JPS63303705A - Manufacture of large carbon containing brick - Google Patents

Abstract

PURPOSE:To obtain a brick with low porosity of at most 3% by a method in which after a primarily formed abject obtained by forming primarily a compound containing carbon has been covered with a rubber mold, the inside of the rubber mold is sucked to vacuum, and then the compound is secondarily molded by an isostatic press. CONSTITUTION:The primary forming of a compound containing carbon is carried out by hand blow, oil press, friction press or vibration, etc. After the primarily formed object with plasticity has been covered with a rubber mold, the inside of the rubber mold is sucked to vacuum, and the object is isostatically pressed. The rubber mold has preferably the thickness of 5-10mm, and its material is composed of raw rubber, silicon rubber or urethane rubber, etc. In order to remove the air in the primarily formed object and to heighten the degree of pilling, vacuum treatment is achieved. If air remains inside, inner cracks occurs in isostatic press under reduced pressure. The filling defect due to the friction between the mold and the compound is prevented by the isostatic press. The compound is pressurized on the whole surface by pressure contact of the rubber mold with the compound, whereby the uniformly molded object having less restoration due to the spring back of the carbon, may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing homogeneous and dense large-sized bricks containing carbon.

(Prior art) Carbon-containing refractories for steelmaking furnaces such as converters have been required to have lower porosity and be larger and longer than 1 meter due to harsher operating conditions such as compound blowing. .

Lowering the porosity of refractories reduces air permeability in order to prevent carbon oxidation, which is one of the causes of wear and tear in carbon-containing refractories, and increasing the size and length of refractories is a drawback of conventional tie-laminated structures. This eliminates the increase in erosion rate due to detachment when the remaining amount in the first layer is low, and extends the life of the furnace. In the production of such refractories, it is common to prepare a composition containing carbon, and then to form the mixed and kneaded composition using an oil press, a Frixilane press, or the like. Oil press and Frixilan press are so-called uniaxial pressure molding in which a predetermined amount of the compound is put into a fixed mold and pressurized from above and below. The carbon raw material used is usually scaly graphite, which is added in an amount of 10 to 25 wt%.

Uniaxial pressure molding of a compound containing phosphorescent graphite shows a tendency for phosphorescent graphite to be aligned perpendicular to the pressure direction, and in an evaluation of reduction firing treatment assuming heating when using refractories, In addition to increasing the porosity due to carbon returning due to springback, it also had physical drawbacks such as non-uniform filling distribution.

- In the case of shaft processing molding, the larger and longer the pressurized area increases, the pressurizing force per unit area decreases, and the filling rate decreases.

Therefore, the porosity increases, and there are restrictions on the size of the brick and the size of the pressurized area. In the case of shaft processing molding, ceramics 1881111 P979 (198
3) As described in lines 6 to 16 on the right side, the pressure is not transmitted smoothly to the inside of the molded body due to the friction of the compound in contact with the inner wall of the mold, so the filling pressure as described above is lowered. It is difficult to obtain a homogeneous molded body with a uniform distribution, and the height of the molded body is thick (as the height of the molded body becomes thicker, filling defects also occur in the center).

(Problems to be Solved by the Invention) As described above, in the conventional method, as the size and length are increased due to -axis processing molding, insufficient filling of the inside tends to occur. In order to solve this shortage of filling, large molding equipment was required, and the investment in this equipment was significant. Generally, carbon-containing large bricks are mainly used in converters, electric furnaces, pig iron mixers, vacuum degassing furnaces, etc.

This magnesia-carbon brick is unfired and has a porosity of about 3 to 7%. Small size made of the same material.

Medium-sized bricks (approximately 5 to 80 kg) are made using an ordinary molding machine.
Although it is possible to obtain a material with a porosity of about ~3%, large-sized long bricks (100~
There was a strong demand for a material with a low porosity of 3% or less even when the weight was 300 kg or more.

(Means for solving the problem) In order to solve the problem, the present inventors conducted various studies, and as a result, completed the method of the present invention by adopting two different molding methods. be. That is, after primary molding a carbon-containing compound and covering the obtained primary molded body with a rubber mold, the inside of the rubber mold is evacuated and the molded body is secondary molded using an isostatic press.

