JP2980301B2 - Manufacturing method of ferrite alloy sintered body - 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 a ferrite alloy sintered body applicable to parts requiring wear resistance, such as blades, gears, shafts, and chucks.

[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.

When an alloy material is used On the other hand, a metal material which is awarded as a super-hard material has excellent toughness, but has a surface hardness (Hv = 1100) of that of a ceramic sintered product (Hv = 2000). Above), 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, for example, by a method such as a sputtering method or a CVD method,
A film such as TiN or ZrN is formed on the metal surface.
In this case, the interface between the metal and the coating formed on the surface of the metal has a boundary surface that is formed uniquely 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.

Therefore, the inventors have found that the surface hardness is large,
In order to obtain a ferrite alloy sintered body having excellent abrasion resistance and hardly causing chipping or cracking, and to find a method having suitability for mass production, studies were conducted from various angles. As a result, Fe-Cr-Ni-Al
Achieved the purpose if the molded body obtained by molding the base ferrite alloy powder into a predetermined shape is sintered in a non-oxidizing atmosphere, and heat treatment is performed in an oxidizing gas atmosphere to precipitate the alumina component on the surface. It has been found that significant progress has been made in. By subjecting the surface of the obtained sintered body to a heat treatment in an oxidizing gas atmosphere, a hard and sufficiently thick ceramic film mainly composed of an alumina component is formed on the surface. However, this ceramic film was not sufficient in terms of adhesion and could not be said to be perfect, indicating that there was room for improvement.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a ferrite alloy sintering method in which a ceramic film for improving the surface hardness and abrasion resistance is firmly adhered to the surface and is hardly chipped or cracked. It is an object to provide a method capable of obtaining a body and having suitability for mass production.

[0006]

Means for Solving the Problems In order to solve the above problems, a method for producing a ferrite alloy sintered body according to the present invention comprises:
Cr: 15 to 40% by weight: Ni: 2 to 25% by weight, A
1: 2 to 8% by weight, Zr, Y, Ce, Hf, La, Nd
And any one or more of Gd: 1-2.
5% by weight (excluding 1.0% by weight), Ti: 0
0.5% by weight, Fe: Fe-Cr- having a composition consisting of the balance
A compact formed by molding a Ni-Al-based ferrite alloy powder is sintered in a non-oxidizing atmosphere and then heat-treated in an oxidizing gas atmosphere to precipitate an alumina component on the surface.

[0007] Fe-Cr-Ni-Al in the present invention
Ferrite alloy powder (hereinafter referred to as "ferrite alloy powder")
Abbreviated as "): 25 to 35% by weight of Cr: 2 to 25% of Ni
% By weight, Al: 2 to 8% by weight, Zr, Y, Ce, Hf,
Any one or more of La, Nd and Gd: 1 to 2.5% by weight (but not including 1.0% by weight);
The composition is preferably composed of Ti: 0 to 0.5% by weight and Fe: the balance, Cr: 25 to 35% by weight: Ni: 1
5 to 25% by weight, Al: 2 to 8% by weight, Zr, Y, C
e, one or more of Hf, La, Nd and Gd: 1 to 2.5% by weight (excluding 1.0% by weight); Ti: 0 to 0.5% by weight; Fe: More preferably, the composition is composed of the balance.

The non-oxidizing atmosphere in the present invention includes an inert gas atmosphere and a reducing gas atmosphere in addition to a vacuum atmosphere. The heat treatment temperature during sintering in a non-oxidizing atmosphere is preferably in the range of 1300 to 1400 ° C. Of course, the heat treatment temperature at the time of sintering is not limited to this range, but if it is outside the temperature range of 1300 to 1400 ° C., there is a disadvantage that the applicable molding pressure range is narrowed.

Hereinafter, the present invention will be described more specifically. First, Cr: 15 to 40% by weight: Ni: 2 to 25% by weight, Al: 2 to 8% by weight, Zr, Y, Ce, Hf, L
one or more of a, Nd and Gd:
1 to 2.5% by weight (excluding 1.0% by weight), T
i: 0 to 0.5% by weight, Fe: The remainder is substantially dissolved at a compounding ratio of Fe, for example, by pulverizing the alloy by atomization or pulverizing the alloy by mechanical pulverization. , To obtain ferrite alloy powder.

The ferrite alloy powder thus obtained is mixed with an organic binder, and molded (formed) into a predetermined shape by 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.
Examples of the organic binder include organic compounds such as polyvinyl alcohol (PVA) and paraffin wax.

