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Abstract

A crescente demanda por aços de alta qualidade com elevada limpeza interna tem levado a uma contínua melhoria nas práticas de produção do aço, em especial na etapa de refino secundário. O interesse especial é no controle das inclusões não-metálicas, devido ao seu efeito prejudicial nas etapas subseqüentes (lingotamento e conformação plástica) e devido às sua grande influência nas propriedades do produto final. Através do controle do tamanho, da quantidade e da composição química das inclusões, é possível obter um produto final de alta qualidade. O controle da formação das inclusões não-metálicas e a identificação de suas fases constituintes são de suma importância para a obtenção de aços limpos. Nesse trabalho, amostras de aço de baixo teor de carbono, desoxidado ao silício, coletadas em uma indústria siderúrgica, são analisadas e é demonstrado que, pela comparação do teor total de cálcio e de oxigênio no aço, é possível prever os tipos de inclusões presentes no aço. Palavras-chave:Inclusões não-metálicas, refino secundário, indústria siderúrgica. Abstract The increasing demand in recent years for highquality steel products has led to the continuous improvement of steelmaking practices. There is a special interest in the control of non-metallic inclusions due to

Application of Raman Spectroscopy for Characterizing Synthetic Non-Metallic Inclusions Consisting of Calcium Sulphide and Oxides

“…The calcium treatment for aluminum-killed steels is commonly used to modify non-metallic inclusion (NMI) such as Al 2 O 3 to less detrimental inclusions [1,2]. The main aim of the modification of inclusions is the control and transformation of the solid inclusions into fully or partially liquid inclusions by changing their chemical or phase composition.…”

Quantification of Synthetic Nonmetallic Inclusion Multiphase Mixtures from a CaO–Al2O3–MgO–CaS System Using Raman Spectroscopy

“…[1,2] For aluminum-killed steels, calcium treatment is mostly used for transforming solid Al 2 O 3 inclusions into low-melting calcium aluminate inclusions of C12A7 or phases close to C12A7 such as CA and C3A and also reduce the total oxygen content. [2,3] However, the presence and high content of elements such as Mg and S in molten steel, as well as the effectiveness of the deoxidation and Ca treatment processes, could result in the formation of potentially detrimental inclusions such as magnesium aluminate spinel (MgO.Al 2 O 3 or MA) and solid CaS and could cause process issues such as submerged entry nozzle (SEN) clogging. [1] Numerous works [4][5][6][7][8][9][10][11][12] in the literature have been dedicated to the study of inclusion formation, evolution, and modification for Al-killed calcium-treated steels with the aim of ensuring steel cleanliness and process control.…”

Applicability of Time-Gated Raman Spectroscopy in the Characterisation of Calcium-Aluminate Inclusions

“…Calcium treatment is used in aluminium-killed steel with the aim of generating calcium aluminate inclusions with a low liquidus temperature, such as 12CaO.7Al 2 O 3 (C12A7). [8][9][10][11][12] The amount of calcium-containing wire, such as CaSi added during calcium treatment, needs to be in the correct range. The excess addition of Ca in the presence of sulfur in the molten steel may form CaS, while adding too little Ca may lead to incomplete modification of alumina inclusions, which in turn generates solid calcium aluminates, which have high melting temperatures.…”