抄録
Environmental cracking tests for deep-drawn austenitic stainless steel cases were carried out in standing water in a manhole and under accelerated conditions, to test for hydrogen embrittlement. The main results are as follows.
(1) 8.6% and 9.1% Ni austenitic stainless steel cases with a sacrificial zinc electrode became cracked after setting for several months in standing water in a manhole. The electrochemical condition was -790mV at the lowest electrode potential, and a current density of 50mA/m2.
(2) 8.6%, 9.1% and 10% Ni austenitic stainless steel cases became cracked under accelerated conditions, to test for hydrogen embrittlement. The electrochemical conditions were the same for those cases with a sacrificial zinc electrode in sea water. However, 12% Ni austenitic stainless steel case did not become cracked under these conditions.
(3) Susceptibility to hydrogen embrittlement depended on the ratio of residual stress to tensile strength, and on martensite content. Thus, the cracking probability of deep-drawn cases in this environment could be estimated.
(4) Stable austenitic stainless steel cases did not became cracked after more than 7 years in these manholes.
