The performance of titanium and titanium alloy welding has many characteristics, and these welding characteristics are determined by the physical and chemical functions of titanium and titanium alloys. In the meantime, gas and impurity contamination has a great influence on the welding function. So what is the welding performance of titanium alloys? Presumably many of my friends don't know much about it, so now please see the detailed introduction below!

At room temperature, titanium and titanium alloys are relatively stable. However, in the test table, during the welding process, the liquid droplet and molten pool metal have the effect of strongly absorbing hydrogen, oxygen, and nitrogen, and in the solid state, these gases have had an effect on it. As the temperature increases, the ability of titanium and titanium alloys to absorb hydrogen, oxygen and nitrogen also increases significantly. It begins to absorb hydrogen at about 250 ° C, absorbs oxygen from 400 ° C, and absorbs nitrogen from 600 ° C. These gases After being absorbed, it will directly cause embrittlement of the welded joint, which is an extremely important factor affecting the welding quality.

1. The influence of hydrogen

Hydrogen is the most severe element of the gaseous impurities that affects the mechanical properties of titanium. The change of the hydrogen content of the weld has the most obvious effect on the impact function of the weld. The main reason is that with the increase of the hydrogen bomb content of the weld, the flaky or needle-like TiH2 in the weld increases. The strength of TiH2 is very low, so the effect of flaky or needle-shaped HiH2 is notched, and the impact function is obviously reduced; the effect of changing the hydrogen content of the weld on the improvement of strength and the reduction of plasticity is not obvious.

2. The influence of oxygen

Oxygen has a high degree of solubility in both the α phase and the β phase of titanium, and can form a solid and deep phase of voids. The crystal wound of titanium is severely distorted, so that the hardness and strength of titanium and titanium alloys can be improved, and the plasticity can be improved. has dropped significantly. In order to ensure the function of the welding connection, in addition to strictly preventing the main oxidation of the weld and the heat affected zone during the welding process, the oxygen content in the base metal and the welding wire should also be restricted at this time.

3. The effect of nitrogen

At high temperatures above 700 °C, nitrogen and titanium have a dramatic effect, forming brittle and hard titanium nitride (riN), and the degree of lattice distortion caused by nitrogen and titanium forming a void solid solution is the result of the amount of oxygen. It is more severe. Therefore, nitrogen is more obvious than oxygen in improving the tensile strength and hardness of industrial pure titanium welds and reducing the plasticity of welds.

4. The impact of carbon

Carbon is also a common impurity in titanium and titanium alloys. Tests show that when the carbon content is 0.13%, the carbon is deep in α titanium, the strength limit of the weld is somewhat improved, and the plasticity is somewhat reduced, but the effect is not as intense as that of oxygen and nitrogen. However, when the carbon content of the weld is further increased, the weld shows a network of TiC, and its number increases with the increase of the carbon content, so that the plasticity of the weld decreases sharply, and cracks are prone to appear under the effect of welding stress. Therefore, the carbon content of the base metal of titanium and titanium alloys should not exceed 0.1%, and the carbon content of the weld should not exceed the carbon content of the base metal.