JPH07112623B2 - Low melting point molten metal processing tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention [Industrial field of use] The present invention relates to a low melting point molten metal treating tool, and in particular to a low melting point molten metal such as molten aluminum using a titanium boride ceramics sintered body. The present invention relates to a low-melting-point molten metal processing tool in which a portion to be contacted with is formed.

[Prior Art] Conventionally, as a low melting point molten metal treating tool of this type, alumina is used.
The one formed by sintering Al ₂ O ₃ or tungsten carbide WC has been proposed.

[Problems to be Solved] However, in the conventional low melting point molten metal treating tool, (i)
Alumina Al ₂ O _{3 has} a small Vickers hardness of 1500 Hv and a bending strength of 400 to 150 at room temperature to 1200 ° C.
It has a small value of MPa, a large porosity of 1.0%, a small thermal shock resistance of about 275 ° C, and poor corrosion resistance. Therefore, it is fragile and has a short service life. Yes, and (ii) tungsten carbide WC
In this case, the Vickers hardness was as low as 400 Hv, and the bending strength was extremely low at 70 MPa at room temperature, and the corrosion resistance was also extremely poor, and there was a drawback that it was practically impossible.

Therefore, it has been proposed recently to form a low melting point molten metal treatment tool by sintering silicon nitride Si ₃ N ₄ . In this case, although the bending strength and the thermal shock resistance could be improved as compared with the case where alumina Al ₂ O ₃ or tungsten carbide WC was sintered, the Vickers hardness was deteriorated and the corrosion resistance was slightly improved. Since it was inferior, the low melting point molten metal treating tool was still fragile and had a drawback that it could not have a long life.

Therefore, in order to solve these drawbacks, the present invention improves the Vickers hardness, bending strength, thermal shock resistance, etc. by forming at least a portion in contact with a low melting point molten metal by using a titanium boride ceramics sintered body. At the same time, it is intended to provide a low melting point molten metal treating tool which does not require preheating and has a long life.

(2) Configuration of the Invention [Means for Solving the Problems] The means for solving the problems provided by the present invention is a low melting point molten metal treating tool which is brought into contact with a low melting point molten metal, and boride of chromium and carbonization. A portion in which a matrix layer mixed and solid-dissolved with titanium is arranged between titanium boride particles and is in contact with at least the low melting point molten metal by a titanium boride ceramics sintered body having a porosity of 5% or less. It is a low melting point molten metal processing tool characterized by being formed.

[Operation] In the low melting point molten metal treating tool according to the present invention, the matrix layer in which chromium boride and titanium carbide are mixed and solid-dissolved is arranged between titanium boride particles and has a porosity of 5% or less. Since the titanium boride ceramics sintered body forms at least a portion in contact with the low melting point molten metal, Vicker hardness, bending strength, porosity and thermal shock resistance of the portion in contact with the low melting point molten metal It has an effect of improving the above-mentioned effects, and thus an effect of avoiding preheating at the time of use, an effect of sufficiently suppressing the reaction with the low melting point molten metal, and an effect of achieving a long life as a result.

[Examples] Next, the present invention will be specifically described with reference to the accompanying drawings. Here, for convenience, a casting nozzle will be described as a specific example of the low melting point molten metal treating tool according to the present invention.

FIG. 1 is a partial cross-sectional view showing a casting nozzle as an example of a low melting point molten metal treating tool according to the present invention,
A protective layer 12 formed of a titanium boride ceramics sintered body is arranged on the inner peripheral surface of the nozzle body 11, and the nozzle body 11 has a thermal expansion coefficient close to that of the titanium boride ceramics sintered body. It is formed of the material that it has.

FIG. 2 is an enlarged cross-sectional view showing a protective layer arranged on the inner peripheral surface of the nozzle body of FIG. 1 embodiment.

FIG. 3 is an optical micrograph showing the structure of the surface of the protective layer which has been subjected to the polishing treatment in the embodiment of FIG. 1 and shows the case of Experimental Example 18.

FIG. 4 is a scanning electron micrograph showing the structure of the fracture surface of the protective layer in the embodiment of FIG. 1, showing the case of the embodiment 18.

FIG. 5 is an optical micrograph showing the structure of the surface of the protective layer which has been subjected to the etching treatment of FIG. 1 and shows the case of Example 18.

FIG. 6 is a scanning electron micrograph showing the structure of the surface of the protective layer subjected to the etching treatment of the embodiment of FIG.
The case of 18 is shown.

FIG. 7 is a scanning electron micrograph showing the structure of the surface of the protective layer which has been subjected to the polishing treatment of FIG. 1 and shows the case of Example 18, in which the dropout portion of particles during the polishing treatment is black. Indicated by.

