JPS62112052A - Surface defect detecting device for ferromagnetic body - Google Patents

Abstract

PURPOSE:To eliminate variance depending upon an operator by measuring magnetic flux density on a magnetized ferromagnetic body surface, operating the position of a defect part from the measurement data, and detecting the surface defect. CONSTITUTION:When a current flows through the coil 1a of a yoke 1, produced lines 12 of magnetic force magnetize the surface of a steel plate 2. If there is the defect part 13, leak magnetic flux is produced and the magnetic flux density B increases at the part, but the X-directional component Bx and Z- directional component Bz are large and the Y-directional component By is small. The X-directional component Bx of the magnetic flux density B on the surface of a steel plate 2 is measured continuously by plural magnetic sensors 3 mounted on a slide bark. Then, the positions of the sensors 3 on the X axis are found by a movement extent measuring means 11 for the slide bark and stored in a memory successively while made correspond to measured values Bx. A computing element accesses data Bx on magnetic flux density stored in the memory and performs arithmetic to find the position of the defect part on the surface of the steel plate 2, detecting the surface defect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a surface defect detection device that detects surface defects in a ferromagnetic material such as a steel plate using leakage magnetic flux.

[Prior art and its problems]

Detection of surface defects existing on or near the surface of a steel plate using leakage magnetic flux has conventionally been carried out as follows. That is, after the surface of the steel plate is magnetized to a strength around so% of magnetic saturation, magnetic powder (fine ferromagnetic powder) is dispersed on the surface of the steel plate by an appropriate method such as suspending it in a liquid.
At that time, the patterns created by the magnetic particles are visually observed to determine where surface defects exist.

Generally, when a ferromagnetic material such as steel is magnetized, magnetic flux leaks into the air near the defective part, producing leakage magnetic flux, and the strength of the magnetic field becomes stronger there than elsewhere.

When magnetic particles are scattered here, they are attracted and create a wide pattern, so the patterns created by the magnetic particles differ between defective areas and healthy areas. Therefore, by visually observing the pattern created by the magnetic particles, it is possible to identify locations where surface defects exist.

As described above, conventionally, surface defects on steel sheets are detected by magnetizing the surface of the steel sheet, then scattering magnetic particles one by one, and visually observing the patterns created by the magnetic particles. There was also the problem that it took a long time and that variations occurred depending on the operator.

[Purpose of the invention]

In view of the above-mentioned current situation, it is an object of the present invention to provide a surface defect detection device that can accurately and easily detect surface defects of ferromagnetic materials such as steel plates without causing variations due to the operator. There is a particular thing.

[Summary of the Invention] A surface defect detection device for a ferromagnetic material according to the present invention includes: a magnetizing yoke for magnetizing the surface of the ferromagnetic material, which is disposed close to the surface of the ferromagnetic material; A plurality of magnetic sensors are arranged below the yoke in a direction perpendicular to the longitudinal direction of the yoke, and are arranged to measure the magnetic flux density on the surface of the ferromagnetic material. Calculating the position of a defective portion existing on the surface of the ferromagnetic material from the data of the magnetic flux density on the surface of the ferromagnetic material measured by the moving means for moving in the longitudinal direction and the plurality of magnetic sensors. It is characterized by consisting of an arithmetic unit for performing the calculation.

[Structure of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ferromagnetic surface defect detection device of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view showing a measuring section in one embodiment of the surface defect detection device of the present invention.

In FIG. 1, l denotes a magnetizing yoke for magnetizing the surface of the steel plate 2, 3 denotes a plurality of magnetic sensors for measuring the magnetic flux density on the surface of the steel plate 20, and 4 denotes a magnetic sensor 3 connected to the magnetizing yoke 1. It is a moving means for moving in the longitudinal direction.

The magnetizing yoke 1 consists of a U-shaped electromagnet with a coil 1a wound around it. The magnetizing yoke 1 is
It is placed on the two opposing frames 5a, 5b of the moving means 4, and is placed close to the surface of the steel plate 2 so that its longitudinal force crosses the frames 5a, 5b at right angles.

