JP2006281291A - Method for producing long cast block of active high melting point metal alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a long cast block containing active high melting point metal elements such as Y, REM, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn and Re, as alloy components with a CCIM (Cold Crucible Induction Melting) method without developing component segregation. <P>SOLUTION: In a method for producing a long cast block of the active high melting point metal containing alloy, having the length of ≥1.5 times to the diameter or short side length of a copper crucible under vacuum or inert gas atmosphere with the CCIM method by using the water-cooling type copper crucible 2 whose bottom can be moved in the vertical direction and a high frequency induction heating coil 1 surrounding the outer periphery of the crucible 2; the production method is characterized in that a molten raw material is supplied into the copper crucible 2 under melting state and also, the crucible bottom is pulled down together with the molten metal pool while holding the shape of the molten metal pool 6 in the region of the heating coil 1 positioned at the upper side of the bottom part of the copper crucible and the molten metal is solidified from the lower part step by step and continuously performing casting. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an active refractory metal alloy such as rare earth, Ti, Zr, V, Nb or Cr, represented by TiAl based alloy, NbTi based alloy, Zr based alloy, V based alloy or Cr based alloy, for example. The present invention relates to a method for continuously producing a long ingot by so-called cold crucible induction melting by high frequency induction heating.

  Ingots of active refractory metal alloys such as titanium alloys and zircaloy that are widely used are currently manufactured by vacuum arc melting, plasma arc melting, electron beam melting, or the like. In all of these melting methods, a water-cooled copper crucible is used for the melting container, and the entire amount of the melting raw material is not melted all at once, but it is melted while supplying little by little, and the molten metal bath that is formed is sequentially solidified from below. The mainstream is to produce ingots. And industrially, the ingot of 1-10 tons is manufactured with these methods.

  In the vacuum arc melting method, a melting raw material prepared in a predetermined alloy composition is formed into a rod shape by press molding, welding, or the like, and is melted and alloyed. In this method, since the melting raw material is gradually dissolved and solidified little by little, in the case of an alloy component containing a large amount of elements having a large melting point difference, the low melting point component is put first and the high melting point component is dissolved. Therefore, there is a problem of causing significant component segregation in the ingot.

  According to this method, in the case of an alloy with a low content of low melting point alloy elements such as Al (melting point 660 ° C.) or Sn (melting point 232 ° C.), such as typical Ti · 6Al4V and Ti · 15V3Al3Cr3Sn A homogeneous alloy ingot can be produced without causing the above-described component segregation. However, in the case of a TiAl-based intermetallic compound containing a large amount of Al, when a consumable electrode made of a combination of high melting point Ti (melting point 1680 ° C.) and low melting point Al is vacuum melted, Al is dissolved first. Then, Ti becomes insufficiently dissolved and remains undissolved during wear, and the electrode becomes insufficiently strong and falls undissolved, or after dissolving Al, only Ti may be dissolved. . As a result, alloying becomes insufficient, and an ingot having a large component segregation tends to be formed.

  Further, in the case of the plasma arc melting method and the electron beam melting method, by using a water-cooled copper hearth, that is, a dish-shaped melting vessel, homogeneous alloying in a molten metal bath can be performed in the hearth. However, the volume of the molten metal bath is too small as compared with the entire volume of the target ingot, so that a raw material adjusted to a minute size in the raw material blending process is required, and is subject to industrial restrictions. On the other hand, the electron beam melting that requires high vacuum has a difficulty in that the ingot components tend to fluctuate due to evaporation loss of alloy components such as Al and Sn.

  In contrast to these methods, the cold-crucible induction melting method (CCIM method) using a water-cooled copper crucible equipped with a high-frequency coil is used to melt the entire melting raw material at once, alloy it, and then solidify it to produce an ingot. To do. This method facilitates alloying and melting between elements having a large melting point difference, and a molten metal having a homogeneous alloy component can be obtained. Patent Document 1 below discloses a CCIM method in which a raw material is melted in a water-cooled copper crucible and solidified as it is, but in order to produce a long ingot with respect to the diameter by this method, a long high-frequency coil is required. And not realistic. For example, the production of a long ingot having a length / diameter ratio of 1.5 or more leaves a facility problem. In this CCIM method, a molten ingot in a water-cooled copper crucible can be poured into a mold to obtain a long ingot, but there is a risk that a shrinkage defect will occur at the center of the ingot when the molten metal is solidified.

