JP3007198B2 - Method for producing composite powder comprising titanium powder and mother alloy powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a titanium alloy by a powder metallurgy method. More specifically, the present invention relates to a method for producing a composite powder composed of a titanium powder and a mother alloy powder as a raw material powder used in the elementary powder mixing method.

[0002]

2. Description of the Related Art Titanium alloys have been actively applied to aircraft, etc. in order to make use of the characteristics of light weight and high strength.
Since the workability, formability and machinability in hot and cold are inferior, the production cost is disadvantageously increased. In order to compensate for this drawback, various methods have been studied for directly manufacturing a product very close to the final shape by a so-called near-net shape processing means. Powder metallurgy is one of the representative methods.

[0003] The powder metallurgy method for titanium alloys includes an alloy powder method in which a pre-alloyed powder is filled in a container, and molding and sintering, or a method in which titanium powder and a master alloy element powder are mixed and filled in a container. There is an elementary powder method in which a mixed powder body is manufactured by performing the method, the molded body is molded, and then sintering and alloying are simultaneously performed. In particular, in the elemental powder method, soft titanium powder occupies a large part during molding, so that there is an advantage that moldability is good, and there is an advantage that manufacturing cost is relatively low because alloying heat treatment and sintering are performed simultaneously. However, the titanium powder and the master alloy powder have different weights, dimensions, and surface conditions.When filling the container with the mixed powder, the titanium powder and the master alloy powder are partially separated by the influence of vibration or gravity. , Sintering
In the course of the alloying heat treatment, there is a problem that a non-uniform structure is formed due to segregation and material properties are deteriorated.

[0004] As a means for solving such a problem, Powder Metallu published in 1974 has been proposed.
rgy magazine vol. 17, page 271 to page 287. In other words, the main metal powder and the relatively fine master alloy powder are mixed and pre-sintered before filling in a molding container, so that the master alloy powder surrounds the main metal powder, and This is a method of producing a composite powder that is slightly loosely bound to such an extent that no cracking occurs. When the composite powder is filled, the main metal powder and the mother alloy powder do not separate, so that a non-uniform structure due to segregation is not formed in the subsequent sintering / alloying heat treatment process. Moreover, since the full-scale alloying does not occur in the preliminary sintering, the excellent formability of the main metal powder is not impaired.

[0005] When the composite powder is used as described above, uniform filling and molding can be performed, and uniform material characteristics without segregation can be obtained. However, since titanium is a very active metal, titanium powder and a master alloy are used. When the powders are mixed and pre-sintered, it is difficult to achieve a loose bond between the titanium powder and the master alloy powder as shown in FIGS. 1 (a) and 1 (b), and the alloying proceeds in a very short time. However, there has been a problem that the formability is reduced and that the alloyed powder becomes coarse due to the progress of sintering. Furthermore, since one heat treatment step is added, the amount of infiltration of oxygen is increased, which has a disadvantage that moldability and material properties are adversely affected.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a method for producing a composite powder comprising titanium powder and a master alloy powder and having excellent moldability. It is intended to do so.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have considered that it is extremely important to manufacture a homogeneous material without segregation in order to improve the material properties of a powder metallurgy titanium alloy. As a result of daily efforts to develop a method for producing a composite powder composed of a powder and a mother alloy powder, a method for easily producing a composite powder having excellent formability was found. That is, the present invention provides: (1) mixing titanium hydride powder and a relatively fine mother alloy powder, and mixing them in a vacuum atmosphere at a pressure of 1 × 10 ⁻³ Torr or less.
It is characterized by heating and holding at a temperature of 0 ° C or more and 800 ° C or less for 10 minutes or more and 10 hours or less. It is characterized by the following.

As the mother alloy powder in the present invention , two or more kinds of relatively fine powders may be mixed and used.
May be included. For example, when manufacturing a Ti-6Al-4V alloy, a (60Al-40V) master alloy powder may be used, or a (50Al-50Ti) master alloy powder and a (50Al-50V) master alloy powder may be mixed and used. You may. Furthermore, (85V-15Al) master alloy and the like and the above-mentioned master alloy can be mixed and used in various combinations. The titanium hydride powder contains, in addition to Ti,
Fe, about the same as that contained in normal titanium powder,
O, C, and N may be contained as impurities.

