaneously, the roller system is controlled to rotate around the first roller axis, while the placement plane remains stationary relative to the ground," it can be inferred that if the reference frame does not change, then: if the second roller rotates clockwise around the first roller axis, the roller system rotates counterclockwise around the first roller axis; if the second roller rotates counterclockwise around the first roller axis, the roller system rotates clockwise around the first roller axis.

[0063] It should be noted that those skilled in the art can directly and without doubt understand that for "the second floating: the first roller is stationary relative to the ground, the second roller is controlled to rotate once around the first roller axis without stopping, and at the same time, the roller system is controlled to rotate around the first roller axis, and the placement plane is always stationary relative to the ground", the magnitudes of "the angular velocity of the second roller rotating around the first roller axis" and "the angular velocity of the roller system rotating around the first roller axis" are the same, but their directions are opposite.

[0064] It should be noted that those skilled in the art can directly and without doubt know that "the first roller is stationary relative to the ground" does not include the rotation of the first roller itself; similarly, "the second roller is stationary relative to the ground" does not include the rotation of the second roller itself.

[0065] It is understandable that, since "the second roller is stationary relative to the ground, the first roller is controlled to rotate once around the second roller shaft without stopping, and at the same time, the roller system is controlled to rotate around the second roller shaft", the opening of the roller gap does not change during the "first floating" process.

[0066] It is understandable that, since "the first roller is stationary relative to the ground, the second roller is controlled to rotate once around the first roller shaft without stopping, and at the same time, the roller system is controlled to rotate around the first roller shaft", the opening of the roller gap does not change during the "second floating" process.

[0067] It is understandable that "the second roller is stationary relative to the ground, the first roller is controlled to rotate once without stopping around the second roller axis, and at the same time, the roller system is controlled to rotate around the second roller axis," where "rotation" means that during the relative motion between the two rollers, the first roller performs a circular motion around the second roller axis (or, the second roller itself), and the roller gap opening remains constant. Similarly, this also applies to "the first roller is stationary relative to the ground, the second roller is controlled to rotate once without stopping around the first roller axis, and at the same time, the roller system is controlled to rotate around the first roller axis."

[0068] It is understandable that "controlling the first roller to rotate around the second roller shaft once without stopping" is achieved by "a single, uninterrupted relative motion between the first roller and the second roller"; similarly, "controlling the second roller to rotate around the first roller shaft once without stopping" is achieved by "a single, uninterrupted relative motion between the first roller and the second roller".

[0069] It should be noted that "a non-stop relative motion between the first roller and the second roller is completed" means: from the moment a relative motion occurs between the two rollers until the end of this relative motion; and at the beginning and end of this relative motion, the speed of one roller relative to the other roller is zero.

[0070] Understandably, once a relative motion begins between the two rollers, it ends as long as the relative speed between the two rollers is zero.

[0071] It is understood that in the present invention patent application, during the relative motion between the two rollers, the first roller rotates around the second roller shaft (or, the second roller rotates around the first roller shaft; or, the first roller rotates around the second roller; or, the second roller rotates around the first roller), where "rotation" refers to circular motion.

[0072] It should be noted that those skilled in the art can directly and unequivocally determine that "the placement plane is always stationary relative to the ground" includes "the placement plane is always nearly stationary relative to the ground"; where "the placement plane is always nearly stationary relative to the ground" means that there may be a definite but unavoidable deviation between the "stationary" achievable under current technological conditions and "absolute, idealized stationary".

[0073] It is understood that in the present invention patent application document, "the placement plane is always stationary relative to the ground", where "stationary" includes "nearly stationary"; that is, "stationary" should be understood as "stationary or nearly stationary", or "substantially stationary", or "approximately stationary".

[0074] Furthermore, in a method for floating the roll gap of a twin-roll thin strip, the minimum distance between the first roll and the second roll is called the roll gap; the midpoint of the roll gap is called the Nip point; the moving speed of the blank at the Nip point is called the preparation speed; the moving speed of the Nip point caused by the relative motion between the first roll and the second roll is called the floating speed of the Nip point; during each occurrence of the first floating, the inner product of the floating speed and the preparation speed is called the first inner product; during each occurrence of the second floating, the inner product of the floating speed and the preparation speed is called the second inner product; during each occurrence of the first floating, the first inner product is always less than zero; and during each occurrence of the second floating, the second inner product is always less than zero.

[0075] It should be noted that the moving speed of the billet (or strip; or material; or the material to be cast and rolled) at the Nip point is called the preparation speed; the preparation speed is used to measure how fast the billet preparation process is; the direction of the preparation speed is called the preparation direction; the preparation direction is always perpendicular to the placement plane.

[0076] It should be noted that the normal to the plane on which the object is placed is called the placement normal; there are infinitely many placement normals.

[0077] It is understandable that the preparation speed reflects how fast the billet preparation process is; the magnitude of the preparation speed is only related to the opposing rotation of the two rollers, and is not related to the movement of the roller system or the relative movement between the two rollers; the preparation direction is always along the placement normal and points in the direction in which the billet moves out of the molten pool.

[0078] It should be noted that the component of the "floating velocity" in the preparation direction is also known as the "effective velocity".

[0079] It is understandable that "floating velocity" can be decomposed into "partial velocity in the preparation direction" and "partial velocity in the placement plane".

[0080] It is understandable that both "floating speed" and "preparation speed" are vectors (or vectors).

[0081] It should be noted that, under natural conditions: the plane in which the first and second rollers are placed is also called the reference plane; the preparation speed is also called the reference speed; and the preparation direction is also called the reference direction.

[0082] It is understandable that "natural state" refers to a state in which the relative positions of the two rollers to the ground remain unchanged throughout the preparation process; that is, the "roller gap floating process" mentioned in the patent application documents never occurs during the preparation process, nor does the "roller system movement process" mentioned in the patent application documents occur. In fact, it is precisely because the preparation process in the natural state has diverse process stability issues and / or billet quality issues that this field has proposed such a method. Figures 4 to 7 The traditional roll gap floating method is shown.

[0083] It should be noted that, under natural conditions, the normal to the reference plane that passes through point Nip is called the reference line.