The frames 5a and 5b of the moving means 4 are made of elongated casings. The frames 5a and 5b are connected by two guide shafts 6a and 6b, and between the two guide shafts 6a and 6b is a slide par 7 that is slidable in the longitudinal direction of the yoke l. is installed.

The plurality of magnetic sensors 3 are placed on the slider 7 and arranged below the magnetizing yoke in a direction perpendicular to the longitudinal direction of the yoke 1. Note that the plurality of magnetic sensors 3 are arranged in a staggered manner so as to be closely arranged on the slider 7, but the arrangement is not necessarily limited to this. good.

The slider '2 is moved by a motor 9 provided near the connecting part of the guide shaft 6a on the one frame 5a, with a wire valve attached to its outer ends 7a and 7b. It is supposed to be done. That is, in the one frame 5a, one guide 7
As shown in FIG. 2, one pulley loa driven by the motor 9 is located near the connecting portion of the guide shaft 6b, and two independent upper and lower boots IJ lob and loc are located near the connecting portion of the other guide shaft 6b. In the other frame 5b, there is one boob IJ rod near the connection part of one guide shaft 6a, and two independent upper and lower boos near the connection part of the other guide shaft 6b. ) 10e and lof are provided. wire 8
is from one outer end 7a of the slide par 7 to the boo I
Jloa! 10c and 10f to the other outer end 7b, and from the other end 7b, the goo IJ
10b, 10e and lod to reach the one outer end 7a, a pulley loa=lOf
It is being passed around. Therefore, motor 9 causes Boo+)
By rotationally driving loa in the direction of the arrow, the slide par 7 is moved through the wire 8 to the guide shaft 6a,
6b as a guide, it moves in the direction of the arrow along the longitudinal direction of the magnetizing yoke l.

The amount of movement of the slider 7 is measured by a movement amount measuring means 11 such as a rotary encoder or a potentiometer mounted on the motor 9. By this measurement, the first
The position of the magnetic sensor 3 on the X-axis is determined when the XY coordinates are taken in the direction shown in the figure. Note that the X axis of the X and Y coordinates is the center line extending in the longitudinal direction of the magnetic yoke l,
Y@ is taken at right angles to this. The origin 0 is determined as appropriate.

The detection device of the present invention magnetizes the surface of the steel plate 20 with the magnetization yoke 1 of the measuring section as described above, and continuously measures the magnetic flux density on the surface of the steel plate 20 while moving the plurality of magnetic sensors 3 using the slider 7. The position of the defective portion existing on the surface of the steel plate 2 is calculated by a calculator (not shown) from the magnetic flux density data obtained thereby, and the surface defect is detected.

When a current is passed through the coil la of the magnetizing yoke l to generate magnetic lines of force 12 from the yoke 1, the lines of magnetic force 12 pass through the surface of the steel plate 2, and the surface of the steel plate 2 is magnetized, as shown in FIG. This magnetized steel plate 2 has defects such as scratches 13 on the surface or near the surface, as shown in the bottom of FIG.
If there is, leakage magnetic flux will occur, so the magnetic flux density B
is large because the direction of magnetization is in the X-axis direction.

Regarding the directional components of the magnetic flux density B, as shown in FIG. 5, the X-direction component Bx and the Z-direction component BZ are large, and the Y-direction component BY is small. Therefore, when measuring the magnetic flux density B on the surface of the steel plate 2, one of the X-direction component Bx or the Z-direction component Bz, for example,
This is performed for the direction component Bx. For this purpose, each of the plurality of magnetic sensors 3 is placed on the slider 7 in a posture that allows measurement of the X-direction component Bx of the magnetic flux density B.

