Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
  • G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws

Definitions

• a vertical magnetic sensor rather than a horizontal magnetic sensor. That is, as described above, it is generally said that obtaining an output similar to a differential waveform like a vertical magnetic sensor is more convenient for detecting a magnetically abnormal portion c.
• the output of the horizontal magnetic sensor must be once processed by a differentiating circuit, which complicates the entire device.
• the time variation (frequency) of the stray magnetic flux that occurs even in the healthy part of the subject is much lower than the frequency of the leakage magnetic flux caused by the magnetically abnormal part of the subject moving in the magnetic field. Therefore, the signal component of the stray magnetic flux included in the output signal of the magnetic sensor can be extracted by the low-pass filter. If the low frequency signal component is applied to the compensation coil with, for example, a reverse polarity, a magnetic flux in a direction to cancel the stray magnetic flux is generated by the compensation coil. As a result, the stray magnetic flux crossing the magnetic sensor is canceled by the magnetic flux generated by the capture coil. Therefore, a signal component caused by the stray magnetic flux is removed from the output signal of the magnetic sensor.
• FIG. 6A is a cross-sectional view showing a vertical magnetic sensor and a compensation coil incorporated in the magnetic detection device of the embodiment.
• FIG. 7 is a block diagram showing an electrical configuration of the magnetic detection device shown in FIG. 2A.
• FIG. 29B is a block diagram showing a magnetic detector according to still another embodiment of the present invention.
• Figure 31 is a schematic diagram showing a rolling line in an ironworks.
• FIG. 32 is a side view showing a schematic configuration of a magnetic detection device incorporated in the rolling line.
• the low-pass filter 107 extracts a low-frequency signal component included in the output signal 106.
• the low-frequency signal component extracted by the low-pass filter 107 is sent to the amplifier 110.
• the amplifier 110 amplifies the low frequency signal component and applies it to the capture coil 111 wound around the outer peripheral surface of the magnetic sensor 104.
• the moving speed V of the thin steel strip 101 is detected by the speed detector 112 and input to the cut-off frequency control circuit 113.
• the cutoff frequency control circuit 113 changes the cutoff frequency of the high-pass filter 108 according to the input moving speed V.
• the high-pass filter 108 removes low-frequency signal components included in the output signal 106 of the magnetic detection circuit 105 and outputs the signal from the output terminal 115 as a defect signal 114.
• the above-described supersaturated magnetic sensors having high detection sensitivity are best, but known magnetic detecting elements such as MR elements, Hall elements, and magnetic diodes should be used. Is also possible.
• the signal level of the defect signal e also increases with the increase of the exciting current I, but when the switch 25 is opened (no feedback), it saturates at the exciting current I of about 0.2 A. However, in the example device with switch 25 (with feedback), the defect signal e continues to increase to the excitation current I of about 0.5 A. That is, the exciting current value applied to the magnetizing coil 6 of the magnetizer 4 is increased. Thus, the detection sensitivity can be easily increased.
• the magnetizer 55 and the magnetic sensors 7a are housed in the rolls 44c, it is possible to mount the magnetic detection device even in a narrow place such as a manufacturing site. is there.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
• Measuring Magnetic Variables (AREA)

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• 1991
  • 1991-12-03 WO PCT/JP1991/001685 patent/WO1992021963A1/ja not_active Ceased
• 1992
  • 1992-02-24 WO PCT/JP1992/000191 patent/WO1992021964A1/ja not_active Ceased
  • 1992-02-24 DE DE69221829T patent/DE69221829T2/de not_active Expired - Fee Related
  • 1992-02-24 EP EP92905103A patent/EP0544911B1/en not_active Expired - Lifetime

Patent Citations (2)

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