JP2893410B2 - BN ceramics with excellent erosion resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an h-BN ceramic having excellent resistance to erosion to a molten metal such as metal or glass.

<Conventional technology> h-BN ceramics exhibit extremely excellent wettability to heated melts such as metal and glass,
Since it is a hard-to-sinter material, it is usually made by a hot press method, and is therefore extremely expensive and not widely used as a heated melt.

Also, in the production of hot press, since the binder is made of B2O3-based glass which is relatively wettable with h-BN ceramics, the binder softens at high temperature, and BN
It is eluted on the ceramic surface, causing an extreme decrease in high-temperature strength and erosion due to reaction with the heated melt, which is one of the reasons why it is not widely used as a heated melt member at high temperatures.

Recently, BN such as Si3N4-h-BN that does not contain B2O3-based glass
There are normal-pressure or reaction-sintered composites mainly composed of ceramics other than the components, but these originally ignore the excellent properties of h-BN such as poor wettability, high corrosion resistance, and thermal shock resistance. is there. These materials can only slightly improve the thermal shock resistance by adding a small amount of the BN component, and are currently not generally used as a heated melt member. Therefore, in order to widely adapt as a material for heated melt while maintaining the excellent properties of BN ceramic, it is necessary to use a h-BN component as the main component and to have excellent erosion resistance, poor wettability, and thermal shock resistance. It is necessary to develop a new material that does not exist until now.

<Problems to be Solved by the Invention> The present invention has been made in view of the problems of the current state of the art, and has as its object the object of being excellent in erosion resistance to a heated melt such as metal or glass, and at normal pressure. It is an object of the present invention to provide an inexpensive h-BN ceramic material that can be manufactured by a sintering method.

<Means for Solving the Problems> As a result of earnest studies on the above problems, the present inventors have obtained the following new knowledge.

More than 50% of h-BN and (AlN, Si3N4, Al2O
3, if less than 1 to 50% of a composite compound composed of two or more compounds selected from SiO2), the erosion resistance to a hot melt such as metal or glass is remarkably improved.

More than 50% of h-BN and (AlN, Si3N4, Al2O
(3, SiO2) When the content of a composite compound composed of two or more compounds selected from less than 30% is contained in less than 30%, the strength is remarkably improved while maintaining the erosion resistance.

In particular, when Al6Si2O13, Si2Al3O7N, Si3Al2.67N4O4, Si3Al3O3N5, Al3O3N, Si6Al10O21N4 are contained as the above-mentioned composite compound, it has been found that the original properties of BN, such as resistance to wettability and thermal shock resistance, in addition to erosion resistance are extremely improved. Was.

 The present invention has been made based on the above findings.

<Function> The reason why the amount of h-BN in ceramics is set to 50% or more in the present invention is that if the amount is less than 50%, other ceramic components are necessarily 50%.
Rather, the properties of this ceramic component become stronger, and the properties inherent to h-BN, especially the erosion resistance and thermal shock resistance, are reduced. Therefore, the upper limit of the composite compound composed of two or more compounds selected from (AlN, Si3N4, Al2O3, SiO2) as a ceramic component other than h-BN must necessarily be less than 50%. The reason why the lower limit of the composite compound is set to 1% is that if it is less than 1%, a sufficient effect is not exhibited in the erosion resistance to a heated melt such as metal or glass. Although BN ceramics are originally excellent in thermal shock resistance, the thermal shock resistance changes depending on the amount of ceramic components other than h-BN. h-BN component is 50% or more, that is, h-BN
In most cases, if the ceramic component other than 50% is less than 50%, it can be applied without any problem as a heated melt member. For example, when used in a joint portion between a feed nozzle and a Cu mold of a horizontal continuous caster, a lining material of a ceramic mold or a Cu mold, a drawing nozzle for glass molding, etc.), preferably h-BN70
%, Less than 1 to 30% of components other than h-BN, more preferably 70 to 97% of h-BN, and 3 to 30% of components other than h-BN.

