Title:
PRODUCTION OF HIGH CLEAN HIC-RESISTANT STEEL
Document Type and Number:
Japanese Patent JP3417311
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To reduce the harmful inclusion to HIC-resistant characteristic by spreading CaO-containing flux on the molten steel surface in the vacuum vessel of an RH vacuum degassing apparatus, adding Ca and/or Ca alloy into the molten steel in a ladle while keeping the vacuum after regulating total oxygen concn. and sulfur concn. in the molten steel to the specific ranges and regulating the Ca concn. to a specific range.
SOLUTION: The flux 8 is spread onto the surface of the molten steel 3 from a top-blown lance 7 in the vacuum vessel 1. The composition of the flux 8 is desirable to be 40-80% CaO and ≤40% Al2O3. In this way, the total oxygen concn. in the molten steel is regulated to 5-15 ppm and the sulfur concn. is regulated to ≤4 ppm. Successively, a Ca wire 9 is added into the molten steel 3 in the ladle 2 with a wire feeding method. This additional quantity is desirable to 0.07-0.5 kg/t of molten steel as Ca pure content. At this time, the vacuum degree in the vacuum vessel 1 is desirable to be kept to ≤80 Torr. In this way, the Ca concn. in the molten steel is regulated to 5-27 ppm.
Inventors:
Mitsuhiro Numata
Yoshihiko Higuchi
Yoshihiko Higuchi
Application Number:
JP25130398A
Publication Date:
June 16, 2003
Filing Date:
September 04, 1998
Export Citation:
Assignee:
SUMITOMO METAL INDUSTRIES,LTD.
International Classes:
C21C7/00; C21C7/06; C21C7/10; (IPC1-7): C21C7/00; C21C7/06; C21C7/10
Domestic Patent References:
| JP987732A | ||||
| JP8333619A | ||||
| JP83620A | ||||
| JP200073116A | ||||
| JP4259352A | ||||
| JP5171247A |
Attorney, Agent or Firm:
Shoichi Hirose