JP2806511B2 - Manufacturing method of sintered alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an alloy-based sintered body which can be applied to a part requiring wear resistance, such as a blade, a gear, a shaft, and the like.

[0002]

2. Description of the Related Art Conventionally, ceramic materials or alloy materials have been used for such applications. Use of Ceramic Material There is a ceramic sintered product in which a ceramic powder for a raw material and an organic binder are mixed, molded into a predetermined shape by injection molding or direct pressure molding, the binder is removed by heat treatment, and then sintered. The sintered product manufactured in this way has a hardness of Hv = 2000 or more, but has a drawback that it is liable to chip or crack due to lack of toughness.

[0003] On the other hand, when an alloy material is used, a metal material that is awarded as a super-hard material has excellent toughness, but has a surface hardness (Hv = about 1100) of a ceramic sintered product. 2000 or more), and it is difficult to say that the abrasion resistance is sufficient. Therefore, an attempt has been made to improve the wear resistance by forming a film having wear resistance on the surface of the metal and forming a composite. Specifically, a film such as TiN or ZrN is formed on the metal surface by a method such as a sputtering method or a CVD method. In this case, the interface between the metal and the film formed on the surface of the metal has a boundary surface that is inherently formed when a heterogeneous material is compounded. It is practically difficult to make the thickness sufficiently thick, and there is a problem that a sufficient abrasion resistance cannot be ensured because the thickness is limited.

[0004]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention can provide an alloy-based sintered body having a large surface hardness, excellent abrasion resistance, and hardly causing chipping or cracking. It is an object to provide a method having suitability for mass production.

[0005]

Means for Solving the Problems In order to solve the above problems, in the method for producing an alloy-based sintered body of the present invention, Cr: 20 to
35% by weight , Ni: 2 to 25% by weight, Al: 2 to 8% by weight, Ti: 0.5% by weight or less, Zr, Y, Hf, Ce,
One or more of La, Nd and Gd: 0.05 to 1.0% by weight, Fe: A ferrite alloy (hereinafter referred to as “Al-containing ferrite alloy”) powder composed of the balance is prescribed. Is sintered at a temperature of 1250 to 1400 ° C. in a non-oxidizing atmosphere by heating, and then heat-treated in an oxidizing gas atmosphere to precipitate an alumina component on the surface. "A
ferrite alloy containing l, not containing Ti
Can also be used.

[0006] As non-oxidizing atmosphere, inert gas atmosphere or, - reducing gas atmosphere, and further include vacuum atmosphere. The heat treatment temperature during sintering in a non-oxidizing atmosphere is set to a temperature range of 1250 to 1400 ° C. If the temperature is out of this range, the applicable molding pressure range may be narrowed.

As a ferrite alloy containing Al, Fe
-Cr-Al-based alloys and Fe-Cr-Ni-Al-based alloys. The hardness of the base material of these alloys depends on the type and content of the metal elements constituting the alloy, and Hv = 200.
Hv = 300 or more, or the value is different. Even though Fe-Cr-Al alloys generally satisfy toughness, their hardness is Hv = 200 or less, and therefore they are not suitable for applications requiring hardness (for example, mechanical parts such as gears and shafts).

Therefore, the type of the ferrite alloy containing Al is selected according to the application. For applications requiring a hardness of Hv = 300 or more, an Fe-Cr-Ni-Al-based alloy is suitable. In particular, the composition is Cr: 20 to 35% by weight: N
i: 2 to 25% by weight, Al: 2 to 8% by weight, Ti: 0.
5% by weight or less, any one or more of Zr, Y, Hf, Ce, La, Nd and Gd: 0.05 to
1.0% by weight, Fe: Fe-Cr-Ni-
Al-based ferrite alloys are most suitable. Knife, or
It is easy to obtain sintered products suitable for machine parts requiring wear resistance such as gears and shafts .

Hereinafter, the present invention will be described more specifically. First, for example, Cr: 20 to 35% by weight: Ni: 2
-25% by weight, Al: 2-8% by weight, Ti: 0.5% by weight or less, Zr, Y, Hf, Ce, La, Nd and Gd
Any one or more of them: 0.05 to 1.0
The ferrite alloy powder containing Al is obtained by dissolving all the components in a mixing ratio of substantially wt%, and the balance being substantially Fe, and pulverizing the alloy by, for example, an atomizing method or pulverizing the alloy by a mechanical pulverizing method. .

