Technical field

[0001]

　The present invention relates to transport of molten metal, storage, relates magnesia carbon brick suitable for use in the lining material of the kiln in general to the purification like.

Background technique

[0002]

　Magnesia carbon brick (hereinafter referred to as "MgO-C brick.") Corrosion resistance composed of magnesia and graphite as the main bone material, it is an excellent brick in spalling resistance, lining material of the kiln in general, including the converter It has been used as Hiroshiku.

[0003]

　With the operations demanding in recent years of refining vessel, MgO-C brick with more excellent durability is now demanded. It includes oxidation resistance and corrosion resistance as a measure of the durability of the MgO-C brick. In order to improve these properties is to densify the MgO-C bricks, lowering the air permeability of the outside air, it is effective to suppress the penetration of slag and molten iron. Until now, because of the densification of MgO-C brick organization, improvement of the formulation content, been achieved a significant low porosity reduction due to the introduction of large-capacity vacuum molding machine, it is confirmed that also simultaneously improved durability, We've made a significant contribution to the reduction of the furnace ZaiHara unit.

[0004]

　On the other hand, the evaluation technology MgO-C brick also progress is seen, whereas the characteristics of the latter in the past exclusively drying had been evaluated, pre-reduction firing the MgO-C brick in recent years, its characteristics are evaluated It became way. Even 3% or less after it and the apparent porosity by this drying, a 3 hours after reduction firing at 1400 ℃ may reach 10% or more, whereby the closer the value of the brick after use is obtained. In other words, it can be better to pre-reduction firing the samples representing the state closer to the sample at the time of actual use, it is determined to be valid as an improved indication of the material.

[0005]

　Further, Al as the purposes of denseness improvement of MgO-C bricks, also adding a metal such as Si is to be constantly performed, the addition amount, shape, and have been studied for grain size. For example MgO-C brick of the following atomized metal Al powder particle size 0.1mm were added 1-8% by weight in Patent Document 1 has been shown to be effective in improving durability. The reason to use where atomized powder, the reaction because the specific surface area is small is mentioned to be easily inhibited sustained, the tissue formed by the time the heat receiving is considered to become slower. Furthermore, the addition amount thereof has been that it is desirable that metallic Al required still antioxidant is consumed in the generation of aluminum carbide is a relatively large amount so that the remaining, eventually with the temperature rise MgO-C bricks by spinel produced expands, denseness by increasing for example the residual expansion is likely to become impaired.

[0006]

　Meanwhile, the metallic Si in trace amounts have been shown to be oxidation resistance, the effect of improving the hot strength by the combined addition of the metal Al Patent Document 2. However, where the efficacy regarding denseness That apparent porosity of the bricks are not clarified, the amount of metallic Al is also is a more desirable relatively high, lowering of denseness as described above is concerned that.

[0007]

　Patent Document 3 was used together adding a metal Al and metal Si, high heat between the strength is disclosed excellent MgO-C bricks corrosion resistance, this Among metals Al as well as the present invention to be described later to, the addition of Si It is also included relatively small. However, these particle sizes have been used or less and a relatively coarse 150μm, it is not possible to fall below 9% Both porosity after 1200 ℃ reduction firing, densification is insufficient .

[0008]

　The particle size configuration of magnesia raw material are known to affect the densification of MgO-C bricks, for example, 30-45% by weight of intermediate particles in the range of 1 ~ 0.2mm Patent Document 4, 0.2mm or less oxidation resistance of fine by 15 to 25 wt%, the corrosion resistance, increase the hot strength is dense MgO-C bricks which can have been proposed. Although the densification is achieved by extending the intermediate grains is where, with the same purpose with the present invention, does not improve the denseness to impair the filling property by this time not to some extent a small amount limit the amount of fines, Furthermore it would be accompanied by spalling resistance deterioration.

CITATION

Patent literature

[0009]

Patent Document 1: Patent Publication No. 2001-72474
Patent Document 2: JP 56-59669 JP-
Patent Document 3: JP 56-59668 Japanese
Patent Document 4: JP-A-1-270564

Summary of the invention

Problems that the Invention is to Solve

[0010]

　An object of the present invention is to provide is to ensure further improvement in compactness of the MgO-C bricks (the porosity decrease), is to provide a was not tolerated high MgO-C bricks before.

Means for Solving the Problems

[0011]

　The present invention relates to the type of additive metal in order to solve the above problems, the addition amount, further to achieving the porosity reduction, durability with high MgO never before the MgO-C brick by optimizing the particle size and it is obtained by enabling the provision of -C bricks.

