Technical and commercial interest in silver-free brazing filler metals (SFBM) is directly related to their low cost which is approximately more than half that of silver filler metals. The rapid solidification method was developed to manufacture cost-effective SFBM in the form of rods, wires, and strips. Principles of this method are presented in the paper, and properties on brazing filler metals are discussed.

Some of these SFBM such as P81 and P14 of the Cu-Zn-P-Ni and Cu-P-Sn systems and P21 of the Cu-Zn-Sn-Ni system are qualified as the full value substitutes of silver alloys in the manufacture of both copper and steel brazed structures. Another one filler metal P47 of the Cu-Zn-Mn-Sn-Ni system is also successfully used for brazing cemented carbide tools.

The P81 and P14 filler metals have the same brazing temperature range as 40-50% silver alloys and provide sufficient strength of 17-23 ksi ( 120-158 MPa) for copper brazed joints, 42-46 ksi (290-320 MPa) for brass joints, and about 24 ksi (170 MPa) for copper-to-steel joints. However, the brittle iron-phosphides affect impact strength.

In order to avoid this negative effect and eliminate phosphorus from the alloy compositions, the P21 and P47 were designed and are being used for making steel joints and carbide tools by induction and torch brazing. Steel joints brazed by the P21 filler metal have shear strength of 17-20 ksi (120-140 MPa), while steel joints brazed by the P47 filler metal exhibit higher shear strength in the range of 42-45 ksi (290-310 MPa).