JP6979708B2 - Manufacturing method of titanium sintered material - Google Patents

Description

The present invention relates to a method for producing a titanium sintered material having high strength and high toughness.

Japanese Patent No. 3459342 (Patent Document 1) describes a method of hydrogenating titanium or a titanium alloy by utilizing the hydrogen brittleness of titanium or a titanium alloy and then pulverizing the titanium or the titanium alloy to an arbitrary particle size to obtain hydride titanium powder. A hydrodehydrogenation method for dehydrogenizing this by vacuum heating and converting it into titanium powder is described.

In the titanium-based powder, the oxygen content of the entire powder increases as the number of fine powders having a small particle size increases. The reason is that, for example, hydrogenated fine powder having a particle size of 10 μm or less has a large specific surface area and takes in oxygen in the air by the processing heat at the time of pulverization, resulting in a high oxygen concentration.

In the invention described in Japanese Patent No. 3459342 (Patent Document 1), the amount of oxygen contained in the titanium hydride powder is within an allowable range of 0.15% by weight by adjusting the powder ratio of the fine powder having a particle size of 10 μm or less. It is controlled as follows. Specifically, after the hydrogenated titanium powder is pulverized, the fine powder having a particle size of 10 μm or less is selectively removed from the obtained hydrogenated titanium powder having a maximum particle size of substantially 150 μm or less. The ratio of powder having a particle size of 10 μm or less is adjusted to be 8% by weight or less.

Japanese Patent No. 3459342

As described in Patent Document 1, titanium hydride powder having a particle size of 10 μm or less is not used as an alloy raw material.

An object of the present invention is to provide a high-strength, high-toughness titanium sintered material while reducing production costs by positively utilizing hydrogenated titanium powder having a particle size of 10 μm or less, which is normally discarded. be.

In one aspect, the method for producing a titanium sintered material according to the present invention includes the following steps.

(A) Hydrogenated titanium powder containing 90% by weight or more in the particle size range of 10 μm or less and 90% by weight or more in the particle size range of 10 μm or more and 150 μm or less, and the average particle size is 20 μm or more. The process of preparing titanium powder.

(B) A step of mixing the titanium hydride powder and the titanium powder by blending so that the amount of the titanium hydride powder is 15% or more and 75% or less based on the weight of the whole.

(C) A step of sintering a mixed powder that has been mixed and treated to obtain a titanium sintered material.

Preferably, the oxygen content in the titanium hydride powder is 0.3% or more and 1.2% or less on a weight basis, and the oxygen content in the titanium powder is 0.1% or more and 1 on a weight basis. It is less than 5.5%.

The above mixing step may include adding and mixing titanium oxide powder in addition to the titanium hydride powder and the titanium powder.

In one embodiment, the titanium powder is a hydrogenated / dehydrogenated titanium powder obtained by hydrogenating a titanium ingot and then crushing and dehydrogenating it. In another embodiment, the titanium powder is an atomized powder produced by the atomizing method.

Preferably, the density of the titanium sintered material is 95% or more. Further, preferably, the oxygen content of the titanium sintered material is 0.25% or more and 0.65% or less on a weight basis.

The method for producing the titanium sintered material may further include a step of performing hot plastic working on the titanium sintered material. In this case, preferably, the titanium sintered material after hot plastic working has a hardness (HV) of 250 or more, a maximum tensile strength (UTS) of 580 MPa or more, and an elongation (ε) of 18% or more. The hot plastic working includes hot rolling, hot pressing, hot forging, and the like, in which the material is hotly plastically deformed.

In another aspect, the method for producing a titanium sintered material according to the present invention includes the following steps.

(D) A step of preparing a hydrogenated titanium powder having an average particle size of 10 μm or less and a titanium powder having an average particle size of 20 μm or more.

(E) A step of mixing the titanium hydride powder and the titanium powder by blending so that the amount of the titanium hydride powder is 15% or more and 75% or less based on the weight of the whole.

(F) A step of sintering a mixed powder that has been mixed and treated to obtain a titanium sintered material.

In still another aspect, the method for producing a titanium sintered material according to the present invention includes the following steps.

(G) A step of preparing a hydrogenated titanium alloy powder having an average particle size of 10 μm or less and a pure titanium powder having an average particle size of 20 μm or more.

(H) A step of mixing the hydrogenated titanium alloy powder and the pure titanium powder by blending so that the amount of the hydrogenated titanium alloy powder is 5% or more and 55% or less based on the weight of the whole.

(I) A step of sintering a mixed powder that has been mixed and treated to obtain a titanium alloy sintered material.

The composition of the titanium hydride alloy powder is, for example, Ti-6Al-4V. In this case, preferably, the titanium hydride alloy powder contains 65% by weight or more in a particle size range of 10 μm.

Preferably, the density of the titanium alloy sintered material is 95% or more.

