In this paper, the effects of the deposition speed and thermal cycles in gas-metal arc-welding (GMAW) additive manufacturing on the quality of as-built 308L stainless steel thin walls were investigated. The results exhibit that the deposition speed and thermal cycles play a crucial role in the quality of produced parts. An increase in deposition speed results in an improvement in the surface waviness. The surface waviness (Sa) decreases from 286 to 138 µm as the deposition speed increases from 0.2 to 0.4 m/min. On the other hand, the growth of microstructures in the walls fabricated with different deposition speeds shows a similar trend. The microstructure of as-built 308L-stainless-steel walls consists of dominant columnar/equiaxed dendrites of austenite and small amount of ferrite remaining in grain boundaries. The deposition speed mainly influences the grain size in microstructures. In the middle part of the walls, an augmentation in the deposition speed leads to a decrease of the secondary dendrite arm spacing, which results in an enhancement in mechanical properties of the walls. The microhardness and ultimate tensile strength increase from 153 ± 7.16 to 164 ± 8.96 HV0.1 and from 483 ± 4.24 to 518 ± 2.83 MPa, respectively, when the deposition speed increases from 0.2 to 0.4 m/min.
Wire arc additive manufacturing (WAAM) is nowadays gaining much attention from both the academic and industrial sectors for the manufacture of medium and large dimension metal parts because of its high deposition rate and low costs of equipment investment. In the literature, WAAM has been extensively investigated in terms of the shape and dimension accuracy of built parts. However, limited research has focused on the effects of welding parameters on the microstructural characteristics of parts manufactured by this process. In this paper, the effects of welding current in the WAAM process on the shape and the microstructure formation of built thin-walled low-carbon steel components were studied. For this purpose, the thin-walled low-carbon steel samples were built layer-by-layer on the substrates by using an industrial gas metal arc welding robot with different levels of welding current. The shape, microstructures and mechanical properties of built samples were then analyzed. The obtained results show that the welding current plays an important role in the shape stability, but does not significantly influence on the microstructure formation of built thin-walled samples. The increase of the welding current only leads to coarser grain size and resulting in decreasing the hardness of built materials in each zone of the built sample. The mechanical properties (hardness and tensile properties) of the WAAM-built thin-walled low-carbon steel parts are also comparable to those of wrought low-carbon steel, and to be adequate with real applications.
This paper aims to investigate the fabrication of high strength low alloy (HSLA) steels by wire and arc-based directed energy deposition (WADED). Firstly, the relationship between the process variables (including the travel speed-V, the current-C, and the voltage-U) and the geometrical characteristics of weld beads (including the bead height (BH), bead width (BW), and melting pool length (MPL)) was investigated. Secondly, the optimal process variables were identified using the desirability approach. The results indicate that voltage-U has the highest impact on BW and MPL, meanwhile the travel speed-V is the most impacting factor on BH. The optimal variables for the WADED process of HSAL steels are V = 0.3 m/min, C = 160 A, and U = 19 V. The component fabricated with the optimal variables is fully dense without spatters and defects, confirming the efficiency of the WADED process for HSLA steels.
Аннотация: в данной статье представлен результат расчета и проектирования платформы движения для симулятора пролета с использованием механизма Hexapod и других структурных элементов большого и престижного производи теля Hexapod в мире, такого как Rexroth. Кинематика поведения Hexapod исследуется с применением программного обеспечения MATLAB с входными условиями, которые являются результатами решения обратной кинематики. Исследование показало, что результаты расчета и проектирования согласуются с симуляцией при обследовании кинематики Hexapod. Таким образом, этот результат может быть применен к новому проектированию и производству.
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