TECHNICAL FIELD

The present invention relates to a titanium alloy material excellent in high-temperature strength and forming workability that is used suitably for exhaust system components and so on, for example.

BACKGROUND ART

Stainless steel excellent in corrosion resistance, strength, workability, and so on has been used for a composing member of an exhaust device in a four-wheel vehicle and a two-wheel vehicle (to be referred to as automobiles, or the like, below) conventionally, but in recent years, titanium materials that are lighter than stainless steel, have high strength, and are also excellent in corrosion resistance are being used. For example, for the exhaust device of the two-wheel vehicle, a titanium material defined in JIS type 2 (what is called, industrial pure titanium) has been used. Further, recently, in place of the titanium material defined in JIS type 2, a titanium alloy material having higher heat resistance has been used. Further, in recent years, mufflers equipped with catalysts used at high temperatures have also been used to remove harmful components of exhaust gas.

The exhaust device of automobiles, and so on is provided with an exhaust manifold and an exhaust pipe. The exhaust pipe is composed of divided several parts to accommodate a catalyst device with a catalyst mounted or applied and a muffler in the middle of the pipe. In this description, the entire part from the exhaust manifold to the exhaust pipe and an exhaust port is referred to as an “exhaust device.” Further, components composing the exhaust device are referred to as “exhaust system components.” Combustion gas emitted from an engine of an automobile, or the like is collected by the exhaust manifold to be exhausted from the exhaust port at the rear of the vehicle through the exhaust pipe. The exhaust device is exposed to high-temperature exhaust gas, so that the titanium material forming the exhaust device is required to have strength and corrosion resistance in a high-temperature range. Further, these components of the exhaust device are complicated in shape, so that forming workability at room temperature is also required.

Patent Document 1 describes a heat-resistant titanium alloy material for exhaust system components that is excellent in oxidation resistance and contains Cu, Sn, Si, and O, the total content of Cu and Sn being 1.4 to 2.7%, and the balance composed of Ti and inevitable impurities. Further, in Patent Document 1, a titanium alloy containing the above-described components is hot rolled and further is cold rolled to be annealed at 750 to 830° C., and thereby the heat-resistant titanium alloy material for exhaust system components is manufactured.

Further, Patent Document 2 describes a heat-resistant titanium alloy plate excellent in cold workability that contains Cu,0, and Fe and the balance composed of Ti and 0.3% or less of impurities. In Patent Document 2, a titanium alloy containing the above-described components is subjected to steps of hot rolling, hot-rolled sheet annealing, cold rolling, intermediate annealing, final annealing, and so on, and the final annealing is performed at a temperature of 600 to 650° C., and thereby the heat-resistant titanium alloy plate excellent in cold workability is manufactured.

Further, Patent Document 3 describes a heat-resistant titanium alloy material for exhaust system components that is excellent in oxidation resistance and formability and contains Cu, Si, and O and the balance composed of Ti and inevitable impurities. In Patent Document 3, a titanium alloy containing the above-described components is subjected to steps of hot rolling, hot-rolled sheet annealing, cold rolling, final annealing, and so on, and the final annealing is performed at a temperature of 630 to 700° C., and thereby the heat-resistant titanium alloy material for exhaust system components excellent in oxidation resistance and workability is manufactured.

However, even with the titanium alloy materials described in Patent Document 1 to Patent Document 3, compatibility between strength in a high-temperature zone and forming workability at room temperature was not sufficient.

PRIOR ART DOCUMENT

Patent Document

[Patent Document 1] Japanese Patent No. 4819200

[Patent Document 2] Japanese Laid-open Patent Publication No. 2005-298970

[Patent Document 3] Japanese Laid-open Patent Publication No. 2009-68026

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

The present invention has been made in consideration of the above-described circumstances, and has an object to provide a titanium alloy material excellent in high-temperature strength and forming workability at room temperature and a manufacturing method thereof.

Means for Solving the Problems

The gist of the present invention is as follows.

[1]

A titanium alloy material contains: in mass %,

Cu: 0.7% to 1.4%;

Sn: 0.5% to 1.5%;

Si: 0.10% to 0.45%;

Nb: 0.05% to 0.50%;

Fe: 0.001% to 0.08%;

O: 0.001% to 0.08%; and

the balance composed of Ti and impurities, in which

in a structure, an area fraction of an α phase is 96.0% or more and an area fraction of an intermetallic compound is 1.0% or more, and

an average crystal grain size of the α phase is 10 μm or more and 100 μm or less and an average grain size of the intermetallic compound is 0.1 to 3.0 μm.

[2]

The titanium alloy material according to [1], further contains: one or both of in mass %,

Bi: 0.1 to 2.0%; and

Ge: 0.1 to 1.5%, in which

a total content of one or both of Bi and Ge is less than 3.0%.

[3]

The titanium alloy material according to [1], in which

fracture elongation at 25° C. is 25.0% or more, 0.2% proof stress at 25° C. is 340 MPa or less, and a tensile strength at 700° C. is 60 MPa or more.

Effect of the Invention

According to the present invention, it is possible to provide a titanium alloy material excellent in high-temperature strength and forming workability at room temperature. This titanium alloy material is excellent also in oxidation resistance and appearance after forming.

