JPH05161902A - Hot rolling equipment - Google Patents

Abstract

PURPOSE:To lower the extracting temp. from a heating furnace and to reduce bend of material by constituting a part of roughing mill group of a specified number of reversible 2-high mill and making the distance between mutual mills a specified condition. CONSTITUTION:Two reversible 2-high roughing mills 2, 3 are arranged on the downstream side of the heating furnace 1 and the distance between the mutual roughing mills 2, 3 is taken as within 6m. A slab 16 is heated in the heating furnace 1 and made to coincide with the center position of the work rolls 4 of the roughing mill 2 with a side guide 5. Oxidized film generated on the slab 16 is removed with high-pressure water from a spray 13 and the slab 16 is once stopped after rolling with the roughing mill 2 and successively with the roughing mill 3. The slab 16 is inversely fed to the roughing mills 3, 2 and rolled after aligning with a side guide 6 and removing the oxidized film with high-pressure water spray 14. The slab 16 is worked into a crude bar by rough rolling of six passes, fed to a crop shear 7, bar joining machine 8 and finishing mill group 10 and coiled with a down coilers 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot strip rolling mill, and more particularly to a hot rolling mill having a rough rolling mill with a small material temperature drop and a short installation space.

[0002]

2. Description of the Related Art Conventionally, with respect to the layout of rough rolling mills, various studies and announcements and patent applications based on the layout have been made in addition to the existing layout plans of hot strip mills.
For the equipment layout of hot strip mills in Japan, "The latest hot strip manufacturing technology in Japan" issued by the Iron and Steel Institute of Japan on August 10, 1987, P1
According to 87-P190 (mill layout), the equipment with the shortest distance between the rough rolling mills is 11m between R3 and R4 of Nippon Steel Oita. These two rough mills are so-called closed couple type. The material is rolled in only one direction in an arrangement called. However, in many cases, 2 of R3 and R4
It is not possible to obtain a rough bar having a desired thickness from a slab having a predetermined thickness in one rolling, and in most cases, two rough rolling machines R1 and R2 are arranged upstream of the rolling machines R3 and R4. In fact, R2 is a reversible rolling mill, which normally rolls for 3 passes and then rolls for a total of 6 passes to a predetermined rough bar thickness. Therefore, even if there are two rough rolling mills arranged close to each other, it is necessary to install another rough rolling mill unless the reversing type is used, and the effect of shortening the entire installation space is small.

An example of performing reversible rolling by arranging two rough rolling mills close to each other is "IRON AND STEEL ENGINEE"
R ”May 1976, P48 to P52, the results of the study based on the desk study and the simulation result are reported. According to this known example, six horizontal rough rolling mills are arranged in the conventional continuous type, and the distance between R5 and R6 is about 11 m.
As a closed couple system separated from each other, the one having an arrangement length of 350 m between the heating furnace and the crop shear was reversibly rolled by two quadruple rough rolling mills at an interval of 26 m by two reversible rolling machines. Arrangement length between croppers is 277m
There is a report that the total cost including mechanical, electrical and construction can be reduced to 77% of the conventional level by reducing the cost by about 20%. According to the same paper, the advantage of using this method is that the current equipment length is increased by installing another rough mill close to the existing rough mill in addition to the equipment that performs reversible rolling with one rough mill. Cites the ease of expansion that can increase production volume.

[0004]

As a result of the study by the inventors of the present invention, the above-mentioned known examples have the following problems, and the object of the present invention corresponding to each of them will be explained.

First, descaling will be described. Generally, an iron oxide film is formed on the surface of a steel sheet that is hot-rolled, and if it is rolled by a roll as it is, a hard oxide scale is embedded in the base material and becomes a flaw on the surface of the steel sheet. Therefore, descaling by spraying with high pressure water is usually performed before the material is caught in the horizontal roll. However, in order to obtain a sufficient descaling effect, it is necessary to spray high-pressure water with a certain amount or more of water, which causes the temperature of the material to drop. Also in the above-mentioned known example, it is described that it is necessary to provide a descaling device before and after each pass of two rough rolling mills arranged close to each other, and to spray high-pressure water at the entrance side of each horizontal pass or the width rolling performed immediately before that. There is.
That is, if the reduction is performed 6 times by changing the direction twice, it is necessary to spray the descaling water 6 times, and it is necessary to extract the temperature of the material from the heating furnace at a high temperature in consideration of the temperature decrease of the material. There is a problem. As a common object of all claims of the present invention, the distance between two rough rolling mills is shortened, and the spraying of descaling water between the rolling mills is omitted.

