JPH02303619A - Method for heating hot sheet bar - Google Patents

Abstract

PURPOSE:To prevent a machine from being damaged by the collision of induction heaters with each other by stopping the movement in the width direction as soon as a distance between plural facing induction heaters is measured, the distance is compared with a set limiting distance and it comes under the set distance. CONSTITUTION:A distance between front end parts of the induction heating coils of the facing induction heaters 7A, 7B is measured by range finders 21, 22. Distance signals from the range finders are inputted into a moving command device 25 for commanding moving positions of the induction heaters, the distance (l) between the induction heaters 7A, 7B is set to operate a moving speed reference signal Vs. The moving position of the induction heater is controlled by a moving controller 26. The distance between two induction heaters is always controlled by an approach limiting distance (l) and as soon as it comes under its set distance the movement in the width direction is stopped. This method prevents the damage of the machine by the collision of the induction heaters with each other and can contribute to the stabilization of rolling operation.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for heating a hot sheet bar, and particularly to a method for heating the ends of a hot sheet bar in the width direction and longitudinal direction during rolling. .

<Prior art> In general, in hot rolling, a heated slab with a thickness of 120 to 300 mm is rolled as shown in FIG.
First, a sheet bar S with a thickness of 15 to 60 mm is rough rolled 811.
This sheet bar S is rolled into a conveyor table roller 2.
The product is transferred to a crop shear 3 through which the tip is sheared, then surface scale is removed by a high-pressure injection descaling device 4, and further finished rolled by a finishing mill 5 to the required product thickness. .

During the processing process from rough rolling to finish rolling, part of the heat retained in the hot sheet bar is released into the air, which is why the heat is released, especially at the side edges in the width direction. There was a problem in that the temperature at the side edges in the width direction was lower than that at the center, and the quality of the side edges of the finish-rolled product deteriorated.

Therefore, in order to solve the above problems,
As shown in the figure, a method has been proposed in which an edge heater 6 is installed upstream of the crop shear 3 to locally heat both ends of the sheet bar S to compensate for the temperature drop (for example, , "Tetsu to Hagane" No. 72 (1986),
No. 2, P, 177-178).

This edge heater 6 is provided in two sets corresponding to both side ends of the seat bar S, each having a pair of upper and lower induction heating coils 6a, 6b, so that even when the width of the seat bar S changes, the edge heater 6 It has a mechanism that follows the section.

However, the inventors of the present invention have conducted intensive studies on making the temperature distribution of hot seat bars uniform; and have found that heat dissipation from the seat bars occurs not only from the widthwise side ends, but also from the front and rear ends of the seat bars. It was discovered that the problem also occurs from the so-called longitudinal ends of the wafer, and as a result, it was found that there were various problems as described below.

(1) Material defects at the front and rear ends of the sheet bar; In finish rolling, the rolling is normally completed at the Ar3 transformation point or higher. However, in the conventional sheet bar rolling method described above, the local temperature drop at the leading and trailing ends of the sheet bar becomes below 3 points Ar, causing abnormal growth of crystal grains called so-called grain gloss. As a result, the workability of the product is reduced, and the rolling workability in the cold rolling step that is performed subsequent to the hot rolling step is also reduced.

(2) Occurrence of roll flaws: For sheet bars made of steel with high deformation resistance, if the above-mentioned material defects occur, when the tip of the sheet bar is bitten by the finishing roll, the roll will be plastically deformed and flaws will occur on the roll surface. arise. Therefore, there is a risk that the roll flaws will be transferred to the product surface and become surface defects, resulting in defective products. Therefore, the rolls must be replaced suddenly, which reduces the operating rate of the mill.

(3) Reduced product yield; To prevent the above problems, it is common to take measures to cut off the front and rear ends of the sheet bar.
Naturally, this will reduce the yield of the product.

(4) Decrease in productivity; In order to solve the problem of product yield decline in (3) above, it is considered best to heat the front and rear ends of the sheet bar. When attempting to heat the entire edge of the sheet, it is necessary to stop conveying the sheet bar or significantly reduce the conveying speed in order to achieve sufficient heating, which creates a new problem of reducing productivity. This will cause

Therefore, as one means for solving the above-mentioned problems, there is a method of heating a hot sheet bar, which has already been proposed by the present applicant in Japanese Patent Application No. 156375/1983. The contents will be briefly explained below.

First, as shown in FIGS. 3(a) and 3(b), an induction heating device 7A comprising a pair of upper and lower induction heating coils 8a and 8b.
, 7B are arranged to face each other in the width direction of the seat bar S, and the seat bar S is placed on the rail 9 via the wheels 10.
As shown in FIG.
3 is connected.

The amount of movement of the sheet bar S is detected by a measuring roll 14, its tip is detected by a tip detector 15, its surface temperature is detected by a temperature sensor 1G, and its moving speed is detected by a speed detector 17. and are manually input to the controller 11.

Since the target temperature is set in the controller 11, it calculates the difference between the measured surface temperature and the seat bar S while controlling the output of the high frequency power source 12 based on the detected moving speed signal. By stopping the conveyance or reducing the conveyance speed and moving the induction heating devices 7A and 7B in the width direction, the tip of the sheet bar S is heated to compensate for the temperature drop. At that time, two induction heating devices 7A are used.