FIG. 8 is a copy of FIG. 7, in which the part where the particles fall off during the polishing process is shown in black.

FIG. 9 is an X-ray intensity distribution chart showing the results of EPMA analysis, that is, electron probe microanalysis of the texture of the protective layer surface subjected to the polishing treatment of the embodiment of FIG. 1, which was carried out along the straight line of FIG. It shows the case.

FIG. 10 (a) is an X-ray intensity distribution photograph showing the results of EPMA analysis, that is, electron probe microanalysis of the texture of the protective layer surface after polishing treatment of the embodiment of FIG.
The figure shows the case where it is executed for almost the whole of the figure, and the portion corresponding to chrome is shown in black.

FIG. 10 (b) is an X-ray intensity distribution photograph showing the result of EPMA analysis, that is, electron probe microanalysis of the structure of the protective layer surface after polishing treatment of the embodiment of FIG. 1, and FIGS.
The figure shows the case where it is executed for almost the whole of the figure, and the portion corresponding to titanium is shown in black.

FIG. 10 (c) is a copy diagram created by superimposing FIGS. 10 (a) and 10 (b), in which chrome is shown by a broken line and titanium is shown by a solid line.

FIG. 11 is a graph showing the results of X-ray diffraction analysis carried out on the protective layer of the embodiment of FIG. 1, showing the case of Example 1, where the horizontal axis represents the X-ray diffraction angle. X-ray diffraction intensity is plotted on the vertical axis.

FIG. 12 is a scanning electron micrograph showing the structure of the protective layer fracture surface of the casting nozzle shown as Comparative Example 1.

FIG. 13 is a partial cross-sectional view showing another casting nozzle as another embodiment of the low melting point molten metal treating tool according to the present invention, in which the nozzle main body 11 ′ as a whole is a titanium boride ceramics sintered body. And the protective layer is removed.

First, the configuration and action of an embodiment of the low melting point molten metal treating tool according to the present invention will be described in detail. Reference numeral 10 denotes a low melting point molten metal treatment tool (here, a casting nozzle) of the present invention, which has a coefficient of thermal expansion ρ ₂ close to that of the coefficient of thermal expansion ρ ₁ of the titanium boride ceramics sintered body, that is, there is not much difference.
Which is formed of a material such as a suitable metal having, for example, brass, and which is not in contact with the low melting point molten metal, that is, the nozzle body 11, and the titanium boride ceramics sintered body which is arranged on the inner peripheral surface of the nozzle body 11. It has a portion formed of a united body and in contact with the low melting point molten metal, that is, the protective layer 12. The ratio of the thermal expansion coefficient ρ ₁ of the titanium boride ceramics sintered body forming the protective layer 12 and the thermal expansion coefficient ρ ₂ of the material forming the nozzle body 11 is 1/4 ≦ ρ
It is preferable that ₁ / ρ ₂ ≦ 4.

The low-melting-point molten metal treating tool, that is, the casting nozzle 10, is a means for supplying the low-melting point molten metal (for example, a ladle) in use.
The low melting point molten metal supplied to the upper opening via the supply means is guided by the inner surface of the protective layer 12 arranged with respect to the inner peripheral surface of the nozzle body 11, and from the lower opening to the mold. It is released toward.

At this time, the protective layer 12 is made of a titanium boride ceramics sintered body in which a matrix layer in which chromium boride and titanium carbide are mixed and solid-dissolved is disposed between titanium boride particles and has a porosity of 5% or less. Since it is formed, it is possible to prevent the nozzle body 11 from being corroded by the low melting point molten metal, and it is possible to prevent the raw material of the nozzle body 11 from mixing with the low melting point molten metal. Further, since the protective layer 12 and the nozzle body 11 have a coefficient of thermal expansion that is not so different, a large thermal strain occurs between the protective layer 12 and the nozzle body 11 with the treatment of the low melting point molten metal. Therefore, the protective layer 12 and the nozzle body 11 are not damaged.

Low melting point molten metal processing equipment i.e. casting nozzle 10 into the tissue of the protective layer 12 disposed against the inner peripheral surface of the nozzle body 11, and titanium boride TiB ₂ particles 20, titanium boride TiB ₂ particles
And a mesh-like bonding layer 30 for bonding 20 together.

