JPS6220844A - Manufacture of nb-ti alloy - Google Patents

Abstract

PURPOSE:To manufacture a homogenous Nb-Ti alloy free of impurity contamination stably at a low cost by subjecting a composite material composed by successive lining by use of Ti tubular body, Nb tubular body and Ti stick material to heating by an energy beam to undergo drip melting. CONSTITUTION:The Ti tubular body 1 is lined inside with the Nb tubular body 2 and further the Nb tubular body 2 is lined inside with the Ti stick material 3 to form a three-layer composite body, which is disposed as melting material in a vacuum chamber 4. Subsequently, the above melting material is allowed to move downward with turning and simultaneously its end is melted by heating by means of an energy beam 6 emitted from an energy beam gun 5 or arc. The resulting Nb-Ti alloy melt drips are allowed to drop to form a metal pool 8 in a water-cooled copper mold 7 and solidified, which is subjected to continuous drawing via a dummy 10 in the form of an Nb-Ti alloy ingot 9. In this way, the homogenous Nb-Ti alloy having neither Nb phase as unmelted residue nor segregation and free from impurity contamination can be obtained.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention is characterized in that the melt is made of Nb having a uniform composition in which there is no remaining Nb phase and there is no contamination by impurities resulting from melt preparation work, etc.
The present invention relates to a method of manufacturing -Ti alloy at low cost.

In recent years, the development and practical application of superconducting applied technologies, typified by superconducting electromagnets and superconducting cables, have been in the spotlight.Recently, alloy-based superconducting materials, which are advantageous in terms of manufacturing and processability, have also been developed from the original stage. Nb-Ti alloys have replaced Nb-Zr alloys as the mainstream, and Nb-Ti alloy wires of various wire diameters are now commercially available. It is now possible to display superconducting magnets, etc.

<Prior art and its problems> By the way, in the production of Nb-Ti alloy, both Nb and Ti are used.
Since it is a high-melting point metal, an energy beam (electron beam, plasma beam, etc.) or arc is used as a heating source to melt the molten material (for example, a consumable electrode), and the droplets are continuously poured into a water-cooled copper mold placed below. The "drip melting method" in which melted materials are layered and solidified by dripping and fusion is generally used, and in order to obtain more homogeneous alloy products, various innovations have been made in the past, especially focusing on the melted materials. .

However, if we roughly divide the methods that have been put into practical use into practice, they are: (1) A method that uses a consumable electrode formed by mixing and compressing Nb powder and Ti powder and melting it in a vacuum arc. .

■ As shown in Figure 5, Nb plate 11 and Tl plate 1
A method of vacuum arc melting using a composite consumable bridge formed by alternately pasting 2 and 2 together (Japanese Patent Publication No.
No. 089).

The current situation was that it was concentrated into two.

However, the following problems have been pointed out in the conventional Nb-Ti alloy manufacturing method. That is.

Means of (1) above: 1) There is no low-cost, high-purity Nb powder or Ti powder, and it is difficult to obtain high-quality products at low cost.

11) Powder compression molding work and welding assembly work for assembling melted materials (consumable electrodes) have a high risk of contamination and are complicated.

l11) Materials (consumable electrodes) melted by compression molding of powder are easily chipped or bent during melting, which can easily become a source of trouble during melting work.

iv) During melting, there is a high risk that the fragile parts of the compression-molded melting material (consumable electrode) will fall off and leave "molten residue".

Means 1) In order to form the melted material (consumable electrode) into a cylindrical shape, the material plates must be cut to different widths, which is extremely disadvantageous in terms of man-hours and yield.

11) Since the cut material plates are overlapped and fixed by welding, the work is complicated and there is a high possibility of contamination due to welding.

1ii) This is because the melting point difference between Nb and Ti is as large as approximately 150°C.

During the melting process, the Tl plate part with a low melting point is selectively melted, and the Nb plate part is not melted regularly from the bottom end, so that Nb is supplied to the metal pool in the form of small pieces and the melt leaves behind. .

iv) In melting methods such as vacuum arc melting where it is difficult to control the arc, the arc tends to concentrate on the easily melted part of the consumable electrode, so Nb plates and Ti plates were laminated alternately. If a composite consumable electrode (melting material) is used, the Ti plate portion will be melted as it is being used, which tends to cause non-uniformity of components within the 5 alloy ingot.

