JP5261216B2 - Method for melting long ingots - Google Patents

Description

  The present invention is a cold crucible induction melting (CCIM) method, Ti (titanium), Zr (zirconium), Hf (hafnium), V (vanadium), Nb (niobium), Ta (tantalum), Cr (chromium), Mo (Molybdenum), W (Tungsten), Mn (Manganese), Re (Rhenium), Fe (Iron), Ni (Nickel), Co (Cobalt), Y (Yttrium), and Rare earth elements, etc. are active and relatively high The present invention relates to a method for melting and producing a long ingot that produces a long ingot made of an alloy containing a metal material having a melting point.

  An alloy containing active and relatively high melting point metal materials such as Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ni, Co, Y and rare earth elements. For the production of the ingot, a vacuum arc melting method, a plasma arc melting method, an electron beam melting method and the like are currently employed industrially. These melting methods are characterized in that the entire amount of the melting raw material is not melted at once, but is supplied and dissolved in small amounts, and the molten metal bath that is formed is sequentially solidified from the lower side to produce an ingot. It is said. However, these melting methods also have the problem that the stirring power of the molten metal is small and the alloy components are likely to be uneven.

  On the other hand, the cold crucible induction melting (CCIM) method is a method for producing an ingot by solidifying all the melting raw materials at once to form an alloy and then solidifying them. Although it is considered that this melting method can produce a homogeneous ingot without generating non-uniform alloy components, the technology itself for producing an ingot by the CCIM method is still under development. At present, practical use is not progressing.

  The inventors have been continuing continuous research and development on cold-crucible induction dissolution (CCIM) technology, and have already made proposals based on the research and development results as Patent Document 1, Patent Document 2, Patent Document 3, etc. Is going.

  The feature of the CCIM method is that induction melting is performed using a water-cooled copper crucible. In a method using a refractory crucible such as a general induction melting method, the formed molten metal pool contacts the crucible refractory. Thus, there is a problem that contamination from the refractory material is generated, whereas the problem of occurrence of contamination can be avoided.

  For this reason, in ordinary refractory crucible induction melting, even alloys containing a large amount of active metal elements such as Ti and Zr, which cause contamination problems such as oxygen pick-up, are dissolved without causing contamination in the CCIM method. It becomes possible. In addition, the CCIM method can strongly stir the molten metal pool by the electromagnetic force accompanying induction heating, so that the alloy elements can be easily dissolved, and is suitable for melting and manufacturing alloys containing active and high melting point metal elements. Furthermore, in the induction melting using a normal refractory crucible, the crucible material is melted down, so the combined use of refining materials containing a large amount of fluoride and chloride, which was difficult to apply, is also possible with the CCIM method. In addition, it is possible to remove and dissolve impurities of a metal material having a relatively high melting point such as ultra-high purity Fe, Ni, and Co.

  As described above, the CCIM method is considered to be a very excellent method for producing an ingot. However, when producing an ingot by the CCIM method at present, it is refined into a molten metal pool formed in a water-cooled copper crucible. In general, a method of manufacturing an ingot by inclining a water-cooled copper crucible itself to discharge a molten metal pool, pouring the molten metal into a mold, and solidifying the molten metal is used. Moreover, the method of solidifying a molten metal pool as it is within the water-cooled copper crucible was also employ | adopted. However, with these methods, only relatively small ingots can be produced. When large ingots are melted and produced, solidification defects may occur in the ingots, resulting in large ingots. Some problems remained from the standpoint of practical application.

  In order to melt and manufacture a large ingot, it is natural that a large water-cooled copper crucible must be used. For this purpose, it is necessary to determine various conditions for forming a molten metal pool in the large water-cooled copper crucible. However, Patent Document 1 discloses melting conditions relating to the frequency of a high-frequency power source applied to the large-sized water-cooled copper crucible. Have been described.

  However, technology for melting and casting large ingots without causing solidification defects is still in the development stage. Especially for multi-component alloys and alloys containing a large amount of intermetallic compounds, it is necessary to produce an ingot with few solidification defects in the ingot, but the current technology is not sufficient. Currently.

