CN113354402B

CN113354402B - Surface modification method of used cement kiln silicon mullite brick and iron runner castable

Info

Publication number: CN113354402B
Application number: CN202110709763.3A
Authority: CN
Inventors: 肖国庆; 桑超; 丁冬海; 雷长坤
Original assignee: Xian University of Architecture and Technology
Current assignee: Xian University of Architecture and Technology
Priority date: 2021-06-25
Filing date: 2021-06-25
Publication date: 2023-02-28
Anticipated expiration: 2041-06-25
Also published as: CN113354402A

Abstract

A surface modification method of a used cement kiln silicon mullite brick and an iron runner castable are characterized in that the used cement kiln silicon mullite brick is firstly soaked in water, cleaned, aired and dried to obtain a pretreated cement kiln silicon mullite brick; then, taking a silica sol water solution as an impregnation solution, and fully impregnating the pretreated cement kiln silicon mullite brick in the impregnation solution to obtain an impregnated cement kiln silicon mullite brick; and finally, drying the impregnated cement kiln silicon mullite brick to obtain the modified cement kiln silicon mullite brick. The modified cement kiln silicon mullite brick obtained by the method has the advantages of increased volume density, reduced apparent porosity and water absorption; the modified cement kiln silicon mullite brick is applied to the iron runner castable, the usage amount of brown corundum is reduced, the cost is low, the anti-seismic performance is good, and the problem of resource utilization of the cement kiln silicon mullite brick after use is effectively solved.

Description

Surface modification method of used cement kiln silicon mullite brick and iron runner castable

Technical Field

The invention belongs to the technical field of inorganic non-metallic materials, and particularly relates to a surface modification method of a used cement kiln silicon mullite brick and an iron runner castable.

Background

The consumption of refractory materials by steel, cement, glass, various kilns and other production enterprises in China is large, a large amount of waste refractory materials occupy land, pollute the ecological environment, harm the health of human bodies, cause the waste of a large amount of resources, and urgently need to be treated. At present, the waste materials are mainly treated by adopting a landfill and degradation utilization mode, so that not only is the land resource wasted, but also part of the waste refractory materials have certain radiativity and cause certain pollution to the environment. With the gradual exhaustion of mineral resources in China, under the form of global attention to atmospheric pollution and great advocation of low-carbon economy, if the waste refractory materials can be recycled, resources and energy can be saved, and environmental pollution can be reduced. Therefore, it is necessary to conduct research on recycling of the waste refractory.

At present, the main stream of iron runner castable is made of brown corundum serving as aggregate, the main chemical component of the brown corundum is alumina, and the main chemical component can be seen in documents: van run Dong, zhao Hui Zhong, yujun, etc. aggregate to Al ₂ O ₃ Influence of-SiC-C iron runner castable Properties [ J]Silicate notification, 2019,38 (3): 918-924. The iron runner castable has good high-temperature wear resistance, molten iron and slag scouring resistance, slag erosion resistance, thermal shock resistance and oxidation resistance. However, the brown corundum generates a large amount of dust in the production process, which causes environmental pollution, and the production price of the brown corundum is relatively high, which does not meet the development trend of iron runner castable.

Disclosure of Invention

Aiming at the defects and shortcomings in the prior art, the surface modification method of the used cement kiln silicon mullite brick and the iron runner castable are adopted, and the modified cement kiln silicon mullite brick obtained by the method has the advantages of increased volume density, low apparent porosity and low water absorption rate; the modified cement kiln silicon mullite brick is applied to the castable of the iron runner, the using amount of brown corundum is reduced, the cost is low, the anti-seismic performance is good, and the problem of resource utilization of the cement kiln silicon mullite brick after use is effectively solved.

In order to achieve the technical effects, the technical scheme adopted by the invention is as follows:

a surface modification method of used cement kiln silicon mullite bricks comprises the steps of soaking the used cement kiln silicon mullite bricks in water, cleaning, airing and drying to obtain pretreated cement kiln silicon mullite bricks; then taking a silica sol water solution as an impregnation solution, and fully impregnating the pretreated cement kiln silicon mullite brick in the impregnation solution to obtain an impregnated cement kiln silicon mullite brick; and finally, drying the impregnated cement kiln silicon mullite brick to obtain the modified cement kiln silicon mullite brick.

Preferably, the impregnation liquid is a silica sol aqueous solution with the mass fraction of 5-20%.

