JP2541341B2 - Precision casting method and precision casting apparatus for Ti and Ti alloy - Google Patents

Description

Detailed Description of the Invention [Object of the invention]

(Industrial field of application) The present invention is a precision casting of Ti, Ti alloy used for obtaining a precision casting of Ti, Ti alloy which is lightweight, has excellent heat resistance and corrosion resistance, and has high strength. The present invention relates to a method and a precision casting device. (Prior art) Ti and Ti alloys are lightweight, have excellent heat resistance and corrosion resistance, and have high strength.
It is expected that precision casting of i, Ti alloys will yield useful product parts that have never existed before. (Problems to be solved by the invention) However, such a Ti, Ti alloy has a melting point of 1 or less.
Since it is as high as 400 ° C or higher and is active, there is a problem that melting and casting are often accompanied by great difficulty. That is, for example, when an ordinary ceramic crucible is used to melt Ti, Ti alloy and secure the amount and temperature suitable for casting, dissociation at high temperature (oxide system by Ti) However, there is a problem that it is difficult to use because it is likely to cause reduction of ceramics. In addition, when a graphite crucible is used, C is dissolved in Ti, which is short from the viewpoint of contamination prevention. There is a problem that it is limited to melting a small amount of time, and further, Ti, a mold for casting a melt of a Ti alloy may cause a reaction with the melt, and in this case, the casting temperature is made as low as possible. However, there is a problem that this makes the molten metal of a precision cast product with many complicated thin-walled shapes difficult, and it has been a problem to solve these problems. (Object of the invention) The present invention has been made in view of such conventional problems, and precision casting of Ti, Ti alloys and other refractory metals such as W, Mo, V, Zr, Li and active metals. When performing the, to secure the amount and temperature of any melt metal required for casting while preventing contamination of the melt metal during melting, and to establish good forced casting conditions around the melt even at low temperatures. It is an object of the present invention to provide a precision casting method and a precision casting apparatus capable of obtaining a precision casting product having a high melting point and an active metal by giving the same.

