JP2004100035A - Green compact and powder compaction process, metallic sintered body and its manufacturing method, and worked component part and method of working - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a powder compaction process by which active metal powder can be compacted under high pressure. <P>SOLUTION: The powder compaction process comprises the steps of: applying a higher fatty acid-based lubricant to the inner surface of a die; filling a raw material powder whose major component is an active metallic element into the die after the application step; compacting the raw material powder after the filling step by warm pressing to make a green compact; and ejecting the green compact after the compaction step from the die. The resultant green compact has high density. By this procedure, the active metal powder composed of the active metallic elements, such as Ti and Al, can be pressed under high pressure without causing galling etc. at the inner surface of the die, and the green compact having high density which has not been available conventionally can be obtained. <P>COPYRIGHT: (C)2004,JPO

Description

【図面の簡単な説明】
【図１】純チタン粉末を用いて室温成形および温間成形したときの、成形圧力と成形体密度（相対密度比）との関係を示すグラフである。
【図２】そのときの成形圧力と抜出力との関係を示すグラフである。
【図３】純チタン粉末の成形圧力と得られた粉末成形体を焼結させた金属焼結体の相対密度比との関係を示すグラフである。
【図４】純チタン粉末の成形圧力と粉末成形体の焼結時の寸法変化率との関係を示すグラフである。
【図５】チタン合金粉末を温間成形したときの成形圧力と成形体密度（相対密度比）との関係を示すグラフである。
【図６】そのときの成形圧力と抜出力との関係を示すグラフである。
【図７】チタン合金粉末の成形圧力と得られた粉末成形体を焼結させた金属焼結体の相対密度比との関係を示すグラフである。
【図８】純アルミニウム粉末を用いて室温成形および温間成形したときの、成形圧力と成形体密度（相対密度比）との関係を示すグラフである。
【図９】そのときの成形圧力と抜出力との関係を示すグラフである。
【図１０】純アルミニウム粉末とアルミニウム合金粉末とを用いて室温成形および温間成形したときの、成形圧力と成形体密度（相対密度比）との関係を示すグラフである。
【図１１】そのときの成形圧力と抜出力との関係を示すグラフである。
【図１２】難焼結材の焼結時間と相対密度比との関係を示すグラフである。
【図１３】難焼結材の焼結時間と寸法変化率との関係を示すグラフである。
【図１４】製造条件の相違による相対密度比、引張強度および伸びの相違を対比した棒グラフである。
【図１５】製造条件の相違による疲労強度の相違を対比したグラフである。
【図１６】純Ｔｉ粉末からなる粉末成形体の表面をＴＯＦ−ＳＩＭＳで観察した二次イオン像である。
【図１７】純Ａｌ粉末からなる粉末成形体の表面をＴＯＦ−ＳＩＭＳで観察した二次イオン像である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-density powder compact made of a raw material powder mainly containing an active metal element such as Ti or Al (hereinafter, abbreviated as “active metal powder” as appropriate), a powder compacting method thereof, and a powder compact. The present invention relates to a high-density metal sintered body obtained by sintering a powder compact and a method for producing the same.
The present invention also relates to a formed member formed by forming a metal material containing an active metal element as a main component and a forming method thereof.
[0002]
[Prior art]
In order to reduce the production cost of components by reducing expensive processing costs, and to obtain characteristics that can not be obtained with bulk ingots, powder compacts formed by pressing raw material powders have been used conventionally. I have. Although this powder compact is often subsequently formed into a sintered compact, it may be used as it is, such as a dust core.
By the way, in order to make full use of the features of the powder compact, it is often required that the powder compact has a high density. In order to obtain a high-density powder compact, it is inevitable to press-mold the raw material powder under high pressure. However, generally, the higher the molding pressure, the greater the frictional force between the raw material powder and the mold. As a result, when pressure molding is performed under a large pressure, it is difficult to extract the obtained powder molded body from the mold, or the mold may be damaged due to galling or the like during the extraction, or the powder molded body may be damaged. Or the surface of the surface becomes rough.
Of course, it is conceivable to use a large amount of lubricant to improve them. However, in that case, the density of the powder compact decreases, and a degreasing (dewaxing) step or the like is required separately after pressure molding. Or cost.
[0003]
Under such circumstances, many methods have been proposed for efficiently producing a high-density powder compact by variously devising the type of lubricant, the lubrication method, the mold temperature, and the like. For example, JP-A-62-109902, JP-A-62-294102, JP-A-5-271709, JP-A-8-100203, JP-A-9-104902, JP-A-11-193404 JP, JP-A-11-100602, JP-A-11-140505, JP-A-2000-273502, JP-A-2000-290703, JP-A-2001-294902, International Publication WO98 / 41347, U.S. Pat. No. 4,955,798, a research paper ("INFLUENCE OF TEMPERATURE ON PROPERTIES OF LITHIUM STEARATE LUBRICANT", Powder Metallurgy & Particulate Materials, vol. 1, 1997) Related matters have been disclosed to. However, none of these proposals was sufficient to produce a high-density powder compact at low cost.
Therefore, the present inventor has led the world in a molding method capable of obtaining a high-density powder compact very close to the true density by performing pressure molding at a significantly higher molding pressure than before, while securing the mold life and the like. Developed. This content is disclosed in International Publication WO 01/43900.
[0004]
[Patent Document 1]
JP-A-62-109902
[Patent Document 2]
JP-A-62-294102
[Patent Document 3]
JP-A-5-271709
[Patent Document 4]
JP-A-8-100203
[Patent Document 5]
JP-A-9-104902
[Patent Document 6]
JP-A-11-193404
[Patent Document 7]
JP-A-11-100602
[Patent Document 8]
JP-A-11-140505
[Patent Document 9]
JP-A-2000-273502
[Patent Document 10]
JP 2000-290703 A
[Patent Document 11]
JP-A-2001-294902
[Patent Document 12]
International Publication WO98 / 41347
[Patent Document 13]
U.S. Pat. No. 4,955,798
[Non-patent document 1]
Research paper ("INFLUENCE OF TEMPERATURE ON PROPERTIES OF LITHIUM STEARATE LUBRICANT", Powder Metallurgy & Particulate Materials, vol1, 1997)
[0005]
[Problems to be solved by the invention]
However, even in consideration of the contents of the above-mentioned WO 01/43900, most of the powder molding methods proposed so far consist of a raw material powder composed of iron powder or iron alloy powder. That is, there is hardly any practical proposal for a method for molding a raw material powder mainly containing an active metal element such as Ti or Al.
At least, as far as we know at present, there is no such raw material powder formed by high pressure molding at an industrial level (mass production level) by a mold lubrication method instead of an internal lubrication method (mixing lubrication method).
[0006]
This is not because the demand for a powder compact of a raw material powder mainly composed of Ti, Al or the like is small. Rather, the demand for such powder compacts is great in recent years when weight reduction of various members is required. In particular, in the case of a member made of pure titanium or a titanium alloy that is difficult to process, the use of the powder molding method has a great advantage in that the cost can be reduced by (near) net shape.
[0007]
However, it has been common technical knowledge so far that a raw material powder made of an active metal element such as Ti or Al cannot be formed under high pressure at an industrial level. When such high-pressure molding is performed, galling occurs immediately on the inner surface of the mold, the inner surface of the mold is roughened, and furthermore, it becomes impossible to extract the powder compact from the mold. is there. In addition, very expensive molds cannot be used for one-time molding, which may cause a large loss.
