In the above context, aluminium bronze is a modern
introduction. The combination of copper and aluminium first took place in
the mid 1800’s. It was very expensive to produce and consequently, other
than being an object of investigation for metallurgists, was not much used.
At the turn of the century, additional alloying elements were being investigated
and in 1913 Durville perfected his tilting ladle process to make aluminium
bronze billets. This “Durville Process” was necessary to overcome the problem
of shrinkage defects and oxide inclusions characteristic of the alloys,
partially due to the narrow freezing range. This was so successful that
the French government used the alloy (Cu 9Al) for a range of coins (50 centimes,
1 & 2 Francs).
NAB is twice as resistant to corrosion fatigue as manganese bronze and stainless steel
Charles H Meigh developed this process further and worked with the French Admiralty to produce an early nickel-aluminium bronze (Cu 10Al3Ni3Fe3Mn). Further investigations by metallurgists saw the development of the alloys and its common commercial usage grew with the requirement for ship’s propellers suitable for increasing speeds. As Meigh (2000, xxix) states “… nickel-aluminium bronze (NAB) is twice as resistant to corrosion fatigue as manganese bronze and stainless steel …”, it has become the most popular material for this use. Growth in the oil industry and the need, initially for seawater fire pumps, has also spread the use of NAB. Navies have also used NAB extensively, where its strength and weldability replaced gunmetal (Cu SnPbZn). It is thought that the loss of the US nuclear submarine Thresher in 1963, due to a casting failure, hastened the uptake of NAB for use on submarines. (Meigh, 2000).
More recently, with the advent of super austenitics and various duplex stainless steels, the trend has been towards these newer materials, or even in some cases to the more exotic and expensive titanium. In 1986 copper-nickel pipe seems to have been well established together with NAB valves. For reasons of weight, strength and velocity limitations (erosion damage in the Cu-Ni pipe above 3.5 m/s) the newer materials were considered. For example, a 20” CuNi diameter pipe could be replaced by a 14” 254 SMO material. (Gallager, Mallpas & Shone, 1986). Subsequent experience of these materials, has shown that there are temperature limitations and cost implications with casting quality control.
This website serves as a reminder of the benefits of NAB and suggests that there is still a place for NAB valves between the extremes of the low cost and exotic alternatives.