JP2002102904A - Method and apparatus for rolling hot rolled steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a hot rolled steel strip at a high yield rate excellent both in the shape and precision in the width direction by heating a roughing bar in the uniform temperature distribution in the width direction, without causing a temperature difference between both edge portions and the vicinity of the center portion by precisely correcting misalignments from the center line in the width direction of the roughing bar as well as correcting the failure of flatness of the roughing bar when the roughing bar roughly rolled by the roughing rolling mill is finish-rolled by the finishing rolling mill. SOLUTION: A flatness correcting device 6 to correct flatness of a roughing bar 2 roughly rolled between the roughing rolling mill 1 and the finishing rolling mill 10, and an induction heater 7 to heat the roughing bar 2 all over the width direction are provided, and side guides 3a, 3b, 3c to guide the passing position in the width direction of the roughing bar 2 are respectively provided between the roughing rolling mill 1 and the flatness correcting device 6, between the flatness correcting device 6 and the induction heater 7, between the induction heater 7 and the finishing rolling mill 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for rolling a hot-rolled steel strip which has a uniform temperature distribution in the width direction and has a small variation in quality with a continuous hot rolling mill at a high yield. It is about.

[0002]

2. Description of the Related Art Generally, in a hot-rolled steel strip, a slab is heated to a predetermined temperature in a heating furnace, and the heated slab is rolled to a predetermined thickness by a rough rolling mill to form a coarse bar. After both ends are heated by an edge heater, the roll is finished and rolled into a hot-rolled steel strip having a predetermined thickness by a continuous hot-finishing rolling mill comprising a plurality of stands, and the hot-rolled steel strip is cooled on a run-out table. It is manufactured by cooling in a stand and winding it up with a coiler.

[0003] In such continuous hot rolling, defective shapes such as "warping" and "earing" may occur at the tip of a rough bar rolled to a predetermined thickness by a rough rolling mill. When the above-mentioned shape defect occurs in the rough bar, when the rough bar is heated by the edge heater, the rough bar may collide with the edge heater and be damaged.

In order to prevent the above-mentioned problem, for example, Japanese Patent Laid-Open Publication No. Hei 5-329519 (hereinafter referred to as prior art)
Discloses an apparatus as shown in FIG. As shown in FIG. 4, a flatness correcting device 6 is provided on the entry side of the edge heater 9 between the rough rolling mill 1 and the continuous hot finishing rolling mill 10, and the flatness correcting device 6 is provided. Warp detectors 4a and 4b are provided on the entry side and the exit side.

A rough bar 2 roughly rolled by a rough rolling mill 1
Deformation such as "warping" or "ear-lashing" at the tip of the flatness is detected by the warp detectors 4a and 4b provided on the entrance side and the exit side of the flatness correction device 6, and based on the detection signal. Thus, the flatness correction device 6 is controlled, and the flatness defect of the rough bar 2 is corrected. The rough bar 2 in which the flatness defect has been corrected in this way is sent to the edge heater 9, and the edge heater 9 heats both ends in the width direction, and after the temperature distribution in the width direction becomes uniform, the continuous heat is applied. Finishing mill 1
0 to finish rolling to a predetermined thickness.

[0006]

According to the prior art, the edge heater 9 caused by the poor flatness of the rough bar 2 is produced.
Collision is prevented and damage from the collision is avoided,
As shown in FIG. 5, the lateral bar "shift" (.DELTA.x:
Off-center) cannot be corrected. as a result,
There is a possibility that the side surface of the rough bar 2 collides with the edge heater 9 and is damaged.

Although not shown in FIG. 4, when an induction heating device is provided on the inlet side of the edge heater 9 and the coarse bar 2 is heated by the induction heating device over the entire width thereof,
If the center of the induction heating device and the center in the width direction of the rough bar 2 are displaced from each other, the temperature distribution becomes uneven in the width direction of the rough bar 2, that is, the heat becomes uneven. If the coarse bar 2 has such uneven heat, a deviation occurs in the deformation resistance in the width direction of the rough bar, so that the shape of the steel strip after finish rolling is deteriorated. Meandering, colliding with a side guide provided between finishing mills comprising a plurality of stands, causing a problem that the rear end of the steel strip is broken.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and to correct a flatness defect of a rough bar when finishing a rough bar roughly rolled by a rough rolling machine with a finish rolling machine. Correctly correct the deviation from the center line in the width direction of the bar, heat the coarse bar with a uniform temperature distribution in the width direction without generating a temperature difference between both edges and near the center, It is an object of the present invention to provide a method and an apparatus capable of producing a hot-rolled steel strip having an excellent shape and accuracy in a width direction at a high yield.

