JPH07118851A - High melting point metallic foil and its production - Google Patents

Abstract

PURPOSE:To produce high m.p. metallic foil of high quality at a considerably reduced total draft by forming a tungsten foil laminated in parallel and having a specified thickness on a substrate by chemical vapor deposition. CONSTITUTION:A high m.p. metallic layer having 5-500mum thickness and a metallic structure of the shape of at least one of traces of columnar and fine crystals in the thickness direction is formed on a substrate from tungsten or a tungsten-rhenium alloy by chemical vapor deposition. The metallic layer is separated from the substrate by the difference in the coefft. of thermal expansion between them and the layer is rolled to obtain the objective metallic foil having <=8mum surface roughness Rmax. This high m.p. metallic foil almost free from ruggedness on the front and rear faces and having about 5-100mum thickness is obtd. in a high yield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory metal foil made of refractory metal such as tungsten (W) and a tungsten-rhenium (W-Re) alloy, and a method for producing the same, more specifically, a cathode ray tube (CRT). Used for cathode pipe or sleeve, high temperature heat resistant metal film for hot isostatic pressing (HIP) canning, lining material for melting high melting point substances such as electron beam (EB), coiled ribbon heater material, etc. High melting point metal foil and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, Ta, Mo or the like has been used for a pipe or sleeve for a CRT cathode. Also,
Stainless steel (SUS) is used for the high temperature heat resistant metal film for HIP canning, while no lining lining material is used for melting high melting point substances such as EB. Used in bare land. If high melting point metal foil such as tungsten can be used for these applications,
Heat resistance is also improved, and the life of parts used at high temperatures can be extended. Incidentally, the thinnest refractory metal foil currently manufactured is a tungsten (W) foil, and its thickness is about 100 μm. This W foil is made by sintering by powder metallurgy to make tungsten slag,
It is obtained by repeating the heating and rolling of this tungsten slag.

[0003]

However, since W is a difficult-to-work material and is prone to cracking, it is difficult to roll when using the powder metallurgy method, when processing from the slag to a thickness of several hundred μm, and The yield was very poor, and as a result, a foil of quality that could be put to practical use could not be obtained. Further, the W-Re alloy is also known to be a difficult-to-work material, and has the same drawbacks as the above-mentioned W foil.
Thus, W and W-Re alloys are difficult-to-work materials, and metal foils with a thickness of 100 μm or less have not been obtained.

On the other hand, molybdenum (Mo), which is known as a refractory metal, has been practically used as a packing material, a coating material, and a pipe material, but W is a conventional powder metallurgy even if it is desired to make full use of its heat resistance. The workability is particularly poor in the production of thin plates by the method, and the poor yield is a major obstacle to industrial production.

Therefore, the technical problem of the present invention is 50 to 5
Compared with the conventional powder metallurgical method of W or W-Re alloy, a thin plate of 00 μm W or W-Re alloy can be formed, and the total working rate in rolling can be greatly reduced, and high quality foil can be obtained. To provide a melting point metal foil and a manufacturing method thereof.

[0006]

The present invention is a W foil or W-
It is proposed to use a chemical vapor deposition method (hereinafter referred to as a CVD method) as a method for producing a Re alloy foil, not by the conventional powder metallurgy method. 2 steps of forming the alloy foil on the substrate and separating the W foil or the W-Re alloy foil from the substrate
It consists of three steps, that is, depending on the process, and as an additional process, the W foil or the W-Re alloy foil which is separated is rolled.

According to the present invention, the metallographic structure is made of tungsten or a tungsten-rhenium alloy, has a thickness of 5 to 500 μm, and has at least one of columnar and fine crystal traces in the thickness direction. It is possible to obtain a high melting point metal foil having the following features.

According to the present invention, in the refractory metal foil, a refractory metal foil is obtained in which a metal structure formed by a chemical vapor deposition method is laminated in parallel on one surface. .

According to the present invention, in any of the above high melting point metal foils, a high melting point metal foil having a thickness of 5 to 100 μm and Rmax of 8 μm or less can be obtained.

According to the present invention, a refractory metal layer made of tungsten or a tungsten-rhenium alloy having a thickness of 5 to 500 μm is formed on a substrate by a chemical vapor deposition method and rolled to obtain a favorable Rmax of 8 μm or less. A method for producing a high-melting-point metal rolled foil characterized by forming a surface is obtained.

According to the present invention, a refractory metal layer made of tungsten or a tungsten-rhenium alloy having a thickness of 5 to 500 μm is formed on a substrate by a chemical vapor deposition method, and the refractory metal layer is formed on the substrate. A method for producing a high-melting point metal foil, wherein the difference in coefficient of thermal expansion between the substrate and the high-melting point metal layer is 6 × 10 ^-6 K ^-1 or more. A manufacturing method is obtained.

