JP2018039706A - Monolithic refractory for repair and repairing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnesia-olivine monolithic refractory capable of exhibiting excellent repair effect in the repair of the operation port of an electric furnace for steel making, a molten iron-molten steel container or an immersion tube, and a repairing method using the same.SOLUTION: Provided is a monolithic refractory for repair comprising: a refractory raw material in which fired olivine obtained by firing peridotite as natural raw material at 1,000°C occupies by 25 to 60 mass%, and the balance substantial magnesia; and a binder, in which the content of SiOis 14 to 26 mass. Concretely, in the case the basicity of the slag in contact with the operation port of an electric furnace for steel making, a molten iron-molten steel container or an immersion tube as a repair object being the low one below 1.5, a monolithic refractory for repair in which the content of SiOis regulated to 18 to 26 mass% is used, and, in the case the basicity of the slag being the high one of 1.5 or higher, the monolithic refractory for lining repair in which the content of SiOis regulated to 14 to below 18 mass% is used.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a working port of an electric furnace for iron making (such as a steel outlet), hot metal or a hot metal molten steel container (a hot metal ladle, a molten steel pan, a tundish, etc.) or a dip pipe (RH dip pipe, DH dip pipe). Etc.), and a repair method using the same.

  For example, a general lining structure in an electric furnace for steel making is a structure in which the surface of a lining brick is covered with a refractory stamp material. The top of the lining corresponds to a slag line and is worn ahead. The slag line is usually provided with a magnesia-carbon brick that is excellent in slag resistance. However, the service life of the slag line is still not sufficient and still wears down. Therefore, spray repair is performed on the slag line at any time in anticipation of wear.

  Magnesia is known as a material of the spray material used for such spray repair. Magnesia is a highly corrosion resistant material. However, since the slag easily infiltrates, the structural spalling in which a crack occurs at the boundary between the slag infiltrated portion and the back surface portion easily causes peeling damage. In this peeling damage, unlike melting damage, wear progresses at once and the repair effect is greatly reduced.

  As a countermeasure, it is conceivable to use a magnesia-dolomite material in which dolomite (magnesia-lime) is combined with this magnesia material. Dolomite has excellent resistance to slag infiltration. As a result, it is possible to predict the effect of combining the high corrosion resistance of magnesia and the slag infiltration resistance of dolomite. In addition, it is inferior in storability.

Therefore, Patent Document 1 proposes the use of magnesia-olivine in which peridotite, which is a basic refractory raw material excellent in digestion resistance, is combined with magnesia. Peridotite is a natural raw material mainly composed of MgO and SiO ₂ . During the use of refractory, there is an effect of increasing the viscosity of slag by elution of the SiO ₂ component and suppressing slag infiltration. And the spraying material of patent document 1 exhibits the outstanding repair effect in the lining repair of the electric furnace for steel manufacture by improving the adhesiveness and adhesiveness with respect to the magnesia-olivine repair surface.

  However, when the present inventors used the spraying material (unshaped refractory material) of Patent Document 1 for repairing a work opening of a steelmaking electric furnace, a hot metal molten steel container or a dip tube, an excellent repair effect is not necessarily obtained. could not.

Japanese Patent No. 4273099

  The problem to be solved by the present invention is a magnesia-olivine irregular refractory material capable of exhibiting an excellent repair effect in repairing a work mouth of a steelmaking electric furnace, a hot metal molten steel container or a dip tube, and a repair method using the same Is to provide.

As described above, the present inventors have demonstrated that the spraying material (unshaped refractory) of Patent Document 1 exhibits an excellent repair effect in the lining repair of a steelmaking electric furnace, whereas the working port of the steelmaking electric furnace, One of the reasons why the repair effect of hot metal molten steel container or dip tube is not always excellent is that the lining of the electric furnace for steel making and the working port of the electric furnace for steel making, the working conditions of the hot metal molten steel container or dip tube ( We thought that there was a difference in operating conditions. That is, the working port of an electric furnace for steel making is used for steelmaking work, the hot metal molten steel container is used for receiving and discharging hot metal and molten steel, and the dip tube is used for immersing and pulling up molten steel. Since it was repeatedly exposed to a very large heating and cooling compared to the inner lining of the steel, it was thought that a sufficient repair effect could not be obtained due to the volume change (dimensional change) accompanying this large heating and cooling. Therefore, as a result of repeated investigations aimed at a magnesia-olivine amorphous refractory having excellent volume stability (dimensional stability) during heating and cooling, the present inventors have found that the SiO ₂ content in the amorphous refractory is heated. It was found that volumetric stability (dimensional stability) during cooling was greatly affected, and it was found that volume stability (dimensional stability) during heating and cooling could be improved by controlling this SiO ₂ content. It was.

