Titanium hydride powder and active metal brazing material

Abstract

This titanium hydride powder contains TiH 2 and is used for an active metal brazing material. When an analysis is performed by an image analysis method, the average particle diameter D50 is in the range of 0.1-10.0 μm, and the number ratio of particles having a particle diameter of 15 μm or more is 15% or less.

Description

Titanium hydride powder and active metal brazing material

[0001] This invention relates to titanium hydride powder containing TiH2 and to an active metal brazing filler metal.

[0002] For example, small nodules generated during the crushing of sponge blocks obtained by the reduction of titanium tetrachloride with metallic magnesium, and cutting chips and other scrap generated during the cutting of ingots or slabs made by melting and casting the crushed sponge titanium, may be subjected to a hydrodehydrogenation process (the so-called HDH process).

[0003] In the hydrogenation-dehydrogenation method, the small pieces or scraps are heated in a hydrogen gas atmosphere to be hydrogenated and embrittled, and then crushed to a predetermined particle size to produce titanium hydride powder. The titanium hydride powder is then heated in a vacuum as a dehydrogenation treatment to produce titanium powder (pure titanium powder).

[0004] The titanium hydride powder obtained by the hydrogenation-dehydrogenation method before the dehydrogenation treatment contains TiH2, which is a metal hydride, and can be used for various purposes other than the production of titanium powder by the hydrogenation-dehydrogenation method described above.

[0005] As a related technique, Patent Document 1 describes "a method for producing titanium powder by a hydrogenation-dehydrogenation method, characterized in that titanium hydride is pulverized to an average particle size of 10 μm or less and the dehydrogenation temperature is set to 300 to 600°C."

[0006] Patent Document 2 also describes "a titanium-based powder obtained by a hydrogenation-dehydrogenation method, characterized in that the particle size range is 5 to 74 μm, the average particle size is 20 μm or less, and the flow characteristic is a fluidity of less than 100 sec / 50 g." Patent Document 2 also describes that "the particle size adjusting step of the present invention is an operational step in which the hydrogenated titanium powder or hydrogenated titanium alloy powder pulverized after the hydrogenation step is mechanically pulverized and classified to adjust the particle size range to 5 to 74 μm and the average particle size is 20 μm or less."

[0007] Both the "titanium hydride" described in Patent Document 1 and the "titanium hydride powder" described in Patent Document 2 are recognized as being used in the production of titanium powder by a hydrogenation-dehydrogenation method.

[0008] Patent Document 3 states, "That is, the titanium-based powder for paste according to the present invention is characterized by an average particle size of 20 μm or less, a d90 value of 22.50 μm or less, and particle size distribution parameters α and β satisfying the following relationship: 0.6 < β / α < 1.0 (1) where α = (d90 - d50) / d50 and β = (d50 - d10) / d50, and d10, d50, and d90 represent particle sizes corresponding to 10%, 50%, and 90% of the cumulative weight of the cumulative frequency distribution of the titanium-based powder." It also states, "Furthermore, in a preferred embodiment, the titanium-based powder for paste according to the present invention is a titanium hydride powder produced by a hydrogen pulverization method or a metallic titanium powder produced using the same as a raw material." Patent Document 3 also states, "The present invention has the effect of being suitably usable as a paste for producing titanium sheets suitable for use in electrodes for dye-sensitized solar cells and secondary batteries."

[0009] JP-A-3-122205 JP-A-7-278601 Patent No. 5898761

[0010] Incidentally, active metal brazing filler metals used for joining ceramic materials and metal materials, which are difficult to join with ordinary brazing filler metals, may contain Ti, and titanium hydride powder may be used for these.

[0011] In this case, the titanium hydride powder is required to be capable of improving the reactivity of Ti in the active metal brazing filler metal with the joined materials, such as ceramic materials, and improving the wettability between the active metal brazing filler metal and the joined materials. Patent Documents 1 to 3 do not pay any attention to these uses and aspects of titanium hydride powder.

[0012] An object of the present invention is to provide a titanium hydride powder that can be suitably used in an active metal brazing filler metal, and an active metal brazing filler metal.

