JPS6217112A - Method for coating inner wall of converter with slag - Google Patents

Abstract

PURPOSE:To inhibit the oxidation of a refractory lining forming the inner wall of a converter by splashing molten slag remaining on the bottom of the converter after the tapping of steel on the inner wall of the converter with an inert or reducing gas spouted from a main lance and by substituting with the inert or reducing gas for the atmosphere in the converter. CONSTITUTION:Molten slag remaining on the bottom of a converter for manufacturing steel after the tapping of steel is splashed on the inner wall of the converter with an inert or reducing gas spouted from the tip of a main lance to coat the inner wall with the molten slag. At the same time, the inert or reducing gas is substituted for the atmosphere in the converter.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a slag coating method for coating a refractory lining material forming the inner wall of a steelmaking converter with residual molten slag after tapping.

<Prior art> In general, converters for steelmaking are divided into top-blown converters, top-bottom blowing converters, etc. depending on the method of oxygen and gas injection.For example, in top-bottom blowing converters, hot metal or scrap iron is After inputting the main raw materials, slag-forming agents, and auxiliary materials such as limestone and light calcined dolomite, which serve as solvents, oxygen is blown from above through the main lance, and inert gas etc. is blown from below through the main lance. While burning the carbon and silicon in the hot metal and raising the temperature of the main raw material,
Molten steel is produced by generating molten slag from auxiliary raw materials and performing decarburization and other refining processes.

Magnesia carbon bricks (main components: MgO+C) and magnesia dolomite carbon bricks (main components: MgO+CaO+C), which contain carbon in the form of graphite and tar, are used for the refractory lining material that forms the inner walls of the converter. . Since this refractory lining material is used in a harsh environment where it is constantly exposed to hot metal and molten slag at approximately 1,700°C or higher and a high-temperature oxygen atmosphere inside the furnace, the carbon contained in it is lost by oxidation and the magnesia dissolves into the slag. Significant erosion and damage is caused by That is, (a) graphite in the refractory is oxidized and lost by oxygen in a high-temperature atmosphere, (b) graphite in the refractory is lost by oxidation by oxides (especially Fed) in the slab, and (c) graphite in the refractory is lost by oxidation due to oxygen in the high temperature atmosphere. After the reactions in ) and (b), the refractories are worn out due to factors such as the magnesia (MgO) aggregate being eroded by the slag, shortening its lifespan. Such a shortened lifespan of refractories not only results in frequent repairs to the inner walls accompanied by shutdown of the converter, but also increases the cost of refractories and construction costs, which account for a large proportion of the operating costs of the converter.

Therefore, in order to protect and extend the life of refractories, attention has been focused on the viscosity of slabs with high basicity (CaO/SiO2≧3). The body 21 is tilted back and forth by approximately 90 degrees as shown by the arrow around the trunnion shaft 21a, and the molten slag 22 remaining on the furnace bottom 21b from the previous charging is made to flow along the inner wall, and the molten slag 22 is Refractory surfaces 21e, 21e
The above (a)
Measures were taken to prevent wear and tear. However, as long as this method is used, as shown in FIG. 3(c), although the refractory surfaces 21e and 21e' on the charging side and the exit side are coated to prevent wear and tear, the molten slag cannot flow. The refractory surfaces 21f and 21r' on the trunnion shaft side are not coated at all and suffer significant wear. Therefore, this part must be repaired by spraying an expensive spraying material, which causes the same cost problems as mentioned above.

Therefore, recently, a method called slag blow coating has been proposed to solve the above problem. In this method, as shown in Fig. 4, after tapping, the furnace body 21 is laid down horizontally, and the base end is rotatably supported on a cart (not shown) in the residual molten slag 22 accumulated at the bottom of the furnace body 21. The tip of the nozzle vibe 23 is immersed, and compressed air (see arrow in the figure) is injected from the tip to blow the molten slag onto the refractory surface 21r on the trunnion shaft side.
It scatters toward the surface, where it adheres and solidifies, coating the surface.

<Problems to be Solved by the Invention> However, the above-mentioned conventional slag blow coating method requires specialized equipment for slag blowing, such as a cart and nozzle pipe 23, and a staff of q to 2 people to operate it on site.
It has the disadvantage that the work such as visual inspection inside the furnace and moving the nozzle pipe in the depth direction of the furnace by driving a trolley becomes complicated, and in the case of an operation with short tapping intervals, it is impossible to perform it for each charge due to time constraints. become. In addition, since the tip of the nozzle vibrator 23 is immersed in the slag 22, the nozzle may become clogged due to slag adhesion, and it is difficult to control the direction of slag scattering, making it difficult to obtain a uniform coating over the circumferential surface of the inner wall. There is a drawback. Furthermore, since compressed air is used for blowing gas, the inside of the furnace is rapidly replaced with an oxidizing atmosphere, which promotes oxidation on the surface of refractories with insufficient slag coating and shortens the life of the refractories. It has the big drawback of shrinking.