[0012]

　That is, the present invention provides the following MgO-C brick.
(1) In the magnesia carbon bricks containing a magnesia raw material and graphite, in percentage of total amount of the magnesia raw material and graphite, graphite 3 wt% to 25 wt% or less, a magnesia raw material 75 mass% or 97 mass% containing the following, magnesia carbon brick is 3 hours apparent porosity after reduction firing at 1400 ℃ is less than or equal to 7.8%.
(2) particle size 75μm or less of the content to be added graphite amount of metal Al of more than 85% by weight, and magnesia carbon brick according to containing less than 15% by weight of at least 1% by weight (1).
(3) and magnesia carbon brick according to the particle size 45μm or less of the content with respect to the addition of graphite the amount of metallic Al of more than 85 wt%, containing 15 wt% or less 3% by weight or more (1).
(4) particle size 45μm or less of the content with respect to the addition of graphite the amount of metallic Al of more than 85 wt%, and magnesia carbon brick according to 3 containing 10 mass% (1).
(5) relative to the particle size 45μm or less of the content of additive metals Al content of 85 mass% or more of boron carbide, containing 50 wt% or less than 1 wt% of any one of (2) to (4) magnesia carbon brick.
(6) for the addition of graphite weight of metallic Si of more than 85% by weight a particle size 75μm or less of the content of magnesia carbon bricks of any one of which contains more than 5 wt% (1) to (5).
(7) magnesia carbon bricks according to one of less than 1% by weight in outer percentage relative to the total amount of the content of the pitch-based material is a magnesia raw material and graphite (1) to (6).
(8) as a binder, and magnesia carbon brick according to any one of Zansumi-ritsu has used 48% or more of the phenol resin (1) to (7).

[0013]

　Examples of measuring the porosity and apparent by reduction firing the MgO-C bricks in conventional but are scattered, they are mostly less sintering temperature is 1200 ℃, less 7.8% under high thermal load of 1400 ℃ no example of achieving a low porosity. The present inventors finding that by further be lowered and the apparent porosity of the MgO-C bricks after high thermal loading to 7.8% or less, it is possible to improve the free corrosion resistance and oxidation resistance to the conventional The I got. This is what is achieved by the following techniques, effects.

[0014]

　The addition of the metal Al to the MgO-C brick is known, the method of addition increased modulus of elasticity, a large amount of additives as possible to the extent that spalling resistance degradation is allowed, oxidation resistance, hot strength it has been considered to be obtained an effect. This time, however, alumina by the present inventors is generated in the course of temperature increase and a large amount of addition of the metal Al, spinel and the resulting pores in the fine in the tissue because it involves the volume expansion, further dense tissue due to the rise of the residual expansion rate was knowledge that might reduce the resistance. Although relatively small amounts to keep the decrease in the oxidation resistance and the addition of metallic Al is concerned, oxidation resistance because it can reduce the permeability by ensuring the denseness of the MgO-C bricks is maintained. In order to reduce the porosity of the apparent better the particle size is small is preferred. It is melted in the metal Al is heating process, it is possible to reduce the pore diameter caused by volatilization, the probability of open porosity of is because decreases. More This is considered effective for early form tissue of MgO-C brick.

[0015]

　Meanwhile, it has been found to be effective to reduce also apparent porosity addition of the metal Si. Metal Si is SiC in the MgO-C brick in the course of temperature increase, followed by SiO 2 to generate. This SiO 2 is relatively low melting point reacts with MgO Enstatite, but to generate a Forsterite, liquid phase of the reaction process is low porosity reduction is achieved fill the fine pores of the MgO-C brick. Furthermore the presence of the metal Al, also produces a more low-melting Cordierite, are more efficiently expressed effect of the liquid phase fills the pores. Also is valid for the low porosity of the more even particle size small metallic Si, which is the case as well as melted in a temperature rising process of the metals Al, the probability of open porosity of it is possible to reduce the pore diameter caused by volatilization is decreased It is for.

[0016]

　Boron carbide is used in order to suppress degradation of the brick organization for the long-term thermal history. The mechanism it is considered as follows.

