| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength hot rolled steel sheet excellent in processability and fatigue characteristic, having strength of 500 N/mmclass or more for a press worked automobile part, and to provide its manufacturing method.SOLUTION: There is provided a high strength hot rolled steel sheet excellent in processability and fatigue characteristic, containing, by mass%, C:0.03 to 0.35%, Si:0.01% to 2.0%, Mn:0.3% to 4.0%, P:0.001% to 0.10%, S:0.0005% to 0.05%, N:0.0005% to 0.010%, Al:0.01% to 2.0% and the balance Fe with inevitable impurities with a crystal structure having, by area fraction, a martensite phase of over 5%, a ferrite phase of over 20% and a pearlitic phase of less than 10%, and a coverage factor of ferrite grains by the martensite phase of over 30%. |
