Title: Stress Corrosion Cracking of Welded Joints of Austenitic Stainless Steel
Abstract:Stress corrosion cracking of SUS 304-butt welded joints in 42% boiling MgCl2 solution was studied. The summary of this study and the results obtained are as follows:1) Preliminary tests for welding we...Stress corrosion cracking of SUS 304-butt welded joints in 42% boiling MgCl2 solution was studied. The summary of this study and the results obtained are as follows:1) Preliminary tests for welding were made in order to obtain desirable laboratory test specimens with small angular distorsion and offset. Based on these tests, conditions for welding and cutting size of plate were determined, and desirable specimens with satisfying shapes and reproducibility could be obtained.2) Three kinds of surface finishing of test specimens, i. e., no finishing, abrasing through #1000 emery paper and grinding by surface grinder, were adopted in order to clarify the effect of surface finishing on SCC. Examination of surface roughness, residual stresses and microstructure, etc., showed that i) hot rolled specimen (No. 1 finish) had extremly roughned and hardened surface with relatively higher tensile residual stresses, ii) abrasion by emery paper developed a very smooth surface with compressive residual stresses, iii) grinding developed a sharp kerf surface with higher tensile residual stresses.3) Constant load type SCC tests in 42% boiling MgCl2 solution were carried out on 11 kinds of base metal and welded, specimens. As a results, it was found that both the hot rolled base metal and their welded specimens had a considerably higher susceptibility to SCC, and all failured within 500hr duration at the applied stress as low as 3kg/mm2. On the other hand, 5 kinds of solution heat treated and their welded specimens exhibited proper resistance to SCC and had the threshold stresses higher than 7kg/mm2. Welding operation increases the susceptibility to SCC when the base metal is solution heat treated, but decreased it when the base metal is hot rolled. Abrasion of specimen by emery paper decreases the susceptibility to SCC but the grinding extremly increases the susceptibility. It was pointed out that the grinding, as a practical surface finishing, should be rechecked because of its dangerous effects on SCC.4) Post-weld heat treatment, as a useful method for preventing the SCC of welded joints, was studied. Quantitative relationships between the post-weld heating temperature and the relieving of residual stresses, the metallurgical changes and the SCC susceptibility were clarified. Necessary heating temperature for preventing the welded joints from SCC and/or intergranular corrosion was proposed.Read More
Title: $Stress Corrosion Cracking of Welded Joints of Austenitic Stainless Steel
Abstract: Stress corrosion cracking of SUS 304-butt welded joints in 42% boiling MgCl2 solution was studied. The summary of this study and the results obtained are as follows:1) Preliminary tests for welding were made in order to obtain desirable laboratory test specimens with small angular distorsion and offset. Based on these tests, conditions for welding and cutting size of plate were determined, and desirable specimens with satisfying shapes and reproducibility could be obtained.2) Three kinds of surface finishing of test specimens, i. e., no finishing, abrasing through #1000 emery paper and grinding by surface grinder, were adopted in order to clarify the effect of surface finishing on SCC. Examination of surface roughness, residual stresses and microstructure, etc., showed that i) hot rolled specimen (No. 1 finish) had extremly roughned and hardened surface with relatively higher tensile residual stresses, ii) abrasion by emery paper developed a very smooth surface with compressive residual stresses, iii) grinding developed a sharp kerf surface with higher tensile residual stresses.3) Constant load type SCC tests in 42% boiling MgCl2 solution were carried out on 11 kinds of base metal and welded, specimens. As a results, it was found that both the hot rolled base metal and their welded specimens had a considerably higher susceptibility to SCC, and all failured within 500hr duration at the applied stress as low as 3kg/mm2. On the other hand, 5 kinds of solution heat treated and their welded specimens exhibited proper resistance to SCC and had the threshold stresses higher than 7kg/mm2. Welding operation increases the susceptibility to SCC when the base metal is solution heat treated, but decreased it when the base metal is hot rolled. Abrasion of specimen by emery paper decreases the susceptibility to SCC but the grinding extremly increases the susceptibility. It was pointed out that the grinding, as a practical surface finishing, should be rechecked because of its dangerous effects on SCC.4) Post-weld heat treatment, as a useful method for preventing the SCC of welded joints, was studied. Quantitative relationships between the post-weld heating temperature and the relieving of residual stresses, the metallurgical changes and the SCC susceptibility were clarified. Necessary heating temperature for preventing the welded joints from SCC and/or intergranular corrosion was proposed.