Therefore, the present inventors aimed to solve the above-mentioned problems found in the conventional Nb-Ti alloy manufacturing method, and first developed a method using a Nb pipe with a Ti round rod as the melting material. We proposed a manufacturing method for Nb-Ti alloy, which consists of drip melting the Nb-Ti alloy using an energy beam.

In the method proposed above, the extremely simple method of inserting a Ti round rod into a Nb pipe and fixing one end surface by welding can be used to obtain the melted material.

There is no reduction in raw material yield or impurity contamination of the melted material due to multi-point welding, and the heating source (energy beam) can be reliably irradiated to the Nb part with a high melting point during melting, making it possible to completely remove Nb. Most of the problems pointed out in the conventional Nb-Ti alloy production method were solved, such as the ability to form droplets and the stable production of a homogeneous alloy.

However, the inventors' experiments and
We are also considering the method proposed earlier, in which a melted material with a Ti round rod inside a Nb pipe is used.

It has become clear that there are problems that need to be improved, such as:

That is, as shown in FIG. 6, during the melting operation, the Ti round rod 14 of the melting material 13 melts first due to the difference in melting point between Nb and Ti, resulting in Nb/'! Eve 15 also melts from the inside due to alloying with Ti, and eventually the melting of the melted material 13 tends to progress in a concave shape, which obstructs the beam irradiation to the metal pool 8 (6th 16 in the figure is a shadow caused by the dissolved material).

This can lead to insufficient heating of the metal pool, which prevents smooth operation, which can lead to deterioration of the ingot surface, and can also cause component segregation, which sometimes requires remelting multiple times using vacuum arc melting. There was a fear that this could lead to a situation where

On the other hand, apart from this, there is also a method for manufacturing Nb-Ti alloy which consists of drip melting a melted material made by welding (17) a thin multilayer roll as shown in Fig. 7. 1 In this case, in melting using an energy beam or an arc as a heating source, Ti in the form of a thin plate is
Because it melts quickly and evaporates easily, alloy products obtained by this method also tend to have significant component segregation.

From the above-mentioned viewpoint, the present inventors believe that the remaining Nb
In order to find a method for manufacturing Nb-Ti alloys with a uniform composition without phases or segregation and without contamination by impurities caused by melting preparation work, etc., at low cost and with smooth workability,
As a result of further research, they came to the knowledge shown below. That is.

(a) When melting a high melting point metal such as Nb (melting point: about 2400°C), it is known that it is advantageous to lower the melting point by alloying it with a material with a lower melting point, but energy beams When melting Nb-Ti alloy by the drip melting method using a heating source or an arc, the melted material is
In the case of a composite material wrapped in i, during the melting process, Ti, which is the exterior material, is first melted, and then it is alloyed with Nb, so that the dissolution of the Nb, which is the interior material, progresses smoothly. To become a.

(b) In this case, if the Nb interior material is made into a hollow body such as a pipe, the melting will be smoother, and if a Ti rod is further placed inside the Nb hollow body, it will be possible to melt the Nb material during the melting process. As a result, the outer Ti hollow body and the innermost Ti rod are first melted, and then alloyed with the Nb hollow body that is melted from the inside and outside.
The dissolution of Nb proceeds more smoothly, and the dissolved material is already homogeneous Nb-T at the droplet stage, without leaving any residue.
i) Become an alloy and be supplied to the metal pool.

In other words, in the drip melting method using an electron beam or plasma beam furnace, the metal pool formed is very shallow, so the composition when the melted material is supplied to the metal pool is already equal to the target ingot composition. However, according to the above method, since alloying has already occurred at the stage of falling droplets, a homogeneous ingot with no remaining melt can be obtained.

(C) However, according to the above method, the melted material melts in a deep sill shape starting from the outer side where it is easy to melt (see Figure 2), so there may be a situation where beam irradiation to one metal pool is obstructed by the melted material. 1. Smooth operation is ensured without causing any problems, and therefore, the surface quality and segregation status of the obtained alloy ingot are also extremely good.

