Heat transfer coefficients in the mould were determined by the inverse method and they are related to both process conditions and carbon equivalents of steels. Experimental data were obtained from an industrial plant by temperatures measured in moulds of the continuous casting machine by thermocouples placed in the mould wall in known positions. The temperatures are compared to profiles of simulations by the numerical model of both solidification and heat transfer processes previously examined. As a result, the numerical model calculates the heat transfer coefficients in the metal/mould interface for heats cast with different process parameters. The results make possible the determination of expressions for the calculation of the interfacial metal/ mould heat transfer coefficients that include the effects of steels grades, mould faces, casting speed, mould taper, mould section and pouring temperatures for a range of process parameters.

This work presents the development of a computational algorithm applied to improve the thermal behaviour in the secondary cooling zone of steel billets and blooms produced by continuous casting. A mathematical solidification heat transfer model works integrated with a neural network based algorithm (NNBA) connected to a knowledge base of boundary conditions of operational parameters and metallurgical constraints. The improved strategy selects a set of cooling conditions (in the secondary cooling zone) and metallurgical criteria established to attain high product quality, which are related to a more homogeneous thermal behaviour during solidification. Initially, the results of simulations performed by using the mathematical model are validated against experimental industrial data, and good agreement is observed, in any case examined, permitting the determination of nominal heat transfer conditions by the inverse heat conduction method. By using the numerical model linked to a NNBA results have been produced determining a set of casting conditions, which has permitted better strand surface temperature profile and metallurgical length to be attained during the continuous casting of SAE 1007 billets and SAE 1025 blooms.

No abstract

Aluminium alloy Al-Si5Cu3 (319) is one of the most commonly used casting alloys for automobile components, due to its casting characteristics. Iron is the major impurity element that influences the detrimental β-phase formation in secondary aluminum alloys. In the present study, we investigated the influence of the cooling rate on the formation of iron compounds, α-Al 15 (Mn,Fe) 3 Si 2 and β-Fe 5 AlSi phases, in Al-Si5Cu3 containing 1.0% Fe, 0.5% Mn and 0.2% Mg, by thermal analysis and metallography. The results show that the high cooling rates, between 10-10 3 K/s, are able to reduce and nullify the formation of needle-like β-Al5FeSi phase, and help the formation of the Chinese scripts α-Al 15 (Fe,Mn) 3 Si 2 phase. The analysis of the curves reveals that the increase of the cooling rate increases the temperature of nucleation of the α-Al dendrite and decrease the eutectics Al-Si and Al-Cu phases.

Este trabalho tem como objetivo avaliar a contribuição do componente do rendimento domiciliar "aposentadorias e pensões" para a desigualdade da distribuição do rendimento domiciliar per capita no Brasil, nos meios rural e urbano, em 1998, 1999, 2001, 2002 e 2003. Para isso, utilizaram-se estratos de rendimento domiciliar per capita e a metodologia de decomposição do índice de Gini dos seguintes componentes: rendimento do trabalho principal, rendimento de outros trabalhos, aposentadorias e pensões, doações, rendimentos de aluguel e outros rendimentos (juros, dividendos etc.). Destaca-se, nos resultados, a substancial contribuição das aposentadorias e pensões para a desigualdade da distribuição da renda no Brasil. A estratificação dos rendimentos domiciliares permitiu a constatação de que, no Brasil rural, o percentual de domicílios e pessoas na população e os rendimentos total e das aposentadorias e pensões estão localizados nos estratos inferiores da renda.