US 12,331,368 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. 17/603,592
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Mar. 31, 2020, PCT No. PCT/JP2020/014961
§ 371(c)(1), (2) Date Oct. 14, 2021,
PCT Pub. No. WO2020/213393, PCT Pub. Date Oct. 22, 2020.
Claims priority of application No. 2019-080179 (JP), filed on Apr. 19, 2019.
Prior Publication US 2022/0195545 A1, Jun. 23, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. C21C 5/54 (2006.01); C21C 5/52 (2006.01); C21C 7/00 (2006.01); C22C 33/04 (2006.01)
CPC C21C 7/0006 (2013.01) [C21C 5/527 (2013.01); C21C 5/54 (2013.01); C21C 7/0025 (2013.01); C22C 33/04 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A method for producing chromium-containing molten iron, the method comprising:
charging, into an electric furnace, a charged material containing a metal raw material of at least one of ferrochrome containing metallic Si or ferrosilicon containing metallic Si, and unreduced slag containing Cr oxide generated by oxidative refining, as a mixture in which a mass ratio of an amount of the metallic Si, which is an amount of metallic silicon contained in the metal raw material, to an amount of the Cr oxide is from 0.30 to 0.40, and a C concentration is in a range of from 2.0% by mass to a saturation concentration; and
after the charging, producing molten iron containing Cr obtained due to the Cr oxide undergoing reduction processing, such that, when the charged material is heated and melted in the electric furnace, an attainment temperature is set to from 1400° C. to 1700° C., a maximum average heating rate in any 80° C. interval from 1300° C. to the attainment temperature is set to 15.0° C./min or less, and a minimum average heating rate in any 80° C. interval from 1300° C. to the attainment temperature is set to 3.0° C./min or greater.