Phosphorus transfer behaviours and microstructural responses in EH36 shipbuilding steel subjected to CaF 2 –Ca 3 (PO 4 ) 2 welding fluxes

Abstract

Phosphorus transfer behaviours have been elucidated by employing designed CaF₂–Ca₃(PO₄)₂ fluxes, and influences upon microstructural and mechanical responses have been documented in EH36 shipbuilding steel subjected to submerged arc welding. As the equivalent P₂O₅ content in the flux grows from 0 to 0.664 wt-%, corresponding P and O contents in the weld metals increase from 0.013 to 0.076 wt-% and from 0.012 to 0.020 wt-%, respectively. Additionally, the amount of inclusions is significantly enhanced, with number density being boosted from 1.73 × 10³ to 5.15 × 10³ mm^–2. A closer examination reveals that the microstructures of the weld metal are primarily composed of bainite. Consequently, a reduction in Charpy impact energy is observed, characterised by a distinct brittle fracture mode across all weld metals.