输电铁塔主材角钢的低温拉伸和冲击试验
Low Temperature Tensile and Impact Test of Angle Steel Leg Member in Transmission Tower

低温会影响输电铁塔钢材的力学性能，容易导致塔材的脆性断裂事故，危及铁塔乃至整个电力系统的安全。笔者针对Q345B和Q420C高强度钢材角钢及其焊接接头，通过低温拉伸试验和夏比冲击试验，研究了不同材质、不同厚度角钢及其焊接接头的低温力学性能。结果发现，Q345B角钢和焊接接头、Q420C角钢和焊接接头的韧脆转变温度分别为－2.59，－15.28，－32.33和－6.76 ℃，低温会使4种钢材的的抗拉强度和屈服强度均有所提高，在－45℃的高寒地区的输电铁塔，选择Q420C角钢可以满足设计要求，但是应该尽量避免对Q420C进行焊接处理。
Low temperature will affects the mechanical properties of angel steel transmission tower and weaken its static and dynamic load resistance ability, which may lead to brittle fracture of tower member. Angle steel leg member is the major stress components of transmission tower. Once the leg member brittle failure occurs, it will endanger the operation of the transmission line and the entire power system. In this paper, the low temperature uniaxial tensile test and Charpy impact test are conducted to investigate the low temperature mechanical properties of Q345B and Q420C angle steel as well as its welded joint with various thicknesses.The results show that the ductile brittle transition temperature of Q345B angle steel and its welded joint，as well as Q420C angle steel and its welded joint are -2.59, -15.28, -32.33 and -6.76 ℃ respectively. The tensile strength and yield strength of four kinds of steel will be increased with temperature. In the cold area which temperature reach -45 ℃ or below, Q420C angle steel should be used in transmission towers to meet the design requirements, however the welding process of Q420C angle steel should be avoid.