JPS62119159A - Direct bond brick containing high cr203 for refinement 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 Application Field] The present invention provides a refining processing vessel for refining high-grade steel by adding CaO-based flux. This relates to a direct bond brick containing smelting treatment container yen high (, r, o), which has improved durability by adjusting the content of the flux and suppressing the reaction with the flux.

[Conventional technology]

Vacuum degassing treatment has expanded its functions from the purpose of removing hydrogen in steel by creating a vacuum, to adjusting the components in steel, equalizing temperature, and mass processing, and has been added to the steelmaking process, increasing the operation rate of continuous casting. Contributing to improvement.

In recent years, high-grade steels such as ultra-low sulfur steels have been refined by adding CaO-based flux powder during vacuum degassing treatment to remove sulfur and oxygen. Direct bond magnesia chromium bricks have traditionally been most commonly used as the lining material for vacuum degassing containers. The brick combines high-purity sintered magnesia with low-silica chromite,
Furthermore, if necessary, a small amount of Cr, O, fine powder, and an appropriate amount of electrofused tuna raw material are blended and fired at a high temperature of 1,700° C. or higher. Looking at the Cr2O3 contained in the whole brick, the mainstream is direct bonded magnesia chromium brick with a content of 10 to 20% by weight, but there are also some bricks with a Cr2O3 content of around 30% by weight, as shown in JP-A-59-190257. It is used.

[Problem that the invention seeks to solve]

The above-mentioned direct bonded magnesia brick has excellent resistance to thermal spall, flow wear of molten steel, and erosion by molten steel, and has been used as a lining material for vacuum degassing processing vessels. However, with the trend toward high-grade steel, CaO flux has been added to molten steel, and this CaO-based flux powder permeates into bricks, causing chemical erosion and structural deterioration, which significantly reduces durability. Ta. Therefore, with the increase in the flux addition treatment rate, there has been a rapid demand for improvements in direct bond magnesia chromium bricks.

[Means for solving problems]

The present inventors have solved this problem by using MgO and C as main components.
Cr2O3 contained in the whole brick is 36 to 60% by weight, Al2O. By a high Cr2O-containing direct bond brick for refining processing vessels, which has a content of 10% by weight or less and 46% to 80% by weight of Crz○3 in the fine powder part of 0.1 mm or less, which accounts for 15% to 50% by weight of the whole brick. Settled.

[Effect]

After using a conventional direct bonded magnesia chromium brick with a Cr2O3 content of 30% by weight as the lining material for a vacuum degassing container for Cao flags processing, we observed the amount of foreign components infiltrated and changes in the structure, and found that CaO 5 to 6% by weight of S i O, and 2 to 3% by weight of S i O, were observed. Further, in the magnesia clinker up to about 3 mm below the operating surface, grains larger than 0.1 mm had undergone structural collapse or crystal grain recrystallization from the grain boundaries.

However, 2O. Focusing on the fact that the chromite distributed in the fine powder part of 1 mm or less has no structural deterioration and is in good health.
As a result of repeated experiments to stabilize CaO and increase lomite, 2O
．． It has been found that Cr2O3 of 1 mm or less and Cr2O of the entire brick have a remarkable effect within a certain range of content. Furthermore, it was also found that there is a correlation with the AQ□○ content in chromite.

It was also found that since it is difficult to completely prevent the penetration of foreign components such as CaO-based flux, it is desirable to reduce the apparent porosity to at least 17% by firing at a temperature of 1,800°C or higher. Ta.

The reason why the Cr2O3 contained in the whole brick is set to 36 to 60% by weight is to increase stability against CaO erosion, as is clear from Figure 2, and if it is less than 36% by weight, CaO
Corrosion resistance is expected to decrease due to the collapse of MgO due to the invasion of 5in2. On the other hand, if the amount exceeds 60% by weight, the structural strength will be low due to insufficient sinterability, and the corrosion resistance will also be reduced. Also, it was the 3rd time that AQ2O3 was kept below 10% by weight.
As shown in the figure, when the content exceeds <10% by weight, Mgo, which is a brick component, reacts due to the intrusion of CaO and 5in2, producing monticerite. This is because the AQ2O3 contained in the brick at this point has the effect of lowering the melting point of monticerite.

