The introduction of large amounts of hydrogen into low-carbon steel specimens by cathodic polarization produces hydrogen damage such as blisters, microcracks and dislocations. Hydrogen exists in the specimens as atoms dissolved in the iron lattice, as atoms trapped at lattice defects such as dislocations, and as gas precipitated in void defects such as blisters and microcracks. Hydrogen detected by electrochemical permeation in annealed specimens is one dissolved in the lattice, and the majority of hydrogen detected by glycerol displacement is the precipitated molecular hydrogen. In annealed specimens, a single peak is observed in the thermal evolution spectrum. This peak originates from the evolution of precipitated hydrogen, and the peak temperature depends on the specimen thickness, hydrogen concentration and heating rate. In cold-rolled specimens, two peaks are observed. The lower temperature peak originates from the evolution of precipitated hydrogen and the higher temperature peak from the trapped hydrogen.
(Received July 15, 1997)
Keywords: hydrogen, trapping effect, iron, thermal spectrum, hydrogen damage, microcrack, diffusion, concentration, depth distribution, activation energy
† This paper was originally published in Japanese in J. Japan Inst. Metals, 61 (1997), 274.