  In order to solve these conventional problems, the inventors of the CCIM method are supplying an alloy raw material containing an active refractory metal while pulling the crucible bottom of a water-cooled copper crucible downward, thereby operating the melting casting operation conditions. A method for producing a long, large ingot of an active refractory metal-containing alloy described in Patent Document 2 or Patent Document 3 with respect to a method for producing a healthy large ingot with no melting residue such as a melting raw material As proposed.

  Certainly, the method for producing a long ingot of an active refractory metal-containing alloy described in Patent Document 2 is an excellent method capable of producing a healthy large ingot with no undissolved material such as a melting raw material. However, when a molten raw material such as a solid lump or granule is charged into the molten metal pool, some molten raw material may be trapped at the solidification interface and remain undissolved. In order to reliably produce an ingot without defects, it was also a technology that still has problems.

  On the other hand, the method for producing a long ingot of an active refractory metal-containing alloy described in Patent Document 3 is a technique obtained by improving the technique described in Patent Document 2, and while supplying molten raw material to a molten metal pool, This is an excellent technology that has greatly improved the undissolved problem at the solidification interface of the solid charge by performing lump extraction. However, this technique has also been a technique in which stable charging of the melted raw material remains as a new problem.

  That is, with the technique described in Patent Document 3, the main melting raw material charged into the water-cooled copper crucible is a rod-shaped melting raw material, and a method for stably supplying this rod-shaped melting raw material remains as a problem. It had been.

  In general, compared to the ingot melting manufacturing method in which a relatively small molten pool is formed and the molten raw material is sequentially melted in the molten pool, and the ingot is sequentially drawn, the entire amount of the molten raw material is melted at once. In order to achieve this, a large amount of electric power is required, and a large melting facility is inevitably required. In order to produce a large ingot, it is thought that it is necessary to produce a large rod-shaped melting raw material. However, in the CCIM method in which the entire amount of the melting raw material is melted together, A large scale melting facility is required, which is a major obstacle.

  In the technique described in Patent Document 3, in order to solve this problem, a relatively small long ingot is produced by solidifying in a mold by a crucible tilt casting method, and a plurality of these are combined to form a rod-shaped molten raw material. I was trying.

  However, when a rod-shaped melting raw material is produced by this method, the long ingot is often bent and deformed when solidified, and a gap may be formed in the rod-shaped melting raw material obtained by combining them. When a rod-shaped melting raw material with this gap is used, the splash that scatters from the gap toward the inner wall of the water-cooled copper crucible due to the impact of the molten metal flowing during melting on the rod-shaped melting raw material. It is conceivable that a problem of deteriorating the lump casting surface occurs.

  In addition, there is a possibility that a rod-shaped molten raw material will come into contact with the inner wall of the water-cooled copper crucible due to the bending deformation of the long ingot, and in such a situation, the contact portion is cooled first. Therefore, there is a concern that a solidified shell is formed at the contact portion, and the ingot and the rod-shaped melting raw material are welded, which may affect the drawing operation of the ingot.

Japanese Patent Laid-Open No. 11-310833 JP 2006-122920 A JP 2006-281291 A

  The present invention has been made as a solution to the above-mentioned conventional problems. An ingot of an active refractory metal-containing alloy whose length in the drawing direction is 1.5 times or more of the diameter is easily obtained. Using a granular or powdery raw material as a melting raw material, the molten raw material does not remain as an undissolved residue, and it is possible to suppress the occurrence of casting defects such as surface defects. An object of the present invention is to provide a method for melting and producing a long ingot that can stably produce a healthy long ingot by using the (CCIM) method.

  According to the first aspect of the present invention, a melting raw material charged from above into a water-cooled copper crucible having a crucible bottom movable in the vertical direction is melted by induction heating with a high-frequency coil surrounding the water-cooled copper crucible. The molten metal pool is then moved downward, and the molten metal pool on the bottom of the crucible is pulled out of the induction heating area by the high frequency coil and solidified, and an ingot of an active refractory metal-containing alloy is obtained. A method for melting and manufacturing a long ingot, in which at least one type of melting raw material blended in a predetermined alloy composition is placed in a first water-cooled copper crucible. After melting by induction heating to form a molten metal pool, the lower part of the molten metal pool is pulled out of the induction heating area by the high frequency coil and solidified, and is moved downward to the bottom of the crucible. First, the process of stopping the movement, charging the molten raw material into the first water-cooled copper crucible and dissolving it in the molten metal pool, and then solidifying the molten metal pool several times after the next drawing is repeated And in a second water-cooled copper crucible having an inner diameter larger than that of the first water-cooled copper crucible in a state where the long ingot obtained by the first melt operation is turned upside down. Then, the second melting is performed by sequentially melting from the bottom and moving the crucible bottom downward to draw the molten pool formed on the bottom of the crucible out of the induction heating area by the high frequency coil and sequentially solidify from the bottom. A method for melting and producing a long ingot, characterized by producing an ingot of an active refractory metal-containing alloy whose length in the drawing direction is 1.5 times or more of the diameter by performing the operation. .

