JPS62156233A - Electron beam melting method - Google Patents

Abstract

PURPOSE:To prevent the decrease of a yield by splashing in a melting stage by erecting a wall material made of a spongy active metal to enclose the electron beam irradiation area of a melting vessel for the spongy active metal. CONSTITUTION:The spongy active metal G is continuously supplied from a hopper 3 into a water-cooled vessel 4 in a shielding case 1 and the inside of the case 1 is evacuated by a vacuum evacuation system 5. The active metal G is melted by electron beam irradiating devices 2a, b and a molten metal M is fed from one end of the vessel 4 to a water-cooled casting mold 8 by which the molten metal is successively cooled and solidified. The solidified metal is continuously drawn by an ingot drawing device 9. The wall material 7 made of the spongy active metal is erected in the upper part of the vessel 4 so as to enclose the region to be irradiated by the electron beam from the device 2a. The small drops of the molten metal splashed during melting are captured by the material 7.

Description

[Detailed Description of the Invention] [Industrial Applicability] The present invention is applicable to manufacturing an ingot of active metal such as Ti by irradiating and melting a raw material containing a sponge-like active metal such as Ti sponge with an electron beam. , product yield due to droplet scattering phenomenon called splash.

The present invention relates to an electron beam melting method that can effectively prevent various problems such as a decrease in heat retention.

[Prior Art] The VAR' (vacuum arc remelting) method has been widely used for melting active metals such as Ti. In other words, the VAR method is
The active metal is formed into an electrode shape and heated under high vacuum (10-” to 10-
In this method, an arc is generated between the electrode and the water-cooled crucible at a pressure of about 3 torr), thereby melting the electrode. However, in this method, it is necessary to manufacture an electrode made of an active metal such as Ti prior to arc melting, and the process is complicated, resulting in low productivity and low economic efficiency.

On the other hand, as vacuum technology advances and electron beam irradiation equipment becomes larger, an ingot manufacturing method using electron beam melting has been proposed and is attracting attention. In other words, the electron beam melting and casting method is
This is a method in which molten raw materials are irradiated with an electron beam under high vacuum (approximately 10-2 to 10-6 torr), melted, and sequentially supplied to a water-cooled mold. With this method, granular raw materials and scraps are left as they are. Can be dissolved in form, var
There is no need for any electrode manufacturing process required by the law. Moreover, since the electron beam can be scanned in any direction by electromagnetic field control, even irregularly shaped ingots can be easily melted.

As described above, the electron beam melting and casting method has various advantages, but on the other hand, it has the disadvantage that the raw materials for melting are limited.
In particular, when a sponge-like active metal such as sponge Tt is used as a melting raw material, an extremely undesirable phenomenon (splash phenomenon) in which the molten metal becomes foamy and scatters during the melting process occurs, leading to a decrease in the yield of the molten metal. In addition, the scattered droplets adhere to the inner wall of the melting furnace, the electron beam irradiation device, etc., causing operational troubles and making maintenance work complicated and difficult.

That is, the most common method for producing sponge-like active metals such as sponge Ti and sponge Zr is, for example, sponge T.
In the case of i, TiO2 is chlorinated to form T i C14 and then reduced with Mg, Na or the like. Of these, Mg
When the reduction method is adopted, the chlorine content in TiC14 is separated as MgCl2, etc., but the resulting sponge Ti crude product contains a large amount of MgCl2, etc. and unreacted Mg as impurities. Therefore, purification (vacuum distillation, etc.) is performed to remove these impurities.

However, even when such purification treatment is performed, spon9
There is still about 11,000 pp of M in T1M products.
gC1, etc. remain without being completely removed. On the other hand, T i C
If the method of reducing 14 with metallic Na is adopted, a large amount of NaCl will be mixed into the sponge Ti crude product, so
This is immersed in pure water for a long time to remove NaCl. However, in the sponge Ti purified product obtained in this way,
As in the case of the Mg reduction method, about 2000 pI)m of N
aC1 (chloride) remains without being completely removed.

In this way, no matter which method is used, Mg reduction method or Na reduction method, about 1000 to 200
Chloride (M g C12 and NaC1) around 0 ppm
It is included. Further, the contamination of impurity chlorides is not limited to sponge Ti, but also applies to other sponge-like active metals such as sponge Zr.

