Selection of Ultrasonic Flaw Detector Probes for Butt Welds in Thin Steel Plates

In the ultrasonic inspection of butt welds of thin steel plates, the selection of the probe is a key factor to ensure the inspection quality. Due to the thinner thickness of the steel plates, the difficulty of inspecting the butt welds increases accordingly. Therefore, selecting an appropriate ultrasonic flaw detector probe is crucial for improving inspection accuracy and efficiency.

Ultrasonic Flaw Detector Probe: Selection Principles

When performing ultrasonic inspection of butt welds in thin steel plates, the K value and the front distance L value of the probe are the main factors affecting the inspection effect. The K value is the tangent of the refraction angle of the main sound beam of the oblique probe in the workpiece under inspection, while the front distance L value is the distance from the incident point to the front edge of the probe. These parameters of the probe must be reasonably selected based on the actual condition of the weld to ensure that the ultrasound can accurately scan all parts of the weld.

For example, for an8mmthick steel plate butt weld, it is very important to choose the appropriate ultrasonic flaw detector probe. A probe such as 5Z8×12K3.0 with a front distance L of 10mm, although it has a moderate K value, may not effectively meet the detection requirements due to its larger front distance. Therefore, a probe with a shorter front distance such as 5P6×6K3.0 (L=4mm) may be more suitable for this type of inspection.

Selection of Ultrasonic Flaw Detector Probes for One-pass Scanning of the Weld Root

When performing one-pass scanning of an8mmthick steel plate butt weld, the selection of the probe requires special attention. The groove type of the steel plate is generally V-shaped, and the width of the weld cap is usually around 22mm. To ensure that the ultrasonic flaw detector probe can effectively scan the root of the weld, the front distance L value and K value of the probe must meet specific calculation formulas.

For example, using a 5P6×6K3.0 probe (L=4mm), this probe can meet the requirements under the 22mm weld width, ensuring that a one-pass scan can reach the weld root. On the other hand, using a 5Z8×12K3.0 probe (L=10mm), may lead to ineffective detection due to its larger front distance, thus affecting the inspection of the weld root.

Selection of Ultrasonic Flaw Detector Probes for Second-pass Scanning of the Upper Part of the Weld

In the second-pass scanning, the choice of probe is equally important. For an 8mm thick steel plate butt weld, the width of the weld and the back bead width affect the probe selection. In this case, the probe needs to be able to effectively scan the upper part of the weld to ensure no missed areas are left undetected.

The K value and the front distance L value of the probe should meet specific calculation requirements to ensure that the ultrasound can comprehensively scan the area 3mm from the bottom to the centerline of the weld width. If the K value of the probe is too small or the front distance is too large, it may lead to missed inspections, thereby affecting the comprehensiveness and accuracy of the detection.

In actual ultrasonic inspections, selecting an appropriate ultrasonic flaw detector probe is crucial. One needs to consider the K value and the front distance L value of the probe comprehensively to meet specific inspection requirements. Choosing a probe that conforms to the calculation requirements can effectively improve inspection accuracy, reduce missed inspections, and thus ensure the inspection quality of thin steel plate butt welds.