JP3295580B2 - Basic amorphous refractories - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a basic amorphous refractory excellent in digestion resistance, corrosion resistance and spoiling resistance.

[0002]

2. Description of the Related Art The lining of steelmaking furnaces is shifting from regular refractories to irregular refractories in order to save labor. In particular, in ladle and tundish used in continuous casting of steel, the lining of irregular shaped refractories is increasing.

[0003] Taking an example of an amorphous refractory for a ladle, a neutral refractory such as alumina-spinel, which is more excellent in corrosion resistance, is replaced with a conventional acidic refractory such as fluorite or zircon. Became used. However, with the recent severer furnace operation and reduction in refractory unit consumption, the durability of the alumina-spinel material is not sufficient. In addition, acidic or neutral amorphous refractories are not preferable from the viewpoint of cleansing.

[0004] Irregular refractories are classified into cast materials, sprayed materials, press-fitting materials, and the like according to differences in construction methods, but the same problem applies to any irregular refractories.

[0005] Therefore, basic amorphous refractories using magnesia as an aggregate have been proposed. For example, JP-A-54-70
No. 312, JP-A-1-111779, JP-A-4-19864, and the like.
This property is excellent in clean steel formation and corrosion resistance to basic slag. However, since the coefficient of thermal expansion and slag penetration are large, thermal or structural resistance to spoiling is poor.

[0006] On the other hand, among the basic amorphous refractories, the material made of calcia-magnesia clinker as an aggregate is not only cleansed and corrosion resistant to basic slag, but also has a higher quality than the above-mentioned magnesia. And excellent in strength and toughness. It also has excellent spalling resistance due to its slag penetration resistance.

However, this calcia-magnesia substance is digested by the reaction with construction water, and the volume expansion accompanying the digestion causes cracks or collapses in the construction body tissue. Also,
Calcium hydroxide generated by the digestion reaction generates steam by thermal decomposition, and when the temperature rises rapidly, the construction body explodes due to the rise in internal pressure.

[0008] The digestion reaction also occurs in magnesia, but C
Calcia-magnesia, which has a high content of aO component, is digested more remarkably than magnesia, which hinders the practical use of amorphous refractories made of calcia-magnesia.

Conventionally, as a measure for improving the digestion resistance of calcia-magnesia clinker, a method such as addition of impurities, coating of a hydration-resistant layer, or surface treatment has been known. For example, the Al ₂ O ₃ in JP 62-182137 0.2
~ 2% is added. As an example of forming a hydration resistant layer,
Japanese Patent Application Laid-Open No. 61-256961 discloses carbonation of the surface of aggregates, and Japanese Patent Publication No. 3-71385 discloses coating with calcium phosphate salts. As the surface treatment, Japanese Patent Application Laid-Open No.
No. 13, surface treatment with a phosphoric acid and acidic phosphate solution together with adjustment of the contents of TiO ₂ and Fe ₂ O ₃ .

[0010]

However, in the case of an amorphous refractory which receives a large amount of construction water and a high-temperature atmosphere during use, even if the calcia-magnesia clinker treated by the above-mentioned conventional method is used, the digestion-resistant material is used. Sex is still not enough. Further, the clinker disclosed in Japanese Patent Application Laid-Open No. 5-294713 also has a problem that the spalling resistance is reduced due to slag penetration.

[0011]

Means for Solving the Problems The present inventors have proposed Calcia
In the study of basic amorphous refractories mainly composed of magnesia clinker, we have studied ways to improve the digestion resistance of the calcia-magnesia material without compromising the corrosion and spalling resistance effects. as a result,
When a sintered calcia / magnesia clinker containing MgO, CaO and Al ₂ O ₃ in a specific range as a chemical component and further having a surface layer of calcium phosphate and magnesium phosphate is blended into a part or the whole of the aggregate, It has been found that the object of the present invention can be achieved, and the present invention has been completed. And the features are:
It is as described in the claims.

Hereinafter, the present invention will be described in more detail.

The chemical composition of the sintered calcia magnesia clinker used in the present invention is MgO + CaO on a burning basis.
Is 97% by weight or more, CaO is 10 to 30% by weight, Al ₂
O ₃ is 0.5 to 3% by weight, and the weight ratio of Al ₂ O ₃ / CaO is 0.05 or more.

If the content of CaO is more than the above range, digestion resistance and corrosion resistance are reduced, and if the content is small, the ratio of MgO is increased and slag penetration resistance, hot strength and spoiling resistance are inferior.