The titanium boride TiB ₂ particles 20 have an average particle size of 0.5 to 10 μm and a maximum particle size of 12 μm, and particularly an average particle size of 0.5 to 3
It is preferable that the particle size is μm and the maximum particle size is 6 μm. Here, the basis for setting the average particle size of the titanium boride TiB ₂ particles 20 to 0.5 to 10 μm is (i) when the average particle size is less than 0.5 μm, the surface oxidation of the titanium boride TiB ₂ particles 20 becomes remarkable, In addition, the agglomeration between the titanium boride TiB ₂ particles 20 becomes remarkable, and the sintering of the titanium boride ceramics sintered body according to the present invention, that is, the protective layer 12 of the casting nozzle 10 is significantly hindered. ) If the average particle size exceeds 10 μm, the driving force for sintering becomes small, making it difficult to densify the protective layer 12 of the casting nozzle 10 according to the present invention, and existing titanium boride TiB ₂ particles 20 exist. The cracks are enlarged and the strength of the protective layer 12 of the casting nozzle 10 according to the present invention is reduced. In addition, the maximum particle size of titanium boride TiB ₂ particles 20 is 12
The reason why it is defined as μm is that if the maximum particle size exceeds 12 μm, it will be present as coarse particles in the protective layer 12 of the casting nozzle 10 according to the present invention, and the protective layer of the casting nozzle 10 according to the present invention will be present. It is to prevent the density and strength of 12 from increasing.

Titanium boride TiB ₂
A grain boundary phase 21 is formed which is a mixed solid solution phase of TiB ₂ and a boride MB, MB ₂ or M ₃ B of metal M described later. As a result, the bonding force between the titanium boride TiB ₂ particles 20 and the bonding layer 30 is made sufficiently large, and as a result, the strength of the protective layer 12 of the casting nozzle 10 according to the present invention and the like are secured. ing.

The bonding layer 30 includes chromium Cr (hereinafter, referred to as metal M or simply M for convenience of description) (hereinafter, the same) and titanium boride TiB ₂
And _{TiB 2 + 2M + C → 2MB} + TiC or _{TiB 2 + M + C → MB} 2 + TiC or _{TiB 2 + 6M + C → 2M} 3 B + boride MB of metal boride i.e. metal M generated by the reaction such as TiC between carbon C, MB ₂ or M _This is a matrix layer in which ₃ B and the like and titanium carbide TiC are mixed and solid-solved, and voids are sufficiently removed. As a result, the bonding strength between the titanium boride TiB ₂ particles 20 is made sufficiently large, and the porosity (that is, the value obtained by dividing the pore volume by the total volume) of the protective layer 12 of the casting nozzle 10 is 5%. %, The density and strength of the protective layer 12 of the casting nozzle 10 according to the large invention are secured as a result. Here, the reason why the voids are substantially removed from the bonding layer, that is, the matrix layer 30, is as follows.
Boride of metal M, that is, metal boride MB, MB ₂ or M ₃
The particle sizes of B and the like and the particle size of titanium carbide TiC are almost the same, and they are in the form of a homogeneous mixed solution.

Furthermore, the manufacturing procedure of one embodiment of the low melting point molten metal treating tool according to the present invention will be described.

In the first step, a ceramic blend is prepared by blending titanium boride TiB ₂ powder with metal M powder and carbon C powder at an appropriate blending ratio.

That is, (i) the average particle size is 0.5 to 8 μm (preferably 0.5
Titanium boride TiB ₂ having a maximum particle size of 12 μm (preferably 6 μm) and a purity of 99% by weight or more, and (ii)
A metal M having an average particle size of 1 to 5 μm (preferably 1 to 3 μm) and a maximum particle size of 12 μm (preferably 6 μm), (ii
i) Specific surface area of 50 to 150 m ² / g (preferably 80 to 150 m ² / g)
With a purity of 99.9% by weight or more and an average particle size of 10 to 100 nm
Carbon (for example, carbon black) C having a maximum particle size of 150 nm (preferably 100 nm) (preferably 10 to 50 nm)
And are blended with each other to form a ceramic blend.
In the ceramic composition, titanium boride TiB ₂ is 11 to 99.9% by weight with respect to the mixture of metal M and carbon C 0.1 to 89% by weight (particularly 2.5 to 25.0% by weight is preferable).
(In particular, 75.0 to 97.5% by weight is preferable). Further, the mixing ratio of the metal M and the carbon C is a weight ratio.
It is 7: 0.1 to 10 (particularly preferably 7: 0.2 to 5).

Here, the reason why the purity of titanium boride TiB ₂ is 99% by weight or more is to avoid the adverse effect of impurities during sintering.

