WO1990005123A1

WO1990005123A1 - Refractory for cast molding

Info

Publication number: WO1990005123A1
Application number: PCT/JP1989/001137
Authority: WO
Inventors: Teruyuki Nishitani; Naoki Tsutsui; Tateo Hanai; Kazuhiko Takahashi; Fumiyuki Inoue; Hideaki Ohashi; Shinji Motoike
Original assignee: Nippon Steel Corporation; Nippon Crucible Co., Ltd.
Priority date: 1988-11-04
Filing date: 1989-11-02
Publication date: 1990-05-17
Also published as: JPH02124782A; BR8907150A; DE3991306C2; JPH0631177B2

Abstract

The invention relates to a refractory for cast molding to be used as, for example, lining of a molten metal container, which contains a proper amount of an organic foaming agent generating an incombustible gas upon decomposition, such as 4,4-oxybis(benzenesulfonohydrazide). This refractory can solve the conventional problem of explosive cracking to be caused upon drying the refractory by heat.

Description

Specification

Refractory for casting

Technical field

The present invention is applicable to lining of various metal melting furnaces, heating furnaces, firing furnaces, etc., and molten metal containers including blast furnaces such as floor gutters, ladle, tundish, etc. The purpose of the present invention is to improve the explosion resistance of cast refractories used for stirring propeller pipes, nozzles, and the like used during heating and drying during heating and drying.

Background art

Various metal melting furnaces, heating furnaces, firing furnaces, etc., and lining of molten metal containers such as floor gutters, ladle, tundish, etc. of blast furnaces, as well as stirring propellers and induction mixers for molten metal processing Casting refractories used for pipes, nozzles, etc. are mainly aluminum or high-alumina materials mixed with silicon carbide, graphite, etc., depending on the application. In addition, clay and Z or powdered pitch or resin may be mixed if necessary. Further, a fluidity-imparting agent may be added in some cases. In use, a mixture obtained by mixing and kneading these compositions with water is poured into a space of a predetermined framework to form a predetermined structure. Next, when the molded body is naturally cured, or when short-time deframing is required, it is cured by heating and cured, then deframed, and heated and dried for use. Water is added in an amount of about 4 to 20 external weight% based on the powder composition. Most of the water is used to provide fluidity during the casting, and Remains in free water in the tissue. And in part, Aruminaseme down bets components in casting material composition _{_{(CaO · A £ 2 0 3}} ) are reacted, is consumed to produce a hydrate. This hydration product fills the voids of the compact and becomes a colloidal amorphous or crystalline compound exhibiting a binding force between the products or between the product and the aggregate particles. This hydrate changes into a metastable hydrate by ripening. Therefore, the main purpose of heating and drying before entering the use state is to remove free water, which accounts for most of the added water, rather than to change the state of the hydrate.

In general, when the cast material is heated and dried, the surface layer of the formed body emits an explosion and may be scattered and separated (explosion). Occasionally, explosions that burst from the inside of the compact and fly in large chunks may occur. This explosion occurs when the vapor pressure of free water generated in the molded body due to heating becomes greater than the strength of the base material of the molded body, but the mechanism that causes the explosion is complicated. Therefore, appropriate precautionary measures are often not taken. On the other hand, in the case of gutters for blast furnace slabs, organic binders such as powdered pitch or resin may be added to the composition in order to improve the corrosion resistance and thermal shock resistance of the cast material. These pitches and cashiers // may become softened and melted in the structure of the molded body, usually in the range of slightly less than 100'C to more than one hundred and several'c, due to the heat received during heating and drying. The open pores and the open pores formed after free water is scattered are sealed. Therefore, preventing the subsequent free scattering, the molded body significantly increases the internal vapor pressure, and is more likely to explode than the case of a single aluminum nascent binder. Situation. This explosion is dangerous, not only impairs the planned operation of various furnaces, etc., but also can cause personal injury.

In order to solve the above problems, as a measure to prevent explosion, a method of adding metallic aluminum powder to the casting material is generally used, and a method of adding sodium perborate powder is experimentally performed. Was done. However, when metal aluminum powder is added to a casting material using water as a kneading liquid, the aluminum reacts with the kneading liquid, and as a result, generates heat and hydrogen gas. Due to the decrease in water content due to the heat generation and the increase in the air permeability due to the generation of gas, the molded body becomes a structure that easily dehydrates during heating and drying, thereby preventing explosion. However, the problem was that the hydrogen gas generated at that time had a risk of causing a hydrogen gas explosion by fire.

