JPH059642A - Molybdenum material with good workability and its manufacturing method - Google Patents

Abstract

(57) [Abstract] [Purpose] Mo or Mo alloy material that has excellent workability such as plastic workability and weldability and does not generate impurity gas even when used under high temperature and high vacuum is used on an industrial scale. Provide stable in. [Structure] For example, in an apparatus as shown in FIG. 1, Mo or Mo alloy material is melted by an electron beam cold hearth remelt method, and at the same time, vibration is applied to a molten pool in the mold. Solidification by adding or adding molybdenum or molybdenum alloy particles to the molten pool, or by proceeding with solidification while simultaneously carrying out both of these means to refine the crystal grains and withdraw from the mold. By secondarily cooling the material and promoting cooling, the growth and coarsening of the crystal grains are prevented, thereby realizing a Mo or Mo alloy molten material having a crystal grain size of 10 mm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has excellent workability (plastic workability, weldability, etc.) and, even when used under high temperature and high vacuum, almost no generation of impurity gas is observed. The present invention relates to a molybdenum or molybdenum alloy ingot material that exhibits extremely excellent performance as a material for an aerospace equipment member, an electron tube member, an electric resistance member, a reactor member, a corrosion-resistant equipment member, and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Molybdenum is one of the refractory metals that has been industrially produced for a relatively long time and has been used as a heat-resistant material, vacuum tube material, electric resistor, etc. . In particular, the strength of molybdenum and molybdenum alloys at high temperatures is outstanding among practical metal materials, and a huge number of studies aiming at application to aerospace equipment-related members etc. as the only heat-resistant material reliable at around 1000 ° C. Is up.

However, molybdenum has a melting point of 2600 ° C.
It is difficult to produce the required parts by means that are usually applied to metals due to the physical properties that the vapor pressure of oxides is extremely low in addition to the high value exceeding the above, and metal parts made of molybdenum or molybdenum alloys. Manufacturing required a special method.

For these reasons, conventionally, the following method has been generally adopted for industrial production of metal members made of molybdenum or molybdenum alloy. (a) A molybdenum or molybdenum alloy powder is pressure-molded and then sintered to form an ingot, and the ingot is subjected to plastic working such as forging and rolling to obtain a desired shape. (b) A molybdenum or molybdenum alloy virgin material or scrap material is compression-molded, or these raw materials are packed in a box or tube made of the same material to form a melting electrode, and the electrode is an electronic beam. After melting and melting by vacuum arc melting to produce an ingot, the ingot is subjected to plastic working such as forging and rolling to finish into a desired shape.

However, in the molybdenum or molybdenum alloy member manufactured by the method described in the item (a),
Impurities (especially gas components such as O, N, C, S, H, etc.) are present in a "sintered ingot" obtained by sintering a raw material powder, so that these impurities are brought to a product member after plastic working. However, when used under high temperature and high vacuum, there is a problem that gas is released from the member during use and the performance is adversely affected. In addition, it has been pointed out that the member manufactured in this manner is vulnerable to thermal stress, and that the weldability is poor, such as the generation of gas in the melted portion.

On the other hand, in the case of the method described in the above item (b), the polycrystalline melting material (ingot etc.) of molybdenum or molybdenum alloy obtained by electron beam melting or vacuum arc melting is a grain boundary. Is fragile, and plastic working such as forging and rolling is extremely difficult, so cracks are likely to occur during processing, and impurities are reduced to the extent that gas emission under high temperature and high vacuum is sufficiently suppressed in one melting operation. However, there is a problem that it is difficult to do so, and it is not sufficiently satisfactory when a high performance member is required.

For this reason, recently, molybdenum is melted by an electron beam melting method or a vacuum arc melting method to be poured into a cooling mold, and the molybdenum melt held in the cooling mold is melted. Proposal to improve the workability of the solidified material by controlling the cooling so that the crystal growth rate becomes slow and thereby unidirectionally solidifying the molybdenum melt vertically downward to form a coarse grain structure. (JP-A-2-298227). But with this method,
In order to obtain the desired effect, it is necessary to grow the coarse crystal grains sufficiently, and therefore, the casting rate must be kept low, and the productivity is very poor.

