JP2007039255A - Spraying material for repairing lining of steelmaking electric furnace and method for repairing lining of steelmaking electric furnace using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a magnesia-olivine-based spraying material to exhibit excellent repairing effects under operation conditions of a steelmaking electric furnace by improving adhesion of the magnesia-olivine-based spraying material and utilizing the effects of corrosion resistance and resistance to the penetration of slag possessed by magnesia-olivine. <P>SOLUTION: In a spraying material for repairing the lining of a steelmaking electric furnace, a refractory raw material comprising coarse particles and fine particles, each containing 25-80 mass% fired olivine and the balance being mainly fired magnesia and/or electrofused magnesia, and a binder are blended, and the coarse particles having particle sizes of ≥1 mm contained in the refractory raw material is composed of only fired olivine or a mixture in which the ratio of the fired olivine is higher than the ratio of the fired magnesia and/or the electrofused magnesia. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a spray material used for lining repair of an electric furnace for steel making, and a spray repair method for an electric furnace lining for steel making using the same.

  In a steelmaking electric furnace that melts scrap or the like by an arc, the general lining structure 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.

  This slag line is usually provided with MgO—C brick having excellent slag resistance. However, the service life of the slag line is still not sufficient and still wears down. Therefore, spray repairs are carried out on the slag line as needed in anticipation of wear and tear.

  The cross-sectional view of the main part of FIG. 1 shows the spray repair situation of the electric furnace lining for steel making. The spray material 2 is sprayed mainly on the slag line 1 which is a preceding wear spot. This figure is a vertical cross section of the upper part of the side wall. Here, a water cooling jacket 4 is provided above the MgO—C brick 3 located in the slag line 1, but it may be a refractory. Further, the material of the lining brick 5 is generally a fired magnesia brick, and the fireproof stamp material 6 is typically a magnesia stamp material, for example.

  Magnesia is known as a material for the spray material used here. 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, but in actual use, magnesia-dolomite is significantly digested by the hydration reaction of dolomite, and adhesion and corrosion resistance are reduced. In addition, it is inferior in storability.

Therefore, the present inventors considered the use of magnesia-olivine in which olivine, which is a basic refractory raw material excellent in digestion resistance, was combined with magnesia. Olivine 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. This magnesia-olivine spray material is described, for example, in the Example column of Patent Document 1.
JP-A-10-101440

  From the construction form, the spraying material is important for adhesion and adhesion to the repaired surface. No matter how excellent the corrosion resistance is, if the adhesion or adhesion is poor, the effect of the corrosion resistance will not be exhibited.

  Here, the adhesion is a good adhesion rate at the time of spraying. Adhesiveness is the adhesive force of the sprayed construction body to the repaired surface after the spraying material is attached.

  The lining of an electric furnace for steel making is subjected to heating-cooling associated with the operation of the furnace, impact during scrap input, and the like. When the spray material is inferior in adhesiveness, it is peeled off from the repaired surface without waiting for disappearance due to melting damage. The slag line is located on the vertical wall surface, and unlike the horizontal or inclined surface, the spray material is easily peeled off.

  Adhesion of the spray material can be sufficiently improved by material design by adjusting the binder. The adhesion of the magnesia-olivine spray material is no different than that of the magnesia spray material. However, the spraying on the lining of a steelmaking electric furnace is not sufficient in adhesion, and the effects of the corrosion resistance and slag penetration resistance that magnesia-olivine has can not be utilized.

  Therefore, the object of the present invention is to improve the adhesiveness of the magnesia-olivine spraying material and take advantage of the effects of the corrosion resistance and slag penetration resistance of the magnesia-olivine material, making it an excellent repair under the operating conditions of the electric furnace for steelmaking. It is to be able to demonstrate the effect.

  The present invention is a spray material for repairing an electric furnace lining for steel making, characterized in that the olivine is 25 to 80% by mass, and the balance is coarse or fine particles mainly composed of calcined magnesia and / or electrofused magnesia. The adjusted refractory raw material and a binder are blended, and the coarse particles having a particle size of 1 mm or more in the refractory raw material are only fired olivine, or the ratio of the fired olivine is higher than that of fired magnesia and / or electrofused magnesia. It is to have done.

  According to the spray material of the present invention, an excellent repair effect is exhibited under the operating conditions of the steel furnace. The reason is considered as follows.