Ceramic components other than h-BN (AlN, Si3N4,
(Al2O3, SiO2) is not only excellent in erosion resistance, but also very difficult to find in conventional h-BN composites. This is because they exhibit excellent thermal shock resistance and poor wettability. In particular, the composite compound composition is Al6Si2O13, Si2Al3O7N, Si3Al2.67N4O4, S
i3Al3O3N5, Al3O3N, Si6Al10O21N4, for example, 3Al2O3 ・ 2SiO2, 2SiO2 ・ AlN ・ Al2O3, 2SiO2 ・ 2.6
7AlN ・ 1 / 3Si3N4, AlN, Si3N4 ・ Al2O3, Al2O3 ・ AlN, 6Si
The effect is remarkable when it becomes O2 · 3Al2O3 · 4AlN.

These composite compounds can be applied by any production method as long as they are present in the above-mentioned range in the sintered body h-BN ceramics. For example, a single component of the composite compound composition may be contained as a starting material and sintered, or the composite compound may be generated during the sintering process.

As components other than the composite component, AlN, Si3N4, Al2O3, SiO
The reason why 2 was selected is that these were determined by the present inventors in Japanese Patent Application No. 63-19542.
As disclosed in No. 4, even when BN is contained as a single component, it shows excellent fusion resistance, and depending on the production method, h-
This is because they are contained as inevitable impurities of the composite compound component in BN.

<Example> The present invention will be described in detail with reference to an example.

Example 1 Samples Nos. 1 to 8 were formed into rods by a rubber press, then sintered under normal pressure at 1,500 ° C. to 1,800 ° C. in an N 2 atmosphere, and processed to 10φ × 70 l.

These sample sintered phases were investigated by X-ray diffraction. Also, 0.02% of Al was added to molten steel (JIS. Sus-304) melted at 1,500 ° C to 1,550 ° C in a high-frequency melting furnace, and the samples of Nos. 1 to 8 were immersed in the steel for 0.5h while rotating at a speed of 60 rpm.
r. Hold and measure the amount of erosion.

The results are shown in Table 1.

The sintered components of Nos. 1 to 8 are h-BN and (AlN, Si3N4, Al2O
3, SiO2) is composed of two or more compound compounds selected from the group consisting of other compounds (AlN, Si3N4, Al2O3, SiO2). The diameter of each sample after immersion is almost 10mmφ before immersion. It was the same and very excellent in erosion resistance.

Example 2 Samples Nos. 9 to 14 were formed into square bars by a rubber press, then sintered under normal pressure at 1,800 ° C. in an N 2 atmosphere, and processed to 25 □ × 220 l. The sintered phases of these samples were investigated by X-ray diffraction.

Also, 0.053% of Al was added to molten steel (JIS.SCR-420) melted at 1,550 ° C to 1,568 ° C in a high-frequency melting furnace, and samples of Nos. 9 to 14 were immersed and rotated at a speed of 0.33 rps for 3 hours.
r. Hold and measure the amount of erosion.

 The results are shown in Table 2.

Samples Nos. 9 to 13 did not show any erosion after immersion in any case, and were very excellent in erosion resistance. No.14
The sample failed during the test due to thermal stress.

Example 3 Samples Nos. 9 to 14 of Example 2 were formed into a pipe shape by a rubber press, then sintered under normal pressure at 1,800 ° C. in an N 2 atmosphere, and processed into ID50 mmφ × OD60 mmφ × 50 mml.

These samples are heated for 30 minutes at room temperature or a predetermined temperature up to 900 ° C, immersed in molten steel at 1600 ° C for 1 minute,
Thermal shock resistance was investigated. The results are shown in FIG.

Very high ΔT ≒ 1,300 ℃ at 50% h-BN content, 70%
Did not break even when immersed directly in molten steel at ΔT = 1,600 ° C., that is, from room temperature to 1,600 ° C.

