Morphology of Inclusions and Its Refinement Mechanism in the New P91 Heat-Resistant Pipeline Steel

A new type of P91 heat-resistant pipeline steel ingot was prepared by feeding Al twisted wire into a melt through multi-point regional micro-supply method, combined with electromagnetic stirring. The type, shape, and size inclusions in the after forging were then analyzed scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), transmission (TEM). results showed that four types detected steel, including: spherical independent Al2O3 inclusions, irregular Al2O3-SiO2 composite nearly MgO-Al2O3 (Ca, Mg, Al) (O) inclusions. Compared traditional significantly refined. Refining mechanisms inclusion oxide particles distributed dispersedly fine sizes could be obtained method. Further, act as nucleation core to form “core-shell” structure play role heterogeneous refine SiO2, MgO, Mg) (O), other steel.