Effect of Q value on geometric tolerance, roughness and texture evolution of GH4145 alloy tubes

Abstract

The Q value represents the ratio of the relative reduction in the wall thickness to the relative reduction in the outer diameter during cold-rolling of a tube. The influence of the Q value on the geometric tolerance, roughness, and plastic deformation was determined through laser scanning confocal microscopy, white light interferometry, and electron backscattering diffraction. In this study, nine tube blanks with the same specifications were divided equally into three groups. The outer diameter of each group was reduced by 1 mm, 2 mm, and 3 mm, and the wall thickness of each tube blank was reduced by different amounts. Thus, each group contained one tube with Q values of 0.76, 1.52, and 2.28. Compared with the corresponding blank, the eccentricity, ovality, and roughness of the tube were reduced with a Q value of 0.76. The ovality and roughness of the tube were decreased and the eccentricity was increased with a Q value of 2.28. The eccentricity, ovality, and roughness of the tube were increased with a Q value of 1.52. In terms of texture evolution, with an increase in Q, the < 101 > //radial-direction (RD), < 111 > //axial-direction (AD), and < 101 > //tangential-direction (TD) fibre textures first increased and then decreased. The texture strength was the highest in tubes with a Q value of 1.52, mainly concentrated in the Goss, {011}< 122 > , and copper texture. In the cold-rolling process, the plastic deformation of the tube with a Q value of 0.76 was uniform throughout the section; the plastic deformation of the tube with a Q value of 1.52 near the inner wall was greater; the plastic deformation of the tube with a Q value of 2.28 near the outer wall was even greater. In summary, in the cold-rolling process, the Q value affects the location of plastic deformation and the evolution of grain orientation, which affects the flow of materials and ultimately affects the geometric tolerance and roughness of the tube. Thus, a tube with good surface quality and high-dimensional precision can be obtained by controlling the Q value.