JP3379203B2 - High-rigidity iron-based alloy and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-rigidity iron-based alloy and a method for producing the same, and more particularly to an iron-based alloy having an excellent specific Young's modulus and useful as a highly rigid structural metal material, and a method for producing the same.

[0002]

2. Description of the Related Art At present, steel or iron alloy is most widely used as a structural metal material. These metallic materials show extremely various structural changes due to addition of alloying elements and heat treatment, and mechanical properties such as strength and toughness can be widely controlled. However, since the rigidity, which is important in the design of actual parts, is a value peculiar to a substance that directly participates in the bonding force between atoms, it has been considered difficult to significantly improve the rigidity.

[0003] There are not many studies on the high rigidity of these steels and iron alloys. As one of them, a method of improving the Young's modulus only in a specific direction by utilizing the texture of steel and iron alloy has been proposed for a long time (for example, JL Lyttonof Applied Physics, 35-8).
(1964), 2397.). However, this method is limited to application to thin plates, and has a problem that it is not a practical technique applicable to bulk materials.

On the other hand, in a composite material using a lightweight metal such as a magnesium alloy, an aluminum alloy, and a titanium alloy, which has been attracting attention in recent years, as a matrix, it is possible to increase strength or rigidity by combining reinforcing fibers and particles. Research and development at a practical level. That is, in the above-mentioned composite material using the lightweight metal as a matrix, the high Young's modulus particles are dispersed to realize high rigidity of the bulk material.

However, for steel or iron alloys, it is difficult to apply the concept of increasing the rigidity of the above lightweight alloys. This is because the strengthening particles that are thermodynamically stable in the iron alloy are limited to some carbides and nitrides, and it is not possible to expect a significant increase in the Young's modulus by dispersing the particles of such a substance. is there. For example, in conventional steels (particularly tool steels), wear resistance is mainly strengthened by precipitating various types of carbide particles such as molybdenum-based, vanadium-based, chromium-based, and tungsten-based particles. However, these carbides all have the chemical formulas MC, M3C, M6C, M7.
C3, M23C6, etc. are thermodynamically stable carbides in iron alloys, but by dissolving a large amount of iron in the iron alloy, a high Young's modulus that contributes to high rigidity can be obtained. I will not have it.

By the way, among various compound particles, many boride compounds of transition metal elements have relatively high Young's modulus.
However, regarding the effect of increasing the rigidity when these boride compounds are compounded and dispersed using an iron alloy as a matrix,
Little known.

As described above, in iron alloys, there are few examples of research and development in which compound particles of boride or the like are dispersed for the purpose of increasing the rigidity. High rigidity iron-based alloys (NJSaunders, LMPan, K.Clay, C.Small and
APMiodownik; In User Aspects of Phase Diagrams,
Inst. Materials, UK, (1991), 64.). This is a product obtained from the above iron-based alloy by hot extrusion and heat treatment using a rapidly solidified amorphous foil as a raw material, and a Young's modulus of around 25,000 kgf / mm ² is shown.

As another example in which compound particles are dispersed for high rigidity, "high rigidity material and method for producing the same" in which high Young's modulus particles of 20 vol% or less are dispersed in a Fe-based metal matrix ( JP-A-5-239504) has been proposed. This material has high rigidity and tough ductility with a Young's modulus of 22,500 kgf / mm ² or more and an impact value of 8 kgf-m / cm ² or more by dispersing general high Young's modulus particles by a mechanical alloying method. It is said that a dispersed iron-based alloy material can be obtained.

[0009]

However, the boride in the high-rigidity iron-based alloy proposed by Myodonik et al.
It is a molybdenum-chromium-iron-based complex boride formed by reaction with an iron alloy matrix, and the specific gravity of the complex boride is 8.49, which is large relative to the iron alloy matrix. Therefore,
The high rigidity iron-based alloy is inferior in specific Young's modulus. In addition, the amorphous foil used as a raw material in the manufacturing method has a problem that it cannot be easily manufactured using existing equipment because it requires a special manufacturing method to forcibly dissolve a high concentration of boron into a solid solution. is doing.

The high-rigidity material described in Japanese Patent Laid-Open No. 5-239504 is a carbide having a covalent bond crystal structure,
Although various compound particles such as borides and nitrides have been disclosed, generally, carbides and nitrides of these transition metal elements have high Young's modulus, but in the iron alloy matrix, they are Substitution with iron atoms in the matrix significantly reduces Young's modulus. Therefore, it is not possible to achieve the high rigidity according to the compounding rules such as the Young's modulus disclosed in the examples of JP-A-5-239504. In addition, even if these particles exist stably, it is unlikely that they will conform to the compounding rules.
As theoretically described in Science and Technology vol. 8, (1992), 922., it is appropriate that the strength characteristics change along the curve below the mixing rule for the volume fraction of particles. .