The reason why the average particle size of the metal M is 1 to 5 μm is as follows.
(I) If the average particle size is less than 1 μm, the surface oxidation of the metal M particles becomes remarkable, and the metal M particles are aggregated or the metal M particles are aggregated with titanium boride TiB ₂ particles or carbon C particles. And the sintering of the protective layer 12 of the low melting point molten metal treating tool, that is, the casting nozzle 10 according to the present invention is significantly hindered, and (ii) the average particle diameter is 5 μm.
If it exceeds m, the protective layer of the casting nozzle 10 according to the present invention
12 matrix layers 30 or titanium boride TiB ₂ particles 20
Coarse particles are present as coarse particles in the grain boundary phase 21 formed in the vicinity of the grain boundary, and the strength of the protective layer 12 of the casting nozzle 10 according to the present invention is reduced. The reason why the maximum particle size of the metal M is 12 μm is that the maximum particle size is 12 μm.
If it exceeds, the existing cracks will be expanded in the metal M particles, and the strength of the protective layer 12 of the casting nozzle 10 according to the present invention will be lowered.

The reason why the average particle size of carbon C is 10 to 100 nm is that (i) if the average particle size is less than 10 nm, the surface oxidation of the carbon C particles becomes remarkable and the aggregation between the carbon C particles becomes remarkable. Therefore, the sintering of the protective layer 12 of the casting nozzle 10 according to the present invention is significantly hindered, and (ii) the average particle size is
If it exceeds 100 nm, it will be present as coarse particles in the matrix layer 30, and the casting nozzle according to the present invention.
The purpose is to reduce the strength of the protective layer 12 of 10 . The reason why the maximum particle size of carbon C is 150 nm is that if the maximum particle size exceeds 150 nm, the existing cracks in the carbon C particles or titanium carbide TiC particles generated by the reaction with titanium boride TiB ₂ This is to expand existing cracks and reduce the strength of the protective layer 12 of the casting nozzle 10 according to the present invention.

Further grounds for the specific surface area of the carbon C is a 50 to 150 m ² / g is, (i) if the specific surface area is less than 50 m ² / g, titanium boride TiB ₂ become the carbon C particles is too large If the specific surface area exceeds 150 m ² / g, the carbon C particles will agglomerate with each other, and the titanium boride TiB ₂ and the metal M will not react with each other. The problem is that they cannot mix.

In the second step, the ceramic mixture is homogeneously mixed with an appropriate mixer to prepare a ceramic mixture.

In the third step, the ceramic mixture is put in an appropriate mold together with a binder (for example, polyvinyl alcohol), and then an appropriate pressure (for example, 100 to 800 kg / cm ²
Is applied to uniaxially apply pressure to produce a ceramic green compact.

In the fourth step, the ceramic green compact is subjected to a CIP process, that is, a normal temperature isostatic pressing process by applying an appropriate pressure (for example, a pressure of 800 to 3500 kg / cm ² ), to obtain a ceramic green body.

In the fifth step, the ceramic compact is placed in a non-oxidizing atmosphere (that is, a neutral or reducing atmosphere) such as a vacuum atmosphere (preferably having an atmospheric pressure of 10 ⁻³ Torr or less), an argon atmosphere or a hydrogen gas atmosphere. In a non-pressurized state or a pressurized state (applying a pressure of 100 to 500 kg / cm ² ), the ceramic is sintered at a temperature of 1500 to 2000 ° C (preferably 1700 to 1900 ° C) for an appropriate time. The body. The reason for the non-oxidizing atmosphere here is titanium.
It is to prevent Ti, boron B, metal M or carbon C from being oxidized.

In the sixth step, a ceramic sintered body, that is, a protective layer
12 is finished, that is, its inner surface is polished with a desired accuracy.

In the seventh step, the nozzle body 11 is formed by using a metal or the like (such as brass) having a thermal expansion coefficient close to that of the protective layer 12 as a raw material.

In the eighth step, a protective layer is formed on the inner peripheral surface of the nozzle body 11.
The 12 is bonded using an appropriate adhesive (for example, an inorganic adhesive).

As described above, the low melting point molten metal treating tool, that is, the casting nozzle 10 according to the present invention is manufactured.

In addition, one embodiment of the low melting point molten metal treating tool according to the present invention will be described with specific numerical values and the like for better understanding.

(Examples 1 to 7) Chromium Cr having an average particle size of 1 μm and a specific surface area of 135 m ² /
The average particle size was 3 μm and the maximum particle size was 6 μm, and the purity was 99% by weight, based on 2.5% by weight of the mixture prepared by changing the mixing ratio with carbon black C having a purity of 99% by weight in g.
100 parts of a ceramic compound prepared by mixing 97.5% by weight of titanium boride TiB ₂ is a plastic container with urethane balls and 300 parts of ethylene alcohol, and wet-mixed for 24 hours. A ceramic mixture was created.

The ceramic mixture was kept at a temperature of 60 ° C. for 10 hours to be thoroughly dried. After that, 100 parts of the ceramic mixture
It was housed in an appropriate mold together with 2 parts of polyvinyl alcohol as a binder, and a pressure of 300 kg / cm ² was applied to uniaxially press to obtain a ceramic green compact.

