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By Dagoberto Brandão Santos, Marcus Vinícius Pereira Arruda, Fernando de Souza Costa, Túlio Magno Fuzessy de Melo

The development of advanced high strength steels (AHSS) is motivated by the automotive industry demands for higher strength steels with better formability and stretch-flangeability to avoid fractures during parts forming. In response to this, the new steel grades must have special microstructures in terms of constitution, morphology, distribution and hardness, which are strongly dependent on the chemical composition of the steel sheet and its processing, especially in the continuous annealing stage, in the case of cold rolled sheets. In this study the influence of the annealing heating rate and intercritical temperature (IT) on the microstructural evolution and the final hole expansion ratio of a cold rolled 980 MPa AHSS grade was evaluated. The annealing process was simulated using a Dilatometer and a Gleeble machine, and the microstructures were characterized using scanning electron microscopy, electron backscattered diffraction (EBSD) and nanohardness measurements. The increase of heating rate resulted in an overlap between ferrite recrystallization and austenite formation, changing the austenite morphology from a random to a fibrous distribution, while a higher IT resulted in more homogeneous microstructures and higher hole expansion ratios. This microestructural homogeneity, confirmed by nanohardness measurements, suggested that the difference in hardness between ferrite and the second phase affects the micro-void formation and crack propagation during the hole expansion test.

Oct 1, 2019

By Pedro Henrique Coutinho

Este trabalho teve como objetivo a redução do custo de transformação da Aciaria de Resende (Votorantim Siderurgia), visando à redução do Cash Cost do tarugo, ponto fundamental no atual cenário econômico da siderurgia brasileira. Para priorizar as ações, otimizar recursos e tratar o tema de forma estruturada foi utilizada a metodologia DMAIC na execução deste projeto. Como resultado houve redução no custo de transformação, alcançado por melhorias nas linhas de Energia Elétrica, Ligas, Escorificantes, Eletrodos e Outras Variáveis.

Aug 16, 2017

By Jean-Philippe Houde

The Blast Furnace Campaign lifetime is highly depending on the wear progress of the hearth lining. This progress is monitored in general through single and double thermocouples at the cold side of the lining. This type of monitoring becomes ineffective as soon as heat resistance will be formed in the refractory lining. Paul Wurth’s monitoring system, consisting of MTP-Sensor and Heat Flux Probes, is able to identify such heat resistances to give a true hearth lining wear. Since last year Paul Wurth is also able to install safely those MTP-Sensor and Heat Flux Probes on running blast furnace without salamander tapping, thanks to a newly developed cooled core drilling device. Blast Furnaces that are equipped with Paul Wurth’s monitoring system have optimized their campaign lifetime as they received right information upon the true wear lining such as detection of heat flux transfer failure, detection and monitoring of brittle layer or detection of hot spot.

Aug 16, 2017

By Douglas Glenn Stalheim

The uniformity of the final cross sectional microstructure and subsequent final mechanical properties and shape of structural steels is dependent on the type or types of recrystallization behaviors that are created. There are three main recrystallization behaviors that are the foundation of the metallurgy created during production. Alloy design and subsequent processing design strategy drive how much of each recrystallization behavior is created through the cross section of the product. Carbon manganese steels create only one basic behavior while the addition of microalloys, in particular niobium, can add two additional behaviors. The behaviors are intertwined with each other and build upon each other. The three behaviors are Type I, static recrystallization, Type II, no-recrystallization, and Type III, metadynamic/dynamic recrystallization. How much of each behavior is generated through the cross section through the production influences the final transformed microstructure and corresponding mechanical properties and shape performance. This paper will discuss the three behaviors, how they are generated, how to identify which behavior is occurring through modeling or actual mill data. Actual examples from production will be discussed.

Aug 16, 2017

By Gabriel Felipe Tavares de Barros

O presente trabalho estuda a cinética de dessorção do hidrogênio em aços 9% níquel, comercial e tratado termicamente em diferentes condições, através da técnica de Espectroscopia de Dessorção Térmica (TDS). Para a identificação dos aprisionadores de hidrogênio e a determinação da energia de ativação para a dessorção, ensaios de TDS foram realizados a 3, 5, 6, 10 e 15°C/min. Foi identificado um pico de dessorção a 124,66 kJ/mol, classificando o referido sítio aprisionador de hidrogênio como interfaces de grãos de austenita retida, cuja presença é confirmada por microscopia eletrônica e difração de raios-X.

