Influences of die shape and calibration strokes on surface near residual stresses of rotary swaged steel tubes

Abstract

Abstract. Forming processes offer a great potential to make production more sustainable by including both the shaping of the geometry and the improvement of the material properties. Through a better understanding of the decisive influencing factors on the resulting material properties of the part, this potential can be particularly exploited and leads to the chance of shortening process chains by e.g. saving heat treatment steps. The part properties during rotary swaging can be improved by strain-induced residual stresses. Thereby, compressive residual stresses can increase the resistance to fatigue fracture, to crack propagation and to corrosion. However, rotary swaging of tubes can lead to undesirable residual tensile stresses at the surface with high fluctuations. Therefore, a better understanding of the rotary swaging process and the actual material flow is necessary. The aim is to realize compressive residual stresses with low fluctuations. Thereby, it is of interest to be able to set residual stresses independently of the desired workpiece geometry. In this paper, rotary swaging of E355 steel tubes (Ø20 mm x 3 mm) was carried out with two different process adaptions. These two adaptions are the number of calibration strokes and the die geometry. They show different influences on surface near residual stresses.