JPH0824932A - Continuous hot rolling method of slab - Google Patents

Abstract

PURPOSE:To achieve the continuous hot rolling with high productivity by adjusting the opening of a side guide according to the expansion of the width of a joined part due to the rolling. CONSTITUTION:In achieving the continuous rolling, the rear end part of a preceding slab 1 and the fore end part of a succeeding slab 2 cut by a cutting device are adjusted to be positioned at a joining equipment, and the slabs 1, 2 are heated in this condition and pressed against each other to be joined. These slabs are fed to a finish rolling mill to achieve the hot finish rolling. When the joined part is brought close to a side guide 9 arranged immediately before a work roll 11 by passing the slabs 1, 2, the preset opening (a) of the side guide 9 to the width of a regular width part of the slab is changed to the opening (b) according to the expansion of the width of the joined part. The opening (a) is newly set after passing the joined part. This constitution prevents the meandering in the vicinity of the joined part and at the regular width part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention joins steel pieces such as a sheet bar, slab, billet or bloom,
The present invention relates to a method of continuously rolling several to several tens of wires, and particularly proposes a method capable of performing stable striping while avoiding interference with a side guide.

[0002]

2. Description of the Related Art Conventionally, in a hot rolling line, steel pieces to be rolled are subjected to rough rolling one by one and then finish rolling to finish them to a predetermined thickness. In finish rolling, line stoppage was likely to occur due to defective biting of the rolled material, and the yield was significantly reduced due to defective shape of the leading end and the trailing end of the rolled material. Therefore, recently, in order to avoid the above-mentioned problems, a rolling method in which the front end portion and the rear end portion of these steel pieces are connected to each other prior to finish rolling, and this is continuously supplied to a hot rolling line has been proposed. It has come to be adopted (for example, JP-A-58-122109).

As a method of joining the steel pieces for enabling such continuous rolling, the front end of the preceding steel piece and the front end of the following steel piece are provided at the entrance side of the finishing rolling equipment for the steel pieces. Butt a small gap between them and place coils for induction heating directly above and just below the ends of the butted steel pieces, and supply AC power to the pair of coils to induce induction heating of the steel pieces ends. However, JP-A-62-234679 proposes a method for joining steel pieces in which both steel pieces are welded by pressing each other.

[0004]

However, according to the billet joining method using induction heating as described above, since the eddy current induced in the billet by the coil is hard to pass through the corner portion of the billet, The amount of temperature rise in the corner portion of the steel piece is smaller than that in the end surface of the steel piece other than the corner portion. Therefore, as a result of not joining the corner portions when pressing both steel pieces, an unjoined portion remains at the end portion in the width direction.

When finish rolling is performed in such a state,
Since the width ends are not joined, the width in the vicinity of the longitudinal direction of the joint part locally widens with rolling, so this joint part prevents rolling material centering and camber during striping. For this reason, there is a problem that the side guides installed between the stands are brought into contact with each other, which leads to problems such as defective threading and plate breakage.

The present invention advantageously solves the above problems, and an object of the present invention is to propose a continuous hot rolling method for a steel slab capable of stably passing a joint in finish rolling.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a trailing end portion of a preceding steel piece that has been subjected to rough rolling in hot rolling, and a leading end portion of a following steel piece that has undergone rough rolling following this steel piece. And, joined at the entrance side of the finishing rolling equipment consisting of rolling mills with a plurality of stands, and feeding these steel pieces to the above finishing rolling equipment for continuous finish rolling, a continuous hot rolling method for billets. In, when the joint between the trailing end of the preceding steel slab and the leading end of the following steel slab passes through a pair of side guides installed between the stands of the finishing mill, the opening of this side guide is It is a continuous hot rolling method for a steel slab, which is characterized in that it is adjusted according to the width expansion of the joined portion by rolling.

In the present invention, the plate width measuring device installed between the stands of the finish rolling mill measures the width expansion amount of the joint portion and its vicinity during the finish rolling, and the plate width measurement is performed based on the measured value. It is preferable to adjust the opening of the side guide between the stands on the downstream side of the container.

