J. Mater. Sci. Technol., 2011, 27(4), 377-381. Effect of Silver Content on Microstructure and Properties of Brass/steel Induction Brazing Joint Using Ag-Cu-Zn-Sn Filler Metal J. Cao 1,2)† , L.X. Zhang 1) , H.Q. Wang 1) , L.Z. Wu 2) and J.C. Feng 1) 1) State Key Lab of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001, China 2) Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150001, China [Manuscript received May 5, 2009, in revised form December 19, 2009] The induction brazing of brass to steel using Ag-Cu-Zn-Sn filler metal was investigated in this study. The influence of Ag content on the microstructure and properties were analyzed by means of optical microscopy, scanning electron microscopy and electron probe microanalysis. Defect free joint was achieved using Ag- Cu-Zn-Sn filler metal. The microstructure of the joint was mainly composed of Ag-based solid solution and Cu-based solid solution. The increase of Ag content and the cooling rate both led to the increase of the needle like eutectic structure. The tensile strength decreased with the increase of Ag content. The tensile strength at room temperature using Ag25CuZnSn filler metal reached 445 MPa. All fractures using Ag-Cu-Zn-Sn filler metal presented ductile characteristic. KEY WORDS: Induction brazing; Brass; Steel; Microstructure; Tensile strength 1. Introduction The joining technique of copper alloy to steel has been widely applied in nuclear, aerospace and indus- try fields [1–3] . The conventional fusion welding of these materials usually leads to the irregularity in- terface and welding deficiency between copper alloy and steel [4,5] . The microstructure evolution and so- lidification cracking susceptibility of Cu deposits on steel has been systematically investigated [6–8] . The hot isostatic pressing and explosive bonding joint of copper alloy to steel can reach high joining strength, but the shape requirement of the based metal limits the application of these methods [9–13] . No microstruc- tural deficiency joint can be obtained using diffusion bonding method [14–17] . However, the vacuum equip- ment is required and the deformation of the substrate is usually large. Especially, brass cannot be intro- duced in a vacuum condition due to the inclusion of evaporable Zn element. Thus, induction brazing in air was the optimal joining method to achieve regular † Corresponding author. Ph.D.; Tel.: +86 451 86418882; Fax: +86 451 86418146; E-mail address: cao jian@hit.edu.cn (J. Cao). interface, accurate dimension and low cost brass/steel joint. The selection of filler metal was the foundational step for induction brazing of brass to steel [18,19] . The Ag-Cu based filler metal has been widely applied for joining steel to other materials [20] . The low melting point of brass leads to the selection of filler metal with low melting point. The Ag-Cu-Zn-Sn filler metal, which served as the replacement of poisonous Ag-Cu- Zn-Cd filler metal, was selected in this study. Al- though the Ag-Cu-Zn-Sn filler metal has been devel- oped for a long time, few investigations on the mi- crostructure and joining properties have been system- atically carried out. Accordingly, the aim of this work was to investigate induction brazing of brass to steel using Ag-Cu-Zn-Sn filler metal. In particular, the ef- fect of Ag content on the interfacial microstructure and joining strength of brass/steel joint was investi- gated. 2. Experimental The substrates were commercial H62 brass and 10# steel. The metallographic observation and ten-