Ceramic green compacts are applied with a pressure of 3000 kg / cm ²
A ceramic compact was obtained by performing P treatment, that is, normal temperature isostatic pressing treatment.

The ceramic molded body was heated to a temperature of 1900 ° C. at a temperature rising rate of 15 ° C./min in an unpressurized argon atmosphere and maintained at a temperature of 1900 ° C. for 1 hour to obtain a ceramic sintered body. did.

The ceramics sintered body was subjected to finishing processing, that is, the inner surface was mainly polished to a desired accuracy to obtain a protective layer divided body.

On the other hand, the nozzle body was formed by using brass having a thermal expansion coefficient close to that of the protective layer 12 as a raw material.

A plurality of protective layer divided bodies were bonded to the inner surface of the nozzle body 11 by using an appropriate adhesive (in this case, an inorganic adhesive), and arranged as the protective layer 12. This produced the casting nozzle 10 .

The total length of the casting nozzle 10 is 150 mm, the openings of the protective layer 12 at the upper end opening and the lower end opening of the nozzle body 11 are 80 mm and 20 mm, respectively, and the nozzle body is
The thickness of 11 was 10 mm.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 1.

The casting nozzle 10 supplies molten aluminum as a low melting point molten metal to the upper opening thereof, and while guiding the molten aluminum as the inner peripheral surface of the protective layer 12 arranged in the nozzle body 11, supplies it to the mold from the lower opening. . When continuously used in this state, the casting nozzle 10 could be used for 95 days ("life" in Table 1).
reference).

(Examples 8 to 14) Examples 1 to 7 were repeated, except that titanium boride TiB ₂ was mixed in an amount of 95.0% by weight with respect to 5.0% by weight of the mixture of chromium Cr and carbon black C.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 1.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

To (Example 15-21) mixture 7.5 wt% of chromium Cr and carbon black C, except that the blended titanium boride TiB ₂ only 92.5 wt%, was repeated Examples 1-7, respectively.

The casting nozzle 10 was as shown in FIG. 3 when the outer surface of the protective layer 12 subjected to the polishing treatment in the case of Example 18 (the same applies hereinafter) was photographically observed with an optical microscope. That is, it was found that the recesses formed by the falling off of the titanium boride particles 20 were arranged in a scattered manner, and the bonding layer 30 had no pores and was dense.

The casting nozzle 10 fractured the protective layer 12 by an appropriate force, and the fractured surface was photographically observed with a scanning electron microscope, and it was as shown in FIG. That is, it was found that intragranular fracture occurred in the titanium boride TiB ₂ particles 20, and the titanium boride TiB ₂ particles 20 were strongly bonded by the bonding layer 30. The bonding layer 30 is formed by X-ray diffraction analysis and EP
MA analysis revealed that the reaction between titanium boride TiB ₂ , chromium Cr and carbon black C TiB ₂ + 2Cr + C → 2CrB + TiC resulted in a mixed solid solution matrix layer of chromium boride CrB and titanium carbide TiC (see FIGS. (See Fig. 11).

The casting nozzle 10 had its outer surface etched by immersing the protective layer 12 in aqua regia heated to 60 ° C. for 3 minutes, and then photograph-observed with an optical microscope.
It was as shown in FIG. That is, it was found that the average particle size of the titanium boride TiB ₂ particles 20 was kept at _{2 to 4} μm by measuring the recesses formed by the titanium boride TiB ₂ particles 20 falling off by the etching treatment. In other words, it was found that the titanium boride TiB ₂ particles 20 did not grow much compared to the beginning. This is because chromium Cr and carbon black C cause a reaction of TiB ₂ + 2Cr + C → 2CrB + TiC during sintering, and the growth of titanium boride TiB ₂ particles 20 is suppressed. Also titanium boride TiB ₂ particles
It was also found by X-ray diffraction analysis and EPMA analysis that a grain boundary phase 21 composed of a mixed solid solution phase of titanium boride TiB ₂ and chromium Cr was formed near the grain boundary of 20 (Fig. 7). ~
(See Figure 11).