  Does the invention according to claim 2 carry out the third melting operation similar to the second melting operation using the long ingot obtained by the second melting operation according to claim 1? Alternatively, the third melting operation is repeated as the fourth and subsequent melting operations to produce an ingot of an active refractory metal-containing alloy whose length in the drawing direction is 1.5 times or more of the diameter. It is the melt | dissolution manufacturing method of the long ingot characterized by these.

  According to the method for melting and manufacturing a long ingot according to claim 1 of the present invention, it is easy to obtain an ingot of an active refractory metal-containing alloy whose length in the drawing direction is 1.5 times or more of the diameter. A lump, granular, powdery raw material is used as a melting raw material, and the molten raw material does not remain as a final undissolved material, and also suppresses the occurrence of casting defects such as surface defects. Long ingots can be stably produced by the cold crucible induction melting (CCIM) method.

  According to the method for melting and producing a long ingot according to claim 2 of the present invention, it is possible to more reliably suppress the occurrence of casting defects and stably produce a healthy long ingot.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing a manufacturing process of a first melting operation, showing an embodiment of the present invention. FIG. 4 is a longitudinal sectional view showing a manufacturing process of a second melting operation, showing an embodiment of the present invention. It is a longitudinal cross-sectional perspective view which shows a cold crucible induction dissolution apparatus. It is a longitudinal cross-sectional view which shows the state which is manufacturing the elongate ingot by the 2nd melting operation using the cold crucible induction melting apparatus incorporated in the vacuum chamber.

  The cold crucible induction melting (CCIM) method is an effective method capable of producing a homogeneous ingot without generating non-uniformity of alloy components, and also causes Ti and Zr that cause contamination problems such as oxygen pickup. Even an alloy containing a large amount of an active metal element such as an alloy can be dissolved without causing contamination, and a metal material having a relatively high melting point such as ultra-high purity Fe, Ni, Co, etc. It has various features such as impurity removal and dissolution.

  The present inventors have developed a cold crucible induction melting (CCIM) method having these various features, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ni, Co. In order to put it into practical use in the production of an ingot made of an alloy containing a metal material having a relatively high melting point, such as Y, Y and rare earth elements, diligently experimented and researched.

  As a result, while supplying alloy raw materials containing active refractory metals, the crucible bottom of the water-cooled copper crucible is drawn downward, optimizing the operating conditions for melting and casting, so that there is no component segregation or shrinkage and homogeneous It was found that it is possible to produce a long ingot containing an active refractory metal having a simple composition, and it was filed as Patent Document 2.

  However, when a molten raw material such as a solid lump or granule is charged into the molten metal pool, if the molten raw material is too large or the melting time is too short, a part of the molten raw material may enter the solidification interface. There is a possibility that it may be trapped and remain melted, and there is a concern that the unmelted region may become a defective part of the ingot. Therefore, it was decided to further experiment and research.

  As a result, it was found that the melted raw material could be completely eliminated by supplying the melted raw material of a predetermined composition into a water-cooled copper crucible in a molten state.

  However, in this method, it is necessary to supply the molten raw material into a water-cooled copper crucible in a molten state, and it has been very troublesome to prepare the molten raw material. Specifically, a rod-shaped melting raw material is charged from above, and melted raw material is supplied by sequentially melting from the tip portion. As the melting raw material, a plurality of small long ingots are used. What was bundled was used as a rod-shaped melting raw material, and it took much time to prepare in advance.

