Estudo dos principais parâmetros da caracterização microestrutural de aços de alta resistência utilizando o método de Taguchi
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Data
2016-06-23
Autores
Fukugauchi, Cristina Sayuri [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O desempenho dos aços multifásicos é estreitamente relacionado com seus microconstituintes. Assim, a caracterização e controle efetivo da microestrutura desses materiais são cruciais, sendo que os processos de ataques químicos são essenciais para que isso ocorra. Neste contexto, com o intuito de discutir como os fatores envolvidos nos processos de ataques químicos com os reagentes de Nital e LePera influenciam na caracterização metalográfica dos aços TRIP800, DP600 e CP800, este estudo foi realizado. A utilização do Método de Taguchi para a realização deste trabalho possibilitou a geração de resultados com respaldo estatístico, confiabilidade, ao mesmo tempo em que o estudo foi otimizado, tanto no que concerne ao número de ensaios realizados quanto pela existência de ferramentas para a realização da análise dos resultados. Para os experimentos com o reagente Nital, os fatores considerados foram: concentração da solução de reagente, tempo e modo de ataque, e modo de limpeza. Para os ensaios realizados com o reagente LePera, as variáveis analisadas foram: concentração da solução de picral e metabissulfito de sódio, pré-ataque, modo de secagem e tempo de ataque. Comprovou-se a influência do fator concentração da solução de Nital nos experimentos realizados com os três materiais analisados, contudo, para o aço CP 800, o fator tempo de ataque não apresentou impacto relevante para o processo. A realização de limpeza utilizando solução de bicarbonato de sódio das amostras após ataque com o reagente Nital se mostrou relevante para os processos envolvendo os aços DP e CP. Em relação aos experimentos envolvendo o reagente LePera, sugeriu-se o emprego de uma escala qualitativa (IQ - índice de qualidade) para classificar as imagens obtidas nos experimentos realizados. O uso do IQ possibilitou a análise dos dados de maneira quantitativa e identificação das variáveis que possuem maior impacto sobre o processo. Comprovou-se também, a influência dos fatores ruído (temperatura e umidade relativa).
The performance of the multiphase steels is closely related to their microconstituents. Therefore, the characterization and effective control of these materials microstructure are crucial, being that the processes of chemical etching are essential for this to occur. In order to discuss how the factors involved in the chemical etching with the Nital and LePera reagents influence in the metallographic characterization of the TRIP800, DP600 and CP800 steels, this study was conducted. The use of the Taguchi method for conducting of this study allowed the generation of results with statistical support, reliability, and at the same time the study was optimized, both as regards to the number of tests carried out as for existence of tools for carrying out the analysis of the results. For the experiments with Nital reagent, the considered factors were: concentration of the reagent solution, time and method of etching besides cleaning method. For the tests performed with LePera reagent, the analyzed variables were: concentration of picral and sodium metabisulfite solution, pre-etching, drying method and the etching time. It was proved the influence of the concentration of Nital solution in the carried experiments with the three analyzed materials, however, for the CP 800 steel, the etching time factor showed no significant impact on the process. The performance of cleaning using sodium bicarbonate the samples after etching with Nital reagent proved to be relevant for processes involving DP and CP steels. Regarding the experiments involving the LePera reagent, it was suggested the use of a qualitative scale (IQ - Quality Index) to classify the images obtained in the experiments. The use of IQ allowed the analysis of the data in a quantitative manner and the identification of the variables that have the most impact on the process. It also proved the influence of noise factors (temperature and relative humidity).
The performance of the multiphase steels is closely related to their microconstituents. Therefore, the characterization and effective control of these materials microstructure are crucial, being that the processes of chemical etching are essential for this to occur. In order to discuss how the factors involved in the chemical etching with the Nital and LePera reagents influence in the metallographic characterization of the TRIP800, DP600 and CP800 steels, this study was conducted. The use of the Taguchi method for conducting of this study allowed the generation of results with statistical support, reliability, and at the same time the study was optimized, both as regards to the number of tests carried out as for existence of tools for carrying out the analysis of the results. For the experiments with Nital reagent, the considered factors were: concentration of the reagent solution, time and method of etching besides cleaning method. For the tests performed with LePera reagent, the analyzed variables were: concentration of picral and sodium metabisulfite solution, pre-etching, drying method and the etching time. It was proved the influence of the concentration of Nital solution in the carried experiments with the three analyzed materials, however, for the CP 800 steel, the etching time factor showed no significant impact on the process. The performance of cleaning using sodium bicarbonate the samples after etching with Nital reagent proved to be relevant for processes involving DP and CP steels. Regarding the experiments involving the LePera reagent, it was suggested the use of a qualitative scale (IQ - Quality Index) to classify the images obtained in the experiments. The use of IQ allowed the analysis of the data in a quantitative manner and the identification of the variables that have the most impact on the process. It also proved the influence of noise factors (temperature and relative humidity).
Descrição
Palavras-chave
Aços avançados, Aço TRIP, Aço complex phase, Aço dual phase, Micrografia, Ataque químico, Nital, LePera, Taguchi, Advanced steels, TRIP steel, Complex phase steel, Dual phase steel, Micrography, Chemical etching