[0017]

　Generation temperature of the reaction product of the metal Al is Al 4 C 3 is about 800 ° C., Al 2 O 3 is about 900 ℃. On the other hand, the oxidation start temperature of boron carbide is about 500 ℃, also, Al in coexistence of boron carbide and the metal Al 4 BC to start generating in the 400 ~ 500 ℃. B produced by the oxidation of boron carbide 2 O 3 is Al 2 O 3 reacts with, 9Al 2 O 3 -2B 2 O 3 , Al 2 O 3 -B 2 O 3 , and Al 2 O 3 and B 2 O 3 but it wants to generate a mixed liquid phase. From these, and by metallic Al is to be contained the boron carbide to the added MgO-C bricks, Al causes that generate magnesia raw material and spinel 2 O 3 to be suppressed the generation of the ambient temperature from a low stage it can. In addition, Al 2 O 3 -B 2 O 3 for based low-melting compound of produce, Al brick tissue 2 O 3 it is possible to reduce the amount. Thus, Al 2 O 3 spinel reaction and the magnesia raw material is suppressed, i is considered to lead to the expansion suppressing the turn brick tissue. Furthermore, they 9Al 2 O 3 -2B 2 O 3 , Al 2 O 3 -B 2 O 3 and Al 2 O 3 and B 2 O 3 are mixed liquid phase to act as an oxidation film at a high temperature, metallic Al I improve the suppressed or oxidation resistance a decrease in the oxidation resistance of MgO-C brick by weight loss.

[0018]

　Although generally phenol resin as a binder of MgO-C brick is used, the residual carbon ratio is higher it is desirable. This volatilization of the solvent during the heating process, is because it can reduce the volatile matter associated with the polycondensation reaction, because the more so-called loophole outside the system when they volatilize to promote open porosity of.

[0019]

　The addition of pitch-based raw materials began to be Hiroshiku implemented in order to compensate for the spalling resistance of MgO-C brick. The pitch-based starting materials various softening points, but are commercially available ones Zansumi-ritsu to be added to any of the pitch-based raw materials tend to become increasing the porosity to contain volatiles. Further lowering the filling property of the brick when the addition amount is large, and the spring back during molding tends to thus reduce the denseness increased. The content of the pitch-based starting material in this respect, it is preferable for the total amount of magnesia raw material and the graphite is less than 1 wt.% In outer percentage, and is not necessarily limited thereto.

[0020]

　Granularity configuration of magnesia raw materials will affect the denseness of the MgO-C brick. Magnesia raw material is heated, the expansion in the course of cooling, the contraction, the gap is generated in its periphery when it shrinks because of greater expansion than the surrounding graphite. Increase in relatively large voids generated by apparent to become easily open porosity of the porosity is large around 1mm than the coarse particles. Porosity apparent by many blending the following particulate 1mm this reason is reduced. More than 75μm fines, the amount of the filling property is secured by so as not to collide with each other keeping a distance between a certain extent suppress magnesia particles, thereby improving the denseness. Also suppressing the amount of fines of less than 75μm is also leads to secure the spalling resistance.

[0021]

　The present invention, in the MgO-C bricks containing a magnesia raw material and graphite, the particle size and the content of metallic Al which constitute the brick texture, and by adjusting the particle size and content of the boron carbide, the long-term over suppresses tissue degradation to exposure of the thermal history, it is characterized in that to maintain the denseness.

[0022]

　Hereinafter, the configuration of the present invention in detail.

[0023]

　Firing temperature when evaluating the apparent porosity of the MgO-C bricks was set to 1400 ℃. Reaction in the internal MgO-C brick is not fully completed in less than this temperature, it is not suitable as an evaluation of denseness for heat load is also not sufficient. Also at temperatures above this, after the sintering becomes difficult to evaluate separately the effect in progress, no more preferably as a load is large stationary measurement evaluation to firing the furnace. The firing time was set to 3 hours as the time the sample is exposed to 1400 ℃. Reaction in the internal MgO-C brick is not suitable not completely completed in less than three hours. Furthermore the long time calcination than this become difficult to assess separately the effect sintering progresses. The present invention relates to a sample after it was calcined for 3 hours a reducing atmosphere at 1400 ℃, Archimedes method and kerosene and liquid medium (JIS R 2205) to inhibit the apparent porosity of 7.8% or less as measured by the It is characterized.

[0024]

　The addition amount of the metal it was defined by the ratio of the addition amount of graphite. It requires the addition amount of the metal of the antioxidant material is because it is reasonable to determine according to the amount of graphite to be lost oxidation.

[0025]

　The addition amount of the metallic Al is suitably 15 mass% or less of the added graphite content, more is desirably 10% by mass or less. By thus keep the amount of metallic Al is relatively small quantities, it is possible to suppress expansion of the metal Al is possible to reduce the porosity caused by volatilization, resulting MgO-C bricks are densified. The reason for adding at least 1% by weight, in which less than the addition amount is for oxidation resistance is insufficient, further desirable addition ratio is 3 mass% or more. This effect is expressed even more effective by using a particle size of 75μm or less of fine metal Al. Specifically, it is desirable that the particle size 75μm or less of the content using a metallic Al of more than 85 mass% as the size configuration, and that the particle size 45μm or less of the content using a metallic Al of more than 85 wt% more desirable.

