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Sidiney Nascimento Silva, Fernando Vernilli, Sergio Murilo Justus,Cla´udio Ma´rcio dos Santos Arau´jo, Elson Longo, Jose´ Arana Varela,Jose´ Milton Gabriel Lopes, and Bruno Vidal de AlmeidaThe growing demand for steels with tighter compositional specifications led theCompanhia Sideru´rgica Nacional (CSN) to develop more efficient processes. To solve thisproblem this paper aims to identify the operational variables more impacting in thedesulfurization process, specifically in torpedo car, as well as its causes and solutions.Then select and test, with laboratorial and industrial tests, desulfurizing agents based ofCaC

In this work it is presented a methodology applied by Companhia Siderurgica Nacional (CSN, Brazil) in order to assess its blast furnace 3 carbon refractory hearth lining conditions. The aim of the investigation was the gathering of critical data base for blast furnace refractories life cycle follow up and eventual repair decision taking. The sample drilling locations were chosen around the tap holes and hearth bottom areas. The advancing drilling depths were based on local temperature profiles. The isotherm limit of 5008C was elected as a control parameter to assess the critical carbon refractory condition. The guidelines for sampling and testing as well as the results obtained through the physical and chemical characterizations of the cored samples are presented. The condition of the refractory lining is discussed under the light of the different known wear mechanisms of blast furnace hearth carbon refractories. It is a well-known fact that the refractory hearth lining is a critical feature in the realm of the life expectancy of a blast furnace. In this sense, invasive procedures were undertaken in order to assess the carbon refractory hearth lining conditions of CSNs blast furnace 3, afterproducing28 million tons ofpigironin11 years of campaign. The guidelines used for the sampling and the information put together by the investigation, conducted on cored specimens, were important for a global understanding of carbon refractories hearth lining wear phenomenology, as well as for the setup refractories selection guidelines and possible repair programs. Historically everysteel millwants toincreaseits blast furnace productivity. The first step commonly taken in this direction consists in the increase of the processing temperature. As a consequence the molten pig iron temperature increases, resulting immediately in an overall increase in the refractory lining wear. This was particularly critical for the crucible lining based on carbon refractories. In order to counterbalance the increased wear, the use of microstructure engineered improved graphite-based carbon refractories (higher thermal conductivity

Over recent years, owing to the need to increase productivity, it has been necessary among other things to increase the hot metal temperature in the blast furnace hearth. As a result, refractory lining wear becomes more intense. While publications present a host of comparative tests for hearth refractories and their performance, hardly any information is available in such publications regarding reaction mechanisms and further deterioration of these materials. Based upon comparative laboratory test results using two carbon materials of different concepts, the various reaction mechanisms and enhanced refractory lining deterioration for the blast furnace hearth have been identified. From an understanding of these wear mechanisms acting upon the hearth lining, it has been decided to introduce some practical operating measures, with a view to extending the blast furnace campaign.

This paper looked into hot metal corrosion behavior for graphite refractory used in blast furnace hearth, consisting of 50% graphite and 50% anthracite, impregnated with TiO 2 , ZrO 2 carrying solutions. The method used for corrosion was the Finger Test, which was conducted in an induction furnace with 30 x 30 x 280 mm bar-shaped test specimens, and the hot metal and slag used were taken from the CSN #2 Blast Furnace runner, the test temperature was 1470°C with a sixty-minute isotherm. After the corrosion test, the specimens were characterized by their dimensional variation, X-ray diffractometry and Scanning Electronic Microscopy (SEM).

This paper investigates corrosion behavior in graphite refractory hot metal impregnated with ZrO 2 and CeO 2 carrying solutions used in Blast Furnace hearth, consisting of 50% graphite and 50% anthracite. Corrosions testswere carried out by means of finger test method in an induction furnace, using bar-shaped 30x30x280 mm test specimens and hot metal from CSN #2 Blast Furnace runner. The temperature chosen for this test was 1 520°C and 60-min isotherm. Upon test completion, test specimens were characterized by their dimensional variation, X-ray diffractometry and Scanning Electronic Microscopy (SEM).

A post mortem study of Al2O3/SiC/C/MgAl2O4 (ASCMg) refractory lining used in Companhia Siderurgica Nacional (CSN) torpedo car was conducted in order to determine the corrosion equation developed during industrial application. Different samples were collected and characterized using the following techniques: Chemical Analysis by X-Ray Fluorescence, Thermal-Gravimeter and Differential Thermal Analysis (TG–DTA), Mercury Porosimetry, Helium Picnometry, Dilatometry, X-Ray Diffractometry, Scanning Electronic Microscopy (SEM) and Energy Dispersive Scanning (EDS). It was found that slag containing a high amount of calcium aluminum silicate interacts with refractory microstructure causing corrosion. From this effect it is noted the introduction of an alkaline incorporating concurrent mechanism, in addition to corundum being turned into β-alumina and the oxidation of SiC through Na2O resulting in better protective conditions to graphite, thereby improving refractory lining shelf life.

The corrosion resistance of resin bonded alumina/magnesia/graphite refractories containing different kinds of aggregates were investigated when submitted to the action of slags of several CaO/SiO2 ratios. The laboratory testing was performed by means of the rotary slag attack test. Specifically evaluated was the influence of alumina/carbon ratio and magnesia and silica contents on the refractories corrosion resistance. It was found that this property could be improved by increasing the refractory Al2O3/SiO2 ratio as well as by choosing the appropriate Al2O3/C ratio.

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:20:33Z No. of bitstreams: 0Bitstream added on 2014-05-27T14:29:06Z : No. of bitstreams: 1 2-s2.0-52649095066.pdf: 619873 bytes, checksum: 7439b2ac0a499e8adda9618c262303c8 (MD5) Made available in DSpace on 2014-05-27T11:20:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-12-01 The work describes actions carried out in colaboration among the National Steel Company - (CSN)-Brazil and the Interdisciplinary Laboratory of Electrochemistry and Ceramic - LIEC of the Federal University of Sao Carlos Brazil (UFSCar-Brazil), in the area of I&D, for integral management and improvement of the quality and performance of the refractory linings in the sintering areas, blast furnace, hot air pipe lines transferency to the blast furnace, pig-iron ladles, running channels, blast furnaces hearths, torpedo car, etc., as well as, the economic impact generated by the installation of the adopted measures. LIEC/CMDMC-Laboratorio Interdisciplinar de Electroquímica y Cerámica UFScar UNESP CSN - Compañía Siderúrgica Nacional Centro Federal de Educacao Tecnológica do Maranhao Departamento de Engenharia de Materials - DEMA UFScar, SP LIEC/CMDMC-Laboratorio Interdisciplinar de Electroquímica y Cerámica UFScar UNESP