JPS637846Y2 - - Google Patents

Description

[Detailed Description of the Invention] Conventionally, the thickness of metal materials is measured using an ultrasonic thickness gauge.

This device measures the thickness of a material based on the time it takes for an ultrasonic wave that enters the material to be reflected by a reflecting surface and return again.

However, the above thickness gage is used to measure the thickness of austenitic stainless steel (hereinafter referred to as overlay) that is applied to the inner surface of pressure vessels for nuclear power, chemical engineering, etc. to increase its corrosion resistance. It was something I couldn't do. The reason for this is (1) The reflected ultrasonic waves are extremely weak, approximately 1/50 to 1/100 compared to ordinary metal materials.

(2) When the transmitted ultrasonic waves are strengthened, a dead zone occurs in the transmitted waves with a single-probe probe, and a dead zone occurs with a two-section probe due to the cross-over phenomenon from the transmitting side to the receiving side.

(3) Forest-like echoes from the overlay layer occur due to the use of high frequencies.

The overlay layer usually needs to have a thickness of 4.5 to 5.5 mm or more, but since the surface is ground with a grinder after the overlay is applied, a measuring method is required to confirm the thickness.

The present invention was developed as a result of intensive research in response to such requests, and as a result of considering the use of ultrasonic waves to measure the thickness of materials that are extremely susceptible to reflected ultrasonic waves, such as overlay layers. This is the discovery of a sonic probe. That is, the present invention provides an ultrasonic probe in which a receiving transducer and a transmitting transducer are mounted at relative positions, in which the width of the transmitting transducer is larger than that of the receiving transducer, and the transmitting point is The spacing between the transmitting transducer and the receiving point is wider than the width of the transmitting transducer.

A specific example of the present invention when applied to an overlay layer is as follows.

(1) Use a two-part type to eliminate the dead zone (short-range resolution).

(2) Use a large oscillator on the transmitting side to increase the transmitting power.

(3) Use a small oscillator on the receiving side to avoid reducing resolution.

(4) In order to prevent the so-called cross-over phenomenon in which ultrasonic waves leak from the transmitting side to the receiving side, the interval between the transmitting point and the receiving point (the position where the ultrasonic waves from the receiving transducer and the transmitting transducer reach the overlay layer) is equal to or larger than the width of the receiving transducer and the transmitting transducer, and the intersection of the acoustic axes is located at a depth 3 to 4 times the measured thickness of the overlay layer.

(5) The flaw detection frequency is set to approximately 2MHz due to the balance between the intensity of reflected ultrasonic waves and the occurrence of forest echoes.

An example of the present invention will be explained in detail based on the drawings.

Electric pulses generated by the ultrasonic flaw detector are applied to the transmitting transducer 2 via the transmitting side plug 1. At this time, the electrical energy is converted into mechanical vibration by the piezoelectric effect of the vibrator, generating ultrasonic waves. Note that since the transmitting transducer 2 is large, it can generate powerful ultrasonic waves.

The generated ultrasonic waves enter the overlay layer 5 from the transmission point 4 via the transmission wedge 3 made of acrylic resin.

In this case, since the transmitting wedge 3 is miniaturized, the attenuation of the ultrasonic waves can be reduced. In addition, a shielding plate 8 is provided to prevent ultrasonic waves from directly reaching the receiving transducer 11 in addition to being incident on the overlay layer 5.
However, it is extremely difficult to completely shield this, and some of it may leak. In other words, a cross-over phenomenon occurs.

In order to prevent this crossover phenomenon, the distance between the transmitting point 4 and the receiving point 9 is made wider than the width A of the transmitting transducer, and the position of the intersection point 7 of the acoustic axis with the transmitting and receiving transducers 2 and 11 is adjusted. The depth should be 3 to 4 times the overlay layer thickness.

In addition, ultrasonic waves are applied to the base metal 13 and overlay layer 5.
When reaching the interface between the overlay layer 5 and the base metal 13, a portion of the light is reflected due to the difference in acoustic impedance between the overlay layer 5 and the base metal 13. At this time, by using ultrasonic waves with a frequency of 2 MHz, attenuation in the overlay layer is reduced and the occurrence of forest echoes is reduced.

Further, the ultrasonic waves reflected at the boundary surface 6 reach the receiving transducer 11 from the receiving point 9 via the receiving wedge 10 . At this time, since the receiving wedge 10 is miniaturized, the attenuation of the ultrasonic waves can be reduced.

Here, the ultrasonic wave is converted into an electric signal by the receiving transducer 11, and is input to the ultrasonic flaw detector via the receiving plug 12.

Therefore, the thickness of the overlay layer 5 can be measured from the time required for the ultrasonic wave to propagate from the transmitting point 4 to the receiving point 9 using a calibrated display (braun tube) of the ultrasonic flaw detector. .

As detailed above, the present invention has remarkable effects such as being able to easily and accurately measure the layer thickness of a metal material whose reflected ultrasonic waves are extremely weak.

[Brief explanation of the drawing]

The drawing is a schematic explanatory diagram showing one example of the ultrasonic probe of the present invention. DESCRIPTION OF SYMBOLS 1... Transmission side plug, 2... Transmission transducer, 3... Transmission wedge, 4... Transmission point, 5... Overlay layer, 6...
Boundary surface, 7... Intersection, 8... Shielding plate, 9... Receiving point, 1
0... Wedge for reception, 11... Vibrator for reception, 12...
Receiving plug, 13...Base metal.

Claims (1)

[Scope of utility model registration request] In an ultrasonic probe in which a receiving transducer and a transmitting transducer are mounted in relative positions, the width of the transmitting transducer is larger than that of the receiving transducer, and the width of the transmitting transducer and the receiving transducer are An ultrasonic probe characterized in that the interval is equal to or wider than the width of a transmitting transducer.