The Al-containing ferrite alloy powder thus obtained is mixed with an organic binder, and molded (formed) into a predetermined shape using a mold by a method such as injection molding or direct pressure molding to obtain a molded body. . This compact is a product shaped into the shape of a product or part according to the application, and is different from a base material such as an ingot that is subjected to processing such as grinding in the next step. As an example of an organic binder,
Organic compounds such as polyvinyl alcohol (PVA) and ethylene glycol are exemplified.

In the case of the present invention, the pressure during molding is 400
There is also application of pressure as low as about MPa, usually 400 to 1
It is selected from the range of about 000 MPa or about 450 to 600 MPa. However, the pressure during molding is 400M
If it is less than Pa, there is a tendency that dimensional accuracy and the like are difficult to appear.
Next, this compact is sintered by heat treatment in a non-oxidizing atmosphere. Heat treatment is 1250-14
It is performed at 00 ° C (preferably 1300 to 1400 ° C). Within this heat treatment temperature range, sufficient hardness (Hv = about 300) and tensile strength of 100 kg / mm without forming a liquid phase.
As a result, a base material having sufficient strength can be obtained as a mechanical component.

The reason for performing the heat treatment in a non-oxidizing atmosphere is that if oxidation occurs, sintering does not proceed and the toughness of the alloy cannot be secured. In the case of an inert gas atmosphere,
For example, an inert gas such as argon or helium is used. In the case of a reducing gas atmosphere, for example, hydrogen gas or the like is used. Since the sintered body obtained in this way is a sintered body of a ferrite alloy powder, unlike the base material of ceramic, before alumina deposition, there is no cracking or chipping, and a machine such as grinding and polishing is used. There is an advantage that machining or electric discharge machining can be easily performed. Therefore, if necessary, machining or electric discharge machining can be performed before the deposition of alumina.

In the case of a conventional ceramic material, it is difficult to obtain dimensional accuracy due to shrinkage of about 20% due to sintering. However, since processing is difficult, it is difficult to increase dimensional accuracy in post-processing. Even in the case of a cemented carbide material, post-processing such as cutting and grinding is not easy, and dimensional accuracy is also difficult to obtain. In any case, it is not suitable for use where precision is required.

However, in the case of the present invention, as described above, the dimensional accuracy can be increased by machining such as grinding and polishing or electric discharge machining without causing cracks or chips before the deposition of alumina. Therefore, the present invention can be sufficiently applied to places where dimensional accuracy is required. Next, the sintered body is subjected to a heat treatment at, for example, a temperature exceeding 1000 ° C. in an atmosphere or an oxidizing gas atmosphere such as an oxygen gas to deposit an alumina (aluminum oxide) component on the surface. By this heat treatment, for example, Fe—Cr—Ni— with a surface layer (alumina film) containing alumina as a main component is used.
An Al alloy sintered product is completed.

Here, the reason why the component deposited on the surface of the alloy constituting the sintered body is limited to alumina is that when heat treatment is performed in an oxidizing gas atmosphere, the Al element is easily oxidized and the alumina is made of high hardness. This is because ceramic can be generated. The alloy-based sintered body thus obtained has a surface layer containing alumina as a main component and thus has a high surface hardness, and has excellent toughness because the base material that fills the inside of the sintered body is an alloy. In addition, when a ceramic film is formed on a metal surface by a sputtering method, a CVD method, or the like, an interface is formed between the film and the metal base material, so that the adhesion strength between the film and the base material is small, and furthermore, While sufficient abrasion resistance cannot be obtained because the thickness of the coating layer is limited,
The surface layer comprising alumina as a main component according to the present invention has high adhesion strength to the base material because the roots of alumina are stretched in the base material, and the thickness of this surface layer can be increased to 10 to 50 μm. . Furthermore, it can be formed into the desired shape by the steps of molding and sintering, and can be manufactured without processing such as inefficient cutting. In this case, it is required for industrial production. Economic efficiency and the effect of mass production are also remarkable. In other words, it is suitable for mass production.

Articles to which the method of the present invention can be applied include the following. [Cutters for household use] Electric razor blades, hair clippers (especially pet clippers and garden tree clippers that can bite pebbles, etc.), mowers, cooking mixers, cutters and other blades , Knives, scissors, do-it-yourself saw blades, etc.

