not Available.

Aiming to simulate the internal corrosion of pipeline and oil tank steels exposed to decanted waters, the electrochemical behavior and corrosion morphology of these steels was studied in 10-2 mol/L Na2SO4 solutions, with additions of naphthenic acids in dependence of the inclusions distribution. A linear correlation between the pitting potential in sulfate solutions and inclusions concentration of -20mV x Inclusions Density (inclusions/mm2) could be determined. The localized attack associated to the sulfide inclusions turns increasingly to a more uniform attack, as the concentration of the naphthenic cyclopentanecarboxylic acid in the dilute sulfate solution is increased.

ResumoDefeitos internos do tipo trinca off-corner são um dos principais problemas relacionados à qualidade em tarugos de aços especiais lingotados continuamente. Este tipo de defeito é bastante crítico, pois além de se apresentar de forma descontínua no tarugo e, consequentemente na barra laminada, não é detectável pelos equipamentos de inspeção em linha usualmente utilizados para garantir a qualidade final do material. Neste trabalho, foram avaliadas amostras de barras laminadas de um aço baixo carbono com e sem a presença do defeito do tipo trinca off-corner a fim de estabelecer um método que permita avaliar a criticidade da trinca. Estes resultados foram relacionados com os principais fatores que influenciam na formação deste defeito, proporcionando alterações de processo com o objetivo de minimizar a sua ocorrência. Palavras-chave: Trinca off-corner; Lingotamento Contínuo; Caracterização de Defeito. CONTRIBUTION TO THE CHARACTERIZATION AND OCCURRENCE MINIMIZATION OF OFF-CORNER CRACKS IN ROLLED BARS AbstractOff-corner internal cracks are one of the major problems related to the quality of special steel billets continuously casted. This defect is quite critical since it is discontinuous and it is not detectable by the inspection lines. In this work samples of low carbon steel rolled bars with and without the presence of off-corner cracks were evaluated in order to create a method to assess the crack criticality. These results were correlated with the main factors which have some influence on the formation of this defect by providing some process modifications in order to minimize their occurrence.