Efeito do desenho de junções e tipo de solda na resistência flexural de barras de liga de Ti-6AL-4V

Abstract

The aim of this study was to evaluate the effect of different drawings of joints and welding processes Tungsten Inert Gas (TIG) and Laser in flexural bar alloy Ti-6Al-4V. Seventy specimens with dimensions of 3.18mm diameter and 40mm length were divided into seven groups (n = 10): C, control group (intact); groups TI, TX30° and TX45° with joint beveled at 0°, 30° and 45° respectively, TIG welded; and Groups LI, LX30° and LX45° with joint beveled at 0 °, 30 ° and 45 ° respectively, Laser welded. After the mechanical test, the values bending fracture strength (N) were converted to maximum bending stress (MPa) and the fracture surfaces were measured to obtain the soldered areas. Data were initially subjected to Factorial ANOVA (2 x 3) followed by Tukey test. Then, only the data of maximum bending stress were analyzed with Analysis of Variance for single factor followed by Dunnett\'s test to detect differences between the control group and six experimental groups. Was applied the Pearson correlation to the factors type of weld and joint type. For all tests were considered statistical differences for α=0.05. Dunnett\'s test showed that the groups TX30° (p=0.990) and TX45º (p=0.995) resulted in values of maximum tension bending similar to the control group. The other experimental groups resulted in significantly lower values than the control group. Comparing the type of solder, the Tukey test showed that the TIG welding resulted in maximum flexion significantly greater than the Laser weld (p<0.05), regardless of the type of junction. For the factor welded joints area with drawing \"X\" resulted in significantly higher values than the junction \"I\" for both welding processes. In comparing the welded areas between the two processes of welding, TIG process resulted in significantly higher values of welded area employed when the junction type \"I\" and significantly lower for the type X30° (p<0.05). For the type of junction X45° no statistical difference (p>0.05). The Pearson correlation between variables welded area and maximum bending stress was moderate (0.5520) and significant (p<0.0001). The images obtained by SEM showed increased presence of pores on the fracture surfaces and Laser welded aspects suggesting the presence of ductility TIG welded surfaces. It was concluded that the use of TIG welding and drawing joint \"X\" resulting in higher flexural strength, which are more suitable for welding bars alloy Ti-6Al-4V 3.18mm in diameter when high values of flexural strength are required.