JPH09249449A - Refractory member for steel material sliding part of induction heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a refractory member excellent in corrosion resistance, mechanical and chemical abrasion resistance and thermal impact resistance at a high temperature region, and capable or using at a high temperature sliding part for a long period of time. SOLUTION: This refractory member for a steel material sliding part of an induction heating furnace, contains 60-98wt.% Al2 O3 , 1-30wt.% TiO2 as chemical compositions, or 60-91wt.% Al2 O3 with 4-14wt.% TiO and besides these, 2.5-18wt.% ZrO2 and/or MgO, and is obtained by burning a formed material made from a prepared unshaped refractories at 1,300-1,500 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear resistance used as a member for a sliding portion at a portion where a steel material heated in a heating portion of a steel material induction heating furnace to which a large thermal shock is applied passes at a high temperature, The present invention relates to a refractory member having excellent thermal shock resistance.

[0002]

2. Description of the Related Art In recent years, in a steel material induction heating furnace, as a sliding member provided with a through hole for inserting a steel material cut into an arbitrary size to be processed at a high temperature, wear resistance and heat resistance are provided. Although various refractory materials have been studied for impact resistance, as a refractory material for such wear resistant and heat shock resistant members, nitrides, oxynitrides, especially However, because of its low coefficient of thermal expansion and excellent mechanical properties at high temperatures, silicon nitride or sialon-based materials have come to be used. However, the nitride and oxynitride-based refractory materials are inexpensive because the oxidization of the base material progresses when the temperature exceeds 1200 ° C, and the mechanical properties originally possessed are lost and the cost is high. Yes Alumina castable is used because it is easy to manufacture.

However, a drawback of this castable alumina material, particularly when it is used as a member of a steel material induction heating furnace sliding portion to which a large thermal shock is applied, is that it is inferior in mechanical stability at high temperatures. For example, Japanese Patent Publication Sho 58-113
Japanese Patent Laid-Open No. 88 discloses that by adding silica to an alumina castable to reduce the water content, a high-density cured product can be obtained. The thermal shock resistance can be improved by forming a silica-containing compound by firing a block obtained from such an amorphous refractory. On the other hand,
The silica component of this matrix part is the scale component (Fe
It reacts with Ox) to form a low-melting point compound, lowers the chemical corrosion resistance, preferentially erodes and wears from the matrix portion, and becomes difficult to use for a long time.

[0004]

An object of the present invention is to provide a sliding member having excellent wear resistance and thermal shock resistance at a place where a steel material passes through a through hole in a high temperature region of a steel material induction heating furnace. It is to improve the chemical stability of a high-alumina refractory used for a refractory-made member to a scale and the like without lowering thermal shock resistance at high temperatures.

[0005]

According to the present invention, by adding a titanium component to a conventional high alumina refractory, corrosion resistance at high temperature, mechanical strength, chemical abrasion resistance, and thermal shock resistance are improved. It was completed based on the finding that a refractory material for heat shock resistant members such as sliding members, which is excellent and has little scale adhesion, can be obtained.

That is, the first aspect of the present invention is characterized by containing 68 to 98% by weight of Al ₂ O ₃ and 1 to 30% by weight of TiO ₂ as a chemical composition. Also, the second invention is
The chemical composition is 60 to 91% by weight of Al ₂ O ₃ , and TiO 2
₂ contains 4 to 14% by weight, and additionally contains _2.5 to 18% by weight of either or both of ZrO _{2 and} MgO.

This refractory member is obtained by firing a molded body of an indeterminate refractory material at 1300 to 1500 ° C.

In the induction heating furnace heating device of the present invention, by heating the refractory at a high temperature while embedding a heating coil around the through-hole of the refractory of the sliding part or winding it around the outer periphery,
Since the steel material passing through the through hole is heated, and the temperature difference between the heated refractory member and the surrounding temperature is large, wear resistance and thermal shock resistance are required.

Usually, the wear of the refractory forming the refractory member is caused by friction with the material sliding on the surface of the refractory when it passes through the through-hole, and contact with the edge portion.
Alternatively, it progresses due to chemical abrasion due to reaction with the oxide and mechanical abrasion due to mechanical damage or lack of refractory material.