The plurality of magnetic sensors 3 as described above continuously measure the X-direction component Bx of B as the magnetic flux density on the surface of the steel plate 2. During measurement, the position of each magnetic sensor 3 on the
1, the measured value Bx of the magnetic flux density is sequentially stored in the memory for each magnetic sensor 3 in correspondence with the position of the magnetic sensor 3 on the X axis. During the measurement or after the measurement is completed, the computing unit calls the magnetic flux density measurement data Bx stored in the memory,
Specifically, calculations as shown in FIG. 6 are performed to find the positions of defects existing on the surface of the steel plate 20, and all surface defects are detected.

That is, the measured value of the magnetic flux density obtained by the magnetic sensor 3 located at the coordinates (Xi, Yi) is expressed as Bx(X
IIYL), Bx(X1+Yt) and B
Difference from x(Xl, -Yi) l Bx(L+ Yt
)-Bx(X++-yi)1 is determined, and it is determined whether the difference exceeds the step value α. In this case, while fixing the position X, = X, ~ x, 1 on the X axis, Y
Symmetrical positions on the axis Y, =:Y, ~Yn and -Yi = -
This is done for all of Y, to -Y. And the difference l
Bx (Xt, Yi) -BX (X,, -Yyu)
1 exceeds α, it is assumed that there is a defect on or near the surface of the steel plate 2 corresponding to the position of the coordinates (X, , Y□)' or (x, , -y□), and the defect is identified. and detect surface defects.

The above is an example of detecting surface defects from the measured value Bx of magnetic flux density, and the measured value Bx (X1+Yl
) of Yl f Y, = const, the peak value, average value, and Bx(χ) + YH"'
It goes without saying that any suitable method can be used, such as determining the position of the defective portion from the integral value of the curve drawn by the curve (const) and detecting the surface defect.

〔Effect of the invention〕

As explained above, in the detection device of the present invention, after magnetizing the surface of a ferromagnetic material such as a steel plate, the magnetic flux density on the surface is measured with a magnetic sensor, and the measured magnetic flux density is Since surface defects are detected by calculating the position of the defect on the surface of the ferromagnetic material, there is no need for the conventional method of scattering magnetic particles on the surface of the magnetized ferromagnetic material.

Further, there is no possibility of variations in the structure of the surface defects caused by the operator, as is the case when surface defects are identified by visually observing the pattern formed by the magnetic particles.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a measuring section in one embodiment of the detection device of the present invention, FIG. 2 is a perspective view showing main parts of a moving means in the measuring section of FIG. 1, and FIG. An explanatory diagram showing where the steel plate surface is magnetized by the magnetization yoke in the measurement part of Fig. 1, Fig. 4 is an explanatory diagram showing the magnetic flux density at the defective part of the magnetized steel plate surface of Fig. 3, Figure 5 is an explanatory diagram showing the components of magnetic flux density in each direction on the surface of the magnetized steel plate in Figure 3, and Figure 6 is the measured value of magnetic flux density obtained by the magnetic sensor of the measurement section in Figure 1. 12 is a flowchart showing how all surface defects are detected. In the drawings, ■...(magnetization yoke, 1a.° coil, 2. steel plate, 3. magnetic sensor, 4. moving means, 6a, 6b... guide shaft, 7)
・Slide bar, 8...wire, 9 motor,
1oa-10f-pulley, 11. Movement amount measuring means, 12. Line of magnetic force, 13. Defect part,
B...Magnetic flux density, Bx...X direction component of magnetic flux density. Figure 1 + 1a 2' Soft 22 b 7a 8 Fist 3 Figure l Size 5Δ Figure 6

Claims (1)

[Claims] a magnetizing yoke for magnetizing the surface of the ferromagnetic material, disposed close to the surface of the ferromagnetic material; and a magnetizing yoke disposed below the magnetizing yoke in a direction perpendicular to the longitudinal direction of the yoke. a plurality of magnetic sensors for measuring magnetic flux density on the surface of a ferromagnetic material; a moving means for moving the plurality of magnetic sensors in the longitudinal direction of the magnetization yoke; A ferromagnetic device comprising: a calculator for calculating the position of a defective portion existing on the surface of the ferromagnetic material from data of the magnetic flux density on the surface of the ferromagnetic material thus measured. Body surface defect detection device.