[0026]

　The addition amount of boron carbide is suitably 50 wt% or less than 1 wt% relative to addition of metallic Al content, and more preferably at most 25 mass%. If the amount of the boron carbide is more than 50 mass%, during the thermal history of exposure, B by oxidation 2 O 3 is generated excessively, Al 2 O 3 extra B can not be reacted with 2 O 3 and the magnesia raw material and react to cause a large amount to produce a low melting material, and causing thus the corrosion resistance decrease. The added amount of boron carbide is less than 1 mass%, the effect can not be obtained. In addition, the effect of boron carbide, the particle size 45μm the following content is prominently expressed by using a 85 wt% or more of boron carbide. As the boron carbide, it is possible to use a commercially available ingredients commonly used in refractory bricks.

[0027]

　The addition amount of the metal Si is sufficient in 5 weight percent or less and a very small amount for the addition of graphite content, particle size 75μm or less of fine metal Si, particle size 75μm or less of the content of 85 mass as specifically grain size configuration % is expressed more effective by using more metals Si. No more excessive addition increases the low-melting product yield in the MgO-C bricks, lowers the durability and cause the corrosion resistance decrease. The addition amount of the lower limit of the metallic Si is not particularly limited, it is desirably not less than 1 wt% relative to the addition amount of graphite in order to significantly express the effect of the metal Si.

[0028]

　Phenolic resin novolak type used as a binder, a resol type, and may be any of the mixed type, and more preferably novolak hardly cause a change over time in the MgO-C brick. Powder or liquid that is dissolved in a suitable solvent, and further none of the liquid and powder combination can be used, usually to secure the residual carbon ratio by adding an appropriate amount of hardener such as hexamethylenetetramine. Its Zansumi-ritsu is desirably not less than 34%, but more preferably not less than 48%, it is not necessarily limited thereto. Such Kozansumi resin with phenol resins for refractory, which is usually commercially available are not well known, but, for example solvent species or is compatible with the pitch as disclosed in Japanese Unexamined Patent Application Publication No. 2010-105891 It is also possible to achieve a residual carbon rate of 50% or more by adjusting the amount.

[0029]

　Pitch-based raw materials the softening point, can also be used any of those Zansumi-ritsu, it may be used together adding more if necessary. It can be obtained even in the spalling resistance improvement effect in helping to suppress the deterioration of the other properties by adding further enhance the dispersibility, as disclosed in WO 2007/011038. However for reasons as described above, an outer seat with respect to the total amount of its addition amount magnesia raw material and graphite, it is desirable to stop less than 1.0 wt%, more desirably less than 0.6 wt% .

[0030]

　0 magnesia feedstock as the particle size configuration, in percentage of total amount of the magnesia raw material and graphite, was formulated or less of a particle diameter 0.075mm than 1mm least 35 wt% and for the magnesia raw material of less than 0.075mm. It is preferably blended such that the weight ratio of 1mm or less magnesia raw material than 075mm (the mass of magnesia raw material is less than the mass /0.075mm of 1mm or less magnesia raw material than 0.075mm) becomes 4.2 or more. 1mm than the magnesia raw material to produce a relatively large open pore by way would be suppressed to less than 57% by weight. Particle size reason to be blended 0.075mm or more 1mm or less of those more than 35% by weight, in less than this amount is because porosity inhibitory effect of the above-mentioned mechanism is insufficient. Further, by making the 4.2 or more mass ratio of the following magnesia raw material particle size 0.075mm more than 1mm for magnesia raw material having a particle size of less than 0.075mm, and that the particles having a particle size of less than 0.075mm is excessive formulated are prevented, as well as the filling of the distance is kept appropriately between the magnesia particles in the matrix can improve the denseness is secured, spalling resistance can also be ensured.

[0031]

　Furthermore the particle size configuration of magnesia raw material, in percentage of total amount of the magnesia raw material and graphite, the particle size 0.075mm least 1mm or less magnesia raw material is 35% by mass or more, magnesia raw material having a particle size of less than 0.075mm 15 formulated mass% or less, and it is preferable that the mass ratio of 1mm or less of magnesia raw material particle size 0.075mm or more for magnesia raw material having a particle size of less than 0.075mm is 4.2 or more.

