JPS6148581B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a boron structural material, and particularly to a method for manufacturing a boron structural material suitable for acoustic materials such as cantilevers of pick-up cartridges. Structure of conventional examples and their problems Boron has a hardness second only to diamond and has very good wear resistance, so it has become a useful material for cutting tools, sliding machine parts, bearings, etc. There is. Furthermore, the specific elastic modulus (elastic modulus/density) is the highest among existing materials. This property means that the propagation velocity of sound waves is the highest among existing materials, making it useful for acoustic materials, especially boron structural materials used in cartridge cantilevers. Traditionally, metals such as aluminum alloys and titanium alloys have been used for cantilevers in cartridges, but both have a lower specific elastic modulus than boron, and their frequency characteristics have a high resonant frequency f ₀ (usually 10KHz to 10KHz).
In the range of 2KHz to 10KHz below 40KHz, the response tends to decrease, the so-called sagging phenomenon occurs, making it difficult to obtain flat frequency characteristics, and it is also difficult to obtain good transient characteristics, which affect the tracking performance of pick-up cartridges. There was a drawback. The appearance of a cantilever for cartridges using boron was expected to overcome the drawbacks of these known materials. Among them, tapered boron pipe cantilevers, which can reduce the effective mass, are more effective than flat boron pipe cantilevers.
Boron is said to greatly contribute to flattening the frequency characteristics in the high frequency range of 40KHz or higher, and its appearance is eagerly awaited, but it is difficult to obtain boron-applied products in the form of dense structures by methods such as casting or rolling. be.
For this reason, when manufacturing various boron-applied products,
In most cases, vapor deposition, sputtering, or chemical vapor deposition (CVD) is applied to a substrate made of a material other than boron.
It is used as a composite with a boron coating formed thereon. Among these conventional methods for forming boron coatings, chemical vapor deposition is considered to be the one that yields the highest quality coatings. In chemical vapor deposition,
Crystalline (β-rombohedral, α-rombohedral, tetragonal) boron and amorphous (mamorphous) boron can be obtained by changing the production conditions, and these crystals have their own precipitation temperature ranges. However, within the precipitation temperature range of the same quality, the precipitation rate differs depending on the temperature (when chemical vapor deposition is performed for a certain period of time, the precipitation rate in the low temperature area is low and the precipitation rate in the high temperature area is high). However, in general, boron deposited on the surface of a substrate will be damaged due to inherent distortions, microcracks, etc.
The mechanical properties are often poor and the substrate is almost destroyed during the removal process, which is indicative of the amount of inherent strain. OBJECTS OF THE INVENTION The present invention aims to provide a method for producing a boron structural material that does not have such drawbacks, has excellent mechanical properties, and can efficiently yield particularly high-quality cantilevers for cartridges. Structure of the Invention The method for manufacturing a boron structural material according to the present invention provides a chromium coating whose thickness changes sequentially from one side to the other on a base of tantalum (Ta), molybdenum (Mo), niobium (Nb), or tungsten (W). The method is characterized in that a boron layer is formed on the surface of the substrate by chemical vapor deposition by heating the substrate with electricity. In other words, the inventors solved the problems in the conventional example by forming a chromium coating layer on the substrate, and at the same time formed a boron layer on the substrate surface by sequentially changing the thickness of this chromium layer from one side to the other. Utilizing the deposition temperature range, which is one of the characteristics of chemical vapor deposition, a temperature difference is actively created, and when the substrate is removed as in the conventional method, the boron structural material does not break, making it an excellent machine. A boron structural material, especially a tapered pipe-shaped boron structural material, which exhibits good physical properties and a good appearance, can be obtained, and the tapered boron pipe made of boron alone obtained in this way is suitable for use in cartridges. It is an excellent boron structural material for cantilevers. The method of forming a chromium coating layer with a thickness varying from one side to the other on a tantalum, molybdenum, niobium, or tungsten substrate is to first coat the entire surface of the substrate with a first layer of chromium by sputtering, vacuum deposition, plating, etc. Then, masking is applied to cover the second layer, and further masking is applied to cover the third layer. Alternatively, the covering layer may be formed while moving the masking position in one direction. In addition, the thickness of the chromium layer to be formed is determined when the heating temperature of the first layer that covers the entire surface is 1350℃, and the thickness of the chromium layer that is larger than that (second layer,
(3rd layer) is determined to be at least 1050℃. In this case, it is appropriate that the thickness of the first layer is 0.1 μm, and the maximum thickness of the second and higher layers is 3 μm. 0.1
This is because strain in the boron layer cannot be sufficiently removed if the layer thickness is less than μm. Next, a method of forming a boron layer by chemical vapor deposition on a substrate on which a chromium coating layer whose thickness changes sequentially from one side to the other as described above includes, for example, placing the substrate in a reactor and heating it by applying an electric current. Boron is precipitated by a reductive decomposition reaction as shown in the following formula. 2BX ₃ +3H ₂ →2B+6HX However, X is a halogen element such as chlorine Cl, bromine Br, or iodine I. Raw material gases used in chemical vapor deposition include BX ₃ and boron hydride.
In addition, in this boron precipitation reaction, various crystal forms can be obtained depending on the heating temperature, gas pressure, amount of raw material gas flowing into the reactor, etc., and each of these crystal forms has its own precipitation zone. Note that in order to obtain a single chromium structural material by dissolving and removing the chromium-coated substrate from the composite thus obtained, mainly Cl ₃ ,
Treat with acids such as HCl, HF, Br methanol, etc. In this way, the substrate is removed and a tapered hollow boron structure is obtained, for example. DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on the drawings.
As shown in Figure 1, a tantalum wire 1 with a diameter of 250 μm and a length of 3 cm is prepared, and after degreasing and cleaning, a boron structural material of 3 mm per chip is continuously applied to the tantalum wire 1 by masking using a sputtering method. A chromium coating layer 2 is formed so that 10 chips are obtained. The chromium coating layer 2 extends from one end of each chip.
A first layer 2a having a thickness of 0.1 μm is formed from 1 mm to 2 mm, a second layer 2b having a thickness of 1 μm from 2 mm to 3 mm, and a third layer 2c having a thickness of 3 μm from 2 mm to 3 mm. Next, the tantalum wire 1 having the chromium coating layer 2 is placed in a reactor as a base, and the first layer 2a is heated by applying electricity.
Heat to 1350℃. At this time, the second layer 2
b is about 1200°C, and the temperature of the third layer 2c is 1050°C. Then, 1 part by volume of boron trichloride (BCl ₃ ) and 3 parts by volume of hydrogen (H ₂ ) were flowed for 60 seconds at a rate of 1 part per minute. At this time, a boron layer of 30 μm was deposited on the first layer, 20 μm on the second layer, and 10 μm on the third layer. The thus prepared sample was cut into 3 mm chips and immersed in a commercially available solution containing 50 gr of bromine dissolved in 200 ml of methanol to dissolve and remove the tantalum wire 1 and the chromium coating layer 2. At this time, the boron layer was not dissolved, and a tapered hollow boron structural material 3 as shown in FIG. 2 was obtained.
Samples of hollow boron structural materials were prepared in the same manner under various conditions, and the bending strength of each sample was measured. The measurement was carried out by setting the beam length to 2 mm, applying a load with the beam supported at both ends, and determining the load at which the sample broke. The number of samples was 20 each, and the average values are shown in the table below. The table also shows the yield and the crystalline state of the surface when a tapered hollow boron structural material is obtained by removing the substrate. However, samples marked with * in the table
No. 5 to No. 8 are comparative examples of samples using various substrates without a chromium coating layer, respectively.