In the iron-based alloy proposed by Myodonik et al. And the high-rigidity material described in JP-A-5-239504, the idea of achieving high rigidity by dispersing high Young's modulus particles is as described above. As described above, the concept is already known as increasing the rigidity of the composite material.

Therefore, the inventors of the present invention have earnestly studied to solve the problems of the prior art as described above, and as a result of various systematic experiments, the present invention has been accomplished.

(Object of the Invention) An object of the present invention is to provide a high-rigidity iron-base alloy having a high specific Young's modulus and useful as a structural metal material, and a practical manufacturing method of the iron-base alloy part. It is in.

The present inventors have focused on the following points with respect to the above-mentioned problems of the prior art. That is, a compound particle having a high Young's modulus usually has a significantly reduced Young's modulus due to the replacement of some of the metal atoms with iron atoms by the reaction with the iron alloy matrix or the formation of other composite compounds. There is a problem in that the expected high rigidity effect cannot be obtained. As mentioned above, even in boride,
It has been generally considered that the complex boride formed by the reaction with the matrix has a much lower Young's modulus than the boride having a simple composition. On the other hand, the inventors of the present invention positively react the dispersed boride particles containing a Group 5A element with iron in the matrix to obtain 5A having a high Young's modulus and a low specific gravity.
Focusing on the formation of complex borides of group elements and iron, a new reinforced particle-dispersed high-strength iron-based alloy with excellent specific Young's modulus was designed.

As a result, the boride of the 5A group element or ferroboron and the ferroalloy containing the 5A group element react with iron in the iron alloy to form a complex boride of the 5A group element and iron, and Have found that the boride can achieve a relatively high Young's modulus. Furthermore, it was revealed that the specific gravity of the iron-based alloy was reduced by the dispersion of the boride, and an excellent specific Young's modulus was expected for the high-rigidity iron-based alloy in which these are dispersed. Therefore, in order to optimize the boride and the matrix composition, metallographical studies have been repeated and the high-strength iron-based alloy of the present invention has been formed. Further, in the process for obtaining the bulk material of the high-rigidity iron-based alloy, it is important to provide it at low cost by a conventionally well-known manufacturing technique that does not include a special method, and the iron-based alloy is directly connected to parts. It was noted that the material would be useful as a practical metal material.
As a result, the method for producing the high-rigidity iron-based alloy of the present invention was completed.

[0016]

Rigid iron-based alloy of the present invention (structure of the first invention) SUMMARY OF THE INVENTION comprises a matrix of iron or an iron alloy, and dispersed 10 to 50% by volume in the matrix, 5A Group with one or more iron elements, characterized in that it consists of at least one or more small complex boride specific gravity than the matrix.

(Structure of the Second Invention) The method for producing a high-rigidity iron-based alloy according to the present invention is a raw material powder comprising iron powder or iron alloy powder and at least one or more boride powders of one or more 5A group elements. From a raw material powder mixing step of mixing the above to form a mixed powder, a forming step of forming the mixed powder into a predetermined shape into a formed body, and a sintering step of sintering the formed body into a sintered body. In a matrix composed of iron or an iron alloy, one or more elements of Group 5A and iron ,
At least one compound boride having a specific gravity smaller than that of the matrix is dispersed in an amount of 10 to 50% by volume .

(Structure of Third Invention) A method of manufacturing a high-rigidity iron-based alloy according to the present invention comprises a raw material containing iron powder or iron alloy powder, ferroboron powder, and ferroalloy powder containing at least one or more 5A group elements. A raw material powder mixing step of mixing powders into a mixed powder, a molding step of molding the mixed powder into a predetermined shape to form a molded body, and a sintering step of sintering the molded body into a sintered body. the matrix of the a becomes, iron or iron alloy, with one or more and iron 5A group element, a at least one or more kinds of small complex boride specific gravity than the matrix by reaction of ferroboron and ferroalloy 10-50 It is characterized by being generated and dispersed by volume% .

[0019]

By the iron-based alloy and the method for producing the same according to the present invention,
The reason why a high-rigidity iron-based alloy having excellent properties is obtained is not clear yet, but it is considered as follows.