[0032]

　That is, since the fine particle size of less than 0.075mm is too much contact of the magnesia raw material between increasing moldability is lowered, in order to improve the filling property after molding is more less are preferred. Specifically, the amount of the fine particle size of less than 0.075mm is preferably at most 15 mass%. Upon the amount of the fine is lowered moldability exceeds 15 mass%, the tissue degradation tends to occur after exposure to the heat history, since a tendency that the porosity is increased undesirably.

[0033]

　Moreover, the magnesia raw material is heated, the expansion in the course of cooling, the contraction, the gap is generated in its periphery when it shrinks because of greater expansion than the surrounding graphite. In particular, a relatively large gap is generated around the particle size 1mm than coarse grains, is large easily open pores of the causes apparent increase in porosity is. Therefore, by increasing the grain amount in the following grain size 0.075mm above 1mm, the particle size 1mm greater than the coarse particles is better to weight loss is preferred. It is preferable blending amount of the grain of the following grain size 0.075mm least 1mm at least 35% by weight in particular, and more preferably 43 mass% or more. In addition, the grain of the mass ratio of the following particle size 0.075mm more than 1mm for the fine particle size of less than 0.075mm (of medium grain mass / fine by mass) is preferably 4.2 or more.

[0034]

　Magnesia raw material used in the MgO-C bricks produced by the present invention fused magnesia, may be any of sintered magnesia, it may be used by mixing them. Although its not particularly defined also the composition, the higher in order to obtain a corrosion resistance better better is using the MgO purity is high magnesia aggregate, MgO purity of 96% or more, more desirably 98% or more.

[0035]

　Graphite is the usual scaly graphite is used, in combination with expanded graphite and is or this instead of this, artificial graphite and the like may be used kish graphite. Its not particularly defined composition, higher in order to obtain corrosion resistance often prefer to using the C high purity graphite, C purity 85% or more, more desirably 98% or more. Since the particle size is difficult to maintain the denseness in extremely fine thing, more than the particle size 0.04mm, it is better and more preferably using the particle size 0.15mm or more of graphite more than 40% by weight of the amount thereof.

[0036]

　As a further objective the properties improvement, Mg, Ca, Cr, other metals such as Zr, and two or more alloys of these elements, it is possible to add them and B, the compounds of the C. The present invention is not intended impair these additives effects, since there are problems such as denseness If these Kata to be added is decreased, the amount added is 15% by mass based on the added amount of graphite as well as the metallic Al It is desirable to be less.

[0037]

　In addition, it is possible to mainly monocytes type and / or aggregates carbon black in order to compensate for spalling resistance, and their dispersion, using, for example, crushing powder. But to reduce the denseness If these Kata to be added, the addition amount thereof is preferably not more than 1.5 mass% in total of C component.

[0038]

　When the production of these MgO-C brick, kneader, molding machine, and does not limit the type and their preparation contents of the dryer. However in order to obtain a dense MgO-C bricks, it is desirable to perform kneading using a kneading machine which can feed the addition performs well dispersed and kneading for kneading. Molding pressure is at least about 120MPa, and more desirably to be molded at least 150MPa. The drying temperature is better, but we need more than the boiling point of the solvent of the binder that was stopped in 400 ℃ or less is preferable in terms of preventing oxidation.

Effect of the invention

[0039]

　Thus obtained was dense, ie low porosity of MgO-C brick corrosion resistance is very good. Further oxidation resistance can not be inferior despite a small metal additive amount since the permeability is also greatly reduced. Since the grain size constituting the magnesia raw material and is designed in consideration of suppressing spalling resistance the amount of fines, that no worry to break during operation is noted.

[0040]

　Further, one obtained by addition of boron carbide, the occurrence of loosening of the brick tissue by the expansion reaction of the metal Al was added as antioxidant material is suppressed, and under conditions exposed to heat history over a long period of time during actual furnace using that may be used, improving durability of the brick makes it possible to keep deterioration of the brick texture is small in denseness, and can contribute to the extension of the turn furnace life. Thus it is possible to extend the maintenance cycle of the furnace, reduction and the furnace ZaiHara unit, which can contribute to the improvement of productivity through furnace repairing span extension.

[0041]

　All sites of such MgO-C brick of the present invention converter, steel pot slag line portion, is suitably applied to the secondary refining vessel, the furnace life improvement, it can contribute significantly to the reduction furnace ZaiHara unit.

