钢/铜火焰钎焊接头组织和性能研究

Study on Microstructure and Properties of Steel/Copper Flame Brazing Joints

采用Cu-Zn系黄铜钎料火焰钎焊钢/铜接头,并利用扫描电镜、显微硬度计和万能拉伸试验机对钎焊接头的显微组织和力学性能进行了分析评估。结果显示:使用含有Si的黄铜钎料钎焊后,钎料/钢界面会出现薄层Fe-Si金属间化合物,并且由于Fe-Si金属间化合物的脆性,导致此处出现微裂纹。由于黄铜钎料的熔化温度较高,钎焊过程中近焊缝的铜管发生再结晶退火,其显微硬度明显降低,强度也相应地降低。但根据以往经验,该接头在家用空调的服役条件下不会发生问题。试样的拉伸断裂位置在远离钎缝的铜管上,抗拉强度达到235 MPa,显示出良好的力学性能。

The steel/ copper joints were flame brazed by using Cu-Zn series brass solder. The microstructure and mechanical properties of the brazed joints were analyzed and evaluated by using scanning electron microscope, microhardness tester and universal tensile testing machine. The results show that there is a thin layer of Fe-Si intermetallic compounds at the interface between the solder and steel after brazing with brass solder containing Si. Meanwhile, because of the brittleness of Fe-Si intermetallic compounds, microcracks are observed at the interface between the solder and steel. Due to the high melting temperature of the solder, the recrystallization annealing of the copper tube near the weld occurs, and the microhardness of the copper is obviously reduced and the strength is reduced accordingly. However, according to the previous experience, the joint has no problem in the service of the household air conditioner. The tensile fracture position of the sample is located at the copper tube far away from the welding seam, and the tensile strength of the joint reaches 235 MPa, which shows good mechanical properties.