Companhia Siderurgica Nacional CSN

Volta Redonda, Brazil

Companhia Siderurgica Nacional CSN

Volta Redonda, Brazil
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Gonzaga F.B.,National Institute of Metrology of Brazil | Braga L.R.,Jr. | Sampaio A.P.,Companhia Siderurgica Nacional CSN | Martins T.S.,Companhia Siderurgica Nacional CSN | And 2 more authors.
Analytical and Bioanalytical Chemistry | Year: 2017

This work presents a new method for forward variable selection and calibration and its evaluation for manganese determination in steel by laser-induced breakdown spectroscopy (LIBS). A compact and low-cost LIBS instrument was used, based on a microchip laser and a grating mini-spectrometer containing a non-intensified, non-gated, and non-cooled linear sensor array. Sixty steel samples were analyzed, with known manganese concentrations from 0.106 to 1.696 wt%. The spectra (1757 variables between 200 and 850 nm) were acquired under the continuous application of laser pulses at 100 Hz and using 80, 400, and 1000 ms integration times. The new method generated a mathematic combination of the selected variables and the results were calibrated against the manganese content by linear or quadratic regression. The best results were obtained using the spectra from all integration times together, with 31 selected variables and root mean square errors of cross-validation and prediction of 0.015 and 0.033, respectively. Compared to Jack-knife partial least squares regression, the new method presented lower prediction errors and numbers of selected variables, with the advantages of no data pretreatment and a simpler mathematic calculation. [Figure not available: see fulltext.] © 2017, Springer-Verlag Berlin Heidelberg.

Sousa P.C.S.,Companhia Siderurgica Nacional CSN | Talaat T.,Companhia Siderurgica Nacional CSN | Souza T.I.,Companhia Siderurgica Nacional CSN | Cordeiro P.R.O.,Companhia Siderurgica Nacional CSN | And 3 more authors.
Proceedings of the Unified International Technical Conference on Refractories, UNITECR 2013 | Year: 2014

The main purpose of this work is present the repair and improvement developed in tapholes areas at CSN’s Blast Furnace 3 to preserve the hearth wall and ensure the campaign until 2021 according to original project in 2001 where the Blast Furnace 3 was relined and installed a new hearth. After an evaluation of tapholes condition, which was done in partnership with TRE Services, was proposed a new repair method named Core & Cast™ and Core & Plug™ that causes less damage in tapholes and spool areas during the maintenance. These methods were applied in 2008 and 2009 and have an expected campaign of 5 years. The results show that the tapholes performance has been as expected and the spool reached an average of 30 months of operation without general repairs and every 10 months are done partial repairs. The benchmark is 13 months for partial repair. Another gain was the execution time of general and partial repairs that were reduced in 7hs and 13hs respectively. © 2014 The American Ceramic Society.

Silva Dias J.,Federal University of Rio de Janeiro | Costa H.R.M.,Federal University of Rio de Janeiro | de Aguiar R.A.A.,Federal University of Rio de Janeiro | de Araujo Alves Lima R.,Federal University of Rio de Janeiro | And 2 more authors.
Materials Science Forum | Year: 2013

The main objective of this work is to optimise welding parameters for the process of resistance spot welding applied to Interstitial Free (IF) steel sheets, in order to increase the life of conventional copper electrodes. The methodology consisted of using a weld tester to ensure the accuracy of the results. The main parameters selected through a weldability survey were force, time and welding current. To evaluate the resistance of the weld and the electrode wear mechanical tests were performed, such as tensile-shear, cross-tension and peel test. A microstructural evaluation by optical microscopy (OM) and scanning electron microscopy (SEM) was carried out. The results show a reduction in the thickness of the coating in the steel shetts, and macro and microstructures were observed in the weld region. The tensile-shear and cross-tension tests were verified using electrode caps of up to 1250 points with acceptable welds. The methodology used for parameter selection has highlighted an optimal combination of 200kgf electrodes force, 9 cy welding time (cycles) and 7.8 kA welding current, in overlapped 0.75mm thick IF steel sheets, thereby increasing the lifetime of the electrode and ensuring a better quality of weld and consequent reduction in the energy applied in the welding process. © (2013) Trans Tech Publications, Switzerland.

Silva S.N.,Companhia Siderurgica Nacional CSN | Romao E.C.,Companhia Siderurgica Nacional CSN | Barbosa G.S.,Companhia Siderurgica Nacional CSN | Da Costa W.B.,Companhia Siderurgica Nacional CSN | And 3 more authors.
Ironmaking and Steelmaking | Year: 2012

CSN BF no. 2 has only three hot blast stoves. Owing to the operational risks as well as output losses associated with the BF operation with just two hot blast stoves, the revamping time of this equipment becomes a crucial issue, requiring special attention in each phase of the project from planning to execution so as to shorten the time as much as possible. According to this context, the present paper describes in detail the main technologies used in the last revamping of hot blast stoves carried out in February 2007. These technologies included an accelerated cooling down curve, air conditioning system (good working condition) and convection heating system, which in association with an innovative construction methodology, involving movable and multilevel platforms, has allowed the project to be completed from blow to blow in a record time of just 67 days and 10 h, resulting in a reduction of costs around R$3·4m. © 2012 Institute of Materials, Minerals and Mining.

