A.28%～48% B.30%～68% C.48%～78% D.78%～95%
A．調(diào)整鋼液溫度和防止?fàn)t渣結(jié)殼 B．均勻鋼水溫度和成份，促進(jìn)夾雜上浮 C．防止鋼液二次氧化
A．先開(kāi)氣后點(diǎn)火 B．先點(diǎn)火后開(kāi)氣 C．邊開(kāi)氣邊點(diǎn)火
