I wish to model a system with a weld beag (TIG, without metal of contribution, with 316L).
Must I import a law of behavior? Does there exist a geometry standardized according to the parameters of welding?
Your question is a week old, so you may have found an answer elsewhere. Weld modelling can be very complex: depending on how detailed you model the physical processes, how much information you have, how accurate and on what size scale you want results. The SYSWELD program is written for the purpose of weld modelling, but again your model depends on what information you have and what tpye of results you want from it.
Weld modelling can be done in ABAQUS. I have done some myself, involving a thermal followed by a mechanical analysis. This involves thermal properties and parameters as a function of temperature (specific heat, conductivity, latent heat, radiation, heat input) and the same for mechanical properties as a function of temperature (elastic moduli, strain-hardening, annealing).
You really need to do some background reading to get an idea of what is involved. Try a Google search for 'weld modelling'.