| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a hot rolled steel sheet having all of high strength, satisfactory ductility and stretch flange property. <P>SOLUTION: The method for manufacturing the hot rolled steel sheet includes: a step of applying a multi-pass hot rolling in which a draft in the last rolling pass is set to 5-50% and the rolling is completed in the temperature range of 860-1,050°C, to a slab having a chemical composition composed of, by mass, >0.08% to <0.30% C, 1.0-4.0% Mn, 0.10% to <3.0% Si, 0.01-3.0% sol.Al (wherein, the total amount of Si and sol-Al is equal to 0.8-3.0%),≤0.05% P,≤0.01% S,≤0.01% N, and the balance Fe with impurities; a step of performing finishing to the sheet thickness of >1.2 mm to≤6 mm; a step of cooling the steel sheet to the temperature zone of≤720°C within 1 second after completing the hot rolling; a step of making the steel sheet stay in the temperature zone of >500°C to≤720°C for 1-20 s staying time; and a step of coiling the steel sheet in the temperature zone of 350-500°C, thereafter. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
