. Transactions. F. after being heat treated. The experiments on which 440 MANGANESE-STEEL CASTINGS IN THE MINING INDUSTRY the foregoing photomicrographs are based were carried out with theaid of an electric furnace equipped with a pyrometer. By the Brinell test, manganese steel toughened or untoughened showsthe moderate average hardness number of about 200. The extreme outersurface of the treated steel shows a slightly lower number than at a depthof about 3^ in., from which point the number remains constant to thecore of the casting. The lowering of the hardness number at the surfaceis due to
. Transactions. F. after being heat treated. The experiments on which 440 MANGANESE-STEEL CASTINGS IN THE MINING INDUSTRY the foregoing photomicrographs are based were carried out with theaid of an electric furnace equipped with a pyrometer. By the Brinell test, manganese steel toughened or untoughened showsthe moderate average hardness number of about 200. The extreme outersurface of the treated steel shows a slightly lower number than at a depthof about 3^ in., from which point the number remains constant to thecore of the casting. The lowering of the hardness number at the surfaceis due to the oxidization of the carbon during the heat treatment. The qualities of manganese steel have led to its adoption extensivelyfor the vital parts of heavy-duty machinery, particularly parts subjectedto unusual wear, shock, etc. Manganese-steel castings are used todayin the construction of wearing parts for the following kinds of machinery:Rock and ore crushers, coal breakers, ball mills, tube mills, pulverizers,. Fig. 5.—The Same Steel Heated to TSOT. and Allowed to Cool in AirResulting in the Precipitation of Cementite Injuring the Quality of theMetal. X 80 Diameters. comminuters, clay mills, traveling cranes, gold dredges, harbor dredges,steam shovels, ditching machines, pig-casting machines, pug mills, cokemachines, steel-rolling machinerj^, stamp mills, cable haulage systems,screening apparatus, centrifugal sand pumps, grab buckets, concretemixers, etc. Manganese steel is also extensively used in the manufactureof steam and electric railway track work, elevator buckets, gears, pinions,mine and skip car wheels, and for numerous other purposes. The use of manganese steel for tube-mill liners is a recent develop-ment which is of special interest at this time because of the curtailmentin the supply of lining materials previously used, by reason of the warabroad. Until the introduction of manganese-steel liners, tube millswere lined almost exclusively with silex blocks importe
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