[0009]

Hereinafter, the present invention will be described in detail. In the present invention (1), titanium hydride powder and a relatively fine mother alloy powder are mixed, and the mixture is heated to a temperature of 450 to 800 ° C. in a vacuum atmosphere of 1 × 10 ⁻³ Torr or less for 10 minutes or more. 10
Hold for less than or equal to time. This is because instead of titanium powder, which is extremely active, titanium hydride powder, which has lower activity than titanium powder, is mixed with a relatively fine mother alloy powder, and pre-sintering is performed, so that titanium and mother powder are mixed. It is a first object of the present invention to suppress an excessive reaction of the alloy powder and to keep the reaction at an appropriate level such that both are loosely bonded. It is a second object of the present invention to simultaneously perform dehydrogenation treatment by performing pre-sintering in a vacuum at a pressure of 1 × 10 ⁻³ Torr or less to convert titanium hydride powder to titanium powder. By this step, as shown in FIG. 2, the composite powder (b) in which the mother alloy powder is loosely bonded around the titanium powder by the preliminary sintering from the mixed state (a) can be produced. At this time, the titanium powder and the mother alloy powder are only loosely bonded, and alloying has progressed only slightly, so that good formability of the titanium powder is not impaired. The method of obtaining titanium powder by dehydrogenating titanium hydride powder is one of the most common methods for obtaining titanium powder. Since the sintering is also performed, there is no increase in the number of heat treatment steps. Therefore, there is no extra oxygen absorption,
There is no increase in manufacturing cost.

Here, the heating and holding temperature of the present invention (1) is set to 4
The reason that the temperature is set to 50 ° C. or higher is that at a temperature lower than 450 ° C., the reaction between the titanium hydride powder and the mother alloy powder is excessively suppressed, and the mother alloy powder does not sufficiently adhere around the titanium hydride powder.
This is because good composite powder cannot be obtained. In addition, the dehydrogenation reaction is significantly delayed and is not effective. On the other hand, the reason why the heating holding temperature is set to 800 ° C. or less is that at a temperature exceeding this,
The reaction between the titanium hydride powder and the mother alloy powder becomes too active, the alloying proceeds, the formability decreases, and the alloyed powder forms a coarse sintered body to obtain a good composite powder. Is not possible. The reason why the heating holding time is set to 10 minutes or more and 10 hours or less is as follows. That is, if the time is less than 10 minutes, the reaction between the titanium hydride powder and the mother alloy powder is insufficient, and a good composite powder in which the mother alloy powder is loosely bonded around the titanium hydride powder cannot be obtained. Also, the dehydrogenation reaction is insufficient.
In the period of 10 hours or more, dehydrogenation was almost completed, titanium hydride had already become active titanium, the reaction with the master alloy became extremely active, and alloying proceeded. The properties are impaired and the powder becomes coarse. Further, in the present invention (1), the heat treatment is performed in a vacuum at a pressure of 1 × 10 ⁻³ Torr or less. Is invaded into titanium and deteriorates formability and material properties.

In the present invention (2), after the step of the present invention (1) is performed, mechanical pulverization is further performed. This is a step for further enhancing the effect of the present invention (1). That is, among the composite powders obtained by performing the process of the present invention (1), a small amount of the composite powders is a coarse powder as shown in FIG. . The purpose of this step is to grind these into a fine composite powder. By the way, as shown in FIG. 3, the coarse powder in which such composite powders are bonded is characterized in that it is bonded not in the titanium powder but in the part of the mother alloy powder. Since the master alloy powder is generally an extremely brittle intermetallic compound, when mechanical pulverization is performed, the mother alloy portion is crushed and a fine composite powder can be obtained very easily. In addition, since titanium powder hardly undergoes plastic deformation, the titanium does not harden, and thus the formability is not impaired.

