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In this study, the influence of the welding speed, the arc power, and the laser focal position on the solidification crack formation for partial penetration laser hybrid–welded thick-walled plates was investigated.
The solidification cracking in the weld root is a result of interaction between metallurgical and geometrical and thermomechanical factors.
Experimentally, a direct correlation between the welding speed and the crack number was observed. That is by reducing the welding velocity, the crack number was decreased. The focal position shows also a significant influence on the crack number. By focusing the laser on the specimen surface, the crack number has been significantly diminished.
The wire feed speed showed a very slight influence on the crack formation. That is due to the large distance between the critical region for cracking and the arc region.
The numerical model shows a high stress concentration in the weld root for both components (vertical and transversal).
Numerically, the reduced welding speed showed a strong impact on stress, as the model demonstrated a lower stress amount by decreasing the welding speed.
The metallurgical factors, such as the assumed accumulation of the low-melting eutectics in the weld root, should be a contribution for solidification cracking, where the tensile stress is acting.
A novel approach for the reconstruction of an equivalent volumetric heat source from a known weld pool shape is proposed. It is based on previously obtained weld pool geometries from a steady-state thermo-fluid dynamics simulation. Hereby, the weld pool dimensions are obtained under consideration of the most crucial physical phenomena, such as phase transformations, thermo-capillary convection, natural convection, and temperature-dependent material properties. The algorithm provides a time and calibration efficient way for the reproduction of the weld pool shape by local Lamé curves. By adjusting their parameters, the identification of the finite elements located within the weld pool is enabled. The heat input due to the equivalent heat source is assured by replacing the detected nodes’ temperature by the melting temperature. The model offers variable parameters making it flexible and adaptable for a wide range of workpiece thicknesses and materials and allows for the investigation of transient thermal effects, e.g., the cooling stage of the workpiece. The calculation times remain acceptably short especially when compared to a fully coupled process simulation. The computational results are in good agreement with performed complete-penetration laser beam welding experiments.