2003 Volume 52 Issue 3 Pages 166-170
Chloride stress corrosion cracking (SCC) of Type 304 and 304L austenitic stainless steels (SS) was studied by a constant load method in air at a temperature of 353K with relative humidity (RH) of 35%. Chlorides simulating sea salt particles were put on the gage section of the SS as droplets of synthetic sea water. The following stress[σap(kgf/mm2)]-minimum rupture time [ζ(h)] relationships were obtained for Type 304 and 304L SS ;
σap=-51log(ζ)+153 (304 SS),
σap=-141log(ζ)+386 (304L SS).
The threshold stress of SCC was as low as 1/2 of the 0.2% proof stress for solution annealed Type 304 and 304L SS, and smaller than 1/4 of the 0.2% proof stress for sensitized Type 304 SS. This result suggests the difficulty of suppressing SCC by reducing the residual tensile stress of a SS structure. SCC test using NaCl and MgCl2 as chlorides suggested that MgCl2 was responsible for cracking in the test condition of 353 K with RH=35%.