JPH07172904A - Production of base resistant fireproof material - Google Patents

Abstract

PURPOSE:To easily produce a fireproof material having excellent corrosion resistance against a basic slag and a baked product containing a large amount of iron oxide. CONSTITUTION:A raw material mixture containing 50-99.1wt.% magnesium oxide and 0.1-<50wt.% titanium oxide as a mixing ratio of magnesium oxide and titanium oxide, preferably 2-20wt.% titanium oxide, is heated and baked at 1400-1700 deg.C to obtain a base resistant and fireproof material consisting mainly of magnesium oxide and magnesium orthotitanate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a refractory material having not only mechanical strength but also excellent corrosion resistance in a basic environment. The refractory material obtained by the production method 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 containing a large amount of iron oxide 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.

[0003]

Among basic refractory bricks, which are typical refractory materials, regarding basic refractory bricks, conventional basic refractory bricks contain chromium oxide in order to improve corrosion resistance in addition to magnesium oxide alone. MgO-Cr ₂ O ₃ based bricks were contained are often used. Although this brick has the advantages of high fire resistance and high softening point under load, there is a problem that chromium or chromium oxide in the component causes pollution depending on the use conditions, and a substitute for it is required. Further, although the oxidized Mg-Cr oxide-based brick shows good corrosion resistance to an ordinary basic melt, a basic high-temperature melt rich in iron oxide,
For example, there is a limit to the corrosion resistance with respect to calcium ferrite slag and the like generated in copper smelting. This is because when the refractory material comes into contact with a basic high-temperature melt rich in iron oxide (hereinafter referred to as an iron oxide-rich atmosphere), magnesium oxide and chromium oxide, which are components of the refractory material, react with Fe oxide in the atmosphere. It is considered that this is because the spinel of MgFe ₂ O ₄ and FeCr ₂ O ₄ is formed. An object of the present invention is to provide a method for producing a base-resistant refractory material, which solves the above-mentioned problems in the conventional refractory material mainly containing magnesium oxide.

[0004]

According to the present invention, a raw material powder obtained by mixing magnesium oxide and titanium oxide is fired to generate magnesium orthotitanate (Mg ₂ TiO ₄ ), and magnesium oxide and this Mg ₂ TiO ₄ are used as main components. By solving the above, the above-mentioned conventional problems have been solved. That is, according to the present invention, there is provided a method for producing a base-resistant refractory material having the following constitution.

(1) A raw material mixture in which the mixing ratio of magnesium oxide and titanium oxide is 50 to 99.1% by weight of magnesium oxide and 0.1 to less than 50% by weight of titanium oxide,
A method for producing a base-resistant refractory material mainly composed of magnesium oxide and magnesium orthotitanate by heating and firing at 1400 to 1700 ° C. (2) The method according to (1) above, wherein the content of titanium oxide is 2 to 20% by weight. (3) The production method according to (1) or (2) above, in which coarse or fine magnesium oxide powder is mixed with fine titanium oxide powder and heated and baked.

[0006]

[Detailed Description] The manufacturing method of the present invention will be specifically described below. In the description,% means% by weight unless otherwise specified. The production method according to the present invention is a method for producing a refractory material composed of magnesium oxide and magnesium orthotitanate (Mg ₂ TiO ₄ ) by heating and firing a mixture of magnesium oxide and titanium oxide at 1400 to 1700 ° C. The mixing ratio of magnesium oxide and titanium oxide is 50 to 99.9% of magnesium oxide and less than 50% to 0.1% of titanium oxide. It is necessary that the content of titanium oxide be smaller than the amount of magnesium oxide, and if the content of titanium oxide is larger than that of magnesium oxide, Mg ₂ TiO ₄ will not be produced. Preferably, magnesium oxide powder 80-95
%, Titanium oxide powder 20 to 5% are suitable. If the amount of titanium oxide is less than 0.1%, sufficient corrosion resistance cannot be obtained with respect to the basic melt, and this corrosion resistance is in the range of 20 to 5% titanium oxide, as shown in Examples described later. The best.