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 a range of about 000 MPa or about 650 to 850 MPa. However, the pressure during molding is 400M
If it is less than Pa, there is a tendency that dimensional accuracy and the like cannot be sufficiently obtained. Next, this compact is sintered by heat treatment (firing) in a non-oxidizing atmosphere. The heat treatment is performed at 1250 to 1400 ° C. (preferably 1300 to 14
(00 ° C.). Within this heat treatment temperature range, sufficient hardness and tensile strength can be imparted without generating a liquid phase, and 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, dimensional accuracy is hardly obtained 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, before alumina deposition, dimensional accuracy can be increased by mechanical processing such as grinding and polishing or electric discharge machining without generating cracks or chips. 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 ceramic film (alumina film) containing alumina as a main component
-An Al ferrite alloy sintered body 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 a ceramic film can be formed. The alloy sintered body thus obtained has a ceramic film 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 film thickness of the film is limited, the ceramic film containing alumina as a main component according to the present invention has a structure in which the roots of alumina are stretched in the base material and the base material has a problem. Has a high adhesion strength, and the thickness of this ceramic film is 10
It can be increased to ５０50 μm, and sufficient abrasion resistance can be obtained. Furthermore, it can be formed into the desired shape by the molding and sintering steps, 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.

Next, the reasons for limiting the contents of the elements contained in the ferrite alloy powder according to the present invention will be described. The ferrite alloy powder of the present invention is an Fe-based alloy powder containing a large amount of Cr and Al, which are ferrite-forming elements, and Ni, which is an austenite-forming element. The reason why the alloy is mainly made into a ferrite phase is as follows. It is. The ferrite phase alloy is made of thick alumina (Al ₂
O ₃ ) A film is easily formed, but the austenitic phase alloy is not uniformly formed with a film containing alumina as a main component, and peels off.

[Cr: 15 to 40 wt%] Cr is necessary to form a dense and uniform ceramic coating mainly composed of alumina on the surface of the alloy. However, since the alloy of the present invention contains Ni, In order to make the alloy into a ferrite phase, even if Ni is the lower limit and Al is the upper limit, 15 wt.
% Or more of Cr is required. Alloys with a Ni content of the lower limit, an Al content near the upper limit, and a Cr content of less than 15 wt% have incomplete ceramic film formation. Therefore, the lower limit of Cr is 15% by weight. Further, as the Cr content in the alloy increases, the tendency of embrittlement increases, so the upper limit of Cr is 40%.
wt%.

[Ni: 2 to 25 wt%] Ni is presumed to precipitate fine NiAl in the alloy to improve the mechanical properties (eg, hardness) of the base material. Is an element indispensable for precipitating NiAl. In order to be effective enough to improve mechanical properties, 2 wt.
% Or more of Ni is required. If the amount of Ni increases, Ni
Although it is convenient for the precipitation of Al, if the content of Ni, which is an austenite-forming element, is increased,
And the content of Al needs to be increased. But,
If the amount of Ni exceeds 25% by weight, the amount of Cr must be increased, which tends to cause embrittlement. Therefore, the upper limit of Ni is 25% by weight.

[Al: 2 to 8 wt%] Al is fine N
iAl is an element indispensable for precipitating iAl in the alloy and for forming a ceramic film mainly composed of alumina on the surface of the alloy by high-temperature oxidation treatment. In order to form a dense and uniform film, it is necessary to contain 2 wt% or more of Al. An increase in the Al content is advantageous for the precipitation of NiAl and the formation of a ceramic film. However, when the content exceeds 8% by weight, the workability of the alloy is reduced.
%.

[One or more of Zr, Y, Ce, Hf, La, Nd and Gd: (total)
1 to 2.5% by weight (but not including 1% by weight; that is, in the range of more than 1% by weight to 2.5% by weight or less)] One of these elements is selectively added. , Mixed into the ceramic coating to improve the brittleness of the coating and to disperse as internal oxide particles in the alloy immediately below the coating to improve the adhesion of the coating. In previous studies by the inventors, it was considered that the total content of Zr, Y, Ce, Hf, La, Nd and Gd was preferably 1% by weight or less, but if the content was 1% by weight or less, Oxidation occurs before heat treatment for precipitation of the alumina component. Therefore, the roots of the ceramic coating containing alumina as a main component are not more than about 30 per mm in cross-sectional observation, and in particular, less than 0.05% by weight. This is less than about this level, and the adhesion of the film is not sufficient. In the case of the present invention, since the content exceeds 1% by weight, the root of the film is appropriate and the adhesion is high. However, if the content exceeds 2.5% by weight, the main component of the film is zirconia (Hv = 1500).
And other components such that the hardness of the ceramic coating is Hv = 1.
It is reduced to about 700 or less, and sufficient surface hardness cannot be secured.