The particle size is limited to 0.1 mm or less because its composition greatly contributes to chemical resistance against foreign components, and at the same time it affects the pore distribution due to sintering of the fine powder and prevents the physical penetration of foreign components. It is. Therefore, even if the proportion of fine powder in the total particle size distribution is low, it has a large effect on physical properties, and the particle size distribution of 2O11 mm or less is 15 to 50%.
It's amazing. If it is less than 15%, there will be a shortage of fine grains filling between the coarse and fine grains, resulting in high porosity due to poor filling and promoting erosion of the matrix. Moreover, if it is more than 50%, high-pressure filling is impossible and the incidence of lamination during molding is high, making it difficult to commercialize the product.

Furthermore, the content of Cr2O3 in the fine powder part of 2O and 1 mm or less was limited to 46 to 80% by weight in the case of CaO-Cr shown in Fig. 4.
As shown in the binary system of 2O3 (Cr203/CaO=,
There is a temperature region where the liquid phase formation temperature is high (Cr2O37 CaO〉3) on the Cr2O3 enriched side from the 75/25 point, and if the CaO penetration ratio into the fine powder part is about 15%, C
r and Oa are required to be at least 46% by weight [15%X3=4F5%]. That is, Cr2O in the fine powder part in Figure 1
As is clear from the 3 content and the erosion ratio, if the CaO content is less than 46% by weight, a composition with a low liquid phase formation temperature is created in the fine powder part due to the intrusion of CaO, resulting in a decrease in corrosion resistance. If it exceeds 80% by weight, C
r2O.

This is because the high melting point of the powder impairs the sinterability of the fine powder portion, resulting in a decrease in strength and corrosion resistance.

〔Example〕

Examples will be described below.

Example I A product of the present invention, a comparative product, and a conventional product were laminated together and used for 200 channels as shown in Table 1 on the side wall of the lower tank of a RH vacuum degassing container. As a result of adding CaO flux to 40 channels, the product of the present invention was approximately 70% better than the conventional product and 40% better than the comparative product in terms of erosion rate (mm/ch). .

Example 2 In the same place as in Example 1, the present invention product, comparative product, and conventional product were laminated together and used for 450 channels. Of that, 27 Oah is CaO.
Results of flux addition treatment.

In terms of erosion rate (mm/ch) ratio, the present invention was about 80% better than the conventional product and 35% better than the comparative product.

As is clear from the above, in the product of the present invention, there is almost no change in matrix quality due to the intrusion of CaO, and the erosion rate is 1 to 4 m.
Very excellent results were confirmed, with m/ch being 1/3 to 115 of the conventional product.

〔Effect of the invention〕

The present invention is a direct bond type lining brick of a refining processing furnace for refining high-grade steel by adding CaO type flux.
36-60% by weight from O3 content.

Al2O. Content is 10% by weight or less, apparent porosity 17%
and 0.1 mm or less of Cr in the fine powder part.

Since the 03 content is 46 to 80% by weight, it is possible to prevent the collapse of MgO due to the intrusion of CaO and Sin, and also to prevent the formation of a structure with a low liquid phase formation temperature. This reduces the loss rate and extends the life of the furnace, thereby reducing refining costs and lengthening the repair cycle, resulting in significant labor savings.

[Brief explanation of drawings]

Figure 1 shows the Cr2O content (
% by weight) and the erosion ratio %. Figure 2 shows the Cr2O3 content (wt%) and brick erosion ratio (
%). Figure 3 shows the Al2O of bricks. The relationship between content (weight %) and erosion dimension (mm) is shown. FIG. 4 is a phase diagram of CaO-Cr2O system components. Patent applicant: Harima Refractory Brick Co., Ltd. Figure 1: Cr2O3 in the fine powder part of 0.1 mm or less! ! (Weight Z
) Figure 3 Contains A1203! (Weight Z)

Claims (2)

[Claims] (1) Consisting of MgO and Cr_2O_3 as main components,
Cr_2O_3 contained in the whole brick is 36-60% by weight
, a high Cr_2O_3-containing direct bond brick for use in a refining processing vessel, comprising 10% by weight or less of Al_2O_3 and 46 to 80% by weight of Cr_2O_3 in the fine powder part of 0.1 mm or less, which accounts for 15 to 50% by weight of the entire brick. (2) The high Cr_2O_3-containing direct bond brick for a refining processing vessel according to claim 1, which has an apparent porosity of 17% or less.