(d) Nb in a hollow body shape is wrapped around Ti, and the Nb is further wrapped around Ti.
b A three-layer composite melting material with a Ti rod inside the hollow body.

For example, it can be manufactured easily and at low cost by inserting a Nb pipe into a Ti-ξ tube and also inserting a Ti round rod into the Nb pipe, and then fixing one end by welding. , Ti pipe, Nb pipe and T
All i-round bars can be obtained with high purity by processing from billets, and since only one end of the assembled three-layer composite material is welded, there is no contamination due to welding, and therefore, from the perspective of impurities, they are also highly pure. It must be possible to stably prepare high-quality dissolved materials.

This invention has been made based on the above knowledge, and when melting an alloy by the drip melting method using an energy beam or an arc as a heating source, for example, the inside of a Ti hollow body 1 as shown in FIG. Nb hollow body 2 is installed inside,
Furthermore, a three-layer composite material comprising a Ti rod 3 inside the Nb hollow body 2 is used as a melting material to carry out melting work, or
Alternatively, by further performing remelting using the ingot thus obtained as a melting material, a homogeneous Nb-Ti alloy can be produced stably and at low cost.

Now, FIG. 2 is a schematic view schematically showing an example of a Nb-Ti alloy manufacturing operation according to the method of the present invention.

In manufacturing the Nb-Ti alloy, first, a Ti hollow body 1
A Nb hollow body 2 is installed inside the Nb hollow body 2, and a Ti
A three-layer composite molten material having a bar inside is placed in a vacuum chamber 4, and is irradiated with an energy beam 6 from an energy beam gun (for example, an electron gun) 5 while slowly rotating and gradually lowering the material. With this, 3
The Ti part of the layer composite melting material melts first, and this alloys with Nb from the inner and outer surfaces to lower its melting point, so that the melting of the Nb hollow body part, which has a higher melting point, proceeds smoothly, and as a result,
The three-layer composite melting material drips Nb-Ti alloy droplets.

The melting does not leave any residue, and the energy beam 6 is melted in a circular shape that does not block the energy beam 6.

The dropping Nb-Ti alloy droplets are stopped by a metal pool 8 formed in a water-cooled copper mold 7 and then solidified, forming Nb-Ti alloy droplets.
- It is continuously drawn out as a Ti alloy ingot 9. In addition,
In FIG. 2, what is indicated by the reference numeral 10 is a dummy.

Furthermore, it is preferable to use the Nb-Ti alloy ingot 9 obtained as described above as a melting material and re-melt it by the same means in order to obtain a more homogeneous alloy.

Next, the invention will be explained by way of examples.

<Example> First, a Nb-Ti alloy was melted using a 60 KW electron beam furnace by the vertical drip melting method as shown in FIG. 2 above.

The melted material has an outer diameter of 63.5M and a wall thickness of 211.
A 5mIIL Tl tube with an outer diameter of 40.0- and a wall thickness of 12.
A three-layer composite material with a weight ratio of Nb and Ti of 1:1 in the cross section, with a 5-frame Nb tube inside, a 14.5 mφ Ti round rod, and one end welded by plasma arc. was used. Then, in the melting work, the above melted material is mixed into 2. The procedure was carried out by supplying the material vertically while rotating it with an Orpm, melting it with an electron beam, and laminating it in a water-cooled copper mold with an inner diameter of 260 mm.

When we observed the melting situation at this time, it was confirmed that the melted material smoothly melted into a silage shape and was supplied to the metal pool as Nb-Ti alloy droplets, and the obtained ingot (diameter: The casting surface of 59Mφ, length: 350mm) was also extremely good.

When we conducted a composition investigation on the longitudinal section of this Nb-Ti alloy ingot, we found that no residual Nb dissolution or segregation of impurities was detected, and the Ti distribution in each part of the ingot was as shown in Figures 3 and 4. It was extremely uniform.

In addition, Fig. 3 shows the Ti distribution in the longitudinal direction of the ingot.
FIG. 4 shows the Ti distribution from the skin to the center of the ingot.

