Luis Felipe Verdeja

Ultrafine Grained HSLA Steels for Cold Forming

The industrial level production of ultrafine grained (or ultrafine ferrite) ferrous alloys was investigated through three examples of steels that complied with the EN 10149-2 Euronorm and were produced by advanced controlled hot rolling techniques. The steel samples were tension tested and chemically analyzed, and the microstructure was evaluated through quantitative metallographic techniques to determine parameters such as yield stress, amount of microalloying elements, strain hardening coefficient, grain size, and grain size distribution. These steels were micro-alloyed with Ti, Nb, and Mn with ASTM grain sizes of approximately 13–15. The careful control of chemical composition and deformation during production, giving a specific attention to the deformation sequences, austenite non-recrystallization temperatures and allotropic transformations during cooling, are indispensable to obtain steels with an adequate strain hardening coefficient that allows cold working operations such as bending, stretching or drawing.

Blast furnace and metallurgical coke's reactivity and its determination by thermal gravimetric analysis

Abstract The aim of the present work is to adapt tests that are typically used for blast furnace cokes, such as coke reactivity index (CRI) and coke strength after reaction, to ferroalloy production in electric furnaces by developing easier equipment that meets with ISO 18894 standards. Moreover, a new technique has also been developed using thermal gravimetric analysis in order to quickly, inexpensively and reliably find the CRI parameter. As result of this work, a polynomial relationship between cokes reactivity and mass loss slopes of the record line obtained in the gravimetric thermal analysis tests was found.

Iron Ore Sintering: Raw Materials and Granulation

ABSTRACT Sintering is an agglomeration process that fuses iron ore fines, fluxes, recycled products, slag-forming elements and coke. The purpose of sintering is to obtain a product with suitable composition, quality and granulometry to be used as burden material in the blast furnace. This process is widely studied and researched in the iron and steelmaking industry. In this context, achieving an adequate sintered product depends on the adequate raw materials supply and the previous stage to the sintering process, granulation. For that reason, in this paper, the granulation process is studied as a consequence of being the source of pre-agglomerated materials for the subsequent sintering process. Thus, the main tests used to the determination of the properties are reviewed as well as the main granulation processes.

Iron Ore Sintering: Process

ABSTRACT Sintering is a thermal agglomeration process that is applied to a mixture of iron ore fines, recycled ironmaking products, fluxes, slag-forming agents, and solid fuel (coke). The purpose of the sintering process is manufacturing a product with the suitable characteristics (thermal, mechanical, physical and chemical) to be fed to the blast furnace. The process has been widely studied and researched in the iron and steelmaking industry to know the best parameters that allow one to obtain the best sinter quality. The present article reviews the sintering process that the mixture follows, once granulated, when it is loaded onto the sinter strand. There, the sinter mixture is partially melted at a temperature between 1300-1480°C and undergoes a series of reactions that forms the sinter cake to be loaded into the blast furnace to produce pig iron.

Production of zirconia powders from the basic disintegration of zircon, and their characterization

Monoclinic ZrO2 has been prepared through the decomposition of ZrSiO4 with soda ash and lime, followed by leaching in hydrochloric acid and sodium hydroxide. The resulting zirconia powders are characterized in terms of their physical and chemical properties.

Iron Ore Sintering: Environment. Automatic and Control Techniques

ABSTRACT Sintering is a process of agglomeration of iron ore fines, fluxes, recycled products, slag-forming elements, and coke with the purpose of achieving an agglomerated product with the suitable composition, quality and granulometry to be used as burden material in the blast furnace. However, the sintering process accounts for an important percentage of the ironmaking and steelmaking emissions, so the minimization of them will promote environmental and health improvements as well as economical profitability. Automatic and control systems contribute to all these objectives.

Mechanical behaviour of thermomechanically produced ultrafine grained dual-phase steels

Abstract Dual-phase (DP) steels are an excellent alternative in the production of automotive parts that require high mechanical resistance, high impact strength and elevated elongation. These materials are produced using low alloy steels as a basis, reducing costs and resulting in a combination of martensite and ferrite structures with ultrafine grain size. These characteristics are achieved through strict control of rolling conditions, strain rate, cooling rate and coiling temperature. This work presents the results of tension testing of two types of DP steels, along with microstructural characterisation, in order to understand the effect of the advanced thermomechanical controlled rolling processes on the formation of the microstructure and resulting mechanical properties. Les aciers biphasés sont une excellente substitution pour la production de composantes automobiles qui requièrent une résistance mécanique élevée, une haute résistance à l’impact et une grande élongation. Ces matériaux sont produits en utilisant des aciers faiblement alliés comme base, réduisant les coûts et engendrant des combinaisons de structures martensitiques et ferritiques à granularité ultrafine. On obtient ces caractéristiques grâce à un contrôle strict des conditions de laminage, de la vitesse de déformation, de la vitesse de refroidissement et de la température d’enroulement. Cet article présente les résultats des essais de traction de deux nuances d’acier biphasé, de même que la caractérisation de la microstructure, afin de comprendre l’effet des procédés avancés de laminage thermomécanique contrôlé sur la formation de la microstructure et les propriétés mécaniques qui en déroulent.

Iron Ore Sintering: Quality Indices

ABSTRACT Sinter plants process a mixture of iron ore fines, recycled ironmaking products, slag-forming agents and solid fuel (coke) with the finality of obtaining a product with the suitable characteristics (thermal, mechanical, physical, and chemical) for being fed to the blast furnace. With this objective a series of parameters are defined, including the nature and composition of each component of the mixture, and the conditions of the sintering process. Sinter characterization includes chemical and granulometric analysis, determination of the mineral phases in its structure, apart from a series of quality indices that includes reducibility, low temperature degradation, reduction degradation and Tumbler. Operated sinter plants with the maximum productivity are also important with the purpose of obtaining a sinter with uniform composition and quality for facilitating the steady state operation of the blast furnace.

Bottom design optimisation of electric arc furnace for ferromanganese production using nodal wear model

Abstract This paper presents the optimisation on the design of the lining of an electric arc furnace that produces refined ferromanganese by applying the nodal wear model. This model is a new tool that systematises the wear/corrosion analysis applied to industrial furnaces linking the basic theoretical knowledge of the physical chemistry of wear/corrosion phenomena and the industrial conditions. The use of this tool to optimise the process helped increase the number of tappings between furnace bottom rebuilds from 19 in 1999 to 1200 in 2005 and the productivity to increase from 1·2 to 2·7 ton h–1.

Monitoring and control of hearth refractory wear to improve blast furnace operation

Abstract Refractory wear and skull growth on the hearth walls and the bottom of the blast furnace have been researched. A series of thermocouples were installed in the hearth, and the temperature measurements were recorded in a structured query language every minute. A heat transfer model was used to study the temperature evolution and hearth wear profile using a commercial software package (MATLAB version 5.0) based on computational fluid dynamics. The location of the 1150°C isotherm in the hearth lining has been calculated. An online monitoring tool was used to analyse the temperature distribution in the hearth and offers, to the plant operators, periodic information on the refractory state. Electromotive force (EMF) probes were installed in the hearth to estimate the variations in the liquid level in the hearth and to determine the thermal state (TS) evolution. Good correlation is seen between EMF and TS, and the EMF amplitudes in the different tapholes follow and even precede the local TS.