JPS6360151A - Thermal shock-resistant magnesia-zirconia base refractory brick - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application of Hada Tojo: The present invention relates to a magnetic screw r-zirconia refractory brick that has excellent thermal shock resistance.

Background of the invention: Magnesia'R refractory bricks have a significantly higher melting point than other gay stone* bricks and chamotite bricks, and have excellent corrosion resistance against monobasic slag, especially in metal tanks.
2. It is widely used as a refractory lining for metal hearths. However, since the input point has poor thermal shock resistance, when operating a metal tree-top soul furnace using it, the thermal shock due to repeated heating and cooling at the start and end of the process is reduced.
Therefore, if there are cracks behind the operating surface, the cracks will cause severe peeling and damage, which will shorten the life of the furnace.

Conventional technology: As a measure to impart heat and impact resistance to magnesia bricks,
A so-called magnesia-chromite direct bonded frozen tile, which has been blended with chromium ore grains and is then fired, has full thermal shock resistance due to the minute 4*vζ generated in the circulation of the chromium ore grains.
- The proposal was made in Publication No. 116661. However, even the magnetic screw arc direct bricks may develop micro-cracks due to repeated thermal shocks. The corrosion resistance properties of the magnesia bricks were not sufficiently developed due to the corrosion resistance characteristics of the magnesia bricks, which were resistant to tetrabase slag.

Problem to be solved by the invention: The present invention has been made to solve the above-mentioned problems, and is capable of heat treatment of all parts by reducing localized microporous areas.
By eliminating the force, the thermal shock resistance of the gold-added magnesia-zirconia roof tile can be improved quickly.

Structure and operation of the invention: To explain the present invention as follows, the unstabilized zirconia raw material is blended with the magnesia raw material as intermediate grains of a ~ 2JIJI diameter so that the amount of refractory material is 5~20 wt. After forming No. 11, it is fired at a high temperature of 1650'C or higher to transform the unstable zirconia grains into t-constant zirconia grains contained in the fine pore gold goo. This part v'cJ? /)pA stress is absorbed and the total #
a 'R shot a k Magnesia-zirconia material (same as above)
It is made of refractory bricks and is made of T-mono.

In the refractory brick of the present invention obtained in this way, stable zirconia is obtained by mixing 7 with the magnesia raw material and reacting with unstable zirconia 4 magnesia of the intermediate variety. The zirconia grains at this time are 5 to 80 μm as shown in Figure 1.
This is a grain that uniformly contains fine pores. These zirconia grains are uniformly dispersed with another 1lIIt refractory material, family-1:lvC, to form a solid magnesia-zirconia refractory brick.

Next, the mechanism by which the thermal shock resistance of the magnesia-zirconia 4 refractory brick with such a structure is developed will be discussed. The structure of the brick after repeated hot surface tests is shown in Figure 2. As is clear from FIG. 2, J-cracks are generated along the fine pores within the zirconia grains, which contain fine pores of 5 to 30 μm.

Cracks are unlikely to occur in other areas of refractory materials.

In other words, this is nothing but the result of the thermal stress caused by thermal shock being absorbed and relaxed only by the occurrence of cracks in this microporous region.In other words, the thermal stress caused by thermal shock is absorbed and relaxed only by the occurrence of cracks in the microporous region. The structure in which grains are uniformly distributed within the magnesia brick is capable of absorbing and relaxing thermal stress.

As is clear from the Examples and Figures 1 and 2 described below, these locally generated cracks have almost no effect on the physical properties of the brick as a whole, and even when heat IJI is repeatedly applied, the strength decreases or the structure deteriorates. Not triggered at all.

The S zirconia raw material blended in the present invention needs to be filled with unstable zirconia, and if stable zirconia is used from the beginning, fine pores of 5 to 80 μm will not be formed within the grains. Particle size of unstabilized zirconia blended ri0.
3-2. Off level is desirable. 0.8 When blended with silk-like fine grains, too many zirconia grains are blended and they play a major role in the brick. Too much will impair spall resistance. When blended with a particle size exceeding 2M, the dispersion within the brick tends to become uneven, and the development of heat resistance and durability becomes a problem.

The amount of unstable zirconia raw material to be blended is as follows:
Within the range of 5 to 20 #t*: Heat-resistant young fruits are observed. If the weight is less than 5wt, cracks occurring only in the zirconia particle portion will not be able to fully absorb the thermal stress, resulting in damage to the entire brick. Also, 20wt%
When the temperature exceeds t, cracks mainly occur in the zirconia particles, and the damage to the entire brick increases.

