JPH1160341A - Castable refractory for spraying and coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce high strength castable refractories without deteriorating heat resistance while reducing the amt. of alumina cement by adding a specified amt. of an org. dispersant to powder prepd. by mixing alumina cement with superfine alumina powder, superfine silica powder and a refractory stock in a specified ratio. SOLUTION: An org. dispersant is added by 0.01-0.1 wt.% to powder prepd. by mixing 5-15 wt.% alumina cement with 3-10 wt.% superfine alumina powder, 1-5 wt.% superfine silica powder and a refractory stock. The org. dispersant is a dispersant for cement, preferably a dispersant for alumina cement. Since the dispersant is chemically adsorbed on slowly leaching Ca ions or forms a slightly soluble hydrate to sequester Ca ions, the rise of conductivity is retarded, the rise of pH is not caused and a kneaded material keeps a flocculated state. Even when the dispersant is consumed and the leaching of Ca ions increases gradually, flowing is not caused because cement begins to flocculate and hardening starts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a castable refractory for spraying and painting, and more particularly to a component adjustment of a high-strength material having a reduced amount of alumina cement.

[0002]

2. Description of the Related Art Castable refractories are generally refractories in which a refractory raw material and a hydraulic cement are mixed and are originally used for pouring, but they can also be used for spraying and painting. . In castable refractories used in spraying or painting construction methods, alumina cement is often used as a binder for hydraulically setting cement. Alumina cement hardens quickly at low temperatures, hardens at high temperatures (25 ° C. or higher) and decreases in strength, but the hardened body is relatively stable and has a small decrease in fire resistance.
Since it is resistant to abrasion and thermal shock, it is used as a repair material in construction of railways, roads, waterworks, etc., mainly in furnace construction or maintenance work.

[0003] Conventionally, castable refractories for spraying and painting have been increased in the amount of alumina cement in order to increase the strength of the cured product.

[0004] However, castable refractories containing a large amount of alumina cement (generally 20% or more) have a high cured body strength but low heat resistance, and have a firing temperature of 800 ° C to 1000 ° C. , The strength decrease in the intermediate temperature range increases. Therefore, a sufficient effect as a castable refractory cannot be obtained depending on the use environment.

[0005] However, in a low cement material in which the content of alumina cement is reduced, a decrease in strength due to heating is reduced, but a special machine and technology are required for construction. Therefore, in order to use it with a very common construction machine, it was necessary to prepare a high-strength material with a reduced amount of alumina cement.

Therefore, the following measures have been proposed as a method of reducing the amount of alumina cement and not losing the effect as a castable refractory. As one method, a slurry is prepared by dispersing ultrafine powder of silicon dioxide and alumina and alumina cement with a dispersant, and the aggregate (refractory raw material), the hardener, and the slurry are mixed at the nozzle of the construction apparatus, There are things to construct. However, this method requires a machine dedicated to slurry preparation, and it takes time and skill to adjust the important slurry. further,
The construction equipment is also special, and the construction management is complicated. In addition, since the material is in a slurry state, the material has fluidity, so it is necessary to prevent the material from flowing down, and it is difficult to finish the construction body.

[0007] As another method, there is a method in which a small amount of water is added in advance to premix a powder containing a dispersant before the powder is added to a spraying machine (gun), and the water is further added at a nozzle portion. . In this method, the time elapsed from the premix of the material is important, and if the spraying is too early, sagging or falling will occur.If the spraying is too slow, the effect of the dispersant will not be recognized, making it difficult to finish as a whole. It is important to determine subtle timing. Also, the amount of water added is delicate,
Requires skill in construction.

Further, the method of using a dispersant and a thickener in combination is intended to prevent the flow of the material dispersed by the dispersant with the thickener. There was a great danger of falling and falling.

[0009]

As described above, according to the prior art, a castable refractory in which the amount of alumina cement is reduced in order to enhance the heat resistance and strength of the castable refractory is adjusted, while a sufficient water reducing effect is obtained. There were secondary problems such as those that did not exist, those that caused danger of flow, and those that required special construction equipment.

[0010] Accordingly, an object of the present invention is to adjust and provide a high-strength material without reducing the heat resistance while reducing the amount of alumina cement, thereby further exerting the water-reducing effect in the cement. , Eliminating the fluidity of the kneaded material,
An object of the present invention is to prevent the occurrence of sagging and downflow by preventing softening, thereby enabling efficient spraying and painting. In addition, the present invention is based on the premise that it can be easily constructed with very common equipment.

[0011]

In order to achieve the above object, a castable refractory for spraying and painting according to the present invention is obtained by mixing an ultrafine powder of alumina and a superfine powder of silica with alumina cement and an organic dispersant. From 0.01 to
It is added within the range of 0.1% by weight.

