JPH0527488B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to the hot rolling of steel strips, in which a roughly rolled hot sheet bar is subjected to winding and unwinding steps using a coiler, and then finish rolling is performed. , relates to a heating method for recovering the temperature drop at the innermost diameter portion of the hot sheet bar coil wound by the coiler.

<Conventional technology> The conventional method of rolling a hot sheet bar in steel strip rolling will be explained below.
The hot sheet bar rolled by the rough rolling mill is transferred to a crop shear by conveying table rollers, and after shearing the tip, it is finished rolled by a finishing mill. During the processing steps from rough rolling to finish rolling, a portion of the heat held by the hot sheet bar is dissipated into the atmosphere. Since the amount of heat dissipated increases in proportion to the processing time, there is a difference in the amount of heat dissipated into the atmosphere between the tip and tail ends of the hot sheet bar in the longitudinal direction, resulting in heat dissipation as shown in Figure 3. The temperature of the seat bar is lower at the tail end than at the tip. The same applies to the width direction, and the widthwise end portions are lower in temperature than the center portion.

When the temperature distribution of the hot sheet bar is uneven in this way, it is difficult to adjust the rolling position of the finishing rolling mill, and there is a problem that it is not possible to roll products of uniform thickness and material. In order to solve this problem, for example,
Publication No. 30028, Special Publication No. 51-26317, Special Publication No. 52
As disclosed in Japanese Patent No. 45304 and the like, it has been proposed to install a coiler between a rough rolling mill and a finishing mill to equalize the temperature distribution in the longitudinal direction of the hot sheet bar.

As shown in FIG. 4, this rolling equipment is provided with a coiler 3 for winding and unwinding the hot sheet bar 1 between a rough rolling mill 2 and a crop shear 4.
Note that the hot sheet bar 1 is transferred to the coiler 3 on conveyance rollers 5. Also,
In the coiler 3, the hot sheet bar 1 is once wound up into a coil shape, and the hot sheet bar 1 is heat-retained and uniformized by its own heat. After the hot sheet bar 1 is soaked, it is rewound and transferred to the crop shear 4.
After that, it enters a finishing mill 10 where it is finished rolled.

Also, "Tetsu to Hagane" No. 72 (1986) No. 2, No. 177
On pages 178 to 178, it is proposed to install an edge heater using an induction heating coil just before the finishing mill to raise the temperature of the edge portion of the hot sheet bar.

FIG. 5 shows the arrangement of the induction heating coils, in which a plurality of pairs of upper and lower induction heating coils 6 are installed between the conveying rollers 5 at both edge portions of the hot sheet bar 1. Each pair of upper and lower induction heating coils 6 has a mechanism that follows the position corresponding to the edge portion of the hot sheet bar 1 even if the width of the hot sheet bar 1 changes. In addition, the induction heating coil 6
The capacity of the hot sheet bar 1 changes depending on the gap between the hot sheet bar 1 and the induction heating coil 6, but in order to avoid contact with the induction heating coil 6 due to warping of the tip of the hot sheet bar 1, a gap adjustment mechanism is provided. In general, the gap is made large until the tip of the hot sheet bar 1 passes, taking into account warpage, and after the tip passes, the gap is made smaller.

As described above, in order to prevent uneven temperature distribution in the longitudinal and width directions of the hot sheet bar between the rough rolling mill and the finishing mill, the winding/unwinding coiler and edge heater are used. This has been proposed in recent years.

<Problems to be Solved by the Invention> However, in this method, although it is possible to prevent the temperature drop at the edge portion of the hot sheet bar by using an edge heater, the following method is required to prevent uneven temperature distribution in the longitudinal direction. I had a problem. That is, while the hot sheet bar 1 is being heat-retained and uniformized by the coiler 3, the innermost diameter portion of the coil of the hot sheet bar 1 is exposed to the atmosphere, and heat radiation progresses. and,
When the temperature distribution of the hot sheet bar 1 at the entry side of the finishing rolling mill 5 is measured, as shown in FIG. 6, from the tip to the tail end of the hot sheet bar 1, the temperature distribution is
Although the temperature is uniform, the temperature of the first turn at the innermost diameter shows a sudden drop.