  The olivine used in the magnesia-olivine spray is a natural raw material also called peridotite. Usually, it is previously dried, but it contains water of crystallization. And, when the magnesia-olivine spray material containing this olivine is subjected to a high temperature in the furnace operation and reaches a certain temperature range, water vapor is generated from the crystal water, and the water vapor pressure acts on the surface to be repaired. It causes a decrease in adhesion.

  As described later, the present invention mainly uses olivine as coarse particles in order to suppress adhesion deterioration due to thermal expansion of the spray material. Although spray material receives high temperature heating by construction, the change in temperature of coarse olivine is smaller than that of fine olivine due to the difference in particle size. Moreover, the specific surface area is also small. For this reason, in coarse-grained olivine, after the spray material adheres to the work surface, after the residual heat of the repaired surface or the high temperature atmosphere in the furnace is received and the spray work body is sufficiently heated, Become.

  On the other hand, in this invention, the baking olivine which baked previously and removed the crystal water is used. This eliminates the problem of reduced adhesiveness caused by water vapor from crystal water contained in olivine.

  Immediately after spraying, even if water vapor is generated from olivine, adhesion is ensured by the action of a binder or the like. Adhesion loss caused by olivine crystal water is manifested by the use of coarse olivine. The effect of improving the adhesiveness by using the baked olivine is an effect peculiar to the present invention in which olivine is mainly used as coarse particles.

  Magnesia is a raw material with particularly large thermal expansion among refractory raw materials. Due to the magnitude of this thermal expansion, the difference in expansion from the repaired surface of the spray material also contributes to a decrease in adhesion. On the other hand, in terms of ensuring corrosion resistance, the amount of magnesia used cannot be reduced below a certain level in the magnesia-olivine spray material.

  The expansion of the spray material is greatly influenced by the expansion of coarse particles in the refractory raw material. On the other hand, the expansion of the fine particle part is absorbed in the gap between the particles, and the influence on the expansion of the spray material is small. In the present invention, from this finding, coarse particles having a particle size of 1 mm or more having a large influence of expansion are mainly blended with baked olivine whose thermal expansion is smaller than magnesia. As a result, the thermal expansion of the spray material was reduced, and in combination with the effect of solving the above-mentioned problem of crystal water by using the fired olivine, the adhesiveness could be improved.

  In the present invention, a part or all of magnesia to be combined with the fired olivine may be used as a waste material of magnesia and / or magnesia-spinel refractory containing at least 60% by mass of MgO as a chemical component value. This refractory brick waste material has an effect of imparting corrosion resistance by including at least 60% by mass of MgO as in magnesia. The use of refractory brick waste is also preferable from the viewpoint of effective use of resources.

  In steel furnace electric furnace linings, the position of the slag line may not always be clear, and in order to perform reliable repairs, even though the slag line is repaired, in fact, as shown in the schematic diagram of FIG. Will also be sprayed.

  Since the upper part of the slag line is not in direct contact with the molten steel / slag, the spray material construction body constructed above the slag line is maintained in an intermediate temperature range. As a result, the dissipation of construction moisture is delayed and exposed to a steam atmosphere for a long time, so magnesia in the spray material composition is digested.

  Unlike dolomite, this digestion is not so remarkable that it lowers the strength of the entire sprayed construction body, but it causes a deterioration in the strength of the interface with the repaired surface, resulting in a decrease in adhesiveness. Since the slag line and the upper part of the slag line are integrally formed in the spray material construction body, if the slag line is peeled upward, the spray material construction body in the portion below the slag line is easily peeled.

In the present invention, when magnesia containing 1 to 10 mass% of SiO ₂ is used as magnesia to be combined with the fired olivine, the adhesiveness of the sprayed construction body above the slag line is further improved. This is because the SiO ₂ becomes a glass coating that blocks the MgO component of magnesia from water vapor, thereby preventing digestion of magnesia and preventing deterioration of the strength of the interface with the repaired surface.

Moreover, since the upper part of the slag line is not in direct contact with the molten steel / slag, the sintering is delayed as compared with the slag line or lower. When magnesia containing 1 to 10% by mass of SiO ₂ with this chemical component is used, the Fe ₂ O ₃ component of olivine melts at a relatively low temperature range, and a low melt is generated to react with the MgO component of magnesia. Thus, sintering is promoted, and there is an effect of imparting strength above the slag line.

