. The Street railway journal . November 24, 1906.] On noting the vast differences which have been shown, thequestion at once arises, why is not the former close-grainedshow wearing structure produced to-day? Is the change duemerely to the insistent efforts of the mills for higher tonnageor do other elements enter into the case. The answer iscomplex. In the first place the increased weight of the pres-ent sections of 90 or 100 lbs. per yard instead of 60 or 65 radically upset the ratio between the various componentsof the area of the rail, that is, head, web and flange. Theformer is far
. The Street railway journal . November 24, 1906.] On noting the vast differences which have been shown, thequestion at once arises, why is not the former close-grainedshow wearing structure produced to-day? Is the change duemerely to the insistent efforts of the mills for higher tonnageor do other elements enter into the case. The answer iscomplex. In the first place the increased weight of the pres-ent sections of 90 or 100 lbs. per yard instead of 60 or 65 radically upset the ratio between the various componentsof the area of the rail, that is, head, web and flange. Theformer is far thicker and of much greater mass than formerly,while the other parts in many cases have increased but littlein thickness or even have decreased. As a result of thesechanges the flange gets to the lowest temperature at whichit can be rolled long before the head reaches the same tem-. FIG. 3 FIG. 4 perature, so that even though the flange be fine grained andtough, as fine even as was obtained in the old practice, thecrystals of steel in the head may be very coarse, since theywere growing in size from the time that pressure upon themin the rolls ceased until the steel at that point had fallenbelow a dull red heat. This condition would mean relativerapid wear and brittleness. From the above it is evident that in order to get fine grainedstructure clear to center of head two courses are open. First,to rearrange the proportions of the rail in such manner thateach component part shall reach the critical temperature atmore nearly the same time, as in the old sections, or, secondly,to change the heat treatment given the steel, either duringthe rolling or subsequently. By the first method the largecrystals would be prevented from forming, while by the sec-ond, even though formed, they would be broken up by thereheating. In some mills it is common practice to hold the rail
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectstreetr, bookyear1884