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 1.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

(Examples 22 to 28) Examples 1 to 7 were repeated, except that titanium boride TiB ₂ was mixed in an amount of 90.0% by weight with respect to 10.0% by weight of a mixture of chromium Cr and carbon black C.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 1.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

Examples 29 to 35 Examples 1 to 7 were repeated except that titanium boride TiB ₂ was added in an amount of 87.5% by weight to 12.5% by weight of a mixture of chromium Cr and carbon black C.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 1.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

(Examples 36 to 42) Examples 1 to 7 were repeated, except that 85.0% by weight of titanium boride TiB ₂ was added to 15.0% by weight of a mixture of chromium Cr and carbon black C.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 1.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

(Examples 43 to 49) Examples 1 to 7 were repeated except that titanium boride TiB ₂ was added in an amount of 82.5% by weight to 17.5% by weight of a mixture of chromium Cr and carbon black C.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 1.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

(Examples 50 to 56) Examples 1 to 7 were repeated except that 80.0% by weight of titanium boride TiB ₂ was added to 20.0% by weight of a mixture of chromium Cr and carbon black C.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 1.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

(Examples 57 to 63) Examples 1 to 7 were repeated except that titanium boride TiB ₂ was added in an amount of 77.5% by weight to 22.5% by weight of a mixture of chromium Cr and carbon black C.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 1.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

(Examples 64-70) Examples 1-7 were repeated except that titanium boride TiB ₂ was added in an amount of 75.0% by weight based on 25.0% by weight of a mixture of chromium Cr and carbon black C.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 1.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

(Examples 71 to 77) Except that 7.5% by weight of a mixture of chromium Cr and carbon black C was mixed with 92.5% by weight of titanium boride TiB ₂ and the sintering temperature was 1500 ° C. Example 1
~ 7 was repeated.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 2.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Examples 78-84 Examples 71-77 were repeated except that the sintering temperature was 1600 ° C.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 2.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Examples 85-91 Examples 71-77 were repeated except that the sintering temperature was 1700 ° C.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body 11 of the casting nozzle 10 were measured and found to be as shown in Table 2.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Examples 92-98 Examples 71-77 were repeated except that the sintering temperature was 1800 ° C.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. Nozzle book of casting nozzle 10 The Vickers hardness, flexural strength, porosity, coefficient of thermal expansion and thermal conductivity of the body 11 were measured and found to be as shown in Table 2.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Examples 99-105 Examples 71-77 were repeated except that the sintering temperature was 1900 ° C.

Vickers hardness of the protective layer 12 of the casting nozzle 10
The bending strength, the porosity, the coefficient of thermal expansion, the thermal conductivity, the thermal shock resistance, and the wettability with respect to the low melting point molten metal were measured. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the main body 11 of the casting nozzle 10 were measured and found to be as shown in Table 2.

The life of the casting nozzle 10 was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Comparative Example 1 Examples 1-70 were repeated except that chromium Cr and carbon black C were removed from the ceramic formulation.

That is, 100 parts of titanium boride TiB ₂ having an average particle size of 3 μm, a maximum particle size of 6 μm, and a purity of 99% by weight is accommodated in an appropriate mold together with 2 parts of polyvinyl alcohol as a binder, and 300 kg / cm ² A ceramic green compact was created by applying pressure and uniaxially pressing.

The ceramic powder compact is CIPed by applying a pressure of 300 kg / cm ^2.
A ceramic molded body was obtained by performing a treatment, that is, a normal temperature isostatic pressing treatment.

The ceramic molded body was heated to a temperature of 1900 ° C. at a temperature rising rate of 15 ° C./min in an unpressurized argon atmosphere and maintained at a temperature of 1900 ° C. for 1 hour to obtain a ceramic sintered body. did.

The ceramics sintered body was subjected to finishing processing, that is, the inner surface was mainly polished to a desired accuracy to obtain a protective layer divided body.

On the other hand, the nozzle body was formed using brass having a thermal expansion coefficient close to that of the protective layer.

A plurality of protective layer divided bodies were bonded to the inner peripheral surface of the nozzle body using an appropriate adhesive (in this case, an inorganic adhesive), and the protective layer was arranged. This produced the casting nozzle.

The casting nozzle fractured the protective layer with an appropriate force, and the fractured surface was photographically observed with a scanning electron microscope.
It was as shown in the figure. That is, the intergranular fracture of titanium boride TiB ₂ particles occurs predominantly, and titanium boride TiB ₂
It was found that the bonds between the particles were not very strong.

