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SOLUTIONS: Copper and Copper Alloys

Introduction

The most common type of copper is electrolytically refined and treated to obtain different qualities. Pure copper has limited use on board except as copper piping. Cast parts are usually in brass or bronze alloy. Copper normally contains a small amount of oxygen. Oxygen combines with the copper forming copper oxide. The oxide is distributed in the metal in very small quantities and does not affect the mechanical characteristics of the metal. However, during welding

the oxide can cause porosity in the weld. Copper which is heated up to approx. 900°C will become brittle and weak as the copper oxide diffuses to the crystal boundaries where it collects and weakens the strength of the metal, in hot and cold condition. In this way, welding will weaken the metal in a joint. The best method of joining copper piping is therefore brazing with FC-BRONZE or with AG 45 or AG 60.

Copper alloys

2.08 Brass

Bronze

Straight brasses

Special brasses Naval brass

Brass

Brass is usually an alloy of copper and zinc, but other alloy elements may also be present. The zinc content in brass may vary from 5–50% in the different types.

The type of straight brasses used for mechanical purposes will usually contain between 63–75% copper, i.e.: – Cu 70%, Zn 30% (70:30 brass) – Cu 60%, Zn 40% (Muntz metal) Brazing: AG 45 or AG 60 with AG 60/45 FLUX FC-BRONZE and BRONZE FLUX FC-WEARBRO and WEARBRO FLUX 104

Admiralty brass

Aluminium brass (Yorcalbro)

Different types of special brasses are also available: e.g. Admiralty brass (Cu 70%, Zn 29%, Sn 1%) or Naval brass (Cu 58–64%, Sn 1%, Zn balance). Both these may be brazed the same way as straight brasses. Aluminium brass however should be treated in a special way.