JPH01201084A - Refractory castable for injection lance for pretreatment of molten iron - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance, penetration resistance, thermal spalling resistance and strength of a refractory castable, by adding colloidal silica and alumina cement to specific aggregate. CONSTITUTION:The objective castable is produced by compounding (A) 20-70% of aggregate having particle diameter of 10-1mm and composed of crushed alumina-SiC-C brick used as a lining brick of mixed metal truck with (B) 1-8% (in terms of solid) of colloidal silica having particle diameter of 0.01-0.02mum as a binding material, (C) 0.5-5% of alumina cement as a gelling assistant and, as necessary, (D) a deflocculant (e.g. sodium tripolyphosphate), (E) 2-5% of vapor-phase silica fume as an assistant for binder and (F) a neutral or acidic refractory raw material such as alumina, mullite and chamotte.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a castable that is used in locations where it comes into contact with hot metal or corrosive slag and requires slag resistance and heat spall resistance. This is particularly suitable for use as a lining material for injection lances for hot metal pretreatment.

(Conventional technology) In recent years, in the steel industry, due to the increasing quality of steel products and the demand for slagless operation, treatment materials are injected into hot metal in a hot metal container such as a mixing car to perform desiliconization, dephosphorization, and desulfurization treatments. This has become commonplace, and blowing oxygen is also being practiced to improve processing efficiency.

Since these processing vessels are exposed to more severe operating conditions than before, alumina-SiC-C bricks, which have excellent corrosion resistance, are used as their lining refractories. However, for safety reasons, the refractory in such processing containers is discarded with some residual thickness remaining.

For castable lances, JP-A-61-2266
Addition of carbon and carbonaceous binder as disclosed in Japanese Patent No. 56 is effective.

Alumina-8iC-C used for mixed iron car interior bricks, etc.
It can be said that crushed brick products meet these requirements.

However, because lance castables are used under conditions in which they are repeatedly immersed in hot metal and cooled in the atmosphere, they are prone to oxidation due to the so-called breathing development of refractories, which prevents them from achieving the desired effect. This is the actual situation.

(Problems to be Solved by the Invention) Conventionally, used alumina-SiC-C bricks have only been used in the form of coarsely crushed products of about 30I as fillers for castables and the like. The reason for this is that when used as the main aggregate for castables, there are problems such as oxidation during the use process and deterioration of sinterability due to carbon in the bricks. Therefore, it cannot be used in an oxidizing atmosphere or in a place where hot spalls occur. Therefore, the purpose of the present invention is to utilize used alumina-3iC-C bricks, which were previously discarded, as the main aggregate, and to improve their characteristics. This product will be utilized as a castable for injector excimin lance for pre-treatment of hot metal.

(Means for Solving the Problems) As a result of intensive research in order to improve the above-mentioned drawbacks, the present inventors have found that colloidal silica is used as a binder and alumina cement is preferably added in an amount of 0.5 to 5% as a gelling agent. It was discovered that the above problem could be solved by using 1 to 2% of the compound, and the present invention was completed.

Currently, we are producing injection lances for hot metal pretreatment,
Refractory castables used in areas that come into contact with hot metal or erosive slag are made of silica fume, alumina cement, and dispersion material, and use less cement.

The fire-resistant castable according to the present invention further develops the fire-resistant castable. Colloidal silica, which is ultrafine particles of O1 to 0.028 Lm, is used as a binder, and alumina cement is used as a gelling aid.

Colloidal silica as a binder has various concentrations (20 to 50% as a commercial product), but any concentration may be used, and the amount added is 1 to 8% in terms of solid content, preferably 2 to 50%.
3% is good, less than 1% is ineffective as a binder, and more than 8% has an adverse effect on corrosion resistance. The stable range of colloidal silica is PH17-3.1 or pH
9°0 to '9.8, and the function of alumina cement as a gelling aid is that CaOA203, the main constituent mineral in alumina cement, gradually dissolves, increasing the pH value, and increasing the pH value of the sol. It gels by exceeding the stabilization region.

If the content of alumina cement is less than 0.5%, it will take time to gel and it will be difficult to remove the mold, and if it exceeds 5.0%, corrosion resistance will decrease and sintering will occur, causing spalling. .

Addition of colloidal silica and alumina cement in the above appropriate amount ranges improves spall resistance (#peelability) and improves oxidation resistance of crushed alumina-SiC-C bricks, making it possible to use them as the main aggregate. It is something to do.

