HIGH TENSILE STRENGTH HOT-ROLLED STEEL SHEET HAVING IMPROVED BAKE HARDENABILITY AND FATIGUE RESISTANCE, CRASH RESISTANCE, AND RESISTANCE TO ROOM TEMPERATURE AGING, AND METHOD OF PRODUCING THE SAME

摘要

Improved with the desired, baking curing, fatigue resistance, impact resistance and resistance to room temperature aging property as a car interior, the hot-rolled steel sheet and to provide a method of manufacturing the same. That is, the present invention is, in wt%, C: 0.01 ~ 0.12%, Si: containing 30 ~ 200ppm: 2.0% or less, Mn: 0.01 ~ 3.0%, P: 0.2% or less, Al: 0.001 ~ 0.1%, N by hot rolling a rolling material, and that, starting the cooling of more than 50 ℃ / s cooling rate to within 0.5sec at the hot rolling exit, the average crystal grain size, and the tissue that the ferrite of the primary phase 8㎛ below, the amount of dissolved N a is characterized in that a 30 ~ 100ppm, ratio, Ngb / Ng between the ferrite crystal average solute N concentration (Ngb) and the ferrite crystal average solute N concentration (Ng) present in the particles that are present in the grain boundaries of 100 to 10,000.