That is, according to one aspect of the present invention, “a calcined olivine obtained by calcining peridotite, which is a natural raw material at 1000 ° C. or more, occupies 25% by mass or more and 60% by mass or less, and the balance is a refractory raw material mainly composed of magnesia. , And a non-fixed refractory for repair of a steelmaking electric furnace, hot metal molten steel container or dip tube, comprising a binder and having a SiO ₂ content of 14 mass% to 26 mass%.

On the other hand, SiO ₂ in the amorphous refractory tends to lower the slag erosion resistance of the amorphous refractory. The upper limit of the above-mentioned SiO ₂ content is defined in consideration of the allowable range of the decrease in the resistance to slag erosion resistance, but according to the test by the present inventors (details will be described later), It was found that the tendency of the loss reduction greatly differs depending on the basicity (C / S) of the slag. That is, when the basicity of slag is increased, it was found that reduction of the resistance to slag corrosion resistance with increasing SiO ₂ content is increased. Therefore, the present inventors effectively use different refractories having different SiO ₂ contents depending on the basicity of the slag with which the work opening of the electric furnace for steelmaking to be repaired, the hot metal molten steel container or the dip tube is in contact. I got the idea.

That is, according to another aspect of the present invention, in the repairing method for a steelmaking electric furnace, a hot metal molten steel container or a dip tube with an indeterminate refractory for repairing according to the present invention, the electric furnace for steelmaking to be repaired is repaired. When the basicity of the slag with which the working port, hot metal molten steel container or dip tube is in contact is a low basicity of less than 1.5, the repaired amorphous refractory with the SiO ₂ content adjusted to 18% by mass or more and 26% by mass or less In the case where the basicity of the slag that contacts the working port of the electric furnace for steelmaking, the hot metal molten steel container, or the dip tube is high basicity of 1.5 or more, the SiO ₂ content is 14 mass% or more and 18 mass% There is provided a repair method for repairing with the repaired irregular refractory adjusted to less than%.

According to the present invention, by limiting the content of SiO ₂ in the magnesia-olivine amorphous refractory, excellent volume stability (dimensional stability) is exhibited during heating and cooling. As a result, an electric furnace for steelmaking Excellent repair effect can be exhibited in repairing the work port, hot metal molten steel container or dip tube.

Magnesia - is a graph showing the relationship between the SiO ₂ content and the rate of dimensional change olivine quality monolithic refractories. Magnesia - is a graph showing the relationship between the SiO ₂ content of olivine quality monolithic refractories and slag infiltration amount. Magnesia - is a graph showing the relationship between the SiO ₂ content of olivine quality monolithic refractories and slag erosion amount.

The calcined olivine used in the irregular refractories for repair of the present invention is obtained by calcining peridotite, which is a natural raw material. Natural peridotite is composed mainly of MgO and SiO _{2 as} chemical components. Forsterite (2MgO · SiO ₂ ), Enstatite (MgO · SiO), Firelite (2FeO · SiO ₂ ), Serpentine (3MgO · 2SiO ₂ · 2H ₂ O) are the main mineral phases, and other glassy materials Including. In the present invention, this natural raw material peridotite is fired and used. The firing temperature is 1000 ° C. or higher, preferably 1200 ° C. or higher and 1500 ° C. or lower.

  The ratio of the calcined olivine in the refractory raw material of the repairable amorphous refractory of the present invention is 25% by mass or more and 60% by mass or less. When the ratio of the baked olivine is outside this range, the dimensional change accompanying heating and cooling becomes large. A desirable ratio of the burned olivine is 45% by mass or more and 55% by mass or less.

