Brazing Alloys

 Select filler metal for a brazed joint depends on five main points:  properties of the filler metal  joint design  service requirements  base metal composition cost and availability 1.Properties. Melting point or melting range determines whether the material flows all at once or over a range of temperatures. Fluidity, poor or good fit up of the braze joint determines if the job needs sluggish or rapid-flowing filler. Knowing the fluidity of the filler metal lets the technician prescribe proper joint clearance. Joint remelt temperature. Filler material alloys with the base material at rates depending on the compositions of both materials and temperature. This interaction determines the composition and the melting temperature of the brazed joint, the temperature at which it will fail by fusion. Vapor pressure. In vacuum brazing the filler metal should have a vapor pressure lower than the vacuum pressure to prevent out gassing of filler metal elements. Such out ga...

The brazing properties of copper and copper alloys mainly depend on the following factors: 1. The stability of the oxide formed on the surface. 2. The influence of brazing heating process on material properties. 3. The sensitivity of the material to stress cracking. Two oxides of Cu2O and CuO may be formed on the surface of pure copper. The copper surface is covered by Cu2O at room temperature; the oxide scale at high temperature is divided into two layers, the outer layer is CuO, and the inner layer is Cu2O. Copper oxides are easy to remove, so the brazing properties of pure copper are very good. Oxygen copper is copper refined by fire and electrolytic toughening grade copper. It contains oxygen with a mass fraction of 0.02% to 0.1%. Oxygen exists in the form of copper oxide and forms a eutectic structure with copper. This eutectic structure is distributed in the copper matrix in the form of small balls. If aerobic copper is brazed in a reducing atmosphere containing hydrogen, hydroge...

A filler metal is a metal added in the making of a joint through welding, brazing, or soldering. Four types of filler metals exist—covered electrodes, bare electrode wire or rod, tubular electrode wire, and welding fluxes. Sometimes non-consumable electrodes are included as well, but since these metals are not consumed by the welding process, they are normally excluded.   A variety of alloys are used as filler metals for brazing depending on the intended use or application method. Such as Copper, Copper-zinc(brass), Nickel alloy and Silver. In general, braze alloys are made up of three or more metals to form an alloy with the desired properties. The filler metal for a particular application is chosen based on its ability to: wet the base metals, withstand the service conditions required, and melt at a lower temperature than the base metals or at a very specific temperature. Braze alloy is generally available as rod, ribbon/strips, powde...