In addition, in the fire-resistant castable of the present invention, it is effective to add condensed phosphate as a defrosting agent to increase fluidity, and to add hydroxide or boric acid as a pH adjusting agent to adjust gelation time. It is.

The use of gas-phase silica fume as an auxiliary binder has the effect of increasing wave properties and filling properties, and the amount added is preferably 2 to 5%, but even without additives, the fire-resistant castable of the present invention can be used. It does not impair the properties.

The crushed product of alumina-3iC-C brick is 20% as the main aggregate.
-70% is used, thereby making effective use of resources and utilizing the functionality of alumina-SiC-C bricks. If it is less than 20%, it is not sufficient to improve the penetration resistance and spalling resistance, and if it exceeds 70%, it is impossible to form a particle size composition necessary to form a castable.

In the refractory castable of the present invention, reduction in fire resistance can be suppressed by adding medium acid refractory raw materials such as alumina, mullite, and chamotte as other raw material components.

The crushed product of alumina-3iC-C brick is approximately 10-4mm.
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It is not preferable to use 10% or more of fine powder of s or less because it adversely affects workability and deteriorates the performance of the refractory castable.

In the case of castables made of silica hume, alumina cement, and a dispersing agent, which use less cement, the silica hume acts as a dispersion aid to ensure uniform dispersion in the cement matrix, and the ultrafine powder of 0 to 1 gm allows for low temperature range. Due to the formation of ceramic ponds and the dense structure due to low moisture content, it has the characteristic that there is little strength loss even after alumina cement is used.

However, due to its manufacturing history, silica hum generally forms secondary particles of 2 to 5 particles (recovery of vaporized SiO during electric melting of ferrosilicon, metasilicon, zirconia, etc.), and is used in actual on-site kneading. Therefore, it is difficult to disperse into complete primary particles.

However, in the castable of the present invention, by using a colloidal dispersion as a binding material, the silica gel can be uniformly bound to the matrix 2 due to the gelling effect of the alumina cement.

Therefore, as in the present invention, alumina-SiC-C
Even when using crushed brick aggregate, stable strength can be obtained because it directly contributes to the bond between the aggregate and matrix formed by the carbon pond.

As a result, it has the corrosion resistance, permeation resistance, and thermal spalling properties required for injection lance materials for hot metal pretreatment, and has made it possible to use crushed alumina-SiC-C brick aggregate. .

The addition of stainless steel fiber to the refractory castable of the present invention brings about favorable effects in increasing bending strength and improving strain resistance. However, the amount added is 2
VOL% (5W7%) or less is preferable. Beyond that, the effect will not increase, but rather there will be adverse effects such as insufficient filling due to poor fluidity.

(Example) Next, an example of the present invention will be reported. Table 1 shows the formulation of each castable in Examples and Comparative Examples, and Table 2 shows the chemical analysis values of the crushed alumina-SiC-C brick aggregate used in Table 1.

Comparative Example 1 clearly showed little strength and was not suitable for practical use, and Comparative Example 2 also had delamination in layers during actual use. In the case of the example, there was no such problem, only smooth melting loss, and the castable material had excellent corrosion resistance, permeation resistance, and heat spalling resistance compared to conventional castable castables.

Table 1 Examples and Comparative Examples Table 2 Example of chemical analysis of crushed aggregate of alumina-SiC-C bricks (effects of the invention) The refractory castable for injection lance for hot metal pretreatment of the present invention is similar to the conventional castable for lance. In comparison, ■ Utilizing used bricks enables effective use of resources and reduces costs; ■ Utilizing the characteristics of alumina SiC-C bricks, it has excellent corrosion resistance, permeation resistance, and thermal spalling properties. (By using colloidal silica as a binder, the strength is stabilized, no peeling occurs, and the durability of the furnace material is improved, which results in a reduction in the original height of the furnace material.)

Claims (2)

[Claims] 1. Alumina-SiC used for mixed iron car interior bricks, etc.
- A hot metal reserve characterized by using crushed C bricks as aggregate, adding 1 to 8% solid content of colloidal silica as a binder and 0.5 to 5% of alumina cement as a gelling agent. Fireproof castable for treatment injection lance. 2. 2. The method according to claim 1, wherein 20 to 70% of crushed alumina-SiC-C bricks are used as the main aggregate, and other raw materials include medium acidic refractory raw materials such as alumina, mullite, and chamotte that do not reduce fire resistance. Fireproof castable.