In the case of aluminum perborate powder, oxygen gas is generated as a reaction with water in the pouring material. However, even if there is no possibility of causing a dangerous phenomenon such as a hydrogen explosion when adding powder of metallic aluminum, oxygen gas promotes combustion, so there is a drawback that safety is not sufficient. .

Disclosure of the invention

The present invention has been made to eliminate the explosion phenomenon at the time of heating and drying the above-described refractory for cast molding. The first invention is to use an appropriate amount of an organic foaming agent that generates nonflammable gas by decomposition. The refractory for cast molding characterized by being blended, and the second invention are characterized in that the refractory for cast molding of the first invention further comprises a foaming aid as described above. The present invention relates to a refractory for cast molding, wherein the refractory is blended in an amount of about ¹ to about ¹ with respect to the amount of the foaming agent. That is, an appropriate amount of an organic foaming agent powder that is harmless, odorless, and inert, that is, emits harmless gas by decomposition, is blended with a refractory for casting including a refractory material and a binder such as alumina cement. By doing so, it was in line with the purpose.

(Operation)

Refractory materials are mainly made of aluminum such as fused aluminum and sintered aluminum, high alumina such as sillimanite, muralite and bauxite, and shamotte silica. Use one or more of a basic material such as magnesia-vinel, silicon carbide, graphite and the like. As the binding material, clay and / or powdered pitch or resin, etc. may be blended as necessary in addition to aluminum nascent. Further, a fluidity-imparting agent such as a deflocculant may be added.

The selection conditions were that the components of the generated gas that forms degassing pores during heating and drying were non-toxic, odorless, and non-flammable, so-called non-polluting. As a result, the organic blowing agents meeting this purpose include 4,4'-oxybisbenzenesulfonyl hydrazide, P—toluenesulfonyl hydrazide, acetate-P—toluenesulfonyl hydrazide, P— Tonolenesulfonylsemicarbazide, hydrazine diisopropyl zolebonate, diphenylsulfon-1--3-3'-disulfonylhydrazide, trihydrazinotriazine and 5-phenylnitrazol, etc. One or more of them were effective. These organic foaming agents are received from low temperatures at the beginning of heating and drying. Since it is thermally decomposed by heat and mainly generates nitrogen gas, there is no danger and there is no pollution.

The refractory for cast molding to which an appropriate amount of the organic foaming agent is added is cast and cured as a mixture of water, cured, cured, deframed, and then heated and dried. When cast at room temperature, drying takes a long time at an ambient temperature of about 100Ϊ and starts at a very low temperature. Therefore, before the reduction of free water scattering inside the molded body becomes active, that is, before the water vapor pressure inside the molded body increases, the decomposition and generation gas of the organic foaming agent proceeds to fill up in the initial stage of heating and drying. As a result, air holes are formed in the structure of the molded body by gas generation from the foaming agent. The presence of these vents, or in other words, deaerated holes, can significantly reduce the risk of explosion. On the other hand, in the case of repairs, there are cases where back lining bricks and remaining old materials have residual heat at the time of cast molding, and casting is performed in a warm or hot atmosphere. In this case, the organic foaming agent gives off a decomposed gas during curing before de-framing, and deaerated pores are formed in the structure of the molded body. Therefore, before the start of heating and drying, the formed body has a good drying property and a structure with excellent explosion resistance, which is advantageous.

Next, the use ratio of the organic foaming agent will be described. The effect of adding the organic foaming agent hardly occurs when it is less than 0.05% by weight, though it varies depending on the type of the organic foaming agent. On the other hand, if the content is 2.0% or more, the amount of generated gas becomes excessive as compared with the formation of gas deaeration holes, the inside of the molded body becomes porous, and lamination (lamellar cracks) is formed. Homogeneity tends to be lost. As described above, the present invention has the advantage of no pollution when casting a casting material, and has an excellent effect as a countermeasure against explosion.However, in the construction site, there are actually various circumstances, The heating temperature may be out of the adjustment range, the temperature may not be adjusted depending on the construction site, or the heating and drying may be completed rapidly depending on the operating conditions, and the product may be used immediately. There are times when you have to come to a situation where it is inevitable. Therefore, the present inventors have further studied and as a result, by adding a blowing agent to the constitutions of the first and third inventions, a lower temperature and faster timing than in the case of the above inventions are obtained. In this way, it was found that foaming was promoted, and that the casting material used for drying in such a way exploded and then heated, and even if the temperature conditions fluctuated in severe directions, it was possible to respond more safely with high flexibility. With this foaming aid, the gas generation start temperature can be shifted from a low temperature range and the gas generation start time can be shifted earlier. Fig. 1 shows an example of this effect. That is, the second or