Under such circumstances, when the raw material powder made of the active metal element is subjected to pressure molding, the molding pressure cannot be increased, and the ultimate density of the obtained powder molded body is naturally low. For example, in the case of a powder compact made of Ti powder, the compact density was only 80% or less of the true density.
[0008]
Further, when the Ti powder is press-formed by the internal lubrication method as in the related art, a separate dewaxing step is required when sintering the obtained powder compact in a vacuum. In addition, hydrogen, nitrogen, carbon, and the like, which are the main components of the lubricant used at that time, are easily dissolved in Ti, so that the internal lubrication method is not preferable.
In order to avoid the use of such a lubricant, there are also CIP molding and RIP molding using a rubber mold. However, even in that case, it is impossible to perform high-pressure molding sufficiently, and the apparatus is very large and expensive. In addition, the dimensional accuracy of the obtained powder compact is low, and it is a reality that a net-shaped member, which is the greatest feature of the powder compact, cannot be obtained.
Such a situation is the same even when Al powder or the like is used. Furthermore, when a powder is formed by mixing a lubricant with Al powder, the dewaxing temperature of the lubricant is close to the sintering temperature of the powder compact (about 500 ° C.), so that sufficient dewaxing cannot be performed. Occurs.
[0009]
The present invention has been made in view of such circumstances. That is, to provide a powder molding method capable of performing high-pressure molding at a realistic level using a raw material powder containing an active metal element such as Ti or Al as a main component, and a high-density powder compact obtained therefrom. With the goal.
It is another object of the present invention to provide a metal sintered body obtained by sintering the powder compact and a method for producing the same.
Still another object of the present invention is to provide not only a powder molding method and the like but also a molding method for molding a metal material containing an active metal element as a main component and a molded member obtained by the method.
[0010]
Means for Solving the Problems and Effects of the Invention
Therefore, the present inventor has conducted intensive studies to solve this problem, and as a result of repeated trial and error, as a result, a raw material powder containing an active metal element as a main component (hereinafter abbreviated as “active metal powder” as appropriate). The present inventors came up with the idea of applying a warm pressure molding method using mold lubrication, and confirmed the effects thereof to complete the present invention.
(Powder molding method)
That is, the powder molding method of the present invention comprises a coating step of applying a higher fatty acid-based lubricant to the inner surface of a mold, and a filling step of filling a raw material powder containing an active metal element as a main component into the mold after the coating step. And a molding step of pressing the raw material powder after the filling step in a warm state to form a powder molded body, and an extraction step of extracting the powder molded body after the molding step from the mold. The obtained powder compact has a high density.
[0011]
According to the present invention, even when an active metal powder is used, a high-density powder compact can be obtained by high-pressure molding. At this time, a powder compact having good dimensional accuracy and surface roughness can be obtained without substantially causing galling or the like on the inner surface of the mold. Therefore, the cost of the powder compact, the sintered compact thereof, and the like can be significantly reduced by extending the life of the mold, improving the yield, and reducing the processing cost by (near) net shape.
Moreover, in the case of the present invention, a sufficient effect can be obtained by mold lubrication without internal lubrication, so that the amount of the lubricant used is small, the density of the powder compact can be increased, and the powder compact is sintered. The dewaxing step at the time can also be omitted. In addition, adverse effects of the lubricant on the powder compact can be avoided.
Further, according to the powder molding method of the present invention, the ejection force is significantly reduced as compared with the conventional one, despite the molding pressure being significantly increased. For this reason, the powder compact can be easily extracted from the mold, and the production efficiency of the powder compact can be greatly enhanced.
[0012]
By the way, in the case of the present invention, the present inventor is now studying why the high pressure molding of active metal powder, which has been considered impossible by those skilled in the art, has become possible. It is thought that the reason for this is that a new metal soap film different from the higher fatty acid-based lubricant used for mold lubrication was formed between the powder compact and the inner surface of the mold, and the friction coefficient was significantly reduced. Rara. Further, it is considered that the higher fatty acid-based lubricant is adsorbed on the surface of the powder molded body, and the Rebinder effect is caused. Furthermore, it is considered that this is due to the superlubricating action which has exceeded the conventional recognition. However, from recent research and research by the present inventor, it seems appropriate that the metal soap film was newly formed on the surface of the powder compact during the molding process. That is, the molding step is considered to be a step in which a new metal soap film containing the active metal element different from the higher fatty acid-based lubricant is formed on the surface of the powder molded body. For example, if the active metal element is Ti, the metal soap is a Ti salt of a higher fatty acid, and if the active metal element is Al, the metal soap is considered to be an Al salt of a higher fatty acid.
[0013]
In any case, since the ejection force is very low, it can be clearly seen that the frictional force between the raw material powder or powder compact and the mold is significantly reduced. However, this does not necessarily lead to an extremely low coefficient of friction. Depending on the type of the raw material powder, the amount of expansion (spring-back amount) after being removed from the mold is small. In this case, even if the friction coefficient is not extremely small, the frictional force at the time of extraction is reduced.
[0014]
The active metal element referred to in the present specification includes Ti, Al, Mg, Zr, Na, rare earth elements (La, Ce, etc.). Ti, Al and Mg are important as practical metal materials. That is, the case where the raw material powder contains Ti, Al, and Mg as main components is particularly industrially important. The details will be described later. The “raw material powder containing an active metal element as a main component” in the present invention refers to a case where the specific active metal element to be treated is 50 at% or more when the entire raw material powder is 100 at%. This raw material powder may be not only a metal powder but also a ceramic powder. Therefore, the obtained powder compact may be not only a metal compact but also a ceramic compact.
[0015]
(Powder compact)
The present invention can be understood not only as the powder molding method but also as a powder molded body obtained as a result.
For example, on the premise that the active metal element is Ti, the present invention is based on the premise that the active metal element is Ti, and the apparent density of the powder compact, that is, the compact density, is determined from the composition of the raw material powder. It may be a powder compact characterized by a high density of 85% or more of the true density.
[0016]
By adjusting the molding pressure, the compact density in this case becomes 88% or more, 90% or more, 95% or more, and 98% or more of the true density, and can approach the upper limit of 100% without limit. .
Similarly, on the premise that the powder is obtained by the powder molding method, the present invention provides that the active metal element is Al, and the apparent density of the powder molded body, that is, the molded body density is calculated from the composition of the raw material powder. It may be a powder compact having a high density of 90% or more of the true density determined.
[0017]
Also in this case, the molded body density can be made 93% or more, 95% or more, and 98% or more of the true density by adjusting the molding pressure, and can be made as close as possible to the upper limit of 100%. .
In the case of a powder compact made of a conventional Ti powder or the like, the density of the compact is at most about 80% of the true density, and in the case of a powder compact made of a conventional Al powder or the like, the density of the compact is at most a true density. It was about 85%. In view of these facts, the high density of the powder compact of the present invention is even surprising. Of course, even when such a high-density molding is performed, according to the present invention, a powder molded body having a low ejection force, good dimensional accuracy and good surface roughness can be obtained without generating a galling or the like in a mold. This is as described above.
[0018]
(Method of manufacturing sintered metal body)
The present invention is not limited to the above-described powder compacting method, but can also be grasped as a method for manufacturing a metal sintered body obtained by sintering a powder compact obtained through the method.
That is, the present invention provides a coating step of applying a higher fatty acid-based lubricant to the inner surface of a mold, a filling step of filling a raw material powder containing an active metal element as a main component into the mold after the coating step, A molding step of pressing the raw material powder after the filling step in a warm state to form a powder molded body, an extraction step of extracting the powder molded body after the molding step from the mold, and a powder after the extraction step And a sintering step of heating the formed body to form a metal sintered body, and the method for producing a metal sintered body characterized in that the obtained metal sintered body has a high density.