Therefore, it is an object of the present invention to provide molybdenum or a molybdenum alloy which is excellent in workability such as plastic workability and weldability and does not generate an impurity gas even when used under high temperature and high vacuum. The aim was to establish a means by which the wood could be provided stably on an industrial scale.

[0009]

Means for Solving the Problems As a result of intensive research conducted by the present inventors while conducting many experiments from various viewpoints in order to achieve the above objects, the following findings were obtained. It was That is, recently, the "electron beam cold hearth remelt method" has been attracting attention as a means for producing a high-purity ingot of a refractory metal material. This "electronic beam cold hearth remelting method" is, as shown in FIG. 8, made of copper in front of a water-cooled copper mold 1 installed in a melt chamber of an electronic beam melting facility. Expression Coldhar
2 is installed, and the “source electrode 3 is set to the electron beam from the electron gun 4”.
The raw material melt melted in the aluminum 5 is once held in the cold heart 2 and then overflowed, which is then cooled by a water-cooled copper mold.
This is a melting and casting method in which the ingot 6 is cast from the bottom and continuously solidified while being pulled out from below. In this method, the molten metal dissolved in the electron beam is allowed to stay in the cold hearth for an appropriate time and then cast into the mold, so that the impurities that are likely to volatilize during the stay in the cold heart are sufficiently introduced into the vacuum environment. Volatilized and removed to obtain a high-purity ingot. Therefore, the inventors of the present invention focused on the excellent purification effect of the "electron beam cold hearth remelting method" were applied to the melting and casting of molybdenum or molybdenum alloys by applying the method to the production experiment of the ingot material. Repeatedly, the obtained molybdenum or molybdenum alloy melting material has sufficiently reduced impurities such as gas components even if it is melted once, "to the extent that almost no gas is generated even when used under high temperature and high vacuum". In addition, it was confirmed that it also exhibits excellent performance in terms of weldability.

However, in this case, the known "electronic beam com-
Even if the “Ludhas-remelt method” is applied as it is, a sufficient improvement effect cannot be recognized in terms of plastic workability. However, while taking measures for refining the crystal grains such as giving vibration or adding a substance that becomes a crystal nucleus when the molten metal overflowed from the cold heart solidifies in the mold, -When secondary cooling of the solidified material pulled out from the slag is carried out to suppress grain growth as much as possible, the brittleness of the ingot is remarkably improved, especially when the crystal grain size becomes a fine structure with a grain size suppressed to 10 mm or less. Have found that they will exhibit very good plastic workability.

The present invention has been completed on the basis of the above findings and the like. "Adjusting the crystal grain size of molybdenum or molybdenum alloy material produced by the electronic beam cold hearth remelt method to 10 mm or less. Has almost no gas generation under high temperature and high vacuum, and has realized good workability (plastic workability, weldability, etc.) molybdenum or molybdenum alloy ingot material. ""Molybdenum or molybdenum alloy materials are used for electronic beam cold hold.
At the same time as melting by the smelt method, vibration is applied to the molten pool in the mold, particles of molybdenum or molybdenum alloy are added to the molten pool, or both these methods are performed at the same time. While performing the solidification, the solidification progresses to reduce the size of the crystal grains, and the solidified material extracted from the mold is secondarily cooled to accelerate the cooling and thereby the growth of the crystal grains.
By preventing coarsening, there is almost no gas generation under high temperature and high vacuum, and good workability (plastic workability,
It is also possible to stably manufacture molybdenum or molybdenum alloy ingots that exhibit weldability, etc.).

[0012]

As described above, the present invention is a melting raw material (molybdenum or molybdenum alloy virgin material or scrap material).
The electron beam cold hearth remelting reduces the amount of impurities mainly composed of gas components, etc., and the obtained coagulated material (melting material) has a fine structure to impart excellent performance. However, these performances are supported by the following matters.

