To provide a method for stably manufacturing high-carbon steel containing extremely little phosphate by using a dephosphorizing agent containing no F, Na and Cl which may affect the environment and a human body.
The smelting method employs two converter vessels of a dephosphorization furnace for molten pig iron and a decarburization refining furnace; and comprises the steps of: at first, when dephosphorizing the molten pig iron in the dephosphorization furnace, using a lime-based dephosphorizing agent as the dephosphorizing agent, and estimating the quantity of produced FeO in the furnace according to the following expression (1): FeO (kg/t)=[quantity of accumulated oxygen (m3 (normal condition)/t)/22.4]×71.85, based on the quantity of accumulated oxygen which is determined by sequentially calculating an oxygen balance from the composition and flow rate of an exhaust gas during a blowing step, a flow rate of an oxygen gas, a charged amount of an auxiliary material and the composition of the molten pig iron; decreasing the concentration of phosphorus after the treatment to 0.015 mass% or lower by adjusting at least one of a height of a top-blowing lance, the flow rate of the oxygen gas and the flow rate of a bottom-blowing gas in accordance with the quantity of the above estimated FeO; then removing slag; and blowing oxygen for decarburization in the decarburization smelting furnace till the carbon concentration is lowered to a desired value.
YATABE KATSUNORI
ASAHINA TAKESHI
KIKUCHI NAOKI
| JPH11323419A | 1999-11-26 | |||
| JP2000073111A | 2000-03-07 | |||
| JP2004107735A | 2004-04-08 |
Hiroshi Tokunaga
Yoshiyuki Iwasa
Shiro Fujitani
Kiyoshi Kuruma
Kazuyuki Tomita