JP4811866B2 - Ramming material for inductor-type inductors in which a core is installed and sintered - Google Patents

Description

The present invention relates to a ramming material for an induction furnace that can be applied to a grooved induction furnace inductor section in which a core is installed and sintered .

  Conventional pig iron and cast steel melting groove induction furnaces have magnesia ramming materials that use magnesia as the main material, alumina as the auxiliary material, alumina raw materials as the main material, and alumina ramming materials that use magnesia material as the auxiliary material. Widely used. (For example, see Patent Document 1)

  These ramming materials cause a chemical reaction that generates spinel in a high-temperature environment, and a sintering phenomenon proceeds using an activated state at that time. For this reason, necessary sintering strength is expressed in the vicinity of the working surface exposed to high temperature. This is generally called a sintered layer. In addition, the ramming material in the region other than the vicinity of the working surface does not reach the temperature necessary for sintering, and thus the unsintered state is maintained. This is generally referred to as a green layer.

  Even if a crack occurs in the sintered layer during the operation of the induction furnace, the crack does not propagate to the unsintered unsintered layer. Also, at that time, the molten metal that is the contents of the furnace enters the crack, but when the molten metal reaches the unsintered layer, the unsintered layer at the location is baked and solidified by receiving the heat of the molten metal. Further, it is possible to suppress the insertion of molten metal beyond that, and it is very effective for preventing the leakage of molten metal from the induction furnace.

  However, since the above-described spinel formation reaction is a chemical reaction that generally occurs in a relatively high temperature environment of 1200 ° C. or higher, the sintering operation of the above-described ramming material before the first receiving hot water needs to be a high temperature of 1200 ° C. or higher. is there. For this reason, it is difficult to ensure sufficient sintering strength at the end of the sintering operation before the first receiving hot water, and the melt pressure and impact at the time of the initial receiving hot water at the end of the sintering operation of the applied ramming material. Due to this, it was easy to cause buckling.

  In addition, in the case of a ramming material that does not use the spinel generation reaction described above, there is a ramming material that needs to be further sintered to a high temperature of 1300 ° C. or higher. It was even higher.

  On the other hand, particularly in the case of a grooved induction furnace inductor portion, at the end of the sintering operation of the applied ramming material, the surface temperature of the core installed at the time of installation may have a temperature difference of about 500 ° C. depending on the location. This is because the core shape is more complicated than that of the crucible induction furnace, and it is difficult to ensure temperature uniformity. For this reason, when a part of the core melts at the end of the sintering operation, there is a part where the temperature is raised only from about 800 ° C. to about 900 ° C. depending on the part of the core. Since the sintering temperature of the ramming material is not reached, the sintering strength is insufficient.

  In this case, conventionally, for example, glass powder or the like is generally added as a low temperature binder exhibiting strength at 800 ° C. to 1200 ° C. However, if the amount of the low temperature binder added is small, Sintering strength will be insufficient. Moreover, when the addition amount increases, the amount of liquid phase generated from the binder in the high temperature range increases rapidly, and the resistance to erosion and creep resistance in the high temperature range is insufficient. In addition, shrinkage due to oversintering occurs during temperature rise, causing cracks in the sintered layer of the ramming material. That is, by adding only the low-temperature binder that exhibits strength at 800 ° C. to 1200 ° C., it is possible to achieve both sufficient strength at the end of the sintering operation of the applied ramming material and durability during steady operation. It was difficult.

  In addition, as a technique for sufficiently performing initial curing of a refractory at a low temperature and suppressing cracking and cracking of the refractory in a high temperature range, a technique for adding a low temperature thermosetting resin and a high temperature thermosetting binder is known. Yes. (For example, see Patent Document 2)

However, the low-temperature thermosetting resin in the present technology performs primary curing of the refractory in the range of approximately room temperature to 200 ° C., and the high-temperature thermosetting binder ensures the strength at approximately 600 ° C. to 800 ° C. It is intended to prevent cracking, peeling and cracking of the refractory. Therefore, when this technology is applied to a ramming material for induction furnaces, the thickness of the unsintered layer is insufficient or the unsintered layer is completely eliminated. It will not be obtained.
JP 2002-265284 A Japanese Patent Laid-Open No. 2004-337956

The present invention aims to solve the above problems. In other words, the present invention is an induction furnace for melting cast steel and cast iron, which prevents the refractory from being buckled at the time of initial hot water by ensuring sufficient strength during the initial sintering operation and oversintering during use. Ramming material for induction furnaces that can be used stably with little cracking by suppressing, and can be used stably with low risk of molten metal leakage by ensuring a sufficiently thick unsintered layer , In particular, it is an object of the present invention to provide a ramming material for a groove type induction furnace inductor section in which a core is installed and sintered .

