Comparing the results of testing a longitudinal tube weld by nondestructive methods

Abstract

Defects of longitudinal tube welds identified by X-ray inspection are studied in order to determine possible causes of their occurrence and to assess the reliability of nondestructive testing results. Metallographic analysis shows that the base metal and weld metal meet the requirements of regulatory documents. The strength properties and the chemical composition conform to the standards. The contamination with non-metallic inclusions in the segregation streamers of the sheet extending to the edge and falling into the fusion zone was detected in X-ray photographs and incorrectly interpreted as a defect. This assumption is based on the correlation of X-ray patterns with the position of the grooves in the zones of the studied welded joints, but it ignores the results of studying by other nondestructive testing methods, and most importantly, it is not confirmed by metallographic studies. Neither were these defects found in the tubes during magnetic flaw detection by means of a UMD-101M device in the line of production of longitudinally electric-welded tubes. Erroneous defect identification during X-ray inspection happens in tube making. The results of the study show the expediency of the integrated application of different testing methods for a reliable assessment of the quality of tubes or pipes of both small and large diameters.