Improvement in toughness of arc weld metal in high strength steels by reducing oxygen content

2016 Fiscal Year Final Research Report

• Project/Area Number: 25420731
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Composite materials/Surface and interface engineering
• Research Institution: Ehime University
• Principal Investigator: OHARA MASAHIRO 愛媛大学, 理工学研究科(工学系), 教授 (10374000)
• Project Period (FY): 2013-04-01 – 2017-03-31
• Keywords: アーク溶接 / 靭性向上 / 高強度鋼板 / ミクロ組織微細化 / 清浄度 / 溶接金属 / シールドガス組成 / 介在物

Outline of Final Research Achievements

The increase in size and weight of recent structures has been demanding application of higher tensile strength steels. In such cases, difficulties have been encountered in obtaining adequate fracture toughness in arc weld metal and, therefore, a method to improve the toughness has been highly required. In this study, an attempt was made to improve the toughness by reducing oxide inclusions since the inclusions have been known to become initiation sites for fracture and so to deteriorate the toughness. In order to achieve this, it was necessary to establish a method to stabilize arc discharge in an atmosphere with less oxygen and to promote a fine acicular ferrite microstructure in weld metal. In contrast to the accepted understanding, it was found that stabilization of arc discharge was achieved by local oxidized gas addition together with pulsation of welding current and that a predominant fine acicular ferrite microstructure was obtained provided that adequate inclusions were formed.

Free Research Field

溶接・接合