JP2000313912A - Slag coating method in converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slag coating method excellent in durability in a top- bottom combined-blown converter. SOLUTION: This slag coating method on a lining refractory surface in the converter is executed by injecting gas from a top-blown lance and a tuyere at the furnace bottom part to the residual slag in the furnace after tapping steel in the top-bottom combined-blown converter. In the case of being >15% iron oxide concn. in the slag and <=200 mm slag thickness, as a means 1, the slag is not discharged from the converter and under state of staying the slag, the following blowing is executed and after making >=200 mm of the slag thickness, the slag splash coating is executed. As a means 2, after adding a material satisfying the following condition from the upper part of the converter or the top-blown lance at 2-10 wt.% to 100% of the slag, the slag splash coating is executed. (1) The m.p. is >=1,600 deg.C, and (2) in the constitution of grain size, the grain size of <=1 mm is contained at >=30%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slag coating method for suppressing abrasion of a refractory lining of a molten metal reactor, particularly a converter.

[0002]

2. Description of the Related Art There is slag coating as a technique for suppressing the wear of refractories lining a top and bottom blown converter. this is,
By attaching the residual slag in the furnace after tapping to the lining refractory and forming a coating layer on the lining refractory surface,
Suppression of erosion of lining refractory by direct contact between slag and lining refractory during blowing, and suppression of exfoliation loss of lining refractory due to thermal stress destruction by reducing generated thermal stress It is.

As this means, Japanese Patent Application Laid-Open No. 59-93816 is disclosed.
As a technique proposed in Japanese Patent Application Laid-Open Publication No. H10-157, a gas is blown from a bottom-blowing tuyere into residual slag in a furnace after tapping, and the slag is blown off in a splash shape to coat a lining refractory surface with a bottom-blow splash. There is a coating method. This bottom-blow splash coating method has a problem in that, when the slag has high iron oxide concentration and low viscosity in the slag remaining in the furnace after tapping, the coating property on the refractory lining surface is poor. there were. This is because if the viscosity of the slag is low, the gas blown from the tuyere through the bottom blows through the residual slag in the furnace, and the slag does not scatter in a splash shape.

As a means of slag reforming to increase the viscosity of the slag in order to prevent gas from flowing out from the bottom blowing tuyere, a thermoplastic refractory composition is added to the slag proposed in JP-A-9-316522. Slag reforming and JP-A-9-
There is slag reforming in which a material accompanying an endothermic decomposition reaction is added to slag proposed in Japanese Patent Publication No. 209022 to cool the slag and lower the temperature of the slag.

Further, as a means for efficiently performing slag coating, residual slag in a furnace after tapping as proposed in JP-A-61-56223 and JP-A-62-17112 is applied to a bottom-blowing tuyere. There is an upper bottom spray coating method in which gas is blown from an upper blowing lance while blowing gas to blow slag in a splash shape and coat the surface of the refractory lining.

[0006]

However, if the slag remaining in the furnace is thin and the viscosity of the slag is low in the state where the converter is upright after tapping, the upper There was a case where a phenomenon that satisfactory slag coating property could not be obtained only by performing the spray coating method. In such a case, a thermoplastic refractory composition or a material accompanied by an endothermic decomposition reaction is added to the slag to perform slag reforming. The composition and the material accompanying the endothermic decomposition reaction are melted into the slag, and the effect of improving the viscosity of the slag is not exhibited. As a result, there is a problem that sufficient slag coating properties cannot be obtained.

[0007] It is an object of the present invention to provide a slag coating method having excellent coating properties regardless of the state of slag remaining in the furnace after tapping.

[0008]

Means for Solving the Problems The present inventors evaluated the effect of slag condition on slag coating property on the surface of a refractory lining by a top and bottom spray coating method. The result was obtained.