4 of invention the first, blending a third organic blowing agent equivalent amount or more of a blowing aid ^_1/5 or more further organic blowing agent in Complex free flow Shi Inclusive molding refractories obtained by the invention It is in. Foaming aids include those which render the refractory composition kneaded with water alkaline, such as sodium or potassium silicates, carbonates, or combinations thereof. is there. In this case, in the amount ^_1/5 less the effect of the is insufficient, the effect levels off is equivalent amount or more and not rather preferable for the refractory burner Application Benefits um, such as the force re um component increases There are evils. When considering that the refractory for casting is a powdered mixed product and the storage stability in stock, Inorganic salts composed of a weak acid and a strong base in the form of fine powder are preferred, and for example, sodium and calcium silicates and carbonates can be easily applied. The above-mentioned organic foaming agent group originally has a property that its decomposition temperature drops to near room temperature in an aqueous alkaline solution, and foaming aid added so that the water-kneaded cast refractory becomes alkaline. As agents, these substances are easy to handle and effective for the purpose of adding.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a chart showing the effect of a foaming aid on an organic foaming agent.

BEST MODE FOR CARRYING OUT THE INVENTION

[Example 1] (Table 1)

For a typical high-alumina bone material, aluminum cement cement bond refractory composition consisting of 50 parts by weight of calcined pork sight, 35 parts by weight of synthetic mist, and 15 parts by weight of aluminum cermet. From the group of organic foaming agents, select 4 44 'oxybisbenzenesulfonyl hydrazide, add 0.5 parts by weight of it, mix with water, and add 100 Φ 讓 X 100 H Specimens were made. After curing the sample in a sealed state at room temperature for 24 hours, an explosion test of the cured specimen was performed. In the explosion test, a specimen was inserted instantaneously from the ceiling outside of the furnace heated and maintained at 60 (TC) to almost the center of the furnace, and the state change due to rapid heating of the specimen was observed. In the case of a change in the state due to, for example, chipping at the tip or rupture of the trunk, the weights of these spalled off were quantitatively compared. Was used as Comparative Example 1. Test The results show that when an aluminum nascent bond pouring material (comparative example 1) without the addition of an organic blowing agent, that is, a conventional, general composition, is exposed to severe rapid heating conditions, Example 1 showed good results without falling off due to the explosion, as compared with the case of exfoliation due to the explosion by weight%. In addition, the physical properties obtained by adding the organic foaming agent are not much different from those of Comparative Example 1.

[Example 2] (Table 1)

75 parts by weight of sintered alumina, 20 parts by weight of silicon carbide, 5 parts by weight of alumina cement, and kneading additive water. Then, 0.7 part by weight of P-toluesulfonyl hydrazide was added to 0.05 parts by weight of the low-aluminum cermet bond refractory composition for cast molding, and this was designated as Example 2. An explosion test was performed in the same manner as in Example 1, and a comparative study was conducted. The results show that even without the addition of an organic blowing agent, that is, even in Comparative Example 2 which is a common low-aluminum cemented bond casting refractory, a 20% by weight explosion occurred due to rapid heating. In contrast to the drop, Example 2 showed sound and good results. Also, the physical properties of Example 2 are almost the same as or comparable to those of Comparative Example 2.

[Example 3] (Table 1)

92 parts by weight of sintered aluminum, 5 parts by weight of magnesia, 3 parts by weight of aluminum cement, and sodium pyrophosphate as a deflocculant to reduce the amount of water added for kneading and improve the compactness of the construction. For the low-alumina cement bond cast refractory composition consisting of 0.05 parts by weight, 4.4'-oxybisbenzenesulfone was used as an organic foaming agent. Example 3 A composition in which 0.3 parts by weight of nilhydrazide and 0.3 part by weight of P-toluenesulfoninolehydrazide were added was designated as Example 3, and a comparative study was conducted in the same manner as in Example 1. In this case, Comparative Example 3 in which no organic foaming agent was added suffered spalling of 50% by weight, while Example 3 showed good results without spalling due to explosion. This indicates that a combination of two organic blowing agents is effective for improving the drying property. Thus, the physical properties of Example 3 are not much different from those of Comparative Example 3.

