JP2015171991A - Iron-making vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an iron-making vessel having an excellent heat loss reduction effect and a materialized long life.SOLUTION: An iron-making vessel 1 receiving and holding molten pig iron 11 tapped from a blast furnace is provided which includes a refractory-lining structure having a steel shell 2, a permanent refractory layer 3, and a work refractory layer 4 in order from the outside. A shaped refractory constituting the work refractory layer is an AlO-pyrophyllite-SiC-C brick obtained by kneading, molding and heating a raw material composition containing a raw material and binder. In the iron-making vessel, carbon content in the raw material is 6 to 9 mass%, pyrophyllite content in the raw material is 10 to 30 mass% and pyrophyllite content having a particle diameter of 1 mm or less in the pyrophyllite is equal to 20 mass% or less.

Description

  The present invention relates to a steelmaking container. In particular, the present invention relates to a steelmaking container suitable for use in conveying hot metal from a blast furnace to a steelmaking factory.

  Conventionally, in steel containers such as blast furnace pans, various shaped refractories (bricks) are used as refractories (hereinafter also referred to as “work refractories”) used for work refractory layers (for example, patents). Reference 1). Further, in Patent Document 2, in a refractory lining structure of a steelmaking container for carrying out a refining process on a hot metal that transports or holds hot metal, the thermal conductivity of the work refractory layer is 12 W / (m · K). It is disclosed that heat dissipation loss from the opening of the container is reduced by the following.

JP 2010-155664 A JP 2011-1445056 A

Recently, in order to protect the global environment, global warming prevention measures such as CO ₂ emission suppression have been demanded on a global scale, and in the steel industry, increasing the use of cold iron sources (scraps, etc.) in the steelmaking process is a problem. It has become. In order to use a cold iron source in a steelmaking process, it is necessary to create a thermal margin for melting the cold iron source. For that purpose, in a steelmaking container such as a blast furnace pan, it is important to reduce the hot metal temperature drop from receiving to dispensing, and exhibit an excellent heat loss reducing effect.
Further, in a steelmaking container such as a blast furnace pan, it is required to prolong the period until cracks occur in the workpiece refractory layer and repair is required, thereby extending the life.
This invention is made | formed in view of the above point, and it aims at providing the container for steel manufacture which was excellent in the heat loss reduction effect and implement | achieved the lifetime improvement.

In particular, when the thermal conductivity of the workpiece refractory layer is reduced as in Patent Document 2, the surface temperature decreases with the passage of time after the hot metal is discharged. There is a problem that becomes larger. In addition, in a refractory material such as Al ₂ O ₃ —SiC—C widely used for hot metal transport containers, a method of reducing the mixing ratio of C and SiC having a high thermal conductivity is preferable for reducing the thermal conductivity. Although used, this method tends to qualitatively lower the thermal shock resistance of the workpiece refractory, and therefore there is a risk of reducing the refractory life combined with an increase in thermal shock. On the other hand, Patent Document 2 proposes improving the refractory life by setting the ratio of the generated thermal stress and the compressive strength of the workpiece refractory to 0.7 or less. However, there is no disclosure of manufacturing methods such as work refractory blending conditions for achieving both the work refractory material adjustment and thermal conductivity adjustment, and specific work refractory manufacture. Depending on the conditions, it may be difficult to achieve both a heat loss reduction effect and a longer life.

  As a result of intensive studies to achieve the above object, the present inventors have obtained a good heat loss reduction effect by using a specific brick and a heat insulating material in combination in a steelmaking container such as a blast furnace pan. In addition, the inventors have found that a long life can be realized and completed the present invention.

That is, the present invention provides the following (1) to (3).
(1) A steelmaking container that receives and holds hot metal discharged from a blast furnace, and includes a refractory lining structure having an iron skin, a permanent refractory layer, and a workpiece refractory layer in order from the outside. The regular refractory constituting the refractory layer is an Al ₂ O ₃ -roxite-SiC-C brick obtained by kneading, forming, and heating a raw material composition containing a raw material and a binder, The content of carbon is 6 to 9% by mass, the content of wax in the raw material is 10 to 30% by mass, and the content of wax in the wax is 1 mm or less in particle size is 20% by mass. The following is a container for iron making.
(2) The iron making container according to (1) above, wherein a particle size of the wax is 3 mm or less.
(3) The iron making container according to (1) or (2), wherein the heat insulating material is applied between the iron skin and the permanent refractory layer.

  ADVANTAGE OF THE INVENTION According to this invention, the container for steel manufacture which was excellent in the heat loss reduction effect and implement | achieved lifetime improvement can be provided.

It is a flowchart which shows the suitable aspect of the manufacturing process of a brick. It is a graph which shows the relationship between carbon content and thermal conductivity. It is a graph which shows the relationship between carbon content and spall resistance. It is a top view which shows typically the test piece for a corrosion resistance evaluation test. It is sectional drawing which shows typically the high frequency induction furnace used for a corrosion-resistance evaluation test. It is a graph which shows the relationship between the particle size of a wax stone and a spall resistance. It is a graph which shows the relationship between the particle size of a wax stone and corrosion resistance. It is a graph which shows the relationship between the particle size of a wax stone and a spall resistance. It is a graph which shows the relationship between the particle size of a wax stone and corrosion resistance. It is a graph which shows the relationship between content of a wax stone and compressive strength. It is a graph which shows the relationship between the content of a wax stone and an elastic modulus. It is a graph which shows the relationship between the content of a wax stone and thermal shock fracture resistance. It is a graph which shows the relationship between content of a wax stone and compressive strength. It is a graph which shows the relationship between the content of a wax stone and an elastic modulus. It is a graph which shows the relationship between the content of a wax stone and thermal shock fracture resistance. It is a graph which shows the relationship between the particle size of a wax stone and compressive strength. It is a graph which shows the relationship between the particle size and elastic modulus of a wax stone. It is a graph which shows the relationship between the particle size of a wax stone and thermal shock fracture resistance. It is a graph which shows the relationship between the particle size of a wax stone and compressive strength. It is a graph which shows the relationship between the particle size and elastic modulus of a wax stone. It is a graph which shows the relationship between the particle size of a wax stone and thermal shock fracture resistance. It is a graph which shows the relationship between content of a wax stone and an expansion coefficient. It is a graph which shows the relationship between the particle size and expansion coefficient of a wax stone. It is a photograph which shows the cross section of a brick. It is a photograph which shows the cross section of a brick. It is the schematic which shows a blast furnace pan typically.

