JPH0523708A - Method for detecting cut position of hot rolled steel sheet - Google Patents

Abstract

PURPOSE:To accurately cut a joined part and to improve the yield and productivity by coating a place to be cut on a steel material with paint on the inlet side of a rolling mill, continuously measuring radiation energy of the surface of the steel material on the outlet side of the rolling mill and detecting a cutting position through the change of the radiation energy. CONSTITUTION:The rear end of a preceeding rolled steel material and the tip end of the following rolled steel material are joined by a joining device 14 before they enter a finishing mill 10. Immediately after it, the joined part is coated by a paint spray gun 16 with paint. Surface temperatures of the steel material are measured by a radiation thermometer 18 continuously on the outlet side of the finishing mill. At this time, since an apparent temperature falls at the coated part only, by which it is decided to be a joined part and cut by a cutting machine 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a cutting position of a hot rolled steel material during continuous hot rolling of a steel strip.

[0002]

2. Description of the Related Art In the rolling process of an iron manufacturing plant, continuous lines are being promoted mainly for the purpose of improving yield and improving productivity.
In particular, what has recently been emphasized is a technique of joining hot-rolled steel products in front of a rolling mill and continuously rolling them. When it comes to finish rolling, at the initial stage of rolling 200 to 300 m / min,
In a steady state, rolling is performed at a high speed of approximately 1000 m / min, so continuous rolling is performed, that is, continuous rolling is always performed at a steady-state speed while sequentially joining the trailing edge of the preceding hot-rolled steel material and the leading edge of the subsequent hot-rolled steel material. Doing becomes important from the viewpoint of productivity improvement.

To date, many patents have been disclosed regarding the joining technique. There is some difficulty in joining coils one after another without stopping rolling,
This is because it requires some ingenuity. On the other hand, after joining and rolling, it is necessary to wind the coil around each coil, so that the joined portion once joined must be cut. However, as far as the inventor knows, there is no disclosure example of a patent regarding detection of a position to be cut. In this respect, conventionally, practically, there has been no choice but to predict the cutting position from the passing speed based on the elapsed time from the time when the joining is completed. In this case, it was generally said that there was a deviation of ± 20 m between the cutting position and the joint.

[0004]

The joint portion has no product value because it contains scale at the joint interface. Therefore,
The cutting position is preferably as close to the joint as possible.
If the joint is removed and cut, a coil containing a part with no product value will be generated, and it will be necessary to separately detect the joint on the rewinding line and excise it again, not only lowering the yield but also productivity. Is also reduced. Therefore, an object of the present invention is to properly recognize and cut the portion where the trailing edge of the preceding material and the leading edge of the following material are joined when cutting the steel strip on the exit side of the finishing rolling mill, and prevent the yield and the productivity from decreasing. Is to provide a way to do.

[0005]

Means for Solving the Problems As a result of various studies on means for achieving the above object, the present inventor applied a coating material to the joint portion after joining and before finish rolling, and radiated on the finish rolling side and before the cutting machine. Detects the difference in radiant energy on the surface of the steel strip with a thermometer,
By sending the signal to the cutting machine and operating the cutting machine, it was found that the above object was achieved, and the present invention was completed. The gist of the present invention is a method for detecting a cutting position of a hot rolled steel material, in which a coating material is applied in advance on a rolling machine entrance side at a planned cutting position after rolling of the steel material, and a steel material is provided on the rolling machine exit side. A method for detecting a cutting position of a hot-rolled steel product, which comprises continuously measuring radiant energy on a surface and detecting a cutting position from a change in the radiant energy.

According to a preferred embodiment thereof, the present invention is
Prior to finishing rolling, joining the leading end of the preceding hot-rolled steel material and the trailing hot-rolled steel material, after finishing rolling, a method for detecting the cutting position of the hot-rolled steel material at the time of cutting the joint portion of both, A coating is applied to the joining part in advance on the finishing rolling mill entrance side, the radiant energy on the steel surface is continuously measured on the rolling mill exit side, and the cutting position is detected from the change in the radiant energy. This is a method for detecting the cutting position of hot rolled steel.

[0007]

1 is a process diagram for carrying out the method according to the present invention. In the figure, before entering the finishing mill 10, steel
12, the rear end of the preceding rolled steel material and the front end of the subsequent hot-rolled steel material are appropriately joined by a joining machine 14. The joining operation itself may be performed by a conventional means, and may be performed by any means. Generally, arc welding is performed while the welding machine is running, and heating with a reducing flame and pressure welding are performed. Immediately after that, the paint is appropriately applied to the joint by the paint sprayer 16. After the joining is completed, finish rolling is performed by the finish rolling machine 10 as usual. The temperature on the surface of the steel material is continuously measured by the radiation thermometer 18 on the exit side of the finishing rolling mill. Even after the finish hot rolling, the paint is still attached to the joint-applied portion even after the finish hot rolling, so that the temperature drop in the joint portion is observed, and the position can be detected. After the position is detected, a position signal is sent to the cutting machine 20, and when that position comes to the position of the cutting machine, the cutting machine 20 is operated to cut the steel material, and then one coil is wound around the winder 22. The winding is finished and the winding on the next coil is started.
The cutting may be done by conventional means, such as a flying shear or a gas torch. There is no particular limitation.

