Effects of Inclusions and Austenite Grain Size on the Impact Behavior of a Newly Developed Low-Carbon Steel Weld Metal

摘要

Inclusion characteristics were altered using intentional oxygen gas additions in GMA welds. Specimens removed from the deposited weld metal were subjected to grain refinement by thermal cycling to 1 1000C for up to 3 cycles using the Gleeble 1500. Each successive cycle resulted in additional grain refinement By systematically varying the oxygen and grain size, the effects of inclusions and grain size on the impact toughness behavior of low carbon steel weld metal was determined. It was concluded that austenite grain refinement was effective at improving toughness across the entire test temperature region, with the exception of the upper shelf energy when the inclusion count and volume fraction were the largest. Although grain refinement resulted in improved toughness, it was concluded that inclusions were the primary factor limiting toughness improvement. It was also concluded that the as-deposited columnar grain structure remaining in the weld metal was somewhat responsible for the lower toughness regions within the weld.