SHEET METALS 453 



pheric influences, and is extensively employed in the manu- 

 facture of knives, forks, spoons, etc., for table use. 



532. Kinds of Bronzes. In the early days of manufacture 

 the term bronze was applied to a non-corrosive metal made 

 of a mixture of copper and tin, dark in color, hard in temper, 

 and of high tensile strength. Today bronze refers to any 

 metal that possesses any of the above characteristics. In 

 order to distinguish the different bronzes, a prefix should 

 ~be used, such as "Tobin," " phosphor," "-naval," "man- 

 ganese," etc. 



Tobin-bronze is a composition of copper, tin, and zinc, in 

 such proportions as are necessary to secure the physical 

 properties and the resistance to corrosion desirable in a 

 metal intended for engineering purposes. It has a bright 

 golden color and resists the corrosive action of sea water. 



Phosphor-bronze, which is bronze containing phosphorus, 

 resists shocks. Hence it is used for the bearings of rolling 

 mills, railway axles, for valves of air pumps, etc. It is 

 affected by the heat more than is gun-metal. Phosphor- 

 bronze offers great resistance to corrosion, has great tensile 

 strength, and has no tendency to disintegration. It may be 

 made into springs without "setting" or crystallizing. It is 

 better than any other copper alloy because of its antifriction 

 properties. 



Naval-bronze is made according to specifications of the 

 United States Navy. It is particularly adapted to marine 

 engineering, where strength must be accompanied by non- 

 corrodibility. 



Manganese-bronze is an alloy of copper, zinc, and tin, de- 

 oxidized by means of manganese. It may be readily rolled 

 or forged at ^ red heat resulting in the production of an 



