8. Brazed Joints

Strong, leak-tight brazed connections for copper tube may be made by brazing with filler metals which melt at temperatures in the range between 1100°F and 1500°F, as listed in Table 14.12. Brazing filler metals are sometimes referred to as "hard solders" or "silver solders." These confusing terms should be avoided.

The temperature at which a filler metal starts to melt on heating is the solidus temperature; the liquidus temperature is the higher temperature at which the filler metal is completely melted. The liquidus temperature is the minimum temperature at which brazing will take place.

The difference between solidus and liquidus is the melting range and may be of importance when selecting a filler metal. It indicates the width of the working range for the filler metal and the speed with which the filler metal will become fully solid after brazing. Filler metals with narrow ranges, with or without silver, solidify more quickly and, therefore, require careful application of heat. The melting ranges of common brazing metals are shown in Figure 14.7.