Brazing copper with stainless steel

Before vacuum brazing of copper alloy and stainless steel, it is necessary to remove oil stains and oxidation film on the surface, or it will hinder the wetting of the solder on the surface.In order to reduce this effect and increase the wettability and diffuse flow ability of brazing solder on the surface of base material, the method of pickling + coating was used for surface treatment.The coating can protect the metal surface from being polluted and oxidized. On the other hand, the wetting of the main elements silver and solder on the coating surface.

First, acid pickling was carried out, and then nickel (8~10 μm) was electroplated on the surface of 1Cr18Ni9Ti specimen, because nickel, iron and copper can form infinite continuous solid solution.Silver plating (5~8 pμm) on QCr0.8 alloy specimen, because silver can effectively improve the strength of copper/stainless steel brazing joint.

Study on vacuum brazing technology of copper alloy and stainless steel
The most important technological parameters in the brazing process are brazing temperature and insulation time.Brazing temperature is usually selected higher than the liquidus line temperature of the solder 25~60℃, but sometimes it is hoped that the solder and the base metal will fully react, brazing temperature may be higher than the solder liquidus temperature of 100℃ above 341.

Due to the low melting point of QCr0.8 in the base material, which is 1070℃, the brazing temperature should not exceed 980℃, and the insulation time should not be too long, otherwise the matrix material will soften and the grain will grow, resulting in the performance decline.Through many tests, the ideal process parameters of vacuum brazing of copper alloy and stainless steel are finally determined: heating temperature is 895~ 920℃, insulation time is 10~ 15min, which can fully combine base metal and solder.

Learn More: Vacuum Brazing Furnace