[0015] Although Al ₂ O ₃ is to generate a low Torubutsu of MgO-CaO-Al ₂ O ₃ system which is effective in preventing digestion, less the no, the effect of the excessively high corrosion resistance and hot strength Causes a decline. Further, the weight ratio of Al ₂ O ₃ to CaO is also important, and the weight ratio of Al ₂ O ₃ / CaO is 0.05 or more, and if it is less than this, sufficient digestion resistance cannot be obtained.

Further, SiO ₂ and Fe ₂ O ₃ are formed by clinker.
Although it has the property of enhancing digestion resistance of itself, it has been found that it acts as a harmful component that promotes digestion in amorphous refractories used in contact with construction water and in high-temperature atmospheres. Therefore, these two components is desirably as small as possible, for example, SiO ₂ is 0.25% by weight% or less,
Fe ₂ O ₃ is at most 0.2% by weight.

In the present invention, by limiting the bulk density of the calcia-magnesia clinker to a relative density of 97% or more, preferably 98% or more, there is an effect on digestion resistance and volume stability. This is presumably because the clinker is less likely to cause wetting and slag penetration due to tissue densification.

The calcia-magnesia clinker used in the present invention further has a surface layer of calcium phosphate and magnesium phosphate. Thus, in combination with the adjustment of the chemical components and the limitation of the bulk density, the basic amorphous refractory of the present invention is a material having corrosion resistance, spalling resistance, and excellent digestion resistance.

The effect of the surface layer in the present invention is closely related to the chemical composition of the clinker. If the chemical component is outside the range limited by the present invention, even if it has this surface layer, it is inferior in digestion resistance, corrosion resistance, slag penetration resistance or spalling resistance, and the effect of the present invention is I can't get it. Although the detailed mechanism is not clear, it is considered that one of the causes is that the Al ₂ O ₃ component in the clinker acts as a catalyst to form firm calcium phosphate and magnesium phosphate layers on the clinker surface.

The calcia-magnesia clinker used in the present invention is produced, for example, as follows. That is, an MgO source such as magnesium hydroxide, magnesite, and brucite, and a CaO source such as calcium hydroxide, quicklime, etc.
The source and further the Al ₂ O ₃ source are mixed in a ratio that becomes the component defined in the present invention, and after pressing, the mixture is mixed with a rotary kiln to obtain 170 parts.
It is fired at a temperature of about 0 to 1900 ° C. Next, the obtained clinker is brought into contact with, for example, phosphoric acid or an aqueous solution containing one or more phosphoric acids, and then dried to form a surface layer of calcium phosphate and magnesium phosphate on the clinker surface.

Here, calcium phosphate as a component of the surface layer refers to monobasic calcium phosphate, dibasic calcium phosphate and various hydrates thereof. On the other hand, magnesium phosphate refers to trihydrate and heptahydrate of magnesium hydrogen phosphate.

The total amount of calcium phosphate and magnesium phosphate constituting the surface layer of the calcia / magnesia clinker is, for example, 0.1 to 1% by weight in terms of P ₂ O ₅ in a clinker having a particle size of 3.35 to ₂ mm. It is desirable that If it is less than 0.1%, the digestion resistance is insufficient.
If the content exceeds 1% by weight, a low-phosphate-based melt is formed, leading to a decrease in corrosion resistance.

1 and 2 show slag penetration resistance,
4 is a graph showing the results of testing for anti-sporing properties. The test of each figure is as follows.

That is, based on an amorphous refractory having the following composition using a magnesia clinker shown in Table 1 below, the magnesia clinker was obtained by using a calcia magnesia clinker shown in Table 1 below. Coarse grain part → medium grain part → fine grain part. That is,
Substitution with calcia magnesia clinker is carried out for coarse grains up to 50% by weight,
Substituted into fine particles in order. The relationship between the replacement amount by the calcia / magnesia clinker and the physical property value of the amorphous refractory was determined.

The test for obtaining the physical properties was performed in the same manner as that described in the section of Examples described later.

Sintered magnesia clinker Coarse particles (10 to 1 mm) 50% by weight 〃 Medium particles (1 mm or less) 20 〃 Fine particles (0.074 mm or less) 30 結合 Binder (alumina cement) Overhang 5 こ う Peptizer Sodium tripolyphosphate 0.1 掛 け Sintered calcia / magnesia clinker has a chemical composition and density within the range defined by the present invention, and has a slag penetration resistance in proportion to the substitution amount. Improvement in both spalling resistance is confirmed. Further, as apparent from the graph results, the substitution amount of this calcia-magnesia clinker was 15% by weight at which the improvement of these physical properties became more remarkable.
The above is preferred.

