JP6567588B2 - High temperature melt refining vessel - Google Patents

Description

  The present invention relates to a vessel for refining a high-temperature melt such as a converter or an electric furnace, and a refining vessel provided with a gas blowing nozzle at the furnace bottom or the like.

  In converters and electric furnaces, for the purpose of improving refining efficiency and alloy yield, so-called bottom blowing, in which stirring gas (usually inert gas such as nitrogen or Ar) or refining gas is blown into the molten metal from the bottom of the furnace. Done. As the bottom blowing method, (1) a double tube method in which oxygen for decarburization is blown from the inner pipe, and hydrocarbon gas (propane, etc.) is blown from the outer pipe for cooling the molten steel contact area. , (2) A slit-shaped aperture is provided in the gap between the metal tube and the brick, and an inert gas is blown through the aperture (slit method). (3) Multiple (several to several hundred) carbon-containing bricks There is a method in which a metal thin tube is embedded, and an inert gas is supplied from the bottom of the brick through a gas introduction tube and a gas reservoir to the metal thin tube, and an inert gas is blown from the metal thin tube.

Of these, in the methods (1) and (2), the tuyere bricks are manufactured in advance by a regular method, and the installation part of the metal pipe forming the double pipe or slit is processed, or divided into two or four parts. Thus, it is common to form a space for installing a metal pipe, set a metal pipe for blowing gas at the time of construction, and construct a tuyere brick around it.
On the other hand, the gas blowing plug (nozzle) used in the method (3) is called a multiple hole plug (hereinafter referred to as MHP). For example, in Patent Document 1, in this MHP, a gas flow rate (0.01 to 0.20 Nm ³ / min) that is 1 to 20 times can be controlled. For this reason, MHP is easier to adopt than the double tube method or the slit method.

MHP has a structure in which a plurality of metal thin tubes connected to a gas reservoir are embedded in a carbon-containing refractory such as magnesia-carbon brick, so its production is different from a double tube type or slit type nozzle. The following method is adopted.
That is, a material obtained by adding a carbon source such as scaly graphite, a binder such as pitch, metal species, and phenol resin to an aggregate such as magnesia material is kneaded using a kneading means such as a high-speed mixer with high dispersion performance, A kneaded material that constitutes a carbon-containing refractory in which a thin tube is embedded is obtained. Then, after laying the metal thin tubes on the kneaded product and burying the metal thin tubes in a laminated shape, the metal thin tubes are molded at a predetermined pressure by a press machine, and then subjected to predetermined drying (the metal thin tubes are thereafter Or by joining a metal thin tube to the gas reservoir member by welding in advance and filling the surrounding kneaded material with a press machine at a predetermined pressure. The MHP is manufactured by a method of performing molding and then performing predetermined drying.

The bottom blowing nozzle has a large amount of damage (amount of wear) compared to refractories such as a furnace wall, and is an important member that affects the life of the furnace. Therefore, various proposals for suppressing damage have been made in the past. For example, the following improvements have been proposed.
In Patent Document 2, the gas injection nozzle portion of MHP and the surrounding tuyere are integrated to reduce the prior melting damage and wear from the joint portion. However, since the damage of MHP occurs even in the portion where the metal thin tube is embedded, this technique cannot be a very effective measure.
Further, as one of the damage factors of MHP, there is a low melting point (preceding damage to the metal thin tube) by carburizing the metal thin tube embedded in the refractory. As countermeasures, the following proposals have been made.

Patent Document 3 proposes forming an oxide layer by thermal spraying on the surface of a thin metal tube in order to suppress carburization of a stainless steel thin tube embedded in a carbon-containing refractory such as magcarbon. However, in a refining furnace that is used for a long period of time such as a converter (for example, a usage period of 2 months to 6 months), there is a problem that the film thickness of the oxide layer is not sufficient and the carburization suppressing effect is small.
Patent Document 4 proposes disposing a refractory sintered body between the metal thin tube and the carbon-containing refractory to suppress carburization of the metal thin tube. However, although this technique has an effect of suppressing carburization, it is difficult to place a fireproof sintered body in a nozzle that embeds a large number of thin metal tubes because the distance between the thin metal tubes is narrow. Is difficult.

JP 59-31810 A JP-A-63-24008 JP 2000-212634 A Japanese Patent Laid-Open No. 2003-231912 JP-A-58-15072 Japanese Patent No. 3201678

In order to increase the refining efficiency in refining high temperature melts, it is preferable to increase the gas flow rate of stirring gas or refining gas. However, increasing the gas flow rate increases wear of the tuyere and shortens the life of the refining vessel. To do. As described above, in a gas blowing nozzle (such as MHP) in which a metal thin tube is embedded in a carbon-containing refractory, various studies have been made on refractory materials and structures in order to enhance the durability, but a sufficient improvement effect Is not obtained.
Accordingly, an object of the present invention is to solve the above-described problems of the prior art and to provide a high-temperature melt refining vessel having a gas blowing nozzle in which one or more metal thin tubes for gas blowing are embedded in a carbon-containing refractory. An object of the present invention is to provide a refining vessel in which the durability of a gas blowing nozzle is high and refining can be performed with high refining efficiency by increasing the flow rate of gas blown from the gas blowing nozzle.

