KR20070066723A - Magnesia-spinel-carbon contained basic castable compositions for repairing of converter - Google Patents

Abstract

A refractory composition of magnesia-spinel-carbon castable is provided to increase strength, spalling resistance and permeation resistance of the castable, and to be effectively used for thermally repairing converters by comprising magnesia clinker, spinel clinker, pitch pellet and calcined alumina in relative ratios by weight thereof. The refractory composition includes 58-72wt.% of magnesia clinker powder, 20-25wt.% of spinel clinker powder, 3-7wt.% of pitch pellet and 5-10wt.% of calcined alumina microfine powder. The composition further contains additional components such as: 1.0-3.0wt.% of silica, 0.5-2.wt% of B4C, 1-3wt.% of SiC, 0.1-0.4wt.% of sodium hexameta phosphate and 0.02-0.04wt.% of citric acid. The spinel clinker powder has a particle size less than 0.074mm and the pitch pellet has a softening point more than 120deg.C and a particle size less than 0.3mm. The calcined alumina microfine powder has a particle size less than 0.5 micrometers.

Description

Magnesia-spinel-carbon contained basic castable compositions for repairing of converter}

The present invention relates to a refractory composition of a carbonaceous basic inflow material for a furnace furnace hot repair, and more particularly, to a refractory composition of a magnesia-spinel-carbon inflow material for high temperature resistance of a furnace body having excellent corrosion resistance and infiltration resistance. will be.

In general, magnesia-like refractories are characterized by excellent corrosion resistance to molten steel and slag, and various irregular refractory materials having magnesia as a main raw material have been developed. Among the refractory refractory, the refractory refractory for inflow construction has high utilization because of its simple construction.

However, the magnesia inflow material using magnesia as the inflow material is, in most cases, a large amount of alumina cement as a binder, and thus has a disadvantage in that molten steel or slag is easily dissolved. The alumina cement used as a binder is mixed with magnesia aggregate and fine powder to add water, and after kneading, the molding material exerts its strength as a furnace body in a short time within 24 hours by hydration reaction. 12% by weight of alumina cement is used.

The alumina cement has the advantage of imparting the strength of the amorphous material in a short time, but at a high temperature, a low melting point material including MgO, Al 2 O 3, CaO, and SiO 2 is included in the matrix at the high temperature, and the melted material of the refractory material is leaked because the produced low melting point material flows out. There is a disadvantage that promotes.

In addition, the low melting point material penetrates through the pores in the refractory tissue together with the external slag and the penetrated material reacts with aggregate and matrix in the tissue to create a deteriorated layer. The altered layer thus produced causes structural spalling, and the refractory is peeled off by such structural spalling. Since the alumina cement-bound magnesia inflow material having such a defect reduces the inherent advantages of the magnesia material having excellent corrosion resistance, it is essential to reduce the amount of alumina cement used to solve this problem.

In addition, the material must be fluid (flowable) in order to repair hot spots from entering the hot spots and to develop strength early to reduce working time. Since ordinary hot repair materials contain a large amount of tar or pitch, there is a problem that corrosion resistance is lowered due to volatilization of tar or pitch after construction.

The present invention has been invented to solve the above-mentioned conventional problems. Instead of the alumina cement used as the binder of the magnesia-spinel-carbon inflow material, ultrafine calcination alumina and silica flower are used as the binders for the magnesia inflow material. The object of the present invention is to provide a fire-resistant composition of a magnesia-spinel-carbon inflow material for converter body hot repair, which improves flaw resistance, corrosion resistance and infiltration resistance, and has excellent workability in hot.

In order to achieve the above object, the present invention is magnesia clinker 58 to 72% by weight, spinel clinker powder 20 to 25% by weight, pitch pellets 3 to 7% by weight, ultra-fine calcined alumina 5 to 10% by weight as a basic composition, Extrapolated silica flower 1.0-3.0 wt%, B4C 0.5-2 wt%, SiC 1-3 wt%, 0.1-0.4 wt% hexametaphosphate, 0.02-0.04 wt% citric acid by extrapolation to the composition It is characterized by the refractory composition of the hot repair magnesia-spinel-carbon input material.

Preferably, the particle size of the spinel clinker powder is 0.074 mm or less.

Preferably, the pitch pellets have a softening point of 120 ° C. or more and a particle size of 0.3 mm or less.

Preferably, the particle size of the ultra finely calcined alumina is 0.5 μm or less.

Hereinafter, the operation of the present invention configured as described above will be described in detail.

It is preferable to use magnesia clinker 58 ~ 72 wt%, spinel clinker powder 20 ~ 25 wt%, pitch pellet 3 ~ 7 wt%, ultra finely calcined alumina 5 ~ 10 wt% as basic composition. The reason for this is as follows.

The purity of the magnesia clinker used in the present invention is preferably to use the content of magnesia (MgO) of more than 98% in order to maintain the high refractory degree of inflow material, and may be used either sintered magnesia clinker or electrolytic magnesia clinker. In order to obtain corrosion resistance, it is preferable to use an electrolytic magnesia clinker.