The method for producing a titanium alloy sintered material preferably further includes a step of performing hot plastic working on the titanium alloy sintered material. In this case, preferably, the titanium alloy sintered material after hot plastic working has a hardness (Hv) of 250 or more, a maximum tensile strength (UTS) of 620 MPa or more, and an elongation (ε) of 14% or more.

In still another aspect, the method for producing a titanium alloy sintered material according to the present invention includes the following steps.

(J) Hydrogenated titanium alloy powder having an average particle size of 10 μm or less and a composition of Ti-6Al-4V and titanium having an average particle size of 20 μm or more and a composition of Ti-6Al-4V. The process of preparing alloy powder.

(K) A step of mixing the hydrogenated titanium alloy powder and the titanium alloy powder.

(L) A step of obtaining a titanium alloy sintered material obtained by sintering a mixed powder that has been mixed.

According to the above method of the present invention, by utilizing hydrogenated titanium powder having a particle size of 10 μm or less, which is normally discarded, a titanium sintered material having high strength and high toughness is provided while reducing the production cost. Can be done.

It is a figure which shows the particle size distribution of titanium hydride powder (powder A). It is a figure which shows the particle size distribution of the hydrogenated / dehydrogenated titanium powder (powder B). It is a figure which shows the particle size distribution of the hydrogenated / dehydrogenated titanium powder (powder C). It is a figure which shows the particle size distribution of the hydrogenated / dehydrogenated titanium powder (powder D). It is a microstructure photograph after sintering (before hot plastic working) of sample numbers 4, 6, 9, 10, 11, 12, and 13. It is a microstructure photograph after sintering and the microstructure photograph after hot plastic working of sample number 13. Is a diagram showing a TiO ₂ additive mixed powder is (a) the appearance of the mixed powder photographs, (b) is an SEM image of the powder mixture. Is a SEM image showing the tissue after sintering of TiO ₂ added mixed powder. 6 is an SEM image of the mixed powder of sample number 10. It is a figure which shows the particle size distribution of an atomize powder. It is a microstructure photograph after sintering of the sample number 9 and the sample number 16. It is a figure which shows the particle size distribution of the hydrogenated 64 titanium fine powder (powder E). It is a figure which shows the particle size distribution of a hydrogenated / dehydrogenated 64 titanium powder (powder F). It is a microstructure photograph after sintering (before hot plastic working) of sample numbers 22, 23, 24, 25, 26, 27, 28, 29.

The inventors of the present invention conducted various experiments and searched for a method for producing a high-strength and high-toughness titanium sintered material using hydrogenated titanium powder having a particle size of 10 μm or less. The details of the experiment, the results of the experiment, and the discussion are described below.

[Confirmation of sinterability]
A hydrogenated titanium fine powder having a particle size of 10 μm or less was formed to prepare a green compact, and then the green compact was sintered under vacuum. Looking at the sintered body, cracks were generated, and a good sintered body could not be obtained. The reason why a good sintered body could not be obtained is considered to be that the titanium hydride fine powder having a particle size of 10 μm or less is too hard and it is difficult to increase the density.

For comparison, hydrogenated and dehydrogenated titanium powder having a particle size of 10 to 45 μm was formed to prepare a green compact, and then the green compact was sintered under vacuum. No cracks were observed in the sintered body, and it was confirmed that the sinterability was good.

In the above experiment, hydrided titanium fine powder and hydrided / dehydrogenated titanium powder were pressure-molded with a press machine to prepare a green compact, and the green compact was sintered. It is expected that the same result will be obtained even if the titanium powder is hardened by the hot isostatic pressing method (HIP) or the cold isostatic pressing method (CIP) and sintered.

From the above experimental results, the following points were considered.

a) If the particle size of the powder is too fine, there is a concern that the sinterability may be impaired.

b) Therefore, it is difficult to produce a good sintered body only with titanium powder having a particle size of 10 μm or less.

c) Titanium hydride powder with a particle size of 10 μm or less takes in a large amount of oxygen, so it is difficult to produce a hard and dense sintered body.

d) It is the density of the powder aggregate that affects the sinterability. If the powder aggregate has a density of, for example, 95% or more, the pores are closed and become independent pores. On the other hand, if the density is, for example, less than 95%, continuous vacancies can be created in addition to independent vacancies. If there are continuous vacancies, air will enter during hot plastic working, and the nitrogen density at that portion will increase.

e) In order to maintain good sinterability while reducing costs, a mixed powder of titanium hydride fine powder with a particle size of 10 μm or less and titanium powder with a particle size of 10 μm or more is prepared, and the powder is molded and sintered. To do.

[Powder used in the experiment]
In order to prepare a mixed powder, the powders shown in Table 1 below were prepared.

The prepared powder A, powder B, powder C, and powder D are commercially available products.

Powder A is titanium hydride powder, and its particle size distribution is shown in Table 2 and FIG. 1 below.

