JPS5874564A - Magnesia lime refractories - 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 is applicable to the tuyere of a steelmaking furnace having sidewalls, the surrounding area of Asahi, the slag line, the membrane wall, and the slag line of a molten steel container for special refining such as VAD and VOD. This invention relates to a highly corrosion-resistant magnesia-lime refractory that is used as a lining furnace material and has improved thermal and structural spalling properties.

Conventionally, when the steelmaking conditions were relatively high basicity operation, furthermore, the furnace structure was relatively open, and in the case of intermittent operation, "magnetic or Mag-lime bricks are used.In high basicity slag operation, high melting point minerals such as 5CaO・sio, 2CaO-8iO1, etc. are generated near the working surface of the magdro bricks. Bricks have low penetration of slag components, excellent corrosion resistance, and a high CaO content.
This is because it is considered to have excellent spalling resistance.

However, in the raw material composition of the conventional Magdro bricks that are actually manufactured, lime-based raw materials are easily digested and difficult to use as fine powder in the manufacturing process, so they are made using fine powder of magnesia clinker. As far as the matrix part of the brick is concerned, it is the same as magnesia brick. Therefore, when such Magdro bricks are used in an actual furnace, the slag components produce low melting substances such as CaO・MgO・Bio, (monticerite), S CaO・Mg0・2sio, (melvinite), etc. It easily penetrates into the matrix, resulting in structural spalling that often results in peeling and wear. Furthermore, with regard to thermal spalling, since the matrix portion is made of magnesia, results as excellent as expected were not obtained.

Furthermore, in recent years, single lime bricks or high lime bricks with Ca050- or higher have been used in actual furnaces by using high-purity, dense electric fusion or sintered lime clinker as a raw material. These bricks, such as lime bricks, whose matrix is CaO,
For 8i01 series slag, the above-mentioned 3 CaO 840. ．． 2CaO-8i0! The slag components remain on the surface of the brick and do not penetrate deeply, and are also excellent against thermal spalling, so they exhibit good durability.

However, A/, 0. , Fe, O, is present in large amounts, Ca01d Ca0-Al2O,,2Ca
Since it produces low-melting minerals such as 0-Ft40B, it has the disadvantage of reduced corrosion resistance. In this case, a matrix with a high MgO ratio has better corrosion resistance than a CaO matrix.

The present inventor has investigated the advantages and disadvantages of limestone bricks in detail and found that mag-lime bricks have high corrosion resistance and excellent thermal and structural poling properties. Brick (...) was successfully developed.

The present invention improves the corrosion resistance and further improves the thermal, structural, and structural spalling properties of a basic brick having matrix portion S1i:t gnesia. That is, the coarse grain and intermediate grain portions are dolomite clinker-1 synthetic magdo clinker, electrofused or sintered lime clinker, electrofused or sintered magnesiac linker.
The basic formulation is a combination of two or more types of 1, and the fine powder part is electrofused or sintered magnesia clinker, while the powder part is electrofused or sintered lime clinker, and the content of CaO and MgO is small. It is characterized by adding 5 to 20 inches of CaO to Mag-Lime clinker, which has a particle size of 0.5 degrees or less, which is analytically 95 degrees or more, and then cross-wires, molds, and fires it. Mag-lime clinker is produced by electrofusion or sintering, and the CaO/MgO ratio is Ca050-100.
It refers to mag-lime clinker, which has MgOO~50 and is obtained by uniformly mixing lime raw materials and magnesia raw materials in advance and treating it at Oto temperature in an electric furnace or firing furnace.

In addition, small amounts of components other than CaO and MgO are analyzed as Fe,
Os is 1 or less, sho is 1- or less, A^0. is 1.
The microstructure of the 6 Mag lime clinker, which is limited to 5 cm or less, has a mottled structure in which MgO solids are uniformly scattered and distributed in CaO solids, and this clinker has a
It has both the properties of lime clinker and MgO clinker.

Although the object of the present invention can be sufficiently achieved using lime clinker, it is even more effective to use mag-lime clinker.

First of all, when applying lime clinker, for the above basic composition, lime clinker is used with a maximum particle size of 0.51 m and a particle size of 5 to 20 cm, with a particle size of 0.2111 or less being 80 cm or more, Desirably, 5 to 10 inches is added. When a brick structure is observed under a microscope, there are some bonded areas of velclay-periclase in the matrix, but most of the periclase is bonded by CaO crystals. The thermal spalling properties of the bricks are much better than those without lime clinker, and this effect is even more pronounced when a dense brick structure is created through particle size structure and high-temperature firing. This is due to the Ca present in the berclace gap.
This is thought to be because O has the property of being highly engineered and slightly softening, absorbing the expansion and contraction of periclase and improving thermal spalling properties. Regarding slag resistance, CaO between periclase is 5 CaO・Sing, 2CaO
-8i0. This suppresses the penetration of slag components into the interior of the brick, making it effective against conventional Magdro brick repellents and preventing structural spalling due to slag absorption.
This is significantly superior to bricks with a magnesia paste matrix.

The amount of lime clinker added is 5 to 5% by weight as CaO.
20-, but the reason why the lower limit was set to 5 is that if it is less than 51, the effect of improving spalling resistance cannot be obtained, and the effect of preventing slag penetration cannot be obtained. - The reason for this is that the proportion of fine particles of 0.5 ms or less in the particle size structure of refractory bricks is generally in the range of 20 to 409 g, but the proportion of CaO due to the addition of lime clinker is 1/2 of the fine particles. It is desirable to set it below, 1/
This is because if it is 2 or more, the corrosion resistance will be significantly lowered.

