Abstract
The flame brazing of H62 brass using a novel, low-silver Cu-P brazing filler metal was investigated in this study. The effect of the addition of a trace amount of Sn on the microstructure and properties of Cu-7P-1Ag filler metals was analyzed by means of X-ray diffractometer, scanning electron microscopy and energy dispersive spectrometer. The addition of trace Sn led to a decrease in the solidus and liquidus temperatures of Cu-7P-1Ag filler metals. Meanwhile, the spreading performance of the filler metals on a H62 brass substrate was improved. The microstructure of the low-silver, Cu-P brazing filler metal was mainly composed of α-Ag solid solution, α-Cu solid solution and Cu3P; an increase of Sn content led to the transformation of the microstructure of the joints from a block to a lamellar structure. When the Sn content was 0.5 wt. %, the shear strength of the joint at room temperature reached 348 MPa, and the fracture morphologies changed from a cleavage to a quasi-cleavage structure.
Highlights
Cu-P brazing filler metals are extensively used to braze copper and its alloys in the aerospace, electronics, energy, transportation, military, automobile, and other industries due to their superior performance, such as low melting point, good wettability, low price and self-brazing property when brazing pure Cu [1,2]
The price of silver is extremely high and volatile, which limits the application of high-silver Cu-P-Ag filler metals in middle- and low-end manufacturing
The flame brazing method was used in this study to braze the H62 brass, and the shear strength of joints with an overlap length of 2 mm and joint clearance of 0.07 mm was tested on an electronic universal testing machine, according to the China’s National Standard GB/T
Summary
Cu-P brazing filler metals are extensively used to braze copper and its alloys in the aerospace, electronics, energy, transportation, military, automobile, and other industries due to their superior performance, such as low melting point, good wettability, low price and self-brazing property when brazing pure Cu [1,2]. The melting temperature of Cu-P brazing filler metal is still too high to braze copper alloys with low melting points, such as brass. Brittle Cu3 P compounds in the brazing filler metal matrix can form eutectic structures with α-Ag solid and α-Cu solid solutions, which greatly improves the plasticity and processing properties of the brazing filler metals. As such, this approach has been widely used in the electronics industry [12]. Sn has limited solid solubility in copper, and excessive Sn can form brittle intermetallic compounds with Cu, negatively affecting the mechanical properties of the filler metals [14]. The mechanical properties and fracture morphologies of brazed joints were studied
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