JP2001303233A - Member for molten metal excellent in erosion resistance to molten metal and producing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a member for molten metal having extremely excellent erosion resistance and releasing property from a mold to the molten metal and excellent heat-fatigue characteristic, mechanical characteristic and wear resistance, and the producing method thereof. SOLUTION: A hard sintered alloy which contains Mo, Cr, Fe, B and further, Mn, rare earth elements, Si and/or Al and limits the contents of Mo, Cr, B in the fixed ranges, or further, suitably contains W, Nb, Zr, Ti, Ta, Hf, Ni and/or Co, V and is composed of a combined phase of fine biboride and Fe group, is heated in the atmosphere to form the oxide film on the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member for molten metal having excellent corrosion resistance to molten metal and a method for producing the same. More specifically, the present invention relates to a member for molten metal in which an oxide is formed on the surface of the member in direct contact with the molten metal, thereby significantly improving the corrosion resistance to the molten metal, and a method for producing the same.

[0002]

2. Description of the Related Art A typical member used in direct contact with a molten metal is a member for a die casting machine part. Die casting machine is plunger, sleeve,
It is constituted by a molding die and is used in direct contact with a metal in a molten state, for example, aluminum, zinc, magnesium or the like. For this reason, the characteristics required for these components in common are: corrosion resistance to the molten metal, such as not being eroded (melted) by the molten metal, and not forming a reaction layer;
There are abrasion resistance and thermal fatigue resistance. Conventionally, tool steel or hot tool steel (SKD) has been used as a member for these parts.
61) has been used, but there is a problem that the life is short due to insufficient corrosion resistance to the molten metal.

[0003] Therefore, in addition to having high hardness and high strength, M has excellent corrosion resistance to molten metal.
o ₂ FeB ₂ type double boride based hard sintered alloy (JP-B 60-5)
No. 7499) applied to die casting parts,
Significant life extension was obtained. However, it has been found that when this member is used for a long time, the reaction between the metal binding phase of the member and the molten metal proceeds, and a problem occurs in that the corrosion resistance and the releasability are reduced. In recent years, attempts have been made to form a thermal spray coating of a ceramic such as alumina or zirconia on the surface of a member in order to improve corrosion resistance and mold release properties against molten metal. However, these thermal spray coatings are susceptible to cracks and peeling such as heat check and heat cracks, and the expected improvement in durability has not been obtained.

Japanese Patent Application Laid-Open Nos. 5-148588 and 9-217167 disclose that the corrosion resistance of members is improved by providing an oxide film on the surface of steel, cast iron, and stainless steel. I have. However, the formed oxide film has problems such as poor adhesion to the member, very thinness, and low hardness, and cannot be applied to plungers and sleeves requiring abrasion resistance strength.

[0005]

SUMMARY OF THE INVENTION In the present invention, the Mo ₂ FeB ₂ type double boride type hard sintered alloy has improved corrosion resistance to molten metal and releasability, and exhibits extremely excellent durability. By developing a hard sintered alloy, a member for molten metal that has extremely excellent corrosion resistance and releasability to molten metal, and also has excellent thermal fatigue properties, mechanical properties, and wear resistance, and a method for producing the same. The purpose is to provide.

[0006]

