Effect of Weight Per Meter of Reinforced Bar on Mechanical Properties and Microstructure

Abstract

Reinforced bars (rebars) are thermomechanically treated (TMT) bars that are hot-rolled from steel billets produced from scrap melted in an electric arc furnace at a temperature of about 1,600°C (usually 1,580°C ). The weight per meter of low-carbon steel rebars is one aspect that has been neglected by some steel producers during the tensile testing in rod mills. Determination of the weight per meter is explicitly required for a TMT rebar. Any reduction in mass will mean a lowering in the capacity of the steel reinforcing bar. A series of "heat" numbers or batches of molten steel from an electric arc furnace for the production of Steel Sample A (Y10 and Y12 rebars) were observed at a steel plant to investigate the effect of the weight per meter of a reinforced bar on the mechanical properties and microstructure. The rolling speed range was 3-14 m/s for different "heat values." Two other steel samples, B and C, were sourced from the local market to compare with Sample A. Samples collected from different sources from the local market, however, showed lower values of weight per meter, different from the prescribed standards. This affected not only the ultimate tensile strengths (UTSs) that were higher than normal, but also the microstructure that deviated from the standard for this material. Sample A showed not only a good combination of tensile strength and yield stress (YS) of 450 MPa and a maximum tensile strength of 650 MPa, but also a standard pearlite-ferrite microstructure, whereas Samples B and C exhibited excessively high strengths and brittle behavior and were prone to failure. 