| 摘要 |
PURPOSE: A hot rolled steel plate and its production method are provided to solve a problem of an existing mini mill process and to use elements such as a Cu, a Cr and so on contained in a scrap iron as corrosion resistant elements, a Ni as a preventing element of surface crack and a nitrogen of high concentration in a steel as a rising resource of hardness. CONSTITUTION: A steel is composed of a C of 0.03-0.06wt%, Mn of 0.25-0.70wt%, Si under 0.4wt%, P of 0.05-0.15wt%, S under 0.006wt%, Cr under 0.6wt%, Ni under 0.4wt%, Cu under 0.5wt%, Sn of 0.001-0.04wt%, a soluble Al of 0.04-0.10wt%, N under 150ppm, Ca of 0.0002-0.008wt%, Fe and other impurities and is satisfied a condition of a ratio of Mn/S larger than 30(1) and a ratio of Cu/Ni larger than 0.5(2). A slab is rolled at first after producing by melting the steel and by continuously casting. A hot rolled steel bar is heated at a temperature under 1080°C in a derived heating furnace. A finishing rolling is performed in the temperature over 870°C by maintaining an atmospheric temperature of coil box under 1080°C. The hot rolled steel bar is wound up at the temperature over 550°C. Thereby the hot rolled steel plate having the excellent workability and the weatherability is produced.
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