JP2006007317A - Dry-type tundish coating material and working method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the strength of a worked body by drying for short time, and also, the operating ratio of a tundish by solving such problem as to the pick-up of carbon caused by the shortage of the strength and the increase of adding amount of a binder in the conventional dry-type coating applied to the tundish. <P>SOLUTION: In the subject dry-type coating material containing a refractory raw material and a silicate and/or a phenol resin, and also, added with an organic hardening agent having 50-120°C melting point at 0.05-5 pts.mass to 100 pts.mass of the refractory raw material, a core is inserted into the tundish and the coating material is filled up into a gap arranged between a lining refractory and the core, and successively, the coating material is heated and hardened through the core to obtain the coating. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a low-temperature curable dry tundish coating material and a construction method thereof.

  In continuous casting of steel, the tundish plays a role in distributing molten steel, uniform temperature, and deoxidation product levitation. The tundish lining refractory is usually coated with a thin refractory coating material mainly composed of basic refractory raw materials such as magnesia and dolomite to prevent molten steel contamination and lining refractory protection. The construction is done by adding water and spraying or troweling.

  The coating material is heated and dried after use and before use. However, the water added to the coating material cannot be completely removed even by drying, and the quality of the steel product is lowered due to the hydrogen pickup caused by the water.

  In addition, the coating material is dismantled and newly constructed when the remaining thickness decreases due to wear, etc., but seizure to the lining refractory requires considerable labor and time to reduce the operating rate of the tundish. ing.

Therefore, in recent years, a dry coating material construction method has been proposed (Patent Documents 1 and 2). In this method, a core is provided in a tundish provided with a lining refractory, and a dry powder coating material made of a refractory raw material and a binder is added between the lining refractory and the core without adding water. After the filling, the coating material is cured by heating from the inside of the core with a gas burner or the like. In this dry method, unlike the spraying or troweling, water is not added to the coating material, so that the problems of hydrogen pickup and image sticking are solved.
Japanese Patent No. 3342427 Japanese Patent No. 2567770

  Conventionally, a thermoplastic resin is used as a binder for the coating material used in the dry method in order to cure by heat drying. However, since the heating at that time is from the inside through the core, and the coating material itself has a heat insulating property, the back portion of the construction body is particularly difficult to receive sufficient heating. Moreover, the actual situation is that the heating temperature raising time cannot be sufficiently taken from the relationship of the operation rate of the tundish.

  For these reasons, the coating material cannot receive sufficient heating in the heat drying after the construction, and the construction body strength is insufficient. Unlike the lining refractory, the construction body of the coating material is generally as thin as about 30 to 100 mm, and if the construction body strength is insufficient, the construction body tends to collapse due to the impact received during the tundish transfer.

  As binders used in this dry coating material, phenolic resins or silicate hydrates are known. If the amount of the binder added is increased, sufficient strength can be obtained even when the construction body is dried at a relatively low temperature. However, when the amount of the phenol resin is increased, the residual carbon component due to carbonization of the resin is increased, causing a problem of molten steel contamination by the carbon pickup, and the effect of preventing the molten steel contamination of the tundish coating material is impaired.

  When hydrated silicate is used for the binder, the coating material structure becomes wet due to the elution of moisture from the silicate during heat drying, which promotes the diffusion of the binder and is effective for hardening the construction body. It is. However, moisture remains as crystal water on the back surface where heat drying tends to be insufficient, causing boiling during heat drying, and a part of the coating material is peeled off from the surface of the tundish lining layer.

  This invention solves the said conventional subject in the dry-type tundish coating material and its construction method. The feature is that it contains a refractory raw material and a silicate and / or a phenol resin as a binder, and an organic curing agent having a melting point of 50 to 120 ° C. is added in an amount of 0.05 to 100 parts by weight of the refractory raw material. It is a dry-type tundish coating material obtained by adding ~ 5 parts by mass. In addition, a dry tank in which a core is placed in a tundish, the gap provided between the lining refractory and the core is filled with the dry tundish coating material, and then the coating material is heated and cured via the core. This is a method of applying a dish coating material.

  The silicate and phenol resin used in the present invention have a role as a binder, and give the strength of the construction body after the core is removed. In addition to this, silicate has the effect of imparting strength at high temperatures when the construction body is used.

  In the present invention, organic binders having a melting point of 50 to 120 ° C. are combined with these binders, and the softening point of the binder is lowered by the compatible action, and sufficient construction body strength is obtained by heat drying at a relatively low temperature. Obtainable. In addition, due to the same effect, even when a phenol resin is used as a binder, a sufficient construction body strength can be obtained without increasing the amount of addition thereof, so that the problem of carbon pickup can also be avoided.

  Compatibilization with the binder by the organic curing imparting agent promotes diffusion of the binder into the coating material structure. Further, when the organic curing imparting agent has a melting point of 50 to 120 ° C., the organic curing imparting agent volatilizes quickly during heat drying or preheating, and uniformly forms fine pores in the coating material construction body. As a result, when a hydrate of silicate is used, water vapor generated from the hydrate during heat drying easily dissipates from the fine pores outside the construction body, and no boiling phenomenon occurs.