[Cutters used for business] Various band saw blades,
Tools such as rotary blades, cutting tools, dies, and screws for kneading machines. [Abrasion resistant parts] Electric drill blades, drill chuck parts, gears, rotating shafts, bearings, etc.

[0018]

In the alloy-based sintered body obtained by the method of the present invention, the alumina component forming the surface layer is formed in the alloy that fills the interior, so that the adhesive strength between the surface layer and the alloy is increased. The precipitation of alumina on the surface has the effect of increasing the surface hardness, and the alloy filling the inside of the sintered body has the effect of increasing the toughness of the sintered body.

Forming and sintering to a desired shape improves the economical efficiency and mass productivity required for industrial production, so that mass production suitability is obtained. In addition, the sintered alloy before sintering and before the precipitation of alumina can be processed to exactly match a predetermined shape without causing chipping or cracking, so that dimensional accuracy can be improved. Also, the present invention can be applied to a case where precision is required.

[0020]

Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments. -Example 1- An alloy having a composition of 24 wt% of Cr, 4 wt% of Ni, 3.5 wt% of Al, 0.05 wt% of Zr, and the balance of Fe was melted in a high frequency melting furnace. 1-2m of ingot made
m, and the obtained plate was cut into chips having a size of 2 to 3 mm and then pulverized to obtain a ferrite alloy powder having a size of 50 mesh or less.

After mixing PVA as a binder with this powder to form a slurry, the powder was filled in a cavity for molding a gear in which ridges were arranged in parallel, and a gear before sintering was molded by direct pressure molding. The green gear as a molded body was sintered at 1250 ° C. for 5 hours in an argon gas atmosphere to obtain a sintered body. Next, heating was performed at 1150 ° C. for 10 hours in the air to deposit alumina on the surface, and as a result, a gear having a gray surface was obtained.

Table 1 shows the surface hardness of the sintered body on which the alumina was precipitated, the hardness of the internal alloy (shown as base material hardness), and the content of the alumina component on the surface. In addition,
When the cross section of the surface layer was observed with an electron microscope, it was confirmed that as the alumina progressed from the surface to the inside, the protrusion of the needle stuck into the internal alloy.

Example 2 Cr: 30% by weight, Ni: 21% by weight, Al: 6% by weight, Ti: 0.5% by weight, Zr: 0.2% by weight, balance:
An alloy having a composition of Fe was melted in a high-frequency melting furnace, and the resulting ingot was turned into a ferrite alloy powder by an atomizing method. Then, molding, sintering, and heat treatment were performed in the same manner as in Example 1.

Table 1 shows the surface hardness of the obtained sintered body, the hardness of the alloy (shown as base material hardness), and the content of the alumina component on the surface. In addition, when the cross section of the surface layer was observed with an electron microscope, it was confirmed that alumina was in a state where needle-like projections pierced the alloy inside as the alumina progressed from the surface to the inside. -Example 3-An alloy having a composition of 26% by weight of Cr, 21% by weight of Ni, 6.5% by weight of Al, 0.2% by weight of Zr, and the balance: Fe was melted in a high-frequency melting furnace, and was formed. After turning the ingot into a ferrite alloy powder by an atomizing method, a gear before sintering was molded in the same manner as in Example 1. The green gear, which was a molded body, was sintered at 1350 ° C. for 5 hours in a hydrogen gas atmosphere to obtain a sintered body. Next, heating was performed at 1150 ° C. for 10 hours in the air to deposit alumina on the surface, and as a result, a gear having a gray surface was obtained.

Table 1 shows the surface hardness of the sintered body on which the alumina was precipitated, the hardness of the internal alloy (shown as base material hardness), and the content of the alumina component on the surface. In addition,
When the cross section of the surface layer was observed with an electron microscope, it was confirmed that as the alumina progressed from the surface to the inside, the protrusion of the needle stuck into the internal alloy.

Reference Examples 1 and 2 Table 1 shows the hardness (in this case, the surface hardness is equal to the base material hardness) of SKH5 which is a hard metal material and alumina which is a ceramic material, as Reference Examples 1 and 2, respectively. I will write it together.

