Effect of annealing temperature on the texture evolution and ovality of GH4145 alloy tubes with various numbers of rolling passes

Abstract

The ovality variation and texture evolution with annealing temperature of GH4145 alloy tubes that were cold rolled through 2 passes, 3 passes, and 6 passes (from ∅32 mm × 3 mm to ∅26 mm × 1 mm) were studied. The mechanism of ovality variation was determined by laser scanning confocal microscopy, electron backscattered diffraction, and X-ray diffraction. The best rolling process for GH4145 alloy tubes was identified: cold rolling through 3 passes, which resulted in an area reduction of approximately 24% per pass, followed by annealing at 920 °C for 30 min, via which the lowest ovality could be obtained. In terms of texture evolution, mainly S, copper, and brass textures were distributed in all cold-rolled tubes, and Goss texture was only observed in 2-pass tubes. With increasing annealing temperature, the texture strength first decreased and then increased, and the type of recrystallization texture was the same as that of cold-rolling texture, which was dominated by oriented nucleation. The higher residual stress in the cold rolling process resulted in higher ovality of the tube due to the higher energy storage. The release of residual stress during heat treatment reduced the ovality, while the enhancement of recrystallization texture led to a slight increase in ovality.