In addition, the magnesia clinker is a main raw material, but should be 58 to 72% by weight, the content of the magnesia clinker is artificial graphite ground powder or calcined alumina powder which is added to coke and spinel clinker fine powder to improve the corrosion resistance and infiltration resistance. And it means to use the remaining portion except the pitch pellets as a fire-resistant aggregate, it is preferable to contain a large amount of magnesia in order to obtain high corrosion resistance to molten steel or slag.

The spinel clinker powder is preferably used with a particle size of less than 0.074mm in consideration of the particle size of the other inflow material,

The reason for using the spinel kringer powder is that a large amount of fine magnesia powder may be used. However, when the fine magnesia powder is used, it is preferable to use the spinel clinker powder.

In addition, the amount of the spinel clinker powder is preferably 20 to 25% by weight.

At this time, the reason for limiting the addition amount of the spinel clinker is effective in improving the infiltration resistance to slag.

The pitch pellet is a softening point of 120 ℃, it is preferable to use 3 to 7% by weight with a particle size of 0.3mm or less.

At this time, when the pitch pellets are used, the fluidity in the heat of the inflow material is increased and the strength is expressed early. If such pitch pellets are used in an amount less than 3% by weight, the fluidity in the hot state is lowered, the strength is lowered, and the infiltration resistance to the slag and the corrosion resistance are lowered. If it exceeds 7% by weight, the fluidity in the hot is improved, but there is a problem that the corrosion resistance is reduced.

In addition, the calcined alumina is preferably 5 to 10% by weight of ultrafine calcined alumina of 0.5 μm or less. The use of ultra finely calcined alumina increases the fluidity of the influent and acts as a binder to increase the dry strength of the influent. When the calcined alumina powder is used in less than 5% by weight, the flowability of the inflow material is lowered and the dry strength is lowered. If it exceeds 10% by weight rather the liquidity is lowered, there is a disadvantage that the price increases.

On the other hand, in the present invention, 1 to 3% by weight of ultrafine silica flower by extrapolation to the basic composition as described above, 0.5 to 2% by weight of B4C, 1 to 3% by weight of SiC, and 0.1 to 4% of hexamethaphosphate as a dispersant. 0.4 wt% and 0.02 to 0.04 wt% citric acid are added as a curing retardant to form a magnesia-spinel-carbon influent. The reason is as follows.

The silica flower is not only to impart fluidity and maintain dry strength in the present invention, but also to maintain bonding strength in an intermediate temperature range (600 to 1000 ° C.). If the amount is too small, the addition of too much fluidity is rather inferior in fluidity and creates a low melting point material of magnesia-alumina-silica-based, which lowers the hot strength and corrosion resistance. Therefore, in the present invention, it is preferable to limit the addition amount of the silica flower to 1 to 3% by weight with respect to the basic composition of the refractory composition.

The B4C and SiC are added to enhance the oxidation resistance of the carbon contained in the inflow material, the B4C is preferably added 0.5 ~ 2% by weight but less than 0.5% by weight does not have an oxidation resistance effect, more than 2.0% by weight There is a problem that the corrosion resistance is lowered. In addition, SiC is preferably added in an amount of 1 to 3% by weight, but less than 1% by weight of carbon has insufficient antioxidant effect, and when it is more than 3% by weight, corrosion resistance is lowered.

The hexametaphosphate is preferably used as a dispersant in the present invention, in consideration of sufficient dispersibility, the addition amount is preferably limited to 0.1 to 0.4% by weight extrapolated to the basic composition. When the addition amount of sodium hexametaphosphate by extrapolation to the basic composition is less than 0.1% by weight, the fluidity of the inflow material is insufficient, and when it exceeds 0.4% by weight, the fluidity and corrosion resistance are rather deteriorated.

The citric acid is to act as a curing retardant in the present invention, in consideration of the working time during the inlet material construction, the addition amount is preferably limited to extrapolation 0.02 ~ 0.04% by weight based on the basic composition. If the content is less than 0.02% by weight, the kneaded product will harden quickly, which may cause trouble in construction. If the content exceeds 0.04% by weight, the flowability of the inflow material will be severely degraded during kneading, making kneading difficult.

Hereinafter, the present invention will be described in detail through examples.

When the components prepared as shown in Table 1 using 6.0 wt% of added water to prepare the converter hot repair inflow material, the flow value for evaluating the workability as the inflow material was measured, and the bending strength after preparing the specimen To evaluate the residual line change rate, erosion resistance is shown in Table 1 below.

At this time, the flow value is 100mm inside the flow cone (flow cone) is placed in the center of the metal plate of the flow meter and filled with about 1Kg kneaded sample and then removed the flow cone and only if the mass remains, the impact on the disc do. Due to the up-and-down impact of the disc, the sample on the disc spreads widely according to the size of fluidity. After hitting 15 times, the longest part and the shortest part of the material which flowed were measured, and the average value was made into the flow value. If such a flow value is 150 or more normally, it can be judged that constructability is favorable.

The specimen size for measuring the bending strength and residual line change rate was manufactured to be 40mmx40mmx160mm, and the specimen for erosion test was inflow molded into 118mm (back side) x 110mm (height) x40mm (thickness) x82mm (front side) size for 24 hours. It was demolded and dried at 110 ° C. for 24 hours to use for the test.

