Experimental investigation of the Annealing Effect on the Mechanical Properties of Girth Welding Using Nanoparticles on Gas Transmission Pipeline

Titanium is one of the most important microalloy elements used in the gas transmission industry. In this paper, titanium nano-oxide and titanium nano-carbide were added to two separate samples. Then the shielded metal arc welding (SMAW) was performed on high-strength low alloy steel according to welding procedure specification of the national Iranian gas company. The effects of annealing heat treatment on girth weld with containing titanium oxide and titanium carbide nanoparticles (X-65 grade of gas transmission pipeline) were evaluated. The Charpy test results show that in the annealed sample containing titanium oxide nanoparticles and titanium carbide nanoparticles compared to the no heat treatment sample (Containing titanium carbide nanoparticles and titanium carbide nanoparticles), energy absorbed has been respectively increased by %13 and %9. Also, the ultimate strength of the annealed sample containing titanium oxide nanoparticles and titanium carbide nanoparticles compared to the non-heat treated sample has been respectively decreased by %8 and %3. The fatigue life in both annealed nano-alloy samples has been increased. Also, the fatigue life in the annealed sample of titanium carbide nanoparticles has increased more than fatigue life in the titanium oxide nanoparticles. The fatigue life (Annealed sample containing titanium carbide nanoparticles compared to the no heat treatment sample) has been increased by %16. The hole drilling strain gage results show that in the annealed sample containing titanium oxide nanoparticles and titanium carbide nanoparticles compared to the non-heat treated sample, hoop residual stresses has been respectively decreased by %31 and %19.