Beta type titanium alloy and manufacturing method thereof

Abstract

The present invention provides a β type titanium alloy characterized by consisting of, by mass %, V: 15 to 25%, Al: 2.5 to 5%, Sn: 0.5 to 4%, O (Oxygen): not more than 0.20%, H: not more than 0.03%, Fe: not more than 0.40%, C: not more than 0.05% and N: not more than 0.02%, and the balance Ti and impurities. The present invention also provides a method of manufacturing a β type titanium alloy characterized by comprising the following steps (a) to (c): (a) Preparing a β type titanium alloy consisting of, by mass %, V: 15 to 25%, Al: 2.5 to 5%, Sn: 0.5 to 4%, O (Oxygen): not more than 0.20%, H: not more than 0.03%, Fe: not more than 0.40%, C: not more than 0.05% and N: not more than 0.02%, and the balance Ti and impurities. (b) Pickling the B type titanium alloy in an aqueous solution including 3 to 40 mass % of HF, and (c) Further pickling the B type titanium alloy in an aqueous solution including 3 to 6 mass % of HF and 5 to 20 mass % of HNO3.

Description

TECHNICAL FIELD [0001] The present invention relates to a β type titanium alloy that has excellent deformability, in a solution-treated state, with a low deformation resistance during cold working, and also has a high strength after aging, and a method of manufacturing the alloy. BACKGROUND ART [0002] Titanium alloys generally have high strength at low density with the higher specific strength (strength / density) among the practical metallic materials and are excellent in corrosion resistance. Therefore, titanium alloys are used for aircraft and automobile parts, medical equipments, glass frames, golf clubs and tableware. With this extension, further improvement in property and reduction in cost are strongly demanded for the titanium alloys. [0003] The titanium alloys are roughly classified to α type, β type and α+β type: α type has a hexagonal close packed (hcp) microstructure, β type has a body centered cubic (bcc) microstructure, and α+β type has both of hcp and bcc microstructure...

AI Technical Summary

Benefits of technology

[0008] The first objective of the present invention is to provide a titanium alloy capable of easily and stably realizing the characteristics of excellent cold workability in a solution-treated state and high strength after an aging treatment.

[0009] The present invention also has a second objective, which is to provide a pickling method for reducing the H (hydrogen) content during manufacturing of the titanium alloy.

[0010] The β type titanium alloy has a metastable β phase that is a high temperature phase of titanium, which is quenched and kept at room temperature. The stabilizing elements for β phase are V, Mo, Nb, Ta, Cr, Fe, Mn, and the like. Among them, V and Mo are particularly given as relatively inexpensive elements, which are capable of minimizing the hardening, by solution treatment with a minimized bad effect on workability, while providing high strength by aging. However, Mo is easy to segregate because of its high melting point, and the addition of Mo leads to an increase in deformation resistance during hot or cold working. Therefore, the Ti-20V-4Al-1Sn alloy, in addition to selecting not Mo but V, is proposed to add Al in order to increase the strength in aging treatment, and also add Sn in order to suppress solid solution hardening.

Problems solved by technology

In the process of preparing this alloy many times, it was found that this alloy has the problem with cold workability and age strengthen ability which cannot be always stably obtained.

However, no remarkable influence was observed on a characteristic change by the variation of the main elements of this alloy, although its effect appears close to the limit of the content ranges.

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