| 摘要 |
<p>PURPOSE: A hot rolled steel sheet with improved internal pressure and fracture strength and a manufacturing method thereof are provided to improve the cleanness of steel by utilizing scrap as a raw material in an electric furnace and adding Ca in secondary refining. CONSTITUTION: A hot rolled steel sheet with improved internal pressure and fracture strength comprises carbon 0.04~0.07 weight%, manganese 0.8~1.0 weight%, phosphorus 0.02 weight% or less, sulfur 0.005 weight% or less, aluminum 0.01~0.06 weight%, niobium 0.01~0.02 weight%, nitrogen 0.007 weight% or less, copper 0.1 weight% or less, and iron and inevitable impurities of the rest amount. The tensile strength of the hot rolled steel sheet, measured at the speed of 20mm/min using the 25 tone Zwick tensile testing machine, is 470~500Mpa, the yield strength 400~430 Mpa, and the elongation ratio 35~42 weight%.</p> |