Oct 30, 2017

By Andrelio Marcos Ribeiro, Lucio Ribeiro Camisao, Antonio Carlos Ataíde, Alan de Sousa Pereira, Renato Siqueira Campos

The annealing and pickling line n. 1, responsible for the production of stainless steel 3xx, 4xx and 430a in thicknesses from 4 to 0.4 mm, has two vertical strip accumulators. These are intended not to let the material exceed the determined time in the furnace and in the pickling, and consequently do not cause defects like burning and excessive pickling. Strip accumulator n. 1 avoids the line from stopping during welding execution of the coils in the welding machine. In sequence, the strip accumulator n. 2 avoids the line from stopping at the end cutting of the tips, and in the coils removal from the pickling. The strip accumulators have a roller table that during the strip accumulation moves vertically downwards while its counterweight moves vertically upwards, and do the inverse movement when the material is released. On December 12th 2018, the failure occurred in the strip accumulator n. 1, where it was verified that the shaft of one of the pulleys had been fractured by high-cycle mechanical fatigue, which was characterized by alternating bending. With the fracture of the shaft, occurred the unevenness of the counterweight that damaged the guides. Failure analysis of this occurrence was based on the PDCA methodology, when was verified a weld between the shaft and the pulley. The analysis of the microstructure transformation in the molten zone, in the heat affected zone and in the base metal was carried out in an optical microscope, and no abnormality was observed. It was also carried out the end test by penetrating liquid, finding an inadequate weld in its geometry, as well as longitudinal trunks along the center of the weld bead. However, after a huge investigation of the causes, it was found that the failure was triggered by an inadequate design of the pulley shaft. It was also verified that the shaft had an open measure, inadequate for the operational context. After the analysis, action plans were drawn up based on the FMEA methodology to inhibit the failure recurrence.

Oct 7, 2019

By Willy Ank de Morais

Este trabalho analisou o caso de emprego de um consumível constituído de aço carbono (ER 70S3) para realizar a soldagem de tubos ASTM A333, empregados em baixas temperaturas, ao invés de empregar consumíveis especiais especificados para emprego em baixas temperaturas, tal como o ER 80S Ni2. Os três pontos centrais considerados neste trabalho foram: (1) compatibilidade entre os materiais envolvidos; (2) análise das características específicas do aço, no grau empregado e do projeto da tubulação e; (3) longevidade da linha, que pode ser prejudicada a longo prazo pelas variações químicas dos metais envolvidos que poderiam induzir corrosão localizada.

Oct 30, 2017

By Guilherme Geada Sampaio

Uma linha contínua não só melhora o conforto aos usuários, mas também melhora as condições de desgaste, fadiga e manutenção dos equipamentos ferroviários. Porém, os parâmetros de soldagem devem ser bem especificados e controlados de forma a obter uma junta soldada adequada. Este trabalho oferece uma revisão geral sobre as características básicas de uniões aluminotérmicas de forma a subsidiar a avaliação e melhoria no desempenho de soldagem aluminotérmicas de trilhos, realizada em um outro trabalho também sendo apresentado neste Congresso.

Aug 16, 2017

By Peter Grawenhof

Universal joint shafts and slipper spindles are commonly used in rolling mills to compensate the design- and process-related offset between the motors and work rolls. Although both types of shafts exhibit on the same kinematic principle, there are basic differences regarding the design concepts. These differences become noticeable on many levels and may become very distinct in terms of Life-Cycle-Costs (LCC). In this respect, a critical comparison between universal joint shafts and slipper spindles can be made.

Aug 16, 2017

By Maycon Athayde

Samarco produces high quality iron ore pellets processed in straight grate furnaces. This process is essential in order to obtain adequate mechanical strength to the pellet transportation and operation in the reduction reactors. All mechanical properties of the agglomerates are obtained during the stage of firing where the slag and sintering bond happens, thus it is a decisive step to improve the pellet quality. Therefore, the velocity distribution of gas flow within this zone must have homogeneous and even velocity distribution. Hence, it was developed a mathematical CFD model to characterize the gas flow in the burning zone, applying the equations of conservation of momentum, mass and energy and an uneven flow distribution was identified and the gas velocity analyzed and validated through experimental data. On the other hand, on the present paper, an improved firing zone burner were developed and industrially implemented in a way to mitigate the uneven flow pattern detected aided by CFD. Different burner designs, based on CFD analysis, were experimented in order to succeed on the aggressive condition. The combustion was investigated and burner efficiency evaluated and compared with the simulation purposed.

