鉻鉬鋼銲件之氫脆行為與詗溫氫損傷研究

• Main Author: 劉冠君
• Other Authors: 陳立業
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/45961346257662983176

碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 83 === 　　This work examine the hydrogen embrittlement and hydrogen damage of ASTM A335 P11 1.25Cr-0.5Mo pipeline steel and its weldments at elevated temperatures. The influence of postweld heat treatment (PWHT) on the mechanical properties and hydrogen embrittlement is discussed. In addition the influence of microstructure on the suseptability to gydrogen embrittlement is studied. The effect of temperature and hydrogen pressure on the mechanical and fracture characteristic of various types of welds is also examined. 　　The results indicate that temperng at 695℃ for 1 hour reduce the hardness of the welded metal zone and the heat-affected zone. It was also found that PWHT increases the time to failure in Constant Load Rupture Tests. Under slow strain rate tesion (SSRT) conditions the as-received microstructure weldments and PWHT weldments failed in the base metal zone while for the Quenched-Tempered microstructure weldments and PWHT weldments failed in HAZ. These SSRT tests were characterized by ductile fracture when carried out in air and by brittle fracture when carried out in an H2s saturated saline solution. 　　Hydrogen damage was evaluate by running the slow strain rate tension tests at 250℃ and 800℃ Psi H2. The samples were characterized by large cross sectional areas and low elongaton at failure. SEM examination if the samples suggested that fatigue was an important fracture mechanism. Further, tests carried out at 350 for 100 hours showed no evidence of hydrogen attack. These results were consistent with predictions from the Nelson curves.