Configuration of the Invention

(Means for Solving the Problems) The precision casting method for Ti, Ti alloys according to the present invention, when melting a Ti, Ti alloy base material by induction heating, a ring-shaped insulating state is provided inside the induction heating coil. While melting inside the water-cooled copper segment assembly placed in,
The molten Ti, Ti compound financial body is characterized in that it is configured to suction casting in a breathable mold installed above it, in one embodiment, the melting atmosphere is an inert atmosphere such as argon, The melted Ti, Ti compound financial body is suction-cast into a breathable mold through a hollow sprue, and the Ti, Ti alloy base material is continuously supplied from below the water-cooled copper segment assembly. The Ti, Ti alloy precision casting apparatus according to the present invention is an induction heating coil, and is arranged inside the induction heating coil in an annularly mutually insulated state from below.
Ti, a structure made up of a water-cooled copper segment assembly to which a Ti alloy base material is supplied, and a breathable mold for suction casting Ti, Ti synthetic financial body melted by induction heating inside the water-cooled copper segment assembly In one embodiment, in suction casting, T
The i, Ti compound financial body is configured to have one or a plurality of hollow sprues for guiding it into the air-permeable mold, and the air-permeable mold has a closed feeder part at the upper part.
It is characterized in that the breathable mold is a ceramic shell mold, and the above-described method of precision casting Ti and Ti alloy and the configuration of the precision casting apparatus are means for solving the above-mentioned conventional problems. (Operation of the Invention) Since the Ti, Ti alloy precision casting method and precision casting apparatus according to the present invention have the above-mentioned configuration, they are made of water-cooled copper that is annularly arranged in an insulating state inside the induction coil. When the Ti, Ti alloy is melted inside the segment assembly, an eddy current group is formed inside the water-cooled copper segment assembly. Therefore, the eddy current, which is the above alternating current, induces a skin eddy current in the base metal and melts it. This causes the molten metal to form a gap slightly away from the water cooled copper segment assembly. As a result, heat transfer from the molten metal to the water-cooled copper segment assembly is suppressed by the formation of the gap, and a thick skull (solidified metal) as found in a conventional water-cooled hearth type furnace such as an arc skull furnace is used. Layer) is hardly generated, the base metal is melted with high yield, and the temperature of the melt metal is easily controlled by adjusting the amount of electric power supplied to the induction coil. Further, since no crucible made of oxide-based ceramics is used, contamination of the molten metal becomes almost zero, and a high quality precision cast product can be obtained. (Embodiment) FIG. 1 and FIG. 2 show a precision casting apparatus used in an embodiment of the method for precision casting Ti and Ti alloys according to the present invention. A water-cooled copper segment assembly 2 consisting of a plurality of water-cooled copper segments 2a ... 2h arranged in an annularly insulated state is installed in the portion, and each water-cooled copper segment 2a ... 2h has a water-cooled pipe. 3a ... 3h are provided.
The water-cooled copper segment assembly 2 is continuously provided with a magnetic shield portion 4 on the upper side thereof. A high frequency induction heating coil 5 is arranged outside the water-cooled copper segment assembly 2, and a Ti, Ti alloy base material 6 is supplied to the inside thereof from below. An annular base 11 is provided above the magnetic shield portion 4 via a seal member 12, and a sleeve 13 is provided inside the annular base 11, and a mold chamber 14 is provided inside the sleeve 13. Is provided, and a melting space 15 is formed in a portion surrounded by the bottom surface of the mold chamber 14 and the inner surfaces of the water-cooled copper segment assembly 2 and the magnetic shield portion 4.
The melting atmosphere in the melting space 15 can be made an inert atmosphere by supplying, for example, argon gas from the gas supply port 16 provided in the. Then, a breathable mold 21 made of a ceramic shell mold is installed in the mold chamber 14, and the turbine wheel-shaped casting space 21a and the melting space 15 in the breathable mold 21 are provided in the breathable mold 21. And a gate 22 and a hollow sprue 23 communicating with the gate 22. Further, a closed feeder is provided on the upper part of the breathable mold 21.
In addition to having 21c, a heat insulating material 24 is provided on the outer surface. Further, a sealing member is provided on the upper end of the mold chamber 14.
A top plate 27 is provided via 26, and the breathable mold 21 is held by a holding rod 29 penetrating the top plate 27 via a sealing member 28. A mouth 27a is provided. Therefore, in the precision casting apparatus 1 shown in this embodiment,
As described above, since the water-cooled copper segment assembly 2 is arranged inside the high-frequency induction heating coil 5, eddy current is formed inside the water-cooled copper segment assembly 2 by high-frequency induction heating by the high-frequency induction heating coil 5. This alternating current eddy current causes Ti, T
A skin eddy current is induced in the i alloy base material 6 and melted. At this time, due to the repulsion of the electric currents whose phases are opposite to each other on the surfaces of the water-cooled copper segment assembly 2 and the Ti, Ti composite financial body 31, the Ti, Ti composite financial body 31 is slightly separated from the inner surface of the water-cooled copper segment assembly 2 and a gap is formed. It is formed. Therefore, the heat transfer from the Ti, Ti combination financial body 31 to the water-cooled copper segment assembly 2 is suppressed by the formation of the cap. As a result, it is possible to melt the Ti, Ti alloy base material 6 with a good yield, with almost no formation of a thick skull as seen in a water-cooled hearth type furnace such as a conventional arc skull furnace. Further, by adjusting the amount of electric power supplied to the high frequency induction heating coil 5,
It is possible to easily control the temperature of Ti, the Ti financial instrument 31. Furthermore, since no oxide-based ceramic crucible is used, the Ti and Ti compound financial body 31 is completely contaminated. In this state, when the pressure is reduced through the decompression suction port 27a provided in the top plate 27, the difference between the internal pressure of the mold chamber 14 and the internal pressure of the melting space 15 causes the inside of the casting space 21a and the feeder 21c of the breathable mold 21. The gas present in the mold flows out of the mold chamber 14 through the breathable mold 21 in the direction of the arrow,
At the same time, the Ti, Ti compound financial body 31 is suction-cast through the hollow sprue 23 and the gate 22 into the casting space 21a. At this time, the Ti, Ti compound financial body 31 is sucked up to the part of the feeder part 21c to prepare for the shrinkage due to the solidification shrinkage of the Ti, Ti compound financial body 31 in the casting space 21a. Then, after solidification in the breathable mold 21, the mold is released to obtain a cast product. In this example, a TiAl intermetallic compound which is lightweight and excellent in high temperature strength was selected as the Ti, Ti alloy base material 6, and this was cast into a turbine wheel for a turbocharger having an outer diameter of 140 mm and a product weight of 1200 g. The capacity of the high frequency power supply for supplying power to the high frequency induction heating coil 5 used here is 60 kw, which is relatively small and simple equipment. This frequency is as high as 30 kHz, which makes it possible to efficiently melt an object to be heated having a small diameter. Further, the blades of the turbine wheel are 12, and a total of 12 gates 22 each having a diameter of 8 mm are provided near the lower part of each blade. Then, an alloy base material 6 made of a TiAl intermetallic compound is supplied from below the water-cooled copper segment assembly 2 and a high frequency power source having a capacity of 60 kw and a frequency of 30 kHz is supplied to the high frequency induction heating coil 5 to form the TiAl alloy base material 6. Induction heating was performed to form an eddy current group inside the water-cooled copper segment assembly 2 and the TiAl alloy base material 6 was melted while inducing a skin eddy current. Then, the casting temperature was set to 1580 ° C by applying superheat at 60 ° C to 1520 ° C which is the melting point of TiAl. The superheat at this time is much lower than the conventional superheat of precision casting superheat of 150 to 250 ° C, and the effect of suppressing the reaction with the metal and alloy of the mold is great. Then, at this casting temperature, for example, 3 through the pressure reducing port 27a.
By reducing the pressure by about 50 mmHg, the casting space 21 is caused by the pressure difference between the internal pressure of the mold chamber 14 and the internal pressure of the melting space 15.
While exhausting the gas in a through the breathable mold 21,
TiAl combined financial body through hollow sprue 23 and gate 22
31 is sucked into the casting space 21a and the riser portion 21c, and the casting space 21
A turbine wheel was obtained by solidifying in a. At this time, since the suction casting was performed in the casting space 21a, the melt spreads evenly around the thin blades, and it was possible to obtain a turbine wheel having extremely high shape accuracy. Therefore, by adopting the precision casting method and the precision casting apparatus according to the present invention, it is possible to manufacture a precision casting product of Ti, a Ti alloy having a complicated and large shape, which was almost impossible in the past, and its ripple effect. Is a big future Ti, Ti
It contributes to the development of precision casting of alloys, and further
It can be applied to high melting point metals such as W, Mo, V, Zr and Li, active metals and precision casting of these alloys.

