- Issue Time
- Dec 3,2021
Titanium pipes are prone to surface defects, especially internal surface cracks and folds, during the cold rolling process. The mechanical properties of pure titanium largely depend on the content of interstitial elements, especially the oxygen content. The reduced oxygen content material has good plasticity and good processing performance, but this method alone does not eliminate defects such as cracks and folds on the inner surface of the pipe on a large scale, and it is difficult to ensure the strength of the pipe. Therefore, it is necessary to analyze the rolling deformation process of thick-walled pipes with different oxygen content to find out the causes of defects. For titanium, due to the effect of work hardening, there is a positive correlation between the degree of deformation and its strength and hardness. Therefore, studying the microhardness and metallographic structure on the deformed section can indirectly display different parts on the section. The size of the degree of deformation, so as to study and analyze the rolling process.
The microstructures near the outer wall and near the inner wall of the titanium tube rolled in each pass. The deformed fibrous structure near the inner wall of the titanium pipe after each pass rolling is finer than that of the outer layer. The hardness value of the inner wall point in the hardness curve during the rolling process is greater than that of the outer wall point, which is basically the same, which also reflects the thick-walled pipe from the side. The phenomenon of uneven deformation along the thickness direction on the cross-section during the deformation process. 1. During the deformation process of thick-walled titanium pipe, the curve, especially the inner hole curve, should be gentle, and the feed amount should be small. 2. From the analysis of the hardness distribution curve, the titanium pipe has uneven deformation along the wall thickness direction during the deformation process, and the increase in oxygen content will make this uneven phenomenon more complicated. In the case of a large deformation rate (35% more) and a low oxygen content, the deformation of the interrupted surface of the thick-walled tube during the rolling process will gradually become uniform. However, when the oxygen content is high, even if the pipe rolling meets the condition of large deformation rate, the deformation on the section is difficult to be uniform.