JPS6277429A - Electron beam melting method - Google Patents

Abstract

PURPOSE:To prevent lowering of yield due to splash phenomenon, by surrounding electron beam irradiated domain for melting a material contg. spongy active metal with a heat resisting wall material to collect and recover molten globules scattering at melting time. CONSTITUTION:In a shielded case 1 connected to an evacuating device 5 and made to a prescribed vacuum degree, the material G contg. spongy active metal such as spongy Ti is supplied from a material supplying hopper 3 into a water cooled vessel 4 for melting the material. Thereat, the material G is melted by irradiating an electron beam B from an electron beam irradiating device 2 to obtain a molten metal M. In method for melting the material G, the heat resisting wall material 7 surrounding electron beam irradiated domain of the vessel 4 is provided to collect molten globules scattered at material melting time with the material 7. Further, metal adhered and solidified at the material 7 is melted and allowed to flow down by irradiating the beam B to recover it in the vessel 4. In this way, yield lowering is prevented and melting operability is stabilized.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention effectively prevents a drop in melting yield due to a droplet scattering phenomenon called nuplash when melting a raw material containing a sponge-like active metal such as sponge Ti. It is related to technology that can prevent this.

[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 involves forming an active metal into an electrode shape and applying it under high vacuum (lθ-2 to l0-
In this method, an arc is generated between the electrode and the molten metal in 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 active gold 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, melting methods using electron beams have been proposed and are attracting attention. In other words, the electron beam melting method is performed under high vacuum (10
This is a method of melting raw materials by irradiating them with an electron beam at a pressure of about 4-10-6 torr).With this method, granular raw materials and scraps can be melted in their original form, which is essential for the vAR method. There is no need for any electrode manufacturing process. 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 method has various characteristics, but on the other hand, it has the disadvantage that the raw material to be melted is limited.Especially when a sponge-like active metal such as sponge Ti is used as the raw material for melting, it is difficult to melt. During the process, an extremely undesirable phenomenon (splash phenomenon) occurs in which the molten metal becomes foamy and scatters, which not only causes a decrease in the yield of the molten metal, but also causes the scattered droplets to adhere to the inner walls of the melting furnace, electron beam irradiation equipment, etc. This causes operational troubles and makes 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 1, for example, sponge T.
In the case of i, the method involves chlorinating T i 02 to form TiCl4 and then reducing it with Mg, Na, or the like. Of these, Mg
When the reduction method is adopted, the non-chlorine in TiCl4 is separated as MgCl2, etc., but the resulting sponge Ti crude product contains MgCl2, etc. and unreacted Mg.
Since a large amount of impurities are mixed in, purification (vacuum distillation, etc.) is performed to remove these impurities.

However, even when such purification treatment is performed, sponge T
i The purified product still contains about 11,000 pp of Mg.
Cl2 etc. cannot be completely removed and remains.

On the other hand, if a method of reducing TiC1a with metallic Na is adopted, a large amount of NaC1 will be mixed into the crude Ti sponge, so NaC1 is removed by immersing it in pure water for a long time. However, the sponge T obtained in this way
i The purified product contains the same 2000 as in the case of the Mg reduction method.
About pp+n of NaCl (chloride) remains without being completely removed.

In this way, even if the Mg reduction method and the Na reduction method are adopted, the sponge Ti purified product contains about 1000 to 200
Contains about 0 ppm of chlorides (MgC12 and NaC1). 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, the chloride evaporates due to the heat during melting and foams. Since the vacuum state must be higher than that in the VAR method, the evaporation and foaming phenomenon (splash phenomenon) of chlorides becomes very noticeable, resulting in a decrease in the yield of molten metal and furthermore, the scattered droplets can damage the inner walls of the melting furnace and the like. It adheres to electron beam irradiation equipment, etc., causing operational troubles.

Therefore, when using raw materials containing sponge-like active metals,
Applying electron beam melting is considered to be substantially difficult.

[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 configuration of the present invention that achieves the above object is that when melting a raw material containing a sponge-like active metal, a heat-resistant wall material is used to surround the electron beam irradiation area of the raw material melting container. erected,
The gist is that the droplets scattered during the melting of the raw materials are collected by the wall material, and the solidified metal adhering to the wall material is irradiated with an electron beam, allowed to flow down, and collected into the container. In the present invention, by installing the heat-resistant wall material mentioned above, it is possible to prevent the molten metal from scattering due to the splash phenomenon that cannot be avoided when raw materials containing sponge-like active metals are used, and to prevent the solidified metal from adhering to the wall surface. The main feature is that the electron beam is used to melt the material at a certain time, and the material is collected in the melting container at the bottom.
On the other hand, a chloride trap may be installed at a suitable location to collect and remove MgC+2 and NaC1 generated during melting, or an electron beam irradiation area for dissolving raw materials surrounded by the wall material may be used. If it is connected to a separate vacuum exhaust system and sucked in, and MgCl2 and NaCl are sucked out of the system, other 1! '! Problem I can also be prevented as much as possible.

