Influence of Mg on Inclusions in 21-4N Valve Steel

Abstract

In order to explore the influence of different magnesium contents on the morphology, size, distribution and composition of inclusions in 21-4N austenitic valve steel, the inclusions in 21-4N austenitic valve steel with different magnesium contents smelted by high temperature resistance furnace were analyzed by Zeiss metallographic microscope and scanning electron microscope. The results show that the average yield of magnesium in steel is only 4.50% due to the high vapor pressure of magnesium in the laboratory smelting process. When the mass fraction of magnesium is 0-60ppm, with the increase of magnesium content, the main inclusions in steel mostly change from the initial Al2O3 and Al-Mn-O inclusions to Al-Mg-O spinel inclusions and Al-Mg-O composite inclusions. With the further addition of Mg, a large number of large-size MgO inclusions began to appear in steel. The average size of inclusions in 21-4N steel decreased from 4.576μm to 2.89μm, and the density of inclusions increased from 54 to 132 /mm2. The distribution uniformity of inclusions is obviously improved.