The high tension hot rolling steel sheet and its production mannered null mass which are superior in printing hardenability, resistance fatigue Characteristic, chip resistance and resistance normal temperature

摘要

PROBLEM TO BE SOLVED: To produce a hot rolled steel plate improved in baking hardenability, fatigue resistance, impact resistance and ordinary temp. aging resistance and suitable for an automotive interior material and to provide a method for producing it. ;SOLUTION: A rolling stock contg. 0.01 to 0.12% C, ≤2.0% Si, 0.01 to 3.0% Mn, ≤0.2% P, 0.001 to 0.1% Al and 0.003 to 0.02% N is hot-rolled, within 0.5 sec after the completion of the hot rolling, cooling is started at a cooling rate of ≥50°C/s to form a structure composed of ferrite of ≤8 μm average crystal grain size as the main phase, the content of solid solution N is controlled to 0.003 to 0.01%, and the ratio between the average concn. Ngb of solid solution N present on the ferrite crystal grain boundary and the average concn. Ng of solid solution N present in the ferrite crystal grains, i.e., Ngb/Ng is controlled to 100 to 10,000.;COPYRIGHT: (C)2000,JPO