[0084] Understandably, during the preparation process under natural conditions, there is no relative movement between the two rollers, nor is there any movement of the roller system; therefore, the floating speed is zero, and the placement plane does not change.

[0085] Understandably, the reference plane is a unique plane determined by the form of the twin-roll casting machine; for a horizontal constant-diameter twin-roll casting machine, the reference plane is parallel to or coincides with the horizontal plane; for an inclined twin-roll casting machine, the reference plane is a plane at a certain fixed angle to the horizontal plane.

[0086] It is understandable that for horizontal equal-diameter twin-roll casting machines, no matter how complex the roll gap floating process and / or roll system movement process occur during the manufacturing process, the position of the reference plane and reference line relative to the ground remains unchanged; the same applies to other types of twin-roll casting machines.

[0087] Understandably, unlike the placement plane, the reference plane is a fixed plane. That is to say, the movement of the roll gap or the movement of the roll system will not affect the position of the reference plane. This is because the range of the roll gap movement or the movement of the roll system is constrained by the form of the twin-roll thin strip casting machine.

[0088] It is understandable that in three-dimensional space, the roll gap is actually a surface, with countless Nip points forming a Nip line and countless Kiss points forming a Kiss line. However, in reality, the terms "Nip line" and "Kiss line" are rarely mentioned in this field. For many years, the terms "Nip point" and "Kiss point" have been widely used in this field. Furthermore, when using "Nip point" and "Kiss point" to describe the molten pool transport behavior and / or roll gap floating involved in this patent application, it is not necessary to specifically state that it is on a plane perpendicular to the roll axis. In other words, using "Nip point" and "Kiss point" is actually the common practice in this field. In this patent application, to describe the proposed technical solution, according to the common practice in this field, a plane perpendicular to the roll axis is selected, and then the technical features of the proposed technical solution are expressed on this plane. This is the clearest way and the way that a person skilled in the art can directly and without doubt understand.

[0089] It should be noted that those skilled in the art can directly and without doubt understand that "the midpoint of the roll gap is called the Nip point".

[0090] It is understandable that when studying the roll gap floating process, the two rolls are considered as ideal rigid rotating bodies with their roller shafts parallel. The floating velocity of the Nip point on any plane perpendicular to the roller shafts follows the same pattern. 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:

[0091] Choose any plane Ω perpendicular to the roller axis i ;

[0092] Nip line and plane Ω i The intersection point is called the Nip point N. i ;

[0093] Study Nip point N i The laws governing motion.

[0094] It is understandable that, from the normal plane of the reference plane, the normal plane passing through the Nip line in its natural state is chosen 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 .

[0095] It is understandable that, disregarding the influence of the roller system's motion, during the relative motion between the two rollers, the Nip line and Nip point N... i And the plane on which it is placed can move relative to the ground.

[0096] It is understandable that "not considering the effects of roller system movement" can also be expressed as "no roller system movement occurs, or the effects of roller system movement are eliminated".

[0097] It is understandable that "eliminating the influence caused by the movement of the roller system" can also be expressed as: removing; or, eliminating; or, excluding.

[0098] It is understandable that during the relative motion between the two rollers, the reference plane and the plane Ω... i Reference plane Π i Reference line π i Its position relative to the ground is fixed.

[0099] It is understandable that there are countless normals to a reference plane; however, 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; that is, the reference line has two characteristics: the reference line is the normal of the reference plane, and the reference line passes through the Nip point in its natural state.

[0100] Understandably, the reference line is the normal to the reference plane passing through the Nip point in its natural state.

[0101] It is understandable that in three-dimensional space, there are countless "Nip points" and countless reference lines, and countless reference lines form a "reference plane".

[0102] It is understandable that whether the reference line passes through the Nip point in its natural state does not affect the description of the scope of protection in the present invention patent application.

[0103] It should be noted that, as Figure 10 As shown, a horizontal equal-diameter twin-roll casting machine is used for illustration. An arbitrary plane perpendicular to the roll shaft is selected, and then a schematic diagram is shown on this plane showing 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 of the roll surface passing through the roll gap, the preparation speed, the preparation direction, and the reference direction under different states.

[0104] Understandably, "in different states" can also be expressed as "in a natural state, or in a non-natural state".

[0105] It should be noted that, as Figure 10 As shown, the "foot of the perpendicular" is a symbol used to indicate a perpendicular relationship; the "foot of the perpendicular" is also called the "perpendicular symbol" or "perpendicular foot symbol".

[0106] It should be noted that, as Figure 10The "speed of the roller surface passing through the roller gap" shown is always the same as the "direction of the speed of the roller surface passing through the roller gap" and the "direction of the preparation speed" because the roller body is regarded as an ideal rigid rotating body; that is, the "direction of the speed of the roller surface passing through the roller gap" and the "preparation direction" are always the same.

[0107] It should be noted that, as Figure 10 As shown, in the natural state, the plane where the two rollers are located is called the reference plane, and the direction of the movement speed of the billet at point Nip is called the "reference direction". The "reference direction" is always perpendicular to the reference plane. In the natural state, the placement plane coincides with the reference plane, and the preparation direction is the same as the reference direction. That is to say, the reference plane is a special case of the placement plane, the reference direction is a special case of the preparation direction, and the reference line is a special case of the placement normal.

[0108] It should be noted that, “during the first floating process, the inner product of the floating speed and the preparation speed is called the first inner product; during the second floating process, the inner product of the floating speed and the preparation speed is called the second inner product; the first inner product and / or the second inner product are always greater than zero”, wherein those skilled in the art can directly and without doubt know the meaning of “inner product”.

[0109] 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.

[0110] It should be noted that the "inner product" is also called the "scalar product" or the "dot product".

[0111] It should be noted that the "roll system" is also called the "double roll system"; the relative movement between the two rolls is the internal movement of the roll system, and the internal movement of the roll system will cause the roll gap to float.

[0112] It should be noted that the roller system can move as a whole on a twin-roll thin strip casting machine.

[0113] It should be noted that the movement of the roller system does not cause a change in the relative position between the two rollers; that is, the movement of the roller system neither causes nor affects the roll gap.