  Further, Non-Patent Document 1 below introduces a method of manufacturing a long ingot by a method called an induct slag melting method similar to the CCIM method. In this method, the molten metal formed in the water-cooled copper crucible is continuously cast by pulling out the bottom of the crucible. In this case, a fluoride-based slag such as calcium fluoride is added between the crucible and the molten metal to achieve a refining effect, an electrical insulation effect, or a lubrication effect during drawing. This method shows that a long ingot can be produced from titanium sponge, but an alloy containing an active refractory metal element in which the fluoride contacts the molten metal and several ppm of fluoride is mixed in the ingot. There are problems in producing a highly clean ingot of material.

It should be noted that, without using such slag, the bottom of the crucible is pulled down by the electromagnetic force from the high frequency coil while the molten metal is held, and the CCMI method is used in the same manner as the above induct slag melting method in the long casting. It is possible to make a lump. In this way, slag contamination as described above can be avoided. However, when producing an ingot having a complicated alloy composition, the ingot remains with the added molten raw material remaining undissolved unless the operating conditions are so appropriate. It remains in the process, and it is difficult to obtain a uniform and sound long ingot.
JP 2003-293051 A US Bureau of Mines Bulletin 673, 1982. PG Clitsler "InductslagMelting Process."

  The present invention is a long ingot containing an active refractory metal element such as Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Y or rare earth as an alloy component, that is, a diameter. Alternatively, when continuously producing an ingot having a length with respect to the short side length of 1.5 or more by using the CCIM method, the problem is to prevent the occurrence of component segregation as described above in the ingot. And

The present invention has been completed in order to solve the above problems,
(1) Using a water-cooled copper crucible whose crucible bottom can be driven in the vertical direction and a high-frequency induction heating coil surrounding the outer periphery of the crucible, the diameter of the copper crucible or the above-mentioned by high-frequency induction heating in a vacuum or an inert gas atmosphere A method for producing a long ingot of an active refractory metal-containing alloy having a length of 1.5 times or more with respect to a short side length, wherein a melting raw material of a predetermined composition is supplied in a molten state into a copper crucible The crucible bottom is pulled down together with the molten pool while the molten metal pool is formed and held in the heating coil region located above the bottom of the copper crucible, and the molten metal is sequentially solidified from below to continuously cast the activity. Long ingot manufacturing method for refractory metal-containing alloy,
(2) The rod-shaped melting raw material is charged into the inside of the copper crucible from the upper side to the lower side than the height position of the upper end of the heating coil, and is sequentially melted so as not to contact the solidification interface. A method for producing a long ingot of an active refractory metal-containing alloy as described in (1) above,
(3) The tip of the rod-shaped melting raw material is melted by induction heat generation from the heating coil, or the tip is immersed in the molten metal pool and melted by heat transfer from the pool, or these induction heating and heat transfer The method for producing a long ingot of an active refractory metal-containing alloy according to the above (2), characterized in that it is melted by simultaneous heating of both,
(4) Melting an ingot containing one or more metal elements selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Y and rare earth. A method for producing a long ingot of an active refractory metal-containing alloy according to any one of (1) to (3) above, and
(5) The ingot is pulled out at a speed of 50 mm or less, preferably 30 mm or less, more preferably 2 to 25 mm per minute by pulling down the crucible bottom. This is a method for producing a long ingot of an active high melting point metal-containing alloy.

  As described above, in the present invention, when continuously melting a long ingot of an active refractory metal alloy by the CCIM method, a melting raw material is always added to a copper crucible under a molten state. As a result, the above-mentioned problems seen when supplying raw materials on solid are not caused. That is, a long ingot of an active high-melting-point alloy such as a TiAl-based alloy, NbTi-based alloy, Zr, V, or Cr-based alloy can be manufactured without component segregation or solidification defects in the central portion. Therefore, it is possible to open the way to the production of long high-grade alloy ingots of various new compositions of this kind of alloy system.

  The present invention relates to an active refractory metal alloy casting containing one or more metal elements selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Y and rare earths. The purpose is to produce lumps. For example, TiAl-based alloy, NbTi-based alloy, Zr-based alloy, V-based alloy, Cr-based alloy, etc., which are cylinders or prisms having a length of 1.5 times or more the diameter or short side length Produces long ingots.

  As shown in FIG. 1, the present invention is based on the so-called CCIM method in which a melting raw material is melted and solidified using a copper crucible (2) with a high frequency induction heating coil (1). In the present invention, the bottom plate (3) of the copper crucible can be driven in the vertical direction by an appropriate drawing mechanism, and the solid rod-shaped raw material (4), which has been manufactured separately from the melting raw material, is used as the support (5). Attach and hang to the center of the copper crucible (2). The entire apparatus is placed in a vacuum or an inert gas atmosphere during operation.