First, when the virgin material or scrap material of molybdenum or molybdenum alloy is melted by the electronic beam cold hearth remelt method, as described above, volatile impurities mainly composed of gas components are easily dissolved. Prompt removal is performed, and a high-purity molybdenum or molybdenum alloy ingot with less gas components is obtained. Therefore, when the obtained ingot material is exposed to a high temperature / low pressure (vacuum) environment or melted for welding, almost no gas is generated, and there is very little risk of environmental pollution or welding defects. In addition, since molybdenum or molybdenum alloy treated by the electron beam cold hearth remelt method is a molten material, it is resistant to thermal stress, and this point is also a major factor leading to good weldability.

In addition to this, in the present invention, crystal nucleation is promoted when solidifying the molybdenum or molybdenum alloy molten metal, and at the same time, cooling of the molten material solidified by the secondary cooling is promoted to grow crystal grains. Although the grain size of the ingot is made finer by suppressing the grain size, the fine grain size significantly increases the total area of grain boundaries. Therefore, in combination with the effect of reducing the amount of impurities by the electron beam cold hearth remelt method,
The amount of impurity segregation per grain boundary area at the crystal grain boundary, which reduces the segregation of gas components and the like at the crystal grain boundary, is extremely small. And this leads to remarkable improvement in plastic workability. That is, the biggest cause of deteriorating the plastic workability of molybdenum or molybdenum alloy ingot is segregation of gas components and the like in the crystal grain boundaries, which is considered to weaken the grain boundaries, but if the above measures are taken. The segregation of impurities at the grain boundaries is remarkably reduced, and good plastic workability is restored. The molybdenum or molybdenum alloy ingot produced as described above can be easily subjected to plastic working such as forging, extrusion pressing, rolling, etc., to easily form bars, plates and sheets.
Can be manufactured.

By the way, the reason for limiting the crystal grain size to 10 mm or less in the molybdenum or molybdenum alloy ingot according to the present invention is to ensure desired good plastic workability when the crystal grain size exceeds 10 mm. This is because it cannot be done.

To refine the crystal grains of molybdenum or molybdenum alloy which solidify in the mold, A) Vibrate the molten pool in the mold to promote solidification while promoting the formation of crystal nuclei. B) Addition of molybdenum or molybdenum alloy particles (Mo granules, etc.) to the molten pool in the mold at any time to form crystal nuclei and suppress the promotion of crystal growth. It is also effective to use both of these means together.

The vibration applied to the molten pool in the mold is
B) Vibration is generated by the vibration generator, b) Mode
It is preferable to transfer the vibration from the vibration generator to the solidified material (ingot) that is gradually pulled out from the container, (c) perform the above-mentioned a and b at the same time, etc. In this case, it is added to the molten pool. The frequency of vibration is preferably 1 Hz or more as the frequency of the mold in the case of (a) and 0.5 to 16 KHz as the frequency of the solidified material in the case of (2). This is because when the frequency is out of the above range, the effect of promoting the generation of crystal nuclei is rapidly reduced.

Further, it is appropriate that the grain size of molybdenum or molybdenum alloy grains, which is added to the molten pool in the mold at any time, be 5 mm or less. If the grain size exceeds 5 mm, the homogeneity of the ingot will be impaired. There is a fear.

Then, the secondary cooling of the solidified material pulled out from the mold is preferably adjusted so that the solidified molybdenum or molybdenum alloy material stays in the range of 1000 ° C. or higher for 20 minutes or less. Because the coagulant is 10
This is because if exposed to a temperature range of 00 ° C. or higher for a long time of more than 20 minutes, the crystal grains may be abnormally recrystallized and become coarse, and the plastic workability is insufficiently improved.

