JPH0331777B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is a nickel for precision casting with excellent castability.
It relates to titanium alloys, and in particular is used to easily obtain shape memory materials, superelastic materials, vibration-proofing materials, sound-absorbing materials, sliding members, implant materials, and dental materials made of nickel-titanium alloys with complex shapes. . [Prior art] Ni− containing Ni and Ti in an atomic ratio of about 1:1
Although Ti alloys are intermetallic compounds, they can be plastically worked, undergo martensitic transformation at around room temperature, and are attracting attention because of the unique phenomena associated with this transformation. In particular, the shape memory effect and superelastic effect based on martensitic transformation have been actively researched from both basic and applied perspectives, and some of them have been put into practical use. Furthermore, the low-temperature phase (martensite phase) below the martensitic transformation temperature is known to have a very large vibration absorption ability, and is expected to be used as a vibration-proofing material and a sound-absorbing material. In addition, this alloy does not exhibit any unusual phenomena in the high-temperature phase above the martensitic transformation temperature, but exhibits excellent strength, corrosion resistance, and wear resistance. ) to Cr,
Substitution with one or more of Fe, Co, Mo, V, and Pd lowers the martensitic transformation below the practical temperature and further improves its performance, and is used in sliding parts. There is. Furthermore, the above Ni-Ti alloy or a part of Ni, Ti (7at
% or less) with one or more of Cr, Fe, Co, Mo, V, and Pd have good compatibility with living organisms, so they can be implanted into living organisms to function. It is known to be suitable for implant materials or dental materials. [Problem to be solved by the invention] However, all of the above Ni-Ti alloys have very poor machinability, and it takes a great deal of skill and time to manufacture products with complex shapes, especially in areas where drilling is difficult. , which causes increased manufacturing costs. Powder metallurgy and precision casting are known methods for molding such alloys with poor machinability, but they have not been put to practical use because of various problems in producing Ni-Ti alloys. For example, when molded using normal powder metallurgy, a uniform single-phase Ni-Ti alloy cannot be obtained, and the unique properties mentioned above are insufficient.
Ni-Ti alloys have extremely poor flowability, making it impossible to use precision casting. [Means for Solving the Problems] In view of this, the present invention has succeeded in improving the fluidity of the molten metal without impairing the unique characteristics as a result of various studies, and has developed a nickel-titanium alloy for precision casting. It is something. That is, the present invention is a binary alloy of Ni-Ti,
This is a nickel-titanium alloy for precision casting, which is composed of 45 to 55 at% Ni and 45 to 55 at% Ti, and has an oxygen content of 0.08 wt% or less. [Function] As a result of various studies on the flowability of alloys consisting of Ni and Ti, the present invention found that the flowability increases as the amount of oxygen content decreases. In alloys, the amount of oxygen contained
By setting it to 0.08wt% or less, Ni45 to 55at%,
The Ni-Ti alloy, which is composed of 45 to 55 at% Ti, is a nickel-titanium alloy for precision casting that improves flowability without sacrificing the above-mentioned unique properties, and can be directly formed into complex shapes by precision casting. That's what I got. The reason for limiting the content of Ni and Ti as described above is to obtain known properties such as shape memory effect, superelastic effect, strength, and corrosion resistance. The reason why the oxygen content is limited as mentioned above is that if it exceeds 0.08 wt%, the castability will be poor. In addition, even in Ni-Ti alloys in which part of the Ni and/or Ti content (7at% or less) is replaced with one or more of Cr, Fe, Co, Mo, V, and Pd, the content By controlling the oxygen content to 0.08 wt% or less, the fluidity can be improved without impairing the unique properties mentioned above. [Example] Examples of the alloy of the present invention will be described below. Example 1 10 kg of titanium sponge was melted by electron beam melting, and while being melted into a water-cooled copper mold with a diameter of 25 mm, a round bar with a diameter of 24.5 mm was obtained by rotating and lowering the mold. After this was externally milled, it was hot rolled to a thickness of 3 mm.
It was made into a board. Further, 10 kg of electrolytic nickel was melted and cast in the same manner, and then hot rolled into a plate with a thickness of 2 mm. Width 10mm, length by shearing both the above board materials
The scale was removed by pickling as a 300 mm strip. At this time, particular attention was paid to the uniformity of the width of the strips, that is, the parallelism. Using both strips obtained in this way, Ti50.0at
%, Ni50.0 at%, inserted into a crucible made from high-purity graphite for electrodes, melted in a high-frequency vacuum melting furnace, and cast into an iron mold with a diameter of 40 mm and a height of 50 mm. At this time, the degree of vacuum in the high-frequency vacuum melting furnace was adjusted to 10 ^-1 to ^{10 -4} Torr using a variable leak valve.
Melting and casting was performed once at each vacuum level to create Ni-Ti alloy ingots with different oxygen contents. Six 10 mm x 10 mm x 10 mm square blocks were cut out from the Ni-Ti alloy ingots with different oxygen contents by cutting with a grindstone, one block was analyzed for oxygen, and five blocks were used as samples for the castability test. The castability test was performed by cutting sheet wax (#30 manufactured by GC Co., Ltd.) into a 20 mm x 20 mm square and forming it into a mold using the lost wax method using a phosphate-based investment material (Cerabest manufactured by GC Co., Ltd.). This was done by casting using an argon caster manufactured by Co., Ltd. The inside of the argon caster was replaced with argon gas several times by operating a switch just before casting. In this way, as shown in Fig. 1, an ingot with a runner 2 under the riser 1 and a cast plate 3 corresponding to sheet wax is made, and the area of the plate 3 is 20 mm x 20 mm. Castability was determined by subtracting the area of the defective portion 4 from a 20 mm square. The results are shown in Table 1. In Table 1, the x mark indicates that the molten metal did not pass through the runner 2.

〔Effect of the invention〕

As described above, the alloy of the present invention enables precision casting without impairing the shape memory effect, superelastic effect, vibration absorption ability, sliding properties, compatibility with living organisms, etc. of the Ni-Ti alloy. , it brings about remarkable industrial effects such as facilitating the provision of complex members having the above-mentioned unique performance.

[Brief explanation of the drawing]

FIG. 1 is a front view of a cast Ni-Ti alloy in a castability test, and FIG. 2 is a side sectional view showing a method of casting a pipe connecting fitting using the alloy of the present invention. 1... Riser, 2... Runway, 3... Cast plate, 4... Defect, 5... Mold, 6... Casting material, 7... Mold, 8... Cylindrical space.

Claims (1)

[Claims] 1 Ni-Ti binary alloy, containing 45 to 55 at% Ni,
Consisting of Ti45~55at% and oxygen content
A nickel-titanium alloy for precision casting characterized by a content of 0.08wt% or less.