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题名: 304L及316L不銹鋼鹽霧應力腐蝕特性之研究
Stress Corrosion Cracking of 304L and 316L Stainless Steels in Salt-Spray Environment
作者: Yu-Chin Ho
何昱瑾
贡献者: NTOU:Institute of Materials Engineering
國立臺灣海洋大學:材料工程研究所
关键词: 鹽霧;應力腐蝕;輥軋;敏化處理
salt-spray;stress corrosion cracking;rolling;sensitization
日期: 2013
上传时间: 2013-10-07T02:46:17Z
摘要: 本研究係將304L板材先敏化處理後輥軋製程,模擬不完全固溶之劣化材質之應力腐蝕特性,探討原始晶界碳化物析出,對後續輥軋加工試片抗應力腐蝕特性之影響,模擬劣化材質在80℃-10%NaCl之加熱鹽霧環境中,不同試件(BMS、SCR、SHR、SCRS和SHRS)之應力腐蝕龜裂與劣化機制,並探討304L和316L不銹鋼粗大晶粒組織對其應力腐蝕破裂之影響。實驗結果顯示:U型彎曲試件在鹽霧環境中進行144hr測試,晶粒粗大化之輥軋試件(304L-CR(CG))在裂縫起始時呈現穿晶破裂特徵,易從交叉滑移帶侵蝕並生成裂縫,粗晶敏化試件(304L-CRS(CG))在裂縫起始時為穿晶破裂而後轉為沿晶破裂;而先經敏化再輥軋之試件(304L-SCR和SHR),裂縫剛開始以沿晶和穿晶混和之型態出現,之後呈現階梯狀的破壞型態,兩次敏化之試件(304L-SCRS和SHRS)其沿晶破裂特徵更為明顯,但階梯狀破裂模式明顯減少。此外,將各種條件的試片放置在鹽霧條件下,經一段時間後取出並量測其重量損失,结果顯示:在不施加負載的情况下,冷軋和敏化試片有較高的重量損失,而基材在鹽霧下則有較高的抗表面溶解。
In this work, 304L stainless steel (SS) was subjected to either sensitization treatment at 650℃/10hr or grain-coarsening treatment at 1150℃/1hr before rolling to 20% reduction in thickness. The effects of carbide precipitation and coarse grain size on the stress corrosion cracking (SCC) of the specimens were evaluated and compared to the base metal specimen. The susceptibility of distinct specimens to SCC was ranked by determining the maximum and total crack length of the U- bent specimen at 80℃ in a salt-spray environment. The results indicated the effect of grain-coarsening treatment had a minor role on the SCC susceptibility. However, the sensitization before rolling could obviously raise the cracking susceptibility of the specimens in the salt-spray environment. Moreover, the crack path was more likely to change from transgranular to intergranular for the sensitized specimens. It was noted that cracks tended to initiate at the intersection of slip bands in the cold-rolled specimens. The step-wise crack growth in all the specimens was associated with the crack growth along the slip bands or induced martensite therein. Various samples were exposed to the salt-spray environment and periodically measured the weight loss of the samples. The results indicated the cold-rolled and sensitized specimens showed higher weight loss than other specimens. Furthermore, the base metal was more resistant to surface dissolution in the salt-spray condition under the free applied-loading.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0010055015
http://ntour.ntou.edu.tw/handle/987654321/34770
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