Tecnologia em Metalurgia, Materiais e Mineração
https://tecnologiammm.com.br/article/doi/10.4322/2176-1523.20181464
Tecnologia em Metalurgia, Materiais e Mineração
Artigo Original

AVALIAÇÃO DO EFEITO DA OSCILAÇÃO DO MOLDE SOBRE A QUALIDADE DE PLACAS

EVALUATION THE EFFECT OF OSCILLATION MOLD ON SLAB QUALITY

Rafael Fernandes Reis, Everton Paço Cunha, Alexandre de Freitas Gomes Mendonça

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Resumo

A solidificação do aço no molde é determinante para a qualidade superficial da placa, considerando que os principais defeitos tendem a se formar nos primeiros estágios de formação da pele. Assim, diversos parâmetros do processo que afetam a solidificação no molde devem ser considerados e um deles é a oscilação do molde. A partir de amostras obtidas no processo industrial, duas técnicas para avaliar o efeito da oscilação foram desenvolvidas com base em: perfilometria a laser e metalografia. Em relação à primeira, desenvolveu-se uma análise da profundidade das marcas de oscilação. Foi comprovada a correlação da profundidade dessas marcas com o tempo de estripamento negativo. A diminuição do tempo de estripamento em 10% reduziu a profundidade média das marcas de oscilação de 0,32 para 0,28 mm, portanto 12,5%. A segunda refere-se ao ataque metalográfico, que se mostrou eficiente para visualização, via microscopia, do gancho na base da marca de oscilação. Bolhas de argônio e partículas de fluxante podem ser aprisionadas na região do gancho de oscilação, e eventualmente ocasionar defeitos nos produtos laminados. O uso das técnicas forneceu subsídios à tomada de ações visando à diminuição da profundidade do gancho e da marca de oscilação, resultando em melhoria da qualidade superficial das placas produzidas.

Palavras-chave

Oscilação do molde; Profundidade da marca de oscilação; Gancho de oscilação.

Abstract

Mold Steel solidification is very important for slab surface quality, considering that the main defect happens during the first stages of shell formation. Thus, many process parameters which influence mold steel solidification should be considered, and one of them is the mold oscillation. Samples of the narrow side of the slabs were obtained from the industrial process and two techniques were developed to evaluate oscillation effect: laser perfilometry and mettallography. Regarding to laser perfilometry, it was developed an analysis method of oscillation mark depth. It was proven the correlation of the average oscillation mark depth with the negative strip time. The reduction on negative strip time by 10% decrease the oscillation mark depth of 0,32 to 0,28 mm, therefore 12,5% The second technique regards to metallography etching based on picric acid, which showed useful to view, by optical microscopy, the hook at the base of oscillation mark. Argon bubbles and flux particles can be captured at oscillation hook region, and eventually cause defects on rolled products. The use of techniques presented in this study provided subsidies for decision making aiming the reduction of oscillation mark depth and hook, resulting in surface quality improvement of slabs produced.

Keywords

Mold oscillation; Oscillation mark depth; Oscillation hook.

Referências

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