KR102401344B1 - Refractory materials for acupuncture furnaces - Google Patents

Abstract

An object of the present invention is to provide a refractory material for a siliceous treatment furnace with little deterioration or embrittlement and a long lifespan. 35 mass % or more of 1 type or 2 or more types selected from the oxide of silicon, silicon nitride, and silicon oxynitride in total, and 0.05 mass % or less of alkali metal in total, and a porosity is 25 volume% or less , and a compressive strength of 5 MPa or more.

Description

Refractory materials for acupuncture furnaces

The present invention relates to a refractory material used in a furnace using silicon chloride gas, such as a continuous silicification treatment furnace for a steel strip.

Since a silicon steel sheet has excellent soft magnetic properties, it is widely used as a material for iron cores of transformers and motors. It is known that the silicon steel sheet exhibits excellent magnetic properties, such as iron loss decreases as the Si content increases, and when Si is about 6.5 wt%, magnetostriction becomes 0, and maximum magnetic permeability becomes a peak. As a method of industrially manufacturing such a high silicon steel plate, the manufacturing method by the gas immersion method as shown in patent document 1, for example is known. In this manufacturing method, a steel strip having a relatively low Si content is heated and immersed in a non-oxidizing gas atmosphere containing silicon chloride gas (SiCl ₄ ) to infiltrate Si, followed by diffusion heat treatment to diffuse Si in the plate thickness direction. After cooling, a series of processes of winding in a coil shape can be made into a continuous line to efficiently manufacture a high silicon steel strip.

In the continuous silicification process in which the silicification treatment is performed as described above, it is operated for a long time at a furnace temperature of 1200° C. or higher, and the silicon chloride gas (SiCl ₄ ) contained in the atmospheric gas is highly reactive and corrosive gas am. For this reason, there exists a problem that the silicon chloride gas activated in a high temperature furnace reacts with the refractory material which is a furnace material of a continuous silicification process, and deteriorates a refractory material.

As a refractory material for continuous silicification treatment furnaces, it is known to apply the refractory material of patent documents 2, 3, for example.

Japanese Laid-Open Patent Publication No. 62-227078 Japanese Laid-Open Patent Publication No. 10-147856 Japanese Laid-Open Patent Publication No. Hei 08-169750

On the other hand, iron chloride (gas) generated as a by-product during the production of high silicon steel sheet penetrates into the refractory material in the furnace, and there is a problem that agglomerates or solidifies in the temperature lowering portion near the furnace wall or furnace hearth. When this agglomerated and solidified iron chloride is deposited in a refractory material, a reduction reaction with the oxide in a refractory material advances, and quality change and embrittlement of a refractory material are accelerated|stimulated.

Further, when the refractory material in the furnace is exposed to the atmosphere due to maintenance or the like, the iron chloride deposited in the refractory material absorbs moisture in the air and expands. As a result, since the volume of the refractory material itself increases and expands, the furnace wall or the furnace-shaped refractory material bulges into the furnace, or the refractory material cracks and collapses. Therefore, there exists a problem that the lifetime of a refractory body becomes short, and an update period becomes short.

Using the refractory materials described in Patent Documents 2 and 3, although deterioration and embrittlement of the refractory material due to silicon chloride gas can be suppressed, it is found that it is difficult to suppress the deterioration and embrittlement of the refractory material due to iron chloride to the promotion of the refractory material. there was.

The present invention has been made in view of the above situation, and an object of the present invention is to provide a refractory material for a siliceous treatment furnace with little deterioration or embrittlement and a long lifespan.

MEANS TO SOLVE THE PROBLEM The present inventors acquired the recognition that the lifetime of a refractory body improved and the update period could be extended by using a refractory body with a predetermined|prescribed component composition and a low porosity, as a result of earnest examination.

The present invention has been made based on such recognition, and has the following as its gist.

[1] 35% by mass or more in total of one or two or more selected from oxides of silicon, nitrides of silicon and oxynitrides of silicon, and 0.05% by mass or less of alkali metals in total, and a porosity of 25 The refractory material for siliceous treatment furnaces whose compressive strength is 5 Mpa or more of volume% or less.

[2] The refractory material for silicification furnace use as described in [1] which further contains 1.0 mass % or less of each oxide of Mg, Ca, Ti, Fe, Cr, and Zr in total in total.

[3] The refractory material for silicification furnaces as described in [1] or [2], which contains 90 mass % or more in total of 1 type, 2 or more types selected from the oxide of silicon, the nitride of silicon, and the oxynitride of silicon.

