Strength of laser-welded titanium: diameter and distance of weld components

There is a lack of studies associating laser welding, distance between the parts to be welded and the diameter of weld components. Objectives: This study evaluated the tensile strength and elongation of intact and laser welded specimens manufactured in different diameters and distances of welding from commercially pure titanium (CP Ti). Methods: Fifteen dumbbell rods of each diameter (1.5, 2.0 and 5.0 mm) were prepared by lost-wax casting with Rematitan System, and divided for each diameter: 5 intact specimens (control); 5 laser welded closely together; and 5 laser welded leaving a 0.6 mm space between parts filled with a ribbon of titanium, forming a total of 9 groups. All samples (intact and welded) were submitted to tensile test until fracture (1 mm/min). Data were recorded, compared by ANOVA and Tukey test (p<0.05) and fractured surfaces microscopically analyzed (SEM). Results: Tensile strength values (Mpa) for intact specimens were statistically higher than rejoined ones for all diameters. The distance between parts was only significant for 5.0 mm diameter samples, where the ones rejoined with a 0.6 mm space presented the greatest values. Elongation for intact specimens was higher than rejoined ones with 2.0 and 5.0 mm diameters, but was not significant for 1.5 mm diameter specimens. SEM images showed adequate laser penetration only for samples with 1.5 and 2.0 mm diameter. Conclusion: Laser welding procedures were deleterious for the resistance of titanium. Despite being deleterious for the resistance of titanium, it should be done, considering its importance, with a space between the parts to enhance the depth of welding, mainly when dealing with larger diameters.