This effect is the same when a magnesia or magnesia-spinel refractory brick containing 1 to 10% by mass of SiO ₂ as a chemical component is used instead of magnesia. That is, SiO ₂ is a magnesia or magnesia-spinel refractory brick that becomes a glass coating that blocks the MgO component of the waste material from water vapor, thereby preventing digestion. Further, the Fe ₂ O ₃ component of olivine is melted at a relatively low temperature range, and a low melt is generated and reacted with the MgO component to promote sintering.

The use of this magnesia or refractory brick waste material containing 1 to 10% by mass or more of SiO ₂ as a chemical component improves the adhesion and strength of the sprayed material construction body above the slag line, and thus also includes the slag line. The adhesiveness of the entire sprayed material construction body can be improved.

In the present invention, it is preferable to further combine refractory clay as the refractory raw material. Refractory clay is a chemical component and is composed mainly of SiO ₂ and Al ₂ O ₃ . Moreover, they are ultrafine particles. In the present invention, Al ₂ O ₃ reacts with the MgO component of magnesia at a high temperature during furnace operation to produce Al ₂ O ₃ —MgO-based spinel, densifying the sprayed body structure, Improve corrosion resistance.

  The spraying material for repairing an electric furnace lining for steelmaking according to the present invention exhibits an excellent effect in adhesiveness, and can make use of the corrosion resistance and slag penetration resistance of the magnesia-olivine spraying material. As a result, an excellent repair effect can be exhibited under the operating conditions of the steel furnace.

The fired olivine used in the spray material of the present invention is obtained by firing olivine (peridotite), which is a natural raw material. The natural raw material olivine is mainly composed of MgO and SiO _{2 as} chemical components. Forsterite (2MgO · SiO ₂ ), Enstatite (MgO · SiO), Firelite (2FeO · SiO ₂ ), Serpentine (3Mg0 · 2SiO ₂ · 2H ₂ O) are the main mineral phases, and other glassy materials Including. In the present invention, this natural raw material olivine is used after being fired. The preferable baking temperature is 1000 degreeC or more, More preferably, it is 1200-1500 degreeC.

  If the ratio of the fired olivine in the fire-resistant raw material of the spray material is less than 25% by mass, the effect of the present invention cannot be obtained in adhesion and slag penetration resistance. When it exceeds 80 mass%, corrosion resistance will fall. More preferably, it is 30-70 mass%.

  The magnesia is calcined magnesia or electrofused magnesia. A combination of these two may also be used. The ratio is mainly composed of the remainder of the fired olivine in the refractory raw material composition. From the aspect of corrosion resistance, 15 to 70% by mass is preferable as a ratio to the refractory raw material.

In the construction on the upper side of the slag line, magnesia used here is preferably a material containing 1 to 10% by mass of SiO ₂ and 80% by mass or more of MgO in terms of chemical component values in order to improve adhesion. Here, if the proportion of SiO ₂ is less than 1% by mass, the effect of improving the adhesiveness is insufficient in the construction of the spray material on the upper side of the slag line. When the proportion of SiO ₂ exceeds 10% by mass, the corrosion resistance is lowered in the slag line. More preferably, it is 1-6 mass%. From the viewpoint of corrosion resistance, the MgO component is 80% by mass or more, preferably 83 to 98% by mass.

In the case of synthetic magnesia, the production of this magnesia containing 1 to 10 mass% of SiO ₂ and 80 mass% or more of MgO in terms of chemical component values is a calcined magnesia. For example, silica powder is added to magnesium hydroxide extracted from seawater And firing. In the case of molten magnesia, the fired magnesia can be obtained by melting in an electric furnace. For natural magnesia, after firing or electric furnace melting, SiO ₂ in chemical component value from 1 to 10 wt%, MgO selects using natural magnesia as a 80% by mass or more.

  As the magnesia or magnesia-spinel refractory brick waste that can be used in place of the magnesia, a material containing at least 60% by mass of MgO as a chemical component value is used. If the MgO component is less than 60% by mass, the effects of the present invention cannot be obtained in corrosion resistance.

Here, the magnesia refractory brick waste is fired brick whose main material is fired magnesia. On the other hand, the magnesia-spinel brick is a fired brick mainly composed of fired magnesia and Al ₂ O ₃ —MgO-based fired spinel as a refractory raw material. This refractory brick waste material is obtained from, for example, a product after use, and adjusted to an arbitrary particle size by pulverization.

