摘要
采用Ａ００２ ， Ａ１３２ 和Ａ３０２ 三种焊条以及（６００ ，８００ 和１０５０）０Ｃ×６ｈ 三种焊后热处理方式，研究了３０４ 钢不同焊缝的环境断裂行为。试验是用悬臂梁弯曲试样在室温０ ．５ｍｏｌ／ＬＮａＣｌ＋ ２ ．５ｍｏｌ／ＬＨ２ＳＯ４ 溶液中进行的。测定了各种焊缝的ｄａ／ｄｔ ～Ｋ１ 曲线，并作了浸蚀试验、腐蚀电化学试验和断口分析。结果表明：焊缝的ＫＩＳＣＣ 为３０ ～３８ＭＰａｍ １／２，按Ａ００２，Ａ３０２ 和Ａ１３２顺序递增，只及母材的（６２ ～７９）％ ；其裂缝扩展速率ｄａ／ｄｔ 达（５ ～７） ×１０－ ６ ｍ ｍｓ－ １ ，为母材的２ ．８ ～３ ．９ 倍。随焊后热处理温度升高，ｄａ／ｄｔ 下降， ＫＩＳＣＣ 升高。３０４ 母材的环境断裂受应变产生活性通道机理控制；而焊缝主要受预存活性通道机理制约，以沿晶断裂为主，所需ＫＩＳＣＣ 较低，ｄａ／ｄｔ 较大。在焊缝中，铁素体呈阳极而优先溶解，其数量越多，越易呈半连续或连续的网状，意味着预存活性通道越通畅，环境断裂敏感性越高。焊缝成分和焊后热处理的影响。
The environmental fracture behavior of 304 stainless steel base metaland three weld metals with different alloy additions (A002, A132 andA302) under as welded and postweld heat treatment (PWHT) conditions werequantitatively studied in 0.5mol/L NaCl + 2.5mol/L H 2SO 4 solution at room temperature. The tests were carried out with a cantilever bending test machine and the da/dt～ K 1 curves were determined to evaluate the resistance to environmental fracture. The micrography,fractography and electrochemical tests for corrosion were performed formechanism study. The results showed that K ISCC of the weld metals was 30～ 38MPa m 1/2 , increasing in order of A002, A302and A132, being 62%～ 79% of the base metal, and their da/dt reached to (5～ 7)×10 -6 mms -1 , being 2.8～3.9 ×of the base metal. As the PWHT temperature increased, the susceptibility to environmental fracture for the weld metals decreased. The environmental fracture behavior of 304 base metal was controlled by stress assisted active tunnels, showing transgranular (TG) fracture. However, the environmental fracture behavior of the weld metals were mainly controlled by pre-existing active tunnel mechanism, showing intergranular (IG) or IG+TG mode. Since the delta ferrite in the weld metals was an anodic phase to be preferentially corroded, forming pre-existent active tunnels, the resistance to environmental fracture decreased as the ferrite content increased and a continuous network formed. The environmental fracture behavior of 304 steel weld metals was mainly dependent on the ferrite content and morphology. Both the weld metal composition and PWHT would affect the resistance to environmental fracture through the change of microstructure.
出处
《中国腐蚀与防护学报》
CAS
CSCD
1999年第5期265-272,共8页
Journal of Chinese Society For Corrosion and Protection
关键词
焊缝
不锈钢
环境断裂
裂缝扩展速率
steel weld metals, Environmental fracture, Threshold stressintensity, Crack growth rate, Pre existent active tunnel