The molten metal member of the present invention having excellent corrosion resistance to molten metal is obtained by forming an oxide film on the surface of a member made of a hard sintered alloy, which is in direct contact with the molten metal. The member is made of Mo ₂ FeB ₂ type double boride and Fe
Is a hard sintered alloy consisting of groups bonded phase, also the oxide film is Mo, Cr, Fe, a metal element and oxygen B mainly from _{(Fe, Mo, Cr, B} ) m O n -type composite oxide Characterized in that the film is In addition, the hard sintered alloy contains 3 to 7.5% of B, 21 to 79.9% of Mo, and 2 to 30%.
% Of Cr, the balance consisting of 10% or more of Fe and inevitable impurities, and 0.1 to 8% of Mn with respect to the total composition of the hard sintered alloy. Contains at least one or more selected from rare earth elements in a total amount of 0.01 to 5% with respect to the total composition of the hard sintered alloy.
One or both of Si and / or Al are contained in a total amount of 0.03 to 10%, and a part of the Mo content contained in the hard sintered alloy is set to 0% with respect to the total composition. .1 to 30% of W, and a part of the Mo content contained in the hard sintered alloy,
0.1% to 10% of Nb is substituted with respect to the entire composition, and a part of the Mo content contained in the hard sintered alloy is calculated by adding the total of both W and Nb to the entire composition. And a part or all of the Nb content contained in the hard sintered alloy is Zr,
By substituting any one or more of Ti, Ta and Hf, and furthermore, F contained in the hard sintered alloy
e is 0.1 to 20% in total of one or both of Ni and / or Co with respect to the total composition.
Substitution, and furthermore, a part of the Cr content contained in the hard sintered alloy is 0.1 to 25% with respect to the whole composition.
V. Further, the method for producing a member for molten metal having excellent corrosion resistance to molten metal according to the present invention comprises heating any one of the above members in air or an oxidizing atmosphere at 773K or more to form an oxide on the surface. Features.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method of heating a Mo ₂ FeB ₂ type double boride type hard sintered alloy (hereinafter referred to as a base material) in the air or an oxidizing atmosphere to form a B, Mo , F
By forming a stable and dense oxide film mainly composed of e, Cr and oxygen, when used as a member for a molten metal, the molten metal has extremely excellent corrosion resistance and releasability against the molten metal. To provide a member for use.
In the hard sintered alloy serving as the base material of the member for molten metal of the present invention, the content of B, Mo, and Cr is limited to a certain range, so that the fine double boride and the Fe-based bonding phase can be combined. A phase structure is obtained, and not only excellent strength and thermal fatigue characteristics (thermal shock resistance) can be obtained, but also a surface treatment layer composed of the oxide film can be densely and stably formed. Also,
By including Mn in the base material, the mechanical properties of the base material, the corrosion resistance and self-healing properties of the surface treatment layer are improved, and by further including a rare earth element, the corrosion resistance of the surface treatment layer, and the base material The adhesion of the surface treatment layer is improved. Furthermore, the inclusion of Si and Al improves the corrosion resistance of the surface treatment layer, and the inclusion of W improves the mechanical properties of the base material and the corrosion resistance and wear resistance of the surface treatment layer. Furthermore, by including Nb, Zr, Ti, Ta, and Hf, the corrosion resistance and abrasion resistance of the surface treatment layer are improved, and by including Ni and / or Co, the thermal shock resistance and high-temperature strength of the base material are improved. And the addition of V further improves the mechanical properties of the base material and the self-healing properties of the surface treatment layer. Hereinafter, the present invention will be described in detail.

[0008] The present inventors have achieved excellent
Mo with strength and thermal fatigue properties (thermal shock resistance)_TwoFeB_Two
Type double boride based hard sintered alloy is
Has been found to exhibit excellent corrosion resistance to minium.
Was. However, this Mo _TwoFeB_TwoDouble boride type hard
If the sintered alloy contacts the molten metal for a long time,
The mixed phase reacts with the molten metal, and the corrosion resistance and release properties tend to decrease.
And further improvement of corrosion resistance to molten metal is necessary.
It turned out to be. Therefore, as a result of various studies, Mo_Two
FeB_TwoOxide bobbin hard sintering alloy
By forming a surface treatment layer consisting of a film,
Does not react with molten metal even if used, or seizure occurs
Without release agent applied to the surface
Not only can easily release the peeled metal (release properties), but also
Dramatically improved durability with no check
I found that.

