JPH11310815A - Method for working castable refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent the defect of a worked body caused by the explosion at the time of drying and the mechanical damage at the time of removing a core, etc., by casting a castable refractory containing a specific quantity of alumina cement into a worked frame space and removing moisture at a specific temp. after curing at a specific temp. SOLUTION: At the time of working the lining refractory on the inner wall surface of a torpedo car, a backup refractory, such as chamotte brick, is worked along an iron shell and the core is set in the inner side of this car to form a casting space. The castable refractory is cast into this space. This castable refractory contains 0.5-8 wt.% alumina cement and as the other, specific quantities of SiC, artificial graphite, pitch, etc. After casting work, the core and the inside of the car are heated and the castable refractory is heated at 30-80 deg.C and cured for about 30-80 hrs. Thereafter, desirably, the core is removed and the castable refractory is heated to >=100 deg.C by using a burner, etc., to remove the moisture and dry the castable refractory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a cast refractory containing alumina cement, and more particularly to a technique for pouring a cast refractory for lining a mixed iron car into an inner wall surface of the mixed iron car and drying the same. .

[0002]

2. Description of the Related Art Mixed-iron cars are used to transport hot metal from a blast furnace to a converter in a steel making process. Also, this mixed iron wheel has been used for more than 10 years for pretreatment for removing impurities such as silicon, sulfur and phosphorus in hot metal.

[0003] The refractory lining of such a mixed-iron car, that is, the refractory that comes into contact with the hot metal, has conventionally been constructed by stacking refractory bricks. However, in view of the recent shortage of skilled brick-laying workers, and for the purpose of reducing construction costs, recently, instead of brick construction, construction methods using cast refractories (hereinafter simply referred to as cast materials) have been studied. Have been.

[0004] The casting material has been conventionally used as a material for a ladle or a blast furnace tapping gutter, and contributes to cost reduction and achievement of mechanization and automation. In addition, the construction method using this casting material is a molding method in which a casting material obtained by kneading a refractory component such as a metal oxide constituting a refractory into powder and granules using water or the like as a medium to have fluidity is used in a mold. It is a method of pouring and solidifying.

When the construction method using such a casting material is applied to the lining of a mixed iron vehicle, a mold called a core which forms the inner shape of the refractory is installed inside the mixed iron vehicle, and the core and the mixed iron are installed. A construction method is conceivable in which a pouring space is formed between the car interior wall and the permanent brick installed inside the mixed iron car, and the above-mentioned kneaded material of the pouring material and water is poured into the pouring space and cured. .

However, this cast material is widely used as a refractory for lining a mixed iron car because of its difficulty in construction compared to a ladle and the like, and the cast material is not sufficiently durable. The fact is that it has not been reached.

[0007] That is, since the mixed-iron wheel is a container for transporting molten iron as described above and is also used as a pretreatment reaction vessel, its refractory lining has, in addition to refractory properties,
A material having excellent durability against reaction with hot metal or slag is required, and a refractory such as graphite-SiC-alumina is used. However, when such a refractory is used as a pouring material, the strength after pouring and curing is low, so that there is a new problem that the construction body is damaged when the core is removed from the frame. Further, as a common problem of the casting material, there is a problem that the explosion is likely to occur due to rapid vaporization and expansion of the moisture in the construction body during heating and drying after the casting.

As a technique for preventing such a problem from causing damage to the construction body, a method of increasing the amount of cement in the casting material can be considered. However, although this method is a suitable method for increasing the strength of the construction body after curing, it is not an effective measure against the problem of explosion due to rapid vaporization of water during heating and drying after construction.
In particular, when using alumina cement which is considered to be effective for refractories such as the lining of the mixed iron wheel, explosion due to rapid heating and drying was remarkable.

As a technique that can prevent the occurrence of this explosion,
Conventionally, Japanese Unexamined Patent Publication No. 53-66917 discloses that
A method of adding Al and a method of adding organic fibers to a casting material have been proposed in JP-A-56-5172. However, in the former technology, hydrogen gas is generated by the reaction between moisture and metallic Al, and especially in a mixed-iron car with an open port only for an iron port, the hydrogen gas stays inside, and there is a problem in terms of safety. was there. On the other hand, with the latter technology, there is no problem in terms of safety, but the effect of suppressing explosion is small,
It was not practical. In addition, Japanese Patent Application Laid-Open No. Hei 8-260018 proposes a technique of making a lining structure capable of absorbing moisture into a lining refractory of a mixed iron car. The technique according to this proposal is to improve the lining material itself. not,
The measures were indirect and could not be implemented in some cases due to design.

