Soldabilidade do aço USISAC350 na construção metálica

Abstract

This study aimed to determine the welding characteristics of USISAC350 (16.0 and 37.5 mm thick) and ASTMA588B (16.0 mm thick) steel grades. These steel grades present similar mechanical strength and atmospheric corrosion resistance with a significant difference in alloy design. For this characterization, chemical and microstructural analyses as well as tensile and Charpy tests were performed on the base metal and welded joints. The joints were welded by flux core arc welding (FCAW) with two different heat input levels. Tekken test and maximum hardness measurements were performed using shielded metal arc welding (SMAW) to compare the susceptibility to hydrogen cracking of the base metals. Tekken test results indicated that only the lower thickness USISAC350 steel did not require preheating to avoid the hydrogen cracking. The heat affect zone of all studied steel grades presented hardness values below 350HV. This value is generally specified as the maximum allowed hardness value in HAZ to avoid the occurrence of hydrogen cracking. Metallographic analysis of the welded joints was concerned only to the HAZ grain growth region. Martensite was only observed in ASTMA588B steel welded joints. All welded joint presented tensile properties that agreed to the specifications of the base metal. As all specimens broke outside the weld zone, the results were controlled by the base metal strength. In the HAZ analysis, a good toughness/heating input relation was not observed. Nevertheless, the best toughness results were obtained on ASTMA588B welded joints.