[0019]
According to the method for manufacturing a metal sintered body, a high-density metal sintered body can be easily obtained. Further, since the amount of the lubricant used at the time of molding the powder compact is extremely small, the dewaxing step in the sintering step becomes unnecessary, and the sintering step is significantly shortened. Accordingly, the production cost is reduced, and a high-density metal sintered body can be obtained at a lower cost.
[0020]
(Metal sintered body)
Further, the present invention can be understood as a metal sintered body obtained through the manufacturing method.
For example, on the premise that the active metal element is Ti, the present invention is based on the premise that the active metal element is Ti, and the sintered body density, which is the apparent density of the metal sintered body, is determined from the composition of the raw material powder. It may be a metal sintered body characterized by having a high density of 95% or more of the true density.
In this case, the density of the sintered body increases as the density of the green body before sintering increases, and is 97% or more, more preferably 99% or more of the true density, and approaches the upper limit of 100% as much as the density of the green body. .
[0021]
Similarly, on the premise that the active metal element is Al, the present invention is based on the assumption that the active metal element is Al, and the apparent density of the metal sintered body is the sintered density, which is the composition of the raw material powder. It may be a metal sintered body characterized by having a high density of 95% or more of the true density determined from the above.
Also in this case, the density of the sintered body increases as the density of the molded body before sintering increases, and becomes 97% or more, more preferably 99% or more of the true density. Get closer.
[0022]
In any case, the metal sintered body of the present invention has a high density of the compact before sintering, and therefore has a small dimensional change such as dimensional shrinkage after sintering. For this reason, although it is a sintered product made of an active metal element, it is possible to form a net shape, and it is easy to reduce the cost of Ti products and the like.
[0023]
(Molding method and member)
According to the present invention, high-pressure molding of active metal powder is possible, and various forms of the present invention have been described on the premise of this. However, the present invention is considered to have a significant feature in that the frictional force acting between the inner surface of the mold and the active metal powder or the powder compact after pressing is extremely small. Therefore, the present invention is naturally applicable not only to the case where the raw material powder is subjected to pressure molding but also to the case where a tangible metal material is formed into a desired shape.
That is, the present invention provides an application step of applying a higher fatty acid-based lubricant to a surface of a metal material containing an active metal element as a main component and / or a processing surface of a forming die, and And a forming step of forming in a warm state.
According to the present invention, as in the case of the powder molding method described above, even if the metal material is made of an active metal powder, it does not cause galling or the like with a molding die, efficiently, at low cost. It can be formed into a desired shape.
[0024]
The “metal material” here may be an ingot material or a sintered material. Also, regardless of its form, it may be an ingot, a plate, a wire, or a tube. In short, any material having a macroscopic outer shape, unlike metal powder or the like, may be used. "Molding" refers to adjusting the outer shape of a macroscopic material into a desired shape, that is, processing the material into a desired shape.
[0025]
Such forming includes forging, rolling, extrusion, drawing, rolling, coining, sizing or recompression. Although the forming die used varies depending on the type of processing, for example, there are a forging die, a roll, a die and the like.
In order to perform the forming step in a warm state, at least one of the forming die and the metal material may be heated before the step, or may be heated simultaneously with the step.
[0026]
Since the metal material is tangible, the above-described coating step can be performed on the metal material. Of course, as in the case of powder molding, the molding may be performed on a molding die. For example, the coating step may include dipping the heated metal material into a dispersion in which the higher fatty acid-based lubricant is dispersed, or applying the higher fatty acid-based material to the heated metal material or the molding die. The process can be performed by a spray method or the like in which a dispersion liquid in which a lubricant is dispersed is sprayed. Needless to say, the present invention can be grasped as a molded member obtained by the molding method.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described more specifically with reference to embodiments. In addition, the content described below can be appropriately applied to any of the powder molding method, the powder molded body, the metal sintered body and its manufacturing method, the molding method, and the molded member according to the present invention.
(1) Raw material powder
As described above, the raw material powder is composed of a powder containing an active metal element as a main component, and is typically a Ti-based powder or an Al-based powder.
{Circle around (1)} When the active metal element is Ti, the raw material powder includes, for example, pure Ti powder, Ti alloy powder, Ti compound powder and the like. One type of powder alone or a mixture of two or more types of powder may be used. The raw material powder includes, in addition to Ti, Al, Zr, Hf, V, Nb, Ta, Sc, Cr, Fe, Mo, Sn, W, Mn, Ni, Cu, Si, C, B, N, O, etc. It may contain an element.
[0028]
Ti compound powder is, for example, TiB ₂ Boride powder, titanium carbide powder such as TiC, titanium nitride powder such as TiN, TiO ₂ A typical example is a titanium oxide powder composed of such as
Although the form of each element is not limited, for example, the element may be contained in the raw material powder as a pure powder, an alloy powder, a compound powder or the like. Which element is contained in the raw material powder is determined by the use, characteristics, powder cost and the like of the powder compact and its sintered body.
[0029]
{Circle over (2)} When the active metal element is Al, the raw material powder is, for example, a pure Al powder, an Al alloy powder or an Al compound powder. The raw material powder may contain an element such as Cu, Mg, Mn, Zr, Sr, Ni, Cr, Fe, Mo, Sn, Si, C, B, N or O, in addition to Al. The Al compound powder is Al ₂ O ₃ A typical example is aluminum oxide powder consisting of
In the case of this raw material powder, similarly to the case where Ti is used as the active metal element, one kind of powder alone or a mixture of two or more kinds of powders may be used, regardless of the content form of each element.
[0030]
{Circle around (3)} The raw material powder may be a mixed powder in which hard particle powders composed of boride, nitride, oxide or carbide are mixed. The mixed powder may be a mixture of two or more hard particle powders. When the hard particles are made of a compound of Ti or Al, the hard particle powder is the above-mentioned Ti compound powder or Al compound powder.
[0031]
When the raw material powder including the hard particle powder is formed into a powder, a composite material in which the hard particles are uniformly dispersed in a matrix made of an active metal such as Ti or Al or an alloy thereof can be easily obtained. Such a composite material has excellent mechanical properties such as strength, rigidity, heat resistance, and wear resistance. In particular, it is remarkable in the case of a metal sintered body obtained by sintering a powder compact.
The hard particles include the aforementioned TiB ₂ , TiB, TiC, TiN, TiO ₂ , Al ₂ O ₃ Besides, SiC, Si ₂ N ₄ , B ₄ C, CrN, Cr ₂ N, MoB, CrB, Y ₂ O ₃ , ThO ₂ Etc.
[0032]
Conventionally, when such hard particles are dispersed in a large amount in the raw material powder, the formability and sinterability are remarkably inferior even if the raw material powder is pulverized. In the case of the present invention, a high-density powder compact can be obtained even when a large amount of hard particles are contained in the raw material powder. When it is sintered, a high-density sintered body can be obtained by heating for a short time. Further, even if the heating time during the sintering step is extended to sufficiently diffuse the additional element, the dimensional change of the obtained sintered body is small and stable.
[0033]
Therefore, according to the present invention, even if the upper limit of the ratio of the hard particle powder in the raw material powder is increased to 5% by mass, 10% by mass, 15% by mass, and 20% by mass, A sintered body is obtained. Note that the ratio of the hard particle powder is a ratio when the whole raw material powder after mixing is 100% by mass.