  Hereinafter, although the application example to the blast furnace pan which is a container for iron manufacture is demonstrated, it cannot be overemphasized that this invention is not limited to this and can be applied also to the other iron manufacture containers.

[Iron-making container (blast furnace pot)]
FIG. 26 is a schematic view schematically showing a blast furnace pan, and a part of the blast furnace pan is enlarged and viewed in cross section.
First, the blast furnace pot 1 shown in FIG. 26 will be schematically described. The blast furnace pan 1 is a pan-shaped iron-making container having an open top surface that receives and holds hot metal discharged from a blast furnace (a blast furnace). The hot metal held in the blast furnace pan 1 is transferred to the converter as it is and charged, or a refining process such as a hot metal pretreatment is performed in the blast furnace pan 1 before charging into the converter.
The hot metal preliminary process performed in the blast furnace pan 1 mainly includes processes such as a de-Si process, a de-P process, and a de-S process. The Si in the hot metal charged in the converter is first oxidized and reacts with the added lime (CaO) and iron oxide (FeO) to form CaO—FeO—SiO ₂ slag. For this reason, if the Si concentration in the hot metal is low, in the converter, this reaction is shortened, the production efficiency is improved, the amount of generated slag is reduced, and refining with a high yield of metal iron becomes possible.
The Si removal treatment in the blast furnace pan 1 is performed by introducing iron oxide such as mill scale or sintered ore into the hot metal or by blowing oxygen gas upward.
In the de-P treatment, a CaO-based de-P agent or iron oxide is introduced into the hot metal and oxygen gas is blown up, or a de-P agent mixed with lime, iron oxide, fluorite, etc. is blown into the hot metal along with the gas, After transferring P in the hot metal to the slag phase, the slag is discharged. In addition, since the reaction of the de-P process proceeds as the Si concentration decreases, the de-P process is generally performed after the de-Si process. The hot metal is also subjected to a certain degree of S treatment by de-Si treatment or de-P treatment. However, when manufacturing low-sulfur steel, a CaO-based de-S agent is added to the hot metal and mechanically stirred or in the hot metal. A desulfurizing agent such as CaO, Na ₂ CO ₃ , CaC ₂ , Mg, etc. is blown into the glass and further de-S treatment is performed.

[Refractory lining structure]
Next, the refractory lining structure of the blast furnace pan 1 will be described. The refractory lining structure of the blast furnace pan 1 is a structure having an iron skin 2, a permanent refractory layer 3 and a workpiece refractory layer 4 in order from the outside, and the heat insulating material 5 includes an iron shell 2, a workpiece refractory layer 4 and It is desirable that it is constructed during this period.

The iron skin 2 is a steel structure that supports a refractory as the outermost layer of the blast furnace pot 1.
The permanent refractory layer 3 is a brick layer that is constructed to ensure safety so that hot metal does not leak even when the workpiece refractory layer 4 is damaged and falls off, and two layers may be provided. As the refractory constituting the permanent refractory layer 3 (also referred to as “permanent refractory”), for example, a wax stone brick is used.

The workpiece refractory layer 4 is a refractory layer that forms a contact surface (working surface) with the hot metal 11 and has a thickness of about 180 to 200 mm, for example. The workpiece refractory layer 4 is mainly composed of a metal line part that comes into contact with the hot metal 11 held in the blast furnace pan 1, and a slag line part that comes into contact with a slag (not shown) floating on the molten metal surface of the hot metal. It is divided into.
The regular refractory used in the present invention (hereinafter also referred to as “the regular refractory of the present invention” for convenience) is used as the refractory constituting the workpiece refractory layer 4 (also referred to as “work refractory”). It is suitably used, and more particularly, it is more suitably used as a work refractory constituting the metal line portion.

[Standard Refractory (Al ₂ O ₃ -Wollastonite-SiC-C Brick)]
The regular refractory material of the present invention is generally Al obtained by kneading, forming, and heating a raw material composition containing a raw material and a binder (hereinafter also referred to as “raw material composition of the present invention” for convenience). _{It is 2} O ₃ -waxite-SiC-C brick (hereinafter also simply referred to as “brick”).
In addition, with the Al ₂ O ₃ -solumite-SiC-C brick, a raw material (raw material of the present invention) containing alumina (Al ₂ O ₃ ), wax, silicon carbide (SiC), and carbon (C) is used. It is a brick that can be obtained. Examples of the component (composition) of the brick itself to be obtained include Al ₂ O ₃ , SiC, SiO _{2 and the} like. The content range of these components is appropriately set according to the raw material composition, for example, fluorescent X-rays It can be measured by a method, a combustion infrared absorption method, an X-ray diffraction method using an internal standard, and the like.