  The cause of damage to MHP used in converters and electric furnaces has hitherto been thought to be mainly due to melt damage and wear due to the flow of molten steel near the nozzle operating surface, since the gas is blown vigorously from the metal thin tube. It was. The countermeasure of Patent Document 2 is based on this concept. In addition, there is a view that damage is increased when the metal thin tube is first consumed due to carburization or the like, and carburizing into the metal thin tube has been prevented by a technique such as Patent Document 3 or Patent Document 4. On the other hand, the refractory is cooled in order to blow inactive gas vigorously during blowing, and the idea that spalling damage may occur due to the temperature difference between blowing and non-blowing, and also the carbon-containing refractory Since the strength of the object is the lowest at around 600 ° C., there are various ideas such as whether the working surface is cracked and damaged at that part, and no conclusion has been reached. As a result, sufficient measures have not been taken, and the satisfactory durability as described above is not always obtained.

  Therefore, the present inventors collected after-use products (MHP) used in an actual furnace and investigated in detail the refractory structure in the vicinity of the nozzle operating surface in order to find the true cause of damage of MHP. As a result, it was found that a very large temperature change of 500 to 600 ° C. occurred inside the refractory having a depth of about 10 to 20 mm from the working surface, and further a crack parallel to the working surface was confirmed at this part. I was able to. As a result of repeated investigations in the vicinity of the operating surface of the product after use in actual furnaces, the damage form of MHP is not due to damage due to melting or wear, but due to a rapid temperature gradient occurring in the vicinity of the operating surface. It was concluded that the damage caused by thermal shock was mainly.

Up to now, the concept of thermal shock resistance has been improved to reduce the elastic modulus, thermal expansion, and strength of the material in order to prevent cracks in the carbon-containing refractory material that is the base material of the nozzle. Has been done. However, it is difficult to stop the generation of cracks under the conditions where a rapid temperature change occurs in a very narrow range of the operating surface as described above. Therefore, the present inventors proceeded with investigations on whether or not cracks can be improved by making the cracks difficult to extend, and focused on the fracture energy of the carbon-containing refractory.
The fracture energy of a refractory is defined as the energy required for surface formation when a crack extends to form a new surface. If a certain amount of elastic energy is stored on the refractory and a certain amount of elastic energy is stored, and the crack is generated by that energy, the greater the fracture energy, the less likely the crack will extend.

  Conventionally, various methods for improving the breaking energy of a refractory have been studied. For example, it is known that the breaking energy can be improved by adding a carbon long fiber. However, when carbon long fibers are added, there is a disadvantage that the filling property of the carbon-containing refractory is deteriorated. Therefore, a method that can improve the fracture energy relatively easily was examined. As a result, the refractory is fired under non-oxidizing conditions and then impregnated with organic matter (hereinafter, sometimes referred to as “non-oxidative firing / organic impregnation”) to sufficiently fill the pores of the refractory with organic matter. It was found that this is effective in improving the fracture energy.

2. Description of the Related Art Conventionally, a technique in which a refractory is non-oxidatively fired and impregnated with an organic substance is known for the purpose of mainly improving the corrosion resistance and heat spalling resistance of a refractory for furnace lining. For example, in Patent Document 5, a calc carbon brick added with metal Al powder is fired and heated in a non-oxidizing atmosphere at 500 to 1000 ° C., and then impregnated with an organic substance having a carbonization yield of 25% or more in the brick pores. To improve the corrosion resistance as well as the hot strength. Moreover, in patent document 6, heat-resistant slag by the reduction | decrease of slag erosion resistance and elastic modulus is baked in the reducing atmosphere of 600-1500 degreeC by adding 0.5-10 weight% of calcined anthracite. The polling performance is improved. In this patent document 6, as an index of spalling resistance, evaluation is made by an elastic modulus after 1400 ° C. reduction firing, and it is important that the elastic modulus is 1.2 × 10 ⁴ MPa or less. Furthermore, tar may be impregnated after the reduction firing, and it is described that the impregnation improves pore sealing, strength, and digestion resistance, but no examples are described.

  As described above, the conventional technology for non-oxidizing firing / impregnation of refractories is mainly aimed at improving the corrosion resistance and heat spalling resistance of the refractories for furnace lining, and the present invention aims at The effect of suppressing crack extension by improving fracture energy is not known at all. There are also examples in which non-oxidizing firing and organic impregnation technology is applied to manufacture refractories for gas injection nozzles in which metal thin tubes for gas injection are embedded, and the pores of the refractory are filled with organic substances. unknown.

