FАCTORS, АFFECTING THE SENSITIVITY OF MАGNETIC PАRTICLE CONTROL

Abstract

The magnetic powder method is one of the most common methods of non–destructive testing of steel parts. It has found wide application in aviation, railway transport, chemical engineering, in the control of large-sized structures, main pipelines, underwater facilities, shipbuilding, automotive and many other industries

The scale of application of the magnetic powder method is explained by its high performance, visibility of control results and high sensitivity. With the correct technology for monitoring parts, this method detects cracks, fatigue and other defects in the initial stage of their appearance, when it is difficult or impossible to detect them without special means.

The magnetic powder method is designed to detect surface and sub-surface (at а depth of up to 1.5 ... 2 mm) defects such as discontinuity of the product material: cracks, hairlines, delamination’s, non-welding of butt-welded joints, sunsets, etc.

The magnetic flux in the defect-free part of the product does not change its direction; if on its way there are reds with reduced magnetic permeability, for example, defects in the form of а discontinuity of metal (cracks, non-metallic inclusions, etc.), then part of the magnetic field lines leaves the part outside and enters it back, while local magnetic poles and, as а consequence, the magnetic field above the defect.

This article discusses the factors affecting the reliability of magnetic powder control. These factors must be taken into account when carrying out control at railway transport enterprises to prevent parts from being rejected. And also, the ways of distinguishing false factors from real defects are listed.

The differences between dry powder and suspension control are considered.