構造用鋼のエレクトロスラグ溶接金属の靭性向上に関する研究 （第１報） 構造用鋼のエレクトロスラグ溶接金属内における衝撃特性の不均一性に関する研討

Abstract

The purpose of this paper is to clarify the weld joint performance, especially the impact characteristics of the weld metal produced by electroslag welding (ESW) and submerged arc welding (SAW) by directing our attention to the high heat input welding processes which are usually applied for the manufacture of four side thick plate box column. Two types of SM490A 40 mm thickness have been used in this test. The test results are summarized in the following.(1) As for the impact characteristics of high heat input weld metal, the absorption energy values (vE value) of weld metal made by ESW are generally lower than those by SAW.(2) As for the vE values of various locations in high heat input weld metal by ESW, the vE value in the center of weld metal (Core) is considerably lower than those in peripheral locations of weld metal (Rim).(3) Macrostructure of ESW weld metal suggested that fine crystal grains were generated in the core with coarse crystal grains in the rim.(4) In the weld metal by ESW the impact value of fine grain core area is low and those in the peripheral coarse grain rim area are high on the contrary. This result disagrees with the conventional theory about the general relation between impact value and grain size.(5) It is found that the vE value of weld metal by ESW shows a tendency to decrease according to the increase of welding heat input (Q) and becomes low at the Q of 30.0 kJ/mm (up to 80.0 kJ/mm). Furthermore, the decrease of vE value related to the increase of welding heat input has not be caused by the change of chemistry such as C, Si, Mn, P and S in the weld metal.