[0034]
{Circle around (4)} The alloy, compound, hard particles and the like contained in the raw material powder need not necessarily remain in the powdered state in the powder compact or its sintered metal. The state may be changed to a more stable state by pressing during powder molding or heating during sintering. For example, in a titanium-based sintered body, TiB ₂ In some cases, the particles change to more stable and hard TiB.
[0035]
The production method of each powder, such as mechanical pulverized powder, hydrodehydrogenated powder, and atomized powder, does not matter. The raw material powder may be a granulated powder. Although the particle size of the raw material powder is not particularly limited, for example, the average particle size is preferably 1 to 100 μm.
The present invention does not exclude mixing of a lubricant with the raw material powder. By mixing a small amount of lubricant with the raw material powder, the fluidity of the powder can be improved. At this time, it is more preferable to use the higher fatty acid-based lubricant (including one dispersed in a dispersion liquid) according to the present invention. However, as described above, if a large amount of the lubricant is mixed, the ultimate density of the powder compact decreases.
[0036]
(2) Higher fatty acid lubricant
The higher fatty acid-based lubricant in the present invention means both a lubricant composed of a higher fatty acid and a lubricant composed of a metal salt of a higher fatty acid. Higher fatty acids include stearic acid, palmitic acid, oleic acid and the like. Metal salts of higher fatty acids include, for example, lithium salts, calcium salts, and zinc salts. Specific examples include lithium stearate, calcium stearate, zinc stearate, barium stearate, lithium palmitate, lithium oleate, calcium palmitate, calcium oleate, and the like. The higher fatty acid-based lubricant referred to in the present invention suffices if it contains at least one of them as a main component.
[0037]
The higher fatty acid-based lubricant is preferably solid in a room temperature range to a warm range. This is because if the lubricant is liquid, the lubricant flows down and it becomes difficult to uniformly apply the lubricant to the inner surface of the mold.
To efficiently and uniformly apply the higher fatty acid-based lubricant to the inner surface of the mold, the higher fatty acid-based lubricant is preferably dispersed in a dispersion liquid. This dispersion may be water, an alcohol-based solvent, or a mixture of water and an alcohol-based solvent. When a higher fatty acid-based lubricant dispersed in such a dispersion is sprayed on a heated mold, water or an alcohol-based solvent in the dispersion is instantaneously evaporated, and a uniform lubricant film is easily formed. Can be formed. In particular, by mixing an alcohol-based solvent, evaporation of moisture and the like is accelerated, and a uniform and even lubricant film is more easily formed.
[0038]
In the present invention, since an active metal powder which is very easy to seize with a mold is originally used, it is particularly important to form a uniform lubricant film with a higher fatty acid-based lubricant. This makes it possible to stably obtain a high-density and high-quality powder compact while extending the life of the mold.
When heating the mold, the suitable mold temperature depends on the dispersion. For example, when the dispersion comprises water, the mold temperature is preferably set to 100 ° C. or higher. When an alcohol-based solvent is mixed, the temperature may be lower than 100 ° C. depending on the concentration. However, it is more preferable that the mold temperature is such that the molding step can be performed in a warm state. In any case, the mold temperature is preferably set to be higher than the boiling point of the dispersion and lower than the melting point of the higher fatty acid-based lubricant. The reason why the melting point is lower than the melting point of the higher fatty acid-based lubricant is to prevent the higher fatty acid-based lubricant from dripping.
[0039]
When a mixed solution of water and an alcohol solvent is used as a dispersion, the alcohol solvent is preferably 1 to 50% by volume, more preferably 5 to 25% by volume. When the amount of the alcoholic solvent is less than 1% by volume, there is not much meaning in mixing the alcoholic solvent, and when the amount is more than 50% by volume, the working environment is deteriorated due to the odor of the alcoholic solvent and the cost is increased.
[0040]
As such an alcohol solvent, methyl alcohol, ethyl alcohol, isopropyl alcohol and the like can be used. However, it does not matter if it has a lower boiling point than water and is not harmful when volatilized.
The higher fatty acid-based lubricant to be dispersed in the dispersion is preferably in the form of a powder composed of particles having a maximum particle size of 30 μm or less. If there is a particle exceeding 30 μm, the lubricant film formed on the inner surface of the mold becomes uneven. In addition, the particles of the higher fatty acid-based lubricant easily precipitate in the dispersion, making it difficult to uniformly apply the lubricant to the inner surface of the mold.
[0041]
Next, in order to uniformly disperse the higher fatty acid-based lubricant in a dispersion such as water, a surfactant is preferably added to the dispersion in advance.
Examples of the surfactant include an alkylphenol-based surfactant, polyoxyethylene nonyl phenyl ether (EO) 6, polyoxyethylene nonyl phenyl ether (EO) 10, an anionic nonionic surfactant, and a borate-based emalbon. T-80 and the like.
[0042]
One or more surfactants may be appropriately selected depending on the higher fatty acid-based lubricant used. For example, when lithium stearate (LiSt) is used as the higher fatty acid-based lubricant, polyoxyethylene nonyl phenyl ether (EO) 6, polyoxy ethylene nonyl phenyl ether (EO) 10 and borate ester Emalbon T-80 are used. It is preferred to simultaneously add two types of surfactants.
[0043]
This is because LiSt is difficult to disperse in water or the like if only borate ester Emalbon T-80 is used. On the other hand, in the case of polyoxyethylene nonyl phenyl ether (EO) 6 and (EO) 10, LiSt is dispersed in water or the like by using only them. However, it is difficult to uniformly disperse the higher fatty acid-based lubricant when diluting the dispersion. Therefore, when LiSt is used as the higher fatty acid-based lubricant, it is preferable that the above-mentioned three types of surfactants are appropriately added in combination. The amount of the surfactant to be added is preferably 1.5 to 15% by volume when the entire dispersion containing the surfactant is 100% by volume. At this time, it is preferable to mix the three surfactants in a volume ratio of 1: 1: 1.
[0044]
The larger the amount of the surfactant added, the more LiSt and the like can be dispersed. However, when the addition amount of the surfactant increases, the viscosity of the dispersion liquid also increases, and it becomes difficult to make particles such as LiSt fine by the pulverization treatment described later.
Furthermore, when a small amount of an antifoaming agent (such as a silicon-based antifoaming agent) is appropriately added, a uniform lubricant film is easily formed. The addition amount of the defoaming agent may be about 0.1 to 1% by volume, assuming that the volume of the dispersion is generally 100% by volume.
By the way, when a powder of a higher fatty acid-based lubricant is dispersed in a dispersion containing a surfactant, for example, 100 cm of the dispersion is used. ³ To 30 g of LiSt, and then a ball mill type pulverizing process using a Teflon-coated steel ball (diameter: about 5 to 10 mm) is preferable. When this process is performed for approximately 50 to 100 hours, LiSt pulverized to a maximum particle size of 30 μm or less is in a state of being suspended and dispersed in the dispersion.
[0045]
(3) Coating process
When the higher fatty acid-based lubricant is applied to the inner surface of the mold, a dispersion in which the higher fatty acid-based lubricant is dispersed may be appropriately diluted and used. Specifically, when the entire diluted dispersion is 100% by mass, the higher fatty acid-based lubricant (for example, LiSt) is 0.1 to 5% by mass, and further 0.5 to 2% by mass. It is good to dilute to an extent. Such dilution enables the formation of a thin and uniform lubricant film.
