Numerical Simulation of Hot Cracking Tests

One of the main nuclear materials is the austenitic stainless steels, which have good ductility and toughness, high thermal expansion coefficients and a thermal conductivity lower than that of martensitic or ferritic steels. The 316L(N) austenitic stainless steel (X2CrNiMo17-12-2 with controlled nitrogen) is evaluated for structures such as the vessels, which are steel enclosures surrounding the reactor core and its assemblies, in fourth generation nuclear systems. The RCC-MR code, which is used as a frame of reference in the manufacture of SFR (Sodium Fast Reactor concept), recommends the use of austenoferritic filler material for the welding of 316L(N) steel. These recommendations derive from past experience of working with fast neutron reactors (Phenix and Superphenix). In order to guarantee long-term properties at high temperatures, an austenoferritic and an austenitic filler metals are evaluated as filler metals. However, these materials are susceptible to hot cracking. Therefore, a study is conducted to ensure their weldability. The purpose of this work is to evaluate the susceptibility to hot cracking of the studied materials and to present a methodology applied to define a criterion called “laboratory” for each material and its transfer to a structure test. The relative susceptibility to hot cracking of these materials was evaluated using four tests: the Varestraint, the Gleeble, the trapezoid and the skew tests. Numerical simulation using Cast3M code and Sidolo software of these four tests were investigated in order to survey behavior laws of each studied material and solidification cracking thermomechanical criteria intrinsic to the materials. Some test and simulation results as well as hot cracking susceptibility ranking are presented and the transferability to real component welds of hot cracking criteria is discussed.