Secondly, the problem of material bending will be described. In a normal rough rolling mill in which material is rolled independently at each stand, the bending of the rough bar is within a certain allowable range by guiding the center of the rolling mill with a side guide at the entrance side of each pass. However, in the above-mentioned known example in which rolling is performed by two stands at the same time, as shown in FIG. 2, the bending of the leading end generated in the preceding stand remains as it is when the plate is caught in the succeeding stand. The center deviation (dc) of the bar is further promoted, which further promotes the bending of the rough bar. The large bend caused by this impedes productivity such as drawing in a finishing mill and deteriorates product quality. The object common to all the claims of the present invention is to suppress the bending generated in the two rough rolling mills to be small.

Generally, in the case of a rough rolling mill, the side guide on the material entry side of the rolling mill is set wider than the strip width by about 100 mm to 140 mm. This is ideally set to the same width as the plate for the purpose of engaging the material in the center of the mill, but if the gap is small and the friction force between the side guide and the plate is large, it will be used for plate transportation. The set amount is empirically determined because of a slip between the table roller and the plate. In other words, the material can be off-centered up to 1/2 = 70 mm of the side guide width margin maximum setting value of 140 mm, but if it is more than that, the bending of the plate becomes large and there is a problem in product quality during operation. It is also because many things are empirically known.

On the other hand, when performing tandem rolling with a rough mill, the material is bitten into the front stand before it comes out from the rear stand. Since it is rolled by the work rolls, the centering is difficult, and in the end, there is no choice but to roll off-center by the bending amount of the plate generated in the front stand.

In other words, in the case of tandem rough rolling, it is preferable to suppress the bending at the rear stand within 70 mm. In some cases, it may be difficult depending on the rolling conditions.

[0010]

The technical means adopted to achieve the above-mentioned object will be described in correspondence with the above-mentioned object commonly mentioned in each claim.

First, in order to omit the descaling between the stands, the distance between the stands should be made as short as possible, and the oxide scale generated between these stands should be processed in such a short time that the rolling does not hinder rolling. This is achieved by starting rolling on the stand.

Further, as described in claims 3 and 4, by storing two work rolls in one mill housing, the interval between rolling can be further shortened. Further, by making the rolling mill a double type, it becomes easier to store two work rolls in one housing.

Secondly, even in the case of a tandem type rough rolling mill, the above-mentioned object of suppressing the bending of the rough bar rolled by the rolling mill is achieved by making the rolling mill a double rolling mill which is hard to bend. It

Here, in order to explain that the bending of the plate in the double rolling mill is smaller than that in the quadruple rolling mill, the concept of parallel rigidity of the mill is introduced. This will be described with reference to the schematic diagrams of the mill shown in FIGS. 3 and 4. Operation-side / drive-side reduction position difference S _df = S _OP −S _DR , reduction force difference P _df = P _OP −P _DR
The ratio of

[0015]

[Equation 1]

[0016] and represents a parameter representing a tortuous difficulty mil referred to as parallel stiffness mil K _l. Also,
Using the spring constant of each part of the mill, the parallel stiffness K _l of the double rolling mill and the quadruple rolling mill is

[0017]

[Equation 2]

Is represented by

Where K _{h is the} housing spring constant K _{R is the} spring constant per unit width between rolls K _{RO is the} spring constant between the material and the work roll In these equations, the values of K _l are represented by typical hot mill values. When calculated by using, double rolling mill K _l = 220 ton / mm, quadruple rolling mill K _l = 70 ton / mm, and the double rolling mill has parallel rigidity three times or more that of the quadruple rolling mill. Recognize. The result of calculating the bending of the plate using this value is shown in FIG. As the disturbance, the off-center of the plate was assumed to be 50 mm on the entrance side. This corresponds to the case where the side guide is set to the plate width plus 100 mm. As described above, in the case of rough tandem rolling, it is difficult to center the plate at the rear stand by using the entrance side guides.Because of the restraint of the front stand, it is difficult to bend the plate at the front stand. It is preferable that the guide set value is set to 1/2 of the plate width plus 140 mm, that is, 70 mm or less in terms of sheet passing property. In order to satisfy this condition even in the rough final pass where a large amount of bending occurs, it is necessary to use a double rolling mill as shown in FIG. 8 and to keep the distance between stands within 6 m.

