JPH01116018A - Converter steelmaking method - Google Patents

Abstract

PURPOSE:To raise efficiency of blowing operation by charging briquette having the specified sp.gr. together with material mixing one or more kinds of specific material with converter powdery dust containing iron powder from opening part of the converter. CONSTITUTION:The briquette 7 having the sp.gr. between sp.grs. of molten slag 6 and molten steel 5 with pitch series binder is charged into the converter 1 from a hopper 3 through a chute 4 together with the material mixing one or more kinds of coal powder or coke powder with the converter powdery dust and oxygen is blown from an oxygen lance 2 for refining. Then, when the briquette 7 is passed through the slag 6, the briquette 7 is collapsed to fine powder state caused by thermal reaction and reacted with FeO in the slag and generates CO2 or CO and as it is exhausted from the slag as the gas, the slag 7 is killed and foaming can be prevented. By this method, the blowing operation can be executed under good efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a converter steel manufacturing method that prevents slag and molten steel from spewing out during converter blowing.

[Prior Art] In steelmaking operations using a converter, slag containing iron may be ejected from the furnace mouth of the converter during blowing.

Such spouting of slag causes many operational and equipment problems and reduces the yield of steel tapping. Therefore, the following methods have been used to prevent slag and molten steel from spewing out from the converter mouth.

■During blowing, slag is prevented from blowing out by controlling the height of the lance above the molten steel surface in the converter and the flow rate of oxygen sent from the lance.

■If slag eruption occurs, or if it is predicted by a detector such as a probe with a built-in optical fiber scope inserted into the converter, small particles of raw dolomite or Slag eruption is physically prevented by adding a blowout suppressant of sawdust (molded sawdust).

■As mentioned above, when slag eruption occurs or is predicted, coke powder is blown onto the molten steel in the converter using a carrier gas, and the coke powder is used to convert the oxides in the slag into reducing agents. This prevents slag and molten steel from spewing out by reacting with and calming down the molten steel.

<Reference 2 Iron and Steel 1985.8-1045.1046
).

[Problems to be Solved by the Invention] However, the methods (■ to ■) with upper digits have the following problems. ■The control of the lance height and the oxygen flow rate from the lance is greatly influenced by the operator, blowing conditions, etc. Therefore, it is extremely difficult to accurately control the ejection of slag. ■The injection of eruption sedatives such as small grains of raw dolomite or ogalite may have a temporary effect at the time of injection, but it does not last long, and eruptions often occur again.
If the eruption sedative is continuously added at that ε, the amount of heat removed from the molten steel by the eruption sedative increases, resulting in a large amount of heat loss during blowing. Furthermore, the amount of slag increases due to the melting of the blowout suppressant, resulting in a decrease in the yield of 8 steel.

■Blowing coke powder requires special equipment for blowing, which increases equipment costs and running costs.

Furthermore, there is a risk that nitrogen may be mixed into the molten steel due to the carrier gas. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method that can reliably prevent slag and molten steel from spewing out from the furnace mouth during converter blowing.

[Means for Solving the Problems] The converter steel manufacturing method according to the present invention includes a material in which a converter powder dust containing iron is mixed with one or more types of coal powder and coke powder.
The method is characterized in that the material is made into briquettes using a pitch-based binder to have a specific gravity between that of slag and molten steel, and the briquettes are charged from above the converter mouth.

[Function] The converter steel manufacturing method according to the present invention includes a material in which a converter powder dust containing iron is mixed with one or more types of coal powder and coke powder, and a pitch-based binder is added to the material to form a material with a specific gravity between that of slag and molten steel. The briquettes are charged from above the converter mouth, so when the briquettes pass through the slag, the volatile components are instantly volatilized by the heat of the slag, cooling the slag in that area, and at the same time discharging the briquettes. instantly disintegrates into fine powder, reacts with FeO in the slag, and produces CO2.
Or it becomes CO and escapes from the slag as a gas.
Since the slag is calmed down and bubbling can be prevented, slag and molten steel can be prevented from spewing out from the converter mouth.

[Embodiment of the Invention] An embodiment of the invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an embodiment of the present invention. 1 is a converter, 2 is an oxygen lance, 3 is a hopper, 4 is a chute, 5 is a molten steel, 6 is a slag, and 7 is a briquette.

An oxygen lance 2 for blowing oxygen into the hot metal 5 is disposed in an opening at the top of the converter 1 so as to be able to move vertically. A hopper 3 for storing briquettes 7 is disposed above the converter 1, and a chute 4 for charging the briquettes 7 into the converter 1 is disposed below the hopper 3.Operation of this embodiment I will explain about it.

