JPH0687667A - Zirconia-mullite containing castable refractory - Google Patents

Abstract

PURPOSE:To obtain a castable refractory excellent in spalling resistance and slag wetting resistance, extremely improved in heat resistance and structural spalling resistance due to corrosion resistance and excess-sintering restraining effect even in a furnace or the like severe in the condition such as heat changing and exhibiting high stable durability. CONSTITUTION:The castable refractory has a composition made by adding 5-50wt.% zirconia-mullite clinker or zirconia-alumina-mullite clinker of >=0.5mm particle size and having components of 3-60wt.% ZrO2 and (<=20wt.% SiO2, one or more kinds of an electromelting alumina/spinel/magnesia or a sintered alumina/spinel/magnesia or the like, an aggregate containing <1wt.% alumina cement (expressed in terms of CaO), which contains a binder having >=99wt.% total content of Al2O3 and CaO, and <=0.5wt.% SiO2 component having <=0.044mm particle size in external addition and furthermore has a composition made by adding 0.5-8wt.% magnesia powder having <=0.044mm particle size into the aggregate having the described composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various types of steel-making kilns that emphasize spalling resistance and corrosion resistance, as well as non-ferrous refractories used in non-ferrous metal and various industrial kilns of the kiln industry.

[0002]

2. Description of the Related Art The lining work in a furnace is shifting from a regular refractory to an irregular refractory for the purpose of labor saving and environmental improvement. Castable refractories (hereinafter referred to as castables) have become popular because of their fineness, uniformity, and ease of construction.

Castables generally use a large amount of alumina cement as a binder. Therefore, the CaO component of the cement forms a liquid phase at high temperatures, which reduces the castable strength and fire resistance. Therefore, low cement castables, which use ultrafine alumina, calcined alumina or ultrafine silica by reducing the amount of alumina cement, have become the mainstream.

In particular, recent low cement castables are
Low water content and structure densification are achieved by the technology of using ultra-fine powder and dispersant, and for example, materials that emphasize corrosion resistance and heat resistance are also used in various steelmaking kiln furnaces with severe operating conditions such as ladle and secondary refining furnace. If it is provided and chemical corrosion with slag etc. is the main in the actual furnace wear state, even the above-mentioned dense low cement bond is good in terms of durability, but due to thermal spalling accompanied by thermal cycle There is a problem that peeling damage easily occurs and stable durability cannot be obtained.

As a measure for improving such thermal spalling, a particle size of 0.2 to 0.2 is disclosed in Japanese Patent Laid-Open No. 4-42868.
The use of 3 mm silica or mullite with a particle size of 1-10 mm is disclosed. Since the thermal expansion coefficient of silica or mullite is different from that of the main aggregate such as alumina, it is possible to suppress the development of cracks due to the formation of so-called microcracks generated during the process of using the actual furnace. It was

This is effective to some extent as a measure for improving the heat resistant spalling resistance of castables. But,
The silica stones and mullite used are inferior in corrosion resistance to alumina, which is the main aggregate, and oversintering is likely to occur due to the presence of the SiO2 component, making them suitable for use in various steelmaking kilns with severe operating conditions. Was still problematic in terms of heat resistant spalling.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a castable refractory material which has a significantly improved heat resistance spalling resistance due to the corrosion resistance and the effect of suppressing oversintering, and which has a high and stable service life.

[0008]

The castable material of the present invention contains 3 to 60% by weight of ZrO ₂ and contains SiO ₂
5-50% by weight of zirconia mullite clinker or zirconia alumina mullite clinker whose content does not exceed 20% by weight in a particle size range of 0.5 mm or more, fused alumina, sintered alumina, fused spinel, sintered spinel , Bone containing at least one kind of electro-melted magnesia and sintered magnesia and alumina cement having a total amount of Al ₂ O ₃ and CaO as a binder of 99% by weight or more as a CaO amount not exceeding 1% by weight Material and Si of 0.044 mm or less
It is a zirconia-mullite-containing refractory having a composition in which an O ₂ component is added in an amount of 0.5% by weight or less on an external basis, and further, a magnesia powder of 0.044 mm or less is set to 0. 5 to 8% by weight is added.

As aggregates, in addition to the above-mentioned compounds, silicon carbide, carbon, calcined alumina, etc., and general dispersants in amorphous refractories and additives for adjusting workability are It can be used as long as the fire resistance does not decrease.

Further, a metal fiber or an organic or inorganic fiber can be used as long as its corrosion resistance and workability are not deteriorated.

Regarding the construction, it can be used as a molded product such as a precast block from general casting.

