JP3303039B2 - Precast block for electric furnace ceiling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precast block having improved spalling resistance and corrosion resistance in an electric furnace ceiling.

[0002]

2. Description of the Related Art In recent years, electric furnaces for steelmaking have been increasing in facilities due to their low total cost, and the operating rate has also been increasing. Under such circumstances, the ceiling part 1 of the electric furnace was originally a part showing a relatively long service life (1-2 months), but due to furnace repair, extension of the furnace repair period and shortening of work time, etc. It has been targeted for improvement. Conventionally, the ceiling 1 has been constructed of a fixed silica-alumina brick on a complicated design as shown in FIG. In addition, a metal case was often provided to prevent a single brick from falling off. Therefore, the construction time and construction technique are required, and the combination of fine bricks causes the residual size to be small due to damage, and the thermal cycle causes loosening, etc., which may cause falling off during use, shortening the furnace repair period. , Sudden furnace repair had occurred. Use of a large precast block 2 has been started as an improvement. A representative design is shown in FIG. The precast block material has an Al ₂ O ₃ content of 9 in consideration of spalling resistance and corrosion resistance.
A high alumina material of about 0% by weight was employed. The precast block was a very effective improvement measure compared to the fixed brick because it generally has a better spalling property and can be formed in a large shape. In particular, as for the construction, the design of one-piece to three-piece products is the mainstream, and each block is lifted up by a crane, installed on a construction table, and the gap between the blocks is completed simply by casting. The construction time was substantially three hours, which was reduced to about one-fifth of the conventional one. However, the improvement of the material is still inadequate, and the addition of a chromium component in the high-alumina region and the adjustment of the amount of the silica component require spalling and corrosion resistance. Nothing was satisfactory.

[0003]

The current electric furnace ceiling block is mainly caused by structural metal spalling due to adhesion of metal on the surface and infiltration and thermal cycling, and its improvement is a major problem.

[0004]

Means for Solving the Problems It is considered that the electric furnace ceiling block is caused by splash adhesion during scrap melting and penetration into the surface layer by melting arc heat, and peeling of the surface layer due to rapid cooling at the time of scrap input. Therefore, the addition of a Cr ₂ O ₃ component having a permeation preventing effect was considered. However, the addition of Cr ₂ O ₃ Plain is Cr ₂ by atmosphere in use are conventional art
In some cases, a decrease in corrosion resistance due to evaporation of O ₃ , or an increase in expansion coefficient caused by formation of Fe ₂ O ₃ and spinel causes a surface crack, resulting in little effect. Therefore,
It has been devised that Cr ₂ O ₃ is formed into a complex spinel in advance and added and present in a more stable form. That is, the composition is centered on the MgO composition represented by magnesia-chromic brick (hereinafter referred to as magcro brick), and the others are Al ₂ O ₃ and Fe ₂ O _3.
This is the addition of a composite spinel composition. This is one in which magnesia clinker, natural chromium ore, electrofused magcroclinker, and the like are mixed in various ways and fired to obtain a predetermined particle size. Although the composition of the fired body is not limited, the basic region is MgO 50 to 70%,
Cr ₂ O ₃ may be 15 to 25%, and others may be 25% or less. Judging from the general grain size composition of the precast product, the study was conducted at an aggregate area of 5 mm or more. Their effects were confirmed by various trial productions. The base material at the time of the trial production was a castable of high alumina cement type, which is a general product, but it is considered that a magnesia type or the like has the same effect. According to the trial production results shown in Tables 1 and 2, the addition of 40% by weight or more causes a large decrease in strength. Also,
When the content is 10% by weight or less, the effect of contributing to spalling resistance is considered to be small. Further, when the diameter becomes 50 mm or more, the strength of the block is remarkably reduced, so the upper limit of the diameter is set to 50 mm. The magcro-based composite spinel has residual expansion characteristics and serves as a matrix for the block.
Since there is a great difference from the l ₂ O ₃ composition in this respect, there are some small cracks around the added fired body aggregate, which is advantageous for the heat spalling resistance and becomes poor in the spalling test. Good results were shown. In the slag test as well, the penetration of slag was suppressed, and the minus portion of the small crack was combined with the high corrosion resistance of the aggregate itself.

[0005]

[Table 1]

[0006]

EXAMPLE A precast block according to the present invention was applied to a small ceiling of an electric furnace having a capacity of 80 t / ch.
(FIGS. 3 and 4) The material composition was MgO 6 as shown in Table 3.
A sintered body of 0% by weight and 19% by weight of Cr ₂ O ₃
30% by weight in diameter was added. The casting method and drying method were the same as general precast blocks,
The water absorption of the fired body is large, and the kneading water content is 2% by weight
Added.

[0007]

[Table 2]

[0008]

The electric furnace small ceiling precast block according to the present invention was applied to an electric furnace having a capacity of 80 t / ch. Since the spalling resistance was excellent and the peeling was suppressed, the durability of 515 ch was shown, and the improvement effect of 10% was proved with respect to the average 450 ch of the conventional product. According to the present invention, compared to shaped bricks
The precast block is generally excellent in spall,
This is a very effective improvement because a large shape is possible.
The construction time is substantially three hours and reduced to about one-fifth of the conventional one.
Was done.

[0009]

[Table 3]

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a design and construction of a ceiling portion of a conventional electric furnace.

FIG. 2 is a design explanatory view of a conventional large precast block.

FIG. 3 is an explanatory diagram of application of a precast block according to the present invention.

FIG. 4 is a longitudinal sectional view of a main part of a precast block according to the present invention.

[Explanation of symbols]

 1 ceiling of electric furnace 2 large precast block 3 precast block

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F27D 1/04 C04B 35/00 C04B 35/04 C04B 35/10

Claims (1)

(57) [Claims] 1. The particle size is 5 mm or more and 50 mm or less, the main components of which are MgO and Cr ₂ O _3, and the others are Al ₂ O ₃ and F
The sintered body containing e ₂ O ₃ or the like is used as an aggregate and contains 10 to 40% by weight, and a castable or magnesia-based high alumina cement type base material is used as a precast block for an electric furnace ceiling. Precast block for electric furnace ceiling.