JPH0252988B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an eddy current flaw detection method for inspecting rolls for surface flaws.

The rolls used for rolling have a high hardness depth and high hardness from the viewpoint of ensuring accident resistance and wear resistance with the aim of reducing roll consumption. However, on the other hand, there is a problem that the surface layer is thermally and mechanically fragile.

Recent speeding up of rolling mills/WR (Awk Roll)
As diameters become smaller, the operating conditions for rolling rolls become increasingly severe, and as a result, accidents such as roll spalling tend to increase.

Therefore, currently, as a means of managing roll defects,
Surface flaw detection methods and eddy current flaw detection methods using surface etching methods using acid solutions are known, but the etching methods have problems in that they require manpower and have low working efficiency. Furthermore, in the eddy current flaw detection method, false signals may be output not only due to flaws but also due to the material of the material to be inspected, surface texture lift-off, and the like.

Especially when applied to surface flaw inspection of rolling rolls,
In addition to cracks, the material change signal of the part where the hardness has decreased (tempered) may be output more than the flaw signal. This type of item does not require any care if it is light, but cracks require care even if it is light. As a method of distinguishing between the two, a method of separating and identifying them using frequency discrimination has been reported, but surface flaws vary in size (width, depth, length), shape, etc., and are necessary for maintenance grinding. The correlation between depth information and eddy current flaw detection signals is weak. In other words, if conditions are set for a specific flaw, the correlation between flaw depth and defect signal can be strengthened, but Regarding roll flaw detection with various types of flaws, etc., there has been a problem in that it is difficult to determine a highly reliable flaw reject judgment level.

The present invention proposes a new eddy current flaw detection method that solves the above-mentioned problems. In addition to performing two-dimensional analog display, the flaw level of the filter is determined and digitized, and the flaw detection signal is analyzed and simultaneously processed by a filter set to a frequency band different from that of the filter, and both filters are The flaw type is determined based on the comparison value of the output, and these flaw level and flaw type signals are displayed on a two-dimensional digital display corresponding to the flaw position. From both displays, the existence, type, shape, and size of roll surface flaws can be determined. An eddy current flaw detection method for roll surface flaws is characterized in that the flaws on the roll surface are determined. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to the drawings, using an example in which a divider is used as a comparison circuit.

FIG. 1 is a block diagram of an eddy current flaw detector electrical signal circuit for implementing the method of the present invention.
1 is a roll which is the material to be inspected, 2 is an oscillator that oscillates a signal of the inspection frequency, 3 is a power amplifier that amplifies the signal of the oscillator 2, 4 is a detector that outputs an eddy current flaw detection signal on the roll surface, 5 is a detection Balancer, 6, 10 (6
and 10 (hereinafter referred to as the same) are amplifiers that amplify the flaw detection signal; 7 and 13 are phase shifters that rotate the phase angle; 8 and 11 are phase detectors that perform synchronous detection in accordance with the phase of the flaw signal; 9 and 12 are band pass filters (hereinafter referred to as filters) set to a frequency band that makes it easy to detect flaws, 14 is a peak expander (low pass filter) that extends the flaw signal and lowers the frequency to the response speed of the recorder, and 19 is an analog X-Y recorder for display; 16 is a division circuit for dividing the output signals of filters 9 and 12; 17;
15 is a comparator that determines the type of flaw based on the value of the divider circuit 16. 15 is a comparator that divides the output signal level of the filter 9 into 3 ranks and digitizes it for output. 23 is a 1 pulse per roll rotation. a probe position detector which generates a signal and recognizes the flaw position; 18 is a comparator 15,1;
7 and a digital treatment circuit (CPU) that creates a flaw map based on the information from the probe position detector 23, 20 a display device that displays flaw information, 21 a printer, and 22 a floppy disk that stores flaw information. It is.

Next, the operation based on the above configuration will be explained. Excited by oscillator 2 and power amplifier 3,
The eddy current flaw detection signal on the roll surface detected by the detector 4 has unbalanced voltage removed by the balancer 5, and the output signal is branched into two. One signal is amplified by an amplifier 6 and input to a phase detector 8, and the other signal is amplified by an amplifier 10 and input to a phase detector 11. On the other hand, the signal from the oscillator 2 is also branched and input to the phase shifters 7 and 13. The phase shifter 7 is rotated to a phase angle that allows cracks to be detected with a good S/N ratio, and the phase shifter 13 is rotated to an S/N ratio to detect cracks.
The signals are rotated to a phase angle that can be detected with a good N ratio, and are input to phase detectors 8 and 11, respectively, to perform synchronous detection. The output signal of the phase detector 8 is filtered by a filter 9 set to a high frequency band in which cracks can be easily detected. The filtered output A lowers the flaw signal frequency level by the peak expander 14, and is recorded in analog form on the XY recorder 19 in synchronization with the probe position detector 23.

