Effects of Drawn Strain and Aging Temperature on Critical Diffusible Hydrogen Content and Absorbed Hydrogen Content in Pearlitic Steel Wires

It is well-known that pearlitic steel wires have a higher resistance to hydrogen embrittlement than tempered martensitic steels. It is significant to clarify the effect of various mechanisms of the hardening on hydrogen embrittlement for the compatibility between high strength and resistance to hydrogen embrittlement. In this study, effects of drawing strain and aging temperature in pearlitic steel wires on hydrogen embrittlement properties were investigated. Absorbed hydrogen content after cyclic corrosion test (H-E) was increased with added drawn strain and saturated with large amounts of drawn strain. Furthermore, the higher the aging temperature, the smaller H-E is obtained. The critical diffusible hydrogen content (H-C) in pearlitic steel wires aged at 450 degrees C is higher than that aged at 250 degrees C and as-drawn pearlitic steel wires. The reasons are considered to be a decrease in the dislocation density and suppression of crack propagation due to the short length of ferrite-cementite interface. Consequently, the pearlitic steel wires aged at 450 degrees C are excellent in resistance to hydrogen embrittlement because H e is much higher than H-E, although the tensile strength of pearlitic steel wires is decreased by aging at 450 degrees C and above.