[Function] It was previously explained that the splash phenomenon that occurs when a sponge-like active metal is dissolved is caused by the chloride contained in the metal. The following experiments were conducted to quantitatively understand the molten metal scattering situation and yield reduction caused by the phenomenon.

First, Figure 6 (schematic explanatory diagram, 1 is the shield case, 2
3 is an electron beam irradiation device, 3 is a raw material supply hopper, 4 is a container for dissolving raw materials, 5 is a vacuum pumping system, B is an electron beam, G is
The yield of molten metal was investigated when several types of Ti sponges with different amounts of residual chloride were used using the equipment shown in (1) and (M), respectively, a sponge-like active metal and a molten metal. The results are shown in Figure 7, and there is clearly an inverse relationship between the residual chloride itr (ppm) in the Ti sponge and the yield (%), and as the amount of residual chloride increases, the yield rapidly increases. decreases to . Therefore, in order to increase the yield, it is sufficient to reduce the amount of residual chloride in the sponge-like active metal, but as mentioned above, the residual chloride in the sponge-like active metal can be
It is very difficult to reduce it to below pm, so
It is necessary to develop a technology that can ensure a high yield even when a sponge-like active metal containing a considerable amount of chloride is used. Figure 8 (schematic explanatory diagram,
1 to 5 in the figure. B, G, and M have the same meanings as above, and 6 indicates a cylindrical wire mesh). Electron beam melting of Ti sponge was carried out, and the distribution of the amount of metal scattering in the height direction due to the splash phenomenon was performed. When investigated, the results shown in Figure 9 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. Further, according to this figure, at a position exceeding the height corresponding to the inner diameter of the water-cooled container 4, hardly any scattered metal is observed.

As is clear from these results, splatter.

The scattering of the molten metal due to the flash phenomenon can be prevented by providing a scattering prevention wall above the metal melting container 4, which is irradiated with the electron beam, so as to surround the electron beam irradiation area. However, this alone only prevents the molten metal from scattering inside the shield case, but does not directly lead to an improvement in yield. Therefore, in the present invention, the above-mentioned scattering prevention wall is constituted by a heat-resistant wall material, and the molten metal that adheres to the wall material is The purpose is to improve the metal yield by irradiating metal with an electron beam periodically or irregularly, allowing the metal to flow down into the water-cooled container 4 at the bottom and collecting it, and this configuration is currently being adopted. By doing so, the yield of sponge-like active metal melting can be increased by about 5%. That is, the first
As shown in the figure, a water-cooled copper plate 7 constituting a heat-resistant wall material was erected above the opening of the raw material dissolving container 4 having a water-cooled structure (other symbols are the same as in Figures 6 and 8). :
When approximately 101,000 pp of electron beam melting was performed and the Ti adhering to the water-cooled copper plate 7 was periodically melted and recovered using the electron beam, a very high TI melting yield of 88.5% was obtained, indicating that no water-cooled copper plate 7 was used. The dissolution yield obtained in the experiment (
94.1%) was confirmed to be improved by 4.4%. In particular, active metals such as Ti and Zr are very expensive, and even if the melting yield is only a few percent, the economic benefit is extremely large. As shown in the examples below, if the slab is sequentially introduced into a water-cooled mold and continuously pulled out using a slab drawing device, a series of steps from melting to casting can be carried out smoothly. In the above, a water-cooled container was used as the container for dissolving the active metal, but it is of course possible to use a ceramic container other than the water-cooled container as long as it has heat resistance that can withstand the heat of the molten metal and electron beam irradiation. . In addition, the active metal adhering to the heat-resistant wall material is remelted by electron beam irradiation and returned to the container as described above, but the heat source at this time is the same as the electron beam irradiation equipment used for metal melting. What is necessary is to change the irradiation direction of the beam and scan it along the surface of the heat-resistant wall material.

[Example] Figure 2 shows how the yield improvement effect of installing heat-resistant wall materials as described above can be specifically utilized by electron beam melting and PL construction. 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 heat-resistant metal wall with a water-cooled structure, 8 is a water-cooled mold, 9 is a slab drawing device, B is an electron beam, G is a sponge-like active metal, M
indicates molten metal and ■ indicates slab, respectively. Sponge-like active metal G is continuously supplied into water-cooled container 4 and irradiated with electron beam B to melt the molten metal &! M is sent from the other end of the water-cooled container 4 to the water-cooled mold 8, where it is sequentially cooled and solidified.
119, and at this time, as shown in the figure, the electron beam irradiation device 2 for melting the sponge-like active metal
A water-cooled container 4 surrounds the electron beam irradiation area from a.
A water-cooled metal wall 7 is erected in the upper part of the V, and the molten metal scattered by the splash phenomenon when the sponge-like active metal is melted is collected by the water-cooled metal wall 7, and the collected metal is periodically exposed to an electron beam. The active metal is irradiated to melt it and flow down into the water-cooled container 4 at the bottom, thereby preventing loss of active metal due to scattering.

