High-strength α+β type titanium alloy tube and production method therefor

A high strength α+β titanium alloy pipe having an outside diameter of at least 150 mm and a wall thickness of at least 6 mm, said α+β titanium alloy pipe characterized by having a welded seam running in the longitudinal direction of pipe at one location and by having a ratio of a minimum wall thickness to a maximum wall thickness of the portions excluding the weld zone of 0.95 to 0.99;

• wherein the high strength α+β titanium alloy contains by wt %,
• Al:
• 5.5 to 6.75% and V:
• 3.5 to 4.5%, and the balance of Ti and unavoidable impurities.

A method of production of a pipe having an outside diameter of at least 150 mm and a wall thickness of at least 6 mm, comprised of a high strength α+β titanium alloy, having a welded seam running in the longitudinal direction of pipe at one location, and having a ratio of a minimum wall thickness to a maximum wall thickness of the portions excluding the weld zone of 0.95 to 0.99, said method of production of a high strength α+β titanium alloy pipe characterized by cold forming a high strength α+β titanium alloy plate of a thickness of at least 6 mm into a tubular shape by a method comprising U-shape press bending into a U-shape and further O-shape pressing into an O-shape or a method comprising a press-bending method and welding together the abutted plate edges;

• wherein the high strength α+β titanium alloy contains by wt %,
• Al:
• 2.5 to 3.5% and V:
• 2.0 to 3.0% and the balance of Ti and unavoidable impurities;
• performing heat treatment comprising heating the welded pipe to at least the β-transus temperature and cooling at a cooling rate of at least air cooling, and further heating to 650° C. to 850° C., holding it there for at least 30 minutes, and cooling at a cooling rate of not more than air cooling.

A method of production of a pipe having an outside diameter of at least 150 mm and a wall thickness of at least 6 mm, comprised of a high strength α+β titanium alloy, having a welded seam running in the longitudinal direction of pipe at one location, and having a ratio of a minimum wall thickness to a maximum wall thickness of the portions excluding the weld zone of 0.95 to 0.99, said method of production of a high strength α+β titanium alloy pipe characterized by cold forming a high strength α+β titanium alloy plate of a thickness of at least 6 mm into a tubular shape by a method comprising U-shape press bending into a U-shape and further O-shape pressing into an O-shape or a method comprising a press-bending method and welding together the abutted plate edges;

• wherein the high strength α+β titanium alloy contains by wt %,
• Al:
• 2.5 to 3.5% and V:
• 2.0 to 3.0% and the balance of Ti and unavoidable impurities;
• performing a series of heat treatments comprising heating the welded pipe to at least the β-transus temperature and cooling at a cooling rate of at least air cooling, further heating to 650° C. to 850° C., holding it there for at least 30 minutes, and cooling at a cooling rate of not more than air cooling, and heating to 450 to 650° C., holding it there for at least 2 hours, and cooling at a cooling rate of not more than air cooling.

A method of production of a pipe having an outside diameter of at least 150 mm and a wall thickness of at least 6 mm, comprised of a high strength α+β titanium alloy, having a welded seam running in the longitudinal direction of pipe at one location, and having a ratio of a minimum wall thickness to a maximum wall thickness of the portions excluding the weld zone of 0.95 to 0.99, said method of production of a high strength α+β titanium alloy pipe characterized by cold forming a high strength α+β titanium alloy plate of a thickness of at least 6 mm into a tubular shape by a method comprising U-shape press bending into a U-shape and further O-shape pressing into an O-shape or a method comprising a press-bending method and welding together the abutted plate edges;

• wherein the high strength α+β titanium alloy contains by wt %,
• Al:
• 5.5 to 6.75% and V:
• 3.5 to 4.5% and the balance of Ti and unavoidable impurities;
• performing heat treatment comprising heating the welded pipe to at least the β-transus temperature and cooling at a cooling rate of at least air cooling, and further heating to 650° C. to 850° C., holding it there for at least 30 minutes, and cooling at a cooling rate of not more than air cooling.

A method of production of a pipe having an outside diameter of at least 150 mm and a wall thickness of at least 6 mm, comprised of a high strength α+β titanium alloy, having a welded seam running in the longitudinal direction of pipe at one location, and having a ratio of a minimum wall thickness to a maximum wall thickness of the portions excluding the weld zone of 0.95 to 0.99, said method of production of a high strength α+β titanium alloy pipe characterized by cold forming a high strength α+β titanium alloy plate of a thickness of at least 6 mm into a tubular shape by a method comprising U-shape press bending into a U-shape and further O-shape pressing into an O-shape or a method comprising a press-bending method and welding together the abutted plate edges;

• wherein the high strength α+β titanium alloy contains by wt %,
• Al:
• 5.5 to 6.75% and V:
• 3.5 to 4.5% and the balance of Ti and unavoidable impurities;
• performing a series of heat treatments comprising heating the welded pipe to at least the β-transus temperature and cooling at a cooling rate of at least air cooling, further heating to 650° C. to 850° C., holding it there for at least 30 minutes, and cooling at a cooling rate of not more than air cooling, and heating to 450 to 650° C., holding it there for at least 2 hours, and cooling at a cooling rate of not more than air cooling.