[0012]

The use of these clinker is because the clinker itself has a microstructure and contains zirconia in a solid phase in the Al ₂ O ₃ —SiO ₂ -based low-melt composition, so that it becomes a glass having a high viscosity during hot working. , And the effect of suppressing slag infiltration is obtained, which is effective in terms of structural spalling resistance. In addition, since the coefficient of thermal expansion is small, when the castable expands during use, micro cracks (micro cracks) occur due to the gap in the expansion coefficient, which suppresses the spread of the cracks that occur and relaxes the stress that is generated to prevent spalling. Improve sex.

When the amount of ZrO ₂ in the clinker is less than 3% by weight, the difference in expansion with the aggregate such as alumina is small and the effect of improving the spalling resistance is small, and in the range of more than 60% by weight ZrO ₂ is contained. Shows the same expansion behavior as
On the contrary, the difference in expansion from the aggregate such as alumina is excessively large, and there is a concern that the durability will be significantly reduced in terms of strength and corrosion resistance.

20% by weight of SiO ₂ component in the clinker
If the amount exceeds 20% by weight, it will react with alumina, which is an aggregate, and the reaction with the flux due to the penetration of slag will easily form a low-melting substance, which will cause over-burning after long-term use. This will cause a phenomenon of thermal spalling.

The grain size range of the clinker is set to 0.5 mm or more, because in the region smaller than 0.5 mm, the gab due to the difference in expansion is absorbed in the matrix portion, the effect of heat spalling resistance becomes small, and further, in the long-term use. This is because Al ₂ O _{3 in the} matrix portion reacts with the SiO ₂ component in the clinker to cause an oversintering phenomenon and deteriorate the heat resistant spalling property.

If the amount of the clinker used is less than 5% by weight, it is not sufficient to improve the spalling resistance, and if it exceeds 50% by weight, the SiO ₂ component becomes excessive, resulting in a decrease in corrosion resistance and overburning. As a result, a stable phenomenon cannot be obtained due to the formation of a binding phenomenon.

Alumina cement, which is a binder, when the purity thereof is low, is increased by the increase of SiO ₂ , TiO _2, etc.
When the amount of aO exceeds 1% by weight, the corrosion resistance is lowered and the sintering is excessive.

In the fine powder area of 0.044 mm or less, Si
The reason why the O ₂ component is 0.5% by weight on the outside is to increase the curing strength of the refractory by SiO ₂ , and as described above,
It suppresses excessive sintering due to the presence of the iO ₂ component.
When adding fine powder of magnesia, it also plays a role in preventing digestion.

Further, when 0.5 to 8% by weight of magnesia is used together in the fine powder region, secondary spinel or the like is generated on the operating surface, a dense composition is obtained, and it is effective for slag infiltration. That is, if less than 0.5% by weight, the compactness is poor, and 8% by weight
If it exceeds, the spinel formation due to the reaction with Al ₂ O ₃ increases, and there is a problem in volume stability.

[0020]

EXAMPLES Table 1 shows 40 × 40 after kneading the formulations of the invention.
The results of measuring the predetermined physical properties of the molded body that was cast in a metal frame of × 160 mm and deframed after 24 hours were dried at 110 ° C. for 24 hours.

[0021]

[Table 1] Table 2 shows comparative examples outside the scope of the present invention.

[0022]

[Table 2] General physical properties were measured according to JIS standards.

The slag erosion resistance was measured by using a high frequency induction furnace manufactured by Fuji Denpa Kogyo Co., Ltd., and the slag composition was CaO / SiO.
₂ (molar ratio) = 3, Al ₂ O ₃ = 15% by weight was used as an erosion agent, and heated and melted at 1600 ° C., and the erosion amount of each sample was measured. At this time, slag was performed every 0.5 hours for 10 cycles.

The slag permeability was determined by measuring the thickness of the slag permeation layer from the cut surface of the test piece whose slag erosion resistance was measured. For the spalling resistance, the test piece was lined in a rotary slag erosion tester, and the converter slag (CaO / SiO ₂ molar ratio = 3) was used as an erosion agent, and the temperature was 1,600 ° C. × 5 hours for 5 cycles. The test piece after this erosion test is further subjected to 1600 ° C.
The operation of rapidly heating to 500 ° C., holding for 0.5 hour and then rapidly cooling to 500 ° C. was performed for 5 cycles.

The cross section of the sample was observed, and the presence or absence of cracks between the slag permeation layer and the uninfiltrated layer and the degree of cracking were evaluated according to the following criteria.

AA No cracks AB Micro cracks are slightly present BB Micro cracks are present BC Small cracks CC Large cracks are present Examples 1 to 3 use zirconia mullite clinker 5
It is used in the particle size range of ~ 1 mm and 1-0.5 mm. Although the corrosion resistance is slightly inferior to that of the alumina castable material of Comparative Example 1, the spalling resistance and the slag wettability are remarkably improved. The castables using mullite of Comparative Example 2 have the same corrosion resistance, but have a slag-impregnated surface and 15
The strength level after firing at 00 ° C is significantly different, and the sintering is excessive when only mullite is used.

