Xiangdong Jiao

Influence of the Bar Shape on the Welding Quality of Friction Hydro Pillar Processing

Traditional underwater arc welding methods, for example, TIG and MIG, are generally expensive and complex to implement under water. Besides, the welding quality decreases significantly with the increase of depth of water. So a new-style solid phase welding method called friction stitch welding (FSW) is introduced, since the welding quality of which is almost insensitive to water. This article studies the influence of the bar shape on the welding quality. In the experiments, three typical kinds of shape combinations are adopted. Argon is used as protecting gas, and the flux of which is 30L/min. The feed speed of the spindle is 0.5 mm/s, the rotation speed is 4000r/min. Through the comparison of the macro features and microstructure of the welded joints, the influence of the bar shape on the welding quality is analyzed, and static stress distribution along with the influence on welding temperature by different shapes are investigated. The results indicate that the welding quality obtained by using straight bars with round head is much better than the other shape combinations, the welding defects are reduced and the welded material is much finer.

Study on Sub-sea Pipelines Hyperbaric Welding Repair under High Air Pressures

Most Chinese sub-sea pipelines are buried in Bohai Sea less than 60m water depth, where air diving are widely used For the application of offshore pipelines repair, the hyperbaric TIG welding process under high air pressures has been successfully developed. Firstly, the hyperbaric welding test chamber is designed and constructed in laboratory, and the welding machine is manufactured. Then, special welding experiments are carried out based on 16Mn steel plates and pipes under 1-7bar air pressures, and high weld quality is obtained. Lastly, the sea-trial of the welding machine and the welding procedure is carried out in Bohai Sea in China, and a perfect all-position 5G girth weld of 16Mn steel pipe is achieved.