Preferably, the impregnation liquid is a 15% by mass aqueous silica sol solution.

Preferably, the impregnation liquid is a 10% by mass silica sol aqueous solution.

Preferably, the method specifically comprises:

the method comprises the following steps: soaking the used cement kiln silicon mullite brick in water for 3-5 days, changing water midway until no matter such as dust floats on the surface of the water, fishing out and naturally drying, and then putting the naturally dried cement kiln silicon mullite brick into a drying oven for heat preservation at 110 ℃ for 24 hours to obtain a pretreated cement kiln silicon mullite brick;

step two: dipping the pretreated cement kiln silicon mullite brick obtained in the step one in a dipping solution for at least two hours to obtain a dipped cement kiln silicon mullite brick;

and step three, placing the impregnated cement kiln silicon mullite brick obtained in the step two into an oven, baking for 2 hours at the temperature of 80 ℃, and baking for 5 hours at the temperature of 150 ℃ to obtain the modified cement kiln silicon mullite brick.

The iron runner castable comprises the raw materials of aggregate, silicon carbide, white corundum and alpha-Al ₂ O ₃ The aggregate comprises brown corundum, and also comprises modified cement kiln silicon mullite bricks and used cement kiln silicon mullite bricks, wherein the modified cement kiln silicon mullite bricks are prepared by the surface modification method of the used cement kiln silicon mullite bricks disclosed by the invention.

Preferably, 35 to 42 weight percent of brown corundum, 2 weight percent of used cement kiln silicon mullite brick, 12 weight percent of modified cement kiln silicon mullite brick, 15 weight percent of silicon carbide, 15 weight percent of white corundum, alpha-Al ₂ O ₃ 6wt% of powder, 2wt% of silicon powder, 2wt% of metal silicon powder, 2wt% of spherical asphalt, 71 wt% of Secar, 0.1wt% of sodium tripolyphosphate and 0.1wt% of sodium hexametaphosphate, and then uniformly stirring and dispersing to obtain the iron runner castable.

Preferably, the aggregate comprises 23 to 28 weight percent of brown fused alumina with the granularity of 3 to 5mm and not equal to 3mm, 6 to 7 weight percent of brown fused alumina with the granularity of 1 to 3mm and not equal to 1mm, and 6 to 7 weight percent of brown fused alumina with the granularity of 0 to 1mm and not equal to 0; also comprises 2wt% of used cement kiln silicon mullite bricks with the granularity of 0-1 mm and not equal to 0; also comprises 10wt% of modified cement kiln silicon mullite brick with the granularity of 3-5 mm and not equal to 3mm and 2wt% of modified cement kiln silicon mullite brick with the granularity of 1-3 mm and not equal to 1 mm.

Preferably, the silicon carbide with the grain size of 0.045-1 mm and not equal to 0.045mm is 10wt%, and the silicon carbide with the grain size of less than or equal to 0.045mm is 5wt%; white corundum, alpha-Al ₂ O ₃ The particle sizes of the powder, the silicon micropowder, the metal silicon powder, the spherical asphalt and the Secar 71 are less than or equal to 0.045mm.

Due to the adoption of the technical scheme, the method has the following beneficial effects:

(1) The surface modification method of the used cement kiln silicon mullite brick ensures that the impregnation liquid can be coated on the surface of the used cement kiln silicon mullite brick and enter the used cement kiln silicon mullite brick in the impregnation process, so that the original air holes are blocked, the compactness of the used cement kiln silicon mullite brick is improved, the integral volume density is increased, and the apparent porosity and the water absorption rate are reduced.

(2) According to the surface modification method of the used cement kiln silicon mullite brick and the iron runner castable, the modified cement kiln silicon mullite brick prepared by the surface modification method of the used cement kiln silicon mullite brick is used as an aggregate and applied to the iron runner castable, so that the usage amount of brown corundum is reduced, the cost is low, the thermal shock resistance of the iron runner castable can be improved, and the problem of resource utilization of the used cement kiln silicon mullite brick is effectively solved.