[0009] This oxide film, which is the main constituent elements of the matrix Mo, Cr, Fe, composed of a metal element and oxygen B mainly _{(Fe, Mo, Cr, B} ) m O n -type This is because the stable and dense surface treatment layer, which is a composite oxide, serves as a protective film and significantly improves and improves the corrosion resistance to molten metal. The molten metal member of the present invention selectively contains Mn, Si, Al, W, Nb, Zr, Ti, and T in addition to the above four elements.
a, Hf, Ni, Co, and V may be added. In this case, the oxide film formed on the alloy surface is Mo, C
It is formed from the above selectively added elements and oxygen in addition to r, Fe, and B. Mo, Cr, Fe,
When B is not contained, the bonding strength of the surface treatment layer is weak,
In addition, the adhesiveness to the base material is reduced, so that cracks and peeling are likely to occur, and the wear resistance is not sufficient. Specific examples of the composite oxide include (Fe, Mo, Cr, B) 2 O 3 and (F
e, Mo, Cr, B) 3 O4, (Fe, Mo, Cr, B)
O, (Fe, Mo, Cr, B) O3, (Fe, Mo, C
r, B) O2.7-2.9, (Fe, Mo, Cr, B) O2
And the like.

Since the above-mentioned composite oxide is obtained by oxidizing a Mo ₂ FeB ₂ type double boride, the base material has an alloy composition mainly composed of Mo, Cr, Fe and B.
_It must be a ₂ FeB ₂ type double boride hard sintered alloy. In the hard sintered alloy, B is an essential element for forming a double boride as a hard phase of the base material of the molten metal member of the present invention and a surface treatment layer. Further, the surface treatment layer containing B has an effect of improving the adhesion to the base material. If the B content is less than 3%, the ratio of the hard phase is less than 35%, and the mechanical properties are poor. On the other hand, when the content exceeds 7.5%, the proportion of the hard phase exceeds 95%, and the strength and the thermal shock resistance decrease. Therefore, the B content is limited to 3 to 7.5%.

Mo, like B, is an essential element for forming a double boride and a surface treatment layer. In the base material, a part thereof forms a solid solution in the binder phase of the hard alloy to improve the mechanical strength of the base material. However, when the content exceeds an appropriate amount (79.9%), an intermetallic compound such as M ₆ C-type carbide is formed, and the strength of the base material is reduced. On the other hand, the content is 21%
If it is less than 3, Fe boride such as Fe ₂ B is formed, so that the strength of the base material is reduced. Therefore, the Mo content is 21 to 7
Limited to 9.9%.

Similar to Mo, Cr not only improves the mechanical properties by uniformly dissolving in the base material but also in the hard phase as well as the binder phase, and also improves the stable and dense Cr in the surface treatment layer. Is an element indispensable for the formation of a composite oxide combined with However, when the content exceeds 30%, an intermetallic compound such as chromium carbide (Cr ₃ C ₂ ) is formed, and the strength of the base material is reduced. On the other hand, if it is less than 2%, the amount of Cr in the surface treatment layer becomes insufficient, and the corrosion resistance is reduced. Therefore, the Cr content is limited to 2 to 30%.

Mn suppresses the grain growth of the double boride of the base material,
By refining the alloy structure, mechanical properties are significantly improved. In addition, by adding Mn, a sintered body having a good shape with little shape collapse at the time of sintering is obtained, and the effect of forming a near net is exhibited. Further, Mn has a strong affinity with oxygen, so that the surface treatment layer has a self-healing property and enhances the durability of the member. If the content is less than 0.1%, the effect of improving the properties is not recognized, and if the content exceeds 8%, the mechanical properties of the base material deteriorate. Therefore, the content of Mn is limited to 0.1 to 8% based on the entire composition.

The rare earth element has an effect of improving the adhesion between the surface treatment layer and the base material. In addition, even when two or more of these elements are contained, the same effect as in the case where these elements are contained alone can be obtained. If the content is less than 0.01%, no effect of improving properties is observed. If the content exceeds 5%, not only the effect is not so much improved, but also the rare earth element is expensive, which leads to an increase in cost. Therefore, the content of the rare earth element is limited to 0.01 to 5% of the total composition.