  As a result of advancing research and development in order to solve this problem, the present inventor has conceived the following present invention.

That is, the present invention is a ramming material comprising a first binder and a second binder,
The first binder is the first binder alone, or between the first binder and a ramming material component other than the first binder and the second binder, and the first binder. If it is less than ℃, there is no melting or solid solution region, and there are metal oxides, metal nitrides, metal nitride oxides, borides, and fluorides having a melting or solid solution region in the temperature range of 600 to 1200 ° C. As one compound or a mixture of two or more of the compounds belonging to any one of 0.01% to 5.0% by mass,
The second binder is the second binder alone, or between the second binder and a ramming material component other than the second binder and the first binder, and the second binder. Metal oxides, metal nitrides, metal nitride-based oxides, borides, and metal carbides having no melting or solid solution region at temperatures below 1000 ° C. and having a melting or solid solution region in the temperature range of 1000 ° C. to 1500 ° C. As one compound or a mixture of two or more of the compounds belonging to any one, 0.1 to 10.0% by mass is contained,
The compressive strength of the ramming material after firing at 800 ° C. is from 0.2 MPa to 7.0 MPa, the compressive strength of the ramming material after firing at 1400 ° C. is from 3.0 MPa to 30.0 MPa, and from 30 ° C. to 1500 ° C. This is a ramming material for a groove type induction furnace inductor section in which a core is installed and sintered , characterized by having a thermal expansion coefficient of zero or more in the temperature range.

  The induction furnace ramming material of the present invention has a melting or solid solution region in the temperature range of 400 ° C. to 1200 ° C. between the first binder and the second binder, and the first binder is 0 It is desirable to contain 0.01 mass% to 3.0 mass% and 0.1 mass% to 7.0 mass% of the second binder.

Furthermore, 0.01% to 1.0% by mass of boric anhydride (B ₂ O ₃ ) as the first binder, and 0.1% to 5.% of silica (SiO ₂ ) as the second binder. It is desirable to contain 0% by mass.

  According to the first aspect of the present invention, in an induction furnace for melting cast steel and cast iron, it is possible to prevent refractory buckling during initial hot water reception by ensuring sufficient strength during the initial sintering operation. Induction furnace that can be used stably with less cracking by suppressing oversintering of steel, and can be used stably with low risk of molten metal leakage by ensuring a sufficiently thick unsintered layer A ramming material can be provided.

  According to claim 2 of the present invention, the first binder and the second binder have a melting or solid solution region in a temperature range of 400 ° C to 1200 ° C, so that the first binder and By making it possible to reduce the amount of the second binder added, it is possible to improve the erosion resistance.

According to claim 3 of the present invention, by applying boric anhydride (B ₂ O ₃ ) as the first binder and silica (SiO ₂ ) as the second binder, the first binder and the second binder By making it possible to further reduce the amount of the binder added, it is possible to improve the erosion resistance.

  In addition to the main material, the ramming material for an induction furnace of the present invention includes a first binder and a second binder. Hereinafter, these will be described.

(First binder)
The first binder is 600 ° C. between the first binder alone or between the first binder and a ramming material component other than the first binder and the second binder. If it is less than, any of metal oxides, metal nitrides, metal nitride oxides, borides, and fluorides having no melting or solid solution region and having a melting or solid solution region in the temperature range of 600 ° C. to 1200 ° C. By adding 0.01% by mass or more as one compound or a mixture of two or more of the compounds belonging to the above, in a liquid phase sintering or solid solution via a melt in a temperature range of 600 ° C. or more The diffusion rate increases through crystal structure defects, and as a result, the sintering strength at 800 ° C. can be improved to 0.2 MPa or more. When the amount of the first binder added is too large, the diffusion rate increase via liquid phase sintering via the melt or crystal structure defects in the solid solution becomes excessive, and shrinkage occurs at a high temperature of 1200 ° C. or higher. This can be suppressed by suppressing the addition amount of the first binder to 5.0% by mass or less.