FIG. 1 shows the relationship between the slag state determined by the iron oxide concentration in the slag remaining in the furnace after tapping and the slag thickness, and the coating properties in the top and bottom spray coating. . Top and bottom spray splash-
Coating properties in taping include tapping side, charging side,
The degree of adhesion of the slag to the furnace wall in the four directions on both sides of the trunnion was evaluated by scoring by visual judgment as shown below.

[0010] The brick joints are completely covered by slag: 3 points. The brick joints are half covered by slag: 2 points. The brick joints are not covered at all by the slag: 1 point. The evaluation was made based on the total score of the degree of adhesion of each slag to the furnace wall, and the higher the score, the better the slag coating property.

[0011] From this, the iron oxide concentration in the slag is 15
%, And when the slag thickness was 200 mm or less, the coating property was found to be reduced. On the other hand, even if the iron oxide concentration in the slag exceeds 15%, the coating property is excellent if the slag thickness exceeds 200 mm, and if the iron oxide concentration in the slag is 15% or less, the coating property does not depend on the slag thickness. Turned out to be excellent.

In the top and bottom spray coating, the iron oxide concentration in the slag remaining in the furnace after tapping is 1
If the slag thickness is more than 200 mm even if it exceeds 5%, the coating property is excellent because the gas from the upper blowing lance which is the driving force of slag splash when the gas is blown to the slag from the upper blowing lance from the upper part of the converter. This is because the depth of the depression in the slag bath surface generated when the gas is sprayed on the slag bath surface is sufficiently ensured. In addition, the iron oxide concentration in the slag is 15
% Or less does not depend on the slag thickness, and the coating properties are excellent because the viscosity of the slag is high and the gas blown from the furnace bottom tuyere does not blow through the slag, so the slag scatters in a splash shape. is there.

That is, the iron oxide concentration in the slag is 15
% And the slag thickness is 200 mm or less, the next blasting is performed while the slag remains in the furnace without discharging from the converter, and the thickness of the residual slag in the furnace after the next tapping More than 200 mm, or if the viscosity of the slag can be increased to be equal to or higher than the viscosity of the slag having an iron oxide concentration of 15% or less, there is a possibility that excellent coating properties can be imparted. I got the knowledge that there is.

The present invention has been made based on the above findings. Means 1 is an upper-bottom blow converter for blowing molten steel by blowing oxygen from the upper and lower portions of the converter. In the slag coating method for spraying gas from the upper blowing lance from the upper part of the converter and the tuyere tuyere from the lower part of the converter to scatter the slag and coat the surface of the refractory lining of the converter, When the residual slag in the furnace after the steel has an iron oxide concentration of more than 15% and the slag thickness is 200 mm or less, the next blowing is performed while the slag is not discharged from the converter and remains in the furnace. A slag coating method, wherein the slag splash coating is performed after the thickness of residual slag in the furnace after the next tapping exceeds 200 mm.

Further, means 2 is an upper-bottom blow converter for blowing molten steel by blowing oxygen from the upper and lower parts of the converter. Gas is blown from the lance and the converter bottom tuyere,
In the slag coating method in which the slag is scattered and the surface of the converter lining is coated with refractory, the slag remaining in the furnace after the converter tapping has an iron oxide concentration of more than 15% and a slag thickness of 200 mm. In the case of the following, the material satisfying the following conditions (1) and (2) is supplied from the upper part of the converter or the upper blowing lance to the slag 100 wt.
The slag coating method is characterized in that slag splash coating is performed after adding 2 to 10% by weight of the slag. (1) The melting point is 1600 ° C. or higher. (2) 30% or more of a particle size of 1 mm or less in the particle size configuration.

The converter to which the present invention can be applied is MgO
It is also possible to use a refractory lining made of any of -C, MgO-CaO-C, and MgO-Cr2O3.

The gas blown into the residual slag in the furnace after tapping from the upper blowing lance from the upper part of the converter and the furnace bottom is as follows:
Any of N2, Ar, He, CO and CO2 can be used.

