铁塔用角钢性能影响因素及断裂机理分析

Performance Influence Factors and Fracture Mechanism of Angle Steel for Tower Structure

针对北方地区经常发生的高压输电线路铁塔倾倒事件,分析了铁塔断裂机理,并从铁塔用角钢的冶炼制造缺陷、钢铁纯净度、金相组织、力学性能等方面,对Q235B、Q345B、Q420B、Q460B钢的低温性能进行探讨,判断这些输电线路用角钢在寒冷地区使用的安全性。通过大量试验,得出以下结论:输电线路用角钢长期使用后材质没有明显变化,安装时合格的材料长期使用后仍然合格;屈服强度不合格的材料,其金相组织中存在大量非金属夹杂物,部分试样甚至出现了夹杂物导致的分层,如遇较强外力作用,角钢会首先从这些薄弱点断裂;铁塔倾倒的主要原因多为连接螺栓松动或脱落造成铁塔承载力下降;Q345B角钢各项性能指标显示其非常适合在寒冷地区使用,尤其是常温冲击韧性和低温冲击韧性均优于Q235B、Q420B、Q460B,脆性转变温度也较低;常温冲击韧性偏低的材料,脆性转变温度偏高,说明脆性转变温度与材料的冲击韧性密切相关。试验结果可为寒冷地区输电线路选用角钢时提供参考。

From the angle of steel manufacturing defects, purity, microstructure, mechanical properties etc., the author analyzes the low temperature toughness of Q235B, Q345B, Q420B, and Q460B steel, security judgement of transmission line steel used in cold area, draws the below conclusions： Transmission lines using steel angles material with no obvious change after long-term use; Materials of yield strength unqualified, metallurgical structure has plenty of non-metallic inclusions, some specimens even layer caused by the inclusion, in case of a strong force, angle steel first fracture from these weak points; tower structure dumping of main reasons for bearing capacity of bolts are loose or have fallen off causing decline in forcing down under; experimental data indicate that performance indicators Q345B steel is ideal for use in cold areas. Low temperature impact toughness of material brittle transition temperature high, describes the impact toughness of brittle transition temperature and material are closely related.