JP2000275034A - Edge detection method for metal plate - Google Patents

Abstract

(57) Abstract: The present invention is applied to a line-focusing ultrasonic inclusion sensor for detecting inclusions inside a metal plate in a metal plate transfer line. The present invention relates to a metal plate edge detection method for detecting an edge of a metal plate. The transmission time of an ultrasonic pulse from a transmitter to a receiver of a line focus type ultrasonic inclusion sensor is measured, and an ultrasonic wave which is a propagation time of a transmitted wave transmitted through a metal plate among the receivers is measured. The position between the receiver that receives the sound pulse and the receiver that receives the ultrasonic pulse which is the propagation time of the direct wave that does not pass through the metal plate is defined as the edge position of the metal plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a line focus type ultrasonic inclusion sensor capable of detecting inclusions in a metal plate such as a steel plate or a rolled metal plate at a time in the width direction. The present invention relates to a method for detecting an edge position of a plate. Here, it is assumed that a metal band is included in the metal plate. Hereinafter, a steel plate will be described as a typical example of a metal plate, but the present invention is not limited to this.

[0002]

2. Description of the Related Art A line focus type ultrasonic inclusion sensor using an ultrasonic flaw detection method is most suitable for detecting a defect inside a material of a steel sheet, particularly an inclusion. As shown in FIG. 1, the line focus type ultrasonic inclusion sensor has a large number of ultrasonic transmitters and receivers 1 and 2 opposed to each other and continuously arranged in the width direction of the steel plate 3, and a continuous steel plate based on the ultrasonic reception result. This device detects internal inclusions. As the ultrasonic transceivers 1 and 2, a line-focus ultrasonic transmitter and a line-focus ultrasonic receiver are used. Also,
The line focus type ultrasonic transmitter / receiver may be an array type transmitter / receiver.

[0003] In a line focus type ultrasonic inclusion sensor, in order to accurately detect a transmitted wave propagating through a steel plate and a reflected wave from a defect, an edge of the steel plate to be inspected (edge).
It is extremely important to detect In other words, in the vicinity of the edge of the steel sheet, the ultrasonic transmitter / receiver that transmits ultrasonic waves through the inside of the steel sheet and is effectively performing defect detection accurately grasps the position of the transmitter / receiver in the width direction to obtain the edge of the steel sheet. This is to make it possible to detect defects up to.

As a method for detecting an edge of a steel sheet, an optical edge detection method using a fluorescent lamp and a camera, and a method disclosed in
There is a method utilizing magnetic characteristics as disclosed in Japanese Patent Publication No. 265302. However, in the method of detecting inclusions inside a steel sheet by the ultrasonic flaw detection method, in order to apply the edge detection for the line focus type ultrasonic inclusion sensor, in addition to the ultrasonic sensor for the edge position detection, It is necessary to install a fluorescent lamp and a camera, or a device for magnetic detection such as a magnetizing device, which results in a large-scale facility and a large increase in cost.

As a method of detecting the edge of a steel sheet using a line focus type ultrasonic inclusion sensor, a method of monitoring the propagation time of a transmitted wave propagating through the steel sheet and detecting the edge of the steel sheet is also conceivable. . That is, the ultrasonic wave propagation time t _f when a steel plate having a thickness h is present between the probes (transmitter and receiver) at the opposed distance L is represented by V _s , the ultrasonic wave propagation velocity in the steel plate, and Assuming that the ultrasonic wave propagation velocity is V _W , t _f = (L−h) / V _W + h / V _s (1) Then, monitoring the ultrasonic wave propagation time t _f in each probe, it is a method for the position in which t _f significantly changes the edge position of the steel sheet.

However, since the thickness of the steel sheet actually has a variation Δh, the above equation (1) is superimposed on the ultrasonic propagation time t _f by the variation Δt as shown in the following equation (2). However, there is a problem that the edge position is often erroneously recognized.

