JPS5923382B2 - Method for detecting surface scratches on steel materials - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a method for detecting surface flaws on steel materials such as steel ingots and billets, and in particular detects flaws on the entire surface of steel intermediate products during rolling, that is, hot online, using one detection device. Relating to a surface scratch detection method.

Generally, in hot rolling operations, surface flaws on the rolled material are detected either hot or cold, and these surface defects are removed hot or cold using a solvent or the like.

Detection of these surface flaws must be carried out using equipment as simple as possible while not reducing production efficiency. Conventionally, for example, when trying to detect surface flaws on a high-temperature slab after blooming and rolling, four flaw detection devices were placed at the top, bottom, left and right of the slab to simultaneously detect four orthogonal surfaces of the slab to be flaw-detected, or Two VC flaw detection devices were installed to simultaneously detect flaws on two surfaces, the top surface and one side surface, and repeated flaw detection including a slab reversal operation was performed in between, thereby detecting flaws on four surfaces. The former method of simultaneously detecting flaws on four sides of a slab requires four force ζ flaw detection devices and flaw signal processing devices, etc., which has the highest flaw detection efficiency.Especially when using an electronic computer for flaw signal processing, flaws can be detected on all four surfaces. It is necessary to have a storage capacity that allows simultaneous processing of information. On the other hand, the method of simultaneously detecting flaws on two surfaces involves repeated flaw detection, which lowers the flaw detection efficiency but reduces the equipment cost by half.
Therefore, as a flaw detection method, it is necessary to use a method that uses as simple equipment as possible without reducing flaw detection efficiency and production efficiency. In particular, when detecting surface flaws on high-temperature steel materials online, flaw detection efficiency becomes an issue in relation to the production process.
Comparing the production efficiency of rolling mills in blooming and continuous hot rolling, the latter is higher. Therefore, the production amount of directly rolled material is regulated by the production efficiency of the blooming mill. When a steel ingot with an average unit weight of 17 tons is bloomed using a blooming mill with a capacity of about 800 tons per hour, and hot-rolled steel strip is produced by direct rolling, it takes about 1 minute and 30 seconds. Since steel pieces are produced at regular intervals, surface flaw detection must be performed within one minute. When considering not only material-related issues such as temperature drop of the tested material, but also production efficiency,
Traditional flaw detection methods are not satisfactory. Further, on the surface of hot steel materials, there are surface deposits that change rapidly over time, such as secondary scale generated after blooming and water droplets floating on the surface.

It is virtually impossible to distinguish between these surface deposits and original surface flaws by optical flaw detection. Therefore, it is necessary to remove the above-mentioned surface deposits by spraying high-pressure water using a high-pressure fluid scale breaker or the like immediately before flaw detection. The side surface of the slap has a small surface area, so it is relatively easy to remove deposits, but the top and bottom surfaces have a large surface area.
Moreover, since it is in a horizontal state, it is difficult to remove these deposits, and the detection accuracy of surface flaws is also deteriorated. Furthermore, the slabs after blooming and rolling have various thicknesses and widths.
In order to maintain the distance between the flaw detector and the flaw detector at a predetermined value commensurate with the focal length of the flaw detector, the position of the flaw detector is moved back and forth toward the flaw detector each time the cross-sectional shape of the flaw detector changes. There was a problem that I had to move it to . The present invention solves the above-mentioned conventional problems and drawbacks, and enables online flaw detection of four surfaces of a material to be tested with high accuracy without hindering production efficiency and with less surface deposits using a single flaw detection device. The object of the present invention is to provide a method for detecting surface flaws that can be carried out.

In the surface flaw detection method according to the present invention, the flaw detection material is moved back and forth on a conveyance table while the plurality of flaw detection surfaces of the flaw detection material are kept at equal distances from a fixed detector head in the traveling direction. The flaw detection surface is always inverted or rotated by 90 lines around an axis parallel to the VCl8O, and the surface flaws on the flaw detection surface are always detected from the horizontal direction with respect to the flaw detection surface perpendicular to the conveying table of the flaw detection material. It is.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram systematically showing the hot rolling process when the method of the present invention is applied to detect surface flaws in slop during or immediately after blooming.