ADVANTAGE OF THE INVENTION According to this invention, there are few changes in quality and embrittlement, and the refractory body for long siliceous treatment furnaces can be provided. Therefore, when the refractory material of this invention is applied as a refractory material for the continuous silicification process using silicon chloride gas, quality change or embrittlement will not generate|occur|produce over a long period of time, and the outstanding durability will be shown. For this reason, in the continuous manufacturing line of the high silicon steel plate by gas immersion method, long-term stable operation is attained, without generating deterioration of a refractory material, etc.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of the continuous agglomeration treatment facility which manufactures a high silicon steel plate.

(Form for implementing the invention)

Refractories made of various materials were produced. These refractories were placed in a furnace in an atmosphere containing silicon chloride gas (SiCl ₄ : about 15 vol%, furnace temperature: about 1200° C.) for 3 months, and changes in appearance, weight, volume, etc. of each refractory were investigated. As a result, a refractory material containing a large amount of any one or two or more of silicon oxide (silica), silicon nitride (silicon nitride), and silicon oxynitride (silicon oxynitride) has the least damage to silicon chloride gas. could know that In contrast, it was found that the refractory material made of silicon carbide had a large degree of damage.

Next, as an evaluation of the damage resistance of the refractory material to silicon chloride gas, the deterioration and embrittlement condition of the surface of the refractory material is investigated, and the total content of the deterioration condition and embrittlement condition and the silicon oxide, silicon nitride, and silicon oxynitride is calculated. relationship was reviewed.

As a result, a refractory material having a total content of one or more selected from silicon oxide, silicon nitride, and silicon oxynitride of less than 35% by mass is in a state with defects or hair cracks ( hairline cracks), and the occurrence of cracking and spalling was also remarkable. On the other hand, some cracks were also observed in refractory materials having a total content of one or two or more selected from among silicon oxides, silicon nitrides and silicon oxynitrides of 35% by mass or more, but leading to drop-off of the furnace material surface layer portion There was no change in quality or embrittlement like the bar, and it was judged that it could be used almost continuously.

From the above, in this invention, content of the silicon oxide, silicon nitride, and silicon oxynitride contained in a refractory material is 1 type or 2 or more types selected from the oxide of silicon, silicon nitride, and silicon oxynitride. is defined as 35 mass % or more in total. Preferably, 90 mass % or more of 1 type(s) or 2 or more types chosen from the oxide of a silicon, the nitride of a silicon, and the oxynitride of a silicon are contained in total. By setting it as 90 mass % or more, quality change and embrittlement are reduced remarkably, there is no generation|occurrence|production of a crack, and a favorable result is acquired.

In the present invention, as the silicon oxide, silicon nitride, and silicon oxynitride contained in the refractory material, silicon nitride and fused silica are preferable, and fused silica is particularly preferable.

In this invention, content of the alkali metal contained in a refractory body is prescribed|regulated as 0.05 mass % or less in total. The alkali metal contained in the refractory material contributes to the reactivity with silicon chloride gas. When content of an alkali metal exceeds 0.05 mass %, reaction of a refractory material and silicon chloride gas may advance, and there exists a possibility that a crack may generate|occur|produce on the refractory material surface, or a defect may arise.

In this invention, it is preferable to make the sum total of content of each oxide of Mg, Ca, Ti, Fe, Cr, and Zr contained in a refractory material into 1.0 mass % or less. It contributes to the reactivity with silicon chloride gas also about oxides, such as Mg and Ca contained in a refractory material. When content of oxides, such as Mg and Ca, exceeds 1.0 mass %, reaction of a refractory material and silicon chloride gas advances, and there exists a possibility that a crack may generate|occur|produce on the refractory material surface, or a defect may arise.

As remainder other than the above in a refractory body, _it is Al2O3 _and an impurity, and may contain the metal oxide other than the above as an impurity.

There is a problem in that iron chloride (gas) generated as a by-product during the production of high-silicon steel sheet permeates into the refractory material in the furnace and aggregates or solidifies at the furnace wall or the temperature lowering portion near the furnace bed. When this aggregated or solidified iron chloride is deposited in a refractory material, a reduction reaction with the oxide in a refractory material advances, and quality change and embrittlement of a refractory material are accelerated|stimulated. Further, when the refractory material in the furnace is exposed to the atmosphere due to maintenance or the like, the iron chloride deposited in the refractory material absorbs moisture in the air and expands. As a result, since the volume of the refractory material itself increases and expands, the furnace wall and the furnace-shaped refractory material protrude to the inside of the furnace, or the refractory material will crack and collapse. Therefore, there exists a problem that the lifetime of a refractory body becomes short, and an update period becomes short.