[0007]

(Equation 1)

[0008]

SUMMARY OF THE INVENTION The present invention utilizes a line-focus type ultrasonic inclusion sensor for detecting inclusions inside a steel sheet, and does not misidentify the edge position without juxtaposing unnecessary facilities. An object of the present invention is to provide a method for detecting an edge of a steel sheet that can be accurately detected. And
As a final object, it is possible to accurately grasp the edge position of the steel plate and accurately detect inclusions inside the steel plate up to the edge position of the steel plate.

[0009]

According to the present invention, a plurality of pairs of a line focus type ultrasonic transmitter and a line focus type ultrasonic receiver are arranged side by side in the width direction of a metal plate with a metal plate interposed therebetween. Using a line focus type ultrasonic inclusion sensor that transmits ultrasonic pulses from the transmitter to the receiver to detect inclusions inside the metal plate, the edge of the metal plate that detects the edge of the metal plate In the detection method, the propagation time of the ultrasonic pulse from the transmitter to the receiver is measured, and among the receivers, the ultrasonic pulse that is the propagation time of the transmitted wave transmitted through the metal plate is received. A receiver,
The above problem has been solved by an edge detection method of a metal plate, wherein a position between the receiver and the receiver that receives an ultrasonic pulse that is a propagation time of a direct wave that does not pass through the metal plate is an edge position of the metal plate. It is.

[0010] Similarly, a plurality of pairs of line-focusing ultrasonic transmitters and line-focusing ultrasonic receivers are arranged side by side in the width direction of the metal plate with the metal plate interposed therebetween.
Using a line focus ultrasonic inclusion sensor that transmits ultrasonic pulses from the transmitter to the receiver to detect inclusions inside the metal plate, detects the edge of the metal plate to detect the edge of the metal plate A method, comprising:
Metals are characterized in that a position between a receiver that receives a reception wave pulse two or more times and a receiver that receives only once for one transmission wave pulse is defined as an edge position of a metal plate. The above problem was solved by a plate edge detection method.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an ultrasonic wave propagation path in a line focus type ultrasonic inclusion sensor to which the present invention is applied will be described with reference to FIG. However, in FIG. 2, the description of the ultrasonic probe (transmitter and receiver) itself is omitted. In FIG. 2, T ₀ represents a transmission wave emitted from the ultrasonic transmitter. The ultrasonic wave emitted from the ultrasonic transmitter, incident on the steel plate 3 and transmitted through the inside is directly emitted to the outside as a transmitted wave T ₁ , or is reflected once inside the steel plate and emitted as a transmitted wave T _2. Is split into an outgoing wave and is incident on an ultrasonic receiver. Here, there is an ultrasonic wave reflected and emitted twice or more inside the steel plate, but the description is omitted here. It also is reflected by the steel plate 3 inside the inclusions 6, and enters the ultrasonic receiver as a defect reflected wave T _C. Here, the path length of the defect reflected wave T _C is intermediate between the path lengths of the transmitted wave T ₁ and the transmitted wave T ₂ . on the other hand,
Transmitted wave T of ultrasonic wave emitted at the position off the steel plate
₀ will be incident on the ultrasonic receiver as directly as wave T _D.

The line focus type ultrasonic inclusion sensor transmits an ultrasonic pulse from an ultrasonic transmitter to a steel sheet being conveyed at a constant period, and receives a received wave (the above-mentioned transmitted wave and defect reflected wave) for the transmitted wave. This is a device that detects inclusions by detecting them. In addition, the received wave is detected as a direct wave at the position off the steel plate.However, since the position of the edge fluctuates due to fluctuations in the width of the steel plate, movement of the conveyor, etc., up to which probe is off the steel plate Is difficult to identify.

Here, since the inclusion defect is at an irregular position, the defect reflected wave is received at an irregular period, but the transmitted wave and the direct wave are received at a constant period in synchronization with the transmission wave. First, a first embodiment of the present invention will be described with respect to a method of detecting an edge of a steel plate applied to the line focus type ultrasonic inclusion sensor. As shown in FIG. 3A, an ultrasonic transmission wave (T ₀ ) pulse 5a is emitted at time t ₀ .
The emission of the transmission wave pulse is performed at a constant period for each line focus type ultrasonic transmitter.