EMBODIMENTS OF THE INVENTION

[0042]

　Or less, based on examples, we will explain the embodiment of the present invention. The present invention is not limited to these examples.
Example

[0043]

(Example A)
　sample preparation using the product manufacturing line for the converter. Table 1 is performed starting materials weighed in the proportion described in 1-3, kneaded by using a high speed mixer, the molding was molded at a molding pressure of up to 180MPa by vacuum friction in the side walls for the standard shape of length 810mm. Drying was maintained for 5 hours at up to 280 ℃ in a batch furnace.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

　In addition to measuring the porosity is apparent by now cut the physical property measurement for the samples were evaluated for oxidation resistance and corrosion resistance.

[0048]

　In the measurement of the porosity is apparent using the sample shape 60 × 60 × 60mm. Measurement of the apparent porosity was performed after heat treatment in a reducing atmosphere for 3 hours at 1400 ℃. The heat treatment temperature is lower than 1400 ℃, reaction within the MgO-C bricks not completely finished, it is not suitable as an evaluation of the density of the thermal load is also not sufficient. Furthermore the sintering proceeds at temperatures above 1400 ℃, and after that it is difficult to assess separately the effect of sintering as assessment of denseness, a steady measurements large load to the furnace to the heat treatment Preferably it disappears. Time of heat treatment is not suitable not completely finished reaction inside MgO-C bricks is less than 3 hours. Moreover it is evaluated by separating the effect sintering progresses difficult in long-time heat treatment than this. In this example, the sample after heat treatment in a reducing atmosphere for 3 hours at 1400 ℃, liquid medium was measured porosity is apparent in accordance with the Archimedes method using a kerosene (JIS R 2205).

[0049]

　Evaluation of oxidation resistance was excised from the dried sample to φ50 × 50mm, it was fired for 5 hours in an electric furnace in 1400 ℃ in the atmosphere. Then it was cut middle in the height direction of the sample was the average of this value by four direction measurement the thickness of the portion where the carbon component is discolored by decarburization with decarburized layer thickness.

[0050]

　Corrosion resistance, it was evaluated by rotation erosion test. The rotary corrosion test, lined with test bricks in the inner surface of a drum having a horizontal axis of rotation, the slag was charged, and allowed to erode the brick surface by heating. Heating source oxygen - a propane burner, test temperature is 1700 ℃, slag composition is CaO / SiO 2 = 3.4, FeO = 20% by mass, and MgO = 3% by weight, the discharge of slag, put on every 30 minutes It was repeated 10 times. After the test, the dimensions of the maximum erosion of the brick was measured to calculate the erosion amount is displayed in the corrosion resistance index is 100 the erosion amount of the "Comparative Example 1" described in Table 1. This corrosion resistance index indicates that the corrosion resistance is excellent The larger the number, the longer.

[0051]

　Table 1 shows the results of investigating the effects of the addition of metallic Al added to the graphite amount (indicated by percentage of the total amount of the magnesia raw material and graphite. Hereinafter the same.). Corrosion resistance index was expressed in corrosion resistance index is 100 the erosion amount of the "Comparative Example 1" described in Table 1.

[0052]

　Example 1 particle size is added to the following metals Al 75μm 0.13% by mass with respect to 13% by weight graphite, as a result of the metal Al ratio was 1.0% relative to the addition amount of graphite, the apparent porosity of 7.8% There oxidation resistance is achieved, it became a result of the excellent corrosion resistance both. In contrast in Comparative Example 1 has a small ratio of metal Al to the addition amount is small ie the addition of graphite the amount of metallic Al, an apparent porosity increases, has resulted in oxidation resistance, corrosion resistance inferior.

[0053]

　Example 2 The particle size was added the following metals Al 75μm 1.9% by mass with respect to 13% by weight of graphite, as a result of the metallic Al ratio added graphite content 14.6%, and an apparent porosity reduction, acid The results of resistance is improved is obtained. Oxidation resistance for the added amount is a plethora of metal Al relative to the addition amount of graphite Comparative Example 2 In contrast to the apparent porosity of the things you want to improve slightly rose.

[0054]

　Example 3 and 4 Examples 1 and 2 on the basis of the, of the following particle size 0.075mm more than 1mm for magnesia raw material having a particle size of less than 0.075mm of magnesia raw material mass ratio 4.2 or more, 5.38 is a result of evaluation performed adjustment. The apparent porosity, corrosion resistance results were obtained for improved than that of Examples 1 and 2.