Unstabilized zirconia grains react with magnesia and become 5-30μ
In order to transform into particles that uniformly contain m micropores,
It is necessary to set the firing temperature to at least 1650°C or higher.

There are 5 microscopic pores built in after changing to stable zirconia.
When the diameter is less than μm, the role of zirconia becomes smaller and the strength ρS increases, but on the other hand, cracks at zero temperature easily propagate and propagate to the surrounding magnesia. If the size of the pores exceeds 30 μm2, the role within the zirconia grains becomes large and the strength decreases.Example: A refractory material and a binder were blended in the proportions shown in Table 1, and both were kneaded in a breadmill. It was molded into an hourglass shape using a press Vs machine, dried at 81) to 150'C for 48 hours, and fired at 1750C for 7 hours using a barley tunnel kiln. Among the Examples, Arashi 1 to 4 are examples of the present invention, Cases 5 to 6 are comparative examples in which the blending ratio of unstabilized zirconia is outside the D range of the present invention, and Na7
9 to 9 are conventional examples. Incidentally, both sintered magnesia and fused magnesia should have a visual component of 98 or more.

The obtained bricks of each example were tested, and the results are also shown in FIG. The methods and evaluation criteria for various tests were as follows.

[Apparent specific gravity], [Bulk specific gravity], and [Apparent porosity] were determined by ordinary refractory testing methods.

[Compressive strength]

55 x 55 x 55 from continuous bricks! A cube was cut out and measured using a hydraulic compression testing machine.

[Bending strength]

From continuous bricks, width 30H1 thickness 15g, length 120I
A test piece of H was cut out, heated for 1 hour in an electric furnace maintained at 1500'c, and then subjected to an 8-point bending test. A piece was cut out, one side kept in an electric furnace held at 1400"C for 15 minutes, then taken out of the furnace and air cooled for 15 minutes at a maximum of 25 times. The evaluation was based on the number of work cycles required to reach this point.The spalling resistance is better as the number of cycles until peeling is greater.

Almost bright effect: As is clear from the results in Table 1, the examples of the present invention have
All exhibit good spall resistance. In particular, no visible microcracks occurred in fc, b2, and ann 4, which contained unstable zirconia elOwt%. On the other hand, the conventional examples Nagi 7 and Yang 8 are unstabilized zirconia-free υ openings.
The number of repetitions until O1 peeling off was 15 and 2, indicating poor spall resistance.

Furthermore, although the conventional magnet 9 contains chromium ore instead of zirconia, it does not form the microporous structure that occurs with unstable zirconia, and does not peel off after 25 repetitions. Significant cracking was observed.

As described above, the magnesia-zirconia refractory brick of the present invention has significantly improved spalling resistance without any structural deterioration, and exhibits excellent heat resistance.

[Brief explanation of drawings]

FIG. 1 is a reflection microscopic photograph of one embodiment of the present invention, showing that the zirconia vagina with a diameter of about 1×g contains all microscopic pores with a shoulder size of 5 to 30 μm. Figure 2 shows the inside of the magnesia-zirconia grains (A) of the present invention after the spall resistance test.
-A'), but no cracks are observed in the other magnesia areas. Applicant Harima Refractory Brick Co., Ltd. Drawing No. 6 (No change in content) Figure 1 Figure 2 Procedural amendment document Oiren Zirconia refractory brick person who makes amendments Relationship to the case Patent applicant address (residence) Hyogo prefecture 1-3 frei, Arai-cho, Takasago City
Date of order to amend Lu No. 1 meal: August 6, 1985 Target of amendment (1) Specification N: Column for a brief explanation of the drawing. Nawate (2) Drawing. , -1k contents of attached sheet and 2 sheets-"7. Scratches-5, no-)
Correct the word ``of the particle structure in Example 1.'' ■ In the specification, No. 10, line 5, correct the phrase "of the present invention" to read, "Reflection microscopy showing changes in the particle structure of the product of the present invention! Photos are included." ■ The drawings, Figures 1 and 2, are "color photographs" showing the particle structure, but they are supplemented with "black and white photographs" as shown in the attached drawings.

Claims (1)

[Claims] Add unstabilized zirconia raw material to magnesia raw material from 0.3 to
5 to 20 wt% of the total amount of refractory material is blended as 2 mm intermediate grains, mixed and molded, and fired at a high temperature of 1,650°C or higher to transform the unstable zirconia grains into stable zirconia grains uniformly containing fine pores of 5 to 30 μm. A magnesia-zirconia refractory brick with excellent thermal shock resistance.