Bronze is an alloy composed mainly of Copper and Tin. The useful range of composition is 5 to 25 percent Tin and 75 to 95 percent Copper. The alloy is comparatively hard, resist surface wear and can be cast into shape or rolled into wire, rods and sheets very easily. In corrosion resistant properties Bronzes are superior to Brasses. It is used in hydraulic fittings, pump linings, making utensils, bearings, bushes, sheets, rods, wires and many other stamped and drawn articles. Some of the more common types of Bronzes and the special purpose Bronzes are described below.
When Bronze contains Phosphorus, it is called Phosphorus Bronze. A common type of wrought phosphor bronze has Copper 93.7%, Tin 6%, and Phosphorus 0.3 percent. Phosphorus increases the strength, ductility, and soundness of castings. The alloy possesses good wearing quality and high elasticity. The metal is resistant to salt water corrosion.
Uses. It is used for all average bearings in which wearing qualities are desired. Pump parts, lining, and propellers are examples of cast manufacture. A variety of phosphor bronze suitable for casting contains 11 percent Tin and 0.3 percent Phosphorus alloyed with Copper. This is used for bearings, which must carry heavy loads, worm wheels, gears, nuts for machine lead screws, springs etc.
Silicon bronze has an average composition of 96 percent Copper, 3 percent Silicon and 1 percent Manganese or Zinc.
Uses. It has good general corrosion resistance like Copper with higher strength. It can be cast, rolled, stamped, forged, pressed either hot or cold and can be welded by all the usual methods. Silicon bronze finds application in parts of boilers, tanks, stoves or wherever high strength and good corrosion resistance are required.
Manganese bronze is an alloy of Copper, Zinc, Lead and a little percentage of Manganese. The metal is highly resistant to corrosion. It is stronger and harder than phosphor bronze.
Uses. It is generally used for preparing bushes, plungers and feed pumps, rods, etc. Worm gears are frequently made from this bronze.
Gun metal contains 10 percent Tin, 88 percent Copper, and 2 percent Zinc. The Zinc is added to clean the metal and increase its fluidity.
Uses. It is not suitable for being worked in the cold state, but may be forged when at about 600C. The metal is very strong and resistant to corrosion by water and atmosphere. Originally, it was made for casting boiler fittings, bushes, bearings, glands, etc.
It contains 20 percent tin and the rest is Copper. It is hard and resistant to surface wear.
Uses. Bell metal is used for making bells, gongs, utensils, etc.