JPH11244908A - Hot rolling equipment train and hot rolling strip rolling method - Google Patents

Abstract

(57) [Problem] To provide a row of hot rolling equipment and a method of rolling a hot-rolled steel strip, which stabilize run-out running at the tip of a thin hot-rolled steel strip. A rough rolling mill (1) for rough rolling of a slab to a rough bar, a finish rolling mill (6) for finish rolling of a rough bar to a hot rolled steel strip, and a run-out for cooling while transporting the hot rolled steel strip. Table 8 and coiler 10 for winding the cooled hot-rolled steel strip
In a row of hot rolling equipment equipped with a rolling mill, between a rough rolling mill 1 and a finishing rolling mill 6, a rolling reduction device 3 for rolling down a coarse bar in the thickness direction.
And a row of hot rolling equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a row of hot rolling equipment for hot rolling a slab to produce a hot rolled steel strip, and a rolling method using the same.

[0002]

2. Description of the Related Art According to a general method of manufacturing a hot-rolled steel strip,
The hot-rolled steel strip that has exited the finish rolling mill is cooled to a predetermined temperature by cooling water while traveling on the run-out table, and is finally wound around a coiler via a pinch roller. However, this method causes a problem when manufacturing a thin hot-rolled steel strip having a thickness of 2 mm or less. A phenomenon in which the tip of the hot-rolled steel strip jumps up from the finish rolling mill until the tip of the hot-rolled steel strip bites into the pinch roller due to a collision with the transfer table roller or the like. Once it jumps up, the tip falls backwards, resulting in a "two-fold" or unstable running and "wavy".

[0003] These phenomena are more likely to occur as the thickness of the hot-rolled steel strip is smaller and the finish rolling speed is higher. Therefore,
In the production of thin hot-rolled steel strips, finishing accelerated rolling, in which the finishing rolling speed at the tip of the hot-rolled steel strip is reduced and the rolling speed is increased after the tip bites into the pinch roller, is commonly performed. I have. However, at the tip of the hot-rolled steel strip, the rolling speed is slow, so that the temperature is significantly reduced during finish rolling, and the material is significantly deteriorated due to phase transformation during finish rolling. Further, if two sheets are broken or wavy, winding failure, poor winding, and uneven cooling are likely to occur.

As a prior art disclosed for stabilizing the run-out running of a thin hot-rolled steel strip, Japanese Patent Application Laid-Open No.
33119 and JP-A-5-185128. These technologies use a forming machine provided on the exit side of the finishing mill to form the tip of the hot-rolled steel strip, improve the bending rigidity and prevent the tip from flying, so that This stabilizes the run-out running of the vehicle.

[0005]

However, the prior art described in JP-A-56-33119 and JP-A-5-185128 has the following problems. The tip of the hot-rolled steel strip is conveyed on the run-out table at a high speed of 600 mpm or more. As in the prior art, it is technically difficult to process and form the tip of a hot-rolled steel strip with a forming machine on the exit side of a finish rolling mill. If the molding fails and the tip gets clogged at the molding machine, the finish rolling cannot be continued. Even if it can be passed through a molding machine, springback occurs due to the high strain rate, and it is difficult to process it into a predetermined shape.

There is also a problem when the hot-rolled steel strip tip after forming is wound around a coiler via a pinch roller. First, it is not easy to make a molded part bite into a pinch roller and wind it around a mandrel of a coiler. Even if it can be wound around a mandrel, there is a possibility that a part wound around the molded part in contact with the part to be molded may have a flaw or plastic deformation. The wound shape after winding is not so good.

On the other hand, in the prior art patent publication,
There is a description that a straightening machine is installed immediately before a pinch roller to straighten a portion to be formed at the tip of a hot-rolled steel strip and return to a shape before forming. However, it is difficult to bite the molded part into the straightening machine, and even after the straightening, the original shape is not completely obtained by springback. This problem cannot be solved by straightening machines alone. The purpose of the present invention is
Stabilizes run-out running at the tip of thin hot rolled steel strip,
An object of the present invention is to provide a hot rolling equipment train and a method for rolling a hot rolled steel strip.

[0008]

In order to solve the above problems and achieve the object, the present invention uses the following means. (1) The equipment row of the present invention transports a rough rolling mill for rough rolling a slab to a rough bar, a finishing rolling mill for finishing rolling the rough bar to a hot rolled steel strip, and a hot rolling steel strip. In a hot-rolling equipment line equipped with a run-out table for cooling while rolling and a coiler for winding a cooled hot-rolled steel strip, a rolling reduction device for rolling down a coarse bar in a thickness direction between a rough rolling mill and a finishing rolling mill. Is a row of hot rolling equipment.

