The microstructure, texture evolution and plasticity anisotropy of 30SiMn2MoVA high strength alloy steel tube processed by cold radial forging

Abstract

Cold radial forging is an efficient and high-precision process for producing rotary parts such as axles and gun barrels, etc. 30SiMn2MoVA high strength alloy steel is a kind of fine pearlite steel usually used for moulds and barrels. This work focused on the effect of the cold radial forging on the microstructure, texture evolution and plasticity anisotropy of forged steel tube under different forging reductions. The results suggest that most banded structures that are parallel to the axial direction are developed by the radial forging process. The grains are elongated and refined after forging. The increase of dislocation density with the increase of deformation is the reason for grain refinement. Refined grains and high dislocation lead to high strength. Meanwhile, anisotropy was obvious and was exacerbated by the growth of the forging deformation. The circumferential strength and elongation are inferior to the axial. With the increasing of forging ratios, the α-fiber texture is well developed. The relationship between the volume fraction of texture and plastic strain was built. It can predict the volume fractions of the main texture components in the cold radial forged 30SiMn2MoVA steel tube. The Taylor factors of the main orientations were calculated. The {111}<011>(γ-fiber), {110}<110>, {111}<110>(α-fiber), {114}<110>, {112}<110> and {223}<110> texture components help to enhance the axial yield strength. Comparing the ratio of the axial average Taylor factor and the circumferential average Taylor factor with the yield strength ratio, it is found that yield strength anisotropy is not well predicted only taking into account the crystal texture. The effect of banded structures on the strength should also be considered.