Si and Al are dispersed in the composite oxide,
The surface treatment layer is further densified and strengthened. If the content is less than 0.03%, the effect of improving the properties is not recognized. If the content exceeds 10%, the strength of the base material decreases. Therefore, the contents of Si and Al are limited to 0.03 to 10% based on the total composition.

W is an element that can be substituted for Mo, and not only has the effect of improving the strength of the base material, but also improves the corrosion resistance and wear resistance of the surface treatment layer.
However, if the content of Mo is less than 0.1%, the effect of improving the properties is not recognized. On the other hand, if the content exceeds 30%, not only the effect is not recognized, but also the specific gravity of the member increases, and the product weight increases. Therefore, the content of W is limited to 0.1 to 30% of the entire composition.

Nb, Zr, Ti, Ta, and Hf are elements that can be substituted for Mo. They are dissolved in the double boride of the base material and partially form other hard particles (boride, oxide,
Carbides and nitrides) to improve mechanical properties. Further, since these elements have a strong affinity for oxygen, they are combined with the composite oxide, and are effective in forming a denser surface treatment layer having excellent adhesion. In addition, these elements
The same effect can be obtained even if the compound is contained alone or in combination. However, if the content is less than 0.1%, no improvement effect is recognized, and if the content exceeds 10%, the sinterability of the hard alloy is reduced and not only the strength is reduced, but also these elements are reduced. Is expensive and causes an increase in cost. Therefore, the content of Nb, Zr, Ti, Ta, and Hf is 0.1 to 10 in total of one or more of the total composition.
%.

Ni and Co form a solid solution in the Fe-based bonding phase, thereby improving the thermal shock resistance and high-temperature strength of the hard alloy. If the content is less than 0.1%, the effect of improving the properties is not recognized, and if the content exceeds 20%, the effect of improving the characteristics is not recognized. Therefore, the contents of Ni and Co are limited to 0.1 to 20% based on the total composition.

V is an element that can be substituted for Cr, and the mechanical properties of the base material can be improved by adding a small amount of V. Further, the surface treatment layer has an effect of improving self-healing properties. When the content is less than 0.1%, the effect of improving the properties is not recognized. When the content is more than 25%, the adhesion of the oxide film is reduced, which may cause impurities to be mixed into the molten metal. Therefore, the content of V is 0.1 to 2 with respect to the total composition.
Limited to 5%.

[0020] The hard alloy of the present invention contains, in addition to the above component elements,
The balance is made of Fe. Fe is an element constituting the double boride and the binder phase, and is indispensable for forming the composite oxide constituting the surface treatment layer. In the hard alloy of the present invention, if the Fe content is less than 10%, not only the double boride cannot be sufficiently formed, but also the F in the binder phase cannot be sufficiently formed.
e Insufficient content lowers strength. Therefore, the hard alloy of the present invention needs to contain 10% or more of Fe. When Fe cannot be contained in the hard alloy of the present invention in an amount of 10% or more, it goes without saying that the content of each element other than Fe is reduced within the allowable range to contain 10% or more of Fe.

The main unavoidable impurity elements contained in the hard sintered alloy of the present invention are P, S, N, C and the like. It is desirable to minimize this. If the total content of these elements is 1% or less, the effect on the mechanical properties is relatively small.

