JPS6278151A - Non-burnt refractory brick for molten metal vessel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a hot metal pretreatment vessel for carrying out treatments such as dephosphorization of hot metal;
Or it relates to an unfired refractory brick that is lined in a molten metal container such as a ladle for molten steel.

[Conventional technology]

In general, containers for handling molten metal include, for example, molten metal ladle and mixer truck for transporting molten metal as containers for hot metal pretreatment, and ladles and tundishes for molten steel.

Traditionally, these containers were lined with Rouseki, Chamotsite, and high alumina bricks, but in recent years, as pre-MI treatment of hot metal and secondary smelting of molten steel have become more frequent and continuous, The bricks used to line the containers have become more susceptible to erosion, and the durability of the containers has been significantly reduced. In order to cope with this, AQ203 as in Japanese Patent Application Laid-Open No. 60-42273
-5iC-C bricks are often used because they are particularly resistant to structural spalling and erosion, and have excellent corrosion resistance.

However, recently, the hot metal pretreatment rate and the secondary smelting rate of molten steel have been increasing, and i20. Even with -3iC-C bricks, the erosion loss became large, and the durability of the container was significantly reduced due to abnormal erosion loss at the joints of the bricks. The cause is A
Q20. -5iC-C bricks shrink during cooling due to repeated heating and cooling during use, causing joints to open between the bricks, and molten slag intrudes into these joints during pig iron or molten steel processing, resulting in the joints becoming narrower. The problem is that the melting loss becomes large and the durability is significantly reduced.

[Problem that the invention seeks to solve]

An object of the present invention is to provide an unfired refractory brick that is used as a lining material for a molten metal container and can suppress melting loss of bricks and wear of joints, and can provide stable durability over a long period of time.

[Means for solving problems]

The present inventors focused on the fact that Rouseki has a large residual expandability in order to suppress the above-mentioned joint opening. However, although Rouseki has traditionally been used as a Rouseki brick as a lining material for ladles, tundishes, etc., it has extremely low corrosion resistance against molten slag. Therefore, we used alumina, magnesia, zircon, silicon carbide, graphite, etc., which have better corrosion resistance than Rouseki, and conducted research on corrosion resistance and residual expansion by varying the amounts of these raw materials and Rouseki. As a result, we found that with the raw materials and appropriate ranges specified in the present invention, significantly superior durability compared to conventional products can be obtained, leading to the present invention. That is, the unfired refractory brick for molten metal containers of the present invention contains 3 to 30% by weight of Rouseki and 5 to 30% by weight of graphite.
, 3 to 20% by weight of silicon carbide, with the remainder consisting of zircon and unavoidable impurities. The refractory raw materials used in the present invention are natural zircon raw materials and natural waxite raw materials, and the most suitable graphite raw material is pulverized natural graphite.

Silicon carbide is artificially synthesized and pulverized. If necessary, metal powder such as AQ or Si can be added to the brick of the present invention to improve its properties. Also, since coarse grains cannot be obtained from natural zircon raw materials, rough corners are created and crushed. I'm here later. Furthermore, it is also possible to use silica, which has the same effect as Rouseki.

In the present invention, using zircon is inexpensive;
This is because it is a raw material that suffers less erosion from slag and has excellent corrosion resistance compared to Rouseki.

The reason for using graphite is to prevent slag penetration and crack peeling due to thermal spalling, and it is 5 to 30% by weight.
Preferably limited to 10-20% by weight is 5% by weight
If it is less than 30% by weight, the above effect cannot be obtained, and if it is more than 30% by weight, the mechanical strength will be reduced and it will be difficult to resist the wear of hot metal or molten steel.
This is due to the lack of resistance. 3-20% by weight of silicon carbide
The reason why it is preferably added in an amount of 5 to 15% by weight is that if it is less than 3% by weight, the oxidation of graphite cannot be prevented, and if it is more than 20% by weight, corrosion resistance will be reduced.

Adding 3 to 30% by weight of Rouseki, preferably 5 to 20% by weight, effectively prevents joint opening due to heating and cooling, and below 3% by weight, the residual expansion is sufficient to prevent joint opening. is not obtained, and if the content exceeds 30% by weight, corrosion resistance decreases. In addition to these, this refractory brick also contains some unavoidable impurities.

More specifically, in a combination of Rouseki, zircon, silicon carbide, and graphite, bricks containing 5% by weight of silicon carbide and 10% by weight of graphite were created with varying ratios of Rouseki and zircon, and the corrosion resistance and residual expansion characteristics were investigated. Ta.

As is clear from FIG. 1, when the amount of Rouseki added is 0%, the residual expansion property is almost 0%, and no effect of suppressing joint opening due to expansion can be expected. As Rouseki is added, the residual expansion increases, making it possible to suppress joint opening. However, as shown in FIG. 2, as the proportion of Rouseki increases, the erosion loss increases. Particularly when the content exceeds 30% by weight, melting loss becomes significant. For the above reasons, the amount of Rouseki added was limited within the range of the present invention. Therefore, by taking advantage of the properties of Rouseki, it is possible to suppress joint erosion and improve durability as a lining material for containers that are corrosion resistant. .

〔Example〕

Examples will be described below.

Each of the mixtures having the proportions shown in Table 1 was kneaded in a conventional manner, molded into a predetermined shape, and then heated and dried at 250° C. for 24 hours to prepare test specimens Nos. 001 to 7. Physical property values are JI
Measured based on S. As a result, as shown in the physical properties column of Table 1, the products of the present invention Nos. 001 to 4 had a smaller erosion index and were better than those of the conventional product No. 006 and the comparative product No. 015.

Furthermore, as a result of using the same test product in the slag line of a hot metal processing ladle in the same position as the conventional product using high alumina, products No. 011 to 4 of the present invention were separately installed, and the actual furnace test column in Table 1 As is clear from 30 to 40 per mm/ch
% of the amount of erosion at the joints was reduced, and as a result, the durability of the container was significantly improved.

〔Effect of the invention〕

As described above, the present invention makes good use of the expansion properties of Rouseki to prevent wear and tear on the refractories due to joint openings, provides sufficient corrosion resistance by using zircon, and further improves the properties of each composition. By identifying the optimal composition range that maximizes the properties, a longer life of the container can be achieved.

[Brief explanation of drawings]

Figure 1 shows the relationship between the amount of Rouseki added and the residual expansion coefficient.
The figure is a diagram showing the relationship between the amount of Rouseki added and the erosion index. Add nail stone! (X) Figure 1 Added amount of Yushi stone (Z) Figure 2 Procedural amendment document October 24, 1985

Claims (1)

[Claims] An unfired refractory brick for a molten metal container characterized by comprising 3 to 30% by weight of Rouseki, 5 to 30% by weight of graphite, 3 to 20% by weight of silicon carbide, and the remainder consisting of zircon and inevitable impurities.