α+β type titanium alloy wire and manufacturing method of α+β type titanium alloy wire

A manufacturing method of an α+β type titanium alloy wire being a method of manufacturing a α+β type titanium alloy wire, containing:

• in mass %,
• Al:
• 4.50 to 6.75%;
• Si:
• 0 to 0.50%;
• C:
• 0.080% or less;
• N:
• 0.050% or less;
• H:
• 0.016% or less;
• O:
• 0.25% or less;
• Mo:
• 0 to 5.5%;
• V:
• 0 to 4.50%;
• Nb:
• 0 to 3.0%;
• Fe:
• 0 to 2.10%;
• Cr:
• 0 to less than 0.25%;
• Ni:
• 0 to less than 0.15%;
• Mn:
• 0 to less than 0.25%;
• and
• the balance being Ti and impurities,
• the contents of Al, Mo, V, Nb, Fe, Cr, Ni, and Mn satisfying the following equation (1), wherein:
• a diameter of the wire is 15 mm ore less:
• an average aspect ratio of an α crystal grain is 1.0 to 3.0;
• a maximum crystal grain diameter of the α crystal grain is 30.0 μm or less;
• an average crystal grain diameter of the α crystal grain is 1.0 μm to 15.0 μm;
• and
• an area ratio of the α crystal gram, out of the α crystal grains in a cross section orthogonal to a long axis direction of the wire, regarding which an inclination angle in a c-axis direction of a hexagonal close packing crystal that forms the α crystal grain relative to the long axis direction is within a range of 15° to 40°, is 5% or less,
• −4.0≤[Mo]0.67 [V]+0.28 [Nb]+2.9 [Fe]+1.6 [Cr]+1.1 [Ni]+1.6 [Mn]−[Al]≤2.0 (1)
• in the above equation (1), notation of [symbol of element] represents a content (mass %) of a corresponding symbol of element, and a symbol of element which is not contained, is substituted by 0,
• the method comprising:
• first performing working of one time or two times or more on a titanium alloy material comprising the chemical components in the α+β type titanium alloy wire at a working temperature in a range of 0° C. to 500° C., in which a reduction of area per one time of working is set to 10 to 50%, and a total reduction of area is set to 50% or more;
• and
• second performing, with respect to the titanium alloy material after being subjected to the first performing, final heat treatment in which a heat treatment temperature T is set to fall within a range of 700° C. to 950° C., and a heat treatment time t is set to a heat treatment time satisfying the following equation (2),
• 21000<(T+273.15)×(log10(t)+20)<24000 (2)
• Here, in the above equation (2), T indicates the heat treatment temperature (° C.) in the second performing, and t indicates the heat treatment time (hr) in the second performing.