Hot-dip galvanized cold-rolled steel sheet and process for producing same

A hot-dip galvanized cold-rolled steel sheet having a hot-dip galvanized layer on a surface of a cold-rolled steel sheet, characterized by having a chemical composition comprising, in mass percent, C:

• more than 0.10% and less than 0.25%, Si:
• more than 0.50% and less than 2.0%, Mn:
• more than 1.50% and at most 3.0%, P:
• less than 0.050%, S:
• at most 0.010%, sol. Al:
• at least 0% and at most 0.50%, N:
• at least 0.010%, Ti:
• at least 0% and less than 0.040%, Nb:
• at least 0% and less than 0.030%, V:
• at least 0% and at most 0.50%, Cr:
• at least 0% and at most 1.0%, Mo:
• at least 0% and less than 0.20%, B:
• at least 0% and at most 0.010%, Ca:
• at least 0% and at most 0.010%, Mg:
• at least 0% and at most 0.010%, REM:
• at least 0% and at most 0.050%, Bi:
• at least 0% and at most 0.050%, and the remainder being Fe and impurities, and
• by having a metallurgical structure in which a main phase is a low-temperature transformation product and a second phase contains retained austenite, wherein
• the retained austenite has a volume fraction of more than 4.0% to less than 25.0% with respect to a whole structure, and an average grain size of less than 0.80 μm, and in the retained austenite, a number density of retained austenite grains having a grain size of 1.2 μm or more is 3.0×10−2/μm2 or less.