[0027]

[Table 1]

Example 4 Cr: 32% by weight, Ni: 21% by weight, Al: 6.5% by weight, Zr: 0.8% by weight, balance: Fe, and then pulverized by atomizing. Fe-Cr-Ni-
An Al-based ferrite alloy powder was obtained. The alloy powder thus obtained and PVA for a binder were mixed, and 45
It was molded at a pressure of 0 MPa. Next, the formed body was sintered by performing a heat treatment at 1350 ° C. for 3 hours in a vacuum, followed by grinding to precisely match a predetermined shape. Next, a heat treatment is performed in the atmosphere at 1150 ° C. for 20 hours and a heat treatment at 1250 ° C. for 30 minutes to form an alumina film, and air-cooled to cool the Fe—Cr—Ni—Al-based sintered product (alloy-based sintered product). Body).

Example 5 An Fe—Cr—Ni—Al sintered product was obtained in the same manner as in Example 4 except that the molding pressure was 600 MPa. Example 6 Cr: 24% by weight, Ni: 4% by weight, Al: 3.5% by weight, Zr: 0.05% by weight, and the balance being substantially Fe was melted in a high frequency melting furnace. Thus, an alloy ingot was obtained. This ingot is rolled to a thickness of 1 to 2 mm, and the plate is cut into chips of 2 to 3 mm square.
Mechanically pulverized, Fe-Cr-Ni of 50 mesh or less
-An Al-based ferrite alloy powder was obtained.

The alloy powder thus obtained and PVA for a binder were mixed and molded under a suitable pressure in the range of 1000 MPa. Next, the molded body was sintered by performing a heat treatment at 1300 ° C. for 5 hours in an argon gas atmosphere, and then ground and accurately adjusted to a predetermined shape. Next, a heat treatment is performed in air at 1150 ° C. for 20 hours and a heat treatment at 1250 ° C. for 30 minutes to form an alumina film, and air-cooled to form Fe—Cr—Ni—A.
An 1-type sintered product was obtained.

Example 7 Cr: 35% by weight, Ni: 21% by weight, Al: 7% by weight, Zr: 0.4% by weight, and the balance substantially consisting of Fe was melted in a high frequency melting furnace. It was pulverized by an atomizing method to obtain an Fe-Cr-Ni-Al ferrite alloy powder. The alloy powder thus obtained and PV for binder
A was mixed and molded at an appropriate pressure in the range of 700 MPa. Next, the compact is placed in a vacuum at 1350
After sintering by heat treatment at 4 ° C. for 4 hours, it was ground and adjusted to a predetermined shape. Next, in air, heat treatment at 1150 ° C. for 20 hours and 1250 ° C.
A heat treatment was performed for 30 minutes to form an alumina film, and the resultant was air-cooled to obtain a Fe-Cr-Ni-Al-based sintered product.

Example 8 The procedure of Example 7 was repeated except that the molding pressure was 900 MPa and the heat treatment temperature for sintering was 1300 ° C.
An e-Cr-Ni-Al-based sintered product was obtained. -Example 9-The alloy powder used in Example 4 was classified to have an average particle size of 30 µm or less, and about 10% by weight of paraffin wax.
Knead with a binder containing stearic acid as a main component,
Injection molding was performed at 50 ° C. into a predetermined shape. The obtained molded body was degreased while being kept at 400 ° C. for 50 hours in a vacuum. The degreased molded body was sintered in vacuum at 1350 ° C. for 3 hours, and then oxygen gas was fed into the furnace and held at 1250 ° C. for 30 minutes to deposit an alumina film on the surface. Fe
-A Cr-Ni-Al based sintered product was obtained.

Example 10 An injection-molded product obtained in the same manner as in Example 9 was degreased by holding it at 500 ° C. for 50 hours in an argon gas atmosphere. The degreased molded body is heated to 1350 ° C. in an argon gas atmosphere at 3350 ° C.
After sintering for a time, the gas in the furnace was replaced with oxygen gas, and the temperature was maintained at 1250 ° C. for 30 minutes to deposit an alumina film on the surface to obtain a Fe—Cr—Ni—Al-based sintered product. Was.

Example 11 The same procedure as in Example 9 was carried out except that the alloy powder used in Example 7 was classified and an alloy powder having a size of 30 μm or less was used.
An e-Cr-Ni-Al-based sintered product was obtained. Examples 4 to 11
The state of the alumina film, the base material hardness and the dimensional accuracy of the sintered product of Example 1 were examined. The results are shown in Table 2. In Table 2,
○ in the data column of the dimensional accuracy indicates that the dimensional error is less than 5%.

