welding speeds, and should therefore occur more easily during laser welding. Both the solidification behavior and thermal strain change depend on the welding speed, and therefore, the critical strain for solidification cracking must be measured to clarify the factors influencing the solidification cracking susceptibility. However, the critical strain required for solidification cracking under high welding speed conditions has not yet been determined. The aim of this work was to investigate the effect of welding speed on the solidification cracking susceptibility of Type 310S stainless steel. U-type hot cracking tests were conducted using a developed in-situ observation technique with high-speed camera, and the critical strain for solidification cracking was evaluated quantitatively. The critical strain for solidification crack initiation decreased with increasing welding speed. The distribution of residual liquid depended on the microstructure, and the morphological distribution of the residual liquid changed from a droplet to a thin film with increasing welding speed. The transition in distribution morphology of the residual liquid implies the material is susceptible to solidification cracking. Keywords (IIW-Thesaurus) Hot cracking . Solidification cracking . Laser weldingA technique to prevent solidification cracking is required in the welding process, because stainless steels, nickelbased superalloys and dissimilar welded joints are susceptible to this phenomenon. Solidification cracking becomes a more serious problem when different materials and an increased welding speed are used for the high functionalization of the mechanical structure and to increase productivity [1]. Optimization of the welding joint design and development of the welding material have been attempted to prevent the occurrence of solidification cracks. However, a definite prevention technique for solidification cracking has not yet been developed. Thus, it is necessary to investigate both the solidification phenomenon and distribution of loaded strain during welding in detail, and to elucidate the mechanism of the solidification cracking phenomenon.It is well known that solidification cracking occurs between the liquidus and solidus temperatures by the strain loaded on the residual liquid from solidification shrinkage and constraint forces. The critical stain for initiating cracks is affected by factors such as the solidification morphology, corresponding to chemical composition, segregation of sulfur and phosphorus, strain rate, welding condition and so on [1][2][3][4][5]. To date, the solidification cracking susceptibility has been evaluated using a high temperature ductility curve, which is the relationship between the critical strain and temperature for solidification crack initiation. Thus, the critical strains and solidification crack initiation temperature must be measured quantitatively and precisely to understand in detail the solidification cracking phenomenon.Laser welding is an attractive welding processes, and is expected to ...

No abstract

Experimental investigation of the foam stabilizing factors that influence aluminum foam fabrication is crucial to improve the foaming process. Solid particles contribute to an increase of the viscosity of the liquid phase and overall foam stability. Foam stability depends on the liquid type, wettability and the shape of solid particles. Even though a poor wettable particle contributes effectively to enhance liquid viscosity, the particle leads to the collapse of the foam cell due to the poor energy balance at the interface between the solid and the liquid. In our study, the effect of particles was investigated using both water solutions and an aluminum melts. We show that not only the relative viscosity, but also the physical properties of solid particles need consideration during aluminum foam production.

No abstract

The aim of this paper is to develop the high efficiency and high quality fillet welding technique using the combination of hot wire system and Laser welding. The melting of filler wire depends on wire current and there is an adequate vale of the current in each wire feeding speed. The leg length increases by the addition of filler wire compared with the non filler welding. The length is also larger than the laser irradiated area. This must be caused by the laser beam reflection on the molten pool surface. The results reveal that the parameter optimization leads to the stationary welding phenomenon. Besides, obtained welds have attractive properties, namely low heat input and low dilution.