Here, the reason why the fracture energy is increased by applying the non-oxidized firing / organic impregnation technique and filling the pores of the carbon-containing fired refractory with organic matter is not necessarily clear, but is considered as follows.
Carbon-containing refractories (brick) are generally manufactured using a phenol resin or the like as a binder. The phenolic resin is thermally decomposed at a high temperature, a part of the carbon remains, and functions as a binder for the carbon-containing refractory. However, the degree of bonding is not large, and the fracture energy is not so large because it easily extends when a crack occurs. In contrast, when impregnated with organic matter after non-oxidizing firing, the organic matter diffuses and penetrates evenly to the inside of the refractory, and in the pores formed in the matrix portion of the refractory or between the scale graphite layers. Organic matter enters. These organic substances are decomposed by heating when the nozzle is used, and carbon bonds are formed. As a result, a loose bond is formed between the carbon material such as scaly graphite and the refractory aggregate, and the degree of the bond is increased. As a result, even if a crack occurs, it becomes difficult to extend easily. In addition, the carbon bond derived from the organic matter described above is peeled off by moderate stress due to the occurrence of a loose bond, and acts as a bridge between the brick structures in the same manner as when carbon long fibers are added. As a result, the destruction energy increases.

As described above, the carbon-containing refractory in which the metal thin tube for MHP is embedded is filled with the organic matter in the pores by using the non-oxidizing firing / organic impregnation technique, and the refractory forming the periphery of the metal thin tube is formed. It has been found that by increasing the fracture energy, the extension of cracks generated near the working surface of the MHP can be suppressed and the life of the MHP can be greatly improved. Therefore, by providing such a MHP in the refining vessel, it is possible to increase the gas flow rate, which has been avoided from the viewpoint of preventing the decrease in the lifetime of the MHP so far, and it is possible to realize a refining vessel with high refining efficiency.
The present invention has been made on the basis of such knowledge and has the following gist.

[1] A gas blowing nozzle having a carbon-containing fired refractory in which one or more metal thin tubes for gas blowing are embedded, and the carbon-containing fired refractory constituting the gas blowing nozzle is disposed in the pores. A high temperature melt refining vessel characterized by being filled with an organic substance having a residual carbon ratio of 30% by mass or more, a porosity of 3% or less, and a fracture energy of 120 J / m ² or more.
[2] The high temperature melt refining vessel according to [1], wherein the carbon-containing fired refractory constituting the gas blowing nozzle has a fracture energy of 150 J / m ² or more.

[3] In the refining vessel according to the above [1] or [2], the carbon-containing fired refractory constituting the gas blowing nozzle has a porosity of 1.5% or less, and a high-temperature melt refining vessel .
[4] In the refining vessel according to any one of [1] to [3], the organic matter filled in the pores of the carbon-containing baked refractory constituting the gas blowing nozzle has a residual carbon ratio of 35% by mass or more. A high temperature melt refining vessel.
[5] In the smelting vessel according to any one of the above [1] to [4], the carbon-containing baked refractory constituting the gas blowing nozzle is filled with organic matter in the pores formed between the matrix portion and the scale graphite layer. A high temperature melt refining vessel characterized by being made.

[6] In the refining vessel according to any one of [1] to [5] above, the organic matter filled in the pores of the carbon-containing baked refractory constituting the gas blowing nozzle is coal tar pitch, phenol resin, furan resin. A high temperature melt refining vessel characterized by being at least one selected from the inside.
[7] In the refining vessel according to any one of [1] to [6], the high-temperature melt refining is characterized in that the carbon content of the metal thin tube constituting the gas blowing nozzle is 2.0% by mass or less. container.
[8] In the refining vessel according to any one of [1] to [6], the high-temperature melt refining is characterized in that the carbon content of the metal thin tube constituting the gas blowing nozzle is 1.0% by mass or less. container.

  The refining vessel of the present invention suppresses the extension of cracks generated near the working surface of the gas blowing nozzle, so that the gas blowing nozzle has high durability and a long life, and thus can be a long-life refining vessel. . Further, by optimizing the carbon content of the metal thin tube provided in the gas blowing nozzle, the life of the refining vessel can be further increased. Accordingly, the refining vessel of the present invention can be refined with high refining efficiency by increasing the gas flow rate blown from the gas blowing nozzle.

The refining vessel of the present invention has a gas blowing nozzle provided with a carbon-containing fired refractory in which one or more metal thin tubes for gas blowing are embedded, and the gas blowing nozzle is embedded with a metal thin tube. The carbon-containing refractory is obtained by non-oxidizing firing / impregnation with an organic matter, and the carbon-containing fired refractory is filled with an organic matter having a residual carbon ratio of 30% by mass or more in the pores. Satisfies the conditions of 3% or less and the fracture energy of 120 J / m ² or more.
In the following description, a gas blowing nozzle in which several tens or more of metal thin tubes are embedded in a carbon-containing refractory may be referred to as “MHP” for convenience of description.

Hereinafter, the gas blowing nozzle provided in the refining vessel of the present invention will be described.
One or more metal thin tubes for gas blowing are embedded in the carbon-containing fired refractory constituting the gas blowing nozzle. This carbon-containing fired refractory is obtained by firing (non-oxidizing firing) a carbon-containing refractory.
The material (raw material) and forming method of the carbon-containing refractory, the material and number of the metal thin tubes, the method of embedding the metal thin tubes in the carbon-containing refractory will be described in detail later.