Aug 2, 2018

By Richard Harvey, Robert Paul Mawer

In recent times there has been an increase in the demand from Steel plants for a technology that offers the most economical environmentally sustainable solution. In terms of blast furnace off gas cleaning this has seen a drive towards Cyclone technology replacing the older Dustcatchers. Cyclone technology can achieve dust removal efficiencies as high as 95% increasing the dust yield at the primary stage of gas cleaning. The dry dust (rich in Fe and C) can then be recycled to the Sinter Plant or Blast Furnace. Capture of dust at this stage also has the benefit that sludge generation from the secondary stage is also reduced meaning less waste to landfill and / or recovery of some of the by-products for further use. Primetals Technologies already offer a state of the art Tri-Axial Cyclone installed on many sites world-wide, however, this paper focuses on a hybrid of this technology, the DustClone. The DustClone is a low CAPEX unit that is essentially a Cyclone housed inside the Dustcatcher. This unit is aimed at operators who may be carrying out smaller scaled shutdowns / repairs that normally have a reduced CAPEX. This paper describes the technology that Primetals Technologies have developed.

Oct 1, 2019

By Luís Gustavo Costa de Castro

Neste trabalho foram utilizadas amostras dos aços CA-50 e CA-60 utilizados na construção civil, para avaliar a corrosão pelos íons cloreto. Para tanto, medidas eletroquímicas foram realizadas em soluções de NaCl 2,0 g/L e 4,0 g/L, naturalmente aeradas. Verificou-se um processo de corrosão generalizada dos aços CA-50 e CA-60 nas duas concentrações avaliadas e uma forte influência do aumento da concentração no comportamento corrosivo de ambos os tipos de aço. Neste estudo comparativo, verificou-se que, além dos perfis potenciodinâmicos serem similares, a resistência de polarização conduziu a resultados da mesma ordem de magnitude, concluindo-se que não existe uma vantagem significativa ao uso de um em relação ao outro, no que se refere à resistência à corrosão.

Aug 7, 2018

By Leonardo Semedo de Mattos Siqueira, Renata Ferreira Muller

The Granulometric Ratio (RG) is one of the most important indicators related to the pelletizing product. Through it, it guarantees good permeability of the bed of pellets, optimization of the thermal cycle and, thus, better results of physical quality and consumption of the energy matrix. To guarantee this indicator, it is necessary that the processes of agglomeration of pellets, classification of raw pellets and screening of burned pellets are under control of certain parameters and with a level of stability assured.

Oct 1, 2019

By Renan Tavares Ruy

Esse trabalho tem como objetivo buscar um melhor entendimento dos fatores que influenciam de forma significativa nas propriedades mecânicas do vergalhão 1350AA, avaliando especificamente a influência da temperatura de bobinamento. Foram retiradas amostras de seis bobinas e então submetidas à diferentes temperaturas de recozimento por um período específico e analisadas mecanicamente e microscopicamente. Os ensaios de tração mostraram que o alumínio 1350 AA sofre uma influência significativa da temperatura, cujo comportamento foi muito similar ao apresentado na literatura. Constatou-se que o fenômeno de recuperação ocorreu de forma mais significativa a temperaturas elevadas. O trabalho permitiu concluir que é necessário um resfriamento mais eficiente no vergalhão para que a variação de LRT seja minimizada.

Aug 16, 2017

By Jan Bak

Rourkela Steel Plant (RSP), which is operated by the Steel Authority of India Limited (SAIL), was inaugurated in 1959 and was the first Integrated Steel Plant in the public sector in India. In 2013, RSP commissioned their No. 5, 4060 m³ Blast Furnace, India's largest. It was built as a turn-key project by a consortium consisting of Danieli Corus and Tata Projects Ltd. and is entirely based on the technology and know-how of Danieli Corus. The new Blast Furnace is the key element of an expansion program that doubles the plant's production capacity and with much of the existing ironmaking capacity reaching the end of its technical and economic life span, it enables RSP to meet existing as well as growing demand for its products. This article discusses how this greenfield Blast Furnace was built in an existing and operating Integrated Steel Plant. It covers the accommodation of land, planning of the new installation to fit the available plot as well as the updated logistical lay-out of the plant. Technical details of the installation are presented, including their consequences for RSP's environmental performance and new perspectives for campaign planning.