According to the present invention, a refractory metal layer made of tungsten having a thickness of 5 to 500 μm is formed on a metal substrate by a chemical vapor deposition method, and the substrate is made of a liquid mixture of hydrofluoric acid and nitric acid. A method for producing a high-melting point metal foil, which comprises removing the metal foil with an acidic solution of 1.

According to the present invention, a refractory metal layer made of tungsten or a tungsten-rhenium alloy having a thickness of 5 to 500 μm is formed on a graphite substrate by a chemical vapor deposition method at a temperature of 800 ° C. or lower. A method for producing a high melting point metal foil, characterized in that the substrate is mechanically removed, is obtained.

Here, the details of the present invention will be explained by taking W as an example of the refractory metal.

First, as a method of obtaining W by the CVD method which is the first step of the present invention, (1) a method of reducing tungsten hexafluoride gas (WF ₆ ) with hydrogen, (2) a tungsten chloride gas (WCl) ₆ ) is reduced by hydrogen, and (3) tungsten chloride gas (WCl ₆ ) is thermally decomposed.

As a recent technological trend, the method (1) is most suitable for obtaining W in the most stable manner. CV
Since the method D is produced from the gas phase, it is generally known that highly pure W can be obtained.

The present inventors have also confirmed that W having a smooth surface state can be obtained on the substrate by the CVD method.
Both gas impurities and metal impurities are low, and the purity is 6N (ni
I got a ne) W.

Specifically, for hydrogen gas (H ₂ ), W
W is obtained by supplying F ₆ at a rate of 1/3 to 1/10 and heating the film formation substrate to 400 to 1000 ° C. Here, in order to make the structure suitable for rolling in the subsequent process, C
It is desirable that the VD crystal structure (hereinafter referred to as a CVD layer) be laminated in the horizontal direction on the substrate. Such a CVD layer is obtained by intermittently supplying a raw material gas such as rotating a substrate, and the present inventors have found that the thickness of one layer is 0.2 to 0.
A 6 μm W CVD layered structure is obtained. When the CVD layer crystal extends in the direction perpendicular to the substrate surface, there is a disadvantage that cracks easily occur when an external force in the direction perpendicular is applied in the rolling process, which is not preferable. The thickness of the W layer formed by the CVD method is 5 to 500 μm, preferably 50 to 200 μm. It is expected that the CVD layer in the film thickness direction after the formation of the CVD layer will have metallic characteristics if it has 5 or more layers. From that viewpoint, the CVD layer thickness is 3 μm.
Is the limit. The reason is that if the thickness of the formed CVD layer is too thin, the strength of the separated W foil is insufficient, and conversely if it is too thick, it is necessary to increase the number of times of rolling, and the number of rolling processes increases. Not only that, the W foil surface is hardened due to the rolling process and the yield is deteriorated. In addition,
When a W-Re alloy is formed by the CVD method, it can be obtained by adding a rhenium hexafluoride gas (ReF ₆ ) to a source gas so that a predetermined composition ratio is obtained.

Next, a method for separating the W foil or the W-Re alloy foil obtained by the CVD method, which is the second step of the present invention, from the substrate will be described.

The method (4) utilizes the difference in thermal expansion between the substrate and the formed W foil or W-Re alloy foil,
There are three methods: (5) removing the substrate by chemical treatment, and (6) removing the substrate by a mechanical method.

First, a method of utilizing the difference in the coefficient of thermal expansion from the substrate of (4) will be described. The thermal expansion coefficient of W at 20 to 500 ° C. is 4.6 × 10 ⁻⁶ K ⁻¹ , and the substrate has a thermal expansion coefficient of 6.0 × 10 ⁻⁶ K ⁻¹ or more, preferably ^{6 to} 19
× 10 ^-6 K ^-1 is suitable. If the difference in the coefficient of thermal expansion is too large, large warpage or cracking may occur when the substrate is separated from the substrate. Thus, W can be separated from the substrate by heating W to 400 to 1000 ° C. to form a film on the substrate having a different coefficient of thermal expansion and then cooling.

It is preferable that the surface of the substrate is smooth in order to improve the separation between the W foil and the substrate. From the experience of the present inventors up to now, as a substrate, a stainless steel (SUS30) having a thermal expansion coefficient of 18.4 × 10 ⁻⁶ K ⁻¹ at 20 to 500 ° C.
In the case of using 4), the substrate could be separated by gradually cooling to room temperature after forming the W foil. The thermal expansion coefficient of the substrate at 20 to 500 ° C. is 11.1 × 10.
^-6 K ^-1 titanium, likewise when W foil was formed and then slowly cooled to room temperature, separation was possible.

