anti-friction alloys

anti-friction alloys defined in 1909 year

anti-friction alloys - Anti-friction Alloys;
anti-friction alloys - A good white metal for lining journal boxes, pillow-blocks, etc., is made of Copper - 4 parts, Tin - 96 parts and Antimony - 8 parts. In this the tin is in excess, and the alloy is prepared in a roundabout way: 12 parts copper are first melted, and then 36 of tin are added; 24 of antimony are put in, and then 36 of tin, the temperature being lowered as soon as the copper is melted, in order not to oxidise the tin and antimony, the surface of the bath being protected from contact with the air. The alloy thus made is subsequently remelted in the proportion of 50 parts alloy to 100 tin. For small journals, where the friction is not great, both the copper and antimony may be doubled in quantity. An alloy of 1 part copper, 50 tin, and 5 antimony, has a greasy feel, and is good for machines not overworked; but a better metal for lining bearings subjected to rapid, not heavy friction, is made of 85 parts lead, 15 antimony. Vaucher's alloy is composed mainly of zinc and tin, with small quantities of lead and antimony, the last being melted separately. Brasses for locomotive bearings are usually made of Copper - 64 parts, Tin - 7 parts and Zinc - 1 part.

Babbitt's metal (see below) may be described as a tin alloy, 10 parts of that metal being used in conjunction with 1 each of copper and antimony. In recent years, phosphor bronze and manganese bronze have established a good reputation, and latterly cadmium has attracted some attention as an ingredient in alloys for bearings. It fuses below a red heat, and volatilises so readily at the ordinary temperatures necessary for making alloys, that great difficulty has been experienced in using it as an ingredient. 16 is malleable and ductile, is harder and more tenacious than tin, but soils paper as lead does when it is rubbed over it. Possibly this property has attracted inventors to it, as the fine particles thus removed on slight friction would probably produce a highly smooth surface on a bearing made of an alloy containing cadmium. The proportions preferred are Copper - 650 parts, Nickel - 275 parts, Cadmium - 50 parts, Zinc and Tin - 25 parts. On different lines of railway, and in various countries, a very large number of alloys have been tried for bearings. Thus, where the freight is light, bearings made of an alloy of lead and antimony have been found to give good results - the life of the journal being prolonged at the expense of the bearing and with an increased consumption of lubricant. Alloys of tin and copper have been tried; but, except in some few proportions, they are too hard; though when the tin preponderates, and there is an addition of antimony, a good bearing is obtained, but at too high a price. Bearings of white metal, and of an alloy of antimony and lead, possess the advantage that they are easily replaced; but unless the supply of lubricant is kept up, they soon wear out, and the latter rapidly fuse, if the journal becomes heated. White metal bearings, with the copper and antimony preponderating, are too hard, too brittle, and break under heavy loads; while, if the tin is in excess, and they are subjected to great pressure, they soon wear out of shape. Dr. Kiinzel made many experiments on bearings, and concluded that for a bearing to possess all the required qualities it should be heterogeneous in constitution, and that its skeleton, so to speak, should be made of a metal as tenacious as possible, the hardness of which is nearly equal to that of the journal, so as to enable it to resist the shocks to which it is subjected without changing its shape. The insterstices or pores of the skeleton should contain a soft metal. The final result of Dr. Kiinzel's investigations was the invention of his patented alloy, which consists of phosphor-bronze, with certain quantities of lead and tin added to form the soft alloy for filling the pores. By varying the proportions of the ingredients, and by adding or omitting the proportion of zinc, the hardness of the bearing may be adapted to that of the journal. ('Eng. Mech.').

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