  In addition, when a long ingot is manufactured by using a rod-shaped melting raw material having such a configuration, new problems such as casting defects occurring on the ingot surface can occur as described in the background art section. Sex was also a concern.

  Therefore, in order to invent a method for melting and producing a long ingot that can solve all the above problems, the present inventors have further advanced experiments and research. As a result, by carrying out cold crucible induction melting (CCIM) using the method of pulling out the crucible bottom of the water-cooled copper crucible downward twice or more times, the molten raw material remains as undissolved. In addition, it has been found that a sound long ingot can be stably produced by suppressing the occurrence of casting defects such as surface defects, and the present invention has been completed.

  Hereinafter, the present invention will be described in more detail based on embodiments shown in the accompanying drawings.

  First, the cold crucible induction melting (CCIM) apparatus A used in the method for melting and manufacturing a long ingot of the present invention will be described. The long ingot 4 manufactured according to the present invention includes, for example, a water-cooled copper crucible 1 in which a crucible bottom 2 is formed to be movable in the vertical direction as shown in FIGS. 3 and 4, and the water-cooled copper crucible 1. It is manufactured using a cold crucible induction melting apparatus A composed of a high frequency coil 3 arranged so as to surround the periphery. 3 shows a first water-cooled copper crucible 1a used for the first melting operation, and FIG. 4 shows a second water-cooled copper crucible 1b used for the second melting operation. The configuration is substantially the same except that the inner diameter of 1 is different.

The water-cooled copper crucible 1 constituting the cold crucible induction melting apparatus A is configured by combining a plurality of copper segments 7 in a cylindrical shape, and a circular copper crucible bottom 2 is disposed at the bottom. Between each copper segment 7, 0.05-2 mm slits are provided, and these slits are provided with yttria (Y ₂ O ₃ ) cement or alumina (Al ₂ O) for electrical insulation. ₃ ) An insulating material such as cement is embedded. The high-frequency coil 3 is provided slightly apart from the surface of the water-cooled copper crucible 1 so as to surround the water-cooled copper crucible 1 with its upper and lower ends to some extent, and is connected to a high-power high-frequency power source 8. ing. The copper segment 7, the crucible bottom 2, and the high-frequency coil 3 are hollow, and cooling water is injected into the hollow. The crucible bottom 2 is connected to an extraction mechanism 9 such as a lower cylinder and is configured to be movable in the vertical direction, and is moved so as to be extracted downward from a cylindrical main body formed of the copper segment 7 of the water-cooled copper crucible 1. be able to.

  This cold crucible induction melting apparatus A is used to manufacture the long ingots 4 and 4a. This cold crucible induction melting apparatus A is provided in a vacuum chamber B and is in a vacuum or inert gas atmosphere. As described above, the production of the long ingots 4 and 4a is performed. Further, a bottom plate 10 serving as a starting material at the start of melting is attached to the upper surface of the crucible bottom 2. The bottom plate 10 is formed of a metal material considering the material of the long ingots 4 and 4a to be manufactured. In addition, in FIG.1, FIG.2, FIG.4 and this specification, it manufactures by the 1st melting operation in distinction from the long ingot 4 of the final product manufactured by the 2nd melting operation. The long ingot of the intermediate product used as the rod-shaped melting material in the second melting operation is denoted by reference numeral 4a.

  The length of the long ingot 4 targeted by the present invention is such that the length in the drawing direction is 1.5 times or more the diameter. The reason why the ingot of which the length in the drawing direction is less than 1.5 times the diameter is not the object of the present invention is that the center of the ingot is not subjected to any special operation by cooling from the crucible bottom 2. This is because solidification defects such as shrinkage nest regions hardly occur, and a sound ingot can be produced without using the CCIM method.

  Hereinafter, the method for melting and manufacturing a long ingot according to the present invention will be described by dividing it into a first melting operation shown in FIG. 1 and a second melting operation shown in FIG.

  First, before starting the operation | work which manufactures the long ingot 4 using the cold crucible induction melting apparatus A, the melt | dissolution raw material 5 is prepared. The melting raw material 5 is a lump, granular, powdery melting raw material 5 blended in a predetermined alloy composition, and any melting raw material 5 in at least one of these forms may be used, and it is very easy to obtain. . First, as shown in FIG. 1A, the melting raw material 5 is charged into a first water-cooled copper crucible 1a. In addition, the form of the melt | dissolution raw material 5 shown here is a block shape (shaft shape) and a granular form.