[0009]

The present invention will be described in more detail with reference to the drawings. FIG. 1 schematically shows an example of hot rolling equipment suitable for carrying out the present invention. In the figure, number 1 is a preceding steel slab that has passed through the rough rolling mill 3 (hereinafter referred to as the preceding steel slab), 2 is a subsequent steel slab that is subsequently conveyed to the preceding steel slab 1 (hereinafter referred to as the following steel slab) 4 is rolling mill stand F1, F2, ----- F
7 is a tandem hot rolling mill, 5 is a cutting device that cuts the trailing end of the leading steel strip 1 and / or the leading end of the trailing steel billet, and 6 is the cutting steel strip 1 A joining device for heating and pressing the rear end portion and / or the front end portion of the trailing steel piece 2, 7 is a scale breaker for removing scale generated on the surface of the steel pieces 1, 2 prior to finish rolling, 8 is an edger, 9 is a side guide between stands,
10 is a board width measuring device.

When performing continuous rolling using the above equipment, first, the trailing end of the preceding steel piece 1 and the leading end of the following steel piece 2 cut by the cutting device 5 are joined by the joining device 6
Are adjusted so that they come to the position of, and in this state, both steel pieces are heated and pressed against each other to join them. As described above, a part of the steel pieces joined in this way has an unjoined portion at the end in the plate width direction. However, the steel pieces are fed to the finish rolling mill 4 to perform hot finish rolling. Then, the shape in the vicinity of the joint changes as shown in time series in FIGS. 2 (a) to 2 (d). That is, the joint at the end of the plate width is opened in the longitudinal direction due to rolling, and a local width expansion occurs. For this reason,
The opening of a pair of side guides placed on both sides of the billet is used to effectively center the rolled material and prevent camber.
In the conventional case where it was set close to the plate width of the steady part, when the part near the joint passes, it contacts the side guide,
As described above, a problem such as a defective threading occurs.

In order to solve such a problem, the gist of the present invention is to adjust the opening of the side guide according to the width of the joint and its vicinity. FIG. 3 is a plan view in the vicinity of the side guides shown in time series (a) to (c) in order to explain the method of operating the side guides according to the present invention. When the joining part comes close to the side guide 9 placed immediately before the work roll 11 due to the passage of the steel pieces 1 and 2, the setting guide of the side guide 9 for the width of the steady part of the steel piece as shown in FIG. When the joint passes between the side guides 9 from the state a, the opening b is changed according to the width expansion of the joint as shown in FIG. Further, after passing through the joining portion, as shown in FIG. 7C, it is quickly returned to the steady portion set opening degree a '. Here, when the plate widths of the preceding billet 1 and the following billet 2 are the same, the set opening a'for the following billet may be equal to the opening a for the preceding billet. If the board width is different, use the value corresponding to it.

During the period when the opening is changed, the original purpose of the side guide is to prevent the meandering and bending from being limited as much as possible during the passage of the side guide area in the area where the width is increased in the vicinity of the joint. It is desirable for effective performance. For this reason, it is a matter of course that the opening degree is changed in accordance with the tracking of the welded portion in advance, but since the width expansion occurs over a predetermined range in the longitudinal direction from the welded portion, a change in the width of the billet occurs. It is also important to grasp the longitudinal region that is present. The region of width change also changes depending on the width of the unbonded part, but it is about 5-10% of the plate thickness before finish rolling on the preceding material side.
2 times the length before the finish rolling on the trailing material side
It is a length corresponding to 5 times. The amount of width expansion is about 0.5 to 2 times the plate thickness before finish rolling. The opening may be set based on these predicted values or actual values, but a plate width gauge 10 is installed between the stands and the side guide opening on the entrance side of the next stand is corrected by the measured value, and It is also effective to add the predicted value of the width expansion amount at the stand to set the side guide opening on the entrance side after the stand one after another.

[0013]

Example Continuous hot rolling was carried out in the following manner using the hot rolling equipment shown in FIG. 1 above. As the billet, a sheet bar having a width of 1600 mm and a thickness of 30 mm was used for both the leading and trailing billets as the size after rough rolling. Now, after cutting the trailing end of the preceding sheet bar and the leading end of the trailing sheet bar by a cutting device, respectively, align the trailing end of the leading sheet bar and the leading end of the trailing sheet bar with the joining device position, and in this state Heat the sheet bar by high frequency induction heating for 10 seconds,
After melting the end faces, a pressing process was performed to join the steel pieces. At this time, the temperature rise was insufficient in the area of about 100 mm from the plate edge, and the joining was not performed. After this,
The joined sheet bar was subjected to finish rolling to obtain a hot rolled sheet having a thickness of 3 mm.

