Due to various factors such as grain size, internal stress, structure, coupling agent, surface conditions, temperature, internal defects, etc., the thickness measurement of the steel plate will have a certain negligent effect on the thickness measurement results. Therefore, the ultrasonic thickness gauge is used to accurately measure the steel plate. The process of thickness should try to avoid the influence of the above factors to determine the measurement method.

"Ultrasonic Thickness Gauge's Method for Accurately Measuring the Thickness of Steel Plates" refers to the above-mentioned factors and proposes corresponding thickness measurement methods. The corresponding thickness measurement method progresses as follows:

Surface treatment of steel plate inspection site

Eradicate the dust, dirt, scale, rust, paint and other coverings on the surface of the inspection site required for the steel plate. The rough surface can be polished with 400 # sandpaper to expose the metallic luster. The area size is about 30 × 30mm.

Production of comparative test blocks

1) Selection of comparative test blocks. The key to the quality of the material of the competition block is that its acoustic characteristics must be together with the substrate of the workpiece to be inspected, that is, the grain size, heat treatment, physical function, and chemical composition of the material must be with the inspected component. For this purpose, the steel plate body to be inspected is selected to make the competition block to ensure that the acoustic functions of the two materials of the test block and the steel plate to be inspected are together.

2) Production of comparative test blocks. In a flat area at a distance of 10 mm from the edge of the steel plate to be inspected, according to the request of measurement process 1, the surface of the steel plate in an upward and downward relative orientation is processed, and the area is about 30 × 50 mm. Use a micrometer to measure the thickness of the steel plate at the four corners and the base of the area. Record the results. Compare the results of the five measurements. If the error of the measured value is within 0.002mm, the flatness of the steel plate in this area is considered. Satisfy the request for making thickness test blocks, and use the steel plate in this area as a pulse reflection type ultrasonic thickness measurement competition.

3) Measurement of test block thickness. Using a micrometer that has passed the calibration and calibration, measure the base of the game block 3 times at 30 × 50mm, and take the average value of 3 times as the measurement value of this orientation. Taking a rolled steel plate with a thickness of 25 mm as an example, if the measured value H of the practice is 24.982 mm, 24.983 mm, and 24.984 mm, the three-time average of 24.983 mm is the thickness of the steel plate.

4) Probe selection. The probe is selected according to the thickness and accuracy of the workpiece. When the workpiece is thin, a dual-frequency probe or a probe with a delay block is used. When the workpiece is thick, a low-frequency single-crystal probe is used. As far as possible, a broadband probe is used.

5) Surface inspection of the probe. Check whether the surface of the probe is stable. If it affects the measurement accuracy, it is necessary to sand the probe with 500 # metallographic sandpaper to make the surface smooth and ensure parallelism, or replace the probe with a new one.

6) Calibration of zero point of thickness gauge. Adjust the speed of sound to 5900m / s and press the ZERO key to enter the calibration situation. Coupling agent is applied to the random test block, and the probe and random test block are coupled until the screen flashes the test block thickness is 4mm, which means the calibration is complete.

7) Measuring the sound velocity of steel plates

(1) Coupling the probe with the micrometer measuring part on the base of the competition block, flash the thickness value, then roll the probe 90 degrees, so that the probe crosstalk sound insulation board is perpendicular to the previous one, and measure the thickness of the test block again, and take 2 measurements The smaller the median value is the thickness of the test block. If the measured values of the two measurements are 24.88mm and 24.90mm, the first 24.88mm is used as the thickness value of this area. The probe should be placed stably and the pressure should be appropriate during the inspection.

(2) Use the fine adjustment button ▲ or fine-tune the thickness display value, adjust the screen display value to an average value of 24.98mm measured by a micrometer (the third digit after the decimal point is rounded to 4), and press the VEL key to flash the measured sound velocity of the steel 5924m / s.

8) Measurement of steel plate practice thickness. Under this sound velocity condition, the inspected part of the steel plate surface that has been cleaned is measured and recorded. Each thickness measurement direction is measured once in the mutually perpendicular direction, and the thickness is based on the small value.

Each step in the process of measuring steel plates is planned to eliminate a certain influence factor, in order to reach a more accurate measurement of the thickness of the steel plate, and reduce the fault of the influence of the factors.