In-Process Control of Residual Stress in Drawn Tubing

Abstract

Experimental work directed toward the development of means for in-process control of residual stress during tube drawing is described. Experiments were done on 304 and 321 stainless steels, Incoloy 800, and copper tubing. While classical tube reducing processes, such as mandrel and plug drawing and sinking were the main objective, limited data on the effects of reeling and rock-rolling were also included. The distribution of residual axial and hoop stresses across the wall was determined by a Sachs’ analysis. Tandem drawing, wherein a small reduction (∼2 percent) was taken in the second die, produced a drastic reduction of the residual stress levels. A tapered bearing exit-die was specially efficient in this respect. However, the method was inefficient in pure sinking which always left residual stresses of high magnitude.