| 摘要 |
The present invention provides a hot dip galvanized composite high strength steel sheet excellent in shapeability and hole enlargement ability and a method of production of the same, that is, a hot dip galvanized composite high strength steel sheet excellent in shapeability and hole enlargement ability containing C: 0.01 to 0.3%, Si: 0.005 to 0.6%, Mn: 0.1 to 3.3%, P: 0.001 to 0.06%, S: 0.001 to 0.01%, Al: 0.01 to 1.8%, and N: 0.0005 to 0.01% and having a metal structure of ferrite and, by area rate, 5% to 60% of tempered martensite and a method of production of the same comprising hot rolling, then cold rolling a slab including the above ingredients, heating the sheet in the hot dip galvanization heating process to Ac 1 to Ac 3 +100°C, holding it there for 30 seconds to 30 minutes, then cooling it by a 1°C/s or higher cooling rate to 450 to 600°C, hot dip galvanizing it at that temperature, then cooling it at a 1°C/s or higher cooling rate to the martensite transformation point or lower in temperature, holding it there at 200°C to 500°C for 1 second to 5 minutes, then cooling it at a 5°C/s or higher cooling rate to 100°C or less. |
