KR20010031851A - Sheet hot rolling mill - Google Patents

Abstract

The finishing mill 30 of the hot rolling mill is divided into the front end 31 and the rear end 32, and two or more CVC mills 31A and 31B are disposed on the front end 31, and the rear end 32 Two diameter roll mills 32A, 32B or more are arranged on the stand. As a result, when rolling a thin plate having a thickness of about 1.2 mm or less, it is possible to suppress the occurrence of crowns or edge drops, and to prevent the occurrence of throttling at the end of the plate, thereby smoothly manufacturing the rolled plate. .

Description

Hot Rolling Mill of Sheet Steel {SHEET HOT ROLLING MILL}

When manufacturing a thin plate by hot rolling, it is an important subject to make the thickness of a plate uniform, and to pass the end part of a plate smoothly through each rolling mill. In the case of rolling a plate by a roll, an edge drop in which the thickness is sharply reduced in the crown (main body crown) or both ends of the plate (a part of the ear) thickening near the center in the width direction of the plate tends to be uneven. In addition, especially when the plate thickness is thin, a problem called "Pincher" which frequently bends the end of the plate and passes through the rolling mill often occurs. The crown is a phenomenon in which the vicinity of the center of the amplitude is thickened based on the bending deformation of the roll, and the edge drop is a portion which sandwiches the plate of the roll (the portion that is pressed against the plate) and the portion that does not sandwich the plate (plate). This is a phenomenon in which the steep gradient is reduced so that the thickness of both ends of the plate decreases to the arc toward the outside due to the formation of an arc-shaped step on the circumferential surface of the roll. In addition, throttling is a phenomenon in which the tail end part of the board which becomes unstable because tension is not applied between rolling mills is bent against a side guide, etc., and enters between rolls of the rolling mill in the bent state. If a crown or edge drop occurs, the dimensional accuracy of the plate thickness is lowered, and if a throttle occurs, problems such as scratches on the roll and regrinding of the roll occur, which significantly delays production.

The thinner the plate thickness is, the easier it is to occur at the end of the plate. The reason for this is that the rolling reduction increases in order to reduce the thickness of the plate, so that the rolling load is increased, and the force for moving the plate in the lateral direction is also increased by the amount, and when the plate is brought into contact with a guide installed directly in front of the rolling mill, It is because the edge part is easy to bend. Therefore, the thickness of the steel plate which can be rolled realistically in a hot rolling mill was 1.2 mm.

The technique for smoothly hot rolling a steel sheet having a thickness of about 1.2 mm or less while preventing the occurrence of throttling is described in (280) Chiba 3 of the Japan Steel Association Lecture Preliminary Manuscript (CAMP-ISIJ VOL.10 (1997) -1088). General outline of endless rolling in H0T, JP-A-6-106207, and the like. The technique described in these publications joins the tip of the next plate to the trailing end of the plate (sheet bar) immediately in front of the finishing mill, thereby reducing the number of parts of the trailing end that are not subjected to tension. In this case, the thickness of the part which cannot be avoided to be the end is rolled to 1.6 mm or more to prevent the occurrence of the throttle.

In order to produce a thin sheet smoothly by the technique described in the above publication, the required equipment cost is considerably increased as compared with the conventional hot rolling mill. This is because, in addition to the need for a special bonding device for smoothly joining the plates in a short time, the addition of a cutting device, and the like, the arrangement of the entire line of the hot rolling mill must be changed. Therefore, even in the case of using a hot rolling mill already installed, in order to realize the above technique, a significant renovation is required, and the period of the renovation work is prolonged, and the operation must be stopped for a long time. In addition, although the above-mentioned means alone can prevent the occurrence of the throttle, it is difficult to suppress the occurrence of the crown and the edge drop on the plate.

An object of the present invention is to provide a hot rolling mill that is capable of preventing the occurrence of throttling at the end portion while suppressing the occurrence of crowns or edge drops even when producing thin sheets having a thickness of about 1.2 mm or less. It is done.

The present invention relates to a hot rolling mill that makes it possible to smoothly manufacture a thin plate (steel sheet) having a uniform thickness.