It is desirable that the W foil separated from the substrate in this manner be etched for a very short time with a mixed solution of hydrofluoric acid and nitric acid depending on the state of impurities adhering to the surface.

The coefficient of thermal expansion of the W-Re alloy varies depending on its composition, but when the coefficient of thermal expansion of the substrate is 8 × 10 ^-6 K ^-1 or more, it can be separated as in the case of W.

Next, a method of separating and removing the substrate of (5) by a chemical treatment will be described.

W is industrially used as a material having excellent corrosion resistance, and is a mixed solution of hydrofluoric acid and nitric acid (HF + HN).
O ₃ ) rapidly mixes hydrochloric acid and nitric acid (HCl + H
NO ₃ ) is slightly corroded, but other acidic solutions,
It is known that it is not corroded by caustic soda (NaOH) and aqueous ammonia (NH ₃ aq). It becomes possible to chemically remove the metal substrate by utilizing the corrosion resistance of W. For example, when Mo is used as the substrate, since the thermal expansion coefficient is relatively close, it is difficult to separate the W foil during the cooling from room temperature to room temperature due to the difference in thermal expansion. However, Mo is nitric acid (HNO ₃ ), high concentration sulfuric acid (H ₂ S
O ₄ ) and a mixture of hydrochloric acid and nitric acid (HCl + HN
Since it is strongly corroded by O ₃ ), it can be separated from the formed W foil. According to this method, since the difference in thermal expansion between W and Mo substrates is small and the separated W foil is not subjected to a great stress during cooling, there is an advantage that a W foil with less warpage after separation can be obtained. Needless to say, when the required W does not require high strength, the W foil can be obtained without rolling in the subsequent step.

In the case of a W-Re alloy foil, Re dissolves in nitric acid, so this method is not preferable.

Furthermore, the method of removing the substrate of (6) above by a mechanical method will be described by taking W as an example. When the thickness of the formed W foil is relatively thin, insufficient strength of the W foil becomes a problem when the external force when removing the substrate is large. Therefore, when the substrate is removed by a mechanical method, the thickness of W formed is 100.
It is preferable that the thickness is at least μm. Specific substrate removing methods include blasting and cutting.

For example, a W foil can be obtained by forming W by a CVD method using graphite, which is relatively easy to mechanically remove as a substrate, and then removing the graphite substrate by blasting using alumina abrasive grains. did it. When graphite is used as the substrate, tungsten carbide is not generated at the interface between graphite and W. Therefore, when W is generated by the CVD method,
The heating temperature needs to be 800 ° C. or lower. It is desirable that the W foil separated from the substrate in this way be etched with HF + HNO ₃ or the like for an extremely short time depending on the state of impurities adhering to the surface. Note that the same can be obtained in the case of W-Re alloy foil.

Next, the rolling process of the separated W or W-Re alloy foil, which is the third step of the present invention, will be described.
This process consists of W or W-Re obtained by the CVD method.
The purpose is to remove irregularities of 10 to 30 μm on the surface generated during the formation of the alloy foil and to roll to the required plate thickness. The crystal structure of the rolled W or W-Re alloy foil is
Since it is laminated in the horizontal direction on the substrate, it is relatively strong against the external force applied during rolling, but it is suitable to sandwich it between other metals such as stainless steel for rolling. It should be noted that rolling can be performed by cold rolling, and a high quality product having Rmax of 3 μm or less can be obtained. According to the observation of the present inventors, the crystal structure of the alloy foil obtained by the above rolling is 0.05
Traces of fine crystals of ˜5 μm were left.

As described above, in the present invention, the above 3
Depending on the two processes, for example, thickness of 30μm or more, Rmax 5
It provides a very smooth W or W-Re alloy foil having a thickness of not more than μm, and is useful as a heat-resistant material used at high temperatures and also as a heat-resistant material under high vacuum since it contains few gas components.

[0032]

EXAMPLES Examples of the present invention will be described below.

Example 1 A stainless steel plate (SUS304) having a diameter of 100 mm was used as a substrate and heated to 500 ° C.
It was rotated at a rotation speed of 10 rpm. W as a source gas
F ₆ gas was supplied at 100 cc / min and H ₂ gas was supplied at 1000 cc / min for 1 hour to form a W layer of 120 μm. By gradually cooling to room temperature, the W layer, that is, the W foil could be separated from the substrate. As a result of observing the structure after etching, it was confirmed that the layered structure had a fine crystal grain of about 0.2 μm per layer. In addition, SUS304,
And the coefficient of thermal expansion of W at 20 to 500 ° C. is 18.
4 × 10 ^-6 K ^-1, was 4.6 × 10 ^-6 K ^-1. This W
The structure is shown in FIG. The surface roughness Rmax of the obtained W foil was 12 μm. This was sandwiched between 1 mm thick stainless steel plates and cold rolled to obtain a W foil having a thickness of 100 μm and Rmax of 2 μm.

