A Workability Criterion for the Transformed Adiabatic Shear Band Phenomena during Cold Heading of 1038 Steel

摘要

A criterion for predicting the workability limits for internal brittle failure was developed for cold-heading of 1038 steel. The criterion considers internal defects caused by the transformed adiabatic shear band (TASB) phenomena. The defect that develops is the formation of brittle martensite as a result of phase transformation due to the temperature rise inside the adiabatic shear band (ASB). In this work, the material is considered to have a TASB defect when the temperature inside the ASB exceeds the phase transformation temperature (AC3). The empirical formulas provided by Andrews [1] were used to determine transformation temperatures. In addition, microhardness testing and etching with 2 percent Nital and Le Pera etchants were performed on the sectioned specimens to locate and study the TASB. In order to simulate the cold heading process a drop weight compression test was used along with finite element analysis (implemented within ABAQUS/Explicit).