Thermodynamics of Amorphous Silicon Oxides in Sub-rapid Solidified Low Carbon Steel

摘要

Strip casting technology leads a new revolutionary change for steel industry, which solidification rate could be 100-1000 K/s. The study on the size and structure of deoxidation products from the sub-rapid solidification will be of great significant in promoting the mechanical properties of the strip continuous casting steels. In the paper, the silicon oxide inclusions precipitated in sub-rapid solidified low carbon steel were investigated by transmission electron microscopy. The experimental results indicated that a large number of spherical silicon oxides were dispersed as amorphous state, and the size range was in hundreds nanometers. According to the thermodynamic calculation and inference, the silicon oxides would precipitate during the sub-rapid solidification of low carbon steel. SiO_2, which structure is as approximate "liquid" and the melting temperature has been reduced under nano-effect, has been frozen in amorphous state under high solidification rate. Amorphous SiO_2 precipitated in steel may be due to the structural relaxation caused by high viscosity. The larger average size of amorphous SiO_2 was detected at higher solidification rate, which is attributed to the cause to the higher hardening rate.