THERMAL EVOLUTION SPECTRUM OF HYDROGEN FR OM LOW-CARBON STEEL CHARGEDBY CATHODIC POLARIZATION

Introduction of a large amount of hydrogen into specimens of a low car bon steel by cathodic polarization produces hydrogen damages such as b listers, microcracks, and dislocations. Hydrogen in the specimen exist s as hydrogen atoms dissolved in iron lattice, atoms trapped at lattic e defects such as dislocations, and gas precipitated in void-type defe cts such as blisters and microcracks. Hydrogen in the annealed specime ns detected by the electrochemical permeation method was the lattice d issolved hydrogen, and the majority of hydrogen detected by the glycer ol displacement method was the precipitated molecular hydrogen. In the case of the annealed specimens, one peak was observed in the thermal spectrum of hydrogen evolution rate. This peak originated in evolution of the precipitated hydrogen, and the peak temperature depended on sp ecimen thickness, hydrogen concentration, and heating rate. In the cas e of cold-rolled specimens, two peaks were observed, The lower and hig her temperature peaks originated in evolution of the precipitated hydr ogen and the trapped hydrogen, respectively.