In addition to the calcia-magnesia clinker as a refractory aggregate, within the range not impairing the effects of the present invention,
You may use together with other refractory raw materials. For example, electrofused or sintered magnesia clinker, magnesite ore, Al ₂ O ₃
-MgO-based spinel clinker, zircon, zirconia and the like. Alternatively, calcined products of sand shale, bo
Calcite calcined or sintered products, sillimanites, synthetic mullite, fused or sintered alumina, activated alumina,
Dianapores and aluminum oxide by a via method may be used.

In order to make use of the corrosion resistance and clean steel effect of the basic properties, magnesia clinker is most preferably used in combination with other refractory raw materials. The combined use of magnesia clinker improves corrosion resistance.

The magnesia clinker may be either a sintered product or an electrofused product, and preferably has a MgO purity of 90% by weight or more. In order not to impair the effects of the present invention, the amount of use is less than 85% by weight based on the total aggregate.

As the binder, hydraulic cement such as alumina cement and Portland cement, colloidal silica
Amorphous silica such as vaporizable silica and gel silica, alkali metal salts such as sodium phosphate, phosphate glass, sodium silicate, and potassium nitrate; alkaline earths such as aluminum phosphate, aluminum sulfate, and potassium phosphate Inorganic binders such as metal salts and orthophosphoric acid, or carbons such as tar and pitch, resin such as phenolic resin and furan resin, pulp waste liquid, bitter and the like can be mentioned. The added amount is 1 to 15% by weight based on the outer weight of the refractory aggregate.
Is added in an appropriate amount according to the type of each binder.

As in the case of conventional amorphous refractories, depending on the construction method or use conditions, coarse particles of refractories, peptizers, curing agents, curing retarders, silica flowers, clay, silicon carbide,
Carbon powder, graphite, metal powder, metal fiber, organic fiber, inorganic fiber, etc. are added.

In the pouring work, in order to impart fluidity,
The addition of a peptizer is preferred. Specific examples of peptizers include sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, sodium acid hexametaphosphate, sodium borate carbonate, sodium citrate, sodium tartrate,
Examples thereof include sodium polyacrylate and sodium sulfonate.
The amount of addition is an outer coat for the refractory aggregate, and is preferably 0.
01 to 0.5% by weight.

[0033]

EXAMPLES Table 1 shows the characteristics of the refractory aggregate used in each example. Table 2 shows Examples of the present invention and Comparative Examples, and Table 3 shows the test results.

In Table 1, calcia-magnesia clinker,... Having characteristics within the range defined in the present invention, calcia-magnesia clinker
(a), (b), (c), (d), and (e) have characteristics outside the scope of the present invention.

In each example, 7% by weight of construction water was added, and after kneading,
It was poured into a vibrating mold, cured, dried and then tested. The test results in Table 2 were measured under the following conditions.

Slag erosion resistance: Using a high frequency induction furnace manufactured by Fuji Denpa Kogyo KK, CaO / SiO ₂ molar ratio = 3,
Slag having a composition of 10% by weight of Al ₂ O ₃ was used as an erosion agent. 1
The test piece was immersed in the erosion agent heated and melted at 600 ° C. for 30 minutes, and the test piece was subjected to 10 cycles, and then the erosion dimension of the test piece was measured.

Slag penetration resistance: The thickness of the slag permeation layer was measured from the cut surface of the test piece for which the above-mentioned slag erosion resistance was measured.

Spalling resistance: A test piece was lined in a rotary slag erosion tester manufactured by Toda Super Refractory Co., Ltd., and converter slag (CaO / SiO ₂ molar ratio = 3) was used as an erosion agent at a temperature of 1600 ° C. Slag infiltration was attempted in 5 cycles of × 1 hour. Next, the test piece after the slag infiltration was rapidly heated to 1600 ° C., held for 30 minutes, rapidly cooled to 500 ° C., and this operation was performed for 5 cycles. The presence / absence of cracks and the degree of cracks with the non-penetrable layer were evaluated according to the following criteria.

A: no cracks, B: small cracks, C: large cracks Digestion resistance: Test pieces were placed in an autoclave at a temperature of 130 ° C.
After holding at 2.7 atm for 10 hours, the linear change rate, the appearance of cracks in appearance, and the degree of cracks were evaluated.

The degree of cracking was evaluated according to the following criteria.