(2) The equipment line according to the present invention is characterized in that a cooling device for cooling a material to be rolled is installed between the rolling-down device and the run-out table. It is a rolling equipment line.

(3) The equipment line according to the present invention is characterized in that a heating device for heating the tip of the coarse bar is installed on the inlet side or the outlet side of the pressing-down device, wherein )
2 is a series of hot rolling equipment. (4) The equipment line of the present invention is characterized in that a rough bar storage device for temporarily storing a rough bar is installed between the rough rolling mill and the rolling-down device, wherein (1) to (1) are provided. The hot rolling equipment line according to any one of (3). (5) In the method of the present invention, the slab is roughly rolled into a rough bar, the rough bar is finish-rolled into a hot-rolled steel strip, and the hot-rolled steel strip is cooled and wound while being conveyed by a run-out table. In a method of rolling a hot-rolled steel strip to be taken, a rolling device for rolling down a rough bar in a thickness direction, a process of rolling down a tip portion of the rough bar to a target plate thickness, and finish rolling the rough bar whose tip portion is rolled down. Forming a hot-rolled steel strip having a predetermined temperature at a tip end of the hot-rolled steel strip. (6) In the method of the present invention, after the step of rolling down the leading end of the rough bar, further cooling the leading end of the material to be rolled by a cooling device installed between the rolling-down device and the run-out table. The method for rolling a hot-rolled steel strip according to the above (5), comprising:

(7) The method according to the present invention is characterized in that, in the step of rolling down the leading end of the rough bar, when the leading end of the rough bar is reduced to a target thickness by a plurality of times by the rolling-down device, the rough bar leading end is reduced. The method of rolling a hot-rolled steel strip according to the above (5) or (6), wherein the leading end of the rough bar is heated during each reduction with a heating device that compensates for a temperature drop in the portion.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, in order to stabilize the run-out running of the leading end of a thin hot-rolled steel strip, a finish rolling mill is required. To reduce the temperature at the tip of the hot-rolled steel strip on the side and improve the bending stiffness at the tip of the hot-rolled steel strip, it was found that it is effective to reduce the tip of the coarse bar prior to finish rolling. .

Based on this finding, the present inventors have developed a rough rolling mill for roughly rolling a slab to obtain a rough bar, a finish rolling mill for finishing rolling a rough bar to obtain a hot-rolled steel strip, and a hot rolling mill. In a row of hot rolling equipment equipped with a coiler that cools and winds a steel strip while transporting it by a run-out table, a rolling reduction device that reduces a coarse bar in the thickness direction is installed between a rough rolling mill and a finishing rolling mill. Using a row of hot rolling equipment, the slab was roughly rolled into a coarse bar, the tip of the coarse bar was lowered in the thickness direction, and the rough bar was finish-rolled and the tip was at a predetermined temperature. The present inventors have found a row of hot rolling equipment and a method of rolling a hot-rolled steel strip to stabilize the run-out running at the tip of the thin hot-rolled steel strip so as to form a hot-rolled steel strip, and have completed the present invention.

An embodiment of the present invention will be described below. FIG. 1 is a schematic side view showing a row of hot rolling equipment according to the present invention. In a normal hot-rolled steel strip rolling method, a slab having a predetermined temperature is roughly rolled by a rough rolling mill 1 to form a rough bar 11, and the rough bar 11 is finish-rolled by a finishing mill 6 to be a hot-rolled steel strip. The hot-rolled steel strip is cooled to a predetermined temperature by cooling water while being conveyed on the run-out table 8, and is wound by a coiler 10 via a pinch roller 9.

The row of hot rolling equipment according to the present invention is a rolling device 3 for rolling down the tip of the rough bar 11 in the thickness direction between the rough rolling mill 1 and the finishing mill 6, and heating the tip of the rough bar 11. A heating device 4 and a coarse bar storage device 2 are provided. A pressing device or a planetary mill can be used as the pressing-down device 3, and a looper or a coil box can be used as the rough bar storage device 2.
A descaling device 5 on the input side of the finishing mill 6 and a stand-to-stand spray 7 provided between stands of the finishing mill 6
Corresponds to the cooling device described in claim 2.

