| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a hot rolled steel sheet with good workability and a high strength which has high dynamic impact energy absorbability by specifing the components and microstructure of the steel sheet, and to provide its producing method. SOLUTION: This high strength hot rolled steel sheet having high dynamic deformation resistance and good workability, includes 0.01 to 3 mass % Co and has specified microstructure in a composite, one composed of ferrite or bainite as a phase having the maximum volume fractional ratio and the second phase containing retained austenite of >=3% by volume fractional ratio, and the value M=(678-428×[C]-33×Mneq) decided by the content of solid solution C [C] in the retained austenite. The average Mn equivalent Mneq in the steel is -140 to 180, the static average stress of 3 to 10%σst, the static maximum stress TS and the dynamic average stress of 3 to 10%σdyn satisfy the inequality of (σdyn-σst) TS/1,000>=40, and the producing method for it is provided.</p> |
