JPS60138028A - Production of nickel-titanium alloy - Google Patents

Abstract

PURPOSE:To prevent intrusion of a crucible material into an Ni-Ti alloy as a shape memory alloy and hydrogen storage alloy and the deterioration in the characteristic thereof in the stage of producing said alloy by constituting the crucible for melting of a specific material. CONSTITUTION:An Ni49Ti51 alloy which is an alloy having a shape memory characteristic and an Ni36Ti64 alloy or the like having a hydrogen storage characteristic are melted and produced by using sponge Ti and granular Ni respectively having high purity as a raw material. The material which contacts with the molten metal in a crucible, etc. to be used in this case is constituted of at least one kind among metallic elements such as Ca, Rb, Sr, Y, Cs, Ba, La, Eu, Tl, Pb, Bi, Th, etc. of which the interatomic distance between the nearest atoms in the crystal is >=3.4Angstrom or the oxide and nitride thereof. The alloy having the high-purity compsn. is obtd. without intrusion of the crucible material into the Ni-Ti alloy and the deterioration in the shape memory characteristic and hydrogen storage characteristic is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing a nickel-titanium alloy used for shape memory alloys, hydrogen storage alloys, and the like.

Structures of conventional examples and their problems Recently, nickel-titanium alloys have been attracting attention as shape memory alloys, hydrogen storage alloys, and the like. Generally, this alloy is prepared by preparing appropriate amounts of nickel metal and titanium metal,
It is obtained by cooling and solidifying after mixing and dissolving. However, this alloy and various metals or metal oxides (S
(including iO) is very reactive, and in particular during melting in the above manufacturing process, it reacts with the crucible material holding this molten metal, causing the elements constituting the crucible material to diffuse into the nickel-titanium alloy, or vice versa. Nickel and titanium enter the crucible, changing the crucible material and causing its destruction. For these reasons, until now there has been no suitable crucible material for producing nickel-titanium alloys. recently,
Carbon crucibles are beginning to be widely used as melting crucibles for this alloy, but it is necessary to melt at the lowest possible temperature, and even with these considerations, more than a few hundred ppm of carbon will be mixed into the nickel-titanium alloy. . Further, the amount of carbon mixed in increases as the dissolution time increases.

Inclusion of such a crucible material such as carbon in a nickel-titanium alloy lowers the mechanical properties of the alloy or has a complicated effect on the shape memory properties, making control of the properties extremely complicated. In addition, the intrusion of carbon into these alloys also affects the hydrogen storage properties, and as the amount of invading elements increases, the amount of hydrogen storage decreases. As described above,
Intrusion of foreign atoms into a nickel-titanium alloy has a significant effect on the properties of the alloy, and it is necessary to eliminate these intrusion atoms as much as possible.

Purpose of the Invention The present invention aims to reduce the intrusion of foreign atoms into the nickel-titanium alloy during melting as described above, and to obtain stable mechanical properties, shape memory properties, and hydrogen storage properties. The purpose is to supply titanium alloys.

Structure of the Invention In order to achieve the above object, in a method for producing a nickel-based titanium alloy in which nickel and titanium metals are mixed and melted and solidified, the molten metal holder that comes into contact with the molten metal during melting contains calcium, rubidium, strontium, yttrium, cesium, and barium. , lanthanum, europium, thallium, lead, hismuth, thorium, etc., a nickel-base titanium alloy containing a metal element whose nearest atom-1 distance in the crystal is 3.4 A or more, or at least one of its oxides or nitrides. This is the manufacturing method.

When melting nickel and titanium metals, if a metal element or its oxide whose nearest atomic distance in the crystal of the element is 3.4A or more is used as a molten metal holding material, other metal atoms that enter the molten metal during melting will be prevented. Very few, I
It was below Qppm. On the other hand, when the oxide was used as a molten metal holding material, the amount of metal intrusion into the nickel-titanium alloy was 10 ppm or less, and the oxygen content of the alloy did not increase. The nitride showed similar behavior to that of oxygen. Therefore, the molten metal holding material became extremely stable and could be reused several times.

On the other hand, the distance between the nearest atoms in the crystal of the above element is 3
．． When a metal element or its oxide having a concentration of less than 4A is used as a molten metal holding material, several hundred ppm or more of the element invades the nickel-titanium alloy, and the nickel-titanium alloy also invades the molten metal holding material.