1A is a system diagram of a hot rolling mill according to one embodiment of the present invention.

Fig. 1B is a front view schematically showing the main part of the CVC mill as seen from the direction of the b-b arrow in Fig. 1A.

FIG. 1C is a view showing a state in which the roll gap is changed due to the work roll being displaced in the axial direction in FIG. 1B.

FIG. 1D is a detailed view of the portion d in FIG. 1A, and is a side view schematically showing the main portion of the diameter roll mill. FIG.

2A is a system diagram of a hot rolling mill according to another embodiment of the present invention.

2B is a system diagram of a hot rolling mill according to still another embodiment of the present invention.

2C is a system diagram of a hot rolling mill according to another embodiment of the present invention.

3 shows a fair cross mill.

Fig. 4 is a graph showing the temperature of the plate at the inlet side of the finish rolling mill.

The hot rolling mill of the thin plate according to the present invention includes a finishing rolling mill constituted by a front end and a rear end,

① The front end is composed of CVC mill or pair cross mill of two or more stands,

(2) The rear end is characterized by being constituted by two or more diameter roll mills.

The CVC mill of the above ① means a roll in which the outer diameter is continuously changed in the axial length direction, and includes a known rolling mill including one capable of moving in the axial length direction (CVC roll). In addition, a pair cross mill is a known rolling mill in which a pair of work rolls and a backup roll are arranged in a cross shape that is closest to each other in the vicinity of the center without being parallel at the same time so that the mutual positional relationship (angle, etc.) can be changed. it means. These rolling mills all have the ability to change the roll gap shape. That is, in the case of the CVC mill, the roll gap shape is changed by moving the CVC roll having the outer diameter change as described above in the axial length direction, and in the case of the pair cross mill, by changing the positional relationship of the rolls arranged in the cross shape as described above. You can change it. In addition, such a mill has a large ability to change the roll gap shape as compared with means such as simply performing roll bending.

On the other hand, the above-mentioned two-diameter roll mill means that the rolling mill does not have the same diameter with respect to a pair of work rolls, and only a large diameter work roll is rotationally driven. Since one working roll is a small diameter, it is easy to increase the amount of reduction even with a small reduction force, and the shear force can be applied to the rolled material by driving only a large diameter working roll. It is easy to take large reduction ratio compared with the general rolling mill of which all diameters are large (the same diameter). Therefore, even when the rolling pressure is reduced compared to the rolling mill of the above-mentioned ① provided in the general rolling mill or the front end part, the two-diameter roll mill can realize the reduction ratio equivalent to each rolling mill. Therefore, it can also be said that the above-described effect can be achieved even in the case of a small arrangement having a small number of stands, and a sufficient reduction ratio can be realized. In addition, since the diameter roll mill can be configured only by making minor modifications (that is, changing one roll to a smaller diameter) to a general rolling mill having a large diameter of the work roll, it is already installed which may be useful. When there is a rolling mill, the hot rolling mill of the present invention can be configured simply and at low cost.

According to the hot rolling mill of the present invention having the arrangements of ① and ② described above, it is possible to suppress occurrence of crowns or edge drops in the thin plate and to reduce the frequency of the throttling at the end portions at the same time. This is based on the action of a) to c) below.

a) The crown which arises in a board | plate can be suppressed by performing control of the change of a roll gap shape in (1) part of a front end among finishing mills. The crown of the plate is caused by uneven roll gap in the amplitude direction (i.e., the axial length direction of the roll) due to the bending of the roll of the rolling mill.However, if the roll gap of the rolling mill is changed and controlled appropriately, the crown of the plate is controlled. It is possible to make the plate small in size and to have an optimal crown. In addition, although the control of the crown by changing the roll gap often lowers the flatness of the plate or the like, such control is performed at the front end portion of the finish rolling mill, so that the flatness and the like is improved at the intermediate end or the rear end portion. It is possible to let. Moreover, if the crown is made small in this way in the front end part, the rolling which hold | maintains this in the back end part etc. may be carried out, and operation of the diameter roll rolling mentioned later can be made stable.