Therefore, the purpose of the present invention is to disperse the molten slag remaining at the bottom of the furnace evenly with a simple operation without having to topple the furnace, without requiring special equipment for slag blowing or on-site workers, and to use this slag to blow the inner walls of the furnace. It coats the entire surface of the refractory, maintains the atmosphere inside the furnace inert or reducing, protects the refractory,
It is an object of the present invention to provide a method for coating the inner wall of a converter with slag, which can extend the life of a converter.

<Means for Solving the Problems> In order to achieve the above object, the slag coating method of the present invention is applied to a converter for making steel by removing the molten slag remaining at the bottom of the converter from the tip of the main lance after tapping the steel. The method is characterized in that the inert gas or reducing gas is ejected and splashed, and is attached to the inner wall of the converter to cover the inner wall surface, and the inside of the converter is replaced with the above-mentioned inert gas or reducing gas. .

Effect〉 The highly fluid molten slab remaining at the bottom of the converter after tapping (1
400 to 15008C) are blown up or scattered upward along the inner wall surface of the converter in a radial manner centered around the main lance by injecting inert gas or reducing gas from the tip of the main lance, while The inert gas or reducing gas that is released quickly displaces the air in the existing furnace by displacing it. The above-mentioned molten slab, which is blown up and scattered almost uniformly on the inner wall of the converter, is then exposed to the furnace atmosphere (inert gas or reducing gas).
It is cooled and solidified on the refractory surface that forms the inner wall, forming a uniform coating. This slag coating prevents oxidation and wear of the refractory.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

In FIG. 1, 1 is a converter that is tilted upright around a trunnion shaft 1a after tapping, 2 is molten slag remaining on the bottom 1b of the converter from the previous charging, and 3 is driven up and down by a winch (not shown). A main lance is inserted vertically into the center of the converter l from above, 4 is an oxygen pipe that supplies oxygen for blowing to this main lance 3, 5 is an electric valve installed in this oxygen pipe, 6 is this electric Oxygen piping 4 downstream of valve 5
an inert gas pipe connected to and equipped with an electric valve 7, 8
a, 8b are a cooling water supply pipe and a cooling water discharge pipe connected to the main lance 3, respectively, and 9 is the electrically operated valve 5, 7.
This is a control room where the main lance lifting winch, etc. are remotely controlled via signal lines.

As shown in FIG. 2, the main lance 3 is coated on the outside with a castable refractory 10, and on the inside there are a semi-annular water injection pipe 11a connected to the cooling water supply pipe 8a, and a cooling water discharge pipe 8b. and a condensate pipe 11b which is connected to the outgoing water pipe 11a at the tip of the main lance, and an oxygen supply pipe 1 which is connected to the oxygen pipe 4 in the center.
2 is extended.

Using the above-mentioned apparatus, slag coating is performed on the inner wall of the converter according to the following procedure.

First, when refining hot metal in a converter (processing name steel weight: 8 tons), the main lance 3 is
The tip is held at a height of 1 to 3 m above the hot metal surface by the winch's lifting and lowering drive, and the electric valve 5 is opened (arrow 0.) to generate 240 Nm3/min from the nozzle at the tip of the main lance.
Oxygen gas is injected at a certain flow rate, and blowing is performed using this oxygen gas. Note that at this time, the electric valve 7 is closed, and Ar gas as an inert gas is not supplied to the main lance 3. Next, when the two-legged blowing is completed, the electric valve 5 is closed by remote control from the control room 9 to stop the supply of oxygen gas, and the tip of the main lance is raised above the furnace mouth 1c by the winch. is,
Subsequently, the converter 1 is tilted approximately 90 degrees rearward around the trunnion axis +a in a direction perpendicular to the plane of the paper in FIG. ).

When tapping is finished, the converter I is tilted again to return to its original upright position, and the winch is lowered to move the tip of the main lance 3 away from the molten slag from the previous charge remaining in the furnace bottom 1b (
2) Approach the surface to a height of 30 to 50 cm, then open the electric valve 7 by remote control (arrow Ar)
50~134 r gas from the nozzle at the tip of the main lance
It is injected for about 0.2 to 2 minutes at a flow rate of Nm'/min. The molten slag, which is highly fluid at a high temperature (1,400 to 500°C), is radially distributed approximately evenly around the main lance 3 by Ar gas that is blown into the center from above at high speed as shown by the arrows in the figure. As shown by the broken line in the middle, it is blown upward and scattered along the inner wall of the converter. On the other hand, the injected Ar gas rapidly expels the air in the furnace as shown by the arrow in the figure and replaces it with air. The molten slag, which is blown up and scattered almost evenly on the inner wall surface of the converter, comes into contact with the atmosphere inside the furnace which has become Ar gas over a wide area, and is cooled to form the magnenocarbonite bricks that constitute the inner wall. It solidifies on the surface of the refractory material 1e made of carbonaceous bricks, magnesia dolomite, etc., and forms a uniform coating.