If the amount of h-BN is 50% or more, the thermal shock resistance inherent in h-BN is not impaired, and if it is 70% or more, it can be used as a member in which the heated melt solidifies at least partially.

Example 4. The samples of Nos. 15 to 19 were formed into a crucible shape by a rubber press, and then were sintered under normal pressure at 1,800 ° C. in an N2 atmosphere, and ID10m
It was processed into a crucible with mφ and thickness of about 5mmφ.

The sintered phase was investigated by X-ray diffraction, and the corrosion resistance was measured by using a metal (JIS.
The sample was dissolved under the condition of holding at 0 ° C. for 1 hour and examined. The results are shown in Table 3.

The erosion status in Table 3 is shown in FIG.

If the melting is severe, the inner surface of the crucible in contact with the metal may be severely enlarged or the crucible may have holes.

All the samples of Nos. 15 to 19 were excellent in erosion resistance.

After melting in any of the samples Nos. 15 to 19, the solidified metal (SUS-304) of the crucible could be taken out without strongly reacting and adhering to the inner surface of the crucible.

The condition of the crucible was No. 15-17, and the inside was discolored reddish brown. In Nos. 18 and 19, a glassy blue substance that had reacted with the metal adhered to the upper or inner surface. In addition, the state of the metal coagulated body was No. 18 and No. 19, showing the luster of the metal, and apparently poor wettability.

Example 5 Samples Nos. 15 to 19 in Table 3 were adapted as drawing nozzles for glass forming. FIG. 3 shows a schematic view of glass forming, which will be described below with reference to FIG.

The heated melt starts to solidify from the inside of the nozzle (part B in the figure), and the solidified body 2 is drawn out while being formed into the nozzle inner surface shape (the direction of the arrow in the figure). Therefore, the inner surface of the nozzle (B in the figure)
Part) is below the solidification temperature. On the other hand, the nozzle is heated melt 1
Both of them are in contact at the portion A in the figure, and the temperature is higher than the inner surface of the nozzle. That is, the nozzle comes into contact with the two phases of the heat-melted phase and the solidified phase, and a large temperature difference occurs in the nozzle. As a result, the nozzle material must have excellent thermal shock resistance and thermal stress resistance in addition to erosion resistance.

No. of ID17.5mmφ, OD27mmφ, length 20mml as nozzle.
Sintered bodies of 15 to 19 were produced, and SiO2 glass was used as the heated melt, and the glass that was heated and melted at a temperature of about 1,400 ° C was drawn out. Was done.

Example 6. Samples Nos. 18 and 19 in Table 3 were used as break rings in a horizontal continuous caster.

FIG. 4 shows a schematic view of a horizontal continuous casting machine, which will be described below with reference to FIG.

As shown in FIG. 4, the break ring is a member for connecting the tundish and the water-cooled Cu mold 3. The heated melt 1 in the tundish is a water-cooled Cu mold 3
The heat is deprived of heat and solidification is started from the break ring (part B in the figure). Therefore, the break ring is in contact with the heated melt phase in part A in the figure, its solidified phase in part B in the figure, and the two phases. Further, the break ring is also in contact with the water-cooled Cu mold 3 at the portion C in the figure, and the temperature gradient of the break ring material is The temperature increases to 1,500 ° C. As a result, the break ring material needs to have excellent thermal shock resistance and thermal stress resistance in addition to corrosion resistance.

The solidified body 2 is continuously drawn out (in the direction of the arrow in the drawing) and cast according to the shape of the Cu mold 3. No.18 and 19 of ID180mmφ, OD210mmφ, height 20mmH as break ring
As a result of casting molten steel heated and melted at a temperature of about 1,520 ° C using a molten steel (JIS.Sus-304) as a heated melt, the break ring has no cracks, no deformation, and little wear It was good. In addition, as a result of examining the inner surface of the break ring after use, formation of a compound containing MnO was observed. Since these melting points were lower than molten steel, it was thought that they existed as a liquid phase during operation, contributed to lubrication between the solidified shell and the break ring, and reduced wear. The quality of the cast product was also good.

