JP2583313B2 - Method for producing Nb-Ti alloy - Google Patents

Description

The present invention relates to a method for producing an Nb—Ti alloy.

[Conventional technology]

Conventionally, an ingot of an Nb-Ti alloy used as a superconducting material or the like has been manufactured by the following method. (A) As shown in FIG. 2, a thin niobium rod and a thin titanium rod are bundled so as to have a desired composition ratio, for example, 50 wt%: 50 wt% to form a mixture (1). 1) and the water-cooled mold (2) are set in the vacuum vessel (3), and the power supply (4) is operated to generate an arc (5) between the mixture (1) and the water-cooled mold (2); The alloy drop (6) formed by melting the mixture (1) with the heat is dropped into a pool portion (7) in a water-cooled mold (2) and solidified to form an alloy ingot (8) by arc melting. Law.

B) An electron beam melting method in which the mixture is irradiated with an electron beam, and the mixture is melted by the heat to drop an alloy drop formed in a pool in a water-cooled mold and solidify to form an alloy ingot. .

C) A powder method in which a compressed mixture is formed from niobium powder and titanium powder, heated and compressed in a vacuum vessel, and cooled to form an alloy ingot.

[Problems to be solved by the invention]

However, the above-described method for producing an Nb-Ti alloy has the following problems. That is, a) In the arc melting method, a large temperature gradient is generated between the vicinity of the mold and the center of the pool, so that Ti segregates, and the Ti temperature is high at the outer periphery of the ingot, and the crystal grains become large.

B) In the electron beam melting method, since the high vacuum is required for the same operation, the yield of Ti is poor, and the Ti concentration is high at the outer periphery of the ingot due to the temperature gradient of the pool, and the crystal grains become large.

C) In the powder method, there is no large change in the Ti concentration, but there are many voids, and as for the crystal grains, there are many mixed grains and coarse grains.

[Means and actions for solving the problem]

The present invention provides a method for producing an Nb-Ti alloy that solves the above problems, and a step of forming a mixture by mixing at least two kinds of raw materials of pure niobium and pure titanium; and Compressing to form a compressed body, heating the compressed body to make a part thereof a semi-molten body, and relatively rotating the semi-molten body portion and the non-semi-melted body portion; A first invention in which a body part is moved in a compressed body, cooled and solidified, and a second invention is that the relative rotational speed of the semi-molten body part and the non-semi-melted body part is 100 rpm or more. A third invention is that the solidification temperature of the semi-solid portion is 1 ° C./min or more.

The present invention is an application of a recently developed semi-solid processing method. In the semi-solidification method, in a state in which a molten metal and a solidified metal coexist, mechanically stirring vigorously destroys dendrites that are formed, and forms a slurry in which metal particles and a liquid are mixed. It is a method of making and forming it. The alloy manufactured by the semi-solidification processing method is characterized by having no defects such as segregation and having fine crystal grains.

As described above, the compressed body formed by mixing pure niobium and pure titanium is partially heated to a semi-molten body, and when the semi-molten body part and the non-semi-melted body part are relatively rotated, NbTi Slurry is produced. At this time, if the rotation speed is set to 100 rpm or more, the crystal grains can be refined to 1 mm or less. Further, when the semi-solid portion is moved and cooled, by setting the cooling temperature to 1 ° C./min or more, crystal grains can be further refined. If the cooling rate is lower than this, the grains become coarse but segregation is reduced. However, coarsening of crystal grains is not preferable because it impairs workability.