By spraying the diluted dispersion with, for example, a spray gun for coating or the like, uniform application of the higher fatty acid-based lubricant to the inner surface of the mold can be easily performed. This coating can also be performed using an electrostatic coating device such as an electrostatic gun. In addition, for a specific method of uniformly applying the higher fatty acid-based lubricant to the inner surface of the mold, the method disclosed in FIG. 1 or 2 of International Publication WO 01/43900 described above may be appropriately referred to. .
[0046]
(4) Forming process
The molding step of the present invention is a step of pressing the active metal powder filled in a mold coated with a higher fatty acid-based lubricant in a warm state.
{Circle around (1)} The warm state referred to in the present invention differs depending on the raw material powder, higher fatty acid-based lubricant and the like used, and it seems difficult to uniformly define a specific temperature. To put it bluntly, the temperature range is such that the effect of reducing the ejection force can be obtained even when high-pressure molding is performed. However, according to the inventor's experience, it is sufficient that at least the temperature of the portion where the inner surface of the mold contacts the raw material powder (contact portion temperature) is in a warm state of 100 to 225 ° C, more preferably 100 to 180 ° C. . If optimization is performed for each active metal powder, for example, when the active metal element is Ti, it is better to set the contact portion temperature to 130 to 160 ° C. If the active metal element is Al, it is better to set the contact portion temperature to 100 to 160 ° C.
Such a warm state can be achieved by heating at least one of the mold and the raw material powder. By heating both of them to substantially the same temperature, a more stable warm state can be obtained.
[0047]
{Circle around (2)} In the case of the present invention, there is no upper limit on the molding pressure. To be sure, it is within a range where the mold and the molding apparatus are not damaged or broken. Therefore, even at a high molding pressure (about 2500 MPa) which cannot be considered in ordinary powder molding, particularly molding of active metal powder, powder molding can be performed without any problem. However, the molding pressure is preferably 392 to 2000 MPa, and more preferably 588 to 1568 MPa, as a range in which sufficient high density can be obtained and productivity can be improved. If the molding pressure is less than the lower limit (392 MPa), a high-density powder molded body cannot be obtained, and is at a level that can be achieved by the conventional powder molding method without using the powder molding method of the present invention. In the case of the present invention, the lower limit of the molding pressure can be 686 MPa or more, and furthermore, 784 MPa or more.
[0048]
In order to optimize the molding pressure for each active metal powder, for example, when the active metal element is Ti, the molding pressure may be 500 to 2500 MPa, and more preferably 784 to 1568 MPa. If the active metal element is Al, it is better to set the molding pressure to 392 to 2500 MPa, and more preferably 588 to 1568 MPa.
[0049]
(3) Next, the relationship between the molding pressure and the ejection force will be described.
In the case of ordinary powder molding, the higher the molding pressure, the greater the extraction power when extracting the powder compact from the mold. However, in the case of the present invention, although the density of the powder compact is increased by increasing the molding pressure, the ejection force hardly changes or is only slightly increased. Moreover, the ejection force in the case of the present invention is reduced to about 1/10 as compared with the case where the conventional powder molding method is used.
For example, when the molding pressure in the molding step is 784 MPa or more, the output in the extraction step is 10 MPa or less. This does not change even if the molding pressure is 980 MPa or more, 1176 MPa or more, or 1372 MPa or more. More specifically, the output power is 5 MPa or less, and further 3 MPa or less.
[0050]
Looking at each active metal powder, when the active metal element is Ti, the molding pressure is 784 MPa or more, and the ejection force is 10 MPa or less, and further 3 MPa or less. When the active metal element is Al, the molding pressure is 392 MPa or more, the ejection force is 5 MPa or less, and further, the molding pressure is 588 MPa or more, and the ejection force is 1 MPa or less.
In the case of the present invention, when looking at the pressure ratio of the ejection force to the molding pressure, the change in the ejection force is small, so that the pressure ratio tends to decrease with an increase in the molding pressure.
[0051]
(5) Other
{Circle around (1)} The mold in the present invention may be made of high-speed steel (high-speed tool steel) or cemented carbide. The inner surface of the mold may be subjected to a TiN coating treatment or the like. The smaller the surface roughness of the inner surface of the mold, the more effective it is in reducing the frictional force between the mold and the powder compact, and the better the surface roughness and dimensional accuracy of the obtained powder compact.
[0052]
{Circle over (2)} The powder compact of the present invention and the metal sintered compact obtained by sintering the powder compact have a high density very close to the true density, and therefore have excellent mechanical properties such as strength. Therefore, it can be used as a structural member as well as various members.
[0053]
In particular, the effectiveness of the powder compact and the metal sintered compact obtained by the present invention using Ti as the active metal element is very large. Conventionally, in various fields such as aviation, space, and military, titanium alloys that are lightweight and have high strength (that is, have excellent specific strength) have been frequently used. However, in general, titanium alloys are rarely applied to mass-produced consumer products. In particular, there has never been a case in which a titanium alloy is applied as a substitute for a mass-produced part that frequently uses steel materials. If a titanium alloy is used, its production cost becomes extremely high, and it is not suitable for mass-produced parts requiring low cost. The biggest factor that raises the manufacturing cost is not only the raw material cost but also the secondary processing cost when processing the material into each member because the shape of the titanium alloy material is limited, is very high. is there.
[0054]
On the other hand, if the powder molding method of the present invention is used, a member made of a titanium alloy that is lightweight and has excellent strength and the like can be obtained without substantially incurring high secondary processing costs. Can be replaced with titanium alloy from conventional steel.
As such, there are, for example, automobile parts, various sporting goods, tools and the like which require all strengths. More specifically, in the case of an automobile part, an automobile engine part such as an engine valve, a valve retainer, a valve lifter, a piston pin, a valve guide, a connecting rod, a rocker arm and the like can be mentioned. Power transmission system components such as gears, drive shafts, and CVT blocks are also included. In the case of sports equipment, golf clubs such as drivers, irons, and putters are typical.
[0055]
By the way, the molding of a cylindrical member (such as an extruded billet), a piston pin, a valve guide, a valve retainer, a connecting rod, a CVT block, an iron, a putter, and the like are performed by using the powder molding method of the present invention in addition to the conventional molding method. It becomes possible by applying a forming method or the like.
Molding of engine valves, valve lifters, rocker arms, gears, drive shafts, golf shoes, etc. is possible by applying the powder molding method and molding method of the present invention to advanced molding methods such as CNC press. Become.
[0056]
【Example】
The present invention will be described more specifically with reference to examples.
(1) Example
(1) Raw material powder
At the time of mixing the raw material powders, first, five kinds of powders were prepared. That is, pure titanium powder (manufactured by WUYI: average particle size: 42 μm), pure aluminum powder (manufactured by Fukuda Metal Foil Powder Co., average particle size: 30 μm), Al-6% Zn-2% Mg-1.5% Cu alloy powder (Manufactured by Sumitomo Light Metal Co., Ltd .: average particle size 35 μm), Al ₃ V powder (manufactured by Nippon Denko: average particle size 20 μm), TiB ₂ It is a powder (manufactured by Nippon Shinmetal Co., Ltd .: average particle size 3.5 μm). The unit of the alloy composition is mass% (the same applies hereinafter). TiB ₂ The powder corresponds to the hard particle powder in the present invention.
Next, these powders were used alone or mixed appropriately to prepare active metal powders having the five compositions shown in Table 1.