  After the molten raw material 5 is inserted into the first water-cooled copper crucible 1a, a high-frequency current is passed through the high-frequency coil 3, so that the initial state in the induction heat generation region by the high-frequency coil 3 is obtained as shown in FIG. The melting raw material 5 is melted by induction heating. The melted initial melt raw material 5 forms an initial melt pool 6.

  Next, as shown in FIG. 1C, if the crucible bottom 2 is gradually lowered downward, the molten metal pool 6 on the crucible bottom 2 is gradually extracted downward from the induction heat generation region by the high-frequency coil 4. Thus, coagulation starts from below. In addition, since the solidification layer 12 is started in advance by water cooling from the outer surface of the molten metal pool 6 in contact with the inner wall surface of the water-cooled copper crucible 1, the molten metal pool 6 flows out even if it is drawn downward. There is no.

  As the molten pool 6 is gradually pulled out downward, the molten pool 6 starts to solidify from below, but, for example, in a state where more than half of the molten pool 6 has solidified, the downward movement of the crucible bottom 2 is stopped. With the movement of the crucible bottom 2 stopped, as shown in FIG. 1 (d), an additional molten raw material 5 is charged into the first water-cooled copper crucible 1a, as shown in FIG. 1 (e). Next, it is dissolved in the molten metal pool 6.

  If the crucible bottom 2 is pulled downward again after the additional melting raw material 5 is melted, the molten metal pool 6 on the crucible bottom 2 will be gradually extracted downward from the induction heat generation region by the high frequency coil 4. Start clotting from below. The long ingot 4a can be obtained by repeating the above steps several times as shown in FIGS. 1 (f) and 1 (g). The above is the first melting operation.

  Subsequently, the second melting operation shown in FIG. 2 is performed. The inner diameter of the second water-cooled copper crucible 1b used in the second melting operation is larger than the inner diameter of the first water-cooled copper crucible 1a used in the first melting operation. The reason is that in the second melting operation, the long ingot 4a manufactured by the first melting operation is used as a rod-shaped melting raw material. When the inner diameter of the first water-cooled copper crucible 1a is the same as the inner diameter of the second water-cooled copper crucible 1b, it becomes difficult to charge the rod-shaped molten raw material into the second water-cooled copper crucible 1b. The inner diameter of the second water-cooled copper crucible 1b is desirably 10 mm or more larger than the inner diameter of the first water-cooled copper crucible 1a. When the inner diameter is less than 10 mm, it is difficult to observe the molten pool 6 from above, and the rod-shaped molten raw material comes into contact with the inner wall of the water-cooled copper crucible 1a, and a solidified skull is formed in the molten pool 6 to melt the rod. This is because the situation cannot be grasped even if the raw material and the lower solidified ingot are welded. Therefore, it is necessary to be able to observe the outer peripheral part of the molten metal pool 6 by forming a gap of at least 10 mm. The inner diameter of the second water-cooled copper crucible 1b is more preferably 20 mm or more, and more preferably 30 mm or more larger than the inner diameter of the first water-cooled copper crucible 1a.

  In the second melting operation, the long ingot 4a produced by the first melting operation is turned upside down and used as a rod-shaped melting raw material. The reason for this is that concentrated segregation of the alloy element occurs in the final solidified portion of the long ingot 4a, that is, the upper end portion thereof, but the portion is first melted by turning the long ingot 4a upside down. This is because it can be the lower end portion, and an effect of alleviating dilution segregation of the alloy element normally generated at the lower end portion of the second melting operation can be expected.

  In the second melting operation, first, as shown in FIG. 2 (a), the long ingot 4a manufactured by the first melting operation is turned upside down, and suspended from the vacuum chamber B. The state is suspended from the mechanism 11. In this state, the initial molten raw material 5 obtained by cutting out a part of the long ingot 4a is charged into the second water-cooled copper crucible 1b. Next, by applying a high-frequency current to the high-frequency coil 3, as shown in FIG. 2B, the initial melting raw material 5 in the induction heating region by the high-frequency coil 3 is melted by induction heating. The melted initial melt raw material 5 forms an initial melt pool 6.

