Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1982-04-30
1983-12-27
Rosenberg, Peter D.
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
75 59, 75 60, C21C 534, C21C 536
Patent
active
044228732
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a blowing method in a converter, especially in a top and bottom blowing converter among steel-making furnaces, and more particularly relates to a blowing method capable of preventing the blowing up of slag and metal, which blowing up is apt to occur at the initial stage of blowing of molten steel in a converter, and further capable of removing advantageously phosphorus from the molten steel at the same time with the prevention of the blowing up of molten steel.
BACKGROUND ART
There has been often experienced the blowing up of slag and metal at the initial stage of blowing of molten steel in a bottom blowing converter. The initial stage blowing up is a phenomenon, in which several 10 tons of slag and metal is bumped from the feed opening of a converter near the time of completion of desilication during the course of blowing in a bottom blowing converter. Particularly, the blowing up phenomenon has often occurred in case of the operation of a bottom blowing converter without lime powder injection. Therefore, it is eagerly demanded to prevent the initial stage blowing up in a stable operation of a top and bottom blowing converter, of which capacity of lime powder injection for the total amount of oxygen is considerably poorer than the bottom blowing converter.
While, it is commonly known that calcined lime is used in order to promote the dephosphorization of molten steel. It can be expected the same effect in the blowing of calcined fine lime powder into a top and bottom blowing converter through its bottom tuyere and in the blowing of lump-shaped lime into a top and bottom blowing converter through its feed opening similarly to the case of conventional top blowing converter. However, the reaction velocity in the top and bottom blowing converter is increased due to oxygen blown into the bottom of the converter and therefore there is a risk of initial stage blowing up before and after the completion of the above described desiliconization, and it is not advantageous to use lump-shaped lime.
Although the above described blowing of lime powder can decrease the above described risk, the risk can not be completely obviated. Therefore, a method for carrying out a stable operation in a top and bottom blowing converter is required.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a method for preventing advantageously the initial stage blowing up, which would occur at the initial stage of blowing of a molten steel in a top and bottom blowing converter, in order to carry out a stable operation in the converter.
Another object of the present invention is to provide a method capable of removing phosphorus from the molten steel as well as the prevention of the initial stage blowing up.
The inventors have investigated a blowing pattern of lime powder during the blowing, and found out that, when the amount of lime powder to be supplied into a top and bottom blowing converter is controlled depending upon the basicity of slag and the amount of SiO.sub.2 formed in the converter at the initial stage of the blowing, which initial stage is from the beginning of the blowing to the completion of desiliconization, the above described objects can be advantageously attained.
The first aspect of the present invention lies in a method of blowing a molten steel in a top and bottom blowing converter, comprising blowing lime powder into the converter through tuyeres arranged on the bottom thereof according to such a blowing pattern at the initial stage of the blowing, which initial stage is from the beginning of the blowing to the completion of desiliconization, that the lime powder is blown into the converter in an amount satisfying the following formula the converter during the initial stage of the blowing.
The second aspect of the present invention lies in a method, wherein lime powder is blown into the converter according to such a blowing pattern, in addition to the blowing pattern defined in the first aspect, that the lime powder is blown into the
REFERENCES:
patent: 3771998 (1973-11-01), Knuppl
Omori Hisashi
Yamada Hirosuke
Kawasaki Steel Corporation
Rosenberg Peter D.
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