[0114] Understandably, during the first float, the change to the placement plane caused by "controlling the first roller to rotate once without stopping around the second roller axis" and the change to the placement plane caused by "controlling the roller system to rotate around the second roller axis" are real-time and completely cancel each other out; therefore, superficially, the position of the placement plane relative to the ground does not change. The second float is similar.

[0115] It is understandable that "the apparent position of the placement plane relative to the ground does not change" can also be expressed as: "Ignoring the rotation of the rollers, the apparent positions of the first and second rollers relative to the ground do not change."

[0116] It should be noted that although "the apparent positions of the first and second rollers relative to the ground do not change," a viscosity-independent (or shear-independent) driving force can still be applied to the semi-solid material in the molten pool when the "inner product of the floating speed and the preparation speed" is less than zero. Those skilled in the art can directly and unambiguously understand that it is possible to "appear unchanged in relation to the ground, but still apply a viscosity-independent driving force to the semi-solid material in the molten pool when the apparent positions of the first and second rollers relative to the ground do not change, but the "inner product of the floating speed and the preparation speed" is less than zero."

[0117] It should be noted that although "the apparent positions of the first and second rollers relative to the ground do not change", the pressure in the molten pool can still be reduced when "the inner product of the floating speed and the preparation speed" is greater than zero.

[0118] It is understandable that "change in the placement plane" means: when there is no movement of the roller system (or, eliminating the influence of roller system movement), and no relative movement between the two rollers has occurred (or, in the natural state), assuming the two roller shafts are located on the placement plane Θ. 1s After only the relative motion between the two rollers has occurred, assume that the two roller shafts are located on the placement plane Θ. 2s ; plane Θ 1s and plane Θ 2s Non-coincident, plane Θ 1s and plane Θ 2s Intersecting or parallel.

[0119] It is understandable that at the beginning of the first float (or the second float), the effective velocity is zero; at the end of the first float (or the second float), the effective velocity is zero; there is no moment when the effective velocity is zero between the beginning and the end of a first float (or the second float); that is to say, during the occurrence of a first float (or the second float), the effective velocity is never equal to zero.

[0120] It is understandable that the roller system moves on a twin-roll casting machine; however, if there is no relative movement between the two rollers, then the floating speed is zero and the effective speed is zero.

[0121] As can be understood, as mentioned above, "effective speed" is the component of "floating speed" in the preparation direction; "effective speed" and / or "change in effective speed" can be used to measure the degree to which the roll gap floating process affects the molten pool transport behavior.

[0122] It is understandable that at some point during the first (or second) float, the velocity of point Nip relative to the ground (expressed as vector V) T The representation includes two aspects: firstly, the velocity component of the Nip point relative to the ground caused by the movement of the roller system, expressed as a vector V. W On the other hand, the velocity component of the Nip point relative to the ground caused by the relative motion between the two rollers is represented by the vector V. F Therefore, the floating speed = V F =V T -V W ; Due to V T =0; therefore, V F =-V W .

[0123] It is understood that in this invention patent application document, "floating velocity" (or, vector V) F The change in the state of the Nip point is completely unrelated to the movement of the roller system. This is because: the simple movement of the roller system will cause a change in the position of the Nip point relative to the ground, and the simple floating of the roll gap will also cause a change in the position of the Nip point relative to the ground; however, the simple movement of the roller system and the simple floating of the roll gap have completely different effects on the molten pool transport behavior; if only the movement of the roller system occurs, without the floating of the roll gap, then 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 without the floating of the roll gap is meaningless for the purposes of this patent application.

[0124] Understandably, based on the above explanation of "floating speed", it can be clearly stated that "floating speed" must be generated solely by the relative motion between the two rollers.

[0125] It should be noted that even without the above detailed explanation of "floating speed", those skilled in the art can directly and without doubt know that "floating speed" must be generated solely by the relative motion between the two rollers.

[0126] It should be noted that what a person skilled in the art can directly and unequivocally determine are "floating speed equal to zero" and "effective speed equal to zero." "Equal to zero" includes "approaching zero." "Approaching zero" means that, under current technological conditions, there may be a definite but unavoidable deviation between "speed" and "zero." For example, during the manufacturing process, the deformation and vibration of the two rollers under load cannot be completely eliminated; or, during the roller movement, because the transport behavior in the molten pool is not under ideal conditions, this will also lead to an unavoidable deviation between the actual and intended movement of the rollers.

[0127] It is understood that, unless otherwise specified, in this patent application, "equal to zero" includes "approaching zero"; that is, "equal to zero" should be understood as "equal to zero or approaching zero", or "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".

[0128] It should be noted that what a person skilled in the art can directly and unequivocally determine is that during the movement of the roller system, the two rollers move as a "whole" on the twin-roll thin strip casting machine. Components on 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, and drive mechanisms, can be configured to follow the movement of the roller system or not, as needed. It is only necessary to ensure that the relative movement between the two rollers and the movement of the roller system can operate without interference; that is, it is only necessary to ensure that the movement of the roller system and the movement within the roller system can operate without interference.

[0129] It is understandable that at the beginning and end of the first float: the effective velocity is zero; the float velocity is zero.

[0130] It is understandable that "the floating speed is equal to zero" means that "there is no relative movement between the two rollers".

[0131] Understandably, similar to the "first float," at the start and end of the second float: the effective velocity is zero; the float velocity is zero.

[0132] It is understandable that "the first inner product is less than zero" means that during the first floating process, the inner product of the floating speed and the preparation speed is less than zero, so as to allow the active increase of the molten pool pressure, apply a normal driving force unrelated to viscosity to the semi-solid material in the molten pool, maintain the stability of the total driving force, and promote the renewal of the Kiss angle.

[0133] It should be noted that during the preparation of billets using the twin-roll method, especially in the preparation of aluminum and its alloys, and magnesium alloys, hydrogen evolution can lead to the appearance of micron-sized shrinkage cavities in the final product. The inventors have discovered that "the inner product of the floating speed and the preparation speed is less than zero" can apply pressure to the molten pool, which reduces the probability of shrinkage cavities and thus improves the quality of the billet.

[0134] Furthermore, in a method for roll gap floating of twin-roll thin strip, the first inner product is always greater than zero during each occurrence of the first floating.

