TITANIUM SHEET AND METHOD FOR PRODUCING THE SAME
A titanium sheet having a sheet thickness of 0.2 mm or less and including a hardened layer on a surface, the titanium sheet including a chemical composition containing, in mass percent: Fe: 0.001 to 0.08%; and O: 0.03 to 0.08%, wherein a grain size satisfies following Formulas (1) to (3), a thickness of the hardened layer is 0.1 to 2.0 μm. The titanium sheet has both a sufficient strength and an excellent workability. Formulas (1) to (3) are d ave ≥2.5 (1), t/d ave ≥3.0 (2), and t/d max —1.5 (3), where, in Formulas (1) to (3), t denotes the sheet thickness (μm), d ave denotes an average grain size (μm), and d max denotes a maximum grain size (μm).
1 . A titanium sheet having a sheet thickness of 0.2 mm or less and including a hardened layer on a surface, the titanium sheet having a chemical composition containing, in mass percent:
Fe: 0.001 to 0.08%; and
O: 0.03 to 0.08%, wherein
a grain size satisfies following Formulas (1) to (3),
a thickness of the hardened layer is 0.1 to 2.0 μm, and
a maximum height Rz is 3.0 μm or less:
d ave ≥2.5 (1)
t/d ave ≥3.0 (2)
t/d max ≥1.5 (3)
where, in Formulas (1) to (3), t denotes the sheet thickness (μm), d ave denotes an average grain size (μm), and dmax denotes a maximum grain size (μm).
2 . The titanium sheet according to claim 1 , wherein a number ratio of grains each having a grain size of t/2 or more is 15% or less.
3 . A method for producing the titanium sheet according to claim 1 having steps of cold rolling and annealing repeated on a titanium product a plurality of times, wherein the titanium product having an average grain size adjusted to 2.0 μm or less is finish cold rolled with a rolling ratio of 50 to 80% and thereafter finish annealed in an inert atmosphere at 570 to 750° C.
4 . A method for producing the titanium sheet according to claim 2 having steps of cold rolling and annealing repeated on a titanium product a plurality of times, wherein the titanium product having an average grain size adjusted to 2.0 μm or less is finish cold rolled with a rolling ratio of 50 to 80% and thereafter finish annealed in an inert atmosphere at 570 to 750° C.