1. Renovation of the detection surface: Spatter, oxide scale, pits and rust on the welding working surface should be removed. The smoothness is generally lower than ▽4. The trimming width of the flaw detection surfaces on both sides of the weld is generally greater than or equal to 2KT+50mm, (K: probe K value, T: workpiece thickness). Generally, a probe with a K value of 2.5 is selected based on the base material of the weldment. For example: if the base metal thickness of the workpiece to be tested is 10mm, then 100mm should be ground on both sides of the weld.
2. The selection of coupling agent should take into account the viscosity, fluidity, adhesion, non-corrosion to the workpiece surface, easy cleaning, and economy. Based on the above factors, paste is selected as the coupling agent.
3. Due to the thin thickness of the base material, the detection direction is carried out on one side and both sides.
4. Since the plate thickness is less than 20mm, the horizontal positioning method is used to adjust the scanning speed of the instrument.
5. Use rough flaw detection and fine flaw detection during the flaw detection operation. In order to roughly understand the presence, distribution, quantification, and positioning of defects, precision flaw detection is used. Several scanning methods such as zigzag scanning, left and right scanning, front and back scanning, corner scanning, and surround scanning are used to discover various defects and determine the nature of the defects.
6. Record the detection results and evaluate and analyze any internal defects if found. The classification of internal defects of the welding butt joints should comply with the provisions of the current national standard GB11345-89 "Manual Ultrasonic Flaw Detection Methods and Classification of Flaw Detection Results for Steel Welds" to judge whether the weld is qualified. If defects exceeding the standard are found, a rectification notice will be issued to the workshop, and the workshop will be ordered to make rectifications and re-inspect until they pass the inspection.
Common defects in general welds include: pores, slag inclusions, incomplete penetration, incomplete fusion and cracks, etc. So far (2013), there is no mature method to accurately judge the nature of the defect. It only comprehensively evaluates the defect based on the shape of the defect wave and the change in the height of the reflected wave obtained on the fluorescent screen, combined with the location of the defect and the welding process. Judgment.
May 07, 2024