  The rod-shaped raw material (4) is manufactured by a method in which a predetermined alloy material whose components have been adjusted is melted in advance and cast into a rod shape, or a method in which scrap, raw material, or the like is mechanically press-formed.

And in order to implement the method of this invention using the said apparatus and raw material, the molten raw material which should be charged is supplied in a copper crucible in a molten state, and the volume of the molten metal pool (6) is kept substantially constant. Meanwhile, the ingot (8) solidified by cooling from below is pulled down.
In this case, what is necessary is to keep the molten pool volume constant and at the same time keep the progress speed of the solidification interface (7) constant. For this purpose, the ingot (8) is pulled out in accordance with the progress speed of the solidification interface determined by the cooling capacity, and at the same time, the molten raw material in an amount corresponding to the amount of drawing is supplied.

  In this method, the level of the solidification interface (7) of the molten metal pool (6) formed inscribed in the crucible is located between the lower end and the upper end of the heating coil (1) as shown in FIG. Under the condition, it is important to supply a liquid melting raw material from above.

  In addition, in order to obtain a liquid melt | dissolution raw material, although it is good by the melt | dissolution method by the CCIM equipment prepared separately, the plasma arc melt | dissolution method, or the arc melt | dissolution method etc., such special equipment is large-scale and not economical. Therefore, although it is most practical to use the means and method illustrated in FIG. 1, the present invention is not limited to this method.

  The method shown in FIG. 1 will be described. After the initial raw material described below has melted and reached a steady state, the rod-shaped molten raw material (4) can be directly brought into contact with the solidification interface (7). So that it is held from above by the support (5). Then, the melting raw material is melted at a level near the upper end of the molten metal pool (6). For this purpose, the rod-shaped molten raw material (4) may be melted by induction heating from a heating coil, or the tip of the rod-shaped molten raw material is immersed in the molten pool itself to transfer heat from the molten pool. And may be melted. Regardless of which method is used, it is indispensable that the melting raw material (4) is melted and supplied at a level lower than the upper end level of the heating coil (1) as shown in FIG. If the rod-shaped melted raw material is melted early at a position above this level, it drops as a drop or is directly absorbed by the melt and the amount of the melt pool increases, making the above-mentioned speed control difficult. Cause defects such as component segregation.

When the above operation is performed, the ingot drawing speed is 50 mm or less per minute, preferably 30 mm or less, more preferably 2 to 25 mm because direct water cooling is difficult.
(Example)
A long ingot of a TiAl-based (50/50 at%) intermetallic compound was manufactured by an ingot drawing and casting method according to the CCIM method having the following specifications.

・ High frequency power output: Max 400kW
・ Frequency: about 3000Hz
・ Water-cooled copper crucible: Inner diameter 210mm, Cooling water used 400L / min
Side surface: Consists of 24 water-cooled copper segments Bottom: Water-cooled copper bottom plate attached to the pulling mechanism ・ High-frequency heating coil: 7 turns installed on the outer periphery of the side water-cooled copper crucible ・ Vacuum chamber: 10 m ³
First, a drawing start board made of industrial pure titanium material is attached to a water-cooled copper bottom board (3) connected to a bottom drawing mechanism, and is inserted into a copper crucible (2), the upper surface of which is the heating coil (1). The level was set 10 mm above the lower end. Thereon, as initial spectacles wear material, the raw material for melting 15kg of TiAl composition was charged in the form of bulk. The melting raw material to be additionally charged is a raw material suspension mechanism in which TiAl having the above composition has a diameter of 150 to 180 mm and a cylindrical bar having a length of about 600 mm is installed at the top of a vacuum chamber (not shown). It was attached to the support (5). In addition, this rod-shaped raw material (4) used what manufactured the rod shape of about 40 kg in weight by joining several ingots.

Next, the vacuum chamber was evacuated to 5 × 10 ⁻⁴ Torr with a diffusion pump and then filled with high-purity argon up to 200 Torr, followed by replacement with an inert atmosphere. Next, the output of the high frequency power supply was turned on, and it was maintained at 100 kW (10 minutes) → 200 kW (10 minutes) → 300 kW (10 minutes). By this operation, the TiAl alloy as the initial material melted to form a molten metal pool in the copper crucible. Therefore, the rod-shaped melting raw material (4) was pushed down so as to be charged at a level below the upper end of the heating coil (1) at the upper part of the molten metal pool. By operating in this way, it is confirmed that the tip of the melting raw material melts by induction heat generation, falls as a droplet and is absorbed by the molten pool below, and the molten raw material can be supplied to the molten pool in a molten state it can.