The carbon-containing baked refractory constituting the gas blowing nozzle is filled with an organic substance having a residual carbon ratio of 30% by mass or more in the pores. This organic matter is filled in the pores by impregnating the carbon-containing fired refractory that has been non-oxidized and fired with the organic matter. The residual carbon ratio of the organic matter is measured based on the fixed carbon measurement method described in JIS K6910 (phenol resin test method). If the residual carbon ratio of the organic substance filled in the pores of the carbon-containing fired refractory is less than 30% by mass, the effect of strengthening the refractory structure by the residual carbon is not preferable. From this viewpoint, a more preferable residual carbon ratio is 35% by mass or more.
Here, the main pores filled with the organic substance are pores formed between the matrix portion of the carbon-containing fired refractory and the interlayer of the scaly graphite.

  Examples of the organic material filled in the pores of the carbon-containing baked refractory include coal tar pitch, phenol resin, furan resin, and the like, and one or more of these can be used. preferable. This is because the coal tar pitch contributes to the improvement of fracture energy because carbon after pyrolysis is easily crystallized. On the other hand, since the carbon after pyrolysis is difficult to crystallize and the phenol resin tends to become glassy carbon, the effect of improving the fracture energy is relatively low compared to coal tar pitch.

The carbon-containing fired refractory constituting the gas blowing nozzle has a porosity of 3% or less. When the porosity exceeds 3%, the effect of filling the pores with organic matter is reduced, the effect of strengthening the refractory structure and improving the toughness is reduced, and the fracture energy is 120 J / m ² or more. It becomes difficult to secure. The more preferable porosity of the carbon-containing fired refractory is 1.5% or less. In order to reduce the porosity of the carbon-containing baked refractory, it is effective to sufficiently impregnate the pores of the carbon-containing baked refractory with an organic substance.

The carbon-containing baked refractory constituting the gas blowing nozzle has a breaking energy of 120 J / m ² or more. When the fracture energy is less than 120 J / m ² , the difference from the conventional incombustible refractory is small, and the life improvement effect of the gas blowing nozzle is small. That is, when the fracture energy of the carbon-containing refractory is 120 J / m ² or more, it becomes possible to particularly effectively suppress the extension of cracks generated by a rapid temperature gradient in the vicinity of the nozzle operating surface. The lifetime can be greatly improved. Moreover, the more preferable destruction energy of a carbon containing refractory is 150 J / m < ² > or more.
The fracture energy is measured using a three-point bending test method. That is, a 100 mm span three-point bending test was performed on a 25 × 25 × 140 mm test piece in an inert atmosphere at 800 ° C., and a bending load was applied to the test piece at a speed of 0.1 mm / min to apply stress / strain. A curve is obtained, and the fracture energy is obtained from the area formed by the stress / strain curve.

It is preferable that the carbon content of the metal thin tube (metal thin tube embedded in the carbon-containing fired refractory) constituting the gas blowing nozzle is 2.0% by mass or less. If the carbon content of the metal thin tube exceeds 2.0 mass%, the melting point of the metal thin tube is lowered, so that the metal thin tube may be melted in the vicinity of the working surface of the nozzle tip, and the durability of the nozzle itself is lowered. . Moreover, from the above viewpoint, the carbon content of a more preferable metal capillary is 1.0% by mass or less. As a bottom blowing nozzle, a test operation was performed in a 250 t converter using MHP that satisfied the conditions of the present invention and the carbon content of the metal thin tube was kept to 1.0 mass% or less. % Reduction of wear amount was confirmed.
The refining vessel of the present invention is provided with one or more gas blowing nozzles as described above at the furnace bottom or the like.

Next, the manufacturing method of the gas blowing nozzle with which the smelting container of this invention is provided is demonstrated.
The gas blowing nozzle provided in the smelting vessel of the present invention non-oxidizing and firing the carbon-containing refractory in which the metal thin tube is embedded (non-oxidizing firing step), and then the carbon-containing refractory has a residual carbon ratio of 30% by mass or more. It can manufacture by performing the impregnation process which impregnates the organic substance of (impregnation process process).
Here, when the gas blowing nozzle is manufactured, the object to be impregnated with non-oxidized firing / organic matter is a carbon-containing refractory with a metal thin tube embedded therein, but the gas blowing nozzle is a type having a gas reservoir. The object may be a carbon-containing refractory in which a metal thin tube is simply embedded, or a carbon-containing refractory in which a metal thin tube is embedded and all or part of a gas reservoir member is joined to the metal thin tube. It can be a thing.

  When producing a gas blowing nozzle, the carbon-containing refractory is non-oxidatively fired and then subjected to an impregnation treatment with an organic substance. Carbon-containing refractory (brick) is basically a non-fired refractory obtained without going through the firing process, and the porosity of the refractory is as low as several percent as the binder is cured. It is difficult to impregnate the entire refractory with organic matter. Therefore, in order to fully impregnate the entire refractory with organic matter and fill the pores with organic matter, non-oxidizing firing is required in advance. Furthermore, in non-oxidizing firing, the entire refractory is heat-treated, so that carbon components derived from binders and the like are homogeneously generated as binders. It is possible to easily impregnate organic matter while obtaining a homogeneous refractory structure.

