Sequence architecture and sedimentary characteristics of a Middle Jurassic incised valley,western Sichuan depression,China

The Middle Jurassic Shaximiao Formation encompasses tens of meters of thick lowstand meandering valley （LMV） strata in the western Sichuan foreland basin. Ancient LMVs newly discovered in this area were further studied based on sequence stratigraphy and seismic sedimentology. The aim of the present study was to investigate the sedimentary characteristics, sequence architecture, and the controls on LMV deposition in this tectonically active basin using field survey data, seismic sections, seismic amplitude imaging, core description, and comprehensive application of drilling data. The results show the following： （1） Three regional sequence boundaries and two flooding surfaces were recognized, and the Shaximiao For- mation was divided into two-third-order sequences and four systems tracts. （2） Three sedimentary facies associations were identified： incised valley-fill, tributary channel, and overbank facies. Incised valleys are 5-17 km wide, 20-60 m deep and traceable for 120 km along their axes. （3） In the downstream segment, the role of tectonism gradually diminishes, and periodic base-level changes control the form and evolution of the incised valleys. Three types of LMVs--AI, A2, and A3--developed with changes in base level （lake level）; of these types, the base level of the A3 LMV was likely the lowest.

Oxygen transfer phenomenon between slag and molten steel for production of IF steel

FeO-containing slag originated from the basic oxygen furnace to the ladle is a major reoxidation source during the following secondary refining.Ladle slag reduction treatment(slag treatment)is one of the common countermeasures adopted to eliminate the steel contamination by FeO reoxidation.The oxygen transfer phenomenon between molten steel and slag was studied during the industrial production of interstitial-free(IF)steel,the measured and calculated oxygen activities in steel were compared,and the Fe–O equilibrium at the slag–molten steel interface was investigated by thermodynamic analysis.With slag treatment,the oxygen potential is higher in the molten steel than in the pre-deoxidation slag;this causes oxygen transfer from the molten steel to the slag,decreasing the efficiency of slag treatment.Based on this,a two-step slag deoxidation process was optimized.The second step further reduced the FeO content.On the other hand,the CaO/Al2O3(C/A)ratio in the refining slag must be controlled,because it affects the FeO activity and inclusion absorption capacity of the slag.The results suggest that the C/A ratio of 1.2–1.5 and the FeO content of\6%are beneficial to refine IF steel.

Desulfurization Behavior and Mechanism of CaO-saturated Slag

To develop a high-efficiency desulfurizer for the production of pipeline steel with the LD-RH-CC process,the desulfurization efficiency and mechanism of CaO-saturated slag were studied using a vacuum-induction furnace and Si-Mo electric resistance furnace.The results show that the desulfurization ability for slag with a small amount of solid CaO was highly enhanced under conditions of satisfied kinetics.The desulfurization reaction of CaO-saturated slag depended on the liquid slag rather than the solid CaO,as sulfur was not detected inside the solid CaO.The desulfurization efficiency of CaO-saturated slag was also influenced by the amount of residual liquid slag and its sulfur absorption ability.The sulfur absorption ability of CaO-CaF2 slag was analyzed to be much higher than that of CaOAl2O3-CaF2-（SiO2）slag.Moreover,the effect of solid CaO on the desulfurization kinetics was evaluated and the application conditions of CaO-saturated slag were discussed.