Normally, approximately 20 to 80 kg of slag is used per ton of crude steel, so in an 80 ton converter, the remaining m slag is 1.6 to 6.
It will be 4 tons. Of this, about 10% is emitted by scattering to the outside from the furnace mouth during blowing (so-called slopping), about 10 to 20% is emitted by adjusting the composition of the tapped surface, and a few percent is received during tapping. Discharged into a steel pot. Therefore, the amount of slag remaining at the bottom of the converter after copper is approximately 1 to 5 tons. This residual slab was scattered as described above, and as a result, the thickness of the slag adhering to the refractory surface of the converter inner wall was investigated over the entire inner wall using a laser beam furnace wall residual thickness measuring device.

According to this measurement, approximately 50 to 60
It was confirmed that a slag coating was formed with a thickness of mm.

In the above embodiment, the converter is stood upright, and Ar gas is injected from the tip of the main lance (not immersed in the slag) inserted vertically into the center of the bottom of the converter from above to blow the slag.
In addition to obtaining uniform slag coverage over the circumferential surface of the inner wall, the blow nozzle position can be easily and accurately controlled using an existing winch, and nozzle clogging due to slag adhesion does not occur. Furthermore, since the lifting and lowering of the main lance, the opening and closing of electric valves, the tilting of the converter, etc. are centrally controlled remotely from the control room 9, there is no need for specialized equipment for slag blowing or on-site workers. efficiency will also increase. If the effect of the slag coating according to this embodiment is shown in concrete numerical values as an example, the amount of refractory spraying material used for repairing inner walls can be reduced by 50 to 80 kg per 1 charge, and the service life of the converter can be reduced by 50 to 80 kg. It was possible to extend the charge from the conventional 1400 charge to 1600 charge.

Although Ar was used as the blow gas in the above embodiments, other inert gases such as He and N2 or reducing gases such as CO may be used instead. Further, a lid may be provided at the furnace mouth to prevent the Ar gas that replaced the air in the furnace from escaping during the furnace shutdown, thereby making it possible to further completely prevent oxidation of the refractory surface.

<Effects of the Invention> As is clear from the above explanation, the method for coating the inner wall of a converter with slag according to the present invention removes the molten slag remaining at the bottom of the converter after tapping by inert gas or reducing gas from the tip of the main lance. The inert gas or reducing gas is ejected and splashed and attached to the inner wall of the converter to coat the inner wall surface, and the inside of the converter is replaced with the above-mentioned inert gas or reducing gas.
With simple equipment, the combination of the uniform coating described above and the inert or reducing atmosphere inside the furnace can prevent oxidation and wear of the refractory lining material forming the inner wall, and the coating can also prevent slag formation at the beginning of the next blowing process. Protecting the refractory lining against previous oxidizing atmospheres and low basicity slag reduces the frequency of internal wall repairs, thus reducing converter maintenance costs and significantly extending the service life of the converter. It is possible to achieve remarkable effects.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing one embodiment of the present invention, and Fig. 2 is a schematic diagram showing an embodiment of the present invention.
■-■ Cross-sectional view of the figure, Figure 3 (a), (b), (c)
4 is a cross-sectional view of a converter, and FIG. 4 is a diagram showing a conventional slag coating method. ! ... Converter, Ib... Converter bottom, le... Refractory,
2... Molten slag, 3... Main lance, 4...
Oxygen piping, 6...Inert gas piping, 9...Control room.

Claims (2)

[Claims] (1) In a converter for steelmaking, the molten slag remaining at the bottom of the converter after tapping is splashed by inert gas or reducing gas jetted from the tip of the main lance, and the slag is deposited on the inner wall of the converter. A slag for the inner wall of a converter, which coats the inner wall surface and replaces the inside of the converter with the above-mentioned inert gas or reducing gas to prevent oxidation of the refractory lining material forming the inner wall of the converter. Coating method. (2) In the method for slag coating an inner wall of a converter according to claim 1, the inert gas or reducing gas is ejected from a vertical main lance with the converter standing upright. A slag coating method for the inner wall of a converter.