The mixing ratio of magnesium oxide and titanium oxide will be described with reference to the state diagram of FIG.
FIG. 3 is a phase diagram of a MgO—TiO ₂ system compound at up to 1800 ° C., and as shown in the figure, the content of titanium oxide is 50% or less with respect to magnesium oxide;
At a temperature of ˜1750 ° C., it becomes a mineral phase of magnesium orthotitanate represented by Mg ₂ TiO ₄ , but when the amount of titanium oxide is larger than that of magnesium oxide, titanium oxide 50
In the range of about 65% to about 65%, magnesium metatitanate represented by MgOTiO ₂ is produced, and titanium oxide is about 65 to 8%.
In the range of 0%, magnesium dititanate represented by MgO.2TiO ₂ is obtained, and magnesium orthotitanate (Mg ₂ TiO ₄ ) which is the object of the present invention cannot be obtained in any case. As described above, when the content of titanium oxide is less than that of magnesium oxide, it forms a mineral phase of magnesium orthotitanate (Mg ₂ TiO ₄ ), and the residual magnesium oxide that does not react with titanium oxide remains and the framework of the refractory material remains. Becomes

The above raw materials are fired at 1400 to 1700 ° C. If the firing temperature is lower than 1400 ° C, the formation of Mg ₂ TiO ₄ may be insufficient. At 1756 ° C or higher, a mixed phase of MgO and a liquid phase is formed as shown in the figure, and Mg ₂
The mineral phase of TiO ₄ cannot be obtained. The raw material may be fired in the air.

The particle size of magnesium oxide and titanium oxide is
It is preferable that the particle size of titanium oxide is smaller than that of magnesium oxide. That is, it is preferable to mix fine-grained titanium oxide powder with coarse-grained or fine-grained magnesium oxide powder and to heat and sinter. In this case, the titanium oxide particles surround the magnesium oxide particles as the main component, and a mineral phase of Mg ₂ TiO ₄ is formed at the grain boundary of magnesium oxide having a relatively large particle size.

As an example, magnesium oxide powder is used in which the proportions of coarse particles (average particle diameter of 2 to 5 mm), medium particles (average particle diameter of about 1 mm) and fine particles (average particle diameter of 0.1 mm or less) are 10 to 10, respectively.
50%, 10 to 50%, 10 to 50% are mixed, fine titanium oxide powder is added to this and uniformly mixed, and after compression molding, 5 to 30 at 1400 to 1700 ° C.
Porosity is 12 to 20% by firing over time
It is possible to manufacture a refractory material having a relatively low density. In addition, titanium oxide powder having a particle size of 50 μm or less is added to magnesium oxide powder (average particle size of 100 μm or less), uniformly mixed, and compression molded, and then 1 to 10 at 1500 to 1700 ° C.
By firing for a long time, a relatively high density refractory material having a density of 90% or more (porosity of 10% or less) can be manufactured.

Since the refractory material having a low density has many voids and has a high heat insulating effect, it is suitable for a refractory brick for linings such as a smelting furnace handling a basic melt. On the other hand, the high-density refractory material is oxidized M
Since g particles and Ti oxide particles are densely sintered and have good solid thermal conductivity with these particles as a medium and have good heat transfer properties, a material for crucible or furnace core tube that melts a basic raw material. Is suitable as Further, since this high-density refractory material has high airtightness and excellent permeation resistance, conventionally, a sensor for a high-temperature melt in which an alumina tube or the like has been used, for example,
It can also be used as a protective tube for various measuring terminals that come into contact with a high-temperature melt such as a thermocouple.

The refractory material obtained by the manufacturing method of the present invention has excellent corrosion resistance to a basic atmosphere rich in iron oxide. The reason is that when the refractory material comes into contact with an atmosphere rich in iron oxide, the refractory materials magnesium oxide and Mg ₂ T
The iO ₄ mineral phase reacts with iron oxide in the atmosphere to react with MgO-T
A complex oxide (Mg ₂ TiO ₄ —MgFe ₂ O ₄ ) of a solid solution phase of ternary system of iO ₂ —Fe ₂ O ₃ (Mg ₂ TiO ₄ —MgFe ₂ O ₄ ) is formed, which covers the surface of the refractory material and forms a basic melt inside the refractory material. It is believed that this is to prevent the invasion of That is, the MgO
And a Mg ₂ TiO ₄ mineral refractory material in contact with a high temperature iron oxide-rich basic melt such as calcium ferrite slag, MgO particles and Mg ₂ TiO ₄
The basic melt penetrates into the surface layer of the refractory material through the interstices of the mineral phase and reacts with MgO and Mg ₂ TiO ₄ to form MgO.
A ternary composite oxide of —TiO ₂ —Fe ₂ O ₃ is formed. The composite oxide is MgO-TiO ₂ -Fe in FIG
_{In the 2} O ₃ system ternary phase diagram, MgO with respect to TiO ₂
High melting point complex oxide of solid solution phase having a melting point of about 1750 ° C. or higher occupying the range on the MgO side connecting the two points of about 42% in amount and about 8% in amount of MgO to Fe ₂ O ₃ (Magnesiowus
tite). This complex oxide is formed in the surface layer and prevents the basic melt from penetrating into the refractory material. In addition, unlike the conventional spinel phase, this composite oxide does not cause strength deterioration of the refractory material because it has a small thermal expansion, and exhibits excellent corrosion resistance because it is difficult to be corroded by the alkaline component in the melt.

