Avaliação prática da efetividade da nodularização in mold e sua aplicação na definição da microestrutura e das características dos ferros fundidos nodulares
Practical evaluation of the effectiveness of nodularization in mold and its application in defining the microstructure and characteristics of ductile iron
Cláudio Lúcio Pereira dos Santos, Elaine Carballo Siqueira Corrêa, Joel Lima
Resumo
Uma das etapas mais importantes da tecnologia de fabricação de ferros fundidos nodulares está relacionada aos processos de nodularização. Entretanto, há escassez de fontes de informações técnicas que sintetizem e comparem as características dos processos de nodularização, induzindo sua realização de modo empírico (tentativa e erro), e levando à adoção de processos com baixo desempenho, altos custos, elevados riscos e impactos ambientais. O presente artigo descreve os principais processos de nodularização, destacando o rendimento residual de magnésio em cada um deles. A partir deste levantamento, foi desenvolvido procedimento experimental para avaliar e comprovar a maior eficiência da nodularização “in mold”, em relação aos demais processos descritos, por meio do rendimento do magnésio. Nos experimentos foram utilizados corpos de prova escalonados com diferentes seções para verificar a influência da velocidade de resfriamento na formação da grafita esferoidal e na constituição da matriz metálica, de forma a demonstrar a eficácia da nodularização in mold e apresentar os resultados de microestrutura para cada espessura. Constatamos que o processo “in mold” possibilita um eficiente controle da nodularização, alcança maior rendimento do magnésio (acima de 80%), conforme descrito na bibliografia e, como consequência, elevado grau de nodularização (acima de 90%).
Palavras-chave
Abstract
One of the most important steps in the manufacturing technology of ductile iron is related to the nodularization processes. However, there is a scarcity of sources of technical information that synthesize and compare the characteristics of the nodularization processes, inducing their realization in an empirical way (trial and error), and leading to the adoption of processes with low performance, high costs, high risks and environmental impacts. This article describes the main nodularization processes, highlighting the residual magnesium yield in each of them. From this survey, an experimental procedure was developed to evaluate and prove the greater efficiency of “in mold” nodularization, in relation to the other processes described, through the magnesium yield. In the experiments, staggered specimens with different sections were used to verify the influence of the cooling rate on the formation of spheroidal graphite and on the constitution of the metallic matrix, in order to demonstrate the effectiveness of nodularization in mold and present the microstructure results for each thickness. We found that the “in mold” process allows for an efficient control of nodularization, achieves a higher yield of magnesium (above 80%), as described in the bibliography and, as a consequence, a high degree of nodularization (above 90%).
Keywords
Referências
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Submetido em:
11/08/2022
Aceito em:
30/09/2022
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