Permeation measurements were carried out on hot-rolled micro-alloyed steels with various C and Ti contents in order to determine the number of irreversible and reversible traps. The number, per unit volume, of irreversible traps was related to the calculated volume fraction of Ti(C,N) precipitates. These results, combined with transmission electron microscopy, showed that the largest number of irreversible traps was associated with steels that had the largest volume fractions of fine coherent Ti(C,N) precipitates. Reversible traps were associated with free Ti atoms, dislocations, and ferritic grain boundaries. Theoretical calculations confirmed that the H binding energy of free Ti atoms was 27.1kJ/mol.

R.Valentini, A.Solina, S.Matera, P.De Gregorio: Metallurgical and Materials Transactions A, 1996, 27[12], 3773-80