The Research of Modified 9Cr-1Mo Steel in Welded Microstructure and Carbon Migration

• Main Authors: You Yuh Ying, 游郁塋
• Other Authors: 薛人愷
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/25569100026836285494

碩士 === 國立東華大學 === 材料科學與工程研究所 === 88 === The modified 9Cr-1Mo steel was widely used in high Temperature and pressure tubes of fossil power plants due to its excellent high temperature mechanical properties and corrosion resistance. Its weldability is deteriorated due to the increment of its hardenability resulted from minor alloying element additions. The purpose of this experiment is to study the phenomena of interfacial carbon migration in dissimilar metal welding of the modified 9Cr-1Mo steel (e.g., 2.25Cr-1Mo, 304SS and 316SS …etc.). A soft zone with low carbon content and low hardness will be formed at the low alloy base metal close to the fusion line. The mechanical property at elevated temperatures of the weldment can be affected by the soft zone. To evaluate the effect of soft zone in the welds of modified 9Cr-1Mo steels and different dissimilar metals, bead-on-plate of various filler on modified 9Cr-1Mo base metal was applied in this research. SMAW was used in modified 9Cr-1Mo welding. Based on the experimental results, the use of Ni base filler metal is the only way to impede the carbon migration of the dissimilar joint. Meanwhile, using intermediate layer can not retard the existence of carbon migration in low alloy steel.