As the first binder, cryolite (Na ₃ AlF ₆ ), boric anhydride (B ₂ O ₃ ), soda (Na ₂ O), glass powder and the like can be used.

(Second binder)
However, it is difficult to sufficiently improve the firing strength (compression strength) at 1400 ° C. even if only a small amount of the first binder is added to such an extent that no shrinkage occurs at a high temperature of 1200 ° C. or higher. Therefore, the second binder may be the second binder alone, or between the second binder and the ramming material component other than the first binder and the second binder, Metal oxides, metal nitrides, metal nitride-based oxides, borides, and metal carbides having no melting or solid solution region below 1000 ° C. and having a melting or solid solution region in the temperature range of 1000 ° C. to 1500 ° C. By adding 0.1% by mass or more as one compound or a mixture of two or more of the compounds belonging to any of the above, liquid phase sintering or solid solution via a melt in a temperature range of 1000 ° C. or more The diffusion rate increases through the crystal structure defects inside, and as a result, the sintering strength (compression strength) at 1400 ° C. can be improved. When the amount of the second binder added is too large, the liquid phase sintering via the melt or the diffusion rate increase via the crystal structure defects in the solid solution becomes excessive, and shrinkage occurs at a high temperature of 1400 ° C. or higher. This can be suppressed by suppressing the addition amount of the second binder to 10.0% by mass or less.

As the second binder, wollastonite (CaO · SiO ₂ ), silica (SiO ₂ ), a combination of alumina (Al ₂ O ₃ ) and magnesia (MgO), alumina (Al ₂ O ₃ ) and silica (SiO ₂ ) ) And the like can be used.

  When both of the first binder and the second binder are added in a small amount, sufficient strength cannot be obtained, and when the amount is increased, the amount of liquid phase generated from these binders increases in a high temperature range. Insufficient melting resistance and creep resistance in the region, and lead to cracking due to shrinkage due to oversintering. In particular, the excessive addition of the first binder has a large adverse effect on the resistance to melting loss, creep resistance and oversintering at high temperatures.

(Combination of first binder and second binder)
When the first binder and the second binder are selected such that the first binder and the second binder have a melting or solid solution region in a temperature range of 400 ° C. to 1200 ° C. between the first binder and the second binder, It is possible to further improve the sintering strength.

As such a combination, 0.01 to 1.0 mass% of soda (Na ₂ O) or boric anhydride (B ₂ O ₃ ) is used as the first binder, and “wollastonite ( CaO · _SiO 2) "or" silica (SiO ₂₎ and the alumina _(Al 2 _{O 3)} "to be added 0.1 to 5.0 wt% is effective. In particular, it is effective to select boric anhydride (B ₂ O ₃ ) as the first binder and silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) as the second binder. This is because a part of boric anhydride (B ₂ O ₃ ) and part of silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) are mixed and melted together to form an aluminoborosilicate glass at 400 ° C. A liquid phase starts to be generated from the vicinity, and an aluminosilicate glass derived from surplus silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) is generated in a temperature range of 1200 ° C. or higher. Therefore, a sufficient initial strength can be obtained because moderate liquid phase sintering proceeds in a relatively wide temperature range up to 1200 ° C. where the first hot water is received. In addition, since a liquid phase contributing to sintering is not generated in a temperature range of less than 400 ° C., an unsintered layer having a sufficient thickness can be ensured if necessary. Furthermore, Na atoms exist as a network modifier in the glass, whereas B atoms exist as a network former, so that it is more anhydrous than selecting soda (Na ₂ O) as the first binder. Higher corrosion resistance can be expected by selecting boric acid (B ₂ O ₃ ). Further, when boric anhydride (B ₂ O ₃ ) is selected as the first binder and silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) are selected as the second binder, deliquescence due to moisture during storage, etc. Since there is almost no quality deterioration, there is also an advantage that it is excellent in storability and easy to obtain.