In the method of rolling a hot-rolled steel strip according to the present invention, as shown in FIG. 2, prior to finish rolling, the tip of the rough bar 11 is lowered by a reduction device 3 so that the thickness of the lower portion of the rolled steel sheet is reduced. The target thickness of the belt should be about the same as the target thickness. By this operation, the temperature of the lower part to be pressed is rapidly lowered before leaving the finishing mill 6. According to the normal rolling method, the temperature of the tip of the thin hot-rolled steel strip on the exit side of the finishing mill 6 is 80 °.
Although it is about 0 to 850 ° C., the temperature can be lowered to about 100 ° C. by using this method. In other words, this means that the bending stiffness at the tip of the hot-rolled steel strip is improved. Thus, even if the tip of the hot-rolled steel strip collides with the table roller of the run-out table 8 or the like, the tip becomes difficult to jump up, and the two sheets are prevented from breaking or waving. It is sufficient that the length of the lower end of the rough bar 11 in the conveying direction in the direction of pressure is equal to the number of table rollers of the run-out table 8.
The pressing device 3 shown in FIG. 2 is a press device, but a planetary mill may be used instead.

During the reduction by the reduction device 3, the temperature at the tip of the rough bar 11 is reduced by heat removal from the mold,
The rolling load increases. Therefore, the heating device 4 for compensating for the temperature drop at the tip of the rough bar 11 is installed in the hot rolling equipment line of the present invention. As shown in FIG. 3, the leading end of the rough bar 11 is sent to the heating device 4 to be heated in the middle of the reduction, and is again reduced by the reduction device 3. In addition, before the rolling down by the rolling down device 3, the tip of the rough bar 11 may be heated by the heating device 4,
It is effective in reducing the rolling load. As the heating device 4, an induction heating device capable of rapid heating is preferable. The installation location of the heating device 4 may be on the entrance side or the exit side of the screw-down device 3 as long as it is close to the screw-down device 3. The tip of the rough bar 11 must be stopped while the pressure is lowered by the pressing device 3 or the heating is performed by the heating device 4. When the leading end of the rough bar 11 reaches the position of the screw-down device 3 or the heating device 4, if the rough bar 11 is bitten by the rough rolling mill 1, the rough bar 11 is temporarily moved. A coarse bar storage device 2 for temporarily storing is required. The coarse bar storage device 2 shown in FIG. 2 or 3 is a looper type storage device. As the rough bar storage device 2, a coil box can be applied. Of course, when the tip of the rough bar 11 is located at the position of the screw-down device 3 or the heating device 4, the rough bar storage device 2 is not required if the entire rough bar 11 has finished rough rolling.

The original purpose of the descaling device 5 and the stand-to-stand spray 7 is to remove scale on the surface of the material to be rolled or to cool the material to be rolled. However, in the present invention, it is used particularly for cooling the pressurized lower part at the tip of the material to be rolled. By this operation, the temperature at the tip of the material to be rolled decreases,
The bending stiffness of the end of the hot-rolled steel strip on the exit side of the finishing mill 6
Can be larger. Hereinafter, examples of the present invention will be described to demonstrate the effects of the present invention.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The difficulty of bending at the tip of a hot-rolled steel strip is represented by bending stiffness. The bending stiffness is defined by the product of the Young's modulus E and the second moment of area I. Thickness h, since the second moment of the width b is ^{I = b · h 3/12} , flexural rigidity E
I is calculated by the following equation.

E · I = E · (b · h ³ ) / 12 (1) Using the equation (1), the bending stiffness of a hot-rolled steel strip having a certain thickness at 100 ° C. is 800 ° C. The thickness of the hot-rolled steel strip was calculated. Young's modulus is 2 at 100 ° C.
FIG. 4 shows the results at 1,000 MPa and 14,000 MPa at 800 ° C. For example, the bending stiffness of a hot-rolled steel strip having a thickness of 1.5 mm at 100 ° C. is 1.7 at 800 ° C.
It is the same as the bending stiffness of a 2 mm hot-rolled steel strip. From FIG.
It can be seen that the same effect as when the sheet thickness is increased can be obtained by cooling the tip of the hot-rolled steel strip.

A rough bar 2 having a thickness of 30 mm and a width of 1,000 mm is finish-rolled to obtain a thickness of 1.2 mm and a width of 1,000 mm.
In the case where the hot-rolled steel strip was manufactured, the ordinary method and the method of the present invention were compared. The hot rolling equipment train on which the test was performed is as shown in FIG. When rolling is performed by a normal method without rolling down the tip of the rough bar 2 by the press device, the threading speed is set to 620 m because run-out running performance deteriorates.
pm only. According to the method of the present invention, the leading end of the rough bar 2 is pressed down by a press device to obtain a plate thickness of 1.
When a 5 mm-long and 2 m-long pressurized lower part was formed and finish rolling was performed, the rolling finish temperature of the pressurized lower part became 100 ° C. by using the descaling device 5 and the stand-to-stand spray 7. As shown in FIG. 4, the bending stiffness at the tip of the hot-rolled steel strip was improved, and it was possible to convey the strip at the run-out table 8 even at a threading speed of 680 mpm.