  Furthermore, when the amount of the molten metal pool increases, the tip of the rod-shaped molten raw material eventually comes into contact with the liquid surface of the molten metal pool and is further immersed in the molten metal pool. It can be dissolved. Then, when the amount of the molten metal pool increases to about 20 kg, the ingot that has already solidified is pulled downward by operating the pulling mechanism. In this example, the drawing speed was set to 5 mm per minute so that the liquid level of the molten metal pool could be kept constant, and the casting was continuously drawn.

  The cylindrical ingot of φ210 × (400 to 500) Lmm produced in this way was cut in the longitudinal direction, and the internal quality and macro structure of the ingot were used for inspection.

  In addition, as a comparative example, the melt | dissolution raw material made into the size of 50x50x20mm size was used, and the 2 types of method melt | dissolved basically with the same facilities as the above were implemented. That is, a method (A) in which a lump of molten raw material is intermittently added to the molten metal 2 kg at a time using a feeder, and the ingot is continuously withdrawn at a rate of 2 mm / min. After the lump drawing operation was interrupted and the molten metal pool was held for 3 minutes, the operation of drawing the ingot corresponding to the amount added was continued 20 times (B).

  The test results for each example are as shown in Table 1, and the internal quality due to the undissolved residue of the added raw material is clearly good in the examples of the present invention. There is no segregation along the line according to the present invention.

  By the way, when trying to produce a long ingot of an active refractory metal alloy by drawing operation using the CCIM method, in order to suppress the melting of the melting raw material, optimization of the operating conditions is required. It is important to measure. That is, the occurrence of component segregation tends to be inversely proportional to the speed of progress of the solidification interface, and when supplying a bulk or solid melting raw material, a difference in melting occurs in the molten metal depending on the size. The undissolved residue causes segregation of components. As one means for solving such a problem, the comparative method B is combined with intermittent stopping of the drawing of the solidified ingot, but the present invention is more active than this method. It can be seen that the metal alloy is stable in that it can stably produce a high-quality long ingot without component segregation regardless of the component composition of the metal alloy.

It is a schematic diagram which shows the outline | summary of the cold crucible induction | guidance | derivation melt | dissolution equipment and melt | dissolution condition which are used when implementing this invention.

Explanation of symbols

1: high frequency induction heating coil 5: raw material support 2: water-cooled copper crucible 6: molten metal pool 3: copper crucible bottom 7: solidified interface 4 of molten metal 8: rod-shaped molten raw material 8: drawn ingot

Claims (5)

Using a water-cooled copper crucible whose crucible bottom can be driven in the vertical direction and a high-frequency induction heating coil surrounding the outer periphery of the crucible, the diameter or short side length of the copper crucible is obtained by high-frequency induction heating in a vacuum or inert gas atmosphere. Is a method of manufacturing a long ingot of an active refractory metal-containing alloy having a length of 1.5 times or more of the length, and supplying a melting raw material of a predetermined composition into a copper crucible in a molten state, An active refractory metal characterized in that the molten metal pool is formed and held in the region of the heating coil located on the upper side of the crucible bottom, the crucible bottom is pulled down together with the molten metal pool, and the molten metal is sequentially solidified from below to continuously cast. A method for producing long ingots of contained alloys.   The rod-shaped melting raw material is inserted into the copper crucible from the upper side to the lower side of the height position of the upper end of the heating coil, and the melting is sequentially performed so that the tip does not contact the solidification interface. The long ingot manufacturing method of the active high melting point metal containing alloy of Claim 1 characterized by the above-mentioned.   The tip of the rod-shaped melting raw material is melted by induction heat generation from the heating coil, or the tip is immersed in the molten metal pool and melted by heat transfer from the pool, or both induction heating and heat transfer are performed simultaneously. The method for producing a long ingot of an active refractory metal-containing alloy according to claim 2, wherein the alloy is melted by heating.   It is characterized by melting an ingot containing one or more metal elements selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Y and rare earth elements. The long ingot manufacturing method of the active high melting point metal containing alloy in any one of Claims 1-3. The active refractory metal-containing material according to any one of claims 1 to 4, wherein the ingot is pulled out at a rate of 50 mm or less, preferably 30 mm or less, more preferably 2 to 25 mm per minute by lowering the crucible bottom. A long ingot manufacturing method for alloys.

Images