In the refractory used in the present invention, the TiO ₂ component in the matrix has a high liquid phase formation temperature between the infiltrating scale and the alumina component in the matrix, as compared with silica. Chemical erosion of the refractory itself is suppressed. Further, it is considered that a dense reaction phase containing TiO ₂ is formed, and it is also considered that this also effectively works to prevent penetration of the scale to a certain depth or more. In any case, by adding the TiO ₂ component, excellent chemical abrasion resistance is exhibited. For excellent scale deposition preventive effect, usually, Al ₂ O ₃ is the high melting point of the compound to form a clear reaction phase and scale adhesion layer by reaction with the scale is formed, the TiO ₂ are mixed, the It is presumed that the adhesion strength between the reaction product and the scale is weakened, and the scale deposition is suppressed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a refractory which does not use a raw material aggregate containing a large amount of SiO ₂ component because of its improved sinterability and thermal stability, and also as an impurity in the raw material. It is desirable to select a raw material containing as little SiO ₂ as possible. SiO ₂ itself is preferably 0.4% by weight or less. It is necessary to avoid coexistence of chemical components that generate SiO _2, and therefore the total amount of impurities is preferably 3% by weight or less, and particularly preferably 2% by weight or less.

The aggregate of the refractory used for the member having the wear resistance and the thermal shock resistance such as the sliding portion of the steel material induction heating furnace of the present invention includes alumina, titanium, etc. 15 except that Al ₂ O ₃ and a titanium component are contained in an amount of 1 to 30% by weight or 4 to 14% by weight in terms of TiO _2.
As long as the refractory raw material has a refractory degree of 00 ° C. or higher and does not contain silica as a constituent component, one or a combination of zirconia, spinel, fine powder of magnesia and these composite raw materials can be used. Besides, oxides such as chromia can also be used.

As the alumina aggregate, fused alumina, sintered alumina, etc. can be used, and the particle size depends on the shape of the product. For example, in the case of a tube having a thickness of about 10 mm, 5 mm or less is preferable, and 6 mm is preferable. 3m for the following thickness
m or less is preferable. Other fine alumina powders may be fused alumina, sintered alumina, calcined alumina, or other oxides that can be heated to form alumina oxides or synthesized compounds. In addition to these aggregates, high-alumina cement
It is contained as an l ₂ O ₃ component.

[0014] Al ₂ O ₃ and to obtain the effect of coexistence of TiO ₂ component, Al ₂ O ₃ component can range from 60 to 98 _{wt%, Al 2 O 3 Al 2} O 3 is a component less than 60 wt% Even if the amount of TiO ₂ component increases, the effect does not improve further. If it is more than 98% by weight, the effect of TiO ₂ component on thermal shock resistance, corrosion resistance and scale adhesion prevention is lost. Be seen.

Further, in the case of combination with other compounds, it is preferable that the Al ₂ O ₃ component is within the range of 60 to 91% by weight, and the other components are effectively utilized.

As a material containing components other than the Al ₂ O ₃ component and the TiO ₂ component, zirconia-based or magnesia-based aggregate is used, and ZrO ₂ or MgO or both of them are used.
It is preferable to contain 5 to 18% by weight. ZrO ₂ improves corrosion resistance and scale adhesion prevention effect, but
If it is less than 18% by weight, the effect is small, and if it is more than 18% by weight, the thermal expansion coefficient of the refractory increases, which is not preferable.

Further, MgO is preferably present as spinel, and the thermal shock resistance is improved due to the low coefficient of thermal expansion, but if it is less than 2.5% by weight, the amount of spinel produced is small and the thermal shock resistance is ineffective. If it exceeds 5% by weight, the reaction with scale impairs the scale adhesion preventing effect of the TiO ₂ component. MgO as an Al ₂ O ₃ and spinel (MgAl ₂ O ₄ ) component has a small coefficient of thermal expansion, and therefore improves the thermal shock resistance of the refractory composition, and the ZrO ₂ component, in order to improve the corrosion resistance, 2. Coexistence of 5 to 18% by weight helps the function of the TiO ₂ component.

In addition, when an oxide such as chromia is used, it can be present in the range that contributes to the improvement of corrosion resistance and the prevention of scale adhesion like ZrO ₂ .

The TiO ₂ component is used as an oxide of rutile, anatase, titanium monoxide, titanium trioxide or the like, or as a composite oxide containing titanium such as aluminum titanate, calcium titanate, magnesium titanate or iron titanate. To be done. Further, titanium salts such as titanium alkoxide and titanium chloride, or metallic titanium and titanium alloy can be used. However, it is generally preferable to use it as an oxide of rutile, anatase or the like. There is no particular problem as long as the particle size is within the range available.