  On the other hand, when a phenol resin is used as the binder, the formation of the fine pores by the organic curing imparting agent promotes the volatilization of the volatile components of the phenol resin, promotes the curing of the coating material, and provides early strength. This further improves the effect of preventing the construction body from collapsing.

  As described above, the dry tundish coating material of the present invention can impart sufficient dry strength to the construction body even in heat drying at a relatively low temperature. There is no need to add a large amount of binder, and there is no problem of carbon pickup. Further, no boiling occurs when a silicate hydrate is used as a binder.

  Peeling and collapsing the tundish coating material is noticeable because the coating material is very thin unlike the lining refractory, and it is dry construction that does not cause seizure by not adding water during construction. It is a problem that arises. Prevention of carbon pickup is also an extremely important issue for the purpose of using tundish coating materials. The present invention is intended to solve problems and problems peculiar and important in this dry tundish coating material, and its industrial applicability is extremely high.

  The refractory raw material used in the present invention is not particularly different from conventional materials. For example, magnesia, magnesite, dolomite, calcia, alumina, silica, and combinations thereof are used. Among these, from the viewpoint of steel cleaning, it is preferable to use mainly magnesia, magnesite, dolomite and calcia basic raw materials. Moreover, it is good also as a refractory recycled product which has the said basic material as a main body. The particle size is, for example, 1 to 3 mm at maximum, and is appropriately adjusted to coarse particles, medium particles and fine particles.

The binder is silicate and / or phenol resin, and the amount of these binders used is optimally 1 to 10 parts by mass with respect to 100 parts by mass of the refractory raw material. If it is less than 1 part by mass, the curability tends to be inferior. When the amount exceeds 10 parts by mass, the phenol resin is not preferable because the carbon pickup to the molten steel may be caused by the residual carbon component. When the silicate is a hydrate, if it is too much, the corrosion resistance is lowered and the coating material is likely to change with time due to crystal water. The silicate is powdered silicate or a hydrate thereof. Specific examples thereof are selected from Na ₂ SiO ₃ , Na ₂ SiO ₃ .4H ₂ O, Na ₂ SiO ₃ .5H ₂ O, Na ₂ SiO ₃ .6H ₂ O, Na ₂ SiO ₃ .9H ₂ O. One or more.

  Silicate hydrates have the problem of aging due to crystal water as described above. Therefore, when a silicate hydrate is used, the addition amount is preferably small. In the present invention, by combining a specific organic curing agent, sufficient construction strength can be obtained even if the amount of silicate hydrate added is less than that of conventional materials.

  The phenol resin is a thermoplastic or thermosetting powder or flake. A thermosetting phenol resin having a melting point of 120 ° C. or lower is preferable from the viewpoint of compatibility with the organic curing imparting agent.

  The organic curing agent has a melting point of 50 to 120 ° C. When the melting point is less than 50 ° C., the coating material reacts with the refractory raw material during storage and solidifies, making it difficult to construct. When the melting point exceeds 120 ° C., the back surface of the construction body is not sufficiently cured in the short-time drying in the dry construction, and there is a concern that the construction body collapses, and the effect of the present invention cannot be obtained.

  Specific examples of the organic curing agent used in the present invention are one or more selected from lactams, acetanilides, alkylphenols and the like. More specifically, ε-caprolactam for lactams, acetanilide and / or acetoacetanilide for acetanilides, pt-butylphenol and / or p-octylphenol for alkylphenols, and the like. Further, in the case of acetanilide and acetoacetanilide, methyl dimethyl derivatives, methoxy ethoxy derivatives, carboxylic acid derivatives, acetylamino derivatives, sulfamic acid derivatives and salts thereof, chloro derivatives and the like are also included.

  Of the above organic curing imparting agents, acetanilide or acetanilide of acetoacetanilide is particularly preferable. Acetanilides are non-deliquescent and odorless unlike other organic curing agents. In the case of deliquescence, the coating material is likely to change with time by reacting with the refractory fine powder when the coating material is stored with the moisture.

  Further, the residual carbon property of the organic curing imparting agent tends to be an adverse effect of the formation of fine pores that are effective in improving the drying property. Acetanilides have no residual charcoal and are superior in heat drying properties of coating materials compared to residual charcoal alkylphenols.

  The amount of the organic curing agent used is 0.05 to 5 parts by mass on the basis of 100 parts by mass of the refractory raw material powder. If it is less than 0.05 part by mass, the curability is insufficient and the drying property is also inferior. Conversely, when it exceeds 5 mass parts, a construction body will become porous and corrosion resistance will fall. A more preferable range is 0.1 to 3 parts by mass.

  In addition, organic short fibers, organic wetting agents and the like may be added to the coating material composition of the present invention as necessary. For example, the thermal expansion stress of the construction body can be relaxed by adding 0.5 parts by mass or less of organic short fibers to 100 parts by mass of the refractory raw material.

  Organic wetting agents have the effect of preventing dust generation. Specific examples include coal / petroleum oil, vegetable oil, animal oil and the like. The addition amount is preferably 0.05 to 0.5 parts by mass with respect to 100 parts by mass of the refractory raw material powder.