[0057]
(2) Preparation of mold lubricant
As a surfactant, polyoxyethylene nonyl phenyl ether (EO) 6, (EO) 10 and borate ester Emalbon T-80 were prepared. These three surfactants were mixed at a ratio of 1: 1: 1 and contained at a ratio of 1.5% by volume of the surfactant to 100% by volume of water (dispersion liquid). Further, an antifoaming agent antifoam was added thereto at a ratio of 0.1% by volume. 25 g of lithium stearate (LiSt) powder was dispersed in 100 cc of water containing the surfactant. This LiSt has a melting point of about 225 ° C. and an average particle size of 20 μm.
[0058]
Next, this dispersion was subjected to a fine pulverization treatment with a ball mill type pulverizer (Teflon-coated steel balls) for 100 hours. The stock solution after the pulverization was diluted with water and an ethyl alcohol-based solvent. The ratio at this time was 14 parts by volume of water and 5 parts by volume of an ethyl alcohol-based solvent with respect to 1 part by volume of the stock solution. This means that 25% by volume of the alcohol solvent was added to water. Thus, a mold lubricant to be applied to the inner surface of the mold was obtained.
[0059]
(3) Mold
A mold made of cemented carbide having a cylindrical cavity (φ23.000 ± 0.005 × 50 mm) and upper and lower punches made of high-speed steel were prepared. The inner surface of this mold was previously subjected to a TiN coating treatment, and the surface roughness was set to 0.4Z. A band heater was wound around the mold so that heating could be performed as appropriate.
[0060]
▲ 4 ▼ Molding
The mold and each raw material powder were heated to 150 ° C. The heating of the raw material powder was performed by an oven (electric furnace) in the air atmosphere.
The above-mentioned mold lubricant was sprayed onto the inner surface of the mold at a mold temperature of 150 ° C. with a spray gun for 1 cm. ³ / Uniformly at a rate of about / s. Thus, a lubricant film having a thickness of about 1.5 μm was formed on the inner surface of the mold (coating step).
[0061]
The heated various raw material powders were filled in the mold (filling step). Then, the molding pressure was appropriately changed within the range of 392 to 1568 MPa, and warm pressure molding was performed (molding step). The molding pressure at that time is also shown in Table 1.
By driving the punch, each molded powder body was extracted from the mold (extraction step). The extraction power at this time was also measured.
[0062]
5) Sintering
Regarding the powder compact made of titanium-based powder, sintering was also performed at 1300 ° C. for 4 hours in a vacuum (sintering step).
[0063]
(2) Comparative example
As a comparative example, a powder compact formed at room temperature using the pure titanium powder and the pure aluminum powder was prepared. At this time, the commercially available dry fluorine lubricant Unon S was used as a mold lubricant and spray-coated on the inner surface of the mold in the same manner as in the example. The molding pressure was basically within a range where damage to the mold due to galling or the like did not occur. The molding pressure at that time is also shown in Table 1.
[0064]
(3) Measurement
With respect to the powder compacts obtained in the above Examples and Comparative Examples, the compact densities and ejection powers were determined, respectively. The results are shown in Table 1. Table 1 also shows the ratio of the density of each compact to the true density (relative density ratio). Note that the true density is a density obtained for a smelting material having the same composition as the composition of each raw material powder. The compact density is obtained by measuring the weight and dimensions of each compact and calculating from the measured values.
The extraction output was determined by measuring the extraction load using a load cell and dividing the extraction load by the side area of the powder compact.
Further, for the metal sintered body, a dimensional change due to the sintering process was also determined from dimensions measured before and after the sintering process. The sintered body density was measured by the Archimedes method.
[0065]
(4) Evaluation
A. Powder compaction of titanium raw material powder
(1) Pure titanium powder
Sample No. 1 in Table 1. 1-1 to 1-6, sample no. C1-1 to C1-3 and FIGS. 1 to 4 show the respective properties when the pure titanium powder was molded at various molding pressures.
As is evident from the above, in the warm-formed embodiment, high-pressure forming exceeding 1,500 MPa was realized for pure titanium powder, which is an active metal powder. And a very high-density powder molding method was obtained.
Specifically, the relative density ratio of the powder compact greatly exceeded the conventional maximum level of 85%, and reached 98 to 99%, and a powder compact having a true density was obtained.
[0066]
In Table 1 and FIG. 1, etc., the relative density ratio is used as an index of the compact density because the true density varies depending on the composition. This is for objectively evaluating the ratio. The same applies to the sintered body density.
[0067]
As is clear from FIG. 2, in the case of the present example, the ejection force hardly changed despite the molding pressure being significantly increased. In addition, since the molding pressure exceeded 600 MPa, the ejection force became a very low value of 5 MPa or less. In addition, when the output power exceeded 784 MPa, the extraction power became almost constant at an extremely low value of about 2.5 MPa.
On the other hand, in the comparative example molded at room temperature, the molding pressure was at most 588 MPa, and the mold was seized. The relative density ratio of the obtained powder compact did not reach even 85% at most. In addition, in the case of molding at room temperature, the ejection force sharply increased almost in proportion to the increase in the molding pressure.
[0068]
As is apparent from FIG. 3, the density of the compact increases with the increase of the molding pressure, and the density of the sintered compact increases accordingly. In particular, in this example, when a powder compact having a compacting pressure of 1176 MPa or more was sintered, the density of the sintered compact increased to almost the true density.
Moreover, as can be seen from FIG. 4, in the case of the present embodiment, the dimensional change before and after sintering was as small as about 1 to 3%. On the other hand, in the case of the comparative example formed at room temperature, since the density of the original compact itself was low, the dimensional change before and after sintering was considerably large, 4 to 10%.
[0069]
(2) In the case of titanium alloy powder
Pure titanium powder and Al ₃ Alloy powder mixed with V powder and TiB ₂ TiB mixed with powder ₂ Table 1 shows the characteristics of each of the alloy mixed powders when molded at various molding pressures. 2-1 to 2-3, sample no. The results are shown in FIGS.
[0070]
First, when a mixed powder having an alloy composition of Ti-6Al-4V was warm compacted, a very high compact density and a sintered compact density were obtained as in the case of the pure titanium powder. In particular, the sintered body density was stabilized at an extremely high value of about 99.5% relative density ratio. Further, the output at that time was stable at a very low value of about 1 MPa or less.
[0071]
Next, TiB which is a hard particle powder is added to the alloy mixed powder. ₂ When the powder obtained by mixing the powders was subjected to pressure molding, sufficiently high compact density and sintered compact density and sufficiently low ejection force were obtained. For example, when the molding pressure was 1176 MPa, the relative density ratio of the powder compact reached 94%, and the relative density ratio of the metal sintered compact reached 99%. At that time, the output of the powder compact was 5 MPa or less in each case.
Also, as can be seen from FIG. ₂ Is 6% by mass, a peculiar phenomenon that the ejection force decreases as the molding pressure increases.
[0072]
However, TiB ₂ Although it depends on the amount of powder mixed, TiB ₂ When the powder was mixed, the respective densities were slightly lower and the ejection force was slightly higher when viewed at the same molding pressure than when the powder was not mixed. Needless to say, all of these values are significantly superior to those at room temperature.
FIG. 7 also shows that the density of each of the present examples is higher than that of the conventional example (the case of molding at 392 MPa by the CIP method).
[0073]
B. Powder compaction of aluminum raw material powder
(1) Pure aluminum powder
Sample No. 1 in Table 1. 4-1 to 4-7, sample no. C2-1 to C2-3 and FIGS. 8 and 9 show the respective characteristics when the pure aluminum powder was molded at various molding pressures.
The overall tendency was the same as in the case of the pure titanium powder, and the powder compact according to this example had a very high density.
