500kV多回路输电线路Q460钢铁塔服役性能研究

Study on Service Performance of Q460 Steel Tower for 500 kV Multi-circuit Transmission Line

采用箱式电阻炉对输电铁塔用Q460钢板进行了不同工艺的正火和回火处理,采用光学显微镜对热处理试样显微组织进行了观察,并对拉伸、冲击、硬度进行了检测,研究了热处理对输电塔服役性能的影响。结果表明,钢材正火组织主要为珠光体+铁素体+贝氏体以及少量M-A组织,随正火温度升高,铁素体、珠光体含量逐渐减少,材料拉伸性能小幅提高,冲击功和硬度增加;随回火温度升高,M-A岛逐渐分解,贝氏体基体上析出较多颗粒状碳化物,钢的抗拉强度和屈服强度均降低,伸长率先小幅增加,在温度超过400℃后有所降低,硬度则几乎不变,860℃正火钢断面收缩率先降低后升高,冲击功先升高后降低,均在回火温度为300℃时达到极值,920℃正火钢断面收缩率和冲击功先升高后几乎保持不变。

The different normalizing and tempering treatments of Q460 steel plate for the transmission tower were carried out using box type resistance furnace. The microstructures of heat treated specimens were observed by OM. And the tensile, impact and hardness were tested. The effects of heat treatment on transmission tower service performance were studied. The results show that, the normalizing microstructure of the steel is mainly pearlite ＋ ferrite ＋ bainite and a small amount of M-A microstructure. With the increase of normalizing temperature, the pearlite and ferrite content decrease, tensile properties improve slightly, the impact energy and hardness increase. With the increase of tempering temperature, the M-A island is gradually decomposed, and more granular carbides precipitated in bainite matrix were separated out. The tensile strength and yield strength decrease, the percentage elongation firstly increases slightly, and then decreases after the temperature exceeds 400℃, the hardness is almost unaffected. The reduction of area at 860℃ normalized steel decreases firstly and then increases, the impact energy increases firstly and then decreases, and they reach the extreme value at 300℃. The reduction of area and impact energy at 920℃ normalized steel firstly increase and then retain almost constant.