JPS6329237A - Detecting method for surface of hearth roll - Google Patents

Abstract

PURPOSE:To clearly observe the surface state of a hearth roll in a high- temperature furnace by photographing a picture with only an external strobe light source which radiates on object with light having higher illuminance than in-furnace background light. CONSTITUTION:The hearth roll 1 as the object is heated to high temperature in a continuous annealing furnace wall 2 and the surface of the roll 1 is detected by being detected by a camera 6. A strobe 5 is capable of radiating the surface of the roll 1 to larger than the illuminance of the background and also positioned so that when the surface of the roll 1 is radiated with light having higher illuminance than the background light, reflected light from the surface of the roll 1 never enters the visual field of the camera 6 directly. Further, the lens 7 of the camera 6 is set to 280mm focal length, a 157HX105Vmm determined field angle, and F8 diaphragm, the light emission time of the strobe 5 is set to <=1/(33600)sec, and an ASA1600 film is used. Thus, the surface condition of the hearth roll can be observed in the high temperature furnace clearly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical detection method for accurately observing the surface of a hearth roll heated to a high temperature in a furnace.

[Conventional technology]

For example, when annealing a copper strip in a continuous annealing furnace, 600 to 1
The steel plate is passed through an oxidizing or reducing atmosphere at 300°C, but the hearth roll used to transport the steel plate is used continuously for a long time, so its surface is subject to wear and conversely, the steel plate is exposed to wear. Adhering oxides or iron powder adhere and accumulate on the surface of the hearth roll, forming so-called build-up.

If such wear and build-up occur, the surface of the steel plate will be damaged while it is being conveyed on the hearth rolls, causing deterioration in the quality of the steel plate, and sometimes production operations will be immediately interrupted and the surface of the hearth rolls will be damaged. You will be forced to take care of the grinding.

Conventionally known countermeasures include changing the material of the hearth roll, coating the hearth roll surface with a thermal spray coating such as zirconia or alumina, cooling the inside of the hearth roll, and scraping the hearth roll surface during operation. Methods such as grinding have been proposed, and have shown some effectiveness, but no absolute countermeasure has been completed, and it will be necessary to wait for future research.

Therefore, there is a need for a means that can accurately observe the surface condition of the hearth roll during actual operation to detect the wear and build-up phenomenon of the hearth roll described above.

A means for observing the combustion state in the furnace using a monitoring television camera was introduced as an in-furnace combustion monitoring device in, for example, Japanese Patent Publication No. 59-26232, which monitors the combustion state in the furnace using a video signal output from a monitoring television. abnormal combustion is detected by focusing on the fluctuations in the furnace, that is, the frequency of changes in the video signal level.

[Problem that the invention seeks to solve]

However, although this in-furnace combustion monitoring device is effective in checking the combustion state in the furnace, it cannot be used as a means for accurately observing the surface of the hearth roll in the furnace.

On the other hand, if you try to take a photo to observe the surface of the hearth roll heated to a high temperature in the furnace, you will find that the temperature inside the furnace is uniform and that the entire field of the photograph emits orange light. If you passively stop receiving them, unless there is a temperature difference between the build-up parts that occur on the roll surface, the roll and build-up will appear to be the same color, making it difficult to tell them apart.

An object of the present invention is to provide a surface detection method that can clearly observe the surface condition of a hearth roll inside a high-temperature furnace, which eliminates such conventional drawbacks.

[Means and effects for solving the problem] That is, in the present invention, in a method of detecting the surface of a hearth roll heated to a high temperature in a furnace using optical means, This paper proposes a method for detecting the surface of a hearth roll in which photography is performed using only a strobe light source that emits light with higher illuminance than ground light. In this way, when the surface of the hearth roll, which is the object to be photographed, is illuminated with light that has a higher illuminance than the bank ground light, the coloring of the bank ground disappears,
The surface condition of the hearth roll can be clearly image analyzed.

The present invention will be explained in detail below using examples.

FIG. 1 is a conceptual diagram of a system that employs the method of the present invention, and is an example of a system that succeeded in photographing the surface condition of the hearth roll in the soaking zone of an annealing furnace during continuous annealing of steel plates.