[Example 4] (Table 2)

Refractory for cast molding containing 72 parts by weight of fused aluminum, 20 parts by weight of silicon carbide, 5 parts by weight of powdered pitch, 1.5 parts by weight of Kibushi clay, and 1.5 parts by weight of aluminum cermet In addition, 0.05 parts by weight of sodium pyrophosphate was kneaded and added for the purpose of improving the compactness of the construction by reducing the amount of water added. Example 4 was prepared by selecting and adding 0.5 and 5 parts by weight of xylbisbenzenesulfonyl hydrazide, and mixed with water to prepare a columnar sample of 100 sq. X 100 H thigh. After curing the sample in a sealed state at 60'CX for 3 hours, an explosion test of the cured specimen was performed. In the explosion test, the specimen was inserted from the outside of the furnace heated to 600 ° C in the ceiling direction to the center of the furnace almost instantaneously, and the state change due to rapid heating of the specimen was observed. As Comparative Examples, Comparative Example 4 without additives and no additive was taken as Comparative Example 4, and Comparative Example 5 with metallic aluminum powder added by the conventional method (0.2%). As a result of the test, Comparative Example 4 without any additive showed a burst in a state in which the specimen did not remain in the original shape. That is, while the amount of peeling was 100%, No. 4 showed no drop due to explosion and showed the same good results as Comparative Example 5 with the addition of metal aluminum powder. Comparative Example 5 is a typical example of a composition used as a cast refractory for a blast furnace floor gutter, but is intended to improve properties such as corrosion resistance and thermal shock resistance. Here, powder pitch is blended. As described in the section of the background art, this powder pitch is likely to cause the molded body to easily become more easily explosive during heating and drying.For example, a comparative example in which no explosion countermeasures are taken In the case of 4, the test piece was in a state where it could not remain in its original form after the test (100% drop).

Next, what was shown in the present example was subjected to an actual furnace test for a blast furnace tapping gutter. 25 tons were poured into the large gutter in front of the tapping hole of the 3000m ³ class large blast furnace at the old residual material surface temperature of 80'C, and put into practical use. After curing overnight, as in the case of the cast material for gutter to which metal aluminum powder was added to deal with the conventional explosion resistance using a hydrogen gas generation mechanism, deframed, heat-dried for 2 days, and then passed Started. In the actual furnace test, there were no problems such as explosions, cracks, or delaminations from drying to completion of hot-rolling, and the gutter durability was equal to or better than that of conventional products.

[Example 5] (Table 2)

To the composition used in Example 4, 0.2 part by weight of lithium carbonate was further added as a foaming aid, and a specimen was prepared in the same manner as in Example 4. The cells were sealed at room temperature (25'C) for 24 hours. A burst test was performed in the same manner as in Example 4. As a result of performing with Comparative Example 4 and Comparative Example 5, Comparative Example 4 without the additive exhibited a burst in a state where the specimen did not remain in the original shape and was disjointed. That is, while the drop amount was 100%, Example 5 did not show any drop due to the explosion and showed good results as in Comparative Example 5 in which the metal aluminum powder was added.

The thing shown in the present example was subjected to an actual furnace test for a blast furnace tapping gutter. A 30-ton pouring process was applied to the old gutter before the tap hole of the 4000m ³ class large-scale blast furnace at a tapping temperature of 30'C, and put into practical use. In each case, after curing overnight, as in the case of the flow-in material for gutters to which metal aluminum powder was added to deal with the conventional explosion resistance by the hydrogen gas generation mechanism, the frame was removed, and after heating and drying in the process for 2 days, Iron pouring has started. In the actual furnace test, there were no problems such as explosions, cracks, or delaminations from drying to completion of hot-rolling, and the gutter durability was equal to or better than that of conventional products.