Drawings

FIG. 1 is a diagram of a manufacturing process of the present invention;

FIG. 2 is an XRD pattern of a post-use cement kiln silicon mullite brick of the present invention;

FIG. 3 is a Raman diagram of the used cement kiln silicon mullite brick of the invention;

FIG. 4 is a TG-DSC curve of the surface of the used cement kiln silicon mullite brick of the invention;

FIG. 5 is an SEM image of the surface of a used cement kiln silicon mullite brick of the invention;

fig. 6 is a characterization of a GT aggregate made by a comparative example of the present invention (where fig. 6a is an SEM image of the GT aggregate and fig. 6b is an EDS plot of point a in fig. 6 a);

FIG. 7 is a representation of the G20 aggregate prepared in example 4 of the present invention (wherein FIG. 7a is an SEM photograph of the G20 aggregate and FIG. 7B is an EDS photograph at point B in FIG. 7 a);

FIG. 8 is a comparison of GT aggregate prepared by a comparative example of the present invention and G20 aggregate prepared by example 4 before and after mixing (wherein FIG. 8a is a comparison before mixing and FIG. 8b is a comparison after mixing);

FIG. 9 is a representation of GT aggregate of a comparative example of the present invention after agitation in water (where FIG. 9a is an SEM image of the GT aggregate after agitation in water and FIG. 9b is an EDS image at point C in FIG. 9 a);

FIG. 10 is a representation of the aggregate G20 prepared in example 4 of the present invention after stirring in water (wherein FIG. 10a is a SEM image of the aggregate G20 after stirring in water, and FIG. 10b is an EDS image at point D in FIG. 10 a);

FIG. 11 is a graph showing the flow values of the iron runner castable prepared in examples 1 to 4 of the present invention using post-cement kiln silicon mullite bricks instead of brown corundum as aggregates;

FIG. 12 is a graph showing the thermal shock resistance of the iron runner castable prepared in examples 1-4 of the present invention using post-cement kiln silicon mullite brick instead of brown corundum as an aggregate.

The invention is described in detail below with reference to the drawings and the detailed description.

Detailed Description

The present invention will be described in detail below with reference to the drawings and embodiments, and it should not be construed that the embodiments of the present invention are limited to these descriptions. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

The used cement kiln silicon mullite brick is obtained by exposing the cement kiln silicon mullite brick to high-temperature airflow for a long time in the operation process of a cement kiln; the used cement kiln silicon mullite brick adopts the used cement kiln silicon mullite brick of Yongsheng refractory material factory of consolidation city in Henan province, the main chemical composition of the used cement kiln silicon mullite brick is shown in table 1, and an XRD (X-ray diffraction) diagram, a Raman diagram, a TG-DSC (TG-DSC) curve diagram and an SEM (scanning electron microscope) diagram of the surface of the used cement kiln silicon mullite brick are sequentially shown in figures 2-5.

TABLE 1 Main chemical composition of post-use cement kiln silicon mullite brick

Example 1

In the embodiment, the used cement kiln silicon mullite brick is pretreated firstly, specifically, 5kg of used cement kiln silicon mullite brick aggregate is put in a large container, water is added for soaking for 3-5 days, and water is changed for 10 times in the midway. Then fishing out the cleaned and soaked used cement kiln silicon mullite bricks, airing, and putting the aired used cement kiln silicon mullite bricks into a baking oven for heat preservation at 110 ℃ for 24 hours to obtain pretreated cement kiln silicon mullite bricks;

then, preparing an impregnation liquid, taking silica sol with the mass fraction of 30% as a raw material, and according to the mass percentage, preparing the following silica sol: deionized water is 50;

and finally, adding 5% silica sol impregnation liquid into the pretreated used cement kiln silicon mullite brick for full impregnation for 2 hours, fishing out the impregnated used cement kiln silicon mullite brick, draining, putting the soaked used cement kiln silicon mullite brick into an oven, keeping the temperature for 2 hours at 80 ℃, and keeping the temperature for 2 hours at 150 ℃ to obtain the modified used cement kiln silicon mullite brick.

Compared with the quality of the silicon mullite brick for the cement kiln before modification, the quality of the silicon mullite brick for the cement kiln after modification is increased by 1.35%.

Example 2

This example differs from example 1 in that: during preparation of the impregnation liquid, the weight percentage of silica sol is as follows: deionized water is 50.

Compared with the quality of the silicon mullite brick of the cement kiln before modification, the quality of the modified silicon mullite brick of the cement kiln after modification is increased, and the mass increase ratio is 2.26%.

Example 3

This example differs from example 1 in that: during preparation of the impregnation liquid, the weight percentage of silica sol is as follows: deionized water 50.

