Distortion Analysis in the Manufacturing of Cold-Drawn and Induction-Hardened Components

In this investigation, a design of experiments analysis of distortion for a typical manufacturing process involving pre-straightening, cold drawing, and induction hardening of AISI 1045 cylindrical steel bars was carried out. A careful characterization of the material, including residual stress states and geometrical changes, was done for the different manufacturing steps. In order to identify effects and correlations on distortion behavior, the investigated variables included the batch influence, the combined drawing process itself with two different drawing angles and two different polishing and straightening (P.S.) angles, a stress relief treatment which was applied to a part of the samples, and finally induction hardening with two different surface hardening depths. Main and statistically significant effects on the distortion of the induction-hardened samples were found to be in this order: first, the interaction between the drawing angle and batch, then the interaction between drawing angles, and finally drawing angle and induction hardened layer. It was also found that the distortion potentials are transmitted from the drawing process to further manufacturing steps and, consequently, from one production site to the next.