JPS6156223A - Method for coating converter with slag - Google Patents

Abstract

PURPOSE:To increase the amount of slag stuck to a converter by coating and to prolong the life of the converter by adding a modifier to slag remaining in the converter and coating the surface of the inner wall of the converter with the slag by means of a lance for blowing oxygen. CONSTITUTION:A modifier is added to slag 3 remaining in a top or top and bottom blowing converter 1 after finishing refining, and air or a slow reactive gas is blown on the modified slag through a top blowing lance 4 to mix and scatter the slag. The scattered slag is solidified by cooling and stuck to the surface of the peripheral wall of the converter 1. Thus, the coating time is shortened, the amount of slag stuck is increased, and the life of the converter is prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a slag coating method for protecting the refractory lining of a converter.

Conventional technology Generally, when molten steel is produced in a top-blown or bottom-blown converter, the refractory lining of the converter suffers from erosion due to reaction with slag, wear caused by the molten steel, or spalling due to thermal changes. It is well known that it is subject to considerable wear and tear due to

This wear and tear of refractories naturally shortens the lifespan of the converter, increases the cost of refractories, and requires a great deal of time and effort for repair and construction. This has led to economic losses such as a large decline in

Therefore, a method is usually used to prolong the life of the converter by projecting or spraying repair refractories onto locally worn parts of the refractory lining of the converter used for refining.

However, the method of projecting or spraying repair refractories uses expensive refractories and has problems such as extremely low repair efficiency for the repaired surface and a long time required for repair. ing.

Therefore, in order to improve the problems of the conventional repair methods as described above, for example, as shown in Japanese Patent Application Laid-Open No. 57-18111, the gas remaining in the furnace is A method has been proposed (hereinafter simply referred to as the bottom blowing method) in which the slag is reformed and then a gaseous fluid is blown through the tuyere to coat the furnace wall with the slag.

Problems to be Solved by the Invention This bottom blowing method can be expected to be quite effective in extending the life of the furnace by coating the furnace wall with slag after refining. [Due to the need to prevent clogging (1), a constant high flow rate must be ensured, and the coating range due to flying slag is limited no matter how the furnace is shaken.

Furthermore, since these bottom-blown slats are designed in a constant flow region to simplify operation, the above-mentioned phenomenon is more restricted. In addition, if the φ of the slag remaining in the converter is small, the gas blown from the bottom blowhole will cause blow-by.
Even if the furnace is rocked, this phenomenon cannot be suppressed, and as a result, slag coating cannot be achieved sufficiently, and the blade [
It is difficult to operate the gas flow with a mouse, move the furnace, etc., and has drawbacks such as the fact that it takes a long time to coat one coat.

The present invention improves the drawbacks of the conventional slag coating as described above, and has a wide coating range due to slag scattering.■ It does not require any shaking of the furnace, and it can reduce the amount of slag remaining in the converter. However, it is possible to easily and effectively coat the desired area in a short period of time.

Means for Solving the Problems The present invention is characterized in that after adding a modifier to the remaining slag, the modifier is added to the remaining slag by blowing a single wave of air or slow-reacting gas through a top blowing lance. This is an extremely excellent slag coating method in which modified slag is mixed, scattered, and allowed to adhere to the inner wall surface while being cooled.

Function The slag coating method for a converter according to the present invention will be described below.

The present inventors have conducted intensive studies on a method of protecting the inner wall of the refining core and extending the life of the refining core by slag coating the inner wall surface of a top-blown or -L bottom-blown converter (hereinafter simply referred to as a converter). As a result of experiments, it was found that the slag coating on the inner wall surface of the converter can be applied extremely effectively using the oxygen injection lance conventionally used for refining molten iron.

That is, the present invention uses a lance of a converter, passes air or a slow-reacting gas through the lance, and adjusts the height of the lance from the bottom of the furnace or increases or decreases the amount of blown gas depending on the damaged area of the inner wall surface. slag coating, or a combination of both. This coating is applied by blowing the modified slag loosely onto almost the entire inner wall of the converter, or around the slag line or trunnion, which is most susceptible to wear and tear), and by blowing the molten and softened modified slag through a lance. It is cooled by the released gas and allowed to coagulate.

As the residual slag, the entire amount generated during refining or a part of the slag remaining in the furnace after slag removal is used.

Modified slag is used by adding a modifier to residual slag.

As a method of adding the modifier, for example, Mg
By adding O-containing refractory scrap, dolomite, MgO clinker, etc., the MgO content is 5% or more and P.05
The slag is defined as a low phosphorous, high Mg[l-containing slag with a content of 1.0%.

This low phosphorus and high MgO content slag can promote the reaction between molten steel and slag during refining, suppress the erosion of refractories by the high MgO slag, and suppress phosphorus contamination of the subsequent refining charge. By adding, for example, raw dolomite or brick scraps as a modifier to the low-phosphorous, high-MgO slag remaining in the furnace after steel tapping, a refractory layer consisting of slag adhered to the inner surface of the furnace wall is created. This is preferable because it can improve the fire resistance of the material as much as possible.