(Effect of the First Invention) The high-rigidity iron-based alloy of the present invention comprises a matrix composed of iron or an iron alloy, and a complex boride of iron and one or more Group 5A elements dispersed in the matrix. At least one or more of. In the high-rigidity iron-based alloy, the complex boride of at least one Group 5A element dispersed in the matrix and iron is a complex boride having a high Young's modulus formed by the reaction with the matrix iron. Since this compound boride has a regular crystal structure and the constituent atoms are strongly bonded, the Young's modulus in which the bonding force is directly reflected is extremely high. Also,
Since the boride is thermodynamically stable in the iron alloy, it contributes effectively as reinforcing particles for increasing the rigidity of the iron-based alloy. Furthermore, the specific gravity of the boride is small with respect to the iron alloy matrix, and the iron-based alloy of the present invention in which these are dispersed is considered to have an extremely high specific Young's modulus.

(Operation of Second Invention) In the method for producing a high-rigidity iron-based alloy of the present invention, first, iron powder or iron alloy powder and 5
At least one or more boride powders of one or more Group A elements are prepared, and these raw material powders are mixed to form a mixed powder (raw material powder mixing step). In this process,
Since a well-known powder mixing method can be adopted, a uniform mixed powder of each raw material powder can be obtained without performing any special means or pretreatment.

Next, the mixed powder obtained in the raw material powder mixing step is molded into a predetermined shape to obtain a molded body (molding step). Since the above-mentioned mixed powder is based on iron powder or iron alloy powder having high compressibility, molding is performed by using a well-known metal powder molding method, and by carrying out at each normal pressure, it has sufficient strength for handling. It is possible to easily obtain a molded product having a desired shape.

Next, the molded body obtained by the molding step is heated and sintered (sintering step). Since the above-mentioned molded body is based on iron powder or iron alloy powder having good sinterability, sintering can be carried out in a furnace in a vacuum or protective atmosphere at a normal temperature and time. In the high sintering temperature range, iron in the matrix reacts with one or more borides of Group 5A elements to form a complex boride having a high Young's modulus. Therefore, by this step, a sintered body having an intended structure can be obtained, and a bulk material having a desired shape can be obtained. From this, it is considered that it is possible to easily obtain a high-rigidity iron-based alloy in which one or more Group 5A elements and at least one complex boride of iron are dispersed in a matrix composed of iron or an iron alloy. To be In addition, this manufacturing method is a manufacturing method in accordance with a usual powder metallurgy technique, and since easily available raw material powder and existing equipment can be used, a high-rigidity iron-based alloy can be manufactured at low cost. .

(Operation of Third Invention) In the method for producing a high-rigidity iron-based alloy of the present invention, first, iron powder or iron alloy powder, ferroboron powder, and ferroalloy powder containing at least one or more 5A group elements are used. Each is prepared, and raw material powders containing these powders are mixed to obtain a mixed powder (raw material powder mixing step). In this step, since a well-known powder mixing method can be adopted, a uniform mixed powder of each raw material powder can be obtained without performing any special means or pretreatment.

Next, the mixed powder obtained in the raw material powder mixing step is molded into a predetermined shape to obtain a molded body (molding step). Since the above-mentioned mixed powder is based on iron powder or iron alloy powder having high compressibility, molding is performed by using a well-known metal powder molding method, and by carrying out at each normal pressure, it has sufficient strength for handling. A molded product having a desired shape can be easily obtained.

Next, the molded body obtained by the molding step is heated and sintered (sintering step). Since the above-mentioned molded body is based on iron powder or iron alloy powder having good sinterability, sintering can be carried out in a furnace in a vacuum or protective atmosphere at a normal temperature and time. At this time, the ferroboron powder has an effect of promoting the densification of the iron-based sintered body. Further, in the high sintering temperature range, iron in the matrix, boron in ferroboron, and 5 in ferroalloy.
The group A element reacts with each other to form a new complex boride having a high Young's modulus. Therefore, by this step, a sintered body having an intended structure can be obtained, and a bulk material having a desired shape can be obtained. As a result, a high-rigidity iron-based alloy in which one or more 5A group elements and at least one compound boride of iron are generated and dispersed by the reaction of ferroboron and ferroalloy in a matrix composed of iron or an iron alloy is obtained. It is thought that it can be easily obtained. In addition, this production method can use a cheaper raw material powder than the production method of the second aspect of the present invention, and since it is possible to promote densification by adding ferroboron, it is possible to produce a high rigidity iron-based alloy at a lower cost. It is considered to be easily manufactured.

[0027]

【The invention's effect】

(Effect of the first invention) The iron-based alloy of the present invention is a high-rigidity iron-based alloy having an extremely high Young's modulus. That is, the complex boride of at least one of the Group 5A elements and iron uniformly dispersed in the iron alloy matrix has a high Young's modulus and
Since it is thermodynamically stable, it exhibits excellent properties as reinforcing particles for iron-based alloys. Moreover, the dispersion of the boride reduces the specific gravity of the iron-based alloy. Therefore, even when particles having the same volume ratio are dispersed, the effect of increasing the rigidity, in particular, improving the specific Young's modulus is greater than that of the conventional reinforced particle-dispersed iron-based alloy.