Next, a method of manufacturing a member for a molten metal according to the present invention will be described. First, a method for manufacturing a hard alloy as a base material will be described. Fe, Mo, Cr, Mn, Si, A
1, W, Nb, Zr, Ti, Ta, Hf, Ni, Co,
V, powder of a B alloy comprising one or more rare earth elements and B, or powder of an alloy comprising these B alloy powders and one or more of these elements, or B
Simple substance and Fe, Mo, Cr, Mn, Si, Al, W, N
b, Zr, Ti, Ta, Hf, Ni, Co, V, a rare earth element simple substance powder, or B simple substance and one or two of these
Powders composed of more than one kind of alloy are blended so as to have a predetermined alloy composition, wet-pulverized in an organic solvent using a vibrating ball mill or the like, granulated, molded, and the molded body is vacuum, in a reducing gas, Alternatively, it is manufactured by liquid phase sintering in a non-oxidizing atmosphere such as in an inert gas.

The double boride as the hard phase of the hard alloy is formed by the reaction of the raw material powder during sintering. Double boride consisting of element or B
By reacting a single powder with powders of Mo and Fe and the above-mentioned selectively added elements in a furnace, Mo
₂ FeB ₂ type double boride is produced, and further,
A powder in which Mo, Ni, Co, and the powder of the above-mentioned selectively added element are blended so as to have a predetermined alloy composition may be used.

The liquid phase sintering is usually performed at a sintering temperature of 1373 to 1673K for 5 to 90 minutes. When the sintering temperature is lower than 1373K, a liquid phase does not sufficiently appear, a sintered body having many pores is obtained, and sufficient strength cannot be obtained. On the other hand, when the sintering temperature is 16
When the temperature exceeds 73K, the liquid phase appears sufficiently, but the crystal grains become coarse and the strength decreases. On the other hand, if the sintering time is less than 5 minutes, the diffusion of elements is not sufficient, and the density is not sufficiently increased. On the other hand, if the sintering is performed for more than 90 minutes, no further increase in strength is observed, and in some cases, the strength may be reduced. By sintering under the sintering conditions under which the liquid phase appears, the pores disappear, and a hard alloy having a density of almost 100% is obtained. Hot isostatic pressing, hot pressing, as a method of eliminating pores without the appearance of a liquid phase,
There are an electric current sintering method and the like, and even by using these methods, pores can be eliminated. These methods may be used in combination with the liquid phase sintering method.

The hard alloy obtained as described above, which is the base material of the molten metal member of the present invention, can be used not only as a single sintered body but also as a composite material by joining with a steel material. It is. That is, the hard alloy of the present invention can be used not only by brazing to a steel material like a cemented carbide, but also by directly joining to a steel material without using a brazing material, and a strong bond is obtained. . It is also possible to apply a sinter joining method in which sintering and steel are joined at the same time.For steel, the composite material can be used as a die-casting member for molten metals such as aluminum without causing a decrease in strength due to thermal damage. In the case where the molten metal is used, only parts where corrosion resistance and wear resistance are required for the molten metal, by using the hard alloy, which is the parent phase of the molten metal member of the present invention, to the minimum necessary, the member such as a mold Can be manufactured at a low price. Next, a method for producing a surface treatment layer to be formed on the surface of the base material obtained as described above will be described.

The obtained base material is machined into a desired shape, the treated surface is cleaned and degreased, and then maintained at a temperature of 773 to 1873K for 5 minutes to 30 hours in the air or an oxidizing atmosphere. An oxide film with an appropriate amount is formed. Means for forming the surface treatment layer of the present invention include a high-temperature atmospheric oxidation method and a high-temperature wet hydrogen oxidation method, but are not particularly limited. When the treatment temperature is lower than 773K, an oxide film having a sufficient thickness for obtaining excellent corrosion resistance is not formed even if the treatment is performed for a long time. On the other hand, when the treatment is performed at a treatment temperature exceeding 1873K, the oxide film is peeled off. If the treatment time is less than 5 minutes, the formation of an oxide film having a sufficient thickness is not recognized, and even if the treatment is carried out for more than 30 hours, the growth of the oxide film is not only saturated, but also exfoliated, and the cost is reduced. Leads to a rise. Therefore, the surface treatment is 773-18.
5 minutes to 30 hours at a temperature of 73K, preferably 873 to 1
Perform at 273K for 1-20 hours. As a means for forming the oxide film, not only a high-temperature heat treatment in an oxidizing atmosphere but also an anodic electrolysis method or a pressurized steam method can be used. Hereinafter, the present invention will be described specifically with reference to examples.