The powder particles constituting the powder A (titanium hydride powder) contain 90% by weight or more in a particle size range of 10 μm or less. Its average particle size (median diameter) is 5.7 μm. In the tables and drawings below, powder A may be referred to as "TF".

Powder B is hydrogenated / dehydrogenated titanium powder, and its particle size distribution is shown in Table 3 and FIG. 2 below.

The powder particles constituting the powder B (hydrogenated / dehydrogenated titanium powder) contain 90% by weight or more in a particle size range of 10 μm or more and 150 μm or less. The average particle size (median diameter) is 63.4 μm. In the following tables and drawings, powder B may be referred to as "HDH".

Powder C is hydrogenated / dehydrogenated titanium powder, and its particle size distribution is shown in Table 4 and FIG. 3 below.

The powder particles constituting the powder C (hydrogenated / dehydrogenated titanium powder) contain 85% by weight or more in the particle size range of 10 μm or more and 45 μm or less. The average particle size (median diameter) is 28.7 μm.

Powder D is hydrogenated / dehydrogenated titanium powder, and its particle size distribution is shown in Table 5 and FIG. 4 below.

The powder particles constituting the powder D (hydrogenated / dehydrogenated titanium powder) contain 85% by weight or more in a particle size range of 45 μm or more and 150 μm or less. The average particle size is 80.2 μm.

[Manufacturing of sintered body]
Mixed powders in which the ratios of powder A (TF: hydrogenated titanium fine powder) and powder B (HDH: hydrogenated / dehydrogenated titanium powder) were changed were prepared, and they were molded and subjected to dehydrogenation heat treatment. It was later sintered under vacuum.

The specific manufacturing conditions were as follows.

Powder A (TF) and powder B (HDH) are prepared in the mixing ratio shown in Table 6, and the mixed powder after the mixing treatment is formed into a φ41 × 30 mmH shape at a pressurizing pressure of 710 MPa and dehydrogenated at 600 ° C. After applying × 7.2 ks, vacuum holding was performed under the condition of 1000 ° C. × 10.8 ks to obtain a sintered body.

[Measurement of sintered body density, hardness, maximum tensile strength, and elongation]
"Density (after sintering)" in Table 6 is the density of the sintered body obtained by the above-mentioned manufacturing method.

The obtained sintered body (sample numbers 1 to 13 in Table 6) was cut into 20 mmt × 30 mmt × 40 mmL to prepare a hot plastically worked sample. Each sample was held at 850 ° C. for 1.8 ks in the air atmosphere, then rolled from 20 mmt to 2.5 mmt (rolling ratio 87%), and then annealed. The "density (after hot plastic working)" in Table 2 is the density of the sintered body after the hot plastic working.

Structural analysis of the obtained rolled sample by X-ray diffraction (Ultima IV: manufactured by Rigaku), microstructure observation by microscope (VHX-1000: manufactured by KEYENCE), SEM-EDX (JCM-6000EDS: manufactured by JEOL Ltd.) Elemental analysis of the precipitation part was performed.

Regarding the mechanical properties, a tensile test (AUTOGRAPH AG-X: manufactured by Shimadzu Corporation) was conducted at ^{a strain rate of 5 × 10 -4} / s using tensile test pieces collected along the rolling direction, and the hardness was determined. It was measured using a Vickers hardness tester (HMV-G: manufactured by Shimadzu Corporation). The density of each sample was evaluated by the Archimedes method.

Table 6 shows the measured density, hardness, maximum tensile strength (UTS), and elongation (ε).

The following points can be read from the results shown in Table 6.

a) The higher the ratio of the titanium hydride fine powder (powder A (TF)), the larger the amount of oxygen in the sintered body, and the higher the hardness and the maximum tensile strength. The reason for this is that the titanium hydride fine powder contains a large amount of oxygen, so it is a source for strengthening the solid solution of oxygen. This is because the amount of dissolved oxygen is increasing.

b) Regarding the elongation value (ε), if the ratio of titanium hydride fine powder (TF) is 75% or less, the density of the sintered body before hot plastic working is 95% or more, and the strength and elongation are high. The balance is properly obtained. However, when the ratio is 77% or more, the density of the sintered body before the hot plastic working is less than 95%, and it is recognized that the elongation value (ε) is sharply lowered. It is considered that this is because it is difficult to increase the density of the sintered body to 95% or more when the ratio of the titanium hydride fine powder is 75% or more, and continuous pores are formed in addition to the independent pores. .. It is considered that if there are continuous vacancies, air enters the continuous vacancies during hot plastic working, the nitrogen concentration in that portion increases, and the ductility is lowered. It is observed that the nitrogen contents of sample numbers 12 and 13 are rapidly increasing. If the ratio of titanium hydride fine powder (TF) is 75% or less, the density of the sintered body before hot plastic working is 95% or more, the pores are closed, and only independent pores are left. It is thought that it is.