The magnesia or magnesia-spinel refractory brick waste material increases the amount of SiO ₂ when, for example, ultrafine silica powder or clay is used as the binder. In order to obtain sufficient adhesion in spraying over the slag line, a magnesia or magnesia-spinel refractory brick is selected from a waste material containing 1 to 10% by mass of SiO ₂ and used.

  The particle size of the baked olivine, magnesia, and refractory brick waste is adjusted to coarse and fine in order to achieve close packing of the construction body. The maximum particle size is preferably 2 to 5 mm as in the prior art. The ratio of coarse particles having a particle size of 1 mm or more is also not particularly different from that of conventional spray materials, and is preferably 50 to 75% by mass.

  In the present invention, in the combination of calcined olivine and magnesia as the refractory raw material, the coarse particles having a particle size of 1 mm or more in the refractory raw material are only calcined olivine, or the ratio of the calcined olivine is larger than that of magnesia. Further, in the combination of fired olivine and magnesia as the refractory raw material, when a part or all of magnesia is used as the refractory brick as a waste material, the coarse particles having a particle size of 1 mm or more in the refractory raw material are only fired olivine, or magnesia. Or the ratio of baking olivine is increased rather than the total amount of magnesia and the said refractory brick waste material.

  In the case of coarse particles having a particle size of 1 mm or more, if the ratio of the fired olivine is small, the effect of the present invention cannot be obtained in the adhesive strength. More preferably, the ratio of the calcined olivine in the coarse particles having a particle size of 1 mm or more is 1.2 times or more larger than the total amount of magnesia or magnesia and the refractory brick.

  The particle size adjustment of the refractory raw material can be adjusted by 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, a particle size of less than 1 mm is a sieve under a sieve having an opening of 1 mm.

Specific examples of the refractory clay include kaolin, ball clay, bentonite, and hydrated clay. The amount used is 10% by mass or less as a ratio of the spray material to the refractory raw material. If it exceeds 10% by mass, the SiO ₂ component of the refractory clay produces a SiO ₂ -based low melt, and the corrosion resistance of the spraying material is reduced. In order to make the effect of densification of a spray construction body sufficient with refractory clay, it is preferable that it is at least 0.5 mass%.

  In addition to the above olivine, magnesia, and refractory clay, other refractory raw materials may be added as long as the present invention is not impaired. For example, a small amount of addition of volatile silica, ultrafine powder alumina, or the like. Carbon-based raw materials such as carbon or silicon carbide lower the adhesion due to poor sintering with other refractory raw materials. When using a carbon-type raw material, it is preferable to keep in less than 5 mass% in the ratio occupied to a 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, alumina cement, Portland cement and the like. The addition amount is a ratio with respect to the refractory raw material and is preferably 1 to 15% by mass as an outer shell. More preferably, it is 3-10 mass%. 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.

  Moreover, you may add fibers, metal powder, a dispersing agent, aluminum lactates, CMC etc. as needed.

  Specific examples of the fibers are polypropylene, nylon, PVA, vinylon, polyethylene, acrylic, polyester, pulp, paper fiber, sepiolite and the like. Addition of 0.05 to 1% by mass of the outer shell is preferred as a ratio to the refractory raw material.

  The spray material consisting of the above composition is constructed by a dry method using, for example, an arbitrary spray device. That is, a spray material is conveyed to a nozzle with a spraying apparatus, and construction water is added or sprayed at or near the nozzle. At this time, a part of the construction water may be added to the spray material in advance to prevent dust generation.

  Table 1 shows the chemical component values of the refractory raw materials used for the spray materials of each example. Olivine is a heat-dried product at 110 ° C. The fired olivine is fired at 1400 ° C. in a rotary kiln. Also, the magnesia-spinel refractory brick waste material was obtained from a cement rotary kiln after use of the lining. Tables 2 and 3 show the blending compositions of the spray materials of each example and the test results.

  In Tables 2 and 3, the particle size of the refractory raw material was adjusted using sieves of 4 mm, 2 mm, 1 mm, 0.5 mm, and 0.075 mm with JIS sieve openings. The particle size of 4 to 1 mm was adjusted by removing less than 1 mm with a 1 mm sieve for those under a 4 mm sieve. The group of fired olivine and olivine and the group of fired magnesia, electrofused magnesia, and refractory bricks are classified into waste materials, and shows the total amount of the particle size of 1 mm or more in each refractory raw material, but for example, less than 2 mm, The particle size of 1 mm or more contained in the 2 mm sieve was also included in the total amount of particle size of 1 mm or more in the entire refractory raw material.

