JP2517377B2 - Carbon-containing basic refractory brick - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to carbon suitable as a lining material for a portion where corrosion resistance and wear resistance are particularly required, such as a slag line portion in various steelmaking furnaces such as a converter. Containing basic refractory bricks.

In the specification of the present application, “%” means “% by weight” in all cases.

Conventional technology and its problems Carbon-containing basic refractory bricks have excellent spalling resistance and corrosion resistance based on the excellent properties of carbon materials, that is, high thermal shock resistance and resistance to wetting by slag. Widely used as a lining material for steelmaking furnaces. However, in the slag line portion of the converter such as slag erosion, molten steel wear, air oxidation, etc., the wear of the refractory material is large, so the life of the furnace is often shortened. Generally, carbon-containing basic refractory bricks for converter linings are disclosed in JP-A-57-11874 and JP-A-59-3.
As seen in JP-A-5062 and JP-A-58-185457, coarse aggregates having a maximum particle size of up to about 5 mm are often used. However, in the converter lining material, the oxidative decarburization layer on the operating surface may reach up to about 5 mm. In such a case, the coarse-grained aggregate is also washed away, and the wear of the lining refractory brick becomes significant. . In order to prevent the oxidation of carbon-containing refractory bricks, addition of metal powders such as Al, Mg and Si, and boron-containing compounds such as Bn and B ₄ C have been tried. Although the corrosion resistance is reduced, the wear resistance of the lining refractory material may be increased.

Means for Solving the Problems The present inventor has conducted research in view of the current state of the art as described above, and as a result, increased carbon content by increasing the amount of coarse-grained components in the basic refractory aggregate. It has been found that the problem of basic refractory bricks is substantially eliminated or greatly reduced.

That is, the present invention provides the following carbon-containing basic refractory bricks: In a carbon-containing basic brick having a basic refractory material as an aggregate, 20-80% of the aggregate has a particle size of 6- A refractory brick characterized in that it is made of an aggregate whose surface of 50 mm is coated with phenol resin in advance.

Generally, the carbon-containing basic refractory brick lined in the slag line is subjected to oxidation by air or liquid phase oxidation by slag on the operating surface, and usually about 1 to 3 mm, maximum 5
A decarburized layer of about mm is generated. The decarburized layer is generated in the matrix portion where carbon is present, and the strength thereof is remarkably reduced, so that the decarburized layer easily flows out due to flowing slag, molten steel, and the like.
In this case, if the grain size of the coarse-grained aggregate is equal to or less than the thickness of the decarburized layer, the coarse-grained aggregate flows out together with the decarburized layer. However, it has been found that when the grain size of the coarse-grained aggregate exceeds the thickness of the decarburized layer, not only the coarse grains but also the outflow of the decarburized layer are less likely to occur. That is, due to the coarse aggregate remaining on the operating surface,
The outflow of the decarburized layer is prevented and the formation of a new decarburized layer is also suppressed. Further, the presence of the coarse-grained aggregate on the operating surface reduces the contact area between the slag and the matrix portion, and reduces the erosion of the refractory bricks by the slag.

Since the coarse-grained aggregate has a smaller specific surface area than the fine-grained aggregate, the bond strength with the matrix portion in the refractory brick structure tends to decrease. In particular, the tendency becomes remarkable as the amount of coarse-grained aggregate used increases. Therefore, in the present invention, if necessary, by coating the surface of the coarse aggregate with a phenol resin widely used as a binder for refractory bricks, the binding force between the coarse aggregate and the matrix portion can be improved. It is possible to improve the quality of the refractory bricks, and thus to reduce the dropout of the coarse-grained aggregate from the working surface of the refractory brick. Further, when the surface of the coarse-grained aggregate is coated with the phenol resin, segregation of the kneaded material is less likely to occur, and the stability of the quality is remarkably improved.

The basic refractory material used as the aggregate in the present invention is not particularly limited, and examples thereof include magnesia, dolomite, magnesia-chromia, calcia, and spinel (MgO.Al ₂ O ₃ ). The grain size of coarse particles, which occupy 20 to 80% of the aggregate, is usually about 6 to 50 mm. If the particle size of the coarse particles is less than 6 mm, it flows out together with the structure-deteriorated layer on the working surface of the refractory brick, so that the effect as the coarse particle aggregate is not exhibited. Theoretically, the larger the grain size, the more preferable it is, but in practice, it is limited mainly by the size of the refractory brick, and usually 1/3 to 1/5 of the minimum size of the refractory brick is used. It is preferable to set the upper limit. When the particle size of the coarse particles is larger than this, the coarse particles are unevenly distributed at the time of manufacturing the refractory brick, which not only hinders the formability of the refractory brick but also deteriorates the performance of the refractory brick. More specifically, since the cross-sectional dimension of a general refractory brick is about 150 mm × 150 mm or less,
The particle size of the coarse aggregate is preferably about 50 mm or less. The proportion of coarse particles in the total aggregate weight is 20-80%. When the proportion of coarse particles is less than 20%, the shielding effect on the operating surface of the refractory brick is not sufficiently exerted, while when it exceeds 80%, the coarse-grained aggregate tends to be unevenly distributed in the refractory brick. Since the matrix part is insufficiently filled, the performance of the refractory brick is significantly reduced.

Further, in the present invention, as described above, the performance of the refractory brick can be improved by coating the surface of the coarse-grained aggregate with the phenol resin. As the phenol resin, the one used as a binder in the field of refractory bricks can be used as it is, and the powdered one may be used by dissolving it in a suitable solvent. The coating amount of the phenol resin is not particularly limited, and is usually 0.1 to 10% by weight of the coarse-grained aggregate.
About 5% is enough.

