1. The impact of carbon
Titanium and titanium alloys are relatively stable but in the welding process at room temperature. Liquid droplet and pool metal have strong absorption of hydrogen, oxygen, nitrogen, and in the solid state, these gases have acted on them. With the increase of temperature, the ability of titanium and titanium alloy to absorb hydrogen, oxygen and nitrogen also rises significantly. About 250℃ titanium begins to absorb hydrogen, from 400℃ to absorb oxygen, from 600℃ to absorb nitrogen. After these gases are absorbed, they will directly cause embrittleness of welded joints, which is a very important factor affecting the quality of welding.
2. Hydrogen is the influence
The main reason is that hydrogen is the most serious factor affecting the mechanical properties of titanium among the gas impurities. The hydrogen content of weld has the most significant effect on weld impact property. The precipitation of flake or acicular TiH2 in the weld increased. The strength of TiH2 is very low, so flaky or acicular HiH2 acts as a notch, and the combined impact performance is significantly reduced. The effect of hydrogen content variation on the increase of strength and the decrease of plasticity is not very obvious.
3. The influence of oxygen
The hardness and tensile strength of the weld increased obviously, and the oxygen content of the weld basically increased with the increase of oxygen content in argon, which increased with the increase of oxygen content in the weld. And plasticity is significantly reduced. In order to ensure the performance of welded joints, oxidation of weld and heat affected zone should be strictly prevented during welding.
4. The effect of nitrogen
Nitrogen and titanium plates have dramatic effects at high temperatures above 700℃. The formation of brittle and hard titanium nitride (TiN and the lattice deflection caused by the formation of a gap solid solution between nitrogen and titanium is more serious than that caused by the same amount of oxygen). Therefore, nitrogen can improve the tensile strength and hardness of industrial pure titanium weld, and reduce the plastic performance of the weld is more significant than oxygen. When the nitrogen content of the weld is more than 0.13%, the weld cracks due to excessive embrittlement.
Mechanism and physicochemical properties of titanium alloy welding
Titanium and Welded Titanium Tube have very strict requirements for welding protection. When the carbon content of the weld is 0.55%, the weld plasticity will almost disappear and become very brittle materials. Hot treatment after welding can not eliminate this brittleness. The country's technical conditions stipulate that the carbon content of titanium alloy base material is not more than 0.1%. The carbon content of weld does not exceed the carbon content of base material. Titanium alloy has a lot of elements, they have an impact on the physical properties of titanium, carbon is a common impurity in titanium and titanium alloy, when the carbon content is 0.13% below, carbon due to deep in α titanium, weld strength limit some increase, some decrease in plasticity, but not as strong as oxygen and nitrogen. However, when the carbon content of the weld is further increased, the number of TiC network appears in the weld increases with the increase of carbon content, so that the weld plasticity drops sharply, and cracks are easy to appear under the action of welding stress.
The defect of titanium tube weld is due to the fact that the argon gas maintenance layer formed by argon arc welding gun can only protect the welding pool from the harmful effect of air during the welding of titanium tube, but has no protective effect on the solidified weld and its nearby area in high temperature. However, the titanium tube weld and its nearby area in this state still have a strong ability to absorb nitrogen and oxygen in the air. Oxygen is absorbed from 400℃ and nitrogen is absorbed from 600℃, and air species contain a lot of nitrogen and oxygen. With the increasing oxidation level, the weld color changes and the weld plasticity decreases. Silver white (no oxidation) golden yellow (TiO, around 250℃ titanium begins to absorb hydrogen. Slightly oxidized) blue (Ti2O3 oxidized slightly severely) gray (TiO2 oxidized severely).
1. The impact of carbon
Titanium and titanium alloys are relatively stable but in the welding process at room temperature. Liquid droplet and pool metal have strong absorption of hydrogen, oxygen, nitrogen, and in the solid state, these gases have acted on them. With the increase of temperature, the ability of titanium and titanium alloy to absorb hydrogen, oxygen and nitrogen also rises significantly. About 250℃ titanium begins to absorb hydrogen, from 400℃ to absorb oxygen, from 600℃ to absorb nitrogen. After these gases are absorbed, they will directly cause embrittleness of welded joints, which is a very important factor affecting the quality of welding.
2. Hydrogen is the influence
The main reason is that hydrogen is the most serious factor affecting the mechanical properties of titanium among the gas impurities. The hydrogen content of weld has the most significant effect on weld impact property. The precipitation of flake or acicular TiH2 in the weld increased. The strength of TiH2 is very low, so flaky or acicular HiH2 acts as a notch, and the combined impact performance is significantly reduced. The effect of hydrogen content variation on the increase of strength and the decrease of plasticity is not very obvious.
3. The influence of oxygen
The hardness and tensile strength of the weld increased obviously, and the oxygen content of the weld basically increased with the increase of oxygen content in argon, which increased with the increase of oxygen content in the weld. And plasticity is significantly reduced. In order to ensure the performance of welded joints, oxidation of weld and heat affected zone should be strictly prevented during welding.
4. The effect of nitrogen
Nitrogen and titanium plates have dramatic effects at high temperatures above 700℃. The formation of brittle and hard titanium nitride (TiN and the lattice deflection caused by the formation of a gap solid solution between nitrogen and titanium is more serious than that caused by the same amount of oxygen). Therefore, nitrogen can improve the tensile strength and hardness of industrial pure titanium weld, and reduce the plastic performance of the weld is more significant than oxygen. When the nitrogen content of the weld is more than 0.13%, the weld cracks due to excessive embrittlement.
1. The impact of carbon
Titanium and titanium alloys are relatively stable but in the welding process at room temperature. Liquid droplet and pool metal have strong absorption of hydrogen, oxygen, nitrogen, and in the solid state, these gases have acted on them. With the increase of temperature, the ability of titanium and titanium alloy to absorb hydrogen, oxygen and nitrogen also rises significantly. About 250℃ titanium begins to absorb hydrogen, from 400℃ to absorb oxygen, from 600℃ to absorb nitrogen. After these gases are absorbed, they will directly cause embrittleness of welded joints, which is a very important factor affecting the quality of welding.
2. Hydrogen is the influence
The main reason is that hydrogen is the most serious factor affecting the mechanical properties of titanium among the gas impurities. The hydrogen content of weld has the most significant effect on weld impact property. The precipitation of flake or acicular TiH2 in the weld increased. The strength of TiH2 is very low, so flaky or acicular HiH2 acts as a notch, and the combined impact performance is significantly reduced. The effect of hydrogen content variation on the increase of strength and the decrease of plasticity is not very obvious.
3. The influence of oxygen
The hardness and tensile strength of the weld increased obviously, and the oxygen content of the weld basically increased with the increase of oxygen content in argon, which increased with the increase of oxygen content in the weld. And plasticity is significantly reduced. In order to ensure the performance of welded joints, oxidation of weld and heat affected zone should be strictly prevented during welding.
4. The effect of nitrogen
Nitrogen and titanium plates have dramatic effects at high temperatures above 700℃. The formation of brittle and hard titanium nitride (TiN and the lattice deflection caused by the formation of a gap solid solution between nitrogen and titanium is more serious than that caused by the same amount of oxygen). Therefore, nitrogen can improve the tensile strength and hardness of industrial pure titanium weld, and reduce the plastic performance of the weld is more significant than oxygen. When the nitrogen content of the weld is more than 0.13%, the weld cracks due to excessive embrittlement.