Effect of Aging Treatment on Hydrogen Embrittlement of Drawn Pearlitic Steel Wire

Hydrogen embrittlement has become a crucial issue with the promotion of high-strength steel. As-drawn pearlitic steel wire is well known to have superior resistance to hydrogen embrittlement. The resistance to hydrogen embrittlement is clarified as being further improved by aging treatment at 100-degrees C and 300-degrees C for 10-min. of as-drawn 0.8 mass% C pearlitic steel wire with phi 5.0 mm (epsilon=1.9). The higher the aging temperature is, the better the resistance to hydrogen embrittlement becomes. Simultaneously, the strength even increased slightly by aging treatment. The mechanism is investigated by exploiting thermal desorption analysis (TDA) and the newly developed TEM precession analysis. Aging at 100-degrees C led to a decrease in the hydrogen content at peak I around 100-degrees C in the TDA curve, which is inferred to be caused by C segregation to dislocations resulting in improvement of hydrogen embrittlement. Aging at 300-degrees C further improved the resistance to hydrogen embrittlement, which is presumably brought about by the local recovery of the heterogeneously deformed lamellar ferrite area together with the C segregation to dislocations. Here, the strength increased slightly by aging due to the softening factor of recovery and the hardening factor of strain aging.