JPS6254565A - Production of nickel-titanium alloy wire - Google Patents

Abstract

PURPOSE:To obtain an Ni-Ti alloy wire having a uniform compsn. by forming a molten metal subjected to electron beam melting or electron beam plasma melting to a long-sized ingot by a water cooled mold pulling down method then subjecting the ingot to hot drawing. CONSTITUTION:The raw material of the Ni-Ti alloy having >=45 deg.C transformation initiation temp. to be used as a shape memory alloy is subjected to the electron beam melting or electron beam plasma melting and thereafter the long-sized ingot having >=4 aspect ratio is formed by the water-cooled mold pulling up method. The ingot is subjected to the conditioning of the casting surface as necessary in the stage for hot drawing and direct rolling is repeated immediately thereafter, by which the ingot is subjected to hot swaging and drawing. The working includes a stage for butt joining. The Ni-Ti alloy wire having the uniform compsn. is thus produced.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a nickel-based material used as a shape memory alloy wire.
The present invention relates to a method for manufacturing titanium-based alloy wire.

[Technical background of the invention and its problems 1 Shape memory alloys have been developed in recent years as they are expected to have great applications in industrial, dental, and medical applications.
A typical example is a nickel-titanium alloy.

Conventionally, this nickel-titanium alloy wire rod is produced by casting molten metal by high-frequency induction melting (VIM) or vacuum arc remelting (MAR), forging and hot rolling, and then hot swaging. It was manufactured by repeating cold drawing, processing and annealing.

However, since the specific gravity and melting point of the raw materials nickel and titanium are significantly different from each other, the conventional methods described above have various restrictions in order to form an ingot in which the molten metal is uniformly mixed in the mold. Ta. In other words, if we try to increase the unit size f+1 of the ingot in order to improve the economic efficiency of processing, the uniformity of the composition of each metal component will decrease, and the aspect ratio of the ingot will also decrease to 2.
．． 5 to 3.3 is the limit, and if it exceeds that, there is a problem that the composition of the metal component becomes non-uniform near the ends of the ingot.

In particular, in the case of nickel-titanium alloys that have a transformation start temperature (Ms point) of 45°C or lower and in which the nickel component accounts for 55.5% or more of the total, forging is difficult and processing is time-consuming, resulting in manufacturing costs. This resulted in high costs.

[Objective of the Invention 1] The present invention was made in order to solve the above-mentioned conventional problems, and it is an object of the present invention to provide a method for manufacturing a nickel-titanium alloy wire rod that simplifies the manufacturing process and has a uniform composition. With the goal.

(Summary of the Invention) That is, the method for producing a nickel-titanium alloy wire rod of the present invention involves forming a molten metal by electron beam melting or electron beam plasma melting into a long ingot by a water-cooled mold drawing method, and then hot wire drawing. It is characterized by applying.

According to the method of the present invention, the metal raw material is melted with an electron beam or electron beam-plasma, and an ingot is formed using a water-cooled mold drawing method, so that the aspect ratio (ratio of ingot length/ingot diameter) is 4 or more. Usually 4 to 15 ingots are obtained, and the ingot diameter is 80 mm or less, usually 30 to 80 mm, and 19 ingots are obtained.

In addition, in the hot wire drawing process, after the casting surface of the ingot 1- is corrected as necessary, direct rolling is repeated, and hot swaging and drawing are performed.

In the handling process, hot to warm drawing is performed until several tens of percent of the final finished size is processed, and if necessary, the wire is finally cold drawn to form a wire having a diameter of, for example, 0.3 ml.

Furthermore, during the hot wire drawing process, preferably a diameter of 3 to 8 mm.
It is preferable to butt weld the wire at the wire stage and remove the molten metal (deburring) so that it can be processed into a long length, making it easier to handle and having excellent redness.

[Embodiments of the invention] Next, the present invention will be explained by examples.

Example A metal raw material consisting of 55.5 wt% Ni and 44.5 wt% Ti was made into an ingot with a diameter of 50 mm and a length of 650 mm by electron beam melting and water-cooled mold pulling method.

Next! ! After slightly modifying 1111, it immediately became 700~
It was directly rolled at 800°C to obtain a wire rod with a diameter of 8+ nm, and then hot swaged at 700-750°C.

In the middle, three of these wires were connected when the diameter was 6 mm, and the respective contacts were butt-joined under the condition of 1000Δ/w+i, and then deburred. After further hot swaging processing until the diameter becomes 1 mm, 400 to 500
Warm drawing was performed at 0.degree. C. to obtain a wire rod with a diameter of 1 mm, and finally cold drawing was performed to obtain a wire rod with a diameter of 0.3 mm. The area reduction rate during the above process is approximately 25% in hot swaging processing.
In warm drawing, it was about 20-30%.

On the other hand, as a comparative example, a nickel-titanium alloy wire was manufactured using the following conventional method.

The same metal raw material as in the example was melted by high frequency induction and poured into a mold to form an ingot with a diameter of 100 mm and a thickness of 330 mm. After peeling this ingot (removing surface oxides), it was hot forged into a round bar with a diameter of 80 mm, and then hot rolled and hot swaged to a diameter of 4 mm.
It was made into a wire rod. Next, cold drawing and annealing were repeated to finally obtain a wire rod with a diameter of 0.5 mm. Note that the area reduction rate in this cold drawing process was about 20%.

Comparing the method of the present invention based on the ft1j for manufacturing nickel-titanium alloy wire obtained by the above method, it is found that the conventional method has 100, while the method of the present invention has ft1j of 38.
It was reduced to

[Effects of the Invention] As explained above, according to the method of the present invention, an ingot having a uniform composition and a large aspect ratio can be obtained, thereby facilitating the subsequent wire drawing process. Also, since the casting surface is good, there is almost no need for cutting. Furthermore, by butt-joining during hot processing, long lengths can be processed, making handling easier and reducing the number of drawing steps compared to conventional methods. Because of the various advantages described above, it is possible to produce a nickel-roditane alloy wire rod that is cheaper and more excellent than conventional ones.

Claims (4)

[Claims] (1) Electron beam melting or electron beam-plasma melted molten metal is made into a long ingot by a water-cooled mold drawing method, and then hot wire drawing is performed to produce a nickel-titanium alloy wire rod. Production method. (2) The method for producing a nickel-titanium alloy wire according to claim 1, wherein the ingot has an aspect ratio of 4 or more. (3) Nickel-titanium alloy wire has a transformation start temperature of 4
The nickel according to claim 1, which has a temperature of 5°C or less.
A method for manufacturing titanium alloy wire. (4) The method for manufacturing a nickel-titanium alloy wire according to claim 1, wherein the hot wire drawing process includes a step of butt joining.