  The coating material is applied to a tundish in which a refractory is newly lined or after use. For the tundish after use, install after removing the residual coating material.

  The core is put, and the above-mentioned dry powder coating material is charged into the gap between the refractory lining and the core. At the time of filling, as in the conventional method, it is preferable to apply vibration with a vibrator attached to the core to improve the filling rate of the coating material. The thickness of the coating material is preferably 20 to 60 mm. Next, the core is removed after being heated and cured from the inside of the core with a gas burner or the like.

  Examples of the present invention and comparative examples thereof are shown below. Each example was subjected to various tests using the coating materials having the compositions shown in Table 1. The test method is as follows.

  The main materials of the refractory raw material were magnesia and dolomite. The particle size was 2.8 to 1 mm: 30% by mass, 1 mm or less: 40% by mass, and 75 μm or less: 30% by mass with a JIS sieve opening.

  In the curing test, the dry coating material composition was put into a 40 × 40 × 160 mm metal frame in a dry powder state, filled with constant vibration, and then in a temperature atmosphere of 110 ° C., 150 ° C., and 200 ° C. 3 It heated for time and the hardening state was determined by the intensity | strength of the molded object specimen. A: High strength, B: Slightly low, B: Low strength.

  The apparent porosity / compressive strength test is performed on a molded specimen after being filled in a metal frame and heated at 110 ° C., and a molded specimen obtained by heating the specimen at 1500 ° C. The apparent porosity and compressive strength were measured according to JIS: R2205 and JIS: R2206, respectively.

  In the actual machine test, a core was inserted into a 30-ton tundish lined with an alumina brick, and the coating material was charged while being vibrated by a vibrator attached to the core and filled. The thickness of the coating material was about 50 mm. Heat drying was performed by heating with a gas burner from the inner surface of the core.

  As the test results in Table 1 show, the coating materials according to the examples of the present invention all have sufficient strength and denseness by heat drying in a low temperature region of 110 ° C. This can also be confirmed from the measurement of apparent porosity and compressive strength. As a result, the construction body strength can be obtained without waiting for sufficient temperature rise and drying for a long time, and heat drying in a short time required for the dry tundish coating material becomes possible. Next, thermocouple thermometers were arranged between the core and the coating material layer, and between the coating material layer and the lining brick, and the temperature was measured. When the temperature between the coating material layer and the lining brick reached 110 ° C., heating was stopped, a part of the coating material layer was cut out, and the quality of the cured state was judged by visual observation and measurement of compressive strength.

  Among these examples, those using acetoacetanilide as the organic curing agent have a higher compressive strength than the other examples. This is because, unlike others, acetoacetate anilide is non-deliquescent, so that the coating material does not solidify at all due to aging before construction, and the filling rate between the lining refractory and the core is high. by.

  In Comparative Examples 1 to 4 to which no curing imparting agent is added, sufficient strength is not obtained not only at 110 ° C. but also at 150 ° C. in the curing test and the heating test. In Comparative Example 5, the addition amount of the organic curing imparting agent is larger than the range limited in the present invention, so that the apparent porosity of the molded body is high and the corrosion resistance is poor when drying in a low temperature range.

  In Comparative Example 6, o-chlorobenzoic acid having a melting point higher than the range defined in the present invention is used as an organic curing agent. The compatibility temperature with a thermoplastic phenol resin becomes high, and it is difficult to obtain a construction strength at a low temperature of 110 ° C.

  In Comparative Example 7, 2,6-di-tert-butylphenol having a melting point lower than the range defined in the present invention is used as an organic curing agent. Since the coating material reacted with the refractory raw material during storage and solidified, and the construction was not easy, a molded specimen was not obtained and the test was not performed.

  The actual machine test was conducted for Examples 1, 2, and 10 and Comparative Examples 1 and 3. All of the examples show sufficient construction body strength, and there is no concern that the construction body collapses due to an impact received during tundish transfer. Further, although not shown in the table, there is no problem of peeling during heat drying.

The construction body strength of Comparative Example 1 is significantly inferior to that of the Example. If the material of Comparative Example 1 is also heated and dried at a high temperature for a long time, the strength of the construction body is improved. However, the purpose of the present invention is not to be dried for a short time, and the effect of improving the tundish operating rate cannot be obtained. . Although sodium metasilicate nonahydrate was used as a binder and the water of crystallization of sodium metasilicate nonahydrate remained after heating and drying, although not shown in the table, when receiving tundish water Boiling phenomenon occurred, and part of the construction body was peeled off.

Claims (3)

  While containing a refractory raw material and a silicate and / or phenol resin as a binder, an organic curing agent having a melting point of 50 to 120 ° C. is added in an amount of 0.05 to 5 parts by weight with respect to 100 parts by weight of the refractory raw material. Dry tundish coating material.   The dry tundish coating material according to claim 1, wherein the organic curing imparting agent is an acetanilide.   A core is placed in a tundish, and a dry tundish coating material according to claim 1 or 2 is filled in a gap provided between the refractory lining and the core, and then the dry tundish coating is passed through the core. Construction method of dry tundish coating material that heat cures the material.