c) Focusing on the sintered material (Sample No. 1) consisting only of hydrogenated / dehydrogenated titanium powder (HDH), its oxygen content is 0.24% by weight, hardness (HV) is 230, and maximum tensile strength. (UTS) is 524 MPa. In order to make a significant difference from the sintered material of Sample No. 1 in terms of oxygen content, hardness and maximum tensile strength, it is desirable that the ratio of titanium hydride fine powder (TF) is 15% or more. Sample No. 4, which has a ratio of titanium hydride powder of 15%, has an oxygen content of 0.29% by weight, a hardness (HV) of 259, and a maximum tensile strength (UTS) of 602 MPa.

d) When the ratio of titanium hydride fine powder (TF) is 77% or more, the elongation value (ε) drops sharply. Therefore, in order to maintain good ductility, the ratio of titanium hydride fine powder (TF) should be 75% or less. It is desirable to set it to.

e) The sintered material of sample numbers 4 to 11 having a ratio of titanium hydride fine powder (TF) of 15% to 75% has a hardness (HV) of 250 or more and a maximum tensile strength (UTS) of 580 MPa or more. The elongation (ε) is 18% or more.

[Tissue observation results]
FIG. 5 shows microstructure observation photographs of sample numbers 4, 6, 9, 10, 11, 12, and 13 after sintering (before hot plastic working). Focusing on sample number 12 with a proportion of titanium hydride fine powder (TF) of 77% and sample number 13 with 80%, it is observed that continuous vacancies appear. No continuous vacancies appear in Sample No. 4, Sample No. 6, Sample No. 9, Sample No. 10 and Sample No. 11 in which the ratio of the titanium hydride fine powder (TF) is 75% or less.

FIG. 6 shows a microstructure photograph of sample number 13 after sintering and a microstructure photograph after hot plastic working. As is clear from the microstructure photograph after hot plastic working, a nitrogen-enriched portion can be seen in sample number 13.

[Effect of particle size of hydrogenated / dehydrogenated titanium powder]
The prepared hydrogenated / dehydrogenated titanium powders are powder B, powder C and powder D (see Table 1). The powder B (HDH) has a particle size of 10 to 150 μm and an average particle size of 63.4 μm. The powder C has a particle size of 10 to 45 μm and an average particle size of 28.7 μm. The powder D has a particle size of 45 to 150 μm and an average particle size of 80.2 μm. It was investigated whether the difference in particle size distribution of the hydrogenated / dehydrogenated titanium powder mixed with the hydrogenated titanium fine powder (TF) affects the characteristics of the finally obtained sintered material. The results are shown in Table 7 below.

Looking at the results in Table 7, no significant difference was observed in the amount of oxygen, density, hardness, maximum tensile strength and elongation value, and it is recognized that the same characteristics were obtained. Therefore, preferably, the titanium powder to be mixed with the titanium hydride powder having a particle size of 10 μm or less (hydrogenated / dehydrogenated titanium powder in this embodiment) is 90% by weight or more in the particle size range of 10 μm or more and 150 μm or less. The average particle size is 20 μm or more. Further, it is desirable to mix the titanium hydride powder and the titanium powder so that the amount of the titanium hydride powder is 15% or more and 75% or less based on the weight of the whole.

[ _{Comparison with TiO 2} addition manufacturing method]
As a method of solidifying oxygen in a titanium material in order to improve the strength of the titanium material, a method of _{adding TiO 2} powder to the titanium powder and sintering this mixed powder is known. In order to compare with the method of the present invention using the fine powder of titanium hydride, a sintered body was prepared by _{the TiO 2 addition method.}

The prepared powders are hydrogenated / dehydrogenated titanium powder (powder B: HDH) having a particle size of 10 to 150 μm and TiO ₂ powder. These two kinds of powders were mixed to obtain a mixed powder. The mixing ratio is 0.7% by weight for the _{TiO 2 powder.} The amount of oxygen in the entire mixed powder corresponds to 0.55% by weight, which is equivalent to sample number 10 (powder A 66% + powder B 34%) in Table 6.

When the TiO ₂ powder is added to the titanium powder, the TiO ₂ powder tends to aggregate. FIG. 7A is a photograph showing the appearance of the mixed powder, and _{agglomeration of the TiO 2} powder can be seen in the portion surrounded by a circle. FIG. 7B is an SEM image of the mixed powder, and _{the aggregation of TiO 2} can be clearly observed.

FIG. 8 is _{an SEM image showing the structure of the TiO 2-} added mixed powder after sintering, and an oxygen-enriched portion that seems to be caused by insufficient mixing is observed.

FIG. 9 is an SEM image of a mixed powder of sample number 10 (powder A 66% + powder B 34%). As can be seen from this figure, fine titanium hydride fine powder having a particle size of 10 μm or less is uniformly dispersed throughout.