(Effect of the Second Invention) According to the production method of the present invention, a high dispersion of at least one compound of at least one 5A group element and iron compound in a matrix of iron or iron alloy is dispersed. A rigid iron-based alloy can be easily manufactured. Further, the high rigidity iron-based alloy can be obtained at a low cost.

(Effect of the third invention) According to the production method of the present invention, at least one compound of at least one Group 5A element and at least one compound of iron and ferroboron and ferroalloy are added to a matrix composed of iron or an iron alloy. The high-rigidity iron-based alloy produced and dispersed by the reaction can be easily manufactured. Further, the high rigidity iron-based alloy can be obtained at a lower cost.

[0030]

EXAMPLES First, the high-rigidity iron-based alloy of the first invention, the second
A more specific invention (other invention) of the method for producing a high-rigidity iron-based alloy of the invention and the method for producing a high-rigidity iron-based alloy of the third invention will be described.

(Description of Other Inventions)

There is a strong need for high rigidity in structural metal materials. At present, steel or iron alloy, which has an overwhelming application record as various structural members and parts, has the highest rigidity among practical metal materials, but is required to have higher rigidity. For example, one of automotive parts is high rigidity for securing strength necessary for designing small / thin-wall / thin shaft parts from the viewpoint of weight reduction for the purpose of improving fuel efficiency. . In fact, even if the rigidity of conventional steel or iron alloy parts is improved by about 20%, it is said that the degree of freedom in design will be greatly expanded. Further, from the viewpoint of placing importance on ride comfort, high rigidity effective for improving vibration characteristics is required. No conventional steel, iron alloy, or reinforced particle-dispersed iron-based alloy has high rigidity that satisfies these needs, but the high-rigidity iron-based alloy of the present invention can satisfy these needs. . Therefore, the high-rigidity iron-based alloy of the present invention can be applied to parts and the like which are required to meet such requirements. For example, there are engine parts for automobiles, chassis parts, suspension parts, and other various shafts. It can also be applied to and audio parts.

Conventionally, it has been attempted to improve strength, rigidity and wear resistance by compounding and dispersing a reinforcing phase.
This is a well-known concept in composite materials. However, it should be noted that in the case of a metal-based composite material, a process in a high temperature region where diffusion and reaction are easy is required in the step of forming a composite with a matrix or the step of solidifying into a bulk material. That is, during the production, the reinforcing phase and the matrix react with each other, and changes such as mutual deterioration, and a change such as the formation of a brittle reaction layer at the interface are likely to occur, and along with this, the characteristics are usually deteriorated,
This is far below the theoretical value calculated from the ideal compound rule. On the other hand, the present inventors
It has been found that one or more borides, or ferroboron and a ferroalloy containing a Group 5A element, reacts with iron in the matrix in the iron alloy to form a complex boride having a relatively high Young's modulus. Moreover, due to the dispersion of the boride, the specific gravity of the iron-based alloy is reduced, and in particular, a highly rigid iron-based alloy having an excellent specific Young's modulus has been realized.

In the high-rigidity iron-based alloy of the present invention, the boride dispersed in a matrix made of iron or an iron alloy is a group 5A element (vanadium [V], niobium [Nb],
One or more of tantalum [Ta]) and one or more of a complex boride of iron. The boride has not been reported so far, and even basic physical properties as a simple substance are not known. However, when estimated from the density and Young's modulus of an iron-based alloy in which these are dispersed as in Examples described later, the specific gravity of the boride simple substance is 6.1 to 6.9, and the Young's modulus is 40,000 k.
It is considered to be around gf / mm ² .

In the high-rigidity iron-based alloy of the present invention, it is preferable that the boride is uniformly dispersed in the alloy as fine particles having a particle size of 100 μm or less. The particle size of boride is 10
When the thickness is 0 μm or less, practical level mechanical properties (strength, toughness and ductility) can be secured in the entire iron-based alloy. In addition, when the particle size is 20 μm or less, an alloy having more excellent mechanical properties can be obtained, which is more preferable.

The content of boride is 5 to 50% by volume.
Is preferred. By setting the content within the above range, a sufficiently high rigidity effect can be exhibited. If the content is less than 5% by volume, a sufficient effect of increasing the rigidity cannot be obtained, and if it exceeds 50% by volume, boride aggregates or coalesces, and the mechanical properties of the iron-based alloy are remarkably increased. It may decrease. Particularly, the content of boride is 10 to 10.
40% by volume is more preferred.