[0009]

From the above-mentioned viewpoints, the present inventors have developed a method capable of heating a rough bar at the entrance side of a finishing mill so as to have a uniform temperature distribution in the width direction thereof. I did my best research. As a result, the amount of warpage of the coarse bar is detected by the warp detector provided between the rough rolling mill and the finish rolling mill, and the detected flatness of the coarse bar is corrected by the coarse bar flatness correcting device. Is corrected, and the coarse bar whose flatness defect has been corrected in this way is guided by a side guide so that the center line in the width direction thereof coincides with each center of the flatness correcting device and the coarse bar heating device,
It has been found that the coarse bar can be heated so as to have a uniform temperature distribution in the width direction by feeding the coarse bar to the rough bar heating device and the edge heater.

[0010] The present invention has been made based on the above findings, and the method according to the first aspect of the present invention comprises a rough rolling step of roughly rolling a slab, and a finishing step of finish rolling a coarsely-rolled coarse bar. In the method for manufacturing a hot-rolled steel strip having a rolling step, between the rough rolling step and the finish rolling step,
Performing a flatness correction step of correcting the flatness of the coarse bar and a coarse bar heating step of heating the coarse bar in this order, and, between the rough rolling step and the flatness correction step, the flatness Between the straightening step and the coarse bar heating step, and
A guide step is provided between the rough bar heating step and the finish rolling step to guide a passing position of the rough bar in the width direction by a side guide.

According to a second aspect of the present invention, there is provided a hot-rolled steel strip rolling apparatus in which a rough rolling device for roughly rolling a slab and a finish rolling device for finish rolling a rough-rolled rough bar are provided. Between the finish rolling device, a flatness correction device that corrects the flatness of the coarsely-rolled coarse bar, and a coarse bar heating device that heats the coarse bar over the entire width direction thereof, and Between the coarse rolling device and the flatness correction device, between the flatness correction device and the coarse bar heating device, and between the coarse bar heating device and the finish rolling device, It is characterized in that a side guide for guiding the passage position in the width direction is provided.

[0012]

FIG. 1 is a schematic side view showing an embodiment of the apparatus of the present invention. As shown in the drawing, a continuous hot finishing rolling mill 10 comprising a rough rolling mill 1 and a plurality of stands.
And a leveler 6 as a coarse bar flatness correction device, and an induction heating device 7 as a heating device for heating the coarse bar.
And the edge heater 9 are provided in this order.

A side guide 3a is provided on the entry side of the flatness correction device 6, a side guide 3b is provided between the leveler 6 and the induction heating device 7, and a side guide 3b is provided between the induction heating device 7 and the edge heater 9. Side guides 3c are provided, respectively. A warp detector 4 is provided on the entrance and exit sides of the leveler 6.
a and 4b are provided, and the leveler 6 is controlled by the control device 5 based on the detected values.

The rough bar 2 rolled by the rough rolling mill 1 is sent to a leveler 6, and the leveler 6 corrects a flatness defect such as upward warpage or waving of the tip portion. At this time, the coarse bar 2 detected by the warp detectors 4a and 4b
The leveler 6 is appropriately controlled by the control device 5 depending on the degree of warpage.

The rough bar 2 whose flatness defect has been corrected in this way is then continuously heated by the induction heating device 7 over the entire width thereof, and the temperature of the entire bar increases.
Further, both edge portions are heated by the edge heater 9 to compensate for the decrease in temperature, and a uniform temperature distribution is obtained in the width direction.

In the meantime, the rough bar 2 is formed by the side guides 3a, 3b and 3c as shown in FIGS. 1 and 2, and the center line 12 in the width direction of the rough bar 2 and the center line of the rolling line shown in FIG. 13 is conveyed so that the deviation (Δx) from it becomes zero. Accordingly, the conveyed rough bar 2 does not collide with the induction heating device 7 or the edge heater 9, and the temperature distribution in the width direction of the rough bar 2 does not become uneven during heating by the induction heating device 7. .

The rough bar 2 is finish-rolled to a predetermined thickness by a finish rolling mill 10 to form a hot-rolled steel strip. The unevenness of the temperature distribution in the width direction caused by heating in the induction heating device 7 and the edge heater 9 is obtained. This prevents the shape defect in the steel strip width direction and the meandering phenomenon of the steel strip during finish rolling caused by the above.

