Avaliação da resitência a corrosão e mecânica em barras nervuradas de aço microligado ao vanádio com diferentes taxas de resfriamento

Abstract

During hot rolling the steel surface is exposed to air and water, the latter is used to control the temperature of the rollers and/or the cooling rate of the steel. This exposure leads to the formation of a layer of oxide on the surface of the bars, this exposure leads to the formation of a layer of oxide on the surface of the bars, which may facilitate or prevent the corrosion, this may act as a barrier or as a pathway for ions present in the atmosphere and, in addition, cause modifications in the mechanical properties. The presente work is based on the evaluation of the effect of the cooling process after hot rolling in the mechanical properties and the formation of the oxide layer in microalloyed steel rebars. The rebars had the following investigations: microstructure analysis, tensile test, microhardness test, folding test, thickness measurement of the oxides scale formed, corrosion analysis and exposure to the atmosphere. The progress of corrosion was evaluated by visual observation of the corrosion product formed on the surface of the bars. The morphology of the oxide layer after the hot rolling was studied by scanning electron microscopy (SEM). The samples with a higher cooling rate, 63% P and 100% P, also had an increase in the mechanical properties. The sample 100% P was the one that obtained the best behavior in the corrosion test. In addition, it was verified that the initial oxide layer in the steel bars, which are associated to the manufacturing process, had different adherence to the rebar, the samples 63%P and 100%Phad the best condition.