〔Example〕

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

FIG. 1 is an explanatory view of one embodiment according to the present invention. In a vacuum vessel (13), a mixture (11) has a rotating shaft (1) at an upper end.
2 '), and the lower end is connected to a rotating shaft (12) having the opposite rotation direction. This mixture (11) was prepared by blending 200 mesh niobium and sponge titanium so as to give Nb-46.5 wt% Ti, compressing the mixture into a column having a diameter of 100 mmφ, cold-forming, and then applying a hot tonometer of 7 tons. After being kept at 1650 ° C for 10 minutes in a water pressure machine, it was cooled and taken out to the atmosphere. A fixed induction coil (14) is arranged around the mixture (11) set in the vacuum vessel (13). The induction coil (14) is energized, and the mixture (1) near the induction coil (14) is turned on.
1) Heat to 1989 ℃ to make a semi-molten body, rotate the upper rotating shaft (12 '), and rotate the lower rotating shaft (12) in the opposite direction.
Rotate at 1 rpm. The induction coil (14) and the semi-molten part (15) are kept in a fixed position and the solidified alloy is made of a water-cooled tube (16)
Is cooled down and pulled down.

Table 1 shows the inspection results of the Nb-Ti alloy ingot sample manufactured as described above and the ingot sample manufactured by the conventional arc melting method and the powder method subjected to hot isostatic pressure treatment for 3 hours. Show.

From this result, it can be seen that the Ti concentration of the sample of this example hardly changed between the outer peripheral portion and the central portion, segregation did not occur, and was improved over the conventional arc method and powder method. Regarding the size of the crystal grains, in this embodiment, by setting the rotation speed to 100 rpm or more and the cooling speed to 1 ° C./min or more, the size of the crystal grains becomes 1 mm or less, and the rotation speed and the cooling speed are increased. It can be seen that the smaller the crystal grain is, the smaller the crystal grain becomes. Further, voids were generated in the arc method and the powder method, but no voids were found in this example.

Next, as another example, an Nb-Ti alloy ingot sample manufactured under the same conditions as in the previous example using a mixture blended to become Nb-3 wt% Ti was subjected to an electron beam method and a powder method. Table 2 shows the comparison data with the ingot sample according to the above.

From the results in Table 2, it can be seen that the Nb-Ti alloy ingot of this example is superior to the ingot manufactured by the conventional manufacturing method in that segregation of Ti is eliminated, crystal grains are refined, and voids are eliminated. It shows the properties.

〔The invention's effect〕

As described above, according to the present invention, a raw material of pure niobium and pure titanium is mixed to form a compressed body, and then the compressed body is heated to form a semi-molten body, and a semi-molten body portion is formed. The non-semi-solid portion is relatively rotated, and then the semi-solid portion is moved in the compact, cooled and solidified, so that there is no segregation of Ti, crystal grains are refined, and void-free Nb −Ti
There is an excellent effect that an alloy ingot can be obtained. Nb
The present invention can be similarly applied to a Ti-based alloy to which third and fourth elements such as Ta, Hf, and Zr are added.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an embodiment of a method for producing an Nb—Ti alloy according to the present invention, and FIG. 2 is an explanatory view of a conventional example of the producing method. 1,11 ... mixture, 2 ... water-cooled mold, 3,13 ... vacuum vessel,
4 ... power supply, 5 ... arc, 6 ... alloy drop, 7 ...
... Pool, 8 ... Ingot, 12,12 '... Rotating axis, 1
4… Induction coil, 15… Semi-melted part, 16… Water-cooled tube.

Claims (3)

(57) [Claims] 1. A step of mixing at least two kinds of raw materials, pure niobium and pure titanium, to form a mixture, a step of compressing the mixture to form a compressed body, and heating the compressed body. A part of which is a semi-molten body, a step of relatively rotating the semi-molten body part and the non-semi-melted body part, and a step of moving the semi-molten body part in a compact, cooling and solidifying A method for producing an Nb-Ti alloy, comprising the steps of: 2. The method according to claim 1, wherein the relative rotation speed of the semi-solid part and the non-semi-solid part is 100 rpm or more.
A method for producing an Nb-Ti alloy. 3. The method for producing an Nb-Ti alloy according to claim 1, wherein the solidification rate of the semi-solid is 1 ° C./min or more.