The use as TiO ₂ not only has the advantage of improving the properties of the refractory composition, but also improves the sinterability,
It enables firing at a lower temperature than ordinary high alumina castables. If the content of TiO ₂ is less than 1% by weight, sufficient effects cannot be obtained for the thermal shock resistance as a refractory member for sliding parts at high temperature, the scale adhesion preventing property, and the sinterability of the matrix part. Even if the amount is more than 30% by weight, no significant improvement in the effect is recognized, so the amount may be 30% by weight or less. Further, it is preferable to use a powder having a particle size of 10 μm or less for improving the sinterability.

When the ZrO ₂ or MgO component is contained, the TiO 2 component is preferably in the range of 4 to 14% by weight.
If it is less than 14% by weight, the effect cannot be obtained, and if it is more than 14% by weight, the amount of unreacted TiO ₂ remaining increases, the coefficient of thermal expansion increases, and the thermal shock resistance decreases.

The refractory member of the present invention can be obtained by a generally known casting method for castable refractories. For example, in the case of the wet method, after premixing the formulation having the desired composition, an appropriate amount of water is added to form a slip,
The slip is cast into a mold having a desired shape. In this case, a molding binder is used, but as far as possible, a compound containing no SiO ₂ is preferable, and 5 to 15% by weight of an inorganic binder such as hydraulic high-alumina cement or phosphate is used, or extrusion molding, etc. PED, PE used for
In addition to G and PVA, a resol-type phenol resin, a cellulose-based thermosetting organic polymer binder, and the like can be added. In addition, in order to improve the dispersibility of the powder, an appropriate dispersant or peptizer can be added.

The slip casting may be performed by ordinary casting, but in the present case, vibration casting was performed. This is effective for imparting fluidity to slips having a low water content, and vacuum vibration casting is effective for removing bubbles. The molded body that has been cast is demolded after curing, dried and fired. The drying time is set at any time depending on the use, the type of binder added, and the amount of water added.

In addition, the dry method can be carried out according to the usual method for forming a regular refractory material. That is, the target formulation is premixed with the binder to form a granulated powder. The granulated powder is uniaxially molded or cold static pressure molded using a mold suitable for the shape. The obtained molded body is fired, or dried and fired, and in some cases processed into a desired shape to obtain a product.

The firing temperature of the amorphous refractory material relating to the chemical composition of the present invention is preferably set to at least 1300 to 1500 ° C. in consideration of the strength development effect. In other words, when a heated sliding object passes through, it will sinter and develop strength even in an unfired amorphous refractory molded body, but it will be burned by contact with a molten metal such as a general refractory. Since it is not a bond, it does not always result in an effective sintered state. Therefore, it is preferable to bake in advance, and the temperature is 1300 °.
If it is less than C, the abrasion resistance is low due to insufficient strength and 1500 °
It is not necessary even if firing is performed at a temperature of C or higher because improvement in characteristics cannot be expected.

[0026]

EXAMPLE An example in which the refractory material of the present invention is applied to a steel material induction heating furnace sliding member will be described.

Table 1 shows examples 1 to 12 of the refractory material of the present invention.
Table 2 shows Examples 13 to 20 and Comparative Examples 1 to 4, and Table 3 shows Examples 21 to 24 and Comparative Examples 5 and 6 as conventional starting materials and calcining materials for alumina refractory and sialon products. It is shown together with temperature, chemical composition, physical property values, and evaluation results.

With respect to the physical property evaluation method, a sample for physical property evaluation of about φ50 × 50 mm was prepared by the vibration casting method in addition to the tube product in all compositions. The specific gravity porosity and compressive strength of this sample by the Archimedes method were measured according to the JIS measurement method.

The chemical composition analysis was determined by X-ray fluorescence analysis by the glass beet method. The SiO ₂ content of the components of the present invention in the examples was 0.2% by weight or less. Further, the CaO component present at 1.5 to 1.7% by weight is due to the high alumina cement.

The high temperature sliding characteristics are as follows: inner diameter φ50 mm, outer diameter φ
70 mm, 100 mm long tube-shaped fired body 13
Fixed in an electric furnace heated to 00 ° C, φ40 × 10
The 0 mm steel material (S45C) was moved to the left and right at a speed of about 10 cm / sec and evaluated by the reduction amount. Test time is 10
A wear resistance test was conducted by changing to a new steel material every 0 hours at 0 hours.

The scale adhesion was evaluated by visually observing the condition of the sample after the high temperature sliding test.

