Heat treatment of soft or half-hard steel

摘要

Properties are improved by procedure after normalising and heat treatment: cooling in a metastable austenite zone to temperature for isothermal formation of bainite, preventing this formation as far as possible; re-heating in metastable austenitic zone to temp. for formation of ferrite; holding this temp. for long enough time for a structure to be formed with >=15% ferrite; and cooling in bainite zone. Preferably, included in heat treatment is an annealing above the boundary temp. of the bainite-forming zone. Advantage: provides steel of intermediate-stage matrix structure having higher impact strength for reinforcing, building, and machine construction steel.