JPH0321606B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for monitoring and automatically removing build-up occurring on the surface of a hearth roll in a non-oxidizing continuous heating furnace.

As is well known, a non-oxidizing continuous hot-dip galvanizing furnace is a furnace for cleaning and activating the surface of a strip as a pretreatment when applying hot-dip galvanizing to the strip, and its structure is shown in Figure 1. As shown in
A non-oxidizing heating zone 1 for incinerating and removing oils and fats adhering to the strip surface, H ₂ - N ₂ , a heating and soaking zone 2 for reducing and activating the steel surface in atmospheric gas, and a cooling zone 3 for cooling to a predetermined temperature. There is a cold holding zone 4 and zone divisions, and the strips 6 on the hearth rolls 5 arranged at approximately equal pitches in the furnace are cleaned and activated while driving the hearth rolls 5. The steel plate whose surface has been cleaned and activated in the continuous hot-dip galvanizing furnace 10 is immersed in the molten zinc bath 7, and the traveling direction is changed by sink rolls in the bath and pulled upward.

Since the hearth roll of this non-oxidizing continuous melting furnace is used at high temperatures (500 to 1250℃),
Heat-resistant steel (25Cr−20Ni) different from general structural steel
However, there is a problem in that scale builds up on the roll surface and causes a type of indentation scratch on the product. Build-up is mainly caused by scale on the strip surface adhering to and depositing on the hearth roll, and it tends to occur in the non-oxidizing heating zone and the front roll of the heating and soaking zone. FIG. 2 shows an example of how build-ups occur, and as shown in the figure, the surface of the hearth roll 5 is usually dotted with protruding build-ups 8.

Conventionally, methods used to counter this build-up include early replacement of the built-up hearth roll, thermal spraying of ceramic material on the roll surface, and water cooling of the inside of the hearth roll. However, method (2) not only requires time to replace the rolls and has problems with the timing of operations, but also has the drawbacks of unavoidable problems such as product defects until the rolls are replaced, decreased productivity due to interruptions in operations, and increased roll costs. Although the method (2) has the advantage of extending the period until build-up occurs, it has the problem that indentation flaws occur until the hearth roll is replaced, as in the case where build-up occurs. A further method can prevent build-up due to the roll cooling effect, but
The disadvantage is that the thermal efficiency of the furnace is significantly reduced.

This invention was made in order to solve the above-mentioned conventional problems, and its characteristics are that a contact body such as a back-up roll or scraper plate for removing build-up is provided inside the furnace, which is operated by a drive device, and the hearth According to the occurrence of build-up determined by optically detecting the surface properties of the roll or strip, a contact member such as the back-up roll or scraping plate is pressed against the hurl roll to compress or scrape off the build-up. be.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

Figure 3 shows the configuration of the device of this invention.
1-1 and 11-2 are back-up rolls or scraping plates for removing build-up installed in the non-oxidizing continuous melting furnace (hereinafter referred to as continuous furnace) 10, and their mounting structure is shown in Figures 4 and 4. As shown in Fig. 5, two horizontal bars 14 are attached to the support shaft 13 that penetrates the furnace wall below the height of the hearth roll group and is supported at both ends by external bearings 12, and that runs along the left and right inner walls.
is supported via a link 15, a back up roll 11-1 or a scraping plate 11-2 is provided for each hearth roll on this horizontal rail, and the support shaft 13 is connected to a cylinder 16 installed outside the furnace via a link 17. By connecting the cylinders 16 and driving the cylinder 16, the support shaft 13 is rotated by the action of the link 17, and the link 15, which is attached integrally with the support shaft, stands up and tilts, and the horizontal bar 14 moves up and down. The back up roll 11-1 or the scraping plate 11-2 attached to the crosspiece is configured to come into contact with and separate from the hearth roll 5 at any time.

20-1 is an image projection device for optically detecting the surface of the hearth roll 5, that is, the build-up, and 20-2 is an image projection device for detecting the back surface of the strip 6, that is, indentation flaws on the outlet side of the continuous furnace. , 21 is an image processing device that uses the image photographed by the image projection device as a still image, detects the presence or absence of build-up or indentation flaws in the strip on the surface of the hearth roll, and converts the detected build-up or indentation flaw into a digital signal. , 22 is a measuring device that calculates the size of build-up or strip indentation flaws on the surface of the hearth roll based on digital signals transmitted from the image processing device, and 23 is a measuring device that calculates the value obtained by the measuring device as a preset tolerance value. A comparator 24 outputs an electric signal when the permissible value is exceeded, and the comparator 24 instructs the drive cylinder 16 of the back-up roll 11-1 or the scraper plate 11-2 to operate based on the electric signal sent from the comparator. The pressing control devices that give the following are shown.

The materials of the back-up roll 11-1 and the scraping plate 11-2 are not particularly limited, but for example, the scraping plate may have a base made of heat-resistant steel and its surface covered with ceramic spraying, or a scraping plate made of ceramic. In addition, an inorganic grindstone or the like may be used as the back-up roll.
Particularly when ceramics or refractory bricks are used, it has traditionally been a problem that they have a short lifespan, but they can withstand use sufficiently if they are used only when build-up occurs. In addition, the installation positions of the image projection device 20-1 that photographs the hearth roll side and the image projection device 20-2 that indirectly detects the build-up are not particularly limited, but the former is likely to cause build-up. The former part of the non-oxidizing heating zone or the heating and soaking zone, and the latter is preferably any location on the exit side of the continuous furnace.

