Prediction of Proper Temperatures for the Hot Stamping Process Based on the Kinetics Models

Abstract

Nowadays, the application of kinetics models for predicting microstructures of steels subjected to thermomechanical treatments has increased to minimize direct experimentation, which is costly and time consuming. In the current work, the final microstructures of AISI 4140 steel sheets after the hot stamping process were predicted using the Kirkaldy and Li kinetics models combined with new thermodynamically based models in order for the determination of the appropriate process temperatures. In this way, the effect of deformation during hot stamping on the Ae 3 , Acm, and Ae 1 temperatures was considered, and then the equilibrium volume fractions of phases at different temperatures were calculated. Moreover, the ferrite transformation rate equations of the Kirkaldy and Li models were modified by a term proposed by Å kerström to consider the influence of plastic deformation. Results showed that the modified Kirkaldy model is satisfactory for the determination of appropriate austenitization temperatures for the hot stamping process of AISI 4140 steel sheets because of agreeable microstructure predictions in comparison with the experimental observations.

Common Defect Analysis for Large Section Special Steel Forging

“…GCr15SiMn [8]. In a word, Mn and Cr segregation was the key cause of the carbides and the cracks, besides, internal stress of the forging during cooling was another reletive factor.…”