Example 2 A Mo foil having a diameter of 100 mm and a thickness of 1 mm was used as a substrate, and 40 μm of W foil was produced in the same manner as in Example 1. The thermal expansion coefficients of W and Mo at 20 to 500 ° C. are 4.6 × 10 ⁻⁶ K ⁻¹ and 5.7 × 10 ⁻⁶ K, respectively.
^{It was -1} , and the W foil obtained and the Mo plate of the substrate were not separated after cooling. The Rmax of the formed W layer surface was 5 μm. This W foil was immersed in aqua regia together with Mo that was the substrate. As a result, Mo was removed, and a W foil having a thickness of 40 μm was obtained. This was sandwiched between 1 mm-thick stainless steel plates and cold-rolled at a working rate of 50%. Thickness is 2 by the above operation
A W foil of 0 μm and Rmax of 2 μm was obtained.

Example 3 A graphite plate having a diameter of 100 mm and a thickness of 1 mm was used as a substrate, heated to 500 ° C., and rotated at a rotation speed of 1
It was rotated at 0 rpm. As a raw material gas, 10 WF ₆
0cc / min, ReF ₆ gas 5cc / min, H ₂ gas 100
It was supplied at 0 cc / min for 1.2 hours to form a W-5% Re alloy foil in a thickness of 150 μm. R of the obtained W-5% Re alloy foil
max was 15. A blast treatment was performed using alumina abrasive grains to remove the graphite substrate. The Rmax of the blasted surface of the W-5% Re alloy foil was 7 μm. The obtained W-5% Re alloy foil was sandwiched between stainless plates having a thickness of 1 mm and cold rolled. By the above operation, a W-5% Re alloy foil having a thickness of 120 μm and Rmax of 3 μm was obtained.

[0036]

As described above, according to the present invention, the CV
Formation of a W or W-Re alloy layer on a substrate by the D method,
It is proposed to obtain a W or W-Re alloy foil by three steps of separating from the substrate and rolling.
By forming a thin plate having a thickness of 5 to 500 μm by the CVD method as the step of 1, the rolling step can be largely omitted as compared with the conventional powder metallurgy method. As a result, there are few surface irregularities, and W or W with a thickness of 5 to 100 μm
-Re alloy foil can be obtained with high yield and CVD
Since it is a W or W-Re alloy produced by the method, a high-purity foil can be formed.

Further, according to the present invention, since a high-purity W foil can be obtained, it is useful as a structural member in a furnace such as a reflector, a heat-resistant component such as a heat sink, or a heat-resistant material under high vacuum.

[Brief description of drawings]

FIG. 1 is a diagram showing a metallographic structure of a W layer according to a first embodiment of the present invention.

Claims (7)

[Claims] 1. A metal structure made of tungsten or a tungsten-rhenium alloy, having a thickness of 5 to 500 μm, and having a metal structure of at least one of a columnar shape and traces of fine crystals in the thickness direction. High melting point metal foil characterized by the above. 2. The high melting point metal foil according to claim 1,
A refractory metal foil having a metal structure formed by a chemical vapor deposition method, which is laminated parallel to one surface. 3. The high melting point metal foil according to claim 1, which has a thickness of 5 to 100 μm and Rmax of 8 μm or less. 4. A refractory metal layer made of tungsten or a tungsten-rhenium alloy having a thickness of 5 to 500 μm is formed on a substrate by a chemical vapor deposition method, and is rolled.
At least one surface has a surface roughness of Rmax of 8 μm or less. 5. A high melting point metal layer, which is made of tungsten or a tungsten-rhenium alloy and has a thickness of 5 to 500 μm, is formed on the substrate by a chemical vapor deposition method, and the high melting point metal layer is separated from the substrate. A method for producing a metal foil, wherein the difference in coefficient of thermal expansion between the substrate and the refractory metal layer is 6 × 10 ^-6 K ^-1 or more. 6. A refractory metal layer of tungsten having a thickness of 5 to 500 μm is formed on a metal substrate by a chemical vapor deposition method, and the substrate is exposed to an acidic solution other than a mixed solution of hydrofluoric acid and nitric acid. A method for producing a high-melting point metal foil, which comprises removing the metal foil with a high melting point. 7. A refractory metal layer made of tungsten or a tungsten-rhenium alloy having a thickness of 5 to 500 μm is formed at a temperature of 800 ° C. or lower on a graphite substrate by a chemical vapor deposition method, and the substrate is machined. A method for producing a high-melting-point metal foil, which is characterized in that it is removed selectively.