For this reason, the shape memory properties of the nickel-titanium alloy, for example, change significantly, making it extremely difficult to control the temperature at which transformation to martensite or austenite begins. Furthermore, the basic characteristics of hydrogen storage properties will change, making it difficult to provide a stable material supply. In addition, the material of the molten metal holding material changes significantly and cracks and other destructive phenomena occur.

It hardly stands up to reuse.

Description of examples Examples will be described below.

Example 1. Sponge titanium (99.7%) and granules --"
/Kel (911, 11%) was dissolved in the crucible. The melting was carried out under argon, and after melting the metal was cast into copper molds. In this way the old 4
An alloy of BTi51 (at%: atomic percent) was produced. This old-Ti alloy contained almost no Tb at 2 ppm. The oxygen content was 350 ppm. Moreover, this alloy showed stable shape memory effect when processed appropriately. This amount differs little from dissolution in a non-oxide crucible, such as a carbon crucible. There was no change in appearance of the crucible used for melting, and the crucible could withstand use even if the same melting was performed again.

Example 2. Sponge titanium (9L?%) and granular nickel (88°9%) are heated and melted in a rubidium metal crucible. The melting was carried out in a vacuum of 10 m+aHg, and after melting the metal was cast into copper molds. In this way, an alloy of old 3sTi64 (at%) was produced.

This Ni-Ti alloy contained almost no Rb at 1 ppm. Furthermore, the oxygen and nitrogen contents were extremely low at 400 PPm and 300 pPIl, respectively. Furthermore, an amorphous alloy produced by a liquid quenching method using this alloy as a master alloy exhibited stable hydrogen storage properties. The crucible did not change in appearance and could be reused as long as it did not come into contact with water molecules.

Example 3. Sponge titanium (911,7%), granular nickel (11
9.9%) is heated and dissolved. The melting was carried out in a 1 atm argon atmosphere, and after melting the metal was cast into copper molds. In this way, an alloy of Ni51 Ti48 (at%) was produced. Th is 2 ppm in this old-Ti alloy.
was hardly included. The oxygen and nitrogen contents were extremely low at 350 PPI and 6.350 ppH, respectively. Moreover, this alloy showed stable shape memory effect when processed appropriately. The crucible could be reused without any change in appearance.

The drawings show Embodiment 1, Embodiment 3 (A), and Embodiment 2 (A) of the present invention.
It is a graph showing the influence of the melting time of the molten metal holding material contained in the old-Ti alloy produced by melting (B) in the conventionally used carbon crucible material (C) (NioTis+). The molten metal temperature was 1400°C in both cases. It can be seen that the preparation according to the invention contains almost no molten metal retaining material.

Although simple examples have been described in the Examples above, similar results can be expected with other materials such as calcium, rubidium, strontium, yttrium, cesium, barium, lanthanum, europium, thallium, lead, bismuth, and thorium.

Effects of the Invention According to the present invention, when producing a nickel-titanium alloy, impurities that enter the alloy from a molten metal holding material such as a crucible are extremely reduced, and the alloy has stable characteristics as a shape memory alloy or a hydrogen storage alloy. supply became possible. In addition, the crucible (molten metal holding material) is now extremely free from nickel and titanium contamination, making it possible to reuse it.

This can be expected to reduce the manufacturing cost of nickel-titanium alloys.

The present invention can also be used as a nozzle material (molten metal holding material) for holding molten metal in the so-called liquid quenching method, in which molten metal is rapidly cooled with a rotating metal cooling body, and can be used as a nozzle material (molten metal holding material) for holding molten metal in the crucible described in the present invention. Similar effects can be expected.

[Brief explanation of the drawing]

The drawing is a graph showing the content of nickel-titanium alloys according to the melting time of the molten metal holding materials of the present invention and conventional examples. Agent Patent Attorney Mr. Oshima

Claims (1)

[Claims] In the manufacturing method of nickel-titanium alloy in which nickel and titanium metals are mixed and melted and solidified, the molten metal holder that comes into contact with the molten metal during melting contains calcium, rubidium, strontium, yttrium, cesium, barium, lanthanum, europium, thallium, lead, The distance between the nearest atoms in crystals such as bismuth and thorium is 3.4
A method for producing a nickel-titanium alloy, characterized in that it contains at least one metal element having a grade A or higher, or its oxide or nitride.