【The invention's effect】

The Ti, Ti alloy precision casting method according to the present invention, when melting the Ti, Ti alloy base material by induction heating, inside the water-cooled copper segment assembly annularly arranged inside the induction heating coil in a mutually insulated state Dissolves in
Since the melted Ti, Ti compound financial body is suction-cast in a breathable mold installed above it, when the Ti, Ti alloy base material is melted, the base material is changed by the eddy current, which is an alternating current, to the base material. Because the skin eddy currents are induced and melted, the repulsion of mutually opposite currents at the water-cooled copper segment assembly and the melt metal surface creates a gap in the melt metal away from the water-cooled copper segment assembly. As a result, heat transfer from the melt metal to the water-cooled copper segment assembly is suppressed, so that the solidified metal layer is not generated on the surface of the water-cooled copper segment assembly, and the yield of the base metal is significantly improved. At the same time, the temperature of the molten metal is easily controlled, and contamination of the molten metal is prevented, and high quality precision cast products can be obtained. The Ti, Ti alloy precision casting apparatus according to the present invention is provided with an induction heating coil and an annularly insulated state inside the induction heating coil. Ti, Ti from below
The water-cooled copper segment assembly to which the alloy base material is supplied, and Ti, which has been melted by induction heating inside the water-cooled copper segment assembly, has a breathable mold for suction-casting a Ti financial product, so that it has been described above.
This has the remarkable effect of enabling the precision casting method of Ti, Ti alloys to be carried out and the precision castings of Ti, Ti alloys to be produced with high yield and high precision.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional explanatory view of a precision casting apparatus showing one embodiment of the present invention, and FIG. 2 is an explanatory view showing the structure of a water-cooled copper segment assembly. 1 ... Precision casting equipment, 2 ... Water-cooled copper segment assembly, 5 ... Induction heating coil, 6 ... Ti, Ti alloy base material, 15 ... Melting space, 21 ... Breathable mold, 21a ... Casting space , 21c …… Oshitobe, 23 …… Hollow sprue, 31 …… Ti, Ti combined financial body.

Claims (8)

(57) [Claims] 1. When melting a Ti, Ti alloy base material by induction heating, the melted Ti is melted in a water-cooled copper segment assembly which is annularly arranged in an insulating state inside an induction heating coil. A precision casting method for Ti and Ti alloys, characterized in that suction casting is performed in a breathable mold installed above the Ti joint financial body. 2. The precision casting method for Ti or Ti alloy according to claim 1, wherein the melting atmosphere is an inert atmosphere such as argon. 3. The precision casting method for Ti and Ti alloys according to claim 1 or 2, wherein the melted Ti, Ti compound financial body is suction-cast into a breathable mold through a hollow sprue. 4. The Ti, Ti alloy base material is continuously supplied from below the water-cooled copper segment assembly.
The method for precision casting of Ti or Ti alloy according to any one of items 2 and 3. 5. An induction heating coil and a ring-shaped insulating ring are disposed inside the induction heating coil in a mutually insulated state from below.
i, a water-cooled copper segment assembly to which the base material of the Ti alloy is supplied, and a ventilation mold for suction casting the Ti, Ti synthetic financial body melted by induction heating inside the water-cooled copper segment assembly, Precision casting equipment for Ti and Ti alloys. 6. The precision casting apparatus for Ti and Ti alloys according to claim 5, further comprising one or a plurality of hollow sprues for guiding the Ti, Ti compound financial body into the air-permeable mold during suction casting. 7. The precision casting apparatus for Ti or Ti alloy according to claim 5 or 6, further comprising a feeder part which is closed above the breathable mold. 8. The breathable mold is a ceramic shell mold according to claim 5, 6, or 7.
Precision casting equipment for Ti and Ti alloys.