HIGH STRENGTH STEEL SHEET AND MANUFACTURING METHOD THEREOF

摘要

PROBLEM TO BE SOLVED: To provide a high strength steel sheet having excellent processability, chemical conversion treatment property and corrosion resistance after an electrodeposition even when contents of Si or Mn are large and a manufacturing method therefor.SOLUTION: Following (Condition 1) to (Condition 3) are used when a steel sheet is continuously fired. (Condition 1) The steel sheet is heated under a condition that a rate of increasing temperature is 7°C/s or more in a temperature range of a temperature inside of a firing furnace of 450°C to A°C (A:500≤A) in the continuously firing process. (Condition 2) A steel sheet maximum reaching temperature is 600°C to 750°C in continuously firing. (Condition 3) A steel sheet transit time in the temperature range of 600°C to 750°C of the steel sheet temperature is 30 sec. to 10 min. and the dew point of atmosphere is -10°C or more.