Silva S.N.,Companhia Siderurgica Nacional CSN | Vernilli F.,University of Sao Paulo | Justus S.M.,São Paulo State University | Araujo C.M.D.S.,Companhia Siderurgica Nacional CSN | And 4 more authors.
Steel Research International | Year: 2013

The growing demand for steels with tighter compositional specifications led the Companhia Siderúrgica Nacional (CSN) to develop more efficient processes. To solve this problem this paper aims to identify the operational variables more impacting in the desulfurization process, specifically in torpedo car, as well as its causes and solutions. Then select and test, with laboratorial and industrial tests, desulfurizing agents based of CaC 2, CaO, CaCO3, and Mg to assess the cost per quantity of product desulfurized. The mixture with best results was not that one with highest content of CaC2. It is believed that this mixture showed better efficiency because of the increased agitation of the bath, produced by the releasing of gas from compound CaCO3 present in this mixture. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Silva S.N.,Companhia Siderurgica Nacional CSN | Vernilli F.,University of Sao Paulo | Justus S.M.,São Paulo State University | Longo E.,São Paulo State University | And 3 more authors.
Materials and Corrosion | Year: 2013

In this work it is presented a methodology applied by Companhia Siderúrgica 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 500 °C 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. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Santos N.A.,Eriez Flotation Division Brazil | Duarte F.,Eriez Flotation Division Brazil | Fan M.,Eriez Flotation Division | Honaker R.,University of Kentucky | And 2 more authors.
6th Int. Congress on the Science and Technology of Ironmaking 2012, ICSTI 2012 - Including Proceedings from the 42nd Ironmaking and Raw Materials Seminar, and the 13th Brazilian Symp. on Iron Ore | Year: 2012

Cavitation is a process of formation, growth and subsequent collapse of gas and/or vapor-filled cavities, or microbubbles, in a fluid. Several fundamental studies about this phenomenon have shown that microbubbles generated on mineral surfaces facilitate bubble-particle attachment, and ultimately improves flotation performance. This work presents the Feed Air Jet, a feed pre-aeration cavitation sparger system developed by Eriez. Using coal, cavitation was applied to a flotation feed stock studied in laboratory setting in the USA. This feed pretreatment technique resulted in a significant increase in recovery and flotation kinetics. The Feed Air Jet was also installed at an industrial plant in Brazil and enhanced the overall metallurgy by increasing the mass recovery of the iron (Fe) values while reducing the amount of entrained iron in the tailings stream.

Da Silva Dias F.M.,Federal University of Fluminense | Da Costa e Silva A.L.V.,Federal University of Fluminense | Fonseca F.A.V.,Companhia Siderurgica Nacional CSN | De Campos M.F.,Federal University of Fluminense
65th ABM International Congress, 18th IFHTSE Congress and 1st TMS/ABM International Materials Congress 2010 | Year: 2010

It is described the methodology employed in the development of a new IF (Interstitial Free) galvanized steel produced by CSN with excellent forming, designed for the automotive industry. It was found need of improvement to fulfill the EDDQ grade (yield point ≤180 MPa), with application for extra deep drawing. A new galvanized Ti-stabilized IF steel was developed, with extra low carbon content, for both external and internal components. The mechanical properties were analyzed to evaluate the forming of the materials and to check if the new steel presents superior behavior. Tensile tests and the statistical software MINITAB 15.1 were employed for the evaluation of the results and process capability analysis.

Da Silveira Sousa P.C.,Companhia Siderurgica Nacional CSN | Fernandes E.G.,Companhia Siderurgica Nacional CSN | Dos Santos M.T.,Companhia Siderurgica Nacional CSN | Da Silva M.J.M.,Companhia Siderurgica Nacional CSN
65th ABM International Congress, 18th IFHTSE Congress and 1st TMS/ABM International Materials Congress 2010 | Year: 2010

Nowadays in a globalized world the major focus is cost down thru operational stability. The straight tubes from blast furnaces which have as main function the transference of the hot air for inside of the same straight tubes, in order to have the charge fusion, which are the most important pillars to guarantee the continuity of hot air blow for production effectivity and also to grab operational indexes highly competitives. However Blast Furnaces Emergency Break-out were occurring in substantial basis, causing an operational stability impact, as well the employees safety in a higher risk, due to the very often straight tubes ruptures, which demonstrated hot spots in an ascending level. Moreover: the maintenance cost of this particular system was highly affected and also became it as the pipeline to the temperature of the blown air. This study has as major target reach the elimination of all existing hot spots of the straight tubes from Blast Furnaces number 2 and 3, and thru this process to assure their operational pre visibility.

Da Silveira Sousa P.C.,Companhia Siderurgica Nacional CSN | Romao E.C.,Companhia Siderurgica Nacional CSN | De Paula Pereira J.,Companhia Siderurgica Nacional CSN | De Avila Mendes M.,Companhia Siderurgica Nacional CSN
65th ABM International Congress, 18th IFHTSE Congress and 1st TMS/ABM International Materials Congress 2010 | Year: 2010

In 2008, it was detected on Stove 2.3 of Blast Furnace #2, the fallen of the refractory wall in the combustion chamber, 12 meters far from the base, during the preventive maintenance service, for the replacement of the hot blast valve -VAQ. On emergency basis, refractory castable was gunned to rebuild the wall. Since then, studies were made to carry out a partial revamp, which took place in 2009, together with the revamp of Blast Furnace #2. This paper presents a brief description of the state of the refractory, the solutions adopted and the repairs made to maintain the operational functions of the equipment. Copyright © (2010) by Associação Brasileira de Metalurgia Materiais e Mineração (ABM).

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