In this case, the flaw detection device 2 used to carry out the method of the present invention is installed downstream of the blooming mill 1 and at a suitable location on the side of the line as close as possible to the blooming mill. A is a hot steel material to be bloomed and rolled, that is, usually a steel ingot (slap) extracted from a soaking furnace (not shown). B is a hot-rolled steel strip manufactured by a series of steps from the blooming mill 1 to the continuous hot rolling mill 5 shown in FIG. First, a slab undergoing or immediately after blooming by the blooming mill 1 is subjected to a surface inspection on each side by the flaw detection device 2, and detected surface flaws are cleaned by the flaw care device 3. Thereafter, both the top and bottom crops of the steel material are sheared using a 4VC cutter and shaped into a strip using a continuous hot rolling mill 5. FIGS. 2A and 2B are views from above of the conveying line, showing the state in which flaws in a slab are detected by the method of the present invention.

In addition, Fig. 2 a shows the second
FIG. b shows a case where a surface corresponding to the upper or lower surface of the slab 13 is being inspected for flaws. In the figure, 10 is a transport table 14
This is a surface flaw detection device fixedly placed on the side of the Various types of detection devices may be employed, and for example, one or more optical scanning detectors such as a scanning infrared camera, a flying spot device, a flying image device, etc. can be effectively used. As shown, the detection device 10
is arranged so as to face perpendicularly to the side surface or surface of the material 13 to be detected, and detects flaws by perpendicularly receiving reflected light or self-luminescence from the surface. 67
A pair of side guides are fixedly arranged between the conveyor rolls 15, and a pair of fingers 8 and 9 are movable in a direction perpendicular to the conveyance direction of the slab 13, that is, in the width direction of the table 14 and in the vertical direction.

The fingers 8 and 9 are operated by the operator to invert and invert the slab 13 at a predetermined position on the rolling pass, and also move the slab 13 onto the conveying table 14 by moving it along the side guides 6 and 7.
The flaw detection surface of the slab 13 is held at a constant distance L from the detection device 10 by pressing the same. Detection device 10
Scale breakers 11 and 12 are provided near the. When the slab 13 moves downward from Hijikata in Figure 2 A and b, the scale breaker 11 moves the slab 13 downward.
After removing surface deposits such as secondary scale, the detection device 10VC detects surface flaws. slab 13
When the scale breaker 1 moves from the bottom to the top, the scale breaker 1
2 cleans the surface. As mentioned above, the position of the detection device 10 is fixed and the position of the flaw detection surface of the slab is determined by the side guides 6 and 7, so the distance L between the slab 13 and the detection head of the detection device 10 is always constant. equal to focal length. FIG. 3 schematically shows the flaw detection process when flaw detection is performed on each surface of a slab during blooming with the arrangement shown in FIGS. 2A and 2B.

In the illustrated embodiment, a steel ingot is rolled into a steel billet 16 in N passes using a universal blooming mill (not shown).
The surface of the steel piece 16 is the a side (top surface), the b side (side surface), and the c side (
bottom surface) and d surface (side surface). If flaw detection is performed during rolling, it is best to perform it as close to the end of the rolling operation as possible or immediately after rolling. Therefore, for example, in N-pass rolling, the steel billet 16 that has finished rolling on the (N-4)th pass and has flowed downstream of the rolling mill is moved by the fingers 8 and 9 of the manipulator to the rolling mill as shown in FIG. Turn it upside down to the state shown in b and feed it backwards.
On the way, as shown in FIG. 3, the detection device 10 performs flaw detection on the a-plane. When the flaw detection is completed, the finger is rotated 90 times and rolled in the blooming mill for the (N-3) pass and the (N-2) pass.
Perform flaw detection on the b-side under the conditions shown in . The state of the steel billet at this time is exactly reversed from the rolling of the (N-4)th pass. After the flaw detection on the b side is completed, the flaw detection is carried out on the c side by rotating it by 90° in the same direction using the fingers 8 and 9 while being fed backwards and standing it upside down. After the flaw detection on the c-plane is completed, the steel is further rotated 900 revolutions and subjected to the rolling (N1) pass and the final rolling on the N-th pass in the rolling mill. After leaving the rolling mill, the flaw detection on the d-plane is performed. In this way, by performing flaw detection while inverting and inverting the steel piece during rolling, it is possible to detect flaws on four orthogonal sides of the steel piece with one detection device. The flaw information on each flaw detection surface is immediately processed by the signal processing device (not shown) VC, and by the time the next flaw care device 3VC steel piece is transported, the flaw information on the steel piece (on the flaw detection surface of the flaw) has already been processed. address, size, type, etc.) are transmitted to the control unit of the scratch care device. As the scratch care device, for example, a spot scarf, a full surface hot scarf that has been improved so that the amount of solvent can be controlled for each nozzle, or other hot grinders can be used. In general, when cleaning scratches using a hot partial solvent, it is difficult to reduce the area of solvent at one time to less than 200 mm x nozzle width.