[0013] After extensive research, the inventors have found that when titanium hydride powder having a predetermined particle size or particle size distribution is used in an active brazing filler metal, compounds are formed almost uniformly at the bonding interface between the Ti in the active brazing filler metal and the materials to be bonded. The inventors believe that this is achieved because, by adjusting the particle size as described above, the number of powder particles per unit volume of the brazing filler metal is increased compared to conventional methods, reducing the difference in powder density within the brazing filler metal, and because the particle size difference is small and the specific surface area is large, compounds with relatively uniform sizes are formed uniformly and uniformly in the reaction process.

[0014] The titanium hydride powder of the present invention contains TiH2 and is used in active metal brazing filler metals. When analyzed by image analysis, the average particle size D50 is in the range of 0.1 μm to 10.0 μm, and the proportion of particles having a particle size of 15 μm or more is 15% or less.

[0015] When the titanium hydride powder is analyzed by image analysis, it is preferable that the percentage of particles having a particle diameter of 15 μm or more is 10% or less.

[0016] The titanium hydride powder preferably has a maximum particle size of 50 μm or less as determined by image analysis.

[0017] The titanium hydride powder preferably has a maximum particle size of 35 μm or less as determined by image analysis.

[0018] When the titanium hydride powder is analyzed by image analysis, it is preferable that the larger of the difference between the average particle size D50 and the 10% particle size D10 and the difference between the 90% particle size D90 and the average particle size D50 is 10 μm or less.

[0019] When the titanium hydride powder is analyzed by image analysis, it is preferable that the larger of the difference between the average particle size D50 and the 10% particle size D10 and the difference between the 90% particle size D90 and the average particle size D50 is 8 μm or less.

[0020] The titanium hydride powder is particularly suitable for use in active metal brazing filler metals used to join ceramic materials and metal materials.

[0021] The active metal brazing material of the present invention contains any one of the titanium hydride powders described above.

[0022] The titanium hydride powder of the present invention can be suitably used for active metal brazing filler metals.

[0023] Hereinafter, an embodiment of the present invention will be described in detail.

[0024] (Titanium hydride powder) Titanium hydride powder according to one embodiment of the present invention contains TiH2 and is used in active metal brazing filler metals.

[0025] Active metal brazing, which uses an active metal brazing material, is a method often applied to joining ceramic materials together or joining ceramic materials to metal materials, and may also be referred to as the active-metal method. In active metal brazing, Ti contained in the titanium hydride powder in the active metal brazing material reacts with the materials to be joined, thereby improving the wettability between the active metal brazing material and the materials to be joined, and therefore, it can be applied to materials that are difficult to join with ordinary brazing materials.

[0026] On the other hand, the properties of titanium hydride powder that can enhance the reactivity between Ti and the joined materials in an active brazing filler metal have not been fully investigated. In response to this, the inventors have newly discovered that when titanium hydride powder with a relatively small particle size and a relatively small amount of particles with a predetermined large particle size is used in an active brazing filler metal, compounds are uniformly formed at the joining interface between Ti and the joined materials. The inventors believe that this is achieved because, by adjusting the particle size as described above, the number of powder particles per unit volume of the brazing filler metal is increased compared to conventional methods, reducing the powder density difference within the brazing filler metal. Furthermore, the small particle size difference and large specific surface area allow compounds with a relatively uniform size to be uniformly formed during the reaction process.

[0027] Based on this knowledge, the titanium hydride powder of this embodiment has an average particle size D50 in the range of 0.1 μm to 10.0 μm, and the proportion of particles having a particle size of 15 μm or more is 15% or less.

[0028] If the average particle diameter D50 is larger than 10.0 μm, the specific surface area will be small, resulting in insufficient reactivity with the workpiece during active metal brazing. On the other hand, if the average particle diameter D50 is smaller than 0.1 μm, handling in the atmosphere will be difficult due to the risk of fire, making it impractical. From this perspective, the average particle diameter D50 of the titanium hydride powder is preferably 0.1 μm to 10.0 μm, and more preferably 5.0 μm to 8.0 μm.