b) By performing rolling with a low rolling pressure in the part (2) of the rear end of the finish rolling mill, the axle hardly occurs in the tail end of the plate. The axial shaft is caused by the end of the untensioned plate swinging horizontally (right or left of the pass line) and touching the guide of the rolling mill. Became clear. The reason for this is presumed that the rolling means cannot be produced completely symmetrically. That is, on the basis of the fact that the rolling mill or the rolling roll is not strictly symmetrical, it is considered that an asymmetrical force acting on either side of the plate acts on the plate. Therefore, the smaller the rolling pressure is, the more the force is directed from side to side. It is thought that it becomes small and becomes difficult to shake a tail end. Therefore, in this rolling mill, even when rolling a considerably thin plate, the problem that a bridge is produced in the end part is hard to arise. In addition, since the amount (amplitude) at which the tail end of the plate shakes horizontally in the finishing rolling mill is generally increased as the rolling mill at the rear end is used, rolling with a low rolling pressure at the rear end of the rolling mill is performed in terms of prevention of throttling. effective.

c) In addition, since rolling with low rolling pressure is performed in part (2) of a rear end, generation | occurrence | production of an edge drop can also be suppressed. Edge drop occurs due to the formation of arc-shaped step on the roll surface at the boundary line between the part pressed against the plate of the roll and the outer part of the width of the plate. By making the recess shallow, this can be made small.

In this hot rolling mill, the above-mentioned rolling mill (CVC mill or fair cross mill) is disposed at two or more stands, so that the crown of the plate can be effectively suppressed, and the rolling mill (two-roll roll mill) of ② is also disposed at two or more stands. By remarkably lowering the pressure, the required reduction ratio can be realized while effectively suppressing the occurrence of throttling and edge drop.

In the hot rolling mill of this invention, in addition to the above, the means which prevents the temperature drop of a board | plate can be arrange | positioned between the rough rolling mill (last stand of the upstream stand) and said finish rolling mill (frontmost stand of) mentioned above. As means for preventing the temperature drop, there are a tunnel furnace, a sheet bar winding and unwinding device, a sheet bar heater and the like.

Since the plate before being sent to the finish rolling mill is at a low speed determined by the speed at the exit side of the finish rolling mill, the residence time is long, and the temperature begins to drop as the back of the plate (near end) is reached. Also in the finishing rolling mill, the temperature of the plate decreases toward the rear end portion. However, in this hot rolling mill, the temperature is maintained with respect to the plate before being sent to the finish rolling mill by the above means for preventing the temperature drop of the plate, and the temperature is raised. If the temperature of the plate is sufficiently high, the rolling pressure required for the finish rolling may be low compared with the case where it is not. Therefore, in this hot rolling mill which prevents the temperature drop of a plate by the said means, finish rolling (particularly the rear end part) can be performed by low rolling pressure. Moreover, since the temperature of the front-end | tip part of a board | substrate and the rear end part can be made the same, there is no fluctuation | variation of rolling load and stable rolling can be performed. Therefore, it is possible to effectively suppress the occurrence of edge drop and throttling.

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of this invention is described. FIG. 1A generally shows a hot rolling mill A according to an embodiment, and FIG. 1B schematically shows a pair of work rolls 31a and 31b of a CVC mill of the hot rolling mill A shown in FIG. 1A. (View from bb arrow direction in Fig. 1A). In Fig. 1B, the change in the work roll outer diameter is exaggerated. Fig. 1C shows a state where the work gap is displaced in the axial direction so that the roll gap is changed. FIG. 1D schematically shows two-diameter roll mills 32a and 32b in the hot rolling mill A in FIG. 1A (detailed view of part d in FIG. 1A).