  A protector gun was used as a spraying device, and the spraying materials of each example were constructed by a dry method and tested. The construction water was 24 to 28% by mass of the outer coating with respect to the entire spray material. The work surface was made of alumina fired bricks. This work surface was heated to a surface temperature of about 800 ° C. and sprayed assuming hot spray repair.

  The adhesion is cut out with the spraying material adhered to the work surface, placed in a 1000 ° C. heating test electric furnace, heated for 30 minutes, then pulled out of the heating test electric furnace and air-cooled, and this heating-cooling is repeated three times. After that, the adhesive shear stress of the sprayed material against the alumina fired brick on the work surface was measured. Corrosion resistance was measured by conducting a rotary erosion test at 1650 ° C. using an electric furnace slag for steel making as an erodant and measuring the wear size. For slag penetration resistance, the slag penetration dimension was measured after this rotary erosion test.

In the actual machine test, using the above-described spraying device, a part of the spray material from the examples and comparative examples was sprayed mainly on the slag line, which is the preceding damage site, against the lining of the electric furnace for 100 t steelmaking. . In that case, the furnace wall surface temperature was 800-1000 degreeC with the residual heat. The adhesion test on the upper part of the slag line was evaluated by observing and evaluating the adhesion durability of the sprayed material after spraying until the sprayed material reaches the end of its life (○… good adhesion, Δ… adhesiveness Inferior, Δ… adhesiveness is inferior). The durability test was determined by the number of times the electric furnace for steel making was used until the spray material reached the end of its life.

The examples of the present invention exhibited excellent effects in any of adhesiveness, slag penetration resistance, and corrosion resistance. Above all in the case in which the content of SiO ₂ was used magnesia or refractory brick waste more than 1 wt% in the chemical component values, the result is excellent in adhesion with respect to the slag line upward in physical testing, its durability is further improved ing.

  On the other hand, Comparative Example 1 is an example using olivine dried at 110 ° C. and is inferior in adhesiveness. Comparative Example 2 in which the amount of baked olivine is less than the range defined in the present invention and Comparative Example 6 in which no olivine is used are inferior in adhesion and slag penetration resistance.

  In Comparative Examples 3 and 7, the amount of baked olivine is larger than the range limited in the present invention, and is inferior in corrosion resistance. Comparative Examples 4 and 8 satisfy the calcined olivine amount but do not use calcined olivine in coarse particles of 1 mm or more, and are inferior in adhesiveness and corrosion resistance. Comparative Examples 5 and 9 are examples in which the amount of magnesia is large in coarse grains of 1 mm or more, although the amount of fired olivine is satisfied, and the adhesiveness and corrosion resistance are poor.

It is principal part sectional drawing which shows the spray repair condition of the electric furnace lining for steel making.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Slag line 2 Spraying material 3 MgO-C quality brick 4 Water-cooled jacket 5 Lined brick 6 Fireproof stamp material

Claims (6)

  Firing olivine 25 to 80% by mass, the balance is coarse particles mainly composed of calcined magnesia and / or electrofused magnesia, a refractory raw material adjusted to fine particles, and a binder, and a particle size of 1 mm or more in the refractory raw material A spray material for repairing an electric furnace lining for steel making, in which the coarse particles of the baked olivine are made only of fired olivine or the ratio of the fired olivine is higher than that of fired magnesia and / or electrofused magnesia. The blowing material for repairing an electric furnace lining for steel making according to claim 1, wherein the sintered magnesia and / or the electrofused magnesia contains 1 to 10 mass% of SiO ₂ as a chemical component.   2. The electric furnace for steelmaking according to claim 1, wherein a part or all of the sintered magnesia and / or the electrofused magnesia is a magnesia and / or magnesia-spinel refractory brick containing at least 60% by mass of MgO as a chemical component value. Spray material for lining repair. Refractory brick scrap is claim 3 steelmaking electric furnaces lining repair Coatings according containing SiO ₂ 1 to 10 wt% in the chemical composition.   The spray material for repairing an electric furnace lining for steel making according to any one of claims 1 to 4, wherein the refractory raw material further contains 10 mass% or less of refractory clay.   A spray repairing method for an electric furnace lining for steelmaking, wherein the slag line part is repaired with the spraying material for repairing an electric furnace lining for steelmaking according to any one of claims 1 to 5, by a dry spraying method.

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