Development of Covered Electrode with Good CTOD Properties for YS 500 MPa Class High-Strength Steel

摘要

Offshore structures have recently been constructed with larger designs and operated in colder and deeper seas to explore energy resources. In this trend, higher strength and higher toughness have been required for the component materials including welding consumables. The authors have studied on improvement of the CTOD properties of weld metal for high strength steel to realize the development target: yield strength ≥ 500 MPa, tensile strength ≥ 610 MPa, and CTOD values at –40 °C ≥ 0.1 mm. This report discusses the influences of some dominant factors (oxygen, Mo and Si content in weld metals) on the toughness of the weld metal for high strength steel. Through this research, an advanced covered electrode has been developed with an optimized chemistry formula as introduced in the following.