In particular, as in Examples 2 and 3, 0.044 m
Addition of 3% by weight of sintered magnesia in the particle size range of m improves the effects on the slag infiltration surface and the corrosion resistance surface. Comparative Example 6
Is based on Example 2 and contains 9% by weight of sintered magnesia in the same particle size range. However, due to excessive spinel expansion due to reaction with alumina as an aggregate, the porosity after firing at 1500 ° C. was increased. , Induces deterioration of corrosion resistance.

In Comparative Example 3, zirconia mullite containing 80% by weight of zirconia was used, but the expansion gap of the clinker was large, so that deterioration of the structure after high temperature firing (increased porosity). ) Shows the phenomenon. Further, Comparative Example 4 uses zirconia mullite having a small amount of zirconia, and it can be seen that the effect of improving the spalling property is small as in Comparative Example 1.

In Examples 4 to 7, zirconia-alumina-
Mullite clinker is used in the particle size range of 5 to 1 mm and 1 to 0.5 mm. Compared with the alumina castables of Comparative Example 1, the corrosion resistance was less deteriorated, and the spalling resistance and the slag infiltration resistance were significantly improved.

In Example 7, 0.5% of ultrafine SiO ₂ was used.
Although it was added by weight%, the physical properties are almost the same as those in Example 2. On the other hand, in Comparative Example 5, 3.0% by weight of ultrafine SiO ₂ was added, and the spalling resistance was greatly reduced due to excessive sintering after high temperature firing.

The castable refractory material of Example 2 was applied to the ladle hot water contact portion and the dipping lance, which are areas where spalling resistance is important. As a result of use, as compared with Comparative Example 1, a durability of about 1.6 times in the ladle hot water contact portion and a durability of about 1.8 times in the immersion lance were demonstrated, demonstrating the superiority of the product of the present invention.

[0032]

EFFECTS OF THE INVENTION According to the present invention, it is excellent in spalling resistance and slag infiltration resistance, and even in a kiln or the like where conditions such as heat change are severe, it is highly stable and durable in structural and thermal spalling. Indicates. Even with a construction method similar to that of conventional castable refractories, a construction body having excellent durability can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Fujii 1-1, Higashihama-cho, Hachimansai-ku, Kitakyushu, Fukuoka Prefecture Kurosaki Kiln Co., Ltd. (72) Makoto Iida 3-1-1, Matsubara-cho, Oita-shi, Oita Pref. Co., Ltd. Oita Sales Office (72) Inventor Shiro Yunari 1st Nishinosu, Oita-shi, Oita Shin Nippon Steel Co., Ltd. Inside Oita Works (72) Inventor Yuichi Kurosuchi 1st Nishinosu, Oita-shi, Oita New Nippon Steel Oita Steel Co., Ltd. (72) Inventor Akihiko Takayama 1 Nishinosu, Oita City, Oita Prefecture Shin Nippon Steel Co., Ltd. Inside Oita Steel Co., Ltd. (72) Yoshikazu Miyagawa 1 Nishinosu, Oita City, Oita Prefecture New Japan Oita Steel Co., Ltd. (72) Inventor Seiji Hanagiri 1 Nishinosu, Oita-shi, Oita Pref. Nippon Steel Oita Co., Ltd. Tetsu house

Claims (2)

[Claims] 1. Zirconia containing 3 to 60% by weight of ZrO ₂ and having a SiO ₂ component not exceeding 20% by weight.
5-50% by weight of mullite clinker or zirconia-alumina-mullite clinker in a particle size range of 0.5 mm or more, 1 of fused alumina, sintered alumina, fused spinel, sintered spinel, fused magnesia, and sintered magnesia The total amount of Al ₂ O ₃ and CaO as the binder is 99% by weight or more.
Zirconia mullite having a composition in which the above-mentioned alumina cement is contained in a range of not more than 1% by weight as the amount of CaO, and a SiO ₂ component of 0.044 mm or less is added so as to be 0.5% by weight or less on the outside. Castable refractories containing. _2. Zirconia containing 3 to 60% by weight of ZrO ₂ and having a SiO ₂ component not exceeding 20% by weight.
5-50% by weight of mullite clinker or zirconia-alumina-mullite clinker in a particle size range of 0.5 mm or more, 1 of fused alumina, sintered alumina, fused spinel, sintered spinel, fused magnesia, and sintered magnesia The total amount of Al ₂ O ₃ and CaO as the binder is 99% by weight or more.
Aggregate containing the above alumina cement in the range of not more than 1 wt% as CaO, 0.5 wt% or less of SiO ₂ component of 0.044 mm or less and Magnesia powder of 0.044 mm or less At 0.5 ~
Castable refractory containing zirconia mullite added with 8% by weight.