The following apparatus is arrange | positioned at this hot rolling mill A. As shown in FIG. First, the heating furnace 1 is located in the most upstream part (left side of FIG. 1A), and the rough rolling machine 10 is arrange | positioned after that. The heating furnace 1 is a means for heating the continuous casting piece (slab) made of a material to about 1200 degreeC, and the roughing mill 10 rolls the heated slab to thickness about 30 mm. Although one stand is typically shown in the figure as rough rolling machine 10, in some cases, multiple stands may be arrange | positioned. Downstream of the roughing mill 10, the finishing rolling mill 30 which consists of 6 stands is arrange | positioned as shown, and the winding machine 40 of the rolled board is provided in the end.

In this hot rolling mill A, the following structure is employ | adopted so that even if it is a thin steel plate of thickness 1.2mm or less (especially 1.0 mm or less), the thing with high shape precision can be produced smoothly.

Three stands 31A, 31B, and 31C constituting the front end 31 of the finish rolling mill 30 are constituted of so-called CVC mills (mills whose roll diameters change continuously). That is, they are comprised as a quadruple rolling mill which consists of work roll 31a, 31b and backup roll 31c, 31d like FIG. 1A. The work rolls 31a and 31b of each stand are provided with a crown (CVC, that is, a continuous change in diameter) as shown in Fig. 1B. The work rolls 31a and 31b can be moved in opposite axial length directions at the same time as shown in Fig. 1C. By adjusting the positional relationship between the work rolls 31a and 31b by such movement, the shape of the roll gap (part in contact with the plate x) can be changed. A well-known roll bender may also be provided for the work rolls 31a and 31b of each stand.

The three stands 32A, 32B, and 32C which comprise the rear end 32 of the finish rolling mill 30 are comprised as what is called a diameter roll mill. That is, they are comprised as a quadruple rolling mill which consists of work rolls 32a and 32b and backup rolls 32c and 32d like FIG. 1A. As the work rolls 32a and 32b of each stand, as shown in Fig. 1D, different diameters are used. Then, only the large diameter roll 32b in the lower portion of the work rolls 32a and 32b is rotated and driven by a motor or the like (not shown), and the small diameter roll 32a in the upper portion is rotatable so that a driving force is not applied thereto. have. In addition, a well-known work roll bender (not shown) is attached to each stand, and the work rolls 32a and 32b are bent. These three stands 32A, 32B, and 32C as two-diameter roll mills drive only the point where one (upper) work roll 32a is small and the other (lower) work roll 32b. Because of the fact that the shearing force acts on and the upper roll has a small diameter, the rolling can be performed at a sufficient reduction ratio even at a relatively low rolling pressure.

In such a hot rolling mill A, first, in the three stands 31A, 31B, 31C of the front end 31 of the finishing rolling mill 30, as shown in FIG. 1C, the work roll 31a, 31b is shown. By axially displacing and changing the roll gap of each CVC roll suitably, the crown of the plate x can be corrected regardless of thickness and width, and it can be made optimal. Moreover, the edge drop can be reduced with respect to the board | substrate x by rolling with low rolling pressure in the three stands 32A, 32B, and 32C of the rear end 32 which are two diameter roll mills. That is, the board | plate with high shape precision which suppressed crown and edge drop by the hot rolling mill A containing these 6 stand finishing mills 30 can be produced. In the case of rolling a steel plate having a thickness of 1.2 mm and a width of 1220 mm by a conventional hot rolling mill, a crown having an average of about 50 μm occurred on the plate at a position of 25 mm from the width end (edge) of the plate. The average value of the crown at a position of 25 mm from the edge is 15 µm in any situation when the steel sheet having a thickness of 1.2 mm and a width of 1220 mm or a steel sheet having a thickness of 1.0 mm and a width of 100 mm is produced by the rolling mill A. The maximum value can be set to about 30 m.

In this rolling mill A, low-pressure rolling is performed on the three stands 32A, 32B, and 32C of the rear end 32 at the same time, thereby effectively preventing the throttling phenomenon from occurring at the tail end of the plate x. can do. This is because by lowering the rolling pressure, each work roll 32a, 32b can suppress the asymmetrical forces (i.e., left and right) exerted on the plate x, thereby reducing the shaking of the plate from side to side. to be. In the rolling mill A, even if the plate x is thin with a thickness of 1.2 mm or less, the frequency of occurrence of the throttle can be suppressed and smooth production can be continued. In the case of producing a steel sheet having a thickness of 1.2 mm and a width of 1220 mm using a conventional hot rolling mill, throttling occurred at a frequency of about 3% (three times per 100 times), but in the test of the inventors, throttling occurred in the rolling mill (A). The frequency can be about 0.5% when obtaining the steel plate of the said dimension, and about 3% when obtaining the steel plate of thickness 1.0mm and width 1220mm.