And in said raw material (henceforth "the raw material of this invention" for convenience), the carbon content is 6-9 mass%, the content of the wax is 10-30 mass%, The content of the wax with a particle size of 1 mm or less in the stone is 20% by mass or less. The content of the wax having a particle size of 1 mm or less in the wax is preferably 15% by mass or less, more preferably 10% by mass or less. Here, the content of the wax having a particle size of 1 mm or less is a mass ratio of the wax that passes through a sieve having a nominal opening of 1 mm.
The reason why the carbon content is 6 to 9% by mass is that if the carbon content is within this range, the heat conduction is maintained while maintaining the thermal shock resistance by adjusting the content and particle size composition of the wax described later. This is because the rate can be reduced to 10 W / (m · K) or less.

  The reason why the content of the wax is 10 to 30% by mass and the content of the wax having a particle diameter of 1 mm or less in the wax is 20% by mass or less is that when a wax having a particle diameter exceeding 1 mm is blended, 1400 There are many microcracks in the matrix of refractory due to expansion due to the transformation of wax stone particles above ℃, the elastic modulus is greatly reduced and the thermal shock fracture resistance (= strength / elastic modulus) is large Therefore, the spall resistance is excellent. On the other hand, when the blending amount of the wax is increased, the corrosion resistance to the slag tends to decrease. Adjust with. At this time, a wax with a particle size of 1 mm or less has little microcracking and a small contribution to the improvement of the spall resistance and lowers the corrosion resistance against slag. The stone content is 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less.

  Such a regular refractory according to the present invention is excellent in low thermal conductivity as shown in [Example] described later. For this reason, when the regular refractory of the present invention is constructed and operated as a work refractory for the blast furnace pan 1, the temperature drop of the hot metal until the hot metal is received in the blast furnace and the hot metal is pretreated and discharged The amount (amount of hot metal temperature drop) can be reduced.

Moreover, the regular refractory of the present invention is excellent in spall resistance, as will be described later in [Example]. For this reason, when the regular refractory of the present invention is constructed as a workpiece refractory of the blast furnace pan 1, the number of charges until the crack in the height direction of the blast furnace pan 1 occurs in the workpiece refractory layer 4 (from receiving to dispensing) Is one charge).
Furthermore, the regular refractory of the present invention is excellent in corrosion resistance as shown in [Examples] described later. For this reason, when the regular refractory of the present invention is applied as a work refractory for the blast furnace pan 1, the amount of wear of the work refractory layer 4 is reduced.

[Raw material composition]
The wax contained in the raw material of the present invention is an aggregate containing SiO ₂ , and the particle size (particle size classification) thereof is the content of the wax with a particle size of 1 mm or less in the total wax as described above. It is 20 mass% or less, More preferably, it is 15 mass% or less, More preferably, you may be 10 mass% or less.
The raw material of the present invention further contains an aggregate containing Al ₂ O _3, and specific examples thereof include band shale, brown alumina, white alumina, etc. For example, 5 mm or less, more than 3 mm, 3 mm or less, more than 1 mm, 1 mm or less, more than 0.075 mm, or 0.075 mm or less.
In the following, wax stones, band shale, etc. may be collectively referred to as “aggregates”.
Although content of the aggregate in the raw material of this invention is not specifically limited, Although it sets suitably, For example, 75-95 mass% is mentioned, 80-90 mass% is preferable.

  Examples of the carbon contained in the raw material of the present invention include scale-like graphite, earth-like graphite, artificial graphite, expanded graphite, and powder pitch. The particle size (particle size classification) is, for example, more than 0.15 mm. 1 mm or less and more than 0.15 mm are preferable.

  The raw material of the present invention contains SiC fine powder, and examples of the particle size (particle size classification) include 0.075 mm or less. In the raw material of the present invention, the content of SiC is, for example, 3 to 7% by mass, and preferably 4 to 6% by mass.

  The raw material of the present invention may contain metal Si powder, and examples of the particle size (particle size classification) include 0.075 mm or less. Metal Si powder reacts with carbon to generate β-SiC bonds by heating (firing) in a reducing atmosphere, contributing to improvement in hot bending strength, oxidation wear resistance, and corrosion resistance. Take a role.

Hereinafter, carbon, SiC, metal Si powder, and the like may be collectively referred to as “functional materials”.
In the present invention, the particle size (particle size classification) of the raw materials (aggregate and functional material) is defined by a sieve test, and corresponds to the nominal opening of the corresponding sieve.

  It does not specifically limit as a binder which the raw material composition of this invention contains, The binder used in the conventional brick manufacture can be used, For example, a phenol resin, hexamine, etc. are mentioned suitably. At this time, although content of a binder is not specifically limited, For example, 1-5 mass% of phenol resins is preferable with respect to the raw material of this invention. Moreover, 0.1-1 mass% of hexamine is preferable with respect to the raw material of this invention.

[Method for manufacturing regular refractory]
The method for producing the shaped refractory of the present invention is not particularly limited as long as it is a method for obtaining the shaped refractory of the present invention by kneading, molding and heating the raw material composition of the present invention. As shown, five steps of kneading, molding, heating, processing, and firing may be provided as necessary.
FIG. 1 is a flowchart showing a preferred embodiment of a brick manufacturing process.
In the kneading, the surface of an aggregate such as a wax stone is mixed so that the binder is familiar, and then a functional material such as carbon is added and mixed at a high speed.
In molding, the kneaded raw material composition is put in a mold and molded while applying a pressure of 1.5 to 2.0 t / cm ² several times, for example.
In heating, the raw material composition after molding is heated at, for example, 200 to 250 ° C. for 12 to 24 hours to thermally cure the binder, thereby obtaining a brick.
In processing, the heat-cured brick is cut into a specified shape with a cutter if necessary.
In firing, the heat-cured brick or the processed brick is fired in a reducing atmosphere at, for example, 1000 to 1500 ° C. for 2 to 5 hours to obtain a reduced fired brick.

[Insulation]
Next, the heat insulating material 5 will be described. The heat insulating material 5 is a material that exhibits a heat insulating function, and is preferably constructed between the iron skin and the workpiece refractory layer. Examples of the material include SiO ₂ and Al ₂ O ₃ . As the heat insulating material 5, it is preferable to use a material having a compressive strength higher than the static iron pressure. For example, a heat insulating material to which silicon carbide (SiC), titanium oxide or the like is added may be used, and a fiber (fiber). It is also possible to use a heat insulating material in which strength is ensured by mixing them.

The construction position of the heat insulating material 5 is preferably between the iron skin 2 and the workpiece refractory layer 4, the temperature of the heat insulating material 5 can be operated low, and the heat insulating performance can be exhibited for a long time (for example, two years or more). As shown in FIG. 1, the space between the iron skin 2 and the permanent refractory layer 3 is preferable.
In addition, when the heat insulating material 5 is constructed on the iron skin 2 side (also referred to as “back side”) of the workpiece refractory layer 4, it may be constructed on a part of the back side including the metal line portion and the slag line portion. It may be constructed on the back side of the entire workpiece refractory layer 4.

  The thermal conductivity of the heat insulating material 5 is preferably 0.10 W / (m · K) or less. Thereby, in the blast furnace pan 1, the heat transfer resistance to the outer wall surface side of an iron skin increases, and the outstanding heat loss reduction effect is acquired. The lower limit value of the thermal conductivity of the heat insulating material 5 is not particularly limited, but is preferably 0.01 W / (m · K) or more, for example.

As the heat insulating material 5 is thicker, the thermal resistance can be increased. When the heat insulating material 5 is extremely thin, the workability is inferior and the thermal resistance tends to be uneven.
In addition, although the upper limit of the thickness of the heat insulating material 5 is not specifically limited, For example, 50 mm or less is preferable and 7 mm or less is more preferable because the fall of a container capacity | capacitance is small.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.

  First, in order to investigate the relationship between the carbon content in the raw material in brick and the thermal conductivity of the brick, bricks were manufactured by varying the carbon content in the raw material as shown in Table 1 below. In order to investigate the influence of the carbon content in the raw material on the thermal conductivity of the brick, only the content of scaly graphite was changed in the functional material, and the content of SiC and metal Si powder was constant. In the aggregate, only the content of the band shale having a particle size of 1 mm or less and more than 0.075 mm was changed, and the contents of other aggregates were made constant. That is, the increase / decrease amount of scaly graphite was replaced with the increase / decrease amount of the band shale whose particle size is 1 mm or less and more than 0.075 mm.

Brick was produced in accordance with the formulation shown in Table 1 (unit: parts by mass (hereinafter the same)) and the process shown in the flowchart of FIG. In the process shown in the flowchart of FIG. 1, a pressure of ² t / cm ² was applied 6 times for molding, heating was performed at 230 ° C. for 18 hours, and reduction firing was performed at 1400 ° C. for 4 hours ( The same applies hereinafter).

Then, about the manufactured brick, the heat conductivity was measured by the hot wire method. The measurement results are shown in the graph of FIG.
FIG. 2 is a graph showing the relationship between the carbon content and the thermal conductivity. The horizontal axis represents the carbon content (unit: mass%) in the raw material, and the vertical axis represents the thermal conductivity of brick (unit: W). / (M · K)).
As shown in the graph of FIG. 2, the thermal conductivity decreased when the carbon content decreased, but the thermal conductivity was almost the same when the carbon content in the raw material was 9% by mass or less. From this result, it became clear that if the carbon content in the raw material is 9% by mass or less, it is possible to realize low thermal conductivity of the brick.

Next, in Table 1, the spall resistance of bricks (Comparative Experimental Examples 1 to 5) whose carbon content in the raw material was 9% by mass or less was evaluated by the following method.
As a sample for the spalling test, a rectangular parallelepiped of 30 mm × 30 mm × 100 mm was cut out from the brick, and after measuring the longitudinal elastic modulus E ₀ , the spalling test was performed. In the spalling test, heating, water cooling, and air cooling were set as one cycle, and the number of cycles (also referred to as “the number of spalling tests”) was set to once, three times, and five times. In the test, the heating time was 10 minutes / time, the water cooling time was 5 minutes / time, the air cooling was 10 minutes / time, and the heating temperature was about 1400 ° C. because the hot metal temperature in the blast furnace pan was about 1400 ° C. C.
After the test, the dynamic elastic modulus E in the longitudinal direction of the sample was measured, and the change rate (E / E ₀ ) of the dynamic elastic modulus before and after the test was calculated. The larger the value of change rate (E / E ₀ ) (closer to 1), the better the spall resistance. In addition, the measuring method of dynamic elastic modulus followed the ultrasonic pulse method shown by JISR1605. The test results are shown in the graph of FIG.
FIG. 3 is a graph showing the relationship between the carbon content and the spall resistance. The horizontal axis indicates the number of spalling tests (unit: times), and the vertical axis indicates the spall resistance (E / E ₀ ).
As shown in the graph of FIG. 3, the spall resistance of the bricks whose carbon content in the raw material is 6% by mass and 9% by mass was almost the same, but the carbon content in the raw material was more than 6% by mass. The spall resistance of low bricks was significantly reduced. From this result, it was clarified that if the carbon content in the raw material is set to 6 to 9% by mass, the low thermal conductivity and spall resistance of the resulting brick can be maintained.

Next, the carbon content in the raw material is 6% by mass or 9% by mass, and the content of the wax is 0% by mass, 10% by mass, 20% by mass, 30% by mass, 40% by mass, Manufactured and evaluated for spall resistance and corrosion resistance.
At this time, when only a stone having a particle size (particle size classification) of 3 mm or less and more than 1 mm is blended, when only a stone having a particle size (particle size classification) of 1 mm or less is blended, the particle size (particle size classification) is 3 mm or less. Evaluation was performed on a case where a granite exceeding 1 mm and a granite having a particle size (particle size classification) of 1 mm or less were blended at a mass ratio of 50:50.
The formulations when the carbon content is 6% by mass are shown in Tables 2 to 4, and the formulations when the carbon content is 9% by mass are shown in Tables 5 to 7.
Further, by changing the ratio of the wax with a particle size of 1 mm or less, a stone with a particle size (particle size classification) of 3 mm or less and more than 1 mm and a stone with a particle size (particle size classification) of 1 mm or less is 95: 5 , 90:10, 80:20 and 70:30.
Tables 8 and 9 show the formulations when the carbon content is 6% by mass and the ratio of the wax with a particle size of 1 mm or less in the wax is 5% by mass and 10% by mass, respectively. Tables 10 and 11 show the blends when the ratio of 9% by mass is 20% by mass and 30% by mass is the ratio of the wax having a particle size of 1 mm or less in the wax. The formulation was adjusted to reduce the corresponding grain size band shale as the amount of wax was increased.

Bricks were manufactured according to the formulations shown in Tables 2 to 11 and the process shown in the flowchart of FIG. 1, and the spall resistance and corrosion resistance of the manufactured bricks were measured. The spall resistance was measured by the same method as described above, with the number of spalling tests being three. The corrosion resistance was evaluated by the following method.
FIG. 4 is a plan view schematically showing a test piece for a corrosion resistance evaluation test, and FIG. 5 is a cross-sectional view schematically showing a high-frequency induction furnace used for the corrosion resistance evaluation test.
First, as shown in FIG. 4, as a test piece 51 for a corrosion resistance evaluation test, a trapezoid having a thickness of 35 mm was cut out from a brick and assembled into a regular octagon. Thereafter, as shown in FIG. 5, in a high-frequency induction furnace having a water-cooled induction coil 55, a test piece 51 is placed on a bottom plate 54, a pig iron 52 serving as a heat source, and a table 8 shown below thereon. The slag 53 of the component shown in FIG. The evaluation temperature was 1650 ° C., the evaluation time was 4 hours, and the slag was added 4 times per hour. After completion of the test, the amount of erosion was determined from the dimensional difference before and after the test, and the erosion index was calculated with the amount of erosion of the brick whose content of wax was 0% by mass being 100.
The evaluation results of the spall resistance when the carbon content is 6% by mass and 9% by mass are shown in the graphs of FIGS. 6 and 8, respectively, and the evaluation result of the corrosion resistance when the carbon content is 6% by mass and 9% by mass. Are shown in the graphs of FIGS. 7 and 9, respectively.

6 and 8 are graphs showing the relationship between the particle size of the wax and the spall resistance, the horizontal axis indicates the content of the wax in the raw material (unit: mass%), and the vertical axis indicates the spalling test. The spall resistance (E ₃ / E ₀ ) of the brick when the number of times is three is shown.
In each drawing, for example, “3 mm or less and more than 1 mm” may be expressed as “3-1 mm”, or “1 mm or less” may be expressed as “−1 mm”, for example. (Same for other numerical ranges).

As shown in the graphs of FIG. 6 and FIG. 8, when only a stone with a particle size of 3 mm or less and more than 1 mm is used, a stone with a particle size (particle size classification) of 3 mm or less and more than 1 mm and a particle size (particle size classification) When blended with a stone with a diameter of 1 mm or less at a mass ratio of 95: 5, 90:10, and 80:20, the spall resistance is reduced from 0% by mass to 10% by mass. When increased from 10% to 20% and from 20% to 30%, it increases only slightly. When increased from 30% to 40%, it increases. There wasn't.
FIG. 7 and FIG. 9 are graphs showing the relationship between the particle size and corrosion resistance of the wax, the horizontal axis indicates the content of the wax in the raw material (unit: mass%), and the vertical axis indicates the erosion index. .
As shown in the graphs of FIGS. 7 and 9, the corrosion resistance is decreased when the content of the wax is increased from 0% by mass to 10% by mass in any particle size blend of the wax, and the mass is reduced from 10% by mass to 20%. Even when the mass was increased from 20% by mass to 30% by mass, it decreased only slightly, and when it was increased from 30% by mass to 40% by mass, it was significantly decreased.

In the case of using only a stone with a particle size of 1 mm or less, the spall resistance increased as the mass was increased from 0% by mass to 10% by mass, but compared with the case of using a stone with a particle size of 3 mm or less and more than 1 mm. The rate of increase was low, and even when increased from 10% by mass to 20% by mass, from 20% by mass to 30% by mass, and from 30% by mass to 40% by mass, there was only a slight increase. That is, bricks using a wax with a particle size of 1 mm or less had a lower spall resistance than bricks using a wax with a particle size of 3 mm or less and more than 1 mm. In addition, about corrosion resistance, it is a grade comparable as the case where a particle diameter is 3 mm or less and more than 1 mm, and the relationship between the content of a wax stone and corrosion resistance showed the same tendency.
In addition, when a wax having a particle size of 3 mm or less and more than 1 mm and a wax having a particle size of 1 mm or less are used in a ratio (mass ratio) of 50:50, and the particle size (particle size classification) is 3 mm or less and more than 1 mm In the case where a wax stone and a wax stone having a particle size (particle size classification) of 1 mm or less are blended at a mass ratio of 70:30, the spall resistance and corrosion resistance are obtained when only the wax stone having a particle size of 1 mm or less is used. It was the same result.

  From these results, if the content of the wax is 10-30% by mass and the content of the wax having a particle size of 1 mm or less in the wax is 20% by mass or less, both the spall resistance and the corrosion resistance can be achieved. I understood.

By the way, the main damage factor of bricks in a blast furnace pan is cracking due to cracking, and since the spall resistance is increased by increasing the content of granite and coarsening, The mechanism of increase in spall resistance by addition was investigated.
First, the relationship between the firing temperature of bricks with different carbonite content and wax particle size (grain size classification), compression strength, elastic modulus, and thermal shock resistance Examined.
The sample to be investigated is
A brick having a carbon content of 6% by mass, a particle size of the wax of 3 mm or less and more than 1 mm, and a content of the wax of 0% by mass (Comparative Experimental Example 9)
Brick with carbon content of 6% by mass, wax particle size of 3 mm or less and more than 1 mm, and wax content of 30% by mass (Experimental Example 3)
A brick having a carbon content of 9% by mass, a particle size of the wax of 3 mm or less and more than 1 mm, and a content of the wax of 0% by mass (Comparative Experimental Example 21)
A brick having a carbon content of 9% by mass, a particle size of the wax of 3 mm or less and more than 1 mm, and a content of the wax of 30% by mass (Experimental Example 6)
A brick having a particle size of 1 mm or less, a wax content of 30% by mass, and a carbon content of 6% by mass (Comparative Experimental Example 14)
A brick having a particle size of 1 mm or less, a wax content of 30% by mass, and a carbon content of 9% by mass (Comparative Experimental Example 26)
6 types in total.
In a reducing atmosphere, the rate of temperature increase was 5 ° C./min, the temperature was raised to 1000 ° C. and 1500 ° C. and baked for 3 hours. The compressive strength was in accordance with JIS R 2206, and the elastic modulus was JIS R as described above. Measurement was conducted according to 1605, and the thermal shock fracture resistance, which is the ratio of strength to elastic modulus, was determined.

FIG. 10 is a graph showing the relationship between the wax content and the compressive strength when the carbon content is 6 mass% and the particle size of the wax is 3 mm or less and more than 1 mm. FIG. 12 is a graph showing the relationship between the rock content and the elastic modulus, and FIG. 12 is a graph showing the relationship between the wax content and the thermal shock resistance.
The horizontal axis indicates the firing temperature (unit: ° C.), and the vertical axis indicates the compressive strength (unit: MPa), the elastic modulus (unit: GPa), and the thermal shock resistance (hereinafter, FIG. 13 to FIG. 13). 15, the same applies to FIGS. 16 to 18 and FIGS. 19 to 21).
As shown in the graphs of FIGS. 10 to 12, when the carbon content is 6 mass% and the particle size of the wax is 3 mm or less and more than 1 mm, the brick with the wax content of 0 mass% is 1000 ° C. When baked at 1, the compressive strength and elastic modulus decreased, and increased when baked at 1500 ° C. On the other hand, bricks with a content of 30% by weight of the wax were reduced in compressive strength and elastic modulus when fired at 1000 ° C, but were almost constant even when fired at 1500 ° C. Regarding the thermal shock fracture resistance, which is the ratio of strength to elastic modulus, the brick with a content of the wax of 30% by mass was twice as much as the brick with the content of the wax of 0% by mass.
FIG. 13 is a graph showing the relationship between the wax content and the compressive strength when the carbon content is 9% by mass and the particle size of the wax is 3 mm or less and more than 1 mm, and FIG. FIG. 15 is a graph showing the relationship between the rock content and the elastic modulus, and FIG. 15 is a graph showing the relationship between the wax content and the thermal shock resistance.
As shown in the graphs of FIGS. 13 to 15, similar results were observed when the carbon content was 9 mass%.

FIG. 16 is a graph showing the relationship between the particle size of the wax and the compressive strength when the carbon content is 6% by mass and the content of the wax is 30% by mass. FIG. FIG. 18 is a graph showing the relationship between the particle size of the wax and the thermal shock resistance.
As shown in the graphs of FIGS. 16 to 18, when the carbon content is 6 mass% and the content of the wax is 30 mass%, the brick using only the wax having a particle size of 1 mm or less is When the firing temperature was raised to 1000 ° C., the compressive strength and elastic modulus were lowered, and when raised to 1500 ° C., it was raised. On the other hand, bricks using only wax stones having a particle size of 3 mm or less and more than 1 mm decreased in compressive strength and elastic modulus when raised to 1000 ° C., but remained almost constant even when raised to 1500 ° C. Regarding thermal shock fracture resistance when fired at 1000 ° C. and 1500 ° C., a brick using only a wax stone having a particle size of 3 mm or less and more than 1 mm is equivalent to a brick using only a wax stone having a particle size of 1 mm or less. It was 1.5 times.
FIG. 19 is a graph showing the relationship between the particle size of the wax and the compressive strength when the carbon content is 9% by mass and the content of the wax is 30% by mass. FIG. FIG. 21 is a graph showing the relationship between the particle size of the wax and the thermal shock fracture resistance.
As shown in the graphs of FIGS. 19 to 21, similar results were observed when the carbon content was 9 mass%.

Furthermore, since the brick expands due to phase transformation, and the decrease in the elastic modulus due to the addition of the wax content and the coarsening of the particle size composition is estimated to be related to the thermal expansion, the thermal expansion of the above six types of bricks The rate was measured according to JIS R 2207.
FIG. 22 is a graph showing the relationship between the content of the wax and the expansion coefficient when the carbon content is 6 mass% and the particle size of the wax is 3 mm or less and more than 1 mm, and the horizontal axis indicates the firing temperature. (Unit: ° C.) is shown, and the vertical axis shows the expansion rate (unit:%).
As shown in the graph of FIG. 22, the carbon content is 6% by mass and the particle size of the wax is around 1400 ° C., which is the phase transition from quartz to cristobalite and the formation temperature of mullite (3Al ₂ O ₃ .2SiO ₂ ). 3 mm or less and more than 1 mm, the brick (Experimental Example 3) whose content of the wax is 30% by mass is about 9 times that of the brick (Comparative Experimental Example 9) whose content of the wax is 0% by mass. Although not shown, this was the same result even when the carbon content was 9% by mass.
FIG. 23 is a graph showing the relationship between the particle size of the wax and the coefficient of expansion when the carbon content is 6% by mass and the content of the wax is 30% by mass. : ° C.) or holding time (unit: min), and the vertical axis indicates the expansion rate (unit:%).
As shown in the graph of FIG. 23, in a brick having a carbon content of 6 mass% and a wax mass of 30 mass%, when only a wax having a particle size of 3 mm or less and more than 1 mm is used (experimental example) 3) When the cristobalite formation of quartz is slow, the expansion rate at the time of reaching the maximum temperature is small, and it expands even while maintaining the temperature, but only the wax with a particle size of 1 mm or less is used (Comparative Experimental Example 14). Since the formation of cristobalite in quartz was fast, the expansion rate when the maximum temperature was reached was large, and hardly expanded during the temperature holding. In addition, although the expansion amount at the time of completion | finish of temperature holding | maintenance is comparable, although not shown in figure, it was the same result also when the carbon content was 9 mass%.
From these results, it is estimated that the expansion amount depends on the content of the fluorite, the expansion rate depends on the particle size (size classification) of the fluorite, and the expansion region corresponds to the α-β transition of quartz and the cristobaliteization and mullite of quartz. Is done.

Next, in order to investigate the difference in structure due to the difference in thermal expansion behavior, the cross section of the brick fired at 1500 ° C. for 3 hours was observed.
FIG. 24 is a photograph showing a cross section of a brick using only a wax having a carbon content of 6 mass% and a particle size of 3 mm or less and more than 1 mm. As shown in the photograph of FIG. 24, in the brick using only a wax having a carbon content of 6 mass% and a particle size of 3 mm or less and more than 1 mm, the content of the wax is 30 mass% (FIG. 24). (B): Microcracks (denoted by reference numeral 101 in the figure) were clearly seen in Experimental Example 3), but when the content of the wax was 0% by mass (FIG. 24A: Comparative Experimental Example) 9) was not seen at all.
FIG. 25 is a photograph showing a cross section of a brick having a carbon content of 6% by mass and a waxy stone content of 30% by mass. As shown in the photograph of FIG. 25, in a brick having a carbon content of 6% by mass and a wax content of 30% by mass, only a wax having a particle size of 3 mm or less and more than 1 mm is used (FIG. 25). 25 (A): Experimental Example 3) shows a large crack (indicated by reference numeral 103 in the figure) that occurs during expansion due to the coarse wax stone (indicated by reference numeral 102 in the figure), and is clearly confirmed around the wax stone. However, when only a wax stone having a particle size of 1 mm or less was used (FIG. 25B: Comparative Experimental Example 14), the cracks generated at the time of expansion were small due to the fine wax stones, and the circumference of the wax stones was clear. Was not seen. It can be said that the occurrence of these cracks inhibited the firing and had an effect on the decrease in the elastic modulus.

From the above results, in order to satisfy all of the low thermal conductivity, high spall resistance, and high corrosion resistance of the brick, the carbon content is 6-9% by mass, and the content of the wax is 10-30% by mass. % Al ₂ O ₃ -Paleolithic-SiC-C brick, it is clear that the content of the granite with a particle size of 1 mm or less in the granite may be reduced. Next, the actual blast furnace pan The demonstration test in 1 was conducted.

Some of the bricks described above (experimental example and comparative experimental example) are refractory work of a blast furnace pot 1 (height: 5300 mm, height from upper surface to lower limit of metal line part: 4250 mm, upper surface radius: 2550 mm). Construction as a product, conventional brick (carbon content: 12% by mass, content of wax stone (particle size 3 mm or less): 10% by mass, content of wax stone with particle size 1 mm or less in the wax stone: 50 Contrast with the conventional example in which mass%) was applied.
The thickness of the iron skin 2 was 30 mm, the thickness of the permanent refractory layer 3 was 50 mm, and the thickness of the workpiece refractory layer 4 was 180 mm.

  Here, as bricks, bricks of Experimental Examples 1-6, 10, 12, 13 and 15 and bricks of Comparative Experimental Examples 12-14, 24-26, 36 and 38 (that is, carbon content: 6% by mass or 9% by mass, content of wax stone: 10 to 30% by mass, particle size constitution of wax stone: mass ratio of 1 mm or less and 3 mm or less and more than 1 mm is 0/100, 10/90, 20/80, 30/70 and 100 / 0) was used.

  Moreover, as the heat insulating material 5, it constructs between the iron shell 2 and the permanent refractory layer 3, and thermal conductivity is 0.01, 0.05, 0.10, 0.15, or 0.20 W / Five types of heat insulating materials (thickness: 5 mm) which are (m · K) were used.