Compared with the quality of the silicon mullite brick of the cement kiln before modification, the quality of the modified silicon mullite brick of the cement kiln after modification is increased by 3.99 percent.

Example 4

Compared with the quality of the silicon mullite brick of the cement kiln before modification, the quality of the modified silicon mullite brick of the cement kiln after modification is increased, and the mass increase ratio is 4.70%.

Comparative example

This comparative example differs from example 1 in that: during preparation of the impregnation liquid, citric acid monohydrate, polyvinylpyrrolidone (PVP), carbon black and deionized water are used as raw materials, and the citric acid monohydrate is as follows by mass percent: polyvinylpyrrolidone (PVP): carbon black: deionized water is 10. The preparation method specifically comprises the steps of dry-mixing carbon black and polyvinylpyrrolidone (PVP) for 10min, adding citric acid monohydrate into a beaker filled with deionized water, adding mixed powder of the carbon black and the polyvinylpyrrolidone into an aqueous solution of the citric acid monohydrate 6 times, and stirring with a glass rod. After stirring, the beaker is placed into an ultrasonic cleaning machine for ultrasonic treatment for 20min, so that the dispersion is more uniform, and the impregnation liquid of the comparative example is obtained.

Compared with the quality of the silicon mullite brick in the cement kiln before modification, the quality of the silicon mullite brick in the cement kiln after modification is increased by 1.72%.

And (I) result characterization:

(1.1) measurement of bulk density, apparent porosity, water absorption:

the brown corundum, the used cement kiln silicon mullite brick, the modified cement kiln silicon mullite brick prepared in the comparative example and the examples 1-4 are taken as aggregates and named as Z aggregate, GT aggregate, G5 aggregate, G10 aggregate, G15 aggregate and G20 aggregate, and the volume density, the apparent porosity and the water absorption of the modified cement kiln silicon mullite brick prepared in the traditional brown corundum, the used cement kiln silicon mullite brick, the comparative example and the examples 1-4 are measured, and the measurement results are shown in Table 2.

TABLE 2 aggregate bulk density, apparent porosity and Water absorption

From the results of the above measurements it can be seen that: the aggregates prepared in the comparative example and examples 1 to 4 had increased mass, increased bulk density, and decreased apparent porosity and water absorption; the aggregates prepared in examples 1-4 were better than the aggregates prepared in comparative examples, and the mass of the aggregates was gradually increased, the bulk density was gradually increased, and the apparent porosity and water absorption were gradually decreased with the increase of the silica sol concentration in the impregnation solution, which was shown to be the best performance of the G20 aggregate (i.e., the modified post-cement kiln silica mullite brick prepared in example 4).

(1.2) observing by a scanning electron microscope before and after the surface modification of the aggregate:

SEM observation of the surface of the unmodified used cement kiln silicon mullite brick aggregate is shown in figure 5. As can be seen from the figure, the surface of the aggregate was uneven with many pores.

SEM observation of the surface of the GT aggregate prepared in comparative example gave an SEM image as shown in fig. 6 (a), in which the EDS of point a is shown in fig. 6 (b). As can be seen from the figure, the GT aggregate becomes flat and the pores are filled, and it is confirmed by combining FIG. 6 (b) that carbon black is coated on the surface of the silica mullite brick aggregate.

The surface of the G20 aggregate obtained in example 4 was observed by SEM, and the SEM image obtained is shown in fig. 7 (a), in which the EDS image of the point B is shown in fig. 7 (B). It can be seen from the figure that G20 aggregate surface becomes flat, air holes are filled, and the surface of the aggregate has cracks, and by combining with fig. 7 (b), it is proved that silica sol is coated on the surface of the mullite brick aggregate, and the cracks on the surface of the aggregate cause shrinkage of the silica sol layer due to moisture volatilization in the process of redrying the silica sol impregnation liquid on the surface of the aggregate.

(1.3) comparison before and after the surface of the aggregate is modified and soaked in water and stirred

51.41G of the aggregates GT obtained in the comparative example and 52.59G of the aggregates G20 after modification obtained in example 4 were taken respectively and placed in a beaker (GT aggregates and G20 aggregates have masses of 51.41G and 52.59G respectively) and flooded with water as shown in FIG. 8 (a). Then, 180s of the GT aggregate and the G20 aggregate in the beaker were stirred with a glass rod, and whether the carbon black and silica sol coated on the surfaces of the GT aggregate and the G20 aggregate fell or not was observed, as shown in FIG. 8 (b) after the stirring. As can be seen from the comparative figures, the carbon black on the surface of the GT aggregate and the silica sol on the surface of the G20 aggregate both dropped to different degrees. The GT aggregate and G20 aggregate were then drained, dried and the mass recorded again (GT aggregate and G20 aggregate mass 50.98G and 52.29G respectively).