[0035]

[Table 2]

From the results shown in Table 2, it can be seen that the sintered products of Examples 4 to 11 have good dimensional accuracy, high surface hardness, and are strong. FIG. 1 is an optical microscope photograph (700 times magnification) showing the metal structure near the surface of the Fe—Cr—Ni—Al sintered product with an alumina film of Example 4.
In the photograph of FIG. 1, the white portion with black spots, which occupies substantially the lower half, is the base material, the black layer above it is the alumina film, and the black layer above it is the protective Ni film. FIG. 2 is an Fe—Cr—Ni—Al with an alumina coating of Example 4.
It is an optical microscope photograph (700 times magnification) showing the metal structure inside a system sintered product. FIG. 3 schematically shows the outline of the metal structure near the surface of the sintered product of Example 4. In the base material portion of FIGS. 1 and 2, as shown in FIG. 2, the black portion is a cavity, the gray portion is a NiAl phase, and the white portion is a ferrite phase. FIG. 3 shows that an alumina film 2 is formed on the surface of a base material 3 and a protective N
3 illustrates a certain configuration of the i-film 3.

In Example 4, when the treatment temperature for sintering was 1200 ° C., the base material hardness tended to be insufficient. Then, in Example 6, an Fe-Cr-Ni-Al-based sintered product was obtained in exactly the same manner except that the molding pressure was 350 MPa, but the dimensional accuracy (error exceeded 5%), the base material hardness and The alumina film states tended to be considerably inferior to those of Example 6.

[0038]

As described above, according to the present invention, it is possible to obtain a useful alloy-based sintered body having a high surface hardness and excellent abrasion resistance which is not easily chipped or cracked.
Very useful because of its suitability for mass production. In particular,
By using a ferrite alloy powder containing Al having a specific composition as described above, by sintering under the specific temperature conditions described above ,
There is an advantage that an alloy-based sintered body suitable for applications requiring both surface hardness and base material hardness, such as mechanical parts, can be reliably obtained.

[Brief description of the drawings]

FIG. 1 is an optical micrograph (× 700) showing a metal structure near the surface of a sintered product of Example 4.

FIG. 2 is an optical micrograph (× 700) showing a metal structure inside a sintered product of Example 4.

FIG. 3 is an explanatory view schematically showing a metal structure near the surface of a sintered product of Example 4.

[Explanation of symbols]

 1 Protective Ni film 2 Alumina film 3 Base material

Continuing on the front page (72) Inventor: Tadashi Hamada, Kazuma, Kazuma, Osaka 1048, Matsushita Electric Works, Ltd. Masao 1048 Kazuma Kadoma, Kadoma City, Osaka Pref. Matsushita Electric Works, Ltd.

Claims (5)

(57) [Claims] 1. Cr: 20-35% by weight , Ni: 2-2
5% by weight, Al: 2 to 8% by weight, Ti: 0.5% by weight or less, any one or more of Zr, Y, Hf, Ce, La, Nd and Gd: 0.05 to A ferrite alloy powder consisting of 1.0% by weight, Fe: balance is molded into a predetermined shape in a non-oxidizing atmosphere at 1250-1%.
A method for producing an alloy-based sintered body, comprising sintering by heating at a temperature of 400 ° C. and heat-treating in an oxidizing gas atmosphere to precipitate an alumina component on the surface. 2. Cr: 20 to 35% by weight, Ni: 2-2.
5% by weight, Al: 2 to 8% by weight, Zr, Y, Hf, C
any one or two of e, La, Nd and Gd
Species or more: 0.05 to 1.0% by weight, Fe: the balance
A molded body made by molding ferrite alloy powder into a predetermined shape
Heat at a temperature of 1250-1400 ° C in an oxidizing atmosphere
And heat treatment in an oxidizing gas atmosphere
Feature to precipitate alumina component on the surface
A method for producing an alloy-based sintered body. 3. The method for producing an alloy-based sintered body according to claim 1, wherein the non-oxidizing atmosphere is an inert gas atmosphere. 4. The method for producing an alloy-based sintered body according to claim 1, wherein the non-oxidizing atmosphere is a reducing gas atmosphere. 5. The method for producing an alloy-based sintered body according to claim 1, wherein the non-oxidizing atmosphere is a vacuum atmosphere.