In the manufacturing method of the present invention, a small amount of a subcomponent such as aluminum oxide may be added to the raw material powder obtained by mixing magnesium oxide and titanium oxide. In the case of aluminum oxide, the addition amount is 1 to 20%, preferably 5 to 10%. The addition of aluminum oxide increases the denseness and further improves the corrosion resistance.

[0014]

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 A mixed raw material of 80% of magnesium oxide powder (particle size 40 to 200 μm) and 20% of titanium oxide powder (particle size 40 to 200 μm) was pressure-molded (pressure 1500 kg / cm ² ) and left in the atmosphere at 1500 Firing at 48 ° C. for 48 hours produced a refractory material sample of about 7 g per piece. The refractory material had an apparent specific gravity of 3.07 g / cm ³ and an apparent porosity of 15.43%, and had good sinterability. The above refractory material sample was subjected to calcium ferrite slag (copper smelting slag: component%, Fe ₂ O ₃ : 7) at a temperature of 1300 ° C.
0, CaO: 15, Cu ₂ O: 15) and left for 48 hours to examine its corrosion resistance. As a result, no significant change was observed in the appearance of the refractory material. In addition, in order to study the corrosion resistance in more detail, during immersion of the slag, the slag was collected with a steel rod at regular intervals, and TiO ₂ and Mg eluted in the slag were collected.
The amount of O was measured. The results are shown in FIGS. 3 (A) and 3 (B). As shown in the figure, the elution of the above components into the slag was at an extremely low level, and there was no significant change over time.

The structure of the refractory material after immersion in slag is shown in FIG. The figure is a micrograph of the slag contact portion of the refractory material, and the components of each mineral phase were confirmed by EPMA analysis. As shown, the refractory material 30 is made of MgO particles 3
1. It is formed by the Mg ₂ TiO ₄ mineral phase 32 existing in the gap. Calcium ferrite slag 33
Two mineral phases were observed in the contact area between the and refractory material 30,
The phase 35 on the refractory side of the interface is Mg ₂ TiO ₄ —MgFe ₂
Solid solution phase consisting of O ₄ (MgO: 39.27%, TiO ₂ : 35.40
%, Fe ₂ O ₃ : 18.86%, Cu ₂ O: 1.19%, CaO: 0.16%), and the slag-side phase 34 is a MgFe ₂ O ₄ spinel phase. The solid solution phase 35 is a complex metal oxide phase having a melting point of about 1900 ° C., and the surface layer of the refractory material is covered with this complex oxide phase 35, so that no slag penetrates inside. In the figure, the shaded area is the resin portion filled in the voids during sample preparation.

Example 2 and Comparative Example A refractory material sample was manufactured under the same conditions as in Example 1 except that the mixing ratio of magnesium oxide and titanium oxide and the firing temperature were set within the ranges shown in Table 1. This refractory material was examined for spalling resistance, creep resistance and corrosion resistance against basic slag. For comparison, MgO · 2TiO
_A similar test was performed on a refractory material containing ₂ (magnesium dititanate). The results are shown in Table 1. Each test was conducted by the following method. (1) Spalling resistance test Using a test piece formed on a normal brick (230 × 114 × 65 mm),
One-third of its longitudinal direction is projected into the furnace of the test furnace and the center 1
Installed so that / 3 is sandwiched between the bricks of the furnace door and the remaining 1/3 is exposed to the outside air outside the furnace, and it is kept for 30 minutes in the furnace at 1400 ° C and then taken out of the furnace for 30 minutes. Air cool. This operation was repeated and the time when a part of the test piece came off was defined as the number of spalling.

