Ribbed reinforcing bars for concrete - where bar surface is quenched and tempered before cold deformation applied to make the ribs

摘要

Mfr. of ribbed reinforcing bars, in which the bars, upon leaving the last stand of a hot rolling mill, are surface quenched to form a surface layer of martensite and/or bainite, but sufficient heat is retained in the core so that during a subsequent period in air the surface layer is tempered; the bar is then subjected to transverse cold deformation to provide along its entire length, a transverse section possessing at least two zones with a radius of curvature larger than the initial bar radius, the zones being connected by anchoring ribs which are flattened where they join the surface of the bar.