As a result, when the hot sheet bar 1 is finish rolled, the deformation resistance of the portion where the temperature is decreasing becomes higher in a stepwise manner than other portions. In order to cope with this deformation resistance, the rolling position of the finishing mill 10 is controlled by an automatic plate thickness control device. However, since this automatic plate thickness control device has a response delay, it cannot follow the step-like change in deformation resistance.

Therefore, the thickness of the strip corresponding to the innermost diameter part after finishing rolling is about 100μ thicker than other parts, as shown in Figure 7, and there is a problem that the thickness accuracy cannot be ensured. It was hot.

The present invention provides a method for heating a hot sheet bar that solves the above problems.

<Means for solving the problem> The present invention increases the gap between the induction heating coil and the hot sheet bar in consideration of the warpage of the hot sheet bar tip until the hot sheet bar passes through. Nitori,
The conventional method of narrowing this gap after the tip of the hot sheet bar has passed has low heating efficiency and setting the heating capacity with a large gap, so when the gap is narrowed, the excess heating capacity is Taking note of the fact that this occurs, this extra heating capacity is used to increase the temperature of one turn of the innermost diameter portion of the hot sheet bar coil.

That is, the present invention provides a method for heating a hot sheet bar that has been subjected to a coil winding/unwinding process using a plurality of sets of heating devices that are installed upstream of a finishing mill and are movable up and down and in the width direction. Initially, the heating device is set at the edge of the hot sheet bar to heat it, and then the heating is performed based on a passing signal of the tip of the hot sheet bar detected by a detector installed downstream of the heating device. Narrowing the gap between the device and the hot sheet bar tube to heat the tube, and stopping the output of at least one set of the heating devices, and then moving the heating device whose output has been stopped to the center in the width direction of the hot sheet bar. Then, based on a passing signal from the tip of the innermost diameter part of the hot sheet bar during coil winding, the heating device that had stopped the heating is made to output power again. As described above, these heating devices are arranged symmetrically in pairs, upper and lower, with the hot sheet bar in between, so one set is composed of at least four devices of the same type.

<Function> In the method of the present invention, first, a plurality of sets of heating devices are set at the edge portion of a hot sheet bar to heat the hot sheet bar, and then the hot sheet is detected by a detector installed downstream of the heating device. Based on the passing signal from the tip of the bar, the gap between the heating device and the hot sheet bar is narrowed to heat the bar, and the output of at least one set of the heating devices is stopped, and then the heating device stops the output. The heating device is moved to the center in the width direction of the hot sheet bar, and the heating device that has stopped the heating described above is output again based on the passing signal of the tip of the innermost diameter part during coil winding of the hot sheet bar. By doing so, the temperature of one turn of the innermost diameter portion of the hot sheet bar coil can be increased.

<Example> A first example of an apparatus used for carrying out the present invention is described below.
This will be explained based on the diagram. Reference numerals 6a and 6b each indicate a plurality of pairs of upper and lower upstream and downstream induction heating coils, and each induction heating coil can separately control its output and adjust its position in the width direction. A detector 7 is installed on the upstream side to detect when the tip of the hot sheet bar 1 enters the upstream induction heating coil 6a. 8 is a detector installed on the downstream side to detect when the tip of the hot sheet bar 1 passes through the downstream induction heating coil 6b. Reference numeral 9 indicates that the upstream and downstream induction heating coils 6a,
6b and the position in the width direction of the upstream induction heating coil 6a.

Next, the method of the present invention will be explained with reference to FIG. In FIG. 2, point A on the horizontal axis indicates when the tip of the hot sheet bar 1 passes the upstream detector 7, and point B indicates when the tip of the hot sheet bar 1 passes the downstream detector 8. Point C indicates the time when the tip of one turn of the innermost diameter portion of the hot sheet bar coil passes the upstream detector 7. FIG. 2a shows the output of the upstream induction coil 6a and downstream induction coil 6b, and FIG. 2b shows the gap between the upstream induction coil 6a and the downstream induction coil 6b. 2c shows the widthwise positions of the upstream induction coil 7a and the downstream induction coil 7b.

Therefore, when the upstream detector 7 detects the tip of the hot sheet bar 1 (point A), the upstream and downstream induction heating coils 6a and 6b are not damaged due to the warpage of the tip of the hot sheet bar 1. Through the control device 9, the upstream and downstream induction heating coils 6a,
6b is widened and the output of the upstream and downstream induction heating coils 6a and 6b is increased.