[0135] It is understandable that "the first inner product is greater than zero" means that during the first floating process, the inner product of the floating speed and the preparation speed is greater than zero, so as to allow the active reduction of the molten pool pressure and suppress the Kiss angle update.

[0136] It is understandable that "the first inner product is greater than zero" means that during each occurrence of the first float (or between the start and end of each occurrence of the first float), the inner product of the float speed and the preparation speed is greater than zero; "during each occurrence of the first float, the inner product of the float speed and the preparation speed is greater than zero" means that during each occurrence of the first float, if the preparation speed is vector U and the float speed is vector V, then the inner product of vector U and vector V is always greater than zero.

[0137] It is understandable that "always greater than zero" can also be expressed as "always positive".

[0138] It is understandable that "the first inner product is greater than zero" means that during each first float, let the preparation speed be vector U and the float speed be vector V; then, the inner product of vector U and vector V is always greater than zero.

[0139] It is understandable that "between the start time and the end time" does not include the "start time" or the "end time"; that is, "between the start time and the end time" does not include the endpoint.

[0140] It should be noted that "actively increasing the pressure of the molten pool" can improve the heat transfer performance of the roller, thereby helping to increase production and improve the structure of the billet.

[0141] Furthermore, in a method for roll gap floating of twin-roll thin strip, the first inner product is always less than zero during each occurrence of the first floating.

[0142] It is understandable that "the first inner product is always less than zero", so during each occurrence of the first float (or between the start and end of each occurrence of the first float), the inner product of the float velocity and the preparation velocity is less than zero.

[0143] It is understandable that "the first inner product is always less than zero during each occurrence of the first float" means that during each occurrence of the first float, let the preparation speed be vector U and the float speed be vector V; then, the inner product of vector U and vector V is always less than zero.

[0144] Understandably, "always less than zero" can also be expressed as "always negative".

[0145] It should be noted that prior to this invention, due to the lack of methods for studying actual transport behavior, the transport behavior of high-temperature materials in the molten pool under the single shear driving force provided by the cooling matrix during the billet formation process had not been experimentally studied. It must be acknowledged that while the rotation of the crystallizing roll provides the shear driving force for continuous billet formation, it also makes real-time monitoring of transport behavior in the molten pool difficult. For twin-roll thin-strip processes, it is impossible to monitor the actual transport process in the molten pool in real time by "setting thermocouples in the crystallizing roll." The consensus in the field is that finding methods to study actual transport behavior is crucial for understanding the root causes of process stability and billet quality problems, and this is also a significant driving force behind the increasing complexity of mathematical models. In previous research, this inventor proposed a method for studying actual transport behavior in the molten pool. By implementing this method, this inventor discovered shear rheological behavior of semi-solid materials in the molten pool that was previously unknown in the field, and this shear rheological behavior leads to macroscopic segregation. By analyzing the discovered "semi-solid material shear rheological behavior," the inventors realized that both the solidification process and shear motion (which leads to shear rheology or thixotropic behavior) alter viscosity, thereby affecting the transmission process of shear driving force. The impact of "changes in viscosity caused by shear motion" on the transmission process of shear driving force is the root cause of many technical difficulties overlooked in this field. Based on a detailed study of the "influence of shear motion on viscosity," the inventors proposed applying a second normal driving force by utilizing the relative motion between two crystallizing rollers to make the "inner product of the floating velocity and the preparation velocity" less than zero. The aim is to reduce or eliminate the influence of shear motion on viscosity, allowing the total driving force to remain stable, thereby enhancing process stability and / or improving the quality of the preform.

[0146] It should be noted that, according to the inventors' previous research in "Numerical Simulation of the Fluid Flow, Heat Transfer, and Solidification during the Twin-Roll Continuous Casting of Steel and Aluminum" (Metallurgical and Materials Transactions B, 2016, pp. 740-748), using a 400 mm diameter crystallization roll, the momentum and heat transfer processes in the molten pool can support a casting speed of 30 m / min; of course, this does not consider the interaction between shear motion and viscosity; that is, if the influence of shear motion on viscosity can be avoided by applying a normal driving force ("the inner product of the floating velocity and the preparation velocity" is less than zero), it is feasible to increase the casting speed to 30 m / min from the perspective of momentum and heat transfer.

[0147] Furthermore, in a method for roll gap floating of twin-roll thin strip, the first inner product is always greater than zero during each occurrence of the first floating; and the second inner product is always greater than zero during each occurrence of the second floating.

[0148] It should be noted that the inventors have discovered through research that for some alloy compositions, the two-phase region of the molten pool is difficult to accumulate. Therefore, under the action of "molten pool pressure", the "material in the molten pool" transfers to the "unsolidified area of ​​the core of the billet exiting the molten pool", leading to problems such as egg pancakes, snake eggs, and spines. By reducing the molten pool pressure, this undesirable material transfer phenomenon can be effectively avoided, thereby preventing problems such as egg pancakes, snake eggs, and spines.

[0149] Furthermore, a method for roll gap floating for twin-roll thin strip, wherein the frequency of the first floating and / or the second floating is in the range of 0.1 to 5 Hz.

[0150] Furthermore, a method for roll gap floating for twin-roll thin strip, wherein the frequency of the first floating and / or the second floating occurs in the range of 0.01 to 10 Hz.

[0151] Furthermore, in a method for roll gap floating of twin-roll thin strip, any of the following occurs during a single preparation process:

[0152] One first float and one second float occur, wherein one first float and one second float are any combination;

[0153] One first float and multiple second floats occur, wherein one first float and multiple second floats are any combination;

[0154] Multiple occurrences of the first float and multiple occurrences of the second float occur, wherein the multiple occurrences of the first float and multiple occurrences of the second float are any combination.

[0155] It is understandable that "one first float and one second float occur, wherein one first float and one second float are any combination" means that, since "one first float and one second float occur," there are actually two possible scenarios: one first float occurs first, followed by one second float; or one second float occurs first, followed by one first float.

[0156] Furthermore, in a method for roll gap floating of twin-roll thin strip, any of the following occurs during a single preparation process:

[0157] The number of times the first float occurred is equal to the number of times the second float occurred;

[0158] The first float occurred more often than the second float occurred more often.

[0159] The first float occurs less often than the second float occurs.