[0010] As described above, in the conventional technique of constructing a refractory lining of a mixed iron car using a casting material, the construction material defect due to explosion when the casting material is dried or mechanical damage when the core is removed from the frame is effectively prevented. There was no construction method that was sufficiently satisfactory to prevent such problems.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in order to develop a method of constructing a cast refractory capable of solving the above-mentioned problems. When constructing objects
An object of the present invention is to propose a construction method capable of effectively preventing construction body defects due to explosion during drying and mechanical damage at the time of core removal.

[0012]

The inventors of the present invention have conducted intensive studies for realizing the above object, and as a result, have completed the invention having the following features. That is, the method for constructing a cast refractory according to the present invention is as follows.
In constructing the cast refractory containing at a ratio of, the cast refractory is poured into the space in the construction frame, and then 30 to
It is cured by heating to 80 ° C and then heated at a temperature of 100 ° C or higher to remove moisture.

[0013] In particular, when the refractory is poured into the space formed between the core and the inner wall surface of the mixed-iron car by pouring the refractory into the space, and then drying the refractory, at least the following (a) ~ (C). (a) 0.5 to 8 wt. in the pouring space between the backup refractory constructed along the steel shell and the core set inside the car
(B) heating the cast refractory to 30-80 ° C and curing (c) heating the cast refractory at a temperature of 100 ° C or higher to remove moisture In the above construction method, the step (b) of heating and curing the cast refractory is preferably performed by heating the core or the inside of the core, and is preferably performed before the de-framing step. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an example of a method for constructing a cast refractory according to the present invention, a method for constructing a refractory lining a mixed iron car will be described below. (1) In the present invention, first, a pouring material containing 0.5 to 8 wt% alumina cement is poured into a pouring space between a backup refractory constructed along a steel shell and a core set inside the vehicle. Here, the backup refractory is a refractory brick that is in contact with the inner surface of the steel shell directly or via a filler, and a refractory used in a normal mixed iron wheel such as a chamotte brick can be used.

In the present invention, a refractory containing 0.5 to 8% by weight of alumina cement is used as a casting material. The reason for this is that alumina cement is superior in fire resistance to other cements and is commonly used as a casting material. By using a refractory containing 0.5 to 8 wt% of this alumina cement, This is because a refractory strength of 1000 ° C. or less required as a lining refractory can be obtained. That is, if the content of this alumina cement is too low, the refractory strength at 1000 ° C or less is insufficient, while if the content is too high, there is a problem that the amount of erosion increases, and particularly preferably alumina cement is used. Used at a content of 1-4%.

In particular, in the construction method of the present invention, alumina cement is preferable because it can improve the curing strength of a cast material containing 3 to 18% by weight of graphite having a low curing strength.

In this step, the surface of the backup refractory with which the poured refractory comes into contact is previously covered with a material such as tar pitch which withstands the temperature of the heating and curing step and does not allow moisture to permeate, and then is poured. Is more preferred.

(2) Next, following the pouring step (1), the pouring material is heated to 30 to 80 ° C. and cured. This curing by heating is preferably performed before going through a de-framing step of decomposing and removing the core. By this step, by causing the curing reaction to proceed promptly throughout the construction body, it is possible to effectively prevent construction body defects due to insufficient material strength, which is a problem at the time of frame removal.

Further, by heating to 30 to 80 ° C., the amount of water of crystallization and free water other than water of crystallization in the hydrate composition formed by the curing reaction can be controlled. The risk of explosion in the subsequent drying step can be sufficiently reduced.

