1. The impact of carbon. During the welding process of titanium and titanium alloys, at room temperature, the liquid droplets and molten pool metal have a strong ability to absorb hydrogen, oxygen, and nitrogen. As the temperature increases, the ability of titanium and titanium alloys to absorb hydrogen, oxygen, and nitrogen also increases significantly. Titanium begins to absorb hydrogen at about 250°C, oxygen at 400°C, and nitrogen at 600°C. After the gas is absorbed, it will directly cause the welding joint to embrittle, which is an extremely important factor affecting the welding quality.
2. The influence of hydrogen. Hydrogen is a factor among gas impurities that has a serious impact on the mechanical properties of titanium. Changes in the hydrogen content of the weld have a significant impact on the impact properties of the weld. The flake or needle-like TiH2 precipitated in the weld increases. The strength of TiH2 is very low, so the effect of flaky or needle-shaped HiH2 is to notch, and the impact performance is significantly reduced; the change in the hydrogen content of the weld has little effect on the improvement of strength and the reduction of plasticity.
3. The influence of oxygen. The hardness and tensile strength of the weld increase significantly, and the oxygen content of the weld basically rises linearly with the increase in the oxygen content of the argon gas. The plasticity is significantly reduced. In order to ensure the performance of welded joints, oxidation of the weld seam and welding heat affected zone should be strictly prevented during the welding process.
4. Effect of nitrogen. Nitrogen and titanium plates will react violently, forming brittle and hard titanium nitride (TiN) at high temperatures above 700°C. Moreover, the degree of lattice distortion caused by the formation of interstitial solid solution between nitrogen and titanium is greater than that caused by the same amount of oxygen.