[0012]

The operation of the present invention will be described with reference to the drawings. FIG.
Is the elapsed time (minutes) after adding water to the alumina cement powder on the horizontal axis, and the electric conductivity (mS / c) of the kneaded material on the vertical axis.
m) shows the change in electrical conductivity over time.

When the alumina cement is kneaded with water, Ca ions in the alumina cement are eluted, and the conductivity immediately increases as shown by the curve (a) in FIG. C
When the a-ion elutes, the pH of the kneaded material increases, and the mixture becomes fluid. Therefore, ultrafine alumina powder and ultrafine silica powder are added to the alumina cement in order to suppress the elution of Ca ions, which cause dripping and flow-down. Since these ultrafine powders have the effect of suppressing the elution of Ca ions, immediately after kneading the alumina cement and the ultrafine powder, when water is added only to the alumina cement as shown in the curve (b) of FIG. It can be seen from the curve (a) of No. 1 that the kneaded material is in an agglomerated state. This eliminates the need for an adhesive material (agent), which enables construction with lower moisture than ordinary spray materials.
The calcium hydroxide produced by hydration of the alumina cement reacts with the silica super-differential to promote the hydration reaction in the alumina cement, so that a high-strength construction body can be obtained.

However, in the kneaded product of this combination,
The amount of water added to the alumina cement is sensitive to changes, and Ca ions gradually elute with the passage of time, and the pH of the kneaded material rises, becomes fluid, and softens. Therefore, it is necessary to adjust the construction body in which the amount of water is reduced in order to suppress the occurrence of dripping and flow-down, and as a result, rebound and dust generation often occur during spraying construction.

Therefore, in the present invention, an organic dispersant is added to the alumina cement in addition to the alumina fine powder and the silica fine powder. In a castable powder to which an organic dispersant is added, the dispersant chemically adsorbs to Ca ions that gradually elute, or forms a sparingly soluble hydrate, so that the Ca ions are blocked. Disperse), and as shown by the curve (c) in FIG. 1, the rise in conductivity is delayed, so that the pH does not rise, and the kneaded material keeps an agglomerated state. Even though the dispersant is consumed and the amount of Ca ions eluted gradually increases, in this case the cement begins to aggregate,
Since curing starts, it does not flow.

From such a mechanism, by adding an organic dispersant to a powder obtained by adding alumina cement, alumina ultra-fine powder and silica ultra-fine powder, even if the amount of alumina cement is reduced, the water content of the kneaded material is low even if the amount of alumina cement is reduced. High-strength spraying with high heat resistance and fire resistance while suppressing flow can be performed, and adjustment of castable refractories for painting is possible.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Castable refractories for spraying and painting are mainly composed of specific components including refractory raw materials and hydraulic cement. The following refractory raw materials can be used in the present invention. The main specific components used in the present invention are shown below. 1. Refractory raw materials Alumina Mullite Fired bauxite Fired clay shale Various chamotte Silicon carbide Fused silica Refractory materials other than basic materials 2. Specific constituents Alumina cement Alumina ultrafine powder Silica ultrafine powder Organic dispersant The castable refractory comprises 50 to 70% by weight of an aggregate portion composed of one or more refractory raw materials, and one of the refractory raw materials. The powder portion (fine particle size) composed of a variety or a combination of various types is composed of 10 to 30% by weight and two specific constituents. Depending on the purpose, clays, organic fibers, thickeners, and other workability modifiers can also be used.

Next, castable refractories obtained by variously changing the constituent elements of the specific components in the present invention will be described in more detail with reference to examples. FIG. 2 shows the relationship between the amount of the organic dispersant added and the flow time of the kneaded material for castable refractories when alumina ultrafine powder, silica ultrafine powder, and organic dispersant are all added to alumina cement as a specific component. FIG. The horizontal axis represents the weight ratio (% by weight) of the amount of the organic dispersant added to the total amount of the castable powder (a mixture of alumina cement, alumina ultrafine powder, silica ultrafine powder, and organic dispersant), and the vertical axis represents water in the castable powder. The flow time (minute) of the kneaded material obtained by the addition is determined. The flow time indicates a time during which the kneaded material keeps a fluid state.

FIG. 2 shows that the addition ratio of the organic dispersant is 0.
In the range of 01 to 0.1%, the flow time is 0, and it can be seen that the flowability of the castable refractory does not appear, that is, the castable refractory is in a coagulated state. Therefore, castable refractories having a dispersant addition range of 0.01 to 0.1% do not have the danger of falling or dripping in a state where the flowability is suppressed, and are therefore suitable for spraying and application. Suitable.

