α + β type titanium alloy sheet for welded pipe, manufacturing method thereof, and α + β type titanium alloy welded pipe product

摘要

An α+β type titanium alloy sheet to be used for a welded pipe with a rolling direction of the sheet set to a circumference direction of the pipe includes: a composition containing, in mass %, 0.8 to 1.5% of Fe, 4.8 to 5.5% of Al, 0.020% or less of N, O in a range satisfying Q=0.14 to 0.38, and a balance being composed of Ti and impurities, in which a texture in a sheet plane direction has: a first group of grains oriented in a region where of a (0002) pole figure of an α phase having a hexagonal crystal structure, an angle θ being the angle between a c axis and a sheet normal direction is 0 to 30°; and a second group of grains oriented in a region where the angle θ is 80 to 100° and of the (0002) pole figure of the α phase, an angle φ being the angle between a projection line of the c axis onto the sheet plane and a sheet width direction is −10 to 10°, and a ratio of peak values of X-ray relative intensities from a basal plane in the α phase between the first group of grains and the second group of grains (the second group of grains/the first group of grains) is 5.0 or more.

主权项

1. An α+β titanium alloy sheet for welded pipe being an α+β type titanium alloy sheet to be used for a welded pipe with a rolling direction set to a circumference direction, the α+β type titanium alloy sheet for welded pipe comprising:
a composition containing, in mass %, 0.8 to 1.5% of Fe, 4.8 to 5.5% of Al, 0.020% or less of N, O in a range satisfying Q=0.14 to 0.38 shown in Expression (1) below, and a balance being composed of Ti and impurities, wherein a texture in a sheet plane direction has: a first group of grains oriented in a region where of a (0002) pole figure of an α phase having a hexagonal crystal structure, an angle θ being the angle between a c axis and a sheet normal direction is 0 to 30°; and a second group of grains oriented in a region where the angle θ is 80 to 100° and of the (0002) pole figure of the α phase, an angle φ being the angle between a projection line of the c axis onto the sheet plane and a sheet width direction is −10 to 10°, and a ratio of peak values of X-ray relative intensities from a basal plane in the α phase between the first group of grains and the second group of grains (the second group of grains/the first group of grains) is 5.0 or more,
Q=[O]+2.77×[N]  (1)wherein [O] represents the content of O [mass %] and [N] represents the content of N [mass %].