Brief surface quenching hot rolled steel prod. - leaving a rolling mill, to obtain surface zone of tempered martensite or bainite

摘要

The treatment of rolled prods. leaving the finishing stand of a rolling mill comprises quenching the prod. with a fluid to obtain a martensitic and/or bainitic surface structure on all or part of the prod. whereas the non-quenched zone of the product remains at a sufficiently high temp. so that during subsequent air cooling the surface layer of martensite or bainite is tempered. The novelty is that, starting from the known characteristics of the plant and the product, characteristics are determined for the quenching devices and the flow of fluid applied by these devices. The coolant is pref. water, aq. salt solns., a mist of water in a gas, or a gas such as steam. Used in treating rolled steel, such as concrete reinforcing bars, wire rod, rounds or profiles or flat strip, to obtain optimum properties w.r.t. the highest possible elastic limit, fatigue strength, ductility, weldability, and/or for drawing into wire.