The positional relationship of 7B moves so as to always maintain the approach limit distance 2, which is set as the maximum distance without contacting each other.

Next, both end portions in the width direction of the seat bar S are heated over the entire length in the longitudinal direction, and the rear end portion of the seat bar S is heated in the same manner as the tip portion to compensate for the temperature drop.

<Problems to be Solved by the Invention> However, the above two opposing induction heating devices 7
It may not be possible to always maintain the approach limit distance 2 between A and 7B due to the following reasons, so avoid mechanical damage due to collision between induction heating devices 7A and 7B. There is a risk of inviting

(2) The speed reference signal may be erroneously output from the controller 11 that controls the running of the induction heating devices 7A and 7B, resulting in malfunction.

(2) When the induction heating devices 7A and 7B are moved manually, there is a possibility that the distance between the induction heating devices 7A and 7B may be misjudged and the operation may be performed incorrectly.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a method for heating a hot sheet bar suitable for preventing machine damage even if there is a malfunction or erroneous operation. .

<Means for Solving the Problems> The present invention provides a method for heating the widthwise ends of a sheet bar that has been roughly rolled in a rough rolling mill before finishing rolling in a finishing mill. A plurality of movable induction heating devices are arranged to face each other in the width direction of the sheet bar, and when the longitudinal end of the sheet bar is conveyed to the heating area of the induction heating device, the sheet bar is conveyed. Then, the induction heating device is moved in the width direction of the sheet bar while heating the sheet bar, and the distance between them is measured. This method of heating a hot sheet bar is characterized in that the movement in the width direction is immediately stopped when the distance becomes less than a set approach limit distance.

Effects> According to the present invention, the distance between a plurality of facing induction heating devices is measured, and the distance is compared with a preset approach limit distance to ensure that the distance is less than or equal to the set distance. Since the movement in the width direction is immediately stopped when the heating sheet bar is heated, the induction heating devices do not collide with each other (it is possible to stably heat the front and rear ends of the hot sheet bar).

<Example> Below, an example of the present invention will be described in detail with reference to FIG. In the drawings, the same members as in the conventional example are designated by the same reference numerals.

In the figure, 21 and 22 are, for example, laser distance meters, which are attached to the tops of the induction heating devices 7A and 7B, respectively, and measure the distance to the tip of the induction heating coil of the opposing induction heating device. do.

23 is a drive device such as a motor for driving the induction heating devices 7A and 7E3, and is attached to the shaft of the wheel 10 running on the rail 9.

24 is a rotational speed detector of the drive device 23.

Reference numeral 25 denotes a movement command device that commands the movement position of the induction heating devices 7A and 7B, into which the distance signals from the distance meters 21 and 22 are input, and the approach limit distance 2 between the induction heating devices 7A and 7B. is set, the moving speed reference signal V,
Calculate.

26 controls the movement position of the induction heating devices 7A and 7B.
It is a movement control device that inputs the speed signal from the rotation speed detector 24 and controls the rotation speed of the drive device 23 by comparing it with the movement speed reference signal v8 calculated by the movement command device 25.

With this configuration, two induction heating devices 7
The distance between A and 7B is always controlled by the approach limit distance 2, and if it exceeds this distance, a stop signal is immediately output to the drive device 23 via the movement control bag W26. Since collisions between the induction heating devices can be prevented, it is possible to reliably heat the front and rear ends of the hot sheet bar S.

In addition, the approach limit distance between the induction heating devices 7A and 7B! The size of the drive device 2 that drives the induction heating devices 7A and 7B is
The value is determined for each device depending on the output of the 3rd generation and the inertia (GD'') of the mechanical system, and may be set to, for example, 70C11.

Further, the distance meters 21 and 22 may be of a laser type, for example, a position detector may be attached to the drive device 23, or a limit switch may be used.

<Effects of the Invention> As explained above, according to the present invention, it is possible to prevent damage to the machine due to a collision between the induction heating devices installed opposite to the width direction of the hot sheet bar and movable in the width direction. This reduces equipment maintenance costs and greatly contributes to stabilizing rolling operations.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the main parts of an apparatus for implementing the hot sheet bar heating method according to the present invention, FIG. 2 is a side view showing a conventional example of hot rolling, and FIGS. The figure is an explanatory diagram showing a conventional example of a heating method for a hot sheet bar. 7... Induction heating device, 8... Induction heating coil. 21, 22... Distance meter, 23... Drive device. 24... Rotation speed detector. 25...Movement command device, 2G...Movement control device. S... Seat bar. Patent applicant: Kawasaki Steel Corporation Figure 1

Claims (1)

[Claims] A method for heating the widthwise ends of a sheet bar that has been roughly rolled in a rough rolling mill before finishing rolling in a finishing mill, the method comprising: a plurality of induction heating movable in the width direction of the sheet bar; The devices are disposed so as to face each other in the width direction of the sheet bar, and when the longitudinal end of the sheet bar is conveyed to the heating area of the induction heating device, the conveyance of the sheet bar is stopped or the conveyance speed is adjusted. Then, the induction heating device is moved in the width direction of the seat bar while heating the seat bar, the distance between them is measured, and the distance is less than or equal to a preset approach limit distance. A heating method for a hot sheet bar, characterized in that the movement in the width direction is immediately stopped when the temperature is reached.