Example 7. BN and A were used as starting materials so that h-BN was 70% or more in the sintered body and the composite compound composition was Si6Al2O13 as the remaining component.
lN, Al2O3, and SiO2 were mixed in the specified amounts shown in Table 4 and molded into a crucible by a rubber press.
Under normal pressure and processed into a crucible with ID10mmφ and thickness about 5mmt.

The sintered body phase was examined by X-ray diffraction, and the erosion resistance was examined as in Example 4. The results are shown in Table 4.

In the samples of Nos. 20 and 21, the components Al2O3 and SiO2 reacted during firing to produce an Al6Si2O13 phase, and in No.22, the oxygen and AlN in the BN components reacted during sintering to produce Al2O3, and Al2O3 and SiO2 were further converted. It reacted to produce Si6Al2O13. As described above, in all samples, the composition of the sintered body other than the h-BN component was Si6Al2O13, and the results were excellent in erosion resistance. Table 4 also shows intensity values. Only the sample of No. 20 showed low intensity, but the other samples had no problem with the intensity value.

Example 8. Samples Nos. 15 to 19 were fabricated in a crucible shape in the same manner as in Example 4. The erosion resistance to pure Ni and Fe-50% Ni metal was maintained at 1600 ° C. for 1 hour in an Ar atmosphere. The conditions were investigated. As a result, all samples were excellent in erosion resistance.

Example 9. The sample No. 17 of Example 4 was adapted as a ceramic mold. FIG. 5 is a schematic view of a ceramic mold, which will be described below with reference to FIG.

The basic structure is the same as the horizontal continuous caster shown in the sixth embodiment. The difference between the ceramic mold and the break ring is the shape. Ceramic mold is water-cooled Cu mold 3
It has a shape that covers the entire inner surface, and also serves as a mold for determining the shape of the solidified body 2.

The ceramic mold also comes into contact with the heated melt 1 at the portion A in the figure and with the solidified body at the portion B in the figure. Further, it is in contact with the water-cooled Cu mold at the portion C in the figure, and the same properties as the break ring are required as the mold material.

ID20mmφ, OD36mmφ, length as ceramic mold
No. 17 sintered body of 160 mml, Fe-50
% Ni was cast at a temperature of about 1,600 ° C., and the ceramic mold could be cast without cracking.

Example 10 A protective tube was prepared from the samples Nos. 15 to 19 of the example, and was directly immersed from the upper surface of the molten steel level, and the temperature of the molten steel in the tundish was measured. FIG. 6 shows the shape of the protective tube used at that time. The hatched portion in FIG. 6 is a protection tube made of the samples of Nos. 15 to 19.

As a result, in each case, the protection tube was not damaged, and the temperature of the molten steel could be connected and measured.

Example 11. As in Example 4, samples of Nos. 15 to 19 had an outer diameter of 10 mmφ ×
Made of 100Lmm length round bar, 1550 ℃ molten steel (SS material)
Dipped for 140 min. The diameter of the round bar sample after immersion was measured, and is shown in FIG. 7 as the amount of erosion. Each sample was excellent in erosion resistance without total erosion. In particular, Sample Nos. 15 to 17 were excellent without erosion.

The appearance of these samples was the same white as before immersion in Nos. 18 and 19, and turned reddish brown in Nos. 15 and 16.

Example 12. The samples of Nos. 17 to 22 were formed into a round bar shape by a rubber press, and then were sintered under normal pressure at 1800 ° C. in an N ₂ atmosphere to have an outer diameter of 10
Processed to φmm x length 100Lmm.

