JP2779393B2 - Melting method of high melting point active metal alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to melting of alloys such as Nb-Ti, Ti-Al, Ti-Ni and the like containing at least one high melting point active metal such as Ti, Nb, and Zr. About the method.

[Conventional technology]

The melting of alloys containing high melting point metals such as Ti, Nb and Zr has been conventionally performed by a vacuum arc melting method or the like.

In the case of Nb-Ti alloy, this melting method will be described. Normally, a consumable electrode formed by fixing a Ti plate and an Nb plate alternately on top of each other in the form of the target component values and fixing them by welding is a vacuum. This is a method of setting in an arc furnace, melting by an arc generated between the consumable electrode and the copper mold (the molten metal after the molten metal is formed), and casting the molten metal into the mold.

Recently, an alloy melting method has also been proposed, in which rod-shaped Nb is heated and melted from the tip with an electron beam and dropped into the mold, and titanium sponge is added to the molten pool in the mold to melt the Nb-Ti alloy. (JP-A-60-1748)
No. 38).

However, both methods have the following problems.

[Problems to be solved by the invention]

In the former vacuum arc melting method, (a) the melting point of Nb is 2467 ° C and the melting point of Ti is 1670 ° C,
The melting point of Nb is as high as 797 ° C., so that Ti is preferentially dissolved and Nb is difficult to dissolve, so that Nb remains undissolved in the ingot, and the dissolved component tends to be non-uniform.

(B) It is necessary to use a rolled plate or the like as a consumable electrode, which inevitably increases the cost. Also, welding in which an expendable electrode having a predetermined shape is polymerized and fixed in an inert gas atmosphere is performed. Workability is poor.

In the latter method using drip melting, (c) Ti is added to the molten pool of Nb, so there is no danger of remaining undissolved Nb, and since the manufactured titanium sponge can be used as it is, the melting cost is large. However, in actual operation, it is difficult to adjust the melting components, and a desired alloy ratio may not be obtained.

The alloy ratio has a large effect on the alloy properties, and in particular, in the case of a Ti-Ni alloy used as a shape memory alloy, even a slight deviation results in a large variation in the operating temperature. The present invention improves the method by drip melting, and accurately detects each supply amount and generation amount of the alloy component to thereby reduce the component ratio. It is an object of the present invention to provide a melting method that performs melting at low cost while controlling with high precision.

[Means for solving the problem]

In the method of the present invention, in dissolving an alloy containing at least one high-melting-point active metal, one of the alloy components is made into a rod shape, heated and melted from the tip thereof, dropped into a mold, and the other one is melted. Alternatively, when a metal ingot is produced by supplying a plurality of types of metals in the form of granules or lump into the mold from within the container, the bar-shaped metal, the weight of the metal in the container and the produced ingot are measured, and the rod-shaped metal and the container are measured. The metal supply amount is detected from each weight change of the inner metal, and the metal supply amount and the heating amount are adjusted so as to melt the alloy ingot having a predetermined concentration. This is a method for dissolving a high melting point active metal alloy in which the amount of supplied metal is corrected based on a deviation from each weight change of the metal.

Further, the molten metal in the mold is agitated with an electrode to further sufficiently homogenize the molten metal.

In the method of the present invention, a beam irradiation such as an electron beam or a plasma beam or a plasma arc is used as a heating source for the rod-shaped metal.

In the case of irradiation, the beam is preferably irradiated to the metal surface in the mold together with the tip of the rod-shaped metal to contribute to the stable formation of the molten pool in the mold.

As the rod-shaped metal, the metal with the highest melting point among the alloy components is basically selected, but if there is no significant difference in the melting point between the components, the shape combined with irradiating the metal surface in the mold with the beam is used. Thus, it is possible to supply the high melting point metal into the mold as granules or lump.

The ingot generated in the mold is drawn out sequentially below the mold,
It is desirable to keep the height of the molten pool in the mold constant.

