抄録
Based on the stand-point that the SCC susceptibility of prestrained member should be evaluated by the quantitative analysis of the stress states such as the residual stresses of prestrained condition and the actual stresses under applied stresses, in stead of the apparent applied stresses which were often used in the previous studies, SCC tests of austenitic stainless steel SUS 304 which were abraded with grit paper or eletcropolished and then tensile prestrained up to 20% were carried out in boiling 35wt% magnesium chloride solution.
It was made clear that the surface finishing had great influence on the variation of residual and actual stresses of prestrained specimens, however the SCC susceptibility could be evaluated by the threshold actual stresses at the surface of prestrained specimens.
Results obtained are summarized as follows.
1) Tensile prestraining of electropolished stress-free specimens resulted in the residual stress states where the equi-biaxial stresses were compressive of about -10kg/mm2. The actual stresses at the surface of prestrained specimens under applied stresses could be expressed by the resultant stresses of residual and applied stresses. The apparent threshold applied stresses for SCC increased with the plastic strain, however the threshold actual stresses for SCC were constant at 20kg/mm2 for all specimens prestrained up to 15%.
2) Tensile prestraining of abraded specimens which had biaxial residual compressive stresses of -30kg/mm2 resulted in the residual stress states where the axial stress was tensile of 10kg/mm2 and the transverse stress compressive of -15kg/mm2. Therefore specimens prestrained above 10% underwent SCC without applied stresses. The actual stresses at the surface of prestrained specimens under applied stresses could not be expressed by the resultant stresses, and showed complicated behaviour. The threshold actual stresses for SCC was, however, constant at 10kg/mm2 for all specimens prestrained up to 20%.
3) The surface actual stresses of prestrained specimens could be an effective parameter for the evaluation of SCC susceptibility of prestrained SUS 304 in 35wt% MgCl2 solution.