The molten active metal M flows through an overflow port 4 provided at the other end of the container 4.
The slab I is poured into a water-cooled mold 8 from a to the water-cooled mold 8 and solidified in the water-cooled mold 8 in sequence.The slab I is continuously or intermittently pulled out by a slab drawing device 9 provided at the bottom of the slab I, and is irradiated by an electron beam irradiation device 2b. The electron beam generated plays the role of retaining heat of the active metal M in the water-cooled container 4 and the surface layer of the water-cooled pI type 8, and ensures a smooth flow of the active metal M, but at this point it no longer causes a splash phenomenon. There is no need to install water-cooled metal walls, etc.

Reference numeral 11 shown in FIG. 2 indicates a trap for removing chloride, which is provided as necessary in the upper opening of the water-cooled metal wall 7. In other words, the splash phenomenon causes the chloride (MgC1? As mentioned above, these chlorides are generated by the evaporation of chlorides and NaCl1), but these chlorides can adhere to the inner wall of the shield case l and obstruct high vacuuming, or cause damage to the oil diffusion pump in the vacuum exhaust system. In particular, MgCl2 is highly hygroscopic, so if the inside of the casing is exposed to the atmosphere during interruptions in operation, it will rapidly absorb moisture.
This will significantly impede vacuuming when restarting operations. In order to avoid such problems caused by chloride adhesion, in this example, as shown in Figure 1, a chloride trap 11 is disposed in the upper opening surrounded by the water-cooled gold & I wall 7, and the chloride can be adsorbed and removed. It is configured as follows.

FIG. 3 is a schematic sectional view showing another embodiment of the present invention,
The essential configuration is the same as the example '' in FIG. However, in this example, the molten metal 1 holding container 10 is placed between the water-cooled container 4 and the pI type 8.
is provided so that the activated fully molten metal melted in the water-cooled container 4 is once received in the storage container 10 and then poured into the mold 8 through the injection port 10a.

Electron beam irradiation! :The devices 2b and 2c are used for heat retention of the molten metal M, respectively. In Fig. 2.3, the molten metal inlet 4a (
10a), an example is shown in which one water-cooled mold 8 is provided to produce one slab I, but if necessary, molten metal injection ports 4a (or 10a) may be provided at multiple locations to produce multiple water-cooled molds. It is also possible to manufacture a plurality of slabs in parallel.

4 and 5 are schematic cross-sectional explanatory views showing still other embodiments of the present invention, except that the method for removing chlorides generated in the electron beam melting process of sponge-like active metals has been changed. This is substantially the same as the example in Figure 2.3. That is, in these examples, the Rishiko beam heating and melting region is side-chained by the water-cooled metal wall 7 installed on the water-cooled container 4, and an exhaust line 12 is connected to an appropriate position above to provide a vacuum exclusively for dechlorination. It is connected to system 13 and has a gJ system so that the chlorides generated in the process of melting the active metal in the form of a sponge can be sequentially discharged from the system.
In the figure, reference numeral 14 indicates a trap for removing chlorides, which is provided to prevent the vacuum exhaust system 13 from being contaminated with chlorides. In this case, it is preferable to make the trap 14 a removable cassette type trap because it can be replaced easily when the amount of chloride adsorbed is saturated. Although we showed an example of using it as a melting/casting method using metal,
Kizawa J is characterized by its ability to prevent a drop in yield due to the splash phenomenon that occurs when a raw material containing a sponge-like active metal is melted. Alternatively, it is of course possible to put it into practical use in combination with a batch casting method or other molten metal processing methods, and all of these are included within the scope of the present invention.

[Effects of the Invention] Since the present invention is configured as described above, various problems such as a decrease in yield due to the splash phenomenon that occurs during the melting process of raw materials containing sponge-like active metals can be solved at once. became.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional explanatory diagram showing a basic embodiment of the present invention, and FIGS. Figure 6.8 is an explanatory diagram showing the preliminary experimental method, Figure 7 is a graph showing the relationship between residual chloride r@hair in sponge Ti and the yield during dissolution, and Figure 9 is a graph showing the relationship between the residual chloride r@hair in sponge Ti and the yield during dissolution. It is a graph showing the relationship between the height direction of the wire mesh and metal adhesion; Ij. 1: Shield case 2: Electron beam irradiation device 3: Raw material supply hopper

Claims (1)

[Claims] When melting a raw material containing a sponge-like active metal, a heat-resistant wall material is erected to surround the electron beam irradiation area of the raw material melting container, and droplets scattered during the raw material melting are collected by the wall material, A method for electron beam melting of raw material containing a sponge-like active metal, characterized in that the metal solidified adhering to the wall material is irradiated with an electron beam, allowed to flow down, and collected into the container.