Metal Magnetic Memory Inspection And Research On Authentic Steel

Conventional nondestructive testing technology is difficult to realize the inspection of austenitic stainless steel,and metal magnetic memory testing(MMMT)technique can not only detect macro defects formed in structures,but also can discover the micro defects of components and the budding injury.It shows the unique advantages in austenitic stainless steel equipment examination.However,due to a late start,the mechanism research,experimental study as well as the quantitative and qualitative evaluation remains to be perfect.This paper mainly carry out from two aspects:basic laboratory research and field application.In the laboratory,MMMT of reference blocks,precast defect blocks and tensile test blocks is implemented;In the later stage of field application,combining with the preliminary theory of laboratory,welds and head of austenitic stainless steel equipment are inspected using MMMT.Research findings:(1)The suitable experimental parameter is placed between north and south,positive detection,0.5mm lift-off;(2)Each characteristic parameters of MMMT should be considered.The defect qualitative judgments can take advantage of H-L characteristic curve,for quantitative aspects mainly pay attention to K value and m values,and the other characteristic parameters such as Kmax,Hmax-Hmin,S(K)max,K(x,z)max as a secondary criterion;(3)MMM characteristic parameter X can be a good indication for the maximum stress concentration zones(SCZ)of the selected area,then we can determine the location of the crack tip based on metal magnetic memory technology,as well as to predict the development direction of cracks;(4)MMMT can be used to judge the crack trend and to evaluate the residual stress;(5)Different polarity distribution of channel H-L and K value surge phenomenon between the curves occurs before member fracture;(6)MMMT can be well applied to the detection of austenitic stainless steel equipment.