Additionally, the output signal of the phase detector 11 is passed through a filter 12 set to a low frequency range where it is easy to detect hardness loss.
The output B is input to the divider circuit 16 together with the output A of the filter 9, where B/A is calculated. Division circuit 16
The calculation result is input to the comparator 17.
The comparator 17 is created in a circuit that determines that B/A≦α (α is a constant) indicates a crack, and that B/A>α indicates a decrease in hardness. , 3) and decreased hardness (indicated by B). The discriminated flaw signal is input to the digital processing circuit 18. Further, in the processing circuit 18, a comparator 15 converts the output of the filter 9 into large (3), medium (2), and small flaw levels.
(1) The determined signal and the probe position detector 2
The signal from 3 that recognized the flaw position is input,
Digital processing and CRT display device 20
will be displayed. If necessary, it can be output to the printer 21 and made into a copy. The output signal is also stored on the floppy disk 22.

Fig. 2 is an example of an output display, in which A shows two-dimensional information of developed flaws on the roll to be detected, flaw information obtained from this roll by the flaw detection method of the present invention is B, C, and R. is a digital map display outputted by the printer 21, where the numbers indicate the position of the crack flaw, the size of the number indicates the magnitude of the flaw signal output, and B indicates the position of the hardness drop. C shows an analog display output to the XY recorder, and the height of the peak represents the level of the flaw signal output.

In this way, by comparing and examining two-dimensional flaw maps displayed in analog and digital formats, we can determine the presence or absence of flaws, the type of crack flaw or decreased hardness, and the dimensions of flaws (depth, length, etc.). In addition, the shape of the flaw can be immediately determined, comprehensively evaluated, and reflected in flaw cleaning and grinding. Next, examples will be shown.

Example A general forged steel roll was inspected for flaws under the following conditions.

Roll circumferential speed 60m/min Detector movement speed 24mm/rotation Detection frequency 32KHz Phase rotation angle 40° Filter 60~220Hz (for cracks) 20~80Hz (for hardness reduction) Judgment circuit constant α=1. ³ Comparator 3 : 1. ^0v , 2: 0. ^5v , 1: 0. ^2v When comparing the flaw detection results with actual flaws, it was possible to detect even minute cracks with good accuracy, distinguish between crack flaws and hardness loss, and determine the shape and size of flaws.・Results corresponding to actual defects were obtained.

As described above, the following effects can be expected by the eddy current flaw detection method of the present invention.

1. Roll consumption rate is improved by preventing the progress of spalling, chilling, cracking, etc. due to overlooked defects.

2. The roll flaw map information memory function makes it possible to manage roll flaws in correspondence with the roll usage history.

3. By accumulating data that corresponds to the type of flaw using a digital map and the level of flaw using an analog map, it becomes possible to perform thorough care for a wide variety of flaws, and it is expected that the care will be performed using the optimal roll grinding allowance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing an example of an output display. In the drawing, 4 is a detector, 1 is a roll, 9 and 12 are filters, 14 is a peak expander, 20 is a display, 15 and 17 are discrimination circuits, 16 is a division circuit for comparison, and 18 is a digital processing circuit. .

Claims (1)

[Claims] 1. The flaw detection signal on the roll surface detected by the detector 4 is passed through a filter 9 and a peak expander 14 to display a two-dimensional analog display corresponding to the flaw position (19), and the flaw level of the filter is determined. The flaw detection signal is further branched and simultaneously processed by a filter 12 set to a frequency band different from that of the filter, and the type of flaw is determined based on the comparison value 16 of the outputs of both filters, and the level of these flaws is determined. The flaw type signal is displayed on a two-dimensional digital display corresponding to the flaw position, and both displays indicate the presence, type, and presence of roll surface flaws.
An eddy current flaw detection method for roll display flaws characterized by determining the shape, size, etc.