Low temperature impact toughness of structural steel welds with different welding processes

Abstract

Influence of welding process and welding consumable on the impact toughness at low temperatures of the Heat Affected Zone (HAZ) and the weld metal in a structural steel weldment was investigated. A comparison of the low temperature impact toughness was made between the welded joints fabricated by Shielded Metal Arc Welding (SMAW) and Flux Cored Arc Welding (FCAW) processes, respectively. The Charpy impact tests along with the microstructural observations and the hardness measurements were carried out to derive the effective welding method to guarantee the higher impact toughness of the HAZ and the weld metal at low temperatures. Standard V-notch Charpy impact specimens were prepared and tested under dynamic loading condition. Variation of the Charpy impact energy with respect to the test temperature and that of the hardness across the welds were presented and correlated with the microstructure and the welding process. Analysis of the results unveiled that the weld metal of the FCAW joint has a little higher low temperature impact toughness owing to the higher nickel content, whilst the HAZ of the SMAW joint has much superior impact toughness at low temperatures attributed to the lower heat input; thus the efficient welding method to ensure higher low temperature impact toughness of the HAZ and the weld metal is to employ a low heat input welding process using a welding consumable with high nickel content.