环境温度对Q345C钢MAG焊接头力学性能的影响

Effect of environment temperature on mechanical properties of Q345C steel MAG welded joints

对轨道车辆材料Q345C低合金结构钢MAG焊接头进行了常温、低温(0℃、-10℃、-20℃、-30℃、-40℃)力学性能试验,包括拉伸试验、弯曲试验、冲击试验,得到力学性能随温度的变化规律,同时测量了接头硬度分布,分析了接头硬度分布规律,观察了接头金相组织。研究结果表明,随环境温度下降,其抗拉强度和屈服强度均有所提高,但伸长率和断面收缩率变化不大,冲击吸收功明显降低;Q345C焊接接头有较大的低温冷脆倾向;对在低温环境条件下服役的Q345C低合金结构钢,需重点考虑其低温冷脆倾向。

The normal and low temperature （0 ℃ ,-10℃ ,-20℃ ,-30℃ ,-40℃ ） tensile test, bending test and impact lest were carried out on MAG welded joints of Q345c low ＇alloy structural steel for rail transit bogie in China, the change law of mechanical properties with temperature is obtained. Meanwhile, the hardness of the welded joints are measured and the microstructure of the joints are observed. The results show that the tensile strength and yield strength of the steel are improved with the decrease of temperature, but the elongation and the change of the section shrinkage is little. The impact absorption power decreases rapidly,which indicates that the Q345C welded joints have a relatively large low temperature cold brittle tendency. Q345C low alloy structural steel, which is served at low temperature, shouht be considered tile low temperature cold brittle.