Effect of Melting Interruption on Composition and Microstructure of BT22 Ingot in VAR
BT22 ingot was remelted by vacuum arc remelting (VAR) furnace with a melting rate of 20kg/min. The power of VA R was interrupted for five minutes when the weight of the remelted ingot is approximately 4000 kg. The melting process was then resumed at the same melting rate after the five minutes interruption. Optical microscopy (OM), inductively coupled plasma-mass spectrometry (ICP-MS) and electron probe micro analyzer (EPMA) were utilized to analyze the microstructure, composition and distribution of elements. No significant microstructural difference was oberved at the remelting interrupted region. The variation of Al, Mo, V, Cr, Fe contents between the melting interruption region and normal region is within 0.23 wt%. The distribution of elements in equiaxed grains of the melting interruption region and the normal regions were compared by EPMA analysis. The contents of Al, V, Fe and Cr increase from the center of equiaxed grains to their grain boundaries. The content of Mo decreases from the center of equiaxed grains to their grain boundaries. The trend of element content in the normal region is similar to that of the melting interrupted region. Key words: BT22; ingot; composition; microstructure