[Action]

By detecting the weight change of the rod-shaped metal, the supply amount of the rod-shaped metal is not affected by the heating amount and other dissolution rate fluctuation factors, and furthermore, the phenomenon that the molten metal in the mold is re-attached to the rod-shaped metal by splash. Determined exactly. Similarly, the supply amount of the granular or massive metal in the container can be determined from the change in weight. Then, by adjusting each supply amount and giving a heating amount corresponding to the adjusted supply amount, the alloy concentration is controlled with high accuracy. Further, the components are made more uniform by the electrode stirring.

Further, in dissolving an alloy as the object of the present invention, the alloy component often escapes as a vapor or splash outside the mold. This escape mainly occurs in metals with lower melting points. Therefore, even if a supply amount corresponding to the target alloy ratio is given, the obtained alloy ratio does not always match the target ratio. However, by measuring the weight of the produced alloy ingot, comparing this with the supply amount up to the time of the weight measurement, and correcting the supply amount based on this, the alloy ratio is controlled with higher precision. .

〔Example〕

 Hereinafter, the method of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory view schematically showing a method of melting an Nb—Ti alloy using an electron beam, employing the present invention. The rod-shaped metal 1 is a high-melting metal Nb formed into a rod shape (Nb rod).
The Nb rod 1 is set vertically through the load cell 3 for measuring the weight in the electron beam melting furnace 12 so as to be able to advance in the direction of the arrow. Reference numeral 2 denotes an electron beam gun, which is located in the furnace on the side of the Nb bar 1 and is arranged so that an electron beam emitted from the muzzle can irradiate the tip of the Nb bar 1 and the inside of the mold 10. The mold 10 is a water-cooled copper mold, which is installed immediately below the Nb rod 1, receives the Nb metal melted and dropped from one end of the Nb rod 1, forms a molten pool 6, and sequentially forms the molten pool 6 from the lower side of the molten pool 6 with the water-cooled copper mold. Cooled,
It solidifies to form an ingot 6a and is gradually lowered by the lowering device 9. Numeral 11 denotes an electromagnetic stirrer for uniformly mixing the 6 alloys in the molten pool. 8 is a load cell for measuring the weight of the ingot 6a.

Reference numeral 4 denotes a titanium sponge, which is housed in a hopper 4a provided with a load cell 7 for measuring weight at a lower portion, and is configured to drop the titanium sponge into a melting pool 6 by operating a feeder 5.

In order to melt the Nb-Ti alloy using the apparatus configured as described above, an electron beam is emitted from the electron beam gun 2 to the tip of the Nb rod 1 to melt the tip of the Nb rod 1 and drop the droplet. Then, the molten pool 6 is formed in the water-cooled copper mold 10, and the Nb rod 1 is advanced in the direction of the arrow to continue the molten dropping in response to the consumption by the molten dropping, and the electron beam is also emitted to the molten pool 6. Is done. In this case, the weight of the Nb rod 1 is measured every moment using the load cell 3, and the dissolution rate is detected.

On the other hand, the titanium sponge 4 is charged into the molten pool 6 while operating the feeder 5 from the hopper 4a to adjust the charging amount. The weight of the titanium sponge 4 is measured by a load cell 7 provided below the hopper 4a, and the supply speed is detected and controlled.

By maintaining the melting rate of the Nb rod 1 and the supply rate of the titanium sponge at a predetermined ratio, the alloy components in the molten pool 6 are maintained at target values.

The alloy of the molten pool 6 formed in the water-cooled copper mold 10 is:
While receiving electromagnetic stirring, it is cooled sequentially from the lower side
6a, and the ingot 6a is lowered by the lowering device 9 equipped with the load cell 8 while automatically adjusting and controlling the lowering speed corresponding to the dissolution speed of Nb-Ti. The weight is measured by the load cell 8, and the measured weight is compared with the total value of the supply amount of the Nb bar 1 obtained from the signal of the load cell 3 and the supply amount of the titanium sponge 4 obtained from the signal of the load cell 7.

The above is the description of the melting of the binary alloy of Nb-Ti. However, when it is desired to melt the multi-component alloy by increasing the types of raw materials charged and added to the molten pool 6, a plurality of hoppers 4a are provided. Can be added.

 FIG. 2 is a continuation diagram of the control method in the above method.