[0012]

EXAMPLES Ti-6Al-4V and Ti-5Al-
The present invention will be described in more detail by taking as an example a case where a composite powder is manufactured by applying the present invention to manufacture 2.5Fe. Titanium hydride powder has an average sieve size of 120μ
m, a powder having a maximum sieve size of 150 μm was used. This titanium hydride powder contains 3.9% by weight of hydrogen.
The mother alloy powder used for producing Ti-6Al-4V is a (60Al-40V) mother alloy powder having an average sieve size of 40 μm and a maximum sieve size of 70 μm. Also, Ti
-5Al-2.5Fe is produced by adding (28.6Ti-71.4Al) master alloy powder and (5
0Ti-50Al) master alloy powder. The average sieve size of each of the two types of mother alloys is 30 μm, and the maximum sieve size is 60 μm.
In addition, in order to manufacture some comparative materials, titanium powder produced by dehydrogenating titanium hydride powder was used, and the sieve size of this titanium powder is exactly the same as titanium hydride.

The powder samples subjected to the steps shown in Tables 1 and 2 were measured for average sieve size and maximum sieve size, and evaluated for formability using a press molding tester.
The moldability was evaluated by the molding pressure necessary for the density after molding to be 80% or more, assuming that the density of the molten alloy of the same component was 100%. Tables 3 and 4 show the test results.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

[Table 4]

In Tables 1 and 3, Test No. 1 is the result of examining the moldability of titanium powder as a comparative example. 8
The molding pressure required for 0% relative density was 465 MPa. Table 2
In Test No. 2, the (60Al-40V) master alloy powder and the titanium powder were mixed and pre-sintered.
Are (71.4Al-28.6Ti) master alloy and (50Ti
-50Fe) master alloy and titanium powder mixed and pre-sintered, Ti-6Al-4V and Ti-6Al-4V, respectively.
This corresponds to a conventional method for producing a composite powder of -5Al-2.5Fe. As shown in Table 3, the sieve size was remarkably coarse in both of test numbers 2 and 3, and the average sieve size was 25.
0 μm, and the maximum sieve size is 500 μm or more. Further, the moldability is significantly impaired, and the molding pressure required for 80% relative density is 600 MPa or more. this is,
Since titanium is a very active metal, sintering and alloying progress during pre-sintering, and the amount of oxygen increases,
The powder was remarkably coarsened and the moldability was reduced.

On the other hand, Test No. 4, which is an embodiment of the present invention (1), and Ti-6
In Test No. 5, which is an example of the present invention (1) performed on 5Al-2.5Fe, as shown in Table 3, the average sieve size was slightly larger than that of titanium powder, but was 150 mm.
It is as fine as [mu] m to 160 [mu] m, and the maximum sieve size is relatively fine as 300 [mu] m or less. Also, the molding pressure required for 80% relative density is a good value of 500 MPa or less. this is,
This is because the mother alloy powder is loosely bound around the titanium hydride powder which is inactive as compared with the titanium powder, and at the same time, the titanium hydride is dehydrogenated and converted to titanium powder.

In Table 2, test numbers 7, 9, 1
No. 1 is an example in which the present invention (1) was applied to Ti-6Al-4V, and test numbers 6, 8, 10, 12,
13 is a comparative example. As shown in Table 4, the present invention (1)
Test Nos. 7, 9 and 11, which are examples of the present invention, are relatively fine powder having an average sieve size of 170 μm or less, a maximum sieve size of 300 μm or less, and a molding required for 80% relative density. At a pressure of 500 MPa or less, good moldability is maintained. In contrast, test numbers 6, 8, 10, 1
In Tables 2 and 13, as shown in Table 4, the molding pressure required for the 80% relative density exceeded 500 MPa, and the excellent moldability of titanium powder was lost. In Test Nos. 8 and 13, the maximum sieve size was larger than 300 μm. Further, in Test Nos. 10 and 12, the average sieve size and the maximum sieve size were equal to or less than those of the titanium hydride powder before pre-sintering, and the master alloy powder was sufficiently surrounded by the titanium powder. Is not attached.