While blowing gas to the residual slag in the furnace after tapping from the upper blowing lance and the furnace bottom from the upper part of the converter,
The addition of the material from the upper part of the converter or the upper blowing lance is for improving the viscosity of the slag. The material added to the residual slag in the furnace after tapping is suspended and stably present in the slag melt, thereby increasing the solid phase ratio in the slag melt, thereby increasing the viscosity of the slag melt. .

In order for the material to be suspended and stably present in the residual slag in the furnace, it is desirable that its melting point be 1600 ° C. or more and that its particle size composition contain 30% or more of a particle size of 1 mm or less.

If the melting point of the material is lower than 1600 ° C., the material added to the residual slag in the furnace is melted, and the effect of improving the viscosity of the slag melt is not exhibited. When the particle size of 1 mm or less in the particle size composition of the material is less than 30%, the effect of increasing the solid fraction in the slag melt is not sufficient because the content of the refractory material suspended in the slag melt is low. This is because the viscosity of the slag melt cannot be increased.

The material of the present invention includes quicklime, limestone,
Light burnt dolomite, raw dolomite, magnesite, blue
Either site or converter slag can be used.

As a means for adding the material to the residual slag in the furnace, there is a method of charging the residual slag in the furnace from above the converter when blowing gas from the upper blowing lance and the bottom of the furnace. Further, in order to efficiently suspend the material in the residual slag in the furnace, there is a method of blowing the material together with the jet gas from the upper blowing lance.

The amount of material added was set to 100 wt.
% Is set to 2 to 10% by weight because the slag melt is excellent in coating property at the time of top and bottom coating by increasing viscosity. If the added amount of the material is less than 2 wt%, the content of the material suspended in the slag melt is low, so the effect of increasing the solid phase ratio in the slag melt is not sufficient, and the viscosity of the slag melt is increased. This is because the film cannot be coated and the coating property is poor. On the other hand, if the added amount of the material exceeds 10 wt%, the amount of the added material is too large relative to the amount of the residual slag in the furnace, which causes a phenomenon of solidifying the slag, resulting in poor coating properties.

[0024]

Embodiments of the present invention will be described below. MgO: 80 wt%, C: 20 wt% MgO-C refractory lining, capacity 340 t top and bottom blown converter to blow hot metal into molten steel of a predetermined component, and this molten steel from the converter outlet Tapping. After tapping, the slag remaining in the converter is sampled, and the sampled slag is subjected to X-ray fluorescence analysis to measure the iron oxide concentration in the slag (the slag analysis may be performed by a method other than X-ray fluorescence). .

When the iron oxide concentration exceeds 15%,
If the thickness of the residual slag in the converter calculated from the amount of slag obtained from the auxiliary material used during blowing is not more than 200 mm, any one of the following methods is adopted. The next blowing is performed while the residual slag in the furnace remains in the furnace without being discharged from the converter. The top and bottom blown slag splash coating is performed on the slag remaining in the furnace after the completion of the next blowing and the completion of tapping. The material that satisfies the above (1) and (2) is supplied to the remaining slag in the furnace from above the converter or from the upper blowing lance.
Slag splash coating is performed after adding 2 to 10 wt% to t% to increase the viscosity of the slag. When the slag thickness after tapping exceeds 200 mm, or when the iron oxide concentration of the slag is 15% or less, and the slag thickness is 200 mm or less, the above-described treatment is naturally unnecessary. .

[0026]

EXAMPLE An upper and lower blown converter was composed of 80 wt% MgO and C:
This is a 340 t capacity converter lined with MgO-C refractory having a composition of 20 wt%. Hereinafter, an embodiment corresponding to claim 1 will be described according to Table 1, and an embodiment corresponding to claim 2 will be described according to Tables 2 and 3, respectively.

First, an embodiment of Table 1 corresponding to claim 1 will be described below. In Examples 1 to 3 of the present invention shown in Table 1, the slag remaining in the furnace after tapping from the converter in the corresponding channel was not discharged, and silica was added as a slag forming material during the next blowing, and the furnace was cooled after the blowing. Because the thickness of the residual slag inside was more than 200 mm,
When slag splash coating was performed, excellent coating properties were exhibited.

