Patent ID: 8323561

Claim:
A fire-resistant rolled or worked steel material having HAZ toughness of a welded joint, the fire-resistant rolled or worked steel material comprising, by mass %, C: 0.005% to less than 0.03%, Si: 0.01 to 0.50%, Mn: 0.05 to 0.40%, Cr: 1.50 to 5.00%, V: 0.05 to 0.50%, and N: 0.001 to 0.005%, limiting Ni: less than 0.10%, Cu: less than 0.10%, Mo: less than 0.05%, B: 0.0003% or less, having a balance of Fe and unavoidable impurities, and among said unavoidable impurities, limiting P: less than 0.020%, S: less than 0.0050%, and O: less than 0.010%; wherein the fire-resistant steel material is rolled or worked, and has a bainite structure.