输电线铁塔钢材的低温力学和冲击韧性试验

为选择合适的输电线铁塔钢材,防止杆塔因构件发生低温脆性断裂引起的破坏,通过系列室温和低温条件下的单轴拉伸和冲击试验,研究了输电线铁塔用Q345B、Q420B、Q460C钢管和Q345B、Q420B角钢钢材的力学性能和冲击韧性;通过对比分析,评价了钢管和角钢钢材的塑性指标;利用Boltzmann函数曲线拟合,得到了钢管和角钢钢材的韧-脆转变温度.结果表明:钢材的屈服强度和抗拉强度随温度的降低而增大,其塑性指标均能满足规范要求;钢材夏比冲击功值随温度降低而减小,Q345B钢管和角钢钢材的韧脆转变温度较高,抗低温冷脆性能较差,结合拉伸和冲击试验结果,建议在寒冷地区优先采用Q420B钢管,不宜采用Q345B角钢.

Experimental study on mechanical properties and impact toughness of steel for transmission line towers at low temperatures

In cold region, it is of great significance to select suitable steel material in order to prevent the failure or collapse of transmission line tower, which results from the brittle fracture of construction member at low temperatures. A series of uniaxial tensile tests and Charpy impact tests were performed to investigate the mechanical properties and impact toughness of materials of steel tube(Q345B, Q420B, Q460C) and angle iron(Q345B, Q420B). The plastic indices of steel tube and angle iron materials were evaluated through comparison and analysis. The Boltzmann function was employed to conduct curve fitting for impact energy versus temperature, obtaining the ductile-brittle transition temperatures. Results indicate that the yield strength and ultimate tensile strength increase with the decrease of temperature, and all the plastic indices can meet the prescribed requirement. Charpy impact energy increases as the temperature reduces. Besides, the ductile-brittle transition temperatures of Q345B steel tube and Q345B angle iron are relatively high, indicating the poor resistance ability of cold brittleness failure. Based on the results of tensile tests and impact tests, it is suggested that priority should be given to the adoption of Q420B steel tube, and Q345B angle iron is inadvisable.