[0029] Furthermore, if the number ratio of particles having a particle diameter of 15 μm or more is greater than 15%, there is a high possibility that coarse particles will be generated during active metal brazing, which will inevitably result in a decrease in reactivity with the joined materials. In this case, for example, when using an active metal brazing material to join circuit boards made of ceramic materials or metal materials, there is a concern that the overall or partial thickness of the joining layer formed with the active metal brazing material will increase due to the generation of the coarse particles. For this reason, it is desirable that the number ratio of particles having a particle diameter of 15 μm or more is small, and it is preferable that the number ratio be 13% or less, and even more preferably 10% or less.

[0030] The maximum particle size of the titanium hydride powder is preferably 50 μm or less, and more preferably 35 μm or less. Such a small maximum particle size suppresses the generation of coarse particles during active metal brazing, stabilizing mechanical properties such as joint strength after joining. The maximum particle size of the titanium hydride powder may be, for example, 50 μm or more, typically 60 μm or more.

[0031] For titanium hydride powder, the larger of the difference between the average particle size D50 and the 10% particle size D10 (D50 - D10) and the difference between the 90% particle size D90 and the average particle size D50 (D90 - D50) is preferably 10 μm or less, and even more preferably 8 μm or less. A small difference between the average particle size D50 and the 10% particle size D10 or the difference between the 90% particle size D90 and the average particle size D50 means that the particle size distribution of the titanium hydride powder is sharp. When the larger of these differences is small as described above, it is thought that relatively small particles are generated uniformly during active metal brazing, further stabilizing the mechanical properties.

[0032] The above-mentioned average particle diameter D50, 10% particle diameter D10, and 90% particle diameter D90, as well as the number proportion of particles with a given particle diameter, are each determined by image analysis. More specifically, a particle shape image analyzer PITA-04 (manufactured by Seishin Enterprise Co., Ltd., conditions: dispersant: IPA, pump speed: 2000 Hz) is used to obtain an image containing projected images of 5000 or more titanium hydride powder particles, and the particle diameter is calculated as a sphere with an area equal to the projected area of ​​each particle in the image. This allows a number-based cumulative distribution to be obtained on a graph with particle diameter on the horizontal axis and cumulative frequency of particle number (number) on the vertical axis. The average particle diameter D50, 10% particle diameter D10, and 90% particle diameter D90 refer to particle diameters at which the number-based cumulative frequency in the cumulative distribution is 50%, 10%, or 90%, respectively. Furthermore, the number proportion of particles with a particle diameter of 15 μm or greater can also be determined from the above-mentioned cumulative distribution. The maximum particle size means the particle size of the particle having the largest particle size among the above 5,000 particles.

[0033] The titanium hydride powder has a specific surface area of ​​0.6 to 3.0 m 2 / g, and further 1.0 to 2.0 m 2 / g. This is because a large specific surface area is expected to further improve reactivity due to an increased contact area with the materials to be joined. The specific surface area is measured by the BET method using N2 gas.

[0034] Titanium hydride powder contains TiH2, and typically consists mostly of TiH2. The maximum hydrogen concentration in TiH2 is 4 mass%, and the fact that titanium hydride powder contains TiH2 can be confirmed by analyzing the hydrogen concentration using an inert gas fusion-thermal conductivity method.

[0035] Titanium hydride powder may contain impurities such as Fe, Si, Mn, Mg, Cl, N, and / or O in amounts of 0.1 mass% or less. It may also contain other impurities in amounts below the detection limit. The presence and content of impurities can be confirmed by ICP emission spectroscopy (Fe, Si, Mn, Mg), silver nitrate titration (Cl), ammonia distillation separation / amidosulfuric acid titration (N), and inert gas fusion-infrared absorption spectroscopy (O).

[0036] (Production Method) The titanium hydride powder as described above can be produced, for example, by carrying out the steps up to the dehydrogenation treatment in a hydrodehydrogenation method on a titanium raw material under predetermined conditions. In other words, the titanium hydride powder is obtained before the dehydrogenation step during the hydrodehydrogenation method under predetermined conditions.

[0037] In the hydrodehydrogenation process, a titanium raw material is first subjected to a hydrogenation step. Examples of titanium raw materials that can be used include small pieces generated when crushing titanium sponge blocks, and cuttings or chips and other scrap generated when cutting ingots or slabs produced by melting and casting the titanium sponge obtained by crushing. The titanium sponge blocks are produced by reducing titanium tetrachloride with metallic magnesium and consist primarily of Ti.