FIG. 1 is an explanatory view of essential parts of an example of an apparatus applied to the production of molybdenum or a molybdenum alloy ingot according to the present invention. In FIG. 1, an electron gun 4, a cold heart 2 and a water-cooled copper mold which are arranged in a melt chamber as in the known electron beam cold remelt apparatus are shown.
In addition to the water-cooled copper mold 1, a water-cooled secondary cooling device 7 is arranged below the water-cooled copper mold 1 and supports the "water-cooled copper mold 1" and the "molybdenum or molybdenum alloy ingot 8". A pillar vibrating device 11 and an ingot vibrating device are respectively provided on the columns 10 "of the starting block 9.
12 are arranged so that they can be brought into and out of contact with each other, and a molybdenum or molybdenum alloy grain hopper 13 is installed above the water-cooled copper mold 1.

When the "molybdenum or molybdenum alloy ingot according to the present invention" is manufactured by the above apparatus,
First, melt the molybdenum or molybdenum alloy raw material electrode (such as molybdenum or molybdenum alloy virgin material or scrap compression-molded, and pack the material in a cylinder or box made of the same material) 14 with an electron beam. The molten metal is once received and held in the cold heart 2 to volatilize and remove the gas component in the raw material electrode, and then is overflowed, and the ingot pool in the water-cooled copper mold 1 is formed. Pour into Le 15.

If necessary, the ingot pool 15 is mo
Vibration from either or both of the field vibrating device 11 and the ingot vibrating device 12 is added through the mold 1, the starting block support 10, the starting block 9, and the ingot 8, or as needed. The molybdenum or molybdenum alloy grain hopper 13 is added with molybdenum or molybdenum alloy grains (Mo granules or the like) to increase the number of crystal nuclei, and the grain size of the solidified material is refined.

The molybdenum or molybdenum alloy ingot 8 whose solidification has progressed in this way is continuously pulled out from below the mold 1, but at that time, the ingot in which fine crystal nuclei have been formed does not undergo abnormal recrystallization coarsening. As described above, the secondary cooling device 7 accelerates the cooling to the recrystallization coarsening temperature or lower (1000 ° C. or lower), and the crystal grain size is controlled. As described above, the molybdenum or molybdenum alloy ingot after cooling is excellent in plastic workability and weldability, and almost no gas generation is observed in a high temperature / low pressure environment.

Next, the effects of the present invention will be described more specifically by way of examples.

EXAMPLE Using the apparatus as shown in FIG. 1, 120φ molybdenum ingots were melted in accordance with the “invention method” and the “conventional electronic beam cold hearth remelt method”.

When the "conventional electronic beam cold hearth remelt method" is carried out, the apparatus shown in FIG.
It is needless to say that the magnetic field vibrating device 11 ", the" ingot vibrating device 12 "and the" molybdenum or molybdenum alloy grain hopper-13 "were not used.
It was carried out by the same method. (1) The mold vibrating device allows the ingot pool inside the mold to vibrate at a frequency of 50 Hz to allow solidification to proceed while the ingot is heated to 1000 ° C or more by the secondary cooling device. The temperature staying in the temperature range is controlled for 15 minutes for cooling. (2) The ingot vibrating device advances the solidification while applying the vibration of the frequency of 1 KHz to the ingot pool in the mold through the starting block strut, the starting block and the ingot, and the secondary cooling. The ingot is cooled by controlling the time during which the ingot stays in the temperature range of 1000 ° C. or higher for 15 minutes. (3) The ingot vibrates at frequencies of 50 Hz and 1 KHz by both the mold vibrating device and the ingot vibrating device to allow solidification to proceed, and the secondary cooling device causes the ingot to reach a temperature range of 1000 ° C or more. The cooling time is controlled to 15 minutes. (4) Time during which solidification proceeds while adding molybdenum with a particle size of 4 mm from the molybdenum or molybdenum alloy grain hopper to the ingot pool and the ingot remains in the temperature range of 1000 ° C or higher by the secondary cooling device. Control for 15 minutes to cool. (5) The vibration frequency of 50Hz and 1KHz is applied to the ingot pool by both the mode vibration device and the ingot vibration device, and the particle size from the molybdenum or molybdenum alloy grain hopper to the ingot pool is 4mm. While advancing the solidification while adding the Mo granules, the secondary cooling device controls the time during which the ingot stays in the temperature range of 1000 ° C. or higher to 15 minutes for cooling.

