Steel Refining by Magnesium Injection and its Influence on Steel Quality

Recentl man metallurgists heve been working with steel refining by using maganesium as deoxidizer and desflfurizer which also leads to better morphology of nonmetallic inclusions. That it might be very difficult to add maganesium in was the reason for the previous works to fail. The trouble is that the partial pressure of maganesium is very high at the melting temperatures and at the same time its solubility in the liquid steel is rather small. In this article, the effect of injecting Mg-powder on deoxidation and desulfurization by using Ar-gas as carrier based on thermcdynamic data stove in Aachen university and the effects of the pressure and flow of Ar-gas on the technology mentioned above have been calculated. The effective injecting technology was determined experimeutally and the appropriate controlling parameters were chosen.
Maganesium can be successfully insected into the liquid steel at 0.1~0.3NL/min of Ar-gas flow under 1-3 atm. The oxygen content was decreased to 4ppm in the liquid steel to be refined. The sulfur content 10ppm. The graduation of oxides and sulfides was 0-grade. This sizes are less than 5μm. Mg-oxides and sulfides in the inclusions were increased with the increase of amount of injecting maganesium. However the total amount of inclusions were decreased and the shape appears as sphere. The inclusions remain unchanged shape during hot deformation. The anisotropic characteristic which usually exists in materials disappeared completely especially the notch-impact toughness at the transverse direction was increased by 2-3 times. The impact toughness at the different temperatures the transition temperatures and the inclusion shapes on the fractures for the materials to be refine 1 were also discussed.