JPS6123962A - Detecting method of structure irregularity by eddy current - Google Patents

Abstract

PURPOSE:To detect the structure irregularity of the surface part of an object body quantitatively by moving the object body and probes relatively and detecting variation of an eddy current generated at the surface part of the object body. CONSTITUTION:The probes 4 and 4' have inversely V-shaped coils 10; two coils 10 which differ in spread distance are arranged, spread sides of the coils 10 are arranged opposite a roll 7 which is suppored rotatably, and their tips are put closer to the surface of the roll 7, which while rotated is moved lengthwise to body length to scan the entire surface of the roll. An exciting current of 256KHz high frequency is applied from an eddy current flaw detecting device body 1 to one probe 4 and an exciting current of 65KHz low frequency is applied to the other probe 4 to generate an eddy current at the surface part of the rotating roll 7; and the probes 4 and 4' are moved in the lengthwise direction of the roll 7 to scan the entire surface of the roll 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention mainly relates to a method for quantitatively detecting texture unevenness occurring on the surface and surface layer portion (hereinafter referred to as surface portion) of a rolling roll.

[Conventional technology]

Traditionally, the method of detecting tissue unevenness on the surface was to observe it with a microscope for a narrow area, and to corrode the surface with hydrochloric acid, nitric acid, etc. for a wide area.
A macro-etching method was used to detect tissue unevenness based on the corrosion pattern. Additionally, methods have been implemented in which tissue unevenness is detected by the unevenness of light reflection in processed milk when the surface is shot blasted or processed with a sword bite.

In either case, detection accuracy varies depending on work conditions and observation conditions. Furthermore, because the observation was comparative with a standard sample, it was a qualitative judgment that included personal subjectivity. For this reason,
The distribution and degree of tissue unevenness had not been quantitatively understood.

According to such conventional detection methods, for example, when a rolling roll is subjected to rolling that has extremely slight texture unevenness that is judged to be no problem at all, a structure that is judged to be slight and not a problem may be detected. The unevenness was transferred to the rolled product, resulting in a lower grade of the product, resulting in large losses.

Therefore, in order to solve the problems of the conventional detection method of tissue unevenness mentioned above, if it is possible to quantitatively detect tissue unevenness by eddy current flaw detection using electromagnetic induction, its distribution,
It is possible to judge the effect on rolled products based on the degree of
This makes it possible to prevent losses due to deterioration in product quality.

The eddy current flaw detection method is possible and has been put to practical use in detecting minute surface flaws, distinguishing between different materials, and detecting extremely large structural changes corresponding to the presence of different materials. Particularly in recent years, work rolls for rolling thin plates have become popular for use in detecting flaws generated on the surface during rolling.

[Problem that the invention seeks to solve]

However, with the conventional eddy current flaw detection method described above, for example, when rolling rolls are manufactured using the centrifugal casting method, slight changes in the cast structure that occur even though they are made of the same material, that is, extremely slight structure unevenness, can be detected. is not possible. In addition, there are many types of structural irregularities that occur on rolling rolls, from as small as 1φ to as large as 100φ or more, and even long, thin strips that cannot be detected using conventional eddy current testing. .

In other words, the probe used in conventional eddy current testing is
As shown in the figure, it has coils 10a, 10a that are substantially perpendicular to the surface of the rolling roll and parallel to each other with a coil spacing l maintained. When trying to detect the above-mentioned IS unevenness, it is necessary to increase the sensitivity, but if a tilt occurs between the probe 4a and the surface of the roll 7 due to vibration etc. during scanning, a considerable amount of noise will be mixed into the signal. The lateral sole cannot be used to detect uneven braiding.

The present invention aims to provide an eddy current detection method that can simultaneously quantitatively detect the distribution and extent of the various types of tissue unevenness that could not be detected using conventional eddy current flaw detection methods.

