Non quenched and tempered steel and manufacturing process thereof

Abstract

A non quenched and tempered steel and manufacturing process thereof. The process comprises a cooling step after the finish rolling step; and the process utilizes alternate intense cooling and moderate cooling. The intense cooling can ensure the surface temperature of the steel to decrease rapidly; and the moderate cooling allows the core temperature of the steel to dissipate gradually to the surface; a further intense cooling is carried out to allow rapid heat dissipation. The intense cooling and the moderate cooling can be carried out alternately several times according to practical requirement. A water cooling mode combining intense cooling and moderate cooling allows the core temperature and the surface temperature of the steel to become the same within a short time, and thus ensures the uniformity of the mechanical properties of the steel and improves the production efficiency.

Description

TECHNICAL FIELD

[0001] The present invention relates to a non quenched and tempered steel and its production process, and belongs to the technical field of ferrous metallurgy.BACKGROUND

[0002] Currently, bars for machine cutting in China generally use ordinary steels, such as 45, 40Cr and 42CrMo steels. These bars need quenching and tempering heat treatment when used as raw materials for machine cutting. Quenching and tempering processes are high in cost. Since quenching and tempering processes increase energy consumption, pollute the environment, and bring some waste product loss, they do not meet the energy-saving and environmental protection requirements at present. Therefore, non quenched and tempered steels that do not require quenching and tempering processes and can be directly used for cutting will gradually replace ordinary steels and become a trend in the future. Non quenched and tempered steels means mechanical structural steels that can achieve performance requirements witho...

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