The present inventors earnestly studied about the change of quality and embrittlement of the refractory material caused by such iron chloride. As a result, it discovered that the quality and embrittlement of a refractory body could be suppressed by making the porosity of a refractory body 25 volume% or less.

The iron chloride (solid) deposited in the refractory material tends to be deposited in the refractory material as there are many pores in the refractory material. The iron chloride deposited in the refractory material expands when it comes into contact with the atmosphere, and a pressure is applied to the refractory material from the inside, which causes deterioration of the refractory material. From this point, it is preferable that there are few pores in a refractory body, and by making a porosity into 25 volume% or less, deposition of iron chloride in a refractory body is suppressed, and it becomes possible to prevent deterioration of a refractory body. Therefore, in this invention, the change of quality and embrittlement of a refractory material can be suppressed by making a porosity into 25 volume% or less. As a result, long-term stable operation in the continuous production line of a high silicon steel plate can be implement|achieved.

In addition, various component compositions were constant, and the refractory body from which the compressive strength differs was prepared. These refractories were placed in a furnace in an atmosphere containing iron chloride gas (FeCl ₂ concentration): about 15 vol%, furnace temperature: about 1200° C.) for 1 week, and then the change in the expansion state after exposure to the atmosphere for 2 months was investigated. . As a result, it was found that there is a close relationship between the compressive strength and the expanded state by iron chloride, and when the compressive strength is less than 5 MPa, the expanded state becomes large and collapses. For this reason, in this invention, the compressive strength of a refractory body shall be 5 MPa or more. If the compressive strength is less than 5 MPa, iron chloride gas as a by-product permeates in the refractory material, the refractory material expands, the refractory material collapses, and the surface appearance is affected. Preferably, the compressive strength is 20 to 200 MPa. Moreover, it is preferable that compressive strength is 200 MPa or less.

In addition, in this invention, there is no restriction|limiting in particular about the measuring method of a porosity and compressive strength, What is necessary is just to calculate|require by a normal method. Moreover, a porosity is 25 volume% or less, and a compressive strength can also use the refractory body of 5 Mpa or more.

Example 1

Refractories (50 mm x 50 mm x 50 mm) having various component compositions were produced, and these were installed in the silicification furnace of the continuous production line of high silicon steel sheet shown in FIG. 1 . After setting the atmosphere of the immersion treatment furnace to SiCl ₄ concentration: 15 vol%, and furnace temperature: 1200°C for 3 months, the state of damage to each refractory was investigated. Table 1 shows the results of the component composition, porosity, compressive strength, and damage condition of each refractory material.

As a damage condition, it was judged by surface observation and reactivity. Surface observation observed the external appearance of a refractory body, and evaluated it in 4 steps of defect presence>cracking>discoloration>no change from a deterioration condition. In addition, regarding reactivity, from the deterioration situation, ◎◎, ◎, ○, × 4 steps (◎◎: no reaction, ◎: hardly reacted, ○: reaction is small (deterioration of the refractory material is confirmed, but usable level), x: reaction was remarkable). Surface observation made discoloration and no change pass as pass, and reactivity was set to pass (double-circle), (double-circle), and (circle).

From the results of Table 1, all of the examples of the present invention were favorable results.

Example 2

About No. 10, 19, and 31 which showed the favorable result in Example 1, the update period at the time of using as a refractory body in a silting furnace was investigated. As a result, when No. 10, 19 were used and the update period of the conventional refractory body (refractory body of patent document 3) was made into 1, it became possible to extend an update period to 1.5 times. Further, when No. 31 was used, it became possible to extend the update period three times the conventional one.

Claims (3)

35 mass % or more and 97.5 mass % or less of fused silica and 0.05 mass % or less of an alkali metal are contained in total,
A refractory material for a siliceous treatment furnace having a porosity of 25% by volume or less and a compressive strength of 5 MPa or more. The method of claim 1,
Furthermore, the refractory body for siliceous treatment furnaces containing 1.0 mass % or less of each oxide of Mg, Ca, Ti, Fe, Cr, and Zr in total in total. 3. The method of claim 1 or 2,
The refractory material for silicification furnaces containing 90 mass % or more and 97.5 mass % or less of fused silica.

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