Study of impact strength of C-Mn-Si composition metal after wire-arc additive manufacturing (WAAM)

The results of study of impact strength of C-Mn-Si composition metal after wire-arc additive manufacturing (WAAM) are presented. It was established that destruction of the samples of such composition at the temperatures below tough-brittle transition occurs both via tough and brittle mechanisms. The samples manufactured in the direction along built-up welding are characterized by essentially lower impact strength comparing with those manu-factured in vertical direction of samples cutting. Impact strength of the samples made of 09G2SA standard steel is substantially lower than for C-Mn-Si composition metal which was obtained via additive technology. Fractographic analysis of fractures for C-Mn-Si compositions manufactured via additive technology using carbon dioxide and gas mixture displays tough pit destruction type. The samples with high impact strength are characterized by forming of cleavage facets after tough crack propagation to the sample middle, what is accompanied by significant widening opposite to a notch and narrowing under a notch. The samples with low impact strength are characterized by form-ing of brittle fracture directly under a notch without essential sample plastic deformation. It is shown that built-up welding with partial or complete recrystallization of rolls is required for forming of cold-resistant metal structure. In this case, order of rolls location, heat input and parameters of welding conditions make the direct effect on shape, geometrical dimensions, fusion penetration and number of rolls, as well as on size and morphology of the structural components, percent relation between cast and recrystallized microstructure of seam metal. The complex of these factors finally determines structural state and cold resistance of seam metal.