2A, 2B and 2C show another embodiment of the present invention. First, in the hot rolling mill B shown in FIG. 2A, a tunnel path 21 is provided between the final stand of the rough mill 10 and the first stand 31A of the finish rolling mill 30. The tunnel path 21 is a tunnel furnace along the pass line of the plate, and the plate can be heated by heating means (burner or the like) not shown. Between the final stand of the roughing mill 10 and the first stand 31A of the finish rolling mill 30, there is a difference in the feed speed of the plate (the speed in the former exceeds the speed of the latter) and the plate exits the former. Since the silver is rolled at a low speed determined by the exit speed of the finish rolling mill 30, the temperature at the inlet side of the finish rolling mill 30 decreases toward the end portion as shown in FIG. The tunnel path 21 is provided in order to prevent the temperature fall. Thereby, the rolling pressure required for finish rolling can be made low compared with the case where it does not do so by preventing temperature fall of a board | plate. In this way, the rolling pressure can be lowered, and the rolling pressure of the leading end and the trailing end can be made substantially the same, so that the two diameter roll mills 32A, 32B, 32C of each stand of the finishing mill 30, in particular, the rear end 32 The rolling pressure in) can be set to be considerably low, and it becomes possible to further suppress the occurrence of edge drop and throttling. Since the tail end portion of the plate is usually the largest temperature drop width, the tunnel furnace 21 has a large effect of suppressing the occurrence of throttling. In this hot rolling mill B (also, hot rolling mills C and D described later) It is possible to reduce the frequency of occurrence of the throttle more than in the case of the hot rolling mill A described above.

In this hot rolling mill B, a total of seven stands are arranged as the finish rolling mill 30 as shown in Fig. 2A. That is, the three ends 32A, 32B, and 32C of the rear end 32 are roll roll mills which are the same as the hot rolling mill A of FIG. 1A, but the front end 31 made of the CVC roll shown in FIG. 1B. It differs from the rolling mill A by the point which consists of four stands 31A, 31B, 31C, and 31D. In this manner, the number of rolling mills (stands) in the finish rolling mill 30 may be appropriately changed in accordance with the thickness of the plate, the type of steel, the production speed, and the like as the number of stands of the rough mill 10. In addition, at least one part of the stand of the front end 31 among the finishing mill 30 can be made into the well-known fair cross mill 36 shown in FIG. 3 which can change a roll gap shape. The pair cross mill 36 arranges a pair of work rolls 36a and 36b and backup rolls 36c and 36d at the same time in a cross shape (crossing type) which is not parallel but most approaches near the center part, and is mutually positioned. It is a rolling mill which can change (angle, etc.). In addition, the stand of the rear end 32 may be appropriately implemented as a design change within the scope of the invention, for example, to make an outside diameter roll mill including a CVC roll. Such a change is also possible for the following hot rolling mills C and D shown in Figs. 2B and 2C and the hot rolling mill A of Fig. 1A.

In the hot rolling mill C of FIG. 2B, the sheet bar winding-up and unwinding device 22 is provided between the final stand of the rough mill 10 and the frontmost stand 31A of the finishing mill 30. The winding-up / winding-up device 22 is a device which winds up and rewinds a board (seat bar), for example, is the apparatus marketed by Steltech Ltd. (Canada) under the brand name of Coilbox. Considering that the plate before entering the finish rolling mill 30 is often temperature-decreased as described above, by winding the long plate in a coil shape to reduce the temperature drop, the wound plate is released again and sent to the finishing mill 30. do. As a result, when the temperature drop of the plate is reduced, the rolling pressure required for finish rolling can be lowered as in the above, and the occurrence of edge drop and throttling can be effectively prevented.