As magnesia, natural magnesia, calcined magnesia or electrofused magnesia can be used. The ratio is mainly composed of the remainder of the fired olivine in the refractory raw material composition. The proportion of magnesia in the refractory raw material of the amorphous refractory is preferably 40% by mass or more and 75% by mass or less from the viewpoint of corrosion resistance. Further, magnesia is preferably a material containing 2 mass% or more and 6 mass% or less of SiO ₂ and 90 mass% or more of MgO in terms of chemical component values.

  The particle size of baked olivine and magnesia is coarse (particle size of 1 mm or more), medium (particle size of 0.125 mm or more and less than 1 mm) and fine particles (particle size of less than 0.125 mm) in order to achieve close packing of the construction body. Adjust as appropriate. The maximum particle size (top size) is preferably 2 mm or more and less than 5 mm as in the prior art. In addition, the particle size of a refractory raw material can be adjusted with a sieve. In the present invention, the particle size of 1 mm or more corresponds to a sieve having a mesh size of 1 mm. On the other hand, the particle size of less than 1 mm is a sieve under a sieve having an opening of 1 mm.

  In addition to the above fired olivine and magnesia, other refractory raw materials may be blended as long as the effects of the present invention are not impaired. For example, a small amount of baked dolomite is added. When these other refractory raw materials are used, the total amount is preferably 10% by mass or less as a percentage of the entire refractory raw material.

  The binder is not particularly limited. Examples thereof include phosphates such as sodium phosphate, hexametaphosphate, potassium phosphate, and calcium phosphate, silicates such as sodium silicate, sodium metasilicate, and potassium silicate, or alumina cement and Portland cement. The addition amount is a ratio with respect to the refractory raw material, and is preferably 1% by mass or more and 15% by mass or less as an outer shell. More preferably, it is 3 mass% or more and 10 mass% or less. Depending on the type of binder, a curing accelerator is further added. Specific examples of the curing accelerator include calcium salts such as slaked lime, quicklime, and calcium carbonate.

  If necessary, fibers, metal powder, dispersant, aluminum lactate, CMC, etc. may be added. Specific examples of the fibers are polypropylene, nylon, PVA, vinylon, polyethylene, acrylic, polyester, pulp, paper fiber, sepiolite and the like. Addition of 0.05% by mass or more and 1% by mass or less is preferred as a ratio to the refractory raw material.

In the above composition, the present invention is adjusted so that the SiO ₂ content in the amorphous refractory is 14% by mass or more and 26% by mass or less mainly from the viewpoint of securing volume stability (dimensional stability). This SiO ₂ content is adjusted mainly by the ratio of the baked olivine in the refractory raw material. The SiO ₂ content in the amorphous refractory is preferably 18% by mass or more and 23% by mass or less.

  The irregular refractory material for repair of the present invention can be constructed by any repair method such as spraying, stamping, trowel coating or the like. For example, in spraying, an arbitrary spraying device is used and construction is performed by a dry method. That is, the irregular refractory material for repair according to the present invention is transported to a nozzle by a spraying device as a spraying material, and construction water is added or sprayed at or near the nozzle. In order to prevent dust generation, a part of the construction water may be added to the spray material in advance. Of the hot metal molten steel container, spraying construction is suitable for repairing the lining of the hot metal ladle, the molten steel pan, and the dip portion of the dip tube. On the other hand, stamping is suitable for repairing the work opening of the electric furnace for steel making and repairing the bottom corner of the hot metal molten steel container. Also, iron coating may be applied to repair the tundish lining of the hot metal molten steel container. That is, the irregular refractory for repair is used as a spraying material, a stamp material, a trowel coating material (coating material) or the like according to the construction method.

In such repair with an irregular refractory material for repair according to the present invention, mainly from the viewpoint of securing slag erosion resistance, the work opening of the steel furnace to be repaired, the hot metal molten steel container, or the lining of the dip tube is provided. When the basicity of the slag in contact is less than 1.5 (typically 0.4 or more and less than 1.5), the SiO ₂ content is 18% by mass or more and 26% by mass or less (more preferably 19% by mass). % To 25% by mass) and a relatively high content non-fixed refractory for repair, and the basicity of slag is 1.5 or more (typically 1.5 to 5) In the case of the degree of repair, it is possible to use an amorphous refractory for repair adjusted to a relatively low content of SiO ₂ content of 14% by mass or more and less than 18% by mass (more preferably 14% by mass or more and 16% by mass or less). preferable.