The sintered phase was investigated by X-ray diffraction, and the sample was immersed in a 1550 ° C. molten stainless steel (JIS SUS-321) for 30 min in an Ar atmosphere while rotating at 60 rpm, and the erosion characteristics were examined. The results are shown in Table 4.

Samples Nos. 17 to 21 containing Si ₆ Al ₁₀ O ₂₁ N ₄ , Si ₃ Al ₃ O ₃₁ N ₅ , and Si ₂ Al ₆ O ₁₃ had low erosion rates and were excellent in erosion resistance.

Example 13. The sample of No. 15 in Table 3 was used as a break ring of a horizontal continuous caster in the same manner as in Example 6.

Operating conditions are break ring size outer diameter 210φmm, inner diameter 1
80φmm, thickness 20mmH, steel grade stainless steel (SUS-304) ×
0.02% Al, temperature 1520 ° C.

The operation of the actual machine was completed without any trouble. However, the break ring after operation had a large thermal expansion and was cracked radially probably because of its weakness to thermal stress. In addition, the damage of the break ring was such that the apparent wettability was poor and the solidified body slipped poorly, and the vicinity of the solidification starting portion was selectively worn.

Example 14. The sample No. 20 in Table 4 was used as a break ring in a horizontal continuous caster. Steel type is stainless steel (SUS 321)
The other conditions are the same as in the sixth embodiment.

The break ring was completely cast without cracks and no operational troubles.

<Effects of the Invention> (1) An h-BN ceramic having excellent resistance to erosion to a heated melt can be produced at low cost by normal pressure sintering.

(2) h-BN ceramics excellent in erosion resistance and thermal shock resistance can be manufactured at low cost by normal pressure sintering, and can be applied to break rings and ceramic molds.

(3) The temperature of the heated melt can be easily and inexpensively measured by direct immersion in the heated melt.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the thermal shock resistance ΔT and the BN amount. FIG. 2 is a photograph showing an evaluation photograph of corrosion resistance, and is a top view and a cross-sectional view of the crucible after a dissolution test. FIG. 3 to FIG. 5 are diagrams illustrating the adaptation to a member in which the heated melt solidifies at least partially. DESCRIPTION OF SYMBOLS 1 ... Heated melt, 2 ... Solidified body 3 ... Water-cooled Cu mold A ... Site where an adaptation member comes into contact with a heated melt B ... Site where an adaptation member comes into contact with a solidified body C ... Adaptive member comes into contact with a water-cooled mold Parts FIG. 6 illustrates a protection tube set diagram in which the temperature of the heated melt is measured. FIG. 7 is a diagram for explaining the results of the erosion test.

Claims (5)

(57) [Claims] (1) More than 50% of h-BN and (AlN, Si3
An h-BN ceramic having excellent erosion resistance to a heated melt, characterized by containing less than 1 to 50% of a composite compound comprising two or more compounds selected from N4, Al2O3 and SiO2). 2. The sintered body contains at least 50% of h-BN and (AlN, Si3
N4, Al2O3, SiO2) 1 to less than 50% of a composite compound composed of two or more compounds selected from among the above-mentioned composite compounds (AlN, Si3N4, Al2O3, SiO2) An h-BN ceramic having excellent erosion resistance to a heated melt, characterized by containing less than 30% of two or more compounds. 3. The ceramic according to claim 1, wherein the composite compound is Al6Si2O13, Si2Al3O7N, Si3Al2.67O4N4, Si3Al3O3N5, Al3O3N, Si6Al10O21N4. 4. The ceramic according to claim 1, wherein the composite compound is Al6Si2O13, Si3Al3O3N5, Al3O3N, Si6Al10O21N4, and is used in a portion in contact with a partially solidified phase of the heat-melt. 5. The protective tube ceramic for measuring a temperature of a heated melt according to claim 1, wherein the composite compound is Al6Si2O13, Si3Al3O3N5, Al3O3N, Si6Al10O21N4.