When such a sponge-like active metal containing chloride is used as a raw material for electron beam melting and casting, the chloride evaporates and foams due to the heat during melting, but in the electron beam melting and casting method, an electron beam is generated. Because the melting atmosphere must be in a higher vacuum state than in the VAR method, the evaporation and foaming phenomenon (splash phenomenon) of chloride becomes very noticeable, resulting in a decrease in the yield of molten metal and furthermore, the formation of scattered droplets. can adhere to the inner walls of the melting furnace, electron beam irradiation equipment, etc., causing operational troubles.

Therefore, when using raw materials containing sponge-like active metals,
It is considered that it is substantially difficult to apply the electron beam melting/casting method.

[Problems to be Solved by the Invention] The present invention has been made in view of these circumstances, and its purpose is to solve the problem without causing a drop in yield due to the splash phenomenon even when a sponge-like active metal is used as a raw material. The purpose of the present invention is to provide an electron beam melting method that can ensure stable operability, etc.

[Means for Solving the Problems] The electron beam melting method that achieves the above purpose is that when melting a sponge-like active metal with an electron beam, the electron beam irradiation area in a container for melting the sponge-like active metal is surrounded. The gist of this method is that the wall material made of the active metal is erected and the small droplets of molten metal scattered during melting are collected by the wall material. Furthermore, a method in which a heat-resistant wall material is erected around the active metal wall material and small droplets of the molten metal are collected by the active metal wall material can also achieve the same purpose as the electron beam melting method. be able to.

[Function] As explained above, the splash phenomenon that occurs when dissolving a sponge-like active metal is caused by the chloride contained in the metal. The following experiments were conducted to quantitatively understand the molten metal scattering situation and yield decline associated with this process.

First, Fig. 7 (schematic cross-sectional explanatory diagram, in which 1 is a shield case, 2 is an electron beam irradiation device, 3 is a raw material supply hopper, 4 is a
5 is a container for dissolving raw materials, 5 is a vacuum exhaust system, B is an electron beam, G is a sponge-like active metal, and M is a molten metal.)
Using the equipment shown in Figure 1, the yield of molten metal was investigated when several types of Ti sponges with different amounts of residual chloride were used. The results are shown in Figure 8, and the sponge T
There is clearly an inverse relationship between the amount of residual chloride (ppm) in i and the yield (%), and as the amount of residual chloride increases, the yield rapidly decreases. Therefore, in order to increase the yield, it is sufficient to reduce the amount of residual chloride in the active metal sponge.
Since it is very difficult to reduce the amount of chloride to below m, it is necessary to develop a technique that can ensure a high yield even when using a sponge-like active metal containing a considerable amount of chloride.

Next, in order to clarify the scattering situation of molten metal caused by the splash phenomenon, Figure 9 (schematic explanatory diagram, 1 to 5.B in the figure,
G and M have the same meanings as above, and 6 indicates a cylindrical wire mesh).) Sponge Ti was melted with an electron beam using an apparatus as shown in Fig. 6, and the distribution of the amount of metal scattering in the height direction due to the splash phenomenon was investigated. As a result, the results shown in FIG. 10 were obtained. As is clear from this figure, the amount of molten metal scattered and deposited is greatest at the upper surface of the raw material melting container 4, and decreases as it goes upward. Also, according to this figure, at a position exceeding the height corresponding to the inner diameter of the water-cooled container 4,
Almost no adhesion of scattered metal can be seen.

As is clear from these results, scattering of molten metal due to the splash phenomenon can be prevented by providing a scattering prevention wall surrounding the electron beam irradiation area in the upper part of the metal melting container 4 where the electron beam is irradiated. It is possible to prevent this by As suggested by the results shown in FIG. 10 above, it is sufficient that the scattering prevention wall has a height corresponding to at least the inner diameter of the water-cooled container 4. However, this only prevents the molten metal from scattering inside the shield case, and does not directly lead to an improvement in yield. Therefore, in the present invention, the above-mentioned scattering prevention wall is constituted by the above-mentioned active metal wall material, and the small droplets of molten metal that are scattered during melting are collected by the wall material. I decided to add a process.

(8) After the dissolution is completed, the wall material to which the droplets have adhered is collected and redissolved. Specifically, after dissolving, titanium (sponge Ti
The titanium wall material to which the small droplets of (using the above) were attached was folded into a compact size and placed in the melting container 4, and then subjected to electron beam melting again.

