铜-低碳钢钎焊接头的耐蚀性评价

通过动态挂片腐蚀实验、宏观和金相组织观察、SEM 及能谱分析等方法对采用Cu-Zn钎料、Ag-Cu钎料、Cu-P钎料钎焊的无氧纯铜-低碳钢管钎焊 接头的耐蚀性能进行了评价分析.结果表明：采用Cu-P钎料时钢和钎缝间出现裂纹，接头遭 受腐蚀后铜管内壁普遍腐蚀，同时钎缝因腐蚀而开裂；Cu-Zn钎缝成型好，但钎缝 本身出现由于金相组织发生选择性腐蚀而引起的局部蚀坑，铜管对应处也出现明显减薄性腐 蚀；Ag-Cu钎料所焊接头成型好，接头各处腐蚀轻微.建议采用Ag-Cu钎料进行铜-低碳钢的 钎焊.

EVALUATION OF CORROSION RESISTANCE OF MILD STEEL - COPPER BRAZED JOINTS

Copper-zinc,silver-copper and copper-phosphorus brazing alloys are used in the brazing of mild steel pipe to copper pipe,and the corrosion resistance of brazed joints are evaluated using macroscopic observation,metallographic examination,dynamic corrosion test,SEM and EDX analysis.Cracks appear at the interface between steel and braze metal when copper-phosphorus brazing alloy is used,and the joint fails from this place after being corroded.The appearance of the braze metal is fine when copper-zinc brazing alloy is used,but there is localized corrosion in the braze metal and obvious general corrosion in the wall of the copper pipe after being corroded.In contrast with the above-mentioned two brazing alloys,the joint produced by the silver-copper brazing alloy is sound.Its appearance is fine,and its corrosion resistance is also high enough to meet requirements.It is suggested that silver-copper brazing alloy should be used in the brazing of mild steel to copper.