| 摘要 |
PURPOSE: A draft steel of a hot rolled steel sheet and a manufacturing method thereof are provided to minutely form grain by adding niobium, titanium and boron. CONSTITUTION: A draft steel of a hot rolled steel sheet is made of carbon 0.05~0.20 weight%, silicon 0.01~0.30 weight%, manganese 2.00~3.00 weight%, aluminum 0.10~0.50 weight%, niobium 0.01~0.10 weight%, titanium 0.01~0.10 weight%, nickel 0.02~0.30 weight%, copper 0.01~0.30 weight%, chrome 0.10~2.0 weight%, boron 0.0005~0.0030 weight%, phosphorus less than 0.05 weight%, sulfur less than 0.02 weight%, and nitrogen less than 0.01 weight%. |