The reason why the maximum particle size is set to 0.5 degrees and the particle size of 0.2 m11 or more is set to aOqk or more will be described.

For the purposes of the present invention, the lime clinker and maglime clinker grains [, li O02
However, these clinkers have the property of absorbing moisture in the air and easily becoming hydroxides.
The sieve fraction for producing fine powder is #II of 0.2111 in the process.
When Jt- is used, the sieves tend to become clogged, and the efficiency of the sieves decreases.As a result, the clinker absorbs moisture in the air and turns into hydroxide (ca (OH)!). In bricks manufactured by adding the fine clinker powder containing a large amount of ca(on)x, the hydrate decomposes again during firing and releases water, which inhibits the sintering of the bricks. Therefore, we set the maximum clinker particle size to 0
．． If a 0.5i+n sieve is used as 5111, the sieving process can be speeded up and the generation of hydroxide can be almost ignored.

Furthermore, if the particle size Fi of 0.2 or less is at least 80%, it is possible to sufficiently improve the matrix mainly composed of periclase, which is the object of the present invention, so the lower limit was set at 80%. Of course, even if it is 100- as in Mayuki, the effect of the invention can be further increased.

Another theory E13 where the maximum grain size is O, SO is
If it exceeds 0.5111, stone ash clinker or mag.
Lime clinker is present in the medium-grain region (1-0.5 mm), and as a result, the clinker particles penetrate into the brick structure from the slag components.
This is because it selectively reacts with the harmful components of et On and becomes a low melting mineral, resulting in a decrease in erosion resistance.
This is because if the grain size is 1 or less, the influence will be suppressed to a minimum.

Next, fine powder of mag-lime clinker was converted into CaO with 5
When ~20% is added, the microstructure of the brick matrix consists of Mag-lime clinker particles cross-linked between periclase, but outside the particles @
is Ca0II! 11, and a MgO solid body exists inside it as a skeleton, and the brick has high hot strength.
The spalling resistance was improved, and the slag resistance was also improved, with less slag infiltration as in the case of adding lime clinker and 1Ilf1.

The reason why the MgO content of the lime clinker is limited to 50 is that if it exceeds 50, the anti-spalling effect of CaO decreases.

Lime chestnut 7 car, Mag lime clinker Fe, OH
, 8i02, it is better to reduce the amount of ATOs as small as possible.

In other words, FC! False is 1% or less, preferably 0.5% or less, Sin is 1% or less, preferably 0.5% or less,
Even per 40 g of A, it is required to be 1.5 or less, preferably 1.0 or more. The reason is that these (D small f a min tx, K Ca0-A between CaO
I, O,,2Ca0-Fe,0. Matrix - low melting point minerals such as CaO.

This is because since it forms between MgO crystals, it reduces hot strength and corrosion resistance.

Next, the present invention will be explained using examples.

Table 1 shows examples of the quality of the fused lime clinker and fused mag lime clinker, and Table 2 shows the quality of the fused lime clinker and fused lime clinker.
An example of the quality of mag-lime bricks manufactured using fused mag-lime clinker Φ) was shown.

5 tons of fused lime clinker ((transfer) is used as a fine powder with a particle size of 0.5w1a or less in a mixture of ordinary 7gd bricks.
t110'j is added, kneaded with a binder used in ordinary lime-based basic bricks such as attack poly□propylene, molded under high pressure, fired at a temperature of 1500U or higher, and after firing. In order to impart digestive resistance,
Waxing or tar impregnation was performed.

As a result, the quality of -1 brick was found to be denser with a slight decrease in apparent porosity in proportion to the amount of lime, and high values for compressive strength and strength in hot oil at 1480°C were obtained.

Furthermore, as shown in the drawing, the elastic modulus decreased due to the effect of lime, indicating that thermal spalling properties were improved. In addition, in the drawings, 0) Fi Magdro brick, ■ and ■ are the present invention. After removing the slag from these bricks using a rotary erosion furnace, we conducted a rapid cooling erosion test in which cold air was blown into the furnace.The results of non-invention ■ and ■ were caused by low penetration of slag components and structural spalling. There was little chance that a crack would occur.

Company A's product ■ of this invention? 0"" When used on the siding, tuyere area, and slag line of an AOD furnace, it was found to be 1. - In addition, there were fewer cracks and peeling caused by structural spalling, and improvement in spalling resistance was observed. In addition, the conventional Magdro bricks and tassels were tested on Company B's VOD furnace slag line, and good results were obtained with few cracks and peeling, so they continue to be used.

Table 1 Quality examples of lime clinker and mag-lime clinker 2 Quality examples of mag-lime bricks

[Brief explanation of the drawing]

The drawing is a chart showing the elastic modulus of the Magdro bricks described in Examples and the products of the present invention.

Claims (1)

[Claims] The coarse grains and intermediate grains of the magnesia-lime refractory composition are single or a combination of two or more of dolomite clinker, synthetic magne clinker, lime clinker, and magnesia clinker, and the fine grain part is magnesia clinker. - for the base formulation consisting of CaO/li! gO
Ratio is 100-50/10'-50, minor components are analytically F
e, 0.1% or less, Sin, 1% or less, ) daos
Electro-fused or sintered lime clinker or electro-fused or sintered mag-lime clinker with a size of 1.5- or less, 1, maximum particle size of 0.51 and 80 with a maximum particle size of 0.2111 or less
A magnesia-lime refractory having a grain size and size of 5 to 20% as CaO, cross-wired, molded, and fired at a temperature of 1500° C. or higher.