The carbon source material used in the present invention is the same as that used in the known carbon-containing basic refractory brick, but more preferably, scaly graphite, earthy graphite, coke, carbon fiber, artificial graphite, High density materials such as quiche graphite and calcined anthracite are used.
The particle size of the carbon source material is not particularly limited, but is usually about 3 mm or less. Further, the blending amount thereof is about 0.5 to 50% of the weight of the basic refractory material.

The carbon-containing basic refractory brick of the present invention contains a binder in addition to the aggregate component and carbon. As the binder, an organic binder having a residual carbon property is used, and specific examples thereof include phenol resin and furan resin having coal tar pitch, petroleum pitch, hexamethylenetetramine as a curing agent. The amount of the binder compounded is not particularly limited, but is usually about 1 to 20% by weight of the basic refractory material.

Further, the refractory brick of the present invention, if necessary, in order to prevent the oxidation of carbon components, metals such as Al, Mg and Si, alloys of these metals, B ₄ C, one or more such as BN. Can be blended. The blending amount is not particularly limited, but is usually about 0.5 to 20% by weight of the carbon component.

The carbon-containing basic non-fired refractory brick according to the present invention is produced by kneading each raw material according to a conventional method, molding, and usually drying and curing at a temperature of about 100 to 500 ° C. The carbon-containing basic fired refractory brick according to the present invention can be obtained by kneading and molding each raw material according to a conventional method, and then firing, for example, in a coke breeze at a temperature of usually about 1000 ° C.

Effect of the Invention The carbon-containing basic refractory brick according to the present invention is extremely excellent in corrosion resistance and abrasion resistance. Therefore, the carbon-containing basic refractory brick of the present invention is useful as a refractory brick for lining of a portion such as a slag line portion of a steelmaking furnace where corrosion resistance and wear resistance are particularly required.

When the carbon-containing basic refractory brick of the present invention is used, the life of the steelmaking furnace can be greatly extended.

Examples Examples and comparative examples will be shown below to further clarify the characteristics of the present invention.

Examples 1 and 2 and Comparative Examples 1 to 9 Various raw materials were kneaded at a ratio (parts by weight) shown in Table 1 by a roll pan, and formed into a parallel brick shape by a hydraulic press at a pressure of 1000 kgf / cm ² , and 200 Dry at ℃ for 24 hours,
An unfired refractory brick was produced.

 Table 2 shows the physical properties of the refractory bricks obtained.

The symbols in Tables 1 and 2 represent the following items.

MgO I ... Sintered MgO, purity 98%, particle size 25-12 mm MgO II ... Sintered MgO, purity 98%, particle size 12-6 mm MgO III ... Phenol resin coated MgO, particle size 12-
6mm MgO V… Sintered MgO, purity 98%, particle size 5 to 1mm MgO VI… Sintered MgO, purity 98%, particle size less than 1mm MgO / CaO… Sintered MgO / CaO purity 98%, CaO content 70% ,
Grain size less than 1mm Graphite… scaly graphite, grain size less than 1mm Al… purity 99%, grain size less than 0.15mm B ₄ C… grain size less than 0.01mm Binder… liquid novolac type phenol resin + hexamethylenetetramine Apparent porosity… ( %) Compressive strength… Compressive strength at normal temperature (kgf / cm ² ) Hot bending strength… Bending strength at 1400 ℃ (kgf / cm ² ) Decarburized layer thickness… Cube sample of 70mm × 70mm × 70mm 1500 ℃ The sample was held in the electric furnace for 1 hour and the thickness (mm) of the decarburized layer after cooling was measured.

Erosion index: Relative erosion amount when contacting slag with CaO / SiO ₂ = 2 and 20% iron content for 2 hours at 1750 ° C using a rotary slag tester (Comparative Example 1 is 100) As is clear from the results shown in Table 2, the carbon-containing basic refractory brick according to the present invention has a decarburized layer thickness and a slag erosion index which are equal to or less than those of the carbon-containing basic refractory bricks according to Comparative Examples. Fine particles (MgO
V and MgO VI) are used alone, and the erosion index is significantly reduced compared to the conventional refractory bricks that do not use coarse particles (Comparative Examples 6 to 9), and the corrosion resistance and wear resistance are excellent. It is clear.

Furthermore, the refractory bricks according to the present invention (Examples 1 and 2) are coarse particles (MgO II) not coated with phenol resin instead of sintering (MgO III) coated with phenol resin as sintered MgO which is an aggregate, respectively. ) Is used, the hot bending strength is improved as compared with Comparative Example 2 or Comparative Example 4,
It is clear that it has excellent hot abrasion resistance during use.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masao Oguchi 2 1576, Higashi-oki, Aki, Ako-shi, Hyogo Prefecture 2 Kawasaki Furnace Co., Ltd. (72) Tatsuo Kawakami, 1576 Higashi-oki, Aki, Ako-shi, Hyogo Address No. 2 within Kawasaki Furnace Co., Ltd. (72) Inventor Ritsu Ebisawa, No. 1 Kawasaki Town, Chiba City, Chiba Prefecture Inside Kawasaki Steel Co., Ltd. Chiba Works (56) References JP-A-60-264356 (JP, A)

Claims (1)

(57) [Claims] 1. In a carbon-containing basic refractory brick using a basic refractory material as an aggregate, 20 to 80% of the aggregate is composed of coarse particles having a particle size of 6 to 50 mm, the surface of which is previously coated with a phenol resin. A refractory brick characterized by.