FIG. 5 shows a comparison of the rolling finish temperature between the ordinary method and the method of the present invention. In the method of the present invention, the rolling finish temperature of the pressure-receiving lower part at the tip of the hot-rolled steel strip is about 1
It is 00 ° C. However, this portion is not shown in FIG. 5 because it is only 0.2% of the entire hot-rolled steel strip and is negligibly small. In the usual method, the threading speed is slow, and the amount of heat lost due to contact with the rolling roll and radiation during finish rolling is large, so that 20% from the end of the hot-rolled steel strip
810 ° C required to obtain good material
The above rolling finish temperature could not be secured. In contrast, when the method of the present invention was applied, the threading speed could be increased, so that the rolling finishing temperature was 810 ° C. or higher from the tip, and a good material was obtained over the entire hot-rolled steel strip. I was able to.

[0023]

According to the rolling method using the row of hot rolling equipment of the present invention, the run-out running at the tip of the thin hot rolled steel strip is stabilized. As a result, the finish rolling speed can be increased, and the productivity is improved. Deterioration of the material at the tip is also prevented. In addition, winding failure, winding failure, and uneven cooling do not occur.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing a row of hot rolling equipment according to an embodiment of the present invention.

FIG. 2 is a diagram showing a state in which the tip of a rough bar according to the embodiment of the present invention is being pressed down.

FIG. 3 is a view showing a state in which the tip of a rough bar according to the embodiment of the present invention is being heated.

FIG. 4 shows the bending stiffness of the hot-rolled steel strip according to the example of the present invention as 1
The figure which compared at 00 degreeC and 800 degreeC.

FIG. 5 is a diagram showing a comparison between a normal method and a method of the present invention in terms of a rolling finish temperature according to an example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rough rolling mill, 2 ... Coarse bar storage device, 3 ... Rolling device, 4
... Heating device, 5 ... Descaling device, 6 ... Finishing mill, 7 ... Spray between stands, 8 ... Run-out table, 9 ... Pinch roller, 10 ... Coiler, 11 ... Coarse bar.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Yoshimura 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Sadaka Masuda 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun Honko Co., Ltd.

Claims (7)

[Claims] 1. A rough rolling mill for rough rolling a slab to a rough bar, a finishing rolling mill for finishing rolling the rough bar to a hot rolled steel strip, and a run-out table for cooling while transporting the hot rolled steel strip. And, in a row of hot rolling equipment equipped with a coiler for winding a cooled hot-rolled steel strip, between a rough rolling mill and a finishing rolling mill, a rolling reduction device for rolling down a rough bar in a thickness direction is installed. A row of hot rolling equipment, characterized in that: 2. The hot rolling equipment line according to claim 1, wherein a cooling device for cooling the material to be rolled is provided between the rolling-down device and the run-out table. 3. The hot rolling equipment line according to claim 1, wherein a heating device for heating a leading end portion of the rough bar is installed on an inlet side or an outlet side of the rolling-down device. 4. A rough bar storage device for temporarily storing a rough bar is provided between the rough rolling mill and the rolling-down device. Row of hot rolling equipment. 5. A hot-rolled steel which is subjected to rough rolling of a slab into a rough bar, finish-rolling the rough bar to form a hot-rolled steel strip, and further cooling and winding the hot-rolled steel strip while transporting the strip with a run-out table. In the strip rolling method, a step of rolling down the tip of the coarse bar to a target sheet thickness with a rolling device for rolling down the rough bar in the thickness direction, and finish rolling of the rough bar whose tip is rolled down, Forming a hot-rolled steel strip at a predetermined temperature. 6. A step of cooling the leading end of the material to be rolled by a cooling device installed between the rolling-down device and the run-out table after the step of rolling down the leading end of the rough bar. The method for rolling a hot-rolled steel strip according to claim 5, characterized in that: 7. In the step of rolling down the tip of the rough bar, when the tip of the rough bar is reduced to a target thickness by a plurality of times by the rolling-down device, the temperature drop of the rough bar tip is compensated. The method for rolling a hot-rolled steel strip according to claim 5, wherein a tip portion of the rough bar is heated during each reduction by a heating device.