[0160] Furthermore, a method for roll gap floating for twin-roll thin strips, wherein during all or part of the preparation process, the first floating occurs once or more, followed by the second floating once or more; or, during all or part of the preparation process, the second floating occurs once or more, followed by the first floating once or more.

[0161] Furthermore, in a method for roll gap floating of twin-roll thin strip, the first floating and the second floating occur sequentially and repeatedly during part or all of the time in a single preparation process; or, during all or part of the time in a single preparation process, the second floating and the first floating occur sequentially and repeatedly.

[0162] It is understandable that "the first float and the second float occur sequentially and repeatedly" and "the second float and the first float occur sequentially and repeatedly" are two equivalent ways of describing things; because "first" and "second" are not used to indicate order; in this patent application document, the simultaneous use of "the first float and the second float occur sequentially and repeatedly" and "the second float and the first float occur sequentially and repeatedly" is to emphasize that "'first' and 'second' are not used to indicate order".

[0163] Furthermore, in a method for roller gap floating of twin-roll thin strip, during each occurrence of the first floating, the angle of rotation of the placement plane caused solely by the movement of the roller system is called a first angle; during each occurrence of the second floating, the angle of rotation of the placement plane caused solely by the movement of the roller system is called a second angle; the magnitudes of the first angle and the second angle are equal.

[0164] It is understandable that "the angle of rotation of the placement plane caused solely by the movement of the roller system during each occurrence of the first float" is equal in magnitude but opposite in direction to "the angle of rotation of the placement plane caused solely by the relative movement between the two rollers during each occurrence of the first float".

[0165] It is understandable that "the angle of rotation of the placement plane caused solely by the movement of the roller system during each occurrence of the second float" is equal in magnitude but opposite in direction to "the angle of rotation of the placement plane caused solely by the relative movement between the two rollers during each occurrence of the second float".

[0166] Furthermore, a method for floating the roll gap for twin-roll thin strip, wherein the first angle and / or the second angle are in the range of 0.01 to 0.1 degrees.

[0167] It should be noted that "the first angle and / or the second angle are in the range of 0.01 to 0.1 degrees" includes the end values ​​of 0.01 and 0.1 degrees; that is, in the patent application documents of this invention, unless otherwise specified, "in the range of... to..." includes the end values.

[0168] Furthermore, a method for floating the roll gap for twin-roll thin strip, wherein the first angle and / or the second angle are in the range of 0.1 to 1 degree.

[0169] Furthermore, a method for roll gap floating for twin-roll thin strip, wherein the first angle and / or the second angle are in the range of 1 to 10 degrees.

[0170] Furthermore, in a method for roll gap floating of twin-roll thin strip, the placement plane does not change during the first floating and / or the second floating, and the placement plane coincides with the reference plane.

[0171] It is understandable that, such as Figure 10 As shown, taking a horizontal equal-diameter twin-roll casting machine as an example, the reference plane is plane Ψ0. During a certain period of the preparation process or throughout the entire preparation process, a first float and / or a second float occur; during the occurrence of the first float and / or the second float, the placement plane always coincides with plane Ψ0.

[0172] It is understandable that "the placement plane coincides with the reference plane" is the most important application method.

[0173] Furthermore, in a method for roller gap floating of twin-roll thin strip, the placement plane does not change during the first floating or the second floating process; and the placement plane does not coincide with the reference plane.

[0174] It is understandable that, such as Figure 10 As shown, taking a horizontal equal-diameter twin-roll casting machine as an example, the reference plane is plane Ψ0. During a certain period of the preparation process, due to the movement of the roll system and / or the floating of the roll gap, the placement plane is plane Ψ1. Plane Ψ0 and plane Ψ1 are two non-overlapping planes. Then, the first floating and / or the second floating occur. During the occurrence of the first floating and / or the second floating, the placement plane is always plane Ψ1.

[0175] Understandably, for example Figure 4 The zero-angle roll gap bidirectional floating is shown: when the two rolls are close to each other, the roll gap floating causes the molten pool pressure to increase; when the two rolls are far apart, the roll gap floating causes the molten pool pressure to decrease.

[0176] It should be noted that in the present invention patent application, when the inner product of the floating speed and the preparation speed is less than zero, the roll gap floating causes the molten pool pressure to increase; when the inner product of the floating speed and the preparation speed is greater than zero, the roll gap floating causes the molten pool pressure to decrease.

[0177] It should be noted that in the present invention patent application, "the inner product of the floating speed and the preparation speed is less than zero" can be used to replace, for example, Figure 4 The zero-angle roll gap bidirectional floating configuration shown in the diagram, where "the two rollers move closer to each other" and "the inner product of the floating speed and the preparation speed is greater than zero," can be used to replace, for example, the following: Figure 4 The zero-angle roll gap bidirectional floating shown refers to the "two rollers moving away from each other"; the technical solution proposed in the present invention patent application is, for example... Figure 4The traditional method shown is more efficient; however, the mathematical control model of the technical solution proposed in this patent application is far inferior to that of... Figure 4 The traditional method shown.

[0178] It is understandable that, in summary, the use of phrases such as "during each occurrence of the first float, the first inner product is always less than zero; or, during each occurrence of the first float, the first inner product is always greater than zero" and / or "during each occurrence of the second float, the second inner product is always less than zero; or, during each occurrence of the second float, the second inner product is always greater than zero" to define the proposed technical solution in the patent application of this invention is sufficiently reasonable and practically significant.

[0179] It should be noted that the technical solution proposed in this patent document is different from asynchronous rolling (or differential rolling); the driving force of asynchronous rolling is still a pure shear force, which is transmitted by viscosity; however, the technical solution proposed in this patent uses the relative motion between the two rolls to generate a normal driving force, and the transmission of the normal driving force is independent of viscosity.

[0180] It should be noted that, currently, the equipment involved in the technical solution proposed in this invention does not exist in the industry; however, current technology is sufficient to manufacture the equipment; in other words, the technical solution proposed in this invention is undoubtedly achievable.

[0181] The advantages of the method proposed in this patent application include:

[0182] During the roll gap fixed opening-synchronous floating process, the process parameters of roll gap floating (including amplitude and floating speed) can be set arbitrarily according to actual needs. The setting of the process parameters of roll gap floating is only limited by the equipment conditions.

