ABSTRACT

The steel grade considered in this study, F22V, has some critical and particular features regarding the final chemical analysis and the procedure to obtain it in an electric steel shop. The main application of this material is dedicated to pressure vessels in Oil field. For this reason the steel is exposed to high temperature for a long time. The production of this steel grade are prone to some defect typologies. ABS in collaboration whit CSM performed a study of ingot cooling process. The CSM realised a FEM model integrating an austenite decomposition metallurgical model, to take in account the solid phase transformation. After the validation, the model is used to study ingot cooling process. The study results show that the variation of volume and rheological behaviour of the material in the transition austenite-bainite caused high tension. The high tension of the austenite bainite transition crosses all the length of the ingot. In the macro segregation and porosity zone these tensions should create a fracture. Decreasing the percentage of the steel which transforms in bainite it is possible to reduce the tensions. A slower cooling has to be applied or an ingot reheating has to be carried out to reduce the austenite – bainite allotropic transformation.