Analysis of ASTM X-ray shrinkage rating for steel castings

This paper presents the results of two different studies that examined the ASTM x-ray shrinkage rating system for radiographs of steel castings. The first study evaluated the repeatability and reproducibility of x-ray shrinkage ratings through a statistical study of 128 x-rays that were each rated seven different times. It was found that the seven ratings for each x-ray were in unanimous agreement on both shrinkage type and level for 12.5% of the x-rays. All of the x-rays that had unanimous agreement for both type and level were either completely sound or very unsound (Level 5). The largest variance was found to occur in Level 2 and 3 x-rays, which had 95% confidence intervals of about +/-2 x-ray levels. The average 95% confidence interval for all 128 x-rays was +/-1.4. The second study involved an effort to determine the shrinkage severity level of x-rays through digital analysis of scanned radiographs. It was found that defect area and circumference correlated reasonably well with x-ray level, but only if the shrinkage type was correctly determined first.