[Means for solving problems]

The method of detecting tissue unevenness using an eddy current according to the present invention includes applying an electric current to a probe that has a coil that expands toward the object to be detected and has a magnetic flux focused in a narrow range in close proximity to the surface of the object to be detected;
By moving the object to be detected and the probe relatively and capturing changes in the eddy current generated on the surface of the object,
This method is characterized by detecting tissue unevenness occurring on the surface of the object to be detected.

[For production]

When the object to be detected and the probe are moved relative to each other and the surface of the object to be detected is scanned by the probe, if there is tissue unevenness on the surface of the object to be detected, the magnetic permeability and conductivity will be different from normal. This causes fluctuations in the bridge balance of eddy currents. This variation becomes larger or smaller depending on the degree of tissue unevenness, so this variation can be captured as a signal and, for example, can be used to generate an alarm, display it on a cathode ray tube, or mark the location on the surface of the object to be detected. Furthermore, tissue unevenness is detected by recording its distribution on an X-Y plotter and recording its degree on a Benrecoguru.

The probe used in the present invention is arranged as shown in FIGS. 2(a) and 2(b) so that it expands by a distance t toward the object to be detected (rolling roll in the example) 7 as shown in FIG. It has a coil 10 wound in an inverted V-shape around a coil core 8 made of a non-magnetic material. Therefore, the magnetic force #I9 is the coil 1
0's are concentrated in a narrow range of expanded distance t and are generated in the forward direction.

By focusing the magnetic flux in a narrow range in this way,
Even if a tilt occurs between the probe and the object to be detected due to vibration or the like when the probe is scanned, the effect is less than that of American probes, and the generation of noise can be kept to an extremely low level. Therefore, fluctuations in the minute balance of eddy currents can be reliably captured and displayed, making it possible to detect tissue unevenness, which was previously impossible.

In addition, by using a multi-channel method using two or more probes with different coil expansion distances, changes in eddy currents can be easily detected, and various tissue irregularities ranging from minute tissue irregularities to wide-area tissue irregularities can be detected simultaneously. It is the material that makes detection possible.

〔Example〕

FIG. 1 is an explanatory diagram showing the implementation status of the present invention.

In FIG. 1, 4.4' is a probe having the above-mentioned inverted V-shaped coil 10, and the expansion distance of the coil 10 is 2 on one side.
mm, and the other one has a different expansion distance of 5II+6.
The expanded side of the coil 10 is placed opposite the rotatably supported roll 7, and the tip thereof is placed close to the surface of the roll 7, and the body length is lengthened in the longitudinal direction while rotating the roll °l. It is possible to scan the entire surface of the roll by moving between the two.

That is, in this example, the probe is placed at 4°4' 2
One probe (coil expansion distance 2 mm) is used for detecting micro-tissue irregularities (C, Hl).
), and the other probe (coil expansion distance 5 mm) is for wide range tissue unevenness detection (CH2).

An eddy current is applied to the surface of the rotating roll 7 by applying a high frequency excitation current of 256 kHz from the eddy current flaw detection device body 1 to one probe 4 and a low frequency excitation current of 64 kHz to the other probe 4'. Generate probe 4.4'
is moved in the longitudinal direction of the roll 7 to scan the entire outer surface of the roll 7.

At this time, if there is a tissue unevenness 15 on the surface of the roll 7, the magnetic permeability and electrical conductivity will change, causing fluctuations in the bridge balance of eddy currents, so this fluctuation will be taken as a signal,
The distribution of the tissue unevenness 15 is recorded as a developed roll surface diagram on the X-Y plotter recording paper 11 using the X-Y block 2 as shown in FIG. Record it on the pen record paper 14. Note that 6 is a circumferential position detector.

In addition, in order to record one circumference, the X-Y plotter 2
As shown in Figure 4, No. 1 Ben 12, No. 2 Pen 1
Using the 2 pens No. 3 and 1, record half a turn on the X-Y plotter recording paper 11 with the No. 1 pen 12, return to the original position, and record the next half turn with the next No. 52 pen 13 while returning. No,
It is a continuous recording method in which NO and 1 pens are used to record while the 2 pens and 13 are returning. If there is tissue unevenness, the lines will be recorded in a wavy manner as shown in FIG. Also,
The middle part of FIG. 4 is the body length of the roll 7, and P is the feed pitch of the probe 4.4'.