  In the state where the initial molten metal pool 6 is formed, as shown in FIG. 2 (c), charging of the rod-shaped molten raw material made of the long ingot 4a is started. Further, as shown in FIGS. 2 (d) and 2 (e), if the crucible bottom 2 is gradually lowered downward, the molten metal pool 6 on the crucible bottom 2 gradually lowers from the induction heat generation region by the high frequency coil 3. It will be extracted and coagulation will start from below. In addition, since the solidification layer 12 is started in advance by water cooling from the outer surface in contact with the inner wall surface of the second water-cooled copper crucible 1b in the molten metal pool 6, the molten metal pool 6 flows out even if it is drawn downward. There is nothing.

  As the molten pool 6 is gradually drawn downward, the amount of the molten pool 6 in the second water-cooled copper crucible 1b decreases, so that the rod-shaped molten raw material comprising the long ingot 4a corresponding to the drawn amount is drawn from above. The amount of the molten metal pool 6 can always be kept constant by gradually adding and melting. The ingot solidified by this drawing becomes the target long ingot 4.

  Even if the melted raw material 5 is not melted in the long ingot 4a by the first melting operation, the second melting operation is performed to eliminate defects in the ingot. And a healthy long ingot 4 can be obtained.

  If the defects in the ingot cannot be eliminated even after performing the first melting operation and the second melting operation described above, the long ingot 4 obtained by the second melting operation. Is turned upside down to obtain a rod-shaped melting raw material, using the third water-cooled copper crucible (not shown) having a larger inner diameter than the second water-cooled copper crucible 1b used in the second melting operation, It is possible to eliminate defects in the ingot by performing a third melting operation similar to the melting operation. If the defects in the ingot cannot be eliminated even by this third melting operation, the fourth and subsequent melting operations can be repeated.

  However, in the melting of an alloy ingot containing a large amount of active metal elements such as Ti and Zr, the pick-up of impurity elements such as oxygen is advanced each time the melting operation is performed, and the impurity concentration may increase. Considering this point, it is necessary to proceed with a plurality of melting operations.

  From a melting raw material blended in a predetermined alloy composition, using a cold crucible induction melting (CCIM) apparatus, Ti-30Al-13Cr-3V-4Mn alloy (mass%) and SUS304 (Fe-18Cr-8Ni alloy (mass%) )) Long ingot. In the following description, the Ti-30Al-13Cr-3V-4Mn alloy will be described as alloy A, and SUS304 will be described as alloy B. In addition, the melting raw material used for the production of the alloy A is scrap Ti, granular metal Al, metal Cr, massive AlV master alloy, massive AlMn mother alloy, and the melting raw material used for the production of the alloy B is electrolytic iron, Electrolytic Ni and metal Cr. In any case, a comparative example is obtained by performing only the first melting operation, and an example in which the first melting operation and the second melting operation are performed.

  In addition, the high frequency power supply of the used CCIM apparatus is a power supply of frequency: 3 kHz and output: 400 W at the maximum. The inner diameter of the first water-cooled copper crucible used for the first melting operation is φ220 mm, the inner diameter of the second water-cooled copper crucible used for the second melting operation is φ250 mm, and the ingot drawing length is The first water-cooled copper crucible is 600 to 1000 Lmm, and the second water-cooled copper crucible is 600 Lmm. The number of turns of the spirally wound high-frequency coil is 7 turns. Further, both the first water-cooled copper crucible and the second water-cooled copper crucible have a structure composed of 24 copper segments.

  Hereinafter, for each of the alloys A and B, the first melting operation and the second melting operation will be described.

  In the first melting operation of the alloy A, the melting raw material blended in a predetermined alloy composition was weighed, and the initial charging raw material was 25 kg. Next, a pure Ti stub (bottom plate) was attached to the crucible bottom of the first water-cooled copper crucible, and 25 kg of the initial dissolved raw material was charged thereon. Melting production of the long ingot was performed in an Ar gas atmosphere after evacuation and Ar gas replacement (600 Torr = 79.99 kPa). First, a molten metal pool was formed with a power of 350 kW, held for 15 minutes, and then adjusted to an output of 300 kW. Next, extraction was performed at a pulling speed of 4 mm / min for 25 minutes (extraction length: 100 mm, extraction weight: 15 kg), and then the extraction was stopped.

