Occurrence Of Solidification Cracking Research Articles

Formation Mechanism and Control of Solidification Cracking in Laser-Welded Joints of Steel/Copper Dissimilar Metals

The solidification cracking behavior in laser welds of steel/copper dissimilar metals was systematically investigated. T2 copper and SUS304 stainless steel were used in the study. The results showed that the occurrence of solidification cracking in welds was the synergistic effect of ε phase liquation, inclusions and composition segregation. During the welding process, the liquation of grain boundaries substantially reduced the cohesion between adjacent grains, as well as the resistance for intergranular crack propagation. The composition segregation inside the grains could induce lattice distortion, thus reducing the plastic deformation capacity of the material itself and concurrently increasing the susceptibility to cracks. In addition, an effective solution for inhibiting solidification cracking was proposed by using an oscillating laser, and the inhibition mechanism was further discussed. Laser oscillating welding significantly promoted grain refinement, solute diffusion and the formation of uniformly distributed ε-Cu precipitated phases in welds. It can improve the intergranular bonding, reduce the susceptibility to solidification cracking and increase the resistance to plastic deformation. The tensile strength of joints using laser oscillating welding is 251 MPa, 35.7% more than 185 MPa using laser welding. Meanwhile, the strain of joints using laser oscillating welding is 3.69, a 96% increase compared to 1.88 using laser welding.

Process Parameter Optimization Framework for the Selective Laser Melting of Hastelloy X Alloy Considering Defects and Solidification Crack Occurrence

Recent years have witnessed increasing demand for selective laser melting (SLM) in practical applications; however, determining the appropriate process parameter range remains challenging. In this study, a framework was developed to determine the appropriate process parameter range considering the occurrence of defects and cracks by conducting a single-track test and thermal elastoplastic analysis. Keyholing, balling, and the residual unmelted regions were considered defects. The occurrence of solidification cracking, which is predominant in the SLM of solution-strengthened Ni-based alloys, was considered. Using the proposed framework, we could fabricate a part with largely no defects or cracks, except for the edges, under the determined optimal process parameters.

耐熱マグネシウム合金ダイカスト凝固割れ発生の予測

This study was performed to develop the predicting method of solidification cracking during die-casting of tentative heat-resistant magnesium alloys and commercial ones such as Mg–Al–Ca–RE, Mg–Al–Ca–Mn, Mg–Al–Ca–Sn, AE44 and AZ91D. Both high temperature ductility curve and strain near cracking area of each alloy at liquidus-solidus temperature range were required in order to predict the solidification cracking. High temperature strain was calculated by a casting simulation code,“ProCAST”. High temperature ductility curve of each alloy was measured by the experiment. Comparing with this high temperature strain and ductility at liquidus and solidus temperature range, it was confirmed whether solidification cracking occurs or not in each magnesium alloy. Finally, this predicting method was verified using simple shape of die-casting. Consequently, occurrence of solidification cracking in the simple shape of die-casting in all magnesium alloys used can be predicted by this predicting method.

EXPERIMENTAL RESEARCH AND NUMERICAL SIMULATION OF SOLIDIFICATION CRACK DURING LASER WELDING OF RING STRUCTURE

The combined influence of metallurgical and mechanical factors on welding solidifica- tion cracking structure in laser welded ring was investigated by using both experiments and numerical simulation. It is found that solidification cracking is directly related with the overlap weld part. The microstructure was observed under OM, and the grain size was measured by EBSD observation. The grains in overlap weld part are much bigger than those in single weld part, which results in falling of ductility during solidification. The temperature and strain changes of weld metal in solidification temperature range were calculated out by using 3D finite element analysis. Compared with the single weld part, the strain rate with temperature drop is lower in overlap weld part, i.e., the mechanical driving force to solidification cracking is weaker in overlap weld part. Consequently, it is concluded that the low ductility caused by coarse grain results in the occurrence of solidification cracking in overlap weld part during laser welding of ring structure. This research not only helps to understand the mechanism of solidification cracking in more details, but also guides the study on prediction of solidification cracking occurrence.

Prediction of occurrence of solidification cracking in weld metal

With the developments made in recent years in digital technology, optical technology, image analysis and the like, it has become possible to carry out in situ observations of welding solidification...

溶接凝固割れ発生の予測

溶接凝固割れ発生の予測

Model for solidification cracking in low alloy steel weld metals

Data on the occurrence of solidification cracking in low alloy steel welds have been analysed using a classification neural network based on a Bayesian framework. It has thereby been possible to express quantitatively the effect of variables such as the chemical composition, welding conditions, and weld geometry, on the tendency for solidification cracking during solidification. The ability of the network to express the relationship in a suitably non-linear form is shown to be vital in reproducing known experimental phenomena.

Model for solidification cracking in low alloy steel weld metals

Data on the occurrence of solidification cracking in low alloy steel welds have been analysed using a classification neural network based on a Bayesian framework. It has thereby been possible to express quantitatively the effect of variables such as the chemical composition, welding conditions, and weld geometry, on the tendency for solidification cracking during solidification. The ability of the network to express the relationship in a suitably non-linear form is shown to be vital in reproducing known experimental phenomena.