[0027]

EXAMPLES (Examples) B powder and metal powder are shown in Tables 1 to 3.
After adjusting to the compounding ratio shown in 5, the mixture was wet-mixed and ground in acetone for 25 hours using a vibration ball mill. The powder obtained by pulverizing with a ball mill is dried and granulated, and the obtained fine powder is press-molded into a predetermined shape, and then the degree of vacuum: ≤1.3P
Heated at a heating rate of 10 K / min in the vacuum of a, 1373-
After heating at a temperature of 1673 K for 30 minutes, the furnace was cooled to obtain a sintered alloy. The obtained sintered alloy was processed into a desired shape, degreased, heated in the air under the heating conditions shown in Tables 6 to 14, furnace-cooled, and the surface of the sintered alloy surface comprising a composite oxide film A treatment layer was formed to obtain a member for molten metal. Some of the sintered alloys were subjected to the following property evaluation without being subjected to the heat treatment for comparison.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

[Table 5]

The strength, corrosion resistance, and thermal shock resistance of the hard alloy and molten metal members shown in Tables 6 to 14 obtained as described above were evaluated as follows. [Strength] A test piece is cut out from a sintered hard alloy or a member for molten metal obtained by subjecting the hard alloy to heat treatment in the atmosphere, and the bending strength (three-point bending test) is measured based on JIS H5501. did. The greater the transverse rupture strength, the better the strength, and those exceeding 1.5 GPa are the subject of the present invention.
The results are shown in Tables 6 to 14.

[Corrosion Resistance] A sintered hard alloy and a member for molten metal obtained by subjecting the hard alloy to a heat treatment in the atmosphere were cut into a size of 10 mm × 10 mm × 100 mm to obtain a test piece. (Aluminum alloy for die casting: JIS-A)
After immersion in DC10) for 6 hours, the test piece was cut out in a cross section perpendicular to the longitudinal direction, the cross section was observed with an optical microscope, and the depth at which the test piece was eroded from the surface by the molten aluminum was measured. Was used to evaluate the corrosion resistance. ：: Erosion depth <5 μm, good releasability Δ: Erosion depth ≧ 5 μm and <30 μm, releasability slightly poor ×: Erosion depth ≧ 30 μm, poor releasability The results are shown in Tables 6 to 14. Those marked with ^# in the table are
It refers to the case where the effect of improving the effect is not recognized even if the specific element is added more than necessary.

[Thermal shock resistance] A hard alloy as sintered and a member for molten metal obtained by subjecting the hard alloy to a heat treatment in the atmosphere are cut into a size of 10 mm × 10 mm × 100 mm. A 5 mm wide cut was made into a test piece having a width of 5 mm. The test pieces were heated in the air at 773K and were visually observed for cracks generated after being put into water, and the thermal shock resistance was evaluated. Tables 6 to 14 show the results.

[0036]

[Table 6]

[0037]

[Table 7]

[0038]

[Table 8]

[0039]

[Table 9]

[0040]

[Table 10]

[0041]

[Table 11]

[0042]

[Table 12]

[0043]

[Table 13]

[0044]

[Table 14]

As shown in Tables 6 to 14, the molten metal member of the present invention is excellent in corrosion resistance and thermal shock resistance.