[0018]

Next, the present invention will be described in more detail with reference to examples. Heated to a temperature of 1230 ° C. in a heating furnace, thickness 226 mm, width 1050 mm, length 9200 m
The slab made of carbon steel having a size of m is roughly rolled in the rough rolling mill 1 by the equipment shown in FIG.
The coarse bar 2 was 1050 mm wide. Next, the rough bar 2 is passed through the leveler 6, the flatness of which is corrected in the leveler 6, and then the rough bar 2 is heated by the induction heating device 7 and the edge heater 9 so as to have a predetermined temperature distribution in the width direction. And finish rolling by a continuous hot finish rolling mill 10. Thus, a hot-rolled steel strip having a thickness of 2 mm and a width of 1050 mm was prepared.

The temperature of the rough bar 2 in the rolling process at a position of about 30 m from the tip is measured by a radiation thermometer 8 installed on the outlet side of the induction heating device 7, and the temperature distribution in the width direction is measured. 3 is shown. In FIG. 3, the mark ● indicates that the coarse bar 2 is conveyed by the side guides 3a, 3b, and 3c such that the deviation (Δx) between the center line in the width direction of the coarse bar 2 and the center line of the rolling line becomes zero. Is a temperature distribution when the above-mentioned Δx is 20 without the side guide.
It is a temperature distribution in the case of 0 mm.

As is apparent from FIG. 3, when the side guide was not provided and Δx was 200 mm, the temperature distribution in the width direction was deviated, but when the side guide was provided and Δx was set to 0, almost no deviation occurred. The temperature distribution is symmetrical, so that the rough bar 2 does not collide with the induction heating device 7 or the edge heater 9, and the temperature distribution in the width direction of the rough bar 2 may be biased during heating by the induction heating device 7. Thus, a hot-rolled steel strip with good shape accuracy could be manufactured.

[0021]

As described above, according to the present invention,
When the rough bar roughly rolled by the rough rolling machine is finish-rolled by the finish rolling machine, the flatness defect of the rough bar is corrected, and the deviation of the rough bar from the center line in the width direction is accurately corrected. The bar can be heated with a uniform temperature distribution in the width direction without generating a temperature difference between both edges and the vicinity of the center, and a hot-rolled steel strip with excellent shape and accuracy in the width direction is obtained. An industrially useful effect that can be manufactured with a high yield is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing one embodiment of the device of the present invention.

FIG. 2 is a partially enlarged plan view of the device of the present invention.

FIG. 3 is a diagram showing a temperature distribution in a width direction of a heated coarse bar according to the present invention in comparison with a conventional technology.

FIG. 4 is a schematic side view showing an example of a conventional device.

FIG. 5 is a partially enlarged plan view of a conventional device.

[Explanation of symbols]

 1: Rough rolling mill 2: Rough bar 3a, 3b, 3c: Side guide 4a, 4b: Warpage detector 5: Control device 6: Leveler 7: Induction heating device 8: Radiation thermometer 9: Edge heater 10: Finish rolling mill 11: Table roll 12: Center line in the width direction of the coarse bar 13: Center line of the rolling line

Continued on the front page (72) Inventor Sadaka Masuda 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor Masaaki Yamamoto 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Stock Inside the company (72) Inventor Naoshichi Eda 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Kokan Co., Ltd. (72) Inventor Takuya Terauchi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Stock Company F-term (reference) 4E002 AD04 BA01 BD08 BD20 CA07

Claims (2)

[Claims] 1. A rough rolling step of roughly rolling a slab, and a finish rolling step of finish rolling a rough-rolled rough bar,
In the method of manufacturing a hot-rolled steel strip, between the rough rolling step and the finish rolling step, a flatness correction step of correcting the flatness of the rough bar and a rough bar heating step of heating the rough bar are performed. Performed in order, and between the rough rolling step and the flatness correction step, between the flatness correction step and the coarse bar heating step, and between the coarse bar heating step and the finish rolling step. And a guide step of guiding a passing position of the coarse bar in the width direction by a side guide, respectively. 2. A rough rolling device for roughly rolling a slab and a finish rolling device for finish rolling a rough bar after rough rolling are arranged.
In a rolling device for a hot-rolled steel strip, between the rough rolling device and the finish rolling device, a flatness correcting device for correcting the flatness of the coarsely-rolled coarse bar,
A coarse bar heating device for heating the coarse bar over the entire width direction is provided, and between the coarse rolling device and the flatness correcting device, between the flatness correcting device and the coarse bar heating device. And a rolling device for a hot-rolled steel strip, wherein side guides are provided between the rough bar heating device and the finish rolling device to guide the passing position of the rough bar in the width direction.