As shown in Table 1, repaired amorphous refractories were prepared by changing the blending ratio of natural magnesia and calcined olivine as refractory raw materials, and the dimensional change rate, slag infiltration amount, slag erosion amount of each amorphous refractory, and The pressure strength (compressive strength) was measured as follows. The fired olivine is obtained by firing peridotite at 1100 ° C. in a rotary kiln.
(1) Dimensional change rate A test piece of 40 × 40 × 160 mm was prepared from each amorphous refractory, and the linear change rate after heat treatment at 1500 ° C. × 3 h was measured.
(2) Slag infiltration amount, slag erosion amount Synthetic slag having a basicity (C / S) of 1.0, 2.0, 3.0 or 5.0 (Table) 2), the erosion test was carried out at a maximum temperature of 1500 ° C. for 3 hours by raising the temperature from room temperature, and the slag infiltration amount and slag erosion amount were measured.
(3) Pressure resistance (compressive strength)
A test piece of 40 × 40 × 40 mm is prepared from each irregular refractory, the test piece is set in a compression tester, the pressure plate of the compression tester is lowered at a uniform speed, and the test piece is pressurized to the maximum load. The pressure strength (compressive strength) was calculated from the following formula.
C = W / (a × b)
C: Pressure strength (compressive strength) (MPa)
W: Maximum load (N)
a, b: Vertical and horizontal dimensions (mm) of the pressure surface

FIG. 1 shows the relationship between the SiO ₂ content and the dimensional change rate of the irregular refractories for repair shown in Table 1. As shown in the figure, when the SiO ₂ content is in the range of 14% by mass or more and 26% by mass or less, a reduction in the dimensional change rate is recognized, and the dimensional stability (volume stability) of the repairable refractory is improved. I understand that.

FIG. 2 shows the relationship between the SiO ₂ content of the repairable refractory and the slag infiltration amount, and FIG. 3 shows the relationship between the SiO ₂ content of the repaired refractory and the slag erosion amount. Regarding the slag infiltration, as shown in FIG. 2, the infiltration amount was reduced when the SiO ₂ content was 14% by mass or more in any slag basicity (C / S) of 1.0 to 5.0. On the other hand, as shown in FIG. 3, regarding the slag erosion, the slag basicity (C / S) is 2.0 to 5.0 (high basicity) compared to 1.0 (low basicity). It was found that the increase in the amount of erosion caused by the increase in the SiO ₂ content was larger. From this, it is effective to use different repaired refractories with different SiO ₂ contents according to the basicity of the slag with which the work mouth of the steel furnace to be repaired, the molten steel container or the dip tube is in contact. Recognize. Specifically, when the basicity of the slag is a low basicity of less than 1.5, an irregular refractory for repair with an SiO ₂ content adjusted to 18% by mass or more and 26% by mass or less is used. When the degree of basicity is 1.5 or more, it is preferable to use a repairable refractory having a SiO ₂ content adjusted to 14% by mass or more and less than 18% by mass.

Claims (2)

A calcined olivine obtained by calcining peridotite, which is a natural raw material, at 1000 ° C. or higher occupies 25% by mass or more and 60% by mass or less, and the balance includes a refractory raw material mainly composed of magnesia and a binder, and has an SiO ₂ content. An indeterminate refractory for repairing a work mouth of a steelmaking electric furnace, a hot metal molten steel container or a dip tube, which is 14% by mass or more and 26% by mass or less. In the repairing method of the working port of the electric furnace for steel making, the hot metal molten steel container or the dip tube with the irregular shaped refractory for repair according to claim 1,
When the basicity of the slag in contact with the work opening of the steel furnace to be repaired, hot metal molten steel container or dip tube is low basicity of less than 1.5, the SiO ₂ content is adjusted to 18 mass% or more and 26 mass% or less. Repaired with the above-mentioned irregular refractories for repair,
When the basicity of the slag in contact with the work mouth of the steel furnace to be repaired, hot metal molten steel container or dip tube is high basicity of 1.5 or more, the SiO ₂ content is adjusted to 14 mass% or more and less than 18 mass% The repair method repairs with the said irregular refractory material for repair.