Aug 2, 2018

By Luis Acainas Caballero, Karl Hoen, Stephan Krämer, Christoph Klein

The situation of the steel industry is still challenging. Worldwide overcapacities have an impact on profitability. More than ever, the point at SMS group is to provide the steel industry with flexible and profitable technologies and systems over the whole process chain. One example for that is the thin slab casting and rolling technology and, in particular the CSP® technology (Compact Strip Production), being well established for hot coil production. From its introduction in 1989, CSP® technology has been continuously further developed. Today, on a CSP® plant, the full range of high-quality steel grades can be produced with tightest geometrical and metallurgical tolerances under optimal economic conditions. With the introduction of semi-endless rolling and, as a further step, the endless rolling process, the product range for thin and ultra-thin products has been further enlarged, allowing for the production of hot rolled coils with a thickness of 0.8 mm for low carbon steel grades. Also high-strength steel grades may be produced with gauges below the minimum product thickness that can be achieved in a conventional-type hot rolling mill. Another step in the further development of CSP® technology is digitalization. In December 2016, the CSP® plant of Big River Steel (BRS), located in Arkansas, USA was put into operation. It is the first learning steel mill in the world. The CSP® plant of BRS comes with innovative technologies, providing impressive operational results right from the beginning.

Oct 1, 2019

By Osvaldo Guilherme Comineli

An extensive investigation into the role of low copper contents on the hot ductility of C-Mn-Al steels has been carried out in order to better understanding the problem of “hot shortness”. Previous work has suggested that this problem results from the build up of Cu that occurs at the surface of the steel as a consequence of the preferential oxidation of iron. This causes the formation of a Cu-rich film of low melting point. A nickel addition has been reported as a solution to the problem, since it increases the solubility of copper in the austenite. After hot tensile testing to failure, samples of Cu-containing steels have been examined using optical, scanning and transmission electron microscopes. Recently published results indicate that copper, in addition to precipitating out as CuS, also segregates to MnS inclusions forming a shell around them. This does not seem to impair the hot ductility under an inert atmosphere, but may have serious consequences under an oxidising environment and lead to “hot shortness”. The influence of nickel in improving the hot ductility seems to be due to it forming a higher melting point alloy with the segregated copper. Data from this incomplete work also suggests that Ni reduces the precipitation of CuS particles. Current investigation carried out using confocal microscopy still to be completed will improve the understanding of the role of copper and nickel on the problem of “hot shortness”.

Aug 8, 2018

By M. A. Mekicha, M. B. de Rooij, C. Pelletier, D. T. A. Matthews

One of the main factors that reduce strip cleanliness are iron fines, which are formed due to the abrasive interactions of the roll surface and the strip in the roll bite during cold rolling. They can cause a problem in fouling of the cold rolling mill as well as downstream processes. It has been repeatedly observed that chrome plating the work roll improves strip cleanliness. In the present work, scratch tests and reciprocating sliding tests were carried out under lubricated conditions to explore the influence of chrome plating on iron fines formation. Scratch tests were conducted to study the influence of chrome plating on iron fines formation at single asperity scale due to its intrinsic property. Reciprocating sliding tests were performed to study the influence of chrome plating a rough surface on iron fines formation, taking into account the initial roughness. The scratches made using chrome plated pins showed lower friction, generated less iron fines and exhibited lower material transfer. Reciprocating sliding tests done using the uncoated pins showed galling at different sliding distances depending on the roughness of the pin. On the contrary, reciprocating sliding tests with the chrome plated pins exhibited no galling irrespective of the roughness.

Oct 1, 2019

By Cyro Takano

A degradação durante o processo de redução de minérios de ferro é bastante conhecida pelos fenômenos de crepitação e inchamento. Em aglomerados a frio, auto-redutores utilizando cimento como aglomerante, há também degradação pela decomposição de hidratos que conferem resistência a frio, além de aumentar os vazios deixados pelo consumo do redutor. Outro fenômeno que afeta na velocidade da reação de redução é a formação de escória. Esses aspectos são analisados neste trabalho e principalmente em processos de auto-redução.

Oct 30, 2017

By Emanuelle Garcia Reis, Gustavo de Sousa, Rodney Pardo Alves

Gerdau Ouro Branco´s plate mill started the operation in 2016 with high level technology. In general, national and international plate markets are every day more rigorous about final product quality. Suppliers must be aware about dimensional accuracy, surface quality and flatness of the plates, independent of the quality standards. To guarantee the best service to this increasingly demanding and competitive market, it is extremely important to guarantee the original project conditions executing the right maintenance of the rolling mill main components. In order to maintain the product quality and avoid the production and maintenance cost increase, it is important to find ways to control the mill and the main process variables, through daily measurements of the equipment performance. This paper aims to present the influence of the main equipment variables that affect the mill operational stability and how to control and evaluate the mill performance.

Oct 1, 2019