ABSTRACT
The effects of welding and heat treatment on mechanical properties of duplex stainless steel were investigated. The duplex stainless steel rod of 8mm diameter was cut into length of 100.2mm; they were further cut into two equal parts with the two faces beveled to have a 60� grooved angle, leaving a root and face gap of 2mm. The rods were then joined together using GMAW and SMAW processes using stainless steel coated electrode and bare wire electrode (E308L-16 and Nertalic 50). After welding, some specimens passed through stress relief and quenching heat treatment (in neem oil and gear oil (85W90)) and some samples served as standards for comparison and analysis. Tensile, Charpy impact and hardness tests were carried out. The results of the studies show that welding and heat treatment really affect the mechanical properties of the alloy, the control strength was 811.47MN/m2 while that of gas metal arc welding (GMAW) it ranged from 177.07 to 257.32MN/m2 and for shield metal arc welding (SMAW) from 452.23 to 678.98MN/m2. The control impact energy was 162.70J, while that of the gas metal arc welding (GMAW) ranged from 38.64J to 56.20J and for shield metal arc welding (SMAW) ranged from 148.70 to 156.02J. It was also noted that shield metal arc welding (SMAW) gives better results close to the as received than the gas metal arc welding (GMAW) process and heat treatment improved the mechanical properties of the alloy after welding. The research also showed that the stress relief heat treatment gives better strength (A3 =331MN/m2 and B3 =665MN/m2) compared to those that were quenched in lubricating oil (A2 =329MN/m2 and B2 =601MN/m2) and neem oil (A1 =222MN/m2 and B1 =566MN/m2), while those that were quenched in lubricating oil and neem oil had higher toughness.