A: no cracks, B: small cracks, C: large cracks, actual machine test; lined on slag line of 250 t ladle,
The erosion rate was determined.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

As shown in the test results of the respective examples, the examples of the present invention showed that the slag erosion resistance, the slag penetration resistance, the spalling resistance,
Good results were obtained in both digestion resistance and actual machine tests.

On the other hand, in Comparative Example 1, only the magnesia clinker was used as the aggregate, and the slag penetration resistance and the spoiling resistance were poor. Comparative Example 8 is an alumina-spinel material in which spinel is used in a fine powder portion, and is excellent in digestion resistance but inferior in slag erosion resistance, slag penetration resistance and spoiling resistance. Comparative Example 2 uses calcia-magnesia clinker without a surface layer and is inferior in digestion resistance. Comparative Example 3 using a calcia magnesia clinker having a relative density lower than the limited range of the present invention is inferior in digestion resistance, slag penetration resistance and spoiling resistance. Comparative Example 4 using a calcia-magnesia clinker having an Al ₂ O ₃ / CaO ratio smaller than the limited range of the present invention is inferior in digestion resistance. Comparative Example 5 uses calcia / magnesia clinker having a smaller Al ₂ O ₃ / CaO ratio and a smaller content of Al ₂ O ₃ than the range limited by the present invention, and is inferior in digestion resistance. Comparative Example 6 uses calcia-magnesia clinker having a larger CaO content than the limited range of the present invention, and is inferior in digestion resistance and corrosion resistance. Comparative Example 7 had a high content of magnesia clinker of 90% by weight, and was inferior in slag penetration resistance and spalling resistance. The actual machine test was used for a slag line, and in each of the examples of the present invention, no peeling damage was found, and excellent durability was obtained in each case.

The irregular-shaped refractory of the present invention may have a particle size constitution other than those shown in the above-described embodiments, or may contain an additive, as long as it falls within the scope of the present invention. In addition, good results can be obtained even at sites other than the slag line in the actual machine test.

[0048]

The basic amorphous refractory of the present invention is characterized by solving the problem of digestion in the calcia-magnesia material, and thereby, in addition to the clean steel and slag erosion resistance, which are the characteristics of the basic properties, the calcia-magnesia refractory is improved. The effects of the slag penetration resistance and the spalling resistance of the magnesia can be fully exhibited.

The present invention has an extremely high industrial value as an amorphous refractory material which can cope with severer furnace operation and high quality steel in recent years.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the substitution amount of calcia clinker within a limited range of the present invention and the slag penetration resistance of an amorphous refractory.

FIG. 2 is a graph showing the relationship between the amount of substitution of calcia-clinker within a limited range of the present invention and the spoiling resistance of an amorphous refractory.

Continued on the front page (72) Inventor Toshihiro Isobe 1-3-1, Shinhama, Arai-machi, Takasago City, Hyogo Prefecture Inside Harima Ceramic Co., Ltd. (72) Inventor Kimihiko Takeuchi 1-3-1, Shinhama, Arai-machi, Takasago City, Hyogo Prefecture Harima Ceramics Stock In-company (72) Inventor Shoichi Itase 1-3-1 Shinhama, Arai-machi, Takasago-shi, Hyogo Harima Ceramics Co., Ltd. (56) References JP-A-5-345680 (JP, A) JP-A-59-35060 (JP) , A) JP-A-62-182137 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/66

Claims (3)

(57) [Claims] 1. The chemical composition is MgO + CaO on a burning basis.
97 wt% or more, CaO is 10-30 wt%, Al ₂ O ₃ is 0.5
33% by weight, a weight ratio of Al ₂ O ₃ / CaO of 0.05 or more, a relative density of 97% or more, and a calcia-magnesia clinker having a surface layer of calcium phosphate and magnesium phosphate of 15% in all refractory aggregates. A basic amorphous refractory characterized in that it is used in an amount of not less than 10% by weight. 2. The basic amorphous refractory according to claim 1 , wherein the chemical composition of the calcia-magnesia clinker is:
On a burning basis, MgO + CaO is 97% by weight or more, CaO is 10%
3030% by weight, Al ₂ O ₃ 0.5 to 3% by weight, Al ₂ O ₃ / Ca
O weight ratio is 0.05 or more, SiO ₂ is 0.25 weight% or less, Fe ₂
A basic amorphous refractory in which O ₃ is 0.2% by weight or less. 3. The basic amorphous refractory according to claim 1 , wherein the magnesia clinker containing 90% by weight or more of MgO is 85% by weight based on the ratio of the total refractory aggregate.
Less than basic amorphous refractories.