Changes of Microstructure and Toughness of SPV-50Q Steel After Long-Term Usage Pressure Vessel

• Main Authors: Kung-Hua Yuan, 袁孔華
• Other Authors: Cheng-Hsun Hsu
• Format: Others
• Language: en_US
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/14169877225058229970

碩士 === 大同大學 === 材料工程研究所 === 88 === This research is to study the fracture toughness behavior of SPV-50Q high tension steel in LPG pressure vessel. The as-received SPV-50Qsteel, as well as the steel that has been subjected to hydrogen-induced cracking, will be investigated. The orientation of the fracture toughness specimen will be selected such that the fracture path will be vertical or parallel to the existing hydrogen-induced cracking (HIC) paths. Tensile test will be performed as well to substantiate the fracture toughness data. It is hoped that at the completion of this research the extend of deterioration in the mechanical properties of the LPG SPV-50Q steel vessel before and after HIC attack will be more clearly understood. This will provide some valuable date base for material safety in LPG pressure vessel. The tensile strength of paralleled rolling direction high than vertical rolling direction in SPQ-50Q non-used material. It made by machining hard. The tensile strength of SPV-50Q is large decrease whether in paralleled rolling direction and vertical rolling direction but the elongation has a value of level. The effect of hydrogen on ductile fracture in two rolling direction, paralleled and vertical, have been machining. In used material, the mechanism property is poor. Initiation of microvoids during test occurred, together with enhance microvoid growth. The observation of impact test, the impact value is not large decrease, the fracture in this cause appears consistent with the inclusions. The final fracture process of fatigue cracking has transparently divergent direction in cracking progression. The major effect of fracture toughness for non-used material is rolling direction. The internal microcracking is significantly increase by hydrogen with decrease fracture toughness for used material.