The thermal shock resistance of the above-mentioned cylindrical sample was 1300 °.
It was evaluated by an air cooling spall test in which it was inserted into an electric furnace heated to C, taken out into air, and forced air cooling was repeated 10 times.

[0033]

[Table 1]

Examples 1 to 12 were produced by mixing raw material powders using a V-type mixing mixer, adding water to a slip in a tabletop mixer to make a slip, and casting the mixture into a tube type on a vibration table. After leaving it at room temperature overnight, it was demolded and further dried in a dryer at 100 ° C. High-alumina cement (usually used at 5 to 15% by weight, but used at 10% by weight in this sample) was used as a binder. Molded body 13
Baking for 2 hours in a temperature range of 00 to 1500 ° C, an outer diameter of 70
A refractory member having a shape of mm, inner diameter of 50 mm and length of 800 mm was obtained.

Regarding the chemical composition of the refractory member, Examples 1 to 6 and 9 and 10 are examples in which a TiO ₂ component is added to Al ₂ O _3, and Examples 7 and 8 are examples in which a MgO component is further included. Is obtained from spinel. Examples 11 and 12 are A
The ZrO ₂ component was obtained from Baderite, in the example with l ₂ O ₃ , TiO ₂ and ZrO ₂ components. In Example 6, the firing temperature was 1500 ° C. As a result of the evaluation test, there was no problem in wear resistance and thermal shock resistance, and no scale adhesion was observed.

[0036]

[Table 2]

Examples 14 to 18 are the same manufacturing method as the refractory member of Table 1, and Examples 19 to 20 are the raw material powders mixed by using a V-type mixing mixer, and the mixed powders are mixed with water in a tabletop mixer. Then, thermosetting resin was added to make a slip, and cast molding was performed on a vibration table into a tube type. After gradually raising the temperature to 100 ° C., the binder was cured in a drier and released from the mold. 2 the molded body in a temperature range of 1300 to 1500 ° C.
Fired for an hour, outer diameter 70 mm, inner diameter 50 mm, length 800
A refractory member having a shape of mm was obtained.

As the chemical composition of the refractory member, Example 1 was used.
3, 14 and 17 to 20 are Al ₂ O ₃ and TiO ₂ , but Examples 13 and 14 are examples in which the starting material of TiO ₂ is obtained from a material other than rutile, and Example 17 is the particle size of the alumina material. Example 18 is an example in which the firing temperature was changed. In addition, Examples 19 and 20 are examples in which a binder other than high-alumina cement was externally applied (+), and therefore CaO was not found in the chemical composition. As a result, in the evaluation test, there was no problem in wear resistance and thermal shock resistance,
No scale adhesion was observed.

In Comparative Examples 1 and 2, a tube-shaped molded body containing no titanium was prepared by the same method as in Example 1300.
Firing was performed at ° C and 1600 ° C for 2 hours to obtain a refractory member having an outer diameter of 70 mm, an inner diameter of 50 mm and a length of 800 mm.

In Comparative Example 1, clear wear progressed due to insufficient strength. On the other hand, in Comparative Example 2, no large reduction was observed, but the scale was heavily attached.

In Comparative Examples 3 and 4, 5% by weight of silica raw material was used in place of titanium in the same manner as in Example 1 to prepare tube-shaped molded bodies, which were heated at 1300 ° C and 1500 ° C.
Fired for hours. When fired at 1300 ° C, the outer diameter is 70 mm,
Although a refractory member having an inner diameter of 50 mm and a length of 800 mm was obtained, the fireproof member having the intended shape could not be obtained by the softening deformation and shrinkage cracking of the tube by firing at 1500 ° C.

Regarding the abrasion resistance of Comparative Examples 3 and 4, since silica was used, a reduction of about several mm was observed, and the scale adhered to the working surface in a semi-molten state.

[0043]

[Table 3]

Examples 21 to 24 show examples manufactured by the same method as the refractory member in Table 1. These are Al ₂ O ₃ , TiO ₂ and Mg having a specified chemical composition by combining starting materials.
An example in which it is contained so as to be a component of O and ZrO ₂ will be shown. In the evaluation test results, there was no problem in wear resistance and thermal shock resistance, and no scale adhesion was observed.