Thus, test numbers 6, 8, 10, 1
In Nos. 2 and 13, no good composite powder was obtained, for the following reasons. In Test No. 6, since the pressure of the atmosphere for pre-sintering was higher than the upper limit of the present invention (1), dehydration was insufficient and hard hydrides remained, and hardening was caused by intrusion of oxygen, and moldability was reduced. Dropped. In Test No. 8, since the heating temperature was higher than the upper limit of the present invention (1), the reaction between the titanium hydride powder and the mother alloy powder became excessively active, and the formed composite powder was coarsened and the Formability was reduced by progress. In test number 10,
Since the heating and holding temperature was lower than the lower limit of the present invention (1), dehydrogenation was insufficient and hard hydride remained, and moldability was reduced. Further, in this sample, the reaction between the titanium hydride powder and the mother alloy powder was excessively suppressed, so that the mother alloy element powder did not sufficiently adhere around the titanium hydride powder.
In Test No. 12, since the heating holding time was less than the lower limit of the present invention (1), dehydrogenation was insufficient, hard hydride remained, and moldability was reduced. Further, the reaction between the titanium hydride powder and the mother alloy powder was insufficient, and the mother alloy powder did not sufficiently adhere around the titanium hydride powder. Test number 13
Then, since the heating holding time was longer than the upper limit value of the present invention (1), the active reaction between titanium and the master alloy after the completion of dehydrogenation caused alloying to proceed, and formability decreased,
The sieve size has also increased.

In Table 2, Test Nos. 14 and 15 correspond to Ti-6Al-4V and Ti-5Al-
This is an example in which the present invention (2) is applied to the production of a composite powder for producing 2.5Fe. That is, the test Nos. 4 and 5 to which the present invention (1) was applied were further subjected to mechanical pulverization for 15 minutes by a vibration ball mill.
As shown in Table 4, Test Nos. 14 and 15 are finer powders than Test Nos. 4 and 5, respectively.
In each case, the maximum sieve size is 200 μm or less. Also 80
The molding pressure required for the% relative density is 470 MPa, which is almost the same as that of the titanium powder, and a very good composite powder is obtained. This means that in test numbers 4 and 5, the sieve size contained in a small amount was 190 μm to 280 μm.
This is because the composite powder was pulverized at the brittle master alloy portion by mechanical pulverization and refined.

[0023]

As described above, by applying the present invention, a composite powder composed of a titanium powder and a master alloy powder is used as a material for producing a homogeneous material without segregation. It can be easily manufactured without impairing the moldability.

[Brief description of the drawings]

FIG. 1 (a) shows a state in which a titanium powder and a master alloy powder are mixed, and FIG. 1 (b) is a schematic view showing a change in a case where the powder is preliminarily sintered.

FIG. 2 shows a case where the processing of the present invention (1) is applied,
(A) shows a state in which a titanium hydride powder and a mother alloy powder are mixed, and (b) is a schematic view showing a change when pre-sintering according to the present invention.

FIG. 3 is a schematic diagram showing a change when the present invention (2) is applied.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-303017 (JP, A) JP-A-61-87802 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22F 1/00-9/02

Claims (2)

(57) [Claims] A titanium hydride powder and a relatively fine mother alloy powder are mixed and mixed in a vacuum atmosphere of 1 × 10 ⁻³ Torr or less.
A method for producing a composite powder comprising a titanium powder and a mother alloy powder, wherein the composite powder is heated and maintained in a temperature range of 450 to 800 ° C. for 10 minutes to 10 hours. 2. Titanium hydride powder and a relatively fine mother alloy powder are mixed and mixed in a vacuum atmosphere of 1 × 10 ⁻³ Torr or less.
A method for producing a composite powder comprising a titanium powder and a master alloy powder, wherein the powder is heated and held in a temperature range of 450 to 800 ° C. for 10 minutes to 10 hours and then mechanically pulverized.