  Unlike the groove type induction furnace, when the sintering operation is properly performed in the crucible type induction furnace, the magnesia-based ramming material using the magnesia as the main raw material and alumina as the auxiliary raw material, the main raw material, which is a conventionally known technique An alumina ramming material using an alumina raw material as an auxiliary material and a magnesia raw material as an auxiliary material is often sufficient, but by adding both the first binder and the second binder based on the present invention, molten metal leaks Needless to say, the risk of this can be further reduced.

  As described above, the induction furnace ramming material of the present invention needs to have a compressive strength of 0.2 MPa or more after firing at 800 ° C. This is to prevent the refractory from buckling during the initial hot water reception during the initial sintering operation. Preferably, it is desirable to ensure a compressive strength of 2.0 MPa or more. Although there is no particular upper limit value for compressive strength at 800 ° C., it is usually 7.0 MPa or less in most cases. Moreover, the compressive strength after 1400 degreeC baking needs to be 3.0-30.0 MPa. This is because cracks hardly occur and can be used stably by securing the sintering strength in the vicinity of the working surface and suppressing oversintering during use. The compressive strength is preferably 8.0 to 25.0 MPa, more preferably 15.0 to 20.0 MPa. The compressive strength measurement can be performed according to JIS standard R2206.

(Examples 1-16 and Comparative Examples 1-5)
Ramming materials for induction furnaces were produced with the raw materials and blending ratios shown in Table 1 and Table 2 below, and subjected to a compression strength test, a thermal expansion test, and a sticking test using a high frequency induction furnace.

These ramming materials were produced by applying alumina (Al ₂ O ₃ ) as an aggregate and adding a binder thereto. Since alumina (Al ₂ O ₃ ) is applied as an aggregate, the addition of magnesia (MgO) will act as a binder by the formation of spinel (MgAl ₂ O ₃ ), and in the table as the second binder It is written. The glass powder employed as the first binder is a finely pulverized alumina-silica-lime glass.

  Here, the compressive strength measurement was performed as follows. That is, each test material was molded by hand into a 40 × 40 × 160 mm mold, heated at a heating rate of 2 ° C./min, held at 800 ° C. or 1400 ° C. for 3 hours, and then to room temperature. It cooled naturally and measured the compressive strength according to JIS specification R2206.

About the quality determination of the compressive strength measurement result after 800 degreeC baking, it performed in the following way. That is, the judgment when it is less than 0.2 MPa is x, the judgment when it is 0.2 MPa to 1.0 MPa is Δ, the judgment when it is 1.0 MPa to 2.0 MPa is ○, 2.0 M or more Judgment in the case was ◎.
Moreover, about the quality determination of the compression strength measurement result after 1400 degreeC baking, it performed in the following way. That is, the determination when it is less than 3.0 MPa or 30.0 MPa or more is x, the determination when it is 3.0 to 8.0 MPa or 25.0 to 30.0 MPa is Δ, 8.0 to 15.0 MPa or In the case of 20.0 to 25.0 MPa, the determination in the case of ◯ and in the case of 15.0 to 20.0 M was evaluated as ◎.

  The thermal expansion test was performed as follows. That is, it was molded by hand punching into a 20 × 20 × 80 mm mold, heated to 1500 ° C. at a heating rate of 2 ° C./min, and the hot linear expansion coefficient was measured according to JIS standard R2207.

  About the quality determination of the thermal expansion test, it performed in the following way. That is, during the temperature increase from room temperature to 1500 ° C., the determination is made when the thermal expansion coefficient is always a positive value without shrinkage during the temperature increase and the disturbance of the thermal expansion coefficient is relatively small. If the turbulence is one place and the turbulence is relatively small, for example, the coefficient of thermal expansion is zero or larger compared to the temperature range before and after that, ○, the coefficient of thermal expansion is zero or before and after the temperature rise When the disturbance such as an increase in the temperature range is relatively large or when two or more places are observed, Δ is determined, and when the contraction is observed during the temperature rise, the determination is ×.

  Further, the separation test using the high frequency induction furnace was performed as follows. In other words, four types of dry stamps were pasted separately on the furnace wall of a high-frequency induction furnace with a furnace capacity of 100 kg, a mold was placed, the temperature was raised to 1400 ° C., held for 2 hours, and released to 800 ° C. The operation of cooling and raising the temperature to 1400 ° C. again was repeated for a total of 10 cycles. Thereafter, the mixture was allowed to cool to room temperature, and the cross-section of the dry stamped sintered body was observed.

