JP5726457B2 - Method for manufacturing titanium product or titanium alloy product - Google Patents

Description

  The present invention relates to a method for producing a molded body from titanium powder or titanium alloy powder that has not undergone a dehydrogenation treatment step as a forming raw material.

Conventionally, titanium alloys have high specific strength, excellent heat resistance and corrosion resistance, and have ideal characteristics as materials for aircraft, etc., but have difficulty in workability such as melting, forging, cutting, etc. Since the cost is high, there is a need for a low-cost material manufacturing method.
One of the titanium forming methods is powder metallurgy. The powder metallurgy method is a method in which a powder is heated and pressurized to form a molded body having a uniform and desired shape, and titanium powder or titanium alloy powder is used as a molded body base material.

As a method for producing a titanium product or titanium alloy product from this titanium powder or titanium alloy powder, there is also a method of mechanically pulverizing sponge titanium, which is generally obtained as metal titanium, into a powder. Since it is rich, it is difficult to obtain a fine powder by directly pulverizing it, and it is not suitable for powder metallurgy because of its high chlorine content. Therefore, there is generally an atomizing method in which molten titanium is blown off with a gas to produce a powder, or a rotating electrode method in which a titanium electrode is rotated, the electrode is melted with plasma or the like, and blown off with a centrifugal force to produce a powder. According to this method, titanium powder with relatively high purity can be obtained, but there are disadvantages in the powder shape, particle size, cost and the like.

For this reason, for example, as disclosed in JP-A-6-10016 (Patent Document 1), titanium or a titanium alloy is hydrotreated to form a brittle titanium hydride, which is mechanically pulverized into a powder. After that, the HDH method is generally adopted in which titanium or titanium alloy powder is obtained by dehydrogenation by vacuum heating or the like. In order to obtain a fragile titanium hydride at room temperature, it is necessary to absorb about 3% by weight or more of hydrogen, and this 3% by weight or more of hydride is generally called δ phase, and this is crushed and heated under vacuum. The powder is obtained by dehydrogenating to 300 ppm or less.

A powder is obtained by the powder metallurgy method in which the powder obtained by the HDH method is filled into a capsule and hot-pressed with, for example, HIP to solidify and form. However, since this manufacturing method has a higher cost than general steel materials, the cost performance is poor for application as a structural member, and it cannot be widely used. Therefore, it is also conceivable to solidify and mold the powder in the hydrogenated and pulverized state by powder filling and hot extrusion as disclosed in, for example, Japanese Patent No. 3100280 (Patent Document 2).
JP-A-6-10016 Japanese Patent No. 3100830

  However, the above-mentioned patent solidifies and forms a metal powder reduced in oxygen by hot extrusion. It is possible to dehydrogenate a powder having a high hydrogen content such as titanium or a titanium alloy and solidify and form it by hot extrusion. Because it is not taken into consideration, hydrogen released during heating may swell or tear capsules, and hydrogen gas may be released to the outside during heating or extrusion, which may cause combustion due to reaction with the atmosphere. Is difficult. Moreover, the example which solidified and formed titanium alloy powder, such as Ti-6 mass% Al-4 mass% V, by hot extrusion is not seen.

  In order to solve the above-mentioned problems, the inventors diligently studied the dehydrogenation process of Ti powder or Ti alloy powder, and as a result, filled at 90% or less, and deaeration after canning was performed at 300 ° C. or higher and 850 ° C. In the following, it was found that by performing in an atmosphere of 0.133 Pa or less, it is possible to dehydrogenate all of the filled powder by promoting the hydrogen release behavior from the alloy powder. Further, the above-described HDH-powder metallurgy method, which is pulverized after hydrogenation, and thereafter dehydrogenation step by vacuum heating is omitted. Was found to be manufacturable.

The gist of the invention is that
(1) Titanium powder or titanium alloy powder is filled into an iron-based or titanium or titanium alloy capsule so that the filling rate is 90% or less, and the inside of the capsule is 0.133 Pa or less while heating at 300 to 800 ° C. And then cooled to 100 ° C. or less at a rate of 20 ° C./min or less, and after sealing the capsule, the capsule was heated to 800 ° C. or more at a heating rate of 1 to 50 ° C./min for a certain period of time. A method for producing a titanium product or a titanium alloy product, characterized in that after being held, the capsule is pressurized to solidify and form titanium powder or titanium alloy powder.

(2) A method for producing a titanium product or a titanium alloy product, wherein the average particle size of the titanium powder and the titanium alloy powder described in (1) is 5 to 1000 μm.
(3) The method for producing a titanium product or a titanium alloy product is characterized in that the solidification molding described in (1) above is solidified by hot extrusion at an extrusion ratio of 4 or more.

