The Formation Mechanisms and Evolution of Multi-Phase Inclusions in Ti-Ca Deoxidized Offshore Structural Steel

To understand and clarify the formation mechanisms evolution of complex inclusions in Ti-Ca deoxidized offshore structural steel, industrial steel were systematically investigated. The number density total generally decreased from Ladle Furnace (LF), Vacuum Degassing (VD), Tundish to final product except for Ti Ca addition. major during refining process CaO-Al2O3-SiO2-(MgO)-TiOx CaO-Al2O3-SiO2. inclusion initially originated combination CaO-SiO2-(MgO) slag or refractory deoxidization Al2O3 TiO2. With proceeding addition, concentration gradually dropped while CaO TiO2 concentrations increased. CaO-Al2O3-SiO2 originally came slag, existing as 2CaO? Al2O3? SiO2, maintained a liquid state early stage LF. After treatment, it was transferred SiO2 due continuously being reduced by Ca. liquidus higher than that molten so they presented solid-state process. welding thermal simulation, proven effective inducing intragranular acicular ferrite (IAF) inert IAF promotion. Additionally, Al2O3-MgO spinel multiphase has different mechanisms: (1) initial individual steel; (2) part firstly precipitated its low solubility.