[0028]

[Table 1]

On the other hand, in Comparative Examples 1 and 2 in Table 1, although the residual slag in the furnace after the steel baking of the corresponding channel was not discharged,
Since the thickness of the residual slag in the furnace after the end of the next blowing was 200 mm or less, the coating property at the time of performing the slag splash coating was inferior. Furthermore, in Conventional Example 1 of Table 1, the residual slag in the furnace after tapping from the converter of the channel was discharged, and the thickness of the residual slag in the furnace after the next blowing was 200 mm.
Because of the following, the coating properties during slag splash coating were poor.

Next, embodiments of Tables 2 and 3 corresponding to claim 2 will be described. Table 2 shows the types of materials added to the residual slag in the furnace and the particle size ratio of 1 mm or less in each type of materials used this time. Table 3 shows the operating conditions of the material addition and the evaluation results of the coating properties.

[0031]

[Table 2]

[0032]

[Table 3]

In Examples 1 to 4 of the present invention shown in Table 3, the c
h, since the viscosity of the slag was increased by adding the materials shown in Table 2 from the upper part of the converter or the upper blowing lance to the residual slag in the furnace after tapping from the converter, the slag was excellent in performing slag splash coating. It showed coating properties.
On the other hand, in Comparative Example 1 in Table 3, although the materials shown in Table 2 were added to the residual slag in the furnace after tapping from the converter in the corresponding channel from the top blowing lance, the amount of the added material was less than 2 wt%, and Since no viscosity improving effect was observed, the coating property at the time of slag splash coating was poor.

In Comparative Example 2, although the materials shown in Table 2 were added from the upper part of the converter to the residual slag in the furnace after tapping the converter from the corresponding channel, the added amount of the material exceeded 10 wt% and the slag was solidified. As a result, the coating properties at the time of slag splash coating were poor. Comparative Example 3 is the channel
Although the materials shown in Table 2 were added from the upper part of the converter to the residual slag in the furnace after the tapping of the converter,
Since the particle size of less than 30 mm was less than 30% and the effect of improving the viscosity of the slag was not observed, the coating property at the time of performing the slag splash coating was inferior.

Further, in the conventional example 1 shown in Table 3, lime feldspar having a melting point of less than 1600 ° C. shown in Table 2 is added to the residual slag in the furnace after the baking from the converter of the channel as slag reforming means for increasing the viscosity of the slag. Because it was added from the top blowing lance, lime feldspar did not melt into the slag and the effect of increasing the slag viscosity was not seen.
The coating properties when performing slag splash coating were poor.

Next, FIG. 2 shows a comparison of the change in the amount of wear of the refractory lining of the trunnion portion between when the converter was operated and when it was used 4000 times, and when the conventional example was performed. Show. In the example of the present invention, when the iron oxide concentration of the residual slag in the converter after tapping is more than 15% and the slag thickness is 200 mm or less, the residual slag in the furnace after blowing is converted into the converter. A method in which the next blowing is performed while remaining in the furnace without discharging, and the thickness of the residual slag in the furnace after the next tapping is set to more than 200 mm, and then the upper and lower spray coating is performed (from the upper blowing lance). Nitrogen gas blowing flow rate: 40
000Nm ³ / h, distance between top blowing lance and slag bath surface;
5.5 m, flow rate of nitrogen gas blown from the bottom tuyere; 4
000 Nm ³ / h, top and bottom blown splash coating time; 2 minutes) and a method of adding material from the upper part of the converter or the top blown lance during execution of the top and bottom blown spray coating (nitrogen gas from the top blown lance) Injection flow rate: 35
000Nm ³ / h, distance between top blowing lance and slag bath surface;
6.0 m, flow rate of nitrogen gas blown from the bottom tuyere; 4
000Nm ³ / h, input amount from the top blowing lance of quicklime as material; 3w per 100wt% of residual slag in the furnace
t%, top and bottom spray splash coating time; 2 minutes)
Are performed at an implementation rate of 50%.

