Experimental Determination of the Tempering Effect On Tensile Strength, Impact Strength, Fatigue, Residual Stress of Girth Welding on Gas Transmission Pipelines

The effects of tempering heat treatment on girth weld containing titanium oxide and titanium carbide nanoparticles (X-65 grade of the gas pipeline) were evaluated. The Charpy results show that it has been respectively increased by 26% and 15% in the tempered sample containing titanium oxide and titanium carbide nanoparticles compared to the no heat treatment sample (containing titanium carbide and titanium carbide nanoparticles). Also, the ultimate strength tempered sample containing titanium oxide nanoparticles and titanium carbide nanoparticles compared to the no heat treatment sample (containing titanium oxide and titanium carbide nanoparticles) has been respectively decreased by 6% and 4%. The results show that the fatigue life in both tempered nano-alloy samples has been increased. The fatigue life in the tempered sample of titanium carbide nanoparticles has increased more than the fatigue life in titanium oxide nanoparticles. The fatigue test results show that in the tempered sample containing titanium carbide nanoparticles compared to the tempered sample containing titanium oxide nanoparticles, fatigue life (150-N force) has been increased by 30%. In this loading, the fatigue life (tempered sample containing titanium carbide nanoparticles compared to the no heat treatment sample) has been increased by 19%. The hole drilling strain gage results show that in the tempered sample containing titanium oxide nanoparticles and titanium carbide nanoparticles, hoop residual stresses have been respectively decreased by 48% and 45% compared to the no heat treatment sample (containing titanium oxide and titanium carbide nanoparticles).