  About the quality determination of comprehensive evaluation in view of the high frequency induction furnace sticking test result, it performed in the following way. That is, when a relatively large crack is generated, or when there are 8 or more relatively small cracks, or when there is at least one in the compressive strength test result or the thermal expansion test result, ×, a relatively small crack is small (4 ~ 7) △ if seen, ◯ if relatively small cracks are very small (3 or less), 3 or less relatively small cracks, and ◎ compression test results and thermal expansion test results The case was marked as ◎.

  From Table 1, a first binder having a melting or solid solution region in a temperature range of 600 ° C. to 1200 ° C. between the binder itself or a ramming material component other than the binder and the binder, and the binder itself Alternatively, an appropriate amount of a second binder having a melting or solid solution region in a temperature range of 1200 ° C. or higher between the ramming material component other than the binder and the binder is added to each of the binders, so that it becomes 0 after baking at 800 ° C. .2MPa or higher compressive strength, 8.0 to 25.0MPa compressive strength after firing at 1400 ° C, and suppressing shrinkage during temperature rise, so that cracks occur during hot water receiving and in use It was confirmed that it was possible to use it stably.

From Table 2, when, for example, soda (Na ₂ O) or boric anhydride (B ₂ O ₃ ) is applied as the first binder, for example, finely divided silica (SiO ₂ ) is applied as one of the second binders. Since aluminosilicate glass or borosilicate glass is produced in the temperature range from 400 ° C. to 1200 ° C., it was confirmed that the intended sintering strength and thermal expansion characteristics can be easily secured. Furthermore, it was confirmed that the best results were obtained when the addition amount of boric anhydride (B ₂ O ₃ ) was 0.2 mass% and the addition amount of fine silica (SiO ₂ ) was 1.0 mass%.

Claims (4)

A ramming material comprising a first binder and a second binder,
The first binder is the first binder alone, or between the first binder and a ramming material component other than the first binder and the second binder, and the first binder. If it is less than ℃, there is no melting or solid solution region, and there are metal oxides, metal nitrides, metal nitride oxides, borides, and fluorides having a melting or solid solution region in the temperature range of 600 to 1200 ° C. As one compound or a mixture of two or more of the compounds belonging to any one of 0.01% to 5.0% by mass,
The second binder is the second binder alone, or between the second binder and a ramming material component other than the second binder and the first binder, and the second binder. Metal oxides, metal nitrides, metal nitride-based oxides, borides, and metal carbides having no melting or solid solution region at temperatures below 1000 ° C. and having a melting or solid solution region in the temperature range of 1000 ° C. to 1500 ° C. As one compound or a mixture of two or more of the compounds belonging to any one, 0.1 to 10.0% by mass is contained,
The compressive strength of the ramming material after firing at 800 ° C. is from 0.2 MPa to 7.0 MPa, the compressive strength of the ramming material after firing at 1400 ° C. is from 3.0 MPa to 30.0 MPa, and from 30 ° C. to 1500 ° C. A ramming material for a groove-type induction furnace inductor section in which a core is installed and sintered , characterized in that the thermal expansion coefficient in the temperature range of the core is zero or more. Including 0.01% to 3.0% by weight of the first binder, 0.1% to 7.0% by weight of the second binder, the first binder and the second binder, A ramming material for a groove-type induction furnace inductor section that is sintered by installing the core of claim 1, which has a melting or solid solution region in a temperature range of 400 ° C to 1200 ° C. As a first binder, boric anhydride (B ₂ O ₃ ) is contained in an amount of 0.01% by mass to 1.0% by mass, and as a second binder, silica (SiO ₂ ) is contained in an amount of 0.1% by mass to 5.0% by mass. The ramming material for a groove type induction furnace inductor part , wherein the core is placed and sintered by installing the core .   As a combination of the first binder and the second binder, alumina-silica-lime glass, magnesia (MgO), boric anhydride (B ₂ O ₃ ) And magnesia (MgO), soda (Na ₂ O) and silica (SiO ₂ ) Or boric anhydride (B ₂ O ₃ ) And silica (SiO ₂ 3) A ramming material for a groove type induction furnace inductor section, wherein the core is installed and sintered.