. Electric railway journal . DANGERS OF WELDING—FIG. 3—DIAGRAMS OF ZONES INTIRE METAL AFTER WELDING cooled has taken on a condition similar to that of aquench as the heat has been rapidly withdrawn fromthis section by the surrounding metal. The line of de-marcation between Zones 1 and 2 shows the isothermalline which has been that of the critical temperature ofthe material. It is a characteristic of all steels thatwhen cooled from such a temperature they are in thevery poorest conceivable condition. Thus along theline between Zones 1 and 2 wa have a condition which is. DANGERS OF WELDING—FIG.
. Electric railway journal . DANGERS OF WELDING—FIG. 3—DIAGRAMS OF ZONES INTIRE METAL AFTER WELDING cooled has taken on a condition similar to that of aquench as the heat has been rapidly withdrawn fromthis section by the surrounding metal. The line of de-marcation between Zones 1 and 2 shows the isothermalline which has been that of the critical temperature ofthe material. It is a characteristic of all steels thatwhen cooled from such a temperature they are in thevery poorest conceivable condition. Thus along theline between Zones 1 and 2 wa have a condition which is. DANGERS OF WELDING—FIG. 2—SECTION OF BUILT-UP TIRE WELDED BY ONE FLAME OPERATION 944 ELECTRIC RAILWAY JOURNAL LVol. XLV, NO. 20 the weakest that can possibly be obtained in tire 3—The new metal actually fused into the tire bythe oxy-acetylene flame. In Zone 1 the metal gives scleroscope readings ofabout 34 to 35; in Zone 2, 38 to 40, there being a sharpline of demarcation between the two zones; and in Zone3, about 22, indicating a low-carbon material. Allthree zones appear very distinctly to the naked eye, sideby side, on polishing the sections and etching them withnitric acid. In Fig. 3 it will be noted that the line of demarcationruns diagonally across the tire, showing a zone of weak-ness directly across the tire. Since Zone 3 is soft overhard metal, the only action that could take place is arapid wearing away of Zone 3 and its subsequent shell-ing out. But between Zones 2 and 1 we note that thereis a difference of five points in the scleroscope hardnessin favor of
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