JPS6021868A - Magnesia castable - 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 The present invention relates to a magnesia castable refractory having excellent hot strength, heat spall resistance, infiltration resistance against molten steel and molten slag, and erosion resistance.

For example, castables lined on the ceilings of electric furnaces, V, O, D furnaces, etc. have conventionally been made using oxychloride bond (
bittern), sulfate pound, phosphate bond,
Sodium silicate and cement bond based magnesia castables were used.

However, these castables have poor high-temperature strength and heat spall resistance. For example, when used in combination with maguro fired bricks on the ceiling of a V, O, D furnace, the castables may peel or crumble, causing the bricks to fall off, and their service life will be limited. It was about 100 charges.

In addition, castables have recently been used for injection lances for injecting processing agents for desulfurizing molten steel, but conventional alumina-based castables have a large amount of erosion at the slag line, and magnesia-based cement pond castables have side heating Polling performance is poor, and the number of times it can be used is 2.
It took only ~5 charges (processing time 20-40 minutes).

This invention has been developed from the above-mentioned viewpoints to improve hot strength, 4 heat strength, 1? - Excellent in corrosion resistance, infiltration resistance against molten steel and molten slag, and erosion resistance, and is suitable for electric furnaces, V, 0. A magnesia-based castable suitable for the ceiling and lance pipe of a D-furnace is provided, which is made of a refractory material containing 60 wt% or more of magnesia, and at least one of ultrafine silica powder and ultrafine alumina powder, and the above refractory material. The content of
It is characterized in that the content of at least one of the ultrafine silica powder and the ultrafine alumina powder is 4 to 14 wt%.

In this invention, the refractory material is 60wt of magnesia;
% or more is required.

That is, magnesia'f! By containing 6 Q wt.% or more, high corrosion resistance against molten steel and molten slag and high fire resistance can be obtained.If the magnesia content is less than 60 wt.%, the above-mentioned effects of high corrosion resistance and high fire resistance are obtained. is not obtained.

At least one of the ultrafine silica powder and the ultrafine alumina powder must be contained in a content of 4 to 14 wt%. That is, by containing the ultrafine powder in an amount of 4 to 14 wt.%, construction can be carried out by taking advantage of its thixotropic properties due to a low moisture content of 6.3 to 7.8 wt.%, and the hot strength and
Heat spalling resistance, infiltration resistance against molten steel and molten slag, and erosion resistance can be improved.

Note that if the content of the ultrafine powder is less than 4 wt.%, the desired effect cannot be obtained in the above action. On the other hand, if the content of ultrafine powder exceeds 14'wt%, the coefficient of thermal expansion will not be high, leading to oversintering, deteriorating heat spalling resistance, and increasing viscosity, resulting in poor workability. .

The magnesia castable of this invention has a composition of 1
Spinel (MgO, AI-
zo3 melting point 2135℃) and forsterite (2M
g0, high melting point 1890-1910°C) begins to form, and after completion of firing (1400°C) corundum disappears and the rest is veluclace.

This is thought to be due to the fact that most of the ultrafine powder reacts with magnesia and sinters during firing, thereby improving sinterability. In addition, the content of ultrafine powder in spinel is 14
When it exceeds wt-%, the coefficient of thermal expansion increases. Figure 1 is a graph showing the relationship between heating temperature and coefficient of thermal expansion, where a is when the content of ultrafine powder is 15wt%, and b is when the content of ultrafine powder is 4wt.
,%. As shown in Figure 1, when the content of ultrafine powder is 15wt%, the heating temperature is 1200°.
When the temperature exceeds C, the coefficient of thermal expansion rises sharply.

The refractory material containing 160 wt.% or more of magnesia needs to contain 20 to 50 wt.% of coarse particles having a particle size of 1f1 or more. That is, the content of the coarse particles is 20wt.
If it is less than ,%, it will be sintered too much and the heat spall resistance will deteriorate.
On the other hand, if the content of the coarse particles exceeds 50 wt.%, it becomes difficult to sinter and it becomes impossible to maintain physical properties as a castable.

Further, mullite may be added as a refractory material, but the amount of addition is preferably about 5 to 30 wt%, and if the amount of mullite added exceeds 30 wt.%, corrosion resistance will deteriorate.

