Corrosion Resistance of Dissimilar Welds between Ferritic Stainless Steel with High Corrosion Resistance and Austenitic Stainless Steels

摘要

Intergranular corrosion susceptibilities of the dissimilar welds between SUS 444 which is ferritic stainless steel with high corrosion resistance and austenitic stainless steels were investigated. Judging from the 10 percent oxalic acid etch test results, there are some cases where the welded joints between SUS 444 and SUS 304, SUS 316 have high intergranular corrosion susceptibilities, while the welded joints between SUS 444 and SUS 316 L have low intergranular corrosion susceptibilities. Intergranular corrosion susceptibility of the welded joints between SUS 444 and SUS 316 decreases when over 30 percent martensite phase precipitated with the high penetration ratio of SUS 316. Intergranular corrosion of the dissimilar welds between high purity SUS 444 and austenitic stainless steels is caused by the formation of chromium depleted zone. The countermeasures for the intergranular corrosion of the dissimilar welds are that the martensite phase with high solubility of carbon and nitrogen is forced to precipitate by increasing the penetration ratio of SUS 316 or SUS 316 L is applied for austenitic stainless steel.