[0055]

　Table 2 and 3, the type and the addition amount of the metal to further added, the added amount of graphite, which is the result of investigating the influence of the residual carbon ratio of the phenolic resin. Corrosion index shown in the corrosion resistance index is 100 to erosion of "Comparative Example 3" described in Table 3. Comparative Examples 3 and 4, respectively 0.9% metallic Al ratio added graphite content is a result of 15.4%. As in Comparative Example 1 in Table 1, the apparent porosity is large, it resulted inferior corrosion resistance. EXAMPLE 5 The results of the 7.7% metallic Al ratio added graphite content was metallic Al added amount of 1% by weight, further improvement in the apparent porosity reduction and corrosion resistance were achieved. 0.15mm or less of the relatively coarse grain of the metal Al (particle size 75μm or less of the content of 10 mass also the metal Al Comparative Example 5 contrast as 7.7% of the metal Al ratio of 1% that is added the amount of graphite %) As a result of the addition of a sufficient porosity reducing effect is not obtained, it was a result of oxidation resistance, corrosion resistance inferior.

[0056]

　Examples 6, 7 and 8 are used together metallic Si, are further metallic Al, low porosity reduction by grain refining of Si was achieved. Example 9 B Example 8 4 to C was added 0.1 wt%, are further characteristic improvement effect was confirmed. Example 10, 11, 12 and 13 is a MgO-C brick blended 3,8,18,25% by mass, respectively graphite. Both the oxidation resistance is low apparent porosity, good characteristics were observed in the corrosion resistance both. While contrast Comparative Example 6 is a MgO-C bricks in which the additive amount of graphite and 2 wt%, the apparent porosity increases, oxidation resistance along with it, and decreased corrosion resistance both. In this case, it is thought to be due to the fact that the filling is reduced. Also the added graphite content of 26% by weight of Comparative Example 7, large apparent porosity, corrosion resistance was confirmed that the decrease.

[0057]

　Examples 14, 15 and 16 residual carbon rate of 48%, an MgO-C bricks with 52% of phenolic resin as binder. Both characteristics are improved as compared with the case where the residual carbon rate of Example 9 and 11 were used it 42%. Example 17 is obtained by increasing to 0.9% by weight the amount of the pitch to the embodiment 15, in this case, although little porosity increased corrosion resistance decreases, a sufficient improvement effect can be obtained . EXAMPLE 19 0.2 wt% to the amount of pitch to Example 15, it is obtained by reduction with 0 wt%, reducing further the porosity, it can be confirmed that the corrosion resistance improving effect is obtained . Although Examples 20 and 21 is a MgO-C brick mass ratio of 1mm or less of magnesia raw material particle size 0.075mm or more for magnesia raw material having a particle size of less than 0.075mm are 4.22 and 11.00, the low porosity is a rate, oxidation resistance, has been achieved excellent characteristics in corrosion resistance both. In contrast to Comparative Example 8 but if this mass ratio is 3.90, but greater corrosion resistance porosity apparent when compared to Example 20 has deteriorated significantly. The amount of Comparative Example 9 in particle size 0.075mm or more 1mm or less of magnesia raw material is 35% less than only a formulated particle size 1mm more than the whole of the magnesia raw material particles becomes excessive, a large corrosion resistance also increased apparent porosity The resulted inferior.

[0058]

(Example B)
　In this example, it was investigated the effect of the silicon carbide. Is carried out starting materials weighed in proportions shown in Table 4 and 5, samples were prepared in the same manner as in Example A. As for in the same manner as in Example A obtained samples, as well as measuring the apparent porosity was evaluated for oxidation resistance and corrosion resistance. However, the corrosion resistance of the evaluation results, it was displayed in corrosion resistance index the amount of erosion and 100 of "Comparative Example 31" described in Table 4. This corrosion resistance index indicates that the corrosion resistance is excellent The larger the number, the longer.

[0059]

[Table 4]

[0060]

[Table 5]

[0061]

　In Examples 31-33 and Comparative Examples 31 to 33 graphite content (which means the percentage of the total amount of the magnesia raw material and graphite. Hereinafter the same.) Of 13% by weight of MgO-C bricks, the amount of metallic Al It is a result of investigation of the combined effects of boron carbide when changing the. In Example 31, particle size 75μm or less of metallic Al and 0.13 wt%, it is the case that the particle size 45μm or less of boron carbide was added 0.065% by weight, an apparent porosity of 7.7% is achieved, oxidation resistance, it was a result of excellent corrosion resistance both. In contrast comparative example 31 boron carbide is additive-free, apparent porosity increases, has resulted in oxidation resistance, corrosion resistance inferior.

[0062]

　In Examples 32 and 33, respectively, metallic Al added amount of 1.0 mass%, 1.9 wt%, 0.5 wt% of boron carbide added amount is the case of the 0.95 wt%, reducing further the apparent porosity as compared with Example 31, it was the result of excellent oxidation resistance. For the comparative example 32 In contrast boron carbide is additive-free, porosity apparent when compared has become a result of the increase as in Example 33. Comparative Example 33 was added the amount of porosity is apparent because of the plethora of boron carbide is increased relative to the addition amount of Al metal was added, the corrosion resistance is lowered.

