Nippon Steel Corporation

Casio Computer Co., Ltd.

Hideto Seto

Kazuhiro Takahashi

Koji Mitsuda

Genki Tsukamoto

Junichi Sato

Hidenori Takebe

Naoki Okamura

Joe Ito

A watch part containing a titanium alloy, the titanium alloy, in mass %, includes: Al: 1.0 to 3.5%; Fe: 0.1 to 0.4%; O: 0.00 to 0.15%; C: 0.00 to 0.10%; Sn: 0.00 to 0.20%; Si: 0.00 to 0.15%; and the balance: Ti and impurities, an average grain diameter of &#x3b1; phase crystal grains is 15.0 &#x3bc;m or less, an average aspect ratio of the &#x3b1; phase crystal grains is 1.0 or more and 3.0 or less, and a coefficient of variation of a number density of &#x3b2;-phase crystal grains distributed in the &#x3b1; phase is 0.30 or less.

Watch part

A titanium alloy part is characterized in that it includes, by mass %: Al: 1.0 to 8.0%; Fe: 0.10 to 0.40%; O: 0.00 to 0.30%; C: 0.00 to 0.10%; Sn: 0.00 to 0.20%; Si: 0.00 to 0.15%; and the balance: Ti and impurities, in which: an average grain diameter of &#x3b1;-phase crystal grains is 15.0 &#x3bc;m or less; an average aspect ratio of the &#x3b1;-phase crystal grains is 1.0 or more and 3.0 or less; and a coefficient of variation of a number density of &#x3b2;-phase crystal grains distributed in the &#x3b1; phase is 0.30 or less.

Titanium alloy part

To provide a titanium sheet excellent in formability and a method for manufacturing the same. A titanium sheet, wherein, when a carbon concentration of a base material is C(mass %) and a carbon concentration at a depth d &#x3bc;m from a surface is C(mass %), the depth d (carbon concentrated layer thickness) satisfying C/C&#x3e;1.5 is 1.0 &#x3bc;m or more and less than 10.0 &#x3bc;m or less, wherein a Vickers hardness HVat a load of 0.245 N in the surface is 200 or more, a Vickers hardness HVat a load of 0.49 N in the surface is lower than HV, and a difference between HVand HVis 30 or more, wherein a Vickers hardness HVat a load of 9.8 N in the surface is 150 or less, and wherein an average interval between cracks generated in the surface when a strain of 25% is given in a rolling direction in a bulging forming process is less than 50 &#x3bc;m and a depth thereof is 1 &#x3bc;m or more and less than 10 &#x3bc;m.

Titanium sheet and method for manufacturing the same

A titanium plate is provided in which a Vickers hardness Hvat a load of 0.245 N at a surface is 150 or less, and an average length of the profile elements RSm is 80 &#x3bc;m or less and a maximum height Rz is less than 1.5 &#x3bc;m, RSm and Rz being as defined in JIS B 0601: 2013. The titanium plate has good surface deformability.

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Hideto Seto