As the iron alloy constituting the matrix of the high-rigidity iron-based alloy of the present invention, a wide range of ferrite alloys, austenite alloys, martensite alloys, etc. can be used, but the carbon content is 0. It is preferably 1% by weight or less. When the carbon content in the matrix is set to 0.1% by weight or less,
The group A element and boron do not react preferentially with the contained carbon to form carbides and carbon borides, and it becomes easy to form complex boride having a high Young's modulus, resulting in a more excellent effect of increasing rigidity. Can be realized.

Next, a method for manufacturing the above high-rigidity iron-based alloy will be described. First, as one of the methods for producing the alloy, a raw material powder composed of iron powder or iron alloy powder and at least one or more boride powders of 5A group elements is mixed to obtain a mixed powder (raw material powder Mixing step), and then molding the mixed powder into a predetermined shape to obtain a molded body (molding step), and then sintering the molded body into a sintered body (sintering step). It is possible to obtain a high-rigidity iron-based alloy in which one or more Group 5A elements and at least one or more complex boride of iron are dispersed in the matrix (1st production method).

As the raw material of the iron powder or iron alloy powder used in the raw material powder mixing step, any of commercially available ones and those produced by a known method may be used. For example, inexpensive powders such as commercially available pure iron powder and stainless steel powder manufactured by the atomization method can be used as they are obtained. In addition, the particle size of the powder is often adjusted to about 150 μm (− # 100) or less on the market, but if it is 45 μm (− # 330) or less, the sintered body is densified and the boride particles are It is preferable because it facilitates uniform dispersion. However, in the case of extremely fine powder,
It is not preferable because it is difficult to handle and makes the molding process extremely difficult.

As the boride powder of one or more elements of Group 5A, any of commercially available ones and those prepared by a known method may be used. As the boride of the 5A group element, chemical formulas MB ₂ , M ₃ B ₂ , M ₃ B ₄ (M: 5A
There are several types of elements represented by
Whichever one is used, it changes to the above-mentioned double boride having a high Young's modulus. Among them, the diboride represented by the chemical formula MB ₂ is
It is suitable as a raw material for the production method of the present invention because it is stable as a simple substance and relatively easy to obtain. In addition, it is preferable to use the boride powder having a particle size of about several μm. When a powder having a size larger than that is obtained, the boride powder is crushed to a desired particle size by various crushers such as a ball mill, a vibration mill and an attritor. It is preferable to adjust it before use.

In the above mixing step, the mixing method is not particularly limited, and a V type mixer, a ball mill, a vibration mill or the like can be used. However, in the case where the boride particles are powders such as secondary particles that are significantly aggregated, crushing treatment in an inert gas atmosphere with a high-energy ball mill such as an attritor is effective for fine and uniform dispersion of the particles. It is preferable because it is effective.

In the above-mentioned molding step, as a molding method, any method can be used as long as a desired shape can be obtained, and any method such as mold molding and CIP molding may be used. A molding pressure of 2 ton / cm ² or more is suitable because the obtained molded body will be sufficiently densified when sintered.

In the above sintering step, the atmosphere is preferably vacuum, inert gas, or reducing gas atmosphere. Moreover, it is preferable that the sintering is performed in a temperature range of 1000 ° C. to 1300 ° C. for about 1 to 4 hours. Sintering at less than 1000 ° C. and less than 0.5 hours is not preferable because the density of the sintered body is not sufficiently improved. Further, even if sintering is performed for more than 4 hours, further densification cannot be expected, and energy is uneconomical. Further, sintering at a temperature exceeding 1300 ° C. is not preferable because a large amount of liquid phase is generated depending on the boride and the shape of the sintered body cannot be maintained.

Next, another method for producing the high-rigidity iron-based alloy will be described. That is, first, a raw material powder containing iron powder or iron alloy powder, ferroboron powder, and ferroalloy powder containing at least one or more elements of Group 5A is mixed to form a mixed powder (raw material powder mixing step), and then the mixing is performed. The powder is molded into a predetermined shape to obtain a molded body (molding step), and then the molded body is sintered into a sintered body (sintering step).
It is possible to obtain a high-rigidity iron-based alloy in which at least one or more compound boride of group A element and iron is generated and dispersed by the reaction of ferroboron and ferroalloy (second).
Manufacturing method).

