Analysis of the Main Factors Affecting Welding Quality

At room temperature, titanium alloys exhibit relatively stable performance. However, at elevated temperatures—particularly during welding—they react rapidly with oxygen, hydrogen, and nitrogen. Relevant data show that titanium alloys begin to absorb hydrogen rapidly above 300°C, oxygen above 600°C, and nitrogen above 700°C. Among these, oxidation in air is the most sensitive process.

Experimental results indicate that during welding, if harmful gases such as oxygen and nitrogen contaminate the molten pool, the plasticity, toughness, and surface color of the weld zone will change significantly. In addition, the mechanical properties deteriorate markedly, and the tendency for overheating increases. Bending tests have shown that welds exposed to insufficient protection may fracture easily, and the base metal within approximately 10 mm of the weld may also exhibit obvious cracking.

Therefore, when welding titanium alloys, comprehensive and reliable gas shielding must be applied to the molten pool, droplets, and high-temperature zones on both the front and back sides of the weld. The purpose of gas protection is, first, to prevent harmful gases from entering the molten pool; and second, to control excessive heat accumulation in the welded region. Without effective shielding, welding quality will inevitably deteriorate, and in severe cases, the component may be rendered unusable.

Welding defects in titanium alloys, such as porosity and cracking, are relatively common. These defects are mainly caused by the influence of gases and impurity elements such as hydrogen, iron, and carbon. Studies show that the solubility and diffusion behavior of these elements during welding are temperature-dependent.

The primary sources of these impurities include humid air, insufficient purity of shielding gas, and contamination such as moisture or oil on the workpiece and welding wire. Porosity is mainly caused by oil contamination and impurities in the shielding gas, while cracks are primarily associated with moisture and oil contamination.

The formation of welding defects not only compromises sealing performance but also significantly reduces the strength, toughness, and fatigue resistance of the joint, thereby seriously affecting overall product quality. Therefore, strict control of welding conditions and cleanliness is essential to ensure weld integrity.