After charging hot metal into the converter 1, burnt lime,
Scale, fluorite, etc. are placed in the hopper at the top of the converter (not shown).
Insert from. Oxygen gas is blown onto the hot metal from oxygen lance 2 to start blowing. At the beginning of blowing, carbon in the hot metal reacts with oxygen to generate carbon monoxide gas, and the hot metal 5 is decarburized. On the other hand, the introduced solvent is dissolved by an exothermic reaction when the hot metal is decarburized and floats as slag 6 on top of the hot metal. This slag 6 absorbs phosphorus, sulfur, etc. of the hot metal, thereby reducing the phosphorus, sulfur, etc. of the hot metal. When FeO increases in the slag 6 due to an imbalance between blown oxygen and carbon in the hot metal during the decarburization reaction during blowing, the slag 6 bubbles and expands to the mouth of the converter 1. If the degree of expansion is rapid, the molten steel 5 and slag 6 during blowing are ejected from the furnace mouth of the converter 1 to the outside of the system. In order to prevent this, a detector inserted into the converter, such as a probe with a built-in optical fiber scope, predicts the ejection of slag, and in response to the signal, a hopper 3 for storing briquettes 7 is installed above the converter 1. A valve (not shown) is opened and the briquettes 7 are introduced into the converter 1 through the chute 4. Then, when the briquettes 7 pass through the slag, the volatile components are instantly vaporized by the heat of the slag. At the same time, the slag 6 is cooled, and at the same time, the briquettes 7 instantly disintegrate into fine powder, react with FeO in the slag 6, become CO2 or CO, and escape from the slag 6, which calms the slag 6 and prevents foaming. , molten steel slags 6 and 5 can be prevented from spewing out from the converter mouth.

The reason why the specific gravity of the briquettes 7 is between that of the slag 6 and the molten steel 5 is that if the briquettes 7 cannot fully react when passing through the slag 6 layer, the briquettes 7 will float on the boundary between the slag 6 and the molten steel 5. This is because the reaction occurs there. Table 1 shows a list of ingredients of coal, coke, converter powder dust, pitch binder, and one example of briquettes for producing briquettes.

Table 1 Particle size of coal, coke, and converter powder dust is 0.05 to 0.
．． 4mm, pitch-based binder is charged at 3-5% of the raw material.
Added. The granulation method is performed using a desk pelletizer. The particle size is 10-70 mm.

FIG. 2 is a graph showing the ratio of converter powder dust to coal or coke (ratio of bulk specific gravity) and the time from when briquettes are introduced into the converter to when the bubbling of slag is prevented. As is clear from this figure, when the ratio of converter powder dust to coal or coke (ratio of bulk specific gravity) is in the range of 2:1 to 3:1 (2.9 to 3.2), slag is removed in the shortest period of time. Can prevent foaming. The ratio of converter powder dust to coal or coke (ratio of bulk specific gravity) is 2
If the brigett is less than 1 (2,9), the reaction occurs only in the upper part of the slag layer, and the ratio of converter powder dust to coal or coke (ratio of bulk specific gravity) is 3 = 1 (3,2) or more. In the case of briquettes, the reaction occurs only at the bottom of the slag layer.The ratio of converter powder dust to coal or coke (ratio of bulk specific gravity) is 2:1 to 3.
:1 (2.9 to 3.2) briquettes are uniformly dispersed in the slag layer and react, so slag bubbling can be prevented in a short period of time. Figure 3 shows the particle size of coal or coke and briquettes. This is a graph showing the time taken from the time the slag is introduced into the converter to the time when the slag is prevented from foaming.As is clear from this figure, when the particle size of the coal or coke in the briquettes is small, the briquettes instantly turn into fine powder in the slag layer. The carbon in the briquettes instantly reacts with the FeO in the slag 6.For this reason, the smaller the particle size of the coal or coke in the briquettes, the better; coal powder briquettes are better than coke powder until the slag foaming is prevented. The reason why the time is shorter is that coal powder briquettes have more volatile content than coke powder, so the briquettes are more likely to disintegrate into fine powder instantly.Also, when the particle size of coal or coke is 0.
If it exceeds 3 mm, it will take more than 20 seconds to prevent the slag from bubbling, and when the briquettes are introduced from above the converter mouth, both the slag and molten steel during blowing will be ejected from the furnace mouth, so the grain size of the coal or coke will increase. is preferably 0.3 mm or less. In other words, the material is a mixture of converter powder dust containing iron and one or more types of coal powder and coke powder, and a pitch-based binder is added to the material so that the specific gravity is between that of slag and molten steel. By making the briquettes into such a shape that the briquettes are introduced from above the converter mouth, both the slag and molten steel during blowing can be prevented from entering the furnace mouth.

[Effects of the Invention] As described above, according to the present invention, by introducing briquettes, it is possible to prevent both slag and molten steel from spewing out from the furnace mouth during blowing, resulting in efficient blowing work. Can be done.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing an embodiment of the present invention. Figure 2 is a diagram showing the ratio of powdered dust in the converter to coal or coke (ratio of bulk specific gravity) and the time from when briquettes are introduced into the converter to when the bubbling of slag is prevented. FIG. 3 is a graph showing the particle size of coal or coke and the time from when briquettes are introduced into the converter to when slag foaming is prevented. 1... Converter, 2... Oxygen lance, 3... Hopper, 4... Chute, 5... Molten steel, 6... Slag,
7...briquettes.

Claims (1)

[Claims] A material made by mixing converter powder dust containing iron with one or more types of coal powder and coke powder is made into briquettes using a pitch-based binder to have a specific gravity between that of slag and molten steel, and the briquettes are then transferred to a converter furnace. A converter steel manufacturing method characterized by charging from the top.