Numerical and experimental study of the microstructural evolution and the properties of joints welded on rebars using the GMAW process

Abstract

This paper is a study of CA-50 rebars from SAE steel grade 1026. This study was carried out in order to improve the control of the mechanical properties of welded joints. Knowing certain variables are very important when it comes to finding the ideal welding parameters and the respective microstructural results, and consequently for the mechanical properties of welded joints. In order to carry out this study, a study of the material as received was carried out in order to establish a solid basis for comparison. The material was welded using argon as the shielding gas with 20% carbon dioxide. The wire used was copper-covered ER70S-6, and the welded joints were lap joints. The temperature was monitored using thermocouples for two different heat inputs. A numerical computer code was developed to simulate the phenomena that occur during the process (temperature gradient, phase transformations and heat transfer). The welded joints did not introduce martensite as a brittle phase, the weld metal had a dendritic structure, the heat-affected zone (HAZ) had two different zones with different grain sizes. All of this was due to the temperature gradient, which also led to different characteristics in the weld bead, HAZ, phases formed and different grain sizes.