On the other hand, when the organic dispersant is less than 0.01%, the water reducing effect is hardly recognized in the cement. As shown in FIG. Therefore, the ratio of the organic dispersant added to the castable refractory for spraying and painting according to the present invention is preferably 0.01 to 0.1%.

Therefore, in the present invention, the case where the addition ratio of the organic dispersant is in the range of 0.01 to 0.1% is sprayed,
The application range is effective for castable refractories for painting, and the castable refractories in this range are handled. However, when the proportion of the organic dispersant added is 0.4% or more, the flow time is 40 minutes or more. That is, since the kneaded material keeps a fluid state for a relatively long time, if the addition ratio is 0.4% or more, the dispersant can be used as a castable refractory for casting, which is the original purpose of use.

FIG. 3 shows the softening of the kneaded material in an appropriate amount range (0.01 to 0.1%) when the kneaded material of alumina cement and the organic dispersant is applied for spraying and application. Prevention effect, construction temperature 5 ℃, 20
It is the figure shown about the case of 30 degreeC and 30 degreeC, respectively. The horizontal axis indicates the amount of the organic dispersant added (% by weight), and the vertical axis indicates the softening rate (%). Here, the softening rate is calculated as follows.

[0023]

## EQU1 ## Softening rate (%) = (vibration flow value after 15 minutes−3)
Vibration flow value after min) × Vibration flow value after 100/3 min

The vibration flow value is defined as the diameter of the spread of the kneaded material when the kneaded material is cast into a cone having a diameter of φ75 mm on the upper surface, a diameter of φ85 mm on the lower surface, and a height of 60 mm, and vibrated on a vibration table for 10 seconds. It is shown. Therefore, the larger the vibration flow value is, the softer it is. When the flow value after 15 minutes is larger than the flow value after 3 minutes, that is, when the softening rate is +, the kneaded material softens and becomes 3%.
When the value after minutes is larger, that is, when the softening rate is-, it indicates that the material becomes harder.

At an application temperature of 20 ° C., when the organic dispersant is not added, the initial value of the softening rate is as high as 20%, but as the amount of the organic dispersant added increases, the softening is suppressed. As shown in Fig. 3, when the amount of addition is around 0.04%, the softening ratio shows about 0, and as it exceeds 0.04%, the softening ratio further decreases and the coagulating force gradually increases. on the other hand,
When the working temperature is 5 ° C. or 30 ° C., the fluctuation of the softening rate is small. That is, since the kneaded material basically shows the rheology of the Bingham flow, it is possible to perform spraying and painting, and it is less likely that an error occurs between the time of construction of the construction body and the finish caused by fluctuation due to softening. Particularly at around 0.04%, a sufficient softening preventing effect can be obtained.

Next, in the present invention, an example showing the effectiveness of adding an organic dispersing agent in the case of preparing a castable refractory for spraying and applying with reduced alumina cement content is shown in Table 1 together with a comparative example. Table 1 shows the main components contained in the castable refractory for spraying and painting according to the present invention, and further compares their contents relatively. In addition, the experimental construction of spraying and painting in the comparative examples and the examples according to the present invention was carried out by using an ordinary arriving type machine without performing premixing.

[0027]

[Table 1]

The embodiment shown in Table 1 is an example of the main components of the castable refractory for spraying and painting used in the construction of the present invention. In addition, an organic dispersant is added. Comparative Example 1 differs from Example in that the amount of alumina cement was reduced and ultrafine silica powder was added in addition to ultrafine alumina powder, but no organic dispersant was added. That is, Comparative Example 1 shows a blank test comparison for knowing the direct effect of the organic dispersant in Examples of the present invention.
On the other hand, Comparative Example 2 is a conventional technique in which the amount of alumina cement is increased to increase the strength of the cured body. An example in which ultrafine alumina powder is added to this is shown as a comparative example of the castable refractory of the present invention.

[0029]

[Table 2]

From the viewpoint of workability, a comparison between Example, Comparative Example 1, and Comparative Example 2 shows that, as shown in Table 2, both Example and Comparative Example 2 show less dusting and sagging and show good workability. Comparative Example 1 was sensitive to a change in the amount of water, causing dripping and a large amount of dust. Further, Comparative Example 1 softened after construction and sagged during finishing. In Comparative Example 1, the kneaded material was softened during the application and dripping occurred, and in Comparative Example 2, the workable time was short because the kneaded material was quickly drained and hardened rapidly. However, in the embodiment of the present invention, since the change in the softness of the kneaded material is small, no sagging occurs and the operable time is long.

On the other hand, when compared in terms of the physical properties of the kneaded material, the effect of the organic dispersant added in the example is clear from the comparison with Comparative Example 1 in Table 2, and the amount of water added to the construction body is Reduced, high strength and dense construction can be obtained. In comparison with Comparative Example 2, the difference in dry physical properties was small, but 1000
The difference in physical properties after sintering at ℃ is very large, and in the embodiment according to the present invention, the abrasion resistance in the intermediate temperature range (800 to 1000 ° C.) which is a drawback of the conventional high-strength sprayed material is greatly improved.

