Cold rolled steel sheet and method of manufacturing the same

A cold rolled steel sheet having

• a chemical composition consisting of C:
• 0.06-0.14 mass %, Si:
• less than 0.50 mass %, Mn:
• 1.6-2.5 mass %, P:
• not more than 0.10 mass %, S:
• not more than 0.020 mass %, Al:
• 0.01-0.10 mass %, N:
• not more than 0.010 mass %, Nb:
• not more than 0.080 mass %, Ti:
• not more than 0.080 mass%, provided that Nb and Ti are contained in an amount of 0.020-0.080 mass % in total, one or more selected from Mo:
• not more than 0.3 mass %, B:
• not more than 0.005 mass %, Cu:
• not more than 0.3 mass %, Ni:
• not more than 0.3 mass % and Sb:
• not more than 0.3 mass %, and the remainder being Fe and inevitable impurities,
• a steel structure that an area ratio of ferrite is not less than 85%;
• an area ratio of martensite is 3-15%;
• an area ratio of unrecrystallized ferrite is not more than 5%;
• an average crystal grain size d of the ferrite is 2-8 μm;
• and a ratio (L/d) of an average value L (μm) among intervals between martensite grains closest to each other to the average crystal grain size d of the ferrite is 0.20-0.80, and
• mechanical properties wherein a yield ratio YR in a direction perpendicular to a rolling direction is not less than 0.68 and a ratio (TSD/TSC) of tensile strength TSD in a direction of 45° to the rolling direction to tensile strength TSC in a direction perpendicular to the rolling direction is not less than 0.95.