In addition, Vickers hardness, transverse rupture strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance, and wettability of low melting point molten metal were measured for the protective layer of the casting nozzle. It was as it was. The Vickers hardness, bending strength, porosity, thermal expansion coefficient, and thermal conductivity of the nozzle body of the casting nozzle were measured and found to be as shown in Table 1.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

Comparative Example 2 Examples 1-7 were repeated except that carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
The results are shown in Table 1. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
The results are shown in Table 1.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

Comparative Example 3 Examples 8-14 were repeated except that carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
The results are shown in Table 1. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
The results are shown in Table 1.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

Comparative Example 4 Examples 15-21 were repeated except that carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
The results are shown in Table 1. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
The results are shown in Table 1.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

Comparative Example 5 Examples 22-28 were repeated except that carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
The results are shown in Table 1. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
The results are shown in Table 1.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

Comparative Example 6 Examples 29-35 were repeated except that carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
The results are shown in Table 1. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
The results are shown in Table 1.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

Comparative Example 7 Examples 36-42 were repeated except that the carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
The results are shown in Table 1. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
The results are shown in Table 1.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

Comparative Example 8 Examples 43-49 were repeated except that carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
The results are shown in Table 1. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
The results are shown in Table 1.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

Comparative Example 9 Examples 50-56 were repeated except that carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
The results are shown in Table 1. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
The results are shown in Table 1.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

Comparative Example 10 Examples 57-63 were repeated except that the carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
The results are shown in Table 1. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
The results are shown in Table 1.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

Comparative Example 11 Examples 64-70 were repeated except that carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
The results are shown in Table 1. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
The results are shown in Table 1.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 1.

Comparative Example 12 Examples 71-77 were repeated except that chromium Cr and carbon black C were removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
Each was as shown in Table 2. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
Each was as shown in Table 2.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Comparative Example 13 Examples 78-84 were repeated except that chromium Cr and carbon black C were removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
Each was as shown in Table 2. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
Each was as shown in Table 2.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Comparative Example 14 Examples 85-91 were repeated except that chromium Cr and carbon black C were removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
Each was as shown in Table 2. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
Each was as shown in Table 2.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Comparative Example 15 Examples 92-98 were repeated except that chromium Cr and carbon black C were removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
Each was as shown in Table 2. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
Each was as shown in Table 2.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Comparative Example 16 Examples 99-105 were repeated except that chromium Cr and carbon black C were removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
Each was as shown in Table 2. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
Each was as shown in Table 2.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Comparative Example 17 Examples 71-77 were repeated except that the carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
Each was as shown in Table 2. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
Each was as shown in Table 2.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Comparative Example 18 Examples 78-84 were repeated except that carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
Each was as shown in Table 2. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
Each was as shown in Table 2.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Comparative Example 19 Examples 85-91 were repeated except that carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
Each was as shown in Table 2. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
Each was as shown in Table 2.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Comparative Example 20 Examples 92-98 were repeated except that carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
Each was as shown in Table 2. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
Each was as shown in Table 2.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Comparative Example 21 Examples 99-106 were repeated except that the carbon black C was removed from the ceramic formulation.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
Each was as shown in Table 2. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
Each was as shown in Table 2.

The life of the casting nozzle was measured in the same manner as in Examples 1 to 7, and was as shown in Table 2.

Comparative Example 22 Comparative Example 1 above was repeated except that the ceramic formulation was silicon nitride Si ₃ N ₄ .

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
The results are shown in Table 3, respectively. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
The results are shown in Table 3, respectively.

Further, the life of the casting nozzle is the same as that of Comparative Example 1 and then Example 1.
It was as shown in Table 3 when measured in the same manner as in the above.

Comparative Example 23 Comparative Example 1 above was repeated except that the ceramic formulation was silicon carbide SiC.

Vickers hardness, flexural strength, porosity, coefficient of thermal expansion, thermal conductivity, thermal shock resistance and wettability against low melting point molten metal were measured for the protective layer of the casting nozzle.
The results are shown in Table 3, respectively. In addition, regarding the nozzle body of the casting nozzle, Vickers hardness, bending strength,
When the porosity, thermal expansion coefficient and thermal conductivity were measured,
The results are shown in Table 3, respectively.

Further, the life of the casting nozzle is the same as that of Comparative Example 1 and then Example 1.
It was as shown in Table 3 when measured in the same manner as in the above.

As is clear from a comparison between Examples 1 to 105 and Comparative Examples 1 to 23 described above, according to the present invention, a boride of chromium is formed on a portion in contact with the low melting point molten metal, that is, on the inner peripheral surface of the nozzle body. By arranging a matrix layer formed by mixing and solid-dissolving titanium carbide with titanium boride particles and arranging a protective layer formed by a titanium boride ceramics sintered body having a porosity of 5% or less, It can improve Vickers hardness, bending strength, porosity and thermal shock resistance of the part that comes into contact with the low melting point molten metal, thus avoiding preheating during use and sufficiently suppressing the reaction with the low melting point molten metal. Its life can be greatly extended.
Further, according to the present invention, by forming the nozzle body with a material having a coefficient of thermal expansion close to that of the titanium boride ceramics sintered body, sufficient thermal strain between the protective layer and the nozzle body. It can be suppressed, and as a result, its life can be extended.