[Ti: 0 to 0.5% by weight] Ti is added as needed, and has advantages such as forming a fine intermetallic compound and helping toughening the alloy. However,
If the content exceeds 0.5% by weight, the properties of the ceramic coating may be impaired, so the upper limit is limited to 0.5% by weight.

[Fe: balance] Fe occupies other than the above components. However, the present invention is not limited to the case where the remainder is completely Fe, and there may be unavoidable impurities (such as Si) present in Fe. 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 or garden tree clippers that can bite pebbles, etc.), mowers, cooking mixers, cutters, etc. , 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.

[0024]

In the sintered alloy obtained by the production method of the present invention, since the alloy composition of the ceramic alloy powder is appropriate, a thick ceramic film mainly composed of an alumina component is formed on the surface and the surface hardness is high. And abrasion resistance is sufficient. The ceramic coating is made of Zr, Y, Ce, H
Since the contents of f, La, Nd and Gd are appropriate,
Since the alumina component forming the film acts sufficiently to spread the roots in the alloy filling the inside to increase the adhesion between the film and the alloy, the adhesion of the ceramic film is high.

In addition, the alloy filling the inside of the sintered body has a high toughness of the sintered body and does not cause cracking or chipping. Forming and sintering to a desired shape improves the economic efficiency and mass productivity required for industrial production, and thus suits for mass production. 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.

[0026]

Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments. -Example 1-Cr: 32.0% by weight, Ni: 21.0% by weight, Al:
6.5% by weight, Zr: 2.0% by weight, balance: substantially F
The alloy having the composition e was melted in a high-frequency melting furnace and pulverized by an atomizing method to obtain a ferrite alloy powder.

The obtained powder was mixed with PVA for a binder, and then molded at a pressure of 700 MPa. Next, the compact was heat-treated at 1350 ° C. for 3 hours in a vacuum, sintered, and then subjected to grinding to conform to a predetermined shape. Next, after heat treatment in air at 1150 ° C. for 20 hours, heat treatment in air at 1250 ° C. for 30 minutes is performed to deposit an alumina component to form a ceramic film on the surface, and then air-cooled to form Fe—Cr—Ni. -An Al-based ferrite alloy sintered product was obtained.

When the cross section of this sintered product was observed with an optical microscope, the ceramic film was deposited so as to be rooted on the base material, and the frequency of the roots of this ceramic film was very high, about 70 per mm. Admitted. -Example 2-Cr: 35.0% by weight, Ni: 21.0% by weight, Al:
7.0% by weight, Zr: 1.2% by weight, balance: substantially F
The alloy having the composition e was melted in a high-frequency melting furnace and pulverized by an atomizing method to obtain a ferrite alloy powder.

The obtained powder was mixed with PVA for a binder, and then molded at a pressure of 800 MPa. Next, the compact was heat-treated at 1350 ° C. for 4 hours in a vacuum and sintered, and then ground to conform to a predetermined shape. Next, after heat treatment in air at 1150 ° C. for 20 hours, heat treatment in air at 1250 ° C. for 30 minutes is performed to deposit an alumina component to form a ceramic film on the surface, and then air-cooled to form Fe—Cr—Ni. -Al
A ferrite alloy sintered product was obtained.

When the cross section of this sintered product was observed with an optical microscope, the ceramic film was deposited so as to be rooted on the base material, and the frequency of the roots of this ceramic film was considerably large at about 40 per mm. Admitted. -Example 3-Cr: 33.0% by weight, Ni: 21.0% by weight, Al:
5.8% by weight, Zr: 1.5% by weight, balance: substantially F
The alloy having the composition e was melted in a high-frequency melting furnace and pulverized by an atomizing method to obtain a ferrite alloy powder. Then, the alloy powder was classified, and about 1 μm was added to the alloy powder having a size of 30 μm or less.
A binder having 0% by weight of paraffin wax and a binder mainly containing stearic acid was kneaded, and injection-molded at a temperature of 150 ° C. to obtain a molded article having a predetermined shape.

The obtained molded body was first placed in a vacuum at 400
After holding at a temperature of 50 ° C. for 50 hours and degreasing, holding at 1350 ° C. for 3 hours in a vacuum, sintering the molded body, feeding oxygen gas into the furnace and holding at 1250 ° C. for 30 minutes. Then, an alumina component was precipitated to form a ceramic film on the surface, and the resultant was air-cooled to obtain a Fe-Cr-Ni-Al-based ferrite alloy sintered product.