[0183] During the constant opening of the roll gap and synchronous floating process, the two rolls and the side sealing device remain stationary relative to the ground, which can theoretically completely eliminate the influence of the roll gap floating process on the side sealing device, and thus theoretically provide an infinite range of process parameters.

[0184] During a single unidirectional floating of the roll gap, the casting and rolling force changes unidirectionally. When the inner product of the floating speed and the preparation speed is always less than zero, a normal driving force can be applied to the semi-solid material in the molten pool. The normal driving force is independent of viscosity. Doing so can enhance process stability and / or improve billet quality (e.g., reduce or eliminate cracks in Cu-9Ni-6Sn alloys).

[0185] During the process of constant roll gap opening, the roll gap opening does not change, which theoretically ensures the uniformity of the billet thickness.

[0186] In the process of preparing metal materials with a wide two-phase region using the roll gap fixed opening-unidirectional-synchronous floating method, the shear thinning behavior and / or thixotropic behavior of semi-solid metals can be more effectively suppressed.

[0187] In the process of preparing metallic materials with a wide two-phase region using the roll gap fixed opening-unidirectional-synchronous floating method, segregation, especially macro segregation, can be suppressed.

[0188] During a single roll gap unidirectional floating process, the casting and rolling force changes unidirectionally. When the inner product of the floating speed and the preparation speed is always greater than zero, for materials with a narrow two-phase region, reducing the molten pool pressure can promote the formation of Kiss corners. The semi-solid material in the Kiss corner region can be used to prevent the pressure in the molten pool from connecting with the unsolidified core of the billet exiting the molten pool, thus avoiding billet defects such as "ridges", "snake eggs" and "egg pancakes".

[0189] For materials with a wide two-phase region, when the inner product of the floating velocity and the preparation velocity is always less than zero, a normal driving force independent of the viscosity of the semi-solid metal can be applied to the molten pool to keep the total driving force stable. This can promote the renewal of Kiss corner material, inhibit the rapid development of Kiss corner, reduce the pressure peak when the long-range shear-thinning interface collapses, and prevent various process stability problems and shortened service life of key components caused by excessively high molten pool pressure peaks, such as side sealing plate leakage, side sealing plate damage, jamming, tape breakage, cracks, and edge waves.

[0190] Reduce excessive vibration in twin-roll casting machines caused by collapse due to excessive development of shear-thinning interfaces;

[0191] The roll gap is made floating by the alternating motion of two rolls, which allows for further improvement of the billet structure and properties, such as refining the grains or suppressing segregation.

[0192] By controlling the overall driving force to be stable, the roller diameter can be further increased, thereby significantly increasing the output;

[0193] When the roll gap floating is always used to increase the pressure of the molten pool, it can enhance the heat transfer performance of the roll body and increase the output of the billet.

[0194] Increase the contact pressure between the working surface of the roller and the material being cast and rolled, reduce the heat transfer resistance to increase heat transfer efficiency, and increase billet output.

[0195] When roll gap floating is used to increase the pressure of the molten pool, it can avoid the formation of "scratches" on the surface of the billet (scratches are of great significance for the preparation of aluminum and its alloys). This is because the shear driving force is reduced due to the addition of the independent shear driving force, which can effectively prevent the roll surface from slipping with the material being cast and rolled. The avoidance of "scratches" is crucial for the preparation of aluminum alloy billets.

[0196] During the constant opening of the roll gap and synchronous floating process, due to the action of the roll system movement, the two rolls remain stationary relative to the ground, minimizing the disturbance of the roll gap floating and / or the roll system movement to the melt in the molten pool.

[0197] Using the roll gap fixed opening-synchronous floating method, the roll body and the side sealing device always remain relatively stationary, which expands the process parameter window, extends the service life of the contact side sealing device, and reduces production costs.

[0198] The alternating motion of the two rollers is beneficial to the symmetrical distribution of the billet structure.

[0199] The production of twin-roll cast non-ferrous metals (e.g., aluminum and its alloys) can be significantly increased. In theory, even with a conservative estimate, the production of aluminum and its alloys could increase by several times or even tens of times.

[0200] When the first and second floats are combined in any way, the mathematical model used for real-time control can be simplified.

[0201] When roll gap floating is used to increase the pressure of the molten pool, it can reduce the likelihood of the formation of micron-sized pores, especially aluminum and its alloys, for non-ferrous metals; these pores are caused by factors including hydrogen evolution. Attached Figure Description

[0202] Figure 1 The diagram illustrates the traditional understanding of the development process of solidified shells in this field.

[0203] Figure 2 The figure shown is a diagram of the actual experimental results obtained by implementing the Kiss angle measurement method.

[0204] Figure 3 The diagram shown is a theoretical schematic of the experimental results obtained by implementing the Kiss angle measurement method.

[0205] Figure 4 The diagram shows a schematic of the existing zero-angle roll gap bidirectional floating method.

[0206] Figure 5 The diagram shown is a schematic of the existing vertical roll gap bidirectional floating method.

[0207] Figure 6 The diagram shown is a schematic of the bidirectional floating method of inclined roll gap in the prior art.

[0208] Figure 7 The diagram shows a schematic of a bidirectional floating method for a fixed opening roller gap in the prior art.

[0209] Figure 8 The diagram shown is a schematic of the side sealing device before use.

[0210] Figure 9The diagram shows a side sealing device with a slope after use.

[0211] Figure 10 The diagram shows the placement plane, reference plane, first roll, second roll, Nip point, first roll shaft, second roll shaft, preparation direction, reference speed, reference direction, and reference line of a horizontal equal-diameter twin-roll thin strip casting machine under different conditions.

[0212] Figure 11 The diagram shown is a schematic diagram of the first floating process in Embodiment 1 of the present invention.

[0213] Figure 12 The diagram shown is a schematic diagram of the second floating process in Embodiment 1 of the present invention.

[0214] The correspondence between the figure numbers in the following figures is as follows:

[0215] 1. First roll body, 2. Second roll body, 3. Roll gap, 4. Long-range shear thinning interface, 5. Molten pool, 6. Flow distribution device, 7. Billet, 8. Reference plane, 9. Gravity direction. Detailed Implementation

[0216] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0217] The invention will now be described in further detail with reference to the accompanying drawings.