[0063]

　Example 34 is a case where the addition amount of the boron carbide to the added metallic Al content to 1.0 wt%, have achieved a 7.6% apparent porosity. Example 35 is a case where the addition amount of the boron carbide to the added metallic Al content to 20 wt%, reduces further the apparent porosity as a result of oxidation resistance and corrosion resistance are improved is obtained.

[0064]

　For Comparative Example 34 is added in an amount of boron carbide for the added metal Al amount is appropriate, with the addition of boron carbide as particle size 75μm or less of the relatively coarse grain (particle size 45μm or less of the content of 15% by mass), The apparent porosity is rising.

[0065]

　Examples 36 and 37, it is the result of adjusting the mass ratio of less magnesia raw material particle size 0.075mm than 1mm in 5.38,6.63 and evaluated for magnesia raw material particle size of less than 0.075mm, further The apparent porosity is reduced, the oxidation resistance and corrosion resistance were improved.

[0066]

　Example 38, 39 and 40 is a MgO-C brick in which the graphite content, respectively 8,18,25% by mass. Both, low apparent porosity, exhibited good oxidation resistance and corrosion resistance. In contrast Although Comparative Example 35 is a MgO-C bricks in which the graphite content is 7% by weight, an apparent porosity is increased, oxidation resistance is lowered and accordingly. Also, the porosity graphite content is also apparent in Comparative Example 6 26% by weight increases the corrosion resistance it was confirmed that the decrease.

[0067]

　Example 41 is achieved even lower porosity reduction By grain refining the metal Al. In contrast in Comparative Example 37 is 0.15mm or less of the relatively coarse particles of metallic Al (particle size 75μm or less of the content of 10 wt.%) Results with the addition of 1.0 wt%, a sufficient porosity reducing effect is not, it resulted inferior in oxidation resistance and corrosion resistance as compared with Example 36 and 41.

[0068]

　Example 42 is a case of a combination of particle size 75μm or less of the metal Si. By the combined use of metallic Si, to lower the porosity reduction was observed. In Examples 43 and is obtained by using a particle size 45μm or less of the metallic Si, low porosity reduction is achieved a further.

[0069]

　Example 44 is the case of a combination of particle size 45μm or less of the finely divided metallic Al and a particle size 45μm or less of the finely divided metallic Si, and further a low porosity and by a combination of comminuted metal reduction has been achieved.

[0070]

　Example 45 MgO-C bricks with a residual carbon rate of binder 30% of phenolic resin, although Example 46 is an example content of 2% by weight of the pitch-based materials, within the scope of the invention It has become that there is dense tissue.

Claims

[Claim 1]

　In the magnesia carbon bricks containing a magnesia raw material and graphite, in percentage of total amount of the magnesia raw material and graphite, graphite 3 wt% to 25 wt% or less, magnesia raw material is contained 97 mass% 75 mass% or more , magnesia carbon brick is 3 hours apparent porosity after reduction firing at 1400 ℃ is less than or equal to 7.8%.

[Claim 2]

　For the particle size 75μm or less of the content of added graphite the amount of metallic Al of more than 85 wt%, and magnesia carbon brick according to claim 1 containing 15 wt% or less than 1 wt%.

[Claim 3]

　For the particle size 45μm or less of the content of added graphite the amount of metallic Al of more than 85 wt%, and magnesia carbon brick according to claim 1 containing 15 mass% 3 mass% or more.

[Claim 4]

　For the particle size 45μm or less of the content of added graphite the amount of metallic Al of more than 85 wt%, and magnesia carbon brick according to claim 1 containing 3 mass% to 10 mass%.

[Claim 5]

　For the particle size 45μm or less of the content of additive metals Al content of 85 mass% or more of boron carbide and magnesia carbon brick according to any one of claims 2 to 4 containing 50 mass% or less than 1 wt%.

[6.]

　For the particle size 75μm or less of the content of added graphite the amount of metal Si of more than 85 wt%, and magnesia carbon brick according to any one of claims 1 to 5 containing 5% by mass or less.

[7.]

　Magnesia carbon brick according to any one content of the pitch-based starting material of claims 1 to 6 is less than 1 wt.% In outer percentage relative to the total amount of magnesia raw material and graphite.

[8.]

　As a binder, and magnesia carbon brick according to any one Zansumi-ritsu of claims 1 to 7 using a 48% or more of the phenolic resin.