Furthermore, the recording by the pen recorder 3 is made on the pen recorder recording paper 14 separately for the CH1 probe and the CH2 probe, so that the degree of tissue unevenness can be determined based on the height of the swing width.

Furthermore, if the presence of tissue unevenness is taken as a signal,
Paint is sprayed from a marker 5 provided near the probe 4.4' to clearly indicate the position of the sum unevenness on the roll surface.

In addition, when performing eddy current flaw detection, a probe (CHI, C
Conditions such as H2) excitation current, frequency, circumferential speed of the flaw detection surface (roll surface), distance between the probe and the flaw detection surface, etc. are set.

As a result of performing eddy current flaw detection on the roll surface as described above, the probe with a coil expansion distance of 2 mm can accurately detect small spot-like tissue irregularities, and the coil expansion distance of 5 mm can be detected with high accuracy.
With the mm probe, pattern-like tissue unevenness with unclear boundaries could be detected with high accuracy. In the above-mentioned embodiment of the two-channel method using both probes, it was possible to quantitatively detect various types of tissue unevenness with high accuracy.

〔Effect of the invention〕

As described above, the present invention uses a probe having a coil that expands toward the object to be detected in a so-called inverted V shape, and focuses magnetic flux in a narrow range to generate eddy currents on the surface of the object to be detected. By capturing the change and detecting tissue unevenness, by appropriately setting the expansion distance of the coil,
It is possible to accurately detect small tissue irregularities in the form of spots to large tissue irregularities in the form of patterns, and by using two or more probes with different coil expansion distances, it is possible to detect many types of tissue irregularities with different sizes and shapes. It can be detected with high precision, and by displaying the surface of the object to be detected on a flat surface, tissue unevenness can be quantitatively understood, and losses caused by tissue unevenness can be prevented. This has many effects.

Note that although the present invention has been described above mainly with respect to rolling rolls, the present invention is not limited to rolling rolls, but can be applied to any article that generates an eddy current and can be scanned with a probe. It is effective.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing one embodiment of the present invention, Figure 2 (a)
, (b) is a front view and a bottom view of the coil core of the probe,
Figure 3 is a front view of the probe that connects the inverted V-shaped coil.
FIG. 4 is a plan view of the X, Y block recording paper, FIG. 5 is a plan view of the pen record paper, and FIG. 6 is an explanatory diagram of a conventional probe. 1: Eddy current flaw detection device body, 2: X-Y plotter, 3
: Penre, Kuda, 4.4' nib lobe, 7: Roll, 8: Coil core, 9: Magnetic lines of force, 10: Coil, 11: X-Y θ-tutter recording paper, 14: Be:〉Recorder recording paper substitute Person Patent Attorney Takashi Honma Figure 1 Figure 2 (a) Graduation Figure 3 Figure 6 Procedural Amendment (Showa 5 Cup, August 3)

Claims (4)

[Claims] (1) The probe, which has a coil that expands toward the object to be detected and focuses magnetic flux in a narrow range, is brought close to the surface of the object to be detected and energized, and the object to be detected and the probe are placed relative to each other. A method for detecting tissue unevenness using eddy currents, which detects tissue unevenness occurring on the surface of a detected object by moving the object and capturing changes in eddy currents generated on the surface of the detected object. (2) A method for detecting tissue unevenness using an eddy current according to claim 1, characterized in that two or more probes having different coil expansion distances are used. (3) The surface of the object to be detected is developed into a flat plane in conjunction with the scanning of the probe, and the distribution and degree of tissue unevenness occurring on the surface of the object to be detected is displayed on the developed plane. A method for detecting tissue unevenness using a vortex flow according to claim 1 or 2. (4) The method for detecting tissue unevenness using a vortex flow according to any one of claims 1 to 3, wherein the object to be detected is a rolling roll.