The primary forming in the present invention is carried out by the usual methods for conventional shaped refractories, such as hand hammering, oil press, Frixilan press, vibration, etc. - The filling rate of the fire-formed body is 70 to 97% of the final target filling rate. range is suitable. If it is less than 70%, the compression dimensional change rate from the primary molded body to the secondary molded body is large, and the dimensional accuracy tends to be inaccurate, and no improvement in work efficiency can be expected.If it is more than 97%, it is affected by the filling structure of the primary molded body. The graphite becomes thick (and the densification and arrangement of the phosphor-like graphite show directionality, making it difficult to obtain a homogeneous molded body.

(Function) Isostatic pressing is carried out by covering a fire-molded primary molded body with plasticity in a rubber mold, and then evacuating the inside of the rubber mold.

The suitable thickness of the rubber mold is 5 to 10 cm, and the material is raw rubber, silicone rubber, urethane rubber, etc.

The purpose of vacuum treatment is to remove air within the fire-formed body and increase its filling, and if air is present, internal cracks will occur during isostatic press depressurization. Isostatic press eliminates filling defects caused by friction between the mold and compound, which is a disadvantage of uniaxial pressure molding, and the rubber mold presses against the compound and pressurizes from the entire surface, resulting in a homogeneous product with less return due to carbon springback. A molded body can be obtained.

The molding pressure of isostatic press is 1.0 to 1.3t/
i is suitable, and it was difficult to obtain a low porosity even at a molding pressure of 1.3 t /d or more using the conventional method. The reason for this is simply because the isostatic press applies pressure across the entire surface.

The manufacturing method of the present invention uses conventional molding equipment to manufacture large elongated bricks, and is advantageous in that it does not require any capital investment. Isostatic pressing has been used for a long time, but it is generally carried out by directly introducing the kneaded compound into a rubber mold.In the present invention, by primary forming, the refractory after isostatic pressing is Large, long refractories with accurate, uniform, and dense dimensions can be obtained.

(Example) Examples will be described below.

Magnesia clinker - 80wt% as shown in Table 1
and 20wt% of fiery graphite, and 3% of phenolic resin.
% (external), mixed and kneaded, 300 kg of the mixture was put into a mold with a length of 1.100 m and a width of 300 m, and primary molded to a thickness of 3001 mm using a Frixilane press (750 t) to form a molded product with a filling rate of 2.80. I got it. This molded body was covered with a silicone rubber mold with a thickness of 10 mm, and a 650 mm thick mold was coated with a vacuum device.
The molded body, which was depressurized to , was pressurized at 1.1 t/cd using an isostatic press to obtain a secondary molded body.

The filling rate of this secondary molded body was 3.00.

As a comparative example, the same amount of the same compound was put into a mold of the same shape,
It was molded to a thickness of 300 mm using a 3,000 t oil press at maximum pressure.

The filling rate of this molded body was 2.88.

Samples of the conventional products were also taken from the same locations as the products of the present invention, and the apparent porosity of each was measured based on JIS.

Table 1 Mixing ratio and physical property values * Sampling locations for measuring distribution of apparent porosity were taken at three locations in the lengthwise direction of the large long brick: the upper end surface, the lower end surface, and the center thereof, at a thickness of 50 mm. It was cut out uniformly and collected. These three sections were further cut out into the following nine sections, resulting in a length of 50 squares, a width of 50 cm, and a height of 50 squares.

A specimen was obtained. The cutting method for the 9 parts is as follows: - The upper end that will be on the upper liner side during the next molding is A, the center part is B, and the lower end that will be on the lower liner side is C.

Further, the left end of B and C is At, B+, C+, and the center part is At, Bz, C! , the right end is As, Bs, Cs, total 2
Seven specimens were obtained. Therefore, the center of the brick is Bx.

(Effects of the Invention) As a result, the product of the present invention had an apparent porosity of 2.2 or less, had very small variation, and was homogeneous and dense. In comparison, the apparent porosity of conventional products is 4.
The variation was large when it was 0 or more.

When the above-described products of the present invention and the conventional product were used in the surface of a converter, the product of the present invention showed a corrosion loss rate of 0.8 mm/ch, compared to the erosion rate of 1.2 mm/ch for the conventional product, which was approximately We were able to increase durability by 35%.

Claims (1)

[Claims] 1. Primary molding of the carbon-containing compound, covering the obtained molded body with a rubber mold, evacuating the inside of the rubber mold, and secondary molding of the molded body using an isostatic press. A method for producing large carbon-containing bricks characterized by: 2. The filling rate of the primary molded body is the target filling rate of 70 to 97.
% of the carbon-containing large brick according to claim 1.