US 12,134,799 B2
Method for producing chromium-containing molten iron
Norifumi Asahara, Tokyo (JP); Katsuhiko Kato, Tokyo (JP); Mikio Futaka, Tokyo (JP); Yasuhiro Tanaka, Tokyo (JP); Naoki Kaneko, Tokyo (JP); and Junichi Nakagawa, Tokyo (JP)
Assigned to NIPPON STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/603,593
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Mar. 31, 2020, PCT No. PCT/JP2020/014962
§ 371(c)(1), (2) Date Oct. 14, 2021,
PCT Pub. No. WO2020/217890, PCT Pub. Date Oct. 29, 2020.
Claims priority of application No. 2019-081179 (JP), filed on Apr. 22, 2019.
Prior Publication US 2022/0195546 A1, Jun. 23, 2022
Int. Cl. C21C 7/00 (2006.01); C21C 5/00 (2006.01); C21C 5/52 (2006.01); C21C 5/54 (2006.01); C22C 33/04 (2006.01)
CPC C21C 7/0006 (2013.01) [C21C 5/005 (2013.01); C21C 5/527 (2013.01); C21C 5/54 (2013.01); C21C 7/0025 (2013.01); C22C 33/04 (2013.01); C21C 5/5217 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A method for producing a chromium-containing molten iron, the method comprising:
charging a charged material, containing a metal raw material of at least one of ferrochromium containing metal Si or ferrosilicon and unreduced slag containing Cr oxide generated by oxidation refining, into an AC electric furnace including three electrodes, a mass ratio of a metallic Si amount to a Cr oxide amount being from 0.30 to 0.40, and a C concentration being from 2.0% by mass to a saturation concentration; and generating an arc between each of the electrodes and a molten metal surface, and
when a diameter of a circle passing through the centers of the three electrodes, viewed in a plan view from a central axis direction of the electric furnace, is PCD (m), an average electrode height that is a vertical distance from a tip of each of the three electrodes to a static molten metal surface of molten iron is He (m), a furnace inner diameter is Df (m), a molten slag thickness is Hs (m), a spreading diameter of the arc on the static molten metal surface of the molten iron is Darc (m), and a deflection angle of the arc is θ (deg), performing operation under a condition satisfying relationships of the following formulae (1) to (4) to produce molten iron containing Cr in which the Cr oxide has been reduced:
Darc=PCD+2He·tan θ  (1)
θ=52.5−75·(PCD/Df)  (2)
0.22≤Darc/Df≤0.30  (3)
0.35≤He/Hs≤1.50  (4).