In addition, the hot rolling mill D shown in FIG. 2C is provided with the sheet bar heater 23 in front of the finishing mill 30 following the winding-up / rewinding apparatus 22 of FIG. 1B. The seat bar heater 23 is a means for heating the tip and tail end of a plate by a burner, etc., and even if it is a coil in the winding-up / reeling device 22, temperature rises with respect to the tip and tail end of a board which temperature tends to fall. Promote. Since the throttling is a phenomenon occurring at the end of the plate, when the end of the plate is heated by the seat bar heater 23, the rolling pressure of the portion can be effectively lowered, and the generation rate of the throttle can be greatly reduced.

According to the hot rolling mill of the thin plate according to the present invention has the following effects. In other words,

1) It is possible to suppress the occurrence of crowns or edge drops on the plate, and at the same time reduce the frequency of throttling at the ends. Even if the board is considerably thin, it is difficult for the throttle to occur, so that, for example, a sheet having a thickness of about 1.2 mm or less can be stably produced with high precision.

2) Since special equipment and devices are not necessarily required, it is also possible to construct them in a short time by making simple modifications to already installed hot rolling mills in addition to low equipment costs. In addition, if there is a general rolling mill already installed that may be useful, there is an advantage that it can be configured very simply by applying a slight modification.

3) Moreover, in the case where a means for preventing the temperature drop of the plate is provided between the roughing mill and the finish rolling mill, the occurrence of edge drop and throttling can be more effectively suppressed. This is because the finish rolling can be performed at a lower rolling pressure by preventing the temperature drop with respect to the plate before being sent to the finish rolling mill.

Claims (14)

In a hot rolling mill equipped with a finish rolling mill, The finishing mill has a front end and a rear end, The front end is composed of two or more stand CVC mill, The said rear end is comprised by the two-stage or more diameter roll mill, The hot rolling mill characterized by the above-mentioned. The hot rolling mill according to claim 1, wherein the two-diameter roll mill has a large-diameter roll that is rotationally driven and a small-diameter roll that can be freely rotated. 3. The hot rolling mill of claim 2, wherein the large diameter roll is a lower roll, and the small diameter roll is an upper roll. The hot rolling mill according to claim 1, wherein a rough rolling mill is provided upstream of the finish rolling mill, and a means for preventing a temperature drop of the plate is provided between the rough rolling mill and the finish rolling mill. 5. The hot rolling mill according to claim 4, wherein the means for preventing the temperature drop of the plate is a tunnel furnace having heating means and passing the plate therein. The hot rolling mill according to claim 4, wherein the means for preventing the temperature drop of the plate is a winding / unwinding device of the plate. 5. The hot rolling mill according to claim 4, wherein the means for preventing the temperature drop of the plate is a heater for heating the tip and tail ends of the plate. In a hot rolling mill equipped with a finish rolling mill, The finishing mill has a front end and a rear end, The front end is constituted by two or more pairs cross mill, The said rear end is comprised by the two-stage or more diameter roll mill, The hot rolling mill characterized by the above-mentioned. The hot rolling mill according to claim 8, wherein the two-diameter roll mill has a large-diameter roll that is rotationally driven and a small-diameter roll that can be freely rotated. 10. The hot rolling mill of claim 9, wherein the large diameter roll is a lower roll, and the small diameter roll is an upper roll. The hot rolling mill according to claim 8, wherein a rough rolling mill is provided upstream of the finish rolling mill, and a means for preventing a temperature drop of the plate is provided between the rough rolling mill and the finish rolling mill. The hot rolling mill according to claim 8, wherein the means for preventing the temperature drop of the plate is a tunnel furnace having heating means and passing the plate therein. The hot rolling mill according to claim 8, wherein the means for preventing the temperature drop of the plate is a winding / unwinding device of the plate. The hot rolling mill according to claim 8, wherein the means for preventing the temperature drop of the plate is a heater for heating the leading end and the trailing end of the plate.