GEOMETRICAL AND MECHANICAL-PROPERTIES OF LARGE ROLLED STEEL ANGLES

Steel angles are the most frequently used sections in electrical transmission towers. To carry safely the heavy leg loads of 500 kV towers, N. K. K. Corporation, Japan, developed the world's largest rolled steel angles (300 x 300 x 35 and 350 x 350 x 35 mm size). The paper describes the manufacturing process and presents the geometrical properties. The statistical analysis of samples over a three-year period showed that the steel used is consistently of uniform quality. Based on 12 tensile tests of round specimens in as-supplied condition and another 12 specimens in heat-treated condition carried out at 20 degrees C, -20 degrees C, -40 degrees C, and -65 degrees C, it was concluded that decrease of temperature did not result in any decrease in elongation and only three percent decrease in the reduction of area. Due to heat-treatment, the maximum reduction in yield stress and tensile strength was two percent, maximum reduction in elongation three percent, and maximum reduction of area two percent.