As described above, according to the present invention, the coating material is applied to the joint portion by spraying or brushing immediately after joining.
The application timing may be determined by the elapsed time in consideration of the plate passing speed based on the completion of joining, for example. The error can be reduced by providing the joining machines as close to each other as possible. Alternatively, it may be applied while detecting the joint portion by an appropriate means. Detection is relatively easy at this stage since the joint has not yet been rolled. The application means is not limited to a specific one, but spray application is preferable because it is simple. The coating part is stretched during the finish rolling to reduce the thickness of the coating film, but even a very small amount of coating is not lost at the time of rolling. If the coating width is too narrow, detection will be difficult, while if it is too wide, detection error will be too large. A width of 50 to 200 mm is generally sufficient. The surface of the steel strip is observed with a radiation thermometer on the exit side of the finishing rolling mill and in front of the cutting machine. The principle of the radiation thermometer is based on the Planck's formula below.

J = 2 · ε · C ₁ · λ ⁻⁵ / exp (C ₂ / λT) −1 J: Radiant energy (W / cm ² · h · μm) ε: Emissivity (%) C ₁ : 3.7413 × 10 ⁴ (constant: W · cm ⁻² · μm ⁴ ) λ: wavelength (μm) C ₂ : 1.4788 × 10 ⁴ (constant: μm) T: temperature (° K) Then, as a preliminary experiment of the present invention, A silver paint (SC23 manufactured by Shinto Paint Co., Ltd.) was spray-coated on the surface of the steel sheet so that the width was 100 mm, and hot rolling was performed. After the rolling was completed, the surface temperature of the steel sheet was measured to see if the joint could be detected.

At T = 1173 ° K and λ = 1.1 μm, assuming the normal rolling section ε ₁ = 1.0, the coating coating section ε ₂ = 0.3. That is, in this case, J of the coating portion is reduced by 30%, that is, 70%, as compared with the normal rolling portion. This is fully detectable. Other experimental conditions are finish rolling exit speed 1
000 mpm, finishing entry side coating length 200 mm, plate thickness: entry side 30 mm
The exit side was 1.5 mm.

The results are shown graphically in FIG. The temperature of the steel plate should be constant at 1173 ° C, but the apparent temperature drops only at the coated part. Peak (valley) of this temperature change part
Is judged to be a joint and a signal is sent to the cutting machine, and the cutting machine downstream operates accordingly. The cutting timing at this time may be the same as in the case of the above-mentioned coating, and may be an elapsed time in consideration of the strip running speed with reference to the temperature measurement time point, that is, the joint detection time point.

[0012]

EXAMPLE In the present example, the present invention was carried out using the apparatus shown in FIG. The specifications of each device were as follows. (1) Joining machine Press type (2) Paint spraying machine Silver paint, spraying length 200 mm x plate central part 100 mm width, spraying time 1 second (3) Finishing rolling mill 4Hi x 7 steps Inlet plate thickness 30 mm Inlet speed 50 mpm Output side plate thickness 1.5 mm Output side speed 1000 mpm (4) Radiation thermometer λ = 1.1 μm Detection element Si response speed 10 ms (5) Cutting machine Drum type shear Both coating timing and cutting timing consider the passing speed. It performed based on the elapsed time.

As a result of rolling under the above-mentioned equipment sequence and conditions,
The deviation of the cutting position from the joining position was ± 300 mm, and good results were obtained. In this respect, according to the conventional method, after detecting the end portion at the position of the joining machine, the joining position after the completion of rolling is predicted by the rolling length prediction based on the position, and cutting is performed at the predicted position. Since the cutting position is estimated by the length from the joining position, the prediction error is ± 1%, and (20 ⁺ coil / 1.5 × 10 ^-3 × 1 × 7.85) × 1/100 = ± 17m and ± 17m That is, a large positional deviation is observed, which is not comparable with that of the present invention.

[0014]

As described above, according to the present invention, it becomes possible to correctly recognize and cut the joint portion by a very simple means of applying the coating material to the joint portion, and the yield which is strongly demanded by continuous rolling today. -Productivity is significantly improved.

[Brief description of drawings]

FIG. 1 is a process drawing of an apparatus for carrying out the present invention.

FIG. 2 is a graph showing the results of preliminary experiments of the present invention.

[Explanation of symbols]

10: Finishing mill 12: Steel 14: Joining machine 16: Paint spray machine 18: Radiation thermometer 20: Cutting machine 22: Winder

Claims (2)

[Claims] 1. A method for detecting the cutting position of a hot rolled steel material, wherein a coating material is applied in advance on the planned cutting position after rolling of the steel material on the rolling mill entrance side, and the radiant energy of the steel surface on the rolling mill exit side. Is continuously measured, and the cutting position is detected from the change of the radiant energy. 2. A method for detecting a cutting position of a hot-rolled steel product, in which a trailing end of a preceding hot-rolled steel product and a leading end of a subsequent hot-rolled steel product are joined prior to finish rolling, and after the completion of finish rolling, the joining portion of the both is cut. That is, the coating is previously applied to the joining portion on the entrance side of the finishing rolling mill, the radiant energy of the steel surface is continuously measured on the exit side of the rolling mill, and the cutting position is detected from the change in the radiant energy. A method for detecting a cutting position of a hot rolled steel material, which is characterized in that: