Microstructure and properties of high frequency induction welded joints of ultra-thin walled brass radiator flat tubes
High frequency induction welding technology was used to weld H65 brass flat tubes with a wall thickness of 0.13 mm.Microstructure and mechanical properties of the welded joint were studied using optical microscope,scanning electron microscopy,electron probe,electron backscatter diffraction technique,microhardness tester and tensile tests.The results show that the welding joint of the H65 brass flat tube by high-frequency induction welding has no defects such as cracks and pores,and there is no significant evaporation of Zn in the weld zone.The tensile strength of the welded joint reaches 400 MPa,which is 94％of that of the base metal,and the elongation is 33.89％,which is close to that of the base metal.The microhardness of the welded joint shows a W-shaped distribution,with the highest in the fusion zone,followed by the base metal zone,and the lowest in the heat affected zone.The extrusion effect during the welding leads to an increase of dislocation density in the weld,causing work hardening,which is the main reason affecting the hardness distribution of the welded joint.Compared with the base metal,the microstructure of the welded joint is significantly refined,with an average grain size of 1 μm,which is 50％of the base metal.In addition,small angle grain boundaries increase to 72％,large angle grain boundaries decrease to 28％,and twin boundaries decrease to 2％,further improving the mechanical properties of the welded joint.
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