When the cross section of this sintered product was observed with an optical microscope, the ceramic film was deposited so as to be rooted on the base material, and the frequency of the roots of this ceramic film was very large at about 60 per mm. Admitted. -Comparative Example 1-Cr: 35.0% by weight, Ni: 21.0% by weight, Al:
7.0 wt%, balance: An alloy having a substantially Fe composition was melted in a high-frequency melting furnace and pulverized by an atomizing method to obtain a ferrite alloy powder.

The obtained powder was mixed with PVA for a binder, and then molded at a pressure of 800 MPa. Next, the compact was heat-treated at 1350 ° C. for 4 hours in a vacuum, sintered, and then ground to conform to a predetermined shape. Next, after heat treatment in air at 1150 ° C. for 20 hours, heat treatment in air at 1250 ° C. for 30 minutes is performed to deposit an alumina component to form a ceramic film on the surface, and then air-cooled to form Fe—Cr—Ni. -An Al-based ferrite alloy sintered product was obtained.

When the cross section of this sintered product was observed with an optical microscope, the ceramic film was deposited in parallel with the base material.
There was almost no portion that was precipitated like a root. Further, depending on the cooling rate after the formation of the ceramic film in an oxygen atmosphere, peeling of the ceramic film may occur. -Comparative Example 2-Cr: 33.0% by weight, Ni: 21.0% by weight, Al:
An alloy having a composition of 3.2% by weight, Zr: 2.7% by weight, and the balance: Fe was melted in a high-frequency melting furnace and pulverized by an atomizing method to obtain a ferrite alloy powder. Then, the alloy powder was classified, and about 10% by weight was added to the alloy powder having a size of 30 μm or less.
Was kneaded with a binder mainly composed of paraffin wax and stearic acid, and injection molded at a temperature of 150 ° C. to obtain a molded article having a predetermined shape.

The obtained molded body was first placed in a vacuum at 400
After holding at a temperature of 50 ° C. for 50 hours and degreasing, holding at 1350 ° C. for 3 hours in a vacuum, sintering the molded body, feeding oxygen gas into the furnace and holding at 1250 ° C. for 30 minutes. After forming a ceramic film on the surface,
-A sintered product of a Cr-Ni-Al ferrite alloy was obtained. Observation of the cross section of this sintered product with an optical microscope revealed that the ceramic film was deposited so as to be rooted on the base material, and the frequency of the roots of this ceramic film was very high, about 90 per mm. . However, this ceramic film contains zirconia as a main component and has a low hardness, and therefore does not have a sufficient surface hardness.

With respect to the sintered products of the examples and the comparative examples, the number of roots and the surface hardness of the ceramic film were measured. The measurement results are as follows. Number of roots of ceramic coating (number / mm) Surface hardness (HV) Example 1 70 1900 Example 2 40 2000 Example 3 60 1950 Comparative example 1 0 2100 Comparative example 2 90 1700 It can be clearly seen that the finished product has a sufficient surface hardness and that the ceramic film is deposited in a state of being sufficiently rooted, and that the film has good adhesion.

[0037]

According to the alloy sintered body obtained by the production method of the present invention, a thick ceramic coating mainly composed of an alumina component is formed on the surface because the alloy composition of the ceramic alloy powder is appropriate. With high hardness and sufficient abrasion resistance, and appropriate content of Zr, Y, Ce, Hf, La, Nd and Gd, the ceramic coating is sufficiently rooted in the alloy. Because of this, the adhesion of the ceramic film is high, and furthermore, the alloy inside the sintered body is high in toughness, there is no such thing as cracking or chipping,
In addition, the manufacturing method of the present invention is very useful because it is suitable for mass production and has sufficient dimensional accuracy.

Continuing on the front page (72) Inventor, Tadashi Hamada 1048, Kadoma, Kadoma, Osaka Pref.Matsushita Electric Works, Ltd. Hajime Kojima 1048 Kadoma Kadoma, Kadoma City, Osaka Prefecture (72) Inventor Masao Tanahashi 1048 Kadoma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd. (56) References JP-A-3-150337 (JP, A JP-A-50-17307 (JP, A) JP-A-54-44800 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 33/02 B22F 3/24

Claims (1)

(57) [Claims] 1. Cr: 15 to 40% by weight, Ni: 2 to 2
5% by weight, Al: 2 to 8% by weight, Zr, Y, Ce, H
f, La, Nd and Gd, any one or more of them: 1 to 2.5% by weight (excluding 1.0% by weight), Ti: 0 to 0.5% by weight, Fe: A compact formed by molding an Fe-Cr-Ni-Al-based ferrite alloy powder having a composition consisting of the remainder is sintered in a non-oxidizing atmosphere, and then heat-treated in an oxidizing gas atmosphere to form an alumina on the surface. A method for producing a ferrite alloy sintered body in which components are precipitated.