The mass of the GT aggregate and the mass of the G20 aggregate are both reduced, the mass of the GT aggregate is reduced by 0.84 percent, and the mass of the G20 aggregate is reduced by 0.38 percent; and SEM observation was made on the surfaces of the GT aggregate and the G20 aggregate after stirring. Fig. 9 (a) is an SEM image of the surface of the GT aggregate after stirring, wherein the EDS image of point C is shown in fig. 9 (b); fig. 10 (a) is an SEM image of the surface of the G20 aggregate after stirring, in which an EDS image of a point D is shown in fig. 10 (b). As can be seen from the figure, the surfaces of the GT aggregate and the G20 aggregate become rough compared to the surface of the aggregate before stirring (fig. 6 (a) and 7 (a)), and some coating substances on the surface of the aggregate fall off, and as can be seen from fig. 10 (a) and 10 (b), most of the G20 aggregate remains the original morphology after stirring in water.

In conclusion, after the used cement kiln silicon mullite brick aggregate is subjected to modification treatment by the carbon black impregnation liquid and the silica sol impregnation liquid, the surface of the used cement kiln silicon mullite brick aggregate is coated by the carbon black impregnation liquid and the silica sol impregnation liquid, so that the volume density of the used cement kiln silicon mullite brick aggregate is increased, and the apparent porosity and the water absorption rate are reduced. However, it was found that carbon black and silica sol obtained by modifying the carbon black-impregnated liquid and silica sol-impregnated liquid to obtain GT aggregate and G20 aggregate with surface coating were dropped to different degrees after stirring in water.

By calculating the comparison, it is known that: the bonding degree of the silica sol coating layer of the G20 aggregate and the used cement kiln silica mullite brick aggregate is relatively tighter than the bonding degree of the carbon black coating layer on the surface of the GT aggregate and the used cement kiln silica mullite brick aggregate, and the quality of the used cement kiln silica mullite brick aggregate is increased along with the increase of the silica sol concentration of the G20 aggregate; it can be seen from the mass percentages of the GT aggregate prepared in the comparative example and the G20 aggregate prepared in example 4 that the G20 aggregate prepared in example 4 is less likely to fall off during the preparation of the iron runner castable.

(II) thermal shock resistance experiment of castable

The modified post-cement kiln silicon mullite bricks prepared in examples 1 to 4 are used for replacing brown corundum as an aggregate of an iron runner castable, and the preparation of the iron runner castable is carried out. The materials are mixed according to table 3, and the casting materials of different aggregates are named as SZ casting material, SG5 casting material, SG10 casting material, SG15 casting material and SG20 casting material, wherein the raw materials in table 3 are commercially available raw materials.

Table 3 castable formula (wt./%)

The ingredients are mixed according to the formula shown in the table 3, the ingredients are firstly mixed in a stirrer in a dry mode for 30s, then mixed in a wet mode for 180s, and the flow value of the castable is measured by a jump table method, so that the flow value reaches 120-135 mm, and the workability requirement is met. Pouring the casting material into a mould with the size of 40mm multiplied by 160mm in a vibration mode for 240s; and curing the test mold at room temperature for 24 hours, demolding, standing at room temperature for 24 hours, drying the sample in a constant-temperature oven at 110 ℃ for 24 hours, and finally preserving heat at 1450 ℃ for 3 hours in air atmosphere.

Measuring the flow value of the casting material by adopting a jump table method, measuring the expanded diameters of the casting material in 4 directions by using a vernier caliper, and taking the average value as the flow value of the casting material; and (3) according to GB/T30873-2014, carrying out water-cooling thermal shock circulation on the sample at 1100 ℃ for 3 times after the sample is subjected to heat preservation for 3 hours at 1450 ℃, and evaluating the thermal shock resistance of the castable through the residual breaking strength retention rate.

