PURPOSE: To eliminate the need for pickling after cooling and obtain a steel material of good surface characteristics by using liquid contg. one or more kinds of deoxidized mineral oils and synthetic oils as a cooling medium in cooling the steel material.
CONSTITUTION: In cooling a steel material, the steel material is immersed in liquid of one or more kinds of mineral oils (e.g., kerosene) decreased of dissolved oxygen O2 down to ≤10ppm, and synthetic oils (e.g., silicone oil) as a cooling medium. By this immersion treatment, the steel material is cooled at high cooling rates of about ≥100°C/S. As a result, the formation of thick oxide films during cooling is obviated while high cooling rates are being given to the steel material; hence the need for pickling after cooling is eliminated, and the steel material having good surface characteristics giving no adverse influence upon subsequent plating treatment or zinc phosphate treatment is obtained.
TAKEOKA YOSHIHIKO
NIIHATA YASUSHI
SHOWA OIL