[0218] For ease of explanation, please refer to the following: Figure 10 In this invention patent application, a plane Ω is arbitrarily selected, which is perpendicular to the first roller shaft; the roller shafts of the first roller body 1 and the second roller body 2 are respectively called the first roller shaft and the second roller shaft; the minimum distance between the first roller body 1 and the second roller body 2 is called 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 shaft and the second roller shaft is the reference plane 8; in the natural state, the normal line of the reference plane 8 that passes through the Nip point is called the reference line; in the natural state, the intersection points of the first roller shaft and the second roller shaft with the plane Ω are points O1 and O2, respectively.

[0219] Example 1:

[0220] Embodiment 1 of the present invention discloses a method for roll gap floating for twin-roll thin strip, such as... Figures 11 to 12 As shown.

[0221] In Embodiment 1 of the present invention, a horizontal equal-diameter twin-roll casting machine is used, therefore, the reference direction is the same as the gravity direction 9.

[0222] like Figure 11As shown, during the first floating process, the first roller 1 rotates clockwise around the second roller shaft without stopping, while the roller system rotates counterclockwise around the second roller shaft. The angular velocity of the first roller 1 rotating around the second roller shaft is ω1, and the angular velocity of the roller system rotating around the second roller shaft is ω2. Both ω1 and ω2 are vectors, and ω1 = -ω2. The placement plane is always located on the reference plane 8. During the first floating process, the inner product (or first inner product) of the floating velocity and the preparation velocity is always less than zero to increase the pressure in the molten pool 5, thereby providing additional shearing independent driving force for the semi-solid metal in the molten pool 5. Since the first roller 1 and the second roller 2 are always stationary relative to the ground, the magnitude of ω1 can be arbitrarily set according to actual needs, thus theoretically providing an infinite range of process parameters.

[0223] like Figure 12 As shown, during the second floating process, the second roller 2 rotates counterclockwise around the first roller shaft without stopping, while the roller system rotates clockwise around the first roller shaft. The angular velocity of the second roller 2 rotating around the first roller shaft is ω'1, and the angular velocity of the roller system rotating around the second roller shaft is ω'2. Both ω'1 and ω'2 are vectors, and ω'1 = -ω'2. The placement plane is always located on the reference plane 8. During the second floating process, the inner product (or second inner product) of the floating velocity and the preparation velocity is always less than zero to increase the pressure in the molten pool 5, thereby applying a normal driving force independent of viscosity to the semi-solid material in the molten pool 5. Since the first roller 1 and the second roller 2 are always stationary relative to the ground, the magnitude of ω'1 can be arbitrarily set according to actual needs, thus theoretically providing an infinite range of process parameters.

[0224] In Embodiment 1 of the present invention, during the preparation process, the first float and the second float occur sequentially and repeatedly.

[0225] It is understandable that "the first float and the second float occur in sequence and repeatedly" means that "one first float" and "one second float" occur in sequence and repeatedly.

[0226] During each first float, the angle of rotation of the placement plane caused solely by the movement of the roller system is called the first angle; during each second float, the angle of rotation of the placement plane caused solely by the movement of the roller system is called the second angle.

[0227] In Embodiment 1 of the present invention, the size of the first angle and the size of the second angle are equal.

[0228] It should be noted that what a person skilled in the art can directly and unequivocally determine is that both the first and second angles are less than 360 degrees; in fact, neither the first nor the second angle can exceed 90 degrees, and they may even be less than 15 degrees.

[0229] Alternatively, in another embodiment, "multiple first floats" and "one second float" occur sequentially and repeatedly; or, "one first float" and "multiple second floats" occur sequentially and repeatedly; or, "multiple first floats" and "multiple second floats" occur sequentially and repeatedly; or, "multiple first floats" and "multiple second floats" occur in any combination for more complex real-time control.

[0230] Optionally, the first angle is arbitrary, and / or the second angle is arbitrary.

[0231] Optionally, the first angle and / or the second angle are in the range of 0.01 to 0.1 degrees.

[0232] Optionally, the first angle and / or the second angle are in the range of 0.1 to 1 degree.

[0233] Optionally, the first angle and / or the second angle are in the range of 1 to 10 degrees.

[0234] In Embodiment 1 of the present invention, the frequency of occurrence of the first float and / or the second float is in the range of 0.1 to 5 Hz.

[0235] Optionally, the frequency of the first float and / or the second float is in the range of 0.01 to 10 Hz.

[0236] Alternatively, during a single preparation process, for the sake of actual process requirements, any of the following methods may occur:

[0237] There is one first float and one second float, where the first float and the second float can be any combination;

[0238] There is one first float and multiple second floats, where the combination of the first float and the multiple second floats is arbitrary;

[0239] There are multiple first floats and multiple second floats, where the multiple first floats and multiple second floats can be in any combination.

[0240] Alternatively, in another embodiment, during the first floating process, the inner product of the floating velocity and the preparation velocity (or the first inner product) is always greater than zero; during the second floating process, the inner product of the floating velocity and the preparation velocity (or the second inner product) is always greater than zero; thereby reducing the pressure in the molten pool 5.

[0241] It is understandable that "one preparation process" is a continuous process; in this "continuous process", the composition of the blank 7 does not change as intended.

[0242] It is understandable that "the preparation process is over" could be caused by the "process is over" or by a change in the composition of the prepared blank 7.

[0243] It is understandable that a person skilled in the art can directly and without doubt know that "the process is over"; "the process is over" can be determined by "the billet 7 is no longer removed from the molten pool 5"; "the process is over" can also be determined by "no more substances for preparing the billet 7 are added to the molten pool 5".

[0244] It is understandable that a person skilled in the art would directly and without doubt know that "the composition of the prepared billet 7 has been changed"; in one process, two or more billets 7 with different compositions can be prepared. For example, in one process, a billet 7 with silicon steel composition is prepared first. After the preparation of the silicon steel billet 7 is completed, the composition of the molten metal entering the molten pool 5 is changed to prepare a billet 7 with stainless steel composition, until the process is completed; "the billet 7 with silicon steel composition" and "the billet 7 with stainless steel composition" are billets 7 with different compositions; in this process, two preparation processes occur.