[0046]

According to the present invention, Mo, Cr, Fe, B and Mn, a rare earth element, Si and / or Al are further contained, and the contents of Mo, Cr and B are limited to a certain range, or Further, W, Nb, Zr, Ti, Ta, Hf,
A hard sintered alloy composed of fine double borides and an Fe-based binder phase, which contains Ni and / or Co, V, etc. as appropriate, is heated in air to form an oxide film on the surface. A metal member that exhibits excellent corrosion resistance and thermal shock resistance to molten metal.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 33/02 103 C22C 33/02 103A 38/00 304 38/00 304 (72) Inventor Shinya Ozaki Yamaguchi 1394 Nishi-Toyoi, Kudamatsu City Inside Kotetsu Kogyo Co., Ltd. (72) Inventor Kenichi Takagi 1296-1, Higashi-Toyoi, Kudamatsu City, Yamaguchi Prefecture

Claims (14)

[Claims] 1. A member for molten metal excellent in corrosion resistance to molten metal, characterized in that an oxide film is formed on a surface of a member made of a hard sintered alloy, which is in direct contact with the molten metal. 2. The member is a hard sintered alloy comprising a Mo ₂ FeB ₂ type double boride and an Fe-based bonded phase.
A member for molten metal according to claim 1, which has excellent corrosion resistance to the molten metal. 3. The oxide film is mainly composed of Mo, Cr, Fe, B metal elements and oxygen (Fe, Mo, Cr, B) _m O.
_The molten metal member having excellent corrosion resistance to molten metal according to claim 1 or 2, wherein the member is a film made of an _n- type composite oxide. 4. A hard sintered alloy comprising 3 to 7.5% by weight (hereinafter referred to as%) of B, 21 to 79.9% of Mo, and 2 to 3% by weight.
The molten metal member having excellent corrosion resistance to molten metal according to claim 3, characterized in that it is composed of 0% Cr, the balance being 10% or more of Fe and inevitable impurities. 5. The composition according to claim 1, wherein the total composition of the hard sintered alloy is 0.1%.
The member for molten metal excellent in corrosion resistance to molten metal according to claim 3 or 4, characterized by containing 部 材 8% of Mn. 6. The hard sintered alloy contains 0.01 to 5% in total of one or two or more rare earth elements selected from the total composition of the hard sintered alloy. 3 ~
The member for molten metal excellent in corrosion resistance to the molten metal according to any one of the above items 5. 7. The hard sintered alloy contains 0.03 to 10% of one or both of Si and / or Al with respect to the total composition of the hard sintered alloy. A member for molten metal excellent in corrosion resistance to molten metal according to any one of 6. 8. The method according to claim 3, wherein a part of the Mo content contained in the hard sintered alloy is replaced with 0.1 to 30% of W with respect to the whole composition. The member for molten metal excellent in corrosion resistance to the molten metal according to any one of the above. 9. The method according to claim 3, wherein a part of the Mo content contained in the hard sintered alloy is replaced by 0.1 to 10% of Nb with respect to the entire composition. The member for molten metal excellent in corrosion resistance to the molten metal according to any one of the above. 10. The method according to claim 1, wherein a part of the Mo content contained in the hard sintered alloy is replaced by 0.2 to 30% of the total composition of both W and Nb. Item 3
7. A member for molten metal excellent in corrosion resistance to molten metal according to any one of items 7 to 7. 11. A method in which part or all of the Nb content contained in a hard sintered alloy is replaced with one or more of Zr, Ti, Ta, and Hf.
The molten metal member according to claim 9, which has excellent corrosion resistance to the molten metal. 12. A part of the Fe content contained in the hard sintered alloy is substituted by 0.1 to 20% in total of one or both of Ni and / or Co with respect to the entire composition. The member for molten metal excellent in corrosion resistance to molten metal according to any one of claims 3 to 11, characterized in that: 13. The method according to claim 3, wherein a part of the Cr content contained in the hard sintered alloy is replaced by V of 0.1 to 25% with respect to the whole composition. The member for molten metal excellent in corrosion resistance to the molten metal according to any one of the above. 14. The member according to claim 1, wherein the member is heated in air or an oxidizing atmosphere at a temperature of 773 K or more to form an oxide on the surface thereof. Excellent method for producing molten metal members.