JPH04242109A - Method for measuring film thickness with ultrasonic wave - Google Patents

Abstract

PURPOSE:To measure the film thickness of a coating layer highly accurately by inputting an ultrasonic wave from the outer surface of an L-shaped pipe, and multiplying the time difference between the first and second reflected wave from the interface between the L-shaped pipe and the coating layer and the interface between the coating layer and air by the sound speed which is determined by the material of the coating layer. CONSTITUTION:A coating layer 3 of ceramics is formed on the inner surface of an L-shaped pipe 2 made of cast iron. An ultrasonic probe 4 is brought into contact with the outer surface of the L-shaped pipe 2, and an ultrasonic wave is inputted. Then, the time difference between the first reflected wave from the interface between the L-shaped pipe 2 and the coating layer 3 and the second reflected wave from the interface between the coating layer 3 and air is measured. Then, the time difference is multiplied by the sound speed in the coating layer 3, and the film thickness of the coating layer 3 is computed. In this way, the film thickness of the coating layer 3 can be readily measured at high accuracy.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] The present invention is an ultrasonic film thickness measurement method suitable for measuring the film thickness of a coating layer coated on the inner surface of a metal tubular member. It is about the method. [0002] Conventionally, as a method of measuring the thickness of a coating layer coated on the inner surface of a tubular member, when the base material is a magnetic material, an electromagnetic film thickness meter is used to measure the thickness of the coating layer. A method has been used in which the thickness of the coating layer is measured by applying it to the surface and measuring the magnetic force that attenuates depending on the distance from the magnetic material. In addition, when the base material is a non-magnetic material, a method has been used in which the thickness of the coating layer is measured using eddy current. [0003] In the method of bringing a probe into contact with the surface of a coating layer, the thickness of the coating layer coated on the inner surface of a bent tubular member or a long object is measured. This was extremely difficult, and it was impossible to measure small-diameter tubular members into which a probe could not be inserted. Means for Solving the Problems [0004] According to the present invention, ultrasonic waves are incident on the outer surface of a metal tubular member, and minute primary waves generated at the interface between the tubular member and the coating layer coated on the inner surface of the tubular member. Detect the reflected wave, use it as a reference, measure the time difference between the secondary reflected wave that occurs at the boundary between the coating layer and the air, and calculate the film thickness by multiplying this time difference by the speed of sound determined by the material of the coating layer. It is characterized by: [0005] The present invention will be explained in more detail with reference to the following examples, but the present invention is not limited thereto. A ceramic coating layer 3 having a thickness of about 0.3 mm is formed on the inner surface of a cast iron L-shaped tube 1 shown in FIG.
Apply the ultrasonic probe 4 to parts A, B, C, and D shown in FIG. 1 on the outer surface of this L-shaped tube, and use the method shown in FIG.
An ultrasonic wave of z was applied. At this time, the incident wave 5 shown in FIG.
The waveforms of the reflected waves 6 and 7 were obtained, and the time difference between the primary reflected wave 6 from the interface between the cast iron 2 and the coating layer 3 and the secondary reflected wave 7 from the interface between the coating layer 3 and air was measured. This was multiplied by the sound velocity of the coating layer, 3,860 m/s, to calculate the film thickness. Next, this measurement site was cut in a direction perpendicular to the tube core, and the film thickness was actually measured. Table 1 shows a comparison between the actual measurement values and the ultrasonic measurement values. [Table 1] Unit: m
[Effects of the Invention] As is clear from the above explanation, the method for measuring film thickness using ultrasonic waves of the present invention makes it easy to measure the thickness of a coating layer coated on the inner surface of a metal member having a complex shape, and also with high accuracy. It is measurable and has excellent industrial effects.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an L-shaped tube and measurement positions.

FIG. 2 is an explanatory diagram showing an incident part and a reflecting part of ultrasonic waves.

[Figure 3] Explanatory diagram of ultrasonic incident wave, primary reflected wave, and secondary reflected wave

[Explanation of symbols]

1 L-shaped tube 2 Cast iron 3 Coating layer 4 Ultrasonic probe 5 Transmission wave 6　Primary reflected wave of boundary surface 7 Secondary reflected wave of boundary surface

Claims (1)

[Claims] Claim 1: When measuring the thickness of a coating layer coated on the inner surface of a metal tubular member, ultrasonic waves are incident on the outer surface of the tubular member, and ultrasonic waves are measured from the interface between the tubular member and the coating layer.
The film thickness obtained by ultrasonic waves is calculated by measuring the time difference between the secondary reflected wave and the secondary reflected wave from the interface between the coating layer and the air, and multiplying the time difference by the speed of sound determined by the material of the coating layer. Measuring method.