Mechanism of inclusion formation during smelting process of NO8810 corrosion resistant alloy
In order to study the characteristics and formation mechanism of inclusions in the smelting process of Fe-Cr-Ni corrosion-resistant alloy,industrial experiments were conducted to sample the entire process of 8810 nickel based alloy.Scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS)were used,and ther-modynamic and kinetic calculations were combined to explore the characteristics and formation mechanism of large-sized inclusions.The research results indicate that the large-sized inclusions appearing in steel can be mainly divided into two types.One type is the micro inclusions of low melting point SiO2-CaO-Al2O3-MgO large particles contain-ing mass percent of SiO2 bout 37％-45％,another type is low melting point CaO-Al2O3-MgO large particle micro inclusions without SiO2.By comparing the composition of inclusions and slag,as well as calculating the size of slag inclusions using a model,it was verified that both types of inclusions were formed due to the inclusion of slag during the AOD stage steel stirring.However,during the AOD reduction period,the former was either removed or modi-fied as CaO-Al2O3-MgO inclusions due to the recreation of slag and the increase of Al content.In the statistical analysis of inclusions,it is indicated that,the CaO-Al2O3-MgO inclusion is more severe than the SiO2-CaO-Al2O3-MgO inclusion in the subsequent process,and it still exists until the casting period.Therefore,the behavior of low melting point CaO-Al2O3-MgO inclusions in subsequent smelting was analyzed through dynamic calculations and Thermo Calc software.The results show that the inclusions are not easy to float and remove from the appearance of AOD tapping until the end of LF hanging ladle.At the same time,it leads to the precipitation of TiN with CaO-Al2O3-MgO inclusions as the core during the solidification stage of mold casting,forming composite inclusions,as well as single TiN inclusions appearing during the solidification stage,which ultimately become the main types of inclusions in the ingot.
NETL
NSTL
万方数据
