Abstract: The inclusions at different holding time after VD were detected by Zeiss electron microscope + INCA software for gear steel produced at Baosteel. It is found that the amount of inclusions larger than 5 〖WTBZ〗μ〖WTB4〗m is positively correlated with the amount of inclusions larger than 10 μm, and decreases first and then increases with the increase of holding time. The largest inclusions are mainly spherical CaO-Al2O3+MgO-Al2O3 composite inclusions at different holding time after VD. The size of inclusions increases with the increase of CaO-Al2O3 area proportion of the inclusion. It is suggested that the holding time should be controlled for about 15 minutes.

Key words: holding time, inclusion, CaO-Al2O3, INCA software