The method for strengthening the oxygen solid solution of a titanium material by adding _{TiO 2 may cause problems such as aggregation of TiO 2} and indulgence of oxygen-enriched portions when a large amount of _{TiO 2 is added.} On the other hand, the oxygen solid solution strengthening method for titanium materials using hydrogenated titanium fine powder is advantageous in that it does not cause problems such as agglutination and scattered oxygen-enriched portions.

_{In addition to the two types of powder, titanium hydride powder and titanium powder, TIO 2} powder is used to adjust the amount of oxygen, based on the oxygen solid solution strengthening method for titanium materials using titanium hydride fine powder. They may be mixed in addition to the extent that aggregation does not occur.

[Use of atomized powder]
In the above-described embodiment, titanium hydride fine powder and hydrogenated / dehydrogenated titanium powder were prepared as starting materials for the mixed powder. It is possible to use atomized powder instead of hydrogenated / dehydrogenated titanium powder.

Even when atomized powder is used instead of hydrogenated / dehydrogenated titanium powder, a mixed powder (mixed) of titanium hydride powder and atomized powder is used to confirm whether the same oxygen solidification enhancement is obtained. The ratio was 50:50), which was cold-formed, subjected to dehydrogenation heat treatment, and then sintered under vacuum (Sample No. 16).

The prepared titanium hydride powder is the powder A shown in Table 1, and contains 90% by weight or more in a particle size range of 10 μm or less, and the average particle size is 5.7 μm. The prepared atomized powder was produced by the gas atomizing method, and had an oxygen concentration of 0.10% by weight, a nitrogen concentration of 0.02% by weight, a hydrogen concentration of less than 0.01% by weight, and a carbon concentration of 0.01. Less than% by weight.

The particle size distribution of the atomized powder is shown in Table 8 and FIG.

As shown in Table 8 and FIG. 10, the powder particles constituting the atomized powder contain 90% by weight or more in the particle size range of 20 μm or more and 150 μm or less. The average particle size (median diameter) is 67.8 μm.

Table 9 below shows the strength characteristics of Sample No. 9 and Sample No. 16 after sintering and hot plastic working.

As can be seen from Table 9, the sintered material (sample number 9) starting from a mixed powder of 50% titanium hydride powder (powder A) and 50% hydride / dehydrogenated titanium powder (powder B), and hydrogenation. The sintered material (Sample No. 16) starting from a mixed powder of 50% titanium powder (powder A) and 50% atomized powder is equivalent in density, hardness, maximum tensile strength, and elongation characteristics.

FIG. 11 is a microstructure photograph of Sample No. 9 and Sample No. 16 after sintering. From these photographs, it can be confirmed that both Sample No. 9 and Sample No. 16 have good tissues with no continuous pores.

Even when atomized powder is used instead of hydrogenated / dehydrogenated titanium powder, it is possible to obtain high-strength and high-toughness titanium sintered material while reducing production costs by utilizing titanium hydride fine powder. can.

[Application to titanium alloy sintered material]
From the viewpoint of providing a high-strength and high-toughness titanium sintered material while reducing production costs by utilizing titanium hydride powder with a particle size of 10 μm or less, which is normally discarded, it is a pure titanium sintered material. There is no need to limit it. For example, a hydrogenated titanium powder having a particle size of 10 μm or less can be used as a starting material for producing a titanium alloy sintered material such as Ti-6% Al-4% V. As the titanium hydride powder, both pure titanium hydride powder and titanium hydride alloy powder can be considered.

A possible combination as a starting material for producing a Ti-6% Al-4% V sintered material is, for example, the following pattern.

Pattern 1: Hydrogenated pure titanium powder + pure titanium powder + AlV alloy powder

Pattern 2: Titanium hydride alloy powder (Ti-Al-V) + Titanium alloy powder (Ti-Al-V)

[Manufacturing of titanium alloy sintered material containing Al and V]
The powders shown in Table 10 below were prepared as raw material powders for a titanium alloy sintered material containing aluminum (Al) and vanadium (V).

The powder E has a composition of Ti-6Al-4V (64 titanium) and is hydrogenated. The particle size distribution of this hydrogenated 64 titanium fine powder is shown in Table 11 and FIG. 12 below.

The powder particles constituting the powder E (hydrogenated 64 titanium fine powder) contain 65% by weight or more in a particle size range of 10 μm or less. Its average particle size (median diameter) is 8.13 μm. In the tables and drawings below, powder E may be referred to as "64TF".

The powder C (hydrogenated / dehydrogenated titanium powder) is the same as the “powder C” shown in Table 1, and is a hydrogenated / dehydrogenated pure titanium powder. The particle size distribution is as shown in Table 4 and FIG. The powder particles constituting the powder C contain 85% by weight or more in a particle size range of 10 μm or more and 45 μm or less, and the average particle size (median diameter) is 28.7 μm.

