Articles of manufacture in the form of an annular ductile iron piece at least a portion of which has its carbon content in the form of flattened bodies disposed in planes parallel to the central axis of the piece and normal to the outer surface of the piece, the iron grains of the piece being extended significantly both in a direction parallel to the central axis and in directions which are transverse to the central axis and parallel to planes occupied by the flattened carbon bodies, the outer surface of the piece being smooth and uninterrupted without machining and the article being free from structural failure discontinuities.