That is, it is sufficient to virtually divide the address on the surface of the hot steel piece into sections of nozzle width x 200 m and classify them into sections with flaws and sections without flaws. Therefore, in the present invention, the flaw detection surface of the material to be flawed is divided into detection widths of 2007 m to 300 m2, and the flaws are detected in the cylinder and processed continuously.
In Fig. 4A and b, the detection width of one detector is 200WrIn.
This figure shows a case in which a plurality of test tubes having a capacity of ~300 wfL are vertically stacked and the material to be tested is divided and tested. In the BVC of FIG. 4, the field width W of one detector is approximately equal to the width of the nozzle (not shown) (for example, 200rWL to 300Tfr1n). 1), 10(2)
, . . . 10 (N), N pieces are arranged vertically and arranged on the side of the conveyance table. As shown in FIG.
Flaws are detected by When a scanning type flaw detector is used as a detector, the signals received in time series are transmitted to each detector 10(1), 10(2), . . . 1 along a path as shown in FIG.
0 (N) separately, a unit of a predetermined length in the longitudinal direction of the hot steel piece (usually 200 m to 300 Trtm)
If there is a flaw signal in the area that exceeds the allowable value, the area is treated as a flawed area and is subject to maintenance processing. The output signals of each microprocessor are processed by one computer,
The edited scratch information is transmitted to the control section of the scratch care device 3. When a 1TV with a shutter mechanism is used as a detector to capture information in a field of view of, for example, 275Tm width x 200m length, high-speed A-D conversion (analog-
This process is performed using an IC memory and a microprocessor to determine whether a section has scratches or a section without scratches. The method of the present invention has the following advantages compared to the conventional method for detecting flaws on the surface of a hot steel billet. b) Since flaw detection is performed while the hot steel material being tested is turned upside down in the middle of the rolling pass, four sides of the hot steel material can be continuously detected with one detection device and signal processing device, which increases the flaw detection time. ,
It is possible to reduce flaw detection equipment costs without reducing flaw detection efficiency.

In the present invention, in order to perform flaw detection with a detector installed horizontally (laterally) with the flaw detection surface always perpendicular to the surface of the traveling table, surface deposits other than scratches, especially water droplets on the flaw detection surface, are removed. This improves flaw detection accuracy.

... Since the detector is fixed and configured to press the subject in one direction on the table, the distance between the detector head and the subject is always constant, improving work efficiency.

Since the detector moving mechanism is eliminated, the configuration of the detector is also simplified. 2. The field of view of one detector is made as small as the nozzle width of a scarf, and multiple detectors are stacked vertically to form a single flaw detection device, which reduces the amount of heat received by the detector head compared to conventional methods. Furthermore, the flaw detection accuracy can be made equal between side flaw detection and surface flaw detection.

E) The signal processing itself becomes much more efficient by dividing the inspection surface of the test object into virtual small sections and performing divided inspection, and by processing the information from each detector separately. Furthermore, the signal processing device is simplified and the scratch care device operates more reliably.

Since flaw detection of the material during rolling can be performed from a point close to the final pass of blooming rolling, there is no need to reduce production efficiency due to surface flaw inspection.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a hot rolling process to which the method of the present invention is applied, and FIG. 2A, . Fig. 3 is a diagram schematically showing the flaw detection process according to the method of the present invention; Figures A and b are perspective views showing a state in which a plurality of detectors are stacked to perform divided flaw detection, and Fig. 5 is a diagram showing a processing system for flaw detection signals. 6, 7... Side guide, 8, 9...
Finger 1, 10...detection device, 11, 12...
...Scale breaker, 13... Material to be tested (slab).

Claims (1)

[Claims] 1. While reciprocating the test object on a transport table, a plurality of test surfaces parallel to the transport direction are maintained at equal distances from a fixed detector to a fixed detector. A method for detecting surface flaws on a steel material, characterized in that the surface flaws on a steel material are always detected from a direction parallel to the surface of the conveyance table, with an inspection surface perpendicular to the surface of the conveyance table of the object being inverted around an axis. 2. The method for detecting surface flaws on steel materials according to claim 1, characterized in that the inspection surface of the object to be inspected is further divided into detection widths of 200 to 300 mm and detected separately.