[0020]

By arranging the two rough rolling mills at a short distance from each other, it is possible to bite into the succeeding stand in a time that does not cause oxide scale on the material surface after rolling at the preceding stand. There is. In order to arrange these two rolling mills at a close distance, each rolling mill is made into a double type and accommodated in a space shorter than the quadruple type. Alternatively, they can be arranged closer to each other by implementing the contents of the claims of the present invention such as storing two work rolls in one mill housing. Further, the double rolling mill has higher parallel rigidity of the mill than the quadruple rolling mill, and it is based on the effect that the bending can be suppressed to be small even in the closed-coupling type rough mill in which the material originally tends to bend.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. Two double reversible rough rolling mills 2 and 3 are arranged on the downstream side of the heating furnace 1, and side guides 5 and 6 are provided on the upstream side of the rough rolling machine 2 on the upstream side and on the downstream side of the downstream side 3, respectively. Deploy. Further, on the downstream side, a crop shear 7, a bar joining machine 8, a bar looper 9, a finishing rolling machine group 10, a split flying shear 11, and a down coiler 12 are further arranged on the downstream side. The slab 16 heated to around 1200 ° C. in the heating furnace 1 guides the material 13 to the center position in the width direction of the work roll 4 of the rough rolling mill 2 by the side guide 5 on the upstream side, and the iron oxide film formed on the material surface. High pressure water (usually about 150 kg / cm ² )
After being removed by the spray 13, the rolling is performed by the rough rolling mill 2 and then by the rough rolling mill 3, and after the material passes through the rolling mill 3, the material is temporarily stopped. After that, the center of the material is again aligned with the center of the rolling mill 3 by the side guide 6, and the oxide film that has regrown after the descaling work is removed again by the high-pressure water spray 14, and then in the opposite direction to the rolling process. The material is fed to the rolling mills 3 and 2 in this order. Further, after going through the same steps and rolling in the order of the rolling mills 2 and 3, and after the rough rolling of 6 passes for convenience,
A coarse bar having a predetermined thickness (usually around 30 mm) is obtained. afterwards,
Further, the material sent to the downstream side is sheared by the crop shear 7 at the leading and trailing ends of the irregular shape (generally called fish tail and tongue), and after the leading end of the material reaches the joining machine 8, it is already in the finish rolling machine 10. After joining the tail end of the preceding material that has started rolling, the oxide film is continuously removed through the looper 9 once again by the high pressure water spray 15, and then the finishing rolling mill group 1
Sent to 0. After finishing rolling, the material is cut to a suitable length with a split flying shear 11 and down coiler 1
It is rolled up by 2. The present embodiment is particularly suitable for the case where the equipment length is desired to be suppressed but the production amount is not so required.

FIG. 2 shows an embodiment in which the rough rolling mills 2 and 3 of this embodiment are housed in one housing. Two sets of work rolls 23, 24 are housed in the housing 20, and the work roll chocks 25, 26 are used to apply a pressing force by the piston 22 arranged in the hydraulic jack 21 on the upper side, and the pass line adjusting device 27 on the lower side. Adjust the height. Material 16
Is fed into the mill from the right side of the drawing by a feed roll 28, and is first rolled by a pair of work rolls 23 and then by a work roll 24. When reverse rolling is further required, the material 16 temporarily stopped on the left side of the drawing is fed to the work rolls 24, 2
Roll in 3 in order.

Another embodiment having the configuration of FIG. 1 will be described.
In the present embodiment, the material 16 heated in the heating furnace 1 is rolled by the rolling mills 2 and 3 only once, and a rough bar is obtained after two rough rollings. This embodiment is particularly suitable for obtaining a rough bar without lowering the temperature of the material in a shorter time, when the thickness of the rough bar is large and a large number of times of rough rolling is not required.

In another embodiment with the configuration of FIG.
The material 16 is rolled back and forth between the rolling mills 2 and 3 for 2.5 times in a manner that can be adopted when a rough bar having a desired thickness cannot be obtained even by the rough rolling of 6 passes as described above. Rough rolling of passes is usually unnecessary and the temperature drop of the material is large. Therefore, the first two passes, that is, the first passes of the rolling mills 2 and 3 are not performed as dummy passes and are not descaled. It is effective when the material 16 can be rolled down in the remaining 8 passes to obtain a coarse bar having a desired thickness. Another embodiment will be described with reference to FIG. This embodiment is an example in which a rough mill 17 is arranged on the upstream side of the crop shear 7 in addition to the configuration of the embodiment described in FIG. The bar is obtained by rolling with a rolling mill 17. This embodiment is particularly suitable for equipment that wants to increase the production amount even if the equipment length is increased to some extent.

