PHYSICAL MODELING OF LIQUID LIQUID MASS-TRANSFER IN GAS STIRRED LADLES

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ON THE HOT METAL DESULFURIZATION

Although there is no thermodynamic limitation to the desulfurization of carbon-saturated iron with CaO, the process is well-known to be slow. Consequently, the desulfurization of carbon-saturated Fe-S, Fe-S-Si, Fe-S-Si-Al, Fe-S-Zr alloys be CaO, and Fe-S-Si alloys by CaO-10 % CaF2 were investigated to determine the reaction mechanism. For this purpose, dense CaO and CaO-10 % CaF2 discs were cemented to the bottoms of graphite crucibles containing the carbon-saturated alloys. The desulfurization experiments were run at 1450 degrees C in an SiC resistance furnace under argon gas atmosphere. The results indicate that the desulfurization of hot metal by CaO is greatly improved by prior addition of aluminum to the hot metal. The addition of 10 % CaF2 to CaO also increases the rate of desulfurization. Ziroonium, which has a stronger affinity for oxygen than aluminum did not increase the rate. SEM and X-ray diffraction studies on the surfaces of CaO discs used to desulfurize carbon-saturated Fe-S, and Fe-S-Si alloys showed that solid CaS, and solid CaS plus small amount of solid 2 CaO . SiO2 compounds form on the limo surface, respectively. The slow reaction rate with CaO is attributed to the solid reaction products which block the reaction by preventing the occurrence of interfacial turbulence

Automated Steel Cleanliness Analysis Tool (ASCAT)

The objective of this study was to develop the Automated Steel Cleanliness Analysis Tool (ASCATTM) to permit steelmakers to evaluate the quality of the steel through the analysis of individual inclusions. By characterizing individual inclusions, determinations can be made as to the cleanliness of the steel. Understanding the complicating effects of inclusions in the steelmaking process and on the resulting properties of steel allows the steel producer to increase throughput, better control the process, reduce remelts, and improve the quality of the product. The ASCAT (Figure 1) is a steel-smart inclusion analysis tool developed around a customized next-generation computer controlled scanning electron microscopy (NG-CCSEM) hardware platform that permits acquisition of inclusion size and composition data at a rate never before possible in SEM-based instruments. With built-in customized ''intelligent'' software, the inclusion data is automatically sorted into clusters representing different inclusion types to define the characteristics of a particular heat (Figure 2). The ASCAT represents an innovative new tool for the collection of statistically meaningful data on inclusions, and provides a means of understanding the complicated effects of inclusions in the steel making process and on the resulting properties of steel. Research conducted by RJLG with AISI (American Iron and Steel Institute) and SMA (Steel Manufactures of America) members indicates that the ASCAT has application in high-grade bar, sheet, plate, tin products, pipes, SBQ, tire cord, welding rod, and specialty steels and alloys where control of inclusions, whether natural or engineered, are crucial to their specification for a given end-use. Example applications include castability of calcium treated steel; interstitial free (IF) degasser grade slag conditioning practice; tundish clogging and erosion minimization; degasser circulation and optimization; quality assessment/steel cleanliness; slab, billet or bloom disposition; and alloy development. Additional benefits of ASCAT include the identification of inclusions that tend to clog nozzles or interact with refractory materials. Several papers outlining the benefits of the ASCAT have been presented and published in the literature. The paper entitled ''Inclusion Analysis to Predict Casting Behavior'' was awarded the American Iron and Steel Institute (AISI) Medal in 2004 for special merit and importance to the steel industry. The ASCAT represents a quantum leap in inclusion analysis and will allow steel producers to evaluate the quality of steel and implement appropriate process improvements. In terms of performance, the ASCAT (1) allows for accurate classification of inclusions by chemistry and morphological parameters, (2) can characterize hundreds of inclusions within minutes, (3) is easy to use (does not require experts), (4) is robust, and (5) has excellent image quality for conventional SEM investigations (e.g., the ASCAT can be utilized as a dual use instrument). In summary, the ASCAT will significantly advance the tools of the industry and addresses an urgent and broadly recognized need of the steel industry. Commercialization of the ASCAT will focus on (1) a sales strategy that leverages our Industry Partners; (2) use of ''technical selling'' through papers and seminars; (3) leveraging RJ Lee Group's consulting services, and packaging of the product with a extensive consulting and training program; (4) partnering with established SEM distributors; (5) establishing relationships with professional organizations associated with the steel industry; and (6) an individualized plant by plant direct sales program