Abstract
Electroslag welding (ESW) is known to show higher heat input than electrogas welding (EGW), resulting in poor low-temperature toughness. However, a newly developed ESW (dev. ESW) method using low-resistivity slag bath exhibited excellent low-temperature toughness as a result of lower effective heat input than conventional EGW, as demonstrated by the faster cooling rates measured in weld metals and estimated using finite element method analyses. This led to much shallower molten pool in the dev. ESW, resulting in much finer columnar grains and thinner centerline axial grains. High cooling speed in the dev. ESW method appeared to contribute to increased acicular ferrite proportion. The uniform microstructure with large acicular ferrite proportion and small number of inclusions in the weld metal permitted the dev. ESW weld metal to possess little variation in Charpy impact energy across the center of weld metal.
Highlights
Electrogas arc welding (EGW) is a well-known method for upward butt-welding of steel plates in the vertical position with high heat input, leading to high-efficiency welding, e.g., for shipbuilding [1]
Referring to the relationship among deposition rate, welding current, and welding speed in vertical position welding, a higher deposition rate can be obtained in EGW and electroslag welding (ESW) compared to other welding processes such as shield metal arc welding and gas metal arc welding [2]
The remained B can react with N in molten steel, and there is an optimum range of B content to make a high acicular ferrite content in the weld metals [8]
Summary
Electrogas arc welding (EGW) is a well-known method for upward butt-welding of steel plates in the vertical position with high heat input, leading to high-efficiency welding, e.g., for shipbuilding [1]. EGW specimens with those estimated by FEM analysis using several combinations of η and d with similar dilution ratios of η = 1.00 and d = 33 exhibited a small deviation especially below 750°C at which phase transformation occurs This is probably caused by difference of heat sources in the conv. ESW specimens using lower and higher resistivity flux, the liquid area was estimated to be + 4% and + 2%, respectively, heat input was set to 28% increase and 15% decrease This indicates that the molten-pool and slag-bath volume increased with increasing slag resistivity under the same heat input.
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