Abstract
In this study, the effects of remaining hydrogen content on the lower critical stress of weld metal (LCS) in high strength steels were evaluated, because it was reasonably considered that remaining hydrogen content related with LCS more closely than initial hydrogen content at high temperature measured by JIS or IIW method.
The remaining hydrogen contents at 100°C on bond line ((HR)100) of HT60, HT80, HY130 and HY 180 weldments were measured in the LB-TRC test specimen using GTA welding with Ar-H2 mixed shielding gases by means of gas chromatograph, of which the measurement accuracy was 0.01 ml. Those were measured under four kinds of thermal cycles and then the relations between (HR)100 and the thermal factor ((ΣDΔt)100) which related with thermal cycle were deduced. Consequently, the experimental equations between (ΣDΔt)100 and (HR)100/H0 of all materials used were deduced as follows.
(HR)100/H0=exp {-A(ΣDΔt)100}
where A; 83 (HT60), 69 (HT80), 46 (HY130) and 41 (HY180)
H0; initial hydrogen content
Moreover, the relations between the LCS obtained by the LB-TRC test and (HR)100 were evaluated, but the LCS were not related to (HR)100. Therefore, the remaining hydrogen contents of weld metal ((HRW)100) were calculated using the analytical solutions of one-dimensional diffusion equation. Consequently, the lower critical stress of weld metal strongly depended on (HRW)100 than (HR)100.
