Titanium pressure vessel titanium welding and titanium base metal there are these differences in the titanium wire impurity content and the same base material, titanium weld plasticity and toughness must be much lower than the titanium base metal. Titanium weld and titanium base metal, mechanical properties with the following differences:

(1) titanium weld for the casting organization, than the pressure processing of titanium matrix material loose, and inevitably have dendritic organization, pores, shrinkage, internal stress and other defects (within the allowable range of non-destructive testing), titanium weld plastic Toughness lower than titanium base metal.

(2) nitrogen, oxygen, carbon and other impurities in the liquid phase of titanium, R phase and metallographic solubility in different phase change will cause the redistribution of impurity elements, welding after welding faster cooling, impurity elements in the various parts too late Diffusion uniformity of the impurity element of the dendritic segregation, there is local high impurity content area, resulting in local lattice distortion. When the phase transition of the p phase to the a phase occurs during the cooling process, the R phase transition occurs in part. 'Martensite phase transformation, resulting in metastable phase. While the titanium element matrix element content distribution is more uniform, which also makes the titanium weld plastic toughness lower than titanium base metal.

(3) titanium welding as far as possible with inert gas protection, the purpose of protection is to make the environment of iron, carbon, nitrogen, oxygen, hydrogen and other impurities as little as possible into the titanium weld, the protection is good, can only reduce pollution , The welding process is not to reduce the process of impurities in the weld, but only the number of pollution problems, so the weld is always higher than the impurities in the wire, such as welding wire and base material impurities, the weld impurity composition is always higher than Base material, so that the plastic toughness of the weld is lower than the base metal.

(4) titanium pressure vessels are generally not annealed after welding, the weld for the welding state, while the titanium base material was annealed, which also makes the weld plastic toughness lower than the base metal.

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