Here, the steel sheet was injected at a position where it was removed.
Transmitted wave (T₀) The pulse is intact as shown in (b)
Direct wave (T_D) Pal
(Time t_Three). At this time, the direct wave
(T_D) Propagation time t_DIs t _D= T_Three-T₀But
This value is that the distance L between the opposing probes is constant
From a constant value regardless of the variation in the thickness of the steel sheet.
You. That is, t_D= L / V_W... (3)

On the other hand, the ultrasonic pulse incident on the steel plate and transmitted through the inside is transmitted to the line focus type ultrasonic receiver by a transmitted wave (T ₁ ) pulse 7a (reception time t ₁ ) as shown in FIG. It is received as a wave (T ₂ ) pulse 7b (reception time t ₂ ). Here, when there is inclusion defects inside the steel sheet, the transmitted wave as shown in (d) (T ₁₎ pulse 7a and transmitted wave (T ₂₎ intermediate the defect reflected wave pulse 7b (T _C) Pulse 8 appears.

Here, the propagation time t _f of the transmitted wave (T ₁ ) pulse 7a is already shown in the equation (1). This propagation time t
_f varies depending on the thickness of the steel sheet,
The speed of sound in a steel plate (5900 m / s) is the same as the speed of sound in water (1480 m / s).
(Seconds), the relationship of t _D > t _f + Δt (4) is normally satisfied even when the variation Δt is expected.

Therefore, the time t from the ultrasonic transmission time t _0
The signal received after the passage of _D can be regarded as a direct wave, and all the receivers that have detected the direct wave can be judged to be off the edge of the steel sheet, and the edge position can be detected. However, even with the direct wave detected as described above, the influence of the large thickness variation and the surface flaw of the steel sheet is compounded, so that the transmitted wave propagation time t _f is equal to the direct wave propagation time t _D. It is possible that they match, and there is no danger of erroneous detection.

Therefore, in the present invention, the propagation time is monitored from both ends of the probe arranged in the width direction toward the center, and it is assumed that the propagation time is a direct wave continuously. It is preferable that it is preferable to determine that the probe immediately before the probe is off the edge of the steel plate. For example, in the case of a line focus type ultrasonic inclusion sensor having N = 200 channels, two adjacent channels (n, n + 1) are sequentially monitored, and (n, n +
1) = (1,2) to (9,10) have no abnormality and all are determined to be direct waves. If (n, n + 1) = (10,11) and there is abnormality, then n <100 10 channels and 11
The middle position of the channel is recognized as the edge of the steel plate.

If there is an abnormality at (n, n + 1) = (190, 191), and if all the direct waves from (191, 192) to (199, 200) are determined to be direct waves, then n> 100. 19
The middle position between channel 0 and channel 191 is recognized as the edge of the steel plate. Next, regarding a method of detecting an edge of a steel sheet applied to the line-focus type ultrasonic inclusion sensor,
A second embodiment of the present invention will be described.

The second embodiment of the present invention is an invention utilizing gate processing used for detecting inclusions.
Hereinafter, description will be made with reference to FIG. As shown in FIG. 4A, an ultrasonic transmission wave (T ₀ ) pulse 5a is emitted. The emission of the transmission wave (T ₀ ) pulse is performed at a constant period for each line focus type ultrasonic transmitter.

When the ultrasonic wave is transmitted through the steel plate, the transmitted wave (T ₁ ) pulse is transmitted as shown in FIG.
7a and a transmitted wave (T ₂ ) pulse 7b are received. Inclusion defects are caused by the transmitted wave (T) as already shown in FIG.
₁ ) It is detected at an intermediate position between the pulse 7a and the transmitted wave (T ₂ ) pulse 7b. In order to detect this inclusion defect, a gate is set.
As shown in (c), the transmission wave (T ₁ ) is gradually expanded from the end point of the pulse 7a as a starting point, is automatically adjusted to have an optimum width, and reaches the start position of the transmission wave (T ₂ ) pulse 7b. Is set as the optimum gate width. In this way, in the case of a transmitted wave, it is possible to recognize that there are two received wave pulses since the optimum gate width is set.