Further, in the configuration of FIG. 6, it is conceivable that various pass configurations as described in FIG. 1 can be considered, and a combination of the rough rolling mills 2 and 3 shown in FIG. Is also possible.

[0026]

The present invention has the following effects.

First, the effect of maintaining the temperature of the rolled material will be described. FIG. 7 illustrates an example of a simulation result of the inventors. In the present invention, by keeping the distance between two adjacent rough mills as close as possible and omitting the descaling spray between stands, a heat retention effect of about 80 ° C. can be obtained after the completion of rough rolling for 6 passes. As a result, it is possible to lower the temperature of the furnace (1150 ° C in this simulation), which not only saves energy but also saves descaling water, which leads to power saving of the descaling pump. Many.

Secondly, the effect of suppressing the bending of the material to be small as described above by constructing the rough mill with the double rolling mill will be quantitatively explained by using the simulation result. As described above, FIG. 8 is a simulation assuming the rough first rolling mill. Considering the rough first pass as a representative, the plate width is 1500 mm, the inlet plate thickness is 293 mm, and the outlet plate thickness is 24.
With a 0 mm pass schedule, the rolling load is 2124 tons. When the initial plate deviation (off-center amount from the mill center to the plate center) of 50 mm is given as a disturbance, how the meandering amount increases is investigated. Aforementioned essential generally parallel rigid K _L is small amount meandering easier to increase because of the spring between the work rolls and backup rolls in the quadruple rolling mill as shown in formula.

In the example of FIG. 8, assuming that the position of the succeeding stand is 6 m, it is 4
In the H mill, the meandering amount is about 63 mm, whereas in the 2H mill, it is about 54 mm, which is a slight increase from the initial off-center amount of 50 mm. As described above, the 2H mill has a small meandering tendency, and by forming a rough rolling mill with two 2H mills as in the present invention, it is possible to suppress the bending of the rough bar to be small. Also, this effect has a great effect on the productivity and the operation stability by improving the reliability of joining in the subsequent bar joining machine and reducing the drawing in the finish rolling mill.

[Brief description of drawings]

FIG. 1 is a layout view of equipment of a hot rolling equipment according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a rough rolling mill according to another embodiment of the present invention.

3A and 3B are a plan view and a side view schematically showing bending of a plate in a conventional rough rolling mill.

FIG. 4 is a front view of the quadruple rolling mill viewed from the entry side (or the exit side).

FIG. 5 is a front view of the double rolling mill as viewed from the entrance side (or exit side).

FIG. 6 is a layout view of equipment of hot rolling equipment according to an embodiment of the present invention.

FIG. 7 is a characteristic diagram of simulation results showing the effect of maintaining the temperature of the material of the present invention.

FIG. 8 is an explanatory diagram of a simulation result of the effect of curving the material of the present invention.

[Explanation of symbols]

1 ... Heating furnace, 2, 3 ... Rough rolling machine, 7 ... Crop shear,
8 ... Joining machine, 10 ... Finishing rolling machine, 11 ... Dividing shear, 1
2 ... Down coiler, 13-15 ... Descaling spray header, 23, 24 ... Work roll.

Claims (4)

[Claims] 1. A hot rolling facility comprising at least a rough rolling mill group and a finishing rolling mill group, wherein a part of the rough rolling mill group is constituted by two double type rolling mills, and the two rolling mills are provided. The hot rolling equipment is characterized in that the distance between the rough rolling mills is within 6 m. 2. A hot rolling facility comprising at least a rough rolling mill group and a finishing rolling mill group, wherein a part of the rough rolling mill group is constituted by two double reversible rolling mills, The hot rolling equipment is characterized in that the distance between the rough rolling mills is 6 m or less. 3. A hot rolling facility comprising at least a rough rolling mill group and a finishing rolling mill group, wherein a part of the rough rolling mill group is composed of two double reversible rolling mills. A hot rolling facility, characterized in that one rough rolling mill is configured by accommodating two sets of work rolls in one mill housing. 4. A hot rolling facility comprising at least a group of rough rolling mills and a group of finish rolling mills, wherein a part of the group of rough rolling mills is composed of two double reversible rolling mills. A hot rolling facility, characterized in that one rough rolling mill is configured by accommodating two sets of work rolls in one mill housing.