In the finish rolling, first, as a comparative example, the side guide opening in the finish rolling mill was fixedly set to 1650 mm, which is larger than the normal set value of 1610 mm, and the strip was rolled. The maximum value of the plate width near the joint after finish rolling was 1640 mm, which was within the range of the side guide opening, but meandering occurred in the finish rolling machine, and the plate thickness of the product was about 30 μm on the left and right in the width direction. In addition to the above difference, the material spreads to one side at the preceding material stationary part before the joining part is threaded, so that the widened part hits the guide and may be broken and broken.

Next, as an example, after joining both steel pieces in the same manner as described above, finish rolling was performed by sequentially changing the opening of the side guide only when the joining portion was threaded. Side guide opening is steady
1610mm, F2-F3 opening is 1640mm, F
4 to F5 are 1645 mm and F6 to F7 are 1650 mm. The speed of the material entering the finishing mill was 1000 mm / s, and the timing of changing the side guide opening of each stand was set to 0.5 seconds before the time when the joint was engaged with the guide. This is the material before finish rolling
It is equivalent to 500 mm, which is slightly earlier, but was decided considering the responsiveness of the guide opening change and the tracking error of the joint. In addition, 0.3 seconds after the joint passed, the side guide opening was returned to the set value for the steady part. As a result, it was possible to perform stable rolling without causing meandering or contact at the joint.

Further, a plate width meter was installed between F1 and F2 and between F5 and F6, and the guide was adjusted based on the measured values. That is, the plate width change after F1 where the width change is large is measured, and the F2 entrance side guide opening is corrected, and F3 to F5 are also corrected.
For the entrance side guide, the opening was set by adding the predicted value of the width expansion amount at each stand. In addition, in order to make accurate settings in the latter stage where there is a high possibility of narrowing down,
The guide settings for the F6 entry side and the F7 entry side were set using the measured values of the plate width between 6 and 6. The setting was changed by calculating the time required to reach each side guide from the position of the plate width meter using the material speed between the stands calculated from the roll speed, and delaying the output of the plate width meter during this period. . As a result, it is possible to reliably guide the joint to the immediate vicinity, and especially, the bending near the joint is improved, and contact due to the prediction error of the width spread is eliminated.

[0017]

As described above, according to the present invention, during finish rolling of the joint, the opening of the side guide is opened or adjusted only when the joint passes, so that the joint having a wide width can be stably threaded. Therefore, continuous hot rolling with high productivity can be realized without causing meandering in the vicinity of the joint and in the steady part.

[Brief description of drawings]

FIG. 1 is a schematic diagram of hot rolling equipment suitable for use in implementing the present invention.

FIG. 2 is a diagram showing, in a time series manner, a change in the shape of a steel slab in the vicinity of a joint portion due to rolling in (a) to (d).

FIG. 3 is a diagram showing, in a time series manner, the opening states of the side guides when the joining portion is threaded according to the present invention (a) to (c).

[Explanation of symbols]

 1 Leading steel strip 2 Trailing steel strip 3 Rough rolling mill 4 Hot finishing rolling mill 5 Cutting machine 6 Joining device 7 Scale breaker 8 Edger 9 Side guide 10 Sheet width gauge 11 Work roll

Front page continuation (72) Inventor Toshio Imae 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Steel Research & Development Division Steel Research Laboratory (72) Inventor Kunio Isobe Kawasaki-cho, Chiba-shi, Chiba No. 1 Kawasaki Steel Co., Ltd. Steel Research and Development Division, Steel Research Laboratory (72) Inventor Shigeru Isoyama 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Chiba Works

Claims (2)

[Claims] 1. A rolling mill having a plurality of stands, comprising a trailing end portion of a preceding steel piece subjected to rough rolling of hot rolling and a leading end portion of a following steel piece subjected to rough rolling following this steel piece. In the continuous hot rolling method for billets, which is performed by joining at the entrance side of the finish rolling equipment consisting of, feeding these billets to the above finishing rolling equipment and continuously performing finish rolling. When the joint between the end and the tip of the following steel slab passes through a pair of side guides installed between the stands of the finish rolling mill, the opening of this side guide is set to the width of the joint widened by rolling. A method for continuously hot rolling a steel slab, which is characterized in that 2. The method according to claim 1, wherein a plate width measuring device installed between stands of a finish rolling mill measures a width expansion amount of a joint portion and its vicinity during finish rolling, and based on the measured value. The method for continuous hot rolling of steel slabs, wherein the opening of the side guide between the stands on the downstream side of the strip width measuring device is adjusted.