The macrostructures of the respective ingots thus obtained are shown in FIG. 2 [according to the conventional electron beam cold hearth remelt method] and FIG. 3 [according to the method of the present invention].
Shown in. It is to be noted that FIG. 3 is a photograph of the macro structure of the method (3) according to the present invention.
The differences due to (1), (2), (4), and (5) did not differ from Fig. 3 in particular. 2 and 3 also show that the molybdenum ingot obtained by the "conventional electron beam cold hearth remelt method" has a grain size of 10 to 50 mm and is nonuniform. Thus, it can be seen that the molybdenum ingot obtained by the "method of the present invention" has a fine crystal grain size of 10 mm or less and is uniform.

When the impurity contents of the above molybdenum ingots were compared, the results shown in Table 1 were obtained. {As for the impurity analysis value, the method (3) of the present invention and the method (1), ( 2), (4), and (5), there was no remarkable difference.

Next, when each of the above molybdenum ingots was subjected to forging (forging temperature 1300 ° C.), an ingot obtained by the “conventional electronic beam cold hearth remelt method” was forged with a reduction rate of 10%. Although cracking occurred as shown in Fig. 4, the ingot obtained by the "method of the present invention" (material of the present invention) had a rolling reduction of 60% as shown in Fig. 5.
No cracks were generated even in the forging of {it was also confirmed that all of the excellent workability obtained by the methods (1), (2), (4), and (5) of the present invention were the same. Already done}.

On the other hand, FIG. 6 and FIG. 7 respectively compare the weldability of a conventional rolled plate of molybdenum sintered material and a rolled plate of a molybdenum ingot obtained by the above-mentioned “method of the present invention”. In the electron beam welded portion of the molybdenum sintered material, a gas hole (pinhole) as shown in FIG. 6 was generated, whereas in the case of the material of the present invention as shown in FIG. It can be confirmed that an extremely sound weld can be obtained.

[0029]

[Summary of Effects] As described above, according to the present invention, it is possible to stabilize molybdenum or a molybdenum alloy material which is excellent in workability and does not generate an impurity gas even when used under high temperature and high vacuum. It becomes possible to mass-produce,
It has an extremely useful effect on the industry.

[Brief description of drawings]

FIG. 1 is a principal part explanatory view of an example of an apparatus applied to the production of molybdenum or a molybdenum alloy ingot according to the present invention.

FIG. 2 is a macrostructure photograph of a molybdenum ingot obtained by a conventional electron beam cold hearth remelt method.

FIG. 3 is a macrostructure photograph of a molybdenum ingot obtained by the method of the present invention.

FIG. 4 is a drawing showing a state after forging of a molybdenum ingot obtained by a conventional electron beam cold hearth remelt method.

FIG. 5 is a drawing showing a state after forging of a molybdenum ingot obtained by the method of the present invention.

FIG. 6 is a state diagram of an electron beam welded portion of a conventional molybdenum sintered material.

FIG. 7 is a state diagram of an electron beam welded portion of a molybdenum ingot material obtained by the method of the present invention.

FIG. 8 is a schematic explanatory diagram relating to a known electronic beam cold hearth remelt method.

