Investigation On The Magnetic Monitoring Technology For The Residual Stress Of Austenitic Stainless Steel

Stainless steel plays an important role in industrial fields such as nuclear energy,shipping, aviation etc. because of its excellent performance. According to a series ofphenomenon we can find that, a test object that with strong stress will produce crack orlead to breakage during usage after receiving external force of environmental effect,leading to serious accident. It’s significant to study the inspection technology of theresidual stress of stainless steel.This issue proposes a new assumption and method to the residual stress exists orproduced in stainless steel test objects. This method is based on magnetic inspectionmethod, and using high precision magnetic vector sensor to inspect the magneticinduction intensity produced in the surface of the test object, in the background ofgeomagnetic field. Due to the residual stress, there will have some effect on thepermeability to some extent which then affects the magnetic induction intensity on thesurface of the test object. After repeatable studies, the experimental results verify theavailability and reliability of the magnetic technology in the residual stress inspection.Firstly, measuring the original magnetic signal using the independent developedinstrument, and then measuring the residual stress and strain in the test object.In thefollowing, make heat treatment and do load experiment on the test object respectively.The heat treatment is under500℃to reduce the residual stress and the strain, changethe treatment time(4h、6h、8h、10h、12h),and then measure corresponding data(themagnetic intensity, residual stress, strain, grain size etc.), then make a conclusion of thediscipline. With the residual stress and strain reducing, the magnetic intensity will getdown, but the grain size instead. In load experiment, using the same loading(differenttime)and different loading(same time)on the test object, after analyzing theexperimental results we can discover that when apply the same loading with differenttime, there is little change on the stress and the strain, and the Magnetic inductionintensity range is reducing; While applying different load with same time, the magneticintensity increase with the increasing of the loading, and the amplitude amplifies a little,also the stress and the strain increase with the decreasing of the grain size.Through the residual stress inspection study, the results show that this methodhave good inspection effect on the distribution of the residual stress of the304stainlesssteel.