Looking at the results of the evaluation test of the conventional product,
Comparative Example 5 used the most common alumina ceramics, but showed the same tendency as Comparative Example 2 and no reduction in size was observed, but the scale was heavily adhered, and was subjected to thermal shock immediately after use in one air-cooled spall test. It fell apart and the test could not be continued. Further, in the case of the sialon ceramics of Comparative Example 6 having excellent thermal shock resistance, cracking due to thermal shock was not observed, but the residual dimension disappeared after a few hours of operation, so the test was stopped.

Examples 6, 18 calcined at 1500 ° C
And the refractory members according to the present invention products of other examples obtained by firing at 1300 ° C. have compressive strengths of 138 to 181 MPa.
Comparative Example 2 (129 MPa) in which no TiO ₂ component was fired at 1600 ° C. and Comparative Example 3 in which silica was used.
The strength is higher than (120 MPa). As described above, the product of the present invention was able to obtain a high-strength refractory member by low temperature firing.

In the sliding test in the induction heating furnace by the evaluation of the actual product of the present invention, the high temperature sliding test of the tube prepared in the example was conducted in the direct sliding induction heating furnace. The produced tube was cut into a length of 720 mm and used as a set of two tubes. The steel material passing through the inside of the tube reaches a maximum of about 1320 ° C while moving about 400 mm. The physical properties were evaluated by the appearance of the tube after 30 days of operation, the amount of adhered scale, and the amount of abrasion of the tube. For comparison, Comparative Examples 2 and 3
Was used.

In the case of the examples of the present invention, large cracks were observed after 30 days of operation, but the shape was maintained, and there was no problem in use. The smaller the amount of TiO _{2 was, the} larger the reduction amount tended to be, but the reduction amount was all 1 mm or less, and no clear scale deposition was observed. On the other hand, in Comparative Example 2 in which titanium was not used, the reduction in size of the base material was not observed, but cracking proceeded from the operating part, and it was partially small fragments. Also, clear scale deposition was observed. Comparative Example 3 using silica has 2-3 in the moving part.
A reduction of mm was observed.

The superiority of the present invention can be clarified by observing the microstructure of the sample after use in a micrograph. FIG.
The optical micrograph of shows the texture of Example 3. As seen in FIG. 1, a slightly densified reaction layer of several hundred μm was seen in the operating part, and almost no scale adhesion. The other samples were almost the same.

FIG. 2 is an optical microscope photograph of Comparative Example 2 after the high temperature sliding test. Looking at this FIG. 2, a clear reaction layer of alumina and scale and an adhesion layer of scale are observed. Further, FIG. 3 shows an optical microscope photograph of Comparative Example 3 after the high temperature sliding test. As shown in FIG. 3, a reaction layer having a glass-like structure due to scale impregnation and reaction and a scale adhesion layer can be seen.

As described above, in the case of the present invention, it is understood that the corrosion resistance and the effect of preventing scale from adhering are exhibited due to the characteristic change in the microstructure which is not present in conventional materials.

[0052]

【The invention's effect】

(1) Excellent corrosion resistance in high temperature range, mechanical and chemical abrasion resistance and thermal shock resistance, less scale adhesion,
It is possible to obtain a refractory member for a sliding portion that can be used for a long time at a site where a steel material has a large thermal shock in an induction heating furnace.

(2) A compound having a high reactivity at a high temperature, such as a scale, coexists, and can be used in applications where a large thermal shock is applied.

[Brief description of drawings]

FIG. 1 is an optical micrograph of a refractory structure after a high temperature sliding test in Example 3.

2 is an optical micrograph of a refractory structure after a high temperature sliding test of Comparative Example 2. FIG.

FIG. 3 is an optical micrograph of a refractory structure after a high temperature sliding test of Comparative Example 3.

Claims (3)

[Claims] 1. An induction heating furnace comprising a refractory material containing 68 to 98% by weight of Al ₂ O ₃ and 1 to 30% by weight of TiO ₂ as a chemical composition, wherein the refractory material is provided with a through hole for inserting a steel material. Refractory material for steel sliding parts. 2. The chemical composition of Al ₂ O ₃ is 60 to 91% by weight, TiO _{2 is} 4 to 15% by weight, and one or both of ZrO ₂ and MgO is 2.5 to 5% by weight.
A refractory member for an induction heating furnace steel sliding part, comprising a refractory material containing 18% by weight, and having a through hole for inserting a steel material into the refractory material. 3. The induction heating steel material obtained by firing the shaped product of the irregular refractory at 1300 to 1500 ° C., wherein the refractory according to claim 1 or 2 is an irregular refractory. Refractory material for sliding parts.