[0038] In the hydrogenation process, the titanium raw material may be heated to a temperature of, for example, 500° C. or higher and hydrogen gas may be supplied to the titanium raw material, causing the titanium raw material to absorb hydrogen and generate TiH2, which becomes a hydrogenated raw material.

[0039] The hydrogenation raw material is then subjected to a pulverization process and a classification process. A pulverization device equipped with an impact pulverization rotor and an air classifier equipped with a classification rotor may be used for this process. Air classification can classify powders in a relatively fine range, and the classification point can be finely adjusted, making it suitable for use in producing the titanium hydride powder of the above-mentioned embodiment. By adjusting the rotation speed of the impact pulverization rotor and classification rotor, titanium hydride powder with a predetermined particle size and particle size distribution can be obtained. On the other hand, when titanium powder is produced, the titanium hydride powder is recovered and then subjected to a dehydrogenation process.

[0040] The titanium hydride powder produced as described above is often polygonal rather than spherical due to the pulverization process. This is thought to significantly enhance the reactivity of the titanium hydride powder with the workpiece materials when used in an active brazing filler metal. The titanium powder obtained after the dehydrogenation process tends to have a larger particle size due to the sintering promoted during the dehydrogenation process. Therefore, even if further hydrogenation is performed, the fine titanium hydride powder as described in this embodiment may not be obtained. The term "fine titanium hydride powder" as used herein refers to a powder having an average particle size D50 of 0.1 μm to 10.0 μm and a number ratio (cumulative distribution based on number) of particles with a particle size of 15 μm or greater of 15% or less when analyzed using the image analysis method described above.

[0041] (Active Metal Brazing Filler Metal) The titanium hydride powder described above is used in an active metal brazing filler metal. At least a part of the active metal brazing filler metal may contain the titanium hydride powder.

[0042] Active metal brazing materials are typically used for joining ceramic materials, such as circuit boards, to metal materials by active metal brazing. Examples of ceramic materials include oxide-based, nitride-based, and carbide-based ceramics, specifically Al2O3, SiC, Si3N4, AlN, ZrO2, etc. Examples of metal materials include Cu.

[0043] The active metal brazing material may be in the form of a powder, a sheet, or a paste. For example, a paste active metal brazing material may contain, in addition to the titanium hydride powder, an organic substance such as an organic solvent, and may be, for example, a powder containing titanium hydride powder dispersed in an organic solvent. Powders other than the titanium hydride powder contained in the active metal brazing material include silver powder and copper powder. The titanium hydride powder may be mixed into such powders as an additive.

[0044] Active metal brazing is sometimes performed by placing an active metal brazing material on one of the workpieces by coating or other means, sandwiching the active metal brazing material between the two workpieces, and then heating them. During this process, the organic solvent in the paste-like active metal brazing material evaporates, melting other powders, and Ti reacts with components of the workpieces (e.g., Al2O3) to form compounds (e.g., Al-Ti-O), chemically bonding the active metal brazing material and the workpieces. In the case of the active metal brazing material containing titanium hydride powder of the above-mentioned embodiment, the titanium hydride powder, which is distributed relatively uniformly and densely on the target surfaces, uniformly forms compounds of similar size. This increases the effective reactivity between Ti and the workpieces, which is thought to improve the bond strength between the workpieces using the active metal brazing material.

[0045] Next, a titanium hydride powder according to the present invention was produced as a prototype, which will be described below, although the description here is for illustrative purposes only and is not intended to be limiting.

[0046] (Examples 1 to 4) The cutting chips generated during the cutting of a titanium ingot were subjected to a hydrogenation process using a hydrogenation-dehydrogenation method, a pulverization process, and a classification process to produce hydrogenated titanium powder. In the hydrogenation process, the cutting chips were heated to 600°C or higher, and hydrogen gas was supplied to create a hydrogen gas atmosphere, thereby obtaining a hydrogenated raw material.

[0047] In the subsequent pulverization and classification steps, the pulverization and classification conditions were finely adjusted at a classification point of around 10 μm, and the fine powder was collected to obtain titanium hydride powders with different particle size distributions.

