TOUGHNESS CHARACTERISTICS AND ITS IMPROVEMENT OF ELECTROSLAG WELD METAL OF STRUCTURAL-STEEL PLATE

High heat input electroslag welding (ESW) is widely used for the four side welding of 490 N/mm(2) class steel between thick flange or web pl ate and diaphragm without Post Weld Heat Treatment (PWHT). The notch t oughness of ESW weld metal is generally lower in the central part (C z one) than in the peripheral part (R zone) of the weld metal. This repo rt has treated from metallurgical investigation the reason why the not ch toughness of C zone is inferior to R zone. Moreover the improvement of the notch toughness in C zone has been investigated with the chang e of chemical element in the weld metal. As a result the reduction of Si content in weld metal is beneficial to improve the notch toughness of C zone acid equalizes the ductility of both zones.