Technique for smelting ultra-pure TiNi shape memory alloy

Abstract

The invention relates to a method for ultra-pure smelting of a TiNi shape-memory alloy, in particular to an ultra-pure smelting process for the TiNi shape-memory alloy. Because TiNi shape memory alloy is a material that requires high compositional accuracy, a change of 0.1%at in the Ni content will cause a change in the phase transition temperature of 10-20 degrees, and the impurity content is controlled as follows: O<500ppm , N<30ppm, only in this way can it have good superelastic properties, and can achieve accurate phase transition temperature according to the composition.

Description

1. Technical field [0001] The invention belongs to the field of material metallurgy, and designs a method for ultra-pure smelting of TiNi shape memory alloys. Specifically, it is suitable for the process method of controlling accurate composition of TiNi shape memory alloy. 2. Background technology [0002] The shape memory effect of TiNi memory alloy is realized through martensitic phase transformation. Therefore, controlling the martensitic transformation temperature of the alloy is the key to producing this alloy. In TiNi memory alloy, the most sensitive elements to martensitic transformation temperature are C, N, O, and it is difficult to strictly control these elements in this alloy. [0003] Ti in TiNi alloy belongs to group IVB in the periodic table. It is a strong metallic element and is particularly active. It has a strong tendency to combine with non-metallic O, N, and C, which brings great benefits to the production of high-quality TiNi alloys. big difficulty. ...

AI Technical Summary

Problems solved by technology

[0015] However, the applicant found that although the oxygen content in the TiNi alloy can be partially reduced only by using the CaO crucible, the effect is still ideal, because although the CaO crucible can reduce the introduction of oxygen into the reaction system by itself, due to the extreme activity of Ti in the alloy, and The irreversibility of the compound formed by the reaction of oxygen and Ti cannot prevent the reaction of Ti with oxygen due to its own reasons during the reaction process, such as the inevitable decomposition of impurity oxygen and water vapor in the crucible, etc.

There are some reports in the prior art that use CaO crucibles for memory alloy smelting, but the applicant found that the process disclosed in the prior art is too general and ambiguous, and it is still difficult to obtain high performance in the actual smelting process only based on the described steps. The reason is that due to the intense reaction of TiNi alloy, in the smelting process of TiNi memory alloy, not only the selection of the crucible is also very important for the control of the smelting process

Although the above-mentioned technical scheme adopted in the prior art adopts the CAO crucible to intelligently control part of the gas content, it does not fully consider the special process of Ni and Ti reaction itself, so that it cannot effectively control the oxidation of TI caused by overheating; the present invention thus overcomes the The above-mentioned defects, after a large number of tests, analyzes and summaries, corresponding improvements have been made to the process, process steps, process conditions, etc., so that the smelting process can overcome the deficiencies of the above-mentioned documents, and better obtain high-performance TiNi memory alloys

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