. The car wheel; giving the results of a series of investigations . carbon content is aboutthe same as that in the A tire. Here again, owingto the absence of sufficient ferrite to outline the grainclearly, it was necessary to photograph by obliqueillumination, and it was under this light that the ac-companying sketches to show the grains size weremade. The microphotographs closely check theabrasion tests and the determinations of specificgravity. There are two well-defined zones in the rim ofthe Schoen wheel that are evidently due to therolling. One is at a depth of | in. and the otherf in. be
. The car wheel; giving the results of a series of investigations . carbon content is aboutthe same as that in the A tire. Here again, owingto the absence of sufficient ferrite to outline the grainclearly, it was necessary to photograph by obliqueillumination, and it was under this light that the ac-companying sketches to show the grains size weremade. The microphotographs closely check theabrasion tests and the determinations of specificgravity. There are two well-defined zones in the rim ofthe Schoen wheel that are evidently due to therolling. One is at a depth of | in. and the otherf in. below the surface of the tread. This is bestillustrated by the accompanying diagram of themicrostructure in the Schoen wheel, in which thefour strips and the location of the microphotographsare roughly indicated. Strip No. I shows a very fine grain at the surfacewith carbon well below per cent. This structureruns down for about -^ in., where there begins agradual increase of the grain size until the normaldimensions are reached at about yV in. below the top 40. No. 19. % In. Below Tread. No. 20. i In. Below Tread. MICROPHOTOGRAPHS OF WHEEL E. 88 DIAMETERS. 41 of the flange. The first 2V iri- is formed of a veryfine mixture of about equal proportions of ferriteand pearlite, and below this the ferrite gradually dis-appears and the grains increase in size. At a depthof -Y2 in. the ferrite appears as a discontinuous bandor envelope around the grains of pearlite, indicatingthat the carbon content is about per cent. Thisincrease in the size of the grains continues dow^n-ward until they reach their maximum at a depth ofabout I in. In strip No. 2 there is the same fine-grained sur-face structure {a) corresponding to that of No. depth of this decreases from one side of thestrip to the other and is about ^ in. thick at thecorner. This structure is shown in the photographNo. 31. On the right hand side two zones will beseen, one of which, starting at /i, is of very finepearli
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Keywords: ., bookaut, bookcentury1900, bookdecade1900, booksubjectrailroadcars
