1. Introduction

The assembly and thermomechanical treatment operations that metal components undergo REP power plants, can generate stress fields in the materials that constitute them, so-called residual, which exist before any service charge. Metallurgical transformations and primarily, structural transformations are an important cause of these stress fields. because they modify behavior (by changing physical characteristics) and generate thermo-mechanical stresses within the materials which are subjected to them (latent heat, deformations due to differences in density of the various metallurgical phases).

These structural transformations are mainly due to the succession of heating (often beyond \(800°C\)) and a more or less rapid cooling of the parts during their manufacture. These thermal « cycles » can be wanted (case of heat treatments) or « undergone » (case of welding). In any case, they are very variable from one point in the room to another.

This document concerns the modeling of these structural transformations under heating and cooling. cooling for low-alloy steels at a scale that, while remaining « reasonable » for the metallurgist, or easily usable by the mechanic.

This type of modeling is feasible for all the elements (PLAN, AXIS, 3D) of the « PHENOMENE = » THERMIQUE «  » by using the CALC_META operator in « post-processing » of a thermal evolution calculation. The behavioral relationship dedicated to steel, in contrast to that dedicated to zircaloys, to be used under the operator’s COMPORTEMENT keyword is the relationship « RELATION =” ACIER “``. For the definition of the metallurgical behavior of steel, order information DEFI_TRC and the META_ACIER factor keyword under the command DEFI_MATERIAU is needed. Finally, the definition of the initial metallurgical state is possible using the command CREA_CHAMP, under the ETAT_INIT factor keyword of the CALC_META operator. Metallurgy calculation is necessary to carry out mechanical calculations that take into account mechanical consequences of these metallurgical phenomena [Modélisation élasto(visco)plastique prenant en compte des transformations métallurgiques].

The models presented (for heating and cooling) are formulated within the framework of the relationships of behavior with internal variables (or memory variables), and allow simple identification and fast based on experimental diagrams. The choice of variables and the forms of laws selected trends are given and the description of the implementation of the models (method identification number) is also presented.

Finally, the hardness calculation model is presented, which can, if necessary, complete the calculations. metallurgical.

Notes:

• The basic metallurgical concepts necessary to understand the general problem and the approach adopted are gathered in [bia1] _ and [bib2] _ where we will also find a study bibliographical overview of the problem.

• This document is taken from [bib3] _ and [bib4] _ where a more detailed overview of models and some validation elements. More comprehensive validation elements can also be found in [bib5] _ for the cooling model and in [bib14] _ for the hardness model.