(2) Creep resistance test A compressive force of 10 kg / cm ² was applied to a cylindrical test piece (50 mmφ, 50 mmH), the test piece was held at 1250 ° C. for 50 hours, and the compression rate was measured. (3) Slag erosion resistance test Using a rotary erosion tester, columnar bricks (bottom 100 × 16
A test piece of 0 mm in height, 50 mm in height, and 40 × 160 mm in the upper surface was mounted in a rotary furnace. While rotating the rotary furnace at 3 rpm, an oxygen / acetylene burner mounted on one side of the furnace was used to oxidize the atmosphere in the furnace. After heating to 1300 ° C, 1 kg of ferrite slag (Fe oxide: 62 wt%, Ca oxide: 16 wt%, Cu oxide: 17 wt%) was charged and held for 1 hour, then the furnace was tilted and the above The slag is discharged, 500 g of the above slag is newly charged, and this operation is repeated every one hour, for a total of 12
After continuing for a period of time, the sample was cut, and the erosion depth and penetration depth by slag were examined by microscopic observation. The erosion depth is shown by comparing the brick thickness before the test with the brick thickness after the test at the furnace inner edge of the test piece and showing it by the reduction amount.The penetration depth is the thickness of the altered layer from the solution contact surface to the outer periphery. Showed by

[0019]

[Table 1]

As shown in Table 1, the sample of this example having a titanium oxide content of 0.1 to less than 50%, preferably 2 to 20%, is excellent in spall resistance in a basic environment and has a mechanical property. The target strength is also large. On the other hand, the comparative sample (No. 1) has a significantly low spall resistance in a basic environment, and the MgO.
The refractory material (No. 9) of the comparative example containing 2TiO ₂ has excellent spall resistance in a basic environment, but its corrosion resistance is lower than that of the sample of this example.

FIG. 5 (A) is a micrograph showing the structure of the refractory material (No. 3) of this example. Further, FIG. 5 (B) is a micrograph showing the microstructure of the same sample after immersion in slag. Each mineral phase shown is E
The component was confirmed by PMA analysis. As shown in FIG. 3A, the inside of the refractory material comes into contact with the MgO phase and Mg ₂ T
It can be seen that the iO ₄ phase exists and the refractory material is formed by both phases. It should be noted that what is present in the gap between both phases is the resin filled for sample preparation. When this refractory material is dipped in calcium ferrite slag, the structure of the refractory material becomes Mg at the interface between the refractory material and the slag as shown in FIG.
A complex oxide phase of ₂ TiO ₄ -MgFe ₂ O ₄ is formed, which covers the surface of the refractory material and prevents the slag from entering the refractory material. Therefore, the interior of the refractory material is the same as before the slag immersion. In addition, the MgO phase and the Mg ₂ TiO ₄ phase are maintained.

[0022]

EFFECTS OF THE INVENTION According to the production method of the present invention, extremely good corrosion resistance is obtained against basic slag containing a large amount of iron oxide such as calcium ferrite slag and ferrite-containing cement produced in copper smelting and fired products. The refractory material that it has can be easily manufactured. This refractory material is most suitable as a refractory brick for lining of a copper smelting furnace, and a material with high sintering density has good thermal conductivity and high airtightness, so it has excellent penetration resistance, so it can be used in crucibles and core tubes. It is also useful as a protective tube for various sensors that come into contact with the high temperature melt. Further, since it does not contain chromium oxide that causes pollution, it does not require special disposal treatment after use, which is advantageous from the viewpoint of environmental protection.

[Brief description of drawings]

FIG. 1 is a phase diagram of MgO—TiO ₂ system.

FIG. 2 is a ternary phase diagram of a MgO—TiO ₂ —Fe ₂ O ₃ system.

FIG. 3 is a graph showing the change over time in the elution amount of TiO ₂ and MgO in slag in Example 1. FIG.
Indicates the elution amount of TiO ₂ and FIG. (B) indicates the elution amount of MgO.

FIG. 4 is a micrograph showing a structural state of a slag contact portion of the refractory material of Example 1.

5 (A) is a micrograph (magnification 40) showing the microstructure of the refractory material of Example 2, and FIG. 5 (B) is a micrograph (magnification 40) showing the microstructure of the same sample after immersion in slag. is there.

[Explanation of symbols]

30-Refractory material, 31-MgO particles, 32-Mg ₂ Ti
O ₄ mineral phase, 33-slag, 34-MgFe ₂ O ₄ spinel phase, 35-high melting point complex oxide phase

Claims (3)

[Claims] 1. A raw material mixture having a mixing ratio of magnesium oxide and titanium oxide of 50 to 99.1% by weight of magnesium oxide and 0.1 to less than 50% by weight of titanium oxide,
A method for producing a base-resistant refractory material mainly composed of magnesium oxide and magnesium orthotitanate by heating and firing at 0 to 1700 ° C. 2. The method according to claim 1, wherein the content of titanium oxide is 2 to 20% by weight. 3. The production method according to claim 1, wherein coarse or fine magnesium oxide powder is mixed with fine titanium oxide powder and the mixture is heated and baked.