[Explanation of symbols]

1 Water-cooled copper mold 2 cold hearths 3 Raw material electrode 4 electron gun 5 e-beam 6 Ingot 7 Secondary cooling device 8 Molybdenum or molybdenum alloy ingot 9 Starting block 10 Starting block support 11 Mold vibration device 12 Ingot vibrator 13 Molybdenum or molybdenum alloy grain hopper 14 Molybdenum or molybdenum alloy raw material electrode 15 Ingot pool

Claims (18)

[Claims] 1. An electronic beam cold hearth remelt material having a grain size adjusted to 10 mm or less.
Molybdenum or molybdenum alloy molten material with good workability. 2. A molybdenum or molybdenum alloy material is melted by an electron beam cold hearth remelt method, and
At that time, molybdenum or molybdenum characterized by promoting solidification while applying vibration to the molten pool in the mold and secondary cooling the solidified material withdrawn from the mold to promote cooling Manufacturing method of alloy melting material. 3. The method for producing a molybdenum or molybdenum alloy ingot according to claim 2, wherein the vibration is applied to the molten pool in the mold by vibrating the mold. 4. The method for manufacturing a molybdenum or molybdenum alloy ingot according to claim 3, wherein the frequency of vibration applied to the mold is 1 Hz or higher. 5. The production of molybdenum or molybdenum alloy ingot according to claim 2, wherein vibration is applied to the molten pool in the mold by vibrating the solidified material drawn from the mold. Method. 6. The frequency of vibration applied to the solidified material is 0.5 to 1
The method for producing a molybdenum or molybdenum alloy ingot according to claim 5, wherein the frequency is 6 KHz. 7. The molybdenum according to claim 2, wherein vibration is applied to the molten metal pool in the mold by vibrating both the mold and the solidified material drawn from the mold. Alternatively, a method for producing a molybdenum alloy ingot. 8. The method for producing molybdenum or a molybdenum alloy ingot according to claim 7, wherein the frequency of vibration applied to the mold is 1 Hz or more and the frequency of vibration applied to the solidified material is 0.5 to 16 KHz. 9. A molybdenum or molybdenum alloy material is melted by an electron beam cold hearth remelt method, and
At that time, solidification proceeds while adding molybdenum or molybdenum alloy particles to the molten pool in the mold, and
A method for producing a molybdenum or molybdenum alloy ingot, which comprises secondarily cooling a solidified material pulled out from a container to accelerate the cooling. 10. A molybdenum or molybdenum alloy material is melted by an electronic beam cold hearth remelt method, and at the same time, vibration is applied to the molten metal pool in the mold, and at the same time, the molybdenum or molybdenum alloy material is melted. A method for producing molybdenum or a molybdenum alloy ingot, which comprises advancing solidification while adding grains and secondarily cooling the solidified material drawn from the mold to accelerate cooling. 11. The method for producing a molybdenum or molybdenum alloy ingot according to claim 10, wherein vibration is applied to the molten pool in the mold by vibrating the mold. 12. The frequency of vibration applied to the mold is 1 Hz.
The method for producing a molybdenum or molybdenum alloy ingot according to claim 11, which is as described above. 13. The production of molybdenum or molybdenum alloy ingot according to claim 10, wherein vibration is applied to the molten pool in the mold by vibrating the solidified material drawn from the mold. Method. 14. The frequency of vibration applied to the solidified material is 0.5 to
The method for producing a molybdenum or molybdenum alloy ingot according to claim 13, wherein the frequency is 16 KHz. 15. The molybdenum according to claim 10, wherein vibration is applied to the molten metal pool in the mold by vibrating both the mold and the solidified material drawn from the mold. Alternatively, a method for producing a molybdenum alloy ingot. 16. The frequency of vibration applied to the mold is set to 1 Hz.
16. The method for producing a molybdenum or molybdenum alloy ingot according to claim 15, wherein the frequency of vibration applied to the solidified material is 0.5 to 16 KHz. 17. The method for producing molybdenum or a molybdenum alloy ingot according to claim 9, wherein the grain size of the added molybdenum or molybdenum alloy grains is 5 mm or less. 18. The secondary cooling of the solidified material drawn from the mold, and the cooling is promoted so that the solidified material remains in the temperature range of 1000 ° C. or higher for 20 minutes or less. A method for producing a molybdenum or molybdenum alloy ingot according to any one of claims 2 to 17.