On the other hand, in the case of the direct wave pulse 9a emitted at a position where there is no steel plate (FIG. 4D), the gate width is increased as shown in FIG. Therefore, the gate width only increases. here,
In the second embodiment of the present invention, a threshold value t _th is provided in advance for the gate width, and the gate width exceeds the threshold value t _th , and the optimum gate setting cannot be performed. Detect that there is only a direct wave pulse 9a. Here, it is natural that the value of the threshold value t _th is set to a value larger than the value of the optimum gate width.

It is possible to determine whether the received wave pulse has been received twice or only once, depending on whether the optimum gate width can be set in this way. And the received wave pulse is 2
Receiving once means that the pulse is a transmitted wave, and receiving only once means that the pulse is a direct wave. Even in the above manner, it is possible to accurately detect the edge of the steel plate.

In the second embodiment as well, similarly to the first embodiment, whether or not the gates can be set from both ends of the probe arranged in the width direction toward the center is determined. Is monitored, and it can be determined that the probe up to the immediately preceding probe has deviated from the edge of the steel plate for a probe in which the gate cannot be set continuously.

[0025]

According to the present invention, in the detection of inclusions on a steel plate in a line-focus type ultrasonic inclusion sensor,
The ultrasonic transducers arranged in a large number in the width direction can be used as they are, and the edges of the steel sheet can be detected accurately and continuously in a non-contact manner without being affected by the thickness variation. Thus, the main purpose of detecting inclusions inside the steel plate can be accurately detected up to the edge of the steel plate.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a line focus type ultrasonic inclusion sensor to which a metal plate edge detection method of the present invention is applied.

FIG. 2 is a schematic diagram illustrating a path of an ultrasonic wave in a cross section of a metal plate.

FIG. 3 is a time chart of an ultrasonic pulse explaining a first embodiment of the metal plate edge detection method of the present invention.

FIG. 4 is a time chart of an ultrasonic pulse explaining a second embodiment of the metal plate edge detection method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ultrasonic transmitter (line focus ultrasonic transmitter) 2 Ultrasonic receiver (line focus ultrasonic receiver) 3 Metal plate (steel plate) 4 Ultrasonic reception beam 5 Ultrasonic transmission beam 5a Transmission wave (T ₀ ) pulse 6 inclusions (defects) 7a transmitted wave (T ₁₎ pulse 7b transmitted wave (T ₂₎ pulse 8 defects reflected wave (T _C) pulse 9 direct wave (T _D) pulse 31 ends (edges) t ₀ greater Sound wave transmission time t _D Direct wave propagation time t _f Transmission wave propagation time t ₁ , t ₂ Steel plate transmission wave reception time t ₃ Direct wave reception time t _th Gate width threshold value T ₀ Transmission wave T ₁ , T ₂ Transmission wave T _C defect reflected wave T _D direct wave

Claims (2)

[Claims] 1. A plurality of pairs of a line-focusing ultrasonic transmitter and a line-focusing ultrasonic receiver are arranged side by side in a width direction of a metal plate with a metal plate interposed therebetween. Using a line focus type ultrasonic inclusion sensor that transmits ultrasonic pulses toward and detects inclusions inside the metal plate, an edge detection method of the metal plate that detects the edge of the metal plate, The propagation time of the ultrasonic pulse from the transmitter to the receiver is measured, and among the receivers, the receiver that receives the ultrasonic pulse that is the propagation time of the transmitted wave transmitted through the metal plate, and the transmitter that transmits the ultrasonic pulse A method for detecting an edge of a metal plate, wherein a position between the ultrasonic wave pulse and a receiver that receives an ultrasonic pulse having a propagation time of a direct wave is set as an edge position of the metal plate. 2. A plurality of pairs of a line-focusing ultrasonic transmitter and a line-focusing ultrasonic receiver are arranged side by side in a width direction of a metal plate with a metal plate interposed therebetween. A metal plate edge detection method for detecting an edge of a metal plate by using a line-focus type ultrasonic inclusion sensor for transmitting an ultrasonic pulse toward the metal plate to detect an inclusion inside the metal plate, The position of the edge of the metal plate between the receiver that receives the reception wave pulse twice or more for one transmission wave pulse and the receiver that only receives the reception wave pulse once. An edge detection method for a metal plate.