In the above description, the protective layer is disposed on the inner peripheral surface of the nozzle body after being sintered, but the present invention is not limited to this, and is applied to the inner peripheral surface of the nozzle body. The protective layer may be formed by arranging the ceramic mixture by coating and then sintering the mixture.

In addition, in the above, only the portion that contacts the low-melting-point molten metal (in the above, the protective layer) is formed of the titanium boride ceramics sintered body, but the present invention is not limited to this. Nozzle body of casting nozzle 10 '
As is clear from Fig. 13 in which 11 'is formed entirely by the titanium boride ceramics sintered body, it is included when the whole, that is, even the portion not contacted with the low melting point molten metal is formed by the titanium boride ceramics sintered body. is doing.

(3) Effects of the Invention As is clear from the above, the low melting point molten metal treating tool according to the present invention is a low melting point molten metal treating tool which is brought into contact with a low melting point molten metal, and particularly, a chromium boride and A matrix layer mixed and solid-dissolved with titanium carbide is arranged between the titanium boride particles, and 5%
Since the titanium boride ceramics sintered body having the following porosity forms at least the portion in contact with the low melting point molten metal, (i) the Vickers hardness of the portion in contact with the low melting point molten metal , It has the effect of improving the transverse strength, porosity and thermal shock resistance, and (ii) it has the effect of avoiding preheating during use, and (iii) sufficiently suppresses the reaction with low melting point molten metal. It has an effect that can be achieved, and consequently (iv) has an effect that the life can be extended.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing a casting nozzle as an embodiment of a low melting point molten metal treating tool according to the present invention, and FIG. 2 is arranged with respect to an inner peripheral surface of a nozzle body of the embodiment shown in FIG. FIG. 3 is an enlarged cross-sectional view showing the protective layer, FIG. 3 is an optical micrograph showing the structure of the surface of the protective layer that has been subjected to the polishing treatment of FIG. 1, and FIG. 4 shows the structure of the fracture surface of the protective layer of FIG. Scanning electron micrograph, FIG. 5 is an optical micrograph showing the structure of the surface of the protective layer which was subjected to the etching treatment of FIG. 1, and FIG.
FIG. 7 is a scanning electron micrograph showing the structure of the surface of the protective layer which has been subjected to the etching treatment of the example, FIG. 7 is a scanning electron micrograph showing the structure of the surface of the protective layer which has been subjected to the polishing treatment of the example of FIG.
FIG. 8 is a copy of FIG. 7, FIG. 9 is an X-ray intensity distribution diagram showing the results of EPMA analysis, that is, electron probe microanalysis of the texture of the protective layer surface after polishing treatment of the embodiment of FIG. 1, FIG. (A) is an X-ray intensity distribution photograph showing the result of EPMA analysis, that is, electron probe microanalysis of the structure of the protective layer surface after polishing treatment in FIG. 1 embodiment, and FIG. 10 (b) is the polishing of FIG. 1 embodiment. An X-ray intensity distribution photograph showing the results of EPMA analysis of the surface of the treated protective layer, that is, electron probe microanalysis, FIG. 10 (c) is a duplicated drawing made by superimposing FIGS. 10 (a) and (b), FIG. 11 is a graph showing the result of X-ray diffraction analysis of the protective layer of FIG. 1, and FIG. 12 is a scanning electron microscope showing the structure of the fracture surface of the protective layer of the casting nozzle shown as Comparative Example 1. FIG. 13 is a photograph showing another embodiment of the low melting point molten metal treating tool according to the present invention. It is a partial sectional view showing a forming nozzle. 10 , 10 ′ …… Nozzle for casting 11,11 ′ …… Nozzle body 12 …… Protective layer 20 …… Titanium boride particles 21 …… Grain boundary phase 30 …… Matrix layer

Claims (4)

[Claims] 1. A low melting point metal treating tool which is contacted with a low melting point molten metal, wherein a matrix layer of a mixed solid solution of a boride of chromium and titanium carbide is arranged between the titanium boride particles and 5 A low melting point molten metal treating tool, characterized in that at least a portion in contact with the low melting point molten metal is formed by a titanium boride ceramics sintered body having a porosity of not more than%. 2. The portion which is not in contact with the low melting point molten metal is formed of a material having a coefficient of thermal expansion close to that of the titanium boride ceramics sintered body. The low melting point molten metal treatment tool according to the item (1). 3. A low melting point according to claim 2, wherein the material having a coefficient of thermal expansion close to that of the titanium boride ceramics sintered body is formed of brass. Molten metal processing tool. 4. Titanium boride particles having an average particle size of 0.5 to 8 μm, according to any one of claims (1) to (3). Low melting point molten metal processing tool.