Effect of Boron Content on Strain-Hardening Exponent in Recycled Steel
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While the elastic zone in the deformation process of materials is mainly represented by a linear function of gradient E, the plastic portion has been characterized by various exponential functions with an exponent n that varies with its chemical composition, the level of work hardening and the material in question among others. Recycled steel, whose composition depends on the source and availability of its raw material, has an extremely vulnerable n-value. In this paper, the effect of the boron content in recycled steel on the n-value of thermo-mechanically treated bars made from it has been studied. To do this, TMT bars were subjected to tensile testing and the corresponding force extension diagrams plotted. The values of εi10 and εi20 for the interval between 10% and 20% deformation respectively were determined to correspond to the stress values σi10 and σi20 so that was calculated as the ruling n-value for each interval. Spectro-analysis was used to determine the chemical composition of the samples so that the percentage boron content by weight was plotted against the n-value. The growth of the n-value with boron content has been shown to obey a polynomial function and to enhance the tendency to strain-hardening, implying early onset of failure in pronounced cold deformation.