  The firing temperature (heat treatment temperature) in the non-oxidizing firing of the carbon-containing refractory is preferably 400 ° C. or higher and 1500 ° C. or lower. If the firing temperature is less than 400 ° C., the thermal decomposition of the binder (usually a resin such as a phenol resin) does not occur sufficiently, impregnation with organic matter becomes insufficient in the impregnation treatment after non-oxidation firing, and the fracture energy is not sufficiently improved. There is a fear. On the other hand, if the firing temperature exceeds 1500 ° C., the embedded metal thin tube may be melted or blocked, and the gas blowing function as the gas blowing nozzle may be lost.

In order to more effectively impregnate the organic matter in the impregnation treatment after non-oxidizing firing, the firing temperature is preferably 800 ° C. or higher. On the other hand, if the firing temperature exceeds 1200 ° C., there is a risk of lowering the melting point of the metal thin tube due to carburization of the carbon component derived from the carbon-containing refractory into the metal thin tube. Therefore, from such a viewpoint, the firing temperature is preferably 1200 ° C. or lower, more preferably 1100 ° C. or lower.
The firing time (holding time) for non-oxidizing firing is preferably 1 to 20 hours. If the firing time is less than 1 hour, the heat treatment of the entire nozzle tends to be insufficient. On the other hand, if the firing time exceeds 20 hours, carburization of the metal capillaries occurs as in the case where the firing temperature exceeds 1200 ° C., which may lead to a lower melting point of the metal capillaries. From such a viewpoint, a more preferable firing time is 3 to 15 hours.

The firing of carbon-containing refractories is non-oxidizing firing. (I) The destruction energy of the fired refractories is 120 J / m ² or more, and (ii) the heat-resistant spalling and slag penetration inherent in carbon-containing refractories. This is to ensure that characteristics such as sex are not impaired. In other words, if firing is performed under conditions that significantly reduce the carbon contained in the carbon-containing refractory, for example, heating under high-temperature and long-term conditions in an oxidizing atmosphere, the carbon in the carbon-containing refractory is oxidized and lost. Therefore, the porosity is remarkably increased and the strength is decreased. For this reason, it cannot be set as the destruction energy of 120 J / m < ² > or more, and characteristics, such as heat spalling resistance and slag penetration resistance which a carbon containing refractory has, will be lost. Therefore, firing is performed under non-oxidizing conditions so that a predetermined breaking energy can be obtained and the above characteristics and the like are not lost.

The conditions for non-oxidizing firing are not particularly limited as long as carbon such as scaly graphite contained in the carbon-containing refractory does not substantially disappear. For example, reducing firing, firing in a reducing atmosphere, non-firing Firing in an oxidizing atmosphere, short-time firing in an oxidizing atmosphere, and the like can be applied.
There is no restriction | limiting in particular in the implementation method of non-oxidation baking, What is necessary is just to implement by a conventional method. For example, a sheath made of bricks and a metal container are installed on a carriage loaded in a firing furnace, and a carbon-containing refractory (carbon-containing refractory with metal thin tubes embedded) is set inside it. To do. Then, after putting a carbon source such as coke around the carbon-containing refractory, a reduction firing (heat treatment) is performed at a predetermined temperature and time while covering the top and shielding the outside air.

Also, the firing atmosphere is a reducing atmosphere firing in which a reducing atmosphere containing a combustible gas such as NX gas is used, or the firing atmosphere is an inert gas such as nitrogen or argon, or a non-oxidizing gas atmosphere. Oxidizing atmosphere firing can also be used. In the case of reducing atmosphere firing or non-oxidizing atmosphere firing, a sheath or a metal container can be omitted.
Furthermore, even if it is baking by oxidation atmosphere, it is set as baking for a short time, the decarburization layer formed in the surface is removed after baking, and the part which has not been decarburized inside a refractory can also be used. In this method, the surface of the carbon-containing refractory is in an oxidized state, but with the oxidation of the surface, the part works as a protective layer, and the inside of the refractory can be baked under non-oxidizing conditions. It can be regarded as substantially non-oxidizing firing. In addition, a method such as applying an anti-oxidation glaze to the surface of the carbon-containing refractory in advance can also be employed.
However, among the above methods, reduction firing, firing in a reducing atmosphere, and firing in a non-oxidizing atmosphere are more preferable. Firing in an oxidizing atmosphere is not economical because it is necessary to remove the decarburized layer on the surface.

As described above, the carbon content of the metal thin tube (metal thin tube embedded in the carbon-containing fired refractory) constituting the gas blowing nozzle is preferably 2.0% by mass or less, and 1.0% by mass or less. More preferably, for this purpose, the carbon content of the thin metal tube after non-oxidizing firing should be 2.0% by mass or less, preferably 1.0% by mass or less.
Examples of the method for setting the carbon content of the metal thin tube after non-oxidizing firing to 2.0 mass% or less include, for example, (i) lowering the non-oxidizing firing temperature and not excessively increasing the non-oxidizing firing time. The non-oxidizing firing temperature is set to 1200 ° C. or less, the non-oxidizing firing time is set to 20 hours or less, (ii) a coating film having no gas permeability is applied to the surface of the metal thin tube, and carburization is suppressed. In particular, the method (i) is effective.

