Cold rolling pass design and process based on controlling the distribution of material strain energy density

To address the problem of excessive grain boundaries and difficulty in eliminating defects on the inner surface of a pipe under a cold rolling pass, a method to control the distribution of material strain energy density is proposed, and a reasonable reduction in wall thickness is designed. An analysis model for inner surface defects was established using the inner wall adhesion value as the main criterion to quantitatively analyze the degree of defects on the pipe's inner surface. A systematic analysis of the rolling process of three different pass-opening shapes revealed that the opening shape dramatically affects the deformation and flow of the metal. During the rolling process, because of the unreasonable distribution of metal deformation caused by the existing pass design, the pipe is prone to high or concentrated stress, resulting in a low adhesion value for the inner wall and a greater degree of defects on the inner surface. Therefore, we propose a new opening shape and reasonably allocate the wall thickness reduction of the pipe to obtain a new pass. Numerical simulation reveals that, after rolling with the new pass, the inner wall adhesion value becomes relatively high, and the mechanics parameters have also been improved. The experimental results show that, under the new pass design, grain boundaries on the inner surface of the pipe are reduced and the smoothness is significantly improved, proving the feasibility of a cold rolling pass design based on controlling the distribution of material strain energy density.