The reason for this is that, in the drying and removal of water in a later step, removal of free water and crystallization water is necessary. In particular, removal of crystallization water is more difficult than removal of free water, and explosion occurs. It is because it is related. Specifically, when removing free water, the free water flows efficiently from the inside of the body below the boiling point to the surface of the body above the boiling point in a liquid state, so that evaporation on the surface of the body becomes the rate-determining stage, Until the removal of free water is completed, the temperature inside the construction body does not rise above the boiling point, and an excessive rise in vapor pressure which causes explosion is unlikely to occur. On the other hand, when removing the water of crystallization, the water of crystallization from the hydrate often occurs at a temperature higher than the boiling point of water, and the water of crystallization released from the hydrate immediately becomes steam. Therefore, the movement of water vapor is significantly less efficient than the movement of liquid water. As a result, in the process of removing water of crystallization,
If the diffusion and transfer of steam from the place where the crystal water was released to the surface of the construction body is the rate-determining stage, and the release of crystal water is significantly faster than the diffusion and transfer of steam, a pressure rise will occur inside the construction body, An explosion occurs. Therefore, in order to prevent explosion in the drying step, it is important to increase the proportion of free water and decrease the proportion of water of crystallization in the moisture to be dried.

In the present invention, the curing temperature is set to 30 to 80 ° C. because the alumina cement produces a hydrate having a different proportion of water of crystallization depending on the curing temperature. Specifically, the reason is as follows. That is, when the curing temperature falls below 30 ° C, 5
Produces a large amount of CaO.Al ₂ O ₃ .10H ₂ O containing 3.3% water of crystallization, and rapidly releases water of crystallization in a narrow range of 100 to 200 ° C in the subsequent drying process, increasing the risk of explosion I do. In this regard, when the curing temperature is 30 ° C. or higher, 3CaO.Al ₂ O ₃ .6H ₂ O containing 28.6% of crystallization water is generated in a large amount, and the crystallization water in a wide range of 100 to 55 ° C. Releases the risk of explosion. Therefore, the curing temperature needs to be 30 ° C. or higher. On the other hand, the curing temperature
If the temperature exceeds 80 ° C., the curing proceeds too quickly, and it is practically difficult to uniformly cure the entire construction. For uniform curing, the allowable upper limit is 80 ° C, so the curing temperature is
It must be below 80 ° C.

As a heating method, a method of providing a constant temperature chamber dedicated to heating, a method of providing a temporary constant temperature chamber covered with a vinyl sheet or the like, or a method of blowing hot air into a mixed iron car to heat the inside of the core of the core is used. And a method of directly heating the core by attaching an electric heater or the like to the core. In particular, in the present invention, it is preferable to heat the core or the inside of the core to cure the pouring material at 30 to 80 ° C. The heating curing time is preferably about 3 to 48 hours.

(3) Subsequent to the heating and curing step (2), the cast material is heated at a temperature of 100 ° C. or higher to remove moisture, thereby forming a lining refractory layer on the inner wall surface of the mixed iron wheel. In this step, since the ratio of the crystallization water in the cast material after the heat curing is small, the water can be quickly removed. In addition, this heat drying is performed by heating at a maximum temperature of 600 to 1000 ° C. for about 0.5 to 4 days using a heating burner in the same manner as in the known method. The disassembly of the core,
Removal is performed at a stage prior to the heating step performed at a temperature of 100 ° C. or higher, regardless of the stage before or after the heating curing step (2). However, in order to prevent the occurrence of defects in the construction body at the time of deframing, it is preferable to perform after step (2).

[0024]

The effects of the present invention will be described below in detail with reference to examples. In the present embodiment, an example in which the construction method of the present invention is applied to a refractory lining of a mixed iron car will be described.
The construction method of the present invention is not limited to this embodiment.

First, prior to actual casting of the cast material into the mixed iron wheel, first, the effect of the present invention was examined using a model experimental apparatus shown in FIG. 10% SiC as casting material
-5% artificial graphite-2% pitch-2% alumina cement-
A material consisting of residual alumina was used. In particular, the alumina cement consists of 75% alumina and residual calcia. To this casting material, 6.2% water was added, kneaded with a mortar mixer for 4 minutes, and poured into the frame of the experimental apparatus. The construction thickness at this time was 300 mm. After the pouring was completed, the pouring material was cured at various temperatures for 12 hours. Then, while measuring the surface temperature of the cast material, the construction body was dried by burner heating, and the presence or absence of explosion was examined.