  After the drawing was stopped, 15 kg of molten raw material was additionally charged using a raw material supply feeder, a molten metal pool was formed with a power of 350 kW, held for 15 minutes, and adjusted to an output of 300 kW. Next, extraction was performed at a pulling speed of 4 mm / min for 25 minutes (extraction length: 100 mm, extraction weight: 15 kg), and then the extraction was stopped. This process was repeated a total of 7 times. A total of 130 kg (initial loading: 25 kg, additional loading: 15 kg × 7 = 105 kg) of molten raw material was charged, and the ingot was drawn to obtain a long ingot of φ215 × 800 Lmm.

  In the first melting operation of the alloy B, the melting raw material blended in a predetermined alloy composition was weighed, and the initial charging raw material was 40 kg. Next, a SUS304 stub (bottom plate) was attached to the crucible bottom of the first water-cooled copper crucible, and 40 kg of the above-mentioned initial dissolved raw material was charged thereon. Melting production of the long ingot was performed in an Ar gas atmosphere after evacuation and Ar gas replacement (600 Torr = 79.99 kPa). First, a molten metal pool was formed with a power of 330 kW, held for 15 minutes, and then adjusted to an output of 300 kW. Next, extraction was performed at a pulling speed of 4 mm / min for 25 minutes (extraction length: 100 mm, extraction weight: 30 kg), and then the extraction was stopped.

  After the drawing was stopped, 30 kg of molten raw material was additionally charged using a raw material supply feeder, a molten metal pool was formed with an electric power of 330 kW, held for 15 minutes, and adjusted to an output of 300 kW. Next, extraction was performed at a pulling speed of 4 mm / min for 25 minutes (extraction length: 100 mm, extraction weight: 30 kg), and then the extraction was stopped. This process was repeated a total of 6 times. A total of 220 kg (initial loading: 40 kg, additional loading: 30 kg × 6 = 180 kg) of molten raw material was charged and the ingot was drawn to obtain a long ingot of φ215 × 800 Lmm.

  In the second melting operation of Alloy A, 20 kg was cut out from another long ingot obtained by the first melting operation as an initial charging raw material. Next, a pure Ti stub (bottom plate) was attached to the crucible bottom of the second water-cooled copper crucible, and 20 kg of the above-mentioned initial dissolved raw material was charged thereon. Melting production of the long ingot was performed in an Ar gas atmosphere after evacuation and after replacement with Ar gas (200 Torr = 26.66 kPa). First, a molten metal pool was formed with a power of 260 kW, held for 5 minutes, and then adjusted to an output of 250 kW. Next, drawing was performed at a pulling speed of 2 mm / min for 20 minutes (drawing length: 40 mm, drawing weight: 4 kg), and then drawing was stopped.

  After the drawing was stopped, the long ingot obtained by the first melting operation was used as a rod-shaped melting raw material (φ215 × 800 Lmm), and was charged up to just above the molten metal pool for preheating. Thereafter, the rod-shaped melting raw material was gradually charged into the molten metal pool at a speed of 2.7 mm / min from the lower end, and the electric power was adjusted to 210 kW. Corresponding to the charging of the rod-shaped melted raw material, the ingot was drawn at a speed of 2 mm / min, and when the rod-shaped melted raw material was almost dissolved, the remaining part of the melted raw material was pulled up. After that, the ingot was continuously drawn at a drawing speed of 2 mm / min. After the molten pool surface solidified, heating and drawing of the ingot were continued for 30 minutes. The lump withdrawal was stopped. After stopping, it was placed until the next day, and then a long ingot of φ245 × 600 Lmm was taken out.

  In the second melting operation of Alloy B, 30 kg was cut out from another long ingot obtained by the first melting operation as an initial charging raw material. Next, a SUS304 stub (bottom plate) was attached to the crucible bottom of the second water-cooled copper crucible, and 30 kg of the initial dissolved raw material was charged thereon. The long ingot was melted and manufactured in an Ar gas atmosphere that was evacuated and purged with Ar gas (200 Torr 26.66 kPa). First, a molten metal pool was formed with a power of 330 kW, held for 5 minutes, and then adjusted to an output of 300 kW. Next, after drawing for 10 minutes (drawing length: 40 mm, drawing weight: 8 kg) at a pulling speed of 4 mm / min, the drawing was stopped.