The raw material of the iron powder or the iron alloy powder used in the raw material powder mixing step may be the same as the iron powder and the iron alloy powder in the description of the method for producing the high-rigidity iron-based alloy, which is commercially available. For example, commercially available pure iron powder, stainless steel powder, and other inexpensive powders can be used as they are obtained. Next, as the ferroboron powder and the ferroalloy powder containing the Group 5A element, any of commercially available ones and those produced by a known method may be used. These are commercially available after being crushed from ingots having various compositions, but it is preferable that they are close to the composition of each intermetallic compound. If the powder having such a composition is used, the particle size can be easily adjusted by using various crushers such as a ball mill, a vibration mill and an attritor.

The mixing step, molding step, and sintering step are
The steps are the same as those in the description of the method for producing the high-rigidity iron-based alloy. In addition, in the mixing step, the compounding ratio of the ferroboron powder and the ferroalloy powder needs to be determined by calculating the volume ratio of the boride formed by the reaction of the two from each composition. Further, in the sintering step, it is possible to carry out the sintering step under milder conditions because of the effect of promoting densification at the time of sintering with ferroboron.

In the first manufacturing method and the second manufacturing method of the method for manufacturing a high-rigidity iron-based alloy, it is preferable that hot working is performed after the sintering step. That is, in the first manufacturing method and the second manufacturing method, when the densification is insufficient by only the sintering step, or when more sufficient densification is required, the sintered body is subjected to various hot workings. By performing the processing, it is possible to easily densify to the true density. As the hot working method, hot forging, extrusion, swaging, etc. are used. Processing temperature is 900 ℃
It is preferable to carry out in the range of 1300 ° C. Processing at a temperature of less than 900 ° C has a large deformation resistance, and if it exceeds 1300 ° C, a liquid phase may occur, which is not preferable. Further, it is possible to densify by HIP processing without performing hot working. Regarding the conditions in this case, the processing conditions are appropriately set in consideration of the reactivity with the atmospheric gas, the densification behavior, the economical efficiency, etc., but 900 ° C. to 1200 ° C., 500 to 20 ° C.
It is preferable to carry out the treatment at 00 atm for 1 to 10 hours.

Examples of the present invention will be described below.

(First Example) As a raw material powder, commercially available S
US430 stainless steel powder (-# 330) and vanadium diboride powder (average particle size: 2 μm) were prepared. next,
A powder prepared by mixing SUS430 stainless steel powder and vanadium boride powder in the ratio shown in Table 1 was mixed for 10 minutes in an attritor in an argon atmosphere. The mixed powder was molded into a cylinder with a diameter of 12.7 mm and a height of 12 mm at a pressure of 4 ton / mm ² , and then this compact was sintered in a vacuum furnace in an atmosphere of 1 × 10 ^-5 torr for 1 hour. did. Furthermore, in order to promote the densification of the sintered body, 1 × 10 ⁻⁵ to
In a vacuum of rr, compression processing was performed at 1150 ° C. to a processing speed of 0.05 mm / s and a rolling reduction of 75%. As a result, the diameter is about 25 mm
A disc-shaped test piece was obtained (Sample Nos. 1 and 2).

[0050]

[Table 1]

A micrograph showing the metal structure of the obtained iron-based alloy sintered body (magnification: 600 times) is shown in FIG. 1 (sample number:
2). As is clear from Fig. 1, the structure is SUS4.
1 diameter in 30 ferritic matrix of 30 stainless steel
It can be seen that it has a structure in which fine complex boride particles of μm to several μm are uniformly dispersed. Table 1 also shows the results of measuring the volume ratio and the density of the boride particles.
Further, as a result of locally analyzing the concentration of each element in these boride particles by EPMA, the boride particles contained 25.4 atom% of vanadium and 20.5 atom% of iron, which is a constituent element of the matrix. , And it was confirmed to be a vanadium-iron-based complex boride. That is, the vanadium diboride compounded in the raw material powder reacts with the iron in the matrix to form a vanadium-iron compound boride by the above-described manufacturing method of the present example involving sintering at high temperature and hot working. It was confirmed to do.

Further, the density and Young's modulus of the obtained iron-based alloy were measured. First, the Young's modulus was measured by cutting out a 1 mm × 2 mm × 11.2 mm prism as a test piece and performing a composite oscillator method using a crystal oscillator. The results are shown in Table 1.
Are also shown. As is clear from Table 1, the Young's modulus of the iron-based alloys in which the vanadium-iron compound boride of Sample No. 1 and Sample No. 2 are dispersed is improved with an increase in the volume ratio of boride particles, and is about 31% by volume. It can be seen that it reaches about 26,500 kgf / mm ² . This is an improvement rate of 30% or more as compared with the conventional iron alloy. Moreover, the density of the iron-based alloy decreases with an increase in the volume ratio of boride particles, suggesting that the specific gravity of the dispersed vanadium-iron-based complex boride is smaller than that of the iron alloy matrix.

