Through Process Modelling of Rolling and Controlled Cooling of TRIP Assisted Bainitic Steel Rods and Prediction of the Retained Austenite in Products

Roman Kuziak,Valeriy Pidvysots'Kyy,Maciej Pietrzyk,Hans Roelofs,Zofia Kania,Monika Pernach

doi:10.4028/www.scientific.net/msf.892.23

Abstract

Simulation of the rolling and controlled cooling sequence for bainitic steel rods was the general objective of the paper. The main focus was put on exploring possibility of prediction of the retained austenite occurrence in TRIP assisted bainitic steels. Existing discrete phase transformation models require long computing times and their application to optimization of industrial processes is limited. Therefore, a model based on the modified JMAK equation was proposed. The occurrence of the retained austenite was predicted by carbon distribution calculations in the austenite during bainite transformation. This model was implemented into the FE software for simulation of cooling of rods. The model was verified by comparison of results with the physical simulations during rolling in the pilot mill and during cooling. The first part of the paper contains thermal-mechanical-microstructural simulations of rod hot rolling process. The objective of this part was to determine temperature and grain size distribution at the rod cross section at the beginning of phase transformations. FE simulations of the cooling were performed next. Correlation between cooling parameters and the volume fraction of the retained austenite in rod was determined.

Highlights

Due to a wide range of mechanical properties, bainitic steels are good candidates for many applications, for example in automobile and power generating industries, as well as in the production of armoured plates with outstanding ballistic properties [1,2]
Simulation of the whole manufacturing cycle composed of hot rolling and controlled cooling was performed and selected results are presented
It is seen that reasonably good agreement between calculations and measurements was obtained and that the model predicts properly heat generated due to bainitic transformation

Summary

Introduction

Due to a wide range of mechanical properties, bainitic steels are good candidates for many applications, for example in automobile and power generating industries, as well as in the production of armoured plates with outstanding ballistic properties [1,2]. The objective of this paper was to investigate a selected bainitic steel behaviour during hot rolling. The emphasis was put on application of numerical modelling to predict microstructure and properties of products. The efficient and reliable application of modern models combined with iterative optimization techniques is strongly dependent on the correctness of material’s behaviour description. Prediction of microstructure and products properties became an inseparable part of simulations and these parameters are often used in objective functions in process optimization. The main objective of the present paper was exploring possibilities of efficient prediction of products microstructure by simulations of the

Objectives

Results

Conclusion