However, in the case of this embodiment, the ejection force was as small as about 1 MPa or less regardless of the molding pressure. That is, even when the molding pressure was low (392 MPa in this example), the ejection force was low. This is presumably because, as can be seen from the outer diameter in Table 1, the outer diameter of the powder molded body after the extraction was substantially equal to or slightly smaller than the inner diameter of the mold. However, such a tendency is not observed in the comparative example formed at room temperature, as can be seen from Table 1 and FIG.
[0074]
(2) In the case of aluminum alloy powder
The properties of the alloy powder (only one kind) having an alloy composition of Al-6Zn-2Mg-1.5Cu when molded at various molding pressures are shown in Sample No. 1 of Table 1. 5-1 to 5-3 and shown in FIGS. 10 and 11. The overall trend was similar to that of pure aluminum powder.
[0075]
However, when viewed at the same molding pressure, in the case of this alloy powder, the compact density was slightly lower and the ejection force was slightly higher than in the case of the pure aluminum powder. This is presumably because the alloy powder was composed of particles having higher strength than the pure aluminum powder, and the compressibility was reduced. Nevertheless, the relative density ratio of the powder compact reached 94% or more, indicating that a powder compact having a sufficiently high density was obtained. Needless to say, all of these values are far superior to those at room temperature.
[0076]
C. Metal sintered body with increased content of hard particles
TiB ₂ As the content of Ni increases, a sintered metal body having high rigidity and high strength can be obtained. ₂ In general, as the content of N increases, moldability and sinterability decrease. Therefore, TiB ₂ Was newly increased to 12% by mass, and the moldability and sinterability according to the present invention were evaluated.
[0077]
The test material according to the embodiment of the present invention is TiB ₂ Except for the sample amount, It produced under the same conditions as 3-3. That is, the powder is molded at a mold temperature of 150 ° C. and a molding pressure of 1568 MPa, and then sintered at 1300 ° C. The test material as a comparative example was obtained by molding a raw material powder having the same composition by the above-mentioned room temperature molding (molding pressure: 588 MPa) and sintering it at 1300 ° C.
Here, FIGS. 12 and 13 show how the relative density ratio and the dimensional change rate of the test material change when the sintering time is changed. By the way, in each drawing, 20 vol% TiB is represented by 12 mass% TiB. ₂ Is changed to 20% by volume of TiB by sintering.
[0078]
First, as can be seen from FIG. 12, in the case of the example, a sufficiently high sintered body having a relative density ratio close to 100% was obtained by sintering for an extremely short time. On the other hand, in the case of the comparative example, a long sintering time was required to increase the relative density ratio of the sintered body. In addition, in the conventional manufacturing method as in the comparative example, even if the raw material powder is pulverized, when the hard particles are dispersed in a large amount in the raw material powder, the powder formability and sinterability are remarkably inferior. A high density sintered body cannot be obtained.
[0079]
Next, as can be seen from FIG. 13, in the case of the example, the dimensional change rate was extremely small and stable at about 2% even when the sintering time was long. On the other hand, in the case of the comparative example, the dimensional change rate was greatly reduced with the sintering time and was not stable.
As described above, according to the examples of the present invention, it has been clarified that a metal sintered body having high density and excellent dimensional stability can be obtained, which has not been achieved in the past.
[0080]
D. Mechanical Properties of Sintered Metal with Hard Particles Dispersed
TiB ₂ , A tensile strength, a rigidity, a fatigue strength, and the like were evaluated for a test material obtained by powder molding and sintering of a raw material powder containing.
The composition of the raw material powder used at this time was as follows: Same as 3-3. The test materials of the examples are sample Nos. Manufactured similarly to 3-3. However, the shape was a 10 × 10 × 55 mm bending test piece shape. The test material of the comparative example was obtained by sintering a powder compact of the same shape that was CIP-molded at 392 MPa at 1300 ° C. The case where the sintering time was 4 hours was Comparative Example 1 and the case where the sintering time was 16 hours was Comparative Example 2. Each of the obtained test materials was processed into a tensile test piece and a rotating bending fatigue test piece, and the mechanical properties of each test piece were evaluated. The results are shown in FIG. 14 and FIG. Incidentally, 10 vol% TiB is shown in each figure because 6 mass% of TiB ₂ Was changed to 10% by volume of TiB by sintering.
[0081]
As is clear from FIGS. 14 and 15, the sintered body of the example has a very high relative density ratio of the sintered body to the sintered body of the comparative example, and any one of the tensile strength, elongation and fatigue strength. In particular, it was confirmed that the material was excellent.
[0082]
E. FIG. Regarding the surface analysis result of the powder compact according to the present invention
Sample No. 1 in Table 1. 1-4 (when the raw material powder is pure Ti) and sample Nos. The surface of the powder compact shown in 4-5 (when the raw material powder was pure Ti) was subjected to surface analysis by TOF-SIMS (Time of Flight Secondary Ion Mass Spectrometer). FIGS. 16 and 17 show the respective secondary ion images obtained as a result.
[0083]
From these, it was confirmed in each case that the distribution of stearic acid was closer to the distribution of Ti or Al than the distribution of Li. This suggests that, during the molding step according to the present example, a mechanochemical reaction occurred, and a new metal soap film that appeared to be titanium stearate or aluminum stearate was formed on the surface of each powder compact. Seems to be doing.
[0084]
[Table 1]

[Brief description of the drawings]
FIG. 1 is a graph showing a relationship between a molding pressure and a green body density (relative density ratio) when room temperature molding and warm molding are performed using pure titanium powder.
FIG. 2 is a graph showing the relationship between molding pressure and ejection force at that time.
FIG. 3 is a graph showing a relationship between a molding pressure of pure titanium powder and a relative density ratio of a metal sintered body obtained by sintering the obtained powder molded body.
FIG. 4 is a graph showing a relationship between a molding pressure of pure titanium powder and a dimensional change rate during sintering of a powder compact.
FIG. 5 is a graph showing the relationship between compacting pressure and compact density (relative density ratio) when warm-forming titanium alloy powder.
FIG. 6 is a graph showing the relationship between molding pressure and ejection force at that time.
FIG. 7 is a graph showing a relationship between a molding pressure of a titanium alloy powder and a relative density ratio of a metal sintered body obtained by sintering the obtained powder molded body.
FIG. 8 is a graph showing the relationship between molding pressure and compact density (relative density ratio) when compacting at room temperature and during warm compaction using pure aluminum powder.
FIG. 9 is a graph showing the relationship between molding pressure and ejection force at that time.
FIG. 10 is a graph showing the relationship between the molding pressure and the compact density (relative density ratio) when room temperature compaction and warm compaction are performed using pure aluminum powder and aluminum alloy powder.
FIG. 11 is a graph showing the relationship between molding pressure and ejection force at that time.
FIG. 12 is a graph showing a relationship between a sintering time of a non-sinterable material and a relative density ratio.
FIG. 13 is a graph showing the relationship between the sintering time of the hardly sinterable material and the dimensional change.
FIG. 14 is a bar graph comparing differences in relative density ratio, tensile strength, and elongation due to differences in manufacturing conditions.
FIG. 15 is a graph comparing differences in fatigue strength due to differences in manufacturing conditions.
FIG. 16 is a secondary ion image obtained by observing the surface of a powder compact made of pure Ti powder by TOF-SIMS.
FIG. 17 is a secondary ion image obtained by observing the surface of a powder compact made of pure Al powder by TOF-SIMS.