The oxide layer area ratio was oxidized for 3 hours at 1400 ° C. for each specimen, and then the specimen was cut and the ratio of the decarburized area was obtained to show oxidation resistance. The higher the decarburized area ratio, the worse the oxidation resistance.

The erosion depth and the depth of infiltration were measured by cutting the center of the specimen after rotational erosion test at 1650 ℃ ~ 1700 ℃ for 4 hours using the converter slag with basicity (CaO / SiO2 ratio) 3.5 and total Fe 17% as erosion agent. will be.

As can be seen in Table 1 and Table 2, in the case of Example (1-2) that satisfies the scope of the present invention than in the case of Comparative Example (1-14) that does not satisfy the scope of the present invention It was found that the characteristics were excellent.

On the other hand, the pitch pellets of Comparative Examples 1 and 2 deviated from the added content of 3 to 7% by weight of the present invention, it can be seen that the infiltration resistance and the corrosion resistance and the poor workability.

Comparative Example 3 is the addition of ultra finely calcined alumina less than 5% by weight in the addition amount of 5 ~ 10% by weight of the present invention, the dry strength is weak and shows residual shrinkage,

The ultra finely calcined alumina of Comparative Example 4 was more than 10% by weight based on the addition amount of 5 to 10% by weight of the present invention, and the flowability of the kneaded product was lowered, and the residual expansion ratio was excessive, resulting in structural stability.

Comparative Example 5 and Comparative Example 6 is that the addition amount of the silica flower deviates from 1.0 to 3.0% by weight of the present invention, when less than 1.0% by weight is added, the dry strength and the plastic strength at 1000 ° C. are weak and exceed the 3.0% by weight. Lower fluidity and lower corrosion resistance.

Comparative Examples 7, 8, and 9 are antioxidants, and B4C deviates from 0.5 to 2% by weight of the present invention and 1 to 3% by weight of SiC, and when less than 1% by weight is added as in Comparative Example 7, 8 Oxidation resistance was inferior, and when more than 3 weight% was added like Comparative Example 9, corrosion resistance fell.

In Comparative Example 10, alumina cement, which is not included in the present invention, was added as a binder, indicating that corrosion resistance was remarkably reduced.

In Comparative Example 11, citric acid, which was a curing retardant, was not added, and the kneaded product was quickly quenched within 10 minutes.

Citric acid of Comparative Example 12 is more than 0.04% by weight from 0.02 to 0.04% by weight of the present invention, the flow rate of the kneaded material is significantly reduced, it was impossible to produce a specimen.

In Comparative Example 13 and Comparative Example 14, the dispersant hexametaphosphate was more than 0.1 to 0.4% by weight of the added amount of the present invention, the fluidity was lowered and the test piece could not be prepared.

 As described above, the present invention relates to an inflow material of a magnesia-spinel-carbon system for hot repair of a converter, and contains carbon having excellent corrosion resistance and infiltration resistance to slag and molten steel, and as a binder, ultrafine powder instead of ordinary alumina cement. By using calcined alumina and silica flower, and adding hexametaphosphate and citric acid as dispersant and curing retardant, it was possible to improve the corrosion resistance without deterioration of strength by preparing refractory composition of carbon-containing basic inflow material for hot body repair.

As described above, in the detailed description of the present invention has been described with respect to specific embodiments, which are merely exemplary and various modifications are possible without departing from the scope of the technical idea of the present invention, of course, disclosed in the present invention Obviously, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims and equivalents described below as well as the claims. Should.

As described in detail above, if the refractory composition of the magnesia-spinel-carbon inflow material for the furnace body hot repair of the present invention is used, the ultrafine powder calcined alumina and the alumina cement usually used as a binder of the magnesia inflow material are not used. Pitch pellet and ultra fine silica flower are used as binders to improve the strength, spalling resistance, erosion resistance and infiltration resistance of the magnesia-spinel-carbon hot repair inflow material.

Claims (4)

Magnesia clinker 58 to 72% by weight, spinel clinker powder 20 to 25% by weight, pitch pellets 3 to 7% by weight, ultra finely calcined alumina 5 to 10% by weight as a basic composition, Ultrafine silica flower 1.0 to 3.0% by weight, B4C 0.5 to 2% by weight, SiC 1 to 3% by weight, 0.1 to 0.4% by weight of hexametaphosphate, 0.02 to 0.04% by weight citric acid Refractory composition of the magnesia-spinel-carbon inlet material for the heat exchanger for the furnace body. The method of claim 1, The particle size of the spinel clinker powder is less than 0.074mm fireproof composition of the magnesia-spinel-carbon inlet material for hot repair. The method of claim 1, The pitch pellet has a softening point of more than 120 ℃, the particle size of the refractory composition of the magnesia-spinel-carbon inflow material for the furnace body hot repair, characterized in that less than 0.3mm. The method of claim 1, The ultra finely calcined alumina is a refractory composition of a magnesia-spinel-carbon inflow material for hot furnace repair, characterized in that less than 0.5㎛.