Effects of heat input and niobium addition on haz of microalloyed steels for reinforcing bars

Abstract

Niobium or vanadium addition provides homogeneous microstructures formation, strengthening and toughness improvement in steels. However, alloying elements increase can negatively affect Pcm (material parameter) value, which can lead to deleterious effects under welding conditions. Thus, welding trials were carried out on a novel microalloyed steel with 0.2%C by autogenous GTAW (Gas-Shielded Tungsten Arc Welding) process. The results indicate that coarse grains region of heat affected zone (CGHAZ) is the most critical area. This was due abnormal grains size (>100µm), achieving more than 4 times the average size of base metal (BM) grains, or the presence of high hardness microstructures. In addition, the results do not indicate softness in any region of HAZ, proving to be an advantage of these materials.