Estudio de los efectos de la temperatura de precalentamiento sobre la microestructura y propiedades mecánicas de aceros ASTM A36 Y ASTM 572 gr. 50 soldados mediante proceso SMAW

Abstract

The main objective of this research was to study the effect of preheating temperatures on the microstructure and mechanical properties of welded joints made of ASTM A36 and ASTM A572 Gr. 50 steel, welded using the SMAW process. Joints were made without preheating and with preheating temperatures of 115ºC, 300ºC and 500ºC. The electrode used was E6011. Preheat temperatures were monitored by a pyrometer. An electric induction oven with temperature control was used for preheating. Additionally, to heat the plates of larger dimensions, a LPG torch was used, with a protection plate so that the soot generated does not affect the final properties. Subsequently, metallographic, and mechanical tests were carried out to determine the properties of each joint. By means of a metallographic analysis of the samples, it is evidenced that, in the heat affected zone, microstructures such as acicular ferrite and Widmanstaten are formed with the presence of Bainite slats and as the preheating temperature increases, they decrease. After this, the Vickers microhardness test is carried out in each joint, which shows a decrease in microhardness values as the preheating temperature increases this in the Cordon and the HAZ. Regarding mechanical properties, the tensile test showed that by applying a preheating the tensile strength increases. While, through the Charpy impact test, it was evidenced that the impact resistance decreases while the preheating temperature increases. Finally, the results obtained are compared with the calculated grain size that is refined as the preheating temperature increases.