As can be seen in fig. 11: along with the increase of the content of the silica sol, the water demand of casting material samples (SG 5 casting material, SG10 casting material, SG15 casting material and SG20 casting material) taking the modified silicon mullite brick as the aggregate is gradually reduced. When the water requirements of the SG20 castable sample and the SZ castable are consistent, the difference between the flow value (128 mm) of the SZ castable sample and the flow value (130 mm) of the SG20 castable sample is not large, which indicates that the castable taking the modified silicon mullite brick as the aggregate has better construction performance.

As can be seen from fig. 12: with the addition of silica sol, the normal-temperature breaking strength of the castable sample is increased and then reduced, the residual breaking strength retention rate of the SZ castable is 29%, the residual breaking strength retention rate of the SG15 castable sample reaches 36%, and the thermal shock resistance is improved by 24.1% compared with the SZ castable sample. Therefore, the thermal shock resistance of the SG15 castable sample is better than that of the SZ castable sample.

Claims

1. The iron runner castable comprises the raw materials of aggregate, silicon carbide, white corundum and alpha-Al ₂ O ₃ The aggregate comprises brown corundum, and is characterized by also comprising modified cement kiln silicon mullite bricks and used cement kiln silicon mullite bricks;

the iron runner castable is prepared from 35-42 wt% of brown corundum, 2wt% of used cement kiln silicon mullite brick, 12wt% of modified cement kiln silicon mullite brick, 15wt% of silicon carbide, 15wt% of white corundum, and alpha-Al ₂ O ₃ 6wt% of powder, 2wt% of silicon powder, 2wt% of metal silicon powder, 2wt% of spherical asphalt, 71 wt% of Secar, 0.1wt% of sodium tripolyphosphate and 0.1wt% of sodium hexametaphosphate, and uniformly stirring and dispersing to obtain the silicon-based composite material, wherein the sum of the mass percentages of the components is 100%;

the modified cement kiln silicon mullite brick is prepared by a surface modification method of a used cement kiln silicon mullite brick;

the surface modification method of the used cement kiln silicon mullite brick comprises the steps of firstly soaking, cleaning, airing and drying the used cement kiln silicon mullite brick to obtain a pretreated cement kiln silicon mullite brick; then, taking a silica sol water solution with the mass fraction of 5-20% as an impregnation solution, and fully impregnating the pretreated cement kiln silicon mullite brick in the impregnation solution to obtain an impregnated cement kiln silicon mullite brick; and finally, drying the impregnated cement kiln silicon mullite brick to obtain the modified cement kiln silicon mullite brick.

2. The castable for an iron runner according to claim 1, wherein the impregnating solution is 15% by mass of a silica sol aqueous solution.

3. The castable for iron runners according to claim 1, wherein the impregnating solution is 10% by mass of silica sol aqueous solution.

4. The iron runner castable material according to any one of claims 1 to 3, wherein the surface modification method of the post-use cement kiln silicon mullite brick specifically comprises the following steps:

the method comprises the following steps: soaking the used cement kiln silicon mullite brick in water for 3-5 days, changing water halfway until no dust matter floats on the surface of the water, fishing out and naturally drying, and then putting the naturally dried cement kiln silicon mullite brick into a drying oven for heat preservation at 110 ℃ for 24 hours to obtain a pretreated cement kiln silicon mullite brick;

step two: dipping the pretreated cement kiln silicon mullite brick obtained in the step one in the dipping solution for at least two hours to obtain a dipped cement kiln silicon mullite brick;

5. The iron runner castable according to claim 4, wherein the aggregate comprises 23-28 wt% of brown fused alumina with the granularity of 3-5mm and not equal to 3mm, 6-7 wt% of brown fused alumina with the granularity of 1-3mm and not equal to 1mm, and 6-7 wt% of brown fused alumina with the granularity of 0-1mm and not equal to 0;

also comprises 2wt% of used cement kiln silicon mullite bricks with the granularity of 0-1mm and not equal to 0;

also comprises 10wt% of modified cement kiln silicon mullite brick with the granularity of 3-5mm which is not equal to 3mm and 2wt% of modified cement kiln silicon mullite brick with the granularity of 1-3mm which is not equal to 1 mm.

6. The castable for iron runners according to claim 4, wherein 10wt% of silicon carbide with grain size of 0.045 to 1mm and not equal to 0.045mm and 5wt% of silicon carbide with grain size of less than or equal to 0.045mm are contained;

the white corundum, alpha-Al ₂ O ₃ The particle sizes of the powder, the silicon micropowder, the metal silicon powder, the spherical asphalt and the Secar 71 are less than or equal to 0.045mm.