Table 1 shows the results. As is clear from the results shown in this table, when the curing temperature was 15 ° C. (Comparative Example 1), there was no explosion under the drying condition where the surface temperature was 600 ° C., but the surface temperature was 800 ° C. Exploded under dry conditions. When the curing temperature is 85 ° C (Comparative Example 2)
Cracks occurred in the curing stage before drying (hereinafter, the experiment was stopped). On the other hand, when treated at 30 to 80 ° C according to the curing conditions of the present invention (Examples 1 to 4), no explosion was observed even under the drying condition where the surface temperature was 800 ° C.
It was found that the effect of the present invention was clear.

Next, the casting material used in the above model test apparatus was installed on the inner wall surface of an actual mixed iron wheel having a capacity of 250 tons, and the effect of the present invention was confirmed in comparison with the conventional installation method. FIG. 2 shows the structure of the lining formed on the inner wall surface of the mixed iron vehicle by pouring. First, using a mixer truck and a pressure pump, 70 t of the material to be poured was poured into the inner wall surface of the mixed iron truck over 1.5 hours. The construction thickness at this time is 3
00 mm. After the pouring was completed, the atmosphere in the mixed-iron car was maintained at a predetermined temperature for 12 hours by a hot-air blower to perform heat curing. Then, using a burner, the atmosphere inside the mixed iron car was heated to 600 ° C at a constant speed and dried.

As a result, as shown in Table 1, in Comparative Example 1, it took four days to dry the construction without defects.
In Examples 1 to 4 according to the construction method of the present invention, the construction body could be dried without defects in two days.

[0029]

[Table 1]

[0030]

As described above, according to the method for constructing a refractory of the present invention, when a refractory such as a refractory for lining a mixed iron car is constructed by using a pouring material, the explosion during drying and the explosion during de-framing are required. The construction body defect due to mechanical damage or the like can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a model experiment apparatus used in Example 1.

FIG. 2 is a diagram showing a lining structure of an inner surface of a mixed iron vehicle constructed in Example 2.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masato Kumagai 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Pref. Kawasaki Steel Engineering Co., Ltd. (72) Inventor Masato Nambu 1-chome Mizushima Kawasaki-dori, Kurashiki City, Okayama Prefecture None) Inside the Mizushima Works, Kawasaki Steel Corporation (72) Inventor Masakazu Iida 2576, east offshore, Naka-hiroji, Ako City, Hyogo Prefecture Inside Kawasaki Furnace Materials Co., Ltd. (72) Inventor Noboru Komatsubara Mizushima Kawasaki, Kurashiki City, Okayama Prefecture Kawasaki Reactor Co., Ltd. (72) Inventor Toyohide Yamaguchi 1-chome, Kawasaki Reactor Co., Ltd. Kurashiki City, Okayama Pref.

Claims (3)

[Claims] When a cast refractory containing alumina cement in a ratio of 0.5 to 8 wt% is applied, the cast refractory is poured into a space in a construction frame, and then heated to 30 to 80 ° C. to be cured. A method for constructing a cast refractory, characterized by heating at a temperature of 100 ° C or higher to remove moisture. 2. When the refractory is poured into a space formed between the core and the inner wall surface of the mixed-iron car by flowing into the space formed between the core and the refractory, and then dried, at least the following (a) to (c) The method for constructing a cast refractory, characterized by passing through the step (c). (a) 0.5 to 8 wt. in the pouring space between the backup refractory constructed along the steel shell and the core set inside the car
(B) heating the cast refractory to 30-80 ° C and curing (c) heating the cast refractory at a temperature of 100 ° C or higher to remove moisture Process 3. When the refractory lining is constructed by pouring the refractory into the space formed between the core and the inner wall surface of the mixed-iron car, and then pouring the refractory, at least the following (a) to (c) (d) A method for constructing a cast refractory, characterized by passing through the step (d). (a) 0.5 to 8 wt. in the pouring space between the backup refractory constructed along the steel shell and the core set inside the car
(B) by heating the core or the car interior of the core,
Curing the refractory at 30-80 ° C (c) Decomposing and removing the core (d) Heating the refractory at a temperature of 100 ° C or higher to remove moisture