In addition, an Nb-Ti alloy was melted in the same manner as described above except that a melted material with a Ti content of 46.5% by weight in the cross section was used, but the resulting Nb-Ti alloy ingot was The casting surface and longitudinal cross-sectional properties of the ingot were as good as the previous ones, and the Ti distribution in each part of the ingot was also extremely uniform as shown in FIGS. 4 and 5.

Next, two electron beam melted ingots of the Nb-50Ti alloy obtained above were brought together and used as consumable electrodes, and then remelted in a vacuum arc furnace with a mold l-゛inner diameter: 100-. By doing so, diameter: 98mmφ, length: 245m
An ingot of x was manufactured.

Table 1 shows the composition values of each part of this Nb-Ti alloy ingot, and as is clear from Table 1, the obtained ingot has homogeneous composition and extremely few impurities. I understand that there is something.

Table 1 On the other hand, for comparison, a Tl plate and a Nb plate with a thickness of 5 mm were stacked together as shown in Figure 5 so that the weight ratio in the cross section was 1:1.
A consumable electrode with a diameter of 56 mm, whose outer circumference was plasma arc welded into a hoop shape, was melted in a vacuum arc furnace (mold diameter: 100 wφ).

A Nb-Ti alloy ingot having a diameter of 98FJφ and a length of 150+nm was obtained.

However, we investigated the remaining Nb dissolution in this ingot.

A large number of melts were detected, with the largest number remaining in the ingot, and it was also confirmed that the Ti distribution in each part of the ingot was segregated as shown in FIGS. 3 and 4. Also.

Traces of prior dissolution of the Ti portion are also evident in the electrode material, and Nb
The board part was also melted in an ``icicle-like'' manner, and there was evidence of chips falling off, and it is thought that these were the cause of the remaining melt.

Furthermore, when the above investigation was conducted on the ingot obtained by this comparative method after secondary vacuum arc melting using the ingot as a consumable electrode, residual Nb melt was found to remain.

<Overall Effects> As described above, according to the present invention, a homogeneous Nb-Ti alloy with no residual Nb phase or segregation and no impurity contamination can be melted into one layer under smooth workability. This brings about extremely useful effects industrially, such as making it possible to manufacture stably and at low cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a composite melting material used in the method of the present invention. FIG. 2 is a schematic diagram showing an example of the Nb-Ti alloy manufacturing method of the present invention. FIG. 3 is a diagram comparing Ti distribution conditions in the length direction of Nb-Ti alloy ingots obtained in Examples. FIG. 4 is a diagram comparing the Ti distribution from the skin to the center of the Nb-Ti alloy ingots obtained in Examples. FIG. 5 is a schematic diagram showing an example of a melted material used for conventional Nb-Ti alloy melting. FIG. 6 is a schematic diagram showing the previously proposed Nb-Ti alloy manufacturing method. FIG. 7 is a schematic diagram showing an example of a melted material formed by winding thin plates in multiple layers. In the drawings, 1...Ti hollow body, 2...Nb hollow body, 3...
...Ti bar material, 4...vacuum chamber. 5...Energy beam gun. 6...Energy beam. 7...Water-cooled copper mold, 8...Metal pool. 9...Nb-Ti alloy ingot, 10...Dummy, 1
1...Nb plate, 12...Ti plate. 13...Dissolved material 1 14...Ti round bar. 15...Nb pipe, 16...Shadow of energy beam caused by melted material. 17...Welding part. Applicant Sumitomo Metal Industries Co., Ltd. Agent Tomi 1) Kazuo and two others Figure 1 O Ti content (wt%) Ti content (wt%)

Claims (2)

[Claims] (1) When melting an alloy by the drip melting method using an energy beam or an arc as a heating source, a Nb hollow body is placed inside a Ti hollow body, and a Ti rod is further placed inside the Nb hollow body. A method for producing an Nb-Ti alloy, characterized in that a three-layer composite material consisting of the following is used as a melting material. (2) When melting an alloy by the drip melting method using an energy beam or an arc as a heating source, first a Nb hollow body is placed inside a Ti hollow body, and then a T
An Nb-Ti alloy characterized in that after obtaining an ingot using a three-layer composite material having an i-bar inside as a melting material, the obtained ingot is further melted again as a melting material. manufacturing method.