[0245] It is understandable that the above-mentioned "one process" includes two "preparation processes"; one "preparation process" refers to "a process in which the composition of the billet 7 does not change"; in the above-mentioned "one process", the preparation of "the billet 7 with silicon steel composition" and "the billet 7 with stainless steel composition" were completed successively, which is considered as two preparation processes; that is to say, at least one "preparation process" occurs in the "one process".

[0246] It is understandable that "two or more blanks 7 with different compositions can be prepared in one process" is to avoid the cost of replacing the distribution device 6 and / or the side sealing device, and to improve equipment utilization so as to reduce production costs as much as possible.

[0247] Understandably, during a single preparation process, the first inner product can always be greater than zero or always be less than zero.

[0248] It should be noted that, under normal circumstances, when directly preparing the metal blank 7 using liquid metal, there are some different opinions in the field regarding the upper limit of the roll gap 3 opening; however, the roll gap 3 opening mentioned in the publicly available information that the inventor has been able to find is all below 8 mm; in fact, the upper limit of the roll gap 3 opening tried in industrial practice, under normal circumstances, does not exceed 3 mm when preparing steel materials; the diameter of the roll body is above 400 mm; therefore, whether the roll gap 3 opening is "8 mm" or "3 mm", it is much smaller than the diameter of the roll body.

[0249] It is understood that the drawing scale of the first roller 1, the second roller 2, the roller gap 3, etc. in this patent is significantly different from the actual situation. Only by doing so can the features of the technical solution mentioned in the patent application be clearly demonstrated.

[0250] It should be noted that even without the above explanation of the drawing scale, those skilled in the art can directly and without doubt understand the schematic diagrams involved in this patent application.

[0251] In this invention patent application, the embodiment uses a horizontal equal-diameter twin-roll thin strip casting machine, which is only one type of twin-roll thin strip casting machine. Twin-roll thin strip casting machines come in many forms and can be classified in many ways: according to the difference in roll diameter, twin-roll thin strip casting machines include equal-diameter, unequal-diameter, and variable-diameter types; according to the arrangement of the two rolls, twin-roll thin strip casting machines include horizontal, inclined, and vertical types; according to the billet extraction method, twin-roll thin strip casting machines include extraction along the direction of gravity, extraction at an angle less than 180 degrees to the direction of gravity, and extraction in the direction completely opposite to the direction of gravity. The variable-diameter twin-roll casting process belongs to the field of twin-roll thin strip. A variable-diameter twin-roll thin strip casting machine refers to a machine where the diameter of at least one of the two rolls changes along its roll axis. The variable-diameter twin-roll thin strip process can be used to prepare cladding materials such as clad tubes, clad rods, and clad sheets.

[0252] It should be noted that the embodiments described in this patent application can be used for any type of twin-roll thin strip casting machine.

[0253] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify or make equivalent substitutions to the specific embodiments of the present invention after reading the specification of this application, but such modifications or changes do not depart from the protection scope of the pending claims of this application.

Claims

1. A method for floating the roll gap in twin-roll thin strip, wherein the roll system is movably mounted on a twin-roll thin strip casting machine, the roll system comprising a first roll body and a second roll body arranged opposite each other for preparing a billet; the roll shaft of the first roll body is referred to as the first roll shaft, and the roll shaft of the second roll body is referred to as the second roll shaft; the plane in which the first roll shaft and the second roll shaft are located is referred to as the placement plane of the roll system; Its features are, The method includes the following steps: First floating: The second roller body is stationary relative to the ground, and the first roller body is controlled to rotate once without stopping around the second roller axis. At the same time, the roller system is controlled to rotate around the second roller axis, and the placement plane is always stationary relative to the ground. Second floating: The first roller is stationary relative to the ground, and the second roller is controlled to rotate around the first roller shaft once without stopping. At the same time, the roller system is controlled to rotate around the first roller shaft, and the placement plane is always stationary relative to the ground. In a single preparation process, the first float occurs at least once, and the second float occurs at least once.

2. The method for roll gap floating for twin-roll thin strip according to claim 1, Its features are: The minimum distance between the first roller and the second roller is called the roller gap; the midpoint of the roller gap is called the Nip point; the moving speed of the blank at the Nip point is called the preparation speed; the moving speed of the Nip point caused by the relative motion between the first roller and the second roller is called the floating speed of the Nip point; during each occurrence of the first floating, the inner product of the floating speed and the preparation speed is called the first inner product; during each occurrence of the second floating, the inner product of the floating speed and the preparation speed is called the second inner product. During each occurrence of the first float, the first inner product is always less than zero; and during each occurrence of the second float, the second inner product is always less than zero.

3. The method for roll gap floating for twin-roll thin strip according to claim 1, Its features are: The frequency of the first float and / or the second float is in the range of 0.1 to 5 Hz.

4. The method for roll gap floating for twin-roll thin strip according to claim 1, Its features are: The frequency of the first float and / or the second float is in the range of 0.01 to 10 Hz.

5. A method for roller gap floating for twin-roll thin strip according to claim 1, Its features are: During a single preparation process, any of the following occurs: One first float and one second float occur, wherein one first float and one second float are any combination; One first float and multiple second floats occur, wherein one first float and multiple second floats are any combination; Multiple occurrences of the first float and multiple occurrences of the second float occur, wherein the multiple occurrences of the first float and multiple occurrences of the second float are any combination.

6. A method for roll gap floating for twin-roll thin strip according to claim 1, Its features are: The first float and the second float occur sequentially and repeatedly.

7. A method for roll gap floating for twin-roll thin strip according to claim 1, Its features are: During each occurrence of the first float, the angle of rotation of the placement plane caused solely by the movement of the roller system is called the first angle; during each occurrence of the second float, the angle of rotation of the placement plane caused solely by the movement of the roller system is called the second angle; the magnitudes of the first angle and the second angle are equal.

8. A method for roll gap floating for twin-roll thin strip according to claim 7. Its features are: The first angle and / or the second angle are in the range of 0.01 to 10 degrees.

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