The thickness of the residual slag in the furnace after tapping is 2
When it exceeds 00 mm, the flow rate of nitrogen gas blown from the top blow lance; 50,000 Nm ³ / h, the distance between the top blow lance and the slag bath surface: 3.5 m, the flow rate of nitrogen gas blow from the bottom blow tuyere; 4000 Nm ³ / H, top and bottom spray coating time; top and bottom spray coating was performed under the condition of 2 minutes. Furthermore, when the iron oxide concentration of the residual slag in the furnace after tapping becomes 15% or less, the flow rate of nitrogen gas blown from the top blowing lance: 350
00Nm ³ / h, distance between top blowing lance and slag bath surface;
5.0 m, flow rate of nitrogen gas blown from the bottom tuyere; 4
The top and bottom spray coating was performed under the conditions of 000 Nm ³ / h and a top and bottom spray coating time of 2 minutes.

On the other hand, in the conventional example, regardless of the state of the residual slag in the furnace after tapping, the top-bottom-blow-spray coating (flow rate of nitrogen gas from the top-blowing lance;
00Nm ³ / h, distance between top blowing lance and slag bath surface;
4.5 m, flow rate of nitrogen gas blown from the bottom tuyere; 4
000 Nm ³ / h, top and bottom spray coating time; 2 minutes).

As is clear from FIG. 2, the effect of reducing the amount of wear of the refractory lining by 200 mm was confirmed at the time when the present invention was used 4000 times as compared with the conventional example.

[0040]

According to the present invention, the slag coating property can be improved even for slag in which the conventional slag coating property has not been sufficiently obtained, and as a result, the amount of wear of the refractory lining of the converter can be reduced. In this case, it is possible to prolong the life of the converter furnace and to reduce the cost of refractories by reducing the amount of repair materials.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a state of slag and a coating property at the time of performing a top and bottom spray splash coating.

FIG. 2 is a diagram showing a change in the amount of wear of a refractory lining of a converter in a trunnion portion according to an example of the present invention and an example.

Continued on the front page (72) Inventor Tomoaki Yoshiyama 1 Nishinosu, Oita, Oita City, Oita Prefecture F-term in Nippon Steel Corporation Oita Works (reference) 4K002 AC07 AE10 BB02 BC02 BC10 4K051 AA02 AB03 LA02 LA11 LA11 LJ01

Claims (2)

[Claims] 1. An upper-bottom blow converter for blowing molten steel by blowing oxygen from an upper part and a lower part of a converter. In the slag coating method of spraying gas from the bottom tuyere of the converter furnace to scatter the slag and coat the surface of the refractory lining of the converter, the residual slag in the furnace after tapping the converter has an iron oxide concentration of 15%. % And the slag thickness is 200 mm or less, the next slag is carried out while the slag is kept in the furnace without being discharged from the converter, and the thickness of the residual slag in the furnace after the next tapping is reduced. A slag coating method comprising performing slag splash coating after the thickness exceeds 200 mm. 2. An upper-bottom blowing converter for blowing molten steel by blowing oxygen from an upper part and a lower part of a converter. In the slag coating method of spraying a gas from a converter bottom tuyere and scattering the slag to coat the surface of the converter lining refractory, the residual slag in the furnace after the converter tapping has an iron oxide concentration. When the slag thickness is more than 15% and the slag thickness is 200 mm or less, a material satisfying the following conditions (1) and (2) is supplied from the upper part of the converter or the upper blowing lance with respect to 100 wt% of the slag. 10wt
% Slag coating method, wherein slag splash coating is performed after the addition. (1) The material has a melting point of 1600 ° C. or higher. (2) The particle size is such that the material contains 30% or more of a particle size of 1 mm or less.