Refractory for cast molding of anoremi nasemene bond (compounding: parts by weight) Implementation Comparison Comparison

Example 1 Example 1 Example 2

Sintered alumina 75 75 92 92

Calcined bauxite 50 50

Fire

Synthetic mullite 35 35

Sex

Silicon carbide 20 20

Lumber

Magnesia 55 fee

Aluminum cemet 15 15 5 5 3 3 Sodium pyrophosphate-0.05 0.05 0.05 0.05

Yes 4 4 'oxybis 0.5 _ 0.3

Benzens Reho ―

Nilhi Drazid

Departure 1rn

Foam P— Toluenesul 0.7 0.3 — Agent Honi Lehi Drazide

Water added for kneading 12 12 5 5 6 6

(Outer weight%)

Physical properties after drying at 110'C

Remaining line rate of change) - 0.1 - 0.1 -0.1 -0.1 -0.1 -0.1 bending strength ^{(kg / cm 2) 60 70} 75 60 50 55 Compressive strength ^{(kg / cm 2) 150 160} 180 140 130 145 Burst Test Result Abnormal Tortoise 異常 Abnormal Abnormal

at600 ° C None Many None Many None Many

0 30 0 20 0 50 Two

Refractory for cast molding for blast furnace Kotobuki (mixing: parts by weight)

¾Example ¾Example Comparative example Comparative example 4 5 4 5 Electro-fused aluminum 72 72 72 72 Fire Silicon carbide 20 20 20 20 Properties Powder pitch 5 5 5 5 Material Kibushi clay 1.5 1.5 1.5 1.5 Material Alumina cement 1 5 1 5 1 5 1 5 Sodium pyrophosphate 0.05 0.05 0.05 0.05 Aluminum metal powder 0.2 Yes

Machine 4 ♦ 4 'oxybis 0.5 0.5 ― One

Benzenes Norejo

Ni Nore Hydra Zid

Bubbles

Agent foam Carbonated lime 0 2

Assistance

Agent

5.5 5.5 5.5 5.5

(Outer weight V)

Physical properties after drying

Remaining line rate of change (%) -0.1 one 0.1 -0.1 one 0.1 Flexural strength ^{(kg / cm 2) 60 55} 65 50 Compressive strength ^{(kg / cm 2) 180 160} 175 145 Burst Test Results Failure Failure original sea lions Abnormal at 600 ° C None None None None

剝 Drop weight (%) 0 0 100 0 Industrial applicability

① Improvement of safety

Cast refractories are excellent in workability, but have the disadvantage of exploding depending on the conditions of use. In order to prevent explosion, measures such as slow heating and heating are taken, but forming a myriad of deaerated holes in the compact is also an effective preventive measure. The use of metal aluminum powder for forming the degassing pores is performed, but has a drawback that the generated gas has a risk of causing a hydrogen gas explosion as described above.

INDUSTRIAL APPLICABILITY The present invention is a cast molding refractory in which degassed pores are formed by non-hazardous nitrogen gas.

② Shortening of construction period

Since the refractory for cast molding of the present invention has excellent drying properties, the period for heating and drying is shortened, and the construction period for drying is shortened.

③ Effect of energy saving

Since the drying time can be shortened, fuel cost can be saved, and the energy saving energy is very effective.

性 Responsiveness to change in furnace rolling

Even if the so-called furnace operation, such as the furnace operation plan, is changed and its use is accelerated, heating and drying can be handled with considerable flexibility. As described above, the present invention has extremely high industrial utility value from the viewpoint of safety, construction period, energy saving, furnace operation plan and the like.

Claims

The scope of the claims

(1) A refractory for cast molding, comprising an appropriate amount of an organic foaming agent that generates a nonflammable gas upon decomposition.

(2) a blowing aid that promotes foaming of the organic foaming agent to claim 1, characterized in that in proportions of approximately ^_1/5 to approximately equivalent amount relative to the amount of the organic blowing agent Refractory for cast molding as described.

(3) 4 and 4'-Oxybisbenzenesulfonyl hydrazide, P — Toluenesulfonyl hydrazide, Acetone P — Toluenesulfonyl hydrazide, P — Tonorenen Honinoresemi canolenozide, hydrazide force, olevonic acid sap mouth pill, diphenylsulfone-1

. One or more organic blowing agents that generate nonflammable gases upon decomposition, such as 3'disulfonylhydrazide, trihydrazinotriazine, and 5-phenyltetrazole And 0.05 to 2.0 parts by weight per 100 parts by weight of the refractory material.

(4) Claims characterized in that one or more of sodium and potassium silicates or carbonates are blended in an amount of about 0.01 to 2.00 parts by weight. 4. The refractory for cast molding according to item 3 of the above item.