  After the drawing was stopped, the long ingot obtained by the first melting operation was used as a rod-shaped melting raw material (φ215 × 800 Lmm), and was charged up to just above the molten metal pool for preheating. Then, the rod-shaped melting raw material was gradually charged into the molten metal pool at a speed of 5.4 mm / min from the lower end, and the electric power was adjusted to 250 kW. Corresponding to the charging of the rod-shaped melted raw material, the ingot was pulled out at a speed of 4 mm / min, and when the rod-shaped melted raw material was almost dissolved, the remaining part of the melted raw material was pulled up. After that, the ingot was continuously drawn at a drawing speed of 4 mm / min. After the molten pool surface solidified, heating and drawing of the ingot were continued for 30 minutes, and then the power was turned off. The lump withdrawal was stopped. After stopping, it was placed until the next day, and then a long ingot of φ245 × 600 Lmm was taken out.

  Four types of long ingots obtained by the above melting production were cut in the height direction (length direction) of the long ingots, and cross-sectional observation was performed. The results are shown in Table 1.

  According to the cross-sectional observation results, in both the alloy A and the alloy B, in the long ingot of the comparative example in which only the first melting operation was performed, the molten raw material was partially added to the solidification interface when the molten raw material was additionally charged. In the long ingot of the example of the present invention in which both the first melting operation and the second melting operation were performed, no melting residue was observed at all. That is, it was confirmed that the undissolved residue of the melting raw material generated in the first melting operation disappeared by performing the second melting operation.

DESCRIPTION OF SYMBOLS 1 ... Water-cooled copper crucible 1a ... 1st water-cooled copper crucible 1b ... 2nd water-cooled copper crucible 2 ... Crucible bottom 3 ... High frequency coil 4 ... Long ingot 4a ... Long ingot 5 ... Melting raw material 6 ... Molten metal pool 7 ... Copper segment 8 ... High frequency power supply 9 ... Pulling mechanism 10 ... Bottom base 11 ... Hanging mechanism 12 ... Solidified layer A ... Cold crucible induction melting apparatus B ... Vacuum chamber

Claims (2)

The melting raw material charged from above into a water-cooled copper crucible whose crucible bottom is movable in the vertical direction is melted by induction heating with a high-frequency coil surrounding the water-cooled copper crucible to form a molten metal pool. By moving the bottom downward, the molten metal pool on the bottom of the crucible is pulled out of the induction heating region by the high frequency coil and solidified to produce an ingot of an active refractory metal-containing alloy. A melt production method comprising:
The molten raw material of at least one of the lump, granule, and powder blended in a predetermined alloy composition is charged into the first water-cooled copper crucible and melted by induction heating to form a molten metal pool. After that, with the lower part of the molten metal pool pulled out of the induction heating area by the high frequency coil and solidified, the downward movement of the bottom of the crucible is stopped, and the molten raw material is loaded into the first water-cooled copper crucible. First melting operation of repeating the process of solidifying the molten metal pool by performing the next drawing after having been melted in the molten metal pool,
In a state where the long ingot obtained by the first melting operation is turned upside down, it is inserted into a second water-cooled copper crucible having an inner diameter larger than that of the first water-cooled copper crucible, and sequentially from the bottom. By melting and moving the bottom of the crucible downward, a second melting operation is performed in which the molten metal pool formed on the bottom of the crucible is pulled out of the induction heating area by the high frequency coil and solidified sequentially from the bottom. ,
A method for melting and producing a long ingot, comprising producing an ingot of an active refractory metal-containing alloy having a length in a drawing direction of 1.5 times or more of a diameter.   Using the long ingot obtained by the second melting operation according to claim 1, the third melting operation similar to the second melting operation is performed, or the third melting operation is performed. A long ingot characterized by producing an ingot of an active refractory metal-containing alloy whose length in the drawing direction is 1.5 times or more of the diameter by repeatedly performing as the fourth and subsequent melting operations The manufacturing method of melt | dissolution.

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