By employing such a configuration, the yield of sponge-like active metal can be increased by about 5%. That is, the first
As shown in Figure 1, a titanium wall material 7 is erected above the opening of the raw material dissolving container 4 having a water-cooled structure.
Same as the figure) Sponge Ti (chloride amount: approx. 101000p
Then, the titanium wall material 7 was remelted as described above. The dissolution yield of Ti at this time was 9
It showed a very high value of 8.8%, and it was confirmed that the dissolution yield was improved by 4.7 points compared to the melting yield obtained in the experiment without titanium wall material 7 (94.1%). In particular, active metals such as Ti and Zr are very expensive, and even if the melting yield is improved by only a few percent, the economic benefit is extremely large. For g, we chose the period after melting from the viewpoint of operability in the melting furnace, and the specific work involved collecting the active metal wall and charging it into a melting container during another melting process. do. .

CB) providing a heat-resistant wall material on the outside of the active metal wall material,
After melting the sponge-like active metal, the active metal wall material to which small droplets of molten metal have adhered is directly irradiated with an electron beam to melt it and drop it into the molten metal boule. In this case, the heat-resistant wall material is installed outside the active metal wall material in consideration of the case where the electron beam is irradiated outside the active metal wall material when melting the active metal wall material with the electron beam. . In this method, although it is necessary to install the above-mentioned heat-resistant wall material, it eliminates the trouble of collecting the active metal wall material with molten metal droplets attached or charging it into the melting container. .

The present invention is characterized in that the above active metal wall material is erected to prevent the molten metal from scattering due to the splash phenomenon that cannot be avoided when using a sponge-like active metal. A trap for collecting chloride is installed in the upper part of the surrounding area to collect MgC1 generated during dissolution.
, and NaCl are collected and removed, or the irradiation area of the raw material melting electron beam surrounded by the wall material is connected to a separate vacuum exhaust system and suctioned to suck and exhaust MgCl2 and NaCl out of the system. By doing so, other problems caused by these chlorides can be prevented as much as possible.

[Example] The present invention achieves the yield improvement effect during melting and casting by using the same metal wall material as the melting material. This is shown using Figure 1. That is, in FIG. 1, 1 is a shield case, 2a and 2b are electron beam irradiation devices, 3 is a raw material supply hopper, 4 is a water cooling container, 5 is a vacuum exhaust system, 7 is a metal wall having the same composition as the melting material, and 8 is a Water-cooled mold, 9 is slab drawing device, B is electron beam, G is sponge-like active metal, M
denotes a molten metal, and l denotes a slab. Sponge-like active metal G is continuously supplied into the water-cooled container 4 and irradiated with an electron beam B to melt it, and the molten metal M is supplied from the other end of the water-cooled container 4. The slab is sent to a water-cooled mold 8 to be sequentially cooled and solidified, and then continuously pulled out by a slab drawing device 9. At this time, as shown in the figure, the metal wall 7 is erected on the upper part of the water-cooled container 4 so as to surround the electron beam irradiation area from the electron beam irradiation device 2a for dissolving the sponge-like active metal, and the splash when melting the sponge-like active metal is erected. If the molten metal scattered due to the phenomenon is collected by the metal wall 7, the packed metal wall is collected after melting, and is melted together with the sponge-like active metal G during another melting, the yield can be improved as described above. Improvement is possible. Note that the electron beam irradiated from the electron beam irradiation device 2a serves to retain heat of the active metal M in the water-cooled container 4 and the surface layer of the water-cooled mold 8, and to ensure smooth flow of the activated gold RM. Since the splash phenomenon no longer occurs, there is no need to install a water-cooled metal wall or the like.

Reference numeral 11 shown in FIG. 1 indicates a chloride trap provided at the upper opening of the metal wall 7, if necessary. That is, as mentioned above, the splash phenomenon is caused by the chlorides (MgC1□ and NaC1) (7)i remaining in the sponge-like active metal, but these chlorides are It causes many problems such as adhering to the inner wall and obstructing high vacuum drawing, or contaminating the oil in the oil diffusion pump, rotary pump, etc. of the vacuum exhaust system. In particular, MgCL has a high hygroscopicity, so if the inside of the casing is exposed to the atmosphere during a suspension of operation, it will rapidly absorb moisture, which will significantly inhibit evacuation when restarting operation. In order to avoid such problems caused by chloride adhesion, in this example, a chloride trap 11 is disposed in an upper opening surrounded by a metal wall 7 as shown in the figure, so that chloride can be adsorbed and removed. are doing.

