•Li2O show more pronounced effect on decreasing viscosity at a lower temperature, and increasing Li2O content can decrease the decreasing rate of viscosities.•Increasing Li2O addition from 10 to 14 mass%, the O2- dissociated from Li2O just cut the network formed by [AlO4]-tetrahedrons.•More O2- ions dissociated from Li2O, and more [AlO6]-octahedrons formed when the content of Li2O exceeded 14 mass%.Well understanding the role fluxing agents in the CaO-Al2O3-based slag system is essential to devise new mold fluxes for heat-resistant steel as well as for further improvement of data for viscosities and structure properties of the molten fluxes. The role of Li2O in CaO-Al2O3-Li2O-Ce2O3 slag system was investigated through measuring viscosity combined with the FTIR spectra analysis. It was noted that Li2O show obvious effect of decreasing viscosity in the CaO-Al2O3-based slag system. The viscosity of the CaO-Al2O3-Li2O-Ce2O3 slag melts decreased with increasing Li2O content. The relationship between the viscosity and the slag structure was discussed. Under the condition of increasing Li2O addition from 10 to 14 mass%, the relative ratio of [AlO4]-tetrahedrons and [AlO6]-octahedrons remain constant. The O2– dissociated from Li2O just cut the network formed by [AlO4]-tetrahedrons. The depolymerization of [AlO4]-tetrahedrons from Q4 units to Q3 and Q2 units was the main reason of the decrease of the viscosity. When the content of Li2O increased from 14 to 18 mass%, more and more O2– dissociated from Li2O reacted with [AlO4]-tetrahedrons to form [AlO6]-octahedrons. The decrease of viscosity was mainly induced by the increase of free oxygen and the formation of [AlO6]-octahedrons, which acts as a network modifier.

Spinel phase is considered to be the optimal phase for stabilization of chromium in stainless steel slag. In order to restrain chromium leaching from slag for the effective environmental protection, Al2O3 was utilized for the modification treatment, and the effects on the enrichment and stabilization of chromium were investigated. The mineral phases and the existence state of chromium in slag with various Al2O3 contents at different basicities (wCaO/wSiO2) were analyzed by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). The results showed that chromium mainly existed in the glass and spinel phases at basicity of 1.0 and 1.5. As the slag basicity increased to 2.0, chromium was also found in periclase phase. Al2O3 in the stainless steel slag reacted with MgO and Cr2O3, which could generate the Al-rich Mg(Crx Al1–x)2O4 solid solution. Moreover, the addition of Al2O3 was favorable to reduce the solubility of chromium oxide in liquid phase and suppress the precipitation of periclase phase. The experimental results demonstrated that Al2O3 modification has a positive influence on the enrichment and the stabilization of chromium in the stainless steel slag.

Aiming at devising new mold flux for Ce-bearing stainless steel, a fundamental investigation on the effect of Ce2O3 on properties of the CaO-Al2O3-Li2O-Ce2O3 slag was provided by the present work. The results show that adding Ce2O3 could decrease the viscosity of the slag due to its effects on decreasing the polymerization of the slag. The crystalline process was restrained by increasing the content of Ce2O3, and the crystalline phases also can be influenced by the slag structure. The crystalline phases were transferred from LiAlO2 and CaO to LiAlO2 and CaCeAlO4 with the addition of Ce2O3 to the slag, which could be well confirmed by the structure of the unit cell of the crystals.

AbstractThe conventional mould fluxes can not be applied to the continuous casting of RE alloyed heat resistant steel, because severe slag-metal interface reactions occur generally in the mold. To restrain the interface reaction and improve conditions for continuous casting, a new mould flux based on aluminate system was devised. The viscous properties were investigated. Scanning electron microscopy and X-ray diffraction were applied to detect and characterize the crystalline phases in the continuous cooling process. The results showed that appropriate addition of CeO2 could avoid the precipitation of CaO and decrease the viscosity of the mould flux. Increasing the mass ratio of CaO/Al2O3, especially to a value exceeding 1, could worsen the stability of the mould flux. With a content of less than 14 wt.%, Li2O could reduce the viscosity and breaking temperature, but its effect could be weakened for the promoted precipitation of LiAlO2. To obtain a mould flux with stable viscous properties, such as viscosity and breaking temperature, appropriate contents of CeO2 and Li2O should be controlled to around 10 wt.% and 14 wt.%, while the mass ratio of CaO/Al2O3 should not be more than 1.Effects of CeO2 on the breaking temperature and the viscosities at 1300 and 1225 °C

The cleanness and usability of silicon steel are seriously affected by the type, number, size of the non-metallic inclusions. The evolution behaviors of the type, number, and size of inclusions in the non-oriented silicon steel slabs, which were subjected to different deoxidation processes (Si or Al deoxidation), were systematically investigated by using industrial testing and sampling analysis. The results indicate that the number and size of the inclusions are over larger during the starting-cast stage, and the reasonable cutting length for the first casting slab is 6 m. During steady-casting stage, the main types of the inclusions in Al deoxidization slab are Al2O3, Al2O3-MnS, Al2O3-MgO, Al2O3-AlN and their complex inclusions, and the main types of the inclusions in Si deoxidization slab are Al2O3, SiO2, Al2O3-SiO2 and a small amount of Al2O3-MnS, Al2O3-MgO complex inclusions. The number density and the occupation area fraction of inclusions in Al deoxidization slab are less than that in Si deoxidization slab. However, the stability of slab cleanliness in Al deoxidization process condition is inferior to that in Si deoxidization process condition.