A Comparative Investigation of the Mechanical Properties of Mild Steel Rods Produced by two Local Steel Manufacturers in Nigeria

摘要

Recent increases in the unexpected collapses of residential buildings necessitated an investigation as well as a comparison of the mechanical and chemical properties of local steel bars produced by various firms in Nigeria. A number of tests such as hardness, impact and tensile tests and also chemical compositions were carried out on those steel bars received from Kastina and Sharada steel manufactures. Results revealed that the carbon contents of the samples varied between 0.35 - 0.41 %, i.e. above those limits recommended by the ASTM standards for reinforcing steel bars. The hardness values were found to be more than the estimated standard values and increased with the carbon content. The ultimate tensile strengths and yield strengths were noted as 621.6 MPa and 441.1 MPa for Sharada and 473.7 MPa and 324.5 MPa for Kastina mills, respectively. The ASTM and NQSA standards required ultimate tensile strengths as 620 MPa - 690 MPa and this was fulfilled by the Sharada company. The yield strength of samples from both steel producers were below the recommended values, i.e. 420 MPa – 520 MPa of the standards. It can be recommended that strict laws and regulations are needed to guide and control the production and application of steel reinforcement bars.