Next, the effects of the above device will be explained.
First, the case of photographing the hearth roll side, monitoring the roll surface, and removing build-up will be explained. When a build-up occurs on the hearth roll 5, the image is captured by the image projection device 20-1, and the build-up is detected by the image processing device 21. The amount is converted into a digital signal, and the measurement device 22 determines the size (height, width) of the buildup. Then, the comparator 23 compares the above-mentioned value with a preset tolerance value, and when the actual measured value exceeds the tolerance value, a generated signal is output to the pressing control device 24, and the back-up roll 11- 1
Alternatively, an operation command is given to the drive cylinder 16 of the scraping plate 11-2. Note that if the actual measured value does not exceed the allowable value, no electrical signal is output for removing the build-up. When an operation command is given to the drive cylinder 16, the back up roll 11-1 or scraping plate 11- provided for each hearth roll is activated.
2 rises, and in the case of a back-up roll, it rolls against the hearth roll 5 and crushes the build-up on the surface of the hearth roll. In the case of the scraping plate 11-2, the tip comes into sliding contact with the circumferential surface of the hearth roll 5, scraping off build-up on the roll surface.

In addition, an image projection device 20 provided on the exit side of the continuous furnace
-2, when photographing the back side of the strip 6 to remove the build-up, the image projection device 20-2
The imaged indentation flaw is converted into a digital signal by the image processing device 21, the size (depth, diameter) of the indentation flaw is determined by the measuring device 22, and a comparator compares the actual measured value with the preset value of the flaw. When the actual measured value exceeds the allowable value, a generated signal is output to the pressing control device 24, and an operation command is sent from the device to the drive cylinder 16. In this case as well, if the measured value does not exceed the allowable value, no electrical signal is output for removing the build-up. Further, if even minute indentation flaws are not allowed on the product, a signal may be sent directly from the image processing device 21 to the push control device 24 after detecting the indentation flaw to give an operation command to the drive cylinder 16.

As an embodiment of the present invention, a steel strip plating process has been described as an example, but the present invention can also be applied to a continuous cold rolled steel strip treatment process and a thick steel plate heat treatment furnace.

Although it is most preferable for the build-up monitoring device to directly monitor the roll surface inside the furnace, it is also possible to monitor the back side of the steel strip passing through the furnace from below if there is an open space such as a heating radiant tube. good. However, there are problems with ambient light and falling objects inside the furnace, so for stable measurements it is preferable to install it on the exit side of the furnace, for example in the snout. The surveillance camera may be installed in a cooling box whose entire surface is covered with heat-resistant glass, and illumination is directed obliquely toward the camera's field of view to form a shadow due to the unevenness of the back surface of the steel strip. Due to the resolution, the camera field of view can only see a portion of the steel strip, but in actual operation, build-up occurs over the entire surface, so the camera should be set in the center of the steel strip, where the field of view will not deviate even if the strip width changes. Bye. Further, to determine the amount of build-up, the image taken by the camera may be binarized into bright and dark areas, and the area of the dark area (shadow area) (or the length of the dark area in the case of continuous scanning lines) may be used for evaluation.

As described above, this invention is a device that optically captures the occurrence of build-up, processes it electrically, and automatically operates a back-up roll or scraping plate installed in a continuous furnace to remove build-up. In addition, the back-up rolls, scraping plates, and optical devices for detecting build-up are installed in locations where they do not interfere with the running of the strip, making it possible to continuously detect and eliminate build-up conditions without interrupting operations. It has the effect of Therefore, according to the present invention, not only can indentation defects caused by build-up be prevented and the quality (surface quality) of the product can be significantly improved, but also
Effects include reducing roll costs by extending the usage period of the hearth rolls, improving productivity by increasing the operating rate of the continuous furnace, and reducing fuel consumption by reducing the number of roll changes (reducing the drop in furnace temperature). It is extremely useful.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of a non-oxidizing continuous melting furnace, Fig. 2 is a perspective view showing the build-up of hearth rolls in the same continuous furnace, and Fig. 3 is an embodiment of the present invention. FIGS. 4 and 5 are explanatory diagrams showing the apparatus, and are perspective views showing an example of the operating mechanism of the build-up removal back-up roll and scraping plate in the same apparatus. 1... Non-oxidation heating zone, 2... Heating and soaking zone, 3...
...Cooling zone, 4...Low temperature holding zone, 5...Hearth roll, 6...Strip, 7... Molten zinc bath, 8...
...Build-up, 10...Non-oxidation furnace type continuous melting plating furnace, 11-1...Backup roll, 1
1-2...Scraping board, 12...Bearing, 13...Spindle, 14...Horizontal bar, 15, 17...Link, 20
-1, 20-2... Image projection device, 21... Image processing device, 22... Measuring device, 23... Comparator,
24...Press control device.

Claims (1)

[Claims] 1. In a non-oxidizing furnace type continuous heating furnace, a contact body that is driven up and down by a driving means provided directly below the hearth roll in the furnace, an image projection device that optically captures the surface of the hearth roll or the back surface of the strip; An image processing device that converts the image captured by the image projection device into a still image, detects the presence or absence of build-up on the surface of the hearth roll or indentation flaws in the strip, and converts it into a digital signal; a measuring device that calculates the size of surface build-up or indentation flaws in the strip; a comparator that compares the value obtained by the measuring device with a preset tolerance value and outputs an electrical signal if the tolerance value is exceeded; A build-up removal device for a hearth roll, comprising a pressing control device that gives an operating command to a contact body drive device by an electric signal transmitted from the comparator, and which uses the contact body to crush or scrape build-up on the surface of the hearth roll.