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Full text of "Metallurgy Of Cast Iron"

448
METALLURGY   OF   CAST   IRON.
without breaking out a piece. The Pennsylvania Railroad specifications, I believe, require wheels tested to stand twelve blows under the M. C. B. drop without breaking out a piece. It would seem fair to assume that the Barr drop would find the weak or dangerous part of the wheel more readily than the M. C. B. drop. The treatment and handling of the hot wheel has nearly as much to do with the strength as has the material used. Cold iron will produce seams in the tread and internal strains, because the molten iron sets in the mould as fast as it is poured. Hot iron, with slow and uneven pouring, produces sweat in the throat, uneven chill, and internal strains; delay in getting the hot wheel into the pit after being shaken out of the mould will also produce strains in the wheel by uneven contraction. Wheels should be poured with fairly hot irons and fast. The limit of time in pouring a 3 3-inch wheel should not exceed twelve seconds. Table 88 gives the analysis of a number of wheels tested under the Barr drop, and in the thermal test:''
TABLE
t	Wheels that failed in thermal test.		Wheels that stood thermal test.		Wheels that failed under 50 blows, Barr drop.		Wheels that stood 50 blows and over, Barr drop.	
	Max.	Min.	Max.	Min.	Max.	Min.	Max.	Min.
Total carbon ............	3-f)i	3-63	_>fK>_ 2.q8~	3.38 2.71	3.87 "3-iq"	3-42 2.90	.>VL "3.02	3<4<L 2.0"
Graphitic carbon	3.02	2.Q2						
Combined, carbon .............	_.8_9_ .090	__-.7.L .042	.<)2	.67	.68 .080	.52	.01 .070 - - ;72	50 05
Sulphur .........			.IO	.oSo		.020 " ".40 ...... -67		
Manganese .......	.60	49	.58	___4.8_ .50 "~'.26~	.62			47
Silicon ...............        ........	.82	50	.<)!		97		1. 10	.68 ..... .2,S"
Phosphorus ........ ............	.48	39	52		.58	30	53	
A part of the wheels failing under these tests caimot be ascribed to the composition.teel-tiredrcf.    Ilirlinn* whrii thr pomm-'r-r.r-,