Abstract
The effect of residual stress and thickness of SUS 304 stainless steel tubes on the SCC were studied in boiling 45% MgCl2 solution. The SCC test were carried out in a specially designed cell in which cracks propagated from outside to inside of tubes. The main results obtained are as follows.
Tangential residual stresses of metal roll straightened tubes were 2-14kg/mm2, and those of rubber roll straightened tubes are 0-6kg/mm2. All tubing specimens caused SCC in boiling 45% MgCl2 solution in a week when the residual stress, δt, was higher than 4.5kg/mm2. However no crack was observed when δt was lower than 2.5kg/mm2 in the same condition. The time to cause SCC leak, Tf, increased logarithmically with the decrease of δt and with the increase of tube thickness, t, respectively. These relations can be described by the following experimental equation, logTf=a-bδt/t, whrer Tf: time to cause SCC leak, δt: tangential residual stress, t: wall thickness of tube, a, b: constant.