Next, the present invention will be explained based on examples.

Table 1 shows the blending ratios of conventional castable Nαl~5 and castable N[16~15 of the present invention, and their hot bending strength and porosity.

In the castable Na6-15 of the present invention, high alumina cement is added as a binder to maintain strength after drying.

As can be seen from Table 1, the castable of the present invention had significantly improved strength and reduced porosity when hot bent, compared to the conventional castable.

Next, the amount of erosion and infiltration of the castable of the present invention was investigated. Table 2 shows the conventional castable Nαl~5 and the present invention castable Nα6, 9, and Nα10.
A sample in the shape of 40DX23OL was prepared, and the sample was
These are the amounts of erosion and infiltration of the sample when immersed for 3 hours in a molten metal in which steel (SS41) and converter slag are melted at a temperature of 1620 to 1650° C. in a high frequency induction furnace.

As can be seen from Table 2, the inventive castable has a smaller amount of infiltration and erosion than the conventional castable.
Copper wettability and erosion resistance could be improved.

Next, we examined the heat-resistant spalling properties of the castable according to the present invention. Table 3 shows that the above-mentioned samples of the conventional castable N[L 1 to 5 and the inventive castable Nα6, 9 and Nα1o were heated to 13008C in an electric furnace without preheating.
, 1500° C. and 1600° C. for 5 minutes each, then taken out from the electric furnace and left to cool for 15 minutes. As a result, the sample showed cracks. This is the number of times it started.

Table 3 As can be seen from Table 3, conventional castables cracked after one spall test, but the castables of the present invention were tested a maximum of 6 times before cracking, and were extremely superior. It showed heat-resistant spalling properties.

Furthermore, the castable of the present invention and the conventional castable were subjected to rotary erosion (Spoortes) to examine the amount of solenoid erosion, amount of infiltration, cracking state, and texture.

In the test, as shown in FIG.
Put the steel (SS41) 3 and converter slag 4 into the tank and raise to 12 r.
, p, and m for one hour, and then, after discharging the molten copper 3 and the molten slag 4'e, the rotating drum 1
A test was conducted in which air was blown into the test piece to cool it for 30 minutes as one cycle, and the texture due to the temperature gradient between the operating surface and the outer surface of the test piece 2 was investigated.

Table 4 shows the test results after three cycles, and FIG. 3 shows the test items in Table 4 in a cross-sectional view of test piece 2. In FIG. 3, A indicates the amount of erosion, B indicates the amount of infiltration, C indicates the crack, and D indicates the distance to the crack.

As can be seen from Table 4, the castable of the present invention had a smaller amount of erosion loss, a smaller amount of infiltration, and a smaller distance from the operating surface to the crack than the conventional castable. Further, while all conventional castables suffered from fraying, the castable of the present invention did not suffer from fraying and its structure was good.

As a result of using the castable of the present invention in combination with maguro fired bricks on the ceiling of V, O, and D furnaces, its service life was as follows:
The lifespan was significantly improved to 150 to 180 charges compared to the conventional approximately 100 charges. In addition, as a result of using the castable of the present invention in an injection lance for inputting processing materials in molten steel desulfurization work, the number of times it was used was 6 to 9 charges compared to the conventional 2 to 5 charges. ]The number of times of use increased significantly.

As mentioned above, according to the castable of this invention,
The excellent effects of significantly improving hot strength, four-heat spalling properties, infiltration resistance against molten steel and molten slag, and severe erosion resistance are brought about.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the influence of the contents of ultrafine silica powder and ultrafine alumina powder on the coefficient of thermal expansion, Figure 2 is an illustration of the rotary erosion spall test, and Figure 3 is a cross-sectional view of a test piece in the rotary spall test. It is. In the drawings, 1... Rotating drum, 2... Test piece, 3... Molten steel, 4... Molten slag. Applicant Tokyo Ceramics Co., Ltd. Agent Natsuo Shioya (and 2 others)

Claims (1)

[Claims] A refractory material containing 1 or more of magnesia f 60 wt, and at least 1 of ultrafine silica powder and ultrafine alumina powder.
The content of the refractory material is 86 to 96 wt.
A magnesia castable, characterized in that the content of at least one of the ultrafine silica powder and the ultrafine alumina powder is 4 to 14 wt%.