  The carbon-containing refractory material (carbon-containing fired refractory material) that has been subjected to the non-oxidizing firing process as described above is subjected to an impregnation treatment for impregnating an organic material with a residual carbon ratio of 30% by mass or more, preferably 35% by mass or more. Examples of the organic substance to be impregnated include coal tar pitch (heated melt), phenol resin (liquid resin), furan resin (liquid resin) and the like, and one or more of these can be used. For the reasons described above, coal tar pitch is particularly preferable.

The method for impregnating the organic substance is not particularly limited, but it is preferable that the organic substance is impregnated under pressure after the pressure is reduced to a vacuum once. For example, after the pressure is reduced to 100 Torr or less, the organic material is impregnated by holding at a pressure of 5 kgf / cm ² or more for 2 hours or more. When the vacuum pressure is high, bubbles remaining in the refractory may not be able to uniformly impregnate the organic matter into the refractory during pressurization. Therefore, the vacuum pressure when reducing the pressure is preferably 100 Torr or less, more preferably 60 Torr or less. Further, if the applied pressure after decompression is low or the pressurization holding time is short, the refractory may not be sufficiently impregnated with organic matter. For this reason, it is preferable that the applied pressure after depressurization is 5 kgf / cm ² or more, more desirably 10 kgf / cm ² or more, and the pressure holding time is 2 hours or more, more desirably 4 hours or more. By satisfying these impregnation conditions, the organic matter uniformly penetrates into the carbon-containing refractory, and the effect of improving the breaking energy of the carbon-containing refractory according to the principle as described above can be obtained particularly effectively.

As described above, as a facility for reducing the carbon-containing refractory to a predetermined vacuum pressure and then maintaining the predetermined pressure, and impregnating the organic material, a general method used when impregnating the organic material with a slide plate or the like is used. Impregnation equipment can be used. In addition, after the impregnation, a drying treatment at about 200 ° C. may be performed in order to remove volatile components remaining in the carbon-containing refractory.
The porosity of the carbon-containing fired refractory is reduced to 3% or less (preferably 1.5% or less) by sufficiently impregnating and filling the pores of the carbon-containing fired refractory with the organic matter by the impregnation treatment as described above. can do.

By the above production method, the pores are filled with an organic substance having a residual carbon ratio of 30% by mass or more (preferably 35% by mass or more), and the porosity is 3% or less (preferably 1.5% or less). , and the and breaking energy can be 120 J / ^{m 2} or more (preferably 150 J / ^{m 2} or more) to obtain a gas blowing nozzle with a carbon-containing sintered refractory it is.
Samples of carbon-containing refractories of the same material that have been subjected to normal drying after molding, samples that have been non-oxidized and fired after drying, and samples that have been non-oxidized and organically impregnated under the conditions described above after drying a comparison of the breaking energy, the breaking energy was respectively ^{85J / m 2, 62J / m} 2, 160J / m 2. In this way, the destruction energy is effectively increased by non-oxidizing firing and impregnation with organic matter.

  In addition, as a method of increasing the destruction energy of the refractory, there is a method of adding carbon fiber (carbon long fiber) as described above, but the addition of carbon fiber is effective in increasing the destruction energy, Carbon fiber and refractory are very unsuitable, resulting in a porous structure with a very high porosity. For this reason, a material to which carbon fiber is added has a large decrease in corrosion resistance and is difficult to put into practical use. On the other hand, non-oxidized firing / impregnation with organic matter is preferable because it can increase the fracture energy while maintaining the denseness of the refractory structure.

Next, regarding the gas blowing nozzle provided in the smelting vessel of the present invention, the material (raw material) and forming method of the carbon-containing refractory (carbon-containing fired refractory), the material and number of the metal capillaries, and the metal capillaries as carbon-containing refractories A method of embedding will be described.
The raw material for the carbon-containing refractory is generally composed of an aggregate, a carbon source, other additive materials, a binder, and the like.
Examples of the aggregate include magnesia, alumina, dolomite, zirconia, chromia, spinel (alumina-magnesia, chromia-magnesia) and the like, and one or more of these can be used. From the viewpoint of corrosion resistance against molten slag, magnesia is particularly preferable.

The carbon source is not particularly limited, and commonly used materials such as scaly graphite, soil graphite, petroleum pitch, and carbon black can be applied, and one or more of these can be used. The blending amount of the carbon source in the carbon-containing refractory is not particularly limited, but generally about 10 to 25% by mass is appropriate.
Examples of other materials include, but are not limited to, metal species such as metal Al, metal Si, and Al—Mg alloy, and carbides such as SiC and B ₄ C.
As the binder, there can be used those which can be generally applied as a binder for a regular refractory, such as phenol resin and liquid pitch.

  The metal thin tube is usually a metal tube having an inner diameter of about 1 to 5 mm and a tube thickness of about 0.5 to 4 mm. The material of the metal thin tube is not particularly limited, but it is preferable to use a metal material having a melting point of 1300 ° C. or higher. For example, a metal material (metal or alloy) containing one or more of iron, chromium, cobalt, and nickel is mentioned, and stainless steel (ferritic, martensitic, austenitic) and ordinary steel are particularly common. It is.

