titanium alloy pump Titanium tube weld crack problem

Titanium tube weld cracks and pores problems

Titanium tube weld crack problem

When the possibility of titanium welding, thermal cracking of welded joints is small, it is because few impurities in titanium and titanium alloys S, P, C , etc. , low melting point of S, P eutectic formed at the grain boundaries rarely generation, titanium alloy pump coupled with effective crystallization temperature range narrow, titanium and titanium alloy solidification when a small amount of shrinkage , weld metal does not produce heat cracks.

When titanium and titanium alloy welding, weld when an oxygen , nitrogen is high , the performance of the weld heat affected zone or become brittle in the larger weld stress, cold cracking occurs . Characterized by cracks in the weld called a few hours or even longer delay cracks. The study showed that the hydrogen diffusion welding process is the main cause of such cracks. Hydrogen in the welding process to a lower temperature by diffusion of the high temperature heat affected zone deep pool , the area increase the hydrogen content of the precipitates increased so that the amount of TiH2 , brittle heat affected zone is increased , the other due to volume expansion caused by precipitation of hydrides greater the stress , plus a hydrogen atom diffusion and aggregation to the high stress areas of the area, resulting in the formation of cracks . This delay prevents cracks approach is to reduce the welded joint main source of hydrogen .

Titanium tube weld porosity problems

When titanium pipe welding , porosity is often encountered a major problem. Titanium alloy valve The root cause of the formation of pores is affected as a result of hydrogen .

Prevent blowholes process measures are:

1 ) in high purity argon welding , argon gas purity not less than 99.99%

2 ) the elimination of titanium tubes , oil and other oxide on the surface of titanium and titanium tubes eye organics . Can be cleaned with a chemical and mechanical methods.

3 ) subjected to the bath gas well , control the flow and the flow rate of argon gas , to prevent turbulence , impact protection.

4 ) Choose the appropriate welding process parameters, welding specification , titanium pump increasing the residence time of deep pools to facilitate the use of air bubbles escape , which can effectively reduce porosity.