To absolutely solve SCC problems of Austenitic stainless steel in the water contained [Cl-], we adopt a kind of new stainless steel –SUS444 ultra-purification ferrite stainless steel. It breaks the concepts of ordinary stainless steel and contains lower carbon content and nitrogen content than ultra-low carbon SUS316L. Its main component is 00Cr18Mo2, which is resistant against pitting corrosion compared with Austenitic stainless steel. And its resistance against gap and causticity is similar with SUS316.
Because SUS444 is ferrite stainless steel and it has only 12 slip planes, the bonding force between its crystal lattices is strong, especially the content of molybdenum (MO) is higher, which greatly reinforces causticity resistance against chloride ions. Difference on quantity of slip planes makes ferrite stainless steel uneasy to cause crystal lattice of SCC to slip, thus SCC corrosion will not take place on SUS444 ferrite stainless steel even under the effect of welding and processing residual stresses. Causticity resistance against chloride ion of SUS444 is further better than other stainless steels. So under the condition that there are a lot of chloride ions in tap water in Shanghai and coastal cities, we suggest you use SUS444 stainless steel to make hot water tank. |