The powder F (hydrogenated / dehydrogenated 64 titanium powder) is a 64 titanium powder having a composition of Ti-6Al-4V and dehydrogenated after hydrogenation. The particle size distribution is shown in Table 12 and FIG. 13 below.

The powder particles constituting the powder F (hydrogenated / dehydrogenated 64 titanium powder) contain 60% by weight or more in a particle size range of 10 μm or more and 45 μm, and the average particle size (median diameter) is 39.49 μm.

[Preparation of titanium alloy sintered body containing Al and V]
A mixed powder in which the ratio of powder E (hydrogenated titanium fine powder (64TF)) and powder C (hydrogenated / dehydrogenated pure titanium powder) was changed was prepared, and they were molded and dehydrogenated. It was later sintered under vacuum.

The specific manufacturing conditions were as follows. Powder E and powder C are prepared at the mixing ratios shown in Table 13, the mixed powder after the mixing treatment is molded at a pressurizing pressure of 710 MPa, dehydrogenated at 600 ° C. × 7.2 ks, and then 1050 ° C. × 10. A sintered body was obtained by holding in vacuum under the condition of 8.8 ks.

[Structural observation results of titanium alloy sintered body containing Al and V]
FIG. 14 shows a microstructure observation photograph (× 500) of sample numbers 22 to 29 after sintering (before hot plastic working). Looking at the microstructure observation photograph of the sintered body of the mixed powder (Sample No. 29) containing 60% of powder E (64TF) and 40% of powder C (pure titanium), black continuous pores appear. Is recognized. No continuous pores appear in the microstructure observation photographs of the sintered body of sample numbers 22 to 28 having a powder E content of 5% to 55%.

[Measurement of density, hardness, maximum tensile strength, and elongation of titanium alloy sintered body containing Al and V]
"Density (after sintering)" in Table 13 is the density of the sintered body before hot plastic working. The obtained sintered body (sample numbers 21 to 29 in Table 13) was rolled from a plate thickness of 20 mmt to 2.4 mmt (rolling ratio 88%), and then annealed under the conditions of 750 ° C. × 1.8 ks.

"Density (after hot plastic working)" in Table 13 is the density of the sintered body after the hot plastic working.

A tensile test (AUTOGRAPH AG-X: Shimadzu Corporation) was carried out using tensile test pieces collected along the rolling direction. The hardness was measured using a Vickers hardness tester (HMV-G: Shimadzu Corporation). The density of each sample was evaluated by the Archimedes method.

Table 13 shows the measured densities, hardness (HV), maximum tensile strength (UTS), and elongation (ε). The following points can be read from the results shown in Table 13 and the tissue observation results in FIG.

a) The higher the ratio of powder E (hydrogenated 64 titanium fine powder (64TF)), the larger the amount of oxygen in the sintered body, and the higher the hardness and maximum tensile strength. The reason for this is that since the hydrogenated 64 titanium fine powder contains a large amount of oxygen, it is an oxygen supply source for strengthening the solid solution of oxygen, and the larger the amount of the hydrogenated 64 titanium fine powder, the more in the titanium base material. This is because the amount of oxygen that dissolves in the solid solution is increasing.

b) Regarding the elongation value (ε), if the ratio of hydrogenated 64 titanium fine powder (64TF) is 55% or less, the density of the sintered body before hot plastic working is 95% or more, and the strength and elongation. The balance is properly obtained. However, when the ratio is 60% or more, the density before hot plastic working becomes less than 95%, and it is recognized that the elongation value (ε) drops sharply. This is probably because when the ratio of hydrogenated 64 titanium fine powder is 60% or more, it is difficult to increase the density of the sintered body to 95% or more, and continuous pores are formed in addition to the independent pores. Is done. Therefore, it is desirable to set the upper limit of the content of powder E (hydrogenated 64 titanium fine powder (64TF)) in the mixed powder to 55%.

c) Focusing on the sintered material (Sample No. 21) consisting only of hydrogenated and dehydrogenated pure titanium powder, its oxygen content is 0.24% by weight, hardness (HV) is 230, and maximum tensile strength (sample number 21). UTS) is 524 MPa. In order to make a significant difference from sample number 21 in terms of oxygen content, hardness and maximum tensile strength, the lower limit of the content of powder E (hydrogenated 64 titanium fine powder (64TF)) is set to 5%. Is desirable. According to the data posted on the Nippon Steel website, the oxygen content of Ti-3Al-2.5V is 0.15 wt% or less, the strength is 620 MPa, and the elongation is 15%. The oxygen content of the sample 22 containing 5% of the powder E is 0.31 wt%, the strength is 628 MPa, and the elongation is 31.7%, which are superior in mechanical properties to T-3Al-2.5V.

d) The sintered material of sample numbers 22 to 28 having a ratio of powder E (hydrogenated 64 titanium fine powder (64TF)) of 5% to 55% has a hardness (HV) of 276 or more and a maximum tensile strength (UTS). ) Is 628 MPa or more, and the elongation (ε) is 14% or more.