  As described above, the member obtained by the method of the present invention is to provide a Ti product or a Ti alloy product that has sufficient characteristics as a structural material and can be manufactured at low cost by omitting the steps.

Hereinafter, the present invention will be described in detail.
The raw material according to the present invention is pure Ti, Ti alloy such as Ti-6 mass% Al-4 mass% V alloy powder, etc., hydrogenated titanium or titanium alloy in the HDH process, pulverized, dehydrated Titanium powder or titanium alloy powder containing 3% or more of hydrogen content is used by omitting the elementary process. Regarding the size of the powder, a fine powder having an average particle size of less than 5 μm deteriorates the filling rate and workability. In addition, when only the coarse powder having an average particle size of 1000 μm or more is used, the filling property is deteriorated, so the range is set to 5 to 1000 μm. Preferably, the thickness is 10 to 500 μm.

Ti alloy powder such as pure Ti, Ti-6 mass% Al-4 mass% V or the like alloy powder is filled with iron-based or titanium or titanium alloy capsules at 90% or less with hydrogenated Ti powder or Ti alloy powder. . The capsule filled with the powder is dehydrogenated by holding at 300 ° C. or higher at 0.133 Pa or lower. In this state, a solidified molded body is obtained by hot extrusion at a heating rate of 1 ° C. to 50 ° C./min at 800 ° C. or higher and an extrusion ratio of 4 or higher. The solidified molded body obtained by this method has the same mechanical characteristics as the same component produced by the ingot method.

Hereinafter, the reasons for limitation of the present invention will be described.
Filled into an iron-based or titanium or titanium alloy capsule so that the filling rate is 90% or less. The filling rate can be derived by calculating the weight when 100% is filled from the capsule internal volume based on the density of the powder filled in the capsule and measuring the actually filled weight. That is, it is displayed as filling rate (%) = weight actually filled / weight when the filling rate calculated from the internal volume is 100% × 100. When the filling rate exceeds 90%, it is not possible to secure a sufficient flow path through which hydrogen escapes during vacuum heating and degassing treatment. Therefore, a part of the powder remains containing hydrogen, and the vacuum heating and degassing treatment is performed. However, the amount of hydrogen does not become 300 ppm or less. Therefore, the upper limit is 90%.

  In general, the powder filling rate is about 70% as a spherical powder, and when filling more than that, a press filling method in which filling is performed while applying pressure is applied. The effect is achieved especially by setting it as 50 to 75%. However, when the filling rate is 40% or less, deformation at the time of solidification molding becomes too large, which is not preferable in view of the dimensional accuracy of the solidified molded body. In addition, the reason why the capsule is limited to iron-based or titanium or titanium alloy is that the billet weight is about 10 to 50 kg, so the surface oxidation and deformation during heating may increase in copper and the like, and the heat treatment This is because the strength in the temperature range is taken into consideration.

  The inside of the capsule filled with the powder is depressurized to 0.133 Pa or less and kept at 300 to 800 ° C., and even in the heated state, the inside of the capsule is kept at a reduced pressure of 0.133 Pa or less to completely dehydrogenate the powder inside. Can be This is because the hydrogen release of the Ti alloy powder has a peak at 400 ° C. in a vacuum atmosphere, and the hydrogen content can be reduced from 3% to 300 ppm or less by maintaining the conditions. A desirable temperature is 450 ° C. or higher and 800 ° C. or lower. When the temperature is less than 300 ° C., hydrogen is not sufficiently released, and the amount of hydrogen after treatment does not become 300 ppm. When the temperature exceeds 850 ° C., sintering of the internal titanium powder or titanium alloy powder proceeds and becomes closer to a solidified molded body. The pushing force and the rolling force during rolling are increased, and the size of the extrusion device is increased accordingly.

  After the capsule cooled at a rate of 20 ° C./min or less in the above state becomes 100 ° C. or less, heated at a heating rate of 1 ° C. to 50 ° C./min to 800 ° C. or more, and held for a certain period of time, For example, after holding for 1 to 3 hours, by extruding at an extrusion ratio of 4 or more, the powders can be sufficiently adhered and mutually diffused to obtain a dense solidified product. However, if both of the conditions where the temperature is less than 800 ° C. or the extrusion ratio is less than 4 are overlapped, a dense solidified molded body cannot be formed, and it becomes the starting point of cracking and breaking in the mechanical strength test. The result is inferior to the mechanical properties of. Also, if the heating rate is less than 1 ° C / min, the heating rate is too slow and the efficiency is poor, and if it is faster than 50 ° C / min, the release behavior of hydrogen occurs suddenly, which places a load on the vacuum pump and the like. Therefore, the upper limit was set to 50 ° C./min. Preferably, it is 30 ° C./min.