Claims (35)

An application step of applying a higher fatty acid-based lubricant to the inner surface of the mold,
A filling step of filling a raw material powder containing an active metal element as a main component into the mold after the coating step,
Pressing the raw material powder after the filling step in a warm state to form a powder compact,
An extraction step of extracting the powder compact after the molding step from the mold,
A powder molding method, characterized in that the obtained powder compact has a high density. The powder molding method according to claim 1, wherein the active metal element is titanium (Ti). The raw material powder further includes aluminum (Al), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), scandium (Sc), chromium (Cr), iron ( Fe), molybdenum (Mo), tin (Sn), tungsten (W), manganese (Mn), nickel (Ni), copper (Cu), silicon (Si), carbon (C), boron (B), nitrogen ( The powder molding method according to claim 2, wherein N) or oxygen (O) is contained. The powder molding method according to claim 2, wherein the raw material powder comprises a pure titanium powder, a titanium alloy powder, or a titanium compound powder. The method of claim 1, wherein the active metal element is Al. 6. The raw material powder according to claim 5, further comprising Cu, magnesium (Mg), Mn, Zr, strontium (Sr), Ni, Cr, Fe, Mo, Sn, Si, C, B, N or O. The powder molding method as described in the above. The powder molding method according to claim 5, wherein the raw material powder is made of a pure aluminum powder, an aluminum alloy powder, or an aluminum compound powder. The powder molding method according to claim 1, wherein the raw material powder is a mixed powder in which hard particle powders made of carbide, boride, nitride, or oxide are mixed. The active metal element is Ti;
The powder molding method according to claim 1, wherein a molded body density, which is an apparent density of the powder molded body, is 85% or more of a true density determined from a composition of the raw material powder. The active metal element is Al;
The powder molding method according to claim 1, wherein a molded body density, which is an apparent density of the powder molded body, is 90% or more of a true density determined from a composition of the raw material powder. In the molding step, the molding pressure is set to 392 MPa or more while the contact part temperature, which is the temperature of the part where the inner surface of the mold contacts the raw material powder, is at least 100 to 225 ° C. The powder molding method according to claim 1, wherein the method is a step of carrying out. The active metal element is Ti;
The powder molding method according to claim 11, wherein the contact portion temperature is 100 to 225C, and the molding pressure is 500 to 2500 MPa. The active metal element is Al;
The powder molding method according to claim 11, wherein the contact portion temperature is 100 to 225 ° C, and the molding pressure is 392 to 2500 MPa. The powder molding method according to claim 1, wherein when the molding pressure in the molding step is 784 MPa or more, the extraction output in the extraction step is 10 MPa or less. The active metal element is Ti;
The powder molding method according to claim 14, wherein the molding pressure is 784 MPa or more, and the ejection force is 10 MPa or less. The active metal element is Al;
The powder molding method according to claim 14, wherein the molding pressure is 392 MPa or more, and the ejection force is 5 MPa or less. The powder molding method according to claim 14, wherein a pressure ratio of the ejection force to the molding pressure tends to decrease with an increase in the molding pressure. 2. The powder molding method according to claim 1, wherein the applying step is a step of spraying a powdered higher fatty acid-based lubricant dispersed in a dispersion liquid containing a surfactant onto the heated inner surface of the mold. 3. 19. The method according to claim 18, wherein the dispersion comprises water or an alcohol solvent. 19. The powder molding method according to claim 18, wherein the dispersion comprises a mixture of water and 1 to 50% by volume of an alcohol solvent. 19. The powder molding method according to claim 18, wherein a mold temperature of the heated mold is equal to or higher than a boiling point of the dispersion and lower than a melting point of the higher fatty acid-based lubricant. 19. The powder molding method according to claim 1, wherein the higher fatty acid-based lubricant comprises a metal salt containing a lithium salt, a calcium salt or a zinc salt of a higher fatty acid as a main component. The powder molding method according to claim 18, wherein the higher fatty acid-based lubricant has a maximum particle size of 30 µm or less. The powder molding method according to claim 1, wherein the molding step is a step of forming a new metal soap film containing the active metal element different from the higher fatty acid-based lubricant on the surface of the powder molded body. . The active metal element is Ti;
The powder molding method according to claim 24, wherein the metal soap is a Ti salt of a higher fatty acid. The active metal element is Al;
The powder molding method according to claim 24, wherein the metal soap is an Al salt of a higher fatty acid. An application step of applying a higher fatty acid-based lubricant to the inner surface of the mold,
A filling step of filling a raw material powder containing an active metal element as a main component into the mold after the coating step,
Pressing the raw material powder after the filling step in a warm state to form a powder compact,
An extraction step of extracting the powder compact after the molding step from the mold,
The active metal element is Ti;
A powder compact, wherein a compact density, which is an apparent density of the powder compact, is a high density of 85% or more of a true density determined from a composition of the raw material powder. An application step of applying a higher fatty acid-based lubricant to the inner surface of the mold,
A filling step of filling a raw material powder containing an active metal element as a main component in the mold after the coating step,
Pressing the raw material powder after the filling step in a warm state to form a powder compact,
An extraction step of extracting the powder compact after the molding step from the mold,
The active metal element is Al;
A powder compact, wherein a compact density, which is an apparent density of the powder compact, is 90% or more of a true density determined from a composition of the raw material powder. An application step of applying a higher fatty acid-based lubricant to the inner surface of the mold,
A filling step of filling a raw material powder containing an active metal element as a main component into the mold after the coating step,
Pressing the raw material powder after the filling step in a warm state to form a powder compact,
An extraction step of extracting the powder compact after the molding step from the mold;
A sintering step of heating the powder compact after the extraction step to form a metal sintered body,
A method for producing a metal sintered body, wherein the obtained metal sintered body has a high density. An application step of applying a higher fatty acid-based lubricant to the inner surface of the mold,
A filling step of filling a raw material powder containing an active metal element as a main component into the mold after the coating step,
Pressing the raw material powder after the filling step in a warm state to form a powder compact,
An extraction step of extracting the powder compact after the molding step from the mold;
Heating the powder molded body after the extraction step to obtain a metal sintered body,
The active metal element is Ti;
A metal sintered body, wherein a sintered body density, which is an apparent density of the metal sintered body, is a high density of 85% or more of a true density determined from a composition of the raw material powder. An application step of applying a higher fatty acid-based lubricant to the inner surface of the mold,
A filling step of filling a raw material powder containing an active metal element as a main component into the mold after the coating step,
Pressing the raw material powder after the filling step in a warm state to form a powder compact,
An extraction step of extracting the powder compact after the molding step from the mold;
Heating the powder molded body after the extraction step to obtain a metal sintered body,
The active metal element is Al;
The sintered metal density, which is an apparent density of the sintered metal body, is a high density of 90% or more of a true density determined from a composition of the raw material powder. An application step of applying a higher fatty acid-based lubricant to a surface of a metal material mainly containing an active metal element and / or a processing surface of a molding die;
A forming step of forming the metal material in a warm state by the forming die;
A molding method characterized by comprising: The coating step is a dipping method in which the heated metal material is immersed in a dispersion in which the higher fatty acid-based lubricant is dispersed, or the higher fatty acid-based lubricant is applied to the heated metal material or the molding die. 33. The molding method according to claim 32, wherein the step is performed by a spraying method of spraying a dispersion liquid in which is dispersed. 33. The forming method according to claim 32, wherein the forming step is a step of performing any one of forging, rolling, extrusion, drawing, rolling, coining, sizing, and recompression. An application step of applying a higher fatty acid-based lubricant to a surface of a metal material mainly containing an active metal element and / or a processing surface of a molding die;
And a forming step of forming the metal material in a warm state by the forming die.

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