Hydrogen ( H) is one of the important factors to reduce the mechanical properties of steel

the H content of hot rolled middle carbon bearing steel C56E2 is lower than 0. 02 x 10

-6

and desportion rate of hydrogen content reaches to 95%-98% compared with which content in liquid steel. There are two main H traps

which are carbide Fe

3

C and precipitate/inclusion in hot rolled steel

and the residual H is mainly the precipitate/inclusion hydrogen trap. The two kinds of trapped H were increased in the samples with H charged in condition of 25 ℃

2 mA/cm

2

constant electric current

0.1 mol/L NaOH solution and duration 0-216 h

and the H content were increased at first then decreased with extension of hydrogen charging time. The carbide trapped H ratio (carbide trapped H(0-0.0107) X 10

-6

/total H) was increased and the precipitate/inclusion trapped H ratio (precipitate/inclusion trapped H(0. 003 5-0. 019 0) x 10

-6

/total H) decreased with H charging time increasing. The free energy difference of TDS hydrogen precipitation are mainly affected by the H trap absorb and H hole initial occupied ratio

and it is increased with the H charging time increasing. The active energy of carbide trapped H is decreased with the content increasing of carbide trapped H

and active energy of precipitate/inclusion H is increased with the content accumulation increasing of precipitate/inclusion H at the moment of its desorption peak time.