[0048] (Comparative Examples 1 to 4) The coarse powders recovered in Examples 1 to 4 were further air-classified to obtain titanium hydride powders with different particle size distributions. The classification point for Comparative Example 1 was 20 μm, and the classification points for Comparative Examples 2 to 4 were 45 μm. In Comparative Examples 1, 2, and 4, a dehydrogenation treatment was performed in which the powders were heated to a temperature of 500°C or higher in a vacuum. This resulted in titanium powder (pure titanium).

[0049] (Evaluation 1: Particle size distribution measurement) According to the methods described above, the average particle size D50, 10% particle size D10, 90% particle size D90, maximum particle size, and the number proportion of particles having a particle size of 15 μm or more were measured for each of the titanium hydride powders and titanium powders of Examples 1 to 4 and Comparative Examples 1 to 4. The results are shown in Tables 1 and 2.

[0050] (Evaluation 2: Alumina Plate Bonding Test) An alumina plate bonding test was conducted for each of the titanium hydride powders and titanium powders (hereinafter referred to as "test powders") in Examples 1 to 4 and Comparative Examples 1 to 4 according to the procedure described below. The results are shown in Table 2. (1) Approximately 1 g of the test powder was spread on an alumina plate measuring 15 × 15 × 1.5 mm placed on a stainless steel tray. (2) An alumina plate of the same size as in (1) was placed on top of the alumina plate on which the test powder was spread, and a quartz plate was placed on top of that. (3) Several quartz plates for height adjustment were placed on top of the quartz plate, and a titanium plate weighing approximately 130 g was placed on top of that as a weight to obtain a test sample. (4) The obtained test sample was subjected to heat treatment at 800°C for 90 minutes in a vacuum atmosphere of 10 Pa or less. (5) After the heat treatment, the test sample was checked for the ability to bond to other alumina plates. (6) Regarding the bonding of the test sample after the heat treatment, a shear test was performed in which one end face of the stacked alumina plates was fixed, and a 5 kg weight was placed on the other end face (area: 15 mm × 1.5 mm), and a shear load was applied horizontally to the bonded surfaces to check for damage. If the bonded alumina plates peeled off or the solidified test powder was damaged, and the sample could not be used for the thermal conductivity measurement described below, the result was rated as "fail."

[0051] (Evaluation 3: Thermal Conductivity Measurement) For each of the titanium hydride powders and titanium powders (hereinafter referred to as "test powders") in Examples 1 to 4 and Comparative Examples 1 to 4, test samples were prepared in the same manner as in the alumina plate bonding test in Evaluation 2, and thermal conductivity was measured in accordance with the US standard "ASTM E 1530." The results are shown in Table 2. The measurement device used was a steady-state thermal conductivity measuring device (GH-1, manufactured by Advance Riko Co., Ltd.). When preparing the test samples, alumina plates measuring 25 x 25 x 1.5 mm were used, and the amount of test powder used was approximately 0.1 g.

[0052]

[0053]

Claims

1. A titanium hydride powder containing TiH2 and used in active metal brazing materials, which, when analyzed by image analysis, has an average particle size D50 in the range of 0.1 μm to 10.0 μm, and the percentage of particles with a particle size of 15 μm or more is 15% or less.

2. The titanium hydride powder according to claim 1, wherein when analyzed by image analysis, the proportion of particles having a particle diameter of 15 μm or more is 10% or less.

3. The titanium hydride powder according to claim 1, wherein the maximum particle size measured by image analysis is 50 μm or less.

4. The titanium hydride powder according to claim 3, wherein the maximum particle size measured by image analysis is 35 μm or less.

5. A titanium hydride powder as described in claim 1, in which, when analyzed by image analysis, the larger of the difference between the average particle diameter D50 and the 10% particle diameter D10 and the difference between the 90% particle diameter D90 and the average particle diameter D50 is 10 μm or less.

6. A titanium hydride powder as described in claim 5, in which, when analyzed by image analysis, the larger of the difference between the average particle diameter D50 and the 10% particle diameter D10 and the difference between the 90% particle diameter D90 and the average particle diameter D50 is 8 μm or less.

7. The titanium hydride powder according to claim 1, wherein the active metal brazing material is used for joining a ceramic material to a metal material.

8. An active metal brazing material comprising the titanium hydride powder according to any one of claims 1 to 7.

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