Next, when the downstream detector 8 detects the tip of the hot sheet bar 1 (point B), the control device 9 narrows the gap between the induction heating coils 6a and 6b, and At the same time as stopping the output, this downstream induction heating coil 6b is connected to the hot seat bar 1.
further, the output of the upstream induction heating coil 6a is adjusted to an output corresponding to the amount of heat increase required to raise the temperature of the edge portion of the hot sheet bar 1. Note that by narrowing the induction heating coil after passing through the hot sheet bar 1 as described above, the heating efficiency is significantly increased, and the required amount of heat increase can be covered only by the upstream induction heating coil 6a.

Next, 1 of the innermost diameter part of the hot sheet bar coil 1
When the upstream detector 7 detects the passing of the tip of the winding (point C), the downstream induction heating coil 6b is outputted again, thereby increasing the temperature of the first winding at the innermost diameter part of the hot sheet bar coil. be able to.

At this time, since the innermost diameter of the hot sheet bar coil 1 is constant, it is convenient to arrange the distance between the upstream detector 7 and the downstream induction coil 6b to match this innermost circumference. The passage of the tip of one turn of the innermost diameter portion of the hot sheet bar coil may be predicted by a tracking method.

Note that the functions of the upstream and downstream induction heating coils may be reversed. Furthermore, although the embodiments of the present invention have been described using induction heating, the present invention is not limited thereto, and the same objective can be achieved using other heating means.

To explain more specific effects, thickness 3
This is an example in which the present invention is applied to rolling a SUS304 steel strip with a width of 1000 mm. The capacity of each induction heating coil is
4600kW, and when heating the inner winding of the hot sheet bar coil, the downstream induction heating coils were moved to a position 250mm from the center in the width direction.
The output was 2300kW, and the average temperature in the width direction of one turn of the innermost diameter portion of the hot sheet bar coil was increased by 15°C.
As a result, in the conventional technology, the thickness of one turn at the innermost diameter part of a hot sheet bar coil was increased by 100μ,
With the method of the present invention, the increase in plate thickness could be limited to a few microns.

<Effects of the Invention> As described above, according to the method of the present invention, winding and
It is possible to efficiently prevent the temperature drop of the innermost turn of the hot sheet bar coil due to the use of the unwinding coiler, and has the effect of suppressing the increase in plate thickness.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of one embodiment of the apparatus used to carry out the present invention. FIG. 2 shows one embodiment of the present invention, and shows the positional relationship between the hot sheet bar and the upstream and downstream detectors, as well as the outputs and widthwise positions of the upstream and downstream induction heating coils. FIG. 3 shows the temperature at the tip and tail ends of a hot sheet bar on the entry side of a conventional finishing mill. Figure 4 shows the conventional winding
FIG. 2 is an explanatory diagram of a hot rolling facility having an unwinding coiler device. FIG. 5 shows the arrangement of the induction heating coil, with FIG. 5a being a side view and FIG. 5b being a plan view. FIG. 6 shows the temperature at the tip and tail ends of a hot sheet bar on the entry side of a finishing mill in a hot rolling facility having a conventional winding/unwinding coiler device. 7th
The figure shows the amount of thickness variation at the tip and tail end of a strip after finish rolling in a hot rolling facility equipped with a conventional winding/unwinding coiler device. 1... Hot sheet bar, 2... Rough rolling mill, 3... Winding/unwinding coiler, 5... Conveyance roller, 6a... Upstream induction heating coil, 6b... Downstream induction heating coil, 7... Upstream detector, 8...Downstream detector, 9...
Control device.

Claims (1)

[Claims] 1. In a method of heating a hot sheet bar that has been subjected to a coil winding/unwinding process using multiple sets of heating devices that are installed upstream of a finishing mill and are movable up and down and in the width direction, the above-mentioned heating is performed first. The device is set at the edge of the hot sheet bar to heat it, and then, based on the passing signal of the tip of the hot sheet bar detected by a detector installed downstream of the heating device, the heating device is connected to the hot sheet bar. heating by narrowing the gap between the sheet bars, and stopping the output of at least one set of the heating devices, and then moving the heating device whose output has been stopped to the center in the width direction of the hot sheet bar, A heating method for a hot sheet bar, characterized in that the heating device that has stopped the heating is made to output power again based on a passing signal from the tip of the innermost diameter part of the hot sheet bar during the coiled winding.