Análise comparativa em soldas com e sem pré-aquecimento no aço carbono SAE 1045

Abstract

The usage of the welding process in industries is extremely important for joining structural elements that in mostly cases are made by medium carbon steels such as SAE 1045 steel. The temperature effects in welding may result in cracks, porosity and hardened pearlitic microstructure that cause heterogeneities on mechanical properties in the weld region. To get around this problem, preheating with oxyacetylene will be carried out up to the calculated temperature of 250ºC to then carry out MIG/MAG welding and a coated electrode arc welding that allow a slow cooling rate avoiding the formation of perlite. For analysis of the results, some mechanical tests such as penetrating liquids, hardness and metallographic analysis provide an adequate analysis. Comparing the results of the welding process using the preheating technique with the results of no preheating, a lower incidence of discontinuities was obtained in the analysis of penetrating liquids. In the Rockwell hardness comparison, there was a considerable reduction in hardness in the weld bead and HAZ (Heat-Affected Zone) regions, causing a more ductile structure. The applied metallography allowed to verify a better penetration in the weld when heated, in addition to spawning a larger HAZ, resulting in more uniform properties in the study material due to the lower rate of heat extraction.