[Comparison of microstructure observation results and mechanical properties of different grades]
Table 14 below compares the oxygen content and mechanical properties of materials of different grades. Sample number 31 is a pure titanium material, sample number 32 is a 64 titanium alloy melted material, sample number 33 is a 64 titanium alloy powder sintered material, sample number 34 is a 32 titanium alloy melted material, and sample number 35 is a 32 titanium alloy powder sintered material. Material, sample number 36-a is _{a mixed powder sintered material in which 0.6% of TiO 2} is added to 32 titanium alloy powder, and sample number 36-b is a mixed powder in which 1.1% _{of TiO 2 is added to 32 titanium alloy powder.} Sintered material, sample number 36-c is _{a mixed powder sintered material in which 1.3% of TiO 2} is added to 32 titanium alloy powder, and sample number 37 is powder F (hydrogenated / dehydrogenated 64 titanium) shown in Table 10. A mixed powder sintered material containing 25% of powder E (hydrogenated 64 titanium fine powder (64TF)) added to powder), and sample number 27 is a mixed powder sintered material containing 50% powder E and 50% powder C. Yes, it is the same as the sample number 27 shown in Table 13.

Sample numbers 32, 33 and 37 are all 64 titanium alloy materials. It is recognized that the 64 titanium alloy powder material (sample number 33) is superior in mechanical properties (hardness and maximum tensile strength) to the 64 titanium alloy molten material (sample number 32). Sample number 37 corresponds to one embodiment of the present invention, in which 25% of hydrogenated 64 titanium fine powder (64TF) is added to hydrogenated / dehydrogenated 64 titanium powder (powder F). The mechanical properties (hardness and maximum tensile strength) of sample number 37 are superior to sample number 33 (64Ti alloy powder material). The elongation (ε) of sample number 37 is 7.2%, which is slightly inferior to the elongation value (10%) of sample number 33. Since sample number 37 contains 25% of hydrogenated 64 titanium fine powder that has been disposed of, it is a low-cost material as compared with sample number 33. Therefore, the utility value of sample number 37 is high if the application does not require much elongation characteristics.

The oxygen content of sample number 27 (50% powder E (64TF) + 50% powder C (pure titanium)) is 0.77%. In order to increase the amount of oxygen in the 32Ti alloy powder material, it is necessary to add _{TiO 2.} The oxygen content of sample number 36-a to which 0.6% of TiO2 was added was 0.54%, the oxygen content of sample number 36-b to which 1.1% of TiO2 was added was 0.74%, and the oxygen content of TiO2 was 1. The oxygen content of sample number 36-b added with 3% is 0.80%. The elongation characteristics (ε) of sample numbers 36-b and 36-c having the same amount of oxygen are far inferior to sample number 27 corresponding to one embodiment of the present invention. It is considered that this is because a large amount of TiO ₂ added at the time of powder mixing aggregates and an oxygen-enriched portion is generated even after sintering. On the other hand, in sample number 27 using hydrogenated 64 titanium fine powder, the problem of partial oxygen enrichment does not occur, and a large amount of oxygen can be uniformly dissolved as compared with the method of adding _{TiO 2.} It is possible to obtain better mechanical properties and elongation properties.

As described above, the larger the amount of hydrogenated titanium fine powder having an average particle size of 10 μm or less and the hydrogenated 64 titanium fine powder having an average particle size of 10 μm or less, the more the titanium sintered material. Alternatively, the amount of oxygen in the titanium alloy sintered material increases, and the hardness (HV) and the maximum tensile strength (UTS) increase. On the other hand, if the amount of the hydrogenated titanium fine powder and the hydrogenated 64 titanium fine powder added too much, the elongation value (ε) of the titanium sintered material or the titanium alloy sintered material decreases. Among the applications of titanium sintered materials and titanium alloy sintered materials, there are applications that do not require much elongation characteristics. For example, in cutting tool applications and wear resistance applications, strength (hardness and maximum tensile strength) is more important than elongation characteristics. In such applications where strength is important, if a large amount of hydrogenated titanium fine powder or hydrogenated 64 titanium fine powder is added, the strength of the sintered material can be increased while reducing the raw material cost. ..

