Titanium plate, titanium rod welding joint crack and porosity problems

In the welding process of titanium plate and titanium rod, we usually encounter welding joint cracks and porosity problems in the weld.

1, the porosity in the weld Stomata is often a problem. The root cause of the formation of stomata is the result of hydrogen influence. The porosity of weld metal mainly affects the fatigue strength of joint. The main technological measures to prevent the occurrence of pores are: 1 Maintain neon gas to be pure, titanium and titanium alloy welding. Purity should not be less than 99.99%. 2. completely remove the surface of the solder, the surface of the wire oxide oil and other organic matter. 3. Perform good gas maintenance on the molten pool, control the flow rate and velocity of argon, prevent turbulence and affect the maintenance effect. 4 Correct selection of welding process parameters, increase the retention time of the deep pool to use the bubble escape, can effectively reduce the porosity.

2, welding joint crack problem
The possibility of thermal cracking of welded joints is very small, titanium and titanium alloy welding. This is because the impurity content of SPC and other impurities in titanium and titanium alloy is very small, the low melting point eutectic formed by SP is not easy to appear on the grain boundary, and the effective crystallization temperature range is narrow, the shrinkage amount of titanium and titanium alloy is small during solidification, and the weld metal will not occur hot cracks. When titanium and titanium alloys are welded, cold cracks can occur in the heat affected zone, which is characterized by cracks occurring several hours or even longer after welding called delayed cracks. The research shows that this crack is related to the diffusion of hydrogen bomb during welding. During the welding process, hydrogen diffused from the high-temperature deep pool to the lower-temperature HAZ, and the increase of hydrogen content increased the amount of TiH2 precipitated in the area, which increased the brittleness of the HAZ. In addition, the volume expansion of hydride precipitated caused greater structural stress, and hydrogen atoms diffused and accumulated to the high-stress parts of the area, resulting in the formation of cracks. The method to prevent the occurrence of this delayed crack is mainly to reduce the source of hydrogen in the welded joint, which can generally be vacuum annealing treatment.