Modeling Solid-State Phase Transformations of 13Cr-4Ni Steels in Welding Heat-Affected Zone

Abstract

Fatigue damage is commonly encountered by operators of Francis type hydraulic turbine runners made of 13Cr-4Ni soft martensitic stainless steel. These large and complex welded casting assemblies are subjected to fatigue crack initiation and growth in the vicinity of their welded regions. It is well known that fatigue behavior is influenced by residual stresses and the microstructure. By including solid-state phase transformation models in welding simulations, phase distribution can be evaluated along with their respective volumetric change and their effect on residual stresses. Thus, it enables the assessment of welding process on fatigue crack behavior by numerical methods. This paper focuses on modeling solid-state phase transformations of 13Cr-4Ni soft martensitic stainless steel, used for manufacturing hydraulic turbine runners, occurring upon welding. It proposes to determine the material parameters of the models for both the austenitic and the martensitic transformation by nonisothermal dilatometry tests. The experiments are conducted in a quenching dilatometer with applied thermal conditions as experienced in the heat-affected zone of homogeneous welds. The activation energy and the kinetic parameters of the austenitic transformation from fully martensitic state are measured from the experimental results. The martensitic transformation modeling from a fully austenitic domain is also presented.

Simulation of the Behaviour Laws in the Thermal Affected Zones of the 13Cr-4Ni Martensitic Stainless Steel

“…The numerical solution is compared with the experimental data found by J.B. Levesque [5]. The evolution of the experimental curve is given in Figure 8.…”

“…The chemical composition of the 13Cr-4Ni stainless steel, known by its industrial name S41500, is given in Table 2 extracted from [5]. Modern Mechanical Engineering…”

“…with: In this study, the values of these above cited parameters are given in Table 3 like presenting by J.B. Levesque [5].…”

“…To validate the austenitic phase proportion g γ , the results obtained will be compared with the experimental values found by J.B. Levesque [5].…”

“…The values found by the simulation are compared with the experimental data [5] (Figure 10). So, the correctness of the results is found.…”