(Second Example) As a raw material powder, commercially available S
US430 stainless steel powder (-# 330), vanadium diboride powder (average particle size: 2 μm), and graphite powder were prepared. Next, a powder prepared by mixing SUS430 stainless steel powder, vanadium diboride powder, and graphite powder in the proportions shown in Table 1 was mixed in the same manner as in the first embodiment,
Molding, sintering, and hot compression were performed to obtain a disc-shaped iron-based alloy sintered body test piece having a diameter of about 25 mm (sample number: 3).
The volume ratio, density and Young's modulus of the obtained iron-based alloy sintered body were measured in the same manner as in Example 1. The results are also shown in Table 1. As is clear from Table 1, the iron-based alloy sintered body of Sample No. 3 is improved by about 20% as compared with the conventional iron alloy. However, it can be seen that the Young's modulus is reduced by about 7.9% due to the presence of carbon, although the vanadium boride powder is blended in the same ratio as in the sample No. 2 of the first embodiment.

(Third Example) As a raw material powder, commercially available SUS430 stainless steel powder (-
# 330), and niobium diboride powder (average particle size: 2μ
m) was prepared. Next, SUS430 stainless steel powder and ni
A powder prepared by blending obovide boride powder in a ratio shown in Table 1 was mixed, molded, sintered, and hot-compressed in the same manner as in the first embodiment to form a disk-shaped iron base having a diameter of about 25 mm. The alloy sintered compact test piece was obtained (sample number: 4 and 5).

As a result of observing the metal structure of the obtained iron-based alloy sintered body with a microscope, the structure was found to have a diameter of 1 μm to several μm in the ferrite phase matrix of SUS430 stainless steel.
It was confirmed that the fine double boride particles of No. 2 had a structure in which they were uniformly dispersed. In addition, as a result of locally analyzing the concentration of each element in these boride particles by EPMA, the boride particles contained 29.0 atomic% of niobium and 30.9 atomic% of iron, which is a constituent element of the matrix. Cage, niobium-
It was confirmed to be an iron-based complex boride. That is, the niobium diboride compounded in the raw material powder reacts with the iron in the matrix to form a niobium-iron compound boride by the above-described manufacturing method of the present example involving sintering at high temperature and hot working. It was confirmed to do.

The volume ratio, density and Young's modulus of the obtained iron-based alloy sintered body were measured in the same manner as in the first embodiment. The results are also shown in Table 1. As is clear from Table 1, the Young's modulus of the iron-based alloys of Sample No. 4 and Sample No. 5 in which the niobium-iron-based complex boride was dispersed was improved with an increase in the volume ratio of boride particles, and was about 43% by volume. About 26,120 kgf / mm ²
You can see that This is an improvement rate of about 30% as compared with the conventional iron alloy. Moreover, the density of the iron-based alloy decreases with the volume increase rate of the boride particles, suggesting that the specific gravity of the dispersed niobium-iron-based complex boride is smaller than that of the iron alloy matrix.

Comparative Example 1 Commercially available SUS43 as raw material powder
0 A disk-shaped comparative iron having a diameter of about 25 mm was prepared by mixing, molding, sintering and hot pressing in the same manner as in the first embodiment except that only stainless steel powder (-# 330) was used. A base alloy sintered body test piece was obtained (sample number: C1). The density, volume ratio, density and Young's modulus of the obtained comparative iron-based alloy sintered body were measured in the same manner as in Example 1, and the results are also shown in Table 1. As is clear from Table 1, the Young's modulus of the comparative iron-based alloy sintered body of Sample No. C1 is as low as 20,250 kgf / mm ² .

Comparative Example 2 Commercially available SUS was used as the raw material powder.
430 stainless steel powder (-# 330) and molybdenum boride powder (average particle size: 1.7 μm) were prepared. Then S
Table 1 shows US430 stainless steel powder and molybdenum boride powder.
The powders mixed in the ratio shown in Table 1 were mixed, molded, sintered, and hot-compressed in the same manner as in the first embodiment to have a diameter of about 25.
A mm-shaped disk-shaped comparative iron-based alloy sintered body test piece was obtained (sample number: C2). FIG. 2 shows a micrograph (magnification: 600 times) showing the metal structure of the obtained comparative sintered body. Figure 2
As is clearer, the structure is a structure in which boride particles having a diameter of several μm are dispersed in a ferrite phase matrix of SUS430 stainless steel.