Furthermore, the present invention adds MgO-containing glass slag and raw dolomite to the remaining slag in the furnace obtained by ordinary refining, or these alone, or other materials such as Ca.
A modifier having a fire resistance such as O, ZrO2, etc. may be added.

Next, the slag coating method according to the present invention will be described in further detail based on an embodiment shown in the drawings.

FIG. 1 shows an elevational sectional view of the slag coating of a one-tower blown converter according to the invention, and FIG. 2 shows an elevational sectional view of the slag coating of a top-bottom blown converter.

In the figure, a refractory 2 lined in a converter 1 gradually expands as the slag line portion A or trunnion portion B, etc. are worn out due to refining conditions, heating/cooling, slag composition, etc. In order to prevent the expansion of this wear and tear and to repair the worn parts, for example, in a +70T furnace, brick scraps or raw dolomite, etc., are added as a modifier to the remaining slag3, which is about the same as the entire amount or IOT, although it differs slightly depending on the furnace. Added.

In this state, the pulp 5a of the oxygen pipe 5 connected to the flexible hose 4a at the base end of the secondary lance 4 is closed, and the valve 6a of the air or slow-reactive gas pipe 6 is closed.
is opened, and the air or slow-reacting gas is blown onto the remaining slab through a medium hole or a multi-hole lance hole (not shown) drilled at the tip of the lance 4. Air or a slow-reacting gas is supplied via lance 4 to the furnace, depending on the furnace stand, for example, 4000 N in” / in a +70T furnace.
By spraying Hr~30,000 Nm/Hr, the remaining slag 3 is thoroughly mixed with the added modifier and scattered one after another, and the remaining slag 3 is sprayed onto the furnace inner wall surface 7 while increasing its stickiness due to cooling by the blown gas. It will definitely adhere when it reaches the inner wall surface 7.

In addition, in order to locally coat the slag line part A or the trunnion part B, etc., it is necessary to raise the height of the lance 4 from the bottom inner wall surface 9 of the converter l so that it is at the position 8 indicated by the solid line. Alternatively, by reducing the amount of gas supplied to the lance 4, a discharge with the solid line arrow in FIG. Furthermore, the lance 4 is moved to the furnace bottom inner wall surface 9 as shown in the dotted line position lO.
If the I/runion part B is located close to or the amount of blown gas is increased, the I/runion part B is repaired by the formation of a jet with the dotted line arrow as the main flow.

In addition, as shown in FIG. 2, air or slow-reacting gas is supplied in order to prevent the remaining slag 3 in the furnace from being inserted into the tuyere 11, which is a single tube or multiple tubes provided at the bottom of the furnace. Slag coating is performed in the same manner as in the above-mentioned top blowing converter. At this time, the gas supplied from the slat +1 promotes the mixing of the remaining slag 3 and the added modifier, so that the refractoriness of the adhered slag is greatly improved.

Note that the slow-reactive gases used for blowing include inert gases such as Ar, N2. and CO2, and a mixture of these and less than 40% oxygen as necessary.Especially when the remaining slag 3 is poorly melted and close to condensation, or when it is desired to fuse the modifier, By mixing oxygen in the blown gas, it is possible to maintain the molten state of the remaining slag 3 and promote the fusion of the modifier, but if the oxygen content exceeds 40%, projectiles cooling is inhibited.

Example 17 The slag coating of the present invention was carried out using a 70T blowing converter according to the method shown in FIG. The implementation conditions are shown in Table-1.

Among the slag coating examples (Table 1) in this magazine, No.
1.2 is a coating method in which 3 T/ch of MgO-containing brick scraps and 4 T/ch of dolomite (chemical dolomite) are added during refining, and 2 T/ch of brick scraps and raw dolomite 1 T are added to the slag remaining in the furnace after tapping. Excellent coatings were obtained in all cases. Also, No. 3.4 is ordinary refined slag, brick scraps 3 T/ch and raw dolomite I T/ch.
The same amount of coating was obtained with the addition of

Next, using a 170T top-bottom blowing converter, a comparison was made between a conventional method using a bottom tuyere and the method of the present invention shown in FIG.

The results are shown in Table-2.

As is clear from Table 2 of Effects of the Invention, compared to the conventional method, the method of the present invention shortens the slag coating treatment time, and also greatly improves the coating adhesion, resulting in a reduction in refractory costs by extending the life of the furnace. Significant savings were achieved. Furthermore, when the low phosphorous high MgO slag was used, no phosphorus contamination was observed in the subsequent charge.

ll Table-2

[Brief explanation of the drawing]

FIG. 1 shows an elevational cross-sectional view of the slag coating method for an I-blown converter, and FIG. 2 shows a zeta-plane cross-sectional view of the slag coating method for an L-bottom blowing converter.

Claims (1)

[Claims] In a method of coating the inner wall surface of the converter with the remaining slag after the completion of refining in a top-blown or top-bottom blown converter, after adding a modifier to the remaining slag, air or slow A slag coating method for a converter, characterized in that the reformed slag is mixed and scattered by a spray flow of a reactive gas, and is allowed to adhere to the peripheral wall surface of the converter while being cooled.