Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1982-05-17
1983-12-13
Rosenberg, Peter D.
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
75 59, C21C 532, C21C 534
Patent
active
044203349
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to top-and-bottom blown converter steel making of the type wherein an oxidizing gas such as pure oxygen is blown onto the surface of molten iron in the converter through a lance disposed above the molten iron surface while an oxidizing or inert gas is blown into the molten steel through a tuyere arranged at the bottom of the converter, and more particularly, to a method for changing the kind of the bottom-blowing gas in accordance with a variation in the pressure of the bottom-blowing gas during refining in a controlled manner.
1. Background Art
In order to enhance the agitation of molten iron in an oxygen top-blown converter, i.e., LD converter an a method was developed for blowing an oxidizing or inert gas into the molten iron through a tuyere provided at the bottom for bottom of the converter blowing while blowing an oxidizing gas onto the molten iron surface through a lance. Since such top-and-bottom blown converter steel making affords an improved agitation effect as compared with the top-blown converter steel making, the concentration of iron (T.Fe) in the slag is prevented from increasing during a low carbon period in the final stage of blowing as in top-blown converters, and an outstanding improvement is thus achieved in the yield of iron over top-blown converters.
When an inert gas such as argon gas is used as the bottom-blowing gas in the above-described top-and-bottom blown converter, iron will coagulate at and adhere to the tip of the tuyere because of cooling due to the sensible heat of the inert gas so that the nozzle of the tuyere is gradually blocked, which leads to the problem that the flow rate of the gas is reduced to below that required for the agitation of molten iron. Specifically, the above-described nozzle blockage becomes more severe with time and reduces the flow rate of the bottom-blowing gas in the final stage of blowing which particularly requires agitation to improve the iron yield, and as a result, in some cases, the effect of preventing the increase of the iron value concentration of a slag by bottom blowing to improve the iron yield is not achieved at all.
On the other hand, when an oxidizing gas is used as the bottom-blowing gas, the tuyere tip is heated to elevated temperatures due to the exothermic reaction of the oxidizing gas with carbon, silicon, iron or the like in the molten iron, which leads to the problem that the tuyere is melted off. This problem could be overcome by using a bottom-blowing tuyere having a double pipe structure as in the bottom-blown converter (oxygen bottom-blown converter, Q-BOP) in which an oxidizing gas is blown into the inner pipe and a gas for cooling the tuyere, for example, a hydrocarbon gas, is introduced into the passage between the outer and inner pipes, although this leads to the problem that not only the cost of the tuyere, but also the total amount of gas used and hence, the operating cost are increased.
It is, therefore, an object of this invention to overcome both the above-described problems of nozzle blockage and tuyere melt-off without using a double-pipe tuyere, and to achieve an improvement in the iron yield attributable to the enhanced agitation in the top-and-bottom blown converter while avoiding any increase in the tuyere cost and gas use.
DISCLOSURE OF INVENTION
The method for controlling the bottom-blowing gas in top-and-bottom blown converter steel making according to this invention comprises detecting the pressure of the gas supplied to the bottom-blowing tuyere, changing the gas supplied to the bottom-blowing tuyere to an oxidizing gas containing at least 60% of oxygen gas when the pressure of the inert gas rises and reaches the upper limit of a predetermined pressure range during the supply of the inert gas to the bottom-blowing tuyere, and changing the gas supplied to the bottom-blowing tuyere to the inert gas when the pressure of the oxidizing gas drops and reaches the lower limit of said predetermined pressure range during the supply of the oxidizing gas to
REFERENCES:
patent: 3046107 (1962-07-01), Nelson
patent: 3854932 (1974-12-01), Bishop
patent: 4280838 (1981-07-01), Masukawa
patent: 4334921 (1982-06-01), Herai
Kyoji Nakanishi
Tsutomu Nozaki
Yoshiei Kato
Kawasaki Steel Corporation
Rosenberg Peter D.
LandOfFree
Method for controlling the bottom-blowing gas in top-and-bottom does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for controlling the bottom-blowing gas in top-and-bottom , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for controlling the bottom-blowing gas in top-and-bottom will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-803182