Investigation on formability of ribbed tube and its forming quality by MPCD process.

Ribbed tube is a thin-walled and shaped cladding tube, multi-pass cold drawing (MPCD) is considered to be one of the preferred manufacturing techniques for ribbed tube forming. However, unreasonable process design results in poor forming quality and the number of deformation passes increased in vain. The purpose of this paper is redesigning a reasonable MPCD process to obtain the defect-free ribbed tube and to investigate the surface quality and microstructural evolution of the formed tube comprehensively. The problems of the original MPCD are analyzed, the MPCD process is redesigned by theoretical calculation and the reasonable distribution of deformation degree. Furthermore, the material produces grain refinement due to the cumulative deformation, and lathy α′-martensite at intersections of shear bands and few carbide precipitation are generated. The surface roughness of tube and rib are 2.73 μm and 4.89 μm respectively, which indicates that the forming quality of the tube is good. [ABSTRACT FROM AUTHOR]