Microstructurs and Toughness of High Heat Input Electro-Slag Weld Metal of 50Kgf/mm^2 Class Constructional Steels(Materials, Metallurgy & Weldability)

概要

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Nowaday, the steel frame structure of four side thick plate box column construction are often used for general multistoried buildings. Various high heat input welding process have recently been applied to the manufacture of four side thick plate box column. The purpose of this report is to clarify the joint characteristics and especially the toughness of weld metal in thick plate joints made by some of these high heat input welding processes, which are the method of electro-slag (ES) and heavy current submerged arc (SAW) welding processes. The steel plate of 50kgf/mm^2 grade such as SM 50A of 40mm thickness are used for test plate. The summary of test results is shown in the following ; (1) The impact characteristics of weld joint by one pass welding, the absorbed energy (E_A) by ES procese is found to be generally lower than that by SAW processes. (2) As for the impact characteristics of the weld metal by ES, the absorbed energy (E_A) of core part of weld metal is found to be remarkably lower than that of its periphery part. (3) According to the increase of weld heat input (Q),the E_A value of weld metal made by both procese of ES and SAW showed a tendency to decrease. (4) The decreasing rate of E_A as a function of the increase of Q is found not to specially relate to change of chemical compositions of weld metal such as, C, Si, Mn and N but O is effective.