  The number of metal thin tubes embedded in the carbon-containing refractory is not particularly limited, and is one to a plurality. The number of metal capillaries is determined by the inner diameter of the metal capillaries used and the required amount of gas blown. In a general converter MHP, about 60 to 250 metal capillaries are normally embedded in a carbon-containing refractory. On the other hand, in the case of a nozzle that allows only a small amount of gas to flow, there are one to several metal thin tubes. Even in such a gas blowing nozzle, the tip of the tuyere is cooled by blowing gas vigorously, and crack extension due to thermal shock causes damage, so the present invention is also applied to such a gas blowing nozzle. can do.

  The method for embedding the metal thin tube in the carbon-containing refractory is not particularly limited. For example, the raw materials for the carbon-containing refractory as mentioned above are mixed and kneaded with a mixer. The metal capillaries are laid in a laminated shape while laying the metal capillaries on the kneaded product, and then molded at a predetermined pressure with a press machine, and then dried at an appropriate temperature after molding. Then, the carbon-containing refractory in which the metal thin tube is embedded is subjected to non-oxidizing firing / organic impregnation by the method described above, and then a gas reservoir member necessary for the function of the gas blowing nozzle is attached to the metal thin tube. To the gas blowing nozzle provided in the refining vessel of the present invention.

  As another method, a metal thin tube is joined (welded) to a gas reservoir member (upper surface plate) in advance, and the mixture is filled with a kneaded material, and then molded with a press machine at a predetermined pressure. After the molding, it is dried at an appropriate temperature. Then, the carbon-containing refractory in which the metal thin tube is embedded is subjected to non-oxidizing firing / organic impregnation by the method described above to obtain a gas blowing nozzle provided in the refining vessel of the present invention.

The method for kneading the raw material for the carbon-containing refractory is not particularly limited, and a kneading means used as a kneading facility for a fixed-form refractory, such as a high speed mixer, a tire mixer (Conner mixer), or an Eirich mixer, may be used.
For forming the kneaded material, a general press machine used for forming a refractory such as a uniaxial forming machine such as a hydraulic press or a friction press or an isotropic static pressure forming (CIP) can be used.
The formed carbon-containing refractory may be dried at a drying temperature of 180 ° C. to 350 ° C. and a drying time of about 5 to 30 hours.

Tables 1 to 3 show the configuration and manufacturing conditions of the gas blowing nozzles used in this example (invention example, comparative example).
As raw materials for carbon-containing refractories for embedding metal thin tubes, fusing magnesia (purity 98.2% by mass) is used for the magnesia raw material as an aggregate, and scaly graphite (purity 98.4% by mass, average particle diameter) is used for the carbon source. 0.18 mm), and a phenol resin having a residual carbon content of 46% by mass was used as a binder.
As the metal thin tube embedded in the carbon-containing refractory, one having an outer diameter of 3 mm and an inner diameter of 2 mm made of ordinary steel or stainless steel (SUS430) was used.

Coal tar pitch or phenol resin was used as the organic material (organic material impregnated in the carbon-containing fired refractory) filled in the pores of the carbon-containing fired refractory. In Tables 1 to 3, those having a residual carbon ratio of 42% by mass and 35% by mass are coal tar pitches, and those having a residual carbon ratio of 30% by mass and 15% by mass are phenol resins. The residual carbon ratio was measured based on the fixed carbon measurement method described in JIS K6910 (phenol resin test method).
After blending the raw materials for the carbon-containing refractory in the proportions shown in Tables 1 to 3, this was kneaded using an Eirich mixer, and then a metal thin tube was placed on the kneaded product using a 230 × 200 mm mold. While laying, metal thin tubes were embedded in a laminated form, and then molded with a hydraulic press at a pressure of 2.5 ton / cm ² . This molded refractory was cured and dried at 250 ° C. for 10 hours using a dryer to produce a carbon-containing refractory with a metal capillary embedded therein.

The carbon-containing refractory produced as described above was non-oxidized and fired in coke breeze according to the conditions shown in Tables 1 to 3, and then impregnated with an organic substance to obtain a refractory for a gas blowing nozzle. In the impregnation treatment with the organic matter, it was held at a predetermined pressure for 10 hours.
In addition, the carbon containing refractory which does not embed a metal thin tube with the same raw material and method as the above was produced for the measurement of a porosity and fracture energy.

Some of the comparative examples were subjected to non-oxidizing firing only and not subjected to organic impregnation treatment, and were not subjected to non-oxidizing firing and organic impregnation treatment.
About the refractory for gas blowing nozzles obtained as described above, the carbon content of the metal thin tube was measured. Moreover, the porosity and fracture energy were measured about the refractory which does not embed a metal thin tube. The results are shown in Tables 1 to 3.
The porosity of the refractory was measured according to JIS R2205. At this time, a vacuum method was used, and white kerosene was used for the liquid smoke.