FIG. 2 is a schematic sectional view showing another example of an apparatus in which the present invention is used, and the essential configuration is the same as the example of FIG. 1. However, in this example, a molten metal storage container 1o is provided between the water-cooled container 4 and the mold 8, and the active metal molten metal melted in the water-cooled container 4 is once received in the storage container 1o and then poured into the mold 8 from the injection port 10a. ing. Are the electron beam irradiation devices 2b and 2c melted? Used for WM heat retention. Although Fig. 1.2 shows an example in which one water-cooled mold 8 is disposed for the molten metal injection port 4a (or 10a) to produce one slab l, if necessary, the molten metal injection port 4a (or It is also possible to provide 10a) at a plurality of locations so that the casting can be poured into a plurality of water-cooled molds, so that a plurality of slabs can be manufactured in parallel. Even in such an apparatus, if the metal wall 7 is provided, the above-mentioned yield improvement effect can be enjoyed.

3 and 4 are schematic cross-sectional explanatory views to show an embodiment corresponding to (B) above, in which a water-cooled metal wall 15 is erected on the melting container 4, and an active metal wall 7 is further installed inside the water-cooled metal wall 15. After melting the active metal in the form of a sponge, an electron beam is irradiated onto the active metal wall 7 to which the molten metal has adhered, melting the active metal, and dropping the activated metal into the molten metal boule.

5 and 6 are schematic cross-sectional explanatory diagrams showing still another embodiment corresponding to (B) above, in which a change has been made to the method for removing chloride generated in the electron beam melting process of the sponge-like active metal. The other details are substantially the same as those in FIG. 3.4.

That is, in these examples, the electron beam heating and melting region is sealed off by a water-cooled metal wall 15 erected on the water-cooled container 4, and an exhaust line 12 is connected to a suitable position above to connect to a vacuum exhaust system 13 dedicated to dechlorination. The structure is such that the chlorides generated in the process of melting the sponge-like active metal can be sequentially discharged from the system. In the figure, 14 indicates a trap for removing chlorides, and the vacuum exhaust system 13 removes chlorides. In this case, if the trap 14 is a removable cassette type, it can be easily replaced when the amount of chloride adsorbed is saturated. This is preferable.As already mentioned, in order to recover the debris adhering to the active metal wall 7, the active metal wall 7 is directly irradiated with an electron beam to melt the active metal wall 7.

It goes without saying that the apparatus shown in FIGS. 1 to 6 used in explaining the present invention is also included within the scope of the present invention as an electron beam melting/casting apparatus.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to effectively prevent yield reduction and other problems caused by the splash phenomenon that occurs in the raw material melting process in continuous casting using raw materials containing sponge-like active metals. A series of processes from melting raw materials to casting can be carried out smoothly with high productivity, and the maintainability of the melting/casting equipment can also be improved.

[Brief explanation of drawings]

Figures 1 to 6 are schematic cross-sectional explanatory diagrams of the apparatus in which the method of the present invention is used, Figures 7, 9, and 11 are explanatory diagrams showing the preliminary experimental method, and Figure 8 is the amount of residual chloride in sponge Ti and the time of dissolution. FIG. 10 is a graph showing the relationship between the height direction position of the wire mesh placed upright on the metal melting container and the amount of metal deposited. 1... Shield case 2... Electron beam irradiation device 3... Raw material supply hopper 4... Container for dissolving raw material (water-cooled container) 5... Vacuum exhaust system 6... Wire mesh 7... Melting Wall material made of the same metal as the material 8...Water-cooled mold 9...Slab drawing device representative Patent attorney Hisashi Ueki -::,,3. ,,,: 几'r' Fig. 1 Fig. 3 Gold, @ adhesion amount (q/ex')

Claims (2)

[Claims] (1) When melting a sponge-like active metal with an electron beam, a wall material made of the above-mentioned active metal is erected to surround the electron beam irradiation area in the container for melting the sponge-like active metal, and small pieces of molten metal are scattered during melting. An electron beam melting method characterized in that the droplets are collected by the above-mentioned wall material. (2) When melting a sponge-like active metal with an electron beam, a heat-resistant wall material is erected to surround the electron beam irradiation area in the container for melting the sponge-like active metal, and a wall made of the active metal is further placed inside the heat-resistant wall material. An electron beam melting method characterized in that small droplets of molten metal scattered during melting are collected by the active metal wall material.