  The heated capsule is molded at an extrusion ratio of 4 or more. For example, if the extrusion ratio is 150 mm in diameter, the reciprocal of the cross-sectional area ratio becomes the extrusion ratio, so that the extrusion dimension is 75 mm in diameter. Even in rolling or forging, hot working by reduction is performed so that the reciprocal of the same cross-sectional area ratio is 4 or more, and a solidified molded body is obtained. Subsequent cooling is air cooling or slow cooling. Moreover, not only round bars but also irregular shapes and tube shapes can be solidified by extrusion. Further, the solidification method may be HIP, capsule forging, rolling or the like in addition to extrusion. However, particularly in the case of solidification molding by extrusion, if dehydrogenation does not become 300 ppm or less, the capsule may swell or tear due to heating during extrusion, and solidification molding such as extrusion cannot be performed.

Hereinafter, the present invention will be specifically described by way of examples.
The titanium or titanium alloy having the composition shown in Table 1 is used to hydrogenate and pulverize the titanium or titanium alloy in the HDH process, and the titanium powder contains 3% or more of hydrogen by omitting the dehydrogenation process. Alternatively, titanium alloy powder is used. The above powder is filled into capsules so that the filling rate is 90% or less. The capsule is made of a mild steel container having a diameter of 150 mm, a length of 400 mm, and a thickness of 4 mm, and the inner surface is washed and degreased in a state where a lid on one side is welded and then filled with powder. In some cases, the process from filling to the next degassing step may be performed in a vacuum or an inert gas chamber.

  After sufficiently filling the powder, the other lid is fixed by welding. Then, a hole is made in a part of the lid by machining, and a mild steel pipe (for example, about 10 mm in diameter) filled with a mesh or a porous material is fixed by welding so that the powder does not come out. The pipe is extended to this pipe and heated while degassing with a vacuum pump. In order to prevent the capsule from being oxidized, an atmosphere furnace or a vacuum furnace is desirable for heating. First, it is confirmed that the degree of vacuum is 0.133 Pa or less, and the temperature is set to 450 ° C. or higher and 800 ° C. or lower. As it heats, hydrogen is released from the powder and the degree of vacuum deteriorates. Therefore, it is necessary to continue operating the vacuum pump during heating until it becomes 0.133 Pa or less again.

  When the degree of vacuum becomes sufficient, heating is stopped while the pump is operated, and the cooling is slowly performed at 20 ° C./min or less. When the temperature reaches 100 ° C. or lower, the pipe is sealed and taken out. When a series of steps are performed in the line, the temperature may be kept in the temperature range (800 ° C. or higher) for extrusion, rolling, and forging. The heating method is to heat to 800 ° C. or higher at a heating rate of 1 ° C. to 50 ° C./min, and hold at the temperature until the whole becomes sufficiently uniform. A heating rate of 1 ° C./min or less has no problem in characteristics, but takes too much time for heating and cannot be applied to a mass production process.

  In extrusion (forging, rolling), the heated capsule is molded at an extrusion ratio of 4 or more. For example, if the extrusion ratio is 150 mm in diameter, the reciprocal of the cross-sectional area ratio becomes the extrusion ratio, so that the extrusion dimension is 75 mm in diameter. Even in rolling or forging, hot working by reduction is performed so that the reciprocal of the same cross-sectional area ratio is 4 or more, and a solidified molded body is obtained. Subsequent cooling is air cooling or slow cooling.

  In the hydrogen analysis, the obtained powder was pulverized and measured by an inert gas melting-non-dispersive infrared absorption method. Table 1 shows the raw material and the amount of hydrogen in the raw material, the filling rate when the capsule is filled, and the capsule conditions are the material of the filling container, the heating temperature and the final vacuum, and the method and heating of the solidified molded body The conditions are shown. Table 2 shows the properties of the obtained solidified molded body evaluated.

  The average particle size of the solidified molded body was determined by mirror finishing after indexing the test piece and obtaining the average particle size of 10 fields of view by microscopic observation. The strength of the molded body was measured by applying the tensile strength and elongation at break according to the tensile test method of JIS-Z2241. As the test piece, a JIS-Z2201 No. 14 test piece equivalent (diameter = 6 mm) was used. The molded body has the same strength as the ingot within the patent range, for example, 270 to 410 MPa, elongation 27% or more for pure Ti shown in JIS-H4650, 340 to 510 MPa, elongation 23% or more for two types. Three types are 480 to 620 MPa and elongation is 18% or more. Four types are 550 to 750 MPa and elongation is 15% or more.

