A double-flange trailer wheel, in service on a coke-oven pusher car for about five years, broke. Specifications called for rolled steel track wheels conforming to ASTM A 186 (since reclassified as A 504). Chemical analysis showed the metal in the wheel to be medium-carbon steel within the ranges given in ASTM A 186. Visual examination of the broken wheel revealed that cracks ran parallel with the base of the lower row of numbers stamped with heavy indentation on the web section. Microscopic examination showed the metal in the web, rim, and tread to be in the normalized condition. Evidence...