[Table] Measured values of samples No. 1 to No. 4 in this table using each substrate with a chromium coating layer, and samples No. 5 to No. 8 of each substrate without a chromium coating layer. It is clear that the samples obtained by the method of the present invention have much better mechanical strength and yield than the samples obtained by the conventional method. be. In addition, the tapered hollow boron structural material obtained by the method of the present invention was processed into a cartridge cantilever, and its characteristics were evaluated in comparison with conventional products.
Shown in the graph of Figure. The horizontal axis represents frequency (Hz), and the vertical axis represents response (dB), and the cantilever made by the method of the present invention is represented by a solid line a, and the conventional cantilever is represented by a broken line b. The so-called sagging phenomenon in frequency characteristics, which was considered a drawback of conventional products made of known materials such as aluminum alloy or titanium alloy, and
It was found that the flatness in the high frequency range above 40KHz and the transient characteristics that affect tracking performance were significantly improved. Furthermore, a boron coating layer having a high elastic modulus without such distortion or microtracks has a wide range of uses as a mechanical member. Effects of the Invention According to the method for manufacturing a boron structural material according to the present invention,
Since a chromium coating layer is formed on the substrate on which the boron layer is formed, no distortion or microclocks occur in the boron layer, and the bending strength of the hollow boron structural material obtained by removing the substrate is extremely high. , the yield is also significantly improved. In addition, since the chromium coating layer is formed by changing the thickness sequentially from one side of the substrate to the other, the boron layer formed on it becomes a tapered hollow boron structural material by removing the substrate, and the frequency characteristics and A material for cartridge cantilevers with excellent transient characteristics can be obtained. According to the method of the present invention, it is possible to obtain a boron structural material that does not cause distortion or microclocks in the boron coating layer and has a wide range of uses as a mechanical member having a high modulus of elasticity.

[Brief explanation of the drawing]

The figures show examples of the present invention, in which Fig. 1 is a side view of the substrate, Fig. 2 is a side view of a tapered hollow boron structural material obtained using the substrate of Fig. 1, and Fig. 3 is a side view of the substrate. 2 is a graph comparing and evaluating the characteristics of the cartridge cantilever made of the boron structural material shown in FIG. 2 and a conventional product. 1...Base body, 2...Chromium coating layer, 3...Boron structural material.

Claims (1)

[Claims] 1. A coating layer of chromium whose thickness changes sequentially from one side to the other is formed on a base of tantalum, molybdenum, niobium, or tungsten, the base is heated with electricity, and the surface of the base is coated by chemical vapor deposition. A method for producing a boron structural material, the method comprising forming a boron layer. 2 The thickness of the chromium coating layer is 0.1 μm to 3 μm
A method for manufacturing a boron structural material according to claim 1. 3. The method for manufacturing a boron structural material according to claim 1, wherein the heating temperature of the substrate is 1050°C to 1350°C.