Experimental Study On Metal Megnetic Memory Testing Of Dissimilar Steel Weld

This text discussed in-depth on Metal Magnetic Memory Testing (MMMT for short) from the two sides of mechanism and use, started from basal study of MMMT, the smooth sample and the sample with a circular hole prefabricated in it which were made from 45 # steel was tested in the condition of dead load and stretching to discuss the influence of the test direction to MMMT signal; And we designed a auxiliary assembly for testing, the external factor and shake were prevent from testing then, and MMM signal laws at different working condition of several samples had been got. In addition, this text has a key point at discussing the MMMT signal and changing feature of groups of dissimilar steel such as 0Cr18Ni9-Q345 and 1Cr13-Q345, and we tested the of a vapour-collected jar which was on active service on-site.In allusion to common types dissimilar steel weldings in petrochemical industry, we used MMMT and ultrasonic testing to detect and analyze the surface magnetic flux leakage density and its gradient of several groups of dissimilar steel weld, before and after annealing. The results of the study showed obviously sudden change on the MMM signal feature of the welding joint areas which proving the possibility of MMMT in dissimilar steel weld testing; And multi-group tests data compared before and after the heat treatment (HT) showed that the effect of heat treatment after welding was obviously on decreasing the stress of welding joins, leveling off the structure and performance of it. Also, the numerical valve after HT can also be used to evaluate dissimilar steel weld quality indirectly. Finally, we have a test of residual stress. It shows that this method can express distinctly stress concentration area and distribution of dissimilar steel weld, its valuable significance can be applied in detecting and evaluating flaw of pressure vessel welding point. Field inspection proved the practical applicability of MMMT. The study of this text provided rationale and detection criterion on practical engineering application for this advanced technology.