Radiographic Inspection with Antiscatter Grid
Radiographic testing with anti-scatter grids: using lamellar lead or tungsten grids to reduce Compton scatter and improve image contrast in thick-walled metal parts.
Physical-Chemical Working Principle
The anti-scatter grids consist of thin, parallel layers of materials like lead or tungsten. These grids absorb the Compton scatter that occurs during radiographic testing and can weaken image contrast. The absorption occurs due to the high density and strong electron absorption of these materials.
Metallurgical Relevance & Welding Risks
In thick-walled metal parts, Compton scatter can be strong, leading to a blurrier image. This makes it harder to detect flaws like porosity or other defects. Using anti-scatter grids improves image contrast, making smaller and finer defects more visible. Without grids, this can lead to inspection errors and potential problems in the part being overlooked.
Shop Practice & Procedures
Use anti-scatter grids made of lead or tungsten with a thickness of at least 0.5 mm. Position the grid between the test object and the detector. Make sure the grid is oriented parallel to the radiation direction. This minimizes scatter and improves image quality. For parts with varying material or different wall thicknesses, it may be necessary to use multiple grids in series.