The refractory destruction energy was measured as follows. The test piece size was 25 × 25 × 140 mm, and a three-point bending test with a span of 100 mm was performed. The bending test was performed in an inert atmosphere at 800 ° C. “Autograph AG-X / R” manufactured by Shimadzu Corporation was used as the test machine, and the crosshead speed was set to 0.1 mm / min. Confirm that stable fracture has occurred from the stress / strain curve obtained by the three-point bending test, and divide the area formed by the stress / strain curve by twice the projected area of the cut surface (25 x 25 mm) to obtain the fracture energy. Asked. It was confirmed that stable fracture occurred in all cases of measurement.
The carbon content of the metal thin tube was measured by polishing the cut surface of the non-oxidized and fired test piece in which the metal thin tube was embedded, and performing quantitative analysis by Analytical Electrotechnical Laboratory. The measurement range was the amount of carbon in a field of view of 100 × 100 μm at a portion along the outer periphery of the metal thin tube. As the analyzer, “JXA-8230” manufactured by JEOL Ltd. was used.

According to Tables 1 to 3, all of the examples of the present invention have a low porosity and a high fracture energy.
Although the comparative example 1 is a magnesia carbon brick generally used, the fracture energy is a small value. Comparative Example 2 was obtained by subjecting Comparative Example 1 to non-oxidizing firing at 1400 ° C. (without impregnation with organic matter), but the fracture energy was small, and the carbon content of the metal capillaries was 3.1. Large as mass%. In Comparative Example 3, the non-oxidizing firing temperature is as low as 300 ° C., but the thermal decomposition of the binder due to the non-oxidizing firing does not sufficiently occur, so that impregnation with organic matter cannot be performed, and the fracture energy is small. Comparative Example 4 uses an organic material having a small residual carbon ratio of 15% by mass in the impregnation treatment, but the increase in fracture energy is not at a satisfactory level.

A gas blowing nozzle was manufactured using the refractories for each of the gas blowing nozzles of Invention Examples 1, 3, 6 and Comparative Example 1 (magnesia carbon brick conventionally used) and Comparative Example 2, and this was 250 tons. Used for the bottom brick around the bottom blowing tuyeres of the converter. The gas blowing nozzles after use were collected and their wear rate was examined.
When the wear rate of the gas blowing nozzle by Comparative Example 1 (conventional magnesia carbon brick) is 1, the gas blowing nozzle by Comparative Example 2 was not oxidized and fired at 1400 ° C. and impregnation was not performed. The wear rate of was 1.25.

  In contrast, the wear rate of the gas blowing nozzle according to Invention Example 6 (non-oxidized and fired at 1400 ° C.) was reduced to 0.81. Further, the wear rate of the gas blowing nozzle according to the present invention example 3 (non-oxidized and fired at 800 ° C.) is 0.68, and the wear rate of the gas blowing nozzle according to the present invention example 1 (non-oxidized and fired at 1000 ° C.) is It was 0.70, and the wear rate was significantly reduced.

Furthermore, the test operation which doubled the bottom blowing gas flow rate in the 250-ton bottom blowing converter which installed each gas blowing nozzle of the comparative example 1 and this invention example 3 was performed. As a result, in the converter installed with the nozzle of Comparative Example 1, nozzle wear was severe and the operation became impossible. However, in the converter installed with the nozzle of Example 3 of the present invention, the life of the iron part was reduced without causing a decrease in life. The effect of improving the refining efficiency was seen, such as an increase of 25% and a 20% reduction in the amount of metal Al added after blowing as a deoxidizer.
As described above, in the smelting vessel of the present invention example, the wear rate of the tuyere is reduced compared to the smelting vessel of the comparative example, the gas flow rate can be increased, and high smelting efficiency is obtained.

Claims (8)

The carbon-containing fired refractory having a carbon-containing fired refractory in which one or more metal thin tubes for gas blowing are embedded, and the carbon-containing fired refractory constituting the gas-injecting nozzle has a residual carbon ratio in the pores. Is filled with an organic substance of 30% by mass or more, has a porosity of 3% or less, and has a fracture energy of 120 J / m ² or more. ^2. The high temperature melt refining vessel according to claim 1, wherein the carbon-containing fired refractory constituting the gas blowing nozzle has a fracture energy of 150 J / m ² or more.   The carbon-containing fired refractory constituting the gas blowing nozzle has a porosity of 1.5% or less, and the high temperature melt refining vessel according to claim 1 or 2.   The high temperature melt according to any one of claims 1 to 3, wherein the organic matter filled in the pores of the carbon-containing baked refractory constituting the gas blowing nozzle has a residual carbon ratio of 35% by mass or more. Refining vessel.   The carbon-containing baked refractory constituting the gas blowing nozzle is filled with organic matter in pores formed between the matrix portion and the scale-like graphite layer. High temperature melt refining vessel.   The organic material filled in the pores of the carbon-containing baked refractory constituting the gas blowing nozzle is at least one selected from coal tar pitch, phenol resin, and furan resin. A high temperature melt refining vessel according to any one of the above.   The high-temperature melt refining vessel according to any one of claims 1 to 6, wherein the carbon content of the metal thin tube constituting the gas blowing nozzle is 2.0 mass% or less.   The high-temperature melt refining vessel according to any one of claims 1 to 6, wherein the carbon content of the metal thin tube constituting the gas blowing nozzle is 1.0 mass% or less.