FIG. 4 shows that the castable refractory usefully prepared for spraying and painting according to the present invention and a conventional sprayed material having a high alumina cement content are further refined in bending strength as a function of firing temperature. It is a figure to compare. The sintering temperature (° C.) of the castable refractory is plotted on the horizontal axis, and the bending strength (MPa) is plotted on the vertical axis, and plotted for the above-mentioned Example (castable refractory according to the present invention) and Comparative Example 2 (conventional castable refractory). The obtained curves were designated as curve (a) and curve (b).

FIG. 4 shows the embodiment shown in Table 1 and the comparative example 2.
The change in strength resulting from the difference in the amount of alumina cement mixed is remarkable. In Comparative Example 2, since a large amount of alumina cement is blended, as shown by the curve (b), the porosity increases in the intermediate temperature range (800 to 1000 ° C.) of the sintering temperature, and the bending strength decreases sharply. Inevitable. However, in the castable refractory according to the present invention, the bending strength (strength) in the intermediate temperature range is significantly improved in the curve (a) as apparent from the comparison with the curve (b) due to the reduction of the alumina cement. .

Even when the amount of alumina cement is not reduced, as in the present invention, both dust generation and dripping during construction are small, and there is little difference between dry properties as well, and good workability is exhibited. In addition to the rapid drainage of water, the operable time is shortened, and a sharp decrease in strength is observed in the intermediate temperature range. Therefore, the amount of alumina cement is reduced,
From the above results, it is clear that the castable refractory of the present invention, which has the effect of adding an organic dispersant, is effective for spraying and painting.

As described above, when the results of FIGS. 2 and 3 and Tables 1 and 2 are combined, even if the amount of alumina cement is reduced, it can be effectively used as a castable refractory for spraying and painting. The appropriate content range of the castable refractory for the specific component in the above is determined as follows.

[0036]

[Table 3]

On the other hand, as the type of alumina cement used as the castable refractory for spraying and painting according to the present invention, the one having a small amount of CaO is suitable, but it is preferable to use the one if no additive is added. it can.

As an effective type of the organic dispersant which is an important component for adjusting the castable refractory for spraying and application of the present invention, a dispersant for cement, preferably a dispersant for alumina cement, Organic sulfonates,
Carboxylates, melamine-based water reducing agents and the like are mentioned as examples.

[0039]

The castable refractory according to the present invention achieves a reduction in the alumina cement content by adding an organic dispersant. Further, from the reduction of the amount of alumina cement, the intermediate temperature range of the firing temperature (800 to 10)
(00 ° C), the strength of the refractory is greatly reduced,
A high-strength and dense construction body is obtained, and the wear resistance is also improved. In addition, the addition of an organic dispersant provides a water-reducing effect in the cement, making it possible to work with low moisture.
Since the change in softness of the kneaded material is small and stable, the operable time is extended. On the other hand, the amount of the organic dispersant used is to disperse (fluidize) ordinary cement or ultrafine alumina powder.
Since it is less than the amount, it can be constructed without any problem by a normal construction method. In addition, since there is no danger of drip or flow during construction, the surface can be finished without any problem. From this point, the castable refractory according to the present invention allows not only spraying but also painting.

Accordingly, it is possible to use a spraying material or a coating material on a region where a casting material has been used inevitably from the viewpoint of abrasion resistance. , Construction costs can be reduced. Furthermore, by reducing the amount of cement, a low porosity is achieved, and it can be used in places where corrosion resistance is required. Even in the case of repairing a small area by regular maintenance work or the like, a high-performance construction body can be obtained by painting. In addition, since special equipment and techniques are not required, a high-performance sprayed construction can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the passage of time after the addition of water and the electrical conductivity of the castable refractory of the present invention.

FIG. 2 is a graph showing the relationship between the amount of organic dispersant added to the castable refractory of the present invention and the flow time of the refractory.

FIG. 3 is a graph showing the relationship between the amount of organic dispersant added (in the range of 0.01 to 0.1%) and the softening rate of the castable refractory of the present invention.

FIG. 4 is a diagram showing a relationship between a firing temperature and a bending strength of a castable refractory of the present invention and a conventional castable refractory.

Claims (1)

[Claims] In a castable refractory, an organic dispersant is added to a powder obtained by mixing 5 to 15% by weight of alumina cement, 3 to 10% by weight of ultrafine alumina powder, 1 to 5% by weight of ultrafine silica powder and refractory raw material. Is added to form a castable refractory for spraying and painting.