When welding titanium tubes and titanium alloy tubes, when the content of oxygen and nitrogen in the weld is high, the performance of the weld or heat-affected zone becomes brittle. Titanium begins to absorb hydrogen at about 250 degrees, oxygen from 400 degrees, and oxygen from 600 degrees. The temperature begins to absorb nitrogen, and the air contains a large amount of nitrogen and oxygen. Under the action of large welding stress, cold cracks will appear. It is characterized by cracks occurring several hours or even longer after welding, which is called delayed cracking. Studies have shown that the diffusion of hydrogen during welding is the main cause of such cracks. During the welding process, hydrogen diffuses from the high-temperature deep pool to the lower-temperature heat-affected zone. The increase of hydrogen content increases the amount of TiH2 precipitated in this zone, which increases the brittleness of the heat-affected zone. In addition, due to the volume expansion of the hydride precipitation, large tissue stress is caused, coupled with the diffusion and aggregation of hydrogen atoms to the high-stress parts of the region, resulting in the formation of cracks. The main way to prevent such delayed cracks is to reduce the source of hydrogen in welded joints.
When welding titanium pipe manufacturers, porosity is a major problem often encountered. The root cause of the formation of pores is the result of the influence of hydrogen. The main process measures to prevent the generation of pores are:
1) Welding under the protection of high-purity argon gas, the purity of argon gas should not be lower than 99.99%
2) Thoroughly remove organic substances such as oxide skin and oil stains on the surface of titanium tube, titanium plate, and titanium plate tube eye. Can be cleaned by chemical and mechanical methods
3) Apply good gas protection to the molten pool, and control the flow and flow rate of argon gas to prevent turbulence and affect the protection effect
4) Select the appropriate welding process parameters and titanium tube specifications, increase the residence time of the deep pool, and use it to facilitate the escape of air bubbles, which can effectively reduce the pores