The results of measuring the volume ratio of the boride particles are also shown in Table 1. Further, as a result of locally analyzing the concentration of each element in these boride particles by EPMA, the boride particles contained 19.0 wt% and 3.8 wt% of iron and chromium, which are the constituent elements of the matrix, respectively. Furthermore, it was confirmed by X-ray diffraction that the compound was an iron-chromium-molybdenum-based complex boride. That is, it was found that the molybdenum boride compounded in the raw material powder reacts with iron and chromium in the matrix to change into an iron-chromium-molybdenum complex boride. Moreover, the density and Young's modulus of the obtained iron-based alloy were measured in the same manner as in the first example. The results are also shown in Table 1. The iron-based alloy in which molybdenum boride of sample number C2 is dispersed is sample number C1.
Compared with, the Young's modulus is improved by the dispersion of the boride, but the density is the same as that of Comparative Example 1 (sample number: C
It can be seen that the density is higher than the density of the iron-based alloy sintered body of 1).

(Young's modulus analysis) The Young's modulus of each iron-based alloy and the comparative iron-based alloy obtained in the first, third and comparative examples was divided by the specific gravity. FIG. 3 shows a comparison of the specific Young's modulus for each boride volume ratio. In the figure, “A” indicates the vanadium-iron-based complex boride-dispersed iron-based alloy of the first embodiment, and “B” indicates the niobium of the third embodiment.
Regarding the iron-based double boride-dispersed iron-based alloy, “C” indicates Comparative Example 2
The respective results are shown for the molybdenum-iron based complex boride dispersion comparative iron-based alloy of.

As is apparent from FIG. 3, the iron-based alloy in which the vanadium-iron-based complex boride and the niobium-iron-based complex boride are dispersed according to the embodiment of the present invention has the molybdenum-iron-based complex boride dispersed therein. Even when boride particles having the same volume ratio are dispersed as compared with the comparative iron-based alloy, the specific Young's modulus becomes particularly excellent due to the low specific gravity. This indicates that if a high-rigidity iron-based alloy in which the boride is dispersed is used, the weight can be reduced by downsizing / thinning and the weight can be further reduced by reducing the specific gravity.

[Brief description of drawings]

FIG. 1 is a micrograph showing the metal structure of an iron-based alloy sintered body obtained in the first example of the present invention (magnification: 600).
Times).

FIG. 2 is a micrograph (magnification: 600 times) showing a metal structure of a comparative iron-based alloy sintered body obtained in Comparative Example 2.

FIG. 3 is a diagram comparing the specific Young's moduli of the iron-based alloy sintered bodies obtained in the first example, the third example, and the comparative example 2 of the present invention.

[Explanation of symbols]

A: Vanadium-iron based complex boride-dispersed iron-based alloy (first example) B: Niobium-iron based complex boride-dispersed iron-based alloy (third example)
Example) C ... Molybdenum-iron-based complex boride dispersed iron-based alloy (Comparative Example 2)

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C22C 38/00-38/60 C22C 33/02

Claims (6)

(57) [Claims] 1. A matrix composed of iron or an iron alloy, and 10A to 50% by volume dispersed in the matrix , 5A
With one or more and iron group elements, high rigidity iron-based alloy, characterized in that it consists of at least one or more small complex boride specific gravity than the matrix. 2. The high-rigidity iron-based alloy according to claim 1, wherein the carbon content is 0.1% by weight or less. 3. A raw material powder mixing step of mixing a raw material powder consisting of iron powder or iron alloy powder and at least one or more boride powders of one or more elements of Group 5A into a mixed powder, and the mixed powder. It comprises a forming step of forming a formed body into a predetermined shape and a sintering step of sintering the formed body into a sintered body, wherein one or more elements of Group 5A elements are contained in a matrix made of iron or an iron alloy. and with iron, the manufacturing method of high rigidity iron-based alloy in which the matrix at least one kind of dispersing 10-50% by volume of small complex boride specific gravity than that characterized by comprising. 4. The method for producing a high-rigidity iron-based alloy according to claim 3, wherein the carbon content is 0.1% by weight or less. 5. A raw material powder mixing step of mixing raw material powders containing iron powders or iron alloy powders, ferroboron powders, and ferroalloy powders containing at least one or more 5A group elements to obtain mixed powders, and the mixed powders. Of a group 5A element in a matrix made of iron or an iron alloy, which comprises a forming step of forming a predetermined shape into a formed body and a sintering step of sintering the formed body into a sintered body. rigid iron-based alloy, characterized by comprising and iron, the at least one or more kinds of small complex boride specific gravity than the matrix, reaction 10-50% by volume is generated and distributed by the ferroboron and ferroalloy more Manufacturing method. 6. The method for producing a high-rigidity iron-based alloy according to claim 3, wherein hot working is performed after the sintering step.