Ti-3Al-2.5V, Ti-3Al-3Mo-1V, not limited to pure titanium and 64 titanium, are hydrided titanium powders used to increase the strength of sintered materials while reducing raw material costs. , Ti-4Al-3Mo-1V, Ti-4Al-4Mo-2Sn, Ti-5Al-2Cr-1Fe, Ti-5Al-1.5Fe-1.5Cr-1.5Mo, Ti-5Al-2Sn-2Zr-4Mo -4Cr, Ti-6Al-2Sn-2Zr-2Mo-2Cr, Ti-6Al-2Sn-4Zr-6Mo, Ti-6Al-2Sn-4Zr-2Mo, Ti-5Al-6Sn-2Zr-1Mo, Ti-6Al-2Cb -1Ta-1Mo, Ti-6Al-4V, Ti-6Al-6V-2Sn, Ti-7Al-4V, Ti-8Al-1Mo-1V, Ti-8Al-4Co, Ti-8Mn, and Ti-25Al-11Sn- Titanium-based fine powder such as 5Zr-1Mo can be used.

Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to the embodiments described here, and is within the same or equivalent range as the invention described in the claims. Various changes are possible.

INDUSTRIAL APPLICABILITY The present invention can be advantageously used as a method capable of obtaining a titanium sintered material having high strength and high toughness while reducing production costs. For example, since titanium hydride fine powder is usually discarded, the material purchase cost is equal to zero, and when 66% of hydrogenated titanium fine powder is mixed, the material cost is reduced to 1/3, which can greatly contribute to the reduction of production cost. ..

Claims (11)

1.51Myuemu～ 10 [mu] m looking contains 90 wt% or more in the range of a particle size of less than the average particle size of titanium hydride powder hydrotreated at 10 [mu] m or less, 90 wt% or more in the range of particle size of less than 150μm or 10 [mu] m And a step of preparing a titanium powder having an average particle size of 20 μm or more, including
A step of mixing the hydrogenated titanium powder and the titanium powder so that the amount of the hydrogenated titanium powder is 15% or more and 75% or less based on the weight of the whole.
A method for producing a titanium sintered material, comprising a step of sintering the mixed powder that has been subjected to the mixed treatment to obtain a titanium sintered material. The method for producing a titanium sintered material according to claim 1, wherein the mixing step comprises adding and mixing titanium oxide powder in addition to the titanium hydride powder and the titanium powder. The method for producing a titanium sintered material according to claim 1 or 2, wherein the titanium powder is a hydrogenated / dehydrogenated titanium powder obtained by hydrogenating a titanium ingot and then crushing and dehydrogenating the titanium ingot. The method for producing a titanium sintered material according to claim 1 or 2, wherein the titanium powder is an atomized powder produced by an atomizing method. The method for producing a titanium sintered material according to any one of claims 1 to 4, wherein the density of the titanium sintered material is 95% or more and 97.5% or less. The method for producing a titanium sintered material according to any one of claims 1 to 5, further comprising a step of performing hot plastic working on the titanium sintered material. The titanium sintered material after hot plastic working has a hardness (HV) of 250 or more and 362 or less , a maximum tensile strength (UTS) of 580 MPa or more and 923 MPa or less, and an elongation (ε) of 18% or more and 28.8% or less. The method for producing a titanium sintered material according to claim 6. Hydrogenated 64 titanium alloy powder having a composition of Ti-6Al-4V, containing 65% by weight or more in a particle size range of 1.318 μm to 10 μm or less, and having an average particle size of 10 μm or less, and 10 μm or more. A step of preparing a pure titanium powder containing 85% by weight or more in a particle size range of 45 μm or less and having an average particle size of 20 μm or more.
A step of mixing the hydrogenated 64 titanium alloy powder and the pure titanium powder by blending so that the amount of the hydrogenated 64 titanium alloy powder is 5% or more and 55% or less based on the weight of the whole. ,
A method for producing a titanium alloy sintered material, comprising a step of sintering the mixed powder that has been subjected to the mixed treatment to obtain a titanium alloy sintered material. The method for producing a titanium alloy sintered material according to claim 8, wherein the density of the titanium alloy sintered material is 95% or more and 98.5% or less. Further provided with a step of performing hot plastic working on the titanium alloy sintered material,
The titanium alloy sintered material after hot plastic processing has a hardness (Hv) of 250 or more and 441 or less , a maximum tensile strength (UTS) of 620 MPa or more and 1222 MPa or less, and an elongation (ε) of 14% or more and 31.7% or less. The method for producing a titanium alloy sintered material according to claim 9. Hydrogenated 64 titanium alloy powder having a particle size of 1.318 μm to 10 μm or less, containing 65% by weight or more, an average particle size of 10 μm or less, and a composition of Ti-6Al-4V, and 10 μm or more. A step of preparing a titanium alloy powder containing 60% by weight or more in a particle size range of 45 μm or less, an average particle size of 20 μm or more, and a composition of Ti-6Al-4V.
A step of mixing the hydrogenated 64 titanium alloy powder and the titanium alloy powder by blending so that the amount of the hydrogenated 64 titanium alloy powder is 15% or more and 75% or less based on the weight of the whole. ,
A method for producing a titanium alloy sintered material, comprising a step of obtaining a titanium alloy sintered material obtained by sintering the mixed powder that has been mixed and treated.

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