Estudo de diferentes estratégias de resfriamento de paredes de alumínio fabricadas por manufatura aditiva a arco elétrico

Abstract

Additive manufacturing has been gaining ground in the manufacturing process scenario. The reasons are low production time, reduced financial costs and high versatility in building complex geometries, making product performance the focus. Among its variants, electric arc welding is a technique of material deposition by layers using traditional welding processes already consolidated. The CMT deposition technique, derived from the MIG / MAG (Metal Inert Gas/ Metal Active Gas) processes, is a highly productive and financially viable system with large focus on the production of complex geometry elements. The overheating on the surface of components made by metallic deposition may be responsible for the appearance of residual stresses, degradation of mechanical properties, geometric deviation and decrease of productivity. In order to reduce this overheating, three strategies to cool aluminum walls built by CMT were planned and executed in this work for later analyzes of mechanical properties, geometric and porosity. The strategies are natural to air without water, cooling the support with water and cooling by immersion in water. The whole process counted on the deposition of 28 layers of 300mm each. The temperature field was monitored by thermal camera and thermocouples. The thermal results clearly showed the high temperatures and low cooling rates of the walls made without water. Geometrically the immersion technique showed higher height and regularity, as well as a larger effective area of material which results in possible financial benefits. Tensile tests showed that conditions without water and with cooling only the support tend to have greater ductility in the horizontal directions of the test specimens (in the longitudinal direction of material deposition). The immersion condition decreased the anisotropy of the specimens. A new method to evaluate the deformation of the test specimens was developed, it is a software image analysis that relates a circle drawn at the beginning of the test with its final configuration at the moment of rupture. The results were consistent and slightly different from the displacement method analysis. The porosity of immersed walls did not change in relation to the others and the hardness of the walls was on average very similar. In general, improvements were observed regarding the use of immersion in water, so many other analyzes could be made based on the methodologies and results obtained.