NON-QUENCHED AND TEMPERED STEEL AND MANUFACTURING METHOD THEREFOR

摘要

A non quenched and tempered steel and manufacturing process thereof. The process alters the cooling mode before finish rolling in previous production of non quenched and tempered steel; the process at least has a cooling step after the finish rolling step; in contrast to the cooling mode in the prior art which employs the cooling mode of single water cooling or consistent air cooling, the present 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.