Microstructural Phase Detection in Steel Components by Magnetic NDE Sensor

Abstract

Steel is the most widely used material in structural components due to its superior strength, ductility, and corrosion properties both at room temperature and elevated temperatures. The microstructural phase detection by NDE techniques is advantageous for the identification of any structural damage in steel structures and components so as to avoid any catastrophic failure. With this viewpoint, a magnetic NDE sensor, MagStar, is developed by CSIR-NML in collaboration with M/s, Technofour, Pune (India). The sensing head of this device is placed in contact with steel components and important soft magnetic parameters like coercivity and Barkhausen voltage are measured. Two important steels, interstitial free (IF) and rail steels, are chosen for this research and different annealing treatment is done to generate different microstructural phases. The annealing treatment generates strain-free recrystallized microstructure in cold rolled IF steel and decarburized ferrite layer in rail steel. These structural changes are related to increasing magnetic softness in IF and rail steel, monitored by MagStar. Therefore, the electromagnetic NDE sensor is found a potential tool for monitoring microstructural phases of steel during its processing and service exposure as the components.