Nd:YAG雷射銲接Ti-6Al-4V薄板之製程參數最佳化分析

Abstract

The purpose of this study is to investigate the tensile strength and hardness and their relationship at the welded portion in laser welding Ti-6Al-4V thin plates. The experiments are arranged with an orthogonal array of Taguchi method and used to explore for the objective of tensile strength and the objective of hardness respectively. The analytic procedure of Taguchi method is used to find the welding optimiged parameters combination for these two objectives separately, and the influence of each parameter on the objective was also discussed simultaneously. The overall experimental procedure is divided into three parts. In the first part, according to the preliminary tests there are eight laser welding parameters that showed stronger influence on welding quality have been selected, namely, gas type, peak power, pulse frequency, pulse width, welding speed, focus position, pulse repetition rate and gas pressure. The experiments were conducted based on the arrangement of laser welding parameters by an L18(21×37) orthogonal array of Taguchi method. In the second part, a confirmed test is carried on by using the optimiged parameters combination and the relationship between tensile strength and hardness has been conducted. In the third part, the discussion on the most important parameter affecting the weld quality tendency is investigated. Finally, the relational graph between the tensile strength and hardness has been introduced that shows the welded tensile strength achieves 65% to 66% of the parent material when hardness is HRC 32.8 to 33.1; while tensile strength achieves 63.5% to 64% as hardness is HRC 33.5 to 34. Furthermore the tensile strength of welded portion decreases as the hardness increases. The most important laser parameters affecting welding quality are pulse frequency and gas type. The developed process and obtained results in this study can provide a substantial assistance and reference for laser welding Ti-6Al-4V thin plates.