The reference material necessary for calculation, control, etc. is input to the control device 13, and the load cell 3 measures the weight of the Nb bar every moment,
The load cell 7 measures the weight of the titanium sponge every moment,
The load cell 8 measures the weight of the ingot 6a and inputs the measured weight to the control device 13. Control device 13 based on this input
Calculates the melting speed of the Nb rod 1, the supply speed of titanium sponge, the composition of the molten pool alloy (ingot composition), etc., in comparison with pre-input reference data, and adjusts the output control of the electron beam gun. , The operation control of the titanium sponge supply feeder 5 is commanded, and the lowering speed of the ingot 6a corresponding to the melting speed of the Nb rod 1 and the titanium sponge is calculated.

Next, more specific examples of the method of the present invention will be described.

Using the electron beam melting furnace shown in FIG. 1, the Nb-Ti alloy 10 having a target composition of Ti46.5 wt% and Nb53,5 wt%
0 kg was melted. A rod sample of 100 mmφ was used as the Nb raw material, and a titanium sponge of 1/2 inch to 20 mesh was used as Ti. For comparison, Nb, Ti
Using a consumable electrode on which the plates were stacked, melting was performed twice in a vacuum arc.

FIG. 3 shows the Ti in the ingot surface layer melted by the method of the present invention.
2 shows the analysis results. As shown in the figure, it can be seen that the variation in Ti is kept within ± 0.5%. As a result of cutting the ingot and examining the interior, no undissolved portion of Nb was observed.

On the other hand, the analysis results of Ti in the surface layer of the ingot of the comparative material are also shown in FIG. As shown in the figure, the variation of Ti is spread within ± 1%, and it is understood that the variation is large by the method of the present invention.

〔The invention's effect〕

As described above, the method of the present invention is capable of dissolving a multi-component alloy containing a high melting point active metal without any undissolved portion and uniformly dissolving each component with a high alloy ratio accuracy. This has a great effect that remarkable improvements such as improved workability and cost reduction are possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of melting of an Nb-Ti alloy in the method of the present invention, FIG. 2 is a control method diagram in the method of the present invention, and FIG. 3 is an ingot produced by the melting method of the present invention. FIG. 3 is a diagram showing the results of Ti analysis of FIG. In the figure, 1: rod-shaped metal (Nb rod), 2: electron beam gun, 3, 7, 8: load cell, 4: titanium sponge, 4a: hopper, 5: feeder, 6: molten pool, 9: pull-down device, 10 : Water-cooled copper mold, 11:
Electromagnetic stirrer, 12: electron beam melting furnace, 13: controller.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-174838 (JP, A) JP-A-62-238339 (JP, A) European publication 244255 (EP, A1) (58) Fields studied (Int .Cl. ⁶ , DB name) C22C 1/02

Claims (6)

(57) [Claims] An alloy containing at least one high-melting-point active metal is melted by heating one of the alloy components into a rod shape from the tip thereof and dropping it into a mold. When a metal ingot is produced by supplying a plurality of types of metals in the form of granules or lump into the mold from the inside of the container, the bar-shaped metal, the weight of the metal in the container and the produced ingot are measured, and the rod-shaped metal and the inside of the container are measured. The metal supply amount is detected from each weight change of the metal, and the metal supply amount and the heating amount are adjusted so as to melt the alloy ingot having a predetermined concentration, and the weight change of the produced ingot, the rod-shaped metal and the metal in the container are performed. A method for melting a high melting point active metal alloy, comprising correcting a metal supply amount based on a deviation from each of the weight changes. 2. The method for melting a high melting point active metal alloy according to claim 1, wherein the molten metal in the mold is uniformly mixed by an electromagnetic stirrer. 3. The method for melting a high melting point active metal alloy according to claim 1, wherein the rod-shaped metal is a metal having the highest melting point among the alloy components. 4. A method for melting a high melting point active metal alloy according to claim 1, wherein the means for heating the rod-shaped metal is electron beam irradiation, plasma beam irradiation or plasma arc irradiation. . 5. The method for melting a high melting point active metal alloy according to claim 4, wherein the irradiation is performed on both the tip of the rod-shaped metal and the metal in the mold. 6. The method for melting a high melting point active metal alloy according to claim 1, wherein the formed ingot in the mold is sequentially drawn downward.