In FIG. 1, reference numeral 1 denotes a hearth roll as a subject, 2 a continuous annealing furnace wall, and 3 a detection window, which is provided at the tip of a cylindrical observation tube 4 for heat protection. Note that N2 was used to purge the vicinity of the detection window to prevent fogging. No. 5 requires a strobe that has the ability to emit light to the surface of the hearth roll with an illuminance higher than that of the ground. Further, when the strobe irradiates the roll surface with light having a higher illuminance than the background light, the strobe is positioned so that the reflected light from the roll surface does not directly enter the camera's field of view. 6 is a camera that photographs the surface of the hearth roll, 7 is a lens, and 8 is a motor drive. Reference numerals 51 and 81 indicate power supplies for the strobe 5 and camera motor drive 8, respectively. 9 is a synchronous circuit, and the intermittent timer 10 is turned on.
This circuit detects the position of the hearth roll 1 with a proximity sensor 11, takes only one picture at the destination point, and when the hearth roll 1 is stopped, can take a picture of the stopped position. 12 is an amplification amplifier for the proximity sensor 11. In carrying out the present invention, the usage conditions regarding the selection of (i) lens, (ii) strobe light emission time, and (iii) strobe of the above-mentioned device were such that the following ranges were satisfied.

(i) Lens selection Calculated and focal length assuming that a field of 150H x 100V is desired from a distance of 1500M and that a depth of field of 10mm or more can be ensured taking into account the curvature of the roll.
280 Tsuru determined field of view 157HX105Vm aperture
Set it to F8.

(ii) Strobe light emission time In this example, the subject's hearth roll has a maximum circumferential speed of 7 m/
Since it rotates at a speed of seconds and the shooting distance is 1500 cages, the shutter speed must be 1 to obtain a still image.
/33600 seconds or less (pre-tolerance on film surface 50μ
m). However, with the mechanical shutters attached to existing cameras, the maximum speed is 1 /
It takes about 2000 seconds, and it is difficult to obtain a still image.

Therefore, in this embodiment, the strobe light emission time is 1/3
It is set to 3,600 seconds or less and functions as a shutter.

(iii) Strobe selection A strobe with the following capabilities is required.

b) Capable of emitting light at high speed with a light emission time of 1/33600 seconds or less.

mouth) The amount of light is effective G at the subject surface, N16 or more (AS
(When using A1600 film) Depth of field must be 10 cm or more.

The lens and strobe were selected so as to satisfy each of the above conditions, and photographs were taken of the surface condition of the hearth roll during actual operation in the annealing furnace (furnace temperature 800° C.).

Looking at the photograph, the build-up on the surface of the hearth roll is detected in the form of black dots. In addition, in the photograph showing the surface condition after surface grinding was attempted by contacting the hearth roll surface with a souffle bar during operation, traces of buildup peeled off by grinding were detected in the form of white dots, mixed with unpeeled buildup in the form of black dots. The situation is clearly photographed. In addition, the illuminance of the strobe should be lower than the bank ground light,
I took a photo of the same spot on the hearth roll surface, but the entire roll surface appeared red, making it difficult to distinguish between the build-up part and the surface. This is because the illuminance of the strobe is inferior to the bank ground light, so the roll surface and the build-up area appear to be the same color.

〔Effect of the invention〕

As understood from the above embodiments, the present invention allows the surface of a hearth roll heated to a high temperature to be photographed using only a strobe light source that emits light with higher illuminance than the background light. It is now possible to directly observe what is currently happening on the surface of the hearth roll in the furnace, such as build-up grain growth, disappearance status, roll wear status, etc., which will greatly contribute to the analysis of events over time in the furnace. It is an invention.

[Brief explanation of the drawing]

FIG. 1 is a system outline diagram of an embodiment of the present invention. ■... Hearth roll, 2... Continuous annealing furnace wall, 3...
・Detection window, 4... Observation tube, 5... Strobe, 6...
・Camera, 7... Lens, 8... Motor drive, 9... Synchronous circuit, 10... Intermittent timer, 11.
...Proximity sensor, 12...Amplifier, 51...Strobe power supply, 81...Motor drive power supply.

Claims (1)

[Claims] This method uses optical means to detect the surface of a hearth roll that is heated to a high temperature in a furnace. Photographs are taken using only an external strobe light source that irradiates the subject with light that is higher in intensity than the background light inside the furnace. A hearth roll surface detection method characterized by: