JPH06293580A - Refractory having basic resistance - Google Patents

Abstract

PURPOSE:To improve basic resistance, thermal conductivity and thermal shock resistance by forming a multiple oxide layer comprising essentially MgO on the surface of a base body. CONSTITUTION:MgO, Fe2O and at least one metal oxide selected from TiO2, Nb2O5, Nd2O3, La2O3, NiO, and CoO, and if necessary, 1-20wt.% Al2O3 are mixed. The obtd. mixture is applied onto the surface of a base body and fired at >=1300 deg.C to form a multiple oxide layer having 0.01-10mm thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory material having excellent basic resistance. INDUSTRIAL APPLICABILITY The refractory material of the present invention is particularly useful as a material for refractory bricks or furnace core tubes of smelting furnaces and kilns that come into contact with a basic melt or a fired product.

[0002]

2. Description of the Related Art Various furnaces used in metal smelting and various kilns used for cement production have refractory materials lining the furnace walls to protect the furnace materials from high temperatures. Refractory materials are also used in crucibles, furnace tubes, or muffles, which are used to melt contents at high temperatures. These refractory materials are acidic refractory materials containing SiO ₂ or ZrO ₂ as a main component, neutral refractory materials containing Cr ₂ O ₃ or Al ₂ O ₃ as a main component, and MgO or CaO as a main component, depending on the use environment. The basic refractory material is used. For example, the basic refractory material is used in an environment where it is exposed to a basic melt, a fired product, a gas, or the like.

Among basic refractory bricks, which are typical refractory materials, regarding basic refractory bricks, conventional basic refractory bricks are
In addition to Mg oxide alone, Cr oxide is added to improve corrosion resistance.
An oxide-Mg-Cr oxide-based brick containing a lot of is used. Although this Mg oxide-Cr oxide brick has the advantages of high fire resistance and softening point under load, there is a problem that chromium and its oxides in the components cause pollution, and a substitute for it is required. Further, the Mg oxide-Cr oxide brick shows good corrosion resistance to a normal basic melt, but has a limit to corrosion resistance to a basic high temperature melt rich in Fe oxide. This is because when the basic high-temperature melt rich in iron oxide comes into contact with the refractory material, Mg oxide, which is a component of the refractory material,
And Cr oxide reacts with Fe oxide in the melt to form M
This is probably due to the formation of spinels represented by gFe ₂ O ₄ and FeCr ₂ O ₄ .

This is shown schematically in FIG.
The Cr oxide refractory brick 50 includes Mg oxide particles 51 and Cr oxide.
The particles 52 have a structure in which they are integrally sintered with each other. When this comes into contact with the high-temperature melt 54 rich in Fe oxide, the melt 54 penetrates into the surface layer of the brick 50 through the voids between the particles, and Fe oxide in the melt reacts with Mg oxide and Cr oxide, respectively, At the grain boundary of the surface layer, MgFe ₂ O ₄ and F
An iron-rich spinel phase 53 represented by eCr ₂ O ₄ is formed. During the formation of this spinel phase, the crystal grains of the above particles swell, and the bonds with the non-spinel phase Mg oxide particles 51 and Cr oxide particles 52, which have been sintered together, are broken. In addition, the spinel component MgFe ₂ O ₄ has a melting point of 1
Although it is as high as 900 ℃, it is easily eroded by the alkali component in the melt. It is considered that the surface layer of the refractory brick 50 is melted and damaged due to these causes.

[0005]

As described above, Mg oxide-Cr oxide
Since refractory bricks have a limited corrosion resistance to basic high-temperature melts rich in iron oxide, etc., smelting furnaces and kilns in which such melts and fired products are produced show significant melting loss of refractory bricks. It is uneconomical to take measures such as using electroformed bricks in some places. Therefore, there is a demand for a basic refractory brick having excellent corrosion resistance, which replaces the Mg oxide-Cr oxide refractory brick. In the cement kiln, the above-mentioned Mg oxide-Cr oxide is used.
Although MgO-Al oxide refractory bricks have been tried in place of the refractory bricks, these bricks also have poor corrosion resistance to basic burned materials rich in Fe oxide. An object of the present invention is to provide a base-resistant refractory material that solves the above-mentioned problems in the conventional Mg-Cr oxide refractory bricks and the like.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted various studies on means for solving the above problems, and as a result, covered the surface of the refractory material with a complex oxide having excellent basic resistance, thereby forming a melt inside the refractory material. It has been found that by blocking the infiltration, excellent corrosion resistance can be obtained with respect to the basic melt, and it is optimal as a basic refractory brick. This composite oxide is formed by an oxide containing Mg oxide as a main component and forming a high melting point composite oxide phase together with iron oxide. Specifically, Ti oxide and N oxide, which have not been conventionally used as components of refractory materials, are used.
b, Nd oxide, La oxide, Mn oxide, Ni oxide, and Co oxide are suitable, and it has been found that a desired refractory material can be obtained by adding one or more of them. A refractory material having a relatively low sintered density, such as a brick, provided with the above composite oxide layer is suitable as a basic refractory brick, and the composite oxide has good heat transfer and thermal shock resistance. Therefore, it was also confirmed that the refractory material having the above-mentioned composite oxide layer is suitable as a material for the furnace core tube and the thermocouple protection tube.

[0007]

According to the present invention, the following basic resistant refractory material is provided. (1) Mg oxide as a main component, iron oxide and T oxide
i, Nb oxide, Nd oxide, La oxide, Mn oxide, N oxide
A basic refractory material having a complex oxide layer containing one or more of i and Co oxide on the surface of the substrate. (2) The base-resistant refractory material according to (1) above, which has the complex oxide layer on the surface of a substrate containing Mg oxide as a main component. (3) The substrate containing Mg oxide as a main component contains Al oxide in an amount of 1 to 2
Refractory material of (1) above containing 0 wt%.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The refractory material of the present invention has a high melting point composite oxide layer on the surface of a substrate. The composite oxide contains Mg oxide as a main component and, together with iron oxide, Ti oxide,
Mainly 3 or more of one or more of Nb oxide, Nd oxide, La oxide, Mn oxide, Ni oxide and Co oxide.
It is a component-based oxide. Hereinafter, for convenience, one or more oxides of Ti oxide, Nb oxide, Nd oxide, La oxide, Mn oxide, Ni oxide, and Co oxide are referred to as a second component.

The above-mentioned composite oxide is, for example, MgO-Ti.
The ternary oxide of O ₂ —Fe ₂ O ₃ forms a high melting point composite oxide in the solid solution phase when the MgO content is in the range of about 40 wt% or more. Hard to be attacked by the alkaline component of. Therefore, by covering the surface of the refractory material with the complex oxide layer, the penetration of the basic melt or the like into the refractory material is prevented, and the corrosion of the refractory material is prevented.

MgO and Fe ₂ O in the above composite oxide
The amount ratio of ₃ and the second component differs depending on the kind of the second component, but MgO-TiO containing Ti oxide as the second component.
_{In the} ternary phase diagram, the _2- Fe ₂ O ₃ system is
The amount of MgO with respect to O ₂ is 42 wt%, and the amount of MgO with respect to Fe ₂ O ₃ is 8 wt%.
A solid solution phase high melting point composite oxide (Magnesiowustite) having a melting point of 1750 ° C. or higher is formed. TiO ₂ and F
If the content of e ₂ O ₃ exceeds this range, a spinel phase having a low melting point and rich in iron oxide is formed, which is not preferable.

The layer thickness of the above composite oxide differs depending on the type of refractory material of the substrate. As an example, about 0.01 to 10 mm is suitable for a base-resistant refractory brick mainly composed of Mg oxide. If the complex oxide layer is thinner than this, sufficient corrosion resistance cannot be exhibited, and if it is thicker than the above range, the strength of the refractory material as a structure decreases. For a material having a high density of refractory material, for example, a thermocouple protection tube inserted in a high temperature melt, a thickness of the composite oxide layer of 0.1 to 1 mm is suitable.

As the base material of the refractory material on which the surface layer of the above-mentioned composite oxide is provided, a refractory brick mainly containing Mg oxide, which is general as a basic refractory material, can be used. This oxidation M
The g-based refractory brick may contain subcomponents in the range usually used. Further, this Mg oxide refractory brick is made of Al
₂ O ₃ may be contained in an amount of 1 to 20 wt%, preferably ₅ to 10 wt%. By adding Al ₂ O ₃ , the denseness is increased and the corrosion resistance is improved.

The complex oxide layer is formed by coating the surface of a substrate containing Mg oxide as a main component with a mixture of the second component and Fe ₂ O ₃ and then heating or by using the second layer containing Mg oxide as a main component.
It can be formed by coating the surface of the substrate containing the components with a mixture of Fe ₂ O ₃ and heating. Specifically, (i) the surface of the unbaked substrate after molding is coated with powder containing Fe ₂ O ₃ and baked at 1300 ° C. or higher, or (ii) the baked substrate is melted containing Fe ₂ O _3. Immerse in the body. In the case of (ii), if necessary, after immersing, further baking is performed to fix the composite oxide layer on the substrate.

The surface of the refractory substrate is coated with Mg oxide and T oxide.
An example of covering with a mixture containing i and immersing this in a melt rich in Fe oxide to form the complex oxide layer on the surface is schematically shown in FIG. As shown in the figure, when the surface layer 30 of MgO—TiO ₂ comes into contact with the high-temperature melt 31 rich in Fe oxide, the melt 31 penetrates into the surface layer through the gap between the Mg oxide particles 32 and the Ti oxide particles 33. To fill the voids between the particles, and the main component Mg oxide and the second component Ti oxide react with the Fe oxide in the melt to form MgO—TiO ₂ —Fe ₂ O ₃
A three-component composite oxide 35 is formed. The complex oxide 35 is a solid-solution high-melting-point oxide that fills the surface layer to cover the surface of the refractory material and prevents the melt from entering the refractory material. Moreover, unlike the above spinel phase, this composite oxide does not cause expansion of the sintered particles that constitute the refractory material, so does not cause strength deterioration of the refractory material, and is also resistant to corrosion by the alkaline component in the melt, so it has excellent corrosion resistance. Exert.

By providing the above-mentioned surface layer on various refractory materials having different sintered densities of the substrate, a base refractory material suitable for a wide range of applications can be obtained. For example, a brick having a relatively low sintering density is used as a lining material for a furnace because it has a high heat insulating effect due to internal voids. Since the one provided with is excellent in corrosion resistance against a basic melt or the like, it is suitable as a lining material for various furnaces handling a basic melt or a fired product. On the other hand, in a refractory material having a high sintering density, the internal particles of the refractory material are densely sintered, so that the thermal conductivity is good, and therefore,
Such a refractory material as a base material, on the surface of which the above complex oxide layer is provided, is suitable for a material such as a crucible or a furnace core tube. Further, since the composite oxide is also excellent in thermal shock resistance, a high-density refractory material having the surface layer formed on the surface thereof is a sensor for a high-temperature melt in which an alumina tube or the like has been conventionally used, for example, It is also suitable as a protective tube for various measuring terminals such as thermocouples.

[0016]

EXAMPLES AND COMPARATIVE EXAMPLES Examples of the present invention are shown below together with comparative examples. It should be noted that the present embodiment is an example and does not limit the scope of the present invention.

Example 1 80 wt% MgO powder having a particle size of 40 μm to 200 μm and a particle size of 40 μm
To 200 DEG [mu] m were mixed with TiO ₂ powder 20 wt% of, 1500 kg / c
It was molded into a cylindrical shape at a pressure of m ² and fired in the air at 1500 ° C. for 48 hours to produce a sample pellet of about 7 g per piece. The apparent specific gravity, true specific gravity and apparent porosity of the sample pellets are 3.07 g / cm ³ , 3.63 g / cm ³ and 15.43%, respectively. These sample pellets were mixed with calcium ferrite slag (component wt% Fe ₂ O ₃ : 70, CaO: 15, Cu ₂₎ at a temperature of 1300 ℃.
O: 15) (corresponding to a kind of slag in copper smelting) for 48 hours to form an oxide layer on the surface of the sample pellet. When this oxide layer was examined by EPMA, it was found that MgO-TiO ₂ -Fe ₂ O ₃ (Mg
O: 39.27 wt%, TiO ₂ : 35.40 wt%, Fe ₂ O ₃ : 18.68 wt
%) Was formed, and it was confirmed that the refractory material inside E was covered with this surface layer A. In the figure, D is a slag, and a spinel phase B is formed in the portion in contact with the refractory material surface layer A.
About this sample pellet, while being immersed in 200 g of slag, the slag was sampled with a steel rod at regular intervals and the amounts of TiO ₂ and MgO eluted in the slag were measured.
It was confirmed to have excellent corrosion resistance, with extremely low levels of 0.1 wt% or less and 1.0 wt% or less, with no significant change over time.

Example 2 A sample pellet was produced in the same manner as in Example 1 except that Nb oxide, Nd oxide, La oxide, Mn oxide, Ni oxide and Co were used instead of Ti oxide, and the same slag was produced. An oxide layer was formed on the surface of the pellet by immersion. When these oxide layers were examined by EPMA, it was found that
It was confirmed to be a ternary complex oxide composed of O-Fe ₂ O ₃ and the oxide of the second component. Regarding this sample pellet, the slag was sampled with a steel rod at regular intervals during the slag immersion, and the amounts of the oxide of the second component and MgO eluted in the slag were measured.
%, 2.0 wt% or less, which is an extremely low level, and it was confirmed that the corrosion resistance does not change significantly with the passage of time and that it has excellent corrosion resistance.

Example 3 95% by weight of MgO powder having a particle size of 40 μm to 200 μm and a particle size of 1 μm
Mixing the Fe ₂ O ₃ powder 5 wt% of ~40μm, 1500kg / c
It was molded into a cylindrical shape at a pressure of m ² and fired in the air at 1500 ° C. for 48 hours to produce a sample pellet of about 6 g per piece. The sample pellets are soaked in a copper oxide melt (92% Cu ₂ O-8% Mn ₂ O ₃ ) containing Mn oxide at a temperature of 1200 ° C.,
The surface of the sample pellet consists of MgO-Fe ₂ O ₃ -Mn ₂ O ₃ 3
After forming the original complex oxide layer, it was taken out and cooled.
This sample pellet was immersed in slag in the same manner as in Example 2, and the slag was collected with a steel rod at regular intervals,
When the amounts of Mn ₂ O ₃ and MgO eluted in the slag were measured, they were extremely low levels of 0.1 wt% or less and 1.0 wt% or less, respectively, which did not change significantly over time and had excellent corrosion resistance. It was confirmed.

Example 4 MgO powder having a particle size of 100 μm or less and T having a particle size of 50 μm or less
After thoroughly mixing with the iO ₂ powder in a ratio of 9: 1, 1.5
It was molded into a blind tube having a length of about 20 cm, an outer diameter of 20 mm and a wall thickness of 5 mm under a pressure of ton / cm ² , and fired in an electric furnace at 1500 ° C. for 1 hour. The apparent specific gravity, true specific gravity and apparent porosity of this pipe material were 3.44 g / cm ³ , 3.62 g / cm ³ and 5%, respectively. Calcium ferrite slag is discharged to the tubing from a copper smelting furnace _{(Fe 2 O 3: 70wt%} , CaO: 15wt%, Cu 2 O:
15 wt%) to form a composite oxide layer consisting of MgO-TiO ₂ -Fe ₂ O _{3 on the} surface of the pipe. An attempt was made to measure the temperature by using the above tube material as a protective tube for a sheath type thermocouple.
The measurement temperature (1250 ° C) was stabilized in 5 minutes, and accurate measurement values were obtained. After 2 hours, the measuring tube was pulled up from the slag and the appearance was observed, but no cracking or surface erosion was observed. On the other hand, a tube of the same type and same diameter was made of commercially available high-purity alumina (porosity: 95%), and a similar test was conducted using this as a protective tube. The immersion part of the protective tube was completely removed within 30 minutes. Melted down.

Example 5 MgO powder (40 wt%) having a particle size of 100 μm or less, Fe ₂ O ₃
A mixture of powder (20 wt%) and TiO ₂ powder (40 wt%) was provided on the surface of an unfired refractory brick made of MgO powder to a thickness of 1 to 2 mm. This is 1450 in the atmosphere
Calcination was performed at 2 ° C. for 2 hours to produce about 10 g of sample pellet per piece. This sample pellet was immersed in slag in the same manner as in Example 2, the slag was sampled with a steel rod at regular intervals, and TiO ₂ and Mg eluted in the slag were collected.
When the amount of O was measured, each was 0.1 wt% or less, 1.0
It was confirmed to have excellent corrosion resistance, with a very low level of wt% or less, with no significant change over time.

[0022]

EFFECTS OF THE INVENTION The base-resistant refractory material of the present invention has extremely good corrosion resistance to basic slag and burned material containing a large amount of iron oxide such as calcium ferrite slag and ferrite-containing cement produced in copper smelting. Have. Therefore, a brick having a porosity similar to that of a normal brick is used in a conventional oxide Mg-Cr oxide refractory brick having a problem of corrosion resistance, for example, in a smelting furnace handling a basic melt rich in iron oxide. It is especially useful as a refractory brick for lining. Further, the refractory material of the present invention having a high sintering density is excellent in thermal conductivity and thermal shock resistance, and is useful as a protective tube for various sensors in contact with a crucible, a core tube or a high temperature melt. Further, unlike the conventional Mg oxide-Cr oxide refractory brick, since it does not contain Cr oxide that causes pollution, it does not require special disposal treatment after use, which is advantageous from the viewpoint of environmental protection. is there.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating changes in components near the interface when the refractory material of the present invention is immersed in slag.

FIG. 2 is a schematic diagram showing changes in components near the interface between the refractory material and the slag in Example 1.

FIG. 3 is a schematic diagram showing an eroded state of a conventional Mg oxide-Cr oxide brick.

[Explanation of symbols]

Internal A-MgFe ₂ O ₄ spinel phase B- refractory composite oxide phase C- refractory D- slag E- refractory material

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 7, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

According to the present invention, there is provided a base-resistant refractory material having the following constitution. (1) A composite oxide layer containing magnesium oxide as a main component, iron oxide, and one or more of titanium oxide, niobium oxide, neodymium oxide, lanthanum oxide, manganese oxide, nickel oxide, and cobalt oxide. A base-resistant refractory material characterized by having: (2) The basic refractory material of (1), which has the composite oxide layer on the surface of a substrate containing magnesium oxide as a main component. (3) A composite oxide layer containing magnesium oxide as a main component, containing titanium oxide and iron oxide, and having an amount of magnesium oxide to titanium oxide of 42% by weight or more and an amount of magnesium oxide to iron oxide of 8% by weight or more. The base-resistant fireproof material according to (1) or (2) above. (4) Magnesium oxide as a main component, iron oxide, titanium oxide, niobium oxide, neodymium oxide, lanthanum oxide, manganese oxide, nickel oxide and cobalt oxide together with one or more aluminum oxides The base-resistant refractory material of the above (1), (2) or (3) containing 20% by weight.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

MgO and Fe ₂ in the above composite oxide
The amount ratio of O ₃ and the second component varies depending on the type of the second component, but MgO—Ti having Ti oxide as the second component.
The O ₂ —Fe ₂ O ₃ system has a T
A range on the MgO side connecting two points where the amount of MgO with respect to iO ₂ is 42 wt% and the amount of MgO with respect to Fe ₂ O ₃ is 8 wt%, that is, the amount of magnesium oxide relative to titanium oxide is 42 wt% or more, iron oxide The solid solution high-melting-point composite oxide having a melting point of about 1750 ° C. or more when the amount of magnesium oxide is 8% by weight or more (Magnesiowu).
state) is formed. TiO ₂ and Fe ₂ O ₃
If the content of Cr exceeds this range, a spinel phase having a low melting point and a large amount of iron oxide is formed, which is not preferable.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] Explanation of code

[Correction method] Change

[Correction content]

[EXPLANATION OF SYMBOLS] A- internal refractory composite oxide phase B-MgFe ₂ O ₄ spinel phase C- refractory D- slag E- refractory material

Claims (3)

[Claims] 1. A composite oxide layer containing magnesium oxide as a main component, and one or more of titanium oxide, niobium oxide, neodymium oxide, lanthanum oxide, manganese oxide, nickel oxide and cobalt oxide together with iron oxide. A base-resistant refractory material characterized by having: 2. The base-resistant refractory material according to claim 1, wherein the composite oxide layer is provided on the surface of a substrate containing magnesium oxide as a main component. 3. The refractory material according to claim 1, wherein the substrate containing magnesium oxide as a main component contains 1 to 20 wt% of aluminum oxide.