Dynamic and static strain aging of steel during high-speed wire drawing

Abstract

This article presents the analytical studies results on the effect of high-speed drawing technological parameters on the temperature and deformation conditions of the wire. The temperature increase of the wire during drawing in a monolithic die is the sum of the strain heating and heating caused by sliding friction on the “die–metal” surface. In the course of the research, it was found that the strain heating of the wire does not exceed 50 °C. An increase in the drawing speed from 10 to 40 m/s leads to an increase in deformation heating by 2–4 °C. The heating of the wire due to contact sliding friction, depending on the technological parameters of drawing, can reach 320 °C, while the proportion of metal heated to a temperature above 150 °C does not exceed 5%. The degree of influence of the friction coefficient on the heating of the wire is shown. The average strain rates under the conditions of modern high-speed drawing reach 7000 s‒1. The research results demonstrated that the maximum strain rate during drawing in monolithic dies can exceed twice the average strain rate. Increasing the drawing speed from 10 to 40 m/s leads to an increase in the strain rate up to 5 times. In the course of the research it was established that there are absence of conditions for the occurrence of dynamic strain aging due to impurity atoms of carbon, nitrogen and oxygen was established. At the same time the temperature-rate parameters of high-speed wire drawing creates conditions for the beginning of dynamic deformation aging of steel in the presence of hydrogen atoms. Therefore, during heat treatment and pickling, it is necessary to exclude the hydrogenation of steel. It has been established that in order to exclude static deformation aging of steel during drawing, it is necessary to prevent heating of the wire above 180‒200 °C.