  Further, a Ti-6 mass% Al-4 mass% V alloy can satisfy the standards of a tensile strength of 895 MPa or more and an elongation of 10% or more. Is the starting point of stress concentration and cannot satisfy the standard strength. In addition, when solidification molding is performed without sufficient dehydrogenation to 300 ppm or less, hydrogen embrittlement is likely to occur, and therefore, an elongation standard of 10% or more cannot be ensured in a tensile test. Furthermore, as the characteristics of the solidified molded body, the same or more than the mechanical characteristics of the same component in which the ingot was produced by the centrifugal casting method was evaluated as “B”, and the inferior one as “C”.

表１または２に示すように、Ｎｏ１〜１１は本発明例、Ｎｏ．１２〜１８は比較例である。

As shown in Table 1 or 2, Nos. 1 to 11 are examples of the present invention, Nos. 12 to 18 are comparative examples.

  As shown in Table 1 or 2, Comparative Example No. No. 12 has a high filling rate, and in the vacuum heat degassing treatment, hydrogen does not sufficiently escape and there is a content exceeding 300 ppm. The elongation standard of 23% or more cannot be secured. Comparative Example No. No. 13, since the pressure in the capsule condition cannot be reduced to 0.133 Pa or less, dehydrogenation is not sufficient, and during vacuum heat degassing treatment, hydrogen does not escape sufficiently and the content exceeds 300 ppm For this reason, hydrogen embrittlement occurs during solidification molding, and it is not possible to ensure an elongation standard of 23% or more for the Ti2 type in the tensile test. Moreover, since the speed of the heating conditions is high, the sintering of the Ti powder proceeds and the pressing force and the rolling force during rolling are increased, which causes a problem in equipment.

  Comparative Example No. No. 14, because the temperature in the capsule was low, dehydrogenation was not sufficient, and in the vacuum heat degassing treatment, hydrogen did not escape sufficiently and contained more than 300 ppm, so it was solidified and molded In some cases, hydrogen embrittlement occurs, and in the tensile test, it is not possible to secure an elongation standard of Ti1 of 27% or more. Comparative Example No. Since No. 15 has a low heating temperature, a dense solidified molded body cannot be formed when solidified and is a starting point for cracking or breaking in a mechanical strength test. Comparative Example No. No. 16 has a high filling rate, and in the vacuum heat degassing treatment, hydrogen does not sufficiently escape and has a content exceeding 300 ppm. Therefore, hydrogen embrittlement occurs when solidified, and in the tensile test, Ti6 % Al4% V elongation standard of 10% or more cannot be secured.

  Comparative Example No. No. 17 was solidified and molded because the temperature in the capsule was low, so dehydrogenation was not sufficient, and during the vacuum heat degassing treatment, hydrogen did not escape sufficiently and contained more than 300 ppm. In some cases, hydrogen embrittlement occurs, and in the tensile test, it is not possible to secure an elongation standard of 10% or more of Ti6% Al4% V. Comparative Example No. Since No. 18 has a low heating temperature, a dense solidified molded body cannot be formed when solidified, and the mechanical properties of Ti4 cannot be satisfied since it is the starting point for cracking or breaking in a mechanical strength test.

  On the other hand, the present invention example No. Nos. 1 to 15 all satisfy the conditions of the present invention, so that during the vacuum heat degassing treatment, hydrogen can be sufficiently removed and the amount of hydrogen after the treatment can be reduced to 300 ppm or less. In this case, there is no hydrogen embrittlement and an elongation standard of 10% or more can be secured in the tensile test.

As described above, the solidified molded body obtained by the present invention has mechanical characteristics equal to or higher than those of the same component prepared by the ingot method, and can be manufactured at low cost by omitting the process. It has an excellent effect that it can be solidified not only to round bars but also to irregular shapes and tube shapes by extrusion.



Patent Applicant Sanyo Special Steel Co., Ltd.
Attorney: Attorney Shiina

Claims (3)

Titanium powder or titanium alloy powder is filled into an iron-based or titanium or titanium alloy capsule so that the filling rate is 90% or less, and the pressure inside the capsule is reduced to 0.133 Pa or less while heating at 300 to 800 ° C. Then, after cooling to 100 ° C. or less at a rate of 20 ° C./min or less and sealing the capsule, the capsule is heated to 800 ° C. or more at a heating rate of 1 to 50 ° C./min and held for a certain period of time. A method for producing a titanium product or a titanium alloy product, wherein the capsule is pressurized to solidify and form titanium powder or titanium alloy powder. A method for producing a titanium product or a titanium alloy product, wherein the average particle size of the titanium powder and the titanium alloy powder according to claim 1 is 5 to 1000 µm. A method for producing a titanium product or a titanium alloy product, comprising solidifying and forming the solidified molding according to claim 1 by hot extrusion at an extrusion ratio of 4 or more.