About such a blast furnace pan 1, the hot metal temperature fall amount, the pan life, and the amount of wear were evaluated.
Hot metal temperature drop (unit: ° C) is the average value of hot metal temperature drop from receiving in the blast furnace, through hot metal pretreatment (de-Si treatment, de-P treatment, de-S treatment) to dispensing It was measured by an immersion type consumable thermocouple. The implementation ratio of the hot metal pretreatment was similar in all test conditions.
The pan life (unit: charge (ch)) is 1 charge from receiving to dispensing, until the work refractory falls off and repairs occur or cracks occur as the remaining thickness decreases. The number of charges was, and the occurrence of dropping or cracking was confirmed visually.
The amount of wear (unit: mm) is a value obtained by subtracting the residual thickness of the remaining part of the workpiece refractory layer 4 from the original thickness (180 mm) when the above-mentioned dropout or crack occurs, and the residual thickness is a measure. It was measured.
These results are shown in Tables 13 to 18 below.

As is apparent from the results shown in Tables 13 to 18, in the blast furnace pan using the brick whose carbon content is reduced to 6% by mass or 9% by mass, even when the heat insulating material is not used, the conventional The hot metal temperature drop is reduced compared to the examples, and the hot metal temperature drop is about an average when the carbon content is 9% by mass (Examples 19, 25 and 31, Comparative Examples 19, 25, and 31). When the carbon content is 5% by mass (Examples 1, 7, 13, 37, 39, 41 and 43, Comparative Examples 1, 7, 13, 37 and 39), the average is reduced by about 9 ° C. . Moreover, when the heat insulating material is used in combination, the hot metal temperature drop is further reduced, and in particular, a blast furnace pan using a heat insulating material having a thermal conductivity of 0.01 to 0.10 W / (m · K) (implemented) Examples 2-4, 8-10, 14-16, 20-22, 26-28, 32-34, 38, 40, 42 and 44, Comparative Examples 2-4, 8-10, 14-16, 20-22 , 26-28, 32-34, 38, and 40), the hot metal temperature drop could be further reduced by 20-30 ° C. as compared to the blast furnace pan in which the heat insulating material was not applied. Even when a heat insulating material is used, when the carbon content of the workpiece refractory is 6% by mass, the temperature drop of the hot metal is about 5 ° C. smaller than the average when the carbon content is 9% by mass. It can be seen that the decrease in the thermal conductivity of the refractory is effective in reducing the heat dissipation loss from the opening of the blast furnace pan.
However, regardless of the presence or absence of the heat insulating material and the content of the wax, when the brick having a high ratio of the wax having a particle diameter of 1 mm or less in the wax is used as in the conventional example, the pot is low in the carbon content. When the lifespan was remarkably reduced and the wax particle diameter was 1 mm or less (Comparative Examples 1 to 36), the pan life was about 350 charges and was short-lived. Moreover, even when the content of the wax with a particle size of 1 mm or less in the wax was 30% by mass (Comparative Examples 37 to 40), the pot life was about 420 charges on average, which was significantly lower than the conventional example.

On the other hand, as is clear from the results shown in Tables 14, 15, and 18, a blast furnace pan (Examples 1 to 36) using bricks using only a wax having a particle size of 3 mm or less and more than 1 mm, Blast furnace pans (Examples 37, 38, 41 and 42) using a brick in which a granite having a particle size of 3 mm or less and more than 1 mm and a granite having a particle size of 1 mm or less are mixed at a mass ratio of 90:10 and the particle size Is a conventional example in a blast furnace pan (Examples 39, 40, 43 and 44) using a brick in which a wax stone having a particle size of 3 mm or less and more than 1 mm and a wax stone having a particle diameter of 1 mm or less is blended at a mass ratio of 80:20 In addition to reducing the hot metal temperature drop regardless of the presence or absence of a heat insulating material, the pot life is more than the conventional example regardless of the amount of wax in the range of 10-30% by weight of the wax. Also improved. When the content of 1 mm or less of the wax in the wax was 10% by mass or less (Examples 1 to 38, 41 and 42), the pot life was extended to nearly 550 charges, and a long life could be realized.
The amount of wear was almost the same in all cases, and the pan life increased or decreased depending on the wear rate of the workpiece refractory.

  From the above results, a brick having a carbon content of 6 to 9% by mass, a content of the wax of 10 to 30% by mass, and a content of a 1 mm or less wax in the wax is 20% by mass or less. It has been clarified that the use of can makes it possible to achieve both an excellent heat loss reduction effect and a longer life of the blast furnace pan 1 as compared with the conventional pan.

1: Blast furnace pan (container for iron making)
2: Iron skin 3: Permanent refractory layer 4: Work refractory layer 5: Thermal insulation material 11: Hot metal 51: Test piece 52: Pig iron 53: Slag 54: Bottom plate 55: Water-cooled induction coil 101: Microcrack 102: Brazestone 103 :crack

Claims (3)

A steelmaking container that receives and holds hot metal discharged from a blast furnace,
In order from the outside, it has a refractory lining structure having an iron skin, a permanent refractory layer and a workpiece refractory layer,
The regular refractory constituting the workpiece refractory layer is an Al ₂ O ₃ -fauxite-SiC-C brick obtained by kneading, forming, and heating a raw material composition containing a raw material and a binder. The content of carbon in the raw material is 6 to 9% by mass, the content of wax in the raw material is 10 to 30% by mass, and the content of wax in the wax is 1 mm or less in particle size is 20%. A steelmaking container having a mass% or less.   The ironmaking container according to claim 1, wherein a particle size of the wax is 3 mm or less.   The iron-making container according to claim 1 or 2, wherein the heat insulating material is applied between the iron skin and the permanent refractory layer.