• Proceedings of the KWS Conference
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• v.43
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• pp.101-102
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• 2004

This study was investigated on the impact toughness and microstructure of welded metal and heat affected zone for B grade steel. With welding procedures, welding heat inputs applied were 30, 79 and 264 kJ/cm, Prior austenite grain size in coarse zone has increased with increasing welding heat input for B grade steel. The toughness of fusion line zone of Bgrade steel has decreased with increasing welding heat input while the toughness fusion line +3 and +5 mm zone increased contrarily.

• Korean Journal of Metals and Materials
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• v.46 no.12
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• pp.788-799
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• 2008

This study is concerned with the effects of Mo, Cr, and V addition on tensile and Charpy impact properties of API X80 linepipe steels. Four kinds of steels were processed by varying Mo, Cr, and V additions, and their microstructures and tensile and Charpy impact properties were investigated. Since the addition of Mo and V promoted to form fine acicular ferrite and granular bainite, while prohibiting the coarsening of granular bainite, it increased the strength and upper shelf energy, and decreased the energy transition temperature. The Cr addition promoted the formation of coarse granular bainite and secondary phases such as martensite-austenite constituents, thereby leading to the increased effective grain size, energy transition temperature, and strength and to the decreased